PNPLA3-I148M: a problem of plenty in non-alcoholic fatty liver disease

Association of copy number variation in X chromosome-linked PNPLA4 with heterotaxy and congenital heart disease

BACKGROUND

Heterotaxy (HTX) is a thoracoabdominal organ anomaly syndrome and commonly accompanied by congenital heart disease (CHD). The aim of this study was to analyze rare copy number variations (CNVs) in a HTX/CHD cohort and to examine the potential mechanisms contributing to HTX/CHD.

METHODS

Chromosome microarray analysis was used to identify rare CNVs in a cohort of 120 unrelated HTX/CHD patients, and available samples from parents were used to confirm the inheritance pattern. Potential candidate genes in CNVs region were prioritized via the DECIPHER database, and PNPLA4 was identified as the leading candidate gene. To validate, we generated PNPLA4 -overexpressing human induced pluripotent stem cell lines as well as pnpla4 -overexpressing zebrafish model, followed by a series of transcriptomic, biochemical and cellular analyses.

RESULTS

Seventeen rare CNVs were identified in 15 of the 120 HTX/CHD patients (12.5%). Xp22.31 duplication was one of the inherited CNVs identified in this HTX/CHD cohort, and PNPLA4 in the Xp22.31 was a candidate gene associated with HTX/CHD. PNPLA4 is expressed in the lateral plate mesoderm, which is known to be critical for left/right embryonic patterning as well as cardiomyocyte differentiation, and in the neural crest cell lineage. Through a series of in vivo and in vitro analyses at the molecular and cellular levels, we revealed that the biological function of PNPLA4 is importantly involved in the primary cilia formation and function via its regulation of energy metabolism and mitochondria-mediated ATP production.

CONCLUSIONS

Our findings demonstrated a significant association between CNVs and HTX/CHD. Our data strongly suggested that an increased genetic dose of PNPLA4 due to Xp22.31 duplication is a disease-causing risk factor for HTX/CHD.

Natural compounds proposed for the management of non-alcoholic fatty liver disease

Although non-alcoholic fatty liver disease (NAFLD) presents as an intricate condition characterized by a growing prevalence, the often-recommended lifestyle interventions mostly lack high-level evidence of efficacy and there are currently no effective drugs proposed for this indication. The present review delves into NAFLD pathology, its diverse underlying physiopathological mechanisms and the available in vitro, in vivo, and clinical evidence regarding the use of natural compounds for its management, through three pivotal targets (oxidative stress, cellular inflammation, and insulin resistance). The promising perspectives that natural compounds offer for NAFLD management underscore the need for additional clinical and lifestyle intervention trials. Encouraging further research will contribute to establishing more robust evidence and practical recommendations tailored to patients with varying NAFLD grades.

PNPLA-mediated lipid hydrolysis and transacylation - At the intersection of catabolism and anabolism

Patatin-like phospholipase domain containing proteins (PNPLAs) play diverse roles in lipid metabolism. In this review, we focus on the enzymatic properties and predicted 3D structures of PNPLA1-5. PNPLA2-4 exert both catabolic and anabolic functions. Whereas PNPLA1 is predominantly expressed in the epidermis and involved in sphingolipid biosynthesis, PNPLA2 and 4 are ubiquitously expressed and exhibit several enzymatic activities, including hydrolysis and transacylation of various (glycero-)lipid species. This review summarizes known biological roles for PNPLA-mediated hydrolysis and transacylation reactions and highlights open questions concerning their physiological function.

GLP-1 receptor agonists in the treatment of diabetic non-alcoholic steatohepatitis patients

INTRODUCTION

Nonalcoholic fatty liver disease (NAFLD) is the most common hepatic disease affecting almost 30% of the world population. Approximately 25% of people with NAFLD develop nonalcoholic steatohepatitis (NASH), the fulminant version of the disease. Diabetes mellitus is present in 22.5% of people with NAFLD and 44.60% of individuals with NASH. This review was undertaken to examine the current contribution of glucagon-like peptide 1 (GLP-1) receptor agonists to the pharmacotherapy of diabetic nonalcoholic steatohepatitis.

AREAS COVERED

The author analyzed the current status of GLP-1 receptor agonists for pharmacotherapy of diabetic NASH. Research data and literature reports were taken from the database and or websites of Diabetes UK, American Diabetes Association, ClinicalTrials.gov, PubMed, and Scopus. The keywords utilized included type 2 diabetes, GLP-1, NASH, NAFLD, and clinical trials.

EXPERT OPINION

Since diabetic NASH is associated with obesity, diabetes mellitus, oxidative stress and inflammation, drugs capable of mitigating all of these conditions simultaneously, are most ideal for the treatment of diabetic NASH. These drugs include (in order of relevance), GLP-1 receptor agonists, GLP-1 and GIP dual receptor agonists, sodium-glucose co-transporter-2 (SGLT2) inhibitors, and pioglitazone. The future, FDA-approved drug for diabetic NASH treatment will likely be GLP-1 agonist, which could be used as monotherapy or in combination with other drugs.

Auricularia auricula-judae Attenuates the Progression of Metabolic Syndrome in High-Fat Diet-Induced Obese Rats: Enzymatic Pre-Digestion Technology Is Superior to Superfine Grinding Method

Auricularia auricula-judae (AAJ) has been cultivated for food in China for centuries, and is also used as a folk medicine for the regulation of glucose and lipid metabolism. However, there are few studies on the effects of different processing technologies on the therapeutic efficacy of AAJ to date. This study investigated the effectiveness of the AAJ made by using superfine grinding and enzymatic pre-digestion technologies, respectively, in a high-fat diet obese rat model. It was found that oral administrations of two AAJ products significantly alleviated dyslipidemia by decreasing serum lipid levels and restoring liver functions. AAJ products made by using pre-digestion technology have appreciable potential to ameliorate lipid metabolic disorders over other products, possibly due to the higher levels of dietary fiber, crude polysaccharides, and total flavonoids released from AAJ during processing. By analysis of transcriptome sequencing and protein expression, it was clear that starch and sucrose metabolism and glycerolipid metabolism-related factors involved in fatty acid synthesis and metabolism in the liver of obese rats were significantly improved. This study gives further evidence that AAJ significantly ameliorates the progression of glucose and lipid metabolism in obese rats. Moreover, this study demonstrated for the first time that the pre-digestion method may be a better and more efficient processing approach for the improvement of AAJ bioavailability.

Gene Variants Implicated in Steatotic Liver Disease: Opportunities for Diagnostics and Therapeutics

Non-alcoholic fatty liver disease (NAFLD) describes a steatotic (or fatty) liver occurring as a consequence of a combination of metabolic, environmental, and genetic factors, in the absence of significant alcohol consumption and other liver diseases. NAFLD is a spectrum of conditions. Steatosis in the absence of inflammation is relatively benign, but the disease can progress into more severe forms like non-alcoholic steatohepatitis (NASH), liver cirrhosis, and hepatocellular carcinoma. NAFLD onset and progression are complex, as it is affected by many risk factors. The interaction between genetic predisposition and other factors partially explains the large variability of NAFLD phenotype and natural history. Numerous genes and variants have been identified through large-scale genome-wide association studies (GWAS) that are associated with NAFLD and one or more subtypes of the disease. Among them, the largest effect size and most consistent association have been patatin-like phospholipase domain-containing protein 3 (PNPLA3), transmembrane 6 superfamily member 2 (TM6SF2), and membrane-bound O-acyltransferase domain containing 7 (MBOAT7) genes. Extensive in vitro and in vivo studies have been conducted on these variants to validate these associations. The focus of this review is to highlight the genetics underpinning the molecular mechanisms driving the onset and progression of NAFLD and how they could potentially be used to improve genetic-based diagnostic testing of the disease and develop personalized, targeted therapeutics.

Towards precision medicine in non-alcoholic fatty liver disease

Non-Alcoholic Fatty Liver Disease (NAFLD) refers to the accumulation of lipid laden vacuoles in hepatocytes, occurring in the context of visceral adiposity, insulin resistance and other features of the metabolic syndrome. Its more severe form (NASH, Non-Alcoholic Steatohepatitis) is becoming the leading aetiology of end-stage liver disease and hepatocellular carcinoma, and also contributes to cardiovascular disease, diabetes and extrahepatic malignancy. Management is currently limited to lifestyle modification and optimisation of the metabolic co-morbidities, with some of the drugs used for the latter also having shown some benefit for the liver. Licensed treatment modalities are currently lacking. A particular difficulty is the notorious heterogeneity of the patient population, which is poorly understood. A spectrum of disease severity associates in a non-linear way with a spectrum of severity of underlying metabolic factors. Heterogeneity of the liver in terms of mechanisms to cope with the metabolic and inflammatory stress and in terms of repair mechanisms, and a lack of knowledge hereof, further complicate the understanding of inter-individual variability. Genetic factors act as disease modifiers and potentially allow for some risk stratification, but also only explain a minor fraction of disease heterogeneity. Response to treatment shows a large variation in treatment response, again with little understanding of what is driving the absence of response in individual patients. Management can be tailored to patient's preferences in terms of diet modification, but tailoring treatment to knowledge on disease driving mechanisms in an individual patient is still in its infancy. Recent progress in analysing liver tissue as well as non-invasive tests hold, however, promise to rapidly improve our understanding of disease heterogeneity in NAFLD and provide individualised management.

Advances in genetic variation in metabolism-related fatty liver disease

Metabolism-related fatty liver disease (MAFLD) is the most common form of chronic liver disease in the world. Its pathogenesis is influenced by both environmental and genetic factors. With the upgrading of gene screening methods and the development of human genome project, whole genome scanning has been widely used to screen genes related to MAFLD, and more and more genetic variation factors related to MAFLD susceptibility have been discovered. There are genetic variants that are highly correlated with the occurrence and development of MAFLD, and there are genetic variants that are protective of MAFLD. These genetic variants affect the development of MAFLD by influencing lipid metabolism and insulin resistance. Therefore, in-depth analysis of different mechanisms of genetic variation and targeting of specific genetic variation genes may provide a new idea for the early prediction and diagnosis of diseases and individualized precision therapy, which may be a promising strategy for the treatment of MAFLD.

Patatin-like phospholipase domain-containing 3 gene (PNPLA3) polymorphic (rs738409) single nucleotide polymorphisms and susceptibility to nonalcoholic fatty liver disease: A meta-analysis of twenty studies

BACKGROUND

To investigate the correlation between rs738409 polymorphism of patatin-like phospholipase domain-containing protein 3 (PNPLA3) gene (encoding I148m) and genetic susceptibility to nonalcoholic fatty liver disease (NAFLD).

METHODS

Web of Science, Embase, PubMed, Cochrane Library, China National Knowledge Infrastructure, Wanfang Data Knowledge Service Platform databases were subjected to study retrieving, from the earliest records to November 2022. International databases were searched using the key words (PNPLA3 gene or PNPLA3 polymorphism or patatin-like phospholipase domain-containing pro-tein3) and (nonalcoholic fatty liver disease or NAFLD or nonalcoholic steatohepatitis) and their possible combination. There was no limitation to language. Ethnicity and country restrictions were not applied. Hardy-Weinberg equilibrium about the genotype frequencies of rs738,409 polymorphism in group of controls was assessed using a chi-square goodness-of-fit test (P > .05). A chi-square-based Q test was applied to assess heterogeneity among studies. The random-effect model (DerSimonian-Laird method) was used when a probability value of P < .10, I2 > 50%. If not, the fixed-effect model (Mantel-Haenszel method) was adopted. The current meta-analysis was done by using STATA 16.0.

RESULTS

Twenty studies are selected for this meta-analysis, which includes totally 3240 patients in the treatment group and 5210 patients in the control group. These studies demonstrated a significant increased association between rs738,409 and NAFLD under 5 models: allelic contrast (odds ratio [OR] = 1.98, 95% confidence interval [CI] = 1.65-2.37, Pheterogeneity = 0.000, Z = 7.346, P = .000), homozygote comparison (OR = 3.59, 95% CI = 2.56-5.04, Pheterogeneity = 0.000, Z = 7.416, P = .000), heterozygote comparison (OR = 1.93, 95% CI = 1.63-2.30, Pheterogeneity = 0.002, Z = 7.507, P = .000), the dominant allele model (OR = 2.33, 95% CI = 1.89-2.88, Pheterogeneity = 0.000, Z = 7.856, P = .000), and the recessive allele model (OR = 2.56, 95% CI = 1.96-3.35, Pheterogeneity = 0.000, Z = 6.850, P = .000). Subgroup analysis shows that the rs738,409 polymorphism of PNPLA3 gene in Caucasians and those with a sample size of < 300 is significantly associated with the susceptibility to nonalcoholic fatty liver. Sensitivity analysis shows that the results of meta-analysis are stable.

CONCLUSION

PNPLA3 rs738,409 may play a significant role in increasing risk of NAFLD.

Multiomics study of nonalcoholic fatty liver disease

Nonalcoholic fatty liver (NAFL) and its sequelae are growing health problems. We performed a genome-wide association study of NAFL, cirrhosis and hepatocellular carcinoma, and integrated the findings with expression and proteomic data. For NAFL, we utilized 9,491 clinical cases and proton density fat fraction extracted from 36,116 liver magnetic resonance images. We identified 18 sequence variants associated with NAFL and 4 with cirrhosis, and found rare, protective, predicted loss-of-function variants in MTARC1 and GPAM, underscoring them as potential drug targets. We leveraged messenger RNA expression, splicing and predicted coding effects to identify 16 putative causal genes, of which many are implicated in lipid metabolism. We analyzed levels of 4,907 plasma proteins in 35,559 Icelanders and 1,459 proteins in 47,151 UK Biobank participants, identifying multiple proteins involved in disease pathogenesis. We show that proteomics can discriminate between NAFL and cirrhosis. The present study provides insights into the development of noninvasive evaluation of NAFL and new therapeutic options.

Genetic risk factors have a substantial impact on healthy life years

The impact of genetic variation on overall disease burden has not been comprehensively evaluated. We introduce an approach to estimate the effect of genetic risk factors on disability-adjusted life years (DALYs; 'lost healthy life years'). We use genetic information from 735,748 individuals and consider 80 diseases. Rare variants had the highest effect on DALYs at the individual level. Among common variants, rs3798220 (LPA) had the strongest individual-level effect, with 1.18 DALYs from carrying 1 versus 0 copies. Being in the top 10% versus the bottom 90% of a polygenic score for multisite chronic pain had an effect of 3.63 DALYs. Some common variants had a population-level effect comparable to modifiable risk factors such as high sodium intake and low physical activity. Attributable DALYs vary between males and females for some genetic exposures. Genetic risk factors can explain a sizable number of healthy life years lost both at the individual and population level.

The genetic interactions between non-alcoholic fatty liver disease and cardiovascular diseases

The ongoing debate on whether non-alcoholic fatty liver disease (NAFLD) is an active contributor or an innocent bystander in the development of cardiovascular disease (CVD) has sparked interests in understanding the common mediators between the two biologically distinct entities. This comprehensive review identifies and curates genetic studies of NAFLD overlapping with CVD, and describes the colinear as well as opposing correlations between genetic associations for the two diseases. Here, CVD described in relation to NAFLD are coronary artery disease, cardiomyopathy and atrial fibrillation. Unique findings of this review included certain NAFLD susceptibility genes that possessed cardioprotective properties. Moreover, the complex interactions of genetic and environmental risk factors shed light on the disparity in genetic influence on NAFLD and its incident CVD. This serves to unravel NAFLD-mediated pathways in order to reduce CVD events, and helps identify targeted treatment strategies, develop polygenic risk scores to improve risk prediction and personalise disease prevention.

Intrahepatic triglyceride content: influence of metabolic and genetics drivers

PURPOSE OF REVIEW

Intrahepatic triglyceride (IHTG) content is determined by substrate flux to, fatty acid synthesis and partitioning within, and triglyceride disposal from the liver. Dysregulation of these processes may cause IHTG accumulation, potentially leading to nonalcoholic fatty liver disease. The aetiology of IHTG accumulation has not been fully elucidated; however, environmental factors and heritability are important. Here, we review recent evidence regarding the contribution of metabolic and genetic components of IHTG accumulation.

RECENT FINDINGS

Obesity and insulin resistance are the primary metabolic drivers for IHTG accumulation. These risk factors have pronounced and seemingly overlapping effects on all processes involved in determining IHTG content. The strong and interchangeable associations between obesity, insulin resistance and IHTG make it challenging to determine their relative contributions. Genome-wide association studies have identified a growing list of single nucleotide polymorphisms associated with IHTG content and recent work has begun to elucidate their mechanistic effects. The mechanisms underlying metabolic and genetic drivers of IHTG appear to be distinct.

SUMMARY

Both metabolic and genetic factors influence IHTG content by apparently distinct mechanisms. Further work is needed to determine metabolic and genetic interaction effects, which may lead to more personalized and potentially efficacious therapeutic interventions. The development of a comprehensive polygenic risk score for IHTG content may help facilitate this.

Beneficial Metabolic Effects of Praliciguat, a Soluble Guanylate Cyclase Stimulator, in a Mouse Diet-Induced Obesity Model

Praliciguat is a soluble guanylate cyclase stimulator that elicits hemodynamic, anti-inflammatory, and antifibrotic effects in preclinical models of metabolic dysfunction. We assessed the metabolic effects of praliciguat in a mouse diet-induced obesity (DIO) model housed at thermoneutrality. At 6 weeks old, male C57BL/6N mice were either maintained on low-fat diet (LFD, lean mice) or placed on 60% high-fat diet (HFD, DIO mice). At 14 weeks old, the DIO mice were either maintained on HFD or switched to HFD with praliciguat (6-mg/kg). Day 28 samples were collected for biomarker analysis. In a second study under the same paradigm, indirect calorimetry was performed on days 8, 9, 20, 21, 32, and 33 and an oral lipid tolerance test (LTT) on day 38. Mice treated 28 days with praliciguat had lower levels of fasting plasma insulin, C-peptide, triglycerides, and HOMA-IR (homeostatic model assessment for insulin resistance) than DIO controls. In addition, energy expenditure was higher in praliciguat-treated than in DIO control mice on days 9, 20, 32, and 33; and day-38 triglycerides were lower. HFD-induced increases in gene expression of liver TNF-ɑ, lipoprotein lipase (Lpl), and patatin-like phospholipase domain-containing protein 3 (Pnpla3) in control DIO mice were attenuated in praliciguat-treated DIO mice. The positive metabolic effects observed in praliciguat-treated mice were associated with the restoration of liver PI3K (pAKT-Thr308) signaling, but not MAPK (pERK). In conclusion, praliciguat-treated DIO mice had increased energy utilization, improved insulin sensitivity, and lower plasma triglycerides. These results illustrate metabolic effects associated with praliciguat treatment in DIO mice.

Lipolysis: cellular mechanisms for lipid mobilization from fat stores

The perception that intracellular lipolysis is a straightforward process that releases fatty acids from fat stores in adipose tissue to generate energy has experienced major revisions over the last two decades. The discovery of new lipolytic enzymes and coregulators, the demonstration that lipophagy and lysosomal lipolysis contribute to the degradation of cellular lipid stores and the characterization of numerous factors and signalling pathways that regulate lipid hydrolysis on transcriptional and post-transcriptional levels have revolutionized our understanding of lipolysis. In this review, we focus on the mechanisms that facilitate intracellular fatty-acid mobilization, drawing on canonical and noncanonical enzymatic pathways. We summarize how intracellular lipolysis affects lipid-mediated signalling, metabolic regulation and energy homeostasis in multiple organs. Finally, we examine how these processes affect pathogenesis and how lipolysis may be targeted to potentially prevent or treat various diseases.

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

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

Nonalcohol fatty liver disease: balancing supply and utilization of triglycerides

PURPOSE OF REVIEW

Nonalcoholic fatty liver disease (NAFLD) is defined as the abnormal accumulation of lipids in the liver, called hepatic steatosis, which occurs most often as a concomitant of the metabolic syndrome. Its incidence has surged significantly in recent decades concomitant with the obesity pandemic and increasing consumption of refined carbohydrates and saturated fats. This makes a review of the origins of NAFLD timely and relevant.

RECENT FINDINGS

This disorder, which shares histologic markers found in alcoholic fatty liver disease, was named NAFLD to distinguish it from the latter. Recently, however, the term metabolic-associated fatty liver disease (MAFLD) has been suggested as a refinement of NAFLD that should highlight the central, etiologic role of insulin resistance, obesity, and diabetes mellitus. The complexity of the pathways involved in the regulation of hepatic triglyceride synthesis and utilization have become obvious over the past 10 years, including the recent identification of monogenic causes of metabolic-associated fatty liver disease. These include PNPLA3, transmembrane 6 superfamily member 2, GCKR, membrane-bound O-acyltransferase 7 suggest targets for new therapies for hepatic steatosis.

SUMMARY

The current review can serve as a guide to the complex pathways involved in the maintenance of hepatic triglyceride levels as well as an introduction to the most recent discoveries, including those of key genes that have provided opportunities for new and novel therapeutics.

Genetic and epigenetic factors determining NAFLD risk

BACKGROUND

Hepatic steatosis is a common chronic liver disease that can progress into more severe stages of NAFLD or promote the development of life-threatening secondary diseases for some of those affected. These include the liver itself (nonalcoholic steatohepatitis or NASH; fibrosis and cirrhosis, and hepatocellular carcinoma) or other organs such as the vessels and the heart (cardiovascular disease) or the islets of Langerhans (type 2 diabetes). In addition to elevated caloric intake and a sedentary lifestyle, genetic and epigenetic predisposition contribute to the development of NAFLD and the secondary diseases.

SCOPE OF REVIEW

We present data from genome-wide association studies (GWAS) and functional studies in rodents which describe polymorphisms identified in genes relevant for the disease as well as changes caused by altered DNA methylation and gene regulation via specific miRNAs. The review also provides information on the current status of the use of genetic and epigenetic factors as risk markers.

MAJOR CONCLUSION

With our overview we provide an insight into the genetic and epigenetic landscape of NAFLD and argue about the applicability of currently defined risk scores for risk stratification and conclude that further efforts are needed to make the scores more usable and meaningful.

The proteasome as a druggable target with multiple therapeutic potentialities: Cutting and non-cutting edges

Ubiquitin Proteasome System (UPS) is an adaptable and finely tuned system that sustains proteostasis network under a large variety of physiopathological conditions. Its dysregulation is often associated with the onset and progression of human diseases; hence, UPS modulation has emerged as a promising new avenue for the development of treatments of several relevant pathologies, such as cancer and neurodegeneration. The clinical interest in proteasome inhibition has considerably increased after the FDA approval in 2003 of bortezomib for relapsed/refractory multiple myeloma, which is now used in the front-line setting. Thereafter, two other proteasome inhibitors (carfilzomib and ixazomib), designed to overcome resistance to bortezomib, have been approved for treatment-experienced patients, and a variety of novel inhibitors are currently under preclinical and clinical investigation not only for haematological malignancies but also for solid tumours. However, since UPS collapse leads to toxic misfolded proteins accumulation, proteasome is attracting even more interest as a target for the care of neurodegenerative diseases, which are sustained by UPS impairment. Thus, conceptually, proteasome activation represents an innovative and largely unexplored target for drug development. According to a multidisciplinary approach, spanning from chemistry, biochemistry, molecular biology to pharmacology, this review will summarize the most recent available literature regarding different aspects of proteasome biology, focusing on structure, function and regulation of proteasome in physiological and pathological processes, mostly cancer and neurodegenerative diseases, connecting biochemical features and clinical studies of proteasome targeting drugs.

High carbohydrate and noodle/meat-rich dietary patterns interact with the minor haplotype in the 22q13 loci to increase its association with non-alcoholic fatty liver disease risk in Koreans

Non-alcoholic fatty liver(NAFLD) is prevalent in Asians despite the low obesity rate. We hypothesized that the haplotype of genetic variants in the 22q13 loci has a strong association with non-alcoholic fatty liver disease (NAFLD) that can be identified by genome-wide association study and that lifestyles may interact with the haplotype. We tested the hypothesis in middle-aged and elderly adults in a large city hospital-based cohort from the KoGES study. Men and women diagnosed with fatty liver, but who respectively consumed over 40 and 30 g ethanol per day were excluded. The haplotype of the selected SNPs from the 22q13 loci that influences NAFLD risk was generated. Among the 27374 participants, 1486 (5.4%) were diagnosed with NAFLD. LARGE_rs240072, RBFOX2_rs11089778, TRIOBP_rs12628603, PNPLA3_rs738409, and PARVB_rs2073080 in the 22q13 loci were included in the haplotype. Participants with the minor haplotype had 1.8, 2.3, and 1.8 times higher in the risk for NAFLD and serum AST and ALT activities, respectively, than those with the major haplotype. BMI, waist circumferences, serum glucose concentrations, and blood pressure interacted with the haplotype for NAFLD risk. We also found that a high carbohydrate intake and a dietary pattern characterized by high noodle and meat consumption significantly interacted with the minor haplotype to increase the risk of NAFLD. We hypothesized that the high incidence of NAFLD among Koreans, despite a relatively low incidence of obesity, might be due to genetic factors and perhaps their interactions with dietary patterns. The hypothesis was accepted since this study confirmed that participants with the minor allele of the haplotype in the 22q13 loci had a higher NAFLD risk that was exacerbated by high intakes of carbohydrates and a dietary pattern characterized by high noodle and meat consumption.

Association of PNPLA3 rs738409 G/C gene polymorphism with nonalcoholic fatty liver disease in children: a meta-analysis

Background

Nonalcoholic fatty liver disease (NAFLD) is one of the most common causes of chronic liver disease worldwide. Current studies have shown that PNPLA3 (Patatin-like phospholipase domain containing 3) rs738409 G/C gene polymorphism is associated with adult nonalcoholic fatty liver disease [1, 2].But there is no consensus on the relationship between PNPLA3 rs738409 G/C gene polymorphism and children NAFLD due to differences in population samples. To this end, a meta-analysis of published research is conducted to comprehensively assess the relationship between PNPLA3 gene polymorphism and NAFLD in children.

Methods

We searched MEDLINE, PubMed, EMBASE, and CENTRAL databases from inception to May 2019. Case-control studies assessing the relationship between PNPLA3 rs738409 G/C gene polymorphism with non-alcoholic fatty liver disease in children were selected according to inclusion and exclusion criteria. Random effects model was used to quantify the association between the PNPLA3 rs738409 G/C gene polymorphism and the susceptibility of children’s NAFLD. Fixed effects model was used to quantify the relationship between the PNPLA3 rs738409 G/C gene polymorphism and the severity of NAFLD in children. The Stata 12.0 software was employed for data analysis.

Results

A total of nine case-control studies were included in this meta-analysis containing data of 1173 children with NAFLD and 1792 healthy controls. Five studies compared NAFLD children and non-NAFLD healthy populations. Statistical analysis showed that PNPLA3 gene polymorphism was significantly associated with children’s NAFLD in the allele contrast, dominant, recessive and over dominant models (G vs C,OR = 3.343, 95% CI = 1.524–7.334; GG + GC vs CC,OR = 3.157, 95% CI = 1.446–6.892;GG vs GC + CC,OR = 5.692, 95% CI = 1.941–16.689; GG + CC vs GC,OR = 2.756, 95% CI = 1.729–4.392). Four case-control studies compared Children with nonalcoholic fatty liver (NAFL) and children with nonalcoholic steatohepatitis (NASH). The results showed that the PNPLA3 gene polymorphism was also significantly associated with the severity of NAFLD in children in recessive gene model (GG vs GC + CC,OR = 14.43, 95% CI = 5.985–34.997); The Egger’s test revealed no significant publication bias.

Conclusions

Meta-analysis showed that PNPLA3 gene polymorphism was significantly associated with susceptibility and severity of NAFLD in children.

Genetics and epigenetics purpose in nonalcoholic fatty liver disease

INTRODUCTION

nonalcoholic fatty liver disease (NAFLD) comprises a broad spectrum of diseases, which can progress from benign steatosis to nonalcoholic steatohepatitis, liver cirrhosis and hepatocellular carcinoma. NAFLD is the most common chronic liver disease in developed countries, affecting approximately 25% of the general population. Insulin resistance, adipose tissue dysfunction, mitochondrial and endoplasmic reticulum stress, chronic inflammation, genetic and epigenetic factors are NAFLD triggers that control the disease susceptibility and progression.

AREAS COVERED

In recent years a large number of investigations have been carried out to elucidate genetic and epigenetic factors in the disease pathogenesis, as well as the search for diagnostic markers and therapeutic targets. This paper objective is to report the most studied genetic and epigenetic variants around NAFLD.

EXPERT OPINION

NAFLD lead to various comorbidities, which have a considerable impact on the patient wellness and life quality, as well as on the costs they generate for the country's health services. It is essential to continue with molecular research, since it could be used as a clinical tool for prognosis and disease severity. Specifically, in the field of hepatology, plasma miRNAs could provide a novel tool in liver diseases diagnosis and monitoring, representing an alternative to invasive diagnostic procedures.

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

BACKGROUND AND AIMS

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

METHODS

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

RESULTS

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

CONCLUSIONS

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

Genetic Risk Factors and Disease Modifiers of Nonalcoholic Steatohepatitis

Nonalcoholic fatty liver disease is strongly associated with obesity and the metabolic syndrome, but genetic factors also contribute to disease susceptibility. Human genetic studies have identified several common genetic variants contributing to nonalcoholic fatty liver disease initiation and progression. These findings have provided new insights into the pathogenesis of nonalcoholic fatty liver disease and opened up new avenues for the development of therapeutic interventions. In this review, we summarize the current state of knowledge about the genetic determinants of nonalcoholic fatty liver disease, focusing on the most robustly validated genetic risk factors and on recently discovered modifiers of disease progression.

NASH (nonalcoholic steatohepatitis), diabetes, and macrovascular disease: multiple chronic conditions and a potential treatment at the metabolic root

Introduction: NASH and type 2 diabetes (T2D) are clinical definitions that overlap and result from metabolic dysfunction caused by over-nutrition relative to metabolic need. This volume details drug development programs aimed at specific NASH pathology with a focus on liver outcomes; this commentary suggests a metabolic approach that should not be overlooked based on a new understanding of insulin sensitizers.Areas covered: The overlap of NASH and T2D with respect to metabolic syndrome is discussed in the context of new understandings of insulin sensitizers. Adverse clinical outcomes in subjects with advanced NAFLD (e.g. NASH) and advanced metabolic dysfunction (e.g., T2D) are primarily due to cardiovascular issues. Clinical evidence suggests that insulin resistance and hyperinsulinemia predict adverse cardiovascular outcomes. NALFD/NASH significantly contributes to insulin resistance and hyperinsulinemia. A new insulin sensitizer that targets the newly identified mitochondrial pyruvate carrier could provide an approach.Expert opinion: A metabolic approach is needed for the treatment of NASH. Clinical studies are underway to determine whether a new insulin sensitizer that targets pyruvate metabolism can impact NASH, T2D, and cardiovascular disease. A broader view of metabolic disease may provide a more assessable way to track therapeutic benefit.

PNPLA3 rs738409 is associated with renal glomerular and tubular injury in NAFLD patients with persistently normal ALT levels

BACKGROUND & AIMS

Patatin-like phospholipase domain-containing protein 3 (PNPLA3) rs738409 polymorphism is associated with NAFLD severity and the PNPLA3 gene is expressed in the kidneys, but whether PNPLA3 rs738409 polymorphism is also associated with renal tubular injury (RTI) is uncertain. We assessed the effect of PNPLA3 genotypes on biomarkers of RTI and glomerular function in subjects with NAFLD who had either normal (nALT) or abnormal (abnALT) alanine aminotransaminase levels.

METHODS

Two hundred and seventeen patients with histologically proven NAFLD of which 75 had persistently nALT (below upper limit of normal for 3 months) were included. Multivariable regression analyses were undertaken to test associations between PNPLA3 genotype and biomarkers of kidney dysfunction.

RESULTS

The nALT patient group had higher urinary neutrophil gelatinase-associated lipocalin levels (u-NGAL, a biomarker of RTI) (P < .001), higher albuminuria (P = .039) and greater prevalence of chronic kidney disease (CKD; P = .046) than the abnALT group. The association between PNPLA3 GG genotype and risk of CKD and abnormal albuminuria remained significant after adjustment for kidney risk factors and severity of NAFLD histology, mostly in the nALT group. Similarly, PNPLA3 GG genotype was associated with higher u-NGAL levels in the nALT group, even after adjustment for the aforementioned risk factors and glomerular filtration-based markers (β-coefficient: 22.29, 95% CI: 0.99-43.60, P = .041).

CONCLUSION

Patients with NAFLD and persistently nALT, who carry the PNPLA3 rs738409 G allele, are at higher risk of early glomerular and tubular damage. We suggest PNPLA3 genotyping may help identify patients with NAFLD at higher risk of RTI.