Intraduodenal protein modulates antropyloroduodenal motility, hormone release, glycemia, appetite, and energy intake in lean men

Abstract

BACKGROUND: Intraduodenal fat and carbohydrate modulate antropyloroduodenal motility and hormone release and suppress appetite and energy intake in a load-dependent manner. Protein also suppresses energy intake, but its effects on these gastrointestinal factors and their role in the appetite-suppressive effects of protein remain unclear. OBJECTIVE: We aimed to characterize the effects of different intraduodenal protein loads on antropyloroduodenal pressures, gastrointestinal hormone release, glucose and insulin concentrations, appetite perceptions, and energy intake. DESIGN: Sixteen lean, healthy men were studied on 4 occasions in a randomized, double-blind fashion. Antropyloroduodenal pressures, plasma glucagon-like peptide 1 (GLP-1), cholecystokinin, peptide YY, ghrelin, blood glucose, serum insulin, and appetite were measured during 60-min, 4-mL/min intraduodenal infusions of protein at 0.5, 1.5, or 3 kcal/min or saline (control). Energy intakes at a buffet lunch consumed immediately after the infusion were quantified. RESULTS: Increases in the load of protein resulted in greater suppression of antral motility, greater stimulation of basal and isolated pyloric pressures and plasma cholecystokinin and GLP-1 concentrations, and greater suppression of energy intake. However, energy intake was reduced only after a protein load of 3 kcal/min compared with after all other treatments (P< 0.05). The suppression of energy intake after adjustment for cholecystokinin, GLP-1, and insulin was related inversely with basal pyloric pressure (r = 20.51, P < 0.001). CONCLUSION: The acute effects of intraduodenal protein on antropyloroduodenal motility, gastrointestinal hormone release, glucose, and insulin are load dependent and contribute to the suppression of energy intake.