Dietary chenodeoxycholic acid inclusion improves carbohydrate utilisation and inflammation of largemouth bass (<i>Micropterus salmoides</i>) partly mediated by the activation of farnesoid X receptor

This study evaluated the effects of chenodeoxycholic acid (CDCA), a farnesoid X receptor (FXR) potential activator, on growth performance, antioxidant capacity, glucose metabolism and inflammation in largemouth bass (<i>Micropterus salmoides</i>) (initial body weight: 5·45 ± 0·02 g) fed a high-carbohydrate diet. Experimental diets included a positive control (5 % <i>α</i>-starch), a negative control (10 % <i>α</i>-starch) and two diets containing 10 % <i>α</i>-starch supplemented with either 0·05 % or 0·10 % CDCA. After 8 weeks, the high-carbohydrate diet reduced growth performance and increased hepatosomatic and viscerosomatic indexes, which were mitigated by 0·10 % CDCA supplementation. The high-carbohydrate diet also increased hepatic glycogen and crude lipid content, both of which were reduced by 0·10 % CDCA. Furthermore, the high-carbohydrate diet-induced oxidative stress, histopathological changes and reduced liver lysozyme activity, which were ameliorated by CDCA supplementation. Molecular analysis showed that the high-carbohydrate diet suppressed FXR and phosphorylated AKT1 (p-AKT1) protein expression in the liver, downregulated insulin signalling (<i>ira</i>, <i>irs</i>, <i>pi3kr1</i> and <i>akt1</i>), gluconeogenesis (<i>pepck</i> and <i>g6pc</i>) and glycolysis genes (<i>gk</i>, <i>pk</i> and <i>pfkl</i>). CDCA supplementation upregulated <i>fxr</i> expression, activated <i>shp</i>, enhanced the expression of insulin signalling and glycolytic genes (<i>gk</i>, <i>pk</i> and <i>pfkl</i>) and inhibited gluconeogenesis. Additionally, CDCA reduced inflammatory markers (<i>nf-κb</i> and <i>il-1β</i>) and restored anti-inflammatory mediators (<i>il-10</i>, <i>iκb</i> and <i>tgf-β</i>). In conclusion, 0·10 % CDCA improved carbohydrate metabolism and alleviated liver inflammation in largemouth bass fed a high dietary carbohydrate, partially through FXR activation.