PNPLA3 rs738409 I748M is associated with steatohepatitis in 434 non-obese subjects with hepatitis C

Update in lean metabolic dysfunction-associated steatotic liver disease

BACKGROUND

A new nomenclature consensus has emerged for liver diseases that were previously known as non-alcoholic fatty liver disease (NAFLD) and metabolic dysfunction-associated fatty liver disease (MAFLD). They are now defined as metabolic dysfunction-associated steatotic liver disease (MASLD), which includes cardiometabolic criteria in adults. This condition, extensively studied in obese or overweight patients, constitutes around 30% of the population, with a steady increase worldwide. Lean patients account for approximately 10%-15% of the MASLD population. However, the pathogenesis is complex and is not well understood.

AIM

To systematically review the literature on the diagnosis, pathogenesis, characteristics, and prognosis in lean MASLD patients and provide an interpretation of these new criteria.

METHODS

We conducted a comprehensive database search on PubMed and Google Scholar between January 2012 and September 2023, specifically focusing on lean NAFLD, MAFLD, or MASLD patients. We include original articles with patients aged 18 years or older, with a lean body mass index categorized according to the World Health Organization criteria, using a cutoff of 25 kg/m2 for the general population and 23 kg/m2 for the Asian population.

RESULTS

We include 85 studies in our analysis. Our findings revealed that, for lean NAFLD patients, the prevalence rate varied widely, ranging from 3.8% to 34.1%. The precise pathogenesis mechanism remained elusive, with associations found in genetic variants, epigenetic modifications, and adaptative metabolic response. Common risk factors included metabolic syndrome, hypertension, and type 2 diabetes mellitus, but their prevalence varied based on the comparison group involving lean patients. Regarding non-invasive tools, Fibrosis-4 index outperformed the NAFLD fibrosis score in lean patients. Lifestyle modifications aided in reducing hepatic steatosis and improving cardiometabolic profiles, with some medications showing efficacy to a lesser extent. However, lean NAFLD patients exhibited a worse prognosis compared to the obese or overweight counterpart.

CONCLUSION

MASLD is a complex disease comprising epigenetic, genetic, and metabolic factors in its pathogenesis. Results vary across populations, gender, and age. Limited data exists on clinical practice guidelines for lean patients. Future studies employing this new nomenclature can contribute to standardizing and generalizing results among lean patients with steatotic liver disease.

PNPLA3 and TM6SF2 genetic variants and hepatic fibrosis and cirrhosis in Pakistani chronic hepatitis C patients: a genetic association study

Background

The present study investigates if common missense functional variants p.I148M and p.E167K in PNPLA3 and TM6SF2 genes, respectively, associate with development of hepatic fibrosis and cirrhosis in a geographically novel cohort of Pakistani chronic hepatitis C (CHC) patients.

Methods

In total, 502 Pakistani CHC patients [242 males, median age 40 years, 220 with significant hepatic fibrosis, including 114 with cirrhosis] were genotyped for PNPLA3 and TM6SF2 variants using TaqMan genotyping assays. Associations between genotypes, biochemical and clinical parameters were evaluated.

Results

Genotypic distributions for PNPLA3 and TM6SF2 polymorphisms conformed to Hardy–Weinberg equilibrium and did not associate with fibrosis grades ≥ F2 or cirrhosis in any of the genetic models tested (all p =  > 0.05). PNPLA3 and TM6SF2 variants did not modulate baseline characteristics and serum markers of liver injury in CHC patients. Similarly, increasing number of risk alleles of PNPLA3 and TM6SF2 polymorphisms had no trend effect on serum liver enzyme activities or proportion of CHC patients with significant or advanced fibrosis or cirrhosis (p =  > 0.05). The same trend of no association with hepatic fibrosis or cirrhosis persisted in the multivariate logistic regression models adjusting for age, gender, body mass index and HCV viral load (p =  > 0.05).

Conclusions

PNPLA3 and TM6SF2 variants do not appear to modulate development of hepatic fibrosis or cirrhosis in present CHC patients of Pakistani origin, and may be of more relevance in liver pathology involving abnormalities in hepatic fat accumulation. These results also reflect the divergent associations observed for different genetic modifiers of hepatic fibrosis and cirrhosis in distinct ethnicities.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12876-022-02469-6.

Liver specific, systemic and genetic contributors to alcohol-related liver disease progression

Alcohol-related liver disease (ALD) impacts millions of patients worldwide each year and the numbers are increasing. Disease stages range from steatosis via steatohepatitis and fibrosis to cirrhosis, severe alcohol-associated hepatitis and liver cancer. ALD is usually diagnosed at an advanced stage of progression with no effective therapies. A major research goal is to improve diagnosis, prognosis and also treatments for early ALD. This however needs prioritization of this disease for financial investment in basic and clinical research to more deeply investigate mechanisms and identify biomarkers and therapeutic targets for early detection and intervention. Topics of interest are communication of the liver with other organs of the body, especially the gut microbiome, the individual genetic constitution, systemic and liver innate inflammation, including bacterial infections, as well as fate and number of hepatic stellate cells and the composition of the extracellular matrix in the liver. Additionally, mechanical forces and damaging stresses towards the sophisticated vessel system of the liver, including the especially equipped sinusoidal endothelium and the biliary tract, work together to mediate hepatocytic import and export of nutritional and toxic substances, adapting to chronic liver disease by morphological and functional changes. All the aforementioned parameters contribute to the outcome of alcohol use disorder and the risk to develop advanced disease stages including cirrhosis, severe alcoholic hepatitis and liver cancer. In the present collection, we summarize current knowledge on these alcohol-related liver disease parameters, excluding the aspect of inflammation, which is presented in the accompanying review article by Lotersztajn and colleagues.

The role of PNPLA3 and TM6SF2 polymorphisms on liver fibrosis and metabolic abnormalities in Brazilian patients with chronic hepatitis C

Background

Despite the growing body of knowledge about TM6SF2 and PNPLA3 polymorphisms in non-alcoholic fatty liver disease, their influence in the spectrum of HCV liver disease is not yet fully defined. Besides that, admixed populations, such as Brazilians, were not included in most of the studies.

Methods

This cross-sectional study enrolled 365 treatment-naïve patients with HCV and 134 healthy individuals. TM6SF2 (rs58542926 c.499C > T) and PNPLA3 (rs738409 c.444C > G) polymorphisms were evaluated regarding their association with clinical and laboratory data, histological liver steatosis and fibrosis, and with components of the metabolic syndrome.

Results

In HCV subjects, the frequencies of TM6SF2 CC and CT + TT were 89% and 11%, while PNPLA3 frequencies of CC and CG + GG were 51.4% and 48.6%. In the univariate logistic regression analysis, the TM6SF2 CT + TT genotype in HCV was associated with significant liver fibrosis (p = 0.047; OR 1.953; 95% CI 1.009–3.788). In comparison to the CT + TT genotype, the TM6SF2 CC genotype in HCV was associated with older age (p = 0.002), higher frequency of arterial hypertension (p = 0.032), obesity (p = 0.030), metabolic syndrome (p = 0.014) and lower total cholesterol levels (p = 0.036). The PNPLA3 GG subjects had lower body mass index than CG/ CC individuals (p = 0.047). None of the polymorphisms, or their combinations, was independently associated with hepatic steatosis or fibrosis. On the other hand, older age, lower serum levels of total cholesterol, and higher serum levels of alanine aminotransferase and alkaline phosphatase were associated with liver fibrosis in the multivariate logistic regression analysis.

Conclusion

In this evaluation of an admixed HCV population, neither TM6SF2 nor PNPLA3 polymorphisms were independently associated with hepatic steatosis or fibrosis. Other factors seem more influential than these specific polymorphisms in isolation. More studies are warranted to clarify the role of the TM6SF2 and PNPLA3 polymorphisms in Brazilians with HCV.

Low-Density Lipoprotein (LDL)-Triglyceride and Its Ratio to LDL-Cholesterol as Diagnostic Biomarkers for Nonalcoholic Steatohepatitis

Background

Nonalcoholic fatty liver disease (NAFLD) is the most common type of liver disease, but it is difficult to distinguish its pathogenic phenotype, nonalcoholic steatohepatitis (NASH), from nonalcoholic fatty liver (NAFL) without a liver biopsy. We analyzed serum lipids, including low-density lipoprotein triglyceride (LDL-TG), to elucidate their usefulness for diagnosing NASH.

Patients and Methods

Serum samples obtained from 35 NASH and 9 NAFL biopsy-confirmed patients and 6 healthy volunteers (HLT) were studied for 13 lipid-related markers and compared between HLT, NAFL, and NASH groups. The relationship between histological findings and the lipid markers was also analyzed.

Results

There were significant differences in triglyceride, LDL-TG, the ratio of LDL-TG to the LDL-cholesterol (LDL-TG/LDL-C), small dense LDL-C, and apolipoprotein E between the three groups. Among the 5 lipid components, serum LDL-TG level and the ratio of LDL-TG to the LDL-cholesterol (LDL-TG/LDL-C) were significantly elevated in NASH. The median concentrations of LDL-TG in HLT, NAFL, and NASH were 9, 15, and 20 mg/dL (P < 0.001), and those of LDL-TG/LDL-C were 0.097, 0.102, and 0.173 (P < 0.001), respectively. Although the degree of steatosis was not correlated with the LDL-TG/LDL-C, the ratio was significantly higher in patients with lobular inflammation (P = 0.071), ballooning (P = 0.031), and fibrosis (P < 0.001). The area under the receiver operating characteristic curve of the ratio for distinguishing NASH from NAFL was 0.857. The rest of studied markers showed no significant utility.

Conclusion

Serum LDL-TG levels and the LDL-TG/LDL-C ratio might serve as simple and noninvasive diagnostic biomarkers for NASH.

Low hepatic copper content and PNPLA3 polymorphism in non-alcoholic fatty liver disease in patients without metabolic syndrome

INTRODUCTION

The pathogenesis of non-alcoholic fatty liver disease (NAFLD) is multifactorial including metabolic, genetic (e.g. PNPLA3 [patatin-like phospholipase domain-containing 3 gene]), viral factors and drugs. Besides, there is evidence for a role of copper deficiency. Aim of the study was to evaluate the role of hepatic copper content, PNPLA3 in NAFLD patients with and without metabolic syndrome (MetS).

METHODS

One-hundred seventy-four NAFLD patients, who underwent liver biopsy for diagnostic work-up, were studied. Diagnosis of MetS was based on the WHO Clinical Criteria. Steatosis was semiquantified as percentage of fat containing hepatocytes and was graded according to Brunt. Histological features of non-alcoholic steatohepatitis (NASH) were assessed using the Bedossa classification. Hepatic copper content (in μg/g dry weight) was measured by flame atomic absorption spectroscopy. SNP rs738409 in PNPLA3 was investigated by RT-PCR.

RESULTS

Mean hepatic copper content was 22.3 (19.6-25.1) μg/g. The mean percentage of histologically lipid containing hepatocytes was 42.2% (38.3-46.0) and correlated inversely with hepatic copper content (ρ=-0.358, P<0.001). By subgroup analysis this inverse correlation remained significant only in patients without MetS (OR: 0.959 [CI95%: 0.926-0.944], P=0.020). Presence of minor allele (G) of PNPLA3 was also associated with moderate/severe steatosis (≥33%) both in patients with (OR: 2.405 [CI95%: 1.220-4.744], P=0.011) and without MetS (OR: 2.481 [CI95%: 1.172-5.250], P=0.018), but was only associated with NASH (OR: 2.002 [CI95%: 1.062-3.772], P=0.032) and liver fibrosis (OR: 2.646 [CI95%: 1.299-5.389], P=0.007) in patients without MetS.

CONCLUSION

Hepatic copper content and PNPLA3 mutations are associated with disease activity in NAFLD patients without MetS. Presence of MetS appears to mask the effects of hepatic copper and PNPLA3.

PNPLA3 polymorphism increases risk for and severity of chronic hepatitis C liver disease

AIM

To examine the association of PNPLA3 polymorphisms in chronic hepatitis C patients and development of liver disease spectrum.

METHODS

Literature was searched systematically from PubMed/MEDLINE, EMBASE, and Cochrane search engines for full-length articles written in English that examined PNPLA3 polymorphism in chronic hepatitis C (CHC) patients. Studies evaluating the association of PNPLA3 polymorphism spectrum (fatty liver, steatohepatitis, cirrhosis, and hepatocellular carcinoma) of CHC were included. Pooled data are reported as OR with 95%CI. Our study endpoint was the risk of the entire liver disease spectrum including: Steatosis/fatty liver, cirrhosis, and hepatocellular carcinoma in CHC patients with PNPLA3 polymorphisms.

RESULTS

Of 380 studies identified, a total of 53 studies were included for full-text review. Nineteen on chronic hepatitis C were eligible for analysis. Pooled ORs for rs738409 GG compared to CC and CG among patients with fatty liver was 2.214 (95%CI: 1.719-2.853). ORs among advanced fibrosis/cirrhosis were 1.762 (95%CI: 1.258-2.468). Similar odds ratios among hepatocellular carcinoma patients were 2.002 (95%CI: 1.519-2.639). Pooled ORs for rs738409 GG and CG compared to CC among patients with fatty liver were 1.750 (95%CI: 1.542-1.986). Pooled ORs for advanced fibrosis/cirrhosis patients were 1.613 (95%CI: 1.211-2.147). All analyses were homogenous and without publication bias except one. The associations were maintained after adjusting for publication bias and heterogeneity.

CONCLUSION

PNPLA3 polymorphisms have strong association with increased risk and severity of the liver disease spectrum in CHC patients.

The PNPLA3 Genetic Variant rs738409 Influences the Progression to Cirrhosis in HIV/Hepatitis C Virus Coinfected Patients

Contradictory data about the impact of the rs738409 steatosis-related polymorphism within PNPLA3 gene on liver fibrosis progression in HIV/hepatitis C virus (HIV/HCV)-coinfected patients have been reported. Our objective was to test whether this, and other polymorphisms previously related to fatty liver disease in HIV infection linked to SAMM50 or LPPR4 genes, influence liver fibrosis progression in HIV/HCV-coinfected individuals. Three hundred and thirty two HIV/HCV-coinfected patients who consecutively attended four Spanish university hospitals from November 2011 to July 2013 were included. A liver stiffness cut-off of 14.6 kPa, as determined by transient elastography, was used to diagnose cirrhosis. Liver stiffness progression was studied in 171 individuals who had two available LS determinations without anti-HCV treatment between them. Moreover, 28 HIV/HCV-coinfected patients who underwent liver transplant, as well as 19 non-cirrhotic coinfected individuals used as controls, were included in an additional study. Only rs738409 was associated with cirrhosis: 45 (29.6%) of 152 G allele carriers versus 36 (20.0%) of 180 CC carriers showed cirrhosis (multivariate p = 0.018; adjusted odds ratio = 1.98; 95% confidence interval = 1.12–3.50). Also, 21 (30.4%) of 69 G allele carriers versus 16 (15.7%) of 102 CC patients showed significant liver stiffness progression (adjusted p-value = 0.015; adjusted odds ratio = 2.89; 95% confidence interval = 1.23–6.83). Finally, the proportion of rs738409 G allele carriers was significantly higher in transplanted individuals than in controls (p = 0.044, odds ratio = 3.43; 95% confidence interval = 1.01–11.70). Our results strongly suggest that the rs738409 polymorphism is associated with liver fibrosis progression in HIV/HCV-coinfected patients.

Hepatic steatosis in HCV-infected persons in the direct-acting antiviral era

Hepatitis C virus (HCV) infects 130-170 million people worldwide. Recently, direct-acting antivirals have been shown to eradicate HCV infection in 90-95 % of non-cirrhotic patients depending on genotype, treatment experience, and regimen used. Similar rates are achieved among compensated cirrhotics, although longer treatment duration and/or ribavirin may be required. HCV uses host lipid metabolism for its lifecycle and can cause hepatic steatosis and insulin resistance. Hepatic steatosis, defined as excessive triglyceride deposition in hepatocytes, affects approximately half of HCV-infected individuals. Genetic factors and co-morbidities can drive further steatosis, which in turn can instigate fibrosis and progression to cirrhosis and hepatocellular carcinoma. Polymorphisms in genes that modulate lipid deposition in hepatocytes such as patatin-like phospholipase domain-containing protein 3 (PNPLA3) and transmembrane six superfamily member 2 (TM6SF2) predispose people to steatosis. Metabolic syndrome, obesity, and insulin resistance are increasing worldwide and further contribute to hepatic steatosis, and alcohol has long been recognized as a cause of lipid deposition in the liver. HIV and antiretroviral drugs, but not HBV, may further drive hepatic steatosis. While many of these factors limit response to interferon-based regimens for treating HCV, responses to direct-acting antivirals appear not to be impaired. The effect of HCV eradication on hepatic steatosis and progression to fibrosis, cirrhosis, and hepatocellular carcinoma warrants further study in the era of direct-acting antivirals.

Genetic factors that affect nonalcoholic fatty liver disease: A systematic clinical review

AIM: To investigate roles of genetic polymorphisms in non-alcoholic fatty liver disease (NAFLD) onset, severity, and outcome through systematic literature review.

METHODS: The authors conducted both systematic and specific searches of PubMed through December 2015 with special emphasis on more recent data (from 2012 onward) while still drawing from more historical data for background. We identified several specific genetic polymorphisms that have been most researched and, at this time, appear to have the greatest clinical significance on NAFLD and similar hepatic diseases. These were further investigated to assess their specific effects on disease onset and progression and the mechanisms by which these effects occur.

RESULTS: We focus particularly on genetic polymorphisms of the following genes: PNPLA3, particularly the p. I148M variant, TM6SF2, particularly the p. E167K variant, and on variants in FTO, LIPA, IFNλ4, and iron metabolism, specifically focusing on HFE, and HMOX-1. We discuss the effect of these genetic variations and their resultant protein variants on the onset of fatty liver disease and its severity, including the effect on likelihood of progression to cirrhosis and hepatocellular carcinoma. While our principal focus is on NAFLD, we also discuss briefly effects of some of the variants on development and severity of other hepatic diseases, including hepatitis C and alcoholic liver disease. These results are briefly discussed in terms of clinical application and future potential for personalized medicine.

CONCLUSION: Polymorphisms and genetic factors of several genes contribute to NAFLD and its end results. These genes hold keys to future improvements in diagnosis and management.

The Pathogenesis of Nonalcoholic Fatty Liver Disease: Interplay between Diet, Gut Microbiota, and Genetic Background

Nonalcoholic fatty liver disease (NAFLD) is the most common chronic liver disease in the world, and it comprises a spectrum of hepatic abnormalities from simple hepatic steatosis to steatohepatitis, fibrosis, cirrhosis, and liver cancer. While the pathogenesis of NAFLD remains incompletely understood, a multihit model has been proposed that accommodates causal factors from a variety of sources, including intestinal and adipose proinflammatory stimuli acting on the liver simultaneously. Prior cellular and molecular studies of patient and animal models have characterized several common pathogenic mechanisms of NAFLD, including proinflammation cytokines, lipotoxicity, oxidative stress, and endoplasmic reticulum stress. In recent years, gut microbiota has gained much attention, and dysbiosis is recognized as a crucial factor in NAFLD. Moreover, several genetic variants have been identified through genome-wide association studies, particularly rs738409 (Ile748Met) in PNPLA3 and rs58542926 (Glu167Lys) in TM6SF2, which are critical risk alleles of the disease. Although a high-fat diet and inactive lifestyles are typical risk factors for NAFLD, the interplay between diet, gut microbiota, and genetic background is believed to be more important in the development and progression of NAFLD. This review summarizes the common pathogenic mechanisms, the gut microbiota relevant mechanisms, and the major genetic variants leading to NAFLD and its progression.

I148M variant of PNPLA3 increases the susceptibility to non-alcoholic fatty liver disease caused by obesity and metabolic disorders

BACKGROUND

The patatin-like phospholipase 3 (PNPLA3) rs738409 gene polymorphism is an important genetic determinant of non-alcoholic fatty liver disease (NAFLD). However, the associations between liver fat and metabolic traits in rs738409 G allele carriers and the allelic influence on this association have not been fully studied.

AIM

To investigate the influence of the PNPLA3 gene polymorphism on the association of liver fat with serum metabolic factors and carotid atherosclerosis.

METHODS

Liver fat was measured by quantitative ultrasound in 4300 subjects in the Shanghai Changfeng community and analysed for its association with obesity and metabolic factors in individuals with the PNPLA3 CC, CG and GG genotypes.

RESULTS

Non-alcoholic fatty liver disease occurred in 37.9% and 28.8% of the subjects with the GG and CC genotypes respectively (P < 0.001). Liver fat was significantly associated with body mass index, waist circumference, serum triglycerides, high-density lipoprotein cholesterol, fasting blood glucose and insulin in the PNPLA3 rs738409 G allele carriers (P < 0.001). Compared with the CC homozygotes, the GG homozygotes presented higher liver fat and liver fibrosis scores despite their better metabolic status (comparison of regression line slopes, P < 0.05). An increase in liver fat was accompanied by a significant increase in the average and maximum carotid intima-media thickness in subjects with the PNPLA3 CC genotype but not in those with the GG genotype.

CONCLUSIONS

PNPLA3 rs738409 G allele carriers were found to be more susceptible to the metabolic-related hepatic steatosis, and developed NAFLD and liver fibrosis despite presenting relatively better metabolic statuses and lower risks for carotid atherosclerosis.

Impact of patatin-like phospholipase domain-containing 3 gene polymorphism (rs738409) on severity of liver disease in HIV/hepatitis C virus-coinfected patients

OBJECTIVE

To analyze the association between patatin-like phospholipase domain-containing 3 gene (PNPLA3) rs738409 polymorphism and severity of liver disease in HIV/hepatitis C virus-coinfected patients.

METHODS

We performed a cross-sectional study of 215 patients who underwent a liver biopsy. PNPLA3 rs738409 polymorphism was genotyped using GoldenGate assay. The outcome variables were as follows: advanced fibrosis (F ≥3 and FIB-4 ≥3.25), rapid fibrosis progression (FPR ≥0.10 fibrosis units/year), severe activity grade (A≥3), and steatosis (fatty hepatocytes ≥10%). The genetic association analysis was carried out according to an additive genetic model through logistic regressions adjusted by the most significant covariables.

RESULTS

Overall, 21.4% had F at least 3, 8.9% had FIB-4 at least 3.25, 11.4% had A at least 3, 60.6% had steatosis, and 32.5% had FPR at least 0.10. For each rs738409 G allele, we found an increased frequency of patients with advanced fibrosis (F at least 3) (0% CC, 18.5% CG, and 25.2% GG; P = 0.049) and FIB-4 at least 3.25 (0% CC, 3.8% CG, and 13.2% GG; P = 0.016). Furthermore, for each rs738409 G allele, the odds of having F at least 3 increased 2.15 times (95% confidence interval=1.07; 4.35; P = 0.029) and having FIB-4 at least 3.25 increased 8.77 times (95% of confidence interval = 1.11; 69.0; P = 0.039). Note that rs738409 G allele carriers tended to higher likelihood of having FPR at least 0.10, but statistical significance was not reached (P = 0.054). Finally, we did not find any association for A at least 3 and liver steatosis.

CONCLUSION

PNPLA3 rs738409 polymorphism was associated with the severity of liver fibrosis in patients coinfected with HIV and hepatitis C virus, suggesting that this polymorphism might also play a significant role in the progression of hepatic fibrosis in this group of patients.

Murine models provide insight to the development of non-alcoholic fatty liver disease

Associated with the obesity epidemic, non-alcoholic fatty liver disease (NAFLD) has become the leading liver disease in North America. Approximately 30 % of patients with NAFLD may develop non-alcoholic steatohepatitis (NASH) that can lead to cirrhosis and hepatocellular carcinoma (HCC). Frequently animal models are used to help identify underlying factors contributing to NAFLD including insulin resistance, dysregulated lipid metabolism and mitochondrial stress. However, studying the inflammatory, progressive nature of NASH in the context of obesity has proven to be a challenge in mice. Although the development of effective treatment strategies for NAFLD and NASH is gaining momentum, the field is hindered by a lack of a concise animal model that reflects the development of liver disease during obesity and the metabolic syndrome. Therefore, selecting an animal model to study NAFLD or NASH must be done carefully to ensure the optimal application. The most widely used animal models have been reviewed highlighting their advantages and disadvantages to studying NAFLD and NASH specifically in the context of obesity.

Genetic background in nonalcoholic fatty liver disease: A comprehensive review

In the Western world, nonalcoholic fatty liver disease (NAFLD) is considered as one of the most significant liver diseases of the twenty-first century. Its development is certainly driven by environmental factors, but it is also regulated by genetic background. The role of heritability has been widely demonstrated by several epidemiological, familial, and twin studies and case series, and likely reflects the wide inter-individual and inter-ethnic genetic variability in systemic metabolism and wound healing response processes. Consistent with this idea, genome-wide association studies have clearly identified Patatin-like phosholipase domain-containing 3 gene variant I148M as a major player in the development and progression of NAFLD. More recently, the transmembrane 6 superfamily member 2 E167K variant emerged as a relevant contributor in both NAFLD pathogenesis and cardiovascular outcomes. Furthermore, numerous case-control studies have been performed to elucidate the potential role of candidate genes in the pathogenesis and progression of fatty liver, although findings are sometimes contradictory. Accordingly, we performed a comprehensive literature search and review on the role of genetics in NAFLD. We emphasize the strengths and weaknesses of the available literature and outline the putative role of each genetic variant in influencing susceptibility and/or progression of the disease.

Chronic hepatitis C virus infection and lipoprotein metabolism

Hepatitis C virus (HCV) is a hepatotrophic virus and a major cause of chronic liver disease, including hepatocellular carcinoma, worldwide. The life cycle of HCV is closely associated with the metabolism of lipids and lipoproteins. The main function of lipoproteins is transporting lipids throughout the body. Triglycerides, free cholesterol, cholesteryl esters, and phospholipids are the major components of the transported lipids. The pathway of HCV assembly and secretion is closely linked to lipoprotein production and secretion, and the infectivity of HCV particles largely depends on the interaction of lipoproteins. Moreover, HCV entry into hepatocytes is strongly influenced by lipoproteins. The key lipoprotein molecules mediating these interactions are apolipoproteins. Apolipoproteins are amphipathic proteins on the surface of a lipoprotein particle, which help stabilize lipoprotein structure. They perform a key role in lipoprotein metabolism by serving as receptor ligands, enzyme co-factors, and lipid transport carriers. Understanding the association between the life cycle of HCV and lipoprotein metabolism is important because each step of the life cycle of HCV that is associated with lipoprotein metabolism is a potential target for anti-HCV therapy. In this article, we first concisely review the nature of lipoprotein and its metabolism to better understand the complicated interaction of HCV with lipoprotein. Then, we review the outline of the processes of HCV assembly, secretion, and entry into hepatocytes, focusing on the association with lipoproteins. Finally, we discuss the clinical aspects of disturbed lipid/lipoprotein metabolism and the significance of dyslipoproteinemia in chronic HCV infection with regard to abnormal apolipoproteins.

Patatin-like phospholipase 3 (rs738409) gene polymorphism is associated with increased liver enzymes in obese adolescents and metabolic syndrome in all ages

BACKGROUND

Obesity is associated with non-alcoholic fatty liver disease (NAFLD), and the patatin-like phospholipase 3 (PNPLA3) rs738409 (Ile148Met, C>G) gene polymorphism is one of the most important genetic determinants of NAFLD. Carriers have been reported to better respond to lifestyle modification.

AIM

To investigate the effect of rs738409 on overweight/obese adolescents and adults with and without metabolic syndrome (MetS).

METHODS

Two hundred and eighty-eight overweight/obese and 209 normal weight participants of the STYJOBS/EDECTA cohort (NCT00482924) were analysed for PNPLA3 genotypes.

RESULTS

Compared to overweight/obese without MetS, in overweight/obese study participants with MetS, the presence of the G allele (148Met) was significantly higher (CC: 5.0% vs. 9.2%, Spearman's correlation, 0.12; P = 0.038). Persons with CG (heterozygote for the risk allele) and with GG (homozygote for the risk allele) genotypes showed significantly higher ALT levels than those with CC genotypes. Even young individuals aged below 20 years had significantly increased ALT levels if they were homozygote with the G allele.

CONCLUSIONS

The PNPLA3 rs738409 polymorphism is associated already in youths with increased ALT, and is more frequent in obese with MetS of all ages. Hence, overweight/obese rs738409 carriers should be identified early in life and treated with a rigorous life style intervention.