Iron deposition predominantly in hepatocyes is associated with more severe liver damage in patients with NAFLD. However, HFE mutations cannot be used to identify patients with hepatocellular iron accumulation.

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BackgroundReduced adiponectin is implicated in the pathogenesis of nonalcoholic fatty liver disease (NAFLD) and steatohepatitis (NASH), and the I148M Patatin-like phospholipase domain-containing 3 (PNPLA3) polymorphism predisposes to NAFLD and liver damage progression in NASH and chronic hepatitis C (CHC) by still undefined mechanisms, possibly involving regulation of adipose tissue function. Aim of this study was to evaluate whether the I148M PNPLA3 polymorphism influences serum adiponectin in liver diseases and healthy controls.MethodsTo this end, we considered 144 consecutive Italian patients with NAFLD, 261 with CHC, 35 severely obese subjects, and 257 healthy controls with very low probability of steatosis, all with complete clinical and genetic characterization, including adiponectin (ADIPOQ) genotype. PNPLA3 rs738409 (I148M) and ADIPOQ genotypes were evaluated by Taqman assays, serum adiponectin by ELISA. Adiponectin mRNA levels were evaluated by quantitative real-time PCR in the visceral adipose tissue (VAT) of 35 obese subjects undergoing bariatric surgery.ResultsAdiponectin levels were independently associated with the risk of NAFLD and with the histological severity of the disease. Adiponectin levels decreased with the number of 148 M PNPLA3 alleles at risk of NASH both in patients with NAFLD (p = 0.03), and in healthy subjects (p = 0.04). At multivariate analysis, PNPLA3 148 M alleles were associated with low adiponectin levels (<6 mg/ml, median value) independently of NAFLD diagnosis, age, gender, BMI, and ADIPOQ genotype (OR 1.67, 95% c.i. 1.07-2.1 for each 148 M allele). The p.148 M PNPLA3 variant was associated with decreased adiponectin mRNA levels in the VAT of obese patients (p < 0.05) even in the absence of NASH. In contrast, in CHC, characterized by adiponectin resistance, low adiponectin was associated with male gender and steatosis, but not with PNPLA3 and ADIPOQ genotypes and viral features.ConclusionsThe I148M PNPLA3 variant is associated with adiponectin levels in patients with NAFLD and in healthy subjects, but in the presence of adiponectin resistance not in CHC patients. The I148M PNPLA3 genotype may represent a genetic determinant of serum adiponectin levels. Modulation of serum adiponectin might be involved in mediating the susceptibility to steatosis, NASH, and hepatocellular carcinoma in carriers of the 148 M PNPLA3 variant without CHC, with potential therapeutic implications.

Background & AimsHepatic iron accumulation due to altered trafficking is frequent in patients with nonalcoholic fatty liver disease (NAFLD), and is associated with more severe liver damage and hepatocellular carcinoma. The p.Ala736Val TMPRSS6 variant influences iron metabolism regulating the transcription of the hepatic hormone hepcidin, but its role in the pathogenesis of iron overload disorders is controversial. Aim of this study was to evaluate the whether the TMPRSS6 p.Ala736Val variant influences hepatic iron accumulation in a well-characterized series of Italian patients with histological NAFLD.Methods216 patients with histological NAFLD. TMPRSS6 and HFE variants were assessed by allele specific PCR, liver histology by the NAFLD activity score and Perls' staining for iron.ResultsHomozygosity for the p.736Val allele previously linked to higher hepcidin did not influence transferrin saturation (TS), but was associated with lower hepatic iron stores (p = 0.01), and ferritin levels (median 223 IQR 102–449 vs. 308 IQR 141–618 ng/ml; p = 0.01). Homozygosity for TMPRSS6 p.736Val was nearly associated with lower ballooning (p = 0.05), reflecting hepatocellular damage related to oxidative stress. The influence of TMPRSS6 on hepatic iron accumulation was more marked in patients negative for HFE genotypes predisposing to iron overload (p.Cys282Tyr + and p.His63Asp +/+; p = 0.01), and the p.736Val variant was negatively associated with hepatic iron accumulation independently of age, gender, HFE genotype, and beta-thalassemia trait (OR 0.59, 0.39–0.88).ConclusionsThe p.Ala736Val TMPRSS6 variant influences secondary hepatic iron accumulation in patients with NAFLD.

The anemia of chronic kidney disease and hemodialysis is characterized by chronic inflammation and release of cytokines, resulting in the upregulation of the iron hormone hepcidin, also increased by iron therapy and reduced glomerular filtration, with consequent reduction in iron absorption, recycling, and availability to the erythron. This response proves advantageous in the short-term to restrain iron availability to pathogens, but ultimately leads to severe anemia, and impairs the response to erythropoietin (Epo) and iron. Homozygosity for the common C282Y and H63D HFE polymorphisms influence iron metabolism by hampering hepcidin release by hepatocytes in response to increased iron stores, thereby resulting in inadequate inhibition of the activity of Ferroportin-1, inappropriately high iron absorption and recycling, and iron overload. However, in hemodialysis patients, carriage of HFE mutations may confer an adaptive benefit by decreasing hepcidin release in response to iron infusion and inflammation, thereby improving iron availability to erythropoiesis, anemia control, the response to Epo, and possibly survival. Therefore, anti-hepcidin therapies may improve anemia management in hemodialysis. However, HFE mutations directly favor hemoglobinization independently of hepcidin, and reduce macrophages activation in response to inflammation, whereas hepcidin might also play a beneficial anti-inflammatory and anti-microbic action during sepsis, so that direct inhibition of HFE-mediated regulation of iron metabolism may represent a valuable alternative therapeutic target. Genetic studies may offer a valuable tool to test these hypotheses and guide the research of new therapies.

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