Digestion, absorption, and transport properties of soy-fermented douchi hypoglycemic peptides VY and SFLLR under simulated gastrointestinal digestion and Caco-2 cell monolayers

Two novel hypoglycemic peptides VY and SFLLR were identified from douchi as the major peptides responsible for the glucose uptake activity. The present work aimed to elucidate their digestion, absorption and transport properties using simulated digestion and Caco-2 cell monolayers transport models. Besides, the effects of digestion and absorption on the structure and activity were also studied. The results showed that VY was resistant to gastrointestinal tract digestion and could cross Caco-2 cell monolayers intactly via both TJs-mediated passive paracellular pathway and PepT1-mediated active route. In comparison, SFLLR was partially degraded into small fragments of SFLL, SFL, and SF by the digestive system, leading to increased glucose uptake activity. Notably, SFLLR, SFLL, and SFL were partly hydrolyzed by aminopeptidase N or dipeptidyl peptidase IV during transport, but they were transported intact. SFL was transported via both paracellular diffusion and PepT1-mediated routes, while SFLLR and SFLL were via paracellular route only.

Automated summary

Two novel hypoglycemic peptides, VY and SFLLR, were identified from douchi and found to be the major components responsible for glucose uptake activity. This study aimed to investigate their digestion, absorption, and transport properties using simulated digestion and Caco-2 cell monolayers transport models. The results showed that VY could cross the Caco-2 cell monolayers intact via both passive paracellular pathway and active PepT1-mediated route, while SFLLR was partially degraded but still transported intact through the paracellular route.