Several studies using NorUDCA treatment in murine models of cholestasis,4, 25, 39, 40 and a recently conducted phase II human clinical trial,5 support the benefits of this drug as a treatment option for cholestatic patients.5, 41 In our present work, we show that NorUDCA modulates SIRT1 expression in two alternative models of cholestasis: in SIRToe mice after BDL and in Mdr2–/– mice. The gene discussed is ABCB4; the disease is cholestasis.