Poecilobdella manillensis Bioactive Peptides Reduce Oxidative Stress and Regulate Metabolic Reprogramming via the IIS/FOXO Pathway to Improve Hypoxic Injury

FOXO/DAF-16 is involved in stress resistance and metabolic regulation, but the molecular mechanisms of its interaction with hypoxia remain unclear. This study aimed to evaluate the anti-hypoxic effects of Poecilobdella manillensis bioactive peptide (PMP) and to investigate whether IIS/FOXO acts as a key node in mediating the regulation of oxidative stress and metabolic reprogramming. In the chemical hypoxia model of Caenorhabditis elegans (C. elegans) induced by sodium sulfite, PMP treatment improved the survival status and movement, feeding, and reproductive ability of hypoxic C. elegans, and significantly increased their survival rate. It also reduced reactive oxygen species (ROS) and lipofuscin levels in C. elegans, enhancing their tolerance to oxidative and heat stress. In the terminal normobaric hypoxia mice model, PMP intervention prolonged the survival time of hypoxic mice, alleviated the damage of heart, lung, and brain tissues, and increased superoxide dismutase (SOD) activity and glutathione (GSH) levels, and decreased malondialdehyde (MDA) concentrations and lactate dehydrogenase (LDH) activity in serum and tissues of mice. ¹H-NMR metabolomics analysis showed that PMP treatment reversed hypoxia-induced abnormalities in key metabolites such as glucose, lactic acid, glutamic acid, and taurine. Next, we utilized C. elegans mutants deficient in daf-2, age-1, akt-1, daf-16, and hsp-16.2, and further observed the nuclear translocation of DAF-16 in DAF-16::GFP C. elegans. The results showed PMP induced DAF-16 nuclear translocation and upregulated the expression of downstream SOD-3. Key metabolites representing antioxidant and energy metabolism were measured in the daf-16 mutant C. elegans. The results showed that PMP intervention failed to restore the levels of glucose, lactic acid, glutamic acid, and taurine in the mutant. Finally, 12 peptides containing antioxidant-related bioactive amino acid residues in PMP were screened by UPLC-Q-Exactive-MS and peptide biological activity prediction. Among them, molecular docking showed that KPPGP had a good binding with FOXO1. In conclusion, in C. elegans, PMP activated DAF-16/FOXO by inhibiting the Insulin/insulin-like growth factor-1 signaling (IIS) pathway and regulated redox homeostasis and metabolic reprogramming to resist hypoxia injury, and this protective effect was also observed in mouse models. IIS/FOXO can be used as a key node to regulate oxidative stress and energy metabolism under hypoxic conditions, and the identification of KPPGP provides insights into the screening and study of bioactive peptides in natural products.