Common bean (Phaseolus vulgaris L.) protein-derived peptides increased insulin secretion, inhibited lipid accumulation, increased glucose uptake and reduced the phosphatase and tensin homologue activation in vitro

The objective of this study was to evaluate and compare the effect of peptides produced from hard-to-cook common bean proteins on insulin secretion from pancreatic β-cells and glucose uptake from insulin-resistant adipocytes, and to understand the mechanism of action on markers related to glucose metabolism, in vitro. Hydrolysates and peptide fractions < 1 kDa of two common bean varieties (pinto Durango and black 8025) were produced with alcalase and bromelain, and were further hydrolysed with pepsin-pancreatin to simulate gastrointestinal tract digestion. All bean treatments were able to increase glucose-stimulated insulin secretion from rat insulinoma INS-1E cells, reduced the expression of proteins like dipeptidyl peptidase IV (DPP-IV) and receptor for advanced glycation end products (RAGE) and significantly reduced oxygen species (up to 70%). Peptides also inhibited lipid accumulation in mature adipocytes 3T3-L1 and increased glucose uptake (67%) via Akt modulation in insulin resistant adipocytes enhancing insulin signalling and reducing the phosphatase and tensin homologue (PTEN) activation.