Effects of Glycyrrhizin (GL) Supplementation on Survival, Growth Performance, Expression of Feeding-Related Genes, Activities of Digestive Enzymes, Antioxidant Capacity, and Expression of Inflammatory Factors in Large Yellow Croaker ( Larimichthys crocea ) Larvae.

A 30-day feeding trial was conducted to determine the effects of dietary glycyrrhizin (GL) on survival, growth performance, expression of feeding-related genes, activities of digestive enzymes, antioxidant capacity, and expression of inflammatory factors of large yellow croaker larvae with an initial weight of 3.78 ± 0.27 mg. Four 53.80% crude protein and 16.40% crude lipid diets were formulated with supplementation of 0%, 0.005%, 0.01%, and 0.02% GL, respectively. Results indicated that larvae fed diets with GL had higher survival rate and specific growth rate than the control ( P < 0.05). Compared with the control, the mRNA expression of orexigenic factor genes including neuropeptide Y ( npy ) and agouti-related protein ( agrp ) were significantly increased in larvae fed the diet with 0.005% GL, while the mRNA expression of anorexigenic factor genes including thyrotropin-releasing hormone ( trh ), cocaine and amphetamine regulated transcript ( cart ), and leptin receptor ( lepr ) were significantly decreased in larvae fed the diet with 0.005% GL ( P < 0.05). The trypsin activity in larvae fed the diet with 0.005% GL was significantly higher than the control ( P < 0.05). The alkaline phosphatase (AKP) activity in larvae fed the diet with 0.01% GL was significantly higher than the control ( P < 0.05). A clear increase of total glutathione (T-GSH) content, activities of superoxide dismutase (SOD), and glutathione peroxidase (GSH-Px) was observed in larvae fed the diet with 0.01% GL compared with the control ( P < 0.05). Moreover, the mRNA expression of interleukin-1 β ( il-1β ) and interleukin-6 ( il-6 ) (proinflammatory genes) in larvae fed the diet with 0.02% GL were significantly lower than the control ( P < 0.05). In conclusion, the supplementation of 0.005% -0.01% GL could enhance the expression of orexigenic factor genes, activities of digestive enzymes and antioxidant capacity, ultimately improving the survival, and growth performance of large yellow croaker larvae.