α-lipoic acid regulate growth, antioxidant status and lipid metabolism of Chinese mitten crab Eriocheir sinensis: Optimum supplement level and metabonomics response

The α-lipoic acid (α-LA) is a novel feed additive to improve growth, antioxidant capacity and lipid metabolism in animal husbandry. In this study, isonitrogenous and isoenergetic diets were formulated at seven levels of α-LA (0, 300, 600, 1200, 2400, 4800, or 9600 mg/kg) and fed to the Chinese mitten crab Eriocheir sinensis juveniles for eight weeks. According to weight gain and specific grwoth rate, the optimal level of α-LA supplement in the diet is estimated at 1339–1574 mg/kg for E. sinensis. The α-LA supplement significantly increased the activities of SOD, GSH-Px and T-AOC, and the content of GSH in the hepatopancreas except for SOD in the crabs fed 9600 mg/kg α-LA. Excess dietary α-LA supplement increased the content of MDA in the hepatopancreas. The E. sinensis fed 2400 mg/kg α-LA in the diet showed the highest mRNA expressions of es_TGL1, es_TGL2, es_IL and es_DGL and had higher lipid catabolism when taking 300 mg/kg α-LA than other diets, which coincides with higher mRNA expressions of es_IL, es_DGL and CPT-1 in the hepatopancreas. The crab fed 2400 mg/kg α-LA significantly modified 45 metabolites in serum compared with the control. The supplmentation of α-LA significantly influenced fatty acid metabolism, amino acid metabolism, carnitine metabolism and accumulation of plant antioxidants. This study indicates that α-LA is a promising feed additive to regulate growth, antioxidant status and lipid metabolism in E. sinensis, but its inclusion in the diet should be <2400 mg/kg α-LA to maximize the benefitial effect and minimize side effects.