Reciprocal interference between insulin and interferon-alpha signaling in hepatic cells: a vicious circle of clinical significance?

UNLABELLED: Insulin resistance (IR) is common in chronic hepatitis C (CHC) and associates with reduced virological response to pegylated-interferon (PEG-IFN)/ribavirin therapy, but the underlying mechanisms are still unclear. We have previously shown that, in CHC patients, insulin plasma levels are inversely related to antiviral effect induced by PEG-IFN. Therefore, we investigated the in vitro effect of insulin on interferon alpha (IFN-α) intracellular signaling as well as that of IFN-α on insulin signaling. HepG2 cells, preincubated with or without insulin, were stimulated with IFN-α2b and messenger RNA (mRNA) and protein expression of IFN-stimulated genes (ISGs) were measured at different timepoints. The role of intracellular suppressors of cytokine signaling 3 (SOCS3) was evaluated with the small interfering RNA (siRNA) strategy. To assess the effect of IFN-α on insulin signaling, HepG2 were preincubated with or without IFN before addition of insulin and cells were then analyzed for IRS-1 and for Akt/PKB Ser473 phosphorylation. Insulin (100 and 1000 nM) significantly reduced in a dose-dependent fashion IFN-induced gene expression of PKR (P=0.017 and P=0.0017, respectively), MxA (P=0.0103 and P=0.00186), and 2'-5' oligoadenylatesynthetase 1 (OAS-1) (P=0.002 and P=0.006). Insulin also reduced IFN-α-induced PKR protein expression. Although insulin was confirmed to increase SOCS3 expression, siRNA SOCS3 did not restore ISG expression after insulin treatment. IFN-α was found to reduce, in a dose-dependent fashion, IRS-1 gene expression as well as Akt/PKB Ser473 phosphorylation induced by insulin. CONCLUSION: These results provide evidence of reciprocal interference between insulin and IFN-α signaling in liver cells. These findings may contribute to understand the role of insulin in CHC: IR might be favored by endogenous cytokines including IFN-α, and the resulting hyperinsulinemia then reduces the antiviral response to exogenous IFN in a vicious circle of clinical significance.

A seven-gene signature (cirrhosis risk score) predicts liver fibrosis progression in patients with initially mild chronic hepatitis C.

UNLABELLED: Fibrosis progression is the main determinant of liver disease outcome in chronic hepatitis C, being influenced by environmental and host factors. Recently, a cirrhosis risk score (CRS) based on seven single-nucleotide polymorphisms was proposed as genetic predictor of cirrhosis in hepatitis C. To assess the role of CRS in predicting fibrosis progression in patients with initially no or minimal to moderate fibrosis, we investigated 271 untreated patients with chronic hepatitis C having initial liver biopsy showing METAVIR stage F0 (n = 104), F1 (n = 101), or F2 (n = 59) who had been followed up without antiviral therapies for at least 60 months (mean 108.5 +/- 71.5 months) and had a liver biopsy at the end of this observation period. Of these, 24.4% showed no histologic progression, 75.6% progressed by at least one stage, 45.0% progressed by at least two stages, and 10.3% progressed by more than two stages. The mean CRS was significantly higher (P = 0.005) in patients with fibrosis progression compared with those without progression, and this difference was particularly evident (P = 0.002) with F0 on initial biopsy. Mean CRS scores were not associated with degree of fibrosis progression. The relative risk of fibrosis progression increased with increasing CRS values. This association was significant in males but not in females and was most evident in males with F0 at initial biopsy (odds ratio 16.5, 95% confidence interval 1.6-166; P= 0.02) in the presence of high CRS. Multivariate analysis confirmed the significant association of CRS score with fibrosis progression. The predictive value of CRS was confirmed in hepatitis C virus patients admitting significant alcohol intake. CONCLUSION: Host genetics defined by CRS predict fibrosis progression in males with initially mild chronic hepatitis C and may become a useful parameter for prognostic evaluation and treatment decision.

Microsomal triglyceride transfer protein polymorphism (-493G/T) is associated with hepatic steatosis in patients with chronic hepatitis C.

BACKGROUND: Hepatic steatosis may promote progression of chronic hepatitis C (CHC). Microsomal triglyceride transfer protein (MTP) is required for assembly and secretion of ApoB lipoprotein and is implicated in hepatitis C virus (HCV)-related steatosis. The MTP -493G/T polymorphism may promote liver fat accumulation, but its role in HCV-related steatosis is still unclear. METHODS: Two hundred ninety-eight CHC patients were studied and genotyped for MTP -493G/T variants. Hepatic MTP mRNA expression and activity were determined in a subgroup. RESULTS: Patients with grades 2/3 steatosis were older, had a higher body mass index (BMI), more advanced fibrosis and lower MTP mRNA expression and carried more often HCV genotype 3 and the MTP T allele. Age, BMI, HCV-3 and MTP T allele [odds ratio (OR) 2.05; 95% confidence interval (CI) 1.2-3.53; P=0.009] were independent risk factors for steatosis grades 2/3, and in HCV genotype non-3 patients, the MTP T allele was the strongest predictor for steatosis grade 2/3 (OR 2.17; 95% CI 1.22-3.86; P=0.008). Moreover, TT carriers had higher high-density lipoprotein (65.6+/-14.6 vs 56.1+/-16.2 mg/dl; P=0.003) and apolipoprotein AI (1.80+/-0.3 vs 1.60+/-0.3 g/L; P=0.005) levels than G allele carriers. CONCLUSIONS: Chronic hepatitis C patients with the MTP -493T allele reveal higher grades of steatosis, indicating a relevant contribution to liver fat accumulation, particularly in HCV non-3 patients.

Liver microsomal triglyceride transfer protein is involved in hepatitis C liver steatosis.

BACKGROUND & AIMS: Hepatic steatosis is frequent in chronic hepatitis C. Several mechanisms might be implicated, including metabolic cofactors and direct viral effects on intracellular lipid pathways. In a transgenic mouse model, hepatitis C virus (HCV) was shown to inhibit microsomal triglyceride transfer protein (MTP) activity, which is essential for hepatic lipoprotein assembly and secretion. No data are available on liver MTP activity in HCV-infected patients. We therefore investigated liver MTP gene expression and its lipid transfer activity in untreated cases infected with the major HCV genotypes showing variable degrees of hepatic steatosis. METHODS: MTP messenger RNA (mRNA) levels were measured by real-time polymerase chain reaction, and MTP activity was assessed by fluorescent assay in liver biopsy specimens of 58 HCV-positive patients. A set of metabolic and serum lipid markers was also measured at the time of liver biopsies. RESULTS: MTP mRNA levels showed a statistically significant (P = .001) inverse correlation with the degree of steatosis, independently of the HCV genotype. MTP mRNA levels also had an inverse correlation with serum insulin (P = .0002), homeostasis model assessment-insulin resistance (HOMA-IR) (P = .005), and body mass index (P = .02) in patients with HCV-1 and HCV-2 and with serum HCV-RNA (P = .02) in HCV-3 patients. Liver MTP-specific activity was significantly reduced in HCV-3 patients compared with those with other HCV genotypes (P = .004) and correlated with reduced serum cholesterol, apo B, and low-density lipoproteins. CONCLUSIONS: MTP may play a central role in HCV-related steatosis, being modulated by different genotype-specific mechanisms, mainly hyperinsulinemia in non-HCV-3 patients, and more profound and direct virus-related effects in HCV-3-infected individuals.