Effects of exogenous glucagon-like peptide-1 on the blood pressure, heart rate, mesenteric blood flow, and glycemic responses to intraduodenal glucose in healthy older subjects

Abstract

Context: Studies relating to the cardiovascular effects of glucagon-like peptide-1 (GLP-1) and its agonists, which slow gastric emptying, have not discriminated between fasting and postprandial, blood pressure (BP) and heart rate (HR). Objective: To determine whether exogenous GLP-1 modulates the effects of an intraduodenal (ID) glucose infusion on BP, HR and splanchnic blood flow in healthy older subjects. Design: Double-blind randomised trial. Setting: Community dwelling residents attending a clinical research laboratory. Patients: 10 healthy 'older' subjects (9M,1F; age 73.2 ± 1.5 yr). Interventions: Intravenous infusion of GLP-1 (0.9 pmol/kg/min), or saline (0.9%) for 90 min (t = -30 - 60 min). Between t = 0 - 60 min, ID glucose was infused at 3 kcal/min. Main Outcome Measures: BP and HR were assessed with an automated BP device, superior mesenteric artery (SMA) flow by Doppler ultrasonography and blood glucose and serum insulin were measured. Results: During the 'fasting' period (t = -30 - 0 min), GLP-1 had no effect on BP or HR. In response to ID glucose (t = 0 - 60 min), systolic BP decreased (P < 0.001), and both HR (P < 0.001) and SMA flow (P < 0.05) increased, on both days. GLP-1 attenuated the maximum fall in systolic BP (P < 0.05), tended to increase HR (P = 0.09) and increased SMA flow (P < 0.01). GLP-1 diminished the glycemic response (P < 0.05). Conclusions: In healthy older subjects, acute administration of GLP-1 attenuates the hypotensive response to ID glucose, and potentiates the increase in SMA flow.