Project Summary Nonalcoholic fatty liver disease (NAFLD) affects approximately 30% adults in the US. NAFLD initially manifests hepatic steatosis and progresses to nonalcoholic steatohepatitis (NASH), fibrosis, and even cirrhosis or hepatocellular carcinoma. Liver fibrosis, a condition of elevated accumulation of extracellular matrix in the liver, is a strong indicator of NASH severity. In most NASH patients, environmental factors such as high-calorie diets and sedentary lifestyle are primary contributors to the disease development. Those environmental cues often modulate epigenetic and transcription factors to acquire long-term effects. In our preliminary study, we have identified Sirtuin 6 (Sirt6) as a key suppressor of liver fibrosis. To further investigate the role of Sirt6 in the pathogenesis of liver fibrosis, we plan to carry out both in vitro and in vivo experiments using cell and animal models. Hepatic stellate cells are generally considered as a major contributor to the production of extracellular matrix in the liver after chronic liver injury. Therefore, we will focus on the regulation of hepatic stellate cells by Sirt6 at molecular, cellular, and tissue levels. It is expected that the proposed pathophysiological and mechanistic investigation of liver fibrosis in this application will uncover key pathways or network that is controlled by Sirt6. Moreover, the knowledge gained from this project can help develop therapeutic interventions for hepatic fibrosis.