Human Ghrelin: A Gastric Hormone with Cardiovascular Properties

Ghrelin is a growth hormone-releasing peptide, isolated from the stomach. Researches in progress documented that ghrelin participates in the stimulation of the hypothalamus-pituitary-adrenal axis at the hypothalamic level and in the regulation of energy balance. Growth hormone-independent functions have been ascribed to ghrelin. Among others, a large body of literature demonstrated the presence of specific receptors for ghrelin, distributed at the level of cardiomyocytes and endothelial cells. Therefore, a link between ghrelin and cardiovascular system has been hypothesized and, then, demonstrated in both experimental and clinical studies. Ghrelin has largely documented cardiac beneficial effects, including protection from ischemia/reperfusion injury, attenuation of left ventricular remodeling following myocardial infarction, and improvement of left ventricular function. Exercise level in patients with chronic heart failure had also been seen. Ghrelin exerts these effects through several mechanisms, including the inhibition of apoptosis. At the level of blood vessels, ghrelin exerts a significant impact on vascular function. In particular, acutely infused, ghrelin reverses endothelial dysfunction by increasing NO availability and restores the endothelin-1/nitric oxide imbalance in the peripheral microcirculation of patients with metabolic syndrome. Antioxidant/anti-inflammatory effects, and-or an ameliorated insulin sensitivity are proposed mechanisms whereby ghrelin exerts its vascular protective actions. At higher doses, ghrelin also decreases blood pressure, by mechanisms that involve the modulation of sympathetic nervous system. This finding highlights the ghrelin system as a promising candidate for cardiovascular drug discovery.