FGF21 and viral infectious disease: Taken together, these data show that the mouse models recapitulated the findings in human liver diseases, and FGF21 expression is significantly induced in hepatocytes in response to perturbation of liver functional capacity by liver damage (viral infection, cirrhosis, steatosis and toxins), partial resection and carcinogenic transformation (HCC, clear cell HCC and cholangiocellular carcinoma).