Hepatic SIRT6 protects against cholestatic liver disease primarily via inhibiting bile acid synthesis

Cholestatic liver disease, caused by the accumulation of hazardous bile acids in the liver, may result in cirrhosis, fibrosis, or liver failure. Activation of SIRT6 prevents cholestasis-associated pathological events, such as oxidative stress and mitochondrial biogenesis disorders, and inhibits bile acid synthesis to alleviate cholestatic liver injury. However, it is still uncertain which pathway is responsible for the therapeutic effect of SIRT6 in reducing cholestasis. Therefore, we treated liver-specific Sirt6 knockout mice with N-Acetylcysteine, Keap1-Nrf2-IN-1, or acadesine to remove oxidative stress and/or trigger mitochondrial biogenesis after cholestatic liver disease modeling, but these measures did not significantly improve cholestatic symptoms. However, MDL801, a SIRT6 agonist that downregulating CYP7A1, the key enzyme in bile acid synthesis, exhibited favorable therapeutic effects. In addition, the hepatic knockdown of Cyp7A1 further confirmed that inhibition of hepatic bile acid synthesis might be the main pathway by which SIRT6 alleviates cholestatic liver disease. These findings provide a solid basis for the potential application of SIRT6 agonists in the treatment of cholestatic liver disease.