Regulation of intestinal glucose transport by tea catechins.

Intestinal glucose uptake is mainly performed by its specific transporters, such as SGLT 1, GLUT 2 and 5 expressed in the intestinal epithelial cells. By using human intestinal epithelial Caco-2 cells we observed that intestinal glucose uptake was markedly inhibited by tea extracts. While several substances in green tea seem to be involved in this inhibition, catechins play the major role and epicatechin gallate (ECg) showed the highest inhibitory activity. Since our Caco-2 cells did not express enough amount of SGLT 1, the most abundant intestinal glucose transporter, the effect of ECg on SGLT 1 was evaluated by using brush border membrane vesicles obtained from the rabbit small intestine. ECg inhibited SGLT 1 in a competitive manner, although ECg itself was not transported via the glucose transporters. These results suggest that tea catechins could play a role in controlling the dietary glucose uptake at the intestinal tract and possibly contribute to blood glucose homeostasis.