12α-Hydroxylated bile acid enhances accumulation of adiponectin and immunoglobulin A in the rat ileum.

We previously reported that dietary supplementation with cholic acid (CA), the primary 12α-hydroxylated (12αOH) bile acid (BA), reduces plasma adiponectin concentration in rats. The aim of this study was to examine the distribution of adiponectin in the body of CA-fed rats and its influence on mucosal immunoglobulin A concentration in the intestine. Rats were fed a diet supplemented with or without CA (0.5 g CA/kg diet) for 13 weeks. A reduction in plasma adiponectin level was observed from week 3. At the end of the experiment, the CA diet reduced plasma adiponectin concentration both in the portal and aortic plasma. Accumulation of adiponectin was accompanied by an increase in cadherin-13 mRNA expression in the ileal mucosa of CA-fed rats. No increase was observed in adiponectin mRNA expression in the ileal and adipose tissues of the CA-fed rats. Immunoglobulin A concentration in the ileal mucosa was elevated in the CA-fed rats and was correlated with the ileal adiponectin concentration. 12αOH BAs may modulate mucosal immune response that are involved in the accumulation of adiponectin in the ileum.

Diet supplementation with cholic acid promotes intestinal epithelial proliferation in rats exposed to γ-radiation.

Consumption of a high-fat diet increases some secondary bile acids (BAs) such as deoxycholic acid (DCA) in feces. DCA is derived from cholic acid (CA), a primary BA. We evaluated intestinal epithelial proliferation and BA metabolism in response to oral administration of cholic acid (CA) in rats to determine the influence of a CA diet on the responses of gut epithelia to γ-rays. WKAH/HkmSlc rats were divided into two dietary groups: control diet or CA-supplemented (2g/kg diet) diet. Some of the rats from each group were irradiated with γ-rays, and epithelial cell proliferation in the colon was analyzed histochemically. Unirradiated CA-fed rats had high levels of DCA and CA in the sera, as well as the presence of taurocholic acid in their feces. Significant increases were observed in both epithelial proliferation and the number of epithelial cells in the colon of the CA-fed rats, and this effect was observed at 8 weeks after γ-ray exposure. Furthermore, extracts from both cecal contents and sera of the unirradiated CA-fed rats promoted proliferation of IEC-6 cells. These results indicate that BAs in enterohepatic circulation promote proliferation and survival of the intestinal epithelium after receiving DNA damage.