Dipeptidyl peptidase-IV inhibitory activity of dairy protein hydrolysates

Dipeptidyl peptidase (DPP)-IV inhibitors are promising new therapies for type 2 diabetes. Currently, these inhibitors are only available as synthetic drugs. Therefore, the aim of the present study was to investigate dairy protein hydrolysates as natural sources of DPP-IV inhibitors. While the DPP-IV inhibitory activity of sodium caseinate, skim milk powder and milk protein concentrate hydrolysates increased over the course of in vitro pepsin-pancreatin digestion, whey protein isolate (WPI) hydrolysate showed highest inhibitory activity following peptic digestion. Hydrolysates produced from sodium caseinate using 11 different proteases displayed higher inhibitory activity than most WPI hydrolysates. However, among all enzymatic treatments investigated, peptic digestion of WPI resulted in the greatest DPP-IV inhibitory activity (IC50 of 0.075 mg mL−1). Fractionation of the hydrolysates by size generally improved the inhibitory activity. This study shows that peptides with DPP-IV inhibitory activity can be generated from dairy ingredients.