Influence of dietary alpha-lipoic acid and lipid level on the growth performance, food intake and gene expression of peripheral appetite regulating factors in juvenile grass carp (Ctenopharyngodon idellus)

Higher lipid level used in aquaculture production to improve growth performance, but higher lipid level resulted in lipid accumulation. Our lab previous studies found dietary supplementation 1200 mg kg(-1) LA reduced lipid accumulation and lipid peroxidation in grass carp. So, this study aimed to elucidate the influence of dietary LA supplementation and lipid level on the growth performance, food intake, and gene expression of peripheral appetite factors in juvenile grass carp. A 8-week feeding trial was conducted using four isonitrogenous (32.0% crude protein) diets containing 4% lipid (CT), 4% lipid + 1200 mg kg(-1) LA (CT + LA), 8% lipid (HL), 8% lipid + 1200 mg kg(-1) LA (HL + LA). The results showed that final body weight, weight gain rate, and food intake were significantly decreased by dietary 1200 mg kg(-1) LA supplementation, and the food intake was reduced by high lipid level (P < .05). Meanwhile, the food intake was significantly decreased by LA supplementation after feeding 4 weeks (P < .05). The hepatopancreas lipid content in HL + LA group was significantly lower than that in HL group (P < .05). Furthermore, LA significantly elevated the serum TG and Chol content level in CT + LA group (P < .05). The further study indicated that 1200 mg kg(-1) LA significantly increased mRNA expression of CCK and PYY of intestine, also decreased ghrelin gene expression in CT + LA group (P < .05). The leptin and LEPR gene expression of intraperitoneal fat and liver showed a tendency of increase in CT + LA group, while they were significantly decreased in the liver of HL + LA group (P < .05). The leptin and LEPR gene expression of intraperitoneal fat and liver were significantly increased by dietary high lipid level (P < .05). The leptin gene expression was affected by the the interactions between lipid levels and LA supplementation. Overall, these results suggested that LA supplementation (1200 mg kg(-1)) could promote peripheral anorexigenic factors mRNA expressions and attenuate peripheral orexigenic factors mRNA expressions, thereby reducing food intake and body weight of juvenile grass carp, and dietary high lipid level can increase leptin expression and decrease food intake.