Abstract
AIM: To determine the relative potency and contribution of intestinal nutrients to net gastric accommodative relaxation and conscious perception. METHODS: In 12 healthy subjects, we randomly tested duodenal loads of lipids and carbohydrates (12 mL administered in 4 min) at various caloric concentrations (0.0125-0.8 kcal/mL) separated by 12-24 min wash-out periods of saline infusion. Maximal gastric relaxation was induced at the end of each experiment by i.v glucagon (5 microg/kg), as reference. The reflex gastric response was measured by a barostat, and symptom perception by a 0-6 score questionnaire. RESULTS: Lipids induced a dose-response gastric relaxation with a steep and early rise. Maximal effect (179+/-42 mL relaxation) reached at a relatively low concentration (0.2 kcal/mL), maximal lipid-induced relaxation was 61+/-6% of the glucagon effect. By contrast, duodenal infusion of carbohydrates induced weaker relaxation that became significant only at the high end of the physiological concentration range (65+/-14 mL with 0.8 kcal/mL). Intestinal nutrient loads, either of lipid or carbohydrates, did not induce significant changes in perception (0.6+/-0.4 and 0.1+/-0.4 score increase for the highest concentrations, respectively). CONCLUSION: Chyme entering the small bowel induces nutrient-specific gastric relaxatory reflexes by a physiologically saturable mechanism. Normally, neither the intestinal nutrient load nor the gastric accommodative response is perceived.