Gustavo Castaño

A nonsynonymous gene variant in the adiponutrin gene is associated with nonalcoholic fatty liver disease severity.

We explored the role of the adiponutrin (PNPLA3) nonsynonymous-rs738409 single nucleotide polymorphism (SNP) in genetic susceptibility to nonalcoholic fatty liver disease (NAFLD) and whether this SNP contributes to the severity of histological disease. Two hundred sixty-six individuals were evaluated in a case-control association study, which included 172 patients with features of NAFLD and 94 control subjects. The rs738409 G allele was significantly associated with NAFLD (P < 0.001; OR 2.8 95%, CI 1.5–5.2), independent of age, sex, body mass index (BMI), and Homeostasis Model Assessment (HOMA) index. When we tested the hypothesis of a relation between the SNP and the histological spectrum of NAFLD, a significant association was observed [chi2 19.9, degree of freedom (df): 2, P < 5 × 10−5, adjusted for HOMA and BMI]. The degree of liver steatosis, as evaluated by liver biopsy, was significantly associated with the rs738409 G allele. Patients with CC genotype showed a lower steatosis score (14.9% ± 3.9) in comparison with the CG genotype (26.3% ± 3.5) and GG genotype (33.3% ± 4.0) (P < 0.005). The proportion of the total variation attributed to rs738409 genotypes was 5.3% (&bgr; 0.23 ± 0.07; P < 0.002). Our data suggest that the rs738409 G allele is associated not only with fat accumulation in the liver but also with liver injury, possibly triggered by lipotoxicity.

Circulating microRNA signature in non-alcoholic fatty liver disease: from serum non-coding RNAs to liver histology and disease pathogenesis

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.

Epigenetic regulation of insulin resistance in nonalcoholic fatty liver disease: Impact of liver methylation of the peroxisome proliferator–activated receptor γ coactivator 1α promoter †‡

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 γ coactivator 1α (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 real‐time 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. (HEPATOLOGY 2010)

Epigenetic modification of liver mitochondrial DNA is associated with histological severity of nonalcoholic fatty liver disease

Objective & design Nonalcoholic fatty liver disease (NAFLD) is a clinical condition that refers to progressive histological changes ranging from simple steatosis (SS) to nonalcoholic steatohepatitis (NASH). We evaluated the status of cytosine methylation (5mC) of liver mitochondrial DNA (mtDNA) in selected regions of the mtDNA genome, such as D-loop control region, and mitochondrially encoded NADH dehydrogenase 6 (MT-ND6) and cytochrome C oxidase I (MT-CO1), to contrast the hypothesis that epigenetic modifications play a role in the phenotypic switching from SS to NASH. Methods We studied liver biopsies obtained from patients with NAFLD in a case-control design; 45 patients and 18 near-normal liver-histology subjects. Results MT-ND6 methylation was higher in the liver of NASH than SS patients (p<0.04) and MT-ND6 methylated DNA/unmethylated DNA ratio was significantly associated with NAFLD activity score (p<0.02). Liver MT-ND6 mRNA expression was significantly decreased in NASH patients (0.26±0.30) versus SS (0.74±0.48), p<0.003, and the protein level was also diminished. The status of liver MT-ND6 methylation in NASH group was inversely correlated with the level of regular physical activity (R=-0.54, p<0.02). Hepatic methylation levels of D-Loop and MT-CO1 were not associated with the disease severity. DNA (cytosine-5) methyltransferase 1 was significantly upregulated in NASH patients (p<0.002). Ultrastructural evaluation showed that NASH is associated with mitochondrial defects and peroxisome proliferation. Conclusion 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.

Genetic variation in transmembrane 6 superfamily member 2 and the risk of nonalcoholic fatty liver disease and histological disease severity

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 = 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 = 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 = 0.021; OR, 1.66; 95% CI: 1.08‐2.55). A significant association was found with the histological degree of liver steatosis (β, 0.15; standard error: 0.06; P = 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)

Circulating levels and hepatic expression of molecular mediators of atherosclerosis in nonalcoholic fatty liver disease

OBJECTIVES We evaluated circulating levels of biomarkers of atherosclerosis (soluble intercellular adhesion molecule: sICAM-1, plasminogen activator inhibitor: PAI-1 and soluble CD40 ligand: sCD40L) in patients with NAFLD proven through biopsy and control subjects, and correlated them with the histological disease severity. We further explored liver protein expression of ICAM-1, CD40 and PAI-1 in patients with different histological forms of NAFLD and control liver biopsies. PATIENTS AND METHODS We included 215 individuals: 113 patients with NAFLD (simple steatosis n=45 and NASH n=68) and 102 control subjects. Circulating levels of the biomarkers were measured by ELISA. Liver expression of ICAM-1, CD40 and PAI-1 was assessed by immunohistochemistry using monoclonal antihuman antibodies. RESULTS Patients with NAFLD, in comparison with control subjects, showed significantly higher circulating levels of sICAM-1 (605.3+/-34.6ng/ml vs. 356.5+/-24.6ng/ml, p=5.9 x 10(-6)), PAI-1 (22.8+/-1.7ng/ml vs. 19.0+/-2.1ng/ml, p=0.0149) and sCD40L (1347.5+/-513.7pg/ml vs. 804.5+/-396.1pg/ml, p=0.0229), results expressed as mean+/-SE. sICAM-1 was a strong predictor of histological severity of NAFLD, after adjusting for potential confounders. In addition, patients with NAFLD showed significantly higher liver staining scores for ICAM-1 and PAI-1 than control liver biopsies. ICAM-1 immunoreactivity in lobular inflammatory infiltrate showed high scores in NASH patients; a significant correlation was found between both the degree of liver steatosis and the severity of necroinflammatory activity and liver ICAM-1 expression. CONCLUSIONS Our study shows that NAFLD is associated with elevated circulating levels and abnormal liver expression of molecular mediators of atherosclerosis. Additionally, ICAM-1 may be involved in liver damage and inflammation.

The nuclear receptor PXR gene variants are associated with liver injury in nonalcoholic fatty liver disease.

Objective To explore the contribution of gene variants and derived haplotypes of the pregnane X receptor (NR1I2) to the severity of nonalcoholic fatty liver disease (NAFLD). Methods A total of 290 individuals were evaluated in a case-control association study, including 188 NAFLD patients with different stages of disease severity and 102 healthy individuals. Four tag single nucleotide polymorphisms (SNPs; rs12488820 C/T, rs2472671 C/T, rs2461823 A/G, and rs1054191 A/G) encompassing 36 kb in chromosome 3 and representing 33 polymorphic sites (r2>0.8) were genotyped. Four additional SNPs (rs3814055, rs3814057, rs6785049, and rs7643645) were also included because they showed earlier evidence of functionality. Results Genotypic tests for single SNPs showed that rs7643645 and rs2461823 were significantly associated with disease severity by ordinal multinomial analysis (P<0.0015 and 0.039, respectively). A significant association was also observed under the additive model for both variants (P<0.00038 and 0.012, respectively). Consistent with the analysis of individual markers, we observed that the multimarker composed of rs2461823/A-rs7643645/G was significantly associated with disease severity (P<6.9×10−5, &bgr;: 0.45). In addition, the rs7643645/G variant was significantly associated with ALT level (P<0.026), a surrogate marker of severe liver injury. Finally, in univariate analysis rs7643645/G was significantly associated with fatty liver disease (P<0.04), with an odds ratio of 1.457 (95% confidence interval: 1.018–2.086). Conclusion Our study suggests that pregnane X receptor polymorphisms and related haplotypes may contribute to disease severity in NAFLD by influencing the individual susceptibility to progress to more severe stages of the disease.

Bile acid profiles by capillary electrophoresis in intrahepatic cholestasis of pregnancy

ICP (intrahepatic cholestasis of pregnancy) is characterized by pruritus and biochemical cholestasis, including raised SBAs (serum bile acids) and, usually, elevated aminotransferases levels. However, AHP (asymptomatic hypercholanaemia of pregnancy) is defined as the presence of total SBA levels above the cut-off value (11 microM) in healthy pregnant women, thus elevation of total SBAs do not necessarily reflect an ICP condition. The aim of the present study was to describe clinical, obstetric, perinatal and biochemical findings, as well as the SBA profile, in pregnant women studied in the third trimester of pregnancy in order to define characteristic patterns of individual bile acids that enable women with ICP to be distinguished from AHP and healthy pregnancies. Free and conjugated ursodeoxycholic (UDCA), cholic (CA), lithocholic (LCA), deoxycholic (DCA) and chenodeoxycholic (CDCA) acids were evaluated by CE (capillary electrophoresis) in 41 patients (15 of them simultaneously by HPLC), in 30 healthy pregnant women and in 10 non-pregnant women. A highly significant correlation between CE and HPLC for total SBAs (r=0.990) and for individual SBAs was found. Normal pregnant women had higher total SBA levels than non-pregnant women (due to an increase in taurine-conjugated dihydroxy SBAs). Women with ICP had higher levels of total SBAs, the free/conjugated ratio, LCA, CA, CDCA and DCA than normal pregnant women. Newborns from women with ICP had lower birth weight and gestational age. Women with AHP had higher levels of conjugated dihydroxy SBAs than normocholanaemic patients, without any evidence of a clinical difference. In conclusion, the present study has shown a clear difference in SBA profiles between ICP and normal pregnancies (including AHP), involving a shift towards a characteristic hydrophobic composition in women with ICP.

Liver transcriptional profile of atherosclerosis-related genes in human nonalcoholic fatty liver disease

OBJECTIVES AND DESIGN Epidemiological studies have suggested a role of nonalcoholic fatty liver disease (NAFLD) in the development of cardiovascular disease. We evaluated liver mRNA expression of 84 genes encoding proteins involved in the atherosclerosis pathway in patients with NAFLD proven through biopsy in a case-control design, and examined the putative role of the histological disease severity in the molecular events associated with the atherogenic profile. RESULTS Nonalcoholic steatohepatitis (NASH), when compared with simple steatosis (SS), significantly increases the expression of TGFB1 (6.8, p<0.005), angiotensin I-converting enzyme (ACE) (2.1, p<0.007), LAMA1 (2.1, p<0.007), SERPINB2 (2.1, p<0.007), CSF2 (2.5, p<0.002), IL1A (2.5, p<0.005), IL3 (2.1, p<0.007), IL4 (2.1, p<0.007), LIF (2.1, p<0.007), and MMP1 (2.1, p<0.007), and decreases the transcript levels of genes involved in the negative regulation of cell-death pathways. A post hoc analysis of liver biopsies of NASH patients who were treated with enalapril monotherapy because of arterial hypertension showed a significant association with lower fibrosis scores in comparison with untreated patients. BIRC3, a severe hypoxia-activated gene, was significantly increased in SS (8.2, p<0.004), when compared with the controls. NASH, but not SS, was also associated with a significant increase in platelet abundance of TGFB1 mRNA. Systems biology analysis revealed highly scored pathways involved in the regulation of programmed cell death, angiogenesis, and immune system, in which TGFB1 was mostly involved. CONCLUSION NASH, but not SS, may increase atherosclerotic and cardiovascular risk by local overexpression of mediators of atherogenesis, endothelial damage, and regulators of blood pressure; this observation may have therapeutic implications, because ACE inhibitors may improve both cardiovascular outcomes and liver fibrosis. Hepatocyte hypoxia seems to have an important role in the molecular events activated by liver steatosis.

Polymorphisms of MRP2 (ABCC2) are associated with susceptibility to nonalcoholic fatty liver disease.

AIMS We hypothesized that ABCC2 gene variants may contribute to susceptibility to nonalcoholic fatty liver disease (NAFLD). Additionally, we tested the hypothesis of a relation between gene variants and disease severity. PATIENTS AND METHODS The study involved 167 individuals: 109 consecutively presenting unrelated patients with features of NAFLD and different stages of disease severity, and a group of 58 healthy individuals. Four tag single-nucleotide polymorphisms (SNPs; rs717620 A/G, rs2756105 C/T, rs2002042 C/T and rs3740066 A/G) representing 46 polymorphic sites (r(2)>.8) were genotyped. Furthermore, two additional SNPs (rs17222723 A/T and rs8187710 G/A) were included. RESULTS On univariate analysis, after multiple comparison correction by permutation tests, there were significant differences observed in the allele frequencies of rs17222723 and rs8187710 between healthy individuals and NAFLD patients (empirical P=.037 and .035, respectively). Allelic odds ratios [95% confidence interval] for rs17222723 and rs8187710 were 2.80 [1.11-7.04] and 2.80 [1.11-7.04], respectively. When we tested the hypothesis of a relation between gene variants and the clinical and histological spectra of NAFLD by multinomial regression analysis, a significant association was observed with the same markers: rs17222723 (P=.0029) and rs8187710 (P=.015). CONCLUSIONS Our study suggests a potential role of ABCC2 in susceptibility to NAFLD and disease severity.