Cardioprotective effects of ghrelin and des-octanoyl ghrelin on myocardial injury induced by isoproterenol in rats

AbstractAim:To determine the cardioprotective action of ghrelin and des-octanoyl ghrelin in rats with isoproterenol-induced myocardial injury.Methods:Rats were subcutaneously injected with isoproterenol (ISO; 20, 10, and 5 mg/kg) on d 1, 2 and 3, respectively, and then 3 mg/kg for the next 7 d with or without ghrelin or des-octanoyl-ghrelin (100 μg/kg, twice daily). Plasma ghrelin and growth hormone levels were assayed using radioimmunoassay methods. Growth hormone secretagogue receptor (GHSR) and ghrelin mRNA were determined using RT-PCR. The maximal binding capacity and the affinity for [3H] ghrelin were determined by receptor binding assays.Results:Compared with controls, ISO-treated rats showed severe myocardial injury, cardiomegaly, infarction-like necrosis and massive fibrosis with increases in irradiated-ghrelin (ir-ghrelin) content in plasma by 67% and myocardia by 66% and in the mRNA level in the myocardia by 93% (P<0.01). ISO-treated rats had 95% (P<0.01) higher GHSR mRNA levels in the myocardia. The maximal binding capacity of [3H]ghrelin for myocardial sarcolemma was higher in ISO-treated rats than in controls. Ghrelin administration improved cardiac function and ameliorated cardiomegaly and attenuated myocardial lipid peroxidation injury and relieved cardiac fibrosis as compared with ISO treatment alone. Administration of des-octanoyl ghrelin effectively antagonized ISO-induced myocardial injury and improved all parameters measured. However, the therapeutic effect of des-octanoyl ghrelin was significantly weaker than that of ghrelin. The plasma growth hormone level increased markedly, by 1.5-fold (P<0.01), with ghrelin administration as compared with that in controls, but was unaltered in the des-octanoyl ghrelin group.Conclusion:Myocardial ghrelin and GHSR were up-regulated during ISO-induced myocardial injury. The protective effect of ghrelin against ISO-induced cardiac function injury and fibrosis was more potent than that of des-octanoyl ghrelin, which suggests that ghrelin could be an endogenous cardioprotective factor in ischemic heart disease, and that its effects include growth hormone-dependent and -independent pathways.

[1]  B. Geng,et al.  Protective Effects of Ghrelin on Ischemia/Reperfusion Injury in the Isolated Rat Heart , 2004, Journal of cardiovascular pharmacology.

[2]  S. Banni,et al.  Conjugated dienes detected in tissue lipid extracts by second derivative spectrophotometry. , 1989, Free radical biology & medicine.

[3]  Jing Zhao,et al.  Ghrelin protects myocardium from isoproterenol-induced injury in rats. , 2004, Acta pharmacologica Sinica.

[4]  M. Papotti,et al.  Growth hormone secretagogue binding sites in peripheral human tissues. , 2000, The Journal of clinical endocrinology and metabolism.

[5]  M. M. Bradford.  A rapid and sensitive method for the quantitation of microgram quantities of protein utilizing the principle of protein-dye binding. , 1976, Analytical biochemistry.

[6]  M. Nakashima,et al.  GH suppresses TGF-β-mediated fibrosis and retains cardiac diastolic function , 2004, Molecular and Cellular Endocrinology.

[7]  Hideo Oya,et al.  Cardiovascular and hormonal effects of subcutaneous administration of ghrelin, a novel growth hormone-releasing peptide, in healthy humans. , 2002, Clinical science.

[8]  W. Shimizu,et al.  Hemodynamic, renal, and hormonal effects of ghrelin infusion in patients with chronic heart failure. , 2001, The Journal of clinical endocrinology and metabolism.

[9]  A. Herington,et al.  The potential autocrine/paracrine roles of ghrelin and its receptor in hormone-dependent cancer. , 2003, Cytokine & growth factor reviews.

[10]  M. Tschöp,et al.  Ghrelin induces adiposity in rodents , 2000, Nature.

[11]  Chao-shu Tang,et al.  Effect of ghrelin on septic shock in rats. , 2003, Acta pharmacologica Sinica.

[12]  Márta Korbonits,et al.  The tissue distribution of the mRNA of ghrelin and subtypes of its receptor, GHS-R, in humans. , 2002, The Journal of clinical endocrinology and metabolism.

[13]  K. Chihara,et al.  Cloning and characterization of the 5(')-flanking region of the human ghrelin gene. , 2003, Biochemical and biophysical research communications.

[14]  C. Sigmund,et al.  Ghrelin Inhibits Proinflammatory Responses and Nuclear Factor-κB Activation in Human Endothelial Cells , 2004, Circulation.

[15]  Y. Taché,et al.  Ghrelin: a novel player in the gut-brain regulation of growth hormone and energy balance. , 2003, News in physiological sciences : an international journal of physiology produced jointly by the International Union of Physiological Sciences and the American Physiological Society.

[16]  Maw-Shung Liu,et al.  Initial externalization followed by internalization of beta-adrenergic receptors in rat heart during sepsis. , 1996, The American journal of physiology.

[17]  J. Karliner,et al.  Refined membrane preparations mask ischemic fall in myocardial beta-receptor density. , 1989, The American journal of physiology.

[18]  M. Iida,et al.  Central Ghrelin Modulates Sympathetic Activity in Conscious Rabbits , 2002, Hypertension.

[19]  M. Nakazato,et al.  Plasma ghrelin levels in lean and obese humans and the effect of glucose on ghrelin secretion. , 2002, The Journal of clinical endocrinology and metabolism.

[20]  R. Dilley,et al.  Mineralocorticoids, hypertension, and cardiac fibrosis. , 1994, The Journal of clinical investigation.

[21]  大川 博,et al.  Assay for lipid peroxides in animal tissues by thiobarbituric acid reaction , 1979 .

[22]  N. Kohno,et al.  Ghrelin improves endothelial dysfunction through growth hormone-independent mechanisms in rats. , 2003, Biochemical and biophysical research communications.

[23]  J. Ross,et al.  Progressive cardiac dysfunction and fibrosis in the cardiomyopathic hamster and effects of growth hormone and angiotensin-converting enzyme inhibition. , 1999, Circulation.

[24]  D. Malan,et al.  Cardiac effects of ghrelin and its endogenous derivatives des-octanoyl ghrelin and des-Gln14-ghrelin. , 2003, European journal of pharmacology.

[25]  G. Rona,et al.  An infarct-like myocardial lesion and other toxic manifestations produced by isoproterenol in the rat. , 1959, A.M.A. archives of pathology.

[26]  I. Robinson,et al.  Ghrelin and des-octanoyl ghrelin promote adipogenesis directly in vivo by a mechanism independent of the type 1a growth hormone secretagogue receptor. , 2004, Endocrinology.

[27]  M. Nakashima,et al.  GH suppresses TGF-beta-mediated fibrosis and retains cardiac diastolic function. , 2004, Molecular and cellular endocrinology.

[28]  Chao-shu Tang,et al.  Effects of different peptide fragments derived from proadrenomedullin on gene expression of adrenomedullin gene , 2002, Peptides.

[29]  A. Davenport,et al.  Comparison of vasodilators in human internal mammary artery: ghrelin is a potent physiological antagonist of endothelin‐1 , 2002, British journal of pharmacology.

[30]  M. Nakazato,et al.  Ghrelin is a growth-hormone-releasing acylated peptide from stomach , 1999, Nature.