Helicobacter pylori infection as a risk factor in the development of metabolic dysfunction-associated steatotic liver disease

Abstract

The problem of metabolic dysfunction-associated steatotic liver disease (MASLD) is becoming a non-infectious pandemic, the growth drivers of which are obesity and diabetes mellitus. According to modern concepts, MASLD develops and progresses as a result of the interaction of multiple genetic, environmental and adaptive factors, which include specific genetic polymorphisms (for example, the patatin-like phospholipase domain-containing protein 3 gene) and epigenetic modifications, dietary patterns (for example, high consumption of saturated fats and fructose), physical inactivity, obesity, insulin resistance, dysregulation of adipokine production, lipotoxicity, oxidative stress, intestinal microbiota dysbiosis (small intestinal bacterial overgrowth syndrome). In addition, due to the high infection rate of Helicobacter pylori (up to 80%) of people in the population, the influence of this factor on the development and progression of MASLD cannot be ruled out. Ye et al presented a study investigating the relationship between Helicobacter pylori infection and metabolic dysfunction associated with hepatic steatosis and identified prognostic factors. Certainly, the work of the Chinese authors deserves attention and further study.

Key Words: Helicobacter pylori infection; Metabolic dysfunction-associated steatotic liver disease; Obesity; Lipid profile; Blood glucose; Cytokines

Core Tip: The editorial discusses risk factors (Helicobacter pylori infection, proinflammatory cytokines, adipokines, mitochondrial dysfunction, oxidative stress, insulin resistance, gut microbiota, and other indicators) in the development of metabolic dysfunction-associated steatotic liver disease. This issue is covered in an article by Ye et al, they show that in a large cross-sectional study involving 28624 adults, it was revealed that Helicobacter pylori infection is correlated with metabolic disturbances, particularly in obese and older individuals. This study is distinguished by its extremely promising and strategically new objective and a very impressive methodological level of research.

INTRODUCTION

Metabolic dysfunction-associated steatotic liver disease (MASLD) is a common chronic disease characterized by increased accumulation of fat in the liver, which is based on metabolic dysfunction. According to the latest data, MASLD occupies a leading position among liver diseases[1-5]. Metabolically associated fatty liver disease in most regions of the globe exceeds 20% and is steadily growing[6]. The main reason for the growth of this disease is considered to be an increase in the number of diseases such as diabetes mellitus, obesity, hyperlipidemia, metabolic syndrome, which in turn are predictors of MASLD[7]. The search for risk factors for MASLD is relevant and is currently being actively studied.

Helicobacter pylori (H. pylori) is one of the most well-known human pathogens. According to the latest data, the prevalence of this infection varies from 50% to 80%, depending on the region of the study[8-10]. H. pylori infection can be asymptomatic or cause various clinical manifestations in the form of chronic gastritis, atrophic gastritis, peptic ulcer, gastric adenocarcinoma or gastric mucosa-associated lymphoid tissue lymphoma. On the one hand, H. pylori have been proven to be a carcinogen, on the other hand, its ability to cause metabolic disorders has been revealed. According to the results of a number of studies, H. pylori infection in patients is associated with obesity, impaired glucose metabolism, dyslipidemia and MASLD[11-15]. In connection with new studies on the effect of H. pylori on the progression and course of MASLD, the article by Chinese authors Ye et al[16], published in the journal World Journal of Gastroenterology is a relevant study and deserves special attention.

RISK FACTORS IN THE DEVELOPMENT OF METABOLIC DYSFUNCTION-ASSOCIATED STEATOTIC LIVER DISEASELE

Ye et al[16] carried out a significant cross-sectional study with 28624 adults, revealing a link between H. pylori infection and metabolic disorders, particularly among the obese and elderly participants in the research. The study used 13C urease respiratory test to diagnose H. pylori and abdominal ultrasound to verify fatty liver at the Health Screening Center of the Second Affiliated Hospital of Nanchang University. Every patient delivered comprehensive demographic and clinical information, encompassing gender, age, body mass index (BMI), blood pressure (systolic and diastolic), lipid profile (total cholesterol, triglycerides, low-density lipoprotein, high-density lipoprotein), and fasting glucose.

In the work of Lin Ye et al[16], in individuals included in the study, the use of a respiratory test with 13C urease to detect H. pylori infection revealed infection with the bacterium only in 26.8% of patients, which does not correspond to world statistics and other studies. According to the latest data, the 13C urease respiratory test should not be used to diagnose patients with gastrointestinal diseases (which may be caused by this bacterium), since these diseases affect the test result. Moreover, a false negative result can be a consequence of the influence of the following factors, such as a violation of the time of sample collection earlier than 30 minutes or later than 45 minutes after taking 13C urease, a violation of the technique of taking the first portion of exhaled air from the oral cavity, where its own physicochemical processes occur that change the measurement data, taking proton pump inhibitors within 14 days preceding the test, taking antibiotics within 30 days before the test, physical activity the day before the test. At Maastricht VI in 2022, it was demonstrated that the urease test had a sensitivity and specificity of 87%[17]. This test is exclusively suitable for monitoring the treatment of H. pylori eradication, but not for primary diagnostics. To increase the reliability of the results on the prevalence of H. pylori infection among patients with steatosis, it is necessary to use an enzyme immunoassay to detect the presence of a titer of specific antibodies to the cytotoxin-associated gene A antigen of H. pylori. In addition, the Chinese scientists included patients who had previously undergone eradication therapy in the study, which also does not reflect the reliability of the prevalence of H. pylori infection in patients with steatosis. The exclusion criteria should have included patients who had undergone eradication therapy for H. pylori. A mouse model of fatty liver disease with H. pylori infection was created in research by Chen et al[18], revealing that chronic H. pylori infection notably exacerbated liver lipid accumulation and insulin resistance (IR) induced by a high-fat diet. By analyzing the transcriptome and validating their findings, the authors discovered that H. pylori infection could enhance the progression of fatty liver disease by influencing lipid metabolism. These investigations offer encouraging avenues for determining causal links and evaluating the effects of H. pylori elimination on the advancement of MASLD. In their article, Ye et al[16], when describing the materials and methods in the section “MASLD examination and diagnostics”, indicated that both visualization and histological methods were used to diagnose liver steatosis, which raises the question of which histological methods were used and in which cases and what were the results; perhaps this group should have been formed separately from the others.

In the article ”Helicobacter pylori infection is linked to metabolic dysfunction and associated steatotic liver disease: A large cross-sectional study” the subjects were divided into 4 age groups: Group 1: 18-29 years (4501 cases); group 2: 30-49 years (12047 cases); group 3: 50-69 years (10278 cases); group 4: 70 years and older (1798 cases)[16]. During the study, the authors found that the group of patients aged 50-69 years had the highest rates of H. pylori positivity and MASLD, while the group aged 18-29 years demonstrated the lowest rates. The associations of H. pylori positivity and MASLD increased with increasing age up to 69 years. At the same time, the “Discussion” section indicated the group of 70 years and older with the highest level of H. pylori positivity and MASLD detection. We would like to clarify with the authors, after all, in what age period - 50-69 years (according to the results) or 70 years and older (according to the discussion) - the highest rates of positivity of H. pylori and MASLD were detected, which formed the risk group for these conditions. One study indicated that the 46-55 age bracket showed the greatest prevalence of H. pylori, with a decline noted in those aged over 65. The prevalence of MASLD was highest at ages 40-50 in men and ages 60-69 in women, followed by a slight reduction in older age groups (over 70 years). A separate study indicated that among individuals aged 18-40, the prevalence of H. pylori infection was approximately 52%, linked to elevated rates of MASLD within that age group.

In addition, while reading the article, a question arose about the localization of H. pylori in patients with steatosis. This bacterium detected in liver and bile samples or was it localized on the mucous membrane of the stomach and intestines. The question arises about the influence of H. pylori localization on the development of metabolic disorders, and how local and systemic effects from H. pylori infection differ. H. pylori infection is often associated with gastric diseases. In patients with gastric cancer linked to H. pylori, connections were found between the chemiluminescent activity of neutrophil granulocytes and the lipid peroxidation-antioxidant defense system[19]. However, recently there have been data that H. pylori infection may be associated with extragastric diseases, such as cardiovascular, neurological disorders and metabolic diseases[20-22]. The study of the effect of H. pylori infection on the development of MASLD is currently relevant. Mantovani et al’s research[23] indicated that H. pylori infection is linked to a slight rise in the risk of existing and new cases of MASLD. Given the widespread occurrence, ambiguous cause, and intricate management, verifying the pathogenic role of H. pylori in MASLD will certainly enable the creation of novel approaches for treating MASLD.

In early 1998, Day and James[24] initially introduced the “two-hit” theory to elucidate the development of MASLD. They suggested that the initial hit primarily results from an overload of fat in liver parenchymal cells, while the “second hit” refers to liver injury caused by heightened levels of proinflammatory cytokines, adipokines, mitochondrial impairment, and oxidative stress. Lipid peroxidation and factors related to antioxidant defense are significant biomarkers in the progression of MASLD[25]. These processes lead to disease progression from steatosis to non-alcoholic steatohepatitis (NASH) and progressive fibrosis. Studies by Buzzetti et al[2] and Takaki et al[26] considered multiple factors that interact with each other and can cause MASLD. Such factors include IR, hormones produced by adipose tissue, dietary factors, gut microbiota, and genetic and epigenetic factors. MASLD encompasses a broad range of liver disorders, from uncomplicated steatosis (fat accumulation exceeding 5% of hepatocytes) to metabolic dysfunction-associated steatohepatitis, advancing fibrosis, cirrhosis, and hepatocellular carcinoma[27]. Risk factors for MASLD comprise abdominal obesity, BMI exceeding 30 kg/m², type 2 diabetes, hyperglycemia, arterial hypertension, cardiovascular diseases, dyslipidemia, elevated triglycerides, low high-density lipoprotein levels, hypercholesterolemia, and metabolic syndrome. MASLD is now recognized as a multisystem disorder with interorgan links to extrahepatic conditions; research shows a correlation between MASLD and cardiovascular diseases, type 2 diabetes mellitus, endocrine disorders (such as hypothyroidism), chronic kidney disease, colorectal cancer, obstructive sleep apnea syndrome, osteoporosis, psoriasis, among others[28-30]. Growing evidence indicates that cardiovascular disease is a significant issue for those with MASLD[31], with the likelihood of cardiovascular-related death surpassing liver-related death[32]. This results from shared pathophysiological processes like IR, endothelial dysfunction, oxidative stress, and systemic inflammation[33]. Metabolic syndrome alongside overweight and obesity, along with its advanced state, metabolic-associated steatohepatitis, now stands as the primary reason for liver cirrhosis, liver transplants, hepatocellular carcinoma, and liver-related death[34,35]. Factors predicting MASLD encompass genetic elements, elevated uric acid levels, and additional indicators. Disease biomarkers can encompass antioxidants, metabolic indicators, MASLD early diagnostic measures, adipokines, etc. A recent observational study highlighted notable correlations between the risk of MASLD and immune cell-related inflammatory indices, including neutrophil-to-lymphocyte ratio and systemic immune inflammation index; however, other studies produced inconsistent results[36].

As early as 2001, within a cross-sectional analysis H. pylori DNA was detected in patients with various chronic liver diseases, including hepatitis, liver fibrosis, and hepatocellular carcinoma[37-39]. In 2008, Cindoruk et al[38], first detected 16S recombinant H. pylori RNA in a liver sample from a 44-year-old patient with NASH[40]. This result was validated in another case-control study, where H. pylori DNA was found in 5 out of 11 Liver samples from MASLD patients, in contrast to 2 out of 13 samples from controls[41]. In 2009, an animal model of H. pylori infection demonstrated that orally ingested H. pylori can reach the liver and cause hepatitis. This suggested that H. pylori may be a cause of chronic liver disease[42]. Surprisingly, in a study with a cross-sectional design H. pylori sequence was detected in liver tissues of patients with chronic hepatitis C, despite the fact that serological tests for H. pylori were negative[38]. The authors proposed two potential mechanisms for the entry of H. pylori into the liver: The bacterium may reach the liver from the stomach through the duodenum and bile ducts, or it may enter the liver through the bloodstream via the portal vein[39]. Certain data suggest that entry through the bile ducts is most probable. All research indicates a causal link between H. pylori infection and the onset of MASLD, with H. pylori infection exacerbating the progression of MASLD[43,44].

A Japanese clinical study conducted in 2015, which included 130 patients with biopsy-confirmed MASLD (43 with MASLD and 87 with NASH), revealed that the prevalence of NASH was significantly greater among patients who had a positive H. pylori-specific immunoglobulin G test compared to those who did not[3]. Moreover, the overall MASLD activity score and the level of hepatomegaly were greater in individuals with H. pylori immunoglobulin G positivity compared to those free of the infection. This research established that H. pylori infection could be a contributing factor in the progression of MASLD. Additionally, Abenavoli et al[45] reported in 2013 a clinical case in which a 55-year-old man’s metabolic profile, encompassing homeostatic model assessment of IR, fatty liver index, and liver ultrasound appearance, showed improvement following H. pylori eradication. This adds to the evidence highlighting the significance of H. pylori infection in the progression of MASLD.

Various proinflammatory cytokines are involved in the host defense against H. pylori infection, with the strongest associations found between C-reactive protein (CRP), tumor necrosis factor (TNF)-α, interleukin (IL)-6, and IL-1β[46]. A study examining H. pylori infection in MASLD indicated that TNF-α and IR levels were notably elevated, while circulating adiponectin was reduced in H. pylori seropositive patients with this condition. H. pylori infection might induce an elevation in TNF-α, while adiponectin subsequently rises to counteract the proinflammatory response. TNF-α might facilitate both the direct and indirect impacts of H. pylori infection on MASLD[47]. Hotamisligil et al’s research[48] discovered high sensitivity CRP in MASLD patients infected with H. pylori. A study by Gen et al[49] found that homeostatic model assessment of IR and CRP levels were notably higher in individuals with H. pylori infection than in those without the infection. The mechanisms of inflammation pathogenesis in H. pylori-associated MASLD directly reduce hepatocyte glycogen levels through the c-Jun N-terminal kinase (JNK) signaling pathway[47], which suppresses the expression of key glycolytic genes, accelerates lipolysis[48], and indirectly causes IR.

Many different studies have confirmed the association between chronic H. pylori infection and IR, and that this infection may be an important independent risk factor for the development of IR in MASLD[21,47]. IR results in impaired intracellular triglyceride synthesis and transport. IR in H. pylori-induced MASLD may be indirect due to chronic inflammation or direct due to activation of relevant signaling pathways[49]. Research indicates that persistent inflammation due to H. pylori infection raises the concentrations of CRP, TNF-α, and IL-6[49,50]. These proinflammatory cytokines activate a number of kinases such as IkappaB kinase/nuclear factor kappa-light-chain-enhancer of activated B cells and JNK, which by enhancing serine phosphorylation or suppressing insulin receptor substrate tyrosyl-1 autophosphorylation ultimately cause IR. A study conducted in mice revealed that H. pylori infection suppressed microRNA-203 (miR-203) expression through c-Jun overexpression, which led to the induction of suppressors of cytokine signaling 3 (SOCS3), which is a known inhibitor of insulin signaling. Thus, H. pylori infection induced IR in mice through activation of the c-Jun/miR-203/SOCS3 signaling pathway[51].

Adipose tissue plays a role in the onset of IR by releasing cytokines like leptin and adiponectin, which are implicated in the development of MASLD. Research has indicated that plasma leptin concentrations were increased in the MASLD group[51,52], and it is an independent predictor of liver steatosis[53]. One study found that H. pylori infection can affect the production of leptin[51], which inhibits stearoyl coenzyme A desaturase (delta 9-desaturase) is a key enzyme in fatty acid metabolism) in the liver, thereby reducing very low density lipoprotein cholesterol levels and fatty deposits in the liver tissue[52]. In addition, leptin can phosphorylate serine insulin receptor substrate 1318, thereby interfering with insulin signaling[54,55]. Thus, it can be speculated that H. pylori infection may cause MASLD by affecting fat metabolism, transport of relevant enzymes, or disrupting insulin signaling.

As 16S ribosomal RNA (rRNA) gene sequencing has developed and become widely used, evidence has accumulated linking gut dysbiosis to human liver disease and its role in MASLD[40]. Like 23S rRNA, 16S rRNA plays a structural role by acting as a scaffold that positions ribosomal proteins; its 3’ end contains an anti-Shine-Dalgarno sequence that enables 16S rRNA to bind to the 3’ end of mRNA and factors involved in translation initiation (S1 and S21). 16S rRNA interacts with 23S rRNA to facilitate the association of the large and small ribosomal subunits (50S and 30S). The gene stabilizes the correct pairing of the codon and anticodon at the A site of the large ribosomal subunit by forming a hydrogen bond between the nitrogen atom (N1) of 1492 or 1493 adenine residue and the 2’OH group of the mRNA backbone.

Research involving animal models that alter gut microbiota, along with observational studies in MASLD patients, indicates that dysbiosis of the gut microbiota plays a role in the development of MASLD[55,56]. Dysbiosis raises intestinal permeability to bacterial toxins and elevates liver exposure to harmful compounds, leading to heightened liver inflammation and fibrosis. Fukuda et al[57] evaluated the impact of H. pylori infection on intestinal permeability through a sucrose tolerance test. The findings indicated that the existence of H. pylori is linked to heightened intestinal permeability. Consequently, certain researchers propose that the processes underlying MASLD development prompted by dysbiosis of H. pylori-associated intestinal microbiota involve H. pylori invasion of the intestinal mucosa leading to heightened permeability, the progression of intestinal dysbiosis, and the transfer of bacterial endotoxin (primarily lipopolysaccharide) via the portal vein to the liver, resulting in an inflammatory response.

Thus, on the one hand, H. pylori have been proven to be a carcinogen, on the other hand, its ability to cause metabolic disorders with the development of MASLD has been revealed. In H. pylori infection, the proinflammatory cytokine TNF-α increases, which is a mediator of both the direct and indirect effects of H. pylori infection in MASLD. Additionally, the levels of IL-6 and CRP increase, which activate a number of kinases (IkappaB kinase/nuclear factor kappa-light-chain-enhancer of activated B cells and JNK) that enhance phosphorylation of serine or suppress autophosphorylation of tyrosyl insulin receptor substrate-1, causing IR. IR in MASLD develops due to the activation of the c-Jun/miR-203/SOCS3 signaling pathway. Additional activation of the JNK signaling pathway during chronic inflammation in the liver activates glycogenolysis, lipolysis, inhibits glycolysis, which increases the manifestations of IR. H. pylori increases the production of leptin by adipose tissue, which changes lipogenesis towards an increase in the content of very low density lipoprotein-X, fat deposits in hepatocytes and the development of IR. H. pylori causes intestinal dysbacteriosis with an increase in the permeability of its mucous membrane with the penetration of bacterial endotoxin and the development of inflammation.

Consequently, the bacterium H. pylori might affect the progression of MASLD, yet the findings of research remain uncertain. Some researchers propose that H. pylori infection could worsen MASLD, whereas others claim it is not linked to this condition. Persistent inflammation resulting from H. pylori colonization in the gastric mucosa causes both local and systemic effects, including alterations in intestinal permeability. Alterations in the gut microbiome from H. pylori infection or eradication treatment enhance the permeability of the gastrointestinal mucosa, allowing bacterial endotoxin to pass through the portal vein to the liver and triggering an inflammatory response in the liver. The liver parenchyma is activated for fibrogenesis by the direct action of H. pylori toxins. Nonetheless, there is no direct experimental proof that H. pylori infection directly influences MASLD. A meta-analysis conducted by Chen et al[18], containing 22 cross-sectional studies with over 117 thousand patients, indicated a 27% higher risk of developing MASLD in individuals with an H. pylori infection. A cross-sectional study conducted by Azami et al[13] (involving 369 patients with MASLD, comprising 171 H. pylori-positive and 198 H. pylori-negative individuals) observed for 24 months revealed that eradicating H. pylori significantly diminished IR, enhanced the lipid profile, and improved the liver steatosis index and liver fat content in NAFLD. A cross-sectional study by Mantovani et al[23] (observing 64 patients with MASLD, including 36 H. pylori-positive and 28 H. pylori-negative, for 6 months) discovered that eradicating H. pylori resulted in reduced liver steatosis and enhanced metabolic parameters. Nevertheless, various studies had restrictions, thus additional prospective, larger-scale, and long-duration studies are required to validate their results. Examining the connection between H. pylori and MASLD is crucial for understanding how eradication therapy for H. pylori may slow progression or enhance the metabolic condition of MASLD patients who are H. pylori-positive. Nonetheless, there are no definitive guidelines for treating MASLD patients with H. pylori infections; the treatment regimen choice is based on the antibiotic susceptibility of H. pylori strains and local efficacy data for treatment protocols.

CONCLUSION

MASLD is a complex metabolic disease influenced by genetic and epigenetic factors. The incidence is high, the prognosis depends on the clinical form, and may be complicated by the development of cirrhosis or liver cancer in up to 25% of cases. In recent years, more and more studies have been devoted to the effect of H. pylori infection on MASLD. Some authors consider H. pylori infection as one of the risk factors for MASLD due to the development of inflammation and IR. The mechanisms by which H. pylori infection contributes to the development of MASLD have not been fully determined, in this regard, the article by Ye et al[16], presented in the World Journal of Gastroenterology, is relevant and certainly deserves special attention. This work is distinguished by an extremely promising and very impressive survey of 28624 people. Furthermore, this research offers an innovative perspective on the connection between H. pylori infection and various metabolic factors, including blood glucose, lipid profile, blood pressure, BMI, and MASLD. This extensive cross-sectional study investigates the associations between H. pylori infection and metabolic disorders more thoroughly, indicating that the H. pylori-positive cohort exhibited notably elevated levels of blood glucose, triglycerides, total cholesterol, low density lipoprotein cholesterol, BMI, systolic blood pressure, diastolic blood pressure, along with increased age and MASLD detection rates relative to the H. pylori-negative cohort. Elevated blood glucose, BMI, and diastolic pressure were recognized as key risk factors for H. pylori infection, while high-density lipoprotein was seen as a protective factor. Certainly, this work makes a huge contribution to the development of further studies on the correlation of this pathogen and the severity of MASLD.