Effects of combined GIP and GLP-1 infusion on energy intake, appetite and energy expenditure in overweight/obese individuals: a randomised, crossover study

Aims/hypothesis Glucagon-like peptide 1 (GLP-1) reduces appetite and energy intake in humans, whereas the other incretin hormone, glucose-dependent insulinotropic polypeptide (GIP), seems to have no effect on eating behaviour. Interestingly, studies in rodents have shown that concomitant activation of GIP and GLP-1 receptors may potentiate the satiety-promoting effect of GLP-1, and a novel dual GLP-1/GIP receptor agonist was recently shown to trigger greater weight losses compared with a GLP-1 receptor agonist in individuals with type 2 diabetes. The aim of this study was to delineate the effects of combined GIP and GLP1 receptor activation on energy intake, appetite and resting energy expenditure in humans. Methods We examined 17 overweight/obese men in a crossover design with 5 study days. On day 1, a 50 g OGTT was performed; on the following 4 study days, the men received an isoglycaemic i. v. glucose infusion (IIGI) plus saline (154 mmol/l NaCl; placebo), GIP (4 pmol kg-1 min-1), GLP-1 (1 pmol kg-1 min-1) or GIP+ GLP-1 (4 and 1 pmol kg-1 min-1, respectively). All IIGIs were performed in a randomised order blinded for the participant and the investigators. The primary endpoint was energy intake as measured by an ad libitum meal after 240 min. Secondary endpoints included appetite ratings and resting energy expenditure, as well as insulin, C-peptide and glucagon responses. Results Energy intake was significantly reduced during IIGI+ GLP-1 compared with IIGI+ saline infusion (2715 +/- 409 vs 4483 +/- 568 kJ [ mean +/- SEM, n = 17], p = 0.014), whereas there were no significant differences in energy intake during IIGI+ GIP (4062 +/- 520 kJ) or IIGI+ GIP+ GLP-1 (3875 +/- 451 kJ) infusion compared with IIGI+ saline (p = 0.590 and p = 0.364, respectively). Energy intake was higher during IIGI+ GIP+ GLP-1 compared with IIGI+ GLP-1 infusion (p = 0.039). Conclusions/interpretation While GLP-1 infusion lowered energy intake in overweight/obese men, simultaneous GIP infusion did not potentiate this GLP-1-mediated effect.