7beta-hydroxysteroid dehydrogenase that catalyzes the reduction of the 7-oxo group of 7-oxo-lithocholate (7-oxo-LCA), to yield ursodeoxycholate (UDCA). As R.gnavus is a common core bacterium of the human gut microbiota, this enzyme contributes to the formation of UDCA in the human colon. UDCA is regarded as a chemopreventive beneficial secondary bile acid due to its low hydrophobicity; it protects hepatocytes and bile duct epithelial cells against necrosis and apoptosis induced by more hydrophobic secondary bile acids like deoxycholate (DCA). This enzyme is also able to catalyze the reverse reaction in vitro, i.e. the oxidation of the 7beta-hydroxy group of UDCA to 7-oxo-LCA, but much less efficiently than the reduction reaction. a 7beta-hydroxysteroid + NADP(+) = a 7-oxosteroid + H(+) + NADPH 7-oxolithocholate + H(+) + NADPH = NADP(+) + ursodeoxycholate Belongs to the short-chain dehydrogenases/reductases (SDR) family.