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One of the most abundant flavonoids present in cacao is (−)-epicatechin (Epi) and this flavanol has been linked to the cardiovascular health promoting actions of cocoa products. We previously demonstrated that Epi reduces infarct size in rodent models of ischemia/reperfusion and permanent coronary occlusion. Reduced infarct size was associated with decreased left ventricular (LV) oxidative stress (OS) and indicators of inflammation factors, which foster myocardial fibrosis. In this study, we examine the antifibrotic actions of Epi in an aging female rat model of pre-heart failure with preserved ejection fraction (pre-HFpEF) as well as its potential to mitigate plasma levels of OS, proinflammatory/profibrotic cytokines, and improve passive and active LV function. Epi treatment [1 mg/(kg·d)] was provided daily by gavage from 21 to 22 months of age, whereas controls received water. A Millar catheter was used to assess hemodynamic function. Subsequently, hearts were arrested in diastole, a balloon inserted into the LV and passive pressure–volume curves generated. Fixed LV sections were processed for collagen area fraction quantification using Sirius Red staining. Treatment with Epi did not lead to detectable changes in LV contractile function. However, passive LV pressure volume curves were significantly right shifted with Epi. Collagen area fraction values indicated that Epi treatment significantly reduces LV fibrosis. Epi also significantly reduced plasma OS markers and levels of profibrotic and proinflammatory cytokines. In conclusion, Epi reduces cardiac fibrosis in an aged, female rat model of pre-HFpEF, which correlates with significant reductions in OS and cytokine levels in the absence of changes in LV contractile function. [ABSTRACT FROM AUTHOR]

Cardiac fibrosis is one of the hallmarks of a diabetic cardiomyopathy. When activated, cardiac fibroblasts (CFs) increase the production of extracellular matrix proteins. Transforming growth factor (TGF)-β1 is known to mediate cardiac fibrosis through the SMAD pathway. High glucose (HG = 25 mM) cell culture media can activate CFs using TGF-β1. There is a need to identify effective antifibrotic agents. Studies in animals indicate that treatment with (−)-epicatechin (Epi) appears capable of reducing myocardial fibrosis. Epi binds to G-protein coupled estrogen receptor (GPER) and activates downstream pathways. We evaluated the potential of Epi to mitigate the development of a profibrotic phenotype in HG stimulated CFs. CF primary cultures were isolated from young male rats and were exposed for up to 48 h HG media and treated with vehicle or 1 μM Epi. Relevant profibrotic end points were measured by the use of various biochemical assays. HG exposure of CFs increased TGF-β1 protein levels by ∼15%, fibronectin ∼25%, urea levels ∼60%, proline incorporation ∼70%, and total collagen ∼15%. Epi treatment was able to significantly block HG induced increases in TGF-β1, fibronectin, urea, proline, and total collagen protein levels. GPER levels were reduced by HG and restored in CFs treated with Epi an effect associated with the activation (i.e., phosphorylation) of c-Src. Epi treatment also reverted SMAD levels. Altogether, results demonstrate that CFs cultured in HG acquire a profibrotic phenotype, which is blocked by Epi an effect, likely mediated at least, in part, by GPER effects on the SMAD/TGF-β1 pathway. [ABSTRACT FROM AUTHOR]

Key points: Heart failure with preserved ejection fraction (HFpEF) is seen more frequently in older women; risk factors include age, hypertension and excess weight.No female animal models of early stage remodelling (pre‐HFpEF) have examined the effects that the convergence of such factors have on cardiac structure and function.In this study, we demonstrate that ageing can lead to the development of mild chamber remodelling, diffuse fibrosis and loss of diastolic function.The loss of oestrogens further aggravates such changes by leading to a notable drop in cardiac output (while preserving normal ejection fraction) in the presence of diffuse fibrosis that is more predominant in endocardium and is accompanied by papillary fibrosis.Excess weight did not markedly aggravate such findings.This animal model recapitulates many of the features recognized in older, female HFpEF patients and thus, may serve to examine the effects of candidate therapeutic agents. Two‐thirds of patients with heart failure with preserved ejection fraction (HFpEF) are older women, and risk factors include hypertension and excess weight/obesity. Pathophysiological factors that drive early disease development (before heart failure ensues) remain obscure and female animal models are lacking. The study evaluated the intersecting roles of ageing, oestrogen depletion and excess weight on altering cardiac structure/function. Female, 18‐month‐old, Fischer F344 rats were divided into an aged group, aged + ovariectomy (OVX) and aged + ovariectomy + 10% fructose (OVF) in drinking water (n = 8–16/group) to induce weight gain. Left ventricular (LV) structure/function was monitored by echocardiography. At 22 months of age, animals were anaesthetized and catheter‐based haemodynamics evaluated, followed by histological measures of chamber morphometry and collagen density. All aged animals developed hypertension. OVF animals increased body weight. Echocardiography only detected mild chamber remodelling with ageing while intraventricular pressure–volume loop analysis showed significant (P < 0.05) decreases vs. ageing in stroke volume (13% OVX and 15% for OVF), stroke work (34% and 52%) and cardiac output (29% and 27%), and increases in relaxation time (10% OVX) with preserved ejection fraction. Histology indicated papillary and interstitial fibrosis with ageing, which was higher in the endocardium of OVX and OVF groups. With ageing, ovariectomy leads to the loss of diastolic and global LV function while preserving ejection fraction. This model recapitulates many cardiovascular features present in HFpEF patients and may help understand the roles that ageing and oestrogen depletion play in early (pre‐HFpEF) disease development. Key points: Heart failure with preserved ejection fraction (HFpEF) is seen more frequently in older women; risk factors include age, hypertension and excess weight.No female animal models of early stage remodelling (pre‐HFpEF) have examined the effects that the convergence of such factors have on cardiac structure and function.In this study, we demonstrate that ageing can lead to the development of mild chamber remodelling, diffuse fibrosis and loss of diastolic function.The loss of oestrogens further aggravates such changes by leading to a notable drop in cardiac output (while preserving normal ejection fraction) in the presence of diffuse fibrosis that is more predominant in endocardium and is accompanied by papillary fibrosis.Excess weight did not markedly aggravate such findings.This animal model recapitulates many of the features recognized in older, female HFpEF patients and thus, may serve to examine the effects of candidate therapeutic agents. [ABSTRACT FROM AUTHOR]

Excess enzyme-mediated protein O-GlcNAcylation is known to occur with diabetes mellitus. A characteristic of diabetic cardiomyopathy is the development of myocardial fibrosis. The role that enhanced protein O-GlcNAcylation plays in modulating the phenotype of cardiac fibroblasts (CF) is unknown. To address this issue, rat CF were cultured in normal glucose (NG; 5 mM glucose) or high-glucose (HG; 25 mM) media for 48 h. Results demonstrate that CF cultured in HG have higher levels (~50%) of overall protein O-GlcNAcylation vs. NG cells. Key regulators of collagen synthesis such as transforming-growth factor-β1 (TGF-β1), SMADs 2/3, and SMAD 7 protein levels, including those of arginase I and II, were altered, leading to increases in collagen levels. The nuclear transcription factor Sp1 and arginase II evidence excess O-GlcNAcylation in HG cells. Expression in CF of an adenovirus coding for the enzyme N-acetylglucosaminidase, which removes OGlcNAc moieties from proteins, decreased Sp1 and arginase II OGlcNAcylation and restored HG-induced perturbations in CF back to NG levels. These findings may have important pathophysiological implications for the development of diabetes-induced cardiac fibrosis. [ABSTRACT FROM AUTHOR]