(P26-037-25) Peptides From Adzuki Bean (Vigna angularis) β-Vignin and Soybean β-Conglycinin (Glycine max) Revealed Potential Antidiabetic and Antilipogenic Activity

Objectives: To compare the antidiabetic and antilipogenic potential of adzuki bean β-vignin (AB7S) and soybean β-conglycinin (S7S) functional peptides in regulating hepatic glucose and lipid metabolism.

Methods: Human liver cells (HepG2) were treated with either AB7S peptides—Val-Pro (VP; 215 Da) and Pro-Met (PM; 247 Da)—or S7S peptides—Ile-Pro-Ala (IPA; 300 Da) and Leu-Leu-Ser (LLS; 332 Da)—at various concentrations or gliptin, a dipeptidyl peptidase IV (DPP IV) inhibitor. RP-HPLC and ESI-MS verified the peptide sequence. Cell viability (CV) was measured using MTS-CV and a luminescence-based assay to determine DPP IV activity in the cells. A peptide interaction study was performed to investigate the role of peptides on synergistic, antagonistic, or additive DPP IV inhibition. Western blot was used to evaluate the protein expression of markers in the glucose uptake (GU) and lipogenesis (LG) pathways, such as IRS-1, Akt, GLUT 2, SIRT 1, and SREBP-1. ANOVA and post-hoc tests were conducted, and p < 0.05 was considered statistically significant.

Results: The peptide solubility of VP, PM, IPA, and LLS was ≥ 1 mg/mL in water. VP, PM, and IPA (1.78 nM-1.78 µM) did not affect the CV of HepG2 cells, with no significant difference from the untreated cells (p > 0.05), while peptide LLS (1.78 µM) significantly decreased the CV (89%, p < 0.05). Peptide concentrations needed to inhibit DPP IV activity were 1.13 μM (PM; IC₂₅), 0.72 μM (VP; IC₅₀), 0.083 μM (IPA; IC₅₀), and 0.03 μM (LLS; IC₂₀). IPA treatment (1.78 µM) decreased the protein expression of SIRT-1 (~27%) and active-SREBP-1 (~19%) compared to the untreated cells (p < 0.05). The ratio of active-SREBP-1/inactive SREBP-1 was 0.35, suggesting lower SREBP-1 activity after the IPA treatment. VP treatment (1.78 µM) increased the protein expression of Glut 2 (~34%) compared to the untreated cells (p < 0.05) and comparable to that of gliptin (0.08 µM).

Conclusions: Compared to digested protein AB7S, tested peptides from AB7S and S7S were more effective in DPP IV inhibition. IPA effectively suppressed the hepatic LG pathway, while VP effectively enhanced the GU pathway compared to gliptin, suggesting their effectiveness in modulating type 2 diabetes-related markers.

Funding Sources: Division of Nutritional Sciences, University of Illinois, and USDA Pulse Crop Health Initiative.