Rat Model Of Heart Failure With Preserved Ejection Fraction Research Articles

Empagliflozin Improves Diastolic Function in HFpEF by Restabilizing the Mitochondrial Respiratory Chain.

Clinical studies demonstrated beneficial effects of sodium-glucose-transporter 2 inhibitors on the risk of cardiovascular death in patients with heart failure with preserved ejection fraction (HFpEF). However, underlying processes for cardioprotection remain unclear. The present study focused on the impact of empagliflozin (Empa) on myocardial function in a rat model with established HFpEF and analyzed underlying molecular mechanisms. Obese ZSF1 (Zucker fatty and spontaneously hypertensive) rats were randomized to standard care (HFpEF, n=18) or Empa (HFpEF/Empa, n=18). ZSF1 lean rats (con, n=18) served as healthy controls. Echocardiography was performed at baseline and after 4 and 8 weeks, respectively. After 8 weeks of treatment, hemodynamics were measured invasively, mitochondrial function was assessed and myocardial tissue was collected for either molecular and histological analyses or transmission electron microscopy. In HFpEF Empa significantly improved diastolic function (E/é: con: 17.5±2.8; HFpEF: 24.4±4.6; P<0.001 versus con; HFpEF/Empa: 19.4±3.2; P<0.001 versus HFpEF). This was accompanied by improved hemodynamics and calcium handling and by reduced inflammation, hypertrophy, and fibrosis. Proteomic analysis demonstrated major changes in proteins involved in mitochondrial oxidative phosphorylation. Cardiac mitochondrial respiration was significantly impaired in HFpEF but restored by Empa (Vmax complex IV: con: 0.18±0.07 mmol O2/s/mg; HFpEF: 0.13±0.05 mmol O2/s/mg; P<0.041 versus con; HFpEF/Empa: 0.21±0.05 mmol O2/s/mg; P=0.012 versus HFpEF) without alterations of mitochondrial content. The expression of cardiolipin, an essential stability/functionality-mediating phospholipid of the respiratory chain, was significantly decreased in HFpEF but reverted by Empa (con: 15.9±1.7 nmol/mg protein; HFpEF: 12.5±1.8 nmol/mg protein; P=0.002 versus con; HFpEF/Empa: 14.5±1.8 nmol/mg protein; P=0.03 versus HFpEF). Transmission electron microscopy revealed a reduced size of mitochondria in HFpEF, which was restored by Empa. The study demonstrates beneficial effects of Empa on diastolic function, hemodynamics, inflammation, and cardiac remodeling in a rat model of HFpEF. These effects were mediated by improved mitochondrial respiratory capacity due to modulated cardiolipin and improved calcium handling.

Leucine Supplementation Prevents the Development of Skeletal Muscle Dysfunction in a Rat Model of HFpEF.

Heart failure with preserved ejection fraction (HFpEF) is associated with exercise intolerance due to alterations in the skeletal muscle (SKM). Leucine supplementation is known to alter the anabolic/catabolic balance and to improve mitochondrial function. Thus, we investigated the effect of leucine supplementation in both a primary and a secondary prevention approach on SKM function and factors modulating muscle function in an established HFpEF rat model. Female ZSF1 obese rats were randomized to an untreated, a primary prevention, and a secondary prevention group. For primary prevention, leucine supplementation was started before the onset of HFpEF (8 weeks of age) and for secondary prevention, leucine supplementation was started after the onset of HFpEF (20 weeks of age). SKM function was assessed at an age of 32 weeks, and SKM tissue was collected for the assessment of mitochondrial function and histological and molecular analyses. Leucine supplementation prevented the development of SKM dysfunction whereas it could not reverse it. In the primary prevention group, mitochondrial function improved and higher expressions of mitofilin, Mfn-2, Fis1, and miCK were evident in SKM. The expression of UCP3 was reduced whereas the mitochondrial content and markers for catabolism (MuRF1, MAFBx), muscle cross-sectional area, and SKM mass did not change. Our data show that leucine supplementation prevented the development of skeletal muscle dysfunction in a rat model of HFpEF, which may be mediated by improving mitochondrial function through modulating energy transfer.

Leucine Supplementation Improves Diastolic Function in HFpEF by HDAC4 Inhibition.

Heart failure with preserved ejection fraction (HFpEF) is a complex syndrome associated with a high morbidity and mortality rate. Leucine supplementation has been demonstrated to attenuate cardiac dysfunction in animal models of cachexia and heart failure with reduced ejection fraction (HFrEF). So far, no data exist on leucine supplementation on cardiac function in HFpEF. Thus, the current study aimed to investigate the effect of leucine supplementation on myocardial function and key signaling pathways in an established HFpEF rat model. Female ZSF1 rats were randomized into three groups: Control (untreated lean rats), HFpEF (untreated obese rats), and HFpEF_Leu (obese rats receiving standard chow enriched with 3% leucine). Leucine supplementation started at 20 weeks of age after an established HFpEF was confirmed in obese rats. In all animals, cardiac function was assessed by echocardiography at baseline and throughout the experiment. At the age of 32 weeks, hemodynamics were measured invasively, and myocardial tissue was collected for assessment of mitochondrial function and for histological and molecular analyses. Leucine had already improved diastolic function after 4 weeks of treatment. This was accompanied by improved hemodynamics and reduced stiffness, as well as by reduced left ventricular fibrosis and hypertrophy. Cardiac mitochondrial respiratory function was improved by leucine without alteration of the cardiac mitochondrial content. Lastly, leucine supplementation suppressed the expression and nuclear localization of HDAC4 and was associated with Protein kinase A activation. Our data show that leucine supplementation improves diastolic function and decreases remodeling processes in a rat model of HFpEF. Beneficial effects were associated with HDAC4/TGF-β1/Collagenase downregulation and indicate a potential use in the treatment of HFpEF.

Systemic Delivery of Extracellular Vesicles Attenuates Atrial Fibrillation in Heart Failure With Preserved Ejection Fraction

BackgroundAtrial fibrillation (AF) is a common comorbidity in heart failure with preserved ejection fraction (HFpEF) patients. To date, treatments for HFpEF-related AF have been limited to anti-arrhythmic drugs and ablation. Here we examined the effects of immortalized cardiosphere-derived extracellular vesicles (imCDCevs) in rats with HFpEF. ObjectivesThis study sought to investigate the mechanisms of AF in HFpEF and probe the potential therapeutic efficacy of imCDCevs in HFpEF-related AF. MethodsDahl salt-sensitive rats were fed a high-salt diet for 7 weeks to induce HFpEF and randomized to receive imCDCevs (n = 18) or vehicle intravenously (n = 14). Rats fed a normal-salt diet were used as control animals (n = 26). A comprehensive characterization of atrial remodeling was conducted using functional and molecular techniques. ResultsHFpEF-verified animals showed significantly higher AF inducibility (84%) compared with control animals (15%). These changes were associated with prolonged action potential duration, slowed conduction velocity (connexin 43 lateralization), and fibrotic remodeling in the left atrium of HFpEF compared with control animals. ImCDCevs reversed adverse electrical remodeling (restoration of action potential duration to control levels and reorganization of connexin 43) and reduced AF inducibility (33%). In addition, fibrosis, inflammation, and oxidative stress, which are major pathological AF drivers, were markedly attenuated in imCDCevs-treated animals. Importantly, these effects occurred without changes in blood pressure and diastolic function. ConclusionsThus, imCDCevs attenuated adverse remodeling, and prevented AF in a rat model of HFpEF.

Transcutaneous Vagus Nerve Stimulation Ameliorates the Phenotype of Heart Failure With Preserved Ejection Fraction Through Its Anti-Inflammatory Effects.

A systemic proinflammatory state plays a central role in the development of heart failure with preserved ejection fraction (HFpEF). Low-level transcutaneous vagus nerve stimulation (LLTS) suppresses inflammation in animals and humans, mediated by an α7nAchR (alpha7 nicotinic acetylcholine receptor)-dependent pathway. We examined the effects of LLTS on cardiac function, inflammation, and fibrosis in the presence of α7nAchR pharmacological blockade in a rat model of HFpEF. Dahl salt-sensitive rats at 7 weeks of age were treated with high-salt diet for 6 weeks to induce HFpEF, followed by 4 weeks of (1) LLTS, (2) LLTS with the α7nAchR blocker methyllycaconitine, (3) sham, and (4) olmesartan. Blood pressure, cardiac function by echocardiography, heart rate variability, and serum cytokines were measured at 13 and 17 weeks of age. Cardiac fibrosis, inflammatory cell infiltration, and gene expression were determined at 17 weeks. LLTS attenuated the increase in blood pressure; improved cardiac function; decreased inflammatory cytokines, macrophage infiltration, and fibrosis; and improved survival compared with other groups. Methyllycaconitine attenuated these effects, whereas olmesartan did not improve cardiac function or fibrosis despite maintaining similar blood pressure as LLTS. Heart rate variability was similarly improved in the LLTS and LLTS plus methyllycaconitine groups but remained low in the other groups. LLTS reversed the dysregulated inflammatory signaling pathways in HFpEF hearts. Neuromodulation with LLTS improved cardiac function in a rat model of HFpEF through its anti-inflammatory and antifibrotic effects. These results provide the basis for further clinical trials in humans.

Changes in Cardiac and Vascular Contractile Protein in a Rat Model of Heart Failure with Preserved Ejection Fraction

Heart failure is classified as heart failure with reduced ejection fraction (HFrEF) or heart failure with preserved ejection fraction (HFpEF). Although several therapies have been demonstrated to improve outcomes in patients with HFrEF, none benefit patients with HFpEF. The molecular mechanism that results in HFpEF is unknown and has been impacted by the lack of animal models, and thus, we tested the hypothesis that metabolic and hypertensive stress would result in a rat model of HFpEF. Fischer 344 rats (6mo old) were fed a high fat diet and L‐NAME in the drinking water for 4‐weeks. Invasive and noninvasive hemodynamics demonstrate that the treated animals develop HFpEF; treated animals (n=7) vs controls (n=6) have normal systolic function with LV hypertrophy (20.7±0.4mm v 27.6±2.1mm, p&lt;0.05) and diastolic abnormalities including a decrease in both E (79.4±3.6cm/s v 64.2±3.4cm/s, p=0.003) and dP/dtmin (‐7600±1100mmHg/s v ‐5600±1400mmHg/s, p=0.015), a steeper EDPVR (0.1±1.1mmHg/μl v 3.6±1.7mmHg/μl, p=0.042) and a slower time constant of relaxation (τ; 11±1ms v 16±2ms, p=0.029), as well as edema of the liver and lungs. Compared to controls, in cardiac muscle of HFpEF rats, there is no difference (p&gt;0.05) in the expression and/or phosphorylation of TnI or MyBPC. However, the expression of SERCA2 (p=0.021) and phosphorylation of phospholamban (p=0.046) are reduced, which would be expected to decrease the rate of SR Ca2+ reuptake and slow relaxation. In both the aorta and tertiary mesenteric vessels of HFpEF rats, the expression of nonmuscle myosin was significantly higher and the expression of the leucine zipper positive isoform of myosin light chain phosphatase was reduced, which should increase vascular tone and decrease the sensitivity of the vasculature to NO mediated vasodilatation. This study represents the first rat model of HFpEF and our results define a molecular mechanism that would contribute to both diastolic dysfunction and vascular abnormalities that characterize this disease. This rat HFpEF model could be used in future studies designed to delineate the mechanism(s) that produce the cardiac and vascular abnormalities that produce HFpEF and identify novel targets for rational drug design.

Microtubule detyrosination contributes to mechanical dysfunction in a rat model of HFpEF

Characterized by ventricular stiffening and associated with diabetes, obesity and hypertension, heart failure with preserved ejection fraction (HFpEF) is emerging as the prevalent form of heart failure. Stabilized microtubules stiffen failing myocardium and therefore present a potential therapeutic target for HFpEF, but microtubule network remodeling remains largely uncharacterized in HFpEF. Thus we aimed to quantify microtubule stabilization and its impact on myocyte contractility and mechanics in an established model of HFpEF, the ZSF1 rat.

Sacubitril/Valsartan Improves Diastolic Function But Not Skeletal Muscle Function in a Rat Model of HFpEF.

The angiotensin receptor/neprilysin inhibitor Sacubitril/Valsartan (Sac/Val) has been shown to be beneficial in patients suffering from heart failure with reduced ejection fraction (HFrEF). However, the impact of Sac/Val in patients presenting with heart failure with preserved ejection fraction (HFpEF) is not yet clearly resolved. The present study aimed to reveal the influence of the drug on the functionality of the myocardium, the skeletal muscle, and the vasculature in a rat model of HFpEF. Female obese ZSF-1 rats received Sac/Val as a daily oral gavage for 12 weeks. Left ventricle (LV) function was assessed every four weeks using echocardiography. Prior to organ removal, invasive hemodynamic measurements were performed in both ventricles. Vascular function of the carotid artery and skeletal muscle function were monitored. Sac/Val treatment reduced E/é ratios, left ventricular end diastolic pressure (LVEDP) and myocardial stiffness as well as myocardial fibrosis and heart weight compared to the obese control group. Sac/Val slightly improved endothelial function in the carotid artery but had no impact on skeletal muscle function. Our results demonstrate striking effects of Sac/Val on the myocardial structure and function in a rat model of HFpEF. While vasodilation was slightly improved, functionality of the skeletal muscle remained unaffected.

Abstract 14390: The Cardiac Myosin Inhibitor, Ck-3772271, Attenuates Cardiac Fibrosis and Diastolic Dysfunction in the Dahl/salt Sensitive Rat Model of Heart Failure With Preserved Ejection Fraction

Introduction: Heart failure with preserved ejection fraction (HFpEF) is characterized by underlying contractile dysfunction and progressive myocardial fibrosis and stiffness. CK-3772271 (CK-271) is a novel small molecule cardiac myosin inhibitor that reduces cardiac myosin ATPase activity and reduces cardiac contractility in unloaded isolated cardiomyocytes in vitro and in healthy rats and dogs in vivo . The effect of chronic CK-271 treatment on cardiac function and morphology was evaluated in the Dahl/Salt Sensitive (DSS) rat hypertension model of HFpEF. Methods: DSS male rats were fed either a control low salt (LS, 0.3% NaCl) or high salt (HS, 4% NaCl) diet to induce a hypertension-driven HFpEF disease phenotype. 6 weeks after HS diet treatment, DSS rats were randomized into two sub-groups: continued HS diet or a HS diet formulated with CK-271 (100 ppm) for an additional 6 weeks. Body mass, systolic blood pressure, and cardiac function were measured longitudinally. After 12 weeks of HS treatment, hearts were collected to assess cardiac fibrosis. Results: HS diet treatment increased systolic blood pressure (LS:132.2 ± 4.7 mm Hg vs. HS: 163.5 ± 4.0 mm Hg, mean ± SEM, p&lt; 0.001) and caused cardiac hypercontractility as evidenced by an increase in the end-systolic pressure-volume relationship (LS: 0.8 ± 0.17 vs. HS: 2.1 ± 0.46 mm Hg/ml). HS diet also increased isovolumic relaxation time (IVRT) (LS: 16.8 ± 0.6 vs. HS: 22.8 ± 0.6 ms, p&lt;0.0001), left atrial area (LS: 30.3 ± 0.8 vs. HS: 42.5 ± 2.2 mm 2 , p&lt;0.0001) and cardiac fibrosis (LS: 3.4 ± 0.4 vs. HS: 5.0 ± 0.6 %). 6 weeks of CK-271 treatment reduced fractional shortening (HS: 53.8 ± 1.4 vs. HS+CK-271: 42.7 ± 1.0 %, p&lt;0.0001) and reduced HS diet-induced diastolic dysfunction, including IVRT (HS: 22.8 ± 0.6 vs. HS+CK-271: 19.5 ± 0.5 ms, p&lt;0.0001) and left atrial area (HS: 42.5 ± 2.2 vs. HS+CK-271: 35.4 ± 0.8 mm 2 , p&lt;0.0001). Furthermore CK-271 reduced the development of cardiac fibrosis (HS: 5.0 ± 0.6 vs. HS+CK-271: 3.5 ± 0.3 %, p&lt;0.05) induced by HS diet. Conclusion: The small molecule cardiac myosin inhibitor, CK-3772271, attenuated the development of cardiac hypercontractility, diastolic dysfunction and fibrosis in the DSS rat model of HFpEF. Cardiac myosin inhibition may be a novel approach to mitigate the development of HFpEF.

Metabolic syndrome contributes to the pulmonary arterial dysfunction in pulmonary hypertension in heart failure with preserved ejection fraction

Abstract Background Many Heart Failure with preserved Ejection Fraction (HFpEF) patients have metabolic syndrome and develop Exercise Induced Pulmonary Hypertension (EIPH). The pathogenesis of EIPH in HFpEF remains unclear as there is no rodent model. As the SGLT2 inhibitor Empagliflozin improves clinical outcome in patients with type 2 diabetes and cardiovascular risk, we tested its effect on EIPH in a novel rat model of HFpEF. Methods Obese ZSF1 (HFpEF model) with leptin receptor mutation have metabolic syndrome and received the VEGF-inhibitor SU5416 to stimulate PH (Obese + Sugen). Half also received Empagliflozin (0.2 mg/kg/day) in drinking water from 8 to 22 weeks old. Lean ZSF1 lacking the mutation served as controls. During treadmill exercise, right/left ventricle (RV/LV) hemodynamics were evaluated via catheters. Pulmonary artery vascular smooth muscle cells (PAVSMC) prepared from normal or diabetic patients were cultured in standard media, or with Palmitate acid, Glucose and Insulin (PGI) to induce metabolic stress. Flow cytometry was used to evaluate reactive oxygen species (ROS) in mitochondria (Mitosox) or cytoplasm (CellROX). Results Relative to Lean, Obese + Sugen had increased body weight and HgA1C (Fig. 1A). Relative to Lean and at rest, Obese + Sugen showed mildly elevated RVSP and LVEDP. After exercise, LVSP and LVEDP rose similarly in Lean and Obese + Sugen. However, after exercise, Obese + Sugen showed a markedly greater increase in RVSP and exercise intolerance consistent with EIPH (Fig. 1B). In MR imaging of PA, Lean showed dobutamine (5 μg/kg/min)-induced PA dilation, which was not seen in Obese + Sugen (Fig. 1C). Protein levels of sGCβ1 (key regulator of PA relaxation) and its transcription factor (NFYA) both were decreased in PA from Obese + Sugen relative to Lean (Fig. 1D). Obese + Sugen + SGLT2 inhibitor treated rats showed marked improvements metabolic syndrome (body weight, HgA1c), exercise induced increase in RVSP, PA response to dobutamine, and increased NFYA and sGCβ1 expression (Fig. 1A–D). We observed greater ROS-induced DNA damage (8-OHdG staining) (Fig. 1E) and mitochondrial complex I, III, and IV activity in Obese + Sugen PA that was normalized in Obese + Sugen + SGLT2 inhibitor (Fig. 1F), suggesting a role of ROS in EIPH. Control human PAVSMC treated with PGI media showed elevated cytoplasmic and mitochondrial ROS, associated with increased mitochondrial complex I, III, IV and V activity (Fig. 1F, G). PGI media also accelerated the degradation of NFYA RNA and protein level in a manner mimicked by H2O2, and prevented by catalase/SOD (Fig. 1H, I), suggesting PGI-induced ROS enhanced NFYA degradation. Diabetic human PAVSMCs cultured in normal media resembled PGI-treated normal cells with respect to sGCb1 and NFYA expression, and in response to catalase/SOD (Fig. 1H, I). Conclusions In this PH-HFpEF model, metabolic syndrome contributes to PA dysfunction and EIPH through mitochondrial dysfunction and enhanced ROS, which were improved by Empagliflozin treatment. Figure 1 Funding Acknowledgement Type of funding source: None

Non-invasive vagus nerve stimulation attenuates proinflammatory cytokines and augments antioxidant levels in the brainstem and forebrain regions\xa0of Dahl salt sensitive rats

The anti-inflammatory effects of vagus nerve stimulation are well known. It has recently been shown that low-level, transcutaneous stimulation of vagus nerve at the tragus (LLTS) reduces cardiac inflammation in a rat model of heart failure with preserved ejection fraction (HFpEF). The mechanisms by which LLTS affect the central neural circuits within the brain regions that are important for the regulation of cardiac vagal tone are not clear. Female Dahl salt-sensitive rats were initially fed with either low salt (LS) or high salt (HS) diet for a period of 6 weeks, followed by sham or active stimulation (LLTS) for 30 min daily for 4 weeks. To study the central effects of LLTS, four brainstem (SP5, NAb, NTS, and RVLM) and two forebrain sites (PVN and SFO) were examined. HS diet significantly increased the gene expression of proinflammatory cytokines in the SP5 and SFO. LLTS reversed HS diet-induced changes at both these sites. Furthermore, LLTS augmented the levels of antioxidant Nrf2 in the SP5 and SFO. Taken together, these findings suggest that LLTS has central anti-inflammatory and antioxidant properties that could mediate the neuromodulation of cardiac vagal tone in the rat model of HFpEF.

Low-level transcutaneous vagus nerve stimulation attenuates cardiac remodelling in a rat model of heart failure with preserved ejection fraction.

What is the central question of this study? What is the effect of chronic intermittent low-level transcutaneous vagus nerve stimulation on cardiac inflammation, fibrosis and diastolic dysfunction in a rat model of heart failure with preserved ejection fraction? What is the main finding and its importance? In salt-sensitive rats fed with high salt diet, low-level transcutaneous vagus nerve stimulation significantly attenuated blood pressure elevation, ameliorated diastolic function, and attenuated left ventricular inflammation and fibrosis compared to the sham group. Further studies to examine the efficacy of this novel treatment in humans are warranted. Inflammation and fibrosis play a central role in the development of heart failure with preserved ejection fraction (HFpEF). We previously showed that low-level, transcutaneous stimulation of the vagus nerve at the tragus (LLTS) is anti-inflammatory. We investigated the effect of chronic intermittent LLTS on cardiac inflammation, fibrosis and diastolic dysfunction in a rat model of HFpEF. Dahl salt-sensitive (DS) rats were randomized in three groups: low salt (LS, 0.3% NaCl; n=12; control group without stimulation) and high salt (HS, 4% NaCl) with either active (n=18) or sham (n=18) LLTS at 7weeks of age. After 6weeks of diet (baseline), sham or active LLTS (20Hz, 2mA, 0.2ms) was implemented for 30min daily for 4weeks. Echocardiography was performed at baseline and 4weeks after treatment (endpoint). At endpoint, left ventricle (LV) histology and gene expression were examined. After 6weeks of diets, HS rats developed hypertension and LV hypertrophy compared to LS rats. At endpoint, LLTS significantly attenuated blood pressure elevation, prevented the deterioration of diastolic function and improved LV circumferential strain, compared to the HS sham group. LV inflammatory cell infiltration and fibrosis were attenuated in the HS active compared to the HS sham group. Pro-inflammatory and pro-fibrotic genes (tumour necrosis factor, osteopontin, interleukin (IL)-11, IL-18 and IL-23A) were differentially altered in the two groups. Chronic intermittent LLTS ameliorates diastolic dysfunction, and attenuates cardiac inflammation and fibrosis in a rat model of HFpEF, suggesting that LLTS may be used clinically as a novel non-invasive neuromodulation therapy in HFpEF.

Cellular mechanisms of metabolic syndrome-related atrial decompensation in a rat model of HFpEF

Heart failure (HF) with preserved ejection fraction (HFpEF) is present in about 50% of HF patients. Atrial remodeling is common in HFpEF and associated with increased mortality. We postulate that atrial remodeling is associated with atrial dysfunction in vivo related to alterations in cardiomyocyte Calcium (Ca) signaling and remodeling. We examined atrial function in vivo and Ca transients (CaT) (Fluo4-AM, field stim) in atrial cardiomyocytes of ZSF-1 rats without (Ln; lean hypertensive) and with metabolic syndrome (Ob; obese, hypertensive, diabetic) and HFpEF. ResultsAt 21weeks Ln showed an increased left ventricular (LV) mass and left ventricular end-diastolic pressure (LVEDP), but unchanged left atrial (LA) size and preserved atrial ejection fraction vs. wild-type (WT). CaT amplitude in atrial cardiomyocytes was increased in Ln (2.9±0.2 vs. 2.3±0.2F/F0 in WT; n=22 cells/group; p<0.05). Studying subcellular Ca release in more detail, we found that local central cytosolic CaT amplitude was increased, while subsarcolemmal CaT amplitudes remained unchanged. Moreover, Sarcoplasmic reticulum (SR) Ca content (caffeine) was preserved while Ca spark frequency and tetracaine-dependent SR Ca leak were significantly increased in Ln. Ob mice developed a HFpEF phenotype in vivo, LA area was significantly increased and atrial in vivo function was impaired, despite increased atrial CaT amplitudes in vitro (2.8±0.2; p<0.05 vs. WT). Ob cells showed alterations of the tubular network possibly contributing to the observed phenotype. CaT kinetics as well as SR Ca in Ob were not significantly different from WT, but SR Ca leak remained increased. Angiotensin II (Ang II) reduced in vitro cytosolic CaT amplitudes and let to active nuclear Ca release in Ob but not in Ln or WT. SummaryIn hypertensive ZSF-1 rats, a possibly compensatory increase of cytosolic CaT amplitude and increased SR Ca leak precede atrial remodeling and HFpEF. Atrial remodeling in ZSF-1 HFpEF is associated with an altered tubular network in-vitro and atrial contractile dysfunction in vivo, indicating insufficient compensation. Atrial cardiomyocyte dysfunction in vitro is induced by the addition of angiotensin II.

Effect and mechanism of cardiosphere-derived cells in the treatment of heart failure with preserved ejection fraction in rats

Objective To test whether cardiosphere-derived cells (CDCs) were sufficient to decrease manifestations of heart failure with preserved ejection fraction (HFpEF) in hypertensive rats. Methods DS rats (Charles River, Wilmington, Massachusetts) were fed 0.3% NaCl (low-salt) diet until 7 weeks of age.At that time, the diet was switched to an 8% NaCl (high-salt) diet in rats by random assignment.DS rats fed the low-salt diet constituted the control group (n=20). At 13 to 14 weeks of age, rats with the high-salt diet were randomized to receive allogeneic rat CDCs or PBS.Echocardiography long-axis images of the left ventricular systolic and diastolic dimensions.Sirius red was used to assess fibrosis and proliferation. Results E/A ratio increased in the PBS-treated group compared with the control group and the CDCs-treated group [(1.20±0.30) vs.(1.70±0.20) or (1.80±0.16), t=0.782, 0.844, all P<0.001]. LAA kept increasing in the PBS-treated group[(27.20±1.10) mm2 vs.(19.80±0.76) mm2 or (17.80±0.82) mm2, t=0.892, 0.774, all P<0.001]. The time constant of isovolumic LV pressure fall was prolonged in placebo-treated animals compared with CDCs-treated animals and control rats[(6.2±0.3)×103 mmHg/s vs.(9.4±0.4)×103 mmHg/s, t=0.382, P=0.024; (6.2±0.3)×103 mmHg/s vs.(9.1±0.5)×103 mmHg/s, t=0.883, P=0.022]. LVEDP was 2-fold higher in placebo-treated group than in CDC-treated and control animals[(17±10) mmHg vs.(8±3) mmHg, t=0.922, P=0.003; (17±10) mmHg vs.(9±4) mmHg, t=0.922, P=0.004]. A dramatic improvement of survival was observed in CDC-treated rats (Kaplan-Meier survival curves) (P=0.027). Cardiac myofibroblasts increased dramatically in PBS-treated(110/field vs.46/field, P<0.001). Inflammatory cytokines expression siginficantly increased in PBS-treated group. Conclusion CDCs improves survival in a rat model of HFpEF through reducing inflammation and fibrosis. Key words: Stem cells; Heart failure; Fibrosis; Rats

Exercise Improves Diastolic Function In HFpEF By Reducing Intrinsic Cardiomyocyte Stiffness And Fibrosis

INTRODUCTION In heart failure with preserved ejection fraction (HFpEF), the underlying systemic inflammatory state is related to myocardial stiffening. However, optimal treatment remains largely undefined. PURPOSE: To investigate the effect of exercise training (ExT) on left ventricle (LV) stiffness in a rat model of HFpEF. METHODS: The study was performed with nine-week old ZSF1 obese rats (Ob n=20). At the 16th week, they were randomly divided in sedentary (ObSED, n=10) and exercised (ObEX, n=10; treadmill ExT during 4 weeks, 5 days/week, 60 min/day, at a speed of 20m/min). In the 18th week, all animals underwent echocardiographic evaluation. In the 20th week, animals were sacrificed and samples from heart and LV were collated for: i) histological analysis (cross-sectional area (CSA), collagen content; ii) passive tension analysis in skinned cardiomyocytes); iii) assessment of expression on matrix metaloproteinases (MMP-2,-9) and its tissue inhibitors (TIMP-1 and 2) by western blot analysis and iv) zimography assessment of proteolytic activity. RESULTS: Both groups presented preserved ejection fraction (>70%). ExT improved diastolic function evidenced by E/E´ ratio (14,81±2,27 vs 16,53±1,47 p<0,05). Moreover, in skinned cardiomyocytes, the ObEx showed decreased passive tension, which suggests a reduction in myocardial stiffness (p<0.05). No significant differences were observed between the groups in body mass, heart and LV weight, CSA, and MMPs and TIMPs expression and activity (p>0.05). However, the ratio collagen/muscle was significantly reduced in ObEX, compared to ObSED (0.08 vs. 0.12 p<0.05). CONCLUSION: ExT improves diastolic function mainly due to the decrease on collagen deposition and diminished cardiomyocyte stiffness. FUNDING: Grant from the European Commission FP7-Health-2010; MEDIA-261,409. CIAFEL is funded by European Regional Development Fund through the Operational Competitiveness Programme, and by FCT (UID/DTP/00617/2013). Schmidt, C.: CAPES (BEX 0554/14-6). Moreira-Gonçalves, D.: FCT (SFRH/BPD/90010/2012).

Abstract 19116: Efficacy of a Small Molecule HDAC Inhibitor in a Model of Diastolic Dysfunction with Preserved Ejection Fraction

Heart failure (HF) is a major health problem and growing economic burden worldwide. Of the patients with HF, ∼50% suffer from heart failure with preserved ejection fraction (HFpEF), also known as diastolic HF. Current standards-of-care for systolic HF provide little to no benefit to patients with HFpEF. Histone deacetylase inhibitors (HDACi) have been shown to improve systolic function in a variety of rodent models of HF. However, the impact of HDACi on diastolic function remains poorly understood. This study assessed the efficacy of an HDACi in a rat model of HFpEF. Dahl salt-sensitive (DSS) rats were fed low salt (LS, 0.4% NaCl) or high salt (HS, 4.0% NaCl) diets for 10 weeks. Rats were treated either with vehicle (LS and HS groups) or the pan-HDAC inhibitor, ITF2357, at 3 and 30 mg/kg (HS groups). Serial echocardiography was performed to assess left ventricle (LV) dimensions and function. At study endpoint, pressure-volume analyses were performed to further quantify effects of HS and HDACi on hemodynamic properties. HS feeding caused hypertension, cardiac hypertrophy and diastolic dysfunction, as shown by a 30% reduction of E/A and E’/A’ from baseline (measured by flow and tissue Doppler), a 27% increase of isovolumic relaxation time (IVRT), and a significant increase in LV end-diastolic pressure (LVEDP). EF was preserved in HS fed animals. ITF2357 was well tolerated and did not cause hematological side effects. ITF2357 dose-dependently prevented diastolic dysfunction of the heart; E/A and E’/A’ decreased 14% and 5% from baseline with low and high doses of ITF2357, respectively. Efficacy of ITF2357 was also observed at the level of IVRT and LVEDP. HDAC inhibition-mediated improvement in cardiac function and hemodynamics occurred independently of effects on cardiac hypertrophy and systemic hypertension. These data suggest that HDACs play a critical role in the pathogenesis of diastolic HF and that small molecule HDAC inhibitor have potential as novel therapeutics for HFpEF

Rosuvastatin added to standard heart failure therapy improves cardiac remodelling in heart failure rats with preserved ejection fraction

Although statins may provide potential therapeutic pathways for patients with heart failure with preserved ejection fraction (HFpEF), no studies have evaluated statins in combination with standard HF therapy, which would reflect clinical practice more closely. To address this question, we evaluated whether rosuvastatin added to a standard HF therapy provides additional improvement in cardiac structure and function in rats with hypertensive heart failure (SHHF). Two-month-old SHHF rats were randomly assigned to four groups: (i) non-treated SHHF rats; (ii) rosuvastatin-treated SHHF rats; (iii) SHHF rats treated with quinapril plus torasemide plus carvedilol (considered as standard HF therapy); and (iv) SHHF rats treated with the combination of standard HF therapy and rosuvastatin. The administration of a standard anti-hypertensive HF therapy to SHHF rats for 17 months attenuated left ventricular (LV) chamber dilatation, cardiac hypertrophy, fibrosis, and inflammation compared with non-treated SHHF rats. Rosuvastatin alone prevented LV dilatation and cardiac inflammation similar to standard HF therapy-treated SHHF, despite being unable to normalize blood pressure (BP) or influence cardiac hypertrophy. However, and importantly, the addition of rosuvastatin to the standard HF therapy further prevented LV dilatation, preserved cardiac function, and normalized inflammation. These data show that the use of rosuvastatin plus a standard HF therapy results in a significant additional improvement in HF and cardiac remodelling in a rat model of HFpEF. These beneficial effects were independent of BP and plasma lipid changes, and seem to be due, at least in part, to decreased myocardial inflammation.