Evaluation of novel angiotensin I-converting enzyme and dipeptidyl peptidase IV inhibitory peptides derived from yak milk based on peptidomics and network pharmacology

Dipeptidyl peptidase IV (DPP-IV) has emerged as a crucial target for the treatment of diabetes. Although DPP-IV inhibitory peptides have been found in a variety of milks, research on yak milk after simulated gastrointestinal digestion (SGID) remains limited. In this study, the digestive properties of yak milk after SGID was investigated and the digest have been found to have a strong DPP-IV inhibitory activity. Subsequently, a novel DPP-IV inhibitory peptide, MAMPLW (MW-6) with IC₅₀ 101.6 ± 1.3 μM, was identified in the digest of yak milk using a combination of molecular docking and peptidomics techniques. After studying its digestive stability, its lower stability value was found, but the DPP-IV inhibition in Caco-2 cells shows a 10.2 ± 0.9 % increase following digestion compared to before digestion. Then the digests of MW-6, i.e. MAMP (MP-4) and MAMPL (ML-5), were found to have high DPP-IV inhibitory activity. To further investigate the cause of elevated digestive activity, the DPP-IV inhibitory activity of MP-4 and ML-5 of 1:1 (v/v) mixture was higher than MW-6. Then the synergistic effects of them in ameliorating diabetes were further investigated by network pharmacology. The result revealed that three key pathways (atherosclerosis, diabetic cardiomyopathy and ACE) were interfered by MP-4 and ML-5. Furthermore, the peptides in digest may have angiotensin I-converting enzyme (ACE) inhibitory activity as predicted and displayed ACE inhibitory activity by assays. Finally, the novel dual DPP-IV and ACE inhibitory peptides MAM, MW-6, MP-4, and ML-5 were identified. Our findings provide a scientific basis for the development of novel functional foods.