Hepatitis C virus NS5A promotes insulin resistance through IRS-1 serine phosphorylation and increased gluconeogenesis

AIM: To investigate the mechanisms of insulin resistance in human hepatoma cells expressing hepatitis C virus(HCV) nonstructural protein 5A(NS5A).METHODS: The human hepatoma cell lines,Huh7 and Huh7.5,were infected with HCV or transientlytransfected with a vector expressing HCV NS5 A. The effect of HCV NS5 A on the status of the critical players involved in insulin signaling was analyzed using realtime quantitative polymerase chain reaction and Western blot assays. Data were analyzed using Graph Pad Prism version 5.0.RESULTS: To investigate the effect of insulin treatment on the players involved in insulin signaling pathway,we analyzed the status of insulin receptor substrate-1(IRS-1) phosphorylation in HCV infected cells or Huh7.5 cells transfected with an HCV NS5 A expression vector. Our results indicated that there was an increased phosphorylation of IRS-1(Ser307) in HCV infected or NS5 A transfected Huh7.5 cells compared to their respective controls. Furthermore,an increased phosphorylation of Akt(Ser473) was observed in HCV infected and NS5 A transfected cells compared to their mock infected cells. In contrast,we observed decreased phosphorylation of Akt Thr308 phosphorylation in HCV NS5 A transfected cells. These results suggest that Huh7.5 cells either infected with HCV or ectopically expressing HCV NS5 A alone have the potential to induce insulin resistance by the phosphorylation of IRS-1 at serine residue(Ser307) followed by decreased phosphorylation of Akt Thr308,Fox01 Ser256 and GSK3β Ser9,the downstream players of the insulin signalingpathway. Furthermore,increased expression of PECK and glucose-6-phosphatase,the molecules involved in gluconeogenesis,in HCV NS5 A transfected cells was observed.CONCLUSION: Taken together,our results suggest the role of HCV NS5 A in the induction of insulin resistance by modulating various cellular targets involved in the insulin signaling pathway.