Nano‑selenium supplements in high-fat diets relieve hepatopancreas injury and improve survival of grass carp Ctenopharyngodon Idella by reducing lipid deposition

Abstract

To investigate the effects of supplementing nano‑selenium (Se) in high-fat diet (HFD) on hepatopancreas health and survival of grass carp, six types of experimental diets including low-fat diet (LFD), HFD and HFD supplemented with four levels (0.3 mg kg−1, 0.6 mg kg−1, 0.9 mg kg−1 and 1.2 mg kg−1) of nano-Se were used. After 10 weeks of feeding, growth, survival rate (SR), serum biochemical parameters, lipid contents of hepatopancreas and muscle, hepatopancreas and intraperitoneal fat histology, expression of genes related to lipid metabolism and AMPK activity in grass carp were determined. Results showed that the concentration of ALT and AST (indices for hepatopancreas injury) in serum significantly increased in grass carp fed with HFD, and the SR of grass carp fed with HFD significantly decreased compared to those fed with LFD, indicating the harmful effects of the HFD on grass carp. However, addition of 0.3 mg kg−1-1.2 mg kg−1 and 0.6 mg kg−1-1.2 mg kg−1 of nano-Se significantly reduced the levels of AST and ALT in grass carp compared to the HFD only group, respectively. As such, the improved SR was found in the grass carp fed with HFD supplied with nano-Se. Further, addition of 0.3 mg kg−1-1.2 mg kg−1 nano-Se in the diet significantly decreased the levels of serum triglyceride and total cholesterol, but improved the high-density lipoprotein cholesterol contents of grass carp, compared with the HFD group. The dietary nano-Se also increased the expression of genes related to fatty acid oxidation and triglyceride hydrolyses, such as PPARα, CPT1, ATGL, and LPL in the hepatopancreas which were suppressed by the HFD. A similar trend was observed in the muscle and intraperitoneal fat. Consequently, the decrease in the lipid contents and size of lipid drops in the hepatopancreas, the hepatosomatic index and the intraperitoneal fat index were observed in the grass carp fed with diets containing nano-Se. The alleviated hepatopancreas injury and improved SR of grass carp may be owing to the reduced lipid deposition by the dietary nano-Se. In addition, supplementation of 0.6 mg kg−1-0.9 mg kg−1 nano-Se in diets significantly enhanced the AMPK (key regulatory molecules of lipid metabolism) activity, which was inhibited by the HFD. In conclusion, supplementing 0.3 mg kg−1-0.6 mg kg−1 of nano-Se in diets relieved hepatopancreas injury and improved survival of grass carp by reducing lipid deposition. This could be due to the regulation of the expression of the genes related to lipid metabolism via the AMPK pathway.