Colonic Adaptation Postileal Resection: Bile Acid Absorption in an Ileal Resection Mouse Model

Adaptation of the small intestine and/or colon significantly impacts the prognosis of short bowel syndrome. This study investigated colonic adaptation in a mouse model of ileal resection, with a focus on bile acid absorption.

The ileal resection mouse model (ileal resection group, 8-10-week-old male C57BL/6J mice) was created by resecting 15 cm of the ileum, corresponding to approximately 50% of the small intestine, while preserving the cecum. The sham group underwent intestinal transection and reanastomosis at a site matched in distance from the ligament of Treitz to that used for the resection group. Postoperatively, between Days 1-7 and 7-14, mice received the elemental diet ELENTAL® (0.5 kcal/mL) and a standard solid diet ad libitum, respectively. The mice were euthanized on Day 14. We assessed postoperative body weight; histopathological characteristics of the colon; bile acid metabolism-related gene expression, including Asbt for luminal bile acid uptake, Fabp6 for cytosolic transport, Ostb for bile acid excretion into the circulation, and Fxr, the primary intracellular bile acid receptor regulating the genes; and fecal and serum bile acid concentrations.

Significantly lower changes in body weight and longer colon length were observed in the ileal resection group than in the sham group; however, no histological differences were observed in colonic mucosal height. Furthermore, a significantly increased Asbt expression was detected in the ileal resection group. No significant differences were observed in bile acid concentrations in the feces and serum in both groups.

Our results suggest a colonic adaptation to prevent impairment of bile acid absorption following ileal resection.