Sally D Poppitt, Hyun Sang Shin, Anne-Thea McGill, Stephanie C Budgett, Kim Lo, Malcolm Pahl, Janice Duxfield, Mark Lane, John R Ingram

Background: Activation of the ileal brake through the delivery of nutrients into the distal small intestine to promote satiety and suppress food intake provides a new target for weight loss. Evidence is limited, with support from naso-ileal lipid infusion studies.Objective: The objective of the study was to investigate whether glucose infused into the duodenum and ileum differentially alters appetite response, food intake, and secretion of satiety-related gastrointestinal peptides.Design: Fourteen healthy male participants were randomly assigned to a blinded 4-treatment crossover, with each treatment of single-day duration. On the day before the intervention (day 0), a 380-cm multilumen tube (1.75-mm diameter) with independent port access to the duodenum and ileum was inserted, and position was confirmed by X-ray. Subsequently (days 1-4), a standardized breakfast meal was followed midmorning by a 90-min infusion of isotonic glucose (15 g, 235 kJ) or saline to the duodenum or ileum. Appetite ratings were assessed with the use of visual analog scales (VASs), blood samples collected, and ad libitum energy intake (EI) measured at lunch, afternoon snack, and dinner.Results: Thirteen participants completed the 4 infusion days. There was a significant effect of nutrient infused and site (treatment × time, P < 0.05) such that glucose-to-ileum altered VAS-rated fullness, satisfaction, and thoughts of food compared with saline-to-ileum (Tukey's post hoc, P < 0.05); decreased ad libitum EI at lunch compared with glucose-to-duodenum [-22%, -988 ± 379 kJ (mean ± SEM), Tukey's post hoc, P < 0.05]; and increased glucagon-like peptide-1 (GLP-1) and peptide YY (PYY) compared with all other treatments (Tukey's post hoc, P < 0.05).Conclusions: Macronutrient delivery to the proximal and distal small intestine elicits different outcomes. Glucose infusion to the ileum increased GLP-1 and PYY secretion, suppressed aspects of VAS-rated appetite, and decreased ad libitum EI at a subsequent meal. Although glucose to the duodenum also suppressed appetite ratings, eating behavior was not altered. This trial was registered at www.anzctr.org.au as ACTRN12612000429853.