Effect of Germinated Chickpea Protein Hydrolysate on Markers of Type-2 Diabetes and Its Relationship to Bitter Taste Receptor Expression

OBJECTIVES: To evaluate the effect of an optimized germinated chickpea protein hydrolysate (GCPH) on markers of type-2 diabetes such as dipeptidyl peptidase-IV (DPP-IV) inhibition, glucose uptake and expression of glucose transporters in enterocytes and their relationship to bitter taste receptor expression. METHODS: GCPH was characterized using LC-ESI-MS/MS. The bioactivity of the peptides and bitterness were characterized using the BioPep database. Predicted activation of bitter receptors was determined with BitterX. The energy of affinity was determined using molecular docking with DPP-IV, SGLT1, GLUT2, lipoprotein lipase (LPL) and fatty acid synthase (FAS). Glucose uptake was evaluated in Caco-2 cells and 3T3-L1 MBX adipocytes. The expression of glucose transporters SGLT1and GLUT2, and DPP-IV inhibition after GCPH treatment were also evaluated in Caco-2 cells. Lipid accumulation, triglycerol content, LPL and FAS activities were analyzed in 3T3-L1 MBX adipocytes. RESULTS: Three peptides, FDLPAL, GEAGR and VVFW were identified from legumin, all of which inhibited DPP-IV. Bitter fragments were found in several peptides and were predicted to activate bitter receptor hTAS2R14. FDLPAL was the most potent peptide inhibiting DPP-IV (−9.4 kcal/mol), SGLT1 (−9.3 kcal/mol) the enoyl-acyl carrier protein-reductase domain (−10.5 kcal/mol) and FAS β-ketoacyl reductase domain (−8.9 kcal/mol). VVFW was the most potent in inhibiting LPL (−6.6 kcal/mol) and GLUT2 (−11.2 kcal/mol). GEAGR was the most potent inhibitor of FAS thioesterase domain (−7.4 kcal/mol). GCPH inhibited DPP-IV (P < 0.05) in Caco-2 cells (IC50 2.1 mM) and glucose uptake at 1 mM (22%, P < 0.05) compared to untreated cells. GLUT2 expression was not different from a known inhibitor (phloretin, 100 μM, p > 0.05) at 2.5 mM. Bitter receptor TAS2R38 expression was suppressed with GCPH increasing concentrations up to 6.4-fold at 2.5 mM GCPH. CONCLUSIONS: GCPH inhibited glucose uptake in enterocytes and GLUT2, DPP-IV and TAS2R38 in a dose-dependent manner. GCPH showed potential to be used as a functional ingredient in industrially processed foods. FUNDING SOURCES: USDA\Pulse Crop Health Initiative.