212-LB: Decreasing Drp1 Expression in Mouse Liver Activates the Mitochondrial Integrated Stress Response and Exacerbates NASH

Elevated Drp1-mediated mitochondrial fission was proposed to promote NAFLD, as inhibition of hepatic Drp1 in early life prevented high-fat diet induced liver steatosis in mice. However, whether Drp1-knockdown (Drp1si) can reverse established NASH in adulthood is unknown. Hepatocyte-restricted delivery of siRNA conjugated to N-acetyl-galactosamine (GalNac) is a safe and FDA-approved approach to selectively manipulate hepatic gene expression and treat human liver disease. Here, we show that hepatic Drp1si in adult healthy mice decreased body weight by 12% and induced liver damage, as shown by the elevation in circulating transaminases, liver inflammation, fibrosis and necrosis (p In conclusion, our study supports that increased Drp1 activity is an adaptative mechanism counteracting NASH that prevents ISR overactivation and mitigates ER stress to limit fibrosis, inflammation, and necrosis. Our study argues against blocking Drp1 in hepatocytes to combat NASH. Disclosure J. Steffen: Employee; Janssen Research & Development, LLC. J. Ngo: None. S. Wang: None. H. F. Kramer: Employee; Janssen Research & Development, LLC. L. D. Norquay: Employee; Janssen Pharmaceuticals, Inc. A. Pocai: Employee; Johnson & Johnson. O. Shirihai: None. M. Liesa: None.