High dietary wheat starch negatively regulated growth performance, glucose and lipid metabolisms, liver and intestinal health of juvenile largemouth bass, Micropterus salmoides

Largemouth bass ( Micropterus salmoides ) were fed with three diets containing 6%, 12%, and 18% wheat starch for 70 days to examine their impacts on growth performance, glucose and lipid metabolisms, and liver and intestinal health. The results suggested that the 18% starch group inhibited the growth, and improved the hepatic glycogen content compared with the 6% and 12% starch groups ( P < 0.05). High starch significantly improved the activities of glycolysis-related enzymes, hexokinase (HK), glucokinase (GK), phosphofructokinase (PFK), and pyruvate kinase (PK) ( P < 0.05); promoted the mRNA expression of glycolysis-related phosphofructokinase ( pfk ); decreased the activities of gluconeogenesis-related enzymes, pyruvate carboxylase (PC), and phosphoenolpyruvate carboxykinase (PEPCK); and reduced the mRNA expression of gluconeogenesis-related fructose-1,6-bisphosphatase-1( fbp1 ) ( P < 0.05). High starch reduced the hepatic mRNA expressions of bile acid metabolism–related cholesterol hydroxylase ( cyp7a1 ) and small heterodimer partner ( shp ) ( P < 0.05), increased the activity of hepatic fatty acid synthase (FAS) ( P < 0.05), and reduced the hepatic mRNA expressions of lipid metabolism–related peroxisome proliferator–activated receptor α ( ppar-α ) and carnitine palmitoyltransferase 1α ( cpt-1α ) ( P < 0.05). High starch promoted inflammation; significantly reduced the mRNA expressions of anti-inflammatory cytokines transforming growth factor-β1 ( tgf-β1 ), interleukin-10 ( il-10 ), and interleukin-11β ( il-11β ); and increased the mRNA expressions of pro-inflammatory cytokine tumor necrosis factor-α ( tnf-α ), interleukin-1β ( il-1β ), and interleukin-8 ( il-8 ) in the liver and intestinal tract ( P < 0.05). Additionally, high starch negatively influenced the intestinal microbiota, with the reduced relative abundance of Trichotes and Actinobacteria and the increased relative abundance of Firmicutes and Proteobacteria . In conclusion, low dietary wheat starch level (6%) was more profitable to the growth and health of M. salmoides , while high dietary starch level (12% and 18%) could regulate the glucose and lipid metabolisms, impair the liver and intestinal health, and thus decrease the growth performance of M. salmoides .