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

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: A double-blind randomized trial was conducted. Setting: Community-dwelling residents attended a clinical research laboratory. Patients: Ten healthy “older” subjects (9 male, 1 female; age 73.2 ± 1.5 y) were studied. 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, HR, superior mesenteric artery (SMA) flow, 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 < .001), and both HR (P < .001) and SMA flow (P < .05) increased, on both days. GLP-1 attenuated the maximum decrease in systolic BP (P < .05), tended to increase HR (P = .09), and increased SMA flow (P < .01). GLP-1 diminished the glycemic response (P < .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.