Isolation and characterization of DPP-IV inhibitory peptide from rabbit meat hydrolysate: Mechanism, gastrointestinal resistance, and hypoglycemic effects of Leucyl-Leucine (LL)

The objective of this study was to isolate and purify DPP-IV inhibitory (DPP-IVi) peptides from rabbit meat hydrolysate (RMH) and explore their mechanism of action, stability, and hypoglycemic effects. Various proteases, including pepsin, alcalase, compound proteinase, flavourzyme, and bromelain, were utilized to prepare RMH, with RMH derived from the compound proteinase demonstrating the highest DPP-IV inhibition activity. Employing gel filtration chromatography, RP-HPLC and UPLC-MS/MS, we identified Leucyl-Leucine (LL), a dipeptide exhibiting potent DPP-IV inhibitory activity (IC50 = 99.85 ± 5.45 μM). LL exhibited resistance to simulated gastrointestinal digestion in vitro and competitively inhibited DPP-IV. Molecular docking analysis revealed LL's formation of hydrogen bonds and hydrophobic interactions with key amino acid residues of DPP-IV. Furthermore, LL exhibits good inhibitory activity in situ against DPP-IV., with an IC50 value of 207.40 ± 21.50 μM. In an oral glucose tolerance test (OGTT), LL displayed significant hypoglycemic effects at 30 min after administration. In conclusion, LL derived from rabbit meat hydrolysate exhibited remarkable DPP-IV inhibition activity and hypoglycemic effects, suggesting its potential as a therapeutic candidate for diabetes treatment.