Dietary supplementation with protein hydrolysates from the shell of red swamp crayfish (Procambarus clarkii) affects growth, muscle antioxidant capacity and circadian clock genes expression of zebrafish (Danio rerio)

Protein hydrolysates are rich in amino acids and bioactive peptides, beneficial for the organism health. This study analyzed not only the effects of dietary supplementation with P. clarkii shell protein hydrolysates (PCSPHs) on the growth performance, muscle biochemical indices and histological characteristics of zebrafish, but also the changes of muscle antioxidant capacity and circadian clock genes expression were also evaluated. After feeding, the final body weight, weight gain rate and specific growth rate of zebrafish fed with PCSPHs supplementation were significantly higher than normal diet, and reduced contents of muscle triglyceride and aspartate aminotransferase. Meanwhile, dietary supplementation with PCSPHs improved total amino acid contents and myofiber structure of zebrafish. Antioxidant enzyme activities of total superoxide dismutase (T-SOD), catalase (CAT), glutathione peroxidase (GPx) and glutathione (GSH) content, and the expression of antioxidant related genes increased with PCSPHs supplementation. Furthermore, the expression of Nrf2 protein showed a significantly up-regulated trend with the increasing of dietary PCSPHs levels. However, it was interesting that the expression of circadian rhythm related genes was also affected by dietary PCSPHs levels, and showed a significant up-regulated and down-regulated trend. The above results showed that dietary supplementation with PCSPHs could promote the growth performance, muscle amino acid contents and myofiber structure of zebrafish, but also enhance the muscle antioxidant capacity and regulates the expression of circadian clock genes. It is hypothesized that this may be related to the expression of antioxidant signaling pathway Nrf2/Keap1. Our study will provide a theoretical basis for improving the muscle quality and health of aquatic animals.