Dietary nano-selenium improves health of liver and intestine of grass carp Ctenopharyngodon idella after overwintering

Abstract

The purpose of this study was to examine the effects of nano-selenium (nano-Se) on the health of liver and intestine of grass carp (Ctenopharyngodon idella) after overwintering. Grass carp were fed three diets contained 0 mg/kg (control group, Se0), 0.3 mg/kg (Se0.3) and 0.6 mg/kg (Se0.6) nano-Se for 60 days before the overwintering. After overwintering, evaluation of the Se deposition, biochemical parameters, histopathology, and the expression of genes involved in inflammation, oxidative stress and tight junctions were performed. The results showed that the content of Se in the liver and intestine were significantly increased as dietary nano-Se level increased. The addition of 0.3 and 0.6 mg/kg nano-Se significantly reduced the levels of glutamic oxaloacetic transaminase (GOT), glutamic pyruvic transaminase (GPT) and malondialdehyde (MDA) in the serum (P < 0.05). The activities of catalase (CAT) and glutathione peroxidase (GSH-Px) were significantly increased and the content of MDA was significantly decreased in the liver by 0.3 and 0.6 mg/kg dietary nano-Se (P < 0.05). In the intestine, the activity of GSH-Px was significantly increased and the content of MDA was significantly decreased by 0.6 mg/kg dietary nano-Se (P < 0.05). The histological results showed that dietary nano-Se alleviated the inflammatory cell infiltration of hepatocytes. The addition of 0.6 mg/kg nano-Se significantly down-regulated the expressions of tlr2, tlr4 and nf-κb p65, and up-regulated the expression of il-10 in the liver of grass carp after overwintering (P < 0.05). The expressions of ifn-γ, tgf-β1 and il-6 in the liver were significantly reduced by adding 0.3 and 0.6 mg/kg dietary nano-Se (P < 0.05). The addition of nano-Se reduced the structural disturbance and the pathological phenomena such as atrophy and adhesion in the intestine. At the same time, nano-Se significantly increased the villus height in the intestine (P < 0.05). Nano-Se also enhanced barrier function of intestine by up-regulating the expression of zo-1 (P < 0.05). Besides, the expressions of tlr2, nf-κb p65, ifn-γ and tnf-α in the intestine were significantly down-regulated by adding 0.6 mg/kg dietary nano-Se (P < 0.05). The expressions of gpx4a and gpx4b in the intestine were significantly decreased by adding 0.3 mg/kg dietary nano-Se (P < 0.05). In conclusion, nano-Se effectively improved the liver and intestine health of grass carp after overwintering by reducing oxidative stress and inflammation, and improving intestinal tight junction, thereby reducing the weight loss of grass carp after overwintering.