Abstract
<h2>Summary</h2> <i>Katsuodashi</i> 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% <i>Katsuodashi</i> on postprandial blood glucose levels. Postprandial blood glucose levels were significantly suppressed by 5% <i>Katsuodashi</i>. Thus, 5% <i>Katsuodashi</i> 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 <i>Katsuodashi</i> 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 <i>Katsuodashi</i>. Furthermore, Ala-Trp and Gly-Trp demonstrated inhibitory activity against DPP-IV with an IC<sub>50</sub> value of 85.91 μg/mL and 363.60 μg/mL, respectively. These results indicate that <i>Katsuodashi</i> 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)
Highlights
Japanese cuisine is recognized worldwide as being delicious and healthy
We have previously reported that 10% Katsuodashi suppresses postprandial blood glucose levels and inhibits dipeptidyl peptidase IV (DPP-IV) activity without inhibiting a-glucosidase activity [4]
As several processes are involved from the time of intake of Katsuodashi to insulin secretion, it is assumed that a long time is required for the suppression of postprandial blood glucose levels
Summary
Japanese cuisine is recognized worldwide as being delicious and healthy. Katsuodashi, a soup stock that obtains umami and aroma from Katsuobushi, is one of the most important seasonings in Japanese cuisine. The umami of Katsuodashi improves the palatability of the low-salt, low-sugar, and low-fat cuisine. Japanese people consume thinly shaved Katsuobushi as a health food. Miso soup with thinly shaved Katsuobushi is consumed when people are tired or have a hangover; this soup is known as Kachuyu and Chabushi in Okinawa and Kagoshima, respectively. Katsuobushi and Katsuodashi serve as seasonings and as functional foods.
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