miR-122: A New Target for Diagnosis and Treatment of Liver Diseases

Abstract

miR-122 is a small single-stranded RNA molecule with approximately 20-22 nucleotides in length. It is well documented that miR-122 is a liver-specific miRNA that is expressed predominantly in liver cells and involved in a plenty of physiological processes of the liver function including the regulations of cholesterol level and fatty acid metabolism, liver cell differentiation and liver development, and suppression of hepatocarcinogenesis. miR-122 plays a crucial role in liver diseases, e.g., hepatitis B virus-associated hepatocellular carcinoma and human non-alcoholic steatohepatitis that are associated with reduced miR-122 expression. miR-122 is highly expressed in the adult liver, which can be detected in the circulation and serum. It also serves as a specific biomarker of some forms of liver pathogenesis: miR-122 is a sensitive marker for early detection of paracetamol-induced liver injury at 3 hours when there is neither significant morphological change nor elevation of alanine transaminase (ALT), aspartate transaminase (AST) or total bilirubin (TBIL) that could be detected. Thus, miR-122 is a promising biomarker for diagnosis of drug-induced liver injury, prognosis assessment as well as a drug target (i.e., miRNA-based therapeutic approaches) for treatment of viral hepatitis.