Effects of supplementation with grass carp protein versus peptide on swimming endurance in mice

Objective: We investigated the effects of grass carp protein or peptide administration on swimming endurance in mice. Methods: Grass carp protein or peptide was intragastrically administered to male National Institutes of Health mice at low [1 mg/(g.d)] and high [5 mg/(g.d)] doses, continuously once per day before swimming exercise. After training for 28 d, fatigue-related biochemical parameters, including liver glycogen, gastrocnemius muscle glycogen, plasma glucose, serum lactic acid, blood urea nitrogen, superoxide dismutase (SOD), glutathione peroxidase, and catalase (CAT), were assayed. Results: Compared with the control group, all treatments applied significantly prolonged the exercise time, and high-dose peptide administration was the most effective (P < 0.001). Liver glycogen was remarkably increased by seven times or more by protein or peptide ingestion compared with that of the control group. High-dose protein or peptide addition significantly elevated liver glycogen, muscle glycogen, glucose level, and the removal of metabolites, serum lactic acid, and blood urea nitrogen was greater after exercise. In terms of the comparison between protein versus peptide, high-dose peptide addition significantly enhanced CAT (P = 0.016) and SOD (P = 0.007), while no significant differences were observed for glutathione peroxidase, glucose, liver glycogen, or muscle glycogen between high-dose peptide and protein addition. The difference between low-dose protein and peptide supplementation was not significant. Conclusion: Grass carp protein or peptide significantly improved the endurance capacity of mice. The superiority of peptide over protein was observed at high-dose supplementation, which was mainly attributed to the significant enhancement of antioxidant enzyme levels (CAT and SOD). (C) 2011 Elsevier Inc. All rights reserved.