Polymorphism in microsomal triglyceride transfer protein: a link between liver disease and atherogenic postprandial lipid profile in NASH?

Berberine prevents NAFLD and HCC by modulating metabolic disorders

Non-alcoholic fatty liver disease (NAFLD) is a global metabolic disease with high prevalence in both adults and children. Importantly, NAFLD is becoming the main cause of hepatocellular carcinoma (HCC). Berberine (BBR), a naturally occurring plant component, has been demonstrated to have advantageous effects on a number of metabolic pathways as well as the ability to kill liver tumor cells by causing cell death and other routes. This permits us to speculate and make assumptions about the value of BBR in the prevention and defense against NAFLD and HCC by a global modulation of metabolic disorders. Herein, we briefly describe the etiology of NAFLD and NAFLD-related HCC, with a particular emphasis on analyzing the potential mechanisms of BBR in the treatment of NAFLD from aspects including increasing insulin sensitivity, controlling the intestinal milieu, and controlling lipid metabolism. We also elucidate the mechanism of BBR in the treatment of HCC. More significantly, we provided a list of clinical studies for BBR in NAFLD. Taking into account our conclusions and perspectives, we can make further progress in the treatment of BBR in NAFLD and NAFLD-related HCC.

Cardiac Hepatopathy: New Perspectives on Old Problems through a Prism of Endogenous Metabolic Regulations by Hepatokines

Cardiac hepatopathy refers to acute or chronic liver damage caused by cardiac dysfunction in the absence of any other possible causative reasons of liver injury. There is a large number of evidence of the fact that cardiac hepatopathy is associated with poor clinical outcomes in patients with acute or actually decompensated heart failure (HF). However, the currently dominated pathophysiological background does not explain a role of metabolic regulative proteins secreted by hepatocytes in progression of HF, including adverse cardiac remodeling, kidney injury, skeletal muscle dysfunction, osteopenia, sarcopenia and cardiac cachexia. The aim of this narrative review was to accumulate knowledge of hepatokines (adropin; fetuin-A, selenoprotein P, fibroblast growth factor-21, and alpha-1-microglobulin) as adaptive regulators of metabolic homeostasis in patients with HF. It is suggested that hepatokines play a crucial, causative role in inter-organ interactions and mediate tissue protective effects counteracting oxidative stress, inflammation, mitochondrial dysfunction, apoptosis and necrosis. The discriminative potencies of hepatokines for HF and damage of target organs in patients with known HF is under on-going scientific discussion and requires more investigations in the future.

Elevated Serum Low-Density Lipoproteins-Cholesterol Levels and B1B2/B2B2 CETP Genotype Are Positively Associated with Nonalcoholic Fatty Liver Disease in Women with Gallstone Disease

Background: Nonalcoholic fatty liver disease (NAFLD) is generated by the interaction between environmental and genetic factors, and the presence of metabolic alterations. Since Taq1B cholesteryl ester transfer protein (CETP) polymorphism is associated with abnormal serum lipid values, it could be related to NAFLD. The aim of this study was to determine the role of the Taq1B CETP polymorphism with serum lipids, anthropometric variables, and the extent of steatosis in Mexican-mestizo women with gallstone disease (GD). Methods: Sixty-two women were enrolled in this cross-sectional study. Serum lipids were determined by dry chemistry. The Taq1B CETP polymorphism was determined by allelic discrimination. CETP serum levels were measured by enzyme-linked immunosorbent assay, and the extent of steatosis with a biopsy staining with Oil-Red-O. Results: Subjects with the B1B2/B2B2 genotype had higher percentage of degree of steatosis than those with B1B1 (11.95% vs. 2.19%, P = 0.008). The B1B2/B2B2 genotype (odds ratio [OR] 3.90 [confidence interval {CI} 95% 1.891-8.536], P = 0.04) and an elevated low-density lipoproteins (LDL)-cholesterol (OR 3.54 [CI 95% 1.042-2.058, P = 0.039) significantly increase the risk for NAFLD. Conclusions: This study provides evidence that the B1B2/B2B2 genotype of CETP and the elevated LDL-cholesterol serum levels increase the risk of NAFLD in women with GD.

Genetic Polymorphisms and Diversity in Nonalcoholic Fatty Liver Disease (NAFLD): A Mini Review

Nonalcoholic fatty liver disease (NAFLD) is a common liver disease with a wide spectrum of liver conditions ranging from hepatic steatosis to nonalcoholic steatohepatitis (NASH), fibrosis, cirrhosis, and hepatocellular carcinoma. The prevalence of NAFLD varies across populations, and different ethnicities have specific risks for the disease. NAFLD is a multi-factorial disease where the genetics, metabolic, and environmental factors interplay and modulate the disease's development and progression. Several genetic polymorphisms have been identified and are associated with the disease risk. This mini-review discussed the NAFLD's genetic polymorphisms and focusing on the differences in the findings between the populations (diversity), including of those reports that did not show any significant association. The challenges of genetic diversity are also summarized. Understanding the genetic contribution of NAFLD will allow for better diagnosis and management explicitly tailored for the various populations.

NAFLD-Related Hepatocarcinoma: The Malignant Side of Metabolic Syndrome

Hepatocellular carcinoma (HCC) is the seventh most common cancer worldwide and the second leading cause of cancer-related mortality. HCC typically arises within a cirrhotic liver, but in about 20% of cases occurs in absence of cirrhosis. Among non-cirrhotic risk factors, non-alcoholic fatty liver disease (NAFLD) currently represents the most important emerging cause of HCC in developed countries. It has been estimated that annual incidence of HCC among patients with non-cirrhotic NAFLD is approximately 0.1-1.3 per 1000 patients/year and ranges from 0.5% to 2.6% among patients with non-alcoholic steatohepatitis (NASH) cirrhosis. However, only a few clinical trials enrolling HCC patients actually distinguished NAFLD/NASH-related cases from other non-cirrhotic causes and therefore evidence is still lacking in this subset of patients. This review aims to describe the biology underpinning NAFLD development, to investigate the main molecular pathways involved in its progression to NASH and HCC and to describe how different pathogenetic mechanisms underlying the onset of HCC can have an impact in clinical practice. We hereby also provide an overview of current HCC treatment options, with a particular focus on the available data on NAFLD-related cases in practice-changing clinical trials.

The association of genetic polymorphisms with nonalcoholic fatty liver disease in a longitudinal study

Background

Several genetic variants are known to be associated with nonalcoholic fatty liver disease (NAFLD). We aimed to evaluate the longitudinal associations between genetic variants and NAFLD.

Methods

We performed a genome-wide association study (GWAS) in Korean individuals who underwent repeated health check-ups. NAFLD was defined by ultrasonography and exclusion of secondary causes.

Results

The subjects had a median age of 50.0 years, and 54.8% were male. The median follow-up duration was 39 months. Among the 3905 subjects without NAFLD at baseline, 874 (22.4%) subjects developed NAFLD, and among the 1818 subjects with NAFLD at baseline, NAFLD regressed in 336 (18.5%) subjects during the follow-up period. After adjusting for age, sex and body mass index, no single-nucleotide polymorphism (SNP) passed Bonferroni correction for genome-wide significance in the development or regression of NAFLD. Among the SNPs that passed the genome-wide suggestiveness threshold (p = 1E-04) in the discovery set in the GWAS, only 1 SNP (rs4906353) showed an association with the development of NAFLD, with marginal significance in the validation set (p-value, discovery set = 9.68E-5 and validation set = 0.00531).

Conclusions

This exploratory study suggests that longitudinal changes in NAFLD are not associated with genetic variants in the Korean population. These findings provide new insight into genetic mechanisms in the pathogenesis of NAFLD.

The association between SNPs rs1800591 and rs3816873 of the MTTP gene and nonalcoholic fatty liver disease: A meta-analysis

BACKGROUND/AIMS

: The role of two polymorphisms rs1800591 and rs3816873 of the microsomal triglyceride transfer protein (MTTP) gene in the development of nonalcoholic fatty liver disease (NAFLD) remains controversial. A meta-analysis was conducted to determine the correlation between these MTTP polymorphisms and NAFLD.

MATERIALS AND METHODS

: A systematic search was carried out using PubMed, Embase, and Cochrane Library to retrieve English studies that reported the relationship between MTTP polymorphisms (rs1800591 and rs3816873) and NAFLD published before February 18, 2020. Odds ratio (OR) and 95% confidence interval (CI) were used to appraise the risk of MTTP polymorphism in NAFLD.

RESULTS

: A total of 10 case-control studies, including 1388 cases and 1690 healthy subjects, were included. No significant correlation between the rs1800591 (G vs. T: OR = 1.08, 95% CI = 0.68-1.70, P = 0.76) and rs3816873 (CT + CC vs. TT: OR = 1.23, 95% CI = 0.76-2.01, P = 0.398) polymorphisms of MTTP and NAFLD was found in any of the models. However, when NASH patients confirmed by liver biopsy were extracted alone for rs1800591 polymorphism analysis, it was found that the G allele significantly increased the risk of NASH under the heterozygote model (GT vs. TT: OR = 3.16, 95% CI = 1.13-8.83, P = 0.028) and dominant model (GT + GG vs. TT: OR = 3.03, 95% CI = 1.13-8.09, P = 0.027).

CONCLUSION

The present meta-analysis revealed that the rs1800591 and rs3816873 polymorphisms of the MTTP gene are uncommon in NAFLD. However, the G allele of rs1800591 was more likely to be correlated to NASH susceptibility.

Quantile-dependent expressivity of postprandial lipemia

Purpose

“Quantile-dependent expressivity” describes an effect of the genotype that depends upon the level of the phenotype (e.g., whether a subject’s triglycerides are high or low relative to its population distribution). Prior analyses suggest that the effect of a genetic risk score (GRS) on fasting plasma triglyceride levels increases with the percentile of the triglyceride distribution. Postprandial lipemia is well suited for testing quantile-dependent expressivity because it exposes each individual’s genotype to substantial increases in their plasma triglyceride concentrations. Ninety-seven published papers were identified that plotted mean triglyceride response vs. time and genotype, which were converted into quantitative data. Separately, for each published graph, standard least-squares regression analysis was used to compare the genotype differences at time t (dependent variable) to average triglyceride concentrations at time t (independent variable) to assess whether the genetic effect size increased in association with higher triglyceride concentrations and whether the phenomenon could explain purported genetic interactions with sex, diet, disease, BMI, and drugs.

Results

Consistent with the phenomenon, genetic effect sizes increased (P≤0.05) with increasing triglyceride concentrations for polymorphisms associated with ABCA1, ANGPTL4, APOA1, APOA2, APOA4, APOA5, APOB, APOC3, APOE, CETP, FABP2, FATP6, GALNT2, GCKR, HL, IL1b, LEPR, LOX-1, LPL, MC4R, MTTP, NPY, SORT1, SULF2, TNFA, TCF7L2, and TM6SF2. The effect size for these polymorphisms showed a progressively increasing dose-response, with intermediate effect sizes at intermediate triglyceride concentrations. Quantile-dependent expressivity provided an alternative interpretation to their interactions with sex, drugs, disease, diet, and age, which have been traditionally ascribed to gene-environment interactions and genetic predictors of drug efficacy (i.e., personalized medicine).

Conclusion

Quantile-dependent expressivity applies to the majority of genetic variants affecting postprandial triglycerides, which may arise because the impaired functionalities of these variants increase at higher triglyceride concentrations. Purported gene-drug interactions may be the manifestations of quantile-dependent expressivity, rather than genetic predictors of drug efficacy.

Obesity genetics and cardiometabolic health: Potential for risk prediction

The increasing burden of obesity worldwide and its effect on cardiovascular disease (CVD) risk is an opportunity for evaluation of preventive approaches. Both obesity and CVD have a genetic background and polymorphisms within genes which enhance expression of variant proteins that influence CVD in obesity. Genome-based prediction may therefore be a feasible strategy, but the identification of genetically driven risk factors for CVD manifesting as clinically recognized phenotypes is a major challenge. Clusters of such risk factors include hyperglycaemia, hypertension, ectopic liver fat, and inflammation. All involve multiple genetic pathways having complex interactions with variable environmental influences. The factors that make significant contributions to CVD risk include altered carbohydrate homeostasis, ectopic deposition of fat in muscle and liver, and inflammation, with contributions from the gut microbiome. A futuristic model depends on harnessing the predictive power of plausible genetic variants, phenotype reversibility, and effective therapeutic choices based on genotype-phenotype interactions. Inverting disease phenotypes into ideal cardiovascular health metrics could improve genetic and epigenetic assessment, and form the basis of a future model for risk detection and early intervention.

Relationship Between Nonalcoholic Fatty Liver Disease Susceptibility Genes and Coronary Artery Disease

Coronary artery disease (CAD) is the principal cause of death in patients with nonalcoholic fatty liver disease (NAFLD). The aim of the present study was to investigate whether NAFLD is causally involved in the pathogenesis of CAD. For this, previously reported NAFLD susceptibility genes were clustered and tested for an association with CAD in the Coronary Artery Disease Genome‐Wide Replication and Meta‐Analysis plus the Coronary Artery Disease Genetics (CARDIoGRAMplusC4D) Consortium data set. The role of plasma lipids as a potential mediator was explored by using data from the Global Lipids Genetics Consortium. Statistical analyses revealed that the combination of 12 NAFLD genes was not associated with CAD in 60,801 CAD cases and 123,504 controls (odds ratio [OR] per NAFLD risk allele, 1.0; 95% confidence interval [CI], 0.99‐1.00). In a subsequent sensitivity analysis, a positive relationship was observed after exclusion of gene variants that are implicated in NAFLD through impaired very low‐density lipoprotein secretion (i.e., microsomal triglyceride transfer protein [MTTP], patatin‐like phospholipase domain containing 3 [PNPLA3], phosphatidylethanolamine N‐methyltransferase [PEMT], and transmembrane 6 superfamily member 2 [TM6SF2]) (OR, 1.01; 95% CI, 1.00‐1.02). Clustering of the excluded genes showed a significant negative relationship with CAD (OR, 0.97; 95% CI, 0.96‐0.99). A substantial proportion of the observed heterogeneity between the individual NAFLD genes in relation to CAD could be explained by plasma lipids, as reflected by a strong relationship between plasma lipids and CAD risk conferred by the NAFLD susceptibility genes (r = 0.76; P = 0.004 for low‐density lipoprotein cholesterol). Conclusion: NAFLD susceptibility genes do not cause CAD per se. The relationship between these genes and CAD appears to depend to a large extent on plasma lipids. These observations strongly suggest taking plasma lipids into account when designing a new drug to target NAFLD.

Genetic Polymorphisms of PNPLA3 and SAMM50 Are Associated with Nonalcoholic Fatty Liver Disease in a Korean Population

Background/Aims

The development of nonalcoholic fatty liver disease (NAFLD) is associated with multiple genetic and environmental factors.

Methods

We performed a genome-wide association study to identify the genetic factors related to NAFLD in a Korean population-based sample of 1,593 subjects with NAFLD and 2,816 controls. We replicated the data in another sample that included 744 NAFLD patients and 1,137 controls. We investigated single-nucleotide polymorphisms (SNPs) that were related to NAFLD.

Results

After adjusting for age, sex and body mass index, rs738409, rs12483959 and rs2281135, located in the PNPLA3 gene, were validated in our population (p<8.56×10⁻⁸) in the same linkage disequilibrium block. Additionally, rs2143571, rs3761472, and rs2073080 in the SAMM50 gene showed significant associations with NAFLD (p<8.56×10⁻⁸). Furthermore, these six SNPs showed significant associations with the severity of fatty liver (all p<2.0×10⁻¹⁰ in the discovery set and p<2.0×10⁻⁶ in the validation set) and NAFLD, with elevated levels of alanine aminotransferase (all p<2.0×10⁻¹⁰ in the discovery set and p<2.0×10⁻⁶ in the validation set).

Conclusions

We demonstrated that the PNPLA3 and SAMM50 genes are significantly associated with the presence and severity of NAFLD in a Korean population. These findings confirm the important roles of genetic factors in the pathogenesis of NAFLD.

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

Background and Aim

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

Methods

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

Results

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

Conclusions

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

Personalized therapy when tackling nonalcoholic fatty liver disease: a focus on sex, genes, and drugs

INTRODUCTION

Nonalcoholic fatty liver disease (NAFLD) is the most frequent liver disease in the world. It describes a term for a group of hepatic diseases including steatosis, fibrosis, and cirrhosis that can finally lead to hepatocellular carcinoma. There are many factors influencing NAFLD initiation and progression, such as obesity, dyslipidemia, insulin resistance, genetic factors, and hormonal changes. However, there is also lean-NAFLD which is not associated with obesity. NAFLD is considered to be a sexually dimorphic disease. In most cases, men have a higher prevalence for the disease compared to premenopausal women. Areas covered: In this review, we first summarize the NAFLD disease epidemiology, pathology, and diagnosis. We describe NAFLD progression with the focus on sexual and genetic differences for disease development and pharmacological treatment. Personalized treatment for multifactorial NAFLD is discussed in consideration of different factors, including genetics, gender and sex. Expert opinion: The livers of female and male NAFLD patients have different metabolic capacities which influence the metabolism of all drugs applied to such patients. This aspect is not yet sufficiently taken into account. The liver computational models might quicken the pace toward assessing personalized disease progression and treatment options.

ACE, APOA5, and MTP Gene Polymorphisms Analysis in Relation to Triglyceride and Insulin Levels in Pediatric Patients

BACKGROUND AND AIMS

Obesity is a complex, chronic, and multifactorial disease that has become a major, and worldwide, public health problem contributing to an increased number of pathologies, including type 2 diabetes, cardiovascular disease, hyperlipidemia, and metabolic syndrome, thus suggesting a commolon origin. A diet high in sugar and fats coupled with a sedentary lifestyle has a major role in the development of obesity. However, the genetic background has also been associated with body fat accumulation. The aim of this study was to assess the effect ofACE-rs4646994, APOA5-rs662799, and MTP-rs1800591 gene polymorphisms on clinical and biochemical parameters and to evaluate the association with body phenotypes in children and adolescent population of Saltillo, Coahuila, Mexico.

METHODS

Anthropometric, clinical, biochemical parameters and BMI were obtained from 405 children and adolescents. The BMI was used to determine the body phenotype. The rs4646994 gene polymorphism was determined by PCR, whereas rs662799 and rs1800591 were determined by PCR-RFLP. The obtained results were analyzed to determine their association of these single nucleotide polymorphisms with body phenotype and biochemical parameters.

RESULTS

TT genotype for APOA5-rs662799 was associated with increased levels of HDL-C in the analyzed population (p <0.05). The ACErs4646994gene polymorphism is associated with high Insulin levels, HOMAIR index, and triglyceride levels, mainly when presenting a I/I genotype (p <0.05).

CONCLUSION

The polymorphic allele of the ACE gene is capable of modulating triglyceride levels, insulin levels and HOMA-IR index in the evaluated population; it must be highlighted that this has not been reported in other studied populations elsewhere.

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.

The Association between Pediatric NAFLD and Common Genetic Variants

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

Development of gene polymorphisms in meditators of nonalcoholic fatty liver disease

Nonalcoholic fatty liver disease (NAFLD) is the most prevalent liver disease worldwide, the morbidity of which closely correlates with diversity of ethnicity, minority, family and location. Its histology spans from simple steatosis, to nonalcoholic steatohepatitis, which ultimately results in fibrosis, cirrhosis and hepatocellular carcinoma. The accelerating prevalence of NAFLD is due to an incremental incidence of metabolic syndrome that is distinguished by dyslipidemia, glucose impairment, obesity, excessive oxidative stress and adipocytokine impairment. Additionally, the pathogenesis of NAFLD is thought to be a multifactorial and complicated disease associated with lifestyle habits, nutritional factors and genetics. However, the pathogenesis and underlying mechanism in the development of NAFLD caused by genetics remains unclear. People have been increasingly emphasizing on the relationship between NAFLD and gene polymorphisms in recent years, with the aim of having a comprehensive elucidation of associated gene polymorphisms influencing the pathogenesis of the disease. In the current article, the authors attempted to critically summarize the most recently identified gene polymorphisms from the facets of glucose metabolism, fatty acid metabolism, oxidative stress and related cytokines in NAFLD that contribute to promoting the progression of the disease.

Insulin Clearance Is Associated with Hepatic Lipase Activity and Lipid and Adiposity Traits in Mexican Americans

Reduction in insulin clearance plays an important role in the compensatory response to insulin resistance. Given the importance of this trait to the pathogenesis of diabetes, a deeper understanding of its regulation is warranted. Our goal was to identify metabolic and cardiovascular traits that are independently associated with metabolic clearance rate of insulin (MCRI). We conducted a cross-sectional analysis of metabolic and cardiovascular traits in 765 participants from the Mexican-American Coronary Artery Disease (MACAD) project who had undergone blood sampling, oral glucose tolerance test, euglycemic-hyperinsulinemic clamp, dual-energy X-ray absorptiometry, and carotid ultrasound. We assessed correlations of MCRI with traits from seven domains, including anthropometry, biomarkers, cardiovascular, glucose homeostasis, lipase activity, lipid profile, and liver function tests. We found inverse independent correlations between MCRI and hepatic lipase (P = 0.0004), insulin secretion (P = 0.0002), alanine aminotransferase (P = 0.0045), total fat mass (P = 0.014), and diabetes (P = 0.03). MCRI and apolipoprotein A-I exhibited a positive independent correlation (P = 0.035). These results generate a hypothesis that lipid and adiposity associated traits related to liver function may play a role in insulin clearance.

Characteristics of non-obese non-alcoholic fatty liver disease: Effect of genetic and environmental factors

AIM

There are a considerable number of patients with non-obese non-alcoholic fatty liver disease (NAFLD). However, the clinical characteristics of non-obese NAFLD is not fully understood. We investigated genetic and other clinical parameters in non-obese and obese NAFLD.

METHODS

The single nucleotide polymorphism rs738409 in the patatin-like phospholipase 3 gene (PNPLA3) was genotyped by the Invader assay in 540 NAFLD patients (134 non-obese and 406 obese) and 1012 control subjects (782 non-obese and 230 obese). All NAFLD patients underwent liver biopsy. Odds ratios were calculated by multiple logistic regression analysis using age, sex, body mass index (BMI), type 2 diabetes mellitus (T2DM) and rs738409 genotype as explanatory variables.

RESULTS

Non-obese NAFLD subjects had a higher rs738409 GG genotype than obese NAFLD. Multiple logistic regression analysis indicated that the odds ratios of T2DM and rs738409 GG genotype for NAFLD were higher in non-obese than in obese groups. In non-obese NAFLD, rs738409 GG genotype was associated with lobular inflammation, hepatocyte ballooning and NAFLD activity score. In obese NAFLD, BMI and T2DM but not rs738409 GG genotype were associated with severity of histology.

CONCLUSION

We demonstrated that the risk factors for the development and progression of NAFLD were different between non-obese and obese patients and that PNPLA3 rs738409 was strongly associated with the development and progression of non-obese NAFLD.

Effect of Octreotide on Hepatic Steatosis in Diet-Induced Obesity in Rats

BACKGROUND

Non-alcoholic fatty liver disease (NAFLD) caused by liver lipid dysregulation is linked to obesity. Somatostatin (SST) and its analogs have been used to treat pediatric hypothalamic obesity. However, the application of such drugs for the treatment of NAFLD has not been evaluated.

OBJECTIVE

This study aimed to investigate the expression levels of important regulators of hepatic lipid metabolism and the possible effect of the SST analog octreotide on these regulators.

METHODS

SD rats were assigned to a control group and a high-fat diet group. Obese rats from the high-fat diet group were further divided into the obese and octreotide-treated groups. The body weight, plasma SST, fasting plasma glucose (FPG), insulin, triglyceride (TG), total cholesterol (TC), low-density lipoprotein cholesterol (LDL-C), high-density lipoprotein cholesterol (HDL-C) and free fatty acid (FFA) levels were measured. Hepatic steatosis was evaluated based on the liver TG content, HE staining and oil red O staining. The SREBP-1c, ACC1, FAS, MTP, apoB and ADRP expression levels in the liver were also determined by RT-PCR, qRT-PCR, western blot or ELISA.

RESULTS

The obese rats induced by high-fat diet expressed more SREBP-1c, FAS and ADRP but less MTP protein in the liver than those of control rats, whereas octreotide intervention reversed these changes and increased the level of apoB protein. Compared to the control group, obese rats showed increased liver ACC1, SREBP-1c and apoB mRNA levels, whereas octreotide-treated rats showed decreased mRNA levels of apoB and SREBP-1c. This was accompanied by increased body weight, liver TG contents, FPG, TG, TC, LDL-C, FFA, insulin and derived homeostatic model assessment (HOMA) values. Octreotide intervention significantly decreased these parameters. Compared to the control group, the obese group showed a decreasing trend on plasma SST levels, which were significantly increased by the octreotide intervention.

CONCLUSION

Octreotide can ameliorate hepatic steatosis in obese rats, possibly by decreasing hepatic lipogenesis and increasing TG export from hepatocytes.

Influence of the rs738409 polymorphism in patatin-like phospholipase 3 on the treatment efficacy of non-alcoholic fatty liver disease with type 2 diabetes mellitus

AIM

A genome-wide association study revealed that the single nucleotide polymorphism (SNP) rs738409 in the patatin-like phospholipase 3 gene (PNPLA3) was strongly associated with non-alcoholic fatty liver disease (NAFLD). Recent pilot studies investigated the effects of dipeptidyl peptidase-4 inhibitors on liver function and glucose metabolism in NAFLD with type 2 diabetes mellitus (DM). We herein evaluated the efficacy of alogliptin in NAFLD patients with type 2 DM as well as the relationship between genotypes at rs738409 in PNPLA3 and treatment efficacy.

METHODS

Forty-one biopsy-proven NAFLD patients with type 2 DM treated with 25 mg/day alogliptin were retrospectively enrolled. SNP rs738409 in PNPLA3 was present in all patients. Clinical data were measured before and after the treatment.

RESULTS

Average hemoglobin A1c (HbA1c) levels mostly remained unchanged. Moreover, significant changes were not noted in the levels of aspartate aminotransferase (AST) and alanine aminotransferase (ALT) during the follow-up period. A positive correlation was observed between improvements in HbA1c (ΔHbA1c) levels and changes in AST (ΔAST) and ALT (ΔALT) levels (r = 0.325 and 0.439, respectively). Patients with the risk allele (G-allele) showed more positive correlation between ΔHbA1c and changes in transaminase. Furthermore, improvements in the levels of total cholesterol, triglycerides and hyaluronic acid were significantly greater in G-allele patients in the weight loss group.

CONCLUSION

The treatment of NAFLD with type 2 DM with alogliptin contributed to the amelioration of NAFLD. Our results suggested that differences in the PNPLA3 risk allele affected the therapeutic effects of this treatment.

Genetic and epigenetic mechanisms of NASH

Along with the obesity epidemic, the prevalence of nonalcoholic fatty liver disease (NAFLD) has increased exponentially. The histological disease spectrum of NAFLD ranges from bland fatty liver (hepatic steatosis), to the concomitant presence of inflammation and ballooning which defines nonalcoholic steatohepatitis (NASH). The latter can progress in a subset to fibrosis, leading ultimately to cirrhosis and hepatocellular carcinoma. The past decade has seen tremendous advances in our understanding of the genetic and epigenetic bases of NAFLD, mainly through the application of high end technology platforms including genome-wide association studies (GWAS). These have helped to define common gene variants (minor allele frequency >5 %) that contribute to the NAFLD phenotype. Looking to the future, these discoveries are expected to lead to improved diagnostics, the personalization of medicine, and a better understanding of the pathophysiological underpinnings that drive the transition from NAFLD to steatohepatitis and fibrosis, leading to the identification of novel therapeutic targets. In this review, we summarize data on the current state of knowledge with regard to the genetic and epigenetic mechanisms for the development of NASH.

The effects of PCB126 on intra-hepatic mechanisms associated with non alcoholic fatty liver disease

Background

Non alcoholic fatty liver disease (NAFLD) results from alteration in lipid synthesis and elimination mechanisms such as very-low density lipoprotein (VLDL) production and de novo lipogenesis. Persistent organic pollutants (POPs) are chemicals that were mostly used historically as pesticides, solvents, flame retardant, and other applications. Among POPs, polychlorinated biphenyls (PCB) have been recognized to be of environmental and potential toxicologic concerns. Specifically, PCB126 could act as endocrine disruptors and has recently been associated with hepatic fat accumulation. The purpose of the study was to investigate the effects of PCB126 on the molecular development of NAFLD using hepatocyte and rat models.

Methods

Hepatocytes were exposed to PCB 126 for 72 h and lipid accumulation in cells was quantified by Oil-Red-O. Rats were injected with a single dose of PCB126 or vehicle. Seven days later, liver triglycerides (TAG) content was measured along with protein quantification of hepatic microsomal triglyceride transfer protein (MTP), sterol regulatory element-binding protein 1c (SREBP1c) and diacylglycerol O-acyltransferase 2 (DGAT-2).

Results

Exposure to PCB126 resulted in significant increases of lipid accumulation in hepatocytes (38 %, P <0.05) and hepatic TAG concentrations (64 %, P <0.001) in rats compared to respective control groups. Rats with fatty livers depicted lower MTP (40 %, P <0.02), higher SREBP1c (27 %, P < 0.05) and DGAT-2 (120 %, P < 0.02) protein content levels compared to Placebo group in rats.

Conclusions

It seems that exposure to PCB126 has an important emerging role in the pathophysiology of NAFLD by 1) altering elimination mechanisms such as VLDL synthesis and secretion, through MTP; and 2) increasing hepatic TAG synthesis mechanisms through DGAT 2 and SREBP1c.

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.

Systematic review of genetic association studies involving histologically confirmed non-alcoholic fatty liver disease

Non-alcoholic fatty liver disease has an increasing prevalence in Western countries, affecting up to 20% of the population.

Blood redox status is associated with the likelihood of nonalcoholic fatty liver disease irrespectively of diet's total antioxidant capacity

It is well established that oxidative stress is implicated in nonalcoholic fatty liver disease pathogenesis, whereas the dietary intake of antioxidants has been reported to be low in patients with the disease. We hypothesized that blood redox status measurements would be associated with nonalcoholic fatty liver disease presence and severity, and that diet's total antioxidant capacity could moderate the aforementioned association. The study sample consisted of 73 patients with nonalcoholic fatty liver disease, of which 58 were matched by age, sex, and body mass index with 58 controls. Diet's total antioxidant capacity was estimated through the ferric-reducing antioxidant power, the total radical-trapping antioxidant parameter, and the Trolox equivalent antioxidant capacity scores, whereas blood redox status was assessed by measuring thiobarbituric acid reactive substances levels, the enzymatic activity of glutathione peroxidase, and serum resistance to oxidation. Diet's total antioxidant capacity scores and glutathione peroxidase activity were not significantly associated with the disease presence or severity. Both thiobarbituric acid reactive substances and serum resistance to oxidation were significantly associated with the likelihood of nonalcoholic fatty liver disease (odds ratios [ORs], 7.769 [P= .007] and 0.936 [P= .033], respectively), independently of abdominal fat level, degree of insulin resistance, blood lipid levels, markers of subclinical inflammation, and diet's total antioxidant capacity, but not with the disease histologic severity or stage. Our results support the association between blood redox status and the likelihood of nonalcoholic fatty liver disease regardless of diet's total antioxidant capacity.

Steatosis in the liver

Accumulation of triacylglycerols within the cytoplasm of hepatocytes to the degree that lipid droplets are visible microscopically is called liver steatosis. Most commonly, it occurs when there is an imbalance between the delivery or synthesis of fatty acids in the liver and their disposal through oxidative pathways or secretion into the blood as a component of triacylglycerols in very low density lipoprotein. This disorder is called nonalcoholic fatty liver disease (NAFLD) in the absence of alcoholic abuse and viral hepatitis, and it is often associated with insulin resistance, obesity and type 2 diabetes. Also, liver steatosis can be induced by many other causes including excessive alcohol consumption, infection with genotype 3 hepatitis C virus and certain medications. Whereas hepatic triacylglycerol accumulation was once considered the ultimate effector of hepatic lipotoxicity, triacylglycerols per se are quite inert and do not induce insulin resistance or cellular injury. Rather, lipotoxic injury in the liver appears to be mediated by the global ongoing fatty acid enrichment in the liver, paralleling the development of insulin resistance. A considerable number of fatty acid metabolites may be responsible for hepatic lipotoxicity and liver injury. Additional key contributors include hepatic cytosolic lipases and the "lipophagy" of lipid droplets, as sources of hepatic fatty acids. The specific origin of the lipids, mainly triacylglycerols, accumulating in liver has been unraveled by recent kinetic studies, and identifying the origin of the accumulated triacylglycerols in the liver of patients with NAFLD may direct the prevention and treatment of this condition.

Polydatin supplementation ameliorates diet-induced development of insulin resistance and hepatic steatosis in rats

The pathophysiology of non-alcoholic fatty liver disease remains to be elucidated, and the currently available treatments are not entirely effective. Polydatin, a stilbenoid compound derived from the rhizome of Polygonum cuspidatum, has previously been demonstrated to possess hepatoprotective effects. The present study aimed to determine the effects of polydatin supplementation on hepatic fat accumulation and injury in rats fed a high-fat diet. In addition, the mechanisms underlying the protective effects of polydatin were examined. Male Sprague Dawley rats were randomly divided into four groups and received one of four treatment regimes for 12 weeks: Control diet, control diet supplemented with polydatin, high-fat diet, or high-fat diet supplemented with polydatin. Polydatin was supplemented in the drinking water at a concentration of 0.3% (wt/vol). The results of the present study showed that long-term high-fat feeding resulted in fatty liver in rats, which was manifested by excessive hepatic neutral fat accumulation and elevated plasma alanine aminotransferase and aspartate aminotransferase levels. Polydatin supplementation alleviated the hepatic pathological changes, and attenuated the insulin resistance, as shown by an improved homeostasis model assessment of basal insulin resistance values and a glucose tolerance test. Polydatin supplementation also corrected abnormal leptin and adiponectin levels. Specifically, polydatin supplementation enhanced insulin sensitivity in the liver, as shown by improved insulin receptor substrate 2 expression levels and Akt phosphorylation in the rat liver, following high-fat diet feeding. The results of the present study suggest that polydatin protects rats against high-fat feeding-induced insulin resistance and hepatic steatosis. Polydatin may be an effective hepatoprotective agent and a potential candidate for the prevention of fatty liver disease and insulin resistance.

Nonalcoholic Fatty liver disease/non-alcoholic steatohepatitis in childhood: endocrine-metabolic "mal-programming"

CONTEXT

Nonalcoholic Fatty Liver Disease (NAFLD) is the major chronic liver disease in the pediatric population. NAFLD includes a broad spectrum of abnormalities (inflammation, fibrosis and cirrhosis), ranging from accumulation of fat (also known as steatosis) towards non-alcoholic steatohepatitis (NASH). The development of NAFLD in children is significantly increased.

EVIDENCE ACQUISITION

A literature search of electronic databases was undertaken for the major studies published from 1998 to today. The databases searched were: PubMed, EMBASE, Orphanet, Midline and Cochrane Library. We used the key words: "non-alcoholic fatty liver disease, children, non-alcoholic steatohepatitis and fatty liver".

RESULTS

NAFLD/NASH is probably promoted by "multiple parallel hits": environmental and genetic factors, systemic immunological disorders (oxidative stress, persistent-low grade of inflammation) as well as obesity and metabolic alterations (insulin resistance and metabolic syndrome). However its exact cause still underdiagnosed and unknown.

CONCLUSIONS

Pediatric NAFLD/NASH is emerging problem. Longitudinal follow-up studies, unfortunately still insufficient, are needed to better understand the natural history and outcome of NAFLD in children. This review focuses on the current knowledge regarding the epidemiology, pathogenesis, environmental, genetic and metabolic factors of disease. The review also highlights the importance of studying the underlying mechanisms of pediatric NAFLD and the need for complete and personalized approach in the management of NAFLD/NASH.

MTP -493G>T polymorphism and susceptibility to nonalcoholic fatty liver disease: a meta-analysis

Microsomal transfer protein (MTP), a lipid transfer protein localized in the endoplasmic reticulum of hepatocytes and enterocytes, plays an important role in the development of nonalcoholic fatty liver disease (NAFLD). Many existing studies have demonstrated that a common polymorphism (-493G>T, rs1800591 G>T) in the MTP gene may be implicated in the development and progression of NAFLD, but individually published results are inconclusive. This meta-analysis aimed to investigate whether MTP -493G>T polymorphism may be a potential risk factor for NAFLD. We searched CISCOM, CINAHL, Web of Science, PubMed, Google Scholar, EBSCO, Cochrane Library, and CBM databases from inception through October 1, 2013. Meta-analysis was performed using the STATA 12.0 software. Eleven clinical case-control studies with a total of 636 NAFLD cases and 918 healthy controls met the inclusion criteria. Our meta-analysis results revealed that MTP -493G>T polymorphism was strongly correlated with an increased risk of NAFLD. Subgroup analysis by ethnicity suggested that MTP -493G>T polymorphism might increase individuals' susceptibility to NAFLD among both Caucasian and non-Caucasian populations. No publication bias was observed in this meta-analysis. In short, the present meta-analysis indicates that MTP -493G>T polymorphisms may contribute to individuals' susceptibility to NAFLD. Thus, MTP -493G>T polymorphism may be a valuable and practical biomarker for early detection of NAFLD.

Genetic predisposition in NAFLD and NASH: impact on severity of liver disease and response to treatment

Liver fat deposition related to systemic insulin resistance defines non-alcoholic fatty liver disease (NAFLD) which, when associated with oxidative hepatocellular damage, inflammation, and activation of fibrogenesis, i.e. non-alcoholic steatohepatitis (NASH), can progress towards cirrhosis and hepatocellular carcinoma. Due to the epidemic of obesity, NAFLD is now the most frequent liver disease and the leading cause of altered liver enzymes in Western countries. Epidemiological, familial, and twin studies provide evidence for an element of heritability of NAFLD. Genetic modifiers of disease severity and progression have been identified through genome-wide association studies. These include the Patatin-like phosholipase domain-containing 3 (PNPLA3) gene variant I148M as a major determinant of inter-individual and ethnicity-related differences in hepatic fat content independent of insulin resistance and serum lipid concentration. Association studies confirm that the I148M polymorphism is also a strong modifier of NASH and progressive hepatic injury. Furthermore, a few large multicentre case-control studies have demonstrated a role for genetic variants implicated in insulin signalling, oxidative stress, and fibrogenesis in the progression of NAFLD towards fibrosing NASH, and confirm that hepatocellular fat accumulation and insulin resistance are key operative mechanisms closely involved in the progression of liver damage. It is now important to explore the molecular mechanisms underlying these associations between gene variants and progressive liver disease, and to evaluate their impact on the response to available therapies. It is hoped that this knowledge will offer further insights into pathogenesis, suggest novel therapeutic targets, and could help guide physicians towards individualised therapy that improves clinical outcome.

Host genetic variants in obesity-related nonalcoholic fatty liver disease

Nonalcoholic fatty liver disease (NAFLD) is a complex disease. The considerable variability in the natural history of the disease suggests an important role for genetic variants in the disease development and progression. There is evidence based on genome-wide association studies and/or candidate gene studies that genetic polymorphisms underlying insulin signaling, lipid metabolism, oxidative stress, fibrogenesis, and inflammation can predispose individuals to NAFLD. This review highlights some of the genetic variants in NAFLD.

MTTP polymorphisms and susceptibility to non-alcoholic fatty liver disease in a Han Chinese population

BACKGROUND

The microsomal triglyceride transfer protein (MTP) is required for the assembly and secretion of apolipoprotein B (ApoB)-containing lipoproteins from the liver and intestine. Previous studies showed that functional polymorphisms in the MTTP gene correspond to lower LDL levels and protect against other traits of the metabolic syndrome.

AIMS

Here, we aimed to investigate whether MTTP single nucleotide polymorphisms (SNPs) and their predicted haplotypes of linkage disequilibrium blocks contribute to non-alcoholic fatty liver disease (NAFLD) susceptibility in a Han Chinese population.

METHODS

Seven tag SNPs in the MTTP gene were selected and genotyped in a frequency-matched case-control study in a population from Fuzhou City, China. We enrolled 580 patients with NAFLD and 580 healthy controls.

RESULTS

In the multivariate logistic regression analysis, the rs1800804 (-164 T/C) was associated with an increased risk of NAFLD, while the rs1057613 A/G and rs3805335 C/T SNPs were associated with a decreased risk of NAFLD. The cumulative effect of the rs1800804 (-164 T/C), rs1057613 and rs3805335 was estimated, and a significant increased trend in the risk of NAFLD with increasing genetic risk score was observed (adjusted P(trend) = 0.014). Furthermore, the results of haplotype analysis suggested that the haplotype GC in block 1 containing the -164 C allele was associated with an increased risk of NAFLD, while haplotype TGTTC in block 2 was associated with a decreased risk of NAFLD.

CONCLUSIONS

Our data show that MTTP genetic polymorphisms influence the susceptibility to developing NAFLD independently or jointly in the Han Chinese population.

Novel effect of ezetimibe to inhibit the development of non-alcoholic fatty liver disease in Fatty Liver Shionogi mouse

AIM

Several studies using experimental non-alcoholic fatty liver disease (NAFLD) models have shown that ezetimibe, an inhibitor of cholesterol absorption mainly in the intestine, not only protects against diet-induced hyperlipidemia, but also attenuates liver steatosis. The aim of this study was to clarify whether ezetimibe inhibits the development of NAFLD and to elaborate the mechanism of ezetimibe to inhibit the development of NAFLD using Fatty Liver Shionogi (FLS) mice, a spontaneous model of NAFLD/non-alcoholic steatohepatitis.

METHODS

Male FLS mice at 20 weeks of age were divided into two groups (n = 7 in each group). Mice fed a normal laboratory chow, CRF-1 or CRF-1 containing 0.005% w/w ezetimibe (7 mg/kg per day) for 4 weeks. After 4-week treatment with ezetimibe, the livers of each group of mice were subjected to histological as well as molecular evaluation.

RESULTS

Ezetimibe administration for 4 weeks was associated with improvement of steatosis and fibrosis of the liver in normal diet-fed FLS mice. Ezetimibe reduced hepatic reactive oxygen species generation and prevented ubiquitination and protein degradation of microsomal triglyceride transfer protein (MTP), a key molecule for very low-density lipoprotein assembly and export, via downregulation of the protein expression of Skp2 and CDC20.

CONCLUSION

Ezetimibe not only reduced lipid synthesis in the liver, but also promoted lipid discharge from the liver by preventing post-translational degradation of MTP via a reduction of hepatic reactive oxygen species generation, leading to inhibition of the development of NAFLD.

An integrated view of liver injury and disease progression in nonalcoholic steatohepatitis

Nonalcoholic fatty liver disease (NAFLD) is rapidly becoming the most common cause of chronic liver disease globally. NAFLD represents a host of pathophysiologic mechanisms that culminate in the accumulation of fat, in a predominantly macrovesicular pattern, in the liver along with varying degrees of inflammation, hepatocellular injury, apoptosis and fibrosis. The most common mechanism for the development of NAFLD is insulin resistance. Insulin resistance is commonly associated with obesity, although it can develop in individuals who do not have obesity. A consequence of insulin resistance is increased peripheral lipolysis and increased delivery of free fatty acids to the liver. The concept of lipotoxicity emerged as the mechanisms by which fatty acids produce cell injury, promote apoptosis and activate inflammatory pathways were elucidated. While much work has been done mainly in cell culture models, the free fatty acid concentration in the liver is not significantly changed in NAFLD. Recently, the focus has shifted to alterations in other lipid metabolic pathways that appear to play an important role in the genesis of nonalcoholic steatohepatitis, the aggressive form of NAFLD. The innate immune system and the intestinal microbiota have been implicated in the development of NAFLD. These mechanisms are reviewed in this article.

Association between resistin +299A/A genotype and nonalcoholic fatty liver disease in Chinese patients with type 2 diabetes mellitus

OBJECTIVE

To investigate the relationship between the resistin intronic +299G/A polymorphism and nonalcoholic fatty liver disease (NAFLD) in patients with type 2 diabetes mellitus (T2DM).

METHODS

We selected 738 T2DM patients, including 395 with NAFLD and 343 without fatty liver disease, as well as 279 healthy control individuals, and analyzed their resistin +299G/A polymorphism genotype by polymerase chain reaction-restriction fragment length polymorphism.

RESULTS

Plasma resistin levels in T2DM patients with NAFLD were at the highest (P<0.05). The frequency of AA genotype at the +299 site of the resistin gene in patients with concurrent T2DM combined with NAFLD was significantly different from that in the control (P<0.05). The AA genotype was found to be associated with a 1.80-fold increased risk for T2DM combined with NAFLD, 2.05-fold increased risk for obesity and 2.37-fold increased risk for obesity of abdominal type compared to the GG (P<0.05, respectively). The multivariate non-conditional logistic regression model analysis further shows that the AA genotype is a risk factor for the development of NAFLD in T2DM patients (OR, 2.32; 95% CI, 1.05-4.68; P<0.05).

CONCLUSION

The resistin +299AA genotype may be associated with increases in the risk of the NAFLD development in T2DM patients.

Genomic aspects of NAFLD pathogenesis

Non-alcoholic fatty liver disease (NAFLD) is the most predominant liver disease worldwide and hepatic manifestation of the metabolic syndrome. Its histology spectrum ranges from steatosis, to steatohepatitis (NASH) that can further progress to cirrhosis and hepatocellular carcinoma (HCC). The increasing incidence of NAFLD has contributed to rising numbers of HCC occurrences. NAFLD progression is governed by genetic susceptibility, environmental factors, lifestyle and features of the metabolic syndrome, many of which overlap with HCC. Gene expression profiling and genome wide association studies have identified novel disease pathways and polymorphisms in genes that may be potential biomarkers of NAFLD progression. However, the multifactorial nature of NAFLD and the limited number of sufficiently powered studies are among the current limitations for validated biomarkers of clinical utility. Further studies incorporating the links between circadian regulation and hepatic metabolism might represent an additional direction in the search for predictive biomarkers of liver disease progression and treatment outcomes.

An improved mouse model that rapidly develops fibrosis in non-alcoholic steatohepatitis

Non-alcoholic steatohepatitis (NASH) is a progressive fibrotic disease, the pathogenesis of which has not been fully elucidated. One of the most common models used in NASH research is a nutritional model where NASH is induced by feeding a diet deficient in both methionine and choline. However, the dietary methionine-/choline-deficient model in mice can cause severe weight loss and liver atrophy, which are not characteristics of NASH seen in human patients. Exclusive, long-term feeding with a high-fat diet (HFD) produced fatty liver and obesity in mice, but the HFD for several months did not affect fibrosis. We aimed to establish a mouse model of NASH with fibrosis by optimizing the methionine content in the HFD. Male mice were fed a choline-deficient, L-amino acid-defined, high-fat diet (CDAHFD) consisting of 60 kcal% fat and 0.1% methionine by weight. After 1–14 weeks of being fed CDAHFD, the mice were killed. C57BL/6J mice maintained or gained weight when fed CDAHFD, while A/J mice showed a steady decline in body weight (of up to 20% of initial weight). In both strains of mice, plasma levels of alanine aminotransferase increased from week 1, when hepatic steatosis was also observed. By week 6, C57BL/6J mice had developed enlarged fatty liver with fibrosis as assessed by Masson's trichrome staining and by hydroxyproline assay. Therefore, this improved CDAHFD model may be a mouse model of rapidly progressive liver fibrosis and be potentially useful for better understanding human NASH disease and in the development of efficient therapies for this condition.

Genetic determinants of cardiometabolic risk: a proposed model for phenotype association and interaction

This review provides a translational and unifying summary of metabolic syndrome genetics and highlights evidence that genetic studies are starting to unravel and untangle origins of the complex and challenging cluster of disease phenotypes. The associated genes effectively express in the brain, liver, kidney, arterial endothelium, adipocytes, myocytes, and β cells. Progression of syndrome traits has been associated with ectopic lipid accumulation in the arterial wall, visceral adipocytes, myocytes, and liver. Thus, it follows that the genetics of dyslipidemia, obesity, and nonalcoholic fatty liver disease are central in triggering progression of the syndrome to overt expression of disease traits and have become a key focus of interest for early detection and for designing prevention and treatments. To support the "birds' eye view" approach, we provide a road-map depicting commonality and interrelationships between the traits and their genetic and environmental determinants based on known risk factors, metabolic pathways, pharmacologic targets, treatment responses, gene networks, pleiotropy, and association with circadian rhythm. Although only a small portion of the known heritability is accounted for and there is insufficient support for clinical application of gene-based prediction models, there is direction and encouraging progress in a rapidly moving field that is beginning to show clinical relevance.

Lipoprotein metabolism in nonalcoholic fatty liver disease

Nonalcoholic fatty liver disease (NAFLD), an escalating health problem worldwide, covers a spectrum of pathologies characterized by fatty accumulation in hepatocytes in early stages, with potential progression to liver inflammation, fibrosis, and failure. A close, yet poorly understood link exists between NAFLD and dyslipidemia, a constellation of abnormalities in plasma lipoproteins including triglyceride-rich very low density lipoproteins. Apolipoproteins are a group of primarily liver-derived proteins found in serum lipoproteins; they not only play an extracellular role in lipid transport between vital organs through circulation, but also play an important intracellular role in hepatic lipoprotein assembly and secretion. The liver functions as the central hub for lipoprotein metabolism, as it dictates lipoprotein production and to a significant extent modulates lipoprotein clearance. Lipoprotein metabolism is an integral component of hepatocellular lipid homeostasis and is implicated in the pathogenesis, potential diagnosis, and treatment of NAFLD.

Non-alcoholic fatty liver disease and cardiovascular risk

The term "Non-alcoholic fatty liver disease" (NAFLD) covers a series of liver lesions similar to those induced by alcohol, but not caused by alcohol use. The importance of NAFLD lies in the high prevalence in Western societies and, from the point of view of the liver, in its progression from steatosis to cirrhosis and liver cancer. More recently, NAFLD has been found to be associated with lipid metabolism disorders, the deposition of fat outside of the adipocytes, insulin resistance and Metabolic Syndrome. Also attributed to NAFLD is a heightened systemic pro-inflammatory state, which accelerates arteriosclerosis, thereby increasing cardiovascular risk and associated cardiovascular events. Here we provide an update to the etiopathogenesis of NAFLD, its influence on cardiovascular disease, and the treatment options.

Apolipoprotein A-I modulates processes associated with diet-induced nonalcoholic fatty liver disease in mice

Apolipoprotein A-I (apoA-I) is the main protein of high-density lipoprotein (HDL). We investigated the involvement of apoA-I in diet-induced accumulation of triglycerides in hepatocytes and its potential role in the treatment of nonalcoholic fatty liver disease (NAFLD). ApoA-I-deficient (apoA-I(-/-)) mice showed increased diet-induced hepatic triglyceride deposition and disturbed hepatic histology while they exhibited reduced glucose tolerance and insulin sensitivity. Quantification of FASN (fatty acid synthase) [corrected], DGAT-1 (diacylglycerol O-acyltransferase 1), and PPARγ (peroxisome proliferator-activated receptor γ) mRNA expression suggested that the increased hepatic triglyceride content of the apoA-I(-/-) mice was not due to de novo synthesis of triglycerides. Similarly, metabolic profiling did not reveal differences in the energy expenditure between the two mouse groups. However, apoA-I(-/-) mice exhibited enhanced intestinal absorption of dietary triglycerides (3.6 ± 0.5 mg/dL/min for apoA-I(-/-) versus 2.0 ± 0.7 mg/dL/min for C57BL/6 mice, P < 0.05), accelerated clearance of postprandial triglycerides and a reduced rate of hepatic very low density lipoprotein (VLDL) triglyceride secretion (9.8 ± 1.1 mg/dL/min for apoA-I(-/-) versus 12.5 ± 1.3 mg/dL/min for C57BL/6 mice, P < 0.05). In agreement with these findings, adenovirus-mediated gene transfer of apoA-I(Milano) in apoA-I(-/-) mice fed a Western-type diet for 12 wks resulted in a significant reduction in hepatic triglyceride content and an improvement of hepatic histology and architecture. Our data extend the current knowledge on the functions of apoA-I, indicating that in addition to its well-established properties in atheroprotection, it is also an important modulator of processes associated with diet-induced hepatic lipid deposition and NAFLD development in mice. Our findings raise the interesting possibility that expression of therapeutic forms of apoA-I by gene therapy approaches may have a beneficial effect on NAFLD.

Cholesteryl ester transfer protein gene polymorphisms increase the risk of fatty liver in females independent of adiposity

BACKGROUND AND AIM

Environmental factors including excessive caloric intake lead to disordered lipid metabolism and fatty liver disease (FLD). However, FLD demonstrates heritability suggesting genetic factors are also important. We aimed to use a candidate gene approach to examine the association between FLD and single nucleotide polymorphisms (SNPs) in lipid metabolism genes in the adolescent population-based Western Australian Pregnancy (Raine) Cohort.

METHODS

A total 951 seventeen year-olds underwent hepatic ultrasound, anthropometric and biochemical characterization, DNA extraction and genotyping for 57 SNPs in seven lipid metabolism genes (ApoB100, ATGL, ABHD5, MTTP, CETP, SREBP-1c, PPARα). Associations were adjusted for metabolic factors and Bonferroni corrected.

RESULTS

The prevalence of FLD was 16.2% (11.4% male vs 21.2% female, P=0.001). Multivariate analysis of metabolic factors found suprailiac skinfold thickness (SST) to be the major predictor of FLD in females and males (odds ratio [OR] 1.11, 95% confidence interval [CI] 1.08-1.15, P=1.7×10(-10) and OR 1.17, 95%CI 1.13-1.22, P=2.4×10(-11) , respectively). In females, two SNPs in linkage disequilibrium from the CETP gene were associated with FLD: rs12447924 (OR 2.16, 95%CI 1.42-3.32, P=0.0003) and rs12597002 (OR=2.22, 95%CI 1.46-3.41 P=0.0002). In lean homozygotes, the probability of FLD was over 30%, compared with 10-15% in lean heterozygotes and 3-5% in lean wild-types. However, these associations were modified by SST, such that for obese individuals, the probability of FLD was over 30% in all genotype groups.

CONCLUSIONS

Cholesteryl ester transfer protein gene polymorphisms are associated with an increased risk of FLD in adolescent females. The effect is independent of adiposity in homozygotes, thereby placing lean individuals at a significant risk of FLD.

Genetic variation in the peroxisome proliferator activated receptor-gamma gene is associated with histologically advanced NAFLD

BACKGROUND

The peroxisome proliferator activated receptor-gamma (PPARG) is a nuclear receptor that regulates adipocyte differentiation, insulin sensitivity and lipid metabolism, thus, it represents a good candidate gene for non-alcoholic fatty liver disease (NAFLD).

PURPOSE AND METHOD

We investigated the association of two PPARG variants (Pro12Ala and C1431T) with NAFLD and its histological features. DNA was extracted from 274 archived, formalin-fixed liver biopsy specimens from 212 patients with NAFLD and 62 controls with normal liver histology.

RESULTS

Individual SNPs did not show significant association with NAFLD or its histological features. A haplotype comprised of both minor alleles (GT) was less enriched whereas a haplotype comprised of the two major alleles (CC) was more enriched in subjects with NAFLD compared to controls [9.3% vs. 28.1% for GT (P = 0.001, OR 0.26 (range 0.14-0.48) and 80.4% vs. 64.8% for CC (P = 0.037, OR 2.23 (range 1.30-3.81)]. Both haplotypes were significantly associated with steatosis and fibrosis. The GT haplotype was also associated with lobular inflammation.

CONCLUSIONS

Genetic variation in PPARG is associated with NAFLD, and the GT haplotype is associated with inflammatory and fibrotic changes that denote histologically advanced NAFLD.

MTP -493G/T gene polymorphism is associated with steatosis in hepatitis C-infected patients

The reduction of hepatic microsomal transfer protein (MTP) activity results in fatty liver, worsening hepatic steatosis and fibrosis in chronic hepatitis C (CHC). The G allele of the MTP gene promoter, -493G/T, has been associated with lower transcriptional activity than the T allele. We investigated this association with metabolic and histological variables in patients with CHC. A total of 174 untreated patients with CHC were genotyped for MTP -493G/T by direct sequencing using PCR. All patients were negative for markers of Wilson's disease, hemochromatosis and autoimmune diseases and had current and past daily alcohol intake lower than 100 g/week. The sample distribution was in Hardy-Weinberg equilibrium. Among subjects with genotype 1, 56.8% of the patients with fibrosis grade 3+4 presented at least one G allele versus 34.3% of the patients with fibrosis grade 1+2 (OR = 1.8; 95%CI = 1.3-2.3). Logistic regression analysis with steatosis as the dependent variable identified genotypes GG+GT as independent protective factors against steatosis (OR = 0.4, 95%CI = 0.2-0.8; P = 0.01). The results suggest that the presence of the G allele of MTP -493G/T associated with lower hepatic MTP expression protects against steatosis in our CHC patients.