Effects of taurine on growth, glucolipids metabolism and hepatic antioxidant of largemouth bass (Micropterus salmoides)

To evaluate the effects of taurine on the growth performance, hepatic glucolipids metabolism, and hepatic antioxidant capacities of Micropterus salmoides. The largemouth bass with an initial weight of (19.00±0.20) g were reared in cages (120 cm×80 cm×150 cm) for 8 weeks, the 18% tapioca starch level was set as the high starch control group (CON), and 0.05% and 0.10% taurine (T0.05 and T0.1) were added based on the control group, and total of 3 treatments, 3 replicates of 50 in each replicate. The results showed that: the addition of taurine to high starch diets resulted in a significant increase in weight gain rate (WGR) and specific growth rate (SGR), a significant decrease in liver crude fat and hepatic glycogen content, and a significant increase in intestinal amylase activity. Liver H.E staining, PAS staining and oil red O staining revealed that compared with CON, hepatocytes in the 0.1% taurine group were structurally intact, with reduced glycogen and fat droplets. Serum glucose, low-density lipoprotein cholesterol, glutamic oxalacetic transaminase and glutamate pyruvic transaminase levels of largemouth bass were significantly decreased after taurine addition. In contrast, alkaline phosphatase and high-density lipoprotein cholesterol were significantly increased. Compared with CON, hepatic G6Pase activity was significantly decreased in the taurine group, while GK and PK activities were significantly elevated, while pfk, gk and glut2 expressions were up-regulated. The expression of hepatic lipid synthesis-related genes dgat1, lxr-1, srebp1, acc1α, fasn and gpat4 were down-regulated after the addition of taurine, while the expression of lipolysis-related genes hsl, mgl, pparα, lpl, atgl and acadm were up-regulated. Compared with CON, cat, sod, il-10 and tgf-β gene expression were up-regulated and nf-κb and il-8 were down-regulated in the taurine group. In summary, adding taurine to high-starch feeds can improve growth, regulate hepatic glucose-lipid metabolism, increase carbohydrate utilization, reduce hepatic glycogen deposition and lipid accumulation, and improve the antioxidant capacity of largemouth bass. Under the experimental conditions, the recommended taurine addition in the largemouth bass feed was 0.10%. This study can provide a theoretical basis for taurine to regulate glucose and lipid metabolism, and provide technical support for improving the utilization of carbohydrates in aquatic animals.