Mohammed Eslam

Global burden of NAFLD and NASH: trends, predictions, risk factors and prevention

NAFLD is one of the most important causes of liver disease worldwide and will probably emerge as the leading cause of end-stage liver disease in the coming decades, with the disease affecting both adults and children. The epidemiology and demographic characteristics of NAFLD vary worldwide, usually parallel to the prevalence of obesity, but a substantial proportion of patients are lean. The large number of patients with NAFLD with potential for progressive liver disease creates challenges for screening, as the diagnosis of NASH necessitates invasive liver biopsy. Furthermore, individuals with NAFLD have a high frequency of metabolic comorbidities and could place a growing strain on health-care systems from their need for management. While awaiting the development effective therapies, this disease warrants the attention of primary care physicians, specialists and health policy makers.

IFNL3 polymorphisms predict response to therapy in chronic hepatitis C genotype 2/3 infection

BACKGROUND & AIMS Single nucleotide polymorphisms (SNPs) near the interferon lambda 3 (IFNL3, previously known as IL28B) region are the strongest baseline predictors of sustained virologic response (SVR) to pegylated interferon and ribavirin therapy in hepatitis C virus (HCV) genotype 1 infection. Whether IFNL3 SNPs influence treatment response in genotype 2 and 3 (HCV-2/3) infection remains controversial. This study sought to clarify in a large cohort, whether SNPs in the IFNL3 region are associated with treatment response in HCV-2/3 patients. METHODS The cohort comprised 1002 HCV-2/3 Caucasians patients treated with pegylated interferon-alpha and ribavirin who underwent genotyping for the SNPs rs12979860 and rs8099917. RESULTS Overall, 736 (73.5%) patients achieved SVR (81.9%, 67.9%, and 57.8% for rs12979860 CC, CT, and TT [p = 0.0001]; 78%, 68.7%, and 46.3% for rs8099917 TT, TG, and GG [p = 0.0001]). By logistic regression, both rs12979860 CC and rs8099917 TT were independent predictors of SVR with an odds ratio (OR) of 2.39 (1.19-3.81) p = 0.0001 and OR 1.85 (1.15-2.23) p = 0.0001, respectively. IFNL3 responder genotypes were more frequent in relapsers than null-responders (p = 0.0001 for both SNPs). On-treatment rapid virological response (RVR) was predictive of SVR only in those individuals with IFNL3 non-responder genotypes (rs12979860 CT/TT and rs8099917 TG/GG). CONCLUSIONS This adequately powered study in patients with HCV genotypes 2 or 3 infection clearly demonstrates that IFNL3 genotypes are the strongest baseline predictor of SVR, in keeping with the known association for genotype 1 infection. IFNL3 genotyping can aid in therapeutic decision making for these patients.

Genetics and epigenetics of NAFLD and NASH: Clinical impact

Non-alcoholic fatty liver disease (NAFLD) is now recognised as the most common liver disease worldwide. It encompasses a broad spectrum of conditions, from simple steatosis, through non-alcoholic steatohepatitis, to fibrosis and ultimately cirrhosis and hepatocellular carcinoma. A hallmark of NAFLD is the substantial inter-patient variation in disease progression. NAFLD is considered a complex disease trait such that interactions between the environment and a susceptible polygenic host background determine disease phenotype and influence progression. Recent years have witnessed multiple genome-wide association and large candidate gene studies, which have enriched our understanding of the genetic basis of NAFLD. Notably, the I148M PNPLA3 variant has been identified as the major common genetic determinant of NAFLD. Variants with moderate effect size in TM6SF2, MBOAT7 and GCKR have also been shown to have a significant contribution. The premise for this review is to discuss the status of research into important genetic and epigenetic modifiers of NAFLD progression. The potential to translate the accumulating wealth of genetic data into the design of novel therapeutics and the clinical implementation of diagnostic/prognostic biomarkers will be explored. Finally, personalised medicine and the opportunities for future research and challenges in the immediate post genetics era will be illustrated and discussed.

Diverse impacts of the rs58542926 E167K variant in TM6SF2 on viral and metabolic liver disease phenotypes

A genome‐wide exome association study has identified the transmembrane 6 superfamily member 2 (TM6SF2) rs58542926 variant encoding an E167K substitution as a genetic determinant of hepatic steatosis in nonalcoholic fatty liver disease (NAFLD). The roles of this variant across a spectrum of liver diseases and pathologies and on serum lipids comparing viral hepatitis to NAFLD and viral load in chronic viral hepatitis, as well as its intrahepatic molecular signature, have not been well characterized. We undertook detailed analyses in 3260 subjects with viral and nonviral liver diseases and in healthy controls. Serum inflammatory markers and hepatic expression of TM6SF2 and genes regulating lipid metabolism were assessed in a subset with chronic hepatitis C (CHC). The rs58542926 T allele was more prevalent in 502 NAFLD patients than controls (P = 0.02) but not different in cohorts with CHC (n = 2023) and chronic hepatitis B (n = 507). The T allele was associated with alterations in serum lipids and hepatic steatosis in all diseases and with reduced hepatic TM6SF2 and microsomal triglyceride transfer protein expression. Interestingly, the substitution was associated with reduced CHC viral load but increased hepatitis B virus DNA. The rs58542926 T allele had no effect on inflammation, impacted ≥F2 fibrosis in CHC and NAFLD assessed cross‐sectionally (odds ratio = 1.39, 95% confidence interval 1.04‐1.87, and odds ratio = 1.62, 95% confidence interval 1.03‐2.52, respectively; P < 0.03 for both), but had no effect on fibrosis progression in 1174 patients with CHC and a known duration of infection. Conclusion: The TM6SF2 E167K substitution promotes steatosis and lipid abnormalities in part by altering TM6SF2 and microsomal triglyceride transfer protein expression and differentially impacts CHC and chronic hepatitis B viral load, while effects on fibrosis are marginal. (Hepatology 2016;64:34–46)

MBOAT7 rs641738 increases risk of liver inflammation and transition to fibrosis in chronic hepatitis C

Cirrhosis likely shares common pathophysiological pathways despite arising from a variety of liver diseases. A recent GWAS identified rs641738, a polymorphism in the MBOAT7 locus, as being associated with the development of alcoholic cirrhosis. Here we explore the role of this variant on liver inflammation and fibrosis in two cohorts of patients with chronic hepatitis C. In 2,051 patients, rs641738 associated with severe hepatic inflammation and increased risk of fibrosis, as well as fast fibrosis progression. At functional level, rs641738 associated with MBOAT7 transcript and protein levels in liver and blood, and with serum inflammatory, oxidative stress and macrophage activation markers. MBOAT7 was expressed in immune cell subsets, implying a role in hepatic inflammation. We conclude that the MBOAT7 rs641738 polymorphism is a novel risk variant for liver inflammation in hepatitis C, and thereby for liver fibrosis.

The macrophage activation marker sCD163 is associated with morphological disease stages in patients with non-alcoholic fatty liver disease.

Macrophage activation plays a key pathogenic role in experimental non‐alcoholic fatty liver disease (NAFLD) and contributes to the progression of steatohepatitis (NASH) and fibrosis. We studied macrophage activation in human NAFLD by measuring soluble (s)CD163, a specific macrophage activation marker, hypothesizing that sCD163 would be associated with the patients’ morphological disease grade. Furthermore, we investigated an association between sCD163 and the apoptosis marker cytokeratin‐18 (CK‐18) to explore a link between macrophage activation and apoptosis.

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

The PNPLA3/Adiponutrin rs738409 C/G single nucleotide polymorphism is associated with the severity of steatosis, steatohepatitis and fibrosis in patients with non‐alcoholic fatty liver disease, as well as the severity of steatosis and fibrosis in patients with chronic hepatitis C (CHC).

IFN-λ3, not IFN-λ4, likely mediates IFNL3–IFNL4 haplotype–dependent hepatic inflammation and fibrosis

Genetic variation in the IFNL3–IFNL4 (interferon-λ3–interferon-λ4) region is associated with hepatic inflammation and fibrosis. Whether IFN-λ3 or IFN-λ4 protein drives this association is not known. We demonstrate that hepatic inflammation, fibrosis stage, fibrosis progression rate, hepatic infiltration of immune cells, IFN-λ3 expression, and serum sCD163 levels (a marker of activated macrophages) are greater in individuals with the IFNL3–IFNL4 risk haplotype that does not produce IFN-λ4, but produces IFN-λ3. No difference in these features was observed according to genotype at rs117648444, which encodes a substitution at position 70 of the IFN-λ4 protein and reduces IFN-λ4 activity, or between patients encoding functionally defective IFN-λ4 (IFN-λ4–Ser70) and those encoding fully active IFN-λ4–Pro70. The two proposed functional variants (rs368234815 and rs4803217) were not superior to the discovery SNP rs12979860 with respect to liver inflammation or fibrosis phenotype. IFN-λ3 rather than IFN-λ4 likely mediates IFNL3–IFNL4 haplotype–dependent hepatic inflammation and fibrosis.

The membrane-bound O-acyltransferase domain-containing 7 variant rs641738 increases inflammation and fibrosis in chronic hepatitis B

Chronic hepatitis B (CHB) is characterized by hepatic inflammation that promotes progression to cirrhosis and predisposes to the development of hepatocellular carcinoma (HCC). Subtle interindividual genetic variation as well as viral and environmental factors interact to determine disease progression between individuals. Recently, the rs641738 membrane‐bound O‐acyltransferase domain‐containing 7 (MBOAT7) polymorphism was demonstrated to influence histological liver damage in alcoholic liver disease, nonalcoholic fatty liver disease, and hepatitis C, but no data are available for CHB. We evaluated rs641738 influence on disease severity in a cohort of 1,101 patients with CHB. Forty‐two patients underwent gene expression analysis to assess the functional consequences of rs641738 on hepatic MBOAT7 expression. The minor allele (T) of rs641738 was associated with greater inflammation (odds ratio [OR], 1.45; 95% confidence interval [CI], 1.06‐1.95; P = 0.001) and fibrosis (OR = 1.31; 95% CI, 1.19‐1.92; P = 0.01). Risk allele frequency in whites (0.43) was greater than in Chinese (0.24), translating to a larger size effect in the former. The rs641738 (T) allele was associated with lower hepatic MBOAT7 expression (P = 0.008), and the latter was associated with serum liver enzymes and inflammation. Neither patatin‐like phospholipase domain‐containing protein 3 rs738409 nor transmembrane 6 superfamily member 2 rs58542926 polymorphisms influenced disease severity. Conclusion: In patients with CHB, MBOAT7 rs641738 influences hepatic inflammation and fibrosis stage. (Hepatology 2017;65:1840‐1850).

Genome-Wide Association Studies and Hepatitis C: Harvesting the Benefits of the Genomic Revolution.

Utilizing genome-wide association studies (GWASs) to examine the variation in hepatitis C virus (HCV) phenotypes has led to quantum improvements in our understanding of both the genetic basis and the underlying pathogenesis of HCV infection. In this context, the discovery of interferon lambda polymorphisms is unique with far reaching implications that extend well beyond HCV to various other liver and extrahepatic diseases. In this review, we summarize the data on the impact of GWASs on our understanding of HCV disease.