Regional Differences in the Ghrelin-Growth Hormone Secretagogue Receptor Signalling System in Human Heart Disease

• Published in: CJC open (Online) 2021-02, Vol.3 (2), p.182-194
• Main Authors: Sullivan, Rebecca, Randhawa, Varinder K., Lalonde, Tyler, Yu, Tina, Kiaii, Bob, Luyt, Leonard, Wisenberg, Gerald, Dhanvantari, Savita
• Format: Article
• Language: English
• Subjects: Original
• ISSN: 2589-790X; 2589-790X
• DOI: 10.1016/j.cjco.2020.10.015

The hormone ghrelin and its receptor, the growth hormone secretagogue receptor (GHSR) are expressed in myocardium. GHSR binding activates signalling pathways coupled to cardiomyocyte survival and contractility. These properties have made the ghrelin-GHSR axis a candidate for a biomarker of cardiac function. The dynamics of ghrelin-GHSR are altered significantly in late stages of heart failure (HF) and cardiomyopathy, when left ventricular (LV) function is failing. We examined the relationship of GHSR with ghrelin in cardiac tissue from patients with valvular disease with no detectable changes in LV function. Biopsy samples from the left ventricle and left atrium were obtained from 25 patients with valvular disease (of whom 13 also had coronary artery disease) and preserved LV ejection fraction, and compared to control samples obtained via autopsy. Using quantitative confocal fluorescence microscopy, levels of GHSR were determined using [Dpr3(n-octanoyl),Lys19(sulfo-Cy5)]ghrelin(1-19), and immunofluorescence determined ghrelin, the heart failure marker natriuretic peptide type-B (BNP), and contractility marker sarcoplasmic reticulum ATPase pump (SERCA2a). A positive correlation between GHSR and ghrelin was apparent in only diseased tissue. Ghrelin and BNP significantly correlated in the left ventricle and strongly colocalized to the same intracellular compartment in diseased and control tissue. GHSR, ghrelin, and BNP all strongly and significantly correlated with SERCA2a in the left ventricle of diseased tissue only. Our results suggest that the dynamics of the myocardial ghrelin-GHSR axis is altered in cardiovascular disease in the absence of measurable changes in heart function, and might accompany a regional shift in endocrine programming. L’hormone ghréline et son récepteur, le récepteur sécrétagogue de l’hormone de croissance (GHSR, de l’anglais growth hormone secretagogue receptor), sont exprimés dans le myocarde. La liaison au récepteur GHSR active les voies de signalisation associées à la survie et à la contractilité des cardiomyocytes. Ces propriétés font de l’axe ghréline-récepteur GHSR un bon candidat biomarqueur de la fonction cardiaque. En effet, la dynamique de cet axe est considérablement altérée aux stades avancés de l’insuffisance cardiaque et de la cardiomyopathie, lorsque la fonction ventriculaire gauche décline. Nous avons donc étudié la relation entre le récepteur GHSR et la ghréline dans le tissu cardiaque de patients présentant une va