Modelling Porcine NAFLD by Deletion of Leptin and defining the role of AMPK in hepatic fibrosis

Abstract

Liver fibrosis occurs during chronic liver disease. Advanced liver fibrosis results in cirrhosis, liver failure and often requires liver transplantation. However, due to the lack of human models, mechanisms underlining the pathogenesis of liver fibrosis remain unclear. Recent studies implicated a central role of deranged lipid metabolism in its pathogenesis. In this study, we generated LEPTIN-deficient (LEPTIN-/-) pigs using zinc finger nuclease technology to investigate the mechanisms of liver fibrosis associated with obesity. The LEPTIN-/- pigs showed increased body fat and significant insulin resistance by 12 months of age. To resemble non-alcoholic fatty liver disease (NAFLD) patients, LEPTIN-/- pig developed the phenotypic features of fatty liver, non-alcoholic steatohepatitis (NASH) and hepatic fibrosis with age. Meanwhile, LEPTIN absence reduced phosphorylation of JAK2-STAT3 and AMPK. The alteration of JAK2-STAT3 enhanced fatty acid {beta}-oxidation, whereas inactivation of AMPK led to mitochondrial autophagy, and both contributed to increased oxidative stress in hepatocytes. Although Leptin deletion in the rat liver altered JAK2-STAT3 phosphorylation, it activated the AMPK pathway and prevented liver fibrogenesis in contrast with the LEPTIN-/- pig. To our knowledge, the LEPTIN-/- pig provides the first model recapitulating the full pathogenesis of NAFLD and its progression toward liver fibrosis. The activity of AMPK signaling pathway suggests a potential target for development of new strategies for the diagnosis and treatment of NAFLD.