Effects of Sea Cucumber Crude Peptides on Exercise Fatigue and Gut Microbiota in Mice

To evaluate the regulatory effects of sea cucumber crude peptides (SCP) on exercise fatigue and gut microbiota dysbiosis in mice, SCP was prepared from sea cucumber (Apostichopus japonicus). Six-week-old male C57BL/6J mice were divided into four groups: Control group, exercise fatigue (EF) group, SCP group, and β-nicotinamide mononucleotide (NMN) group. Exercise endurance was assessed by weighted swimming, grip strength, and rotarod tests. Anxiety-like behaviors induced by exercise fatigue were evaluated using the open-field test and elevated plus maze tests. Muscle, serum, and fecal samples were collected for H&E staining, biochemical analysis, RT-qPCR, and 16S rRNA sequencing. The results showed that, compared with the Control group, mice in the EF group exhibited significantly decreased exercise endurance and markedly increased anxiety-like behaviors. Serum levels of alanine aminotransferase, aspartate aminotransferase, urea nitrogen, creatinine, creatine kinase, interleukin-6, and interleukin-1β were significantly elevated, while the serum testosterone/cortisol ratio in EF mice was significantly decreased. Compared with the EF group, supplementation with SCP and NMN significantly prolonged the weighted swimming exhaustion time and increased grip strength and rotarod retention time in mice. The open-field and elevated plus maze tests showed that SCP and NMN supplementation improved anxiety-like behaviors in mice with exercise fatigue. Meanwhile, SCP reduced serum urea nitrogen and creatine kinase levels in mice. RT-qPCR results showed that SCP upregulated the mRNA expression levels of AMPKα1, AMPKα2 and PGC-1α and downregulated the mRNA expression levels of TLR4, MyD88, and p65. The 16S rRNA sequencing results showed that, compared with the Control group, the relative abundance of potentially harmful bacteria, such as Parasutterella and Erysipelotrichaceae, was increased in the gut of EF mice, whereas the relative abundance of beneficial bacteria, including Muribaculaceae, Lactobacillaceae, and Akkermansiaceae, was decreased. Compared with the EF group, SCP intervention increased the relative abundance of Muribaculaceae and Akkermansiaceae. SCP enhanced exercise endurance, alleviated muscle injury, and improved anxiety-like behaviors induced by exercise fatigue in mice. In addition, SCP may exert anti-fatigue effects by regulating the gut microbiota structure. This study may provide new insights into the development and application of SCP in anti-fatigue functional foods.