Hypoglycaemic effects of functional tri-peptides from silk in differentiated adipocytes and streptozotocin-induced diabetic mice

BACKGROUND: In this study, the tri-peptides Gly-Glu-Tyr (GEY) and Gly-Tyr-Gly (GYG), identified previously as active compounds from the silk peptide E5K6, significantly stimulated basal and insulin-mediated glucose uptake by 3T3-L1 fibroblasts in a dose-dependent manner. RESULTS: Synthetic GEY and GYG peptides at a concentration of 500 μmol L^-1 significantly increased glucose transporter type 4 expression by 157% and 239%, respectively. Differentiation of 3T3-L1 cells into adipocytes leads to accumulation of intracellular fat droplets, and GEY and GYG at a concentration of 250 μmol L^-1 suppressed this effect by 72% and 75%, respectively. GYG improved glucose tolerance in steptozotocin (STZ)-induced diabetic mice in a dose-dependent manner. CONCLUSION: These results suggest that GYG isolated from E5K6 has anti-diabetic potential and silk waste products containing bioactive peptides could be used to the developments of treatments to lower blood glucose.