HCV INFECTION REPROGRAMS THE HEPATIC GLUCOSE AND GLUTAMINE METABOLISM

Background and Aims: Hepatitis C virus (HCV) is the only virus that is known to perturb hepatic glucose and lipid metabolism with important patho-physiological consequences. Chronic carriers often develop steatosis, insulin resistance and type 2 diabetes, which resolve with successful antiviral treatment. Therefore it is thought that HCV interferes directly with the lipogenic and glycolytic pathways and requires these changes for its replication. However, the exact circumstances of this metabolic reprogramming still remain vague and require further analysis. Here we investigate some fundamental changes in glucose and glutamine metabolism linked to HCV infection. Methods: RNA derived from Huh7.5 cells infected or not with JFH1 and from biopsies of chronic HCV patients were used for RT-qPCR analysis with primers targeting metabolic genes. Nutrient deprivation and biochemical and NMR-based metabolic flux analysis were performed with JFH1 infected Huh7.5 cell culture extracts. Results: We show that HCV modulates the transcript levels of some key regulators of glucose metabolism (HIF-1 a, PKM2, G6PD) in the hepatocyte-derived cell-line Huh7.5 as well as liver biopsies of patients with chronic hepatitis C, which hinted at changes to glycolytic fluxes. In addition, we found enzymes and factorsregulating glutamine metabolism (MYC, SLC1A5, SLC7A5, GLS) to be upregulated by HCV. Indeed, cell proliferation rates of HCV infected and uninfected cells in conditioned growth media showed that infected cells become dependent on glutamine and lose their glucose dependence. NMR-based metabolomic assays further corroborated these findings. We then showed that silencing of MYC, an oncogene and metabolic transcription factor known to induce glutamine addiction, as well as silencing of GLS, considerably reduced HCV infection. Conclusions: Altogether, these data suggest that HCV reprograms the hepatocyte metabolism and establishes glutamine dependence. This HCV-induced metabolic reprogramming is similar to that commonly found in many types of tumor cells. Because these changes seem to be required for viral replication, we are currently investigating their roles in the various steps of the viral life cycle, and their impact on the pathological features associated with chronic hepatitis C.