Hepatitis C virus, diabetes and steatosis: clinical evidence in favor of a linkage and role of genotypes.

Infection with hepatitis C virus (HCV) primarily causes chronic liver disease with characteristic histopathologic features, including hepatic steatosis. Moreover, chronic hepatitis C is also closely related to insulin resistance (IR) and an increased risk of type 2 diabetes mellitus (DM). This review summarizes the available clinical evidence for a linkage of chronic HCV infection and developing IR or DM that comprises (i) retro- and prospective clinical studies, (ii) the excess risk of chronic hepatitis C patients to develop DM compared to hepatitis B patients, (iii) a preferential relationship of IR with HCV type-1, -2 or -4 infections, (iv) a correlation between IR, viral load and responsiveness to antiviral treatment and (v) a decreased incidence of DM in chronic hepatitis C after sustained virological response. This review further refers to the clinical evidence of a preferential relationship between hepatic steatosis and HCV type-3 infection, and that two distinct genotype-specific pathogenic mechanisms underlie steatosis in hepatitis C. In HCV type-3 infections, steatosis is related to viral load but not to metabolic factors, and, thus, is termed 'viral steatosis'. In HCV type-1, -2 or -4 infections, steatosis appears to be secondary to IR and regarded as 'metabolic steatosis'. In conclusion, multiple lines of clinical evidence support a linkage of HCV infection and both hepatic carbohydrate and lipid metabolism. The extent to which targeting the host's metabolism by drugs or by lifestyle change translates into an improvement of health or in a better response to interferon-alpha will provide further valuable insights into virus-host interactions, and is topic which is currently addressed in clinical studies. Copyright 2010 S. Karger AG, Basel.