Association between the PNPLA3 (rs738409 C>G) variant and hepatocellular carcinoma: Evidence from a meta-analysis of individual participant data

Surveillance for Hepatocellular Carcinoma in Patients with Non-Alcoholic Fatty Liver Disease: Universal or Selective?

Hepatocellular carcinoma (HCC), the most frequent primary liver cancer, is the sixth most common cancer, the fourth leading cause of cancer-related deaths worldwide, and accounts globally for about 800,000 deaths/year. Early detection of HCC is of pivotal importance as it is associated with improved survival and the ability to apply curative treatments. Chronic liver diseases, and in particular cirrhosis, are the main risk factors for HCC, but the etiology of liver disease is rapidly changing due to improvements in the prevention and treatment of HBV (Hepatitis B virus) and HCV (Hepatitis C virus) infections and to the rising incidence of the metabolic syndrome, of which non-alcoholic fatty liver (NAFLD) is a manifestation. NAFLD is now a recognized and rapidly increasing cause of cirrhosis and HCC. Indeed, the most recent guidelines for NAFLD management recommend screening for HCC in patients with established cirrhosis. Screening in NAFLD patients without cirrhosis is not recommended; however, the prevalence of HCC in this group of NAFLD patients has been reported to be as high as 38%, a proportion significantly higher than the one observed in the general population and in non-cirrhotic subjects with other causes of liver disease. Unfortunately, solid data regarding the risk stratification of patients with non-cirrhotic NAFLD who might best benefit from HCC surveillance are scarce, and specific recommendations in this field are urgently needed due to the increasing NAFLD epidemic, at least in Western countries. To further complicate matters, liver ultrasonography, which represents the current standard for HCC surveillance, has a decreased diagnostic accuracy in patients with NAFLD, and therefore disease-specific surveillance tools will be required for the early identification of HCC in this population. In this review, we summarize the most recent evidence on the epidemiology and risk factors for HCC in patients with NAFLD, with and without cirrhosis, and the evidence supporting surveillance for early HCC detection in these patients, reviewing the potential limitations of currently recommended surveillance strategies, and assessing data on the accuracy of potential new screening tools. At this stage it is difficult to propose general recommendations, and best clinical judgement should be exercised, based on the profile of risk factors specific to each patient.

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.

Metabolic regulation of hepatic PNPLA3 expression and severity of liver fibrosis in patients with NASH

BACKGROUND AND AIMS

The genetic PNPLA3 polymorphism I148M has been extensively associated with higher risk for development and progression of NAFLD towards NASH.

METHODS

PNPLA3 and α-SMA expression were quantified in liver biopsies collected from NASH patients (n = 26) with different fibrosis stages and PNPLA3 genotypes. To study the potential mechanisms driving PNPLA3 expression during NASH progression towards fibrosis, hepatocytes and hepatic stellate cells (HSCs) were cultivated in low and high glucose medium. Moreover, hepatocytes were treated with increasing concentrations of palmitic acid alone or in combination with glucose. Conditioned media were collected from challenged hepatocytes to stimulate HSCs.

RESULTS

Tissue expression of PNPLA3 was significantly enhanced in biopsies of patients carrying the I148M polymorphism compared to wild type (WT). In NASH biopsies, PNPLA3 significantly correlated with fibrosis stage and α-SMA levels independently of PNPLA3 genotype. In line, PNPLA3 expression was higher in α-SMA positive cells. Low glucose increased PNPLA3 in HSCs, whereas high glucose induced PNPLA3 and de-novo lipogenesis-related genes expression in hepatocytes. Palmitic acid induced fat accumulation and cell stress markers in hepatocytes, which could be counteracted by oleic acid. Conditioned media collected from lipotoxic challenged hepatocytes markedly induced PNPLA3 mRNA and protein levels, fibrogenic and autophagic markers and promoted migration in HSCs. Notably, conditioned media collected from hepatocytes cultivated with both glucose and palmitic acid exacerbated HSCs migration, PNPLA3 and fibrogenic gene expression, promoting release of cytokines from HSCs.

CONCLUSIONS

Collectively, our observations uncover the diverse metabolic regulation of PNPLA3 among different hepatic cell populations and support its relation to fibrosis progression.

Toward Genetic Prediction of Nonalcoholic Fatty Liver Disease Trajectories: PNPLA3 and Beyond

Nonalcoholic fatty liver disease (NAFLD) is on the verge of becoming the leading cause of liver disease. NAFLD develops at the interface between environmental factors and inherited predisposition. Genome-wide association studies, followed by exome-wide analyses, led to identification of genetic risk variants (eg, PNPLA3, TM6SF2, and SERPINA1) and key pathways involved in fatty liver disease pathobiology. Functional studies improved our understanding of these genetic factors and the molecular mechanisms underlying the trajectories from fat accumulation to fibrosis, cirrhosis, and cancer over time. Here, we summarize key NAFLD risk genes and illustrate their interactions in a 3-dimensional "risk space." Although NAFLD genomics sometimes appears to be "lost in translation," we envision clinical utility in trial design, outcome prediction, and NAFLD surveillance.

The landscape of gene mutations in cirrhosis and hepatocellular carcinoma

Chronic liver disease and primary liver cancer are a massive global problem, with a future increase in incidences predicted. The most prevalent form of primary liver cancer, hepatocellular carcinoma, occurs after years of chronic liver disease. Mutations in the genome are a causative and defining feature of all cancers. Chronic liver disease, mostly at the cirrhotic stage, causes the accumulation of progressive mutations which can drive cancer development. Within the liver, a Darwinian process selects out dominant clones with selected driver mutations but also leaves a trail of passenger mutations which can be used to track the evolution of a tumour. Understanding what causes specific mutations and how they combine with one another to form cancer is a question at the heart of understanding, preventing and tackling liver cancer. Herein, we review the landscape of gene mutations in cirrhosis, especially those paving the way toward hepatocellular carcinoma development, that have been characterised by recent studies capitalising on technological advances in genomic sequencing. With these insights, we are beginning to understand how cancers form in the liver, particularly on the background of chronic liver disease. This knowledge may soon lead to breakthroughs in the way we detect, diagnose and treat this devastating disease.

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

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

PNPLA3 rs738409 is not associated with the risk of hepatocellular carcinoma and persistent infection of hepatitis B virus (HBV) in HBV-related subjects: A case-control study and meta-analysis on Asians

The association between rs738409 (C>G, I148M) with patatin-like phospholipase domain-containing 3 (PNPLA3) gene and the risk of hepatocellular carcinoma (HCC) was controversial in different ethnic populations. Our study aimed to explore the effect of PNPLA3 rs738409 on the risk of HCC and persistent infection of Hepatitis B virus (HBV) in a Chinese HBV-related population, and further evaluate its role in HCC risk among Asians. First, we performed a case-control study by recruiting 786 HBV-related HCC cases, 695 HBV persistent carriers and 719 HBV natural clearance subjects. PNPLA3 rs738409 was genotyped by MassARRAY platform. Second, we conducted a systematic review and meta-analysis on Asians to further validate our results. Our case-control study demonstrated that PNPLA3 rs738409 was not associated with HCC risk or persistent HBV infection (All P > 0.05). The subsequent meta-analysis included 13 Asian studies with 9,802 subjects. Results showed that PNPLA3 rs738409 might increase HCC risk among healthy subjects (pooled odds ratio [OR] = 1.47, 95% confidence interval [CI] = 1.11-1.95), but it had no influence on the development of HCC among HBV-related subjects (pooled OR = 1.07, 95%CI = 0.89-1.30). Our case-control study highlights that PNPLA3 rs738409 is probably not associated with the risk of HCC or persistent HBV infection in a Chinese HBV-related population. Besides, our systematic review and meta-analysis on Asians further suggest that PNPLA3 rs738409 may confer an increased risk of HCC among healthy people, but contribute little to the development of HCC among HBV-related subjects. Future studies are required to confirm these results.

Advances in molecular classification and precision oncology in hepatocellular carcinoma

Hepatocellular carcinoma (HCC) arises from hepatocytes through the sequential accumulation of multiple genomic and epigenomic alterations resulting from Darwinian selection. Genes from various signalling pathways such as telomere maintenance, Wnt/β-catenin, P53/cell cycle regulation, oxidative stress, epigenetic modifiers, AKT/mTOR and MAP kinase are frequently mutated in HCC. Several subclasses of HCC have been identified based on transcriptomic dysregulation and genetic alterations that are closely related to risk factors, pathological features and prognosis. Undoubtedly, integration of data obtained from both preclinical models and human studies can help to accelerate the identification of robust predictive biomarkers of response to targeted biotherapy and immunotherapy. The aim of this review is to describe the main advances in HCC in terms of molecular biology and to discuss how this knowledge could be used in clinical practice in the future.

The effect of PNPLA3 polymorphism as gain in function mutation in the pathogenesis of non-alcoholic fatty liver disease

BACKGROUND

Non-alcoholic fatty liver disease (NAFLD) is often associated with metabolic syndrome (type 2 diabetes, hypertension, hypertriglyceridemia, insulin resistance, and obesity). NAFLD is multi-factorial in pathogenesis with some genetic predisposition. The variant patatin-like phospholipase domain-containing protein 3 (PNPLA3) is known to be an independent risk factor for hepatocellular cancer (HCC). The aim of this study was to investigate the role of PNPLA3 polymorphism as the risk factor for NAFLD.

METHODOLOGY

Patients had histological, ultrasonographic, biopsy evidence of NAFLD (n=248) and 81 controls were studied for PNPLA3 polymorphism. PNPLA3 genotyping was done from peripheral blood DNA by real-time polymerase chain reaction (RT-PCR).

RESULTS

PNPLA3 genotyping of the groups NAFLD (CC [n = 76], CG [n = 83], GG [n = 89]) and control (CC [n= 42], CG [n = 22], GG [n = 17]) was determined. In the patient group, the G allele was 261 (52.63%) and the C allele was 235 (47.37%), whereas in the control group, the G allele was 56 (34.54%) and the C allele was 106 (65.43%). In our study, 53 out of 174 women had GG allele and 54 out of 155 men had GG allele.

CONCLUSION

The findings suggest that there is a predominant relationship between men with PNPLA3 I148M variant with NAFLD in women. Patients with NAFLD carrying PNPLA3 rs738409 G>C variant are at higher risk of NAFLD.

A comprehensive evaluation of single nucleotide polymorphisms associated with hepatocellular carcinoma risk in Asian populations: A systematic review and network meta-analysis

BACKGROUND

Single nucleotide polymorphisms (SNPs) have been inconsistently associated with hepatocellular carcinoma (HCC) risk. This meta-analysis aimed to synthesize relevant data on SNPs associated with HCC in the Asian population.

METHODS

Databases were searched to identify association studies of SNPs and HCC in Asians published through January 2019. Summary odds ratios (ORs) and 95% confidence intervals (CIs) were calculated based on 41 studies (13,167 patients with HCC and 15,886 noncancer controls). Network meta-analysis and Thakkinstian's algorithm were used to select the most appropriate genetic model, along with false positive report probability (FPRP) for noteworthy associations.

RESULTS

Eleven SNPs meeting the inclusion criteria were tested for association with HCC, including CCND1 rs9344, PTGS2 rs689466, IL18 rs187238 and rs1946518, KIF1B rs17401966, MDM2 rs2279744, MIR146A rs2910164, MIR149 rs2292832, MIR196A2 rs11614913, MIR499A rs3746444, and TGFB1 rs1800469. A significant increase for HCC risk was observed for MDM2 rs2279744, and the dominant (pooled OR = 1.59, 95% CI: 1.26-2.00) and codominant (pooled OR = 1.37, 95% CI: 1.18-1.60) models were determined to be the most appropriate models. MIR499A rs3746444 also showed a significant association with HCC risk under the allele contrast model (pooled OR = 1.36, 95% CI: 1.05-1.77). Only the significance of MDM2 rs2279744 was noteworthy (FPRP < 0.2).

CONCLUSIONS

MDM2 rs2279744 is associated with HCC susceptibility in Asians, and the dominant and codominant models are likely the most appropriate models to estimate HCC risk.

Leveraging Human Genetics to Identify Potential New Treatments for Fatty Liver Disease

Fatty liver disease (FLD), including its more severe pathologies, namely steatohepatitis, hepatocarcinoma, and cirrhosis, is the most common cause of chronic liver disease worldwide and is projected to become the leading cause of hepatocellular carcinoma and end-stage liver disease. FLD is heterogeneous with multiple etiologies and diverse histological phenotypes, so therapies will ultimately need to be individualized for relevant targets. Inherited factors contribute to FLD, and most of the genetic variation influencing liver disease development and progression is derived from genes involved in lipid biology, including PNPLA3, TM6SF2, GCKR, MBOAT7, and HSD17B13. From this point of view, we focus in this perspective on how human molecular genetics of FLD have highlighted defects in hepatic lipid handling as a major common mechanism of its pathology and how this insight could be leveraged to treat and prevent its more serious complications.

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.

Alcohol-related liver disease. Clinical practice guidelines. Consensus document sponsored by AEEH

Alcohol-related liver disease (ARLD) is the most prevalent cause of advanced liver disease and liver cirrhosis in Europe, including Spain. According to the World Health Organization the fraction of liver cirrhosis attributable to alcohol use in Spain is 73.8% among men and 56.3% among women. ARLD includes various stages such as steatohepatitis, cirrhosis and hepatocellular cancer. In addition, patients with underlying ARLD and heavy alcohol intake may develop alcoholic hepatitis, which is associated with high mortality. To date, the only effective treatment to treat ARLD is prolonged withdrawal. There are no specific treatments, and the only treatment that increases life expectancy in alcoholic hepatitis is prednisolone. For patients with alcoholic hepatitis who do not respond to treatment, some centres offer the possibility of an early transplant. These clinical practice guidelines aim to propose recommendations on ARLD taking into account their relevance as a cause of advanced chronic liver disease and liver cirrhosis in our setting. This paper aims to answer the key questions for the clinical practice of Gastroenterology, Hepatology, as well as Internal Medicine and Primary Health Centres, making the most up-to-date information regarding the management and treatment of ARLD available to health professionals. These guidelines provide evidence-based recommendations for the clinical management of this disease.

The Burden of Hepatocellular Carcinoma in Non-Alcoholic Fatty Liver Disease: Screening Issue and Future Perspectives

In recent decades, non-alcoholic fatty liver disease (NAFLD) has become the most common liver disease in the Western world, and the occurrence of its complications, such as hepatocellular carcinoma (HCC), has rapidly increased. Obesity and diabetes are considered not only the main triggers for the development of the disease, but also two independent risk factors for HCC. Single nucleotide polymorphisms (such as PNPLA3, TM6SF2 and MBOAT7) are related to the susceptibility to the development of HCC and its progression. Therefore, an appropriate follow-up of these patients is needed for the early diagnosis and treatment of HCC. To date, international guidelines recommend the use of ultrasonography with or without alpha-fetoprotein (AFP) in patients with advanced fibrosis. Furthermore, the use of non-invasive tools could represent a strategy to implement surveillance performance. In this review, we analyzed the main risk factors of NAFLD-related HCC, the validated screening methods and the future perspectives.

The PNPLA3 I148M variant promotes lipid-induced hepatocyte secretion of CXC chemokines establishing a tumorigenic milieu

The I148M variant of the Patatin-like phospholipase domain-containing 3 (PNPLA3) protein is associated with an increased risk for liver inflammation and hepatocellular carcinoma (HCC), but the underlying mechanism is unknown. We hypothesized that enhanced CXC chemokine secretion mediates hepatic inflammation that accelerates development of HCC. Expandable primary human (upcyte®) hepatocytes and human PLC/PRF/5 hepatoma cells were lentivirally transduced with both PNPLA3 I148M variants and stimulated with lipids. Cytokine levels in culture supernatant and patient sera (n = 80) were analyzed by ELISA. Supernatants were assessed in transmigration experiments, tube formation, and proliferation assays. In vitro, lipid stimulation of transduced hepatocytes dose-dependently induced the production of interleukin-8 and CXCL1 in hepatocytes carrying the PNPLA3 148M variant. In line, sera from PNPLA3 148M-positive patients with alcoholic liver cirrhosis contained higher levels of interleukin-8 and CXCL1 than patients with wild-type PNPLA3. Supernatants from lipid-stimulated hepatocytes with the PNPLA3 148M variant induced enhanced migration of white blood cells, angiogenesis, and cell proliferation in comparison with supernatants from wild-type hepatocytes via CXC receptors 1 and 2. Increased production of interleukin-8 and CXCL1 by hepatocytes carrying the PNPLA3 148M variant contributes to a pro-inflammatory and tumorigenic milieu in patients with alcoholic liver disease. KEY MESSAGES: The PNPLA3 148M variant is associated with cirrhosis and hepatocellular carcinoma. Lipid stimulation of hepatocytes with this variant induces IL-8 and CXCL1. Supernatants from hepatocytes with this variant promote migration and angiogenesis. Sera from patients with this variant contained enhanced levels of IL-8 and CXCL1. The PNPLA3 148M variant contributes to a tumorigenic milieu via IL-8 and CXCL1.

American Ancestry Is a Risk Factor for Suspected Nonalcoholic Fatty Liver Disease in Hispanic/Latino Adults

BACKGROUND & AIMS

Nonalcoholic fatty liver disease (NAFLD) disproportionally affects Hispanic/Latino populations. However, the magnitude varies among Hispanic/Latino ethnic groups. We investigated the mechanisms of these disparities.

METHODS

We examined associations of NAFLD-associated genetic variants and continental ancestry with suspected NAFLD, levels of alanine aminotransferase (ALT), and liver fibrosis using data from the Hispanic Community Health Study/Study of Latinos-a population-based study of Hispanic/Latino adults in the United States. We evaluated data from 16,415 Hispanic/Latino adults in 4 cities from 2008 through 2011. Subjects suspected of having NAFLD or liver fibrosis were identified based on unexplained increases in levels of aminotransferases and FIB-4 score, respectively.

RESULTS

Among the 9342 participants with available genetic and aminotransferase data, the PNPLA3 G allele (odds ratio [OR], 1.53; 95% CI, 1.41-1.66), TM6SF2 T allele (OR, 1.41; 95% CI, 1.20-1.67), and PPP1R3B G allele (OR, 1.16; 95% CI, 1.06-1.28) were associated with suspected NAFLD. PNPLA3 G was also associated with increased levels of ALT, except in participants with Dominican and South American backgrounds, and with liver fibrosis. The frequency of PNPLA3 G was high (41%) and TM6SF2 T (5%) was low in Hispanic/Latinos. PNPLA3 G frequency differed among Hispanic background groups with the highest proportion in Mexicans (52%) and the lowest proportion in Dominicans (23%). After adjustment for demographic, clinical, and behavioral factors, as well as PNPLA3 G, TM6SF2 T, and PPP1R3B G, American ancestry had a positive association with level of ALT (r = 6.61%; P < .001), whereas African (r = -3.84%; P < .001) and European (r = -4.31%; P < .001) ancestry were inversely associated with level of ALT.

CONCLUSIONS

American ancestry and PNPLA3 G are independent predictors of ALT levels in US Hispanic/Latinos and may in part explain NAFLD disparities in US Hispanic/Latinos.

PNPLA3 rs738409 G allele carriers with genotype 1b HCV cirrhosis have lower viral load but develop liver failure at younger age

Background

PNPLA3 rs738409 minor allele c.444G represents a risk factor for liver steatosis and fibrosis progression also in chronic hepatitis C (HCV). We investigated its impact on the timing of liver transplantation (LT) in patients with genotype 1b HCV cirrhosis.

Methods

We genotyped and evaluated 172 LT candidates with liver cirrhosis owing to chronic HCV infection, genotype 1b. One hundred patients needed LT for chronic liver failure (CLF) and 72 for a small hepatocellular carcinoma (HCC) in the cirrhotic liver without CLF. Population controls (n = 647) were selected from the Czech cross-sectional study MONICA.

Results

The CLF patients were younger (53.5 ± 7.2 vs. 59.6 ± 6.6, P < 0.001) with more advanced liver disease than HCC patients (Child-Pugh’s score 9.1 ± 1.8 vs. 7.1 ± 1.9, P < 0.001, MELD 14.1 ± 3.9 vs. 11.1 ± 3.7, P < 0.001). PNPLA3 G allele increased the risk of LT for CLF in both allelic and recessive models (CG + GG vs. CC: OR, 1.90; 95% CI, 1.017–3.472, P = 0.045 and GG vs. CC + CG: OR, 2.94; 95% CI, 1.032–7.513, P = 0.042). Multivariate analysis identified younger age (P < 0.001) and the G allele (P < 0.05) as risk factors for CLF. The genotype frequencies between the CLF group and MONICA study significantly differed in both, allelic and recessive model (P = 0.004, OR 1.87, 95% CI 1.222–2.875; P < 0.001, OR 3.33, 95% CI 1.824–6.084, respectively). The OR values almost doubled in the recessive model compared with the allelic model suggesting the additive effect of allele G. In contrast, genotype frequencies in the HCC group were similar to the MONICA study in both models. Pretransplant viral load was significantly lower in GG than in CC + CG genotypes (median, IQR; 162,500 (61,550–319,000) IU/ml vs. 570,000 (172,000–1,595,000) IU/ml, P < 0.0009).

Conclusions

Our results suggest that PNPLA3 rs738409 G allele carriage may be associated with a faster progression of HCV cirrhosis to chronic liver failure.

NAFLD and Diabetes: Two Sides of the Same Coin? Rationale for Gene-Based Personalized NAFLD Treatment

The prevalence of non-alcoholic fatty liver disease (NAFLD) has been increasing rapidly and at the forefront of worldwide concern. Characterized by excessive fat accumulation in the liver, NAFLD regularly coexists with metabolic disorders, including type 2 diabetes, obesity, and cardiovascular disease. It has been well established that the presence of NAFLD increases the incidence of type 2 diabetes, while diabetes aggravates NAFLD to more severe forms of steatohepatitis, cirrhosis, and hepatocellular carcinoma. However, recent progress on the genotype/phenotype relationships in NAFLD patients indicates the development of NAFLD with a relative conservation of glucose metabolism in individuals with specific gene variants, such as the patatin-like phospholipase domain-containing 3 (PNPLA3) and transmembrane 6 superfamily member 2 protein (TM6SF2) variants. This review will focus on the clinical and pathophysiological connections between NAFLD and type 2 diabetes and will also discuss a disproportionate progression of NAFLD and diabetes, and the different responses to lifestyle and drug intervention in NAFLD patients with specific gene variants that may give insight into personalized treatment for NAFLD.

Independent and additive effects of PNPLA3 and TM6SF2 polymorphisms on the development of non-B, non-C hepatocellular carcinoma

BACKGROUND

This study was aimed at evaluating the association between single nucleotide polymorphisms (SNPs) in the PNPLA3, NCAN, TM6SF2 and MBOAT7 and hepatocellular carcinoma (HCC) development in Thai patients according to underlying etiologies of liver disease.

METHODS

These SNPs were determined by allelic discrimination in blood samples of 105 healthy controls and 530 patients with HCC [270 with hepatitis B virus (HBV-HCC), 131 with hepatitis C virus (HCV-HCC), and 129 with non-B, non-C HCC (NBNC-HCC) matched for age and gender].

RESULTS

G allele of PNPLA3 rs738409 variant was significantly higher in NBNC-HCC (49%) compared to healthy controls (32%), HBV-HCC (32%) and HCV-HCC (31%) (P < 0.001). T allele of TM6SF2 rs58542926 was more prevalent in NBNC-HCC (24%) than in healthy controls (8%), HBV-HCC (10%) and HCV-HCC (12%) (P < 0.001). The distribution of NCAN (rs2228603) and MBOAT7 (rs641738) was not different between groups. In multivariate logistic regression analysis, PNPLA3 rs738409 (OR 2.06, 95% CI 1.24-3.43; P = 0.005) and TM6SF2 rs58542926 (OR 2.22, 95% CI 1.34-3.65; P = 0.002) were independently associated with NBNC-HCC compared to viral-related HCC (VR-HCC). The proportion of patients with NBNC-HCC increased significantly along with the increase of the number of risk alleles. There was no association between these SNPs and overall survival in patients with HCC.

CONCLUSIONS

These data showed that PNPLA3 and TM6SF2 polymorphisms were independently linked to NBNC-HCC but not HBV- or HCV-HCC in Thai populations. In addition, the risk genotypes might interact with each other through tumor development in patients with NBNC-HCC.

Hepatocellular Carcinoma Risk Stratification by Genetic Profiling in Patients with Cirrhosis

Prediction of future hepatocellular carcinoma (HCC) risk in the sizable chronic liver disease population is an urgent unmet need to enable regular HCC screening for early detection. Germline deoxyribonucleic acid polymorphisms likely represent etiology-specific host factors that determine HCC susceptibility, including single nucleotide polymorphisms in EGF, IFNL3, MICA, and TLL1 in hepatitis C with or without active viral infection, and PNPLA3, TM6SF2, and MBOAT7 in metabolic liver diseases. Transcriptome-based prognostic liver signature in diseased liver tissue has been associated with long-term HCC risk in viral and metabolic etiologies. Transcriptomic signatures of hepatic injury and specific cell type such as aggregated lymphocytes also predict HCC development. Circulating factors such as proteins and their chemical modification, nucleotides, and metabolites may serve for less-invasive assessment of short- or long-term HCC risk. These biomarkers will enable individual HCC risk-based personalized clinical management for cost-effective early HCC detection and improvement of patient survival.

The PNPLA3 rs738409 C>G variant interacts with changes in body weight over time to aggravate liver steatosis, but reduces the risk of incident type 2 diabetes

AIMS/HYPOTHESIS

The rs738409 C>G variant of the patatin-like phospholipase domain containing 3 gene (PNPLA3) increases the risk of non-alcoholic fatty liver disease (NAFLD) with no predisposition for insulin resistance. In this study, we aimed to investigate the influence of PNPLA3 polymorphisms on liver fat content (LFC) and glucose metabolic variables, and the associations between these, during the natural course of body weight changes in a Chinese adult cohort.

METHODS

The LFC, measured using a quantitative ultrasound method, was prospectively monitored in 2189 middle-aged and elderly adults from the Shanghai Changfeng Study, together with changes in body weight and metabolic variables. General linear models were used to detect interactive effects between the PNPLA3 rs738409 genotype and 4 year changes in body weight on liver steatosis and glucose metabolism.

RESULTS

The PNPLA3 homozygous GG genotype dissociated the changes in the LFC and OGTT 2 h post-load blood glucose (PBG) in relation to 4 year changes in body weight. PNPLA3 GG genotype carriers showed greater increases in the LFC and serum alanine aminotransferase (ALT) but lower PBG elevation and incident diabetes than PNPLA3 wild-type (CC) genotype carriers exhibiting the same degree of body weight increase. The interactions between the PNPLA3 genotype and changes in body weight on the LFC (false discovery rate [FDR]-adjusted p_interaction = 0.044) and ALT (FDR-adjusted p_interaction = 0.044) were significant. Subgroup analyses showed that the effect of the PNPLA3 GG genotype on changes in the LFC and PBG was only observed in metabolically unhealthy participants with insulin resistance or abdominal obesity.

CONCLUSIONS/INTERPRETATION

The PNPLA3 GG genotype interacted with changes in body weight to aggravate liver steatosis but reduced the risk of incident type 2 diabetes in metabolically unhealthy participants.

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.

Genetic and Epigenetic Modifiers of Alcoholic Liver Disease

Alcoholic liver disease (ALD), a disorder caused by excessive alcohol consumption is a global health issue. More than two billion people consume alcohol in the world and about 75 million are classified as having alcohol disorders. ALD embraces a wide spectrum of hepatic lesions including steatosis, alcoholic steatohepatitis (ASH), fibrosis, cirrhosis, and hepatocellular carcinoma (HCC). ALD is a complex disease where environmental, genetic, and epigenetic factors contribute to its pathogenesis and progression. The severity of alcohol-induced liver disease depends on the amount, method of usage and duration of alcohol consumption as well as on age, gender, presence of obesity, and genetic susceptibility. Genome-wide association studies and candidate gene studies have identified genetic modifiers of ALD that can be exploited as non-invasive biomarkers, but which do not completely explain the phenotypic variability. Indeed, ALD development and progression is also modulated by epigenetic factors. The premise of this review is to discuss the role of genetic variants and epigenetic modifications, with particular attention being paid to microRNAs, as pathogenic markers, risk predictors, and therapeutic targets in ALD.

Microbiota, Obesity and NAFLD

Non-alcoholic fatty liver disease (NAFLD) is an increasingly important cause of chronic liver disease globally. Similar to metabolic syndrome and obesity, NAFLD is associated with alternations in the gut microbiota and its related biological pathways. While the exact pathophysiology of NAFLD remains largely unknown, changes in intestinal inflammation, gut permeability, energy harvest, anaerobic fermentation and insulin resistance have been described. In this chapter, we review the relationship between the gut microbiota, obesity and NAFLD, and highlight potential ways to modify the gut microbiota to help managing NAFLD patients.

PNPLA3 and TM6SF2 variants as risk factors of hepatocellular carcinoma across various etiologies and severity of underlying liver diseases

Few single nucleotide polymorphisms (SNPs) have been reproducibly associated with hepatocellular carcinoma (HCC). Our aim was to test the association between nine SNPs and HCC occurrence. SNPs in genes linked to HCC (DEPDC5, GRIK1, KIF1B, STAT4, MICA, DLC1, DDX18) or to liver damage (PNPLA3-rs738409, TM6SF2-rs58542926) in GWAS were genotyped in discovery cohorts including 1,020 HCC, 2,021 controls with chronic liver disease and 2,484 healthy individuals and replication was performed in prospective cohorts of cirrhotic patients with alcoholic liver disease (ALD, n = 249) and hepatitis C (n = 268). In the discovery cohort, PNPLA3 and TM6SF2 SNPs were associated with HCC (OR = 1.67 [CI95%:1.16-2.40], p = 0.005; OR = 1.45 [CI95%:1.08-1.94], p = 0.01) after adjustment for fibrosis, age, gender and etiology. In contrast, STAT4-rs7574865 was associated with HCC only in HBV infected patients (p = 0.03) and the other tested SNP were not linked with HCC risk. PNPLA3 and TM6SF2 variants were independently associated with HCC in patients with ALD (OR = 3.91 [CI95%:2.52-6.06], p = 1.14E-09; OR = 1.79 [CI95%:1.25-2.56], p = 0.001) but not with other etiologies. PNPLA3 SNP was also significantly associated with HCC developed on a nonfibrotic liver (OR = 2.19 [CI95%:1.22-3.92], p = 0.007). The association of PNPLA3 and TM6SF2 with HCC risk was confirmed in the prospective cohort with ALD. A genetic score including PNPLA3 and TM6SF2 minor alleles showed a progressive significant increased risk of HCC in ALD patients. In conclusion, PNPLA3-rs738409 and TM6SF2-rs58542926 are inherited risk variants of HCC development in patients with ALD in a dose dependent manner. The link between PNPLA3 and HCC on nonfibrotic liver suggests a direct role in liver carcinogenesis.

Differences in the genetic backgrounds of patients with alcoholic liver disease and non-alcoholic fatty liver disease

Background and Aim

Alcoholic liver disease (ALD) and non‐alcoholic fatty liver disease (NAFLD) have common hepatic histological features, but few studies have compared the genomic backgrounds of these two diseases. Here, we compared the genetic differences between ALD and NAFLD.

Methods

This study enrolled 318 Japanese patients with ALD (n = 118; male, 86%; median age, 62 years; liver cirrhosis, 58%; hepatocellular carcinoma [HCC], 31%) and NAFLD (n = 200; male, 55%; age, 61 years; cirrhosis, 19%; HCC, 12%). The genotype frequencies of 10 single nucleotide polymorphisms (SNPs) were analyzed.

Results

The ADH1B genotype GG and ALDH2 genotype GG were observed more frequently, and the percentage of patients with the MTP genotype GG was lower in ALD compared with NAFLD patients (ADH1B, 16 vs 4%; ALDH2 84 vs 44%; MTP 62 vs 72%, respectively; all P < 0.01). Comparing noncirrhosis to cirrhosis, the frequency of the potassium voltage‐gated channel subfamily Q member 1 (KCNQ1) genotype TT and adrenoceptor beta 3 (ADRB3) genotype TT was increased significantly in ALD‐related cirrhosis. In contrast, the patatin‐like phospholipase 3 (PNPLA3) genotype CC was decreased significantly in NAFLD‐related cirrhosis. A comparison of patients with and without HCC demonstrated that the KCNQ1 genotype TT was increased significantly in both HCC groups. In addition, associations between the KCNJ15 genotype GG and ALD‐HCC and the G allele of PNPLA3 and NAFLD‐HCC were identified.

Conclusions

SNPs in genes related to ethanol and lipid metabolism clearly differed between patients with ALD and NAFLD. KCNQ1 might affect the progression and hepatocarcinogenesis in both ALD and NAFLD.

Genetic variants in PNPLA3 and TM6SF2 predispose to the development of hepatocellular carcinoma in individuals with alcohol-related cirrhosis

OBJECTIVES

Variants in patatin-like phospholipase domain-containing 3 (PNPLA3; rs738409), transmembrane 6 superfamily member 2 (TM6SF2; rs58542926), and membrane bound O-acyltransferase domain containing 7 (MBOAT7; rs641738) are risk factors for the development of alcohol-related cirrhosis. Within this population, PNPLA3 rs738409 is also an established risk factor for the development of hepatocellular carcinoma (HCC). The aim of this study was to explore possible risk associations of TM6SF2 rs58542926 and MBOAT7 rs641738 with HCC.

METHODS

Risk variants in PNPLA3, TM6SF2, and MBOAT7 were genotyped in 751 cases with alcohol-related cirrhosis and HCC and in 1165 controls with alcohol-related cirrhosis without HCC. Association with the risk of developing HCC was analyzed using multivariate logistic regression.

RESULTS

The development of HCC was independently associated with PNPLA3 rs738409 (OR_adjusted 1.84 [95% CI 1.55-2.18], p = 1.85 × 10^-12) and TM6SF2 rs58542926 (OR_adjusted 1.66 [1.30-2.13], p = 5.13 × 10^-05), using an additive model, and controlling the sex, age, body mass index, and type 2 diabetes mellitus; the risk associated with carriage of MBOAT7 rs641738 (OR_adjusted 1.04 [0.88-1.24], p = 0.61) was not significant. The population-attributable fractions were 43.5% for PNPLA3 rs738409, 11.5% for TM6SF2 rs58542926, and 49.9% for the carriage of both the variants combined.

CONCLUSIONS

Carriage of TM6SF2 rs58542926 is an additional risk factor for the development of HCC in people with alcohol-related cirrhosis. Carriage of both PNPLA3 rs738409 and TM6SF2 rs58542926 accounts for half of the attributable risk for HCC in this population. Genotyping will allow for more precise HCC risk-stratification of patients with alcohol-related cirrhosis, and genotype-guided screening algorithms would optimize patient care.

Genetic Variations Linked to Hepatocellular Carcinoma: Personalized Medicine Takes a Step Forward

: There are strong associations between candidate genetic polymorphisms associated with intrahepatocyte lipid droplet accumulation and the development of cirrhosis, via a common sequence in which lipid accumulation is followed by chronic inflammatory injury and fibrogenesis. Hepatocellular carcinoma (HCC) has also been linked to genetic polymorphisms associated with intracellular lipid trafficking, although, as shown in the present study, not all the candidate polymorphisms implicated in fibrogenesis are also tied to HCC. Genetic analysis may identify at-risk persons who would most benefit from modifying life-style factors linked to cirrhosis and HCC, and also persons most likely to benefit from HCC surveillance.

The Genetics of Clinical Liver Diseases: Insight into the TM6SF2 E167K Variant

The transmembrane 6 superfamily member 2 (TM6SF2) gene E167K variant (rs58542926) was identified by exome-wide association study as a nonsynonymous single nucleotide polymorphism associated with nonalcoholic fatty liver disease. The TM6SF2 E167K variant features a C-to-T substitution at nucleotide 499, encoding a glutamate with lysine change at codon 167 (E167K). TM6SF2 is markedly expressed in the liver, small intestine and kidney, and has been proposed as an important risk factor for diseases associated with lipid metabolism. Subsequently, multifunctional studies of the TM6SF2 E167K variant have been carried out in a spectrum of liver diseases, such as nonalcoholic fatty liver disease, nonalcoholic steatohepatitis, fibrosis, cirrhosis, and viral hepatitis. This review summarizes the research status of the TM6SF2 E167K variant in different liver diseases and specific populations, and discusses the potential mechanisms of the TM6SF2 E167K variant's role in the progression of various liver diseases.

Non-alcoholic fatty liver disease: a narrative review of genetics

Non-alcoholic fatty liver disease (NAFLD) is now the most common cause of chronic liver diseases worldwide. It encompasses a spectrum of disorders ranging from isolated hepatic steatosis to nonalcoholic steatohepatitis (NASH), fibrosis, cirrhosis, and hepatocellular carcinoma. One of the key challenges in NAFLD is identifying which patients will progress. Epidemiological and genetic studies indicate a strong pattern of heritability that may explain some of the variability in NAFLD phenotype and risk of progression. To date, at least three common genetic variants in the PNPLA3, TM6SF2, and GCKR genes have been robustly linked to NAFLD in the population. The function of these genes revealed novel pathways implicated in both the development and progression of NAFLD. In addition, candidate genes previously implicated in NAFLD pathogenesis have also been identified as determinants or modulators of NAFLD phenotype including genes involved in hepatocellular lipid handling, insulin resistance, inflammation, and fibrogenesis. This article will review the current understanding of the genetics underpinning the development of hepatic steatosis and the progression of NASH. These newly acquired insights may transform our strategy to risk-stratify patients with NAFLD and to identify new potential therapeutic targets.

Patatin-like phospholipase domain containing 3 variants differentially impact metabolic traits in individuals at high risk for cardiovascular events

Single nucleotide polymorphism (SNP) rs738409 C>G in the patatin‐like phospholipase domain containing 3 (PNPLA3) gene results in an amino acid exchange from isoleucin to methionine at position I148M of PNPLA3. The expression of this loss‐of‐function mutation leads to impaired hepatocellular triglyceride hydrolysis and is associated with the development of liver steatosis, fibrosis, and hepatocellular carcinoma. In contrast to these well‐established associations, the relationship of the PNPLA3 rs738409 variant with other metabolic traits is incompletely understood. We therefore assessed the association of the PNPLA3 rs738409 genotype with relevant metabolic traits in a prospective study of patients at high risk for cardiovascular events, i.e., patients undergoing coronary angiography. In a total of 270 patients, known associations of the PNPLA3 rs738409 GG genotype with nonalcoholic steatohepatitis and liver fibrosis were confirmed. In addition, we found an association of the PNPLA3 rs738409 G allele with the presence of diabetes (22% versus 28% versus 58% for CC versus CG versus GG genotype, respectively; P = 0.02). In contrast to its association with nonalcoholic fatty liver disease, liver fibrosis, and diabetes, the minor G allele of PNPLA3 rs738409 was inversely associated with total serum cholesterol and low‐density lipoprotein serum levels (P = 0.003 and P = 0.02, respectively). Finally, there was a trend toward an inverse association between the presence of the PNPLA3 rs738409 G allele and significant coronary heart disease. Comparable trends were observed for the transmembrane 6 superfamily member 2 (TM6SF2) 167 K variant, but the sample size was too small to evaluate this rarer variant. Conclusion: The PNPLA3 rs738409 G allele is associated with liver disease but also with a relatively benign cardiovascular risk profile. (Hepatology Communications 2018;2:798‐806)

Host genetic factors associated with hepatocellular carcinoma in patients with hepatitis C virus infection: A systematic review

Hepatitis C virus (HCV)-infected patients are at risk of developing hepatocellular carcinoma (HCC). Individuals at heightened risk could be targeted by intensive follow-up surveillance. We have conducted a systematic review of the literature to identify host genetic predisposition to HCC in HCV-infected patients. A comprehensive search of Medline and Embase databases was performed, and the strength of evidence of associations for each gene on development of HCC was evaluated. We identified 166 relevant studies, relating to 137 different genes, or combinations thereof. Seventeen genes were classified as having "good" evidence of an association, a significant association was observed for 37 genes but this finding had not yet been replicated, 56 genes had mixed or limited evidence of an association, and 27 genes showed no association. IFNL3/4, TNF-α and PNPLA3 genes had the most evidence of an association. There was, however, considerable heterogeneity in study design and data quality. In conclusion, we identified a number of genes with evidence of association with HCC, but also a need for more standardized approaches to address this clinically critical question. It is important to consider the underlying mechanism of these relationships and which are confounded by the presence of other HCC risk factors and response to therapy. We also identified many genes where the evidence of association is contradictory or requires replication, as well as a number where associations have been studied but no evidence found. These findings should help to direct future studies on host genetic predisposition to HCC in HCV-infected patients.

Genetics of alcoholic liver disease and non-alcoholic steatohepatitis

Alcohol-related liver disease (ARLD) and non-alcoholic fatty liver disease (NAFLD) are leading causes of chronic liver disease globally. Both ARLD and NAFLD are multifactorial and refer to a spectrum of disease severity, ranging from steatosis through steatohepatitis to fibrosis and cirrhosis. Both diseases exhibit substantial inter-patient variation in long-term outcomes and are best considered complex disease traits where genetic and environmental factors interact to mediate disease severity and progression. Here, we briefly review the current literature describing the best validated genetic modifiers that influence severity of these liver conditions, including variants of the genes PNPLA3, TM6SF2 and MBOAT7, which have also been implicated in lipid dysregulation.

Patatin-like phospholipase domain–containing protein 3 promotes transfer of essential fatty acids from triglycerides to phospholipids in hepatic lipid droplets

Fatty liver disease (FLD) is a burgeoning health problem. A missense variant (I148M) in patatin-like phospholipase domain-containing protein 3 (PNPLA3) confers susceptibility to FLD, although the mechanism is not known. To glean first insights into the physiological function of PNPLA3, we performed detailed lipidomic profiling of liver lysates and lipid droplets (LDs) from WT and Pnpla3^-/- (KO) mice and from knock-in (ki) mice expressing either the 148M variant (IM-ki mice) or a variant (S47A) that renders the protein catalytically inactive (SA-ki mice). The four strains differed in composition of very-long-chain polyunsaturated fatty acids (vLCPUFA) in hepatic LDs. In the LDs of IM-ki mice, vLCPUFAs were depleted from triglycerides and enriched in phospholipids. Conversely, vLCPUFAs were enriched in triglycerides and depleted from phospholipids in SA-ki and Pnpla3^-/- mice. Release of vLCPUFAs from hepatic LDs incubated ex vivo was increased in droplets from IM-ki mice and decreased from droplets isolated from Pnpla3^-/- and SA-ki mice relative to those of WT mice. Thus, the physiological role of PNPLA3 appears to be to remodel triglycerides and phospholipids in LDs, perhaps to accommodate changes in LD size in response to feeding. Because SA-ki and IM-ki both cause FLD and yet have opposite effects on the lipidomic profile of LDs, we conclude that the FLD associated with genetic variation in PNPLA3 is not related to the enzyme's role in remodeling LD lipids.

Combination of PNPLA3 and TLL1 polymorphism can predict advanced fibrosis in Japanese patients with nonalcoholic fatty liver disease

BACKGROUND

Hepatic fibrosis is an independent risk factor for mortality and liver-related events in patients with nonalcoholic fatty liver disease (NAFLD). PNPLA3 rs738409 has been associated with fibrosis in viral and non-viral hepatitis. TLL1 rs17047200 also has been associated with developing hepatocellular carcinoma probably via hepatic fibrogenesis. We estimated the impact of these genetic polymorphisms on hepatic fibrosis in Japanese patients with NAFLD.

METHODS

We analyzed the association between these genetic variants and the backgrounds of 817 individuals who received health checkups (health check cohort) from 2012 to 2014. Then, we investigated the relationship between genetic variants and liver histology in 258 consecutive patients with biopsy-proven NAFLD in Japan (NAFLD cohort) from 2012 to 2017 (UMIN000027399).

RESULTS

The prevalence of PNPLA3 CG/GG in the NAFLD cohort was higher than that in the health check cohort (p < 0.001). The prevalence of patients with advanced fibrosis (stages 3-4) was higher for PNPLA3 genotype CG/GG than CC (p = 0.048) and for TLL1 genotype AT/TT than AA (p = 0.044). The high-risk group which had at least two risk alleles of these variants was more likely to have advanced fibrosis (p = 0.004). Multivariate analysis identified body mass index [odds ratio (OR) 1.123, serum AST (OR 1.037, p = 0.004], serum albumin (OR 0.247, p = 0.032), and genetic high risk (OR 2.632, p = 0.026) as predictors of advanced fibrosis.

CONCLUSIONS

In Japanese patients with NAFLD, individuals with risk alleles of PNPLA3 and TLL1 may have a risk of advanced fibrosis.

Optimizing therapy of liver diseases not associated with viral infection

The review demonstrated results and prospects of non-pharmacological and drug therapy patients with liver disease, not associated with a viral infection. The presented data emphasize the relevance of studying the problem of effective therapy of diseases of the liver and its role in improving the course and outcomes of liver disease.

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.

Development of hepatocellular carcinoma in Japanese patients with biopsy-proven non-alcoholic fatty liver disease: Association between PNPLA3 genotype and hepatocarcinogenesis/fibrosis progression

AIM

Some patients with non-alcoholic fatty liver disease (NAFLD) develop hepatocellular carcinoma (HCC). Patatin-like phospholipase domain containing 3 (PNPLA3) rs738409 (encoding the I148M variant) has been associated with advanced fibrosis and HCC. We determined the risk factors for HCC, including the PNPLA3 rs738409 polymorphism, in Japanese patients with biopsy-proven NAFLD.

METHODS

In this retrospective cohort study, we analyzed hepatocarcinogenesis in 238 patients. PNPLA3 rs738409 genotype was determined by allelic discrimination in 130 patients. Among them, 86 patients who were followed up for >5 years and without liver cirrhosis were analyzed to clarify the relationship between PNPLA3 genotype and long-term changes in biomarkers.

RESULTS

Of 238 patients, PNPLA3 genotype frequencies were: CC, 0.14; CG, 0.46; and GG, 0.40. During a follow-up period of 6.1 years, 10 patients (4.2%) with non-alcoholic steatohepatitis developed HCC. The cumulative rate of HCC was 1.9% at the end of the 5th year and 8.3% at the end of the 10th year. Multivariate analysis identified PNPLA3 genotype GG (hazard ratio, 6.36; P = 0.019) and fibrosis stage (fibrosis stage 3/4; hazard ratio, 24.4; P = 0.011) as predictors of HCC development. In the long follow-up cohort, a larger reduction in platelet count was found in the GG group (P = 0.032) despite a larger reduction in alanine aminotransferase (P = 0.023) compared to that in the CC/CG group.

CONCLUSIONS

In Japanese patients with NAFLD, severe fibrosis and PNPLA3 GG genotype were predictors of HCC development, independent of other known risk factors. Patients with the PNPLA3 GG genotype have the potential for a decreased platelet count, even when alanine aminotransferase levels are well controlled.

Treatment options for alcoholic and non-alcoholic fatty liver disease: A review

Alcoholic liver disease (ALD) and non-alcoholic fatty liver disease (NAFLD) are serious health problems worldwide. These two diseases have similar pathological spectra, ranging from simple steatosis to hepatitis to cirrhosis and hepatocellular carcinoma. Although most people with excessive alcohol or calorie intake display abnormal fat accumulation in the liver (simple steatosis), a small percentage develops progressive liver disease. Despite extensive research on understanding the pathophysiology of both these diseases there are still no targeted therapies available. The treatment for ALD remains as it was 50 years ago: abstinence, nutritional support and corticosteroids (or pentoxifylline as an alternative if steroids are contraindicated). As for NAFLD, the treatment modality is mainly directed toward weight loss and co-morbidity management. Therefore, new pathophysiology directed therapies are urgently needed. However, the involvement of several inter-related pathways in the pathogenesis of these diseases suggests that a single therapeutic agent is unlikely to be an effective treatment strategy. Hence, a combination therapy towards multiple targets would eventually be required. In this review, we delineate the treatment options in ALD and NAFLD, including various new targeted therapies that are currently under investigation. We hope that soon we will be having an effective multi-therapeutic regimen for each disease.

Nonalcoholic fatty liver disease: Evolving paradigms

In the last years new evidence has accumulated on nonalcoholic fatty liver disease (NAFLD) challenging the paradigms that had been holding the scene over the previous 30 years. NAFLD has such an epidemic prevalence as to make it impossible to screen general population looking for NAFLD cases. Conversely, focusing on those cohorts of individuals exposed to the highest risk of NAFLD could be a more rational approach. NAFLD, which can be diagnosed with either non-invasive strategies or through liver biopsy, is a pathogenically complex and clinically heterogeneous disease. The existence of metabolic as opposed to genetic-associated disease, notably including ”lean NAFLD” has recently been recognized. Moreover, NAFLD is a systemic condition, featuring metabolic, cardiovascular and (hepatic/extra-hepatic) cancer risk. Among the clinico-laboratory features of NAFLD we discuss hyperuricemia, insulin resistance, atherosclerosis, gallstones, psoriasis and selected endocrine derangements. NAFLD is a precursor of type 2 diabetes (T2D) and metabolic syndrome and progressive liver disease develops in T2D patients in whom the course of disease is worsened by NAFLD. Finally, lifestyle changes and drug treatment options to be implemented in the individual patient are also critically discussed. In conclusion, this review emphasizes the new concepts on clinical and pathogenic heterogeneity of NAFLD, a systemic disorder with a multifactorial pathogenesis and protean clinical manifestations. It is highly prevalent in certain cohorts of individuals who are thus potentially amenable to selective screening strategies, intensive follow-up schedules for early identification of liver-related and extrahepatic complications and in whom earlier and more aggressive treatment schedules should be carried out whenever possible.

Polymorphisms in MICA, but not in DEPDC5, HCP5 or PNPLA3, are associated with chronic hepatitis C-related hepatocellular carcinoma

Recently, the MICA rs2596542 and DEPDC5 rs1012068 variants in Japanese individuals as well as the HCP5 rs2244546 and PNPLA3 rs738409 variants in European individuals have been found associated with hepatocellular carcinoma (HCC). The present study determined which single nucleotide polymorphism (SNP) is the most predictive for developing hepatitis C virus (HCV)-related HCC in a Japanese cohort. Of the 4 SNPs analysed, only the MICA genotypes were significantly associated with development of HCC (p = 0.0185). The major (MA), hetero (HE), and minor (MI) genotypes occurred in 40%, 41%, and 19% of HCC patients and in 43%, 47%, and 10% of non-HCC patients, respectively. Interestingly, the MICA genotype was significantly correlated with MICA mRNA and soluble protein levels. In patients older than 70 years, the MI genotype was significantly associated with HCC development. In addition, the MI genotype was related to HCC development when the platelet count range was 10-15 × 104/μL, corresponding with the fibrosis stage; but not when the range was less than 10, indicating advanced fibrosis; or greater than 15 × 104/μL, as mild fibrosis. Thus, polymorphisms in MICA, but not in DEPDC5, HCP5 or PNPLA3, are associated with HCC development in Japanese patients with chronic HCV infection.

MBOAT7 rs641738 variant and hepatocellular carcinoma in non-cirrhotic individuals

Nonalcoholic fatty liver disease (NAFLD) represents an emerging cause of hepatocellular carcinoma (HCC), especially in non-cirrhotic individuals. The rs641738 C > T MBOAT7/TMC4 variant predisposes to progressive NAFLD, but the impact on hepatic carcinogenesis is unknown. In Italian NAFLD patients, the rs641738 T allele was associated with NAFLD-HCC (OR 1.65, 1.08-2.55; n = 765), particularly in those without advanced fibrosis (p < 0.001). The risk T allele was linked to 3'-UTR variation in MBOAT7 and to reduced MBOAT7 expression in patients without severe fibrosis. The number of PNPLA3, TM6SF2, and MBOAT7 risk variants was associated with NAFLD-HCC independently of clinical factors (p < 0.001), but did not significantly improve their predictive accuracy. When combining data from an independent UK NAFLD cohort, in the overall cohort of non-cirrhotic patients (n = 913, 41 with HCC) the T allele remained associated with HCC (OR 2.10, 1.33-3.31). Finally, in a combined cohort of non-cirrhotic patients with chronic hepatitis C or alcoholic liver disease (n = 1121), the T allele was independently associated with HCC risk (OR 1.93, 1.07-3.58). In conclusion, the MBOAT7 rs641738 T allele is associated with reduced MBOAT7 expression and may predispose to HCC in patients without cirrhosis, suggesting it should be evaluated in future prospective studies aimed at stratifying NAFLD-HCC risk.

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.

Non-alcoholic fatty liver disease: An update with special focus on the role of gut microbiota

Non-alcoholic fatty liver disease (NAFLD) is a significant global health burden in children, adolescents and adults with substantial rise in prevalence over the last decades. Accumulating data from manifold studies support the idea of NAFLD as a hepatic manifestation of metabolic syndrome, being rather a systemic metabolic disease than a liver confined pathology. Emerging data support that the gut microbiome represents a significant environmental factor contributing to NAFLD development and progression. Apart from other regimens, probiotics may have a positive role in the management of NAFLD through a plethora of possible mechanisms. The current review focuses on the NAFLD multifactorial pathogenesis, including mainly the role of intestinal microbiome and all relevant issues are raised. Furthermore, the clinical manifestations and appropriate diagnostic approach of the disease are discussed, with all possible therapeutic measures that can be taken, also including the potential beneficial effect of probiotics.

Patatin-like phospholipase domain-containing protein 3 (PNPLA3): A potential role in the association between liver disease and bipolar disorder

OBJECTIVE

Due to the increased prevalence of liver disease in patients with bipolar disorder, we examined the potential role of the patatin-like phospholipase domain-containing protein 3 (PNPLA3) variant among individuals with bipolar disorder and those with no mood disorder.

METHODS

We used the National Health and Nutrition Examination Survey (NHANES) database (aged 15-39 years) to identify a group of individuals with a bipolar diagnosis and a control group of individuals with no mood disorder. A total of 1931 individuals were randomly selected, one from each family containing information on the PNPLA3 genotype to be used in the analysis.

RESULTS

Analyses revealed individuals with the recessive variant genotype (MM) had an adjusted odds ratio for bipolar disorder of about 4.6 compared to individuals with either IM or II genotypes of the PNPLA3 variant.

LIMITATIONS AND CONCLUSIONS

Limitations of this study include the use of a lay-administered survey in for diagnosis of bipolar disorder in NHANES. The association between the PNPLA3 variant and bipolar disorder may help guide further work on medication effectiveness, treatment options, prevention approaches, and understanding potential medication side effects among specific subgroups of individuals with the MM genotype.