Effect and mechanism of action of pine bark extract on glucose uptake by Caco‐2 cells

Abstract

This work investigated the effect of pine bark extract (PBE) on glucose uptake by Caco‐2 cells. Cells were incubated in presence of PBE and [14C] 3‐O‐methyl‐D‐glucose and the change in radioactivity of the incubation medium was measured. PBE reduced significantly glucose uptake but did affect neither the activity nor the expression of the Na+/K+ ATPase suggesting that PBE affects the level of apical glucose transporters. To test this hypothesis, glucose uptake was measured in presence of inhibitors of Sodium‐dependent Glucose Transporter 1(SGLT1) and Facilitated‐Diffusion Glucose Transporter 2 (GLUT2), as well as different signaling mediators known to be involved in glucose transport. The results showed that PBE acts by activating p38 Mitogen‐activated protein (MAP) kinase which in turn activates SGLT1 transporters and two different pathways that target GLUT2: an inhibitory one involving Phosphatidylinositol‐3 kinase and a stimulatory one involving MAP/Extracellular signal‐regulated kinase. The effect of PBE was not attributed to the major ingredient, proanthocyanidins, since glucose uptake was increased in its presence. Supported by URB.