Correlates and Heritability of Nonalcoholic Fatty Liver Disease in a Minority Cohort

Nonalcoholic fatty liver disease (NAFLD) is associated with obesity and insulin resistance. The condition disproportionately affects Hispanic Americans. The aims of this study were to examine the risk factors and heritability of NAFLD in 795 Hispanic American and 347 African‐American adults participating in the Insulin Resistance Atherosclerosis Study (IRAS) Family Study. Computed tomography (CT) scans of the abdomen were evaluated centrally for measures of liver–spleen (LS) density ratio and abdominal fat distribution. Other measures included insulin sensitivity (S_I) calculated from a frequently sampled intravenous glucose tolerance test and various laboratory measures. Statistical models which adjust for familial relationships were estimated separately for the two ethnic groups. Heritability was calculated using a variance components approach. The mean age of the cohort was 49 years (range 22–84); 66% were female. NAFLD (LS ratio <1) was more common in Hispanic Americans (24%) than African Americans (10%). NAFLD was independently associated with S_I and visceral adipose tissue (VAT) area in both ethnic groups, although the proportion of explained variance was considerably higher in the Hispanic models. Adiponectin contributed significantly in the African‐American models whereas triglycerides (TGs) and plasminogen activator inhibitor 1 (PAI‐1) contributed only in the Hispanic models. Liver density was modestly heritable in both ethnic groups (h² ～0.35). In summary, the prevalence of NAFLD was twofold greater in Hispanic than African Americans. Certain correlates of NAFLD were similar between the ethnic groups, whereas others were distinct. NAFLD was modestly heritable. These findings suggest that NAFLD may have a differing environmental and/or genetic basis in these ethnic groups.     

Traditional but Not HIV-Related Factors Are Associated with Nonalcoholic Fatty Liver Disease in Asian Patients with HIV-1 Infection

Background

The prevalence and factors associated with nonalcoholic fatty liver disease (NAFLD) are largely unknown in HIV-1 monoinfected patients.

Methods

The present study elucidated the prevalence and factors associated with NAFLD among Asian patients with HIV-1 infection who underwent abdominal ultrasonography between January 2004 and March 2013. Diagnosis of NAFLD was based on the liver to kidney contrast and diffusion in hepatic echogenicity. Uni- and multi-variate logistic regression analyses were applied to estimate factors associated with NAFLD.

Results

435 Asian patients free of chronic hepatitis B or C virus infection and without excessive alcohol intake were analyzed. NAFLD was diagnosed in 135 (31%) patients. Obesity (BMI >30 kg/m²) was evident in 18 (4.1%) patients, and BMI was >25 kg/m² in 103 (24%). Multivariate analysis identified higher BMI (per 1 kg/m² increment, adjusted OR = 1.198; 95% CI, 1.112–1.290; p<0.001), dyslipidemia (adjusted OR = 2.045; 95% CI, 1.183–3.538; p = 0.010), and higher ALT to AST ratio (per 1 increment, adjusted OR = 3.557; 95% CI, 2.129–5.941; p<0.001) as significant factors associated with NAFLD. No HIV-specific variables, including treatment with dideoxynucleoside analogues (didanosine, stavudine, and zalcitabine) and cumulative duration of antiretroviral therapy (ART), were associated with NAFLD.

Conclusions

The incidence of NALFD among Asian patients with HIV-1 infection is similar to that in Western countries. NAFLD was associated with high BMI, dyslipidemia, and high ALT/AST ratio, but not with HIV-related factors. The results highlight the importance of early recognition and management of NAFLD and traditional factors associated with NAFLD for Asian patients with HIV-1 infection.     

MicroRNAs in the Pathogenesis of Nonalcoholic Fatty Liver Disease

Nonalcoholic fatty liver disease (NAFLD), or, more accurately, metabolic associated fatty liver disease, accounts for a large proportion of chronic liver disorders worldwide and is closely associated with other conditions such as cardiovascular disease, obesity, and type 2 diabetes mellitus. NAFLD ranges from simple steatosis to nonalcoholic steatohepatitis (NASH) and can progress to cirrhosis and, eventually, also hepatocellular carcinoma. The morbidity and mortality associated with NAFLD are increasing rapidly year on year. Consequently, there is an urgent need to understand the etiology and pathogenesis of NAFLD and identify effective therapeutic targets. MicroRNAs (miRNAs), important epigenetic factors, have recently been proposed to participate in NAFLD pathogenesis. Here, we review the roles of miRNAs in lipid metabolism, inflammation, apoptosis, fibrosis, hepatic stellate cell activation, insulin resistance, and oxidative stress, key factors that contribute to the occurrence and progression of NAFLD. Additionally, we summarize the role of miRNA-enriched extracellular vesicles in NAFLD. These miRNAs may comprise suitable therapeutic targets for the treatment of this condition.     

非酒精性脂肪性肝病蛋白质组学研究进展

非酒精性脂肪性肝病(nonalcoholic fatty liver disease,NAFLD)是一种常见慢性肝脏疾病,其发病率呈逐年上升趋势,但发病机制尚未明确,诊疗手段仍不完善.蛋白质组学(proteomics)的出现使NAFLD研究有了进一步的发展,相关研究已达21个.目前,蛋白质组学技术可以研究疾病相关的分子改变,从而寻找新的生物标志物和治疗靶标.在此,对蛋白质组学在NAFLD诊断及分期、发病机制和其他相关领域研究进展作一个较为全面的综述.首先,对研究中遇到的研究对象、样本种类、实验方法和标志物特征选择进行经验性总结.其次,除了介绍如何运用蛋白质组学研究病因、危险因素和重要分子在NAFLD发病机制中的作用,还介绍NAFLD发病机制的亚细胞蛋白质组学、修饰蛋白质组学以及蛋白质组学与转录组学相结合的研究实例.此外,对差异蛋白质的分析策略和价值作了重点阐述,收集到一些有望成为NAFLD治疗靶标的候选分子.最后,结合新技术展望研究新空间,以期能够有助于推动蛋白质组学在寻找新的疾病标志物、探索疾病分子机制和治疗靶标中开辟新的途径.     

Association between Serum Growth Hormone Levels and Nonalcoholic Fatty Liver Disease: A Cross-Sectional Study

Growth hormone (GH) is an important regulator of metabolism and body composition. GH deficiency is associated with increased visceral body fat and other features of the metabolic syndrome. Here we performed a cross-sectional study to explore the association of GH levels with nonalcoholic fatty liver disease (NAFLD), which is considered to be the hepatic manifestation of the metabolic syndrome. A total of 1,667 subjects were diagnosed as NAFLD according the diagnostic criteria, and 5,479 subjects were defined as the controls. The subjects with NAFLD had significantly lower levels of serum GH than the controls. Those with low GH levels had a higher prevalence of NAFLD and the metabolic syndrome. A stepwise logistic regression analysis showed that GH levels were significantly associated with the risk factor for NAFLD (OR = 0.651, 95%CI = 0.574–0.738, P<0.001). Our results showed a significant association between lower serum GH levels and NAFLD.     

Carotid Intima-Media Thickness Is Predicted by Combined Eotaxin Levels and Severity of Hepatic Steatosis at Ultrasonography in Obese Patients with Nonalcoholic Fatty Liver Disease

Background

Non-Alcoholic Fatty Liver Disease (NAFLD) is a distinct coronary artery disease (CAD) risk factor. The atherosclerotic process predisposing to CAD includes altered lipid profile and inflammatory processes. The available evidence suggests that increased circulating levels of eotaxin, an eosinophil chemoattractant cytokine implicated in allergic responses, are detected in the serum of patients with CAD. Relationships were sought between serum eotaxin on the one hand, and intima-media thickness—an early predictor of the atherosclerotic process, hepatic steatosis, arterial blood pressure values, as well as inflammation/immune markers and angiogenetic factors—on the other.

Methods

Eighty obese patients with NAFLD, diagnosed at ultrasonography, without evident cytolysis, formed our study population. Anthropometric measures, metabolic profile, serum concentrations of interleukin-1β, C-reactive protein, interleukin-6, fibrinogen, ferritin, TNF-α, spleen size, vascular endothelial growth factor, platelet-derived growth factor-BB and heat shock protein-70 were evaluated.

Results

Serum eotaxin concentrations were distinctly associated with TNF α, IL-6, IL-1β, VEGF and PDGF-BB levels but not with CRP, fibrinogen, heat shock protein-70 or spleen size. Among the metabolic and anthropometric parameters, a significant predictive power emerged when comparing eotaxin to insulin resistance, expressed as HOMA. NAFLD was distinctly associated with HOMA (P = 0.0005). Intima-media thickness was well predicted by both eotaxin levels and severity of NAFLD at ultrasonography, although no relation was detected between these last two variables.

Discussion and Conclusion

A role for insulin resistance in mediating the interplay between eotaxin and other inflammation/immune parameters could be evidenced in the induction/maintenance of atherosclerosis of obese patients with NAFLD.     

非酒精性脂肪性肝病大鼠肝脏PPAR-γ的表达

目的:研究PPAR-Y在非酒精性脂肪性肝病(NAFLD)大鼠肝脏组织中的表达,探讨非酒精脂肪性肝病可能的发病机制.方法:雄性SD大鼠30只,随机分为A(正常组)15只普通饮食,B(高脂组)15只高脂饮食.8周后,自两组各随机抽取2只大鼠处死,光镜观察证实脂肪肝造模成功,继续喂养4周后处死所有大鼠,取血清做免疫生化检查,取肝组织标本,分别以光镜观察做出NAS评分,免疫组化和PCR法检测肝组织PPAR-Y蛋白的表达.结果:1.高脂饮食可以成功的复制NAFLD的大鼠模型;2.血清GLU、TC、TG、HDL-C、LDLC在高脂组表达量较正常组明显升高,差异具有统计学意义(P＜0.05);3.免疫组化显示:高脂组PPAR-Y表达量较正常组升高;结论:1.高脂饮食可成功复制NAFLD模型;2.PPAR-Y在NAFLD大鼠肝脏成脂性改变中具有重要作用.     

非酒精性脂肪性肝病大鼠肝脏PPAR-γ的表达

目的：研究PPAR-γ在非酒精性脂肪性肝病（NAFLD）大鼠肝脏组织中的表达,探讨非酒精脂肪性肝病可能的发病机制。方法：雄性SD大鼠30只,随机分为A（正常组）15只普通饮食,B（高脂组）15只高脂饮食。8周后,自两组各随机抽取2只大鼠处死,光镜观察证实脂肪肝造模成功,继续喂养4周后处死所有大鼠,取血清做免疫生化检查,取肝组织标本,分别以光镜观察做出NAS评分,免疫组化和PCR法检测肝组织PPAR-γ蛋白的表达。结果：1.高脂饮食可以成功的复制NAFLD的大鼠模型;2.血清GLU、TC、TG、HDL-C、LDL-C在高脂组表达量较正常组明显升高,差异具有统计学意义（P〈0.05）;3.免疫组化显示：高脂组PPAR-γ表达量较正常组升高;结论：1.高脂饮食可成功复制NAFLD模型;2.PPAR-γ在NAFLD大鼠肝脏成脂性改变中具有重要作用。     

非酒精性脂肪肝与脂肪性肝炎动物模型研究进展

非酒精性脂肪肝是无酒精滥用的包括单纯性脂肪肝、脂肪性肝炎、脂肪性肝纤维化和肝硬化的肝病综合征,目前已成为广受关注的肝病医学难题。随着抗脂肪肝药物的深入研究,动物模型制作得到很好发展。近年来,在大鼠、沙鼠、小鼠、兔和小猪等动物种属成功地建立了食物、胃肠外营养与蛋氨酸胆碱缺乏等诱导的单纯性脂肪肝和脂肪性肝炎动物模型,这些模型为研究脂肪肝和脂肪性肝炎的发病机理与治疗提供了机会。每种动物模型各有优缺点,合理应用动物模型能更好地开展脂肪肝病的实验和临床研究。本文综述了非酒精性脂肪肝及脂肪性肝炎动物模型制作方法的若干研究进展。     

Increased Soluble Leptin Receptor Levels in Morbidly Obese Patients With Insulin Resistance and Nonalcoholic Fatty Liver Disease

The adipocyte hormone, leptin has been demonstrated to have profibrogenic actions in vitro and in animal models. However, no correlation was found between plasma leptin levels and fibrosis stage in humans. Thus, our aim was to study whether soluble leptin receptor (SLR) or free leptin index (FLI; calculated as the ratio of leptin to SLR), may correlate better with the features of metabolic syndrome and with the histological grade and stage of nonalcoholic fatty liver disease (NAFLD)/nonalcoholic steatohepatitis (NASH). We studied a population (n = 104) of morbidly obese patients undergoing bariatric surgery. Data including BMI, type 2 diabetes mellitus, hypertension, and hyperlipidemia were obtained. Plasma fasting leptin and SLR, fasting glucose and insulin were measured, and homeostasis model of assessment insulin resistance (HOMA_IR) index and FLI were calculated. All patients had intraoperative liver biopsies. Leptin levels correlated with the BMI. The multiple regression analysis indicated that increasing HOMA and decreasing FLI were predictors of steatosis in the liver (P < 0.0003). SLR levels were positively correlated with the presence of diabetes mellitus and the stage of fibrosis. In conclusion, increased SLR levels in morbidly obese patients with diabetes are correlated with the stage of liver fibrosis, and may reflect progressive liver disease.     

A Sequence Variation (I148M) in PNPLA3 Associated with Nonalcoholic Fatty Liver Disease Disrupts Triglyceride Hydrolysis

Obesity and insulin resistance are associated with deposition of triglycerides in tissues other than adipose tissue. Previously, we showed that a missense mutation (I148M) in PNPLA3 (patatin-like phospholipase domain-containing 3 protein) is associated with increased hepatic triglyceride content in humans. Here we examined the effect of the I148M substitution on the enzymatic activity and cellular location of PNPLA3. Structural modeling predicted that the substitution of methionine for isoleucine at residue 148 would restrict access of substrate to the catalytic serine at residue 47. In vitro assays using recombinant PNPLA3 partially purified from Sf9 cells confirmed that the wild type enzyme hydrolyzes emulsified triglyceride and that the I148M substitution abolishes this activity. Expression of PNPLA3-I148M, but not wild type PNPLA3, in cultured hepatocytes or in the livers of mice increased cellular triglyceride content. Cell fractionation studies revealed that ∼90% of wild type PNPLA3 partitioned between membranes and lipid droplets; substitution of isoleucine for methionine at position 148 did not alter the subcellular distribution of the protein. These data are consistent with PNPLA3-I148M promoting triglyceride accumulation by limiting triglyceride hydrolysis.     

Low Vitamin D Status Is Associated with Nonalcoholic Fatty Liver Disease Independent of Visceral Obesity in Korean Adults

Objective

To investigate the association between serum 25-hydroxyvitamin D [25(OH)D] levels and nonalcoholic fatty liver disease (NAFLD) independent of visceral obesity in Koreans and to examine whether the associations differ according to the presence of diabetes or insulin resistance.

Research Design and Methods

A total of 1081 adults were enrolled from a population-based cohort in Ansan city. Serum 25(OH)D concentrations were measured in all subjects. Insulin resistance was measured by homeostasis model assessment of insulin resistance (HOMA-IR). Using computed tomography, NAFLD was diagnosed if the liver attenuation index (LAI, the difference between the mean hepatic and splenic attenuation) was <5 Hounsfield Units.

Results

In subjects with diabetes (n = 282), 25(OH)D levels were negatively associated with waist circumference, fasting insulin, HOMA-IR, triglyceride levels, and visceral abdominal fat, and were positively associated with LAI after adjusting for age, sex, season, exercise, and vitamin supplementation. In subjects without diabetes, only triglyceride level was negatively associated with 25(OH)D. The adjusted odds ratio (OR) for NAFLD increased sequentially across decreasing quartiles of 25(OH)D in subjects with diabetes even after adjusting for visceral fat [Q1 vs. Q4; OR for NAFLD 2.5 (95% CI:1.0–6.2)]. In contrast, no significant difference in OR was observed in subjects without diabetes. When we classified non-diabetic subjects by HOMA-IR, an increase in the OR for NAFLD across decreasing quartiles of 25(OH)D was observed in the high HOMA-IR (≥2.5) group [n = 207, Q1 vs. Q4; OR 3.8(1.4–10.3)], but not in the low HOMA-IR (<2.5) group [n = 592, OR 0.8 (0.3–1.9)].

Conclusions

Low vitamin D status is closely associated with NAFLD, independent of visceral obesity in subjects with diabetes or insulin resistance.     

非酒精性脂肪性肝病的发病机制及治疗进展

近年来,随着人们生活水平的提高,脂肪性肝病的发病率明显上升,且患病年龄趋于低龄化,已经成为严重危害我国人民健康的常见疾病,我国非酒精性脂肪性肝病的发病率明显高于酒精性脂肪性肝病。本文主要对NAFLD的发病机制及相关治疗进展做简要的综述。NAFLD的发病机制与胰岛素抵抗、氧化应激、代谢综合征、脂肪细胞因子的作用、内质网应激、及铁超载等多种因素有关。NAFLD的治疗可以从防治原发病或相关危险因素、基础治疗(行为或生活方式干预;调整饮食;运动疗法)、药物治疗以及手术治疗等方面进行。了解国际上NAFLD的发病机制以及相关治疗进展,对遏制非酒精性脂肪性肝病的发生、发展趋势有着十分重要的意义。     

Chemokine-Like Receptor 1 Deficiency Does Not Affect the Development of Insulin Resistance and Nonalcoholic Fatty Liver Disease in Mice

The adipokine chemerin and its receptor, chemokine-like receptor 1 (Cmklr1), are associated with insulin resistance and nonalcoholic fatty liver disease (NAFLD), which covers a broad spectrum of liver diseases, ranging from simple steatosis to nonalcoholic steatohepatitis (NASH). It is possible that chemerin and/or Cmklr1 exert their effects on these disorders through inflammation, but so far the data have been controversial. To gain further insight into this matter, we studied the effect of whole-body Cmklr1 deficiency on insulin resistance and NAFLD. In view of the primary role of macrophages in hepatic inflammation, we also transplanted bone marrow from Cmklr1 knock-out (Cmklr1^-/-) mice and wild type (WT) mice into low-density lipoprotein receptor knock-out (Ldlr^-/-) mice, a mouse model for NASH. All mice were fed a high fat, high cholesterol diet containing 21% fat from milk butter and 0.2% cholesterol for 12 weeks. Insulin resistance was assessed by an oral glucose tolerance test, an insulin tolerance test, and by measurement of plasma glucose and insulin levels. Liver pathology was determined by measuring hepatic inflammation, fibrosis, lipid accumulation and the NAFLD activity score (NAS). Whole-body Cmklr1 deficiency did not affect body weight gain or food intake. In addition, we observed no differences between WT and Cmklr1^-/- mice for hepatic inflammatory and fibrotic gene expression, immune cell infiltration, lipid accumulation or NAS. In line with this, we detected no differences in insulin resistance. In concordance with whole-body Cmklr1 deficiency, the absence of Cmklr1 in bone marrow-derived cells in Ldlr^-/- mice did not affect their insulin resistance or liver pathology. Our results indicate that Cmklr1 is not involved in the pathogenesis of insulin resistance or NAFLD. Thus, we recommend that the associations reported between Cmklr1 and insulin resistance or NAFLD should be interpreted with caution.     

The Relationship between Nonalcoholic Fatty Liver Disease and Retinopathy in NHANES III

BackgroundNonalcoholic fatty liver disease (NAFLD), an emerging multisystem disease, has the similar pathogenesis with diabetes and is prevalent in diabetes. This study investigated whether NAFLD is associated with retinopathy in individuals with diabetes and without diabetes.MethodsThe association between NAFLD and retinopathy was investigated in 5963 participants aged 40 years and older who participated in the NHANES III, a nationally representative, population-based and cross-sectional study. NAFLD was detected via ultrasonography, and fundus photographs were obtained to grade retinopathy patterns. We performed multivariate logistic regression analysis to investigate the relationship between the presence of retinopathy and NAFLD and diabetes.ResultsAfter adjusting for multiple covariates, NAFLD population had no evidence of retinopathy increase in population without diabetes (odds ratio [OR]: 0.77; 95% confidence interval [CI]: 0.48 to 1.26). In addition, NAFLD in individuals with diabetes was not significantly associated with retinopathy (OR: 0.77; 95% CI: 0.47 to 1.26), independent of age, gender, ethnicity, waist circumference, serum high-density lipoprotein (HDL) cholesterol, serum triglycerides, systolic blood pressure, and glycated hemoglobin.ConclusionsIn the US general population, NAFLD is not a precipitating factor of retinopathy in population with or without diabetes.