腸管上皮トランスポーターと機能性食品成分の相互作用(<特集>第66回大会シンポジウム「ビタミン・バイオファクタートランスポーター研究の最前線」)

抄録

Intestinal epithelial cells (IECs) have various functions, including absorption of food components, barrier function against xenobiotics, and immune function. In this study, we examined the absorption mechanism of functional food components in IECs. For example, alpha-lipoic acid, widely used as a functional food component or food supplement, is presumably transported through the intestinal epithelial-like Caco-2 monolayer via a proton-coupled medium-chain fatty acid transporter. Furthermore, among methoxyflavonoids which are contained in citrus fruits, nobiletin and tangeretin permeate across the Caco-2 monolayer by passive diffusion, while hesperetin permeates across the Caco-2 monolayer via a proton-coupled transporter. These results suggest that functional food components are absorbed via various pathways. On the other hand, IECs are most frequently exposed to food ingredients. Therefore, it is plausible that the activity of intestinal epithelial transporters is regulated by other food components. We focused on the sodium-dependent glucose transporter 1(SGLT1) and glucose transporter 5 (GLUT5), responsible for intestinal glucose and fructose uptake, respectively, and searched for phytochemicals which inhibit SGLT1 or GLUT5 activity. As a result, some phytochemicals such as epicatechin gallate, which are present in green tea, inhibited SGLT1 and GLUT5 activities. These phytochemicals are expected to be useful for prevention of metabolic syndrome caused by excessive carbohydrate intake.