Abstract:The rapid pace of modern society has led to fatigue becoming a prevalent health problem that affects people of different age groups. Apostichopus japonicus, the only sea cucumber species cultured on a large scale, has recently experienced notable growth in its aquaculture and processing industry. However, approximately 30% of by-products are generated during processing, leading to low utilization and resource wastage. A. japonicus gonads are rich in protein, lipids, polysaccharides, and other nutrients. Studies on its activity mainly focus on antioxidants, immune regulation, and anti-hyperlipidemic effects. However, studies on its anti-fatigue efficacy are limited. Therefore, this study aimed to verify the fatigue-relieving efficacy of A. japonicus gonads. To investigate the anti-fatigue effect of A. japonicus gonads, the basic nutritional composition of the A. japonicus gonads was determined using national standard methods. Healthy male Kunming mice were randomly divided into blank and dose groups, and they performed weight-bearing exhaustion swimming experiments after continuous gavage for 4 weeks. The fatigue model was established to calculate the swimming time and examine the relevant indices of serum and liver tissues in the mice. The results revealed that A. japonicus gonads are rich in various nutrients, with the highest protein content at (56.76±0.04) g/100 g. Lipids were the second most abundant nutrient at (14.65±0.13) g/100 g, providing the necessary energy for the fertilization of the egg. Additionally, A. japonicus gonads contain a certain amount of polysaccharides at (5.35±0.16) g/100g, significantly affecting antioxidant, anti-inflammatory and anticoagulant activity. Mice experiments showed that A. japonicus gonads did not significantly affect the weight gain when comparing blank and dose groups. However, when the liver weight and index of mice were further analyzed, an increase in the liver weight and index of the dose group was observed. However, no significant difference was observed compared with the blank group, possibly because A. japonicus gonads reduced the degree of hepatocyte damage and promoted hepatic glycogen storage. A forced weight-bearing swimming test was used to assess the effect of A. japonicus gonads on the exercise endurance of mice. Mice in the dose group swam significantly longer than those in the blank group, suggesting that A. japonicus gonads enhanced the endurance and anti-fatigue ability of mice. This finding was consistent with previous studies. Further analysis of the serum-related indices revealed that urea nitrogen (BUN) and lactic acid (LA) were significantly reduced after feeding A. japonicus gonads, which may be associated with energy metabolism and reduction of protein catabolism. The reduction of LA content in the body of the exercising mice might alleviate or eliminate the LA accumulation in the mice. Additionally, A. japonicus gonads significantly reduced serum malondialdehyde (MDA) level and creatine kinase (CK) activity and increased the activity of antioxidant-related enzymes, such as superoxide dismutase (SOD), glutathione (GSH) and catalase (CAT). These changes indicated that A. japonicus gonads had good antioxidant capacity, which could effectively slow down or eliminate the mice's oxidative stress damage, thereby alleviating fatigue. In the liver-related index test, the MDA content in the livers of mice was significantly reduced after feeding A. japonicus gonads, whereas SOD, CAT activities and GSH content were significantly increased. These results further confirmed its antioxidant capacity and anti-fatigue effect. However, the anti-fatigue mechanism of A. japonicus gonads remains to be further verified through cellular and molecular experiments. The study results demonstrated that A. japonicus gonads had high nutritional value and were suitable for the development of functional and nutritionally enhanced products. According to the relevant provisions of procedures and test methods for functional evaluation of health food, A. japonicus demonstrated good anti-fatigue ability, effectively alleviating mice's fatigue state by reducing the content of fatigue-related metabolites. It can improve the vitality of antioxidant-related enzymes, alleviating fatigue by reducing oxidative stress damage. This study provides a scientific basis for the high-value utilization of A. japonicus gonads and a novel concept for the development of anti-fatigue-related health food.
