FXR is an orphan nuclear receptor that plays a key role in the regulation of bile acid metabolism and in the pathogenesis of cholestasis.6, 10, 11, 12, 13 Regulation of FXR involves a dynamic acetylation/deacetylation process mediated by p300 and Sirtuin 1 (SIRT1), respectively.14 SIRT1 deacetylates FXR, increasing its DNA binding and dependent gene transcription. This evidence concerns the gene NR1H4 and cholestasis.