Heart Failure and Growth Hormone Releasers: Hexarelin

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Heart Failure and Growth Hormone Releasers: Hexarelin

Bericht door Willy » zo aug 24, 2003 4:36 pm

<H4>GH-independent cardiotropic activities of hexarelin in patients with severe left ventricular dysfunction due to dilated and ischemic cardiomyopathy</H4><I>
Imazio M, Bobbio M, Broglio F, Benso A, Podio V, Valetto MR, Bisi G, Ghigo E, Trevi GP. Division of Cardiology, University Internal Medicine Department, Turin, Italy.</I><BR>
AIM: To investigate acute cardiotropic activities of hexarelin in patients with severe left ventricular dysfunction due to ischemic (iCMP) and dilated cardiomyopathy (dCMP). METHODS AND RESULTS: We studied the effect of intravenous hexarelin administration on growth hormone (GH) levels and left ventricular ejection fraction (LVEF) evaluated by radionuclide angiography in eight patients with dCMP (age 53.0+/-2.8, LVEF 16.7+/-2.1%) and five patients with iCMP (age 52.0+/-2.8 years, LVEF 22.6+/-2.1). Results were compared with a group of seven normal subjects (age 37.4+/-3.4 years, LVEF 64.0+/-1.5%) and seven patients with severe growth-hormone deficiency (GHD; age 42.0+/-4.4 years, LVEF 50.0+/-1.9%) previously studied with the same methodology. In dCMP and iCMP patients hexarelin induced a similar significant (P<0.05) increase in GH levels. In iCMP patients hexarelin induced a LVEF increase (peak LVEF 26.2+/-2.5%, P<0.05) as observed in normals and GHD, while in dCMP LVEF was unchanged (peak LVEF 17.7+/-1.7, P=NS). In all groups other hemodynamic parameters were unchanged.
CONCLUSIONS: Acute hexarelin administration increases LVEF in iCMP patients (as in normals and GHD) but not in dCMP patients in spite of a similar GH releasing effect and basal LVEF. A possible explanation of the positive inotropic effect of hexarelin in iCMP could be a direct stimulation on viable myocardium or myocardial contractile reserve.
Source: http://www.ncbi.nlm.nih.gov/entrez/quer ... t=Abstract
<H4>Growth hormone-independent cardiotropic activities of growth hormone-releasing peptides in normal subjects, in patients with growth hormone deficiency, and in patients with idiopathic or ischemic dilated cardiomyopathy</H4><I>
Broglio F, Benso A, Valetto MR, Gottero C, Quaranta L, Podio V, Arvat E, Bobbio M, Bisi G, Ghigo E. Department of Internal Medicine, University of Turin, Italy.</I><BR>
Growth hormone releasing peptides (GHRPs) are synthetic molecules endowed with potent neuroendocrine activities mediated by specific receptors in the pituitary and in the central nervous system. GHRPs receptors have been reported even in perpheral tissues, particularly in the myocardium, where they probably mediate growth hormone (GH)-independent activities. We studied in humans the cardiac effects of hexarelin administration in 7 normal adults, in 7 severe GH-deficient patients, and in 12 patients with severe dilated cardiomyopathy. Left ventricular ejection fraction (LVEF), mean blood pressure (MBP), heart rate (HR), and GH levels were evaluated at baseline and every 15 min up to 60 min after acute 2.0 microg/kg iv hexarelin administration. Basal LVEF in dilated cardiomyopathy was impaired and lower (p < 0.001) than in GH deficiency, in turn lower (p< 0.001) than in normal subjects. Hexarelin signficantly (p < 0.05) increased LVEF in normal and in GH-deficient subjects, but not in dilated cardiomyopathy, without significant variations in MBP and HR. Hexeralin significantly (p < 0.05) increased GH levels in normal subjects and in dilated cardiomyopathy but not in GH deficiency. These findings suggest that, in humans, the acute administration of hexarelin exerts a GH-independent positive inotropic effect likely mediated by specific GHRPs myocardial receptors.
Source: http://www.ncbi.nlm.nih.gov/entrez/quer ... t=Abstract
<H4>The growth hormone secretagogue hexarelin improves cardiac function in rats after experimental myocardial infarction</h4><I>
Tivesten A, Bollano E, Caidahl K, Kujacic V, Sun XY, Hedner T, Hjalmarson A, Bengtsson BA, Isgaard J. Research Center for Endocrinology and Metabolism, the Department of Internal Medicine, Sahlgrenska University Hospital, Goteborg, Sweden. </I><BR>
Several studies have shown that GH can enhance cardiac performance in rats after experimental myocardial infarction and in humans with congestive heart failure. In the present study, the hemodynamic effects of hexarelin (Hex), an analog of GH-releasing peptide-6 and a potent GH secretagogue, were compared with the effects of GH. Four weeks after ligation of the left coronary artery male rats were treated sc twice daily with hexarelin [10 microg/kg x day (Hex10) or 100 microg/kg x day (Hex100)], recombinant human GH (2.5 mg/kg x day), or 0.9% NaCl for 2 weeks. Transthoracic echocardiography was performed before and after the treatment period. GH, but not Hex, increased body weight gain. GH and Hex100 decreased total peripheral resistance (P < 0.05) and increased stroke volume (P < 0.05 and P < 0.01, respectively) and stroke volume index (P = 0.06 and P < 0.01, respectively) vs. NaCl. Cardiac output was increased by GH and Hex100 (P < 0.05), and cardiac index was increased by Hex100 with a borderline significance for GH (P = 0.06). In conclusion, Hex improves cardiac function and decreases peripheral resistance to a similar extent as exogenous GH in rats postmyocardial infarction. The mechanisms of these effects are unclear; they could be mediated by GH or a direct effect of Hex on the cardiovascular system.
Source: http://www.ncbi.nlm.nih.gov/entrez/quer ... t=Abstract
<H4>The role of the GH/IGF-I axis for cardiac function and structure</h4><I>
Isgaard J, Tivesten A, Friberg P, Bengtsson BA. Research Center for Endocrinology and Metabolism, Sahlgrenska University Hospital, Goteborg, Sweden. jorgen.isgaard@ss.gu.se</I><BR>
There is ample evidence to support a role for the GH/IGF-I axis in regulation of cardiac growth, structure and function. GH may act directly on the heart or through circulating IGF-I (Fig. 1). Moreover, GH has been found to regulate local production of IGF-I in the heart. Both the GH-R and IGF-I-R are expressed in cardiac tissue. Hence, the IGF-I-R receptor can theoretically be activated through locally produced IGF-I acting via autocrine/paracrine mechanisms, or via circulating IGF-I exerting its effects as an endocrine agent. During conditions of pressure and volume overload, an increased systolic wall stress triggers an induction of gene expression of IGF-I GH-R and possibly IGF-J-R implying a potential role for the GH/IGF-I axis in the development of adaptive hypertrophy of the heart and vessels. Cardiovascular effects of GH in clinical studies include beneficial effects on contractility, exercise performance and TPR, and experimental studies suggest an increased Ca2+ responsiveness as one possible underlying cause, although effects of GH and IGF-I on apoptosis may possibly also play a role. The GH secretagogue hexarelin improves cardiac function after experimental myocardial infarction either through an increased GH secretion or possibly through a cardiac GHS receptor, although this needs further investigation. Moreover, it is clear that further basic and clinical studies are required to gain insight into the GH and IGF-I mechanisms of action and to monitor long-term effects when GH is administered as substitution therapy or as an agent in the treatment of congestive heart failure.
Source: http://www.ncbi.nlm.nih.gov/entrez/quer ... t=Abstract

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