In this study, we observed anti-diabetic effects of acid hydrolyzed silk peptides, where the amount of peptides in the total amino acid mixture was strictly regulated. Using in vitro diabetes models, silk peptide-containing amino acid mixtures of 5.60% (G5), 11.30% (G10), 14.50% (G15), and 20.50% (G20) were examined separately in order to determine whether they have biological activities. According to our results, a cytoprotective effect was observed following treatment of interleukin-1β in RINm5f pancreas β-cells. As a consequence, Bax, a pro-apoptotic gene, was down-regulated, while Bcl-2, a pro-survival gene, was retained at normal level. Results of the 4’,6-diamidino-2-phentylindole (DAPI) staining assay confirmed that G20 has a better cytoprotective effect. Insulin release from RINm5f cells showed a significant increase following treatment with G5-G20, suggesting that silk peptide effectively regulated and induced insulin production. Single treatment with G5-G20 resulted in enhanced glucose uptake in L6 skeletal muscle cells. In addition, a higher amount of each group inhibited the activity of α-glucosidase. In summary, these data suggest that silk peptide may have an anti-diabetic effect through protection of pancreas β-cells and enhancement of insulin release, which showed a close association with Type 1 diabetes mellitus (DM), and can improve glucose uptake, which was the major target for therapy of Type 2 diabetes. Taken together, we concluded that acid hydrolyzed silk peptides can be used effectively for control of blood sugar metabolism via improvement of the problematic indices of Type 1 and Type 2 DM.

• Seong Soo Joo(Department of Marine Molecular Biotechnology, College of Life Science, Gangneung-Wonju National University) Corresponding author