Variant adiponutrin (PNPLA3) represents a common fibrosis risk gene: non-invasive elastography-based study in chronic liver disease

Use of PNPLA3, TM6SF2, and HSD17B13 for detection of fibrosis in MASLD in the general population

BACKGROUND

Genetic testing can be used to evaluate disease risk. We evaluated if the use of three Single Nucleotide Polymorphisms (SNPs), alone or combined into a genetic risk score (GRS), can aid identify significant fibrosis in subjects with metabolic dysfunction-associated steatotic liver disease (MASLD).

METHODS

We assessed three known risk variants: PNPLA3 rs738409, TM6SF2 rs58542926, and HSD17B13 rs72613567. The study included 414 adult individuals invited from the Danish population, who were defined as at-risk of MASLD due to elevated ALT and body mass index (BMI) >25 kg/m2. Participants were assessed clinically and by the Fibrosis-4 (FIB-4) index and Fibroscan.

RESULTS

In total, 17 participants (4.1%) had alcohol-related liver disease, 79 (19.1%) had no evidence of liver disease, and four (1.0%) were diagnosed with other liver diseases, including malignant disease. The remaining 314 participants (75.8%) were diagnosed with MASLD. Of the 27 who underwent a liver biopsy for suspected fibrosis, 15 had significant fibrosis (≥F2) and 12 had no/mild fibrosis (F0/F1). The GRS was not associated with significant fibrosis (p=0.09) but PNPLA3 was with an odds ratio of 6.75 (95% CI 1.29 - 50.7; p=0.039) risk allele CG/GG versus CC. The diagnostic accuracy of PNPLA3 combined with an increased Fib-4 (>1.3) was excellent for detecting significant fibrosis with a sensitivity of 1.00 (95% CI 0.72-1.00), but the specificity was no better than for FIB-4 alone.

CONCLUSIONS

This study found no evidence to support the use of GRS for diagnosing significant fibrosis in MASLD. However, the combination of PNPLA3 and Fib-4 increased sensitivity considerably. In addition, ALT remains a useful tool for screening diagnosing other liver diseases than MASLD.

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.

Liver phenotypes in PCOS: Analysis of exogenous and inherited risk factors for liver injury in two European cohorts

BACKGROUND & AIMS

Fatty liver disease (FLD) is common in women with polycystic ovary syndrome (PCOS). Here, we use non-invasive tests to quantify liver injury in women with PCOS and analyse whether FLD-associated genetic variants contribute to liver phenotypes in PCOS.

METHODS

Prospectively, we recruited women with PCOS and controls at two university centres in Germany and Poland. Alcohol abuse was regarded as an exclusion criterion. Genotyping of variants associated with FLD was performed using TaqMan assays. Liver stiffness measurements (LSM), controlled attenuation parameters (CAP) and non-invasive HSI, FLI, FIB-4 scores were determined to assess hepatic steatosis and fibrosis.

RESULTS

A total of 42 German (age range 18-53 years) and 143 Polish (age range 18-40 years) women with PCOS, as well as 245 German and 289 Polish controls were recruited. In contrast to Polish patients, Germans were older, presented with more severe metabolic profiles and had significantly higher LSM (median 5.9 kPa vs. 3.8 kPa). In the German cohort, carriers of the PNPLA3 p.I148M risk variant had an increased LSM (p = .01). In the Polish cohort, the minor MTARC1 allele was linked with significantly lower serum aminotransferases activities, whereas the HSD17B13 polymorphism was associated with lower concentrations of 17-OH progesterone, total testosterone, and androstenedione (all p < .05).

CONCLUSIONS

FLD is common in women with PCOS. Its extent is modulated by both genetic and metabolic risk factors. Genotyping of variants associated with FLD might help to stratify the risk of liver disease progression in women suffering from PCOS.

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.

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.

Elucidating Potential Profibrotic Mechanisms of Emerging Biomarkers for Early Prognosis of Hepatic Fibrosis

Hepatic fibrosis has been associated with a series of pathophysiological processes causing excessive accumulation of extracellular matrix proteins. Several cellular processes and molecular mechanisms have been implicated in the diseased liver that augments fibrogenesis, fibrogenic cytokines and associated liver complications. Liver biopsy remains an essential diagnostic tool for histological evaluation of hepatic fibrosis to establish a prognosis. In addition to being invasive, this methodology presents with several limitations including poor cost-effectiveness, prolonged hospitalizations, and risks of peritoneal bleeding, while the clinical use of this method does not reveal underlying pathogenic mechanisms. Several alternate noninvasive diagnostic strategies have been developed, to determine the extent of hepatic fibrosis, including the use of direct and indirect biomarkers. Immediate diagnosis of hepatic fibrosis by noninvasive means would be more palatable than a biopsy and could assist clinicians in taking early interventions timely, avoiding fatal complications, and improving prognosis. Therefore, we sought to review some common biomarkers of liver fibrosis along with some emerging candidates, including the oxidative stress-mediated biomarkers, epigenetic and genetic markers, exosomes, and miRNAs that needs further evaluation and would have better sensitivity and specificity. We also aim to elucidate the potential role of cardiotonic steroids (CTS) and evaluate the pro-inflammatory and profibrotic effects of CTS in exacerbating hepatic fibrosis. By understanding the underlying pathogenic processes, the efficacy of these biomarkers could allow for early diagnosis and treatment of hepatic fibrosis in chronic liver diseases, once validated.

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.

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.

Risk of chemotherapy-associated liver injury (CALI) in PNPLA3 p.148M allele carriers: Preliminary results of a transient elastography-based study

BACKGROUND AND AIMS

Liver steatosis is one of the side effects of chemotherapy. The PNPLA3 p.I148M, TM6SF2 p.E167K and MBOAT7 p.G17E variants represent genetic determinants for progressive liver diseases. Here, we investigate their association with chemotherapy-associated steatosis.

PATIENTS AND METHODS

Prospectively, we recruited 87 patients undergoing systemic chemotherapy for gastrointestinal cancers. Hepatic fat (controlled attenuation parameter, CAP) and liver stiffness (LSM) were measured non-invasively before the initiation of chemotherapy (T0) and after at least two (T1) and four cycles (T2). Genetic variants were genotyped using allelic discrimination assays.

RESULTS

In the final dataset (n = 60) patients demonstrated the following CAP values: T0 - 215.0 ± 55.7 dB/m, T1 - 223.3 ± 53.6 dB/m, T2 - 223.4 ± 56.7 dB/m, consistent with mild steatosis. Initial CAP correlated with BMI (P < 0.01) and serum triglyceride concentrations (P = 0.03). Whereas at T0 none of the variants was associated with CAP or LSM, carriers of the prosteatotic PNPLA3 p.148M allele showed significantly (P = 0.008) higher steatosis at T1 as compared to patients carrying the homozygous wild-type genotype [II].

CONCLUSIONS

Our preliminary results show that patients carrying the PNPLA3 p.I148 M risk allele might be prone to hepatic fat accumulation during chemotherapy. Further studies are be needed to validate the clinical value of these findings.

Nonalcoholic Fatty Liver Disease: A Challenge from Mechanisms to Therapy

Focusing on previously published mechanisms of non-alcoholic fatty liver disease (NAFLD), their uncertainty does not always permit a clear elucidation of the grassroot alterations that are at the basis of the wide-spread illness, and thus curing it is still a challenge. There is somehow exceptional progress, but many controversies persist in NAFLD research and clinical investigation. It is likely that hidden mechanisms will be brought to light in the near future. Hereby, the authors present, with some criticism, classical mechanisms that stand at the basis of NAFLD, and consider contextually different emerging processes. Without ascertaining these complex interactions, investigators have a long way left ahead before finding an effective therapy for NAFLD beyond diet and exercise.

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.

Hepatic steatosis in patients with acromegaly

OBJECTIVE

Comorbid NAFLD is increasingly being diagnosed in patients with diabetes and nondiabetic endocrinopathies. The aim of this study was to assess hepatic steatosis noninvasively by transient elastography in patients with acromegaly.

DESIGN

A cross-sectional study including 22 patients with acromegaly.

METHODS

Hepatic steatosis was quantified using controlled attenuation parameter (CAP) during elastography. Anthropometric measurements were obtained, serum liver function tests and lipid and hormone profiles were measured, and prosteatogenic gene variants were genotyped using standard assays.

RESULTS

In total, 41% of patients were women (mean age 60 ± 14.7 years, mean BMI 31.2 ± 4.6 kg/m2). Hepatic steatosis, as defined by CAP > 248 dB/m, was present in 66% of patients. Five (45%) of the patients with hepatic steatosis also had fibrosis, and one presented with cirrhosis. Nine patients were carriers of the PNPLA3 p.I148M prosteatogenic [M] risk allele, eight of whom were heterozygotes. CAP values were significantly (P = .045) higher in these patients and corresponded to advanced steatosis, as compared to patients with the wild-type genotype, who demonstrated CAP values consistent with mild steatosis (311 ± 33 dB/m. vs 254 ± 62 dB/m). CAP values did not differ significantly in carriers of distinct TM6SF2 and MBOAT7 genotypes; however, carriers of the risk alleles displayed higher CAP as compared to wild-type patients.

CONCLUSIONS

This study shows that in patients with acromegaly, carriers of the PNPLA3 susceptibility allele are at risk of developing hepatic steatosis, as assessed by CAP. Comorbid NAFLD might compound prognosis in such patients; thus, further research into the pathomechanisms and treatment of NAFLD in acromegaly is warranted.

Four-Week Omega-3 Supplementation in Carriers of the Prosteatotic PNPLA3 p.I148M Genetic Variant: An Open-Label Study

BACKGROUND/AIMS

The PNPLA3 loss-of-function variant p.I148M is a strong genetic determinant of nonalcoholic fatty liver disease. The PNPLA3 protein functions as an intracellular lipase in the liver, with a greater activity on unsaturated fatty acids. This study aimed to determine whether short-term supplementation with omega-3 fatty acids impacts hepatic steatosis differently in PNPLA3 p.148I wild-type individuals as compared to homozygous carriers of the PNPLA3 p.148M variant.

METHODS

Twenty subjects with hepatic steatosis (50% women, age 18-77 years) were included. Ten subjects homozygous for the PNPLA3 148M variant were matched to 10 wild-type individuals. The subjects received 4 g omega-3 fatty acids (1,840 mg eicosapentaenoic acid and 1,520 mg docosahexaenoic acid) a day for 4 weeks. Transient elastography with a controlled attenuation parameter (CAP) was used to quantify liver fat before and after the intervention. Body composition, fibrosis, liver function tests, serum free fatty acids (FFA) and glucose markers were compared.

RESULTS

Patients homozygous for the PNPLA3 p.148M variant (risk group) demonstrated no significant changes in CAP compared to baseline (284 ± 55 vs. 287 ± 65 dB/m) as did the control group (256 ± 56 vs. 262 ± 55 dB/m). While serum liver enzyme activities remained unchanged in both groups, the risk group displayed significantly (p = 0.02) lower baseline FFA concentrations (334.5 [range 281.0-431.0] vs. 564.5 [range 509.0-682.0] μmol/L), which markedly increased by 9.1% after the intervention. In contrast, FFA concentrations decreased significantly (p = 0.01) by 28.3% in the wild-type group.

CONCLUSIONS

Short-term omega-3 fatty acid supplementation did not significantly alter hepatic steatosis. The nutrigenomic and metabolic effects of omega-3 fatty acids should be investigated further in carriers of the PNPLA3 148M risk variant.

Increased Circulating VAP-1 Levels Are Associated with Liver Fibrosis in Chronic Hepatitis C Infection

Vascular adhesion protein-1 (VAP-1) is a multifunction protein. While membrane-bound VAP-1 is an adhesion protein, soluble VAP-1 catalyzes the deamination of primary amines through its semicarbazide-sensitive amino oxidase (SSAO) activity. VAP-1 supports the transmigration of leukocytes and increases oxidative stress. In chronic liver diseases, it plays a role in leukocyte infiltration and fibrogenesis. Here, we measured VAP-1 plasma concentration and its SSAO activity in 322 patients with chronic hepatitis C infection and evaluated the association of VAP-1 with fibrosis stages. VAP-1 concentration strongly correlated with liver stiffness and was the second strongest influencing variable after gamma-glutamytransferase (GGT) for liver stiffness in regression analysis. The VAP-1 concentration increased with advancing fibrosis stages and the highest concentrations were found in patients with cirrhosis. According to the receiver operating characteristic (ROC) analysis, a VAP-1 cut-off value of 541 ng/mL predicted histologically confirmed cirrhosis (sensitivity 74%; specificity 72%). SSAO activity correlated only moderately with liver stiffness, showing a relatively small increase in advanced fibrosis. To our knowledge, this is the first study on VAP-1 in chronic hepatitis C infection showing its association with progressive fibrosis. In conclusion, VAP-1 plasma concentration, rather than its SSAO activity, may represent a non-invasive biomarker for monitoring fibrogenesis in patients with chronic hepatitis C infection.

Effects of Gene Variants Controlling Vitamin D Metabolism and Serum Levels on Hepatic Steatosis

BACKGROUND/AIMS

Common genetic variations in vitamin D metabolism are associated with liver stiffness. Whether these genes are implicated in hepatic steatosis remains unclear. Here we aimed to analyse the association of common vitamin D pathway gene variants with liver steatosis.

METHODS

Liver steatosis was assessed non-invasively in 241 patients with chronic liver conditions by controlled attenuation parameter (CAP). The following polymorphisms were genotyped using TaqMan assays: group-specific component (GC) rs7041, 7-dehydrocholesterol reductase (DHCR7) rs12785878, cytochrome P450 2R1 (CYP2R1) rs10741657, -vitamin D receptor (VDR) rs7974353. Chemiluminescence immunoassay determined serum 25-hydroxyvitamin D (25(OH) D) concentrations.

RESULTS

Vitamin D deficiency (defined by 25(OH)D concentrations <20 ng/mL) occurred in 66% of patients. Median CAP was 296 (100-400) dB/m. Patients with advanced steatosis (CAP ≥280 dB/m) had significantly (p = 0.033) lower 25(OH)D levels as compared to patients with CAP <280 dB/m. Moreover, the rare allele [T] in GC rs7041 was significantly (p = 0.018) associated with higher 25(OH)D levels in patients with CAP <280 dB/m. However, GC, DHCR7, CYP2R1, and VDR polymorphisms were not related to liver steatosis and obesity traits.

CONCLUSIONS

Higher CAP values are associated with low serum 25(OH)D concentrations but not with common vitamin D pathway gene variants.

PNPLA3 p.I148M and TM6SF2 p.E167K variants do not predispose to liver injury in cholestatic liver diseases: A prospective analysis of 178 patients with PSC

Background

The adiponutrin (PNPLA3) p.I148M and transmembrane 6 superfamily member 2 (TM6SF2) p.E167K variants represent major genetic risk factors for progressive liver injury in nonalcoholic fatty liver disease (NAFLD), alcoholic liver disease (ALD) and chronic viral hepatitis. The aim of this study was to find out whether these variants have a detrimental impact on the progression of chronic liver disease in patients with prolonged cholestasis induced by primary sclerosing cholangitis (PSC).

Methods

We prospectively recruited 178 PSC patients (112 male, age range 17–75 years, 55 with liver cirrhosis, 94 with ulcerative colitis, 48 transplanted during follow-up). PNPLA3 rs738409 and TM6SF2 rs58542926 polymorphisms were genotyped using dedicated TaqMan assays. Associations between genotypes, biochemical and clinical phenotypes were analyzed using contingency tables.

Results

Allele and genotype distribution of both variants were consistent with Hardy-Weinberg equilibrium. No significant differences in the genotype distribution of PNPLA3 (P = 0.90) or TM6SF2 (P = 0.72) were observed between patients with cirrhosis and patients without cirrhosis. Serum liver enzyme activities were not modified by the presence of PNPLA3 (ALT P = 0.88, AST P = 0.77) or TM6SF2 (ALT P = 0.92, AST P = 0.49) risk variants. Increasing number of risk alleles had no impact on serum liver enzyme activities, as demonstrated by a separate analysis of patients carrying 0 (n = 99), 1 (n = 64), 2 (n = 12) or 3 (n = 3) risk alleles (P>0.05). No impact of PNPLA3 or TM6SF2 risk variants was detectable in patients with PSC and ulcerative colitis, and none of the variants increased the odds of transplantation.

Conclusions

Neither PNPLA3 nor TM6SF2 polymorphisms seem to contribute significantly towards an increased risk for deterioration of liver function in patients with PSC. These results underscore the divergent mechanisms of liver damage in cholestatic conditions as compared to metabolic and viral liver diseases.

Circulating Phospholipid Patterns in NAFLD Patients Associated with a Combination of Metabolic Risk Factors

Background: Non-alcoholic fatty liver disease (NAFLD) is associated with inefficient macro- and micronutrient metabolism, and alteration of circulating phospholipid compositions defines the signature of NAFLD. This current study aimed to assess the pattern of serum phospholipids in the spectrum of NAFLD, and its related comorbidities and genetic modifications. Methods: 97 patients with diagnosed NAFLD were recruited at a single center during 2013–2016. Based on histological and transient elastography assessment, 69 patients were divided into non-alcoholic steatohepatitis (NASH) and non-alcoholic fatty liver (NAFL) subgroups. 28 patients served as healthy controls. Serum phospholipids were determined by liquid-chromatography mass spectrometry (LC-MS/MS). Results: The total content of phosphatidylcholine (PC) and sphingomyelin in the serum was significantly increased in NAFL and NASH patients, compared to healthy controls. In addition, serum lysophospatidylethanolamine levels were significantly decreased in NAFL and NASH individuals. Circulating PC species, containing linoleic and α-linolenic acids, were markedly increased in NAFLD patients with hypertension, compared to NAFLD patients without hypertension. The pattern of phospholipids did not differ between NAFLD patients with diabetes and those without diabetes. However, NAFLD patients with hyperglycemia (blood glucose level (BGL) >100 mg/dL) exhibited significantly a higher amount of monounsaturated phosphatidylethanolamine than those with low blood glucose levels. In addition, NAFLD patients with proven GG-genotype of PNPLA3, who were at higher risk for the development of progressive disease with fibrosis, showed lower levels of circulating plasmalogens, especially 16:0, compared to those with CC- and CG-allele. Conclusions: Our extended lipidomic study presents a unique metabolic profile of circulating phospholipids associated with the presence of metabolic risk factors or the genetic background of NAFLD patients.

Does transient elastography correlate with liver fibrosis in patients with PSC? Laennec score-based analysis of explanted livers

BACKGROUND AND AIMS

Previous studies demonstrated a close correlation between transient elastography (TE) and liver histology in chronic liver diseases. Data on the accuracy of TE in primary sclerosing cholangitis (PSC) remains scarce. Here, we investigated the association between TE, serum marker of liver injury and histology of explanted livers in PSC patients.

METHODS

Thirty patients were prospectively recruited. TE (Fibroscan^®) and blood sampling were performed during evaluation for liver transplantation (LT); the second blood sampling was performed on the day of LT. Fibrosis of explanted livers according to the seven-point Laennec staging system and liver collagen contents were measured.

RESULTS

TE correlated with Laennec stages of fibrosis (p = .001), collagen contents (p < .001) and with diameter of thickest septa (p = .034) in explanted livers. It also correlated with serum indices of liver injury, namely AST, bilirubin as well as FIB-4 and APRI scores (all p < .05). In a multivariate model, only liver fibrosis, according to either Laennec score (p = .035) or collagen contents (p = .005), was significantly associated with TE. Finally, patients with cirrhosis had increased liver stiffness (p = .002) and the TE cut-off of 13.7 kPa showed the best predictive value (AUC = .90, 95% CI: 0.80-1.00, p < .001) for detecting cirrhosis.

CONCLUSIONS

TE correlates with liver fibrosis and markers of liver injury in patients with PSC. However, liver fibrosis seems to be the strongest predictor of liver stiffness assessed with TE. Hence, we postulate that TE is a reliable tool for non-invasive monitoring of PSC.

PNPLA3 variant and portal/periportal histological pattern in patients with biopsy-proven non-alcoholic fatty liver disease: a possible role for oxidative stress

Pathogenesis of non-alcoholic fatty liver disease (NAFLD) is influenced by predisposing genetic variations, dysmetabolism, systemic oxidative stress, and local cellular and molecular cross-talks. Patatin-like phospholipase domain containing 3 (PNPLA3) gene I148M variant is a known determinant of NAFLD. Aims were to evaluate whether PNPLA3 I148M variant was associated with a specific histological pattern, hepatic stem/progenitor cell (HpSC) niche activation and serum oxidative stress markers. Liver biopsies were obtained from 54 NAFLD patients. The activation of HpSC compartment was evaluated by the extension of ductular reaction (DR); hepatic stellate cells, myofibroblasts (MFs), and macrophages were evaluated by immunohistochemistry. Systemic oxidative stress was assessed measuring serum levels of soluble NOX2-derived peptide (sNOX2-dp) and 8-isoprostaglandin F_2α (8-iso-PGF_2α). PNPLA3 carriers showed higher steatosis, portal inflammation and HpSC niche activation compared to wild-type patients. DR was correlated with NAFLD activity score (NAS) and fibrosis score. Serum 8-iso-PGF_2α were significantly higher in I148M carriers compared to non-carriers and were correlated with DR and portal inflammation. sNox2-dp was correlated with NAS and with HpSC niche activation. In conclusion, NAFLD patients carrying PNPLA3 I148M are characterized by a prominent activation of HpSC niche which is associated with a more aggressive histological pattern (portal fibrogenesis) and increased oxidative stress.

The Association between Pediatric NAFLD and Common Genetic Variants

Non-alcoholic fatty liver disease (NAFLD) is one of the most common complications of obesity. Several studies have shown that genetic predisposition probably plays an important role in its pathogenesis. In fact, in the last few years a large number of genetic studies have provided compelling evidence that some gene variants, especially those in genes encoding proteins regulating lipid metabolism, are associated with intra-hepatic fat accumulation. Here we provide a comprehensive review of the gene variants that have affected the natural history of the disease.

Panel of three novel serum markers predicts liver stiffness and fibrosis stages in patients with chronic liver disease

Latest data suggest that placental growth factor (PLGF), growth differentiation factor-15 (GDF-15) and hepatic growth factor (HGF) are involved in hepatic fibrogenesis. Diagnostic performance of these markers for non-invasive liver fibrosis prediction was evaluated based on liver histology and stiffness. In total 834 patients were recruited. Receiver-operating-characteristics were used to define cut-offs for markers correlating to fibrosis stages. Odds-ratios were calculated for the presence/absence of fibrosis/cirrhosis and confirmed in the sub-group of patients phenotyped by elastography only. Logistic and uni- and multivariate regression analyses were used to test for association of markers with liver fibrosis stages and for independent prediction of liver histology and stiffness. Marker concentrations correlated significantly (P<0.001) with histology and stiffness. Cut-offs for liver fibrosis (≥F2) were PLGF = 20.20 pg/ml, GDF15 = 1582.76 pg/ml and HGF = 2598.00 pg/ml. Logistic regression confirmed an increase of ORs from 3.6 over 33.0 to 108.4 with incremental (1–3) markers positive for increased liver stiffness (≥12.8kPa; all P<0.05). Subgroup analysis revealed associations with advanced fibrosis for HCV (three markers positive: OR = 59.9, CI 23.4–153.4, P<0.001) and non-HCV patients (three markers positive: OR = 144, CI 59–3383, P<0.001). Overall, serum markers identified additional 50% of patients at risk for advanced fibrosis presenting with low elastography results. In conclusion, this novel combination of markers reflects the presence of significant liver fibrosis detected by elastography and histology and may also identify patients at risk presenting with low elastography values.

The PNPLA3 Genetic Variant rs738409 Influences the Progression to Cirrhosis in HIV/Hepatitis C Virus Coinfected Patients

Contradictory data about the impact of the rs738409 steatosis-related polymorphism within PNPLA3 gene on liver fibrosis progression in HIV/hepatitis C virus (HIV/HCV)-coinfected patients have been reported. Our objective was to test whether this, and other polymorphisms previously related to fatty liver disease in HIV infection linked to SAMM50 or LPPR4 genes, influence liver fibrosis progression in HIV/HCV-coinfected individuals. Three hundred and thirty two HIV/HCV-coinfected patients who consecutively attended four Spanish university hospitals from November 2011 to July 2013 were included. A liver stiffness cut-off of 14.6 kPa, as determined by transient elastography, was used to diagnose cirrhosis. Liver stiffness progression was studied in 171 individuals who had two available LS determinations without anti-HCV treatment between them. Moreover, 28 HIV/HCV-coinfected patients who underwent liver transplant, as well as 19 non-cirrhotic coinfected individuals used as controls, were included in an additional study. Only rs738409 was associated with cirrhosis: 45 (29.6%) of 152 G allele carriers versus 36 (20.0%) of 180 CC carriers showed cirrhosis (multivariate p = 0.018; adjusted odds ratio = 1.98; 95% confidence interval = 1.12–3.50). Also, 21 (30.4%) of 69 G allele carriers versus 16 (15.7%) of 102 CC patients showed significant liver stiffness progression (adjusted p-value = 0.015; adjusted odds ratio = 2.89; 95% confidence interval = 1.23–6.83). Finally, the proportion of rs738409 G allele carriers was significantly higher in transplanted individuals than in controls (p = 0.044, odds ratio = 3.43; 95% confidence interval = 1.01–11.70). Our results strongly suggest that the rs738409 polymorphism is associated with liver fibrosis progression in HIV/HCV-coinfected patients.

The role of mitochondrial genomics in patients with non-alcoholic steatohepatitis (NASH)

Background

Visceral obesity and metabolic syndrome are commonly associated with non-alcoholic fatty liver disease (NAFLD). The progression of steatosis to NASH depends on a number of metabolic and patient-related factors. The mechanisms of genetic predisposition towards the development of NASH and related fibrosis remain unclear. In this study, our aim was to utilize mitotyping and identify mitochondrial haplotypes that may be associated with NAFLD.

Methods

We examined mitochondrial haplotypes along with patatin-like phospholipase domain containing 3 (PNPLA3) rs738409 genotype to determine their association with NAFLD phenotypes. Whole blood samples were obtained from 341 patients (BMI > 35) undergoing weight reduction surgery after written consent. Liver biopsies were centrally reviewed by a single pathologist based on predetermined pathologic protocol (41.9 % Non-NASH NAFLD, 30.4 % NASH, 27.5 % controls). A 1,122 bp of the mitochondrial control loop was sequenced for each sample and classified into haplogroups.

Results

The presence of haplogroup L exhibits protection against the development of NASH and pericellular fibrosis. The alleles of PNPLA3 locus showed differential distribution in cohorts with NAFLD, NASH and pericellular fibrosis. Heterozygosity at this locus is independently associated with higher risk of having NASH and pericellular fibrosis.

Conclusion

Mitochondrial genetics play an important role in NASH probably by modulation of oxidative stress and the efficiency of oxidative phosphorylation.

Electronic supplementary material

The online version of this article (doi:10.1186/s12881-016-0324-0) contains supplementary material, which is available to authorized users.

Genetic factors that affect nonalcoholic fatty liver disease: A systematic clinical review

AIM: To investigate roles of genetic polymorphisms in non-alcoholic fatty liver disease (NAFLD) onset, severity, and outcome through systematic literature review.

METHODS: The authors conducted both systematic and specific searches of PubMed through December 2015 with special emphasis on more recent data (from 2012 onward) while still drawing from more historical data for background. We identified several specific genetic polymorphisms that have been most researched and, at this time, appear to have the greatest clinical significance on NAFLD and similar hepatic diseases. These were further investigated to assess their specific effects on disease onset and progression and the mechanisms by which these effects occur.

RESULTS: We focus particularly on genetic polymorphisms of the following genes: PNPLA3, particularly the p. I148M variant, TM6SF2, particularly the p. E167K variant, and on variants in FTO, LIPA, IFNλ4, and iron metabolism, specifically focusing on HFE, and HMOX-1. We discuss the effect of these genetic variations and their resultant protein variants on the onset of fatty liver disease and its severity, including the effect on likelihood of progression to cirrhosis and hepatocellular carcinoma. While our principal focus is on NAFLD, we also discuss briefly effects of some of the variants on development and severity of other hepatic diseases, including hepatitis C and alcoholic liver disease. These results are briefly discussed in terms of clinical application and future potential for personalized medicine.

CONCLUSION: Polymorphisms and genetic factors of several genes contribute to NAFLD and its end results. These genes hold keys to future improvements in diagnosis and management.

PNPLA3 p.I148M variant is associated with greater reduction of liver fat content after bariatric surgery

BACKGROUND

Obesity is the major trigger of nonalcoholic fatty liver disease (NAFLD). NAFLD is further favored by the patatin-like phospholipase domain-containing 3 (PNPLA3) p.I148M, transmembrane 6 superfamily member 2 (TM6SF2) p.E167K, and membrane-bound O-acyltransferase domain containing 7 (MBOAT7) rs641738 variants.

OBJECTIVES

To investigate the relationship between the PNPLA3, TM6SF2, and MBOAT7 genotypes and the outcomes of bariatric surgery.

SETTING

University hospital.

METHODS

Prospectively we monitored 84 obese individuals (body mass index 35-64 kg/m²) scheduled for bariatric surgery. The PNPLA3 p.I148M, TM6SF2 p.E167K, and MBOAT7 rs641738 variants were genotyped using restriction fragment length polymorphism analysis and TaqMan assays. Hepatic steatosis was determined before surgery using analysis of liver biopsy samples and a novel magnetic resonance imaging-based equation. One year later, steatosis was reevaluated by magnetic resonance imaging.

RESULTS

The presence of the PNPLA3 allle [M] was associated with increased hepatic triglyceride content (P = .03), steatosis detected by magnetic resonance imaging (P = 0.04), and decreased serum glucose concentrations (P = .04). Neither variant TM6SF2 nor MBOAT7 increased hepatic steatosis (all P>.05); however, the MBOAT7 polymorphism was associated with increased triglyceride, total cholesterol, low density lipoprotein, and serum glucose levels (all P<.05). Patients carrying the prosteatotic PNPLA3 allele [M] lost more weight (P<.01) and liver fat (P = .04) one year after surgery, as compared to individuals having the common genotype. The PNPLA3 genotype and initial grade of steatosis, but not the TM6SF2 or MBOAT7 variants, were independent predictors of NAFLD improvement (P = .03 and P<.01, respectively).

CONCLUSION

In obese patients, the presence of the PNPLA3 p.I148M allele might be associated with greater improvement of hepatic steatosis after bariatric surgery in comparison to carriers of PNPLA3 wild-type alleles.

Short-Term Hypocaloric High-Fiber and High-Protein Diet Improves Hepatic Steatosis Assessed by Controlled Attenuation Parameter

OBJECTIVES

Non-alcoholic fatty liver disease is one of the most prevalent liver diseases and increases the risk of fibrosis and cirrhosis. Current standard treatment focuses on lifestyle interventions. The primary aim of this study was to assess the effects of a short-term low-calorie diet on hepatic steatosis, using the controlled attenuation parameter (CAP) as quantitative tool.

METHODS

In this prospective observational study, 60 patients with hepatic steatosis were monitored during a hypocaloric high-fiber, high-protein diet containing 1,000 kcal/day. At baseline and after 14 days, we measured hepatic fat contents using CAP during transient elastography, body composition with bioelectrical impedance analysis, and serum liver function tests and lipid profiles using standard clinical-chemical assays.

RESULTS

The median age was 56 years (25-78 years); 51.7% were women and median body mass index was 31.9 kg/m(2) (22.4-44.8 kg/m(2)). After 14 days, a significant CAP reduction (14.0%; P<0.001) was observed from 295 dB/m (216-400 dB/m) to 266 dB/m (100-353 dB/m). In parallel, body weight decreased by 4.6% (P<0.001), of which 61.9% was body fat. In addition, liver stiffness (P=0.002), γ-GT activities, and serum lipid concentrations decreased (all P<0.001).

CONCLUSIONS

This study shows for the first time that non-invasive elastography can be used to monitor rapid effects of dietary treatment for hepatic steatosis. CAP improvements occur after only 14 days on short-term low-calorie diet, together with reductions of body composition parameters, serum lipids, and liver enzymes, pointing to the dynamics of hepatic lipid turnover.

PNPLA3 Expression Is Related to Liver Steatosis in Morbidly Obese Women with Non-Alcoholic Fatty Liver Disease

Recent reports suggest a role for the Patatin-like phospholipase domain-containing protein 3 (PNPLA3) in the pathology of non-alcoholic fatty liver disease (NAFLD). Lipid deposition in the liver seems to be a critical process in the pathogenesis of NAFLD. The aim of the present work was to evaluate the association between the liver PNPLA3 expression, key genes of lipid metabolism, and the presence of NAFLD in morbidly obese women. We used real-time polymerase chain reaction (PCR) analysis to analyze the hepatic expression of PNPLA3 and lipid metabolism-related genes in 55 morbidly obese subjects with normal liver histology (NL, n = 18), simple steatosis (SS, n = 20), and non-alcoholic steatohepatitis (NASH, n = 17). Liver biopsies were collected during bariatric surgery. We observed that liver PNPLA3 expression was increased in NAFLD than in NL. It was also upregulated in SS than in NL. Interestingly, we found that the expression of PNPLA3 was significantly higher in severe than mild SS group. In addition, the expression of the transcription factors LXRα, PPARα, and SREBP2 was positively correlated with PNPLA3 liver expression. Regarding rs738409 polymorphism, GG genotype was positive correlated with the presence of NASH. In conclusion, our results show that PNPLA3 could be related to lipid accumulation in liver, mainly in the development and progression of simple steatosis.

Cirrhosis and Advanced Fibrosis in Hispanics in Texas: The Dominant Contribution of Central Obesity

Liver cirrhosis is a leading cause of death in Hispanics and Hispanics who live in South Texas have the highest incidence of liver cancer in the United States. We aimed at determining the prevalence and associated risk factors of cirrhosis in this population. Clinical and demographic variables were extracted for 2466 participants in the community-based Cameron County Hispanic Cohort in South Texas. Aspartate transaminase to Platelet Ratio Index (APRI) was used to predict cirrhosis in Cameron County Hispanic Cohort. The prevalence of cirrhosis using APRI≥2 was 0.94%, which is nearly 4-fold higher than the national prevalence. Using APRI≥1, the overall prevalence of cirrhosis/advanced fibrosis was 3.54%. In both analyses, highest prevalence was observed in males, specifically in the 25–34 age group. Risk factors independently associated with APRI≥2 and APRI≥1 included hepatitis C, diabetes and central obesity with a remarkable population attributable fraction of 52.5% and 65.3% from central obesity, respectively. Excess alcohol consumption was also independently associated with APRI≥2. The presence of patatin-like phospholipase domain-containing-3 gene variants was independently associated with APRI≥1 in participants >50 years old. Males with both central obesity and excess alcohol consumption presented with cirrhosis/advanced fibrosis at a young age. Alarmingly high prevalence of cirrhosis and advanced fibrosis was identified in Hispanics in South Texas, affecting young males in particular. Central obesity was identified as the major risk factor. Public health efforts are urgently needed to increase awareness and diagnosis of advanced liver fibrosis in Hispanics.

The common PNPLA3 variant p.I148M is associated with liver fat contents as quantified by controlled attenuation parameter (CAP)

BACKGROUND

Non-alcoholic fatty liver disease (NAFLD) is becoming the most prevalent liver disorder. The PNPLA3 (adiponutrin) variant p.I148M has been identified as common genetic modifier of NAFLD. Our aim was to assess the relationships between genetic risk and non-invasively measured liver fat content.

METHODS

Hepatic steatosis was quantified by transient elastography, using the controlled attenuation parameter (CAP) in 174 patients with chronic liver diseases (50% women, age 18-77 years). In addition, a cohort of 174 gender-matched healthy controls (50% women, age 32-77 years) was recruited. The PNPLA3 mutation as well as the novel NAFLD-predisposing genetic variant (TM6SF2 p.E167K) were genotyped with allele-specific probes.

RESULTS

The PNPLA3 genotype correlated significantly (P = 0.001) with hepatic CAP measurements. The p.148M risk allele increased the odds of developing liver steatosis (OR = 2.39, P = 0.023). In multivariate models, BMI and PNPLA3 mutation were both independently associated with CAP values (P < 0.001 and P = 0.007, respectively). Carriers of the TM6SF2 risk allele presented with increased aminotransferase activities (ALT: P = 0.007, AST: P = 0.004), but the presence of this variant did not affect CAP values.

CONCLUSIONS

The PNPLA3 p.I148M variant represents the most important prosteatotic genetic risk factor. NAFLD carriers of this variant should be followed up carefully, with elastography and CAP being ideally suited for this purpose.

Prothrombotic genetic risk factors are associated with an increased risk of liver fibrosis in the general population: The Rotterdam Study

BACKGROUND & AIMS

The coagulation system is known to be involved in fibrogenesis in patients with liver disease. We investigated whether common genetic prothrombotic risk factors are associated with an increased risk of fibrosis in the general population.

METHODS

This investigation was part of the Rotterdam Study, an ongoing, population-based cohort study. Liver stiffness (LS) was measured using transient elastography (Fibroscan) and associated with single nucleotide polymorphisms determining blood group type and presence of the Factor V Leiden (FVL) mutation or prothrombin G20210A gene variant.

RESULTS

Reliable LS measurements and genetic data were obtained from 1055 Caucasian participants. LS ⩾8.0 kPa, suggestive of clinically relevant fibrosis, was observed in 101 subjects (9.6%). Presence of FVL or prothrombin G20210A was independently associated with an increased risk of LS ⩾8.0 kPa (OR 2.09, 95%CI 1.07-4.07, p=0.03). Combination of blood group type non-O and the FVL mutation or prothrombin G20210A variant resulted in an even higher risk of LS ⩾8.0 kPa (OR 3.36, 95%CI 1.50-7.56, p=0.003). Presence of the FVL mutation or prothrombin G20210A variant in participants with blood group non-O was associated with a predicted probability of 14.3% (7.7-23.8) of LS ⩾8.0 kPa.

CONCLUSIONS

Participants carrying the FVL mutation or prothrombin G20210A variant have an increased risk of clinically relevant liver fibrosis, which is even higher in blood group type non-O carriers. The fact that genetic prothrombotic risk factors are associated with an increased risk of liver fibrosis suggests that coagulation plays an important role in fibrogenesis in the general population.

Genetic background in nonalcoholic fatty liver disease: A comprehensive review

In the Western world, nonalcoholic fatty liver disease (NAFLD) is considered as one of the most significant liver diseases of the twenty-first century. Its development is certainly driven by environmental factors, but it is also regulated by genetic background. The role of heritability has been widely demonstrated by several epidemiological, familial, and twin studies and case series, and likely reflects the wide inter-individual and inter-ethnic genetic variability in systemic metabolism and wound healing response processes. Consistent with this idea, genome-wide association studies have clearly identified Patatin-like phosholipase domain-containing 3 gene variant I148M as a major player in the development and progression of NAFLD. More recently, the transmembrane 6 superfamily member 2 E167K variant emerged as a relevant contributor in both NAFLD pathogenesis and cardiovascular outcomes. Furthermore, numerous case-control studies have been performed to elucidate the potential role of candidate genes in the pathogenesis and progression of fatty liver, although findings are sometimes contradictory. Accordingly, we performed a comprehensive literature search and review on the role of genetics in NAFLD. We emphasize the strengths and weaknesses of the available literature and outline the putative role of each genetic variant in influencing susceptibility and/or progression of the disease.

A genetic variant in the promoter of phosphate-activated glutaminase is associated with hepatic encephalopathy

BACKGROUND

Hepatic encephalopathy (HE) is a serious complication of liver cirrhosis. Recently, a microsatellite in the promoter region of the phosphate-activated glutaminase (GLS ) gene was associated with the risk of HE. The aim of the present study was to investigate, using the critical flicker frequency (CFF) test, whether the described GLS variant increases the risk of developing HE in patients with cirrhosis.

METHODS

We recruited 158 patients (66% men; mean age 59 years, range 23-86) with liver cirrhosis. Mean model for end-stage liver disease score was 13.8 (range 5-35); 48% of patients presented with Child-Pugh score B or C. The presence and severity of HE were determined by the CFF test, with frequencies ≤39 Hz denoting cases. GLS variants were genotyped by sequencing the microsatellite in the promoter region and were classified as short, long or short-long forms (depending on the length of the macrosatellite alleles).

RESULTS

In total, 53% of patients had abnormal CFF results (i.e. ≤39 Hz; range for entire cohort 26-57). The GLS microsatellite distribution amongst patients was short form (20%), long form (32%) and short-long form (48%) and was consistent with Hardy-Weinberg equilibrium. CFF values differed significantly between groups (P = 0.043). Carriers of the GLS long microsatellite had a significantly higher risk of HE according to multivariate analyses (odds ratio 3.23, 95% confidence interval 1.46-7.13, P = 0.004).

CONCLUSION

CFF results were significantly lower amongst carriers of the GLS long microsatellite. Our findings support the role of the GLS long microsatellite in the development of HE; this could be important for identifying susceptible patients and for the prevention of this condition.

The Frequent Adiponutrin (PNPLA3) Variant p.Ile148Met Is Associated with Early Liver Injury: Analysis of a German Pediatric Cohort

Introduction. The common adiponutrin (PNPLA3) variant p.Ile148Met is associated with liver injury. Here, we investigate the association of this polymorphism with hepatic and metabolic traits in a pediatric cohort. Patients and Methods. The study cohort comprised 142 German children (age 5-9 years, 98 overweight, 19 children with NAFLD). Results. Overweight children presented with increased serum ALT (P = 0.001) and GGT (P < 0.001) activities. ALT activities differed significantly (P = 0.02) between carriers of different PNPLA3 genotypes in the entire study cohort, in normal weight children (P = 0.02) and in children younger than 7 years (P = 0.02). Carriers of the prosteatotic PNPLA3 genotype p.148Met/Met displayed higher ALT activities as compared to children with the frequent genotype p.148Ile/Ile (P = 0.01). The BMI was however a stronger predictor of ALT activities compared to the PNPLA3 genotype (P < 0.001 and P = 0.06, resp.). The variant was associated with increased serum glucose levels (P = 0.01) and HOMA index (P = 0.02) in carriers of the p.148Ile/Met genotype but did not affect other metabolic traits or the presence of NAFLD. Discussion. The frequent PNPLA3 variant p.Ile148Met is associated with serum ALT activities already at a young age.

Transient elastography for diagnosis of stages of hepatic fibrosis and cirrhosis in people with alcoholic liver disease

BACKGROUND

The presence and progression of hepatic (liver) fibrosis into cirrhosis is a prognostic variable having impact on survival in people with alcoholic liver disease. Liver biopsy, although an invasive method, is the recommended 'reference standard' for diagnosis and staging of hepatic fibrosis in people with liver diseases. Transient elastography is a non-invasive method for assessing and staging hepatic fibrosis.

OBJECTIVES

To determine the diagnostic accuracy of transient elastography for diagnosis and staging hepatic fibrosis in people with alcoholic liver disease when compared with liver biopsy. To identify the optimal cut-off values for differentiating the five stages of hepatic fibrosis.

SEARCH METHODS

The Cochrane Hepato-Biliary Group Controlled and Diagnostic Test Accuracy Studies Registers, The Cochrane Library, MEDLINE (OvidSP), EMBASE (OvidSP), and the Science Citation Index Expanded (last search August 2014).

SELECTION CRITERIA

Diagnostic cohort and diagnostic case-control study designs that assessed hepatic fibrosis in participants with alcoholic liver disease with transient elastography and liver biopsy, irrespective of language or publication status. The study participants could be of any sex and ethnic origin, above 16 years old, hospitalised or managed as outpatients. We excluded participants with viral hepatitis, autoimmunity, metabolic diseases, and toxins.

DATA COLLECTION AND ANALYSIS

We followed the guidelines in the draft Cochrane Handbook for Systematic Reviews of Diagnostic Test Accuracy.

MAIN RESULTS

Five retrospective and nine prospective cohort studies with 834 participants provided data for the review analyses. Authors of seven of those studies sent us individual participant data. The risk of bias in the included studies was high in all but three studies. We could identify no serious concerns regarding the applicability of the studies in answering the main study question of our review, namely to use transient elastography to diagnose hepatic fibrosis. We could not identify the optimal cut-off values for the fibrosis stages. The definition of the diagnosis of alcoholic liver disease was not provided in one study and was not clearly defined in two studies, but it was clear in the remaining 11 studies. The study authors used different liver stiffness cut-off values of transient elastography for the hepatic fibrosis stages.There was only one study (103 participants) with data on hepatic fibrosis stage F1 or worse, with a cut-off of 5.9 kPa, and reporting sensitivity of 0.83 (95% confidence interval (CI) 0.74 to 0.90) and specificity of 0.88 (95% CI 0.47 to 1.00). The summary sensitivity and specificity of transient elastography for F2 or worse (seven studies with 338 participants and with cut-offs around 7.5 kPa (range 7.00 to 7.8 kPa)) were 0.94 and 0.89 with LR+ 8.2 and LR- 0.07, which suggests that transient elastography could be useful to rule out the presence of significant hepatic fibrosis, thus avoiding liver biopsy.Due to the wide range of cut-off values (from 8.0 to 17.0 kPa) found in the 10 studies with 760 participants with hepatic fibrosis F3 or worse, we fitted a hierarchical summary receiver operating characteristic (HSROC) model and estimated a summary ROC (SROC) curve. The sensitivity of the 10 studies varied from 72% to 100% and the specificity from 59% to 89%. We performed an additional analysis by including the studies with a cut-off value of around and equal to 9.5 kPa (range 8.0 to 11.0 kPa). The summary sensitivity and specificity of transient elastography (eight studies with 564 participants) were 0.92 and 0.70 with LR+ 3.1 and LR- 0.11, which suggests that transient elastography could also be useful to rule out the presence of severe hepatic fibrosis (F3 or worse), avoiding liver biopsy. We carried out a sensitivity analysis by considering only the studies with a cut-off value equal to 9.5 kPa and the result did not differ.We performed an HSROC analysis and reported an SROC curve for hepatic fibrosis stage F4 (cirrhosis). The HSROC analysis suggested that when the cut-off value changes, there is a wide variation in specificity and a more limited variation in sensitivity. We performed an additional analysis with the studies with the most commonly used cut-off value of 12.5 kPa. The summary sensitivity and specificity of transient elastography (seven studies with 330 participants) were 0.95 and 0.71 with LR+ 3.3 and LR- 0.07, which again suggests that transient elastography could be useful to rule out the presence of cirrhosis, avoiding liver biopsy.

AUTHORS' CONCLUSIONS

We identified a small number of studies with a few participants and were unable to include several studies, which raises the risk of outcome reporting bias. With these caveats in mind, transient elastography may be used as a diagnostic method to rule out liver cirrhosis (F4) in people with alcoholic liver disease when the pre-test probability is about 51% (range 15% to 79%). Transient elastography may also help in ruling out severe fibrosis (F3 or worse). Liver biopsy investigation remains an option if the certainty to rule in or rule out the stage of hepatic fibrosis or cirrhosis remains insufficient after a clinical follow-up or any other non-invasive test considered useful by the clinician.The proposed cut-off values for the different stages of hepatic fibrosis may be used in clinical practice, but caution is needed, as those values reported in this review are only the most common cut-off values used by the study authors. The best cut-off values for hepatic fibrosis in people with alcoholic liver disease could not be established yet.In order to diagnose correctly the stage of hepatic fibrosis in people with alcoholic liver disease using transient elastography assessment, the studies should consider a single aetiology. Hepatic fibrosis should be diagnosed with both transient elastography and liver biopsy and in this sequence, and transient elastography cut-off values should be pre-specified and validated. The time interval between the two investigations should not exceed three months, which is the interval mainly valid for people without cirrhosis, and assessment of results should be properly blinded. Only studies with low risk of bias, fulfilling the Standards for Reporting of Diagnostic Accuracy may answer the review question.

PNPLA3 I148M variant in nonalcoholic fatty liver disease: Demographic and ethnic characteristics and the role of the variant in nonalcoholic fatty liver fibrosis

Patatin-like phospholipase domain-containing 3 (PNPLA3 or adiponutrin) displays anabolic and catabolic activities in lipid metabolism, and has been reported to be significantly associated with liver fat content. Various studies have established a strong link between the 148 isoleucine to methionine protein variant (I148M) of PNPLA3 and liver diseases, including nonalcoholic fatty liver disease (NAFLD). However, detailed demographic and ethnic characteristics of the I148M variant and its role in the development of nonalcoholic fatty liver fibrosis have not been fully elucidated. The present review summarizes the current knowledge on the association between the PNPLA3 I148M variant and NAFLD, and especially its role in the development of nonalcoholic fatty liver fibrosis. First, we analyze the impact of demographic and ethnic characteristics of the PNPLA3 I148M variant and the presence of metabolic syndrome on the association between PNPLA3 I148M and NAFLD. Then, we explore the role of the PNPLA3 I148M in the development of nonalcoholic fatty liver fibrosis, and hypothesize the underlying mechanisms by speculating a pro-fibrogenic network. Finally, we briefly highlight future research that may elucidate the specific mechanisms of the PNPLA3 I148M variant in fibrogenesis, which, in turn, provides a theoretical foundation and valuable experimental data for the clinical management of nonalcoholic fatty liver fibrosis.

The rs738409 (I148M) variant of the PNPLA3 gene and cirrhosis: a meta-analysis

The human patatin-like phospholipase domain-containing-3 (PNPLA3) gene rs738409 C>G polymorphism is associated with several types of liver disease. The aim of this meta-analysis was to assess the risk of cirrhosis on the basis of rs738409 allele frequency and genotype. Medline, the Cochrane Library, EMBASE, and Google Scholar were searched for prospective and retrospective studies assessing the effect of the rs738409 polymorphism on liver cirrhosis. Seven studies, involving 2,023 patients with cirrhosis, were included. The G allele was associated with a significantly increased risk of cirrhosis versus the C allele [pooled odds ratio (OR) = 1.86, 95% confidence interval (CI) = 1.64-2.12, Z = 9.55, P < 0.001]. Both the GC and GG genotypes were associated with a significantly increased risk of cirrhosis versus the CC genotype (GC vs. CC: pooled OR = 1.73, 95% CI = 1.51-1.98, Z = 7.86, P < 0.001; GG vs. CC: pooled OR = 3.41, 95% CI = 2.77-4.18, Z = 11.65, P < 0.001). There was no evidence of publication bias. Our findings suggest that patients at risk for liver cirrhosis may benefit from PNPLA3 genotyping and thus more intensive monitoring if the rs738409 C>G polymorphism is identified.

Variant adiponutrin confers genetic protection against cholestatic itch

Lysophosphatidic acid (LPA) mediates cholestatic pruritus. Recently the enzyme PNPLA3, expressed in liver and skin, was demonstrated to metabolise LPA. Here we assess the association of the PNPLA3 variant p.Ile148Met, known to be associated with (non-)alcoholic fatty liver disease (NAFLD) in genome-wide association studies, with cholestatic itch in 187 patients with primary biliary cirrhosis (PBC) and 250 PBC-free controls as well as 201 women with intrahepatic cholestasis of pregnancy (ICP) and 198 female controls without a history of ICP. Our hypothesis was that the intensity of cholestatic itch differs in carriers of distinct PNPLA3 p.Ile148Met genotypes. Patients with PBC carrying the allele p.148Met that confers an increased NAFLD risk reported less itching than carriers of the p.148Ile allele (ANOVA P = 0.048). The PNPLA3 p.148Ile allele increased the odds of requiring plasmapheresis for refractory pruritus (OR = 3.94, 95% CI = 0.91–17.00, P = 0.048). In line with these findings, the PNPLA3 p.148Met allele was underrepresented in the ICP cohort (OR = 0.66, 95% CI = 0.47–0.92, P = 0.013). Notwithstanding the need for further replication of these findings, we conclude that the PNPLA3 allele p.148Met might confer protection against cholestatic pruritus, possibly due to increased LPA-acyltransferase activity in liver and/or skin.

Impact of PNPLA3 polymorphisms on the development of hepatocellular carcinoma in patients with chronic hepatitis C virus infection

AIM

The PNPLA3 rs738409 C>G polymorphism (encoding for I148M) has recently been identified as a susceptibility factor for steatosis-mediated liver damage. We evaluated the influence of this polymorphism on hepatocarcinogenesis in patients with chronic hepatitis C (CHC) virus infection.

METHODS

We genotyped the rs738409 single nucleotide polymorphism in 358 hepatitis C-associated hepatocellular carcinoma (HCC) patients and correlated the age at onset of HCC and the interval between hepatitis C virus (HCV) infection and the development of HCC in patients with each genotype.

RESULTS

The frequencies of CC, CG and GG genotypes were 27.9% (100/358), 49.2% (176/358) and 22.9% (82/358), respectively, and were in Hardy-Weinberg equilibrium. The median age at onset of HCC for the GG genotype was significantly younger compared to for non-GG genotypes (67.81 vs 69.87 years, P < 0.001), and the median interval between HCV infection and the development of HCC was significantly shorter in patients with the GG genotype (39.96 vs 40.85 years, P = 0.008). PNPLA3 GG genotype was also associated with a higher aspartate aminotransferase level (69.5 vs 59.0 IU/L, P = 0.02), lower prothrombin time (73.0% vs 78.0%, P = 0.008) and a higher prevalence of histological steatosis (40.0% vs. 22.2%, P = 0.01) at the time of HCC onset.

CONCLUSION

The PNPLA3 genotype GG may be associated with accelerated hepatocarcinogenesis in CHC patients through increased steatosis in the liver.

Systematic review with meta-analysis: the I148M variant of patatin-like phospholipase domain-containing 3 gene (PNPLA3) is significantly associated with alcoholic liver cirrhosis

BACKGROUND

Several studies have reported an association between alcoholic liver cirrhosis (ALC) or other forms of alcoholic liver disease (ALD) and the genetic variant rs738409 (C>G) in adiponutrin/patatin-like phospholipase domain-containing 3 gene (PNPLA3).

AIM

To evaluate the influence of this variant on ALC and other forms of ALD.

METHODS

We performed a systematic review of previous studies on the relationship between rs738409 of PNPLA3 and ALD and meta-analysis was conducted in a random-effects model. Calculations of the odds ratios (ORs) and their confidence intervals (CIs), tests for heterogeneity and sensitivity analyses were performed.

RESULTS

Database search identified 11 previous studies available for inclusion with a total of 3495 patients with ALD (2087 with ALC) and 5038 controls (4007 healthy subjects and 1031 alcoholics without ALD). Patients with ALC compared to controls had a significantly higher prevalence of the G allele when comparing GG vs. CC (OR 4.30, 95% CI 3.25-5.69; P < 0.00001) or GC vs. CC genotypes (GC vs. CC: OR 1.91, 95% CI 1.67-2.17) or under a recessive or dominant model. Similar results were found when comparing separately patients with ALC vs. alcoholics without ALD or healthy subjects. An association of the G allele with ALD emerged when comparing ALD patients vs. alcoholics without ALD and/or healthy subjects although moderate to large heterogeneity was observed. Our data suggested an additive genetic model for this variant in ALD.

CONCLUSION

Our meta-analysis shows that the rs738409 variant of PNPLA3 is clearly associated with alcoholic liver cirrhosis.

The effect of PNPLA3 on fibrosis progression and development of hepatocellular carcinoma: a meta-analysis

OBJECTIVES

The PNPLA3 rs738409 single-nucleotide polymorphism is known to promote nonalcoholic steatohepatitis (NASH), but its association with fibrosis severity and hepatocellular carcinoma (HCC) risk is less well-defined. The objectives of this study were to determine the association between PNPLA3 and liver fibrosis severity, HCC risk, and HCC prognosis among patients with liver disease.

METHODS

We performed a systematic literature review using the Medline, PubMed, Scopus, and Embase databases through May 2013 and a manual search of national meeting abstracts from 2010 to 2012. Two investigators independently extracted data on patient populations, study methods, and results using standardized forms. Pooled odds ratios (ORs), according to PNPLA3 genotype, were calculated using the DerSimonian and Laird method for a random effects model.

RESULTS

Among 24 studies, with 9,915 patients, PNPLA3 was associated with fibrosis severity (OR 1.32, 95% confidence interval (CI) 1.20-1.45), with a consistent increased risk across liver disease etiologies. Among nine studies, with 2,937 patients, PNPLA3 was associated with increased risk of HCC in patients with cirrhosis (OR 1.40, 95% CI 1.12-1.75). On subgroup analysis, increased risk of HCC was demonstrated in patients with NASH or alcohol-related cirrhosis (OR 1.67, 95% CI 1.27-2.21) but not in those with other etiologies of cirrhosis (OR 1.33, 95% CI 0.96-1.82). Three studies, with 463 patients, do not support an association between PNPLA3 and HCC prognosis but are limited by heterogeneous outcome measures. For all outcomes, most studies were conducted in homogenous Caucasian populations, and studies among racially diverse cohorts are needed.

CONCLUSIONS

PNPLA3 is associated with an increased risk of advanced fibrosis among patients with a variety of liver diseases and is an independent risk factor for HCC among patients with nonalcoholic steatohepatitis or alcohol-related cirrhosis.

Systems genetics of liver fibrosis: identification of fibrogenic and expression quantitative trait loci in the BXD murine reference population

The progression of liver fibrosis in response to chronic injury varies considerably among individual patients. The underlying genetics is highly complex due to large numbers of potential genes, environmental factors and cell types involved. Here, we provide the first toxicogenomic analysis of liver fibrosis induced by carbon tetrachloride in the murine ‘genetic reference panel’ of recombinant inbred BXD lines. Our aim was to define the core of risk genes and gene interaction networks that control fibrosis progression. Liver fibrosis phenotypes and gene expression profiles were determined in 35 BXD lines. Quantitative trait locus (QTL) analysis identified seven genomic loci influencing fibrosis phenotypes (pQTLs) with genome-wide significance on chromosomes 4, 5, 7, 12, and 17. Stepwise refinement was based on expression QTL mapping with stringent selection criteria, reducing the number of 1,351 candidate genes located in the pQTLs to a final list of 11 cis-regulated genes. Our findings demonstrate that the BXD reference population represents a powerful experimental resource for shortlisting the genes within a regulatory network that determine the liver's vulnerability to chronic injury.