Apical GLUT2: a major pathway of intestinal sugar absorption.

Understanding the mechanisms that determine postprandial fluctuations in blood glucose concentration is central for effective glycemic control in the management of diabetes. Intestinal sugar absorption is one such mechanism, and studies on its increase in experimental diabetes led us to propose a new model of sugar absorption. In the apical GLUT2 model, the glucose transported by the Na(+)/glucose cotransporter SGLT1 promotes insertion of GLUT2 into the apical membrane within minutes, so that the mechanism operates during assimilation of a meal containing high-glycemic index carbohydrate to provide a facilitated component of absorption up to three times greater than by SGLT1. Here we review the evidence for the apical GLUT2 model and describe how apical GLUT2 is a target for multiple short-term nutrient-sensing mechanisms by dietary sugars, local and endocrine hormones, cellular energy status, stress, and diabetes. These mechanisms suggest that apical GLUT2 is a potential therapeutic target for novel dietary or pharmacological approaches to control intestinal sugar delivery and thereby improve glycemic control.