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BackgroundDiminished growth hormone (GH) is associated with impaired endothelial function and fibrinolysis. GH‐releasing hormone is the primary stimulus for GH secretion and a substrate of dipeptidyl peptidase‐4. We tested the hypothesis that dipeptidyl peptidase‐4 inhibition with sitagliptin increases stimulated GH secretion, vasodilation, and tissue plasminogen activator (tPA) activity. Methods and ResultsHealthy adults participated in a 2‐part double‐blind, randomized, placebo‐controlled, crossover study. First, 39 patients (29 women) received sitagliptin or placebo on each of 2 days separated by a washout. One hour after study drug, blood was sampled and then arginine (30 g IV) was given to stimulate GH. Vasodilation was assessed by plethysmography and blood sampled for 150 minutes. Following a washout, 19 of the original 29 women received sitagliptin alone versus sitagliptin plus antagonist to delineate GH receptor (GHR)– (n=5), nitric oxide– (n=7), or glucagon‐like peptide‐1 receptor– (n=7) dependent effects. Sitagliptin enhanced stimulated GH secretion (P |
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