IL28B rs12979860 is not associated with histologic features of NAFLD in a cohort of Caucasian North American patients

Programmed cell death-1 rs11568821 and interleukin-28B rs12979860 polymorphisms in autoimmune hepatitis

BACKGROUND

Autoimmune hepatitis (AIH) is a relatively rare chronic liver disease of unknown etiology. The genetic background affects susceptibility, clinical phenotype, and prognosis. The programmed cell death-1 rs11568821 polymorphism (PD1.3) has been associated with susceptibility to autoimmune diseases. The interleukin-28B (IL28B) rs12979860 polymorphism has been associated with steatosis, inflammation, and fibrosis in liver diseases.

AIM

Our aim was to investigate for the first time the incidence and clinical significance of PD1.3 and IL28B rs12979860 in AIH.

METHODS

Two hundred patients with AIH were evaluated, while 100 healthy subjects were used as controls. Genotyping was performed with in-house allelic discrimination End-Point PCR.

RESULTS

The SNP PD1.3/A was present in 36/200 (18%) AIH patients compared to 28/100 (28%) healthy controls (p = 0.065). The AA/GA genotypes were not associated with the mode of presentation of AIH, the histological grade or stage, the presence of cirrhosis, risk of disease progression, response to treatment and survival. The IL28B rs12979860 genotype distribution was CC 79/200 (39.5%), TT 36/200 (18%) and CT 85/200 (42.5%), in similar rates with healthy controls (p = 0.878). Inflammatory activity and fibrosis stage did not differ between CC homozygotes and CT/TT carriers. LDL cholesterol was significantly higher in CC than CT/TT patients (P = 0.027), though no differences was found regarding the presence of steatosis or steatohepatitis. On-treatment response to immunosuppressive treatment was not affected by the IL28B rs12979860 polymorphism. However, CC homozygotes AIH patients achieved treatment withdrawal in significantly higher rates (OR 2.3, 95%CI: 1.1-4.7, P = 0.02) irrespective of the presence of steatosis or steatohepatitis.

CONCLUSIONS

The PD1.3 and IL28B rs12979860 variants are unlikely to contribute to AIH susceptibility, disease presentation and prognosis. The IL28B rs12979860 is not associated with the presence of concurrent steatosis or steatohepatitis. However, although on-treatment response rates to immunosuppression were not affected by the IL28B rs12979860 polymorphism, AIH patients with CC homozygosity were more likely to achieve complete treatment withdrawal. This novel finding needs validation and further clarification from larger multicenter studies.

Interferon Lambda and Liver Fibrosis

Fibrosis is a highly conserved and coordinated wound healing response to injury. In the liver, injury is promoted by immune effector mechanisms that are common across various disease etiologies and even between organs such as lungs, kidneys, heart, and other organs. Thus, the liver represents a useful model to study inflammation and repair, particularly as it is frequently biopsied in clinical contexts. Currently, strong evidence implicates IFNL3/4 polymorphisms and interferon (IFN)-λ3 levels as determinants of the extent of hepatic inflammation and fibrosis in viral and nonviral liver diseases, as well as in governing the severity of nonhepatotropic viral diseases. Interestingly, IFNL3/4 polymorphisms and IFN-λ3 levels correlate with fibrosis extent in other organs such as the lung and kidney. In this review, we discuss the association between IFN-λ and tissue inflammation and fibrosis in human disease and the potential clinical utility of the findings.

Interferon lambda 4 rs368234815 TT>δG variant is associated with liver damage in patients with nonalcoholic fatty liver disease

The interferon (IFN) lambda 3/4 (IFNL3/4) locus, influencing innate immunity regulation, has been associated with the severity of hepatitis and fibrosis progression during chronic hepatitis C infection, while contrasting results were reported in nonalcoholic fatty liver disease. In this study, we examined whether rs12979860 and the linked causal rs368234815 variant encoding for the alternative IFNL4 protein variant are associated with liver fibrosis and damage in a large multicenter cohort of patients at risk of nonalcoholic steatohepatitis. To clarify the mechanism, we also evaluated the impact on IFN-stimulated gene hepatic expression in a subset of patients. We considered 946 consecutive Italian individuals at risk of nonalcoholic steatohepatitis with liver histology evaluated according to Kleiner. The rs368234815 TT>δG, rs12979860 C>T, and patatin-like phospholipase-3 rs738409 C>G polymorphisms were genotyped; and IFN-stimulated gene hepatic expression (n = 16) was tested by TaqMan assays. We found that the rs368234815 TT allele was independently associated with severe F3-F4 fibrosis (odds ratio, 1.53; 95% confidence interval, 1.15-2.31; P = 0.005) and with severe (grade 2-3) lobular necroinflammation (odds ratio, 1.47; 95% confidence interval, 1.14-1.88; P = 0.002). The impact of rs368234815 on liver damage was generally more marked in nonobese individuals, where association with severe fibrosis, necroinflammation, and nonalcoholic steatohepatitis was observed (P < 0.05). IFN-stimulated genes were hypo-expressed in the liver of patients carrying the IFNL4 rs368234815 TT/TT genotype (P < 0.05). Similar results were observed when considering the rs12979860 polymorphism, which was in high linkage disequilibrium with rs368234815 (R² = 0.87).

CONCLUSION

The IFNL4 genotype is associated with severity of fibrosis in nonalcoholic fatty liver disease patients of European ancestry, likely by modulating the activation of innate immunity and necroinflammation. (Hepatology 2017;66:1885-1893).

Significance of genetic polymorphisms in patients with nonalcoholic fatty liver disease

Because of recent advances in genetic research such as genome-wide association studies, the underlying genetic mechanisms of nonalcoholic fatty liver disease (NAFLD) pathophysiology have been elucidated. Here, we present a review of the current literature on the impact of genetic polymorphisms in patients with NAFLD. These genetic polymorphisms, which regulate lipid metabolism, glucose metabolism, and the renin-angiotensin system, are involved in NAFLD onset, steatosis, inflammation, fibrosis, and hepatocellular carcinoma (HCC). Among these genetic polymorphisms, many studies and meta-analyses have demonstrated that position 148 (rs738409 C/G) of the patatin-like phospholipase domain-containing protein (PNPLA3) is a genetic factor associated with NAFLD pathophysiological features, such as hepatic fat level, hepatic inflammation, fibrosis, and HCC. However, the impact of genetic polymorphisms on NAFLD pathophysiology appears to differ among ethnic groups. Therefore, further studies with larger sample sizes are needed for each ethnic group.

Gene-disease association with human IFNL locus polymorphisms extends beyond hepatitis C virus infections

Interferon (IFN) lambda (IFN-λ or type III IFN) gene polymorphisms were discovered in the year 2009 to have a strong association with spontaneous and treatment-induced clearance of hepatitis C virus (HCV) infection in human hosts. This landmark discovery also brought renewed interest in type III IFN biology. After more than half a decade since this discovery, we now have reports that show that genetic association of IFNL gene polymorphisms in humans is not limited only to HCV infections but extends beyond, to include varied diseases such as non-alcoholic fatty liver disease, allergy and several other viral diseases including that caused by the human immunodeficiency virus. Notably, all these conditions have strong involvement of host innate immune responses. After the discovery of a deletion polymorphism that leads to the expression of a functional IFN-λ4 as the prime 'functional' variant, the relevance of other polymorphisms regulating the expression of IFN-λ3 is in doubt. Herein, I seek to critically address these issues and review the current literature to provide a framework to help further understanding of IFN-λ biology.

Genetic Factors That Affect Risk of Alcoholic and Nonalcoholic Fatty Liver Disease

Genome-wide association studies and candidate gene studies have informed our understanding of factors contributing to the well-recognized interindividual variation in the progression and outcomes of alcoholic liver disease and nonalcoholic fatty liver disease. We discuss the mounting evidence for shared modifiers and common pathophysiological processes that contribute to development of both diseases. We discuss the functions of proteins encoded by risk variants of genes including patatin-like phospholipase domain-containing 3 and transmembrane 6 superfamily member 2, as well as epigenetic factors that contribute to the pathogenesis of alcoholic liver disease and nonalcoholic fatty liver disease. We also discuss important areas of future genetic research and their potential to affect clinical management of patients.

Insights from Genome-Wide Association Analyses of Nonalcoholic Fatty Liver Disease

Nonalcoholic fatty liver disease (NAFLD) is caused by hepatic steatosis, which can progress to nonalcoholic steatohepatitis, fibrosis/cirrhosis, and hepatocellular carcinoma in the absence of excessive alcohol consumption. Nonalcoholic fatty liver disease will become the number one cause of liver disease worldwide by 2020. Nonalcoholic fatty liver disease is correlated albeit imperfectly with obesity and other metabolic diseases such as diabetes, hyperlipidemia, and cardiovascular disease, but exactly how having one of these diseases contributes to the development of other metabolic diseases is only now being elucidated. Development of NAFLD and related metabolic diseases is genetically influenced in the population, and recent genome-wide association studies (GWASs) have discovered genetic variants that associate with these diseases. These GWAS-associated variants cannot only help us to identify individuals at high risk of developing NAFLD, but also to better understand its pathophysiology so that we can develop more effective treatments for this disease and related metabolic diseases in the future.

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.

Interferon-λ rs12979860 genotype and liver fibrosis in viral and non-viral chronic liver disease

Tissue fibrosis is a core pathologic process that contributes to mortality in ~45% of the population and is likely to be influenced by the host genetic architecture. Here we demonstrate, using liver disease as a model, that a single-nucleotide polymorphism (rs12979860) in the intronic region of interferon-λ4 (IFNL4) is a strong predictor of fibrosis in an aetiology-independent manner. In a cohort of 4,172 patients, including 3,129 with chronic hepatitis C (CHC), 555 with chronic hepatitis B (CHB) and 488 with non-alcoholic fatty liver disease (NAFLD), those with rs12979860CC have greater hepatic inflammation and fibrosis. In CHC, those with rs12979860CC also have greater stage-constant and stage-specific fibrosis progression rates (P<0.0001 for all). The impact of rs12979860 genotypes on fibrosis is maximal in young females, especially those with HCV genotype 3. These findings establish rs12979860 genotype as a strong aetiology-independent predictor of tissue inflammation and fibrosis.

Tissue fibrosis is a major contributor to mortality in the developed world. Here, the authors identify a genetic variant in the intronic region of interferon-λ4 that is a strong predictor of hepatic inflammation and fibrosis, independent of liver disease aetiology