Effect of Oxyntomodulin, Glucagon, GLP-1, and Combined Glucagon +GLP-1 Infusion on Food Intake, Appetite, and Resting Energy Expenditure.

Abstract

The gut hormone, oxyntomodulin, is a proglucagon product with body weight-lowering potential. It binds to both the glucagon-like peptide-1 (GLP-1) receptor and the glucagon receptor; however, the mechanism behind the body weight-lowering effect remains elusive. We wanted to delineate the contributions of separate and combined GLP-1 receptor and glucagon receptor activation to the body weight-reducing mechanisms of oxyntomodulin. This was a double-blinded, randomized, crossover study. The study was conducted at a specialized research unit. Fifteen young healthy male volunteers (aged 22 [range 18-32] y; body mass index 23 [21-26] kg/m(2); fasting plasma glucose 5.1 [4.4-5.4] mmol/L; and glycated hemoglobin A1c 40 (37-42) mmol/mol). Five 4-hour liquid meal tests during the infusion of saline, GLP-1 (1 pmol × kg(-1) × min(-1)), glucagon (0.86 pmol × kg(-1) × min(-1)), oxyntomodulin (3 pmol × kg(-1) × min(-1)), or glucagon+GLP-1 (same doses). We evaluated resting energy expenditure (measured as oxygen uptake, gastric emptying (GE), composite appetite scores (CAS), and food intake. Oxyntomodulin, GLP-1, and GLP-1+glucagon slowed GE and reduced CAS, whereas glucagon did not affect GE and CAS. All infusions caused a similar decrease in food intake compared with saline (total intake (g [95% confidence interval]), saline 811 [729, 892], GLP-1 669 [586, 750], glucagon 686 [604, 768], oxyntomodulin 689 [608, 771], and glucagon+GLP-1 688 [606, 769]). Oxygen uptake did not change significantly from baseline in response to any peptide infusion compared with saline. Oxyntomodulin, GLP-1, and glucagon decreased food intake but with no additional effect of combining GLP-1 and glucagon.