A 17-Beta-Hydroxysteroid Dehydrogenase 13 Variant Protects From Hepatocellular Carcinoma Development in Alcoholic Liver Disease

Genetic Susceptibility to Chronic Liver Disease in Individuals from Pakistan

Chronic liver disease, with viral or non-viral etiology, is endemic in many countries and is a growing burden in Asia. Among the Asian countries, Pakistan has the highest prevalence of chronic liver disease. Despite this, the genetic susceptibility to chronic liver disease in this country has not been investigated. We performed a comprehensive analysis of the most robustly associated common genetic variants influencing chronic liver disease in a cohort of individuals from Pakistan. A total of 587 subjects with chronic liver disease and 68 healthy control individuals were genotyped for the HSD17B13 rs7261356, MBOAT7 rs641738, GCKR rs1260326, PNPLA3 rs738409, TM6SF2 rs58542926 and PPP1R3B rs4841132 variants. The variants distribution between case and control group and their association with chronic liver disease were tested by chi-square and binary logistic analysis, respectively. We report for the first time that HSD17B13 variant results in a 50% reduced risk for chronic liver disease; while MBOAT7; GCKR and PNPLA3 variants increase this risk by more than 35% in Pakistani individuals. Our genetic analysis extends the protective role of the HSD17B13 variant against chronic liver disease and disease risk conferred by the MBOAT7; GCKR and PNPLA3 variants in the Pakistani population.

Interplay of PNPLA3 and HSD17B13 Variants in Modulating the Risk of Hepatocellular Carcinoma among Hepatitis C Patients

A single-nucleotide polymorphism causing a C to G change in the PNPLA3 gene (rs738409) is associated with disease severity and development of hepatocellular carcinoma (HCC) in nonalcoholic fatty liver disease; the insertion variant rs72613567:TA of the 17β-hydroxysteroid dehydrogenase type 13 (HSD17B13) mitigates this detrimental effect. Our aim was to evaluate if the same holds true in chronic hepatitis C virus infection (HCV). With a case control retrospective study design, we selected 110 patients who developed HCC on a background of HCV infection, matching each patient for sex and age (±30 months) to three HCV-infected, non-HCC patients. All participants underwent genotyping for PNPLA3 and HSD17B13 gene variants. Both univariate and multivariate analyses of risk factors for advanced disease and HCC were performed. Carriage of PNPLA3 G∗ allele was associated with a trend of progressively more severe liver disease, from mild fibrosis to significant fibrosis, cirrhosis, and HCC (p = 0.007). When the HSD17B13:TA status of these patients was taken into account, the abovementioned trend was strengthened among HSD17B13 major allele homozygotes and completely blunted among carriers of the minor allele (p = 0.0003 and 0.953, respectively). In a conditional logistic regression model including diabetes and AST to platelet ratio index among predictor variables, the unfavourable genetic profile characterized by the coexistence of the PNPLA3 minor allele and HSD17B13 major allele (vs. all other possible combinations) was an independent risk factor for HCC (OR = 2.00, 95% CI: 1.23-3.26) together with a history of alcohol abuse. In conclusion, carriage of the combination PNPLA3 minor allele and HSD17B13 major allele may represent a risk factor for HCC among HCV-infected patients. The interplay between the two genes may explain some of the controversy on this topic and may be exploited to stratify HCC risk in hepatitis C.

Association of HSD17B13 rs72613567:TA with non-alcoholic fatty liver disease in Hispanics/Latinos

INTRODUCTION

Non-alcoholic fatty liver disease (NAFLD) disproportionately affects Hispanic/Latinos and rates of NAFLD vary among Hispanics from different background groups. Genetic variants and continental ancestry contribute to NAFLD disparities among Hispanics. We evaluated two newly identified NAFLD-associated single nucleotide polymorphisms of HSD17B13, rs72613567:TA and rs62305723:A in Hispanics/Latinos.

METHODS

Clinical data, genotypes of variants of interest and estimates of continental ancestry were extracted from the Hispanic Community Health Study/Study of Latinos (HCHS/SOL) database, which includes a cohort of 16 415 US Hispanic/Latinos. Surrogate endpoints for NAFLD were suspected NAFLD based on unexplained aminotransferase elevation, continuous ALT levels and FIB-4 scores to estimate hepatic fibrosis.

RESULTS

In all, 9342 participants were included for analysis. The rs72613567:TA allele was found in 15.3% and the rs62305723:A allele was identified in 4.5% of HCHS/SOL participants. rs72613567:TA was less frequent in persons with vs without suspected NAFLD (12.4% vs 15.7%, P < .001) and rs72613567:TA was associated with lower FIB-4 scores (P = .01). For persons with the NAFLD-associated PNPLA3 rs738409:G allele, the presence of rs72613567:TA was associated with a lower rate of suspected NAFD (odds ratio = 0.76, P < .001). rs72613567:TA was less frequent in Hispanic/Latino background groups with higher rates of suspected NAFLD. The rs62305723:A allele was not associated with suspected NAFLD or FIB-4 score.

CONCLUSION

The rs72613567:TA allele is associated with lower rates of suspected NAFLD and lower FIB-4 scores among Hispanic/Latinos and with lower rates of suspected NAFLD in persons with the PNPLA3 rs738409:G allele. The rs72613567:TA allele contributes to NAFLD disparities among Hispanic/Latino background groups.

Molecular Mechanisms: Connections between Nonalcoholic Fatty Liver Disease, Steatohepatitis and Hepatocellular Carcinoma

Nonalcoholic fatty liver disease (NAFLD), including nonalcoholic steatohepatitis (NASH), causes hepatic fibrosis, cirrhosis and hepatocellular carcinoma (HCC). The patatin-like phospholipase-3 (PNPLA3) I148M sequence variant is one of the strongest genetic determinants of NAFLD/NASH. PNPLA3 is an independent risk factor for HCC among patients with NASH. The obesity epidemic is closely associated with the rising prevalence and severity of NAFLD/NASH. Furthermore, metabolic syndrome exacerbates the course of NAFLD/NASH. These factors are able to induce apoptosis and activate immune and inflammatory pathways, resulting in the development of hepatic fibrosis and NASH, leading to progression toward HCC. Small intestinal bacterial overgrowth (SIBO), destruction of the intestinal mucosa barrier function and a high-fat diet all seem to exacerbate the development of hepatic fibrosis and NASH, leading to HCC in patients with NAFLD/NASH. Thus, the intestinal microbiota may play a role in the development of NAFLD/NASH. In this review, we describe recent advances in our knowledge of the molecular mechanisms contributing to the development of hepatic fibrosis and HCC in patients with NAFLD/NASH.

Impact of HSD17B13 rs72613567 genotype on hepatic decompensation and mortality in patients with portal hypertension

BACKGROUND & AIMS

The loss-of-function rs72613567 T > TA-variant in the 17β-hydroxysteroid dehydrogenase 13 (HSD17B13) gene might protect from alcoholic and non-alcoholic fatty liver disease (ALD/NAFLD) and associated fibrosis/cirrhosis. We investigated the impact of the T > TA-variant on hepatic decompensation and mortality and investigated its implications on retinol and sex steroid metabolism in patients who had already developed advanced chronic liver disease (ACLD).

METHODS

Retrospective analysis in prospectively characterized patients with viral hepatitis- and ALD/NAFLD-induced portal hypertension (hepatic venous pressure gradient (HVPG) ≥ 6 mmHg) diagnosed at the Medical University of Vienna.

RESULTS

Among 487 patients who were followed longitudinally, 166 (34%) were heterozygous and 24 (5%) were homozygous for the 'protective' TA-allele. Patients harbouring at least one TA-allele had a lower MELD (9 (8-12) vs 10 (8-13) points; P = .003) and showed a trend towards lower HVPG (16 ± 6 vs 17 ± 7 mmHg; P = .067). Interestingly, in competing risk analyses adjusted for age, HVPG and MELD, harbouring the TA-allele was associated with numerically increased risks for mortality (adjusted subdistribution hazard ratio (aSHR): 1.3 (95% confidence interval (95% CI): 0.888-1.91); P = .18), liver-related death (aSHR: 1.34 (95% CI: 0.9-1.98); P = .15) and hepatic decompensation (aSHR: 1.29 (95% CI: 0.945-1.77); P = .11). This might be explained by trends towards worse outcomes (eg liver-related death: aSHR: 1.64 (95% CI: 0.95-2.84); P = .076) in patients with viral hepatitis-induced ACLD. In a cross-sectional analysis of 211 additional patients, serum retinol levels were comparable between HSD17B13 genotypes, but in males, serum testosterone levels numerically decreased with an increasing number of TA-alleles.

CONCLUSION

In patients with viral hepatitis- and ALD-induced portal hypertension, the T > TA-variant was not protective of hepatic decompensation and mortality. Further studies should investigate the pathophysiological mechanisms underlying the effects of HSD17B13 genotype at different stages of liver disease.

PNPLA3-A Potential Therapeutic Target for Personalized Treatment of Chronic Liver Disease

Patatin-like phospholipase domain-containing protein 3 (PNPLA3) is a lipid droplet-associated protein that has been shown to have hydrolase activity toward triglycerides and retinyl esters. The first evidence of PNPLA3 being associated with fatty liver disease was revealed by a genome-wide association study (GWAS) of Hispanic, African American, and European American individuals in the Dallas Heart Study back in 2008. Since then, numerous GWAS reports have shown that PNPLA3 rs738409[G] (148M) variant is associated with hepatic triglyceride accumulation (steatosis), inflammation, fibrosis, cirrhosis, and even hepatocellular carcinoma regardless of etiologies including alcohol- or obesity-related and others. The frequency of PNPLA3(148M) variant ranges from 17% in African Americans, 23% in European Americans, to 49% in Hispanics in the Dallas Heart Study. Due to high prevalence of obesity and alcohol consumption in modern societies, the PNPLA3(148M) gene variant and environment interaction poses a serious concern for public health, especially chronic liver diseases including alcohol-related liver disease (ALD) and nonalcoholic fatty liver disease (NAFLD). Therefore, PNPLA3(148M) variant is a potential therapeutic target for chronic liver disease in the rs738409 allele carriers. Currently, there is no approved drug specifically targeting the PNPLA3(148M) variant yet. With additional mechanistic studies, novel therapeutic strategies are expected to be developed for the treatment of the PNPLA3(148M) variant-associated chronic liver diseases in the near future.

Lipid droplet dynamics in alcoholic fatty liver disease

The rising incidence of alcohol-related liver disease (ALD) demands making urgent progress in understanding the fundamental molecular basis of alcohol-related hepatocellular damage. One of the key early events accompanying chronic alcohol usage is the accumulation of lipid droplets (LDs) in the hepatocellular cytoplasm. LDs are far from inert sites of neutral lipid storage; rather, they represent key organelles that play vital roles in the metabolic state of the cell. In this review, we will examine the biology of these structures and outline recent efforts being made to understand the effects of alcohol exposure on the biogenesis, catabolism, and motility of LDs and how their dynamic nature is perturbed in the context of ALD.