Arterial responses to infusion of glucagon-like peptide-1 in humans: A randomized trial study

Glucagon-like-peptide-1 (GLP-1) is an incretin hormone implicated in several metabolic and neurological disorders. GLP-1 induces vasodilation and increases blood flow in the peripheral circulation. Whether GLP-1 alters cerebral hemodynamics in humans is yet to be elucidated. In a crossover, double-blind, placebo-controlled, and randomized design, 21 healthy volunteers were assigned to receive intravenous GLP-1 infusion (2.5 pmol/kg/min) or placebo over 20 min on two different days separated by at least one week. We used a noninvasive, well-validated transcranial doppler (TCD) and ultrasound dermascan to reveal the effect of GLP-1 on intra- and extracerebral arteries. The mean blood flow velocity in the middle cerebral artery (V_MCA), the diameter of the superficial temporal artery (STA) and radial artery (RA), and facial skin blood flow were measured. In addition, we documented headache and its associated symptoms during and after infusion. Twenty participants were included in the final analysis. We found no difference in the V_MCA (P = 0.227), diameter of the STA (P = 0.096) and the RA (P = 0.221) and facial blood flow (P = 0.814) after GLP-1 compared to placebo. There were no differences in HR, SAT, EtCO₂, or RF (P > 0.05) on the GLP-1 day compared to the placebo day. We found no differences in the incidence of headache after GLP-1 (n = 10) compared to placebo (n = 7) (P = 0.250). GLP-1 infusion did not affect cerebral hemodynamics and induce headache in humans. Further preclinical studies with validated methods are required to determine if intra - and extracerebral vasculature express GLP-1Rs in humans.