ABCB4 and pancreatic serous cystadenoma: NorUDCA has proven efficacy in treating murine cholestasis in Mdr2–/– mice25, 26 and improving cholestasis in PSC patients.5 We previously described that NorUDCA reduced SIRT1 expression in noncholestatic SIRToe mice, which associated with an improved response to injury and restored regenerative capacity of the liver.16 These observations evidenced an alternative mechanism of action of this drug that may be relevant to cholestasis and lead us to investigate the impact of NorUDCA on SIRT1 expression during cholestasis.