Our objective was to estimate the strength of the effect of the I148M (rs738409 C/G) patatin-like phospholipase domain containing 3 (PNPLA3) variant on nonalcoholic fatty liver (NAFLD) and disease severity across different populations. We performed a systematic review by a meta-analysis; literature searches identified 16 studies. Our results showed that rs738409 exerted a strong influence not only on liver fat accumulation (GG homozygous showed 73% higher lipid fat content when compared with CC ones, data from 2,937 subjects; P < 1 3 10 29 ), but also on the susceptibility of a more aggressive disease (GG homozygous had 3.24-fold greater risk of higher necroinflammatory scores and 3.2-fold greater risk of developing fibrosis when compared with CC homozygous; P < 1 3 10 29 ; data from 1,739 and 2,251 individuals, respectively). Nonalcoholic steatohepatitis (NASH) was more frequently observed in GG than CC homozygous (odds ratio [OR] 3.488, 95% confidence interval [CI] 1.859-6.545, random model; P < 2 3 10 24 ; data from 2,124 patients). Evaluation of the risk associated with heterozygosity for the variant suggests that the additive genetic model best explains the effect of rs738409 on the susceptibility to develop NAFLD. Nevertheless, carrying two G alleles does not seem to increase the risk of severe histological features. Meta-regression showed a negative correlation between male sex and the effect of rs738409 on liver fat content (slope: 22.45 6 1.04; P < 0.02). The rs738409 GG genotype versus the CC genotype was associated with a 28% increase in serum alanine aminotransferase levels. Conclusion: By summarizing the amount of evidence, this study provided unequivocal evidence of rs738409 as a strong modifier of the natural history of NAFLD in different populations around the world.

Objectives We used a screening strategy of global serum microRNA (miRNA) profiling, followed by a second stage of independent replication and exploration of liver expression of selected miRNAs to study: (1) the circulating miRNA signature associated with non-alcoholic fatty liver disease (NAFLD) progression and predictive power, (2) the role of miRNAs in disease biology and (3) the association between circulating miRNAs and features of the metabolic syndrome. Methods The study used a case-control design and included patients with NAFLD proven through biopsy and healthy controls. Results Among 84 circulating miRNAs analysed, miR-122, miR-192, miR-19a and miR-19b, miR-125b, and miR-375 were upregulated >2-fold (p<0.05) either in simple steatosis (SS) or non-alcoholic steatohepatitis (NASH). The most dramatic and significant fold changes were observed in the serum levels of miR-122 (7.2-fold change in NASH vs controls and 3.1-fold change in NASH vs SS) and miR-192 (4.4-fold change in NASH vs controls); these results were replicated in the validation set. The majority of serum miR-122 circulate in argonaute2-free forms. Circulating miR-19a/b and miR-125b were correlated with biomarkers of atherosclerosis. Liver miR-122 expression was 10-fold (p<0.03) downregulated in NASH compared with SS and was preferentially expressed at the edge of lipid-laden hepatocytes. In vitro exploration showed that overexpression of miR-122 enhances alanine aminotransferase activity. Conclusions miR-122 plays a role of physiological significance in the biology of NAFLD; circulating miRNAs mirror the histological and molecular events occurring in the liver. NAFLD has a distinguishing circulating miRNA profile associated with a global dysmetabolic disease state and cardiovascular risk.

No abstract

Hepatic methylation and transcriptional activity of the MT-ND6 are associated with the histological severity of NAFLD. Epigenetic changes of mtDNA are potentially reversible by interventional programs, as physical activity could modulate the methylation status of MT-ND6.

Insulin resistance (IR) and mitochondrial dysfunction play a central role in the pathophysiology of nonalcoholic fatty liver disease (NAFLD). We hypothesized that genetic factors and epigenetic modifications occurring in the liver contribute to the IR phenotype. We specifically examined whether fatty liver and IR are modified by hepatic DNA methylation of the peroxisome proliferator-activated receptor c coactivator 1a (PPARGC1A) and mitochondrial transcription factor A (TFAM) promoters, and also evaluated whether liver mitochondrial DNA (mtDNA) content is associated with NAFLD and IR. We studied liver biopsies obtained from NAFLD patients in a case-control design. After bisulfite treatment of DNA, we used methylation-specific polymerase chain reaction (PCR) to assess the putative methylation of three CpG in the PPARGC1A and TFAM promoters. Liver mtDNA quantification using nuclear DNA (nDNA) as a reference was evaluated by way of realtime PCR. Liver PPARGC1A methylated DNA/unmethylated DNA ratio correlated with plasma fasting insulin levels and homeostasis model assessment of insulin resistance (HOMA-IR); TFAM methylated DNA/unmethylated DNA ratio was inversely correlated with insulin levels. PPARGC1A promoter methylation was inversely correlated with the abundance of liver PPARGC1A messenger RNA. The liver mtDNA/nDNA ratio was significantly higher in control livers compared with NAFLD livers. mtDNA/nDNA ratio was inversely correlated with HOMA-IR, fasting glucose, and insulin and was inversely correlated with PPARGC1A promoter methylation. Conclusion: Our data suggest that the IR phenotype and the liver transcriptional activity of PPARGC1A show a tight interaction, probably through epigenetic modifications. Decreased liver mtDNA content concomitantly contributes to peripheral IR.

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We explored the role of transmembrane 6 superfamily member 2 (TM6SF2) rs58542926 C/T nonsynonymous (p.Glu167Lys) variant in genetic susceptibility to nonalcoholic fatty liver disease (NAFLD) and disease severity. A total of 361 individuals (135 control subjects and 226 patients with histologically proven NAFLD) were included in a sample with 97% power for the additive genetic model. A discrete trait analysis of NAFLD showed that rs58542926 was associated with a modest risk of fatty liver (P 5 0.038; odds ratio [OR]: 1.37; 95% confidence interval [CI]: 1.02-1.84); nevertheless, conditioning on patatin-like phospholipase domain-containing 3 (PNPLA3)-rs738409 abolished this effect. We did not observe an interaction between rs738409 and rs58542926 variants on the risk of NAFLD. We observed a significant association of rs58542926 and disease severity (P 5 0.027), but not lobular inflammation or fibrosis; rs58542926 was not associated with levels of liver enzymes. An allelic test showed that the T (Lys167) allele was significantly associated with disease progression (P 5 0.021; OR, 1.66; 95% CI: 1.08-2.55). A significant association was found with the histological degree of liver steatosis (b, 0.15; standard error: 0.06; P 5 0.0299) that was independent of rs738409. Homozygous carriers of the C (Glu167) allele showed increased risk for cardiovascular disease. TM6SF2 protein expression was decreased markedly in liver of NAFLD patients, compared to controls. In addition, TM6SF2 immunoreactivity was reduced in subjects carrying at least one copy of the T allele, consistent with a difference in liver allele-specific transcript abundance. Conclusion: rs58542926 is a low-frequency variant with a modest effect on NAFLD, suggesting that carriers of the T allele are slightly more likely to accumulate fat in the liver and develop nonalcoholic steatohepatitis than those without. TM6SF2 appears to play a significant role in disease biology. (HEPATOLOGY 2015;61:515-525)

Abstract. Sookoian S, Gemma C, Fernández Gianotti T, Burgueño A, Alvarez A, González CD, Pirola CJ (Universidad de Buenos Aires, Ciudad Autó noma de Buenos Aires, Buenos Aires, Argentina). Effects of rotating shift work on biomarkers of metabolic syndrome and inflammation. J Intern Med 2007; 261: 285-292.Objective. The major function of the circadian system is the internal cycling of physiological and metabolic events. The present study sought to explore the effect of rotating shift work schedule on leucocyte count and its relationship with risk factors of metabolic syndrome (MS).Design and participants. From a population-based design, 1351 men of self-reported European ancestry were included in a cross-sectional study: 877 day workers were compared with 474 rotating shift workers. Medical history, health examination including anthropometric and arterial blood pressure measurements, a questionnaire on health-related behaviours and biochemical determinations was given to all participants.Results. In comparison with day workers, rotating shift workers had elevated (mean ± SE) body mass index (27.1 ± 0.3 vs. 26.3 ± 0.2, P < 0.0154), waist-hip ratio (0.95 ± 0.01 vs. 0.93 ± 0.01, P < 0.00024), diastolic arterial blood pressure (78 ± 1 vs. 76 ± 1, P < 0.033), fasting insulin (65.5 ± 2.9 vs. 55.9 ± 1.9 pmol L )1 , P < 0.017), Homeostasis Model Assessment index (2.12 ± 0.11 vs. 1.77 ± 0.07, P < 0.0027), triglycerides (1.71 ± 0.1 vs. 1.5 ± 0.1 mmol L )1 , P < 0.002), uric acid (292.7 ± 2.8 vs. 282 ± 3.4 lmol L )1 , P < 0.01) and leucocyte count (7030 ± 84 vs. 6730 ± 58, P < 0.0094). In multiple regression analysis, leucocyte count was correlated with rotating shift work independently of age, smoking, education and components of MS. Conclusion.The odds ratio for MS in rotating shift workers compared with day workers was 1.51 (95% CI 1.01-2.25), independently of age and physical activity. Increased leucocyte count, a biological marker of systemic inflammation, was associated with rotating shift work.