SIRT1 and metabolic dysfunction-associated steatohepatitis: Hepatic NNMT upregulation promotes SIRT1 stabilization, lowers serum triglycerides and free fatty acids, and protects against the progression of non-alcoholic fatty liver disease (NAFLD), whereas adipose NNMT upregulation depletes methyl donors, fostering insulin resistance and the development of non-alcoholic steatohepatitis (NASH) [16].