Effects of emodin on the physiological responses and antioxidant gene expression of Wuchang bream infected with Aeromonas hydrophila

Abstract

This experiment aimed to investigate the effects of emodin on the physiological responses and antioxidant gene expression of Wuchang bream infected with Aeromonas hydrophila. The experimental diets were prepared with supplementing 0, 30, 100 and 150 mg kg−1 emodin to basal (control) diet respectively, and fed to fish with initial weight of 50.4 ± 2.35 g. All fish were divided into five experimental groups: uninfected fish fed with basal control diet (negative control, NC), infected fish fed with the diet supplemented with 0 (positive control group, PC), 30, 100, and 150 mg kg-1 emodin. The fish were reared for 14 days, sampled at different time points and then analyzed. The results showed that the physiological responses and related antioxidant gene expression of infected Wuchang bream were significantly influenced by the dosage of added emodin and the feeding duration (P < 0.05). Comparing to the positive control group, emodin could inhibit the levels of cortisol (COR), triiodothyronine (T3), and thyroxine (T4) in infected Wuchang bream, with hormone levels reaching equilibrium in the shortest time at 30 and 100 mg kg-1 emodin supplementation. Meanwhile, emodin significantly affected alkaline phosphatase (AKP) activity, glucose (Glu) and triglyceride (TG) contents, and related antioxidant gene expression in infected Wuchang bream (P < 0.05), with the best effect observed at 100 mg kg-1 emodin supplementation in the diet. In conclusion, the supplementation of 100 mg/kg emodin to diet can enhance the resistance of Wuchang bream to A. hydrophila infection via promoting physiological metabolism and antioxidant capacity.