Higher fasting plasma concentrations of glucagon-like peptide 1 are associated with higher resting energy expenditure and fat oxidation rates in humans

BACKGROUND: Glucagon-like peptide 1 (GLP-1) is a gut hormone that decreases appetite and promotes satiety. Its role in energy metabolism regulation is still poorly understood. OBJECTIVE: The aim of the study was to investigate the relation of fasting plasma GLP-1 concentrations to rates of energy expenditure (EE) and substrate oxidation--ie, respiratory quotient (RQ). DESIGN: Forty-six glucose-tolerant white subjects (22 men, 24 women) aged 18-49 y whose adiposity spanned a wide range [body mass index (in kg/m²): 18.5-50] were studied in an inpatient clinic. Main outcome measures included resting EE and RQ (ventilated hood technique), body composition (dual-energy X-ray absorptiometry), and fasting plasma concentrations of GLP-1, pancreatic polypeptide, glucose, and insulin. RESULTS: Fasting plasma GLP-1 concentrations were positively associated with resting EE (after adjustment for age, sex, and body composition) and negatively correlated with RQ (after adjustment for age, sex, and percentage body fat) and fasting plasma pancreatic polypeptide concentrations (both before and after adjustment for age, sex, percentage body fat, and fasting plasma glucose and insulin concentrations). Adjustment for fasting plasma pancreatic polypeptide concentrations, a marker of parasympathetic outflow to the gut, attenuated the strength of the association of fasting plasma GLP-1 concentrations with resting EE and RQ. CONCLUSIONS: Higher fasting plasma GLP-1 concentrations are associated with higher rates of EE and fat oxidation independent of age, sex, and body composition. The autonomic nervous system may have a role in this relation. This effect, along with the established role of GLP-1 in promoting satiety, may further foster its therapeutic potential in the treatment of obesity.