A common variant in the PNPLA3 gene is a risk factor for non-alcoholic fatty liver disease in obese Taiwanese children

Alanine aminotransferase elevation varies by ethnicity among Asian and Pacific Islander children with overweight or obesity

BACKGROUND

Limited research on alanine aminotransferase (ALT) screening for metabolic dysfunction-associated steatotic liver disease (MASLD) among US Asian/Pacific Islander (PI) children necessitates investigation in this heterogeneous population.

OBJECTIVE

Examine ALT elevation among Asian/PI children with overweight or obesity.

METHODS

Elevated ALT prevalence (clinical threshold) and association with body mass index ≥85th percentile were compared among 18 402 Asian/PI and 25 376 non-Hispanic White (NHW) children aged 9-17 years using logistic regression.

RESULTS

ALT elevation was more prevalent among Asian/PI (vs. NHW) males with overweight (4.0% vs. 2.7%), moderate (7.8% vs. 5.3%) and severe obesity (16.6% vs. 11.5%), and females with moderate (5.1% vs. 3.0%) and severe obesity (10.2% vs. 5.2%). Adjusted odds of elevated ALT were 1.6-fold and ~2-fold higher for Asian/PI (vs. NHW) males and females (with obesity), respectively. Filipino, Chinese and Southeast Asian males had 1.7-2.1-fold higher odds, but Native Hawaiian/PI (NHPI) and South Asian males did not significantly differ (vs. NHW). Filipina and Chinese females with obesity had >2-fold higher odds, Southeast and South Asian females did not differ and NHPI findings were mixed (vs. NHW).

CONCLUSION

High elevated ALT prevalence among Asian/PI children with overweight and obesity emphasizes the need for MASLD risk assessment and examination of ethnic subgroups.

PARVB and HSD17B13 variants are associated with nonalcoholic fatty liver disease in children

BACKGROUND AND AIM

The aim of this study was to investigate the comprehensive genetic effects of exploratory variants of LYPLAL1, GCKR, HSD17B13, TRIB1, APOC3, MBOAT7, and PARVB on pediatric nonalcoholic fatty liver disease in addition to the previously reported variants of TM6SF2, PNPLA3, and SAMM50 in Korean children.

METHODS

A prospective case-control study was conducted involving 309 patients diagnosed using ultrasound and 339 controls. Anthropometric measurements, liver function tests, and metabolic marker analysis were conducted, and fibrosis scores were calculated. Transient elastography was performed in 69 some patients with nonalcoholic fatty liver disease. TaqMan allelic discrimination assays were used for genotyping. The genetic risk scores were calculated using significant variants, namely, HSD17B13, PARVB, PNPLA3, SAMM50, and TM6SF2, to evaluate the additive effect.

RESULTS

Risk allele carriers of the PARVB variant showed significantly higher levels of aminotransferases, gamma-glutamyl transferase, alkaline phosphatase, pediatric nonalcoholic fatty liver disease fibrosis score, and aspartate aminotransferase/platelet ratio index. Individuals with a homozygous variant of HSD17B13 showed significantly lower levels of aminotransferase, gamma-glutamyl transferase, liver stiffness measurement, and aspartate aminotransferase/platelet ratio index than those with other genotypes. These parameters did not significantly differ among other variants of LYPLAL1, GCKR, TRIB1, APOC3, and MBOAT7. The genetic risk scores was identified as an independent risk factor for nonalcoholic fatty liver disease and had a positive association with severity.

CONCLUSION

HSD17B13 has protective effects on the severity of pediatric nonalcoholic fatty liver disease. Variants of HSD17B13, PARVB, PNPLA3, SAMM50, and TM6SF2 had an additive effect on nonalcoholic fatty liver disease.

Nonalcoholic Fatty Liver Disease in Lean/Nonobese and Obese Individuals: A Comprehensive Review on Prevalence, Pathogenesis, Clinical Outcomes, and Treatment

Nonalcoholic fatty liver disease (NAFLD) is the most common liver disease worldwide, with an estimated prevalence of 25% globally. NAFLD is closely associated with metabolic syndrome, which are both becoming increasingly more common with increasing rates of insulin resistance, dyslipidemia, and hypertension. Although NAFLD is strongly associated with obesity, lean or nonobese NAFLD is a relatively new phenotype and occurs in patients without increased waist circumference and with or without visceral fat. Currently, there is limited literature comparing and illustrating the differences between lean/nonobese and obese NAFLD patients with regard to risk factors, pathophysiology, and clinical outcomes. In this review, we aim to define and further delineate different phenotypes of NAFLD and present a comprehensive review on the prevalence, incidence, risk factors, genetic predisposition, and pathophysiology. Furthermore, we discuss and compare the clinical outcomes, such as insulin resistance, dyslipidemia, hypertension, coronary artery disease, mortality, and progression to nonalcoholic steatohepatitis, among lean/nonobese and obese NAFLD patients. Finally, we summarize the most up to date current management of NAFLD, including lifestyle interventions, pharmacologic therapies, and surgical options.

Fatty Liver Disease-Alcoholic and Non-Alcoholic: Similar but Different

In alcohol-induced liver disease (ALD) and in non-alcoholic fatty liver disease (NAFLD), there are abnormal accumulations of fat in the liver. This phenomenon may be related to excessive alcohol consumption, as well as the combination of alcohol consumption and medications. There is an evolution from simple steatosis to steatohepatitis, fibrosis and cirrhosis leading to hepatocellular carcinoma (HCC). Hepatic pathology is very similar regarding non-alcoholic fatty liver disease (NAFLD) and ALD. Initially, there is lipid accumulation in parenchyma and progression to lobular inflammation. The morphological changes in the liver mitochondria, perivenular and perisinusoidal fibrosis, and hepatocellular ballooning, apoptosis and necrosis and accumulation of fibrosis may lead to the development of cirrhosis and HCC. Medical history of ethanol consumption, laboratory markers of chronic ethanol intake, AST/ALT ratio on the one hand and features of the metabolic syndrome on the other hand, may help in estimating the contribution of alcohol intake and the metabolic syndrome, respectively, to liver steatosis.

Association of rs738409 Polymorphism in Adiponutrin Gene with Liver Steatosis and Atherosclerosis Risk Factors in Greek Children and Adolescents

Non-alcoholic fatty liver disease (NAFLD) shares several risk factors with atherosclerosis, as it is associated with components of the metabolic syndrome. However, genetic variations have also been linked to the risk of NAFLD, such as adiponutrin/patatin-like phospholipase domain-containing the protein 3 (PNPLA3) rs738409 polymorphism. The aim of the study was to determine the associations of thePNPLA3 rs738409 polymorphism with NAFLD and atherosclerosis risk factors in children and adolescents from northern Greece. A total of 91 children/adolescents who followed a Mediterranean eating pattern with no particular restrictions were studied. They were divided into three subgroups, according to their body mass index (BMI) and the presence or absence of liver disease. Diagnosis of NAFLD was based on a liver ultrasound, while the distribution of the PNPLA3 rs738409 polymorphism was investigated in all the participants. From the components of metabolic syndrome, only BMI, waist circumference, blood pressure, and the homeostasis model of insulin resistance (HOMA-IR) differed significantly between groups. The rs738409 polymorphism was significantly associated with BMI and NAFLD, while lipid values had no significant association with either NAFLD or gene polymorphism. This study shows that in Greekchildren, there is a significant association between the rs738409polymorphism in the PNPLA3 gene and hepatic steatosis, regardless of bodyweight.

Benefits of Physical Exercise as Approach to Prevention and Reversion of Non-Alcoholic Fatty Liver Disease in Children and Adolescents with Obesity

Non-alcoholic fatty liver disease (NAFLD) is an important health concern during childhood; indeed, it is the most frequent cause of chronic liver diseases in obese children. No valid pharmacological therapies for children affected by this condition are available, and the recommended treatment is lifestyle modification, usually including nutrition and exercise interventions. In this narrative review, we summarized up-to-date information on the benefits of physical exercise on NAFLD in children and adolescents with obesity. The role of exercise as non-pharmacological treatment was emphasized in order to provide recent advances on this topic for clinicians not deeply involved in the field. Several studies on obese children and adults confirm the positive role of physical activity (PA) in the treatment of NAFLD, but to date, there are no pediatric randomized clinical trials on exercise versus usual care. Among the pathogenic mechanisms involved in the PA effects on NAFLD, the main players seem to be insulin resistance and related inflammation, oxidative stress, and gut dysbiosis, but further evaluations are necessary to deeply understand whether these factors are correlated and how they synergistically act. Thus, a deeper research on this theme is needed, and it would be extremely interesting.

Effects of PNPLA3, TM6SF2 and SAMM50 on the development and severity of non-alcoholic fatty liver disease in children

BACKGROUND

Although genetic variants of PNPLA3, TM6SF2 and SAMM50 have been reported to increase the risk of non-alcoholic fatty liver disease (NAFLD), no pediatric studies have evaluated the association between SAMM50 and NAFLD.

OBJECTIVE

This study aimed to investigate the risk factors, including genetic variants, of pediatric NAFLD.

METHODS

NAFLD was defined as the presence of hepatic steatosis on ultrasound. We included 228 patients with NAFLD (body mass index-Z [BMI-Z] = 2.51 ± 1.01) and 225 controls (BMI-Z = 0.22 ± 1.48). We genotyped four variants of PNPLA3 (rs738409), TM6SF2 (rs58542926) and SAMM50 (rs2073080 and rs3761472) by TaqMan allelic discrimination. The pediatric NAFLD fibrosis score, aspartate transaminase (AST)/platelet ratio index and fibrosis-4 score were used to evaluate the degree of fibrosis. We calculated the genetic risk score for additive effects according to the sum of risk alleles.

RESULTS

The mean age was 12.6 ± 3.5 years. The four genetic variants, male sex and BMI-Z, independently increased susceptibility to NAFLD. These four variants, in addition to fasting insulin and triglycerides, remained significant risk factors with higher odds ratios in children with overweight. These variants increased the alanine aminotransferase (ALT) level and three fibrosis scores independently. As the genetic risk score increased, AST, ALT and the fibrosis scores increased independently.

CONCLUSION

PNPLA3, TM6SF2 and SAMM50 are associated with the development and severity of pediatric NAFLD. The impact of genetic variants is greater in children with overweight. The four genetic variants have synergetic effects on the severity of pediatric NAFLD.

Heterogeneity of non-alcoholic fatty liver disease: Implications for clinical practice and research activity

Non-alcoholic fatty liver disease (NAFLD) is a heterogeneous condition with a wide spectrum of clinical presentations and natural history and disease severity. There is also substantial inter-individual variation and variable response to a different therapy. This heterogeneity of NAFLD is in turn influenced by various factors primarily demographic/dietary factors, metabolic status, gut microbiome, genetic predisposition together with epigenetic factors. The differential impact of these factors over a variable period of time influences the clinical phenotype and natural history. Failure to address heterogeneity partly explains the sub-optimal response to current and emerging therapies for fatty liver disease. Consequently, leading experts across the globe have recently suggested a change in nomenclature of NAFLD to metabolic-associated fatty liver disease (MAFLD) which can better reflect current knowledge of heterogeneity and does not exclude concomitant factors for fatty liver disease (e.g. alcohol, viral hepatitis, etc.). Precise identification of disease phenotypes is likely to facilitate clinical trial recruitment and expedite translational research for the development of novel and effective therapies for NAFLD/MAFLD.

The PNPLA3 rs738409 Variant but not MBOAT7 rs641738 is a Risk Factor for Nonalcoholic Fatty Liver Disease in Obese U.S. Children of Hispanic Ethnicity

PURPOSE

The rs641738 C>T in membrane-bound O-acyltransferase domain-containing protein 7 (MBOAT7) is implicated, along with the rs738409 C>G polymorphism in patatin-like phospholipase domain-containing protein 3 (PNPLA3), in nonalcoholic fatty liver disease (NAFLD). The association of these polymorphisms and NAFLD are investigated in Hispanic children with obesity.

METHODS

Obese children with and without NAFLD were enrolled at a pediatric tertiary care health system and genotyped for MBOAT7 rs641738 C>T and PNPLA3 rs738409 C>G. NAFLD was characterized by the ultrasonographic presence of hepatic steatosis along with persistently elevated liver enzymes. Genetic variants and demographic and biochemical data were analyzed for the effects on NAFLD.

RESULTS

Among 126 enrolled subjects, 84 in the case group had NAFLD and 42 in the control group did not. The two groups had similar demographic distribution. NAFLD was associated with abnormal liver enzymes and elevated triglycerides and cholesterol (p<0.05). Children with NAFLD had higher percentage of PNPLA3 GG genotype at 70.2% versus 31.0% in non-NAFLD, and lower MBOAT7 TT genotype at 4.8% versus 16.7% in non-NAFLD (p<0.05). PNPLA3 rs738409 C>G had an additive effect in NAFLD; however, MBOAT7 rs641738 C>T had no effects alone or synergistically with PNPLA3 polymorphism. NAFLD risk increased 3.7-fold in subjects carrying PNPLA3 GG genotype and decreased in MBOAT7 TT genotype.

CONCLUSION

In Hispanic children with obesity, PNPLA3 rs738409 C>G polymorphism increased the risk for NAFLD. The role of MBOAT7 rs641738 variant in NAFLD is less evident.

Nonalcoholic Fatty Liver Disease: A Global Perspective

The prevalence of nonalcoholic fatty liver disease (NAFLD) has been increasing over the years and is now as high in Asia as in the Western world, so much so that it should no longer be considered a Western disease. In fact, China is expected to have the largest increase in the number of NAFLD cases in the coming years. The increase in prevalence of NAFLD in Asia lags behind that of the Western world; thus, there will be a lag in more severe liver disease in Asia despite a similar prevalence of the disease. NAFLD is more prevalent among patients with diabetes mellitus, which is also an important risk factor for more severe liver disease. Patients with diabetes mellitus thus represent an important target for screening for NAFLD and more severe liver disease. Although the PNPLA3 gene polymorphism is the most studied in NAFLD, it is increasingly clear that the cumulative effect of multiple genes likely predisposes to NAFLD and more severe liver disease in the different ethnic groups, and polygenic risk scores are emerging. Lean NAFLD has been largely reported in Asia but is increasingly recognized worldwide. Multiple risk factors have been identified for the disease that manifests in metabolically unhealthy normal weight individuals; however, it responds to lifestyle intervention, similar to the disease in obese individuals. Lastly, the newer term "metabolic dysfunction-associated fatty liver disease" provides a more accurate reflection of the disease, giving more focus to clinicians and researchers in tackling this increasingly common and challenging disease.

Effect of the patatin-like phospholipase domain containing 3 gene (PNPLA3) I148M polymorphism on the risk and severity of nonalcoholic fatty liver disease and metabolic syndromes: A meta-analysis of paediatric and adolescent individuals

BACKGROUND

The effect of the patatin-like phospholipase domain containing 3 gene (PNPLA3) I148M polymorphism on the risk and severity of paediatric and adolescent nonalcoholic fatty liver disease (NAFLD) remains inconclusive.

OBJECTIVES

We aimed to estimate the effect of this polymorphism not only on early-onset NAFLD risk and severity but also on metabolic syndromes susceptibility.

METHODS

A systematic literature search was performed to identify relevant datasets. The odds ratio of the dichotomic variables and the standardized mean difference of quantitative variables with corresponding 95% confidence intervals were calculated to assess the strength of the associations.

RESULTS

Twenty-seven studies comprising 10 070 subjects were eligible. The summary effect showed that this polymorphism increased susceptibility to NAFLD development. Furthermore, it also indicated that nonalcoholic steatohepatitis (NASH) was more frequently observed in G allele carriers among paediatric and adolescent NAFLD patients. Moreover, the meta-analysis suggested that the variant was significantly associated with elevated liver damage indexes, including serum alanine transaminase, aspartate transaminase, gamma-glutamyltransferase concentrations, and liver fat content. However, the summary estimates for insulin resistance, lipid metabolism, and adiposity showed no significant associations.

CONCLUSIONS

The PNPLA3 I148M polymorphism is associated with elevated early-onset NAFLD risk, severity, and liver damage but not with related metabolic syndromes.

Liver fat accumulation assessed by computed tomography is an independent risk factor for diabetes mellitus in a population-based study: SESSA (Shiga Epidemiological Study of Subclinical Atherosclerosis)

AIMS

Ectopic fat accumulation is related to insulin resistance and diabetes mellitus (DM). However, the effect of fatty liver on DM in non-obese individuals has not been clarified. We investigated whether liver fat accumulation assessed by computed tomography (CT) is associated with the incidence of DM.

METHODS

In a prospective population-based study, 640 Japanese men were followed up for 5 years. The liver to spleen (L/S) ratio of the CT attenuation value was used as the liver fat accumulation index. We calculated the odds ratio (OR) and 95% confidence interval (CI) for the DM incidence of per 1 standard deviation (SD) lower L/S and those of L/S < 1.0 compared with L/S ≥ 1.0, using logistic regression models.

RESULTS

Both per 1 SD lower L/S and L/S < 1.0 were significantly associated with a risk for DM incidence (1 SD lower L/S: OR = 1.57, 95%CI = 1.14-2.16; L/S < 1.0: OR = 2.27, 95%CI = 1.00-5.14). The relationship between L/S and incidence of DM was consistent in the obese and non-obese groups, with thresholds of BMI 25 kg/m², waist circumference 85 cm, or visceral adipose tissue 100 cm².

CONCLUSIONS

Liver fat accumulation assessed by CT was associated with the incidence of DM.

Association of rs780094 polymorphism of glucokinase regulatory protein with non-alcoholic fatty liver disease

OBJECTIVE

GCK rs780094 polymorphism is a single nucleotide polymorphism that has been associated with obesity, type II diabetes and dyslipidemia in some populations, conditions that highly related to NAFL etiology. The present study aimed to evaluate the relationship between NAFLD and rs780094 polymorphism in patients with NAFLD in Tabriz city, northwest of Iran. The rs780094 polymorphism was determined in 74 patients with NAFLD by PCR-RFLP technique. Demographic information was collected using a questionnaire and biochemical analysis was performed using standard laboratory methods.

RESULTS

There was a significant difference between case and control subjects for alanine aminotransferase, aspartate aminotransferase, HDL-C and triglycerides (P < 0.05). Analysis by PCR-RFLP method revealed that there were no significant differences between NAFLD and healthy subjects for rs780094 polymorphism in the study population. The results of this study indicated that rs780094 polymorphism is not associated with NAFLD in subjects from Tabriz city.

New Perspectives on Genetic Prediction for Pediatric Metabolic Associated Fatty Liver Disease

Non-alcoholic or recently re-defined metabolic associated fatty liver disease (MAFLD), a spectrum of progressive hepatic disease, has become a public health issue in obese children and adolescents. MAFLD is a complex metabolic disease strongly associated with obesity and insulin resistance. It is not known why not every obese subject will develop MAFLD. Different ethnic/racial groups display differences in MAFLD prevalence, indicating genetic factor plays a role. In the past two decades, sequence variations in genetic loci, including PNPLA3, TM6SF2, GCKR, MBOAT7, HSD17B13, etc. have been shown to confer susceptibility to MAFLD in children and adults. This review article provides an updated viewpoint of genetic predictors related to pediatric MAFLD. We discuss whether these susceptible genes can be clinically used for risk stratification and personalized care. Understanding human genetics and molecular mechanisms can give important information not only for prediction of risk but also on how to design drugs. In view of current epidemic of MAFLD worldwide, it is necessary to identify which children with MAFLD progress rapidly and need earlier intervention. In the future, a comprehensive analysis of individualized genetic and environmental factors may help assess the risk of children with MAFLD and personalize their treatment.

New Perspectives in Pediatric Nonalcoholic Fatty Liver Disease: Epidemiology, Genetics, Diagnosis, and Natural History

Nonalcoholic fatty liver disease (NAFLD) is the most common cause of chronic liver disease in children. The global prevalence of pediatric NAFLD from general populations is 7.6%. In obese children, the prevalence is higher in Asia. NAFLD has a strong heritable component based on ethnic difference in the prevalence and clustering within families. Genetic polymorphisms of patatin-like phospholipase domain-containing protein 3 (PNPLA3), transmembrane 6 superfamily member 2, and glucokinase regulatory protein (GCKR) are associated with the risk of NAFLD in children. Variants of PNPLA3 and GCKR are more common in Asians. Alterations of the gut microbiome might contribute to the pathogenesis of NAFLD. High fructose intake increases the risk of NAFLD. Liver fibrosis is a poor prognostic factor for disease progression to cirrhosis. Magnetic resonance spectroscopy and magnetic resonance proton density fat fraction are more accurate for steatosis quantification than ultrasound. Noninvasive imaging methods to assess liver fibrosis, such as transient elastography, shear-wave elastography, and magnetic resonance elastography are useful in predicting advanced fibrosis, but they need further validation. Longitudinal follow-up studies into adulthood are needed to better understand the natural history of pediatric NAFLD.

IL-17A, MCP-1, CCR-2, and ABCA1 polymorphisms in children with non-alcoholic fatty liver disease

OBJECTIVE

The prevalence of non-alcoholic fatty liver disease in children has risen significantly, owing to the worldwide childhood obesity epidemic in the last two decades. Non-alcoholic fatty liver disease is closely linked to sedentary lifestyle, increased body mass index, and visceral adiposity. In addition, individual genetic variations also have a role in the development and progression of non-alcoholic fatty liver disease. The aim of this study was to investigate the gene polymorphisms of MCP-1 (-2518 A/G) (rs1024611), CCR-2 (190 G/A) (rs1799864), ABCA1 (883 G/A) (rs4149313), and IL-17A (-197 G/A) (rs2275913) in obese Turkish children with non-alcoholic fatty liver disease.

METHODS

The study recruited 186 obese children aged 10-17 years, including 101 children with non-alcoholic fatty liver disease and 85 children without non-alcoholic fatty liver disease. Anthropometric measurements, insulin resistance, a liver panel, a lipid profile, liver ultrasound examination, and genotyping of the four variants were performed.

RESULTS

No difference was found between the groups in respect to age and gender, body mass index, waist/hip ratio, or body fat ratio. In addition to the elevated ALT levels, AST and GGT levels were found significantly higher in the non-alcoholic fatty liver disease group compared to the non non-alcoholic fatty liver disease group (p<0.05). The A-allele of IL-17A (-197 G/A) (rs2275913) was associated with non-alcoholic fatty liver disease (odds ratio [OR] 2.05, 95% confidence interval: 1.12-3.77, p=0.02).

CONCLUSIONS

The findings of this study suggest that there may be an association between IL-17A (-197 G/A) (rs2275913) polymorphism and non-alcoholic fatty liver disease development in obese Turkish children.

Comprehensive bioinformatics analysis of critical lncRNAs, mRNAs and miRNAs in non‑alcoholic fatty liver disease

Non‑alcoholic fatty liver disease (NAFLD) is the most common fatty liver disease in developed countries, in which fat accumulation in the liver is induced by non‑alcoholic factors. The present study was conducted to identify NAFLD‑associated long non‑coding RNAs (lncRNAs), mRNAs and microRNAs (miRNAs). The microarray dataset GSE72756, which included 5 NAFLD liver tissues and 5 controls, was acquired from the Gene Expression Omnibus database. Differentially expressed lncRNAs (DE‑lncRNAs) and mRNAs (DE‑mRNAs) were detected using the pheatmap package. Using the clusterProfiler package and Cytoscape software, enrichment and protein‑protein interaction (PPI) network analyses were conducted to evaluate the DE‑mRNAs. Next, the miRNA‑lncRNA‑mRNA interaction network was visualized using Cytoscape software. Additionally, RP11‑279F6.1 and AC004540.4 expression levels were analyzed by reverse transcription quantitative polymerase chain reaction. There were 318 DE‑lncRNAs and 609 DE‑mRNAs identified in the NAFLD tissues compared with the normal tissues. Jun proto‑oncogene, AP‑1 transcription factor subunit (JUN), which is regulated by AC004540.4 and RP11‑279F6.1, exhibited higher degree compared with other nodes in the PPI network. Furthermore, miR‑409‑3p and miR‑139 (targeting JUN) were predicted as PPI network nodes. In the miRNA‑lncRNA‑mRNA network, miR‑20a and B‑cell lymphoma 2‑like 11 (BCL2L11) were among the top 10 nodes. Additionally, BCL2L11, AC004540.4 and RP11‑279F6.1 were targeted by miR‑20a, miR‑409‑3p and miR‑139 in the miRNA‑lncRNA‑mRNA network, respectively. RP11‑279F6.1 and AC004540.4 expression was markedly enhanced in NAFLD liver tissues. These key RNAs may be involved in the pathogenic mechanisms of NAFLD.

Association between PNPLA3 rs738409 polymorphism and nonalcoholic fatty liver disease (NAFLD) susceptibility and severity: A meta-analysis

OBJECTIVE

This meta-analysis is to investigate the relationship between the patatin-like phospholipase domain containing 3 (PNPLA3) rs738409 polymorphism and the susceptibility and severity of nonalcoholic fatty liver disease (NAFLD).

METHODS

Chinese Journal Full-text Database, Wanfang Database, VIP Database, and PubMed Database were subjected to case-control study retrieving, from January 2008 to December 2014. Following key words were used: fatty liver, PNPLA3, and rs738409 gene or variants or polymorphism or alleles. Meta-analysis was performed based on the retrieved articles.

RESULTS

In total 65 studies were first retrieved according to the key words, and finally 21 studies with 14,266 subjects were included. Meta-analysis showed that PNPLA3 rs738409 polymorphism exerted strong influence not only on fatty liver but also on the histological injury. PNPLA3 rs738409 [G] allele was a risk factor for NAFLD (GG vs CC, OR = 4.01, 95% CI 2.93-5.49; GC vs CC, OR = 1.88, 95% CI 1.58-2.24). PNPLA3 gene variant was significantly associated with the increased serum alanine aminotransferase (ALT) levels (GG vs CC, standardized mean difference  = 0.47, 95% CI 0.14-0.81). In addition, nonalcoholic steatohepatitis (NASH) was more frequently observed in G allele carriers (GG vs CC, OR = 3.24, 95% CI 2.79-3.76; GC vs CC, OR = 2.14, 95% CI 1.43-3.19).

CONCLUSION

PNPLA3 rs738409 polymorphism is not only a factor significantly associated with the susceptibility of NAFLD, but also related to the susceptibility of aggressive diseases.

Lean non-alcoholic fatty liver disease

BACKGROUND & AIMS

Non-alcoholic fatty liver disease (NAFLD), with its increasing prevalence and association with various co-morbidities, such as diabetes, cardiovascular disease and metabolic syndrome, is a growing concern. Previously thought to predominantly affect obese individuals, NAFLD has been shown to occur in non-obese subjects. This subset of individuals, known to have 'lean NAFLD' or 'non-obese NAFLD', is also growing increasingly prevalent. We summarize the clinical manifestations, pathophysiology and management of lean NAFLD in both adult and pediatric populations.

METHODS

Two reviewers performed an independent, formal review and analysis of the literature (PubMed and EMBASE search until April 2018).

RESULTS AND CONCLUSIONS

Patients with lean NAFLD share metabolic features of insulin resistance and dyslipidemia, similar to obese patients with NAFLD. Genetic predisposition, dietary and environmental factors may play a role in the pathogenesis of lean NAFLD. Genetic and metabolic conditions should be considered as well. Currently, there are no formal recommendations for the treatment of adult or pediatric lean NAFLD; however, lifestyle changes aimed at improving overall fitness are likely to have a favorable impact.

The Genetics of Pediatric Nonalcoholic Fatty Liver Disease

Nonalcoholic fatty liver disease (NAFLD) is the leading cause of chronic liver disease in children. Severe fibrosis and cirrhosis are potential consequences of pediatric NAFLD and can occur within a few years of diagnosis. Observations suggest that genetics may be a strong modifying factor in the presentation, severity, and natural history of the disease. There is increasing interest in determining at-risk populations based on genetics in the hope of finding genotypes that correlate to NAFLD phenotype. Ultimately, the hope is to be able to tailor therapeutics to genetic predispositions and decrease disease morbidity in children with NAFLD.

MTP genetic variants associated with non-alcoholic fatty liver in metabolic syndrome patients

This study was performed for investigation the relationship between variants of MTP gene polymorphism and the development of NAFLD in patients with and without MS. The study was included 174 NAFLD patients (106 with MS and 68 without MS), and 141 healthy control subjects. The 493 G/T polymorphism of MTP gene was evaluated by PCR-RFLP method. The frequency of MTP TT genotype and T allele were significantly higher in NAFLD patients when compared to healthy controls. Moreover, a significant association in MTP gene polymorphism was observed in NAFLD patients with MS compared to NAFLD patients without MS and controls. Our study suggested that MTP 493 G/T gene polymorphism may act as susceptibility biomarker for NAFLD and MS.

Genome-Wide Associations Related to Hepatic Histology in Nonalcoholic Fatty Liver Disease in Hispanic Boys

OBJECTIVE

To identify genetic loci associated with features of histologic severity of nonalcoholic fatty liver disease in a cohort of Hispanic boys.

STUDY DESIGN

There were 234 eligible Hispanic boys age 2-17 years with clinical, laboratory, and histologic data enrolled in the Nonalcoholic Steatohepatitis Clinical Research Network included in the analysis of 624 297 single nucleotide polymorphisms (SNPs). After the elimination of 4 outliers and 22 boys with cryptic relatedness, association analyses were performed on 208 DNA samples with corresponding liver histology. Logistic regression analyses were carried out for qualitative traits and linear regression analyses were applied for quantitative traits.

RESULTS

The median age and body mass index z-score were 12.0 years (IQR, 11.0-14.0) and 2.4 (IQR, 2.1-2.6), respectively. The nonalcoholic fatty liver disease activity score (scores 1-4 vs 5-8) was associated with SNP rs11166927 on chromosome 8 in the TRAPPC9 region (P = 8.7^-07). Fibrosis stage was associated with SNP rs6128907 on chromosome 20, near actin related protein 5 homolog (p = 9.9^-07). In comparing our results in Hispanic boys with those of previously reported SNPs in adult nonalcoholic steatohepatitis, 2 of 26 susceptibility loci were associated with nonalcoholic fatty liver disease activity score and 2 were associated with fibrosis stage.

CONCLUSIONS

In this discovery genome-wide association study, we found significant novel gene effects on histologic traits associated with nonalcoholic fatty liver disease activity score and fibrosis that are distinct from those previously recognized by adult nonalcoholic fatty liver disease genome-wide association studies.

Non-alcoholic Fatty Liver Disease in Lean Subjects: Characteristics and Implications

Non-alcoholic fatty liver disease (NAFLD) is commonly diagnosed in obese subjects; however, it is not rare among lean individuals. Given the absence of traditional risk factors, it tends to remain under-recognised. The metabolic profiles of lean NAFLD patients are frequently comparable to those of obese NAFLD patients. Though results from several studies have been mixed, it has been generally revealed that lean subjects with NAFLD have minor insulin resistance compared to that in obese NAFLD. Several genetic variants are associated with NAFLD without insulin resistance. Some data suggest that the prevalence of steatohepatitis and advanced fibrosis do not differ significantly between lean and obese NAFLD; however, the former tend to have less severe disease at presentation. The underlying pathophysiology of lean NAFLD may be quite different. Genetic predispositions, fructose- and cholesterol-rich diet, visceral adiposity and dyslipidaemia have potential roles in the pathogenic underpinnings. Lean NAFLD may pose a risk for metabolic disturbances, cardiovascular morbidity or overall mortality. Secondary causes of hepatic steatosis are also needed to be ruled out in lean subjects with NAFLD. The effectiveness of various treatment modalities, such as exercise and pharmacotherapy, on lean NAFLD is not known. Weight loss is expected to help lean NAFLD patients who have visceral obesity. Further investigation is needed for many aspects of lean NAFLD, including mechanistic pathogenesis, risk assessment, natural history and therapeutic approach.

Significance of genetic polymorphisms in patients with nonalcoholic fatty liver disease

Because of recent advances in genetic research such as genome-wide association studies, the underlying genetic mechanisms of nonalcoholic fatty liver disease (NAFLD) pathophysiology have been elucidated. Here, we present a review of the current literature on the impact of genetic polymorphisms in patients with NAFLD. These genetic polymorphisms, which regulate lipid metabolism, glucose metabolism, and the renin-angiotensin system, are involved in NAFLD onset, steatosis, inflammation, fibrosis, and hepatocellular carcinoma (HCC). Among these genetic polymorphisms, many studies and meta-analyses have demonstrated that position 148 (rs738409 C/G) of the patatin-like phospholipase domain-containing protein (PNPLA3) is a genetic factor associated with NAFLD pathophysiological features, such as hepatic fat level, hepatic inflammation, fibrosis, and HCC. However, the impact of genetic polymorphisms on NAFLD pathophysiology appears to differ among ethnic groups. Therefore, further studies with larger sample sizes are needed for each ethnic group.

Variants in the autophagy-related gene IRGM confer susceptibility to non-alcoholic fatty liver disease by modulating lipophagy

BACKGROUND & AIMS

Autophagy has been shown to be crucial in the regulation of the intracellular lipid stores in hepatocytes. We hypothesize that immunity-related GTPase family M (IRGM) gene (an autophagy-related gene) variants confer the susceptibility to non-alcoholic fatty liver disease (NAFLD) development.

METHODS

832 obese children and adolescents aged 6-18years were recruited. NAFLD was determined by liver ultrasonography. We genotyped PNPLA3 rs738409, GCKR rs780094, TM6SF2 rs58542926, six IRGM single nucleotide polymorphisms (rs13361189, rs9637876, rs72553867, rs10065172, rs1000113, and rs11747270). To understand the molecular mechanism, we examined the effects of IRGM knockdown and overexpression on autophagic flux and lipid droplet metabolism in human hepatoma cells.

RESULTS

22.8% of recruited obese children and adolescents had NAFLD. Multiple logistic regression analysis revealed that after controlling for the effects of age- and gender-adjusted body mass index, gender, PNPLA3, GCKR, and TM6SF2 polymorphisms, variant IRGM rs10065172 TT genotype independently increased the odds ratio of NAFLD by 2.04 (95% confidence interval 1.22-3.42; p=0.007), as compared to the CC genotype. The predictive model was validated by means of 10-fold cross validation. Functional assay revealed that IRGM knockdown inhibited autophagic flux and increased lipid droplet content in HepG2 and PLC/PRF/5 cells, which were reversed by the autophagy inducer rapamycin administration. Similarly, wortmannin (an autophagy inhibitor) increased intracellular lipid droplet content. In contrast, overexpression of IRGM caused decreased lipid droplet content in HepG2 cells.

CONCLUSIONS

Our findings suggest that IRGM may contribute to the development of human NAFLD by altering hepatic lipid metabolism through the autophagy pathway.

LAY SUMMARY

Autophagy is involved in the process of lipid metabolism in hepatocytes. The mechanism of autophagy regulation by IRGM has just been unveiled. This study demonstrates that genetic variants in IRGM confer risk of human non-alcoholic fatty liver disease. The functional studies reveal how IRGM regulates hepatic lipid droplet content.

PNPLA3 as a Genetic Determinant of Risk for and Severity of Non-alcoholic Fatty Liver Disease Spectrum

Background and Aims:Patatin-like phospholipase domain protein 3 (PNPLA3) polymorphisms (rs738409 C>G) are associated with non-alcoholic fatty liver disease (NAFLD). We performed a systematic review and meta-analysis to examine the association of PNPLA3 polymorphisms with the spectrum and severity of this disease. Methods: Studies evaluating the association between the PNPLA3 polymorphism spectrum (fatty liver, steatohepatitis, cirrhosis, and hepatocellular carcinoma) and NAFLD were included. Pooled data are reported as odds ratios (ORs) with 95% confidence intervals. Results: Of 393 potentially relevant studies, 35 on NAFLD were included in the analysis. Compared to healthy controls, the pooled ORs for rs738409 CG and GG compared to CC among patients with non-alcoholic fatty liver (NAFL) were 1.46 (1.16-1.85) and 2.76 (2.30-3.13), and were 1.75 (1.24-2.46) and 4.44 (2.92-6.76) among patients with non-alcoholic steatohepatitis respectively. The respective ORs for CG and GG compared to the CC genotype were 2.35 (0.90-6.13) and 5.05 (1.47-17.29) when comparing non-alcoholic hepatocellular carcinoma to NAFL patients. Among the NAFLD patients, the ORs for G allele frequency when comparing steatosis grade 2-3 to grade 0-1 NAFL, when comparing the NAFLD activity score of ≥ 4 to score ≤ 3, when comparing NASH to NAFLD, when comparing the presence of lobular inflammation to absence, and when comparing the presence of hepatocyte ballooning to absence were 2.33 (1.43-3.80), 1.80 (1.36-2.37), 1.66 (1.42-1.94), 1.58 (1.19-2.10), and 2.63 (1.87-3.69) respectively. Subgroup analysis based on ethnicity showed similar results. Conclusions:PNPLA3 polymorphisms have strong association with the risk for and severity of NAFLDs. PNPLA3 polymorphism plays an evolving role in diagnosis and treatment decisions in patients with NAFLD.

Definitions of Normal Liver Fat and the Association of Insulin Sensitivity with Acquired and Genetic NAFLD-A Systematic Review

Non-alcoholic fatty liver disease (NAFLD) covers a spectrum of disease ranging from simple steatosis (NAFL) to non-alcoholic steatohepatitis (NASH) and fibrosis. “Obese/Metabolic NAFLD” is closely associated with obesity and insulin resistance and therefore predisposes to type 2 diabetes and cardiovascular disease. NAFLD can also be caused by common genetic variants, the patatin-like phospholipase domain-containing 3 (PNPLA3) or the transmembrane 6 superfamily member 2 (TM6SF2). Since NAFL, irrespective of its cause, can progress to NASH and liver fibrosis, its definition is of interest. We reviewed the literature to identify data on definition of normal liver fat using liver histology and different imaging tools, and analyzed whether NAFLD caused by the gene variants is associated with insulin resistance. Histologically, normal liver fat content in liver biopsies is most commonly defined as macroscopic steatosis in less than 5% of hepatocytes. In the population-based Dallas Heart Study, the upper 95th percentile of liver fat measured by proton magnetic spectroscopy (¹H-MRS) in healthy subjects was 5.6%, which corresponds to approximately 15% histological liver fat. When measured by magnetic resonance imaging (MRI)-based techniques such as the proton density fat fraction (PDFF), 5% macroscopic steatosis corresponds to a PDFF of 6% to 6.4%. In contrast to “Obese/metabolic NAFLD”, NAFLD caused by genetic variants is not associated with insulin resistance. This implies that NAFLD is heterogeneous and that “Obese/Metabolic NAFLD” but not NAFLD due to the PNPLA3 or TM6SF2 genetic variants predisposes to type 2 diabetes and cardiovascular disease.

Genetic background in nonalcoholic fatty liver disease: A comprehensive review

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

Patatin-like phospholipase 3 (rs738409) gene polymorphism is associated with increased liver enzymes in obese adolescents and metabolic syndrome in all ages

BACKGROUND

Obesity is associated with non-alcoholic fatty liver disease (NAFLD), and the patatin-like phospholipase 3 (PNPLA3) rs738409 (Ile148Met, C>G) gene polymorphism is one of the most important genetic determinants of NAFLD. Carriers have been reported to better respond to lifestyle modification.

AIM

To investigate the effect of rs738409 on overweight/obese adolescents and adults with and without metabolic syndrome (MetS).

METHODS

Two hundred and eighty-eight overweight/obese and 209 normal weight participants of the STYJOBS/EDECTA cohort (NCT00482924) were analysed for PNPLA3 genotypes.

RESULTS

Compared to overweight/obese without MetS, in overweight/obese study participants with MetS, the presence of the G allele (148Met) was significantly higher (CC: 5.0% vs. 9.2%, Spearman's correlation, 0.12; P = 0.038). Persons with CG (heterozygote for the risk allele) and with GG (homozygote for the risk allele) genotypes showed significantly higher ALT levels than those with CC genotypes. Even young individuals aged below 20 years had significantly increased ALT levels if they were homozygote with the G allele.

CONCLUSIONS

The PNPLA3 rs738409 polymorphism is associated already in youths with increased ALT, and is more frequent in obese with MetS of all ages. Hence, overweight/obese rs738409 carriers should be identified early in life and treated with a rigorous life style intervention.

PNPLA3 polymorphisms (rs738409) and non-alcoholic fatty liver disease risk and related phenotypes: a meta-analysis

BACKGROUND AND AIM

One single-nucleotide polymorphisms (SNPs) rs738409 in the patatin-like phospholipase domain-containing 3 gene (PNPLA3) has been implicated in susceptibility to non-alcoholic fatty liver disease (NAFLD) across different populations. One meta-analysis confirmed this association, but within it, only two Asian studies were included. This meta-analysis aimed to investigate the association in Asian population.

METHODS

All eligible case-control studies were identified by searching through PubMed and Chinese language databases (CNKI and WanFang) up to July 1, 2014. Pooled estimates (odds ratio [OR] and standardized mean difference) were used to assess the strength of associations in fixed or random-effects models.

RESULTS

A total of 12 studies with 4495 cases and 7431 controls were included. SNP rs738409 G allele was confirmed as a risk factor for NAFLD (G allele vs C allele: OR = 1.92, 95% confidence interval [95%CI]: 1.54-2.39). In addition, based on studies with certain clinical measurements data, G allele carriers were more likely to have higher level of serum alanine aminotransferase (ALT) (standard mean difference [SMD] = 7.03, 95% CI: 2.47-11.60), and higher fibrosis score (SMD = 0.39, 95% CI: 0.18-0.60).

CONCLUSION

This study provided evidence of SNP rs738409 G allele as a strong risk factor of NAFLD susceptibility and higher level of serum ALT in Asian population.

GWAS-Identified Common Variants With Nonalcoholic Fatty Liver Disease in Chinese Children

OBJECTIVES

Three genome-wide association studies were previously done for nonalcoholic fatty liver disease (NAFLD) among individuals of Western countries and identified several genetic variants associated with NAFLD. The study aimed to identify whether 7 GWAS-identified common variants (GCKR rs780094, PDGFA rs343064, FDFT1 rs2645424, COL13A1 rs1227756, EHBP1L1 rs6591182, NCAN rs2228603, and PNPLA3 rs738409) were associated with NAFLD in Chinese children.

METHODS

This case-control study recruited 1027 Chinese children of age 7 to 18 years, including 162 children with NAFLD and 865 children without NAFLD. Anthropometric measurements, alanine transaminase (ALT) detection, liver ultrasound examination, and genotyping of 7 variants were performed.

RESULTS

The G-allele of PNPLA3 rs738409 was associated with NAFLD (odds ratio [OR] 1.55, 95% confidence interval 1.13-2.11, P = 0.006) and moderate-to-severe steatosis (OR 3.77, 95% confidence interval 1.78-7.98, P = 0.001) adjusted for age, sex, and BMI standard deviation score. In addition, we found each G-allele of rs738409 increased ALT level by 1.09 IU/L (P = 0.011). Subjects carrying 10 or more risk alleles of 7 variants had an OR of 4.76 (P = 0.025) for NAFLD compared with subjects carrying 3 or fewer risk alleles.

CONCLUSIONS

The PNPLA3 rs738409 G-allele was associated with NAFLD and ALT level in Chinese children. It had stronger association with moderate-to-severe steatosis. Children carrying 10 or more risk alleles of 7 variants were susceptible for NAFLD.

Heme oxygenase-1 gene promoter polymorphism and the risk of pediatric nonalcoholic fatty liver disease

BACKGROUND AND OBJECTIVES

Oxidative stress and the insulin-resistant state are thought to be key components in the pathogenesis of pediatric nonalcoholic fatty liver disease (NAFLD). Heme oxygenase (HO) is important in the defense against oxidative stress. This study aimed to assess the association of HO-1 gene promoter polymorphism and insulin resistance with NAFLD among obese children.

METHODS

A total of 101 obese children aged 6-17 years were recruited. Anthropometric, serum biochemical variables and biomarkers for glucose and insulin metabolism were measured. We screened the allelic frequencies of (GT)n repeats in the HO-1 gene promoter among these obese children. NAFLD was determined through liver ultrasonography. Because the distribution of numbers of (GT)n repeats was bimodal, we divided the alleles into two classes: class S included shorter (27) repeats, and class L included longer (⩾27) repeats. We assessed the effects of the length of (GT)n repeats in HO-1 gene promoter on pediatric NAFLD.

RESULTS

Of the 101 obese subjects, 27 (26.7%) had NAFLD. The alanine aminotransferase level was higher in patients carrying L alleles (L/L and L/S) than patients with S alleles (S/S) (46.2±49.3 IU|(-1) versus 30.2±20.1 IU|(-1); P=0.027). The significant risk factors for pediatric NAFLD were patients carrying L alleles (L/L and L/S) (odds ratio (OR)=18.84; 95% confidence interval (CI): 1.45-245.22; P=0.025), homeostasis model assessment of insulin resistance (OR=1.40; 95% CI: 1.07-1.83; P=0.014) and age (OR=1.24; 95% CI: 1.03-1.50; P=0.025).

CONCLUSION

In this hospital-based study, the obese children with longer GT repeats in the HO-1 gene promoter and insulin resistance were susceptible to NAFLD.

Prevalence and correlates of suspected nonalcoholic fatty liver disease in Chinese American children

GOALS

The aim of this study was to evaluate the prevalence and clinical correlates of nonalcoholic fatty liver disease (NAFLD) in children of Chinese immigrants.

BACKGROUND

NAFLD is increasing in prevalence and is frequently identified in children. High rates of NAFLD were found in adult Chinese immigrants. However, there are limited data regarding NAFLD in Chinese American children.

STUDY

Clinical and laboratory data were collected from 407 children, aged 6 to 18 years, who had routine office visits at a Chinatown medical practice. Children were classified as having suspected NAFLD if common causes of liver disease were excluded, alanine aminotransferase levels exceeded established thresholds (>22.1 IU/L for girls and >25.8 IU/L for boys), and elevated alanine aminotransferase levels were confirmed by repeat measurement.

RESULTS

6.1% of Chinese American children had suspected NAFLD, including 33% of obese children. Seventeen percent of children were overweight, 14% were obese, and 52% had 25-hydroxy vitamin D levels <20 ng/mL. In univariable analysis, children with suspected NAFLD were more frequently male, had higher body mass index percentile and lipid levels, and lower vitamin D levels compared with children without evidence of NAFLD. In multivariable analysis, suspected NAFLD was associated with higher BMI percentile and lower vitamin D levels when adjusting for other factors.

CONCLUSIONS

Chinese American children with obesity are at high risk for NAFLD. They should be screened accordingly, including testing for metabolic disorders and low vitamin D levels. Early identification of NAFLD in childhood will allow for intervention with lifestyle modification, providing a means to reduce the prevalence of NAFLD in children and adults.

Associations of I148M variant in PNPLA3 gene with plasma ALT levels during 2-year follow-up in normal weight and overweight children: the PANIC Study

OBJECTIVES

PNPLA3 I148M polymorphism (rs738409) has been strongly associated with liver fat content and plasma alanine aminotransferase (ALT) levels in obese adults and children, but little is known about these relationships in normal weight individuals. We studied the associations and interactions of overweight and the PNPLA3 I148M polymorphism with plasma ALT levels during 2-year follow-up in children.

METHODS

Subjects were a population sample of 481 Caucasian children aged 6-8 years examined at baseline and 419 children re-examined after 2-year follow-up. Altogether, 58 (12%) of 481 children at baseline and 71 (17%) of 419 children after 2-year follow-up were overweight. We assessed plasma ALT levels and other cardiometabolic risk factors and genotyped the PNPLA3 I148M polymorphism.

RESULTS

Being overweight and carrying PNPLA3 148M allele were associated with increased ALT levels at baseline (P = 0.002; P = 0.033) and after 2-year follow-up (P < 0.001; P = 0.001). Being overweight (P < 0.001) and carrying PNPLA3 148M allele (P = 0.001) were also associated with increase in ALT levels during 2-year follow-up. PNPLA3 148M allele carriers had increased ALT levels at baseline (P = 0.024 for interaction) and after 2-year follow-up (P = 0.002 for interaction) as well as a larger increase in ALT levels during 2-year follow-up (P = 0.002 for interaction) if they were overweight but not if they were normal weight. Further adjustment for clinical puberty, dietary factors, physical activity or sedentary behaviour had little or no effect on these associations.

CONCLUSION

PNPLA3 148M allele carriers had higher plasma ALT levels and larger increase in ALT levels during follow-up than non-carriers only among overweight children.

Association between patatin-like phospholipase domain containing 3 gene (PNPLA3) polymorphisms and nonalcoholic fatty liver disease: a HuGE review and meta-analysis

We conducted a meta-analysis to assess the association between patatin-like phospholipase domain-containing 3 (PNPLA3) rs738409 polymorphism and nonalcoholic fatty liver disease (NAFLD) and its subtypes simple steatosis(SS) and nonalcoholic steatohepatitis (NASH). The study-specific odds ratios (ORs) and 95% confidence intervals (CIs) were calculated using fixed-effects or random-effects models, with assessment for heterogeneity and publication bias. Twenty-three case-control studies involving 6071 NAFLD patients and 10366 controls were identified. The combined results showed a significant association between NAFLD risk and the rs738409 polymorphism in all genetic models (additive model: OR = 3.41, 95% CI = 2.57–4.52; P < 0.00001). In addition, evidence indicated that the rs738409 polymorphism was significantly associated with NASH in all genetic models (additive model: OR = 4.44, 95% CI = 3.39–5.82; P < 0.00001). The subgroup and sensitivity analyses showed that these changes were not influenced by the ethnicities and ages of subjects or by the source of controls. The rs738409 polymorphism was only significantly associated with risk of simple steatosis in the allele contrast and had no effect in the other genetic models. These findings suggest that the rs738409 polymorphism in PNPLA3 gene confers high cross-ethnicity risk for NAFLD and NASH development.

Meta-analysis reveals a specific association of the PNPLA3 I148M polymorphism with ALT level in adolescents

AIM

To evaluate potential link between the PNPLA3 rs738409 polymorphism and alanine aminotransferase (ALT) levels through an evidence-based study.

MATERIALS & METHODS

Electronic literature databases, including PubMed, Embase and the Institute for Scientific Information, were searched for relevant studies. Pooling standardized mean differences for quantitative variables and summary odds ratios (OR) were respectively calculated using per-allele comparison.

RESULTS

Although a genotype-phenotype association was inconsistent in adults, this genetic effect was stable in adolescents. There was an approximate increase of 23% in ALT value, and 1.99-fold higher ALT elevation per risk allele increase with low heterogeneity.

CONCLUSION

The PNPLA3 rs738409 polymorphism can have a differentiated influence on ALT level. Our meta-analysis provides reference data for the adjustment of diverse susceptibility due to the rs738409 polymorphism when evaluating liver injury in various populations.

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

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

Role of the PNPLA3 I148M polymorphism in nonalcoholic fatty liver disease and fibrosis in Korea

BACKGROUND

The role of the patatin-like phospholipase domain-containing 3 (PNPLA3) single-nucleotide polymorphism (SNP), rs738409, in the development and progression of nonalcoholic fatty liver disease (NAFLD) has not been studied in the Korean population.

AIMS

The aim of the study was to investigate the genotype frequency and allele distribution of PNPLA3 rs738409 and the association between the SNP and development of NAFLD and liver fibrosis.

METHODS

A total of 339 Korean adults (155 NAFLD patients and 184 healthy controls) were enrolled. PNPLA3 SNP genotyping was carried out using a TaqMan allelic discrimination assay. Liver fibrosis severity was evaluated by NAFLD fibrosis score (NFS) and BARD score.

RESULTS

The frequencies of the PNPLA3 rs738409 genotypes, CC, CG, and GG in the healthy control group were 29.9, 50.0, and 20.1%, respectively, and those in NAFLD patients were 20.0, 48.4, and 31.6%, respectively, showing a higher frequency of the risk allele (G allele) (p = 0.006). Among the NAFLD patients, the CG+GG genotype frequency was significantly higher in patients with advanced fibrosis, defined as NFS ≥ -1.455 or BARD score ≥2, than in patients with mild-to-moderate fibrosis (p = 0.012 and p = 0.046, respectively). In multivariate analysis, the CG+GG genotype was an independent factor for NAFLD development (odds ratio 2.568, 95% CI 1.109-5.945, p = 0.028) and for advanced liver fibrosis according to the criteria of NFS ≥ -1.455 (odds ratio 18.573, 95% CI 2.035-169.526, p = 0.010) or a BARD score ≥2 (odds ratio 4.040, 95% CI 1.084-15.048, p = 0.037).

CONCLUSION

The PNPLA3 rs738409 polymorphism is common and may confer a significant risk of NAFLD and advanced liver fibrosis in the Korean population.

Association between the PNPLA3 I148M polymorphism and non-alcoholic fatty liver disease in the Uygur and Han ethnic groups of northwestern China

Objective

Multiple common gene variants play a role in non-alcoholic fatty liver disease (NAFLD) susceptibility. Our goal was to investigate the association between variants polymorphisms and NAFLD in the Uygur and Han from Northwestern China.

Methods

Eight tag single nucleotide polymorphisms (tSNPs) previously reported to be associated with NAFLD were characterized in 396 NAFLD individuals and 399 controls. The association of variants with NAFLD in the Uygur and Han was assessed using the chi-squared (χ²) test in different gene models. Unconditional logistic regression analysis was performed to obtain the odds ratios (ORs) for risk of NAFLD and their 95% confidence intervals (CI), adjusted for confounding factors. Finally, stratified analysis was used to explore the potential gene-environment interactions on the risk of NAFLD.

Results

In a recessive model, we found a potential association between rs738409 and NAFLD in both ethnic groups: Chinese Han (OR = 1.84, 95% CI: 1.03–3.27, p = 0.036), Uygur (OR = 2.25, 95% CI: 1.23–4.09, p = 0.006). The multiple logistic regression revealed that PNPLA3 rs738409 GG genotype may increase the risk of NAFLD by adjusting some confounding factors: Han (OR = 5.22, 95% CI: 1.94–14.04, p = 0.001), Uygur (OR = 4.29, 95% CI: 1.60–11.48, p = 0.004). Stratified analysis found that rs738409 polymorphism appeared to have interaction with sex, smoking status in Uygur, and have interaction with sex, age, BMI stage, lifestyle in Han.

Conclusion

Our data suggest the PNPLA3 I148M polymorphism influences susceptibility to NAFLD in the Han and Uygur of Northwestern China.

Advances in research of nonalcoholic fatty liver disease

Nonalcoholic fatty liver disease (NAFLD) refers to a clinicopathologic syndrome characterized by a spectrum of histological abnormalities such as hepatocyte fatty degeneration and liver inflammation, not including those caused by alcohol and other specific factors. NAFLD is a heredity, environmental, metabolic disease, and its spectrum ranges from nonalcoholic fatty liver to nonalcoholic steatohepatitis and liver cirrhosis.

Nonalcoholic fatty liver disease and the heart in children and adolescents

Over the last two decades, the rise in the prevalence rates of overweight and obesity explains the emergence of nonalcoholic fatty liver disease (NAFLD) as the leading cause of chronic liver disease worldwide. As described in adults, children and adolescents with fatty liver display insulin resistance, glucose intolerance, and dyslipidemia. Thus NAFLD has emerged as the hepatic component of the metabolic syndrome (MetS) and a strong cardiovascular risk factor even at a very early age. Several studies, including pediatric populations, have reported independent associations between NAFLD and markers of subclinical atherosclerosis including impaired flow-mediated vasodilation, increased carotid artery intima-media thickness, and arterial stiffness, after adjusting for cardiovascular risk factors and MetS. Also, it has been shown that NAFLD is associated with cardiac alterations, including abnormal left ventricular structure and impaired diastolic function. The duration of these subclinical abnormalities may be important, because treatment to reverse the process is most likely to be effective earlier in the disease. In the present review, we examine the current evidence on the association between NAFLD and atherosclerosis as well as between NAFLD and cardiac dysfunction in the pediatric population, and discuss briefly the possible biological mechanisms linking NAFLD and cardiovascular changes. We also address the approach to treatment for this increasingly prevalent disease, which is likely to have an important future global impact on the burden of ill health, to prevent not only end-stage liver disease but also cardiovascular disease.

Association of adiponectin with hepatic steatosis: a study of 1,349 subjects in a random population sample

Background

Objective of the present study was to examine the association between adiponectin and hepatic steatosis, and other biochemical and anthropometric parameters in healthy subjects.

Results

A total of 1349 subjects (age 18–65 years) underwent ultrasound examination of the liver. Mean adiponectin concentration for the study collective was 11.35 ± 6.28 μg/mL. The following parameters were assessed for their association with adiponectin: body-mass index (BMI); age; sex; arterial blood pressure; nicotine use; alcohol consumption; physical activity; metabolic syndrome; total, low-density lipoprotein (LDL) and high-density lipoprotein (HDL) cholesterol; triglycerides; aspartate aminotransferase (AST); alanine aminotransferase (ALT); γ-glutamyltransferase (GGT); alkaline phosphatase (AP); C-reactive protein (CRP); insulin sensitivity according to the Homeostasis Model Assessment (HOMA); random blood glucose; and the degree of steatosis of the liver. The numerical differences in the variables influencing adiponectin returned in the descriptive analysis were confirmed at bivariate analysis for BMI, ALT, AST, GGT, AP, total and HDL cholesterol, triglycerides, CRP, arterial blood pressure, metabolic syndrome, nicotine use and alcohol consumption. The logistic regression of the multivariate analysis showed that male sex, hepatic steatosis, BMI, metabolic syndrome, tobacco smoking and CRP correlate negatively with adiponectin, while age, moderate alcohol consumption and HDL cholesterol exhibit a positive association.

Conclusions

The results of the present study confirm the findings of previous research. Adiponectin correlates negatively with cardiometabolic risk factors and is an independent indicator for non-alcoholic fatty liver disease (NAFLD).

PNPLA3 I148M polymorphism is associated with elevated alanine transaminase levels in Mexican Indigenous and Mestizo populations

The patatin like phospholipase domain-containing (PNPLA3) I148M variant is the strongest genetic factor associated with elevated alanine transaminase (ALT) levels in different populations, particularly in Hispanics who have the highest 148M risk allele frequency reported to date. It has been suggested that Indigenous ancestry is associated with higher ALT levels in Mexicans. The aim of the present study was to assess the frequency of the PNPLA3 148M risk allele in Mexican indigenous and Mestizo individuals, and to examine its association with serum ALT levels. The study included a total of 1624 Mexican individuals: 919 Indigenous subjects from five different native groups and 705 Mexican Mestizo individuals (141 cases with ALT levels ≥ 40 U/L and 564 controls with ALT <40 U/L). The I148M polymorphism was genotyped by TaqMan assays. The frequency of elevated ALT levels in Indigenous populations was 18.7%, and varied according to obesity status: 14.4% in normal weight, 19.9% in overweight and 24.5% in obese individuals. The Mexican indigenous populations showed the highest reported frequency of the PNPLA3 148M risk allele (mean 0.73). The M148M genotype was significantly associated with elevated ALT levels in indigenous individuals (OR = 3.15, 95 % CI 1.91-5.20; P = 7.1 × 10(-6)) and this association was confirmed in Mexican Mestizos (OR = 2.24, 95% CI 1.50-3.33; P = 8.1 × 10(-5)). This is the first study reporting the association between M148M genotype and elevated ALT levels in Indigenous Mexican populations. The 148M allele risk may be considered an important risk factor for liver damage in Mexican indigenous and Mestizo populations.

Genetic variants in GCKR and PNPLA3 confer susceptibility to nonalcoholic fatty liver disease in obese individuals

BACKGROUND

A genome-wide association study identified variants in or near patatin-like phospholipase domain-containing-3 (PNPLA3), neurocan (NCAN), lysophospholipase-like 1 (LYPLAL1), glucokinase regulatory protein (GCKR), and protein phosphatase 1 regulatory subunit 3b (PPP1R3B) that were strongly associated with nonalcoholic fatty liver disease (NAFLD) in adults of European ancestry.

OBJECTIVE

We examined these genetic variants in obese children and tested whether their effects on NAFLD are significant in the Taiwanese Han Chinese population.

DESIGN

We genotyped PNPLA3 rs738409, NCAN rs2228603, LYPLAL1 rs12137855, GCKR rs780094, and PPP1R3B rs4240624 in 797 obese children aged 7-18 y. NAFLD was identified by liver ultrasonography. We analyzed the effect of these genetic variants on NAFLD.

RESULTS

NAFLD was identified in 24% of the recruited obese children. We found significant associations with NAFLD at variants in PNPLA3 and GCKR but not in NCAN, LYPLAL1, and PPP1R3B. Multiple logistic regression analysis showed that, after control for the effects of age- and sex-adjusted body mass index, waist-to-hip ratio, sex, and PNPLA3 rs738409 polymorphism, the variant GCKR rs780094 TT genotype independently increased the OR of NAFLD by 1.997 (95% CI: 1.196, 3.335; P = 0.008) compared with the CC genotype. Subjects with the variant GCKR rs780094 TT genotype had a higher mean serum alanine aminotransferase concentration than did those with the CC genotype (30.8 ± 34.7 compared with 22.2 ± 18.6 IU/L; P = 0.01).

CONCLUSIONS

By studying the genetic variants of obese Taiwanese children, we confirmed that the genetic variants in GCKR rs780094 and PNPLA3 rs738409, but not in NCAN rs2228603, LYPLAL1 rs12137855, and PPP1R3B rs4240624, are associated with an increased risk of NAFLD. GCKR and PNPLA3 variants are the common genetic factors that may confer susceptibility to NAFLD in obese individuals across multiple ethnic groups.