Dietary bile acids inclusion improves dietary carbohydrate utilization, antioxidant capacity and intestinal microbiota and inflammation of largemouth bass (Micropterus salmoides)

The study explored the role of dietary bile acids inclusion in improving dietary carbohydrate utilization, antioxidant capacity and intestinal microbiota and inflammation of largemouth bass (Micropterus salmoides). Two isonitrogenous (50.40%) and isolipidic (12.00%) diets were formulated, containing a positive control with 5% α-starch and a negative control with 10% α-starch, respectively. The other three diets were supplemented with 200 mg, 500 mg, or 1000 mg bile acids kg−1 based on 10% α-starch diet. Different experiment diets were fed to cultured fish twice daily for 8 weeks. The results showed that the growth of cultured fish was inhibited by high carbohydrate diet and hepatic glycogen and lipid inordinate accumulation were induced. Meanwhile, high carbohydrate diet caused liver oxidative damage, but supplementation of bile acids significantly improved the antioxidant capacity. Compared with the negative control group, dietary bile acids supplementation didn't affect the growth of largemouth bass, but significantly reduced hepatic glycogen and lipid inordinate accumulation and the viscerosomatic index and hepatosomatic index. In addition, the increase of dietary carbohydrate increased liver bile acids content, and dietary bile acids inclusion could linearly increase liver bile acids content. Results showed that bile acids supplementation regulated liver bile acid synthesis and metabolism of largemouth bass through activating FXR-FGFR4-CYP7A1 pathway. Meanwhile, bile acids inclusion inhibited the expression of foxo1 and genes related to gluconeogenesis, including g6pc, fbp1 and gs, enhanced the expression of genes related to glycolysis, including pfkl and gk through activating insulin pathway. Moreover, high carbohydrate diet with bile acids supplementation also increased gut microbial diversity, and changed the relative abundance of some phyla and genera related to carbohydrate utilization and energy balance, and improved the intestinal inflammatory response. Those findings indicated that dietary bile acids inclusion improved carbohydrate utilization, antioxidant capacity and intestinal microbiota and inflammation of largemouth bass.