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1
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Zhang J, Zhang X, Li G, Ge J, Feng X. Loureirin B Ameliorates Glycolipid Metabolism Disorders in Ob/ob Mice by Regulating Bile Acid Levels and Modulating Gut Microbiota Composition. Chem Biodivers 2025; 22:e202401793. [PMID: 39431713 DOI: 10.1002/cbdv.202401793] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/24/2024] [Revised: 10/16/2024] [Accepted: 10/21/2024] [Indexed: 10/22/2024]
Abstract
Loureirin B (LB), an active component of Resina Draconis, exhibits hypoglycemic and hypolipidemic effects; however, its mode of action remains unclear. Here, ob/ob mice were utilized to investigate the effects of LB on the regulation of glucolipid metabolism disorders. Non-targeted metabolomics and 16S rDNA sequencing were performed to elucidate the potential mechanisms involved. Results indicated that LB treatment (45 mg/kg) significantly improved glucose intolerance and insulin resistance, reduced lipid levels, and alleviated hepatic steatosis. Non-targeted metabolomics analysis revealed that LB treatment regulated bile acid levels. Quantification of liver bile acids demonstrated that LB treatment significantly decreased the ratio of 12α-OH to non-12α-OH bile acids in the liver. 16S rDNA sequencing results showed that LB treatment increased the abundance of short-chain fatty acid-producing microbiota while decreasing the abundance of bile salt hydrolase (BSH) enzyme-producing microbiota. In conclusion, LB ameliorates glucolipid metabolism disorders by regulating liver bile acid levels and modulating the composition of the gut microbiota.
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Affiliation(s)
- Junyang Zhang
- School of Chinese Materia Medica, State Key Laboratory of Component-based Chinese Medicine, Tianjin Key Laboratory of Therapeutic Substance of Traditional Chinese Medicine, Tianjin University of Traditional Chinese Medicine, 10 Poyang Lake Road, West District, Tuanbo New Town, Jinghai District, Tianjin, China
| | - Xiaoyan Zhang
- School of Chinese Materia Medica, State Key Laboratory of Component-based Chinese Medicine, Tianjin Key Laboratory of Therapeutic Substance of Traditional Chinese Medicine, Tianjin University of Traditional Chinese Medicine, 10 Poyang Lake Road, West District, Tuanbo New Town, Jinghai District, Tianjin, China
| | - Gen Li
- School of Chinese Materia Medica, State Key Laboratory of Component-based Chinese Medicine, Tianjin Key Laboratory of Therapeutic Substance of Traditional Chinese Medicine, Tianjin University of Traditional Chinese Medicine, 10 Poyang Lake Road, West District, Tuanbo New Town, Jinghai District, Tianjin, China
| | - Jun Ge
- School of Chinese Materia Medica, State Key Laboratory of Component-based Chinese Medicine, Tianjin Key Laboratory of Therapeutic Substance of Traditional Chinese Medicine, Tianjin University of Traditional Chinese Medicine, 10 Poyang Lake Road, West District, Tuanbo New Town, Jinghai District, Tianjin, China
| | - Xinchi Feng
- School of Chinese Materia Medica, State Key Laboratory of Component-based Chinese Medicine, Tianjin Key Laboratory of Therapeutic Substance of Traditional Chinese Medicine, Tianjin University of Traditional Chinese Medicine, 10 Poyang Lake Road, West District, Tuanbo New Town, Jinghai District, Tianjin, China
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2
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Liu K, Salvati A, Sabirsh A. Physiology, pathology and the biomolecular corona: the confounding factors in nanomedicine design. NANOSCALE 2022; 14:2136-2154. [PMID: 35103268 DOI: 10.1039/d1nr08101b] [Citation(s) in RCA: 11] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/14/2023]
Abstract
The biomolecular corona that forms on nanomedicines in different physiological and pathological environments confers a new biological identity. How the recipient biological system's state can potentially affect nanomedicine corona formation, and how this can be modulated, remains obscure. With this perspective, this review summarizes the current knowledge about the content of biological fluids in various compartments and how they can be affected by pathological states, thus impacting biomolecular corona formation. The content of representative biological fluids is explored, and the urgency of integrating corona formation, as an essential component of nanomedicine designs for effective cargo delivery, is highlighted.
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Affiliation(s)
- Kai Liu
- Advanced Drug Delivery, Pharmaceutical Sciences, R&D, AstraZeneca, Gothenburg, Sweden.
| | - Anna Salvati
- Department of Nanomedicine & Drug Targeting, Groningen Research Institute of Pharmacy, University of Groningen, Groningen 9713AV, The Netherlands
| | - Alan Sabirsh
- Advanced Drug Delivery, Pharmaceutical Sciences, R&D, AstraZeneca, Gothenburg, Sweden.
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3
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Henning RJ. Obesity and obesity-induced inflammatory disease contribute to atherosclerosis: a review of the pathophysiology and treatment of obesity. AMERICAN JOURNAL OF CARDIOVASCULAR DISEASE 2021; 11:504-529. [PMID: 34548951 PMCID: PMC8449192] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Subscribe] [Scholar Register] [Received: 05/31/2021] [Accepted: 08/06/2021] [Indexed: 06/13/2023]
Abstract
Two billion people worldwide older than 18 years of age, or approximately 30% of the world population, are overweight or obese. In addition, more than 43 million children under the age of 5 are overweight or obese. Among the population in the United States aged 20 and greater, 32.8 percent are overweight and 39.8 percent are obese. Blacks in the United States have the highest age-adjusted prevalence of obesity (49.6%), followed by Hispanics (44.8%), whites (42.2%) and Asians (17.4%). The impact of being overweight or obese on the US economy exceeds $1.7 trillion dollars, which is equivalent to approximately eight percent of the nation's gross domestic product. Obesity causes chronic inflammation that contributes to atherosclerosis and causes >3.4 million deaths/year. The pathophysiologic mechanisms in obesity that contribute to inflammation and atherosclerosis include activation of adipokines/cytokines and increases in aldosterone in the circulation. The adipokines leptin, resistin, IL-6, and monocyte chemoattractant protein activate and chemoattract monocytes/macrophages into adipose tissue that promote visceral adipose and systemic tissue inflammation, oxidative stress, abnormal lipid metabolism, insulin resistance, endothelial dysfunction, and hypercoagulability that contribute to atherosclerosis. In addition in obesity, the adipokines/cytokines IL-1β, IL-18, and TNF are activated and cause endothelial cell dysfunction and hyperpermeability of vascular endothelial junctions. Increased aldosterone in the circulation not only expands the blood volume but also promotes platelet aggregation, vascular endothelial dysfunction, thrombosis, and fibrosis. In order to reduce obesity and obesity-induced inflammation, therapies including diet, medications, and bariatric surgery are discussed that should be considered in patients with BMIs>35-40 kg/m2 if diet and lifestyle interventions fail to achieve weight loss. In addition, antihypertensive therapy, plasma lipid reduction and glucose lowering therapy should be prescribed in obese patients with hypertension, a 10-year CVD risk >7.5%, or prediabetes or diabetes.
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Affiliation(s)
- Robert J Henning
- James A. Haley Hospital, University of South Florida Tampa, Florida 33612-3805, USA
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4
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Li H, Yu XH, Ou X, Ouyang XP, Tang CK. Hepatic cholesterol transport and its role in non-alcoholic fatty liver disease and atherosclerosis. Prog Lipid Res 2021; 83:101109. [PMID: 34097928 DOI: 10.1016/j.plipres.2021.101109] [Citation(s) in RCA: 103] [Impact Index Per Article: 25.8] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/16/2021] [Revised: 05/31/2021] [Accepted: 06/02/2021] [Indexed: 12/12/2022]
Abstract
Non-alcoholic fatty liver disease (NAFLD) is a quickly emerging global health problem representing the most common chronic liver disease in the world. Atherosclerotic cardiovascular disease represents the leading cause of mortality in NAFLD patients. Cholesterol metabolism has a crucial role in the pathogenesis of both NAFLD and atherosclerosis. The liver is the major organ for cholesterol metabolism. Abnormal hepatic cholesterol metabolism not only leads to NAFLD but also drives the development of atherosclerotic dyslipidemia. The cholesterol level in hepatocytes reflects the dynamic balance between endogenous synthesis, uptake, esterification, and export, a process in which cholesterol is converted to neutral cholesteryl esters either for storage in cytosolic lipid droplets or for secretion as a major constituent of plasma lipoproteins, including very-low-density lipoproteins, chylomicrons, high-density lipoproteins, and low-density lipoproteins. In this review, we describe decades of research aimed at identifying key molecules and cellular players involved in each main aspect of hepatic cholesterol metabolism. Furthermore, we summarize the recent advances regarding the biological processes of hepatic cholesterol transport and its role in NAFLD and atherosclerosis.
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Affiliation(s)
- Heng Li
- Institute of Cardiovascular Disease, Key Laboratory for Arteriosclerology of Hunan Province, Hunan International Scientific and Technological Cooperation Base of Arteriosclerotic Disease, Hunan Province Cooperative Innovation Center for Molecular Target New Drug Study, Hengyang Medical College, University of South China, Hengyang, Hunan 421001, China
| | - Xiao-Hua Yu
- Institute of Clinical Medicine, The Second Affiliated Hospital of Hainan Medical University, Haikou, Hainan 460106, China
| | - Xiang Ou
- Department of Endocrinology, the First Hospital of Changsha, Changsha, Hunan 410005, China
| | - Xin-Ping Ouyang
- Department of Physiology, Institute of Neuroscience Research, Hengyang Key Laboratory of Neurodegeneration and Cognitive Impairment, Hunan Province Cooperative Innovation Center for Molecular Target New Drug Study, Hengyang Medical College, University of South China, Hengyang, Hunan 421001, China.
| | - Chao-Ke Tang
- Institute of Cardiovascular Disease, Key Laboratory for Arteriosclerology of Hunan Province, Hunan International Scientific and Technological Cooperation Base of Arteriosclerotic Disease, Hunan Province Cooperative Innovation Center for Molecular Target New Drug Study, Hengyang Medical College, University of South China, Hengyang, Hunan 421001, China.
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5
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Otis JP, Shen MC, Caldwell BA, Reyes Gaido OE, Farber SA. Dietary cholesterol and apolipoprotein A-I are trafficked in endosomes and lysosomes in the live zebrafish intestine. Am J Physiol Gastrointest Liver Physiol 2019; 316:G350-G365. [PMID: 30629468 PMCID: PMC6415739 DOI: 10.1152/ajpgi.00080.2018] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/31/2023]
Abstract
Difficulty in imaging the vertebrate intestine in vivo has hindered our ability to model nutrient and protein trafficking from both the lumenal and basolateral aspects of enterocytes. Our goal was to use live confocal imaging to increase understanding of intestinal trafficking of dietary cholesterol and apolipoprotein A-I (APOA-I), the main structural component of high-density lipoproteins. We developed a novel assay to visualize live dietary cholesterol trafficking in the zebrafish intestine by feeding TopFluor-cholesterol (TF-cholesterol), a fluorescent cholesterol analog, in a lipid-rich, chicken egg yolk feed. Quantitative microscopy of transgenic zebrafish expressing fluorescently tagged protein markers of early, recycling, and late endosomes/lysosomes provided the first evidence, to our knowledge, of cholesterol transport in the intestinal endosomal-lysosomal trafficking system. To study APOA-I dynamics, transgenic zebrafish expressing an APOA-I fluorescent fusion protein (APOA-I-mCherry) from tissue-specific promoters were created. These zebrafish demonstrated that APOA-I-mCherry derived from the intestine accumulated in the liver and vice versa. Additionally, intracellular APOA-I-mCherry localized to endosomes and lysosomes in the intestine and liver. Moreover, live imaging demonstrated that APOA-I-mCherry colocalized with dietary TF-cholesterol in enterocytes, and this colocalization increased with feeding time. This study provides a new set of tools for the study of cellular lipid biology and elucidates a key role for endosomal-lysosomal trafficking of intestinal cholesterol and APOA-I. NEW & NOTEWORTHY A fluorescent cholesterol analog was fed to live, translucent larval zebrafish to visualize intracellular cholesterol and apolipoprotein A-I (APOA-I) trafficking. With this model intestinal endosomal-lysosomal cholesterol trafficking was observed for the first time. A new APOA-I fusion protein (APOA-I-mCherry) expressed from tissue-specific promoters was secreted into the circulation and revealed that liver-derived APOA-I-mCherry accumulates in the intestine and vice versa. Intestinal, intracellular APOA-I-mCherry was observed in endosomes and lysosomes and colocalized with dietary cholesterol.
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Affiliation(s)
- Jessica P. Otis
- 1Department of Embryology, Carnegie Institution for Science, Baltimore, Maryland
| | - Meng-Chieh Shen
- 1Department of Embryology, Carnegie Institution for Science, Baltimore, Maryland
| | - Blake A. Caldwell
- 1Department of Embryology, Carnegie Institution for Science, Baltimore, Maryland
| | - Oscar E. Reyes Gaido
- 1Department of Embryology, Carnegie Institution for Science, Baltimore, Maryland,2Department of Biology, Johns Hopkins University, Baltimore, Maryland
| | - Steven A. Farber
- 1Department of Embryology, Carnegie Institution for Science, Baltimore, Maryland,2Department of Biology, Johns Hopkins University, Baltimore, Maryland
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Lee SX, Heine M, Schlein C, Ramakrishnan R, Liu J, Belnavis G, Haimi I, Fischer AW, Ginsberg HN, Heeren J, Rinninger F, Haeusler RA. FoxO transcription factors are required for hepatic HDL cholesterol clearance. J Clin Invest 2018; 128:1615-1626. [PMID: 29408809 DOI: 10.1172/jci94230] [Citation(s) in RCA: 16] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/04/2017] [Accepted: 02/01/2018] [Indexed: 12/15/2022] Open
Abstract
Insulin resistance and type 2 diabetes are associated with low levels of high-density lipoprotein cholesterol (HDL-C). The insulin-repressible FoxO transcription factors are potential mediators of the effect of insulin on HDL-C. FoxOs mediate a substantial portion of insulin-regulated transcription, and poor FoxO repression is thought to contribute to the excessive glucose production in diabetes. In this work, we show that mice with liver-specific triple FoxO knockout (L-FoxO1,3,4), which are known to have reduced hepatic glucose production, also have increased HDL-C. This was associated with decreased expression of the HDL-C clearance factors scavenger receptor class B type I (SR-BI) and hepatic lipase and defective selective uptake of HDL cholesteryl ester by the liver. The phenotype could be rescued by re-expression of SR-BI. These findings demonstrate that hepatic FoxOs are required for cholesterol homeostasis and HDL-mediated reverse cholesterol transport to the liver.
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Affiliation(s)
- Samuel X Lee
- Naomi Berrie Diabetes Center, Columbia University College of Physicians and Surgeons, New York, New York, USA
| | - Markus Heine
- Department of Biochemistry and Molecular Cell Biology, University Medical Center Hamburg Eppendorf, Hamburg, Germany
| | - Christian Schlein
- Department of Biochemistry and Molecular Cell Biology, University Medical Center Hamburg Eppendorf, Hamburg, Germany
| | - Rajasekhar Ramakrishnan
- Department of Medicine, Columbia University College of Physicians and Surgeons, New York, New York, USA
| | - Jing Liu
- Department of Medicine, Columbia University College of Physicians and Surgeons, New York, New York, USA
| | - Gabriella Belnavis
- Naomi Berrie Diabetes Center, Columbia University College of Physicians and Surgeons, New York, New York, USA
| | - Ido Haimi
- Naomi Berrie Diabetes Center, Columbia University College of Physicians and Surgeons, New York, New York, USA
| | - Alexander W Fischer
- Department of Biochemistry and Molecular Cell Biology, University Medical Center Hamburg Eppendorf, Hamburg, Germany
| | - Henry N Ginsberg
- Department of Medicine, Columbia University College of Physicians and Surgeons, New York, New York, USA
| | - Joerg Heeren
- Department of Biochemistry and Molecular Cell Biology, University Medical Center Hamburg Eppendorf, Hamburg, Germany
| | - Franz Rinninger
- Department of Biochemistry and Molecular Cell Biology, University Medical Center Hamburg Eppendorf, Hamburg, Germany.,Department of Internal Medicine III, University Medical Center Hamburg Eppendorf, Hamburg, Germany
| | - Rebecca A Haeusler
- Naomi Berrie Diabetes Center, Columbia University College of Physicians and Surgeons, New York, New York, USA.,Department of Pathology and Cell Biology, Columbia University College of Physicians and Surgeons, New York, New York, USA
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7
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Zhu L, Shi J, Luu TN, Neuman JC, Trefts E, Yu S, Palmisano BT, Wasserman DH, Linton MF, Stafford JM. Hepatocyte estrogen receptor alpha mediates estrogen action to promote reverse cholesterol transport during Western-type diet feeding. Mol Metab 2017; 8:106-116. [PMID: 29331506 PMCID: PMC5985047 DOI: 10.1016/j.molmet.2017.12.012] [Citation(s) in RCA: 36] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 09/07/2017] [Revised: 12/16/2017] [Accepted: 12/23/2017] [Indexed: 12/17/2022] Open
Abstract
OBJECTIVE Hepatocyte deletion of estrogen receptor alpha (LKO-ERα) worsens fatty liver, dyslipidemia, and insulin resistance in high-fat diet fed female mice. However, whether or not hepatocyte ERα regulates reverse cholesterol transport (RCT) in mice has not yet been reported. METHODS AND RESULTS Using LKO-ERα mice and wild-type (WT) littermates fed a Western-type diet, we found that deletion of hepatocyte ERα impaired in vivo RCT measured by the removal of 3H-cholesterol from macrophages to the liver, and subsequently to feces, in female mice but not in male mice. Deletion of hepatocyte ERα decreased the capacity of isolated HDL to efflux cholesterol from macrophages and reduced the ability of isolated hepatocytes to accept cholesterol from HDL ex vivo in both sexes. However, only in female mice, LKO-ERα increased serum cholesterol levels and increased HDL particle sizes. Deletion of hepatocyte ERα increased adiposity and worsened insulin resistance to a greater degree in female than male mice. All of the changes lead to a 5.6-fold increase in the size of early atherosclerotic lesions in female LKO-ERα mice compared to WT controls. CONCLUSIONS Estrogen signaling through hepatocyte ERα plays an important role in RCT and is protective against lipid retention in the artery wall during early stages of atherosclerosis in female mice fed a Western-type diet.
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Affiliation(s)
- Lin Zhu
- VA Tennessee Valley Healthcare System, USA; Division of Diabetes, Endocrinology, & Metabolism, USA
| | - Jeanne Shi
- Division of Diabetes, Endocrinology, & Metabolism, USA; Trinity College of Arts and Sciences, Duke University, USA
| | - Thao N Luu
- Division of Diabetes, Endocrinology, & Metabolism, USA
| | | | - Elijah Trefts
- Department of Molecular, Physiology and Biophysics, Vanderbilt University, USA
| | - Sophia Yu
- Division of Diabetes, Endocrinology, & Metabolism, USA
| | - Brian T Palmisano
- Department of Molecular, Physiology and Biophysics, Vanderbilt University, USA
| | - David H Wasserman
- Department of Molecular, Physiology and Biophysics, Vanderbilt University, USA
| | - MacRae F Linton
- Division of Cardiovascular Medicine, Vanderbilt University School of Medicine, USA
| | - John M Stafford
- VA Tennessee Valley Healthcare System, USA; Department of Molecular, Physiology and Biophysics, Vanderbilt University, USA; Division of Diabetes, Endocrinology, & Metabolism, USA.
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8
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Li Z, Kabir I, Jiang H, Zhou H, Libien J, Zeng J, Stanek A, Ou P, Li KR, Zhang S, Bui HH, Kuo MS, Park TS, Kim B, Worgall TS, Huan C, Jiang XC. Liver serine palmitoyltransferase activity deficiency in early life impairs adherens junctions and promotes tumorigenesis. Hepatology 2016; 64:2089-2102. [PMID: 27642075 PMCID: PMC5115983 DOI: 10.1002/hep.28845] [Citation(s) in RCA: 21] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 04/13/2016] [Revised: 08/18/2016] [Accepted: 09/08/2016] [Indexed: 12/22/2022]
Abstract
UNLABELLED Serine palmitoyltransferase is the key enzyme in sphingolipid biosynthesis. Mice lacking serine palmitoyltransferase are embryonic lethal. We prepared liver-specific mice deficient in the serine palmitoyltransferase long chain base subunit 2 gene using an albumin-cyclization recombination approach and found that the deficient mice have severe jaundice. Moreover, the deficiency impairs hepatocyte polarity, attenuates liver regeneration after hepatectomy, and promotes tumorigenesis. Importantly, we show that the deficiency significantly reduces sphingomyelin but not other sphingolipids in hepatocyte plasma membrane; greatly reduces cadherin, the major protein in adherens junctions, on the membrane; and greatly induces cadherin phosphorylation, an indication of its degradation. The deficiency affects cellular distribution of β-catenin, the central component of the canonical Wnt pathway. Furthermore, such a defect can be partially corrected by sphingomyelin supplementation in vivo and in vitro. CONCLUSION The plasma membrane sphingomyelin level is one of the key factors in regulating hepatocyte polarity and tumorigenesis. (Hepatology 2016;64:2089-2102).
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Affiliation(s)
- Zhiqiang Li
- Department of Cell Biology, Department of Surgery, and Department of Pathology, SUNY Downstate Medical Center
- Molecular and Cellular Cardiology Program, VA New York Harbor Healthcare System, Brooklyn
| | - Inamul Kabir
- Department of Cell Biology, Department of Surgery, and Department of Pathology, SUNY Downstate Medical Center
| | - Hui Jiang
- Department of Cell Biology, Department of Surgery, and Department of Pathology, SUNY Downstate Medical Center
| | | | - Jenny Libien
- Department of Cell Biology, Department of Surgery, and Department of Pathology, SUNY Downstate Medical Center
| | - Jianying Zeng
- Department of Cell Biology, Department of Surgery, and Department of Pathology, SUNY Downstate Medical Center
| | - Albert Stanek
- Department of Cell Biology, Department of Surgery, and Department of Pathology, SUNY Downstate Medical Center
| | - Peiqi Ou
- Department of Cell Biology, Department of Surgery, and Department of Pathology, SUNY Downstate Medical Center
| | - Kailyn R. Li
- Department of Cell Biology, Department of Surgery, and Department of Pathology, SUNY Downstate Medical Center
| | - Shane Zhang
- Department of Cell Biology, Department of Surgery, and Department of Pathology, SUNY Downstate Medical Center
| | - Hai H. Bui
- Lilly Research Laboratories, Eli Lilly & Company, Indianapolis, IN, 46285
| | - Ming-Shang Kuo
- Lilly Research Laboratories, Eli Lilly & Company, Indianapolis, IN, 46285
| | - Tae-Sik Park
- Department of Life Science, Gachon University, Sungnam, South Korea
| | | | | | - Chongmin Huan
- Department of Cell Biology, Department of Surgery, and Department of Pathology, SUNY Downstate Medical Center
| | - Xian-Cheng Jiang
- Department of Cell Biology, Department of Surgery, and Department of Pathology, SUNY Downstate Medical Center
- Molecular and Cellular Cardiology Program, VA New York Harbor Healthcare System, Brooklyn
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9
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Levenson AE, Haas ME, Miao J, Brown RJ, de Ferranti SD, Muniyappa R, Biddinger SB. Effect of Leptin Replacement on PCSK9 in ob/ob Mice and Female Lipodystrophic Patients. Endocrinology 2016; 157:1421-9. [PMID: 26824363 PMCID: PMC4816729 DOI: 10.1210/en.2015-1624] [Citation(s) in RCA: 19] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/05/2023]
Abstract
Leptin treatment has beneficial effects on plasma lipids in patients with lipodystrophy, but the underlying mechanism is unknown. Proprotein convertase subtilisin/kexin type 9 (PCSK9) decreases low-density lipoprotein (LDL) clearance, promotes hypercholesterolemia, and has recently emerged as a novel therapeutic target. To determine the effect of leptin on PCSK9, we treated male and female ob/ob mice with leptin for 4 days via sc osmotic pumps (∼24 μg/d). Leptin reduced body weight and food intake in all mice, but the effects of leptin on plasma PCSK9 and lipids differed markedly between the sexes. In male mice, leptin suppressed PCSK9 but had no effect on plasma triglycerides or cholesterol. In female mice, leptin suppressed plasma triglycerides and cholesterol but had no effect on plasma PCSK9. In parallel, we treated female lipodystrophic patients (8 females, ages 5-23 y) with sc metreleptin injections (∼4.4 mg/d) for 4-6 months. In this case, leptin reduced plasma PCSK9 by 26% (298 ± 109 vs 221 ± 102 ng/mL; n = 8; P = .008), and the change in PCSK9 was correlated with a decrease in LDL cholesterol (r(2) = 0.564, P = .03). In summary, in leptin-deficient ob/ob mice, the effects of leptin on PCSK9 and plasma lipids appeared to be independent of one another and strongly modified by sex. On the other hand, in lipodystrophic females, leptin treatment reduced plasma PCSK9 in parallel with LDL cholesterol.
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Affiliation(s)
- Amy E Levenson
- Division of Endocrinology (A.E.L., M.E.H., J.M., S.B.B.), Boston Children's Hospital, Harvard Medical School, Boston, Massachusetts 02115; Diabetes, Endocrinology, and Obesity Branch (R.J.B., R.M.), National Institute of Diabetes and Digestive and Kidney Diseases, National Institutes of Health, Bethesda, Maryland 20892; and Department of Cardiology (S.D.d.F.), Boston Children's Hospital, Harvard Medical School, Boston, Massachusetts 02115
| | - Mary E Haas
- Division of Endocrinology (A.E.L., M.E.H., J.M., S.B.B.), Boston Children's Hospital, Harvard Medical School, Boston, Massachusetts 02115; Diabetes, Endocrinology, and Obesity Branch (R.J.B., R.M.), National Institute of Diabetes and Digestive and Kidney Diseases, National Institutes of Health, Bethesda, Maryland 20892; and Department of Cardiology (S.D.d.F.), Boston Children's Hospital, Harvard Medical School, Boston, Massachusetts 02115
| | - Ji Miao
- Division of Endocrinology (A.E.L., M.E.H., J.M., S.B.B.), Boston Children's Hospital, Harvard Medical School, Boston, Massachusetts 02115; Diabetes, Endocrinology, and Obesity Branch (R.J.B., R.M.), National Institute of Diabetes and Digestive and Kidney Diseases, National Institutes of Health, Bethesda, Maryland 20892; and Department of Cardiology (S.D.d.F.), Boston Children's Hospital, Harvard Medical School, Boston, Massachusetts 02115
| | - Rebecca J Brown
- Division of Endocrinology (A.E.L., M.E.H., J.M., S.B.B.), Boston Children's Hospital, Harvard Medical School, Boston, Massachusetts 02115; Diabetes, Endocrinology, and Obesity Branch (R.J.B., R.M.), National Institute of Diabetes and Digestive and Kidney Diseases, National Institutes of Health, Bethesda, Maryland 20892; and Department of Cardiology (S.D.d.F.), Boston Children's Hospital, Harvard Medical School, Boston, Massachusetts 02115
| | - Sarah D de Ferranti
- Division of Endocrinology (A.E.L., M.E.H., J.M., S.B.B.), Boston Children's Hospital, Harvard Medical School, Boston, Massachusetts 02115; Diabetes, Endocrinology, and Obesity Branch (R.J.B., R.M.), National Institute of Diabetes and Digestive and Kidney Diseases, National Institutes of Health, Bethesda, Maryland 20892; and Department of Cardiology (S.D.d.F.), Boston Children's Hospital, Harvard Medical School, Boston, Massachusetts 02115
| | - Ranganath Muniyappa
- Division of Endocrinology (A.E.L., M.E.H., J.M., S.B.B.), Boston Children's Hospital, Harvard Medical School, Boston, Massachusetts 02115; Diabetes, Endocrinology, and Obesity Branch (R.J.B., R.M.), National Institute of Diabetes and Digestive and Kidney Diseases, National Institutes of Health, Bethesda, Maryland 20892; and Department of Cardiology (S.D.d.F.), Boston Children's Hospital, Harvard Medical School, Boston, Massachusetts 02115
| | - Sudha B Biddinger
- Division of Endocrinology (A.E.L., M.E.H., J.M., S.B.B.), Boston Children's Hospital, Harvard Medical School, Boston, Massachusetts 02115; Diabetes, Endocrinology, and Obesity Branch (R.J.B., R.M.), National Institute of Diabetes and Digestive and Kidney Diseases, National Institutes of Health, Bethesda, Maryland 20892; and Department of Cardiology (S.D.d.F.), Boston Children's Hospital, Harvard Medical School, Boston, Massachusetts 02115
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10
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Abstract
The nature of the gastrointestinal microbiome determines the reservoir of lipopolysaccharide, which can migrate from the gut into the circulation, where it contributes to low-grade inflammation. Osteoarthritis (OA) is a low-grade inflammatory condition, and the elevation of levels of lipopolysaccharide in association with obesity and metabolic syndrome could contribute to OA. A 'two- hit' model of OA susceptibility and potentiation suggests that lipopolysaccharide primes the proinflammatory innate immune response via Toll-like receptor 4 and that progression to a full-blown inflammatory response and structural damage of the joint results from coexisting complementary mechanisms, such as inflammasome activation or assembly by damage-associated molecular patterns in the form of fragmented cartilage-matrix molecules. Lipopolysaccharide could be considered a major hidden risk factor that provides a unifying mechanism to explain the association between obesity, metabolic syndrome and OA.
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Affiliation(s)
- Zeyu Huang
- Department of Orthopedic Surgery, West China Hospital, Sichuan University, No. 37 Guo Xue Road, Chengdu, Sichuan, 610041, People's Republic of China
| | - Virginia Byers Kraus
- Duke Molecular Physiology Institute and Division of Rheumatology, Department of Medicine, Duke University School of Medicine, 300 North Duke Street, Durham, North Carolina 27701, USA
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11
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Suzawa M, Miranda DA, Ramos KA, Ang KKH, Faivre EJ, Wilson CG, Caboni L, Arkin MR, Kim YS, Fletterick RJ, Diaz A, Schneekloth JS, Ingraham HA. A gene-expression screen identifies a non-toxic sumoylation inhibitor that mimics SUMO-less human LRH-1 in liver. eLife 2015; 4. [PMID: 26653140 PMCID: PMC4749390 DOI: 10.7554/elife.09003] [Citation(s) in RCA: 41] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/26/2015] [Accepted: 10/20/2015] [Indexed: 02/06/2023] Open
Abstract
SUMO-modification of nuclear proteins has profound effects on gene expression. However, non-toxic chemical tools that modulate sumoylation in cells are lacking. Here, to identify small molecule sumoylation inhibitors we developed a cell-based screen that focused on the well-sumoylated substrate, human Liver Receptor Homolog-1 (hLRH-1, NR5A2). Our primary gene-expression screen assayed two SUMO-sensitive transcripts, APOC3 and MUC1, that are upregulated by SUMO-less hLRH-1 or by siUBC9 knockdown, respectively. A polyphenol, tannic acid (TA) emerged as a potent sumoylation inhibitor in vitro (IC50 = 12.8 µM) and in cells. TA also increased hLRH-1 occupancy on SUMO-sensitive transcripts. Most significantly, when tested in humanized mouse primary hepatocytes, TA inhibits hLRH-1 sumoylation and induces SUMO-sensitive genes, thereby recapitulating the effects of expressing SUMO-less hLRH-1 in mouse liver. Our findings underscore the benefits of phenotypic screening for targeting post-translational modifications, and illustrate the potential utility of TA for probing the cellular consequences of sumoylation. DOI:http://dx.doi.org/10.7554/eLife.09003.001 Proteins in cells carry out diverse tasks. One way in which this diversity is achieved by proteins is through the attachment of molecular tags. SUMO is one such tag that can reversibly attach to proteins and alter their activity. The modification of proteins by SUMO is known as sumoylation, and it regulates many processes that are essential for living cells. In particular, transcription factors—the proteins that bind to DNA to switch genes on or off—are highly modified by SUMO. However, the consequences of sumoylation are not fully understood, and current research into this area has been hindered by a lack of effective and non-toxic chemicals that stop or slow down sumoylation. Suzawa, Miranda, Ramos et al. have now screened a large collection of compounds, which had already been approved for medical use, to find one that could inhibit sumoylation without toxic effects. The compounds were tested for their ability to alter the activity of a transcription factor called human Liver Receptor Homolog-1. This protein, which is referred to as LRH-1 for short, is an ideal candidate to test SUMO inhibitors because it is highly modified by multiple SUMO tags. This screen identified a compound from plants called tannic acid as a non-toxic and potent inhibitor of sumoylation. Further experiments confirmed that tannic acid prevented the modification of LHR-1 as well a number of different proteins that also commonly modified by SUMO. Inhibiting the sumoylation of LRH-1 led to an increase in the expression of genes that are normally silenced by SUMO-modified LRH-1. Similar results were obtained when tannic acid was tested using human cells and “humanized” liver cells from mice that had been engineered to express human LRH-1. The next big challenge is to find new chemical probes that can be used to specifically promote or inhibit SUMO modification of just one particular protein. DOI:http://dx.doi.org/10.7554/eLife.09003.002
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Affiliation(s)
- Miyuki Suzawa
- Department of Cellular and Molecular Pharmacology, University of California, San Francisco, San Francisco, United States
| | - Diego A Miranda
- Department of Cellular and Molecular Pharmacology, University of California, San Francisco, San Francisco, United States
| | - Karmela A Ramos
- Department of Cellular and Molecular Pharmacology, University of California, San Francisco, San Francisco, United States
| | - Kenny K-H Ang
- Small Molecule Discovery Center, Department of Pharmaceutical Chemistry, University of California, San Francisco, San Francisco, United States
| | - Emily J Faivre
- Department of Cellular and Molecular Pharmacology, University of California, San Francisco, San Francisco, United States
| | - Christopher G Wilson
- Small Molecule Discovery Center, Department of Pharmaceutical Chemistry, University of California, San Francisco, San Francisco, United States
| | - Laura Caboni
- Department of Biochemistry and Biophysics, University of California, San Francisco, San Francisco, United States
| | - Michelle R Arkin
- Small Molecule Discovery Center, Department of Pharmaceutical Chemistry, University of California, San Francisco, San Francisco, United States
| | - Yeong-Sang Kim
- Chemical Biology Laboratory, National Cancer Institute, Frederick, United States
| | - Robert J Fletterick
- Department of Biochemistry and Biophysics, University of California, San Francisco, San Francisco, United States
| | - Aaron Diaz
- Department of Epidemiology and Biostatistics, University of California, San Francisco, San Francisco, United States
| | - John S Schneekloth
- Chemical Biology Laboratory, National Cancer Institute, Frederick, United States
| | - Holly A Ingraham
- Department of Cellular and Molecular Pharmacology, University of California, San Francisco, San Francisco, United States
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12
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Berisha SZ, Brubaker G, Kasumov T, Hung KT, DiBello PM, Huang Y, Li L, Willard B, Pollard KA, Nagy LE, Hazen SL, Smith JD. HDL from apoA1 transgenic mice expressing the 4WF isoform is resistant to oxidative loss of function. J Lipid Res 2015; 56:653-664. [PMID: 25561462 DOI: 10.1194/jlr.m056754] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
HDL functions are impaired by myeloperoxidase (MPO), which selectively targets and oxidizes human apoA1. We previously found that the 4WF isoform of human apoA1, in which the four tryptophan residues are substituted with phenylalanine, is resistant to MPO-mediated loss of function. The purpose of this study was to generate 4WF apoA1 transgenic mice and compare functional properties of the 4WF and wild-type human apoA1 isoforms in vivo. Male mice had significantly higher plasma apoA1 levels than females for both isoforms of human apoA1, attributed to different production rates. With matched plasma apoA1 levels, 4WF transgenics had a trend for slightly less HDL-cholesterol versus human apoA1 transgenics. While 4WF transgenics had 31% less reverse cholesterol transport (RCT) to the plasma compartment, equivalent RCT to the liver and feces was observed. Plasma from both strains had similar ability to accept cholesterol and facilitate ex vivo cholesterol efflux from macrophages. Furthermore, we observed that 4WF transgenic HDL was partially (∼50%) protected from MPO-mediated loss of function while human apoA1 transgenic HDL lost all ABCA1-dependent cholesterol acceptor activity. In conclusion, the structure and function of HDL from 4WF transgenic mice was not different than HDL derived from human apoA1 transgenic mice.
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Affiliation(s)
- Stela Z Berisha
- Department of Cellular and Molecular Medicine, Lerner Research Institute, Cleveland Clinic, Cleveland, OH 44195
| | - Greg Brubaker
- Department of Cellular and Molecular Medicine, Lerner Research Institute, Cleveland Clinic, Cleveland, OH 44195
| | - Takhar Kasumov
- Department of Gastroenterology and Hepatology, Lerner Research Institute, Cleveland Clinic, Cleveland, OH 44195
| | - Kimberly T Hung
- Department of Cellular and Molecular Medicine, Lerner Research Institute, Cleveland Clinic, Cleveland, OH 44195
| | - Patricia M DiBello
- Department of Cellular and Molecular Medicine, Lerner Research Institute, Cleveland Clinic, Cleveland, OH 44195
| | - Ying Huang
- Department of Cellular and Molecular Medicine, Lerner Research Institute, Cleveland Clinic, Cleveland, OH 44195
| | - Ling Li
- Department of Research Core Services, Lerner Research Institute, Cleveland Clinic, Cleveland, OH 44195
| | - Belinda Willard
- Department of Research Core Services, Lerner Research Institute, Cleveland Clinic, Cleveland, OH 44195
| | - Katherine A Pollard
- Department of Pathobiology, Lerner Research Institute, Cleveland Clinic, Cleveland, OH 44195
| | - Laura E Nagy
- Department of Pathobiology, Lerner Research Institute, Cleveland Clinic, Cleveland, OH 44195
| | - Stanley L Hazen
- Department of Cellular and Molecular Medicine, Lerner Research Institute, Cleveland Clinic, Cleveland, OH 44195; Department of Molecular Medicine, Cleveland Clinic Lerner College of Medicine of Case Western Reserve University, Cleveland, OH 44195
| | - Jonathan D Smith
- Department of Cellular and Molecular Medicine, Lerner Research Institute, Cleveland Clinic, Cleveland, OH 44195; Department of Molecular Medicine, Cleveland Clinic Lerner College of Medicine of Case Western Reserve University, Cleveland, OH 44195.
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13
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Martineau C, Martin-Falstrault L, Brissette L, Moreau R. Gender- and region-specific alterations in bone metabolism in Scarb1-null female mice. J Endocrinol 2014; 222:277-88. [PMID: 24928939 DOI: 10.1530/joe-14-0147] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/08/2022]
Abstract
A positive correlation between plasma levels of HDL and bone mass has been reported by epidemiological studies. As scavenger receptor class B, type I (SR-BI), the gene product of Scarb1, is known to regulate HDL metabolism, we recently characterized bone metabolism in Scarb1-null mice. These mice display high femoral bone mass associated with enhanced bone formation. As gender differences have been reported in HDL metabolism and SR-BI function, we investigated gender-specific bone alterations in Scarb1-null mice by microtomography and histology. We found 16% greater relative bone volume and 39% higher bone formation rate in the vertebrae from 2-month-old Scarb1-null females. No such alteration was seen in males, indicating gender- and region-specific differences in skeletal phenotype. Total and HDL-associated cholesterol levels, as well as ACTH plasma levels, were increased in both Scarb1-null genders, the latter being concurrent to impaired corticosterone response to fasting. Plasma levels of estradiol did not differ between null and WT females, suggesting that the estrogen metabolism alteration is not relevant to the higher vertebral bone mass in female Scarb1-null mice. Constitutively, high plasma levels of leptin along with 2.5-fold increase in its expression in white adipose tissue were measured in female Scarb1-null mice only. In vitro exposure of bone marrow stromal cells to ACTH and leptin promoted osteoblast differentiation as evidenced by increased gene expression of osterix and collagen type I alpha. Our results suggest that hyperleptinemia may account for the gender-specific high bone mass seen in the vertebrae of female Scarb1-null mice.
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Affiliation(s)
- Corine Martineau
- Laboratoire du Métabolisme OsseuxBioMed, Département des Sciences Biologiques Université du Québec à Montréal, Case Postale 8888, Succursale Centre-ville, Montréal, Quebec, Canada H3C 3P8Laboratoire du Métabolisme des LipoprotéinesBioMed, Département des Sciences Biologiques, Université du Québec à Montréal, Montréal, Quebec, Canada H3C 3P8
| | - Louise Martin-Falstrault
- Laboratoire du Métabolisme OsseuxBioMed, Département des Sciences Biologiques Université du Québec à Montréal, Case Postale 8888, Succursale Centre-ville, Montréal, Quebec, Canada H3C 3P8Laboratoire du Métabolisme des LipoprotéinesBioMed, Département des Sciences Biologiques, Université du Québec à Montréal, Montréal, Quebec, Canada H3C 3P8
| | - Louise Brissette
- Laboratoire du Métabolisme OsseuxBioMed, Département des Sciences Biologiques Université du Québec à Montréal, Case Postale 8888, Succursale Centre-ville, Montréal, Quebec, Canada H3C 3P8Laboratoire du Métabolisme des LipoprotéinesBioMed, Département des Sciences Biologiques, Université du Québec à Montréal, Montréal, Quebec, Canada H3C 3P8
| | - Robert Moreau
- Laboratoire du Métabolisme OsseuxBioMed, Département des Sciences Biologiques Université du Québec à Montréal, Case Postale 8888, Succursale Centre-ville, Montréal, Quebec, Canada H3C 3P8Laboratoire du Métabolisme des LipoprotéinesBioMed, Département des Sciences Biologiques, Université du Québec à Montréal, Montréal, Quebec, Canada H3C 3P8
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Rinninger F, Heine M, Singaraja R, Hayden M, Brundert M, Ramakrishnan R, Heeren J. High density lipoprotein metabolism in low density lipoprotein receptor-deficient mice. J Lipid Res 2014; 55:1914-24. [PMID: 24954421 DOI: 10.1194/jlr.m048819] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
The LDL receptor (LDLR) and scavenger receptor class B type I (SR-BI) play physiological roles in LDL and HDL metabolism in vivo. In this study, we explored HDL metabolism in LDLR-deficient mice in comparison with WT littermates. Murine HDL was radiolabeled in the protein ((125)I) and in the cholesteryl ester (CE) moiety ([(3)H]). The metabolism of (125)I-/[(3)H]HDL was investigated in plasma and in tissues of mice and in murine hepatocytes. In WT mice, liver and adrenals selectively take up HDL-associated CE ([(3)H]). In contrast, in LDLR(-/-) mice, selective HDL CE uptake is significantly reduced in liver and adrenals. In hepatocytes isolated from LDLR(-/-) mice, selective HDL CE uptake is substantially diminished compared with WT liver cells. Hepatic and adrenal protein expression of lipoprotein receptors SR-BI, cluster of differentiation 36 (CD36), and LDL receptor-related protein 1 (LRP1) was analyzed by immunoblots. The respective protein levels were identical both in hepatic and adrenal membranes prepared from WT or from LDLR(-/-) mice. In summary, an LDLR deficiency substantially decreases selective HDL CE uptake by liver and adrenals. This decrease is independent from regulation of receptor proteins like SR-BI, CD36, and LRP1. Thus, LDLR expression has a substantial impact on both HDL and LDL metabolism in mice.
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Affiliation(s)
- Franz Rinninger
- Department of Medicine, University Hospital Hamburg Eppendorf, 20246 Hamburg, Germany
| | - Markus Heine
- Department of Biochemistry and Molecular Cell Biology, University Hospital Hamburg Eppendorf, 20246 Hamburg, Germany
| | - Roshni Singaraja
- Translational Laboratories in Genetic Medicine, Agency for Science, Technology and Research National University of Singapore, Singapore 117609 Department of Medicine, National University of Singapore, Singapore 117609
| | - Michael Hayden
- Centre for Molecular Medicine and Therapeutics and Child and Family Research Institute, University of British Columbia, Vancouver, British Columbia V5Z 4H4, Canada
| | - May Brundert
- Department of Medicine, University Hospital Hamburg Eppendorf, 20246 Hamburg, Germany
| | - Rajasekhar Ramakrishnan
- Department of Pediatrics, College of Physicians and Surgeons of Columbia University, New York, NY 10032
| | - Joerg Heeren
- Department of Biochemistry and Molecular Cell Biology, University Hospital Hamburg Eppendorf, 20246 Hamburg, Germany
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15
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Chulsky S, Paland N, Lazarovich A, Fuhrman B. Urokinase-type plasminogen activator (uPA) decreases hepatic SR-BI expression and impairs HDL-mediated reverse cholesterol transport. Atherosclerosis 2014; 233:11-8. [DOI: 10.1016/j.atherosclerosis.2013.11.070] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 09/16/2013] [Revised: 11/05/2013] [Accepted: 11/27/2013] [Indexed: 11/29/2022]
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16
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The Influence of an Obesogenic Diet on Oxysterol Metabolism in C57BL/6J Mice. CHOLESTEROL 2014; 2014:843468. [PMID: 24672716 PMCID: PMC3941159 DOI: 10.1155/2014/843468] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 10/26/2013] [Revised: 12/18/2013] [Accepted: 12/21/2013] [Indexed: 11/18/2022]
Abstract
Our current understanding of oxysterol metabolism during different disease states such as obesity and dyslipidemia is limited. Therefore, the aim of this study was to determine the effect of diet-induced obesity on the tissue distribution of various oxysterols and the mRNA expression of key enzymes involved in oxysterol metabolism. To induce obesity, male C57BL/6J mice were fed a high fat-cholesterol diet for 24 weeks. Following diet-induced obesity, plasma levels of 4β-hydroxycholesterol, 5,6α-epoxycholesterol, 5,6β-epoxycholesterol, 7α-hydroxycholesterol, 7β-hydroxycholesterol, and 27-hydroxycholesterol were significantly (P < 0.05) increased. In the liver and adipose tissue of the obese mice, 4β-hydroxycholesterol was significantly (P < 0.05) increased, whereas 27-hydroxycholesterol was increased only in the adipose tissue. No significant changes in either hepatic or adipose tissue mRNA expression were observed for oxysterol synthesizing enzymes 4β-hydroxylase, 27-hydroxylase, or 7α-hydroxylase. Hepatic mRNA expression of SULT2B1b, a key enzyme involved in oxysterol detoxification, was significantly (P < 0.05) elevated in the obese mice. Interestingly, the appearance of the large HDL1 lipoprotein was observed with increased oxysterol synthesis during obesity. In diet-induced obese mice, dietary intake and endogenous enzymatic synthesis of oxysterols could not account for the increased oxysterol levels, suggesting that nonenzymatic cholesterol oxidation pathways may be responsible for the changes in oxysterol metabolism.
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17
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Nusshold C, Uellen A, Bernhart E, Hammer A, Damm S, Wintersperger A, Reicher H, Hermetter A, Malle E, Sattler W. Endocytosis and intracellular processing of BODIPY-sphingomyelin by murine CATH.a neurons. BIOCHIMICA ET BIOPHYSICA ACTA 2013; 1831:1665-78. [PMID: 23973266 PMCID: PMC3807659 DOI: 10.1016/j.bbalip.2013.08.007] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 04/26/2013] [Revised: 08/01/2013] [Accepted: 08/06/2013] [Indexed: 01/24/2023]
Abstract
Neuronal sphingolipids (SL) play important roles during axonal extension, neurotrophic receptor signaling and neurotransmitter release. Many of these signaling pathways depend on the presence of specialized membrane microdomains termed lipid rafts. Sphingomyelin (SM), one of the main raft constituents, can be formed de novo or supplied from exogenous sources. The present study aimed to characterize fluorescently-labeled SL turnover in a murine neuronal cell line (CATH.a). Our results demonstrate that at 4°C exogenously added BODIPY-SM accumulates exclusively at the plasma membrane. Treatment of cells with bacterial sphingomyelinase (SMase) and back-exchange experiments revealed that 55-67% of BODIPY-SM resides in the outer leaflet of the plasma membrane. Endocytosis of BODIPY-SM occurs via caveolae with part of internalized BODIPY-fluorescence ending up in the Golgi and the ER. Following endocytosis BODIPY-SM undergoes hydrolysis, a reaction substantially faster than BODIPY-SM synthesis from BODIPY-ceramide. RNAi demonstrated that both, acid (a)SMase and neutral (n)SMases contribute to BODIPY-SM hydrolysis. Finally, high-density lipoprotein (HDL)-associated BODIPY-SM was efficiently taken up by CATH.a cells. Our findings indicate that endocytosis of exogenous SM occurs almost exclusively via caveolin-dependent pathways, that both, a- and nSMases equally contribute to neuronal SM turnover and that HDL-like particles might represent physiological SM carriers/donors in the brain.
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Affiliation(s)
- Christoph Nusshold
- Institute of Molecular Biology and Biochemistry, Medical University of Graz, Graz, Austria
| | - Andreas Uellen
- Institute of Molecular Biology and Biochemistry, Medical University of Graz, Graz, Austria
| | - Eva Bernhart
- Institute of Molecular Biology and Biochemistry, Medical University of Graz, Graz, Austria
| | - Astrid Hammer
- Institute of Cell Biology, Histology and Embryology, Medical University of Graz, Graz, Austria
| | - Sabine Damm
- Institute of Molecular Biology and Biochemistry, Medical University of Graz, Graz, Austria
| | - Andrea Wintersperger
- Institute of Molecular Biology and Biochemistry, Medical University of Graz, Graz, Austria
| | - Helga Reicher
- Institute of Molecular Biology and Biochemistry, Medical University of Graz, Graz, Austria
| | - Albin Hermetter
- Institute of Biochemistry, Graz University of Technology, Graz, Austria
| | - Ernst Malle
- Institute of Molecular Biology and Biochemistry, Medical University of Graz, Graz, Austria
| | - Wolfgang Sattler
- Institute of Molecular Biology and Biochemistry, Medical University of Graz, Graz, Austria
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18
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Fruhwürth S, Pavelka M, Bittman R, Kovacs WJ, Walter KM, Röhrl C, Stangl H. High-density lipoprotein endocytosis in endothelial cells. World J Biol Chem 2013; 4:131-140. [PMID: 24340136 PMCID: PMC3856308 DOI: 10.4331/wjbc.v4.i4.131] [Citation(s) in RCA: 22] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 08/30/2013] [Revised: 11/11/2013] [Accepted: 11/19/2013] [Indexed: 02/05/2023] Open
Abstract
AIM: To describe the way stations of high-density lipoprotein (HDL) uptake and its lipid exchange in endothelial cells in vitro and in vivo.
METHODS: A combination of fluorescence microscopy using novel fluorescent cholesterol surrogates and electron microscopy was used to analyze HDL endocytosis in great detail in primary human endothelial cells. Further, HDL uptake was quantified using radio-labeled HDL particles. To validate the in vitro findings mice were injected with fluorescently labeled HDL and particle uptake in the liver was analyzed using fluorescence microscopy.
RESULTS: HDL uptake occurred via clathrin-coated pits, tubular endosomes and multivesicular bodies in human umbilical vein endothelial cells. During uptake and resecretion, HDL-derived cholesterol was exchanged at a faster rate than cholesteryl oleate, resembling the HDL particle pathway seen in hepatic cells. In addition, lysosomes were not involved in this process and thus HDL degradation was not detectable. In vivo, we found HDL mainly localized in mouse hepatic endothelial cells. HDL was not detected in parenchymal liver cells, indicating that lipid transfer from HDL to hepatocytes occurs primarily via scavenger receptor, class B, type I mediated selective uptake without concomitant HDL endocytosis.
CONCLUSION: HDL endocytosis occurs via clathrin-coated pits, tubular endosomes and multivesicular bodies in human endothelial cells. Mouse endothelial cells showed a similar HDL uptake pattern in vivo indicating that the endothelium is one major site of HDL endocytosis and transcytosis.
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19
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Röhrl C, Stangl H. HDL endocytosis and resecretion. Biochim Biophys Acta Mol Cell Biol Lipids 2013; 1831:1626-33. [PMID: 23939397 PMCID: PMC3795453 DOI: 10.1016/j.bbalip.2013.07.014] [Citation(s) in RCA: 72] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/12/2013] [Revised: 07/22/2013] [Accepted: 07/26/2013] [Indexed: 12/23/2022]
Abstract
HDL removes excess cholesterol from peripheral tissues and delivers it to the liver and steroidogenic tissues via selective lipid uptake without catabolism of the HDL particle itself. In addition, endocytosis of HDL holo-particles has been debated for nearly 40years. However, neither the connection between HDL endocytosis and selective lipid uptake, nor the physiological relevance of HDL uptake has been delineated clearly. This review will focus on HDL endocytosis and resecretion and its relation to cholesterol transfer. We will discuss the role of HDL endocytosis in maintaining cholesterol homeostasis in tissues and cell types involved in atherosclerosis, focusing on liver, macrophages and endothelium. We will critically summarize the current knowledge on the receptors mediating HDL endocytosis including SR-BI, F1-ATPase and CD36 and on intracellular HDL transport routes. Dependent on the tissue, HDL is either resecreted (retro-endocytosis) or degraded after endocytosis. Finally, findings on HDL transcytosis across the endothelial barrier will be summarized. We suggest that HDL endocytosis and resecretion is a rather redundant pathway under physiologic conditions. In case of disturbed lipid metabolism, however, HDL retro-endocytosis represents an alternative pathway that enables tissues to maintain cellular cholesterol homeostasis.
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Affiliation(s)
- Clemens Röhrl
- Department of Medical Chemistry, Center for Pathobiochemistry and Genetics, Medical University of Vienna, Vienna, Austria
| | - Herbert Stangl
- Department of Medical Chemistry, Center for Pathobiochemistry and Genetics, Medical University of Vienna, Vienna, Austria.
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20
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Berger JH, Charron MJ, Silver DL. Major facilitator superfamily domain-containing protein 2a (MFSD2A) has roles in body growth, motor function, and lipid metabolism. PLoS One 2012; 7:e50629. [PMID: 23209793 PMCID: PMC3510178 DOI: 10.1371/journal.pone.0050629] [Citation(s) in RCA: 69] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/04/2012] [Accepted: 10/22/2012] [Indexed: 12/24/2022] Open
Abstract
The metabolic adaptations to fasting in the liver are largely controlled by the nuclear hormone receptor peroxisome proliferator-activated receptor alpha (PPARα), where PPARα upregulates genes encoding the biochemical pathway for β-oxidation of fatty acids and ketogenesis. As part of an effort to identify and characterize nutritionally regulated genes that play physiological roles in the adaptation to fasting, we identified Major facilitator superfamily domain-containing protein 2a (Mfsd2a) as a fasting-induced gene regulated by both PPARα and glucagon signaling in the liver. MFSD2A is a cell-surface protein homologous to bacterial sodium-melibiose transporters. Hepatic expression and turnover of MFSD2A is acutely regulated by fasting/refeeding, but expression in the brain is constitutive. Relative to wildtype mice, gene-targeted Mfsd2a knockout mice are smaller, leaner, and have decreased serum, liver and brown adipose triglycerides. Mfsd2a knockout mice have normal liver lipid metabolism but increased whole body energy expenditure, likely due to increased β-oxidation in brown adipose tissue and significantly increased voluntary movement, but surprisingly exhibited a form of ataxia. Together, these results indicate that MFSD2A is a nutritionally regulated gene that plays myriad roles in body growth and development, motor function, and lipid metabolism. Moreover, these data suggest that the ligand(s) that are transported by MFSD2A play important roles in these physiological processes and await future identification.
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Affiliation(s)
- Justin H. Berger
- Department of Biochemistry, Albert Einstein College of Medicine, Bronx, New York, United States of America
| | - Maureen J. Charron
- Department of Biochemistry, Albert Einstein College of Medicine, Bronx, New York, United States of America
- Department of Medicine, Division of Endocrinology, Albert Einstein College of Medicine, Bronx, New York, United States of America
- Department of Obstetrics and Gynecology and Women’s Health, Albert Einstein College of Medicine, Bronx, New York, United States of America
| | - David L. Silver
- Department of Biochemistry, Albert Einstein College of Medicine, Bronx, New York, United States of America
- Signature Research Program in Cardiovascular & Metabolic Disorders, Duke-NUS Graduate Medical School, Singapore, Singapore
- * E-mail:
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Abstract
The incidence of disorders related to the control of energy homeostasis, such as hypertension, diabetes, obesity, and dyslipidemia, has dramatically increased worldwide in the last decades. The central nervous system (CNS) plays a critical role regulating the energy balance, therefore there has been increasing interest in understanding the mechanisms whereby the brain controls peripheral metabolism, in order to develop new potential therapies to treat those disorders. While the involvement of the CNS in development of hypertension, obesity, and diabetes has been thoroughly investigated, less is known about the specific role of the brain in the control of circulating lipids. Here we summarize the evidence linking CNS disorders with dyslipidemia, as well as the central mechanisms that directly influence plasma cholesterol.
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Affiliation(s)
- Diego Perez-Tilve
- Department of Internal Medicine, Metabolic Diseases Institute & Cincinnati Diabetes and Obesity Centre, Cincinnati, OH 45237, USA
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ApoA-1 mimetic restores adiponectin expression and insulin sensitivity independent of changes in body weight in female obese mice. Nutr Diabetes 2012; 2:e33. [PMID: 23169576 PMCID: PMC3341710 DOI: 10.1038/nutd.2012.4] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/28/2022] Open
Abstract
BACKGROUND We examined the ability of the apolipoprotein AI mimetic peptide L-4F to improve the metabolic state of female and male ob mice and the mechanisms involved. METHODS Female and male lean and obese (ob) mice were administered L-4F or vehicle for 6 weeks. Body weight was measured weekly. Fat distribution, serum cytokines and markers of cardiovascular dysfunction were determined at the end of treatment. RESULTS L-4F significantly decreased serum interleukin (IL)-6, tumor necrosis factor-α and IL-1β. L-4F improved vascular function, and increased serum adiponectin levels and insulin sensitivity compared with untreated mice. In addition, L-4F treatment increased heme oxygenase (HO)-1, pAKT and pAMPK levels in kidneys of ob animals. pAKT and pAMPK levels were significantly reduced in the presence of an HO inhibitor. Interestingly, L4F did not alter body weight in female mice, but caused a significant reduction in males. CONCLUSIONS L-4F treatments reduced cardiovascular risk factors and improved insulin sensitivity in female ob mice independent of body fat changes. Reduced inflammatory cytokine levels accompanied by increased HO activity, serum adiponectin and improved insulin sensitivity suggest that L-4F may promote the conversion of visceral fat to a healthier phenotype. Therefore, L-4F appears to be a promising therapeutic strategy for treating both cardiovascular risk factors and insulin resistance in obese patients of either gender.
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Berglund ED, Vianna CR, Donato J, Kim MH, Chuang JC, Lee CE, Lauzon DA, Lin P, Brule LJ, Scott MM, Coppari R, Elmquist JK. Direct leptin action on POMC neurons regulates glucose homeostasis and hepatic insulin sensitivity in mice. J Clin Invest 2012; 122:1000-9. [PMID: 22326958 DOI: 10.1172/jci59816] [Citation(s) in RCA: 255] [Impact Index Per Article: 19.6] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/05/2011] [Accepted: 01/04/2012] [Indexed: 01/01/2023] Open
Abstract
Leptin action on its receptor (LEPR) stimulates energy expenditure and reduces food intake, thereby lowering body weight. One leptin-sensitive target cell mediating these effects on energy balance is the proopiomelano-cortin (POMC) neuron. Recent evidence suggests that the action of leptin on POMC neurons regulates glucose homeostasis independently of its effects on energy balance. Here, we have dissected the physiological impact of direct leptin action on POMC neurons using a mouse model in which endogenous LEPR expression was prevented by a LoxP-flanked transcription blocker (loxTB), but could be reactivated by Cre recombinase. Mice homozygous for the Lepr(loxTB) allele were obese and exhibited defects characteristic of LEPR deficiency. Reexpression of LEPR only in POMC neurons in the arcuate nucleus of the hypothalamus did not reduce food intake, but partially normalized energy expenditure and modestly reduced body weight. Despite the moderate effects on energy balance and independent of changes in body weight, restoring LEPR in POMC neurons normalized blood glucose and ameliorated hepatic insulin resistance, hyperglucagonemia, and dyslipidemia. Collectively, these results demonstrate that direct leptin action on POMC neurons does not reduce food intake, but is sufficient to normalize glucose and glucagon levels in mice otherwise lacking LEPR.
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Affiliation(s)
- Eric D Berglund
- Division of Hypothalamic Research, Department of Internal Medicine, University of Texas Southwestern Medical School, Dallas, Texas 75390-9051, USA
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24
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Mechanisms regulating hepatic SR-BI expression and their impact on HDL metabolism. Atherosclerosis 2011; 217:299-307. [DOI: 10.1016/j.atherosclerosis.2011.05.036] [Citation(s) in RCA: 55] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 01/11/2011] [Revised: 05/11/2011] [Accepted: 05/26/2011] [Indexed: 11/22/2022]
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Abstract
PURPOSE OF REVIEW The increasing incidence of obesity and diabetes worldwide are critical risk factors for the development of cardiovascular disease. Although the role of the central nervous system (CNS) in the control of fat mass and glucose metabolism has been studied in detail, less is known about the contribution of neural-derived signals in the development of systemic dyslipidemia. In this review we summarize and analyze evidence suggesting a specific role of the CNS in the control of systemic cholesterol metabolism and circulating plasma lipids levels. RECENT FINDINGS Although early reports based in lesions or electrical stimulation suggested a role for CNS-derived signals in the development of dyslipidemia, more recent findings have confirmed the involvement of specific neural pathways critical for the neuroendocrine control of cholesterol metabolism and plasma lipid levels. SUMMARY The identification of the pathways targeted by the CNS to control plasma lipid levels could offer alternative targets to create efficient novel therapies for the treatment of several metabolic syndrome components including dyslipidemia.
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Affiliation(s)
- Diego Perez-Tilve
- Metabolic Diseases Institute, Department of Internal Medicine, University of Cincinnati. Cincinnati, OH 45237, USA
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26
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Brundert M, Heeren J, Merkel M, Carambia A, Herkel J, Groitl P, Dobner T, Ramakrishnan R, Moore KJ, Rinninger F. Scavenger receptor CD36 mediates uptake of high density lipoproteins in mice and by cultured cells. J Lipid Res 2011; 52:745-58. [PMID: 21217164 DOI: 10.1194/jlr.m011981] [Citation(s) in RCA: 55] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
The mechanisms of HDL-mediated cholesterol transport from peripheral tissues to the liver are incompletely defined. Here the function of scavenger receptor cluster of differentiation 36 (CD36) for HDL uptake by the liver was investigated. CD36 knockout (KO) mice, which were the model, have a 37% increase (P = 0.008) of plasma HDL cholesterol compared with wild-type (WT) littermates. To explore the mechanism of this increase, HDL metabolism was investigated with HDL radiolabeled in the apolipoprotein (¹²⁵I) and cholesteryl ester (CE, [³H]) moiety. Liver uptake of [³H] and ¹²⁵I from HDL decreased in CD36 KO mice and the difference, i. e. hepatic selective CE uptake ([³H]¹²⁵I), declined (-33%, P = 0.0003) in CD36 KO compared with WT mice. Hepatic HDL holo-particle uptake (¹²⁵I) decreased (-29%, P = 0.0038) in CD36 KO mice. In vitro, uptake of ¹²⁵I-/[³H]HDL by primary liver cells from WT or CD36 KO mice revealed a diminished HDL uptake in CD36-deficient hepatocytes. Adenovirus-mediated expression of CD36 in cells induced an increase in selective CE uptake from HDL and a stimulation of holo-particle internalization. In conclusion, CD36 plays a role in HDL uptake in mice and by cultured cells. A physiologic function of CD36 in HDL metabolism in vivo is suggested.
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Affiliation(s)
- May Brundert
- University Hospital Hamburg Eppendorf Hamburg, Germany
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27
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Okada T, Ohzeki T, Nakagawa Y, Sugihara S, Arisaka O. Impact of leptin and leptin-receptor gene polymorphisms on serum lipids in Japanese obese children. Acta Paediatr 2010; 99:1213-7. [PMID: 20222875 DOI: 10.1111/j.1651-2227.2010.01778.x] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/27/2022]
Abstract
AIM Leptin is one of the factors affecting serum lipid profile. We investigated the association between serum lipids and leptin/leptin receptor (LEPR) gene polymorphisms in obese Japanese children. METHODS One hundred and thirty-six obese children (99 males and 37 females, relative weight over than 20%) from 5 to 17 years of age were recruited from 10 institutes. Four known polymorphisms in leptin gene [(+19)A G, (-2548)G A, (-188)C A, (-633)C T] and four known polymorphisms in LEPR gene [Lys109Arg, Gln223Arg, Pro(G)1019Pro(A), Ser(T)343Ser(C)] were determined using polymerase chain reaction-restriction fragment length polymorphism-based analyses. RESULTS No associations were found between leptin gene polymorphisms and serum lipid profile. On the other hand, Lys109Arg and Ser343Ser polymorphism in LEPR gene, but not Gln223Arg or Pro1019Pro, had significant relationships with serum lipid profile; lower total and low-density lipoprotein cholesterol levels in Arg109Arg homozygotes, and lower TG levels in Ser343Ser(C/C) homozygotes. In addition, LEPR gene also associated with relative weight; Arg109Arg homozygotes had higher relative weight and Ser343Ser(C/C) homozygotes had lower one. CONCLUSION These results suggest that LEPR gene polymorphisms may partly contribute to serum lipid profile in obese children.
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Affiliation(s)
- T Okada
- Department of Pediatrics and Child Health, Nihon University School of Medicine, Tokyo, Japan.
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28
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Li T, Owsley E, Matozel M, Hsu P, Novak CM, Chiang JYL. Transgenic expression of cholesterol 7alpha-hydroxylase in the liver prevents high-fat diet-induced obesity and insulin resistance in mice. Hepatology 2010; 52:678-90. [PMID: 20623580 PMCID: PMC3700412 DOI: 10.1002/hep.23721] [Citation(s) in RCA: 191] [Impact Index Per Article: 12.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/11/2022]
Abstract
UNLABELLED Cholesterol 7alpha-hydroxylase (CYP7A1) is the rate-limiting enzyme in the bile acid biosynthetic pathway that converts cholesterol into bile acids in the liver. Recent studies have shown that bile acids may play an important role in maintaining lipid, glucose, and energy homeostasis. However, the role of CYP7A1 in the development of obesity and diabetes is currently unclear. In this study, we demonstrated that transgenic mice overexpressing Cyp7a1 in the liver [i.e., Cyp7a1 transgenic (Cyp7a1-tg) mice] were resistant to high-fat diet (HFD)-induced obesity, fatty liver, and insulin resistance. Cyp7a1-tg mice showed increased hepatic cholesterol catabolism and an increased bile acid pool. Cyp7a1-tg mice had increased secretion of hepatic very low density lipoprotein but maintained plasma triglyceride homeostasis. Gene expression analysis showed that the hepatic messenger RNA expression levels of several critical lipogenic and gluconeogenic genes were significantly decreased in HFD-fed Cyp7a1-tg mice. HFD-fed Cyp7a1-tg mice had increased whole body energy expenditure and induction of fatty acid oxidation genes in the brown adipose tissue. CONCLUSION This study shows that Cyp7a1 plays a critical role in maintaining whole body lipid, glucose, and energy homeostasis. The induction of CYP7A1 expression with the expansion of the hydrophobic bile acid pool may be a potential therapeutic strategy for treating metabolic disorders such as fatty liver diseases, obesity, and diabetes in humans.
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Affiliation(s)
- Tiangang Li
- Department of Integrative Medical Sciences, Northeastern Ohio Universities’ Colleges of Medicine and Pharmacy, Rootstown, OH
| | - Erika Owsley
- Department of Integrative Medical Sciences, Northeastern Ohio Universities’ Colleges of Medicine and Pharmacy, Rootstown, OH
| | - Michelle Matozel
- Department of Integrative Medical Sciences, Northeastern Ohio Universities’ Colleges of Medicine and Pharmacy, Rootstown, OH
| | - Peter Hsu
- Department of Integrative Medical Sciences, Northeastern Ohio Universities’ Colleges of Medicine and Pharmacy, Rootstown, OH
| | - Colleen M. Novak
- Department of Biological Sciences, Kent State University, Kent, OH
| | - John Y. L. Chiang
- Department of Integrative Medical Sciences, Northeastern Ohio Universities’ Colleges of Medicine and Pharmacy, Rootstown, OH
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29
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Perez-Tilve D, Hofmann SM, Basford J, Nogueiras R, Pfluger PT, Patterson JT, Grant E, Wilson-Perez HE, Granholm NA, Arnold M, Trevaskis JL, Butler AA, Davidson WS, Woods SC, Benoit SC, Sleeman MW, DiMarchi RD, Hui DY, Tschöp MH. Melanocortin signaling in the CNS directly regulates circulating cholesterol. Nat Neurosci 2010; 13:877-82. [PMID: 20526334 DOI: 10.1038/nn.2569] [Citation(s) in RCA: 73] [Impact Index Per Article: 4.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/22/2010] [Accepted: 04/28/2010] [Indexed: 01/02/2023]
Abstract
Cholesterol circulates in the blood in association with triglycerides and other lipids, and elevated blood low-density lipoprotein cholesterol carries a risk for metabolic and cardiovascular disorders, whereas high-density lipoprotein (HDL) cholesterol in the blood is thought to be beneficial. Circulating cholesterol is the balance among dietary cholesterol absorption, hepatic synthesis and secretion, and the metabolism of lipoproteins by various tissues. We found that the CNS is also an important regulator of cholesterol in rodents. Inhibiting the brain's melanocortin system by pharmacological, genetic or endocrine mechanisms increased circulating HDL cholesterol by reducing its uptake by the liver independent of food intake or body weight. Our data suggest that a neural circuit in the brain is directly involved in the control of cholesterol metabolism by the liver.
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Affiliation(s)
- Diego Perez-Tilve
- Metabolic Diseases Institute, Division of Endocrinology, Department of Medicine, University of Cincinnati College of Medicine, Cincinnati, Ohio, USA
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30
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Kennedy AJ, Ellacott KLJ, King VL, Hasty AH. Mouse models of the metabolic syndrome. Dis Model Mech 2010; 3:156-66. [PMID: 20212084 DOI: 10.1242/dmm.003467] [Citation(s) in RCA: 189] [Impact Index Per Article: 12.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/20/2022] Open
Abstract
The metabolic syndrome (MetS) is characterized by obesity concomitant with other metabolic abnormalities such as hypertriglyceridemia, reduced high-density lipoprotein levels, elevated blood pressure and raised fasting glucose levels. The precise definition of MetS, the relationships of its metabolic features, and what initiates it, are debated. However, obesity is on the rise worldwide, and its association with these metabolic symptoms increases the risk for diabetes and cardiovascular disease (among many other diseases). Research needs to determine the mechanisms by which obesity and MetS increase the risk of disease. In light of this growing epidemic, it is imperative to develop animal models of MetS. These models will help determine the pathophysiological basis for MetS and how MetS increases the risk for other diseases. Among the various animal models available to study MetS, mice are the most commonly used for several reasons. First, there are several spontaneously occurring obese mouse strains that have been used for decades and that are very well characterized. Second, high-fat feeding studies require only months to induce MetS. Third, it is relatively easy to study the effects of single genes by developing transgenic or gene knockouts to determine the influence of a gene on MetS. For these reasons, this review will focus on the benefits and caveats of the most common mouse models of MetS. It is our hope that the reader will be able to use this review as a guide for the selection of mouse models for their own studies.
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Affiliation(s)
- Arion J Kennedy
- Department of Molecular Physiology, Vanderbilt University Medical Center, Nashville, TN 37232, USA
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31
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Röhrl C, Pagler TA, Strobl W, Ellinger A, Neumüller J, Pavelka M, Stangl H, Meisslitzer-Ruppitsch C. Characterization of endocytic compartments after holo-high density lipoprotein particle uptake in HepG2 cells. Histochem Cell Biol 2010; 133:261-72. [PMID: 20039053 PMCID: PMC3182552 DOI: 10.1007/s00418-009-0672-3] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 12/15/2009] [Indexed: 12/27/2022]
Abstract
Holo-high density lipoprotein (HDL) particle uptake, besides selective lipid uptake, constitutes an alternative pathway to regulate cellular cholesterol homeostasis. In the current study, the cellular path of holo-HDL particles was investigated in human liver carcinoma cells (HepG2) using combined light and electron microscopical methods. The apolipoprotein moiety of HDL was visualized with different markers: horseradish peroxidase, colloidal gold and the fluorochrome Alexa(568), used in fluorescence microscopy and after photooxidation correlatively at the ultrastructural level. Time course experiments showed a rapid uptake of holo-HDL particles, an accumulation in endosomal compartments, with a plateau after 1-2 h of continuous uptake, and a clearance 1-2 h upon replacement by unlabeled HDL. Correlative microscopy, using HDL-Alexa(568)-driven diaminobenzidine (DAB) photooxidation, identified the fluorescent organelles as DAB-positive multivesicular bodies (MVBs) in the electron microscope; their luminal contents but not the internal vesicles were stained. Labeled MVBs increased in numbers and changed shapes along with the duration of uptake, from polymorphic organelles with multiple surface domains and differently shaped protrusions dominating at early times of uptake to compact bodies with mainly tubular appendices and densely packed vesicles after later times. Differently shaped and labeled surface domains and appendices, as revealed by three dimensional reconstructions, as well as images of homotypic fusions indicate the dynamics of the HDL-positive MVBs. Double staining visualized by confocal microscopy, along with the electron microscopic data, shows that holo-HDL particles after temporal storage in MVBs are only to a minor degree transported to lysosomes, which suggests that different mechanisms are involved in cellular HDL clearance, including resecretion.
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Affiliation(s)
- Clemens Röhrl
- Center for Physiology and Pathophysiology, Institute of Medical Chemistry, Medical University of Vienna, Vienna, Austria
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32
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Fogarty MP, Xiao R, Prokunina-Olsson L, Scott LJ, Mohlke KL. Allelic expression imbalance at high-density lipoprotein cholesterol locus MMAB-MVK. Hum Mol Genet 2010; 19:1921-9. [PMID: 20159775 DOI: 10.1093/hmg/ddq067] [Citation(s) in RCA: 32] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
Abstract
Genome-wide association studies (GWAS) have identified numerous loci associated with various complex traits for which the underlying susceptibility gene(s) remain unknown. In a GWAS for high-density lipoprotein-cholesterol (HDL-C) level, one strongly associated locus contains at least two biologically compelling candidates, methylmalonic aciduria cblB type (MMAB) and mevalonate kinase (MVK). To detect evidence of cis-acting regulation at this locus, we measured relative allelic expression of transcribed SNPs in five genes using human hepatocyte samples heterozygous for the transcribed SNP. If an HDL-C-associated SNP allele differentially regulates mRNA level in cis, samples heterozygous both for a transcribed SNP and an HDL-C-associated SNP should display allelic expression imbalance (AEI) of the transcribed SNP. We designed statistical tests to detect AEI in a comprehensive set of linkage disequilibrium (LD) scenarios between the transcribed SNP and an HDL-C-associated SNP (rs7298565) in phase unknown samples. We observed significant AEI of 22% in MMAB (P = 1.4 x 10(-13), transcribed SNP rs11067231), and the allele associated with lower HDL-C level was associated with greater MMAB transcript level. The same rs7298565 allele was also associated with higher MMAB mRNA level (P = 0.0081) and higher MMAB protein level (P = 0.0020). In contrast, MVK, UBE3B, KCTD10 and ACACB did not show significant AEI (P > or = 0.05). These data suggest MMAB is the most likely gene influencing HDL-C levels at this locus and demonstrate that measuring AEI at loci containing more than one candidate gene can prioritize genes for functional studies.
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Affiliation(s)
- Marie P Fogarty
- Department of Genetics, University of North Carolina, Chapel Hill, NC 27599, USA
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33
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Prieur X, Tung YCL, Griffin JL, Farooqi IS, O'Rahilly S, Coll AP. Leptin regulates peripheral lipid metabolism primarily through central effects on food intake. Endocrinology 2008; 149:5432-9. [PMID: 18635658 PMCID: PMC2629739 DOI: 10.1210/en.2008-0498] [Citation(s) in RCA: 71] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/01/2023]
Abstract
The metabolic effects of leptin may involve both centrally and peripherally mediated actions with a component of the central actions potentially independent of alterations in food intake. Ob/ob mice have significant abnormalities in lipid metabolism, correctable by leptin administration. We used ob/ob mice to study the relative importance of the subtypes of actions of leptin (central vs. peripheral; food intake dependent vs. independent) on lipid metabolism. Mice were treated for 3 d with leptin, either centrally [intracerebroventricular (icv)] or peripherally (ip), and compared with mice pair-fed to the leptin-treated mice (PF) and with ad libitum-fed controls (C). All treatment groups (icv, ip, PF) showed indistinguishable changes in liver weight; hepatic steatosis; hepatic lipidemic profile; and circulating free fatty acids, triglycerides, and cholesterol lipoprotein profile. Changes in the expression of genes involved in lipogenesis and fatty acid oxidation in liver, muscle, and white fat were broadly similar in ip, icv, and PF groups. Leptin (both icv and ip) stimulated expression of both mitochondrial and peroxisomal acyl-coenzyme A oxidase (liver) and peroxisomal proliferator-activated receptor-alpha (skeletal muscle) to an extent not replicated by pair feeding. Leptin had profound effects on peripheral lipid metabolism, but the majority were explained by its effects on food intake. Leptin had additional centrally mediated effects to increase the expression of a limited number of genes concerned with fatty acid oxidation. Whereas we cannot exclude direct peripheral effects of leptin on certain aspects of lipid metabolism, we were unable to detect any such effects on the parameters measured in this study.
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Affiliation(s)
- Xavier Prieur
- University of Cambridge Metabolic Research Laboratories, Institute of Metabolic Science, Addenbrooke's Hospital, Cambridge CB2 OQQ, United Kingdom
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34
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Wolfrum C, Howell JJ, Ndungo E, Stoffel M. Foxa2 Activity Increases Plasma High Density Lipoprotein Levels by Regulating Apolipoprotein M. J Biol Chem 2008; 283:16940-9. [DOI: 10.1074/jbc.m801930200] [Citation(s) in RCA: 56] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/19/2023] Open
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35
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Plummer MR, Hasty AH. Atherosclerotic lesion formation and triglyceride storage in obese apolipoprotein AI-deficient mice. J Nutr Biochem 2008; 19:664-73. [PMID: 18280133 DOI: 10.1016/j.jnutbio.2007.08.009] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/23/2007] [Revised: 07/19/2007] [Accepted: 08/30/2007] [Indexed: 11/18/2022]
Abstract
Obese leptin-deficient (ob/ob) mice have increased levels of high-density lipoprotein (HDL) and a unique lipoprotein referred to as low-density lipoprotein (LDL)/HDL1. When crossed onto an apolipoprotein AI (apoAI)-deficient (-/-) background, ob/ob;apoAI-/- mice accumulate LDL/HDL1 in the absence of traditional HDL. To determine the role of LDL/HDL1 in atherosclerosis, C57BL/6, apoAI-/-, ob/ob and ob/ob;apoAI-/- mice were placed on butterfat diet. After 20 weeks, all four groups had a significant increase in total cholesterol levels. The cholesterol in C57BL/6 mice was carried on very low-density lipoprotein (VLDL) and LDL and, in ob/ob and ob/ob;apoAI-/- mice, on HDL and LDL/HDL1. Atherosclerotic lesion area was similar among C57BL/6, ob/ob and ob/ob;apoAI-/- groups despite their dissimilar lipoprotein profiles. Hepatic triglyceride production and VLDL clearance rates were similar among the four groups. The ob/ob;apoAI-/- group had a significant decrease in liver weight and an increase in white adipose tissue (WAT) weight compared to the ob/ob group. Hepatic scavenger receptor class B type I (SR-BI) levels were decreased in both liver and WAT in ob/ob;apoAI-/- compared to ob/ob mice. Conclusions regarding the atherogenicity of LDL/HDL1 were confounded by the differences in lipoprotein profiles among the four groups. However, our studies provide support for the concept that apoAI and SR-BI assist in the partitioning of lipid from adipose tissue to the liver.
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Affiliation(s)
- Michelle R Plummer
- Department of Molecular Physiology and Biophysics, Vanderbilt University Medical Center, Nashville, TN 37232, USA
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36
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Atkinson RD, Coenen KR, Plummer MR, Gruen ML, Hasty AH. Macrophage-derived apolipoprotein E ameliorates dyslipidemia and atherosclerosis in obese apolipoprotein E-deficient mice. Am J Physiol Endocrinol Metab 2008; 294:E284-90. [PMID: 18029445 DOI: 10.1152/ajpendo.00601.2007] [Citation(s) in RCA: 15] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
Previous studies have demonstrated that macrophage-derived apolipoprotein E (apoE) reduces atherosclerotic lesion formation in lean apoE-deficient ((-/-)) mice. apoE has also been demonstrated to play a role in adipocyte differentiation and lipid accumulation. Because the prevalence of obesity has grown to epidemic proportions, we sought to determine whether macrophage-derived apoE could impact atherosclerotic lesion formation or adipose tissue expansion and inflammation in obese apoE(-/-) mice. To this end, we transplanted obese leptin-deficient (ob/ob) apoE(-/-) mice with bone marrow from either ob/ob;apoE(-/-) or ob/ob;apoE(+/+) donors. There were no differences in body weight, total body adipose tissue, or visceral fat pad mass between recipient groups. The presence of macrophage-apoE had no impact on adipose tissue macrophage content or inflammatory cytokine expression. Recipients of apoE(+/+) marrow demonstrated 3.7-fold lower plasma cholesterol (P < 0.001) and 1.7-fold lower plasma triglyceride levels (P < 0.01) by 12 wk after transplantation even though apoE was present in plasma at concentrations <10% of wild-type levels. The reduced plasma lipids reflected a dramatic decrease in very low density lipoprotein and a mild increase in high-density lipoprotein levels. Atherosclerotic lesion area was >10-fold lower in recipients of ob/ob;apoE(+/+) marrow (P < 0.005). Similar results were seen in leptin receptor-deficient (db/db) apoE(-/-) mice. Finally, when bone marrow transplantation was performed in 4-mo-old ob/ob;apoE(-/-) and db/db;apoE(-/-) mice with preexisting lesions, recipients of apoE(+/+) marrow had a 2.8-fold lower lesion area than controls (P = 0.0002). These results demonstrate that macrophage-derived apoE does not impact adipose tissue expansion or inflammatory status; however, even very low levels of macrophage-derived apoE are capable of reducing plasma lipids and atherosclerotic lesion area in obese mice.
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Affiliation(s)
- Robin D Atkinson
- Department of Molecular Physiology and Biophysics, Vanderbilt University Medical Center, Nashville, TN 37232-0615, USA
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37
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Kim JY, van de Wall E, Laplante M, Azzara A, Trujillo ME, Hofmann SM, Schraw T, Durand JL, Li H, Li G, Jelicks LA, Mehler MF, Hui DY, Deshaies Y, Shulman GI, Schwartz GJ, Scherer PE. Obesity-associated improvements in metabolic profile through expansion of adipose tissue. J Clin Invest 2007; 117:2621-37. [PMID: 17717599 PMCID: PMC1950456 DOI: 10.1172/jci31021] [Citation(s) in RCA: 1003] [Impact Index Per Article: 55.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/21/2006] [Accepted: 05/31/2007] [Indexed: 02/06/2023] Open
Abstract
Excess caloric intake can lead to insulin resistance. The underlying reasons are complex but likely related to ectopic lipid deposition in nonadipose tissue. We hypothesized that the inability to appropriately expand subcutaneous adipose tissue may be an underlying reason for insulin resistance and beta cell failure. Mice lacking leptin while overexpressing adiponectin showed normalized glucose and insulin levels and dramatically improved glucose as well as positively affected serum triglyceride levels. Therefore, modestly increasing the levels of circulating full-length adiponectin completely rescued the diabetic phenotype in ob/ob mice. They displayed increased expression of PPARgamma target genes and a reduction in macrophage infiltration in adipose tissue and systemic inflammation. As a result, the transgenic mice were morbidly obese, with significantly higher levels of adipose tissue than their ob/ob littermates, leading to an interesting dichotomy of increased fat mass associated with improvement in insulin sensitivity. Based on these data, we propose that adiponectin acts as a peripheral "starvation" signal promoting the storage of triglycerides preferentially in adipose tissue. As a consequence, reduced triglyceride levels in the liver and muscle convey improved systemic insulin sensitivity. These mice therefore represent what we believe is a novel model of morbid obesity associated with an improved metabolic profile.
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Affiliation(s)
- Ja-Young Kim
- Department of Cell Biology and
Department of Medicine, Albert Einstein College of Medicine, New York, New York, USA.
Department of Anatomy and Physiology, Laval University Hospital Centre Research Centre, Laval University School of Medicine, Quebec City, Quebec, Canada.
Department of Pathology, Genome Research Institute, University of Cincinnati, Cincinnati, Ohio, USA.
Department of Physiology and Biophysics and
Department of Neuroscience, Albert Einstein College of Medicine, New York, New York, USA.
Department of Internal Medicine and Department of Cellular and Molecular Physiology, Yale University School of Medicine, and Howard Hughes Medical Institute, New Haven, Connecticut, USA.
Department of Molecular Pharmacology and
Diabetes Research and Training Center, Albert Einstein College of Medicine, New York, New York, USA.
Touchstone Diabetes Center, Department of Internal Medicine, University of Texas Southwestern Medical Center, Dallas, Texas, USA
| | - Esther van de Wall
- Department of Cell Biology and
Department of Medicine, Albert Einstein College of Medicine, New York, New York, USA.
Department of Anatomy and Physiology, Laval University Hospital Centre Research Centre, Laval University School of Medicine, Quebec City, Quebec, Canada.
Department of Pathology, Genome Research Institute, University of Cincinnati, Cincinnati, Ohio, USA.
Department of Physiology and Biophysics and
Department of Neuroscience, Albert Einstein College of Medicine, New York, New York, USA.
Department of Internal Medicine and Department of Cellular and Molecular Physiology, Yale University School of Medicine, and Howard Hughes Medical Institute, New Haven, Connecticut, USA.
Department of Molecular Pharmacology and
Diabetes Research and Training Center, Albert Einstein College of Medicine, New York, New York, USA.
Touchstone Diabetes Center, Department of Internal Medicine, University of Texas Southwestern Medical Center, Dallas, Texas, USA
| | - Mathieu Laplante
- Department of Cell Biology and
Department of Medicine, Albert Einstein College of Medicine, New York, New York, USA.
Department of Anatomy and Physiology, Laval University Hospital Centre Research Centre, Laval University School of Medicine, Quebec City, Quebec, Canada.
Department of Pathology, Genome Research Institute, University of Cincinnati, Cincinnati, Ohio, USA.
Department of Physiology and Biophysics and
Department of Neuroscience, Albert Einstein College of Medicine, New York, New York, USA.
Department of Internal Medicine and Department of Cellular and Molecular Physiology, Yale University School of Medicine, and Howard Hughes Medical Institute, New Haven, Connecticut, USA.
Department of Molecular Pharmacology and
Diabetes Research and Training Center, Albert Einstein College of Medicine, New York, New York, USA.
Touchstone Diabetes Center, Department of Internal Medicine, University of Texas Southwestern Medical Center, Dallas, Texas, USA
| | - Anthony Azzara
- Department of Cell Biology and
Department of Medicine, Albert Einstein College of Medicine, New York, New York, USA.
Department of Anatomy and Physiology, Laval University Hospital Centre Research Centre, Laval University School of Medicine, Quebec City, Quebec, Canada.
Department of Pathology, Genome Research Institute, University of Cincinnati, Cincinnati, Ohio, USA.
Department of Physiology and Biophysics and
Department of Neuroscience, Albert Einstein College of Medicine, New York, New York, USA.
Department of Internal Medicine and Department of Cellular and Molecular Physiology, Yale University School of Medicine, and Howard Hughes Medical Institute, New Haven, Connecticut, USA.
Department of Molecular Pharmacology and
Diabetes Research and Training Center, Albert Einstein College of Medicine, New York, New York, USA.
Touchstone Diabetes Center, Department of Internal Medicine, University of Texas Southwestern Medical Center, Dallas, Texas, USA
| | - Maria E. Trujillo
- Department of Cell Biology and
Department of Medicine, Albert Einstein College of Medicine, New York, New York, USA.
Department of Anatomy and Physiology, Laval University Hospital Centre Research Centre, Laval University School of Medicine, Quebec City, Quebec, Canada.
Department of Pathology, Genome Research Institute, University of Cincinnati, Cincinnati, Ohio, USA.
Department of Physiology and Biophysics and
Department of Neuroscience, Albert Einstein College of Medicine, New York, New York, USA.
Department of Internal Medicine and Department of Cellular and Molecular Physiology, Yale University School of Medicine, and Howard Hughes Medical Institute, New Haven, Connecticut, USA.
Department of Molecular Pharmacology and
Diabetes Research and Training Center, Albert Einstein College of Medicine, New York, New York, USA.
Touchstone Diabetes Center, Department of Internal Medicine, University of Texas Southwestern Medical Center, Dallas, Texas, USA
| | - Susanna M. Hofmann
- Department of Cell Biology and
Department of Medicine, Albert Einstein College of Medicine, New York, New York, USA.
Department of Anatomy and Physiology, Laval University Hospital Centre Research Centre, Laval University School of Medicine, Quebec City, Quebec, Canada.
Department of Pathology, Genome Research Institute, University of Cincinnati, Cincinnati, Ohio, USA.
Department of Physiology and Biophysics and
Department of Neuroscience, Albert Einstein College of Medicine, New York, New York, USA.
Department of Internal Medicine and Department of Cellular and Molecular Physiology, Yale University School of Medicine, and Howard Hughes Medical Institute, New Haven, Connecticut, USA.
Department of Molecular Pharmacology and
Diabetes Research and Training Center, Albert Einstein College of Medicine, New York, New York, USA.
Touchstone Diabetes Center, Department of Internal Medicine, University of Texas Southwestern Medical Center, Dallas, Texas, USA
| | - Todd Schraw
- Department of Cell Biology and
Department of Medicine, Albert Einstein College of Medicine, New York, New York, USA.
Department of Anatomy and Physiology, Laval University Hospital Centre Research Centre, Laval University School of Medicine, Quebec City, Quebec, Canada.
Department of Pathology, Genome Research Institute, University of Cincinnati, Cincinnati, Ohio, USA.
Department of Physiology and Biophysics and
Department of Neuroscience, Albert Einstein College of Medicine, New York, New York, USA.
Department of Internal Medicine and Department of Cellular and Molecular Physiology, Yale University School of Medicine, and Howard Hughes Medical Institute, New Haven, Connecticut, USA.
Department of Molecular Pharmacology and
Diabetes Research and Training Center, Albert Einstein College of Medicine, New York, New York, USA.
Touchstone Diabetes Center, Department of Internal Medicine, University of Texas Southwestern Medical Center, Dallas, Texas, USA
| | - Jorge L. Durand
- Department of Cell Biology and
Department of Medicine, Albert Einstein College of Medicine, New York, New York, USA.
Department of Anatomy and Physiology, Laval University Hospital Centre Research Centre, Laval University School of Medicine, Quebec City, Quebec, Canada.
Department of Pathology, Genome Research Institute, University of Cincinnati, Cincinnati, Ohio, USA.
Department of Physiology and Biophysics and
Department of Neuroscience, Albert Einstein College of Medicine, New York, New York, USA.
Department of Internal Medicine and Department of Cellular and Molecular Physiology, Yale University School of Medicine, and Howard Hughes Medical Institute, New Haven, Connecticut, USA.
Department of Molecular Pharmacology and
Diabetes Research and Training Center, Albert Einstein College of Medicine, New York, New York, USA.
Touchstone Diabetes Center, Department of Internal Medicine, University of Texas Southwestern Medical Center, Dallas, Texas, USA
| | - Hua Li
- Department of Cell Biology and
Department of Medicine, Albert Einstein College of Medicine, New York, New York, USA.
Department of Anatomy and Physiology, Laval University Hospital Centre Research Centre, Laval University School of Medicine, Quebec City, Quebec, Canada.
Department of Pathology, Genome Research Institute, University of Cincinnati, Cincinnati, Ohio, USA.
Department of Physiology and Biophysics and
Department of Neuroscience, Albert Einstein College of Medicine, New York, New York, USA.
Department of Internal Medicine and Department of Cellular and Molecular Physiology, Yale University School of Medicine, and Howard Hughes Medical Institute, New Haven, Connecticut, USA.
Department of Molecular Pharmacology and
Diabetes Research and Training Center, Albert Einstein College of Medicine, New York, New York, USA.
Touchstone Diabetes Center, Department of Internal Medicine, University of Texas Southwestern Medical Center, Dallas, Texas, USA
| | - Guangyu Li
- Department of Cell Biology and
Department of Medicine, Albert Einstein College of Medicine, New York, New York, USA.
Department of Anatomy and Physiology, Laval University Hospital Centre Research Centre, Laval University School of Medicine, Quebec City, Quebec, Canada.
Department of Pathology, Genome Research Institute, University of Cincinnati, Cincinnati, Ohio, USA.
Department of Physiology and Biophysics and
Department of Neuroscience, Albert Einstein College of Medicine, New York, New York, USA.
Department of Internal Medicine and Department of Cellular and Molecular Physiology, Yale University School of Medicine, and Howard Hughes Medical Institute, New Haven, Connecticut, USA.
Department of Molecular Pharmacology and
Diabetes Research and Training Center, Albert Einstein College of Medicine, New York, New York, USA.
Touchstone Diabetes Center, Department of Internal Medicine, University of Texas Southwestern Medical Center, Dallas, Texas, USA
| | - Linda A. Jelicks
- Department of Cell Biology and
Department of Medicine, Albert Einstein College of Medicine, New York, New York, USA.
Department of Anatomy and Physiology, Laval University Hospital Centre Research Centre, Laval University School of Medicine, Quebec City, Quebec, Canada.
Department of Pathology, Genome Research Institute, University of Cincinnati, Cincinnati, Ohio, USA.
Department of Physiology and Biophysics and
Department of Neuroscience, Albert Einstein College of Medicine, New York, New York, USA.
Department of Internal Medicine and Department of Cellular and Molecular Physiology, Yale University School of Medicine, and Howard Hughes Medical Institute, New Haven, Connecticut, USA.
Department of Molecular Pharmacology and
Diabetes Research and Training Center, Albert Einstein College of Medicine, New York, New York, USA.
Touchstone Diabetes Center, Department of Internal Medicine, University of Texas Southwestern Medical Center, Dallas, Texas, USA
| | - Mark F. Mehler
- Department of Cell Biology and
Department of Medicine, Albert Einstein College of Medicine, New York, New York, USA.
Department of Anatomy and Physiology, Laval University Hospital Centre Research Centre, Laval University School of Medicine, Quebec City, Quebec, Canada.
Department of Pathology, Genome Research Institute, University of Cincinnati, Cincinnati, Ohio, USA.
Department of Physiology and Biophysics and
Department of Neuroscience, Albert Einstein College of Medicine, New York, New York, USA.
Department of Internal Medicine and Department of Cellular and Molecular Physiology, Yale University School of Medicine, and Howard Hughes Medical Institute, New Haven, Connecticut, USA.
Department of Molecular Pharmacology and
Diabetes Research and Training Center, Albert Einstein College of Medicine, New York, New York, USA.
Touchstone Diabetes Center, Department of Internal Medicine, University of Texas Southwestern Medical Center, Dallas, Texas, USA
| | - David Y. Hui
- Department of Cell Biology and
Department of Medicine, Albert Einstein College of Medicine, New York, New York, USA.
Department of Anatomy and Physiology, Laval University Hospital Centre Research Centre, Laval University School of Medicine, Quebec City, Quebec, Canada.
Department of Pathology, Genome Research Institute, University of Cincinnati, Cincinnati, Ohio, USA.
Department of Physiology and Biophysics and
Department of Neuroscience, Albert Einstein College of Medicine, New York, New York, USA.
Department of Internal Medicine and Department of Cellular and Molecular Physiology, Yale University School of Medicine, and Howard Hughes Medical Institute, New Haven, Connecticut, USA.
Department of Molecular Pharmacology and
Diabetes Research and Training Center, Albert Einstein College of Medicine, New York, New York, USA.
Touchstone Diabetes Center, Department of Internal Medicine, University of Texas Southwestern Medical Center, Dallas, Texas, USA
| | - Yves Deshaies
- Department of Cell Biology and
Department of Medicine, Albert Einstein College of Medicine, New York, New York, USA.
Department of Anatomy and Physiology, Laval University Hospital Centre Research Centre, Laval University School of Medicine, Quebec City, Quebec, Canada.
Department of Pathology, Genome Research Institute, University of Cincinnati, Cincinnati, Ohio, USA.
Department of Physiology and Biophysics and
Department of Neuroscience, Albert Einstein College of Medicine, New York, New York, USA.
Department of Internal Medicine and Department of Cellular and Molecular Physiology, Yale University School of Medicine, and Howard Hughes Medical Institute, New Haven, Connecticut, USA.
Department of Molecular Pharmacology and
Diabetes Research and Training Center, Albert Einstein College of Medicine, New York, New York, USA.
Touchstone Diabetes Center, Department of Internal Medicine, University of Texas Southwestern Medical Center, Dallas, Texas, USA
| | - Gerald I. Shulman
- Department of Cell Biology and
Department of Medicine, Albert Einstein College of Medicine, New York, New York, USA.
Department of Anatomy and Physiology, Laval University Hospital Centre Research Centre, Laval University School of Medicine, Quebec City, Quebec, Canada.
Department of Pathology, Genome Research Institute, University of Cincinnati, Cincinnati, Ohio, USA.
Department of Physiology and Biophysics and
Department of Neuroscience, Albert Einstein College of Medicine, New York, New York, USA.
Department of Internal Medicine and Department of Cellular and Molecular Physiology, Yale University School of Medicine, and Howard Hughes Medical Institute, New Haven, Connecticut, USA.
Department of Molecular Pharmacology and
Diabetes Research and Training Center, Albert Einstein College of Medicine, New York, New York, USA.
Touchstone Diabetes Center, Department of Internal Medicine, University of Texas Southwestern Medical Center, Dallas, Texas, USA
| | - Gary J. Schwartz
- Department of Cell Biology and
Department of Medicine, Albert Einstein College of Medicine, New York, New York, USA.
Department of Anatomy and Physiology, Laval University Hospital Centre Research Centre, Laval University School of Medicine, Quebec City, Quebec, Canada.
Department of Pathology, Genome Research Institute, University of Cincinnati, Cincinnati, Ohio, USA.
Department of Physiology and Biophysics and
Department of Neuroscience, Albert Einstein College of Medicine, New York, New York, USA.
Department of Internal Medicine and Department of Cellular and Molecular Physiology, Yale University School of Medicine, and Howard Hughes Medical Institute, New Haven, Connecticut, USA.
Department of Molecular Pharmacology and
Diabetes Research and Training Center, Albert Einstein College of Medicine, New York, New York, USA.
Touchstone Diabetes Center, Department of Internal Medicine, University of Texas Southwestern Medical Center, Dallas, Texas, USA
| | - Philipp E. Scherer
- Department of Cell Biology and
Department of Medicine, Albert Einstein College of Medicine, New York, New York, USA.
Department of Anatomy and Physiology, Laval University Hospital Centre Research Centre, Laval University School of Medicine, Quebec City, Quebec, Canada.
Department of Pathology, Genome Research Institute, University of Cincinnati, Cincinnati, Ohio, USA.
Department of Physiology and Biophysics and
Department of Neuroscience, Albert Einstein College of Medicine, New York, New York, USA.
Department of Internal Medicine and Department of Cellular and Molecular Physiology, Yale University School of Medicine, and Howard Hughes Medical Institute, New Haven, Connecticut, USA.
Department of Molecular Pharmacology and
Diabetes Research and Training Center, Albert Einstein College of Medicine, New York, New York, USA.
Touchstone Diabetes Center, Department of Internal Medicine, University of Texas Southwestern Medical Center, Dallas, Texas, USA
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38
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Coenen KR, Hasty AH. Obesity potentiates development of fatty liver and insulin resistance, but not atherosclerosis, in high-fat diet-fed agouti LDLR-deficient mice. Am J Physiol Endocrinol Metab 2007; 293:E492-9. [PMID: 17566116 DOI: 10.1152/ajpendo.00171.2007] [Citation(s) in RCA: 28] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
Obesity is increasing at an alarming rate, and its related disorders are placing a considerable strain on our healthcare system. Although they are not always coincident, obesity is often accompanied by hyperlipidemia. Both obesity and hyperlipidemia are independently associated with atherosclerosis, nonalcoholic fatty liver disease (NAFLD), and insulin resistance (IR). Thus, we sought to determine the relative contributions of obesity and hyperlipidemia to these associated pathologies. Obese agouti (A(y)/a) mice and their littermate controls (a/a) were placed on an LDL receptor (LDLR)(-/-) background. At 4 mo of age, mice were either maintained on chow diet (CD) or placed on Western diet (WD) for 12 wk. These genetic and dietary manipulations yielded four experimental groups: 1) lean, a/a;LDLR(-/-)CD; 2) genetic-induced obesity (GIO), A(y)/a;LDLR(-/-)CD; 3) diet-induced obesity (DIO), a/a;LDLR(-/-)WD; and 4) genetic- plus diet-induced obesity (GIO/DIO), A(y)/a;LDLR(-/-)WD. Lipoprotein profiles revealed increased VLDL and LDL particles in WD-fed mice compared with CD-fed controls. The hyperlipidemia present in this mouse model was the result of both increased hepatic triglyceride production and delayed lipoprotein clearance from the plasma. Both WD-fed groups exhibited similar levels of atherosclerotic lesion area, with increased obesity in the GIO/DIO group having no impact on atherogenesis. However, the severe obesity in the GIO/DIO group did aggravate NAFLD and IR. These findings suggest that, although obesity and hyperlipidemia exert individual pathological effects, the combination of the two has the potential to exert an additive effect on NAFLD and IR but not atherosclerosis in this mouse model.
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Affiliation(s)
- Kimberly R Coenen
- Department of Molecular Physiology and Biophysics, Vanderbilt University Medical Center, Nashville, Tennessee 37232-0615, USA
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Abstract
Liver is one of the most important organs in energy metabolism. Most plasma apolipoproteins and endogenous lipids and lipoproteins are synthesized in the liver. It depends on the integrity of liver cellular function, which ensures homeostasis of lipid and lipoprotein metabolism. When liver cancer occurs, these processes are impaired and the plasma lipid and lipoprotein patterns may be changed. Liver cancer is the fifth common malignant tumor worldwide, and is closely related to the infections of hepatitis B virus (HBV) and hepatitis C virus (HCV). HBV and HCV infections are quite common in China and other Southeast Asian countries. In addition, liver cancer is often followed by a procession of chronic hepatitis or cirrhosis, so that hepatic function is damaged obviously on these bases, which may significantly influence lipid and lipoprotein metabolism in vivo. In this review we summarize the clinical significance of lipid and lipoprotein metabolism under liver cancer.
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Affiliation(s)
- Jing-Ting Jiang
- Department of Tumor Biological Treatment, the Third Affiliated Hospital, Suzhou University, Changzhou, China.
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40
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Huang J, Iqbal J, Saha PK, Liu J, Chan L, Hussain MM, Moore DD, Wang L. Molecular characterization of the role of orphan receptor small heterodimer partner in development of fatty liver. Hepatology 2007; 46:147-57. [PMID: 17526026 DOI: 10.1002/hep.21632] [Citation(s) in RCA: 123] [Impact Index Per Article: 6.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/13/2022]
Abstract
UNLABELLED The orphan receptor Small Heterodimer Partner (SHP, NROB2) regulates metabolic pathways, including hepatic bile acid, lipid, and glucose homeostasis. We reported that SHP-deletion in leptin-deficient OB(-/-) mice increases insulin sensitivity, and prevents the development of fatty liver. The prevention of steatosis in OB(-/-)/SHP(-/-) double mutants is not due to decreased body weight but is associated with increased hepatic very-low-density lipoprotein (VLDL) secretion and elevated microsomal triglyceride transfer protein (MTP) mRNA and protein levels. SHP represses the transactivation of the MTP promoter and the induction of MTP mRNA by LRH-1 in hepatocytes. Adenoviral overexpression of SHP inhibits MTP activity as well as VLDL-apoB protein secretion, and RNAi knockdown of SHP exhibits opposite effects. The expression of SHP in induced in fatty livers of OB(-/-) mice and other genetic or dietary models of steatosis, and acute overexpression of SHP by adenovirus, result in rapid accumulation of neutral lipids in hepatocytes. In addition, the pathways for hepatic lipid uptake and lipogenic program are also downregulated in OB(-/-)/SHP(-/-) mice, which may contribute to the decreased hepatic lipid content. CONCLUSION These studies demonstrate that SHP regulates the development of fatty liver by modulating hepatic lipid export, uptake, and synthesis, and that the improved peripheral insulin sensitivity in OB(-/-)/SHP(-/-) mice is associated with decreased hepatic steatosis.
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Affiliation(s)
- Jiansheng Huang
- Department of Medicine, University of Kansas Medical Center, Kansas, KS 66160, USA
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41
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Abstract
Liver plays a vital role in the production and catabolism of plasma lipoproteins. It depends on the integrity of cellular function of liver, which ensures homeostasis of lipid and lipoprotein metabolism. When liver cancer occurs these processes are impaired and high-density lipoproteins are changed.
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Affiliation(s)
- Jing-Ting Jiang
- Department of Tumor Biological Treatment, the Third Affiliated Hospital of Suzhou University, Changzhou 213003, Jiangsu Province, China.
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42
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Coenen KR, Gruen ML, Hasty AH. Obesity causes very low density lipoprotein clearance defects in low-density lipoprotein receptor-deficient mice. J Nutr Biochem 2007; 18:727-35. [PMID: 17418556 DOI: 10.1016/j.jnutbio.2006.12.010] [Citation(s) in RCA: 16] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/31/2006] [Revised: 11/20/2006] [Accepted: 12/06/2006] [Indexed: 11/29/2022]
Abstract
We have reported that obese leptin-deficient mice (ob/ob) lacking the low-density lipoprotein receptor (LDLR(-/-)) develop severe hyperlipidemia and spontaneous atherosclerosis. In the present study, we show that obese leptin receptor-deficient mice (db/db) lacking LDLR have a similar phenotype, even in the presence of elevated plasma leptin levels. We investigated the mechanism for the hyperlipidemia in obese LDLR(-/-) mice by comparing lipoprotein production and clearance rates in C57BL/6, ob/ob, LDLR(-/-) and ob/ob;LDLR(-/-) mice. Hepatic triglyceride production rates were equally increased ( approximately 1.4-fold, P<.05) in both LDLR(-/-) and ob/ob;LDLR(-/-) mice compared to C57BL/6 and ob/ob mice. LDL clearance was decreased ( approximately 1.3- fold, P<.01) to a similar extent in LDLR(-/-) and ob/ob;LDLR(-/-) mice compared to C57BL/6 and ob/ob controls. While VLDL clearance was delayed in LDLR(-/-) compared to C57BL/6 and ob/ob mice (2-fold, P<.001), this delay was exaggerated in ob/ob;LDLR(-/-) mice (3.8-fold, P<001). The VLDL clearance defects were due to decreased hepatic uptake compared to C57BL/6 (54% and 26% for LDLR(-/-) and ob/ob;LDLR(-/-), respectively, P<.001). When VLDL was collected from C57BL/6, ob/ob, LDLR(-/-), and ob/ob;LDLR(-/-) donors and injected into LDLR(-/-) recipient mice, counts remaining in the liver were 1.4-fold elevated in mice receiving LDLR(-/-) VLDL and 2-fold increased in mice receiving ob/ob;LDLR(-/-) VLDL compared to controls receiving C57BL/6 VLDL (P<.01). Thus, the increase in plasma lipoproteins in ob/ob;LDLR(-/-) mice is caused by delayed VLDL clearance. This appears to be due to defects in both the liver and the lipoproteins themselves in these obese mice.
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Affiliation(s)
- Kimberly R Coenen
- Department of Molecular Physiology and Biophysics, Vanderbilt University Medical Center, Nashville, TN 37232-0615, USA
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43
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Pagler TA, Golsabahi S, Doringer M, Rhode S, Schütz GJ, Pavelka M, Wadsack C, Gauster M, Lohninger A, Laggner H, Strobl W, Stangl H. A Chinese hamster ovarian cell line imports cholesterol by high density lipoprotein degradation. J Biol Chem 2006; 281:38159-71. [PMID: 17038318 DOI: 10.1074/jbc.m603334200] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Plasma high density lipoprotein (HDL) is inversely associated with the development of atherosclerosis. HDL exerts its atheroprotective role through involvement in reverse cholesterol transport in which HDL is loaded with cholesterol at the periphery and transports its lipid load back to the liver for disposal. In this pathway, HDL is not completely dismantled but only transfers its lipids to the cell. Here we present evidence that a Chinese hamster ovarian cell line (CHO7) adapted to grow in lipoprotein-deficient media degrades HDL and concomitantly internalizes HDL-derived cholesterol. Delivery of HDL cholesterol to the cell was demonstrated by a down-regulation of cholesterol biosynthesis, an increase in total cellular cholesterol content and by stimulation of cholesterol esterification after HDL treatment. This HDL degradation pathway is distinct from the low density lipoprotein (LDL) receptor pathway but also degrades LDL. 25-Hydroxycholesterol, a potent inhibitor of the LDL receptor pathway, down-regulated LDL degradation in CHO7 cells only in part and did not down-regulate HDL degradation. Dextran sulfate released HDL bound to the cell surface of CHO7 cells, and heparin treatment released protein(s) contributing to HDL degradation. The involvement of heparan sulfate proteoglycans and lipases in this HDL degradation was further tested by two inhibitors genistein and tetrahydrolipstatin. Both blocked HDL degradation significantly. Thus, we demonstrate that CHO7 cells degrade HDL and LDL to supply themselves with cholesterol via a novel degradation pathway. Interestingly, HDL degradation with similar properties was also observed in a human placental cell line.
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Affiliation(s)
- Tamara A Pagler
- Center for Physiology and Pathophysiology, Institute of Medical Chemistry, Medical University of Vienna, Währingerstrasse 10, A-1090 Vienna, Austria
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Shetty S, Eckhardt ERM, Post SR, van der Westhuyzen DR. Phosphatidylinositol-3-kinase regulates scavenger receptor class B type I subcellular localization and selective lipid uptake in hepatocytes. Arterioscler Thromb Vasc Biol 2006; 26:2125-31. [PMID: 16794223 DOI: 10.1161/01.atv.0000233335.26362.37] [Citation(s) in RCA: 37] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
Abstract
OBJECTIVE The high-density lipoprotein (HDL) receptor scavenger receptor Class B type I (SR-BI) plays a key role in mediating the final step of reverse cholesterol transport. This study examined the possible regulation of hepatic SR-BI by phosphatidylinositol-3-kinase (PI3K), a well known regulator of endocytosis and membrane protein trafficking. METHODS AND RESULTS SR-BI-dependent HDL selective cholesterol ester uptake in human HepG2 hepatoma cells was decreased (approximately 50%) by the PI3K inhibitors wortmannin and LY294002. Insulin increased selective uptake (approximately 30%), and this increase was blocked by PI3K inhibitors. Changes in SR-BI activity could be accounted for by pronounced changes in the subcellular localization and cell surface expression of SR-BI as determined by HDL cell surface binding, receptor biotinylation studies, and confocal fluorescence microscopy of HepG2 cells expressing green fluorescent protein-tagged SR-BI. Thus, under conditions of PI3K activation by insulin, and to a lesser extent by the SR-BI ligand HDL, cell surface expression of SR-BI was promoted, resulting in increased SR-BI-mediated HDL selective lipid uptake. CONCLUSIONS Our data indicate that PI3K activation stimulates hepatic SR-BI function post-translationally by regulating the subcellular localization of SR-BI in a P13K-dependent manner. Decreased hepatocyte PI3K activity in insulin-resistant states, such as type 2 diabetes, obesity, or metabolic syndrome, may impair reverse cholesterol transport by reducing cell surface expression of SR-BI.
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Affiliation(s)
- Shoba Shetty
- Graduate Center for Nutritional Sciences, University of Kentucky, Lexington, KY, USA
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45
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Sun B, Eckhardt ERM, Shetty S, van der Westhuyzen DR, Webb NR. Quantitative analysis of SR-BI-dependent HDL retroendocytosis in hepatocytes and fibroblasts. J Lipid Res 2006; 47:1700-13. [PMID: 16705213 DOI: 10.1194/jlr.m500450-jlr200] [Citation(s) in RCA: 30] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/31/2023] Open
Abstract
Previous studies have suggested that HDL retroendocytosis may play a role in scavenger receptor class B type I (SR-BI)-dependent selective lipid uptake in a cell-specific manner. To investigate this possibility, we developed methods to quantitatively measure HDL uptake and resecretion in fibroblast (COS-7) and hepatocyte (HepG2) cells expressing exogenous SR-BI. Approximately 17% and 24% of HDL associated in an SR-BI-dependent manner with COS-7 and HepG2 cells, respectively, accumulates intracellularly after a 10 min incubation. To determine whether this intracellular HDL undergoes retroendocytosis, we developed a pulse-chase assay whereby internalized biotinylated (125)I-HDL(3) secreted from cells is quantitatively precipitated from cell supernatants using immobilized streptavidin. Our results show a rapid secretion of a portion of intracellular HDL from both cell types (representing 4-7% of the total cell-associated HDL) that is almost complete within 30 min (half-life approximately 10 min). In COS-7 cells, the calculated rate of HDL secretion ( approximately 0.5 ng HDL/mg/min) was >30-fold slower than the rate of SR-BI-dependent selective cholesteryl ester (CE) uptake ( approximately 17 ng HDL/mg/min), whereas the rate of release of HDL from the cell surface ( approximately 19 ng HDL/mg/min) was similar to the rate of selective CE uptake. Notably, the rate of SR-BI-dependent HDL resecretion in COS-7 and HepG2 cells was similar. BLT1, a compound that inhibits selective CE uptake, does not alter the amount of SR-BI-mediated HDL retroendocytosis in COS-7 cells. From these data, we conclude that HDL retroendocytosis in COS-7 and HepG2 cells is similar and that the vast majority of SR-BI-dependent selective uptake occurs at the cell surface in both cell types.
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Affiliation(s)
- Bing Sun
- Department of Internal Medicine, Graduate Center for Nutritional Sciences, University of Kentucky Medical Center, Lexington, 40536, USA
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46
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Wüstner D. Steady State Analysis and Experimental Validation of a Model for Hepatic High-Density Lipoprotein Transport. Traffic 2006; 7:699-715. [PMID: 16637891 DOI: 10.1111/j.1398-9219.2006.00421.x] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/22/2023]
Abstract
Transport of high-density lipoprotein (HDL) in the hepatocyte plays a fundamental role in reverse cholesterol transport and regulation of plasma HDL levels. On the basis of a recently developed kinetic model, the steady state distribution of HDL was analyzed. Fractional fluorescence of labeled HDL in the basolateral membrane, sorting endosomes (SE), the subapical compartment/ apical recycling compartment, the biliary canaliculus and in late endosomes and lysosomes (LE/LYS) including expected standard deviation is predicted. Improved parameter estimation was obtained by including kinetic data of apical endocytosis of fluorescent markers for LE/LYS, asialoorosomucoid and Rhodamine-dextran, in the regression. Predicted values using the refined kinetic parameters are in good agreement with experimental values of compartmental steady state fluorescence of Alexa488-HDL in polarized hepatic HepG2 cells. From calculated steady state fluxes, it is suggested that export of HDL from basolateral SE is the key step for determining the transport of HDL through the hepatocyte. The analysis provides testable predictions for high-throughput fluorescence microscopy screening experiments on potential inhibitors of hepatic HDL processing. By quantitative fluorescence imaging and model analysis, it is shown that the phosphoinositide kinase inhibitor wortmannin prevents apical transport of fluorescent HDL from basolateral SE. The results support that endosomes of polarized hepatic cells have different sorting functions and that apical endocytosis is an integrative trafficking step in hepatocytes.
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Affiliation(s)
- Daniel Wüstner
- Department of Biochemistry and Molecular Biology, University of Southern Denmark, Campusvej 55, DK-5230, Odense M, Denmark.
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47
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Abstract
Leptin, a 167-amino acid peptide hormone produced by white adipose tissue, is primarily involved in the regulation of food intake and energy expenditure. Leptin receptors are expressed in many tissues including the cardiovascular system. Plasma leptin concentration is proportional to body adiposity and is markedly increased in obese individuals. Recent studies suggest that hyperleptinemia may play an important role in obesity-associated cardiovascular diseases including atherosclerosis. Leptin exerts many potentially atherogenic effects such as induction of endothelial dysfunction, stimulation of inflammatory reaction, oxidative stress, decrease in paraoxonase activity, platelet aggregation, migration, hypertrophy and proliferation of vascular smooth muscle cells. Leptin-deficient and leptin receptor-deficient mice are protected from arterial thrombosis and neointimal hyperplasia in response to arterial wall injury. Several clinical studies have demonstrated that high leptin level predicts acute cardiovascular events, restenosis after coronary angioplasty, and cerebral stroke independently of traditional risk factors. In addition, plasma leptin correlates with markers of subclinical atherosclerosis such as carotid artery intima-media thickness and coronary artery calcifications. Inhibition of leptin signaling may be a promising strategy to slow the progression of atherosclerosis in hyperleptinemic obese subjects.
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Affiliation(s)
- Jerzy Beltowski
- Department of Pathophysiology, Medical University, ul. Jaczewskiego 8, 20-090 Lublin, Poland.
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48
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Harder CJ, Vassiliou G, McBride HM, McPherson R. Hepatic SR-BI-mediated cholesteryl ester selective uptake occurs with unaltered efficiency in the absence of cellular energy. J Lipid Res 2005; 47:492-503. [PMID: 16339112 DOI: 10.1194/jlr.m500444-jlr200] [Citation(s) in RCA: 27] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Scavenger receptor class B type I (SR-BI) plays a critical role in the delivery of HDL cholesterol and cholesteryl esters (CEs) to liver and steroidogenic tissues by a selective process that does not result in significant degradation of HDL protein. Recently, SR-BI-mediated endocytosis and recycling of HDL have been demonstrated. However, it remains unclear whether efficient SR-BI-mediated selective uptake occurs strictly at the plasma membrane or at additional sites along its endocytic itinerary. To examine the requirement for SR-BI endocytosis in HDL selective uptake, we determined the effects of energy depletion on the levels of cell-associated HDL protein and CE in primary mouse hepatocytes. Compared with CHO cells, we observed a much larger energy-dependent effect on CE uptake in primary mouse hepatocytes. Although varying the levels of caveolin-1 and carboxyl ester lipase altered the efficiency of selective uptake, neither was able to account for the energy-dependent component of HDL-CE uptake. Finally, we demonstrate that the hepatocyte-specific, energy-dependent effects on HDL-apolipoprotein A-I and -CE uptake are independent of SR-BI and are not required to achieve efficient SR-BI-mediated selective uptake of CE. Together, these data support the conclusion that neither the intracellular trafficking of HDL nor any energy-dependent cellular process affects the ability of the cell to maximally acquire CE through SR-BI-mediated selective uptake from HDL.
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Affiliation(s)
- Chris J Harder
- Lipoprotein and Atherosclerosis Group, University of Ottawa Heart Institute, Ottawa, Ontario, Canada K1Y 4W7
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Wu MK, Cohen DE. Phosphatidylcholine transfer protein regulates size and hepatic uptake of high-density lipoproteins. Am J Physiol Gastrointest Liver Physiol 2005; 289:G1067-74. [PMID: 16099870 DOI: 10.1152/ajpgi.00194.2005] [Citation(s) in RCA: 14] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/31/2023]
Abstract
Phosphatidylcholine transfer protein (PC-TP) is a steroidogenic acute regulatory-related transfer domain protein that is enriched in liver cytosol and binds phosphatidylcholines with high specificity. In tissue culture systems, PC-TP promotes ATP-binding cassette protein A1-mediated efflux of cholesterol and phosphatidylcholine molecules as nascent pre-beta-high-density lipoprotein (HDL) particles. Here, we explored a role for PC-TP in HDL metabolism in vivo utilizing 8-wk-old male Pctp(-/-) and wild-type littermate C57BL/6J mice that were fed for 7 days with either chow or a high-fat/high-cholesterol diet. In chow-fed mice, neither plasma cholesterol concentrations nor the concentrations and compositions of plasma phospholipids were influenced by PC-TP expression. However, in Pctp(-/-) mice, there was an accumulation of small alpha-migrating HDL particles. This occurred without changes in hepatic expression of ATP-binding cassette protein A1 or in proteins that regulate the intravascular metabolism and clearance of HDL particles. In Pctp(-/-) mice fed the high-fat/high-cholesterol diet, HDL particle sizes were normalized, whereas plasma cholesterol and phospholipid concentrations were increased compared with wild-type mice. In the absence of upregulation of hepatic ATP-binding cassette protein A1, reduced HDL uptake from plasma into livers of Pctp(-/-) mice contributed to higher plasma lipid concentrations. These data indicate that PC-TP is not essential for the enrichment of HDL with phosphatidylcholines but that it does modulate particle size and rates of hepatic clearance.
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Affiliation(s)
- Michele K Wu
- Dept. of Biochemistry, Albert Einstein College of Medicine, Bronx, NY, USA
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de Beer MC, van der Westhuyzen DR, Whitaker NL, Webb NR, de Beer FC. SR-BI-mediated selective lipid uptake segregates apoA-I and apoA-II catabolism. J Lipid Res 2005; 46:2143-50. [PMID: 16061955 DOI: 10.1194/jlr.m500068-jlr200] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
The HDL receptor scavenger receptor class B type I (SR-BI) binds HDL and mediates the selective uptake of cholesteryl ester. We previously showed that remnants, produced when human HDL(2) is catabolized in mice overexpressing SR-BI, become incrementally smaller, ultimately consisting of small alpha-migrating particles, distinct from pre-beta HDL. When mixed with mouse plasma, some remnant particles rapidly increase in size by associating with HDL without the mediation of cholesteryl ester transfer protein, LCAT, or phospholipid transfer protein. Here, we show that processing of HDL(2) by SR-BI-overexpressing mice resulted in the preferential loss of apolipoprotein A-II (apoA-II). Short-term processing generated two distinct, small alpha-migrating particles. One particle (8.0 nm diameter) contained apoA-I and apoA-II; the other particle (7.7 nm diameter) contained only apoA-I. With extensive SR-BI processing, only the 7.7 nm particle remained. Only the 8.0 nm remnants were able to associate with HDL. Compared with HDL(2), this remnant was more readily taken up by the liver than by the kidney. We conclude that SR-BI-generated HDL remnants consist of particles with or without apoA-II and that only those containing apoA-II associate with HDL in an enzyme-independent manner. Extensive SR-BI processing generates small apoA-II-depleted particles unable to reassociate with HDL and readily taken up by the liver. This represents a pathway by which apoA-I and apoA-II catabolism are segregated.
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Affiliation(s)
- Maria C de Beer
- Graduate Center for Nutritional Sciences, University of Kentucky Medical Center, Lexington, KY 40536, USA
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