Effect of Katsuodashi on postprandial blood glucose levels and identification of dipeptidyl peptidase IV inhibitory peptides among its components

Summary Katsuodashi is a crucial component of Japanese cuisine. In this study, we performed an oral meal tolerance test in humans to investigate the effect of 5% Katsuodashi on postprandial blood glucose levels. Postprandial blood glucose levels were significantly suppressed by 5% Katsuodashi. Thus, 5% Katsuodashi is a functional food that may also be useful for reducing postprandial increase in blood glucose. Furthermore, the dipeptidyl peptidase IV (DPP-IV) inhibitory peptides in Katsuodashi were identified using liquid chromatography-electrospray ionization-tandem mass spectrometry. Ala-Trp and Gly-Trp were found to be the DPP-IV inhibitory peptides in Katsuodashi. Furthermore, Ala-Trp and Gly-Trp demonstrated inhibitory activity against DPP-IV with an IC50 value of 85.91 μg/mL and 363.60 μg/mL, respectively. These results indicate that Katsuodashi may have a beneficial effect on type 2 diabetes. (Trial registration: UMIN000034776, https://upload.umin.ac.jp/cgi-open-bin/ctr_e/ctr_view.cgi?recptno=R000039564 )