Cardioprotective effects of growth hormone-releasing hormone agonist after myocardial infarction.

Abstract

Whether the growth hormone (GH)/insulin-like growth factor 1(IGF-1) axis exerts cardioprotective effects remains controversial; and the underlying mechanism(s) for such actions are unclear. Here we tested the hypothesis that growth hormone-releasing hormone (GHRH) directly activates cellular reparative mechanisms within the injured heart, in a GH/IGF-1 independent fashion. After experimental myocardial infarction (MI), rats were randomly assigned to receive, during a 4-week period, either placebo (n = 14), rat recombinant GH (n = 8) or JI-38 (n = 8; 50 microg/kg per day), a potent GHRH agonist. JI-38 did not elevate serum levels of GH or IGF-1, but it markedly attenuated the degree of cardiac functional decline and remodeling after injury. In contrast, GH administration markedly elevated body weight, heart weight, and circulating GH and IGF-1, but it did not offset the decline in cardiac structure and function. Whereas both JI-38 and GH augmented levels of cardiac precursor cell proliferation, only JI-38 increased antiapoptotic gene expression. The receptor for GHRH was detectable on myocytes, supporting direct activation of cardiac signal transduction. Collectively, these findings demonstrate that within the heart, GHRH agonists can activate cardiac repair after MI, suggesting the existence of a potential signaling pathway based on GHRH in the heart. The phenotypic profile of the response to a potent GHRH agonist has therapeutic implications.

• Authors: Rosemeire M Kanashiro-Takeuchi, Konstantinos Tziomalos, Lauro M Takeuchi, Adriana V Treuer, Guillaume Lamirault, Raul Dulce, Michael Hurtado, Yun Song, Norman L Block, Ferenc Rick, Anna Klukovits, Qinghua Hu, Jozsef L Varga, Andrew V Schally, Joshua M Hare
• Journal: Proceedings of the National Academy of Sciences of the United States of America (Proc Natl Acad Sci U S A) Vol. 107 Issue 6 Pg. 2604-9 (Feb 09 2010) ISSN: 1091-6490 [Electronic] United States
• PMID: 20133784 (Publication Type: Journal Article, Research Support, N.I.H., Extramural, Research Support, Non-U.S. Gov't, Research Support, U.S. Gov't, Non-P.H.S.)

Chemical References

• Cardiotonic Agents
• JI-38
• Receptors, Neuropeptide
• Receptors, Pituitary Hormone-Regulating Hormone
• Recombinant Proteins
• Insulin-Like Growth Factor I
• Growth Hormone
• Growth Hormone-Releasing Hormone
• somatotropin releasing hormone receptor

Topics

• Animals
• Blotting, Western
• Body Weight (drug effects)
• Cardiotonic Agents (pharmacology)
• Echocardiography
• Female
• Growth Hormone (blood, genetics, pharmacology)
• Growth Hormone-Releasing Hormone (agonists, analogs & derivatives, metabolism, pharmacology)
• Heart (drug effects, physiopathology)
• Hemodynamics (drug effects)
• Immunohistochemistry
• Insulin-Like Growth Factor I (metabolism)
• Myocardial Infarction (pathology, prevention & control)
• Myocardium (metabolism, pathology)
• Organ Size (drug effects)
• Random Allocation
• Rats
• Rats, Inbred F344
• Receptors, Neuropeptide (metabolism)
• Receptors, Pituitary Hormone-Regulating Hormone (metabolism)
• Recombinant Proteins (pharmacology)