Dipeptidyl peptidase-IV inhibitory peptides derived from salmon milt and their effects on postprandial blood glucose level

The hydrolysate of Oncorhynchus keta (chum salmon) milt was found to exhibit strong inhibitory activity against dipeptidyl peptidase-IV (DPP-IV), and the hypoglycaemic effect of these salmon milt peptides (SMPs) was confirmed using oral starch tolerance tests in Sprague–Dawley rats. Specifically, the oral administration of SMPs at a dose of 300 mg/kg body weight for 1 week resulted in a significant decrease in the blood glucose level of the rats 60 min after starch consumption compared with the control. The bioassay-guided separation of SMPs, using a combination of column chromatographic techniques, led to the identification of 12 active di-, tri- and tetrapeptides, including four novel DPP-IV inhibitory peptides, namely Phe-Pro-Val-Gly, Leu-Pro-Val-Leu, Val-Pro-Phe-Pro and Ile-Pro-Leu. Among these 12 peptides, Ile-Pro contributed the most (1.3%) to the total DPP-IV inhibitory activity of SMPs. Therefore, SMPs may have the potential to be used as a suppressor of postprandial hyperglycaemia and to be considered a promising functional food material for the prevention of type II diabetes.