SIRT1 and fatty liver disease: This suggests that both up- and down-regulation of DNA methylation are involved in lipid accumulation and may stimulate or suppress gene expression, and is consistent with reports showing that some genes (FASN, PPARγ, and SREBP1) are increased but others (SIRT1, FOXO1, and ATGL) are decreased in cell models of hepatic steatosis [24, 33].