Chemical characterization and DPP IV inhibitory capacity of purified adzuki bean β-vignin digest in comparison to soybean β-conglycinin and in vitro effect of β-vignin on diabetic-related outcomes

Adzuki bean (AB) is a legume with a low glycemic index and is traditionally used in Asian cultures to modulate type 2 diabetes (T2D). Our objectives were to characterize the functional peptides from purified AB β-vignin after simulated gastrointestinal digestion in comparison to soybean β-conglycinin, to evaluate their DPP IV inhibitory capacity, and to determine in vitro the effect of digested AB β-vignin on diabetic-related outcomes using HepG2 cells in healthy and insulin-resistant states. Five peptides (215-742 Da) from AB β-vignin and five peptides (215-447 Da) from β-conglycinin were identified to exhibit bioactivity as DPP IV inhibitors. Molecular docking demonstrated peptides could bind to DPP IV at the same binding site as a diabetic medication, linagliptin. Digested AB β-vignin significantly increased (p < 0.05) hepatic glucose uptake (> 290 %) via DPP IV inhibition (> 40 %) in healthy and insulin-resistant states. IRS-1, Akt-1, and Glut 2 increased after treating cells with digested AB β-vignin in healthy and insulin-resistant states.