Enzymolysis peptides from Mauremys mutica plastron improve the disorder of neurotransmitter system and facilitate sleep-promoting in the PCPA-induced insomnia mice

For many centuries, Mauremys mutica is highly valued as a food homologous Chinese herbal medicine. It has been considered useful to sedate, nourish brain and promote sleep. However, the animal experimental evidence of its sleep-promoting activity is missing in literature.In this study, PCPA-induced insomnia model was used to explore the sleep-promoting mechanism of enzymolysis peptides from PMM, and its main composition and chemical structure were analyzed.Experiments were performed using PCPA-induced insomnia model, all animals were intraperitoneally injected with PCPA (350 mg/kg·d) for two days. The sleep-promoting effect evaluated using measuring content of 5-HT, GABA, DA, IL-1, BDNF and expression of 5-HT1A receptor and GABAA receptor α1-subunit in mice brain. Primary structure of peptides was identified by HPLC-ESI-QqTOF-MS/MS.Compared with the model group, the content of 5-HT, GABA, IL-1, BDNF in mice brain of PMM peptide groups was increased to varying degrees, the content of DA was decreased, and the gene transcription and protein expression of 5-HT1A receptor and GABAA receptor α1-subunit were almost all returned to normal levels. In addition, the primary structures of most abundant nine typical peptides in PMM peptides were identified.The results showed that PMM peptides could improve the disorder of neurotransmitter system, restore compensatory over-expression 5-HT1A receptor and GABAA receptor α1-subunit, and have a good sleep-promoting effect. The specific amino acid composition, sequence and glycosylation modification of PMM peptides may be the key reason for their activity, which lays a foundation for the subsequent development of sleep-promoting peptide products.