Foregut Exclusion Disrupts Intestinal Glucose Sensing and Alters Portal Nutrient and Hormonal Milieu

The antidiabetes effects of Roux-en-Y gastric bypass (RYGB) are well-known, but the underlying mechanisms remain unclear. Isolating the proximal small intestine, and in particular its luminal glucose sensors, from the nutrient stream has been proposed as a critical change, but the pathways involved are unclear. In a rodent model, we tested the effects of isolating and then stimulating a segment of proximal intestine using glucose analogs to examine their impact on glucose absorption (Gabsorp) and hormone secretion after a glucose bolus into the distal jejunum. Analogs selective for sodium-glucose cotransporter (SGLT) family members and the sweet taste receptor were tested, and measurements of the portosystemic gradient were used to determine Gabsorp and hormone secretion, including GLP-1. Proximal intestinal isolation reduced Gabsorp and GLP-1 secretion. Stimulation of the glucose-sensing protein SGLT3 increased Gabsorp and GLP-1 secretion. These effects were abolished by vagotomy. Sweet taste receptor stimulation only increased GLP-1 secretion. This study suggests a novel role for SGLT3 in coordinating intestinal function, as reflected by the concomitant modulation of Gabsorp and GLP-1 secretion, with these effects being mediated by the vagus nerve. Our findings provide potential mechanistic insights into foregut exclusion in RYGB and identify SGLT3 as a possible antidiabetes therapeutic target.