Dietary sodium butyrate supplementation improves fish growth, intestinal microbiota composition, and liver health in largemouth bass (Micropterus salmoides) fed high-fat diets

The present study evaluated the effect of dietary sodium butyrate (NaBT) supplementation on the growth performance, intestinal microbiota composition, and liver health of largemouth bass Micropterus salmoides fed high-fat diets. Four isonitrogenous and isolipid diets were formulated: a high-fat diet and the high-fat diet supplemented by 0.05% NaBT, 0.1% NaBT, or 0.2% NaBT. Each diet was randomly distributed to triplicate tanks (200 L ) containing 30 fish (initial weight 4.0 ± 0.1 g) per tank. The experimental fish were fed to apparent satiation twice daily for 60 days. The orthogonal polynomial contrasts showed that the weight gain rate (WGR) and specific growth rate (SGR) increased linearly ( P < 0.05) with increasing dietary NaBT levels (P < 0.05). No significant differences were found for feed intake (FI), feed conversion ratio (FCR), condition factor (CF), viscerosomatic index (VSI), and hepatosomatic index (HSI). There were no differences in the alpha diversity indices (including Operational Taxonomic Units, Chao index, and Simpson index) of intestinal microbiota between the various dietary groups ( P > 0.05). For the intestinal microbiota composition, the proportion of Proteobacteria were linearly and cubically increased, whereas the proportion of Tenericutes and Mesomycoplasma were linearly and cubically decreased with the increase of dietary NaBT levels ( P < 0.05). The increasing dietary NaBT levels led to significantly quadratic decrease of alanine aminotransferase (ALT) ( P < 0.05), linear and quadratic decrease of aspartate aminotransferase (AST) ( P < 0.05), and linear, quadratic, and cubic decrease of diamine oxidase (DAO) ( P < 0.05). Hepatic triglyceride (TG) and total cholesterol (TCHO) contents decreased linearly and quadratically with the increase of dietary NaBT levels ( P < 0.05). Increasing dietary NaBT levels linearly, quadratically, and cubically decreased the malondialdehyde (MDA) contents ( P < 0.05). Total superoxide dismutase (T-SOD) and glutathione peroxidase (GPx) activity levels increased linearly with the increasing dietary NaBT levels ( P < 0.05). As the dietary NaBT levels gradually increased, the relative expression of carnitine palmitoyl transferase (CPT1) and peroxisome proliferator-activated receptor α (PPARα) increased linearly, quadratically, and cubically ( P < 0.05), while the relative expression of sterol regulatory element binding protein 1 (SREBP 1) decreased linearly, quadratically, and cubically ( P < 0.05). The relative expression of tumor necrosis factor α (TNF-α) and cysteinyl aspartate specific protease 3 (Caspase 3) decreased linearly and quadratically with the increasing NaBT levels ( P < 0.05). Pearson correlation analysis showed that fish growth was closely correlated with microbiota composition, hepatic lipid accumulation, hepatic antioxidant-related parameters, and hepatic gene expression ( P < 0.05). These results indicated that NaBT could be used to alleviate the negative influence of high-fat diets on fish growth, intestinal microbiota homeostasis, and liver health. • Growth of Micropterus salmoides fed high-fat diets was improved by sodium butyrate. • NaBT alleviates the high-fat diet-induced liver injury and gut microbiota dysbiosis. • The gut microbiota and PPARα play key roles in the beneficial effects of NaBT.