Generation of dipeptidyl peptidase IV (DPP-IV) inhibitory peptides during the enzymatic hydrolysis of tropical banded cricket (Gryllodes sigillatus) proteins

Tropical banded crickets (Gryllodes sigillatus) were studied for their ability to yield hydrolysates with dipeptidyl peptidase IV (DPP-IV) inhibitory properties. A cricket protein isolate (CPI) was prepared following extraction of the water soluble proteins from G. sigillatus powder (CP). The extraction yield and purity were 20.90 +/- 0.35% and 57.0 +/- 2.23%, respectively. Endogenous proteinase activities were detected in the CP, which were linked to the significant protein breakdown seen in this sample. Fifteen CPI hydrolysates (H1-H15) were generated with Protamex(TM) using a design of experiments (DOE) approach combining three parameters, temperature (40, 50 and 60 degrees C), enzyme to substrate ratio (E : S, 0.50, 1.25 and 2.00% (w/w)) and hydrolysis time (60, 150 and 240 min). The DPP-IV half maximal inhibitory concentrations (IC50) of the CPI hydrolysates ranged from 0.40 +/- 0.03/0.40 +/- 0.02 (H2/H3) to 1.01 +/- 0.07 mg mL(-1) (H7). Following simulated gastrointestinal digestion (SGID), the DPP-IV IC50 of CPI decreased (> 3.57 vs. 0.78 +/- 0.04 mg mL(-1)) while that of H5 increased (0.47 +/- 0.03 vs. 0.71 +/- 0.06 mg mL(-1)). This study has demonstrated for the first time that G. sigillatus protein hydrolysates are able to inhibit DPP-IV. The study of these hydrolysates in vivo is needed to evaluate their potential role in glycaemic management.