*2.2. Animal Experiments*

TGR5 transgenic mice were a generous gift from K. Schoonjans and J. Auwerx and have been shown to overexpress TGR5 in different tissues, including liver [28]. TGR5 knockout (KO) mice were kept on a C57BL/6 background and were kindly provided by the Schering-Plough Research-Institute (Kenilworth, NJ, USA) [15,29]. Heterozygous animals were used for breeding to obtain littermate TGR5 knockout and wildtype animals. Mice were bred and kept in the central animal facility of Düsseldorf University (ZETT) and had access to water and food ad libitum. A 12 h light/dark cycle was maintained. TGR5 KO and WT male mice aged 8–12 weeks were fed a diet containing 1% (*w*/*w*) lithocholic acid (LCA, ssniff, Soest, Germany) for 84 h or standard chow diet ad libitum. After 84 h of feeding, mice were anesthetized by intraperitoneal injection of ketamine/sodium pentobarbital solution. Blood was collected and anesthetized animals were subjected to portal vein perfusion prior to collection of liver tissue. All animal experiments were approved by the local authorities (LANUV).
