Organisms require various nutrients to provide energy, support growth, and maintain metabolic balance. Amino acid is among the most basic nutrients, serving as fundamental building blocks for protein synthesis while playing vital roles in growth, development, and reproduction. Understanding the mechanisms by which organisms perceive amino acids is key to unraveling how they select appropriate food sources and adapt to environmental challenges. The fruit fly, Drosophila melanogaster, serves as a powerful model for understanding fundamental genetic and physiological processes. This review focuses on recent advances in amino acid sensing mechanisms in Drosophila melanogaster and their relevance to feeding behavior, nutrient homeostasis, and adaptive responses, and integrates insights into peripheral sensory systems, such as the legs and proboscis, as well as internal regulatory mechanisms within the gut, fat body, and brain. It highlights key molecular players, including ionotropic receptors, gut-derived hormones, neuropeptides, and the microbiome-gut-brain axis. Additionally, the manuscript identifies knowledge gaps and proposes directions for future research, providing a comprehensive overview of this dynamic field.

The neurotransmitter gamma-aminobutyric acid (GABA) has been thought to be involved in the development of some types of cancer. Yet, the de novo synthesis of GABA and how it functions in hepatocellular carcinoma (HCC) remain unclear. Here, we report that SLC6A12 acts as a transporter of GABA, and that aldehyde dehydrogenase 9 family member A1 (ALDH9A1), not glutamate decarboxylase 1 (GAD1), generates GABA in human HCC. Interestingly, SLC6A12 and ALDH9A1 are upregulated during lung metastases of HCC, and depletion of either of them leads to impaired HCC metastasis. Mechanistically, GABA directly binds and stabilizes β-catenin, resulting in activated Wnt/β-catenin signaling, and thereby enhancing HCC metastasis. Reciprocally, β-catenin transcriptionally upregulates SLC6A12 to import more GABA to stabilize β-catenin. Thus, our findings identify ALDH9A1 as the major GABA synthetase in HCC, demonstrate a positive-feedback regulatory mechanism for sustaining Wnt/β-catenin signaling, and reveal a role for β-catenin in sensing GABA, which contributes to HCC metastasis.

Metabolic reprogramming is a hallmark of malignant transformation. While initial studies in the field of cancer metabolism focused on central carbon metabolism, the field has expanded to metabolism beyond glucose and glutamine and uncovered the important role of amino acids in tumorigenesis and tumor immunity as energy sources, signaling molecules, and precursors for (epi)genetic modification. As a result of the development and application of new technologies, a multifaceted picture has emerged, showing that context-dependent heterogeneity in amino acid metabolism exists between tumors and even within distinct regions of solid tumors. Understanding the complexity and flexibility of amino acid metabolism in cancer is critical because it can influence therapeutic responses and predict clinical outcomes. This overview discusses the current findings on the heterogeneity in amino acid metabolism in cancer and how understanding the metabolic diversity of amino acids can be translated into more clinically relevant therapeutic interventions.

Serendipity plays a huge role in science, and having a prepared mind that can seize upon a chance observation or occurrence can drive a project forward. This happened in my lab with a project centered on the regulation of trophoblast cell behavior at implantation. We discovered that amino acids regulate the onset of trophoblast motility through the activation of the kinase complex mTORC1, and that this acts as a checkpoint to trophoblast differentiation. This finding not only broadened our understanding of the mechanisms underlying embryo implantation, but also provided new ways of thinking about the regulation of diapause, a state of suspended embryonic development that occurs in many species. I should say that we re-discovered the fact that amino acids regulate the onset of trophoblast motility, as reading the literature showed us that others had made this same observation some 30 years previously and we were fortuitously able to build upon those findings. This project confirmed to me how valuable it is to read the literature widely, both historical papers and those in fields outside one's area of research, and to go to seminars on topics outside one's area.

Gestational diabetes mellitus (GDM) is a common complication of pregnancy that has short- and long-term adverse effects. Therefore, further exploration of the pathophysiology of GDM and related biomarkers is important. In this study, we performed a systematic review and meta-analysis to investigate the associations between metabolites in blood detected via metabolomics techniques and the risk of GDM and to identify possible biomarkers for predicting the occurrence of GDM. We retrieved case‒control and cohort studies of metabolomics and GDM published in PubMed, Embase, and Web of Science through March 29, 2024; extracted metabolite concentrations, odds ratios (ORs), or relative risks (RRs); and evaluated the integrated results with metabolites per-SD risk estimates and 95% CIs for GDM. We estimated the results via the random effects model and the inverse variance method. Our study is registered in PROSPERO (CRD42024539435). We included a total of 28 case‒control and cohort studies, including 17,370 subjects (4,372 GDM patients and 12,998 non-GDM subjects), and meta-analyzed 67 metabolites. Twenty-five of these metabolites were associated with GDM risk. Some amino acids (isoleucine, leucine, valine, alanine, aspartate, etc.), lipids (C16:0, C18:1n-9, C18:1n-7, lysophosphatidylcholine (LPC) (16:0), LPC (18:0), and palmitoylcarnitine), and carbohydrates and energy metabolites (glucose, pyruvate, lactate, 2-hydroxybutyrate, 3-hydroxybutyrate) were discovered to be associated with increased GDM risk (hazard ratio 1.06-2.77). Glutamine, histidine, C14:0, and sphingomyelin (SM) (34:1) were associated with lower GDM risk (hazard ratio 0.75-0.84). These findings suggest that these metabolites may play essential roles in GDM progression, and serve as biomarkers, contributing to the early diagnosis and prediction of GDM.

Tuberous sclerosis complex (TSC) is an autosomal dominant inherited disease characterized by systemic hamartomas, neuropsychiatric symptoms known as TAND (TSC-associated neuropsychiatric disorders), and vitiligo. These symptoms are attributed to the constant activation of mechanistic target of rapamycin complex 1 (mTORC1) caused by genetic mutations in the causative genes TSC1 or TSC2. The elucidation of the pathogenesis of this disease and advances in diagnostic technologies have led to dramatic changes in the diagnosis and treatment of TSC. Diagnostic criteria have been created at a global level, and mTORC1 inhibitors have emerged as therapeutic agents for this disease. Previously, the treatment strategy was limited to symptomatic treatments such as surgery. Inhibitors of mTORC1 are effective against all symptoms of TSC, but they also have systemic side effects. Therefore, the need for a cross-disciplinary, collaborative medical care system has increased, resulting in the establishment of a practice structure known as the "TSC Board." Furthermore, to reduce the side effects of systemic administration of mTORC1 inhibitors, a topical formulation of mTORC1 inhibitor was developed in Japan for the treatment of skin lesions caused by TSC. This report summarizes the pathogenesis and current status of TSC and the contribution of the Neurocutaneous Syndrome Policy Research Group to the policies of the Ministry of Health, Labor, and Welfare with respect to this rare, intractable disease.

The distinctive colour of brown adipose tissue (BAT) is attributed to its high content of haem-rich mitochondria. However, the mechanisms by which BAT regulates intracellular haem levels remain largely unexplored. Here we demonstrate that haem biosynthesis is the primary source of haem in brown adipocytes. Inhibiting haem biosynthesis results in an accumulation of the branched-chain amino acids (BCAAs) valine and isoleucine, owing to a haem-associated metabolon that channels BCAA-derived carbons into haem biosynthesis. Haem synthesis-deficient brown adipocytes display reduced mitochondrial respiration and lower UCP1 levels than wild-type cells. Although exogenous haem supplementation can restore intracellular haem levels and mitochondrial function, UCP1 downregulation persists. This sustained UCP1 suppression is linked to epigenetic regulation induced by the accumulation of propionyl-CoA, a byproduct of disrupted haem synthesis. Finally, disruption of haem biosynthesis in BAT impairs thermogenic response and, in female but not male mice, hinders the cold-induced clearance of circulating BCAAs in a sex-hormone-dependent manner. These findings establish adipose haem biosynthesis as a key regulator of thermogenesis and sex-dependent BCAA homeostasis.

Diet influences macronutrient availability to cells, and although mechanisms of sensing dietary glucose and amino acids are well characterized, less is known about sensing lipids. We defined a nutrient signaling mechanism involving fatty acid-binding protein 5 (FABP5) and mechanistic target of rapamycin complex 1 (mTORC1) that is activated by the essential polyunsaturated fatty acid (PUFA) ω-6 linoleic acid (LA). FABP5 directly bound to the regulatory-associated protein of mTOR (Raptor) to enhance formation of functional mTORC1 and substrate binding, ultimately converging on increased mTOR signaling and proliferation. The amounts of FABP5 protein were increased in tumors and serum from triple-negative compared with those from receptor-positive breast cancer patients, which highlights its potential role as a biomarker that mediates cellular responses to ω-6 LA intake in this disease subtype.

Pyruvate and branched-chain amino acid (BCAA) metabolism are pivotal pathways in tumor progression, yet the intricate interplay between them and its implications for tumor progression remain elusive. Our research reveals that dihydrolipoamide S-acetyltransferase (DLAT), a pyruvate metabolism enzyme, promotes leucine accumulation and sustains mammalian target of rapamycin (mTOR) complex activation in hepatocellular carcinoma (HCC). Mechanistically, DLAT directly acetylates the K109 residue of AU RNA-binding methylglutaconyl-coenzyme A (CoA) hydratase (AUH), a critical enzyme in leucine catabolism, inhibiting its activity and leading to leucine accumulation. Notably, DLAT upregulation correlates with poor prognosis in patients with HCC. Therefore, we developed an AUHK109R-mRNA lipid nanoparticles (LNPs) therapeutic strategy, which effectively inhibits tumor growth by restoring leucine catabolism and inhibiting mTOR activation in vivo. In summary, our findings uncover DLAT's unexpected role as an acetyltransferase for AUH, suppressing leucine catabolism. Restoring leucine catabolism with AUHK109R-mRNA LNP effectively inhibits HCC development, highlighting a novel direction for cancer research.

Metabolic dysregulation and altered metabolite concentrations are widely recognized as key characteristics of aging. Comprehensive exploration of endogenous metabolites that drive aging remains insufficient. Here, we conducted an untargeted metabolomics analysis of aging mice, revealing citrulline as a consistently down-regulated metabolite associated with aging. Systematic investigations demonstrated that citrulline exhibited antiaging effects by reducing cellular senescence, protecting against DNA damage, preventing cell cycle arrest, modulating macrophage metabolism, and mitigating inflammaging. Long-term citrulline supplementation in aged mice yielded beneficial effects and ameliorated age-associated phenotypes. We further elucidated that citrulline acts as an endogenous metabolite antagonist to inflammation, suppressing proinflammatory responses in macrophages. Mechanistically, citrulline served as a potential inhibitor of mammalian target of rapamycin (mTOR) activation in macrophage and regulated the mTOR-hypoxia-inducible factor 1α-glycolysis signaling pathway to counter inflammation and aging. These findings underscore the significance of citrulline deficiency as a driver of aging, highlighting citrulline supplementation as a promising therapeutic intervention to counteract aging-related changes.

Amino acid transporters are essential for supplying nutrients to cells and are implicated in tumor progression. L-type amino acid transporter 1 (LAT1) is reported to be overexpressed in various cancers, affecting tumor development. However, the exact mechanisms by which LAT1 affects colorectal cancer (CRC) arising from a chronic inflammatory background are not yet fully understood. This study aimed to explore the role of LAT1 in CRC. Mice with intestinal epithelium-specific deletions of LAT1 (LAT1fl/fl; vil-cre) were treated with azoxymethane (AOM)/dextran sulfate sodium (DSS) in a colitis-associated cancer (CAC) model. Our results demonstrated that LAT1 was detected in normal colon crypts and highly expressed in AOM/DSS-induced tumor tissue. During the chronic colitis phase, weight loss was more prominent in LAT1fl/fl; vil-cre mice, compared with that in LAT1fl/fl mice. IL-1β and IL-6 expressions significantly increased in LAT1-deleted tumors; however, no overall difference in colon tumor number or size was observed between LAT1fl/fl and LAT1fl/fl; vil-cre mice. Accordingly, cell proliferation and apoptotic cell number were similar when comparing LAT1-deleted tumors with those with sufficient LAT1. Our findings indicated that LAT1 might not phenotypically affect overall colonic tumor development in this model; however, it affected the chronic colitis phase and inflammatory status within the tumors. These findings suggest that severe inflammation in tumors might have compensated for tumor growth in defects of amino acid supplementation through LAT1 deficiency, and provide insights into the potential of LAT1-targeted therapies for clinical CRC treatment.

L-arginine is the most nitrogen-rich amino acid, acting as a key precursor for the synthesis of nitrogen-containing metabolites and an essential intermediate in the clearance of excess nitrogen. Arginine's side chain possesses a guanidino group which has unique biochemical properties, and plays a primary role in nitrogen excretion (urea), cellular signaling (nitric oxide) and energy buffering (phosphocreatine). The post-translational modification of protein-incorporated arginine by guanidino-group methylation also contributes to epigenetic gene control. Most human cells do not synthesize sufficient arginine to meet demand and are dependent on exogenous arginine. Thus, dietary arginine plays an important role in maintaining health, particularly upon physiologic stress. How cells adapt to changes in extracellular arginine availability is unclear, mostly because nearly all tissue culture media are supplemented with supraphysiologic levels of arginine. Evidence is emerging that arginine-deficiency can influence disease progression. Here, we review new insights into the importance of arginine as a metabolite, emphasizing the central role of mitochondria in arginine synthesis/catabolism and the recent discovery that arginine can act as a signaling molecule regulating gene expression and organelle dynamics.

Sestrin1 and Sestrin2 (SESN1&2) are evolutionarily conserved, stress-responsive proteins that regulate cell growth and viability. The primary target of Sestrins is the mTORC1 protein kinase, an activator of anabolic processes and an autophagy inhibitor. Our previous studies showed that inactivating SESN1&2 in lung adenocarcinoma A549 cells accelerates cell proliferation and confers resistance to cell death without affecting mTORC1 activity, suggesting that SESN1&2 modulate cellular processes via mTORC1-independent mechanisms. This work describes a new mechanism through which SESN1&2 regulate cell proliferation and death by suppressing the STAT3 transcription factor. Normally activated in response to stress and inflammation, STAT3 is frequently overactivated in human cancers. This overactivation promotes the expression of pro-proliferative and anti-apoptotic genes that drive carcinogenesis. We demonstrate that SESN1&2 inactivation stimulates STAT3 by downregulating the PTPRD phosphatase, a protein responsible for STAT3 dephosphorylation. Our study demonstrates that SESN1&2 deficiency may cause STAT3 activation and facilitate carcinogenesis and drug resistance, making SESN1&2 reactivation a potential cancer treatment strategy.

To investigate the relationship between circulating branched-chain amino acids (BCAAs) and the risk of major adverse cardiovascular events (MACE) in a national population-based cohort study.

UK Biobank, a prospective study involving 22 recruitment centers across the United Kingdom. For this analysis, we included 266,840 participants from the UK Biobank who had available BCAA data and no history of MACE at baseline. Cox regression analysis was conducted to evaluate these associations, adjusting for potential confounders.

During a 13.80 ± 0.83-year follow-up, 52,598 participants experienced MACE, with the incidence of MACE increasing progressively across quintiles of circulating BCAAs, isoleucine, leucine, and valine. Overall, the fifth quintile exhibited a 7-12% higher MACE risk compared to the second quintile. In males, BCAAs were not associated with MACE risk. However, increased risks were observed for isoleucine (8-12% in higher quintiles), leucine (9% in the first quintile and 6% in the fifth quintile), and valine (8% in the first quintile). In females, higher quintiles of BCAAs, isoleucine, leucine, and valine were associated with increased MACE risk, ranging from 9% to 12%. Among participants under 65y, higher quintiles of BCAAs, isoleucine, and leucine were associated with increased MACE risk, while valine showed no significant association. No association was found in participants aged 65 and older. These analyses were adjusted for multiple potential confounders.

Generally, higher levels of BCAAs, isoleucine, leucine, and valine were associated with an increased risk of MACE, except in participants older than 65. Additionally, in males, the lowest quintiles of leucine and valine were also associated with an increased risk of MACE.

Autophagy is a lysosome-dependent cellular degradation pathway that responds to a variety of environmental and cellular stresses, which is defective in aging and age-related diseases, therefore, targeting autophagy with small-molecule activators has potential therapeutic benefits. In this study, we successfully completed the first total synthesis of Ivesinol, an identified antibacterial natural product, and efficiently constructed a library of its analogs. To measure the effect of Ivesinol analogs on autophagic activity, we performed cell imaging-based screening approach, and observed that several Ivesinol analogs exhibited potent autophagy-regulating activity. Specifically, the derivative B2 significantly activated autophagy activity in concentration- and time-dependent manners, and even outperformed the commonly used activator Torin1 in activating autophagy in MCF-7 cells at 0.5 μM. Bioinformatics analysis showed that B2 treatment significantly impacted ubiquitin mediated proteolysis and AMPK signaling pathway, with functionally related gene sets displaying strong correlations. Based on these findings, we proposed that B2 activates autophagy by mechanisms involved in downregulation of key HSP70 family members, activation of the UPR, and ultimately leading to autophagy. In conclusion, we suggest that B2 could be a promising and valuable autophagy activator with significant potential for further development.

Serine metabolism provides important metabolic intermediates that support the rapid proliferation of tumor cells. However, the role of serine metabolism in esophageal squamous cell carcinoma (ESCC) and the underlying mechanism remains unclear. Here, we show that serine starvation predominantly inhibits ESCC cell proliferation by suppressing purine nucleotides and NADPH synthesis. Mechanistically, serine depletion led to the accumulation of aminoimidazole carboxamide ribonucleoside (AICAR), an intermediate metabolite of de novo purine synthesis, and AMP/ATP ratio. These increases activated 5'-AMP-activated kinase (AMPK), which subsequently inhibited the mTORC1 pathway by phosphorylating Raptor at Ser792. Moreover, serine depletion decreased NADPH level followed by elevated reactive oxygen species (ROS) production and DNA damage, which induced p53-p21 mediated G1 phase cell cycle arrest. Conversely, serine starvation activated transcription factor 4 (ATF4)-mediated robust expression of phosphoserine aminotransferase 1 (PSAT1) which in turn promoted compensatory endogenous serine synthesis, thus maintaining ESCC cell survival under serine-limited conditions. Accordingly, serine deprivation combined with PSAT1 inhibition significantly suppressed ESCC tumor growth both in vitro and in vivo. Taken together, our findings demonstrate that serine starvation suppresses the proliferation of ESCC cells by disturbing the synthesis of purine nucleotides and NADPH, and the combination of serine deprivation and PSAT1 inhibition significantly impairs ESCC tumor growth. Our study provides a theoretical basis for targeting serine metabolism as a potential therapeutic strategy for ESCC.

Amino acids are pivotal regulators of immune cell metabolism, signaling pathways, and gene expression. In myeloid cells, these processes underlie their functional plasticity, enabling shifts between pro-inflammatory, anti-inflammatory, pro-tumor, and anti-tumor activities. Within the tumor microenvironment, amino acid metabolism plays a crucial role in mediating the immunosuppressive functions of myeloid cells, contributing to tumor progression. This review delves into the mechanisms by which specific amino acids-glutamine, serine, arginine, and tryptophan-regulate myeloid cell function and polarization. Furthermore, we explore the therapeutic potential of targeting amino acid metabolism to enhance anti-tumor immunity, offering insights into novel strategies for cancer treatment.

Propionate metabolism dysregulation has emerged as a source of metabolic health alterations linked to aging, cardiovascular and renal diseases, obesity and diabetes, and cancer. This is supported by several large cohort population studies and recent work revealing its role in cancer progression. Mutations in several enzymes of this metabolic pathway are associated with devastating inborn errors of metabolism, resulting in severe methylmalonic and propionic acidemias. Beyond these rare diseases, however, the broader pathological significance of propionate metabolism and its metabolites has been largely overlooked. Here, we summarize earlier studies and new evidence that the alteration of this pathway and associated metabolites are involved in the development of various metabolic diseases and link aging to cancer progression and metastasis.

This study aimed to investigate branched-chain amino acid (BCAA) catabolism in diabetic retinopathy (DR).

Wild-type and db/db mice were fed BCAAs (5 or 10 mg/kg/day) for 12 weeks, and hyperglycemia-exposed Müller cells were treated with BCAAs (2 or 5 mmol/L) for 24 and 48 h. BCAA levels were measured using MS/MS. Western blotting was performed to detect proteins. Flow cytometry, oxygen consumption rate, and Cell Counting Kit-8 assays were used to evaluate Müller cell viability. Each experiment was conducted at least thrice.

BCAAs and branched-chain α-keto acids (BCKAs) were increased in the retina and systemic tissues of diabetic mice, and these changes were further enhanced to approximately 2-fold by extra BCAAs compared to wild-type group. In vitro, BCAAs and BCKAs were induced in hyperglycemic Müller cells, and augmented by BCAA supplementation. The aberrant BCAA catabolism was accompanied by mTORC1 activation and subsequently induced TNF-ɑ, VEGFA, GS, and GFAP in retinas and Müller cells under diabetic conditions. The cell apoptosis rate increased by approximately 50%, and mitochondrial respiration was inhibited by hyperglycemia and BCAA in Müller cells. Additionally, mTORC1 signaling was activated by leucine in Müller cells. Knockdown of Sestrin2 or LeuRS significantly abolished the leucine-induced mTORC1 phosphorylation and protected Müller cell viability under diabetic conditions.

We found that BCAA catabolism is hindered in DR through mTORC1 activation. Leucine plays a key role in inducing mTORC1 by sensing Sestrin2 in Müller cells. Targeting Sestrin2 may ameliorate the toxic effects of BCAA accumulation on Müller cells in DR.

Branched-chain amino acids (BCAAs), including leucine, isoleucine, and valine, are essential for maintaining physiological functions and metabolic homeostasis. However, chronic elevation of BCAAs causes metabolic diseases such as obesity, type 2 diabetes (T2D), and metabolic-associated fatty liver disease (MAFLD). Adipose tissue, skeletal muscle, and the liver are the three major metabolic tissues not only responsible for controlling glucose, lipid, and energy balance but also for maintaining BCAA homeostasis. Under obese and diabetic conditions, different pathogenic factors like pro-inflammatory cytokines, lipotoxicity, and reduction of adiponectin and peroxisome proliferator-activated receptors γ (PPARγ) disrupt BCAA metabolism, leading to excessive accumulation of BCAAs and their downstream metabolites in metabolic tissues and circulation. Mechanistically, BCAAs and/or their downstream metabolites, such as branched-chain ketoacids (BCKAs) and 3-hydroxyisobutyrate (3-HIB), impair insulin signaling, inhibit adipogenesis, induce inflammatory responses, and cause lipotoxicity in the metabolic tissues, resulting in multiple metabolic disorders. In this review, we summarize the latest studies on the metabolic regulation of BCAA homeostasis by the three major metabolic tissues-adipose tissue, skeletal muscle, and liver-and how dysregulated BCAA metabolism affects glucose, lipid, and energy balance in these active metabolic tissues. We also summarize therapeutic approaches to restore normal BCAA metabolism as a treatment for metabolic diseases.

Pheochromocytoma/paraganglioma (PGPG) is a rare neuroendocrine tumor. Amino acid metabolism is crucial for energy production, redox balance, and metabolic pathways in tumor cell proliferation. This study aimed to build a risk model using amino acid metabolism-related genes, enhancing PGPG diagnosis and treatment decisions. We analyzed RNA-sequencing data from the PCPG cohort in the GEO dataset as our training set and validated our findings using the TCGA dataset and an additional clinical cohort. WGCNA and LASSO were utilized to identify hub genes and develop risk prediction models. The single-sample gene set enrichment analysis, MCPCOUNTER, and ESTIMATE algorithm calculated the relationship between amino acid metabolism and immune cell infiltration in PCPG. The TIDE algorithm predicted the immunotherapy efficacy for PCPG patients. The analysis identified 292 genes with differential expression, which are involved in amino acid metabolism and immune pathways. Six genes (DDC, SYT11, GCLM, PSMB7, TYRO3, AGMAT) were identified as crucial for the risk prediction model. Patients with a high-risk profile demonstrated reduced immune infiltration but potentially higher benefits from immunotherapy. Notably, DDC and SYT11 showed strong diagnostic and prognostic potential. Validation through quantitative Real-Time Polymerase Chain Reaction and immunohistochemistry confirmed their differential expression, underscoring their significance in PCPG diagnosis and in predicting immunotherapy response. This study's integration of amino acid metabolism-related genes into a risk prediction model offers critical clinical insights for PCPG risk stratification, potential immunotherapy responses, drug development, and treatment planning, marking a significant step forward in the management of this complex condition.

Prostate cancer is one of the most common malignancies affecting men worldwide and a leading cause of cancer-related mortality, necessitating a deeper understanding of its underlying biochemical pathways. Similar to other cancer types, prostate cancer is also characterised by aberrantly activated metabolic pathways that support tumour development, such as amino acid metabolism, which is involved in modulating key physiological and pathological cellular processes during the progression of this disease. The metabolism of several amino acids, such as glutamine and methionine, crucial for tumorigenesis, is dysregulated and commonly discussed in prostate cancer. And the roles of some less studied amino acids, such as histidine and glycine, have also been covered in prostate cancer studies. Aberrant regulation of two major signalling pathways, mechanistic target of rapamycin (mTOR) and general amino acid control non-depressible 2 (GCN2), is a key driver of reshaping the amino acid metabolism landscape in prostate cancer. By summarising our current understanding of how amino acid metabolism is modulated in prostate cancer, here, we provide further insights into certain potential therapeutic targets for managing prostate cancer through metabolic interventions.

The mechanistic target of rapamycin (mTOR) pathway senses and integrates various environmental and intracellular cues to regulate cell growth and proliferation. As a key conductor of the balance between anabolic and catabolic processes, mTOR complex 1 (mTORC1) orchestrates the symphonic regulation of glycolysis, nucleic acid and lipid metabolism, protein translation and degradation, and gene expression. Dysregulation of the mTOR pathway is linked to numerous human diseases, including cancer, neurodegenerative disorders, obesity, diabetes, and aging. This review provides an in-depth understanding of how nutrients and growth signals are coordinated to influence mTOR signaling and the extensive metabolic rewiring under its command. Additionally, we discuss the use of mTORC1 inhibitors in various aging-associated metabolic diseases and the current and future potential for targeting mTOR in clinical settings. By deciphering the complex landscape of mTORC1 signaling, this review aims to inform novel therapeutic strategies and provide a road map for future research endeavors in this dynamic and rapidly evolving field.

Neoadjuvant chemotherapy (NACT) is the standard-of-care treatment for patients with locally advanced breast cancer (LABC), providing crucial benefits in tumor downstaging. Clinical parameters, such as molecular subtypes, influence the therapeutic impact of NACT. Moreover, severe adverse events delay the treatment process and reduce the effectiveness of therapy. Although metabolic changes during cancer treatment are crucial determinant factors in therapeutic responses and toxicities, related clinical research remains limited.

One hundred paired blood samples were collected from 50 patients with LABC before and after a complete NACT treatment cycle. Untargeted metabolomics was used by liquid chromatography-mass spectrometry (LC-MS) to investigate the relationship between dynamically changing metabolites in serum and the responses and toxicities of NACT.

Firstly, we observed significant alterations in serum metabolite levels pre- and post-NACT, with a predominant enrichment in the sphingolipid and amino acid metabolism pathways. Second, pre-treatment serum metabolites successfully predicted the therapeutic response and hematotoxicities during NACT. In particular, molecular subtype variations in favorable treatment responses are linked to acyl carnitine levels. Finally, we discovered that the therapeutic effects of NACT could be attributed to essential amino acid metabolism.

This study elucidated the dynamic changes in metabolism during NACT treatment, providing a possibility for developing responsive metabolic signatures for personalized NACT treatment.

As an essential branched amino acid, valine is pivotal for protein synthesis, neurological behaviour, haematopoiesis and leukaemia progression1-3. However, the mechanism by which cellular valine abundancy is sensed for subsequent cellular functions remains undefined. Here we identify that human histone deacetylase 6 (HDAC6) serves as a valine sensor by directly binding valine through a primate-specific SE14 repeat domain. The nucleus and cytoplasm shuttling of human, but not mouse, HDAC6 is tightly controlled by the intracellular levels of valine. Valine deprivation leads to HDAC6 retention in the nucleus and induces DNA damage. Mechanistically, nuclear-localized HDAC6 binds and deacetylates ten-eleven translocation 2 (TET2) to initiate active DNA demethylation, which promotes DNA damage through thymine DNA glycosylase-driven excision. Dietary valine restriction inhibits tumour growth in xenograft and patient-derived xenograft models, and enhances the therapeutic efficacy of PARP inhibitors. Collectively, our study identifies human HDAC6 as a valine sensor that mediates active DNA demethylation and DNA damage in response to valine deprivation, and highlights the potential of dietary valine restriction for cancer treatment.

Cells contain dedicated mechanisms to sense nutrient levels in the environment to regulate their growth by balancing anabolism and catabolism [1, 2]. The mechanistic Target of Rapamycin Complex 1 (mTORC1), a multi-protein kinase complex, serves as an essential growth regulator that integrates various upstream inputs including growth factors and nutrients like amino acids [1, 2] Nutrient sensors upstream of mTORC1 directly bind cognate nutrient ligands to convey their availability and thereby regulate mTORC1 signaling [1, 2]. A reliable method is needed to quantitatively determine the binding affinity (Kd) of the nutrient sensor to its ligand. In parallel, quantitative metabolomic analysis can reveal metabolite levels in fed and starved cells; which represent the physiological range of the nutrient of interest. Whether or not the binding affinity is within the physiological range serves as an indicator to determine the physiological relevance of the sensing mechanism. This chapter describes a generalizable protocol that allows reproducible determination of nutrient ligand-nutrient sensor binding affinity. Here, the S-adenosylmethionine (nutrient ligand)-SAMTOR (nutrient sensor) pair is used as an example [3]. Nutrient sensor purification, radioactive nutrient ligand incubation, and eventual scintillation counting are included, along with a description of the mathematical equation that is used to calculate the binding affinity.

Acute kidney injury (AKI) is a major risk factor for chronic kidney disease (CKD), and there are currently no therapies for AKI. Proximal tubules (PTs) are particularly susceptible to AKI, due to nephrotoxins such as aristolochic acid I (AAI). Normal PTs use fatty acid oxidation and branched chain amino acid (BCAA; valine, leucine, and isoleucine) catabolism to generate ATP; however, in AKI, these pathways are downregulated. Our aim was to investigate the utility of a pharmacological activator of BCAA catabolism, BT2, in preventing nephrotoxic AKI. Mice were administered two injections of AAI 3 days apart to induce AKI, with or without daily BT2 treatment. Mice treated with BT2 had significantly protected kidney function (reduced serum creatinine and urea nitrogen), reduced histological injury, preservation of PT (Lotus lectin staining), and less PT injury (cytokeratin-20 staining) and inflammatory gene expression compared with mice with AAI alone. Mice with AKI had increased circulating BCAA and accumulation of BCAA in the kidney cortex. Leucine is a potent activator of the mechanistic target of rapamycin complex 1 (mTORC1) signaling, and mTORC1 signaling was activated in mice treated with AAI. However, BT2 reduced kidney cortical BCAA accumulation and attenuated the mTORC1 signaling. In vitro, injured primary PT cells had compromised mitochondrial bioenergetics, but cells treated with AAI + BT2 had partially restored mitochondrial bioenergetics and improved injury markers compared with cells treated with AAI alone. Thus, pharmacological activation of BCAA catabolism using BT2 attenuated nephrotoxic AKI in mice.NEW & NOTEWORTHY This study explored the effects of pharmacological activation of branched chain amino acid (BCAA) catabolism using BT2 to prevent nephrotoxic acute kidney injury (AKI) in mice. Our results indicate that activation of BCAA catabolism protects against nephrotoxic AKI, in association with reduced BCAA accumulation, reduced mammalian target of rapamycin protein complex 1 signaling, and improved mitochondrial bioenergetics.

Leucine, isoleucine, and valine are collectively known as branched chain amino acids (BCAAs) and are often discussed in the same physiological and pathological situations. The two consecutive initial reactions of BCAA catabolism are catalyzed by the common enzymes referred to as branched chain aminotransferase (BCAT) and branched chain α-keto acid dehydrogenase (BCKDH). BCAT transfers the amino group of BCAAs to 2-ketoglutarate, which results in corresponding branched chain 2-keto acids (BCKAs) and glutamate. BCKDH performs an oxidative decarboxylation of BCKAs, which produces their coenzyme A-conjugates and NADH. BCAT2 in skeletal muscle dominantly catalyzes the transamination of BCAAs. Low BCAT activity in the liver reduces the metabolization of BCAAs, but the abundant presence of BCKDH promotes the metabolism of muscle-derived BCKAs, which leads to the production of glucose and ketone bodies. While mutations in the genes responsible for BCAA catabolism are involved in rare inherited disorders, an aberrant regulation of their enzymatic activities is associated with major metabolic disorders such as diabetes, cardiovascular disease, and cancer. Therefore, an understanding of the regulatory process of metabolic enzymes, as well as the functions of the BCAAs and their metabolites, make a significant contribution to our health.

Esophageal squamous cell carcinoma (ESCC) remains a significant challenge in oncology due to its aggressive nature and heterogeneity. As one of the deadliest malignancies, ESCC research lags behind other cancer types. The balance between ubiquitination and deubiquitination processes plays a crucial role in cellular functions, with its disruption linked to various diseases, including cancer.

Our study utilized diverse analytical approaches, encompassing Cox regression models, single-cell RNA sequencing, intercellular communication analysis, and Gene Ontology enrichment. We also conducted mutation profiling and explored potential immunotherapeutic agents. Furthermore, in vitro cellular experiments and in vivo mouse models were performed to validate findings. These methodologies aimed to establish deubiquitination-related gene signatures (DRGS) for predicting ESCC patient outcomes and response to immunotherapy.

By integrating datasets from TCGA-ESCC and GSE53624, we developed a DRGS model based on 14 deubiquitination-related genes (DUBGs). This signature effectively forecasts ESCC prognosis, drug responsiveness, and immune cell infiltration patterns. It also influences the mutational landscape of patients. Those classified as high-risk exhibited reduced survival rates, increased genetic alterations, and more complex cellular interactions, potentially explaining their poor outcomes. Notably, in vitro and in vivo experiments identified MTOR, a key component of the signature, as a promising therapeutic target for ESCC treatment.

Our research highlights the significance of 14 DUBGs in ESCC progression. The risk score derived from this gene set enables clinical stratification of patients into distinct prognostic groups. Moreover, MTOR emerges as a potential target for personalized ESCC therapy, offering new avenues for treatment strategies.

Metabolic reprogramming is a crucial characteristic of cancer, allowing cancer cells to acquire metabolic properties that support their survival, immune evasion, and uncontrolled proliferation. Consequently, targeting cancer metabolism has become an essential therapeutic strategy. Abnormal amino acid metabolism is not only a key aspect of metabolic reprogramming but also plays a significant role in chemotherapy resistance and immune evasion, particularly in leukemia. Changes in amino acid metabolism in tumor cells are typically driven by a combination of signaling pathways and transcription factors. Current approaches to targeting amino acid metabolism in leukemia include inhibiting amino acid transporters, blocking amino acid biosynthesis, and depleting specific amino acids to induce apoptosis in leukemic cells. Different types of leukemic cells rely on the exogenous supply of specific amino acids, such as asparagine, glutamine, arginine, and tryptophan. Therefore, disrupting the supply of these amino acids may represent a vulnerability in leukemia. This review focuses on the pivotal role of amino acids in leukemia metabolism, their impact on leukemic stem cells, and their therapeutic potential.

Messenger RNA (mRNA) translation is a tightly controlled process frequently deregulated in cancer. Key to this deregulation are transfer RNAs (tRNAs), whose expression, processing and post-transcriptional modifications are often altered in cancer to support cellular transformation. In conditions of limiting levels of amino acids, this deregulated control of protein synthesis leads to aberrant protein production in the form of ribosomal frameshifting or misincorporation of non-cognate amino acids. Here, we studied leucine, an essential amino acid coded by six different codons. Surprisingly, we found that leucine deprivation leads to ribosomal stalling and aberrant protein production in various cancer cell types, predominantly at one codon, UUA. Similar effects were observed after treatment with chemotherapeutic agents, implying a shared mechanism controlling the downstream effects on mRNA translation. In both conditions, a limitation in the availability of tRNALeu(UAA) for protein production was shown to be the cause for this dominant effect on UUA codons. The induced aberrant proteins can be processed and immune-presented as neoepitopes and can direct T-cell killing. Altogether, we uncovered a novel mode of interplay between DNA damage, regulation of tRNA availability for mRNA translation and aberrant protein production in cancer that could be exploited for anti-cancer therapy.

Ethanol is one of the most common teratogens and causes of human developmental disabilities. Fetal alcohol spectrum disorders (FASD), which describes the wide range of deficits due to prenatal ethanol exposure, are estimated to affect between 1.1 % and 5.0 % of births in the United States. Ethanol dysregulates numerous cellular mechanisms such as programmed cell death (apoptosis), protein synthesis, autophagy, and various aspects of cell signaling, all of which contribute to FASD. The mechanistic target of rapamycin (mTOR) regulates these cellular mechanisms via sensing of nutrients like amino acids and glucose, DNA damage, and growth factor signaling. Despite an extensive literature on ethanol teratogenesis and mTOR signaling, there has been less attention paid to their interaction. Here, we discuss the impact of ethanol teratogenesis on mTORC1's ability to coordinate growth factor and amino acid sensing with protein synthesis, autophagy, and apoptosis. Notably, the effect of ethanol exposure on mTOR signaling depends on the timing and dose of ethanol as well as the system studied. Overall, the overlap between the functions of mTORC1 and the phenotypes observed in FASD suggest a mechanistic interaction. However, more work is required to fully understand the impact of ethanol teratogenesis on mTOR signaling.

Dietary protein quality can be assessed by skeletal muscle protein synthesis (MPS) stimulation. Limited knowledge exists on how consuming isonitrogenous meals with varied protein qualities affects postprandial and 24-h MPS.

We assessed the effects of protein quality and complementary proteins on MPS. We hypothesized that meals containing a moderate amount of high-quality, complete protein would stimulate postprandial and 24-h MPS. Meals containing two complementary, plant-based incomplete proteins would stimulate MPS less, and meals containing plant-based incomplete proteins at each meal, but complementary over 24 h would not stimulate MPS.

This quasi-experimental study included a randomized, crossover design to assess protein quality and a nonrandomized low-protein control. We measured postprandial and 24-h MPS responses of healthy middle-aged women (n = 9, age 56 ± 4 y), to 3 dietary conditions: isonitrogenous meals containing 23 g protein/meal from 1) complete protein (lean beef), 2) 2 incomplete, but complementary protein sources (navy/black beans and whole wheat bread), and 3) single incomplete protein sources (black beans or whole wheat bread at 1 meal), but providing a complete amino acid profile over 24 h. In the low-protein group women (n = 8, 54 ± 5 y) consumed a single breakfast meal containing 5 g of protein. Venous blood and vastus lateralis samples were obtained during primed, constant infusions of L-[ring-13C6]phenylalanine to measure mixed muscle fractional synthetic rates (FSR).

Meals containing complete, complementary, or incomplete proteins did not differentially influence FSR responses after breakfast (P = 0.90) or 24 h (P = 0.38). At breakfast, the complete (P = 0.030) and complementary (P = 0.031) protein meals, but not the incomplete protein meal (P = 0.38), had greater FSR responses compared with the low-protein control meal.

Isonitrogenous meals containing a moderate serving of total protein from foods providing complete, complementary, or incomplete essential amino acid profiles do not differentially stimulate muscle protein synthesis after a meal and daily.

This clinical trial was registered at clinicaltrials.gov as NCT03816579. URL: https://www.

gov/ct2/show/NCT03816579?term=NCT03816579&draw=2&rank=1.

Macrophages are essential for the development of steatosis, hepatic inflammation, and fibrosis in metabolic dysfunction-associated steatohepatitis(MASH). However, the roles of macrophage E2F2 in the progression of MASH have not been elucidated. This study reveals that the expression of macrophage E2F2 is dramatically downregulated in MASH livers from mice and humans, and that this expression is adversely correlated with the severity of the disease. Myeloid-specific E2F2 depletion aggravates intrahepatic inflammation, hepatic stellate cell activation, and hepatocyte lipid accumulation during MASH progression. Mechanistically, E2F2 can inhibit the SLC7A5 transcription directly. E2F2 deficiency upregulates the expression of SLC7A5 to mediate amino acids flux, resulting in enhanced glycolysis, impaired mitochondrial function, and increased macrophages proinflammatory response in a Leu-mTORC1-dependent manner. Moreover, bioinformatics analysis and CUT &Tag assay identify the direct binding of Nrf2 to E2F2 promoter to promote its transcription and nuclear translocation. Genetic or pharmacological activation of Nrf2 effectively activates E2F2 to attenuate the MASH progression. Finally, patients treated with CDK4/6 inhibitors demonstrate reduced E2F2 activity but increased SLC7A5 activity in PBMCs. These findings indicated macrophage E2F2 suppresses MASH progression by reprogramming amino acid metabolism via SLC7A5- Leu-mTORC1 signaling pathway. Activating E2F2 holds promise as a therapeutic strategy for MASH.

Branched-chain amino acids (BCAA: leucine, isoleucine and valine) are three of the nine indispensable amino acids, and are frequently consumed as a dietary supplement by athletes and recreationally active individuals alike. The popularity of BCAA supplements is largely predicated on the notion that they can stimulate rates of muscle protein synthesis (MPS) and suppress rates of muscle protein breakdown (MPB), the combination of which promotes a net anabolic response in skeletal muscle. To date, several studies have shown that BCAA (particularly leucine) increase the phosphorylation status of key proteins within the mechanistic target of rapamycin (mTOR) signalling pathway involved in the regulation of translation initiation in human muscle. Early research in humans demonstrated that BCAA provision reduced indices of whole-body protein breakdown and MPB; however, there was no stimulatory effect of BCAA on MPS. In contrast, recent work has demonstrated that BCAA intake can stimulate postprandial MPS rates at rest and can further increase MPS rates during recovery after a bout of resistance exercise. The purpose of this evidence-based narrative review is to critically appraise the available research pertaining to studies examining the effects of BCAA on MPS, MPB and associated molecular signalling responses in humans. Overall, BCAA can activate molecular pathways that regulate translation initiation, reduce indices of whole-body and MPB, and transiently stimulate MPS rates. However, the stimulatory effect of BCAA on MPS rates is less than the response observed following ingestion of a complete protein source providing the full complement of indispensable amino acids.

The study aimed to investigate whether serum IL-1β, FoxO1and Sesn2 concentrations differed between threatened preterm labor (TPL) and uncomplicated pregnancies. This study was conducted on 54 women with TPL pregnancies and 26 healthy pregnant women. The TPL group was further divided into two subgroups according to the gestational age at delivery. Patients who gave birth within 48-72 hours after the hospitalization were referred to as preterm delivery (PD) and those who gave birth at ≥37 weeks were referred to as term delivery (TD). Maternal levels of serum IL-1β, FoxO1 and Sesn2 were measured with the use of enzyme-linked immunosorbent assay kits. The mean maternal serum IL-1β and FoxO1 of PD were significantly higher than TD (p<.000*) and the control group (p < .000*). The mean maternal serum IL-1β, FoxO1 level of TD was significantly higher than the control group (p<.000*). The mean maternal serum Sesn2 levels of TD and the control group were significantly higher than the preterm group (p<.000*). The mean maternal serum Sesn2 level of the control group was significantly higher than the TD group (p <.000*). A negative correlation was found between serum concentration of serum IL-1β, and FoxO1 with the gestational week of delivery (r= -0.722, p< .000*for, IL-1β; r = -0.625, p < .000* for FoxO1). A positive correlation was found between the serum concentration of serum Sesn2 with the gestational week of delivery (r = 0.507, p<.000* for sesn2). High serum IL-1β, FoxO1 levels, and low Sesn2 levels may have the potential to be used as biomarkers for the differentiation of PD and TD.