Pectin and soybean meal induce stronger inflammatory responses and dysregulation of bile acid (BA) homeostasis than cellulose and cottonseed meal, respectively, in largemouth bass ( Micropterus salmoides ), which might be attributed to their BA binding capacity

Abstract

This study aimed to reveal the impact of excessive dietary fibre (DF) intake on inflammatory responses and bile acid (BA) homeostasis in largemouth bass (Micropterus salmoides) and the potential mechanism. In vitro BA binding capacity was compared, and the results showed that the BA binding capacity to chenodeoxycholic acid and glycocholic acid by pectin and soybean meal was higher than cellulose and cottonseed meal respectively. An in vivo trial was conducted using a diet without DF as a control (CON diet), while test diets contained 150 g/kg cellulose (CEL diet) or pectin (PEC diet), 500 g/kg soybean meal (SBM diet) or cottonseed meal (CSM diet). Fish were overfed and ate ad libitum. Compared to fish fed the CON diet, fish fed the PEC and SBM diets showed high expression of inflammatory factor genes and BA synthesis factor genes and obvious histopathological damage in the gut and liver, while the responses of fish fed the CEL and CSM diets were mild. Whole-body BA contents in fish fed all test diets were lower than those in fish fed the CON diet (p < 0.05). These results support the hypothesis that excessive DF intake induces inflammatory responses and dysregulation of BA homeostasis, which might be attributed to their binding capacity to BAs.