Objective: The short-term cardiovascular effects of continuous ghrelin infusion in healthy humans remain to be studied.
Methods: Fifteen healthy, young and normal-weight men volunteered to participate in a randomized double-blind, placebo-controlled cross-over study. The local ethics committee approved the study. We used a constant infusion of human ghrelin at a rate of 5 pmol/kg body weight per minute for 180 minutes and measured peak left ventricular myocardial systolic velocity Vmax, tissue tracking TT (GE Vivid Seven with a 2.5 MHz transducer) and endothelium-dependent flow-mediated vasodilatation of the radial artery (Acuson Sequoia C256, 8 MHz linear array vascular ultrasound transducer).
Results: Ghrelin infusion increased serum ghrelin levels ∼6-fold (5.2 to 6.5) (P<0.001), Vmax increased ∼9% (P=0.002), TT increased ∼10% (P=0.004), while endothelium-dependent flow-mediated vasodilation did not change (P=0.10). Concomitantly, growth hormone peaked after 60 minutes of infusion (36.8±4.7 ng/ml, P<0.001), glucose levels increased 0.5±0.1 mmol/l (P<0.001), free fatty levels increased 1.7-fold (P=0.002), cortisol levels increased 1.4-fold (P 0.002), while insulin levels were constant.
Conclusion: Supraphysiological levels of ghrelin persistently improve left ventricular function in healthy young normal-weight men without changing endothelium-dependent flow-mediated vasodilation. It remains to be studied whether ghrelin exerts direct myocardial effects or indirect effects through the concomitant changes in glucose, growth hormone, free fatty acids and cortisol levels.