PREVENTIVE AND HYPOGLYCEMIC EFFECTS OF PEPTIDES FROM COMMON BEAN (PHASEOLUS VULGARIS) IN MICE SUBMITTED TO A HIGH-FAT DIET

Food-derived bioactive peptides are promising candidates potentially able to act on metabolic alterations associated with obesity and diabetes. This study evaluated the effects of the low molecular weight peptide fractions from common bean (Phaseolus vulgaris) (<3kDa; PV3) on glucose homeostasis, adiposity, serum lipid profile, and hepatic insulin-signaling markers in mice fed a high-fat diet (HFD). Previous LC–MS/MS profiling identified 35 peptides in PV3, with sequence lengths ranging from 5 to 23 amino acids, with an average molecular mass of 1.14 kDa (Graziani et al.,2021). Male C57BL/6J mice were assigned different groups (n=5 each): control (CT), PV3, HFD, and HFD+PV3 groups. HFD and/or PV3 treatments lasted 10 weeks. PV3 (2.5mg/kg/day) was given orally using a 200-µL micropipette. Body mass, adiposity, fasting glycemia, glucose tolerance (GTT), insulin sensitivity (ITT/kITT), and serum lipids were evaluated. Protein and gene expression were assessed in liver samples at baseline and following ex vivo insulin stimulation. Targets were insulin receptors (IRS), G6Pase, PEPCK, Pi3k, Akt and Pten. Western blotting results were normalized to GAPDH, and RT-qPCR results to Actb mRNA using the 2⁻ΔΔCt method. Data were analyzed by one-way or two-way ANOVA followed by Tukey’s test, with significance set at p < 0.05. Values are mean±SEM. HFD promoted greater body mass gain, adiposity, hyperglycemia, and alterations in serum lipid profile, confirming the establishment of diet-induced metabolic disturbances. PV3 administration attenuated excessive body mass gain (5.87±0.82 vs 8.20±0.47 g in HFD+PV3 and HFD groups, respectively, p=0,068) and reduced epididymal (0.01734±0.00181 vs 0.03275±0.00530 g/g; p=0.0078) and retroperitoneal adipose tissue depots, suggesting a protective effect against the development of diet-induced adiposity. At week nine, fasting glycemia was lower in HFD+PV3 (130.50±6.51 vs 188.75±7.59 mg/dL; p<0.05), whereas GTT AUC did not differ significantly (p=0.9206). PV3-only group showed higher kITT than CT, HFD, and HFD+PV3 (6.21±0.50 vs 1.76±0.30, 3.07±0.40, and 1.90±1.20, respectively; all p<0.05), indicating improved insulin sensitivity. PV3 did not modify the HFD effects on serum lipid profile, but increased protein expression of IRS (p=0.0155), G6Pase (p=0.007) and PEPCk (p=0.0001), and did not affect the consequences of HFD on these hepatic targets. Intriguingly, however, PV3 increased gene expression of IRS in both control (0.0203) and HFD (0.0206) groups while Akt (p=0.01), Pten (p=0.0173) and Pi3k (p<0.001) increases were detected only in liver samples from PV3+HFD group. Current wealth of data suggests that hepatometabolic effects of PV3 rely in the expressed Akt, Pi3K and Pten proteins, whereas PV3 can modulate IRS-triggered genes in HFD. The post-translational mechanisms underlying changes in protein expression ultimately leading to reduced adiposity remain to be elucidated. In conclusion, PV3 improved glycemic control and reduced epididymal adiposity caused by HFD. These results reinforce the potential of common bean peptides as bioactive compounds of nutraceutical interest.