Growth Hormone-Releasing Hormone Peptide Agonists Reduced Heart Attack Damage and Inflammation in Rats

In vitro, H9c2 cardiac cells were cultured in serum-free medium to mimic nutrient deprivation after heart attack. GHRH agonists were tested for effects on calcium influx and cell survival. In vivo, rats with surgically induced myocardial infarction were treated with GHRH agonist peptides or placebo for four weeks. Outcomes included infarct size measurement, counting of c-kit+ cardiac progenitor cells and mitotic divisions, vascular density assessment, plasma cytokine levels (ELISA), and gene expression profiling for apoptotic, fibrotic, and repair pathways.

Heart failure after heart attack is a leading cause of death worldwide, and current treatments only slow progression rather than repair damage. GHRH agonists represent a new peptide-based approach that addresses multiple aspects of cardiac repair simultaneously: reducing inflammation, preventing scar formation, activating cardiac stem cells, and promoting new blood vessel growth. This multi-mechanism action could make them more effective than single-target therapies.

GHRH is traditionally known for stimulating growth hormone release from the pituitary gland, but this study reveals direct cardiac effects through GHRH receptors expressed on heart cells. This 'extrapituitary' action of GHRH peptides is part of a growing recognition that hormonal peptides have broader tissue-specific functions beyond their classical endocrine roles. If translated to humans, GHRH agonists could complement existing heart failure treatments by actively promoting regeneration rather than just managing symptoms.

This is a preclinical study in rats with surgically induced heart attacks — a model that doesn't fully replicate human coronary disease. The four-week treatment period is relatively short, and long-term effects on cardiac remodeling are unknown. Growth hormone-related peptides could potentially stimulate undesirable cell growth in other tissues, which needs safety evaluation. The study used multiple agonists with varying potencies but didn't establish optimal dosing for clinical translation. Gene expression changes don't guarantee functional cardiac improvement.