Characterization of an insulinotropic peptide from skin secretions of Odorrana andersonii.

Insulinotropic peptide agents are regarded as potential candidates for anti-diabetic treatment. In the present study, a novel insulinotropic peptide, termed OA-A1, was purified from frog skin secretions of Odorrana andersonii. Mature OA-A1 was determined to be a 1965.049 Da peptide with an amino acid sequence of LVGKLLKGAVGDVCGLLPIC, in which an intramolecular disulfide bridge was formed by two cysteine residues. At the cellular level, OA-A1 exhibited potent proliferation promoting effects on mouse-derived pancreatic β-TC-6 cells and significantly stimulated insulin release in β-TC-6 cells at a minimum concentration of 1 nM. In the animal model, OA-A1 also showed a dose-dependent insulin-releasing role in mice. At concentrations ranging from 1 nmol/kg to 1 μmol/kg, OA-A1 had a significant acute hypoglycemic effect on streptozotocin (STZ)-induced diabetic mice. The pancreatic islet areas of diabetic mice increased dose-dependently after 21 days of OA-A1 treatment (1-100 nmol/kg) compared with those of the saline control group. Moreover, OA-A1 significantly improved the oral glucose tolerance of STZ-induced diabetic mice. Taken together, these results suggest that OA-A1 provides an excellent template for the development of novel anti-diabetic therapeutic agents. Copyright © 2017 European Peptide Society and John Wiley & Sons, Ltd.