High Risk of Fatty Liver Disease Amplifies the Alanine Transaminase-Lowering Effect of a HSD17B13 Variant

Role of genetic variants and DNA methylation of lipid metabolism-related genes in metabolic dysfunction-associated steatotic liver disease

Metabolic dysfunction-associated steatotic liver disease (MASLD), is one of the most common chronic liver diseases, which encompasses a spectrum of diseases, from metabolic dysfunction-associated steatotic liver (MASL) to metabolic dysfunction-associated steatohepatitis (MASH), and may ultimately progress to MASH-related cirrhosis and hepatocellular carcinoma (HCC). MASLD is a complex disease that is influenced by genetic and environmental factors. Dysregulation of hepatic lipid metabolism plays a crucial role in the development and progression of MASLD. Therefore, the focus of this review is to discuss the links between the genetic variants and DNA methylation of lipid metabolism-related genes and MASLD pathogenesis. We first summarize the interplay between MASLD and the disturbance of hepatic lipid metabolism. Next, we focus on reviewing the role of hepatic lipid related gene loci in the onset and progression of MASLD. We summarize the existing literature around the single nucleotide polymorphisms (SNPs) associated with MASLD identified by genome-wide association studies (GWAS) and candidate gene analyses. Moreover, based on recent evidence from human and animal studies, we further discussed the regulatory function and associated mechanisms of changes in DNA methylation levels in the occurrence and progression of MASLD, with a particular emphasis on its regulatory role of lipid metabolism-related genes in MASLD and MASH. Furthermore, we review the alterations of hepatic DNA and blood DNA methylation levels associated with lipid metabolism-related genes in MASLD and MASH patients. Finally, we introduce potential value of the genetic variants and DNA methylation profiles of lipid metabolism-related genes in developing novel prognostic biomarkers and therapeutic targets for MASLD, intending to provide references for the future studies of MASLD.

Genetic Risk Factors for Metabolic Dysfunction-Associated Steatotic Liver Disease

Metabolic dysfunction-associated steatotic liver disease (MASLD), is the most common cause of liver disease, and its burden on health systems worldwide continues to rise at an alarming rate. MASLD is a complex disease in which the interactions between susceptible genes and the environment influence the disease phenotype and severity. Advances in human genetics over the past few decades have provided new opportunities to improve our understanding of the multiple pathways involved in the pathogenesis of MASLD. Notably, the PNPLA3, TM6SF2, GCKR, MBOAT7 and HSD17B13 single nucleotide polymorphisms have been demonstrated to be robustly associated with MASLD development and disease progression. These genetic variants play crucial roles in lipid droplet remodeling, secretion of hepatic very low-density lipoprotein and lipogenesis, and understanding the biology has brought new insights to this field. This review discusses the current body of knowledge regarding these genetic drivers and how they can lead to development of MASLD, the complex interplay with metabolic factors such as obesity, and how this information has translated clinically into the development of risk prediction models and possible treatment targets.

NAFLD No More: A Review of Current Guidelines in the Diagnosis and Evaluation of Metabolic Dysfunction-Associated Steatotic Liver Disease (MASLD)

PURPOSE OF REVIEW

Provide a concise update on metabolic dysfunction-associated steatotic liver disease (MASLD), formerly known as non-alcoholic fatty liver disease (NAFLD), as well as a practical approach to screening and initial evaluation.

RECENT FINDINGS

Nomenclature changes have placed a greater focus on cardiometabolic risk factors in the definition of MASLD. Screening for MASLD is by stepwise noninvasive serum and imaging tests which can identify patients at risk for advanced fibrosis and liver-related complications. MASLD has been increasing in prevalence and disease burden but is underrecognized in primary care and endocrinology clinics. Multiple society guidelines, synthesized here, provide a framework for the initial approach in the diagnosis and evaluation of MASLD. Recent advances in pharmacologic treatment underline the importance of screening for patients who are at risk for advanced fibrosis as they are most likely to benefit from new drug classes, such as the liver-directed thyroid receptor agonist resmiterom.

Decoding 17-Beta-hydroxysteroid Dehydrogenase 13: A Multifaceted Perspective on Its Role in Hepatic Steatosis and Associated Disorders

Chronic liver disease (CLD) represents a significant global health burden, with hepatic steatosis-associated disorders-such as metabolic dysfunction-associated steatohepatitis (MASH), alcoholic liver disease, and hepatitis C virus infection-being major contributors. Recent genome-wide association studies have identified the rs72613567:TA variant in the 17-beta-hydroxysteroid dehydrogenase 13 (HSD17B13) gene as a protective factor against the development and progression of these conditions. In this review, we summarized the current evidence surrounding the HSD17B13 rs72613567 variant, aiming to elucidate its impact on CLD risk and outcomes, and to explore the potential mechanisms behind its hepatoprotective effects. The rs72613567:TA variant induces a splice donor site mutation, resulting in a truncated, non-functional HSD17B13 protein. Numerous studies have demonstrated that this loss-of-function mutation confers protection against the development of cirrhosis and hepatocellular carcinoma (HCC) in patients with MASH, alcoholic liver disease, and hepatitis C virus infection. Moreover, the rs72613567:TA variant has been associated with reduced liver enzyme levels and improved survival in HCC patients. Integrating this variant into genetic risk scores has shown promise in predicting the progression of fatty liver disease to cirrhosis and HCC. Furthermore, inhibiting HSD17B13 expression through RNA interference and small molecule inhibitors has emerged as a potential therapeutic strategy for MASH. However, the precise molecular mechanisms underlying the hepatoprotective effects of the HSD17B13 rs72613567 variant remain to be fully elucidated. Future research should focus on clarifying the structure-function relationship of HSD17B13 and its role in liver pathophysiology to facilitate the development of targeted therapies for CLD associated with hepatic steatosis.

Epidemiology, pathophysiology and clinical aspects of Hepatocellular Carcinoma in MAFLD patients

Hepatocellular carcinoma (HCC) is undergoing a transformative shift, with metabolic-associated fatty liver disease (MAFLD) emerging as a dominant etiology. Diagnostic criteria for MAFLD involve hepatic steatosis and metabolic dysregulation. Globally, MAFLD prevalence stands at 38.77%, significantly linked to the escalating rates of obesity. Epidemiological data indicate a dynamic shift in the major etiologies of hepatocellular carcinoma (HCC), transitioning from viral to metabolic liver diseases. Besides the degree of liver fibrosis, several modifiable lifestyle risk factors, such as type 2 diabetes, obesity, alcohol use, smoking, and HBV, HCV infection contribute to the pathogenesis of HCC. Moreover  gut microbiota and genetic variants may contribute to HCC development.The pathophysiological link between MAFLD and HCC involves metabolic dysregulation, impairing glucose and lipid metabolism, inflammation and oxidative stress. Silent presentation poses challenges in early MAFLD-HCC diagnosis. Imaging, biopsy, and AI-assisted techniques aid diagnosis, while HCC surveillance in non-cirrhotic MAFLD patients remains debated.ITA.LI.CA. group proposes a survival-based algorithm for treatment based on Barcelona clinic liver cancer (BCLC) algorithm. Liver resection, transplantation, ablation, and locoregional therapies are applied based on the disease stage. Systemic treatments is promising, with initial immunotherapy results indicating a less favorable response in MAFLD-related HCC.Adopting lifestyle interventions and chemopreventive measures with medications, including aspirin, metformin, and statins, constitute promising approaches for the primary prevention of HCC.Prognosis is influenced by multiple factors, with MAFLD-HCC associated with prolonged survival. Emerging diagnostic biomarkers and epigenomic markers, show promising results for early HCC detection in the MAFLD population.

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.

17-Beta-Hydroxysteroid Dehydrogenase 13 Loss of Function Does Not Confer Protection to Nonalcoholic Fatty Liver Disease in Indian Population

Background

A splice variant in HSD17B13 gene is demonstrated to protect against nonalcoholic fatty liver disease (NAFLD), and mitigate the effect of Patatin-like phospholipase domain-containing 3 (PNPLA3-I148M). It is being explored as a putative drug target and in polygenic risk scores. Based on whole exome sequencing (WES) in our cohort of biopsy proven NAFLD and limited data on the variant in our ethnicity, we sought to explore its role.

Methods

This is a cross-sectional study that recruited 1,020 individuals with ultrasound/biopsy-confirmed NAFLD and matched controls. Liver enzymes and lipid profiles were estimated (Beckman coulter LX750/DXH800); WES was performed in NAFLD patients and controls (Illumina; HiSeqX); HSD17B13-A-INS/I148M-PNPLA3 variants were genotyped (sequencing/qR T-PCR); HSD17B13 protein expression was estimated (immunohistochemistry); the Student's t-test/Mann-Whitney U/Chi-square test and odds ratio (95% confidence interval) were used.

Results

There was no significant difference (Odds ratio = 0.76; 95% CI -0.57 to 1.03; P = 0.76) in the frequency of the rs72613567-A-INS between controls and patients (17.8% vs. 14.4%). No difference in the ALT (Alanine transaminase; 72.24 ± 65.13 vs. 73.70 ± 60.06; P = 0.51) and AST levels (Aspartate aminotransferase; 60.72 ± 55.59 vs. 61.63 ± 60.33; P = 0.91) between HSD17B13-wild and variant carriers were noted. Significantly elevated liver enzymes were seen in PNPLA3-148-variant/HSD17B13-wild compared with PNPLA3-148-variant/HSD17B13-variant (90.44 ± 59.0 vs. 112.32 ± 61.78; P = 0.02). No difference in steatosis (P = 0.51) between HSD17B13-wild and variant carriers was noted. No other variants in the intron-exon boundaries were identified. Although, protein expression differences were noted between wild and variant carriers, no difference in the extent of steatosis was seen.

Conclusion

Our study reports lack of association of the splice variant with reduced risk of NAFLD, and mitigating the effect of PNPLA3 variant. Ethnicity-based validation must be carried out before including it in assessing protection against NAFLD.

Personalized medicine and nutrition in hepatology for preventing chronic liver disease in Mexico

Chronic liver disease is a global health issue. Patients with chronic liver disease require a fresh approach that focuses on the genetic and environmental factors that contribute to disease initiation and progression. Emerging knowledge in the fields of Genomic Medicine and Genomic Nutrition demonstrates differences between countries in terms of genetics and lifestyle risk factors such as diet, physical activity, and mental health in chronic liver disease, which serves as the foundation for the implementation of Personalized Medicine and Nutrition (PerMed-Nut) strategies. Most of the world's populations have descended from various ethnic groupings. Mexico's population has a tripartite ancestral background, consisting of Amerindian, European, and African lineages, which is common across Latin America's regional countries. The purpose of this review is to discuss the genetic and environmental components that could be incorporated into a PerMed-Nut model for metabolic-associated liver disease, viral hepatitis B and C, and hepatocellular carcinoma in Mexico. Additionally, the implementation of the PerMed-Nut approach will require updated medicine and nutrition education curricula. Training and equipping future health professionals and researchers with new clinical and investigative abilities focused on preventing liver illnesses in the field of genomic hepatology globally is a vision that clinicians and nutritionists should be concerned about.

Telomere length and risk of cirrhosis, hepatocellular carcinoma, and cholangiocarcinoma in 63,272 individuals from the general population

BACKGROUND AND AIMS

Inherited short telomeres are associated with a risk of liver disease, whereas longer telomeres predispose to cancer. The association between telomere length and risk of HCC and cholangiocarcinoma remains unknown.

APPROACH AND RESULTS

We measured leukocyte telomere length using multiplex PCR in 63,272 individuals from the Danish general population. Telomere length and plasma ALT concentration were not associated (β = 4 ×10 -6 , p -value = 0.06) in a linear regression model, without any signs of a nonlinear relationship. We tested the association between telomere length and risk of cirrhosis, HCC, and cholangiocarcinoma using Cox regression. During a median follow-up of 11 years, 241, 76, and 112 individuals developed cirrhosis, HCC, and cholangiocarcinoma, respectively. Telomere length and risk of cirrhosis were inversely and linearly associated ( p -value = 0.004, p for nonlinearity = 0.27). Individuals with telomeres in the shortest vs. longest quartile had a 2.25-fold higher risk of cirrhosis. Telomere length and risk of HCC were nonlinearly associated ( p -value = 0.009, p -value for nonlinearity = 0.01). This relationship resembled an inverted J-shape, with the highest risk observed in individuals with short telomeres. Individuals with telomeres in the shortest versus longest quartile had a 2.29-fold higher risk of HCC. Telomere length was inversely and linearly associated with the risk of cholangiocarcinoma. Individuals with telomeres in the shortest versus longest quartile had a 1.86-fold higher risk of cholangiocarcinoma.

CONCLUSIONS

Shorter telomere length is associated with a higher risk of cirrhosis, HCC, and cholangiocarcinoma.

MASLD-Related HCC-Update on Pathogenesis and Current Treatment Options

Hepatocellular carcinoma (HCC) is a common complication of chronic liver diseases and remains a relevant cause of cancer-related mortality worldwide. The global prevalence of metabolic dysfunction-associated steatotic liver disease (MASLD) as a risk factor for hepatocarcinogenesis is on the rise. Early detection of HCC has been crucial in improving the survival outcomes of patients with metabolic dysfunction-associated steatohepatitis (MASH), even in the absence of cirrhosis. Understanding how hepatocarcinogenesis develops in MASH is increasingly becoming a current research focus. Additive risk factors such as type 2 diabetes mellitus (T2DM), genetic polymorphisms, and intestinal microbiota may have specific impacts. Pathophysiological and epidemiological associations between MASH and HCC will be discussed in this review. We will additionally review the available tumor therapies concerning their efficacy in MASH-associated HCC treatment.

Novel insights into metabolic-associated steatotic liver disease preclinical models

Metabolic-associated steatotic liver disease (MASLD) encompasses a wide spectrum of metabolic conditions associated with an excess of fat accumulation in the liver, ranging from simple hepatic steatosis to cirrhosis and hepatocellular carcinoma. Finding appropriate tools to study its development and progression is essential to address essential unmet therapeutic and staging needs. This review discusses advantages and shortcomings of different dietary, chemical and genetic factors that can be used to mimic this disease and its progression in mice from a hepatic and metabolic point of view. Also, this review will highlight some additional factors and considerations that could have a strong impact on the outcomes of our model to end up providing recommendations and a checklist to facilitate the selection of the appropriate MASLD preclinical model based on clinical aims.

The rs72613567:TA polymorphism in HSD17B13 is associated with survival benefit after development of hepatocellular carcinoma

BACKGROUND

The influence of genetic factors on survival following a diagnosis of hepatocellular carcinoma (HCC) remains unclear.

AIM

To assess whether genetic polymorphisms influencing the susceptibility to develop HCC are also associated with HCC prognosis.

METHODS

We included United Kingdom Biobank (UKB) participants diagnosed with HCC after study enrolment. The primary outcome was all-cause mortality. Patients were followed from the date of HCC diagnosis to death or the registry completion date. Five HCC susceptibility loci were investigated: rs738409 (PNPLA3), rs58542926 (TM6SF2); rs72613567 (HSD17B13); rs2242652 (TERT) and rs708113 (WNT3A). The associations between these genetic variants and HCC mortality risk were assessed using Cox regression, adjusted for age, sex, ethnicity, aetiology, severity of the underlying liver disease and receipt of curative HCC treatment.

RESULTS

The final sample included 439 patients; 74% had either non-alcoholic fatty liver disease or alcohol-related liver disease. There were 321 deaths during a mean follow-up of 1.9 years per participant. Kaplan-Meier survival estimates at 1, 3 and 5 years were 53.2%, 31.2% and 22.6% respectively. In multivariate analysis, rs72613567:TA (HSD17B13) was the only genetic susceptibility variant significantly associated with all-cause mortality risk (aHR: 0.74; 95% CI: 0.61-0.90; p = 0.003). Other associated factors were Baveno stage 3-4 (aHR: 1.65; 95% CI: 1.05-2.59; p = 0.03) and HCC treatment with curative intent (aHR: 0.25; 95% CI: 0.17-0.37; p < 0.001).

CONCLUSIONS

The rs72613567:TA polymorphism in HSD17B13 is not only associated with a reduction in the risk of developing HCC but with a survival benefit in HCC once established. Therapeutic inhibition of HSD17B13 may augment survival in individuals with HCC.

Association of HSD17B13 and PNPLA3 With Liver Enzymes and Fibrosis in Hispanic/Latino Individuals of Diverse Genetic Ancestries

BACKGROUND & AIMS

Genetic variants affecting liver disease risk vary among racial and ethnic groups. Hispanics/Latinos in the United States have a high prevalence of PNPLA3 I148M, which increases liver disease risk, and a low prevalence of HSD17B13 predicted loss-of-function (pLoF) variants, which reduce risk. Less is known about the prevalence of liver disease-associated variants among Hispanic/Latino subpopulations defined by country of origin and genetic ancestry. We evaluated the prevalence of HSD17B13 pLoF variants and PNPLA3 I148M, and their associations with quantitative liver phenotypes in Hispanic/Latino participants from an electronic health record-linked biobank in New York City.

METHODS

This study included 8739 adult Hispanic/Latino participants of the BioMe biobank with genotyping and exome sequencing data. We estimated the prevalence of Hispanic/Latino individuals harboring HSD17B13 and PNPLA3 variants, stratified by genetic ancestry, and performed association analyses between variants and liver enzymes and Fibrosis-4 (FIB-4) scores.

RESULTS

Individuals with ancestry from Ecuador and Mexico had the lowest frequency of HSD17B13 pLoF variants (10%/7%) and the highest frequency of PNPLA3 I148M (54%/65%). These ancestry groups had the highest outpatient alanine aminotransferase (ALT) and aspartate aminotransferase (AST) levels, and the largest proportion of individuals with a FIB-4 score greater than 2.67. HSD17B13 pLoF variants were associated with reduced ALT level (P = .002), AST level (P < .001), and FIB-4 score (P = .045). PNPLA3 I148M was associated with increased ALT level, AST level, and FIB-4 score (P < .001 for all). HSD17B13 pLoF variants mitigated the increase in ALT conferred by PNPLA3 I148M (P = .006).

CONCLUSIONS

Variation in HSD17B13 and PNPLA3 variants across genetic ancestry groups may contribute to differential risk for liver fibrosis among Hispanic/Latino individuals.

Analysis of genetic factors associated with fatty liver disease-related hepatocellular carcinoma

AIM

Single-nucleotide polymorphisms (SNPs) in PNPLA3 and hydroxysteroid 17-beta dehydrogenase 13 (HSD17B13) genes are associated with fatty liver disease (FLD) progression and carcinogenesis. In the present study, we evaluated the characteristics of Japanese FLD patients according to HSD17B13 polymorphisms.

METHODS

We enrolled 402 patients who were clinically and pathologically diagnosed with FLD (alcoholic: 63 cases, nonalcoholic: 339 cases) at our hospital in 1990-2018 (228 males; median age: 54.9 [14.6-83.6] years). FLD patients with HSD17B13 A/A (212 cases) and others (A/AA or AA/AA; 190 cases) were compared.

RESULTS

Compared to patients with HSD17B13 A/A and others, those with the A/A genotype showed increased incidence of hepatocellular carcinoma (HCC) (A/A vs. others; 18.4% vs. 9.5%, p = 0.01), cardiovascular diseases (14.2% vs. 4.2%, p < 0.01), and hypertension (56.6% vs. 47.4%, p = 0.06). In patients without A/A, the HCC incidence was significantly reduced in those with alcohol-related FLD, fibrosis-4 index <2.67, and the PNPLA3 CC genotype; however, there was no significant difference in nonalcoholic-FLD. Patients without HSD17B13 A/A showed severe steatosis (77% vs. 88.6%, p < 0.01). New HCC developed in 11 cases and the 5-year incidence rate of HCC was 3.3% in patients with both PNPLA3 GG/GC and HSD17B13 A/A, which was significantly higher than the rate for those with other SNP profiles (0.6%, p = 0.03).

CONCLUSIONS

Inhibiting HSD17B13 activity may prevent HCC development, particularly in alcohol-related FLD and low-risk patients. Therefore, combinations of SNPs and other risk factors can be used for screening FLD-HCC.

Genetic risk of fatty liver disease and mortality in the general population: A Mendelian randomization study

BACKGROUND & AIMS

Fatty liver disease has been associated with higher all-cause as well as liver-related, ischemic heart disease (IHD)-related and extrahepatic cancer-related mortality in observational epidemiological studies. We tested the hypothesis that fatty liver disease is a causal risk factor for higher mortality.

METHODS

We genotyped seven genetic variants known to be associated with fatty liver disease (in PNPLA3, TM6SF2, HSD17B13, MTARC1, MBOAT7, GCKR, and GPAM) in 110 913 individuals from the Danish general population. Hepatic steatosis was measured by hepatic computed tomography in n = 6965. Using a Mendelian randomization framework, we tested whether genetically proxied hepatic steatosis and/or elevated plasma alanine transaminase (ALT) was associated with liver-related mortality.

RESULTS

During a median follow-up of 9.5 years, 16 119 individuals died. In observational analyses, baseline elevated plasma ALT was associated with higher all-cause (1.26-fold), liver-related (9-fold), and extrahepatic cancer-related (1.25-fold) mortality. In genetic analyses, the risk alleles in PNPLA3, TM6SF2, and HSD17B13 were individually associated with higher liver-related mortality. The largest effects were seen for the PNPLA3 and TM6SF2 risk alleles, for which homozygous carriers had 3-fold and 6-fold, respectively, higher liver-related mortality than non-carriers. None of the risk alleles, individually or combined into risk scores, were robustly associated with all-cause, IHD-related, or extrahepatic cancer-related mortality. In instrumental variable analyses, genetically proxied hepatic steatosis and higher plasma ALT were associated with liver-related mortality.

CONCLUSIONS

Human genetic data support that fatty liver disease is a causal driver of liver-related mortality.

Advances in the genetics of nonalcoholic fatty liver disease

PURPOSE OF REVIEW

Nonalcoholic fatty liver disease (NAFLD) is the most common cause of liver disease in the United States and has a strong heritable component. Advances in understanding the genetic underpinnings of NAFLD have revealed important insights into NAFLD pathogenesis, prognosis, and potential therapeutic targets. The purpose of this review is to summarize data on common and rare variants associated with NAFLD, combining risk variants into polygenic scores to predict NAFLD and cirrhosis as well as emerging evidence on using gene silencing as a novel therapeutic target in NAFLD.

RECENT FINDINGS

Protective variants in HSD17B13, MARC1 and CIDEB have been identified and a confer 10-50% lower risk of cirrhosis. Together, these as well as other NAFLD risk variants, including those in PNPLA3 and TM6SF2, can be combined to create polygenic risk scores associated with liver fat, cirrhosis, and hepatocellular carcinoma. Genomic analysis of extreme phenotypes including patients with lean NAFLD without visceral adiposity may uncover rare monogenic disorders with pathogenic and therapeutic implications and gene silencing strategies targeting HSD17B13 and PNPLA3 are being evaluated in early phase human studies as treatments for NAFLD.

SUMMARY

Advances in our understanding of the genetics of NAFLD will enable clinical risk stratification and yield potential therapeutic targets.

Abdominal obesity and alcohol use modify the impact of genetic risk for incident advanced liver disease in the general population

BACKGROUND & AIMS

Genetic variants, abdominal obesity and alcohol use are risk factors for incident liver disease (ILD). We aimed to study whether variants either alone or when aggregated into genetic risk scores (GRSs) associate with ILD, and whether waist-hip ratio (WHR) or alcohol use interacts with this risk.

METHODS

Our study included 33 770 persons (mean age 50 years, 47% men) who participated in health-examination surveys (FINRISK 1992-2012 or Health 2000) with data on alcohol use, WHR and 63 genotypes associated with liver disease. Data were linked with national health registers for liver-related outcomes (hospitalizations, malignancies and death). Exclusions were baseline clinical liver disease. Mean follow-up time was 12.2 years. Cox regression analyses between variants and ILD were adjusted for age, sex and BMI.

RESULTS

Variants in PNPLA3, IFNL4, TM6SF2, FDFT1, PPP1R3B, SERPINA1 and HSD17B13 were associated with ILD. GRSs calculated from these variants were not associated with WHR or alcohol use, but were exponentially associated with ILD (up to 25-fold higher risk in high versus low score). The risk of ILD in individuals with high GRS and high WHR or alcohol use compared with those with none of these risk factors was increased by up to 90-fold. GRSs provided new prognostic information particularly in individuals with high WHR.

CONCLUSIONS

The effect of multiple genetic variants on the risk of ILD is potentiated by abdominal obesity and alcohol use. Simple GRSs may help to identify individuals with adverse lifestyle who are at a particularly high risk of ILD.

Discovery of a Novel Potent and Selective HSD17B13 Inhibitor, BI-3231, a Well-Characterized Chemical Probe Available for Open Science

Genome-wide association studies in patients revealed HSD17B13 as a potential new target for the treatment of nonalcoholic steatohepatitis (NASH) and other liver diseases. However, the physiological function and the disease-relevant substrate of HSD17B13 remain unknown. In addition, no suitable chemical probe for HSD17B13 has been published yet. Herein, we report the identification of the novel potent and selective HSD17B13 inhibitor BI-3231. Through high-throughput screening (HTS), using estradiol as substrate, compound 1 was identified and selected for subsequent optimization resulting in compound 45 (BI-3231). In addition to the characterization of compound 45 for its functional, physicochemical, and drug metabolism and pharmacokinetic (DMPK) properties, NAD⁺ dependency was investigated. To support Open Science, the chemical HSD17B13 probe BI-3231 will be available to the scientific community for free via the opnMe platform, and thus can help to elucidate the pharmacology of HSD17B13.

Letrozole ameliorates liver fibrosis through the inhibition of the CTGF pathway and 17β-hydroxysteroid dehydrogenase 13 expression

BACKGROUND

To establish a treatment option for liver fibrosis, the possibility of the drug repurposing theory was investigated, with a focus on the off-target effects of active pharmaceutical ingredients.

METHODS

First, several active pharmaceutical ingredients were screened for their effects on the gene expression in the hepatocytes using chimeric mice with humanized hepatocytes. As per the gene expression-based screening assay for 36 medications, we assessed the mechanism of the antifibrotic effect of letrozole, a third-generation aromatase inhibitor, in mouse models of liver fibrosis induced by carbon tetrachloride (CCl4) and a methionine choline-deficient (MCD) diet. We assessed liver histology, serum biochemical markers, and fibrosis-related gene and protein expressions in the hepatocytes.

RESULTS

A gene expression-based screening assay revealed that letrozole had a modifying effect on fibrosis-related gene expression in the hepatocytes, including YAP, CTGF, TGF-β, and CYP26A1. Letrozole was administered to mouse models of CCl4- and MCD-induced liver fibrosis and it ameliorated the liver fibrosis. The mechanisms involved the inhibition of the Yap-Ctgf profibrotic pathway following a decrease in retinoic acid levels in the hepatocytes caused by suppression of the hepatic retinol dehydrogenase, Hsd17b13 and activation of the retinoic acid hydrogenase, Cyp26a1.

CONCLUSIONS

Letrozole slowed the progression of liver fibrosis by inhibiting the Yap-Ctgf pathway. The mechanisms involved the modification of the Hsd17b13 and Cyp26a1 expressions led to the suppression of retinoic acid in the hepatocytes, which contributed to the activation of Yap-Ctgf pathway. Because of its off-target effect, letrozole could be repurposed for the treatment of liver fibrosis. The third-generation aromatase inhibitor letrozole ameliorated liver fibrosis by suppressing the Yap-Ctgf pathway by partially modifying the Hsd17b13 and Cyp26a1 expressions, which reduced the retinoic acid level in the hepatocytes. The gene expression analysis using chimeric mice with humanized liver revealed that the mechanisms are letrozole specific and, therefore, may be repurposed for the treatment of liver fibrosis.

Review article: the role of HSD17B13 on global epidemiology, natural history, pathogenesis and treatment of NAFLD

BACKGROUND

Non-alcoholic fatty liver disease (NAFLD) occurs in around a quarter of the global population and is one of the leading causes of chronic liver disease. The phenotypic manifestation and the severity of NAFLD are influenced by an interplay of environmental and genetic factors. Recently, several inactivating variants in the novel 17-Beta hydroxysteroid dehydrogenase 13 (HSD17B13) gene have been found to be associated with a reduced risk of chronic liver diseases, including NAFLD.

AIMS

To review the existing literature on the epidemiology of HSD17B13 and discuss its role in the natural history, disease pathogenesis and treatment of NAFLD.

METHODS

We extensively searched relevant literature in PubMed, Google Scholar, clinicaltrials.gov and the reference list of articles included in the review.

RESULTS

HSD17B13 is a liver-specific, lipid droplet (LD)-associated protein that has enzymatic pathways involving steroids, pro-inflammatory lipid mediators and retinol. The estimated prevalence of the best characterised HSD17B13 variant (rs72613567) ranges from 5% in Africa to 34% in East Asia. Loss-of-function variants in HSD17B13 are protective against the progression of NAFLD from simple steatosis to non-alcoholic steatohepatitis (NASH), liver fibrosis, cirrhosis and hepatocellular carcinoma. Emerging data from mechanistic and preclinical studies with RNA interference (RNAi) and small molecule agents indicate that inhibiting HSD17B13 activity may prevent NAFLD progression.

CONCLUSIONS

The loss-of-function polymorphisms of the newly identified HSD17B13 gene mitigate the progression of NAFLD. It is important to understand the exact mechanism by which these variants exert a protective effect and implement the gathered knowledge in the treatment of NAFLD.

Phosphorylation of 17β-hydroxysteroid dehydrogenase 13 at serine 33 attenuates nonalcoholic fatty liver disease in mice

17β-hydroxysteroid dehydrogenase-13 is a hepatocyte-specific, lipid droplet-associated protein. A common loss-of-function variant of HSD17B13 (rs72613567: TA) protects patients against non-alcoholic fatty liver disease with underlying mechanism incompletely understood. In the present study, we identify the serine 33 of 17β-HSD13 as an evolutionally conserved PKA target site and its phosphorylation facilitates lipolysis by promoting its interaction with ATGL on lipid droplets. Targeted mutation of Ser33 to Ala (S33A) decreases ATGL-dependent lipolysis in cultured hepatocytes by reducing CGI-58-mediated ATGL activation. Importantly, a transgenic knock-in mouse strain carrying the HSD17B13 S33A mutation (HSD17B13^33A/A) spontaneously develops hepatic steatosis with reduced lipolysis and increased inflammation. Moreover, Hsd17B13^33A/A mice are more susceptible to high-fat diet-induced nonalcoholic steatohepatitis. Finally, we find reproterol, a potential 17β-HSD13 modulator and FDA-approved drug, confers a protection against nonalcoholic steatohepatitis via PKA-mediated Ser33 phosphorylation of 17β-HSD13. Therefore, targeting the Ser33 phosphorylation site could represent a potential approach to treat NASH.

AGA Clinical Practice Update: Diagnosis and Management of Nonalcoholic Fatty Liver Disease in Lean Individuals: Expert Review

DESCRIPTION

Nonalcoholic fatty liver disease (NAFLD) is well recognized as a leading etiology for chronic liver disease, affecting >25% of the US and global populations. Up to 1 in 4 individuals with NAFLD have nonalcoholic steatohepatitis, which is associated with significant morbidity and mortality due to complications of liver cirrhosis, hepatic decompensation, and hepatocellular carcinoma. Although NAFLD is observed predominantly in persons with obesity and/or type 2 diabetes mellitus, an estimated 7%-20% of individuals with NAFLD have lean body habitus. Limited guidance is available to clinicians on appropriate clinical evaluation in lean individuals with NAFLD, such as for inherited/genetic disorders, lipodystrophy, drug-induced NAFLD, and inflammatory disorders. Emerging data now provide more robust evidence to define the epidemiology, natural history, prognosis, and mortality of lean individuals with NAFLD. Multiple studies have found that NAFLD among lean individuals is associated with increased cardiovascular, liver, and all-cause mortality relative to those without NAFLD. This American Gastroenterological Association Clinical Practice Update provides Best Practice Advice to assist clinicians in evidence-based approaches to the diagnosis, staging, and management of NAFLD in lean individuals.

METHODS

This expert review was commissioned and approved by the American Gastroenterological Association (AGA) Institute Clinical Practice Updates Committee and the AGA Governing Board to provide timely guidance on a topic of high clinical importance to the AGA membership and underwent internal peer review by the Clinical Practice Updates Committee and external peer review through standard procedures of Gastroenterology. Best Practice Advice Statements BEST PRACTICE ADVICE 1: Lean NAFLD should be diagnosed in individuals with NAFLD and body mass index <25 kg/m2 (non-Asian race) or body mass index <23 kg/m2 (Asian race). BEST PRACTICE ADVICE 2: Lean individuals with NAFLD should be evaluated routinely for comorbid conditions, such as type 2 diabetes mellitus, dyslipidemia, and hypertension. BEST PRACTICE ADVICE 3: Lean individuals with NAFLD should be risk stratified for hepatic fibrosis to identify those with advanced fibrosis or cirrhosis. BEST PRACTICE ADVICE 4: Lean individuals in the general population should not undergo routine screening for NAFLD; however, screening should be considered for individuals older than 40 years with type 2 diabetes mellitus. BEST PRACTICE ADVICE 5: NAFLD should be considered in lean individuals with metabolic diseases (such as type 2 diabetes mellitus, dyslipidemia, and hypertension), elevated liver biochemical tests, or incidentally noted hepatic steatosis. BEST PRACTICE ADVICE 6: Clinicians should query patients routinely regarding alcohol consumption patterns in all patients with lean NAFLD. BEST PRACTICE ADVICE 7: In patients with lean NAFLD, other causes of liver disease should be ruled out, including other causes of fatty liver, such as HIV, lipodystrophy, lysosomal acid lipase deficiency, familial hypobetalipoproteinemia, and medication-induced hepatic steatosis (methotrexate, amiodarone, tamoxifen, and steroids). BEST PRACTICE ADVICE 8: Current evidence is inadequate to support routine testing for genetic variants in patients with lean NAFLD. BEST PRACTICE ADVICE 9: Liver biopsy, as the reference standard, should be considered if there is uncertainty regarding contributing causes of liver injury and/or the stage of liver fibrosis. BEST PRACTICE ADVICE 10: Serum indices (NAFLD fibrosis score and Fibrosis-4 score) and imaging techniques (transient elastography and magnetic resonance elastography) may be used as alternatives to liver biopsy for fibrosis staging and patient follow-up. These tests can be performed at the time of diagnosis and repeated at intervals of 6 months to 2 years, depending on fibrosis stage and the patient's response to intervention. BEST PRACTICE ADVICE 11: If noninvasive tests (eg, Fibrosis-4 and NAFLD fibrosis score) are indeterminate, a second noninvasive test (eg, transient elastography or magnetic resonance elastography) should be performed to confirm the stage and prognosis of NAFLD. BEST PRACTICE ADVICE 12: In lean patients with NAFLD, lifestyle intervention, including exercise, diet modification, and avoidance of fructose- and sugar-sweetened drinks, to target a modest weight loss of 3%-5% is suggested. BEST PRACTICE ADVICE 13: Administration of vitamin E may be considered in lean persons with biopsy-confirmed nonalcoholic steatohepatitis, but without type 2 diabetes mellitus or cirrhosis. Oral pioglitazone 30 mg daily may be considered in lean persons with biopsy-confirmed nonalcoholic steatohepatitis without cirrhosis. BEST PRACTICE ADVICE 14: The therapeutic role of glucagon-like peptide-1 agonists and sodium-glucose cotransporter-2 inhibitors in the management of lean NAFLD is not fully defined and requires further investigation. BEST PRACTICE ADVICE 15: Hepatocellular carcinoma surveillance with abdominal ultrasound with or without serum α-fetoprotein twice per year is suggested in patients with lean NAFLD and clinical markers compatible with liver cirrhosis.

Variants in mitochondrial amidoxime reducing component 1 and hydroxysteroid 17-beta dehydrogenase 13 reduce severity of nonalcoholic fatty liver disease in children and suppress fibrotic pathways through distinct mechanisms

Genome-wide association studies in adults have identified variants in hydroxysteroid 17-beta dehydrogenase 13 (HSD17B13) and mitochondrial amidoxime reducing component 1 (MTARC1) as protective against nonalcoholic fatty liver disease (NAFLD). We aimed to test their association with pediatric NAFLD liver histology and investigate their function using metabolomics. A total of 1450 children (729 with NAFLD, 399 with liver histology) were genotyped for rs72613567T>TA in HSD17B13, rs2642438G>A in MTARC1, and rs738409C>G in patatin-like phospholipase domain-containing protein 3 (PNPLA3). Genotype-histology associations were tested using ordinal regression. Untargeted hepatic proteomics and plasma lipidomics were performed in a subset of children. We found rs72613567T>TA in HSD17B13 to be associated with lower odds of NAFLD diagnosis (odds ratio, 0.7; 95% confidence interval, 0.6-0.9) and a lower grade of portal inflammation (p < 0.001). rs2642438G>A in MTARC1 was associated with a lower grade of hepatic steatosis (p = 0.02). Proteomics found reduced expression of HSD17B13 in carriers of the protective -TA allele. MTARC1 levels were unaffected by genotype. Both variants were associated with down-regulation of fibrogenic pathways. HSD17B13 perturbs plasma phosphatidylcholines and triglycerides. In silico modeling suggested p.Ala165Thr disrupts the stability and metal binding of MTARC1. Conclusion: Both HSD17B13 and MTARC1 variants are associated with less severe pediatric NAFLD. These results provide further evidence for shared genetic mechanisms between pediatric and adult NAFLD.

Down-Regulating the High Level of 17-Beta-Hydroxysteroid Dehydrogenase 13 Plays a Therapeutic Role for Non-Alcoholic Fatty Liver Disease

Non-alcoholic fatty liver disease (NAFLD) is the most common chronic liver disease worldwide, and there is no specific drug to treat it. Recent results showed that 17-beta-hydroxysteroid dehydrogenase type 13 (HSD17B13) is associated with liver diseases, but these conclusions are controversial. Here, we showed that HSD17B13 was more highly expressed in the livers of NAFLD patients, and high expression was induced in the livers of murine NAFLD models and cultural hepatocytes treated using various etiologies. The high HSD17B13 expression in the hepatocytes facilitated the progression of NAFLD by directly stabilizing the intracellular lipid drops and by indirectly activating hepatic stellate cells. When HSD17B13 was overexpressed in the liver, it aggravated liver steatosis and fibrosis in mice fed with a high-fat diet, while down-regulated the high expression of HSD17B13 by short hairpin RNAs produced a therapeutic effect in the NAFLD mice. We concluded that high HSD17B13 expression is a good target for the development of drugs to treat NAFLD.

Advances in pediatric non-alcoholic fatty liver disease: From genetics to lipidomics

As a result of the obesity epidemic, non-alcoholic fatty liver disease (NAFLD) represents a global medical concern in childhood with a closely related increased cardiometabolic risk. Knowledge on NAFLD pathophysiology has been largely expanded over the last decades. Besides the well-known key NAFLD genes (including the I148M variant of the PNPLA3 gene, the E167K allele of the TM6SF2, the GCKR gene, the MBOAT7-TMC4 rs641738 variant, and the rs72613567:TA variant in the HSD17B13 gene), an intriguing pathogenic role has also been demonstrated for the gut microbiota. More interestingly, evidence has added new factors involved in the "multiple hits" theory. In particular, omics determinants have been highlighted as potential innovative markers for NAFLD diagnosis and treatment. In fact, different branches of omics including metabolomics, lipidomics (in particular sphingolipids and ceramides), transcriptomics (including micro RNAs), epigenomics (such as DNA methylation), proteomics, and glycomics represent the most attractive pathogenic elements in NAFLD development, by providing insightful perspectives in this field. In this perspective, we aimed to provide a comprehensive overview of NAFLD pathophysiology in children, from the oldest pathogenic elements (including genetics) to the newest intriguing perspectives (such as omics branches).

Association of metabolic dysfunction-associated fatty liver disease with kidney disease

Non-alcoholic fatty liver disease (NAFLD) is characterized by the accumulation of fat in more than 5% of hepatocytes in the absence of excessive alcohol consumption and other secondary causes of hepatic steatosis. In 2020, the more inclusive term metabolic (dysfunction)-associated fatty liver disease (MAFLD) - defined by broader diagnostic criteria - was proposed to replace the term NAFLD. The new terminology and revised definition better emphasize the pathogenic role of metabolic dysfunction and uses a set of definitive, inclusive criteria for diagnosis. Diagnosis of MAFLD is based on evidence of hepatic steatosis (as assessed by liver biopsy, imaging techniques or blood biomarkers and scores) in persons who are overweight or obese and have type 2 diabetes mellitus or metabolic dysregulation, regardless of the coexistence of other liver diseases or excessive alcohol consumption. The known association between NAFLD and chronic kidney disease (CKD) and our understanding that CKD can occur as a consequence of metabolic dysfunction suggests that individuals with MAFLD - who by definition have fatty liver and metabolic comorbidities - are at increased risk of CKD. In this Perspective article, we discuss the clinical associations between MAFLD and CKD, the pathophysiological mechanisms by which MAFLD may increase the risk of CKD and the potential drug treatments that may benefit both conditions.

Hepatocellular carcinoma in patients with metabolic dysfunction-associated fatty liver disease: Can we stratify at-risk populations?

Metabolic dysfunction-associated fatty liver disease (MAFLD) is a new nomenclature recently proposed by a panel of international experts so that the entity is defined based on positive criteria and linked to pathogenesis, replacing the traditional non-alcoholic fatty liver disease (NAFLD), a definition based on exclusion criteria. NAFLD/MAFLD is currently the most common form of chronic liver disease worldwide and is a growing risk factor for development of hepatocellular carcinoma (HCC). It is estimated than 25% of the global population have NAFLD and is projected to increase in the next years. Major Scientific Societies agree that surveillance for HCC should be indicated in patients with NAFLD/ MAFLD and cirrhosis but differ in non-cirrhotic patients (including those with advanced fibrosis). Several studies have shown that the annual incidence rate of HCC in NAFLD-cirrhosis is greater than 1%, thus surveillance for HCC is cost-effective. Risk factors that increase HCC incidence in these patients are male gender, older age, presence of diabetes and any degree of alcohol consumption. In non-cirrhotic patients, the incidence of HCC is much lower and variable, being a great challenge to stratify the risk of HCC in this group. Furthermore, large epidemiological studies based on the general population have shown that diabetes and obesity significantly increase risk of HCC. Some genetic variants may also play a role modifying the HCC occurrence among patients with NAFLD. The purpose of this review is to discuss the epidemiology, clinical and genetic risk factors that may influence the risk of HCC in NAFLD/MAFLD patients and propose screening strategy to translate into better patient care.

Nonalcoholic Fatty Liver Disease (NAFLD): Pathogenesis and Noninvasive Diagnosis

The global prevalence of nonalcoholic fatty liver disease (NAFLD) or metabolic associated fatty liver disease (MAFLD), as it is now known, has gradually increased. NAFLD is a disease with a spectrum of stages ranging from simple fatty liver (steatosis) to a severe form of steatosis, nonalcoholic steatohepatitis (NASH), which could progress to irreversible liver injury (fibrosis) and organ failure, and in some cases hepatocellular carcinoma (HCC). Although a liver biopsy remains the gold standard for accurate detection of this condition, it is unsuitable for clinical screening due to a higher risk of death. There is thus an increased need to find alternative techniques or tools for accurate diagnosis. Early detection for NASH matters for patients because NASH is the marker for severe disease progression. This review summarizes the current noninvasive tools for NAFLD diagnosis and their performance. We also discussed potential and newer alternative tools for diagnosing NAFLD.

Machine learning enables new insights into genetic contributions to liver fat accumulation

Excess liver fat, called hepatic steatosis, is a leading risk factor for end-stage liver disease and cardiometabolic diseases but often remains undiagnosed in clinical practice because of the need for direct imaging assessments. We developed an abdominal MRI-based machine-learning algorithm to accurately estimate liver fat (correlation coefficients, 0.97-0.99) from a truth dataset of 4,511 middle-aged UK Biobank participants, enabling quantification in 32,192 additional individuals. 17% of participants had predicted liver fat levels indicative of steatosis, and liver fat could not have been reliably estimated based on clinical factors such as BMI. A genome-wide association study of common genetic variants and liver fat replicated three known associations and identified five newly associated variants in or near the MTARC1, ADH1B, TRIB1, GPAM, and MAST3 genes (p < 3 × 10-8). A polygenic score integrating these eight genetic variants was strongly associated with future risk of chronic liver disease (hazard ratio > 1.32 per SD score, p < 9 × 10-17). Rare inactivating variants in the APOB or MTTP genes were identified in 0.8% of individuals with steatosis and conferred more than 6-fold risk (p < 2 × 10-5), highlighting a molecular subtype of hepatic steatosis characterized by defective secretion of apolipoprotein B-containing lipoproteins. We demonstrate that our imaging-based machine-learning model accurately estimates liver fat and may be useful in epidemiological and genetic studies of hepatic steatosis.

Genetics Is of the Essence to Face NAFLD

Nonalcoholic fatty liver disease (NAFLD) is the commonest cause of chronic liver disease worldwide. It is closely related to obesity, insulin resistance (IR) and dyslipidemia so much so it is considered the hepatic manifestation of the Metabolic Syndrome. The NAFLD spectrum extends from simple steatosis to nonalcoholic steatohepatitis (NASH), a clinical condition which may progress up to fibrosis, cirrhosis and hepatocellular carcinoma (HCC). NAFLD is a complex disease whose pathogenesis is shaped by both environmental and genetic factors. In the last two decades, several heritable modifications in genes influencing hepatic lipid remodeling, and mitochondrial oxidative status have been emerged as predictors of progressive hepatic damage. Among them, the patatin-like phospholipase domain-containing 3 (PNPLA3) p.I148M, the Transmembrane 6 superfamily member 2 (TM6SF2) p.E167K and the rs641738 membrane bound-o-acyltransferase domain-containing 7 (MBOAT7) polymorphisms are considered the most robust modifiers of NAFLD. However, a forefront frontier in the study of NAFLD heritability is to postulate score-based strategy, building polygenic risk scores (PRS), which aggregate the most relevant genetic determinants of NAFLD and biochemical parameters, with the purpose to foresee patients with greater risk of severe NAFLD, guaranteeing the most highly predictive value, the best diagnostic accuracy and the more precise individualized therapy.

NAFLD and renal function in children: is there a genetic link?

Introduction: Over the past decades, a large amount of both adult and pediatric data has shown relationship between Nonalcoholic Fatty Liver Disease (NAFLD) and chronic kidney disease (CKD), resulting in an overall increased cardiometabolic burden. In view of the remarkable role of the genetic background in the NAFLD pathophysiology, a potential influence of the major NAFLD polymorphisms (e.g. the I148M variant of the Patatin-like phospholipase containing domain 3 (PNPLA3) gene, the E167K allele of the Transmembrane 6 superfamily member 2 (TM6SF2), the hydroxysteroid 17-beta dehydrogenase 13 (HSD17B13), and the Membrane bound O-acyltransferase domain containing 7-transmembrane channel-like 4 (MBOAT7-TMC4) genes) on renal function has been supposed. A shared metabolic and proinflammatory pathogenesis has been hypothesized, but the exact mechanism is still unknown.Areas covered: We provide a comprehensive review of the potential genetic link between NAFLD and CKD in children. Convincing both adult and pediatric evidence supports this association, but there is some dispute especially in childhood.Expert opinion: Evidence supporting a potential genetic link between NAFLD and CKD represents an intriguing aspect with a major clinical implication because of its putative role in improving strategy programs to counteract the higher cardiometabolic risk of these patients.

Lipid Droplet-Associated Factors, PNPLA3, TM6SF2, and HSD17B Proteins in Hepatopancreatobiliary Cancer

Simple Summary

Aberrant lipid synthesis and reprogrammed lipid metabolism are both associated with the development and progression of pancreatic and liver cancer. Most cells store fatty acids in the form of triacylglycerols in lipid droplets. Lipid droplets are intracellular organelles that not only store neutral lipids, but also play roles as molecular messengers and signaling factors. Some cancer cells accumulate massive amount of lipid droplets. Lipid droplets and lipid droplet-associated factors are further implicated to mediate proliferation, invasion, metastasis, as well as chemotherapy resistance in several types of cancer. This review dissected recent findings on the role of several lipid droplet-associated factors, patatin-like phospholipase domain-containing 3 (PNPLA3), Transmembrane 6 superfamily member 2 (TM6SF2), and 17β-hydroxysteroid dehydrogenase (HSD17B) 11 and 13 as well as their genetic variations in hepatopancreatobiliary diseases, especially cancer.

Abstract

Pancreatic and liver cancer are leading causes of cancer deaths, and by 2030, they are projected to become the second and the third deadliest cancer respectively. Cancer metabolism, especially lipid metabolism, plays an important role in progression and metastasis of many types of cancer, including pancreatic and liver cancer. Lipid droplets are intracellular organelles that store neutral lipids, but also act as molecular messengers, and signaling factors. It is becoming increasingly evident that alterations in the regulation of lipid droplets and their associated factors influence the risk of developing not only metabolic disease but also fibrosis and cancer. In the current review article, we summarized recent findings concerning the roles of lipid droplet-associated factors, patatin-like phospholipase domain-containing 3, Transmembrane 6 superfamily member 2, and 17β-hydroxysteroid dehydrogenase 11 and 13 as well as genetic variants in pancreatic and hepatic diseases. A better understanding of cancer type- and cell type-specific roles of lipid droplet-associated factors is important for establishing new therapeutic options in the future.

Excess Body Weight and Metabolic (Dysfunction)-Associated Fatty Liver Disease (MAFLD)

BACKGROUND

Nonalcoholic fatty liver disease (NAFLD) describes a continuum of liver abnormalities from simple nonalcoholic fatty liver (NAFL) to nonalcoholic fatty liver hepatitis or steatohepatitis (NASH) to NASH fibrosis. It has a variable course, but just like alcoholic fatty liver disease, it can lead to liver cirrhosis and cancer (hepatocellular carcinoma).

SUMMARY

NAFLD is a clinical entity characterized by the presence of liver steatosis, which affects at least 5% of hepatocytes. Affected are people who consume little or no alcohol and who have no secondary cause of liver steatosis such as viral hepatitis, drug intake (e.g., tamoxifen, amiodarone, methotrexate, etc.), or lipodystrophy. NAFLD is, nowadays, the most common liver disease in Europe, with an estimated prevalence of 25%. The currently widely recognized recommendation for the therapy of NAFLD is a lifestyle modification with the goal of weight loss. Although no drugs are currently approved for the treatment of NAFLD, several candidates are in clinical trials. Besides weight loss and physical activity, corresponding single active ingredients or combination therapies are intended to stop the progression of the disease and, in the best case, reverse it. The newly propagated name MAFLD (metabolic-associated fatty liver disease) should indicate that the disease is associated with metabolic disorders. The term MAFLD also implies multiple overlapping causes and drivers of this soaring disease.

KEY MESSAGES

The prevalence of NAFLD continues to rise worldwide. NAFLD, NASH, and fibrosis in NAFLD occur predominantly in patients with obesity and type 2 diabetes (T2DM) or else precede these conditions. The progression of NAFLD is highly dependent on changes in glucose, lipid metabolism, and fibrogenesis. A new definition and nomenclature of fatty liver disease, "metabolic associated fatty liver disease" (MAFLD), should be discussed carefully, since around 40% of the global population with NAFLD are classified as non-obese and almost 1/5 as lean. Since the pathogenesis of fatty liver disease, obesity, and glucose and lipid metabolism diseases are very closely related, it is important to continue to look for mechanisms that these diseases have in common and develop new therapeutic approaches.

Mortality in Patients With Genetic and Environmental Risk of Liver Disease

INTRODUCTION

The increasing liver-related mortality calls for hepatic surveillance programs. To design them, factors selectively increasing liver-related vs overall mortality need to be identified.

METHODS

We analyzed mortality data from 467,558 individuals recruited by the community-based UK Biobank. The mean follow-up was 11.4 years.

RESULTS

While all assessed genetic factors associated with increased liver-specific mortality, only homozygous TM6SF2 mutation and SERPINA1 mutation conferred elevated overall mortality. Among the environmental factors, obesity and metabolic syndrome disproportionately contributed to liver-related deaths.

DISCUSSION

Our data demonstrate an interplay between genetics and environment and provide a basis for hepatic surveillance programs.

A genome-first approach to mortality and metabolic phenotypes in MTARC1 p.Ala165Thr (rs2642438) heterozygotes and homozygotes

BACKGROUND

A coding variant in MTARC1 (rs2642438; p.Ala165Thr) was recently associated with protection from cirrhosis in European individuals. However, its impact on overall and cause-specific mortality remained elusive.

METHODS

Using a genome-first approach, we explored a range of metabolic phenotypes and outcomes associated with MTARC1 p.Ala165Thr in the UKBiobank and the Penn-Medicine BioBank.

FINDINGS

MTARC1 p.Ala165Thr was significantly associated with higher triglycerides, lower total cholesterol, lower LDL-C, lower ApoB, lower HDL-C, lower ApoA-I and higher IGF-1. Per each minor allele, the risk of NAFLD was reduced by ~15%. The ALT-lowering and NAFLD-protective effect of MTARC1 p.Ala165Thr was amplified by obesity, diabetes mellitus and presence of PNPLA3 rs738409:G. In African-American and Black-British individuals, the allele frequency of MTARC1 p.Ala165Thr was lower, but carriers showed the same distinctive lipid phenotype. Importantly, MTARC1 p.Ala165Thr carriers did not show higher cardiovascular disease burden as evidenced by cardiac MRI and carotid ultrasound. In prospective analyses, the homozygous minor allele was associated with up to 39% lower rates of liver-related mortality, while no risk of increased overall or cardiovascular death could be observed. Strikingly, liver-related mortality was more than 50% reduced in diabetic participants or carriers of PNPLA3 rs738409:G.

CONCLUSIONS

Together these data highlight MTARC1 as an important liver disease modifier that influences plasma lipids in an allele-dose-dependent manner without increasing cardiovascular outcomes. Our results point toward potential mechanisms and reveal a remarkable association with liver-related mortality calling for future studies exploring its therapeutic potential.

FUNDING

This study was funded by the German Research Foundation (DFG).

The impact of genetic risk on liver fibrosis in non-alcoholic fatty liver disease as assessed by magnetic resonance elastography

BACKGROUND

Variants in multiple genetic loci modify the risk of non-alcoholic fatty liver disease (NAFLD) and cirrhosis but there are limited data on the quantitative impact of variant copies on liver fibrosis.

AIM

To investigate the effect of PNPLA3, TM6SF2, MBOAT7, GCKR and HSD17B13 genotype on liver fibrosis assessed by magnetic resonance elastography (MRE), a reproducible, accurate, continuous biomarker of liver fibrosis.

METHODS

This is a cross-sectional analysis derived from a well-characterised cohort at risk for NAFLD who underwent genotyping and MRE assessment. Liver stiffness (LS) was estimated using MRE and advanced fibrosis was defined as liver stiffness ≥3.63 kilopascals (kPa). Univariable and multivariable linear and logistic regression analysis, were used to assess the association between genotype and MRE.

RESULTS

Two hundred sixty-four patients (63% women) with a mean age 53 (±17) years, and 31% Hispanic ethnicity with genotyping and MRE were included. The odds of advanced fibrosis were 3.1 (95% CI: 1.1-8.9, P = 0.04) for CG and 6.5 (95% CI: 2.2-18.9, P < 0.01) for GG compared to CC PNPLA3 genotype. Each PNPLA3 risk variant copy was associated with 0.40 kPa (95% CI: 0.19-0.61, P < 0.01) increase in LS on MRE in analysis adjusted for age, sex and BMI and there was significant genotype-age interaction (P < 0.01). Conversely, the protective TA allele in HSD17B13 was associated with a -0.41 kPa (95% CI: -0.76 to -0.05, P = 0.03) decrease in liver stiffness on MRE multivariable analysis.

CONCLUSION

Knowledge of PNPLA3 and HSD17B13 genotype may assist in the non-invasive risk stratification of NAFLD with closer monitoring recommended for those with high genetic risk.

Nonalcoholic fatty liver disease or metabolic dysfunction-associated fatty liver disease diagnoses and cardiovascular diseases: From epidemiology to drug approaches

BACKGROUND

A consensus of experts has proposed to replace the term nonalcoholic fatty liver disease (NAFLD), whose global prevalence is 25%, with metabolic dysfunction-associated fatty liver disease (MAFLD), to describe more appropriately the liver disease related to metabolic derangements. MAFLD is closely intertwined with type 2 diabetes, obesity, dyslipidaemia, all linked to a rise in the risk of cardiovascular disease (CVDs). Since controversy still stands on whether or not NAFLD/MAFLD raises the odds of CVD, the present review aims to evaluate the impact of NAFLD/MAFLD aetiologies on CV health and the potential correction by dietary and drug approaches.

RESULTS

Epidemiological studies indicate that NAFLD raises risk of fatal or non-fatal CVD events. NAFLD patients have a higher prevalence of arterial plaques and stiffness, coronary calcification, and endothelial dysfunction. Although genetic and environmental factors strongly contribute to NAFLD pathogenesis, a Mendelian randomization analysis indicated that the PNPLA3 genetic variant leading to NAFLD may not be causally associated with CVD risk. Among other genetic variants related to NAFLD, TM6SF2 appears to be protective, whereas MBOAT7 may favour venous thromboembolism.

CONCLUSIONS

NAFLD is correlated to a higher CVD risk which may be ameliorated by dietary interventions. This is not surprising, since new criteria defining MAFLD include other metabolic risk abnormalities fuelling development of serious adverse extrahepatic outcomes, for example CVD. The present lack of a targeted pharmacological approach makes the identification of patients with liver disease at higher CVD risk (eg diabetes, hypertension, obesity or high levels of C-reactive protein) of major clinical interest.

Is HSD17B13 Genetic Variant a Protector for Liver Dysfunction? Future Perspective as a Potential Therapeutic Target

As diet and lifestyle have changed, fatty liver disease (FLD) has become more and more prevalent. Many genetic risk factors, such as variants of PNPLA3, TM6SF2, GCKR, and MBOAT7, have previously been uncovered via genome wide association studies (GWAS) to be associated with FLD. In 2018, a genetic variant (rs72613567, T > TA) of hydroxysteroid 17-β dehydrogenase family 13 (HSD17B13) was first associated with a lower risk of developing alcoholic liver disease and non-alcoholic fatty liver disease (NAFLD) in minor allele carriers. Other HSD17B13 variants were also later linked with either lower inflammation scores among NAFLD patients or protection against NAFLD (rs6834314, A > G and rs9992651, G > A) respectively. HSD17B13 is a lipid droplet-associated protein, but its function is still ambiguous. Compared to the other genetic variants that increase risk for FLD, HSD17B13 variants serve a protective role, making this gene a potential therapeutic target. However, the mechanism by which these variants reduce the risk of developing FLD is still unclear. Because studies in cell lines and mouse models have produced conflicting results, human liver tissue modeling using induced pluripotent stem cells may be the best way to move forward and solve this mystery.

The HSD17B13 rs72613567 variant is associated with lower levels of albuminuria in patients with biopsy-proven nonalcoholic fatty liver disease

BACKGROUND AND AIMS

Several susceptibility gene variants predisposing to nonalcoholic fatty liver disease (NAFLD) have been identified in chronic kidney disease (CKD). Evidence supports that 17-beta hydroxysteroid dehydrogenase 13 (HSD17B13) rs72613567 plays a role in NAFLD development by affecting lipid homeostasis. Since lipid droplets may accumulate in the kidneys and contribute to renal injury, we investigated the association between the HSD17B13 rs72613567 variant and markers of renal function/injury in NAFLD.

METHODS AND RESULTS

We measured estimated glomerular filtration rate (eGFR), urinary/serum neutrophil gelatinase-associated lipocalin (NGAL), and urinary albumin-to-creatinine ratio (u-ACR) in individuals with biopsy-proven NAFLD. Multivariable regression analyses were undertaken to examine the associations between the HSD17B13 rs72613567 variant and markers of renal function/injury. Individuals were stratified by HSD17B13 rs72613567 genotypes into -/-, A/- and A/A groups. HSD17B13 rs72613567 genotypes were not significantly associated with eGFR and urinary/serum NGAL levels. Conversely, the prevalence of abnormal albuminuria in the A/- + A/A group was lower than in the -/- group (4.92% vs. 19.35%, p = 0.001). Additionally, the mean u-ACR levels were lower among carriers of the A/- or A/A genotypes with coexisting hypertension or diabetes, than among those with the -/- genotype. The risk of abnormal albuminuria (adjusted-odds ratio 0.16, p = 0.001) remained significantly lower in the A/- + A/A group after adjustment for established renal risk factors and histologic severity of NAFLD.

CONCLUSION

HSD17B13 rs72613567: A allele is associated with a lower risk of having abnormal albuminuria, but not with lower eGFR or urinary/serum NGAL levels, in patients with biopsy-proven NAFLD.

Non-Alcoholic Fatty Liver Disease: Metabolic, Genetic, Epigenetic and Environmental Risk Factors

Non-alcoholic fatty liver disease (NAFLD) is one of the most frequent causes of chronic liver disease in the Western world, probably due to the growing prevalence of obesity, metabolic diseases, and exposure to some environmental agents. In certain patients, simple hepatic steatosis can progress to non-alcoholic steatohepatitis (NASH), which can sometimes lead to liver cirrhosis and its complications including hepatocellular carcinoma. Understanding the mechanisms that cause the progression of NAFLD to NASH is crucial to be able to control the advancement of the disease. The main hypothesis considers that it is due to multiple factors that act together on genetically predisposed subjects to suffer from NAFLD including insulin resistance, nutritional factors, gut microbiota, and genetic and epigenetic factors. In this article, we will discuss the epidemiology of NAFLD, and we overview several topics that influence the development of the disease from simple steatosis to liver cirrhosis and its possible complications.

Loss-of-function HSD17B13 variants, non-alcoholic steatohepatitis and adverse liver outcomes: Results from a multi-ethnic Asian cohort

Background/Aims

17β-hydroxysteroid dehydrogenase 13 (HSD17B13) variants were recently reported to have significantly lower odds of non-alcoholic fatty liver disease (NAFLD). This is a two-part study that aimed to evaluate the association of HSD17B13 variants with NAFLD and its histological severity, and to identify the association of the variants with clinical outcomes in a cohort of biopsy-proven NAFLD patients.

Methods

Consecutive biopsy-proven NAFLD patients and controls without fatty liver were recruited for this study between 2009 and 2014. Genotyping for HSD17B13 variants was performed using rhAmp assays. A total of 165 patients with NAFLD were monitored up until August 2019. Clinical outcomes were recorded.

Results

HSD17B13 rs72613567 TA allele and rs6834314 G allele were associated with lower odds of non-alcoholic steatohepatitis (NASH) in the overall cohort and among ethnic Chinese, but not among ethnic Malays or Indians (P<0.05). During a mean follow-up of 89 months, 32 patients (19.4%) experienced at least one clinical outcome (cardiovascular events, n=22; liver-related complications, n=6; extra-hepatic malignancy, n=5; and mortality, n=6). The rs72613567 homozygous TA allele and the rs6834314 homozygous G allele were independently associated with a lower incidence of liver-related complications (hazard ratio [HR], 0.004; 95% confidence interval [CI], 0.00–0.64; P=0.033 and HR, 0.01; 95% CI, 0.00–0.97; P=0.048, respectively) and were associated with lower grade of hepatocyte ballooning among the ethnic Chinese.

Conclusion

HSD17B13 rs72613567 and rs6834314 variants were inversely associated with NAFLD and NASH, and were associated with lower incidence of adverse liver outcomes in a cohort of multi-ethnic Asian patients with NAFLD.

Referral Patterns for Patients with Nonalcoholic Fatty Liver Disease

The incidence of nonalcoholic fatty liver disease (NAFLD) is rapidly increasing. This study evaluates the referral pattern of patients with NAFLD. A cohort study evaluating all patients with NAFLD referred to a single Gastroenterology Department from January 2017 to June 2020. Electronic patient referral letters were reviewed, and patients with NAFLD were diagnosed using standardized tests as part of a prospective cohort study. Predictors of nonalcoholic steatohepatitis (NASH) with significant (≥F2) fibrosis were evaluated in logistic regression analyses. In total, 323 (18.6%) of 1735 patients referred to the Gastro Unit during the study period were diagnosed with NAFLD. Patients were referred from general practitioners (62.5%) or other hospital departments (37.5%). Most referral letters included information suggesting a possible diagnosis of NAFLD (patient history, blood tests, or diagnostic imaging) or used the nonspecific general diagnosis suspected disease (Z.038). Out of 110 patients referred for a liver biopsy, 71 (22%) had NASH with significant fibrosis (F2 n = 39, F3 n = 19, F4 n = 13). Thirty-nine of these patients were referred from the primary sector. A logistic regression analysis (adjusted for age and gender) including all 323 patients showed that type 2 diabetes was the only significant independent predictor of NASH with fibrosis.

Clinical and Molecular Prediction of Hepatocellular Carcinoma Risk

Prediction of hepatocellular carcinoma (HCC) risk becomes increasingly important with recently emerging HCC-predisposing conditions, namely non-alcoholic fatty liver disease and cured hepatitis C virus infection. These etiologies are accompanied with a relatively low HCC incidence rate (~1% per year or less), while affecting a large patient population. Hepatitis B virus infection remains a major HCC risk factor, but a majority of the patients are now on antiviral therapy, which substantially lowers, but does not eliminate, HCC risk. Thus, it is critically important to identify a small subset of patients who have elevated likelihood of developing HCC, to optimize the allocation of limited HCC screening resources to those who need it most and enable cost-effective early HCC diagnosis to prolong patient survival. To date, numerous clinical-variable-based HCC risk scores have been developed for specific clinical contexts defined by liver disease etiology, severity, and other factors. In parallel, various molecular features have been reported as potential HCC risk biomarkers, utilizing both tissue and body-fluid specimens. Deep-learning-based risk modeling is an emerging strategy. Although none of them has been widely incorporated in clinical care of liver disease patients yet, some have been undergoing the process of validation and clinical development. In this review, these risk scores and biomarker candidates are overviewed, and strategic issues in their validation and clinical translation are discussed.

Pediatric non-alcoholic fatty liver disease and kidney function: Effect of HSD17B13 variant

BACKGROUND

Growing evidence supports a genetic link between non-alcoholic fatty liver disease (NAFLD) and chronic kidney disease (CKD). Interesting data demonstrated that both the major NAFLD risk polymorphisms such as the I148M polymorphism in the patatin like phospholipase containing domain 3 (PNPLA3) and the E167K allele in the transmembrane 6 superfamily member 2 gene (TM6SF2) affect renal function. Recently the hydroxysteroid 17-beta dehydrogenase 13 (HSD17B13) gene has been recognized as a novel genetic variant involved in NAFLD pathophysiology. In particular, it has been showed the protective effect of the rs72613567:TA variant of this gene against liver damage both in adults and children.

AIM

To investigate the impact of the rs72613567:TA variant of the HSD17B13 gene on estimated glomerular filtration rate (eGFR) in obese children.

METHODS

We enrolled 684 obese children (mean age 10.56 ± 2.94 years; mean BMI-SDS 2.98 ± 0.78) consecutively attending our Obesity Clinic. All the patients underwent a careful clinical assessment and a comprehensive biochemical evaluation. To detect hepatic steatosis, a liver ultrasound was performed. NAFLD was defined by ultrasound detected liver steatosis and/or alanine aminotransferase (ALT) levels > 40 IU/L. The study population was divided on the basis of the NAFLD presence. Genotyping for the rs72613567:TA variant of the HSD17B13 gene in all the enrolled subjects was also made.

RESULTS

Patients carrying the HSD17B13 rare A allele showed higher eGFR levels compared with homozygous patients both among subjects with and without NAFLD. A general linear model confirmed a direct and significant association of eGFR values with HSD17B13 genotype independently of PNPLA3 and TM6SF2 polymorphisms both in patients with and without NAFLD. A comparison of regression line confirmed the influence of HSD17B13 genotype on the relationship between eGFR and age both among patients with and without NAFLD. Homozygous patients for HSD17B13 genotype with NAFLD showed a significantly higher decline of eGFR with the increase of the age compared with the patients with NAFLD carrying the HSD17B13 rare A allele (P value for intercepts = 0.005; P value for slopes = 0.94). The same effect was observed among patients without NAFLD (P value for intercepts = 0.0012; P value for slopes = 0.87).

CONCLUSION

Carriers of the HSD17B13 rare A allele showed higher eGFR levels than homozygous subjects both among subjects with and without NAFLD and independently of PNPLA3 I148M and TM6SF6 E167K polymorphisms.

Combined Effect of PNPLA3, TM6SF2, and HSD17B13 Variants on Risk of Cirrhosis and Hepatocellular Carcinoma in the General Population

BACKGROUND AND AIMS

We hypothesized that a genetic risk score (GRS) for fatty liver disease influences the risk of cirrhosis and hepatocellular carcinoma (HCC). Three genetic variants (patatin-like phospholipase domain-containing protein 3 [PNPLA3] p.I148M; transmembrane 6, superfamily member 2 [TM6SF2] p.E167K; and hydroxysteroid 17-beta dehydrogenase 13 [HSD17B13] rs72613567) were combined into a risk score, ranging from 0 to 6 for risk-increasing alleles.

APPROACH AND RESULTS

We examined the association of the risk score with plasma markers of liver disease and with cirrhosis and HCC in 110,761 individuals from Copenhagen, Denmark, and 334,691 individuals from the UK Biobank. The frequencies of risk scores of 0, 1, 2, 3, 4, and 5 or 6 were 5%, 25%, 41%, 23%, 5.5%, and 0.5%, respectively. A higher GRS was associated with an increase in plasma alanine aminotransferase (ALT) level of 26% in those with score 5 or 6 versus 0. In meta-analysis of the Copenhagen studies and the UK Biobank, individuals with scores 1, 2, 3, 4, and 5 or 6 had odds ratios (ORs) for cirrhosis of 1.6 (95% confidence interval [CI], 1.3, 1.9), 2.0 (95% CI, 1.8, 2.2), 3.1 (95% CI, 2.7, 3.5), 5.2 (95% CI, 4.2, 6.4), and 12 (95% CI, 7.7, 19), respectively, as compared with those with a score of 0. The corresponding ORs for HCC were 1.2 (95% CI, 0.9, 1.7), 1.0 (95% CI, 0.7, 1.3), 2.4 (95% CI, 1.9, 3.0), 3.3 (95% CI, 2.2, 5.0), and 29 (95% CI, 17, 51).

CONCLUSION

A GRS for fatty liver disease confers up to a 12-fold higher risk of cirrhosis and up to a 29-fold higher risk of HCC in individuals from the general population.

Genetic variant rs72613567 of HSD17B13 gene reduces alcohol-related liver disease risk in Chinese Han population

BACKGROUND & AIMS

Recently, the variant rs72613567:TA in the 17-beta-hydroxysteroid dehydrogenase 13 (HSD17B13) has been associated with reduced levels of ALT and AST and a reduced risk of alcohol-related liver disease (ALD) in the European population. Therefore, the aim of this study was to investigate the association between the polymorphisms of HSD17B13 and ALD, liver serum markers and patatin-like phospholipase domain-containing protein 3 (PNPLA3) p.I148M in the Chinese Han population.

METHODS

A case-control study was performed from five centres and included 769 ALD patients and 767 healthy controls. Two SNPs (rs72613567 and rs6834314) in HSD17B13 were genotyped using the Sequenom MassArray system and allele association analysis was performed using PLINK 1.90 software.

RESULTS

HSD17B13 rs72613567:TA allele was associated with a reduced risk of ALD by 19% (95% confidence interval [CI]: 0.05-0.31, P = .01), uniformly, the G allele in the rs6834314 reduced the risk of ALD by 19% (95% CI: 0.05-0.31, P = 8.28 × 10^-3). And the genotypes of two SNPs were associated with reducing the risk of ALD in three genetic model analysis. In addition, we found that TA allele was associated with lower levels of serum ALT, AST and GGT (P = .005, .007 and .02, respectively), higher level of serum ALB (P = .02), but not associated with ALP. In this cohort, the interaction between HSD17B13 rs72613567 and the steatogenic allele PNPLA3 rs738409 was not validated.

CONCLUSION

The present study revealed that HSD17B13 rs72613567 was significantly associated with a reduced risk of ALD in Chinese Han population.

Genetic and metabolic factors: the perfect combination to treat metabolic associated fatty liver disease

The prevalence of nonalcoholic or more recently re-defined metabolic associated fatty liver disease (MAFLD) is rapidly growing worldwide. It is characterized by hepatic fat accumulation exceeding 5% of liver weight not attributable to alcohol consumption. MAFLD refers to an umbrella of conditions ranging from simple steatosis to nonalcoholic steatohepatitis which may finally progress to cirrhosis and hepatocellular carcinoma. MAFLD is closely related to components of the metabolic syndrome and to environmental factors. In addition to the latter, genetic predisposition plays a key role in MAFLD pathogenesis and strictly contributes to its progressive forms. The candidate genes which have been related to MAFLD hereditability are mainly involved in lipids remodeling, lipid droplets assembly, lipoprotein packaging and secretion, de novo lipogenesis, and mitochondrial redox status. In the recent years, it has emerged the opportunity to translate the genetics into clinics by aggregating the genetic variants mostly associated with MAFLD in polygenic risk scores. These scores might be used in combination with metabolic factors to identify those patients at higher risk to develop more severe liver disease and to schedule an individual therapeutic approach.

Attenuated effect of PNPLA3 on hepatic fibrosis by HSD17B13 in Japanese patients with non-alcoholic fatty liver disease

BACKGROUND & AIMS

PNPLA3 rs738409 has been associated with increased risks of fibrosis in patients with non-alcoholic fatty liver disease (NAFLD). Recently, carriage of the rs6834314 G allele, which is in high linkage with rs72613567 of 17-beta-hydroxysteroid dehydrogenase 13 (HSD17B13), was reported to be associated with a reduced risk of liver injury in NAFLD patients. We estimated the impact of these genetic variants on hepatic fibrosis in Japanese patients with NAFLD.

METHODS

We analysed the associations of these genetic variants with liver histology in 290 Japanese patients with biopsy-proven NAFLD diagnosed during 2002-2019. During follow-up, 14 patients (4.8%) developed hepatocellular carcinoma.

RESULTS

Prevalences of the PNPLA3 rs738409 genotypes were 0.17 for CC, 0.41 for CG, 0.42 for GG, and those for HSD17B13 rs6834314 were 0.54 for AA, 0.39 for AG and 0.07 for GG. There was no significant interaction between the PNPLA3 and HSD17B13 genotypes. Prevalences of advanced fibrosis according to PNPLA3/HSD17B13 genotypes were 0.16 for CC,CG/AG,GG, 0.20 for CC,CG/AA, 0.30 for GG/AG,GG and 0.37 for GG/AA. Multivariate analysis identified PNPLA3 GG as a predictor of advanced fibrosis (stage 3/4) in carriers of HSD17B13 AA (odds ratio 2.4, P = .041), but not HSD17B13 AG/GG (P = .776). The HSD17B13 genotype G was significantly associated with lower prevalences of severe inflammation and ballooning and tended to be associated with a higher prevalence of advanced steatosis.

CONCLUSIONS

In Japanese patients with NAFLD, carriage of the HSD17B13 rs6834314 G allele attenuated the effect of the PNPLA3 rs738409 GG genotype on advanced hepatic fibrosis.