Common polymorphism in the PNPLA3/adiponutrin gene confers higher risk of cirrhosis and liver damage in alcoholic liver disease

The burden of liver disease in Latin America

Liver disease poses a substantial burden in Latin America. This burden is primarily attributed to a high level of alcohol consumption and the increasing prevalence of risk factors associated with metabolic dysfunction-associated steatotic liver disease (MASLD), such as sedentary lifestyles, easy access to ultra-processed foods, obesity, and type 2 diabetes mellitus. These epidemiological trends are cause for concern, especially considering that there are significant challenges in addressing them due to disparities in access to liver disease screening and care. In this article, we aim to provide an overview of the current situation regarding liver disease in Latin America. We also discuss recent multinational proposals designed to address the growing MASLD burden via its integration into existing non-communicable diseases policies, at both local and global levels. Additionally, we emphasize the urgent need to establish effective public health policies that target both MASLD risk factors and excessive alcohol consumption. Furthermore, we discuss the development of liver transplantation programs, areas for improvement in medical education and research capabilities, and how the fostering of extensive collaboration among all stakeholders is crucial for addressing liver disease in the region.

The ubiquitin E3 ligase BFAR promotes degradation of PNPLA3

A missense variant in patatin-like phospholipase domain-containing protein 3 [PNPLA3(I148M)] is the most impactful genetic risk factor for fatty liver disease (FLD). We previously showed that PNPLA3 is ubiquitylated and subsequently degraded by proteasomes and autophagosomes and that the PNPLA3(148M) variant interferes with this process. To define the machinery responsible for PNPLA3 turnover, we used small interfering (si)RNAs to inactivate components of the ubiquitin proteasome system. Inactivation of bifunctional apoptosis regulator (BFAR), a membrane-bound E3 ubiquitin ligase, reproducibly increased PNPLA3 levels in two lines of cultured hepatocytes. Conversely, overexpression of BFAR decreased levels of endogenous PNPLA3 in HuH7 cells. BFAR and PNPLA3 co-immunoprecipitated when co-expressed in cells. BFAR promoted ubiquitylation of PNPLA3 in vitro in a reconstitution assay using purified, epitope-tagged recombinant proteins. To confirm that BFAR targets PNPLA3, we inactivated Bfar in mice. Levels of PNPLA3 protein were increased twofold in hepatic lipid droplets of Bfar-/- mice with no associated increase in PNPLA3 mRNA levels. Taken together these data are consistent with a model in which BFAR plays a role in the post-translational degradation of PNPLA3. The identification of BFAR provides a potential target to enhance PNPLA3 turnover and prevent FLD.

Effect of donor HSD17B13 genotype on patient survival after liver transplant: a retrospective cohort study

Background

Several genetic variants are associated with chronic liver disease. The role of these variants in outcomes after liver transplantation (LT) is uncertain. The aim of this study was to determine if donor genotype at risk-associated variants in PNPLA3 (rs738409 C>G, p.I148M) and HSD17B13 (rs72613567 T>TA; rs80182459, p.A192Lfs∗8) influences post-LT survival.

Methods

In this retrospective cohort study, data on 2346 adults who underwent first-time LT between January 1, 1999 and June 30, 2020 and who had donor DNA samples available at five large Transplant Immunology Laboratories in Texas, USA, were obtained from the United Network for Organ Sharing (UNOS). Duplicates, patients with insufficient donor DNA for genotyping, those who were <18 years of age at the time of transplant, had had a previous transplant or had missing genotype data were excluded. The primary outcomes were patient and graft survival after LT. The association between donor genotype and post-LT survival was examined using Kaplan-Meier method and multivariable-adjusted Cox proportional hazards models.

Findings

Median age of LT recipients was 57 [interquartile range (IQR), 50-62] years; 837 (35.7%) were women; 1362 (58.1%) White, 713 (30.4%) Hispanic, 182 (7.8%) Black/African-American. Median follow-up time was 3.95 years. Post-LT survival was not affected by donor PNPLA3 genotype but was significantly reduced among recipients of livers with two HSD17B13 loss-of-function (LoF) variants compared to those receiving livers with no HSD17B13 LoF alleles (unadjusted one-year survival: 82.6% vs 93.9%, P < 0.0001; five-year survival: 73.1% vs 82.9%, P = 0.0017; adjusted hazard ratio [HR], 2.25; 95% CI, 1.61-3.15 after adjustment for recipient age, sex, and self-reported ethnicity). Excess mortality was restricted to those receiving steroid induction immunosuppression (crude 90-day post-LT mortality, 9.3% [95% CI, 1.9%-16.1%] vs 1.9% [95% CI, 0.9%-2.9%] in recipients of livers with two vs no HSD17B13 LoF alleles, P = 0.0012; age, sex, and ethnicity-adjusted HR, 2.85; 95% CI, 1.72-4.71, P < 0.0001). No reduction was seen among patients who did not receive steroid induction (90-day mortality 3.1% [95% CI, 0%-7.3%] vs 2% [95% CI, 0.9%-3.1%], P = 0.65; adjusted HR, 1.17; 95% CI, 0.66-2.08, P = 0.60).

Interpretation

Donor HSD17B13 genotype adversely affects post-LT survival in patients receiving steroid induction. Additional studies are required to confirm this association.

Funding

The National Institutes of Health and American Society of Transplant Surgeons Collaborative Scientist Grant.

Mechanisms of Lipid Droplet Accumulation in Steatotic Liver Diseases

The steatotic diseases of metabolic dysfunction-associated steatotic liver disease (MASLD), alcohol-associated liver disease (ALD), and chronic hepatitis C (HCV) account for the majority of liver disease prevalence, morbidity, and mortality worldwide. While these diseases have distinct pathogenic and clinical features, dysregulated lipid droplet (LD) organelle biology represents a convergence of pathogenesis in all three. With increasing understanding of hepatocyte LD biology, we now understand the roles of LD proteins involved in these diseases but also how genetics modulate LD biology to either exacerbate or protect against the phenotypes associated with steatotic liver diseases. Here, we review the history of the LD organelle and its biogenesis and catabolism. We also review how this organelle is critical not only for the steatotic phenotype of liver diseases but also for their advanced phenotypes. Finally, we summarize the latest attempts and challenges of leveraging LD biology for therapeutic gain in steatotic diseases. In conclusion, the study of dysregulated LD biology may lead to novel therapeutics for the prevention of disease progression in the highly prevalent steatotic liver diseases of MASLD, ALD, and HCV.

Predictive risk markers in alcoholism

The medical disorders of alcoholism rank among the leading public health problems worldwide and the need for predictive and prognostic risk markers for assessing alcohol use disorders (AUD) has been widely acknowledged. Early-phase detection of problem drinking and associated tissue toxicity are important prerequisites for timely initiations of appropriate treatments and improving patient's committing to the objective of reducing drinking. Recent advances in clinical chemistry have provided novel approaches for a specific detection of heavy drinking through assays of unique ethanol metabolites, phosphatidylethanol (PEth) or ethyl glucuronide (EtG). Carbohydrate-deficient transferrin (CDT) measurements can be used to indicate severe alcohol problems. Hazardous drinking frequently manifests as heavy episodic drinking or in combinations with other unfavorable lifestyle factors, such as smoking, physical inactivity, poor diet or adiposity, which aggravate the metabolic consequences of alcohol intake in a supra-additive manner. Such interactions are also reflected in multiple disease outcomes and distinct abnormalities in biomarkers of liver function, inflammation and oxidative stress. Use of predictive biomarkers either alone or as part of specifically designed biological algorithms helps to predict both hepatic and extrahepatic morbidity in individuals with such risk factors. Novel approaches for assessing progression of fibrosis, a major determinant of prognosis in AUD, have also been made available. Predictive algorithms based on the combined use of biomarkers and clinical observations may prove to have a major impact on clinical decisions to detect AUD in early pre-symptomatic stages, stratify patients according to their substantially different disease risks and predict individual responses to treatment.

Association of TGF-β1 Polymorphism and TGF-β1 Levels With Chronic Hepatitis C and Cirrhosis: A Systematic Review and Meta-Analysis

Despite the extensive research conducted on the relationship between transforming growth factor-beta 1 (TGF-β1) polymorphisms and levels and the onset and development of liver disease, there are still certain gaps that need to be addressed. To address these gaps and provide a comprehensive overview of the current knowledge, this review aimed to identify relevant published research on TGF-β1/TGF-β1 polymorphism, TGF-β1/TGF-β1 levels, and their associations with cirrhosis and hepatitis C. The synthesis of available data was performed to further enhance our understanding in this area. Adopting the Preferred Reporting Items for Systematic Reviews and Meta-Analysis (PRISMA) guidelines, a search strategy was implemented across several online databases to search for relevant articles as per the defined selection criterion. Eight studies were selected after the completion of the search strategy. Of the eight studies, five revealed a considerably high level of TGF-β1 in patients who had hepatitis C virus (HCV) and liver cirrhosis caused by hepatocellular carcinoma (HCC). The forest plot analysis showed a statistically significant impact of TGF-β1 polymorphism and levels on the incidence of hepatic cirrhosis and hepatitis C, with an odds ratio (OR) of 0.65 and a risk ratio (RR) of 0.76. The heterogeneity test showed a high level of heterogeneity at 94% and 95% for OR and RR, respectively, but the overall effect was significant with P < 0.01 for both measures. According to the results obtained, the authors concluded that TGF-β1 polymorphism and its associated levels should be taken into account while developing preventive and therapeutic approaches for hepatic cirrhosis and hepatitis C.

Spectrum, Screening, and Diagnosis of Alcohol-related Liver Disease

Alcohol-related liver disease (ALD) represents one of the leading causes of chronic liver disease and is a major cause of liver-related deaths worldwide. ALD encompasses a range of disorders including simple steatosis, alcoholic steatohepatitis, fibrosis, cirrhosis, and hepatocellular carcinoma. Patients with underlying ALD and continued heavy alcohol consumption can also develop an episode of acute-on-chronic liver injury called alcohol-associated hepatitis, the most severe form of the disease, which portends a poor prognosis. The most important risk factor for the development of ALD is the amount of alcohol consumed. Individual susceptibility to progression to advanced fibrosis among heavy drinkers is likely determined by a combination of behavioral, environmental, genetic, and epigenetic factors, but the mechanisms are largely unknown. The only effective therapy for ALD is prolonged alcohol abstinence. Diagnosis of ALD involves assessing patients for alcohol use disorder and signs of advanced liver disease. In clinical practice, the histological assessment for ALD diagnosis is uncommon, and it is usually based on the medical history, clinical manifestations, and laboratory and imaging tests. Several promising biomarkers that can have both diagnostic and prognostic value in patients with ALD have been identified in recent years. This review provides an overview of the clinical spectrum of ALD, the diagnostic approach of the disease from different perspectives as well as current diagnostic and prognostic biomarkers.

Liver Diseases in Latin America: Current Status, Unmet Needs, and Opportunities for Improvement

Purpose of review

To assess the current challenges regarding liver diseases, including the burden of disease, access to care, screening, and treatment needs in Latin America.

Recent findings

Latin America is a region with a rich multicultural heritage and important socioeconomic differences. The burden of liver diseases is high and mainly determined by a high level of alcohol intake and the surge of risk factors associated with NAFLD (i.e., sedentary lifestyles, broader access to highly processed foods, obesity, and type 2 diabetes mellitus). Hepatotropic viruses also play a role in the development of chronic liver diseases, although their comparative frequency has been decreasing over the last decades. There are important disparities in access to screening and treatment for liver diseases in Latin America, which are reflected in low access to critical treatments such as direct-acting antiviral agents and drugs to treat hepatocellular carcinoma. Also, important barriers to liver transplantation are present in multiple countries, including a low deceased donors' rate and a lack of availability in several countries (especially in Central America). Our region also has disadvantages in research and education in liver diseases, which limits regional academic development and improvement in quality of care of liver diseases.

Summary

In order to tackle an increasing health burden due to liver diseases, Latin America urgently needs tailored interventions aiming to control the main risk factors for these disorders through the establishment of effective public health policies. Also, development of liver transplantation programs and improvement of medical education and research capabilities as well as extensive collaboration between all stakeholders are keys to address the liver disease agenda in the region.

Epigenetics of alcohol-related liver diseases

Alcohol-related liver disease (ARLD) is a primary cause of chronic liver disease in the United States. Despite advances in the diagnosis and management of ARLD, it remains a major public health problem associated with significant morbidity and mortality, emphasising the need to adopt novel approaches to the study of ARLD and its complications. Epigenetic changes are increasingly being recognised as contributing to the pathogenesis of multiple disease states. Harnessing the power of innovative technologies for the study of epigenetics (e.g., next-generation sequencing, DNA methylation assays, histone modification profiling and computational techniques like machine learning) has resulted in a seismic shift in our understanding of the pathophysiology of ARLD. Knowledge of these techniques and advances is of paramount importance for the practicing hepatologist and researchers alike. Accordingly, in this review article we will summarise the current knowledge about alcohol-induced epigenetic alterations in the context of ARLD, including but not limited to, DNA hyper/hypo methylation, histone modifications, changes in non-coding RNA, 3D chromatin architecture and enhancer-promoter interactions. Additionally, we will discuss the state-of-the-art techniques used in the study of ARLD (e.g. single-cell sequencing). We will also highlight the epigenetic regulation of chemokines and their proinflammatory role in the context of ARLD. Lastly, we will examine the clinical applications of epigenetics in the diagnosis and management of ARLD.

Synergistic and Detrimental Effects of Alcohol Intake on Progression of Liver Steatosis

Nonalcoholic fatty liver disease (NAFLD) and alcoholic liver disease (ALD) are the most common liver disorders worldwide and the major causes of non-viral liver cirrhosis in the general population. In NAFLD, metabolic abnormalities, obesity, and metabolic syndrome are the driving factors for liver damage with no or minimal alcohol consumption. ALD refers to liver damage caused by excess alcohol intake in individuals drinking more than 5 to 10 daily units for years. Although NAFLD and ALD are nosologically considered two distinct entities, they show a continuum and exert synergistic effects on the progression toward liver cirrhosis. The current view is that low alcohol use might also increase the risk of advanced clinical liver disease in NAFLD, whereas metabolic factors increase the risk of cirrhosis among alcohol risk drinkers. Therefore, special interest is now addressed to individuals with metabolic abnormalities who consume small amounts of alcohol or who binge drink, for the role of light-to-moderate alcohol use in fibrosis progression and clinical severity of the liver disease. Evidence shows that in the presence of NAFLD, there is no liver-safe limit of alcohol intake. We discuss the epidemiological and clinical features of NAFLD/ALD, aspects of alcohol metabolism, and mechanisms of damage concerning steatosis, fibrosis, cumulative effects, and deleterious consequences which include hepatocellular carcinoma.

PNPLA3 is the dominant SNP linked to liver disease severity at time of first referral to a tertiary center

BACKGROUND

Single nucleotide polymorphisms (SNPs) in genes including PNPLA3, TM6SF2, HSD17B13 and SERPINA1 have been identified as risk modifiers of progression in chronic liver disease (CLD). However, it is unclear whether genotyping for these risk variants is useful in clinical routine.

METHODS

Liver disease severity was assessed by liver stiffness measurement (LSM) and by presence of clinical manifestations of advanced-chronic liver disease (ACLD) in 779 consecutive CLD patients at the time of referral to a tertiary center. The associations of risk variants with CLD severity were calculated individually and in a combined model using a polygenic risk-score.

RESULTS

Non-alcoholic fatty liver disease (NAFLD) was the most common etiology (n = 511, 65.6%), and ACLD was present in 217 (27.9%) patients. The PNPLA3-G-allele remained independently associated with higher LSM (adjusted-B: 2.508 [95%CI: 0.887-4.130], P = 0.002) or the presence of ACLD (aOR: 1.562 [95%CI: 1.097-2.226], P = 0.013). SERPINA1-Z-allele was also independently associated with LSM (adjusted-B: 4.558 [95%CI: 1.182-7.934], P = 0.008), while the other risk alleles did not attain statistical significance. Combining these risk alleles into a polygenic risk-score was significantly associated with LSM (adjusted-B: 0.948 [95%CI: 0.153-1.743], P = 0.020).

CONCLUSION

PNPLA3 risk-variants are linked to liver disease severity at the time of first referral to an outpatient hepatology clinic.

MARC1 p.A165T variant is associated with decreased markers of liver injury and enhanced antioxidant capacity in autoimmune hepatitis

The clinical picture of autoimmune hepatitis (AIH) varies markedly between patients, potentially due to genetic modifiers. The aim of this study was to evaluate genetic variants previously associated with fatty liver as potential modulators of the AIH phenotype. The study cohort comprised 313 non-transplanted adults with AIH. In all patients, the MARC1 (rs2642438), HSD17B13 (rs72613567), PNPLA3 (rs738409), TM6SF2 (rs58542926), and MBOAT7 (rs641738) variants were genotyped using TaqMan assays. Mitochondrial damage markers in serum were analyzed in relation to the MARC1 variant. Carriers of the protective MARC1 allele had lower ALT and AST (both P < 0.05). In patients treated for AIH for ≥ 6 months, MARC1 correlated with reduced AST, ALP, GGT (all P ≤ 0.01), and lower APRI (P = 0.02). Patients carrying the protective MARC1 genotype had higher total antioxidant activity (P < 0.01) and catalase levels (P = 0.02) in serum. The PNPLA3 risk variant was associated with higher MELD (P = 0.02) in treated patients, whereas MBOAT7 increased the odds for liver cancer (OR = 3.71). None of the variants modulated the risk of death or transplantation. In conclusion, the MARC1 polymorphism has protective effects in AIH. Genotyping of MARC1, PNPLA3, and MBOAT7 polymorphisms might help to stratify patients with AIH.

Interaction Between Alcohol Consumption and PNPLA3 Variant in the Prevalence of Hepatic Steatosis in the US Population

BACKGROUND & AIMS

To our knowledge, the interaction between alcohol consumption and PNPLA3 genotype on hepatic steatosis has not been explored in a representative sample. To examine the interaction between alcohol consumption and PNPLA3 genotype on hepatic steatosis in the US adult population.

METHODS

Cross-sectional study of 4,674 adult participants of the Third National Health and Nutrition Examination Survey, Phase 2 (1991-1994) with data on PNPLA3 genotype, self-reported alcohol consumption, ultrasound-defined hepatic steatosis and socio-demographic characteristics.

RESULTS

In 1991-1994 in the U.S. population, the weighted allele frequency of the G (risk) allele of the rs738409 at PNPLA3 was 25.4%. We confirmed both a J shaped association between alcohol consumption and hepatic steatosis among those with the CC genotype of PNPLA3, and a higher prevalence of hepatic steatosis among those with PNPLA3 gene G variant. We found evidence of an interaction of PNPLA3 G allele presence on the association between moderate alcohol consumption and hepatic steatosis on both the multiplicative (relative prevalence ratio [RPR]=1.95, 95% confidence interval [CI] 1.04-3.65) and additive scales (relative excess risk due to interaction=0.49, 95% CI 0.13-0.85). Compared to never drinkers, moderate alcohol drinking was associated with a 48% decreased risk of hepatic steatosis only among those without PNPLA3 G allele (PR=0.52, 95% CI 0.26-1.05), with no association among those with at least one copy of the PNPLA3 G allele (PR=1.02, 95% CI 0.68-1.54).

CONCLUSIONS

Our results suggest that a highly common and strong genetic susceptibility to liver disease is modifiable by the level of alcohol consumption. Keeping alcohol consumption low may offset genetic predisposition to liver disease.

Modeling PNPLA3-Associated NAFLD Using Human-Induced Pluripotent Stem Cells

BACKGROUND AND AIMS

NAFLD is a growing public health burden. However, the pathogenesis of NAFLD has not yet been fully elucidated, and the importance of genetic factors has only recently been appreciated. Genomic studies have revealed a strong association between NAFLD progression and the I148M variant in patatin-like phospholipase domain-containing protein 3 (PNPLA3). Nonetheless, very little is known about the mechanisms by which this gene and its variants can influence disease development. To investigate these mechanisms, we have developed an in vitro model that takes advantage of the unique properties of human-induced pluripotent stem cells (hiPSCs) and the CRISPR/CAS9 gene editing technology.

APPROACH AND RESULTS

We used isogenic hiPSC lines with either a knockout (PNPLA3^KO ) of the PNPLA3 gene or with the I148M variant (PNPLA3^I148M ) to model PNPLA3-associated NAFLD. The resulting hiPSCs were differentiated into hepatocytes, treated with either unsaturated or saturated free fatty acids to induce NAFLD-like phenotypes, and characterized by various functional, transcriptomic, and lipidomic assays. PNPLA3^KO hepatocytes showed higher lipid accumulation as well as an altered pattern of response to lipid-induced stress. Interestingly, loss of PNPLA3 also caused a reduction in xenobiotic metabolism and predisposed PNPLA3^KO cells to be more susceptible to ethanol-induced and methotrexate-induced toxicity. The PNPLA3^I148M cells exhibited an intermediate phenotype between the wild-type and PNPLA3^KO cells.

CONCLUSIONS

Together, these results indicate that the I148M variant induces a loss of function predisposing to steatosis and increased susceptibility to hepatotoxins.

Research progress, challenges and perspectives on PNPLA3 and its variants in Liver Diseases

The human patatin-like phospholipase domain-containing 3 gene (PNPLA3) is highly expressed in liver and adipose tissue and encodes a transmembrane polypeptide chain containing 481 amino acids. The I148M variant of PNPLA3 is a single nucleotide polymorphism, which is related to a variety of liver and cardiovascular diseases and their complications (such as non-alcoholic fatty liver disease, liver fibrosis, coronary artery disease). This review mainly describes the pathophysiological effects of PNPLA3 and its variants, and their roles in the progression of liver disease and its complications.

Genetic Variants of Alcohol Metabolizing Enzymes and Alcohol-Related Liver Cirrhosis Risk

Alcohol-related liver disease (ARLD) is a major public health issue caused by excessive alcohol consumption. ARLD encompasses a wide range of chronic liver lesions, alcohol-related liver cirrhosis being the most severe and harmful state. Variations in the genes encoding the enzymes, which play an active role in ethanol metabolism, might influence alcohol exposure and hence be considered as risk factors of developing cirrhosis. We conducted a case-control study in which 164 alcohol-related liver cirrhosis patients and 272 healthy controls were genotyped for the following functional single nucleotide variations (SNVs): ADH1B gene, rs1229984, rs1041969, rs6413413, and rs2066702; ADH1C gene, rs35385902, rs283413, rs34195308, rs1693482, and rs35719513; CYP2E1 gene, rs3813867. Furthermore, copy number variations (CNVs) for ADH1A, ADH1B, ADH1C, and CYP2E1 genes were analyzed. A significant protective association with the risk of developing alcohol-related liver cirrhosis was observed between the mutant alleles of SNVs ADH1B rs1229984 (P_c value = 0.037) and ADH1C rs283413 (P_c value = 0.037). We identified CNVs in all genes studied, ADH1A gene deletions being more common in alcohol-related liver cirrhosis patients than in control subjects, although the association lost statistical significance after multivariate analyses. Our findings support that susceptibility to alcohol-related liver cirrhosis is related to variations in alcohol metabolism genes.

PNPLA3 and SERPINA1 Variants Are Associated with Severity of Fatty Liver Disease at First Referral to a Tertiary Center

Single nucleotide polymorphisms (SNPs), including PNPLA3 rs738409 and SERPINA1 rs17580, have been identified as risk modifiers in the progression fatty liver disease (alcoholic (ALD) or non-alcoholic (NAFLD)). While PNPLA3 has been studied in various settings, the value of both SNPs has so far not been addressed in a real-world cohort of subjects referred for a diagnostic work-up of liver disease. Thus, liver disease severity was assessed in 1257 consecutive patients with suspected ALD or NAFLD at the time of referral to a tertiary center. Advanced chronic liver disease (ACLD) was present in 309 (24.6%) patients and clinically significant portal hypertension (CSPH) was present in 185 (14.7%) patients. The PNPLA3 G-allele was independently associated with a higher liver stiffness measurement (LSM; adjusted B: 2.707 (1.435–3.979), p < 0.001), and higher odds of ACLD (adjusted odds ratio (aOR): 1.971 (1.448–2.681), p < 0.001) and CSPH (aOR: 1.685 (1.180–2.406), p = 0.004). While the SERPINA1 Z-allele was not associated with a higher LSM or the presence of ACLD, it was independently associated with higher odds of CSPH (aOR: 2.122 (1.067–4.218), p = 0.032). Associations of the PNPLA3 G-allele and the SERPINA1 Z-allele with CSPH were maintained independently of each other. The presence of both risk variants further increased the likelihood of ACLD and CSPH.

Hepatic Fat-Genetic Risk Score Predicts Hepatocellular Carcinoma in Patients With Cirrhotic HCV Treated With DAAs

BACKGROUND AND AIMS

Genetic factors and steatosis predispose to hepatocellular carcinoma (HCC) in patients with chronic hepatitis C virus; however, their impact in patients with cirrhosis cured by direct-acting antivirals (DAAs) is still undefined. We assessed the association between a genetic risk score (GRS) of hepatic fat accumulation, combining variants in PNPLA3 (patatin-like phospholipase domain containing 3), MBOAT7 (membrane bound O-acyltransferase domain containing 7), TM6SF2 (transmembrane 6 superfamily member 2), GCKR (glucokinase regulator), and HCC in patients treated with DAAs.

APPROACH AND RESULTS

We considered 509 consecutive patients with HCV cirrhosis (defined histologically or when liver stiffness ≥12 kPa) treated with DAAs. HCC was diagnosed according to international recommendations. GRS was calculated from the weighted impact of single variants on hepatic fat content quantified by H¹ spectrometry in the general population (Dallas Heart Study). During a median follow-up of 43 (3-57) months after DAA start, 36 of 452 (8%) patients developed de novo HCC, 4-year cumulative probability being 9% (95% confidence interval 7%-12%). Male sex (hazard ratio [HR] 2.54, P = 0.02), diabetes (HR 2.39, P = 0.01), albumin (HR 0.35, P = 0.001), and GRS score >0.597 (HR 2.30, P = 0.04) were independent predictors of de novo HCC. In contrast, single genetic risk variants were not useful in stratifying HCC risk. The proportion of patients who developed HCC according to the combination of the independent risk factors ranged from 11% to 67%. HCC recurred in 28 of 57 (49%) patients with previous history; diabetes and ethnicity were the only independent predictors of HCC recurrence.

CONCLUSIONS

In a large cohort of DAA-treated patients with cirrhotic HCV, GRS was associated with de novo HCC independently of classical risk factors, including liver disease severity. These data suggest that hepatic fat (i.e., lipotoxicity) promotes HCC in this setting and may represent a target for chemoprevention. Combination of clinical and genetic predictors may improve HCC risk stratification.

Genomics of Human Fibrotic Diseases: Disordered Wound Healing Response

Fibrotic disease, which is implicated in almost half of all deaths worldwide, is the result of an uncontrolled wound healing response to injury in which tissue is replaced by deposition of excess extracellular matrix, leading to fibrosis and loss of organ function. A plethora of genome-wide association studies, microarrays, exome sequencing studies, DNA methylation arrays, next-generation sequencing, and profiling of noncoding RNAs have been performed in patient-derived fibrotic tissue, with the shared goal of utilizing genomics to identify the transcriptional networks and biological pathways underlying the development of fibrotic diseases. In this review, we discuss fibrosing disorders of the skin, liver, kidney, lung, and heart, systematically (1) characterizing the initial acute injury that drives unresolved inflammation, (2) identifying genomic studies that have defined the pathologic gene changes leading to excess matrix deposition and fibrogenesis, and (3) summarizing therapies targeting pro-fibrotic genes and networks identified in the genomic studies. Ultimately, successful bench-to-bedside translation of observations from genomic studies will result in the development of novel anti-fibrotic therapeutics that improve functional quality of life for patients and decrease mortality from fibrotic diseases.

The PNPLA3 rs738409 GG genotype is associated with poorer prognosis in 239 patients with autoimmune hepatitis

BACKGROUND

Fibrosis progression in autoimmune hepatitis can be attenuated by immunosuppressive treatment; however, some patients progress despite therapy. Single nucleotide polymorphisms (SNPs) such as PNPLA3-rs738409, TM6SF2-rs58542926 and MBOAT7-rs641738 are associated with non-alcoholic fatty liver disease and fibrosis progression, whereas a splice variant in HSD17B13-rs72613567:TA has been shown to be protective.

AIM

To analyse the impact of different SNPs on the long-term outcome of patients with autoimmune hepatitis.

METHODS

We included 239 patients into this study who had been treated between 1983 and 2018 for autoimmune hepatitis. Genomic DNA was isolated from whole blood and SNPs were determined by PCR analysis. Liver biopsies were available for 215/239 patients (90%). Clinical and laboratory patient data were assessed by chart review.

RESULTS

Mean age at baseline was 42.1 years with 74.1% being female. The median follow-up was 9.4 years (IQR 3.5-15.0), 11.7% of the patients (n = 28) died or required liver transplantation. In the Kaplan-Meier analysis of the combined endpoint time to liver transplantation or death, we observed that patients with the PNPLA3-rs738409 GG variant met more frequently the primary endpoint (P = 0.005). In Cox regression analysis PNPLA3-rs738409 GG as well as liver cirrhosis were identified as strong predictors for time to liver transplantation or death (HR 4.5 [CI 1.48-13.72], P = 0.008 and HR 9.24 [CI 2.11-40.44], P = 0.003, respectively). Neither steatosis, diabetes mellitus nor obesity were associated with outcome.

CONCLUSIONS

PNPLA3-rs738409 variant GG is a predictor for time to liver transplantation or death and may help to identify autoimmune hepatitis patients at risk for disease progression.

A common variant in PNPLA3 is associated with age at diagnosis of NAFLD in patients from a multi-ethnic biobank

BACKGROUND & AIMS

The Ile138Met variant (rs738409) in the PNPLA3 gene has the largest effect on non-alcoholic fatty liver disease (NAFLD), increasing the risk of progression to severe forms of liver disease. It remains unknown if the variant plays a role in age of NAFLD onset. We aimed to determine if rs738409 impacts on the age of NAFLD diagnosis.

METHODS

We applied a novel natural language processing (NLP) algorithm to a longitudinal electronic health records (EHR) dataset of >27,000 individuals with genetic data from a multi-ethnic biobank, defining NAFLD cases (n = 1,703) and confirming controls (n = 8,119). We conducted i) a survival analysis to determine if age at diagnosis differed by rs738409 genotype, ii) a receiver operating characteristics analysis to assess the utility of the rs738409 genotype in discriminating NAFLD cases from controls, and iii) a phenome-wide association study (PheWAS) between rs738409 and 10,095 EHR-derived disease diagnoses.

RESULTS

The PNPLA3 G risk allele was associated with: i) earlier age of NAFLD diagnosis, with the strongest effect in Hispanics (hazard ratio 1.33; 95% CI 1.15-1.53; p <0.0001) among whom a NAFLD diagnosis was 15% more likely in risk allele carriers vs. non-carriers; ii) increased NAFLD risk (odds ratio 1.61; 95% CI 1.349-1.73; p <0.0001), with the strongest effect among Hispanics (odds ratio 1.43; 95% CI 1.28-1.59; p <0.0001); iii) additional liver diseases in a PheWAS (p <4.95 × 10^-6) where the risk variant also associated with earlier age of diagnosis.

CONCLUSION

Given the role of the rs738409 in NAFLD diagnosis age, our results suggest that stratifying risk within populations known to have an enhanced risk of liver disease, such as Hispanic carriers of the rs738409 variant, would be effective in earlier identification of those who would benefit most from early NAFLD prevention and treatment strategies.

LAY SUMMARY

Despite clear associations between the PNPLA3 rs738409 variant and elevated risk of progression from non-alcoholic fatty liver disease (NAFLD) to more severe forms of liver disease, it remains unknown if PNPLA3 rs738409 plays a role in the age of NAFLD onset. Herein, we found that this risk variant is associated with an earlier age of NAFLD and other liver disease diagnoses; an observation most pronounced in Hispanic Americans. We conclude that PNPLA3 rs738409 could be used to better understand liver disease risk within vulnerable populations and identify patients that may benefit from early prevention strategies.

Combined alcoholic and non-alcoholic steatohepatitis

While metabolic syndrome and alcohol consumption are the two main causes of chronic liver disease, one of the two conditions is often predominant, with the other acting as a cofactor of morbimortality. It has been shown that obesity and alcohol act synergistically to increase the risk of fibrosis progression, hepatic carcinogenesis and mortality, while genetic polymorphisms can strongly influence disease progression. Based on common pathogenic pathways, there are several potential targets that could be used to treat both diseases; based on the prevalence and incidence of these diseases, new therapies and clinical trials are needed urgently.

Alcohol-related liver disease: Clinical practice guidelines by the Latin American Association for the Study of the Liver (ALEH)

Alcohol-related liver disease (ALD) is a major cause of advanced chronic liver disease in Latin-America, although data on prevalence is limited. Public health policies aimed at reducing the alarming prevalence of alcohol use disorder in Latin-America should be implemented. ALD comprises a clinical-pathological spectrum that ranges from steatosis, steatohepatitis to advanced forms such as alcoholic hepatitis (AH), cirrhosis and hepatocellular carcinoma. Besides genetic factors, the amount of alcohol consumption is the most important risk factor for the development of ALD. Continuous consumption of more than 3 standard drinks per day in men and more than 2 drinks per day in women increases the risk of developing liver disease. The pathogenesis of ALD is only partially understood and recent translational studies have identified novel therapeutic targets. Early forms of ALD are often missed and most clinical attention is focused on AH, which is defined as an abrupt onset of jaundice and liver-related complications. In patients with potential confounding factors, a transjugular biopsy is recommended. The standard therapy for AH (i.e. prednisolone) has not evolved in the last decades yet promising new therapies (i.e. G-CSF, N-acetylcysteine) have been recently proposed. In both patients with early and severe ALD, prolonged abstinence is the most efficient therapeutic measure to decrease long-term morbidity and mortality. A multidisciplinary team including alcohol addiction specialists is recommended to manage patients with ALD. Liver transplantation should be considered in the management of patients with end-stage ALD that do not recover despite abstinence. In selected cases, increasing number of centers are proposing early transplantation for patients with severe AH not responding to medical therapy.

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.

The relationship among GNB3 rs5443, PNPLA3 rs738409, GCKR rs780094 gene polymorphisms, type of maternal gestational weight gain and neonatal outcomes (STROBE-compliant article)

The gestational weight gain is determined by food habits, environmental and genetic factors.The aims of this paper were to establish relationships between maternal gene polymorphisms (patatin-like phospholipase domain-containing protein 3 rs738409 [PNPLA3 rs738409], glucokinase regulatory protein rs780094 [GCKR rs780094], and guanine nucleotide-binding protein rs5443 [GNB3 rs5443]) and mothers' gestational weight gain, but also neonatal outcomes (birth weight, length, and ponderal index [PI]).We performed a cross-sectional study in a sample of 158 mothers and their product of conception' in an Obstetrics-Gynecology Clinic from Romania. We divided the pregnant women according to the Institute of Medicine recommendations into 3 subgroups: (1) insufficient gestational weight gain; (2) normal gestational weight gain; and (3) excessive gestational weight gain.The gestational weight gain among pregnant women included in this study was classified as insufficient (10.1%), normal (31%), and excessive (58.9%). We found a tendency towards statistical significance for mothers that were overweight or obese before pregnancy to present an excessive gestational weight gain as compared to the normal weight ones. Similarly, we identified a tendency for statistical significance regarding the association between the variant genotype of GNB3 rs5443 and excessive gestational weight gain. We noticed differences that tended to be statistical significant concerning aspartate aminotransferase values between the 3 subgroups, mothers with excessive gestational weight gain having higher values than mothers with normal gestational weight gain (median, IQR: 22.89[17.53; 31.59] for mothers with excessive gestational weight gain versus 22.71[18.58; 27.37] for mothers with normal gestational weight gain). In mothers with excessive gestational weight gain, we found a significant association between the variant genotype of PNPLA3 rs738409 polymorphism and neonatal PI noticing a decrease of this index in case of newborns from mothers carrying the variant genotype.Excessive gestational weight gain was noticed in pregnant women that were obese and overweight before pregnancy. We found a positive association between the variant genotype of GNB3 rs5443 polymorphism and excessive gestational weight gain. Similarly, the presence of variant genotype of PNPLA3 rs738409 in mothers was associated with a lower PI in their newborns. Our study pointed out the most important factors that influence gestational weight gain and related birth outcomes.

Lipoprotein metabolism in liver diseases

PURPOSE OF REVIEW

The liver is the central hub of lipoprotein metabolism. A complex relationship exists between dyslipidemia and chronic liver diseases (CLDs). Recent advances in the genetics of nonalcoholic fatty liver disease (NAFLD) and alcoholic liver disease (ALD) exemplify the pivotal role of lipoprotein metabolism in the pathogenesis of CLD. We review these relationships in four quintessential forms of CLD: NAFLD, ALD, cholestatic liver disease and cirrhosis, with a focus on recent discoveries.

RECENT FINDINGS

An I148 M variant in patatin-like phospholipase domain-containing protein 3 (PNPLA3) and an E167K variant in transmembrane 6 superfamily 2 (TM6SF2) are major genetic risk factors for the development and progression of NAFLD. These genetic variants also increase the risk of ALD. Both PNPLA3 and TM6SF2 are involved in the hepatic assembly of very low-density lipoprotein. The discovery of these two genetic variants highlights the risk of CLD when environmental factors are combined with functional modifications in the lipoprotein metabolism pathway.

SUMMARY

The relationship between CLD and lipoprotein metabolism is reciprocal. On the one hand, the progression of CLD impairs lipoprotein metabolism; on the other hand, modifications in lipoprotein metabolism can substantially increase the risk of CLD. These relationships are at play among the most common forms of CLD affecting a significant proportion of the population.

Hepatocellular carcinoma in the setting of alcohol-related liver disease

Alcohol-related liver disease is the most prevalent type of chronic liver disease worldwide, accounting for 30% of hepatocellular carcinoma (HCC) cases and HCC-specific deaths. Alcohol has been associated with an increased risk of several malignancies, this risk starting at doses as low as 10 g/1 unit/day. The carcinogenic process includes direct acetaldehyde toxicity through the formation of protein and DNA adducts, an increased production of reactive oxygen species, changes to lipid peroxidation and metabolism, inflammation and an impaired immune response and modifications to DNA methylation. A high annual incidence of HCC has been observed in large European cohorts of patients with alcoholic cirrhosis, reaching 2.9%, with numerous host factors modulating this risk (age, gender, liver failure, genetic polymorphisms affecting oncogenic pathways). Because of impaired surveillance and poor patient compliance, HCC is often detected late in patients with chronic liver disease of alcoholic aetiology. This delay in detection, which is frequently made in the context of advanced liver cirrhosis rather than in surveillance programmes, results in more advanced HCC that is less amenable to curative treatment. Consequently, patients with alcohol-related HCC generally have a worse prognosis than those with non-alcoholic HCC.

PNPLA3 variant M148 causes resistance to starvation-mediated lipid droplet autophagy in human hepatocytes

The mechanism of how patatin-like phospholipase domain-containing protein 3 (PNPLA3) variant M148 is associated with increased risk of development of hepatic steatosis is still debated. Here, we propose a novel role of PNPLA3 as a key player during autophagosome formation in the process of lipophagy. A human hepatocyte cell line, HepG2 cells, expressing recombinant I148 or 148M, was used to study lipophagy under energy deprived conditions, and lipid droplet morphology was investigated using florescence microscopy, image analysis and biochemical assays. Autophagic flux was studied using the golden-standard of LC3-II turnover in combination with the well characterized GFP-RFP-LC3 vector. To discriminate between, perturbed autophagic initiation and lysosome functionality, lysosomes were characterized by Lysotracker staining and LAMP1 protein levels as well as activity and activation of cathepsin B. For validation, human liver biopsies genotyped for I148 and 148M were analyzed for the presence of LC3-II and PNPLA3 on lipid droplets. We show that the M148-PNPLA3 variant is associated with lipid droplets that are resistant to starvation-mediated degradation. M148 expressing hepatocytes reveal decreased autophagic flux and reduced lipophagy. Both I148-PNPLA3 and M148-PNPLA3 colocalize and interact with LC3-II, but the M148-PNPLA3 variant has lower ability to bind LC3-II. Together, our data indicate that PNPLA3 might play an essential role in lipophagy in hepatocytes and furthermore that the M148-PNPLA3 variant appears to display a loss in this activity, leading to decreased lipophagy.

PNPLA3 rs738409 Polymorphism Predicts Development and Severity of Hepatic Steatosis but Not Metabolic Syndrome in Celiac Disease

Metabolic syndrome (MS) and hepatic steatosis (HS) have been described in patients with celiac disease (CD) after starting a gluten-free diet (GFD), but data on predictive factors for these conditions are scarce. Recently, the patatin-like phospholipase domain-containing protein 3 (PNPLA3) rs738409 has been identified as a key factor for HS development in the general population. The aim of the study was to evaluate the role of PNPLA3 rs738409 in the development of MS and HS in CD patients after starting GFD. Between June 2014 and September 2016, we consecutively enrolled CD patients with HS, while those without steatosis served as a control group. All patients underwent anthropometric and serologic investigations, ultrasonography (US) to assess the degree and severity of HS, and genotyping of the PNPLA3 rs738409 polymorphism. Finally, 370 subjects were enrolled (136 with and 234 without HS). At genotyping assays, the CC genotype was found in 194 subjects (52.4%), the CG genotype in 138 subjects (37.3%), and the GG genotype in 38 subjects (10.2%). At binary logistic regression, only CG and GG alleles were predictive for the development of HS (odds ratio (OR) 1.97; p < 0.01 for CG and OR 6.9; p < 0.001 for GG). Body mass index (BMI) (OR 3.8; p < 0.001) and waist circumference (OR 2.8; p = 0.03) at CD diagnosis were the only independent factors for the development of MS. Intergroup comparisons showed that the severe grade of HS was more frequently observed in GG than in CC carriers (74% vs. 11.3%, p < 0.001, OR 21.8). PNPLA3 CG and GG carriers with CD have a higher susceptibility to hepatic steatosis, but not to metabolic syndrome. Moreover, patients with GG alleles display more severe forms of HS based on ultrasound.

Single-nucleotide rs738409 polymorphisms in the PNPLA3 gene are strongly associated with alcoholic liver disease in Han Chinese males

OBJECTIVE

Alcoholic liver disease (ALD) is a chronic liver disorder caused by the consumption of large amounts of alcohol. Genome-wide association studies have recently confirmed that polymorphisms in PNPLA3 predispose individuals to ALD and have identified risk loci of MBOAT7 and TM6SF2 in persons of European descent. However, the association with alcoholic liver damage has not been evaluated thus far in a Han Chinese population.

METHODS

We performed a large case-control multicenter study of 507 ALD patients and 645 ethnically matched healthy controls. Five SNPs were genotyped using matrix-assisted laser desorption/ionization time of flight mass spectrometry, and association analysis was performed using PLINK 1.07 software.

RESULTS

The rs738409 in the PNPLA3 gene was found to be significantly associated with ALD in allele and genotype frequencies (p = 6.25 × 10^-14 and p = 9.05 × 10^-13). The frequencies of the risk allele G in rs738409 were notably higher in ALD compared to controls (odds ratio = 1.93, 95% confidence interval = 1.63-2.28). The current study showed that the genotype frequencies of three genetic models were also statistically significant (p = 1.07 × 10^-13, p = 9.3 × 10^-8, and p = 1.57 × 10^-12). Additionally, the G-allele of rs738409 was associated with a variety of clinical manifestations such as elevated alanine aminotransferase (ALT), aspartate aminotransferase (AST), γ-glutamyl transpeptidase (GGT), and mean corpuscular volume (MCV) in the patients with ALD.

CONCLUSION

In a Han Chinese population, the present study confirmed that PNPLA3 polymorphism rs738409 was more likely to influence the susceptibility to ALD. However, no statistically significant differences for the allele and genotype frequencies of rs626283, rs641738 in MBOAT7, rs10401969 in SUGP1 and rs58542926 in TM6SF2 were found between ALD patients and healthy controls.

Impact of patatin-like phospholipase domain containing 3 rs738409 G/G genotype on hepatic decompensation and mortality in patients with portal hypertension

BACKGROUND

The rs738409 C>G p.I148M variant in the patatin-like phospholipase domain containing 3 (PNPLA3)-gene promotes triglyceride accumulation in hepatocytes and hepatic stellate cell activation and has previously been linked to hepatic steatosis/liver fibrosis.

AIM

To investigate its impact on hepatic decompensation and (liver-related) mortality in patients who had already developed portal hypertension. Moreover, we assessed its link with hepatic steatosis as evaluated by controlled attenuation parameter.

METHODS

We performed a retrospective analysis in prospectively characterised patients with viral hepatitis/fatty liver disease-induced portal hypertension (hepatic venous pressure gradient [HVPG] ≥ 6 mm Hg) diagnosed at the Medical University of Vienna who underwent HVPG measurement (until 2013; n = 372; longitudinal study) or simultaneous HVPG and controlled attenuation parameter measurement (2014-2017; n = 153; cross-sectional study).

RESULTS

While survival was similar between PNPLA3-C/C and -C/G patients, we observed substantially increased mortality in PNPLA3-G/G patients. PNPLA3-G/G had no impact on mortality in the subgroup of patients with viral hepatitis; however, we observed a strong independent association between PNPLA3-G/G and hepatic decompensation (adjusted subdistribution hazard ratio [aSHR]: 2.1, 95% confidence interval [95% CI]: 1.1-4; P = 0.024) as well as mortality (overall: aSHR: 2.2, 95% CI: 1.22-3.98; P = 0.009; liver-related: aSHR: 2.2, 95% CI: 1.08-4.46; P = 0.029) in patients with fatty liver disease. Interestingly, even in the subgroup of patients who had already progressed to clinically significant portal hypertension (HVPG ≥ 10 mm Hg), PNPLA3-G/G substantially increased mortality (aSHR: 2.33, 95% CI: 1.27-4.29; P = 0.006). PNPLA3-genotype had no influence on controlled attenuation parameter or the prevalence of values ≥248 dB/m.

CONCLUSION

PNPLA3-G/G-genotype seems to double the risks of hepatic decompensation and (liver-related) mortality in patients with portal hypertension due to fatty liver disease. Further studies are warranted to investigate potential underlying pathophysiological mechanisms unrelated to hepatic steatosis.

Donor PNPLA3 rs738409 genotype is a risk factor for graft steatosis. A post-transplant biopsy-based study

BACKGROUND & AIMS

The rs738409 c.444C > G (p.I148M) polymorphism in PNPLA3 is a major factor predisposing to non-alcoholic fatty liver disease. The aim of the study was to clarify the impact of liver and extrahepatic expression of the PNPLA3 p.148M variant on liver graft steatosis after liver transplantation.

METHODS

Fat content was assessed in liver biopsies from 176 transplant recipients. During a period of 4 ± 1 years after transplantation, 17 patients developed grade 3 steatosis, 14 patients grade 2 steatosis, 56 patients grade 1 steatosis, and 89 patients grade 0 steatosis. The influence of the recipient and donor rs738409 genotype and clinical and laboratory data on liver fat content were analyzed using ordinal logistic regression.

RESULTS

The PNPLA3 rs738409 CC/CG/GG genotype frequencies, respectively, were 0.494/0.449/0.057 in the graft donors and 0.545/0.330/0.125 in the graft recipients. In the multivariate analysis, the presence of the PNPLA3 c.444G allele in donor (OR 1.62; 95%CI 1.12-2.33), post-transplant BMI (OR 1.14; 95%CI 1.07-1.22), diabetes mellitus (OR 1.99; 95%CI 1.22-3.22), and serum triglycerides (OR 1.40; 95%CI 1.11-1.76) were independent risk factors for increased liver graft fat content.

CONCLUSIONS

These data indicate that the liver expression of the PNPLA3 p.148M variant confers a genetic predisposition to liver graft steatosis along with nutritional status and diabetes.

Genetic and Epigenetic Profile of Patients With Alcoholic Liver Disease

Alcoholic liver disease (ALD) is a definition encompassing a spectrum of disorders ranging from simple steatosis to cirrhosis and hepatocellular carcinoma. Excessive alcohol consumption triggers a series of metabolic reactions that affect the liver by inducing lipogenesis, increasing oxidative stress, and causing abnormal inflammatory responses. The metabolic pathways regulating lipids, reactive oxygen species (ROS), and immune system are closely related and in some cases cross-regulate each other. Therefore, it must be taken into account that major genetic and epigenetic abnormalities affecting enzymes involved in one of such pathways can play a pivotal role in ALD pathogenesis. However, recent studies have pointed out how a significant predisposition can also be determined by minor variants, such as relatively common polymorphisms, epigenetic modifications, and microRNA abnormalities. Genetic and epigenetic factors can also affect the progression of liver diseases, promoting fibrogenesis, cirrhosis, and ultimately hepatocellular carcinoma. It is noteworthy that some of these factors, such as some of the cytokines involved in the abnormal inflammatory responses, are shared with non-alcoholic liver disease, while other factors are unique to ALD. The study of the genetic and epigenetic components involved in the liver damages caused by alcohol is crucial to identify individuals with high risk of developing ALD, design personalized protocols for prevention and/or treatment, and select the best molecular targets for new therapies.

The bidirectional impacts of alcohol consumption and the metabolic syndrome: Cofactors for progressive fatty liver disease

Current medical practice artificially dichotomises a diagnosis of fatty liver disease into one of two common forms: alcoholic liver disease (ALD) and non-alcoholic fatty liver disease (NAFLD). Together, these account for the majority of chronic liver diseases worldwide. In recent years, there has been a dramatic increase in the prevalence of obesity and metabolic syndrome within the general population. These factors now coexist with alcohol consumption in a substantial proportion of the population. Each exposure sensitises the liver to the injurious effects of the other; an interaction that drives and potentially accelerates the genesis of liver disease. We review the epidemiological evidence and scientific literature that considers how alcohol consumption interacts with components of the metabolic syndrome to exert synergistic or supra-additive effects on the development and progression of liver disease, before discussing how these interactions may be addressed in clinical practice.

Suppressed Fat Mobilization Due to PNPLA3 rs738409 -Associated Liver Damage in Heavy Drinkers: The Liver Damage Feedback Hypothesis

PNPLA3 variant rs738409 has been identified as important progression factor in patients with ALD and NAFLD, the most common liver diseases worldwide. These findings point towards similarities between metabolism of alcohol and fat with regard to the PNPLA3 gene. However, despite many efforts, neither the mechanisms of PNPLA3-related liver damage nor the physiological role of PNPLA3 are fully understood. Based on a large monocentric cohort of Caucasian heavy drinkers we could recently provide evidence that PNPLA3 GG primarily correlated with signs of liver damage (steatohepatitis, ballooning) but less with steatosis. Moreover, upon alcohol withdrawal, PNPLA3 GG carriers showed a delayed inflammation-associated resolution of liver stiffness. In line with the histological findings, hepatic fat content as quantified by CAP (controlled attenuation parameter) did not depend on PNPLA3 status and decreased equally in all genotypes by ca. 30 dB/m during alcohol withdrawal. Preliminary additional analysis from this large cohort indicates that PNPLA3 GG carriers (8.2%) drink significantly less high percentage beverages (23% vs 55%, p < 0.001) but show no metabolic phenotype such as increased weight, BMI or diabetes. On the molecular level, key molecules, important for lipolysis and flow of free fatty acids to the liver were drastically reduced in G carriers. These included the liver-synthesized serum ApoA1, the LD-associated protein perilipin5 and the recently identified hepato-protective transcriptional cofactor transducin beta-like-related 1 (TBLR1). Based on these findings, we here introduce the liver damage feedback hypothesis. Accordingly, PNPLA3-mediated liver damage (e.g. by enhanced metabolic activity) suppresses the mobilization of fat towards the liver at various levels (reduced serum lipid flux to the liver and fat mobilization from peripheric adipose tissues, suppressed hepatocyte fat release and avoidance of high percentage alcohol beverages). Finally, the liver damage feedback hypothesis identifies a novel and central role of liver damage on systemic fat homeostasis, which has not been appreciated so far.

PNPLA3 expression and its impact on the liver: current perspectives

A single-nucleotide polymorphism occurring in the sequence of the human patatin-like phospholipase domain-containing 3 gene (PNPLA3), known as I148M variant, is one of the best characterized and deeply investigated variants in several clinical scenarios, because of its tight correlation with increased risk for developing hepatic steatosis and more aggressive part of the disease spectrum, such as nonalcoholic steatohepatitis, advanced fibrosis and cirrhosis. Further, the I148M variant is positively associated with alcoholic liver diseases, chronic hepatitis C-related cirrhosis and hepatocellular carcinoma. The native gene encodes for a protein that has not yet a fully defined role in liver lipid metabolism and, according to recent observations, seems to be divergently regulated among distinct liver cells type, such as hepatic stellate cells. Therefore, the aim of this review is to collect the latest data regarding PNPLA3 expression in human liver and to analyze the impact of its genetic variant in human hepatic pathologies. Moreover, a description of the current biochemical and metabolic data pertaining to PNPLA3 function in both animal models and in vitro studies is summarized to allow a better understanding of the relevant pathophysiological role of this enzyme in the progression of hepatic diseases.

Constitutional and functional genetics of human alcohol-related hepatocellular carcinoma

Exploration of the constitutional genetics of hepatocellular carcinoma (HCC) has identified numerous variants associated with a higher risk of liver cancer in alcoholic cirrhotic patients. Although Genome-Wide Association studies have not been carried out in the field of alcohol-related HCC, common single nucleotide polymorphisms conferring a small increase in the risk of liver cancer risk have been identified and shown to modulate ethanol metabolism, inflammation, oxidative stress, iron or lipid metabolism. Specific patterns of gene mutations including CTNNB1, TERT, ARID1A and SMARCA2 exist in alcohol-related HCC. Moreover, a specific mutational process observed at the nucleotide level by next generation sequencing has revealed cooperation between alcohol and tobacco in the development of HCC. Combining this genetic information with epidemiological and clinical data that might define specific HCC risk classes and refine surveillance strategies needs to be assessed in large prospective cohorts of patients with alcoholic cirrhosis.

Association between PNPLA3 (rs738409 C>G) variant and hepatocellular carcinoma in Asian chronic hepatitis C patients: A longitudinal study

BACKGROUND/PURPOSE

Prdevious meta-analyses assess whether or not patatin-like phospholipase domain containing 3 (PNPLA3) (rs738409 C > G) was associated with increased risk of hepatocellular carcinoma (HCC) in Caucasians patients with hepatitis C virus (HCV)-related cirrhosis, these meta-analyses did not provide firm conclusions. Only one cross-sectional study involving Asian patients has previously been conducted to explore this issue. We aim to investigate this in a longitudinal cohort of Asian chronic hepatitis C (CHC) patients.

METHODS

We consecutively enrolled 1011 CHC patients who underwent liver biopsy before initiating interferon-based therapy. These patients were followed-up and screened for HCC up to a median of 6.9 years. The influence of rs738409 (GG) genotype on the occurrence of HCC was assessed using the Kaplan-Meier method, then according to the multivariate Cox model.

RESULTS

During follow-up, 143 (14.1%) patients developed HCC. rs738409 (GG) genotype was not associated with time-to-HCC development on multivariate Cox regression (P = 0.634). When considering the occurrence of these events over time, rs738409 (GG) genotype did not influence the risk of HCC development (log-rank = 0.12). Among 261 patients with liver cirrhosis, rs738409 (GG) genotype was not associated with time-to-HCC development on multivariate Cox regression (P = 0.737). When considering the occurrence of these events over time, rs738409 (GG) genotype did not influence the risk of HCC development (log-rank = 0.72).

CONCLUSION

In this longitudinal study with liver biopsy to stage liver fibrosis, we affirm there is no influence of the rs738409 (GG) genotype on the occurrence of HCC in Asian CHC patients, including cirrhotic patients.

Association between PNPLA3 gene polymorphisms and risk of hepatitis B virus-related hepatocellular carcinoma in Han population in China:a case-control study

BACKGROUND AND AIM

Several recent studies showed that the genetic polymorphisms in the PNPLA3 region (rs738408, rs738409, rs2294918, rs2294919 and rs2281135) were with related to various kinds of liver diseases. We analyzed the five single-nucleotide polymorphisms (SNPs) for major HBV outcomes in Han Chinese.

METHODS

A total of 2410 samples were involved and peripheral blood samples were collected in this study. The SNPs in the PNPLA3 region were genotyped by using Matrix-assisted laser desorption/ionization time of flight mass spectrometry.

RESULTS

Our study indicated the clear relationship between the PNPLA3 rs2294918, rs2294919 and HBV-related HCC after control for the effects of sex, drinking and smoking. Health subjects with the PNPLA3 rs2294919 TC genotype would have a 0.605 (95% CI: 0.413, 0.886; p = .010) times lower odds of having HCC, and those with the rs2294918 AG genotype would have a 1.872 (95% CI: 1.256, 2.792; p = .002) times higher odds of having HCC, whereas the values of sex, age, drinking and smoking were fixed. In addition, CA haplotype of the haplotype block of rs738409 and rs2281135 was also associated with HBV-related HCC.

CONCLUSIONS

Our study suggested that PNPLA3 loci (rs2294918, rs2294919) were associated with HBV-related HCC in Han Chinese.

Homozygosity for rs738409:G in PNPLA3 is associated with increased mortality following an episode of severe alcoholic hepatitis

BACKGROUND & AIMS

Carriage of rs738409:G in PNPLA3 is associated with an increased risk of developing alcohol-related cirrhosis and has a significant negative effect on survival. Short-term mortality in patients with severe alcoholic hepatitis is high; drinking behaviour is a major determinant of outcome in survivors. The aim of this study was to determine whether carriage of rs738409:G has an additional detrimental effect on survival in this patient group.

METHODS

Genotyping was undertaken in 898 cases with severe alcoholic hepatitis, recruited through the UK Steroids or Pentoxifylline for Alcoholic Hepatitis (STOPAH) trial, and 1188 White British/Irish alcohol dependent controls with no liver injury, recruited via University College London. Subsequent drinking behaviour was classified, in cases surviving ≥90days, as abstinent or drinking. The relationship between rs738409 genotype, drinking behaviour and survival was explored.

RESULTS

The frequency of rs738409:G was significantly higher in cases than controls (29.5% vs. 18.9%; p=2.15×10^-15; odds ratio 1.80 [95% confidence interval (CI) 1.55-2.08]). Case-mortality at days 28, 90 and 450 was 16%, 25% and 41% respectively. There was no association between rs738409:G and 28-day mortality. Mortality in the 90 to 450-day period was higher in survivors who subsequently resumed drinking (hazard ratio [HR] 2.77, 95% CI 1.79-4.29; p<0.0001) and in individuals homozygous for rs738409:G (HR 1.69, 95% CI 1.02-2.81, p=0.04).

CONCLUSION

Homozygosity for rs738409:G in PNPLA3 confers significant additional risk of medium-term mortality in patients with severe alcoholic hepatitis. Rs738409 genotype may be taken into account when considering treatment options for these patients.

LAY SUMMARY

Individuals misusing alcohol who carry a particular variant of the gene PNPLA3 are more at risk of developing severe alcoholic hepatitis, a condition with a poor chance of survival. The longer-term outcome in people with this condition who survive the initial illness is strongly influenced by their ability to remain abstinent from alcohol. However, carriers of this gene variant are less likely to survive even if they are able to stop drinking completely. Knowing if someone carries this gene variant could influence the way in which they are managed. Clinical trial numbers: EudraCT reference number: 2009-013897-42; ISRCTN reference number: ISRCTN88782125.

CLINICAL TRIAL NUMBERS

EudraCT reference number: 2009-013897-42; ISRCTN reference number: ISRCTN88782125.

Factors Associated With Persistent Increase in Level of Alanine Aminotransferase in Patients With Chronic Hepatitis B Receiving Oral Antiviral Therapy

BACKGROUND & AIMS

Despite complete suppression of viral DNA with antiviral agents, in some patients with chronic hepatitis B (CHB), serum levels of alanine aminotransferase (ALT) do not normalize. We investigated factors associated with persistent increases in ALT level in patients with CHB given long-term tenofovir disoproxil fumarate.

METHODS

We analyzed data from 471 hepatitis B e antigen (HBeAg)-positive and HBeAg-negative patients with CHB participating in 2 phase 3 trials. We identified patients with an increased level of ALT (above the upper limit of normal range) after 5 years (240 weeks) of tenofovir disoproxil fumarate therapy. We analyzed findings from liver biopsy specimens collected from 467 patients (99%) at baseline and 339 patients (72%) at year 5 of treatment; biopsy specimens were evaluated by an independent pathologist. We performed stepwise, forward, multivariate regression analyses of specified baseline characteristics and on-treatment response parameters to identify factors associated with persistent increases in ALT level.

RESULTS

Of the 471 patients, 87 (18%) still had an increased ALT level at year 5 of treatment. Factors associated significantly with a persistent increase in ALT level were a steatosis score of 5% or greater (grade 1 or more) at baseline (odds ratio [OR], 2.236; 95% confidence interval [CI], 1.031-4.852; P = .042) and at year 5 (OR, 3.392; 95% CI, 1.560 ≥ 7.375; P = .002), HBeAg seropositivity at baseline (OR, 3.297; 95% CI, 1.653-6.576; P < .001), and age 40 years or older (OR, 2.099; 95% CI, 1.014-4.342; P = .046). Of the 42 HBeAg-positive patients with steatosis at baseline, 21 (50%) had an increased ALT level at year 5 of treatment. Patients with persistent increases in ALT level were more likely to have an increase in steatosis at year 5 than those with a normal ALT level.

CONCLUSIONS

HBeAg seropositivity and hepatic steatosis contribute to persistent increases in ALT level in patients with CHB receiving suppressive antiviral treatment. ClinicalTrials.gov registration numbers: NCT00117676 and NCT00116805.

PNPLA3 rs738409 Polymorphism Associated with Hepatic Steatosis and Advanced Fibrosis in Patients with Chronic Hepatitis C Virus: A Meta-Analysis

Background/Aims

The recognition of a correlation between patatin-like phospholipase domain containing-protein 3 (PNPLA3) rs738409 (C>G) and the severity of liver steatosis or fibrosis in chronic hepatitis C (CHC) has not reached a consensus. This meta-analysis sought to investigate with accuracy the association between the PNPLA3 rs738409 (C>G) polymorphism and liver steatosis and advanced fibrosis in CHC patients.

Methods

We performed a comprehensive literature search from the PubMed, Embase, Web of Science, and Google Scholar databases up to December 31, 2014. Crude odds ratios (ORs) with 95% confidence intervals (CIs) were calculated. Statistical analyses were performed using Stata 12.0 software.

Results

The meta-analysis revealed the severity of liver fibrosis was significantly higher in CHC patients with PNPLA3 rs738409 GG in Caucasians (versus CC+CG: OR, 2.29; 95% CI, 1.57 to 3.35; p<0.05) but not Asian populations. In Caucasians, liver steatosis was also more severe in CHC patients with rs738409 GG (versus CC+CG; OR, 4.33; 95% CI, 2.59 to 7.22; p<0.05). The sensitivity analysis indicated the results of this meta-analysis were stable and no publication bias was detected.

Conclusions

PNPLA3 rs738409 (C>G) was associated with the risk of both advanced liver fibrosis and steatosis in patients with CHC, especially among Caucasian populations.

Genetic polymorphisms associated with fatty liver disease and fibrosis in HIV positive patients receiving combined antiretroviral therapy (cART)

Hepatic steatosis can occur with any antiretroviral therapy (cART). Although single nucleotide polymorphisms (SNPs) have been identified to predispose to alcoholic and non-alcoholic fatty liver disease, their role for treatment-associated steatosis in HIV-positive patients remains unclear. We determined the frequency of PNPLA3 (rs738409), CSPG3/NCAN (rs2228603), GCKR (rs780094), PPP1R3B (rs4240624), TM6SF (rs8542926), LYPLAL1 (rs12137855) and MBOAT7 (rs626283) by RT-PCR in 117 HIV-positive patients on cART and stratified participants based on their “controlled attenuation parameter” (CAP) into probable (CAP: 215–300 dB/m) and definite (CAP >300 dB/m) hepatic steatosis. We analyzed CAP values and routine metabolic parameters according to the allele frequencies. Sixty-five (55.6%) and 13 (11.1%) patients were allocated to probable and definite steatosis. CAP values (p = 0.012) and serum triglycerides (p = 0.043) were increased in carriers of the GCKR (rs780094) A allele. Cox logistic regression identified triglycerides (p = 0.006), bilirubin (p = 0.021) and BMI (p = 0.068), but not the genetic parameters as risk factors for the occurrence of hepatic steatosis. Taken together, according to the limited sample size, this exploratory study generates the hypothesis that genetic polymorphisms seem to exert minor effects on the risk for fatty liver disease in HIV-positive patients on cART. Nevertheless, SNPs may modify metabolic complications once metabolic abnormalities have developed. Hence, subsequent analysis of a larger cohort is needed.

Is moderate alcohol use in nonalcoholic fatty liver disease good or bad? A critical review

Moderate alcohol consumption in patients with nonalcoholic fatty liver disease (NAFLD) is common, yet the effects on cardiovascular and liver health are unclear. Moderate alcohol use is associated with improved insulin sensitivity and decreased cardiovascular mortality in the general population, but whether similar benefits would be observed in persons with NAFLD remains largely unstudied. There is significant overlap in the pathogenesis of alcoholic liver disease (ALD) and NAFLD, although studies of ALD have focused on pathological alcohol intake and few mechanistic studies of moderate alcohol use in NAFLD exist. We undertook a critical review of the effect of moderate alcohol use on cardiovascular and liver disease in patients with NAFLD. A total of seven observational studies met the criteria for inclusion (one for cardiovascular endpoints and six for liver endpoints). Insufficient studies have assessed the association of moderate alcohol use with cardiovascular outcomes. There was a positive association between moderate alcohol use and decreased NASH and fibrosis; however, heavy episodic drinking may accelerate fibrosis progression and moderate alcohol use may increase the risk of hepatocellular carcinoma in patients with advanced fibrosis. Significant methodological limitations were present, including incomplete adjustment for confounding factors and failure to measure lifetime use or the pattern of alcohol intake. Thus, a strong recommendation of benefit of moderate alcohol use in NAFLD cannot be made. There remains a need for additional high-quality longitudinal studies that evaluate both cardiovascular and liver outcomes among NAFLD patients with moderate or lesser degrees of alcohol use. (Hepatology 2017;65:2090-2099).

Binge alcohol alters PNPLA3 levels in liver through epigenetic mechanism involving histone H3 acetylation

The human PNPLA3 (patatin-like phospholipase domain-containing 3) gene codes for a protein which is highly expressed in adipose tissue and liver, and is implicated in lipid homeostasis. While PNPLA3 protein contains regions homologous to functional lipolytic proteins, the regulation of its tissue expression is reflective of lipogenic genes. A naturally occurring genetic variant of PNPLA3 in humans has been linked to increased susceptibility to alcoholic liver disease. We have examined the modulatory effect of alcohol on PNPLA3 protein and mRNA expression as well as the association of its gene promoter with acetylated histone H3K9 by chromatin immunoprecipitation (ChIP) assay in rat hepatocytes in vitro, and in vivo in mouse and rat models of acute binge, chronic, and chronic followed by acute binge ethanol administration. Protein expression of PNPLA3 was significantly increased by alcohol in all three models used. PNPLA3 mRNA also increased, albeit to a varying degree. ChIP assay using H3AcK9 antibody showed increased association with the promoter of PNPLA3 in hepatocytes and in mouse liver. This was less evident in rat livers in vivo except under chronic treatment. It is concluded for the first time that histone acetylation plays a role in the modulation of PNPLA3 levels in the liver exposed to binge ethanol both in vitro and in vivo.

The genetics of alcohol dependence and alcohol-related liver disease

The susceptibility to developing alcohol dependence and significant alcohol-related liver injury is determined by a number of constitutional, environmental and genetic factors, although the nature and level of interplay between them remains unclear. The familiality and heritability of alcohol dependence is well-documented but, to date, no strong candidate genes conferring increased risk have emerged, although variants in alcohol dehydrogenase and acetaldehyde dehydrogenase have been shown to confer protection, predominantly in individuals of East Asian ancestry. Population contamination with confounders such as drug co-dependence and psychiatric and physical co-morbidity may explain the essentially negative genome-wide association studies in this disorder. The familiality and hereditability of alcohol-related cirrhosis is not as well-documented but three strong candidate genes PNPLA3, TM6SF2 and MBOAT7, have been identified. The mechanisms by which variants in these genes confer risk and the nature of the functional interplay between them remains to be determined but, when elucidated, will undoubtedly increase our understanding of the pathophysiology of this disease. The way in which this genetic information could potentially inform patient management has yet to be determined and tested.

Spectrum of Alcoholic Liver Disease

Liver disease from excessive alcohol consumption is an important cause of morbidity and mortality worldwide. There is a clear relationship between alcohol and a variety of health and socioeconomic problems. According to the World Health Organization, 3.3 million people die of alcohol-related causes annually. Despite public knowledge of its potential adverse effects, alcohol consumption and the morbidity and mortality from alcoholic liver disease (ALD) have increased. ALD comprises a spectrum of injury, including simple steatosis, acute alcoholic hepatitis, and cirrhosis. Rather than being distinct disease entities, these pathologic processes frequently overlap.