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.