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Mitral regurgitation causes volume overload of the heart, and due to the deregulation of extracellular matrix proteins, the electrical communication between cardiomyocytes provided by connexin channels is disturbed. The aim of this study was to investigate the effect of cardiac volume overload (VO) on its functional parameters, structural remodeling, and connexin43 (Cx43), a protein ensuring electrical synchronization of the heart, and the cardioprotective effect of empagliflozin. Cardiac VO was induced by surgical aortocaval fistula (ACF) in adult, 6-month-old male Wistar rats. Mitral regurgitation and VO developed within four weeks. Subsequently, empagliflozin was administered daily for five weeks at a dose of 10 mg/kg of body weight. Echocardiographic examination showed increased cardiac output and increased Vmax of the aortic valve, decreased ejection fraction and fractional shortening due to ACF-VO. Echocardiographic parameters showed an increase in the diameter of the left ventricle in both systole and diastole, as well as an increase in the volume of the left ventricle at the end of systole and diastole. Empagliflozin normalized the negative parameters in the ACF-VO group. Myocardial protein Cx43 levels were reduced by ACF-VO but normalized by empagliflozin treatment. In addition, empagliflozin suppressed the ACF-VO-induced increase in interstitial collagen detected by van Gieson staining. These findings were consistent with increased protein expression of MMP-2, which is involved in structural remodeling of the extracellular matrix, and was normalized by empagliflozin. Protein kinase C epsilon levels associated with Cx43 and extracellular matrix modulation were reduced by ACF-VO and normalized by empagliflozin. However, protein levels of pro-apoptotic and pro-hypertrophic protein kinase C delta were increased by ACF-VO and normalized by empagliflozin. Protein expression of transforming growth factor beta as well as fibroblast growth factor 21 was increased by ACF-VO and normalized by empagliflozin. The results indicate a cardioprotective effect of empagliflozin due to suppression of myocardial structural remodeling and preservation of Cx43 in an experimental model simulating volume overload. The research was supported by grants APVV-21-0410,VEGA-2/0006/23,VEGA-2/0133/24,VEGA-2/0002/20
Sýkora et al. (Sun,) studied this question.