Bile acid extractions

Liver, ileal lumen, and cecal lumen samples were harvested from mice, and flash frozen in liquid nitrogen. Samples were weighed prior to extraction, and homogenized in Lysing Matrix D tubes (MP Biomedicals) containing 2:1:1 mixture of ethanol:chloroform:methanol using a FastPrep-24 (MP Biomedicals) bead beater for 45 s at 6.5 m/s (repeated 3 times, incubating on ice for 1 minute in between rounds). Homogenates were centrifuged at 20,000 × g at 4°C for 15 minutes to pellet debris. Supernatant was transferred to a clean glass vial, and evaporated under nitrogen gas flow until dry. Samples were reconstituted in methanol prior to LC-MS/MS analysis.