Myocardial stiffness in patients with heart failure and a preserved ejection fraction: contributions of collagen and titin

Deciphering the Dilemma: Anticoagulation for Heart Failure With Preserved Ejection Fraction (HFpEF)

Impairment in ventricular relaxation and preserved left ventricular ejection fraction are the two main features of heart failure with preserved ejection fraction (HFpEF) a difficult clinical condition. Therapeutic choices for HFpEF patients are still scarce despite its rising frequency and negative effects on morbidity and mortality, necessitating creative methods to enhance results. The increased thromboembolic risk seen in these individuals raises questions about the relevance of anticoagulation in the therapy of HFpEF. Although anticoagulation has been shown to be beneficial in heart failure with decreased ejection fraction (HFrEF) and other high-risk cardiovascular disorders, its efficacy and safety in HFpEF present a challenging therapeutic challenge. Anticoagulants have been the subject of clinical trials in HFpEF, but the results have been conflicting, giving clinicians only a little information with which to make decisions. The decision-making process is made more difficult by worries about potential bleeding hazards, particularly in susceptible elderly HFpEF patients with other comorbidities. The link between heart failure and anticoagulant medication in HFpEF is thoroughly analyzed in this narrative review. In HFpEF, cardiac fibrosis and endothelial dysfunction create a prothrombotic milieu, as is highlighted in this passage. Also covered are recent developments in innovative biomarker research and cutting-edge imaging techniques, which may provide ways to spot HFpEF patients who might benefit from anticoagulation. This therapeutic conundrum may be resolved by using precision medicine strategies based on risk classification and individualized therapy choices. This review emphasizes the need for more research to establish the best use of anticoagulation in HFpEF within the framework of personalized therapy and shared decision-making. To successfully manage thromboembolic risk and reduce bleeding consequences in HFpEF patients, it is essential to perform well-designed clinical studies and advance our understanding of the pathophysiology of HFpEF. These developments may ultimately improve the prognosis and quality of life for people who suffer from this difficult and mysterious ailment.

Interventions to Address Cardiovascular Risk in Obese Patients: Many Hands Make Light Work

Obesity is a growing public health epidemic worldwide and is implicated in slowing improved life expectancy and increasing cardiovascular (CV) risk; indeed, several obesity-related mechanisms drive structural, functional, humoral, and hemodynamic heart alterations. On the other hand, obesity may indirectly cause CV disease, mediated through different obesity-associated comorbidities. Diet and physical activity are key points in preventing CV disease and reducing CV risk; however, these strategies alone are not always sufficient, so other approaches, such as pharmacological treatments and bariatric surgery, must support them. Moreover, these strategies are associated with improved CV risk factors and effectively reduce the incidence of death and CV events such as myocardial infarction and stroke; consequently, an individualized care plan with a multidisciplinary approach is recommended. More precisely, this review explores several interventions (diet, physical activity, pharmacological and surgical treatments) to address CV risk in obese patients and emphasizes the importance of adherence to treatments.

Acacetin Alleviates Cardiac Fibrosis via TGF-β1/Smad and AKT/mTOR Signal Pathways in Spontaneous Hypertensive Rats

INTRODUCTION

Attenuating cardiac fibroblasts activation contributes to reducing excessive extracellular matrix deposition and cardiac structural remodeling in hypertensive hearts. Acacetin plays a protective role in doxorubicin-induced cardiomyopathy and ischemia/reperfusion injury. The aim of this study was to investigate the potential molecular mechanisms underlying the protective role of acacetin on hypertension-induced cardiac fibrosis.

METHODS

Echocardiography, histopathological methods, and Western blotting techniques were used to evaluate the anti-fibrosis effects in spontaneous hypertensive rat (SHR) which were daily intragastrically administrated with acacetin (10 mg/kg and 20 mg/kg) for 6 weeks. Angiotensin II (Ang II) was used to induce cellular fibrosis in human cardiac fibroblasts (HCFs) in the absence and presence of acacetin treatment for 48 h.

RESULTS

Acacetin significantly alleviated hypertension-induced increase in left ventricular (LV) posterior wall thickness and LV mass index in SHR. The expressions of collagen-1, collagen-III, and alpha-smooth muscle actin (α-SMA) were remarkedly decreased after treatment with acacetin (n = 6, p < 0.05). In cultured HCFs, acacetin significantly attenuated Ang II-induced migration and proliferation (n = 6, p < 0.05). Moreover, acacetin substantially inhibited Ang II-induced upregulation of collagen-1 and collagen-III (n = 6, p < 0.05) and downregulated the expression of alpha-SMA in HCFs. Additionally, acacetin decreased the expression of TGF-β1, p-Smad3/Smad3, and p-AKT and p-mTOR but increased the expression of Smad7 (n = 6, p < 0.05). Further studies found that acacetin inhibited TGF-β1 agonist SRI and AKT agonist SC79 caused fibrotic effect.

CONCLUSION

Acacetin inhibits the hypertension-associated cardiac fibrotic processes through regulating TGF-β/Smad3, AKT/mTOR signal transduction pathways.

Efficacy of a growth hormone-releasing hormone agonist in a murine model of cardiometabolic heart failure with preserved ejection fraction

Heart failure (HF) with preserved ejection fraction (HFpEF) represents a major unmet medical need owing to its diverse pathophysiology and lack of effective therapies. Potent synthetic, agonists (MR-356 and MR-409) of growth hormone-releasing hormone (GHRH) improve the phenotype of models of HF with reduced ejection fraction (HFrEF) and in cardiorenal models of HFpEF. Endogenous GHRH exhibits a broad range of regulatory influences in the cardiovascular (CV) system and aging and plays a role in several cardiometabolic conditions including obesity and diabetes. Whether agonists of GHRH can improve the phenotype of cardiometabolic HFpEF remains untested and unknown. Here we tested the hypothesis that MR-356 can mitigate/reverse the cardiometabolic HFpEF phenotype. C57BL6N mice received a high-fat diet (HFD) plus the nitric oxide synthase inhibitor (l-NAME) for 9 wk. After 5 wk of HFD + l-NAME regimen, animals were randomized to receive daily injections of MR-356 or placebo during a 4-wk period. Control animals received no HFD + l-NAME or agonist treatment. Our results showed the unique potential of MR-356 to treat several HFpEF-like features including cardiac hypertrophy, fibrosis, capillary rarefaction, and pulmonary congestion. MR-356 improved cardiac performance by improving diastolic function, global longitudinal strain (GLS), and exercise capacity. Importantly, the increased expression of cardiac pro-brain natriuretic peptide (pro-BNP), inducible nitric oxide synthase (iNOS), and vascular endothelial growth factor-A (VEGF-A) was restored to normal levels suggesting that MR-356 reduced myocardial stress associated with metabolic inflammation in HFpEF. Thus, agonists of GHRH may be an effective therapeutic strategy for the treatment of cardiometabolic HFpEF phenotype.NEW & NOTEWORTHY This randomized study used rigorous hemodynamic tools to test the efficacy of a synthetic GHRH agonist to improve cardiac performance in a cardiometabolic HFpEF. Daily injection of the GHRH agonist, MR-356, reduced the HFpEF-like effects as evidenced by improved diastolic dysfunction, reduced cardiac hypertrophy, fibrosis, and pulmonary congestion. Notably, end-diastolic pressure and end-diastolic pressure-volume relationship were reset to control levels. Moreover, treatment with MR-356 increased exercise capacity and reduced myocardial stress associated with metabolic inflammation in HFpEF.

Tumor Necrosis Factor-α Mediates Inflammation-induced Early-Stage Left Ventricular Systolic Dysfunction

ABSTRACT

Elevated systemic inflammation contributes to pathogenesis of heart failure with preserved ejection fraction (HFpEF), but molecular mechanisms are poorly understood. Although left ventricular (LV) diastolic dysfunction is the main cause of HFpEF, subclinical systolic dysfunction also contributes. We have previously shown that rats with collagen-induced arthritis (CIA) have systemic inflammation, LV diastolic dysfunction, and that increased circulating TNF-α contributes to inflammation-induced HFpEF pathogenesis, but does not mediate LV diastolic dysfunction in CIA rats. Contribution of systemic inflammation to dysfunction of the active process of LV diastolic and systolic function are unknown. In the present study, we used the CIA rat model to investigate the effects of systemic inflammation and TNF-α blockade on systolic function, and mRNA expression of genes involved in active diastolic relaxation and of myosin heavy chain (MyHC) isoforms. Collagen inoculation and TNF-α blockade did not affect LV mRNA expression of genes that mediate active LV diastolic function. Collagen-induced inflammation impaired LV global longitudinal strain ( P = 0.03) and velocity ( P = 0.04). This impairment of systolic function was prevented by TNF-α blockade. Collagen inoculation decreased mRNA expression of α-MyHC ( Myh6, P = 0.03) and increased expression of β-MyHC ( Myh7, P = 0.0002), a marker, which is upregulated in failing hearts. TNF-α blockade prevented this MyHC isoform-switch. These results show that increased circulating TNF-α changes the relative expression of MyHC isoforms, favoring β-MyHC, which may underlie changes in contractile function that impair systolic function. Our results indicate that TNF-α initiates early-stage LV systolic, rather than LV diastolic dysfunction.

Cells and Materials for Cardiac Repair and Regeneration

After more than 20 years following the introduction of regenerative medicine to address the problem of cardiac diseases, still questions arise as to the best cell types and materials to use to obtain effective clinical translation. Now that it is definitively clear that the heart does not have a consistent reservoir of stem cells that could give rise to new myocytes, and that there are cells that could contribute, at most, with their pro-angiogenic or immunomodulatory potential, there is fierce debate on what will emerge as the winning strategy. In this regard, new developments in somatic cells' reprogramming, material science and cell biophysics may be of help, not only for protecting the heart from the deleterious consequences of aging, ischemia and metabolic disorders, but also to boost an endogenous regeneration potential that seems to be lost in the adulthood of the human heart.

Heart Failure With Preserved Ejection Fraction: JACC Scientific Statement

The incidence and prevalence of heart failure with preserved ejection fraction (HFpEF) continue to rise in tandem with the increasing age and burdens of obesity, sedentariness, and cardiometabolic disorders. Despite recent advances in the understanding of its pathophysiological effects on the heart, lungs, and extracardiac tissues, and introduction of new, easily implemented approaches to diagnosis, HFpEF remains under-recognized in everyday practice. This under-recognition presents an even greater concern given the recent identification of highly effective pharmacologic-based and lifestyle-based treatments that can improve clinical status and reduce morbidity and mortality. HFpEF is a heterogenous syndrome and recent studies have suggested an important role for careful, pathophysiological-based phenotyping to improve patient characterization and to better individualize treatment. In this JACC Scientific Statement, we provide an in-depth and updated examination of the epidemiology, pathophysiology, diagnosis, and treatment of HFpEF.

Drug-based mobilisation of mesenchymal stem/stromal cells improves cardiac function post myocardial infarction

There is an unmet need for treatments that prevent the progressive cardiac dysfunction following myocardial infarction. Mesenchymal stem/stromal cells (MSCs) are under investigation for cardiac repair; however, culture expansion prior to transplantation is hindering their homing and reparative abilities. Pharmacological mobilisation could be an alternative to MSC transplantation. Here, we report that endogenous MSCs mobilise into the circulation at day 5 post myocardial infarction in male Lewis rats. This mobilisation can be significantly increased by using a combination of the FDA-approved drugs mirabegron (β3-adrenoceptor agonist) and AMD3100 (CXCR4 antagonist). Blinded cardiac magnetic resonance imaging analysis showed the treated group to have increased left ventricular ejection fraction and decreased end systolic volume at 5 weeks post myocardial infarction. The mobilised group had a significant decrease in plasma IL-6 and TNF-α levels, a decrease in interstitial fibrosis, and an increase in the border zone blood vessel density. Conditioned medium from blood-derived MSCs supported angiogenesis in vitro, as shown by tube formation and wound healing assays. Our data suggest a novel pharmacological strategy that enhances myocardial infarction-induced MSC mobilisation and improves cardiac function after myocardial infarction.

Myocardial Metabolomics of Human Heart Failure With Preserved Ejection Fraction

BACKGROUND

The human heart primarily metabolizes fatty acids, and this decreases as alternative fuel use rises in heart failure with reduced ejection fraction (HFrEF). Patients with severe obesity and diabetes are thought to have increased myocardial fatty acid metabolism, but whether this is found in those who also have heart failure with preserved ejection fraction (HFpEF) is unknown.

METHODS

Plasma and endomyocardial biopsies were obtained from HFpEF (n=38), HFrEF (n=30), and nonfailing donor controls (n=20). Quantitative targeted metabolomics measured organic acids, amino acids, and acylcarnitines in myocardium (72 metabolites) and plasma (69 metabolites). The results were integrated with reported RNA sequencing data. Metabolomics were analyzed using agnostic clustering tools, Kruskal-Wallis test with Dunn test, and machine learning.

RESULTS

Agnostic clustering of myocardial but not plasma metabolites separated disease groups. Despite more obesity and diabetes in HFpEF versus HFrEF (body mass index, 39.8 kg/m2 versus 26.1 kg/m2; diabetes, 70% versus 30%; both P<0.0001), medium- and long-chain acylcarnitines (mostly metabolites of fatty acid oxidation) were markedly lower in myocardium from both heart failure groups versus control. In contrast, plasma levels were no different or higher than control. Gene expression linked to fatty acid metabolism was generally lower in HFpEF versus control. Myocardial pyruvate was higher in HFpEF whereas the tricarboxylic acid cycle intermediates succinate and fumarate were lower, as were several genes controlling glucose metabolism. Non-branched-chain and branched-chain amino acids (BCAA) were highest in HFpEF myocardium, yet downstream BCAA metabolites and genes controlling BCAA metabolism were lower. Ketone levels were higher in myocardium and plasma of patients with HFrEF but not HFpEF. HFpEF metabolomic-derived subgroups were differentiated by only a few differences in BCAA metabolites.

CONCLUSIONS

Despite marked obesity and diabetes, HFpEF myocardium exhibited lower fatty acid metabolites compared with HFrEF. Ketones and metabolites of the tricarboxylic acid cycle and BCAA were also lower in HFpEF, suggesting insufficient use of alternative fuels. These differences were not detectable in plasma and challenge conventional views of myocardial fuel use in HFpEF with marked diabetes and obesity and suggest substantial fuel inflexibility in this syndrome.

Functional and Metabolic Imaging in Heart Failure with Preserved Ejection Fraction: Promises, Challenges, and Clinical Utility

Heart failure with preserved ejection fraction (HFpEF) is recognised as an increasingly prevalent, morbid and burdensome condition with a poor outlook. Recent advances in both the understanding of HFpEF and the technological ability to image cardiac function and metabolism in humans have simultaneously shone a light on the molecular basis of this complex condition of diastolic dysfunction, and the inflammatory and metabolic changes that are associated with it, typically in the context of a complex patient. This review both makes the case for an integrated assessment of the condition, and highlights that metabolic alteration may be a measurable outcome for novel targeted forms of medical therapy. It furthermore highlights how recent technological advancements and advanced medical imaging techniques have enabled the characterisation of the metabolism and function of HFpEF within patients, at rest and during exercise.

Inhibition of transglutaminase 2 (TG2) ameliorates ventricular fibrosis in isoproterenol-induced heart failure in rats

AIMS

Transglutaminase (TG) inhibitors represent promising therapeutic interventions in cardiac fibrosis and related dysfunctions. However, it remains unknown how TG inhibition, TG2 in particular, affects the signaling systems that drive pathological fibrosis. This study aimed to examine the effect TG inhibition by cystamine on the progression of isoproterenol (ISO)-induced cardiac fibrosis and dysfunction in rats.

MATERIALS AND METHODS

Cardiac fibrosis was established by intraperitoneal injection of ISO to rats (ISO group), followed by 6 weeks of cystamine injection (ISO + Cys group). The control groups were administered normal saline alone or with cystamine. Hemodynamics, lipid profile, liver enzymes, urea, and creatinine were assessed in conjunction with heart failure markers (serum NT-proANP and cTnI). Left ventricular (LV) and atrial (LA) fibrosis, total collagen content, and mRNA expression of profibrotic markers including TG2 were quantified by Masson's trichrome staining, LC-MS/MS and quantitative PCR, respectively.

KEY FINDINGS

Cystamine administration to ISO rats significantly decreased diastolic and mean arterial pressures, total cholesterol, triglycerides, LDL, liver enzymes, urea, and creatinine levels, while increasing HDL. NT-proANP and cTnI serum levels remained unchanged. In LV tissues, significant reductions in ISO-induced fibrosis and elevated total collagen content were achieved after cystamine treatment, together with a reduction in TG2 concentration. Reduced mRNA expression of several profibrotic genes (COL1A1, FN1, MMP-2, CTGF, periostin, CX43) was also evidenced in LV tissues of ISO rats upon cystamine administration, whereas TGF-β1 expression was depressed in LA tissues. Cystamine decreased TG2 mRNA expression in the LV of control rats, while LV expression of TG2 was relatively low in ISO rats irrespective of cystamine treatment.

SIGNIFICANCE

TG2 inhibition by cystamine in vivo exerted cardioprotective effects against ISO-induced cardiac fibrosis in rats decreasing the LV abundance of several profibrotic markers and the content of TG2 and collagen, suggesting that TG2 pharmacological inhibition could be beneficial to alleviate cardiac fibrosis.

Validating MRI-Derived Myocardial Stiffness Estimates Using In Vitro Synthetic Heart Models

Impaired cardiac filling in response to increased passive myocardial stiffness contributes to the pathophysiology of heart failure. By leveraging cardiac MRI data and ventricular pressure measurements, we can estimate in vivo passive myocardial stiffness using personalized inverse finite element models. While it is well-known that this approach is subject to uncertainties, only few studies quantify the accuracy of these stiffness estimates. This lack of validation is, at least in part, due to the absence of ground truth in vivo passive myocardial stiffness values. Here, using 3D printing, we created soft, homogenous, isotropic, hyperelastic heart phantoms of varying geometry and stiffness and simulate diastolic filling by incorporating the phantoms into an MRI-compatible left ventricular inflation system. We estimate phantom stiffness from MRI and pressure data using inverse finite element analyses based on a Neo-Hookean model. We demonstrate that our identified softest and stiffest values of 215.7 and 512.3 kPa agree well with the ground truth of 226.2 and 526.4 kPa. Overall, our estimated stiffnesses revealed a good agreement with the ground truth ([Formula: see text] error) across all models. Our results suggest that MRI-driven computational constitutive modeling can accurately estimate synthetic heart material stiffnesses in the range of 200-500 kPa.

Texture analysis of native T1 images as a novel method for non-invasive assessment of heart failure with preserved ejection fraction in end-stage renal disease patients

OBJECTIVES

To explore the diagnostic potential of texture analysis applied to native T1 maps obtained from cardiac magnetic resonance (CMR) images for the assessment of heart failure with preserved ejection fraction (HFpEF) among patients with end-stage renal disease (ESRD).

METHODS

This study, conducted from June 2018 to November 2020, included 119 patients (35 on hemodialysis, 55 on peritoneal dialysis, and 29 with kidney transplants) in Renji Hospital. Native T1 maps were assessed with texture analysis, using a freely available software package, in participants who underwent cardiac MRI at 3.0 T. Four texture features, selected by dimension reduction specific to the diagnosis of HFpEF, were analyzed. Multivariate logistic regression was performed to examine the independent association between the selected features and HFpEF in ESRD patients.

RESULTS

Seventy-six of 119 patients were diagnosed with HFpEF. Demographic, laboratory, cardiac MRI, and echocardiogram characteristics were compared between HFpEF and non-HFpEF groups. The four texture features that were analyzed showed statistically significant differences between groups. In multivariate analysis, age, left atrial volume index (LAVI), and sum average 4 (SA4) turned out to be independent predictors for HFpEF in ESRD patients. Combining the texture feature, SA4, with typical predictive factors resulted in higher C-index (0.923 vs. 0.898, p = 0.045) and a sensitivity and specificity of 79.2% and 95.2%, respectively.

CONCLUSIONS

Texture analysis of T1 maps adds diagnostic value to typical clinical parameters for the assessment of heart failure with preserved ejection fraction in patients with end-stage renal disease.

KEY POINTS

• Non-invasive assessment of HFpEF can help predict prognosis in ESRD patients and help them take timely preventative measures. • Texture analysis of native T1 maps adds diagnostic value to the typical clinical parameters for the assessment of HFpEF in patients with ESRD.

Managing Diastolic Dysfunction Perioperatively

Preoperative cardiac evaluation is a cornerstone of the practice of anesthesiology. This consists of a thorough history and physical attempting to elucidate signs and symptoms of heart failure, angina or anginal equivalents, and valvular heart disease. Current guidelines rarely recommend preoperative echocardiography in the setting of an adequate functional capacity. Many patients may have poor functional capacity and/or have medical history such that echocardiographic data is available for review. Much focus is often placed on evaluating major valvular abnormalities and systolic function as measured by ejection fraction, but a key impactful component is often overlooked-diastolic function. A diagnosis of diastolic heart failure is an independent predictor of mortality and is not uncommon in patients with normal systolic function. This narrative review addresses the clinical relevance and management of diastolic dysfunction in the perioperative setting.

The myocardial flow reserve in patients with heart failure with preserved ejection fraction

To evaluate the myocardial flow reserve (MFR) and myocardial blood flow (MBF) parameters in patients with heart failure with preserved ejection fraction (HFpEF) and to assess their relationship with the severity of HF and the levels of soluble ST2 (sST2). A total of 59 consecutive patients (median age of 65.0 (58.0; 69.0) years) with non-obstructive coronary artery disease (CAD) and preserved EF were enrolled. Serum levels biomarkers were measured by enzyme immunoassay. MBF and MFR parameters were evaluated by dynamic CZT-SPECT. All patients were divided into two groups: group 1 comprised patients (n = 41) with HFpEF, and group 2 comprised those (n = 18) without HFpEF. In group 1 global MFR (gMFR) values were lower by 27.8% (p = 0.003) than in group 2. The values of gMFR correlated with NT-proBNP (r = - 0.290) and sST2 (r = -0.331) levels. Based on ROC-analysis, gMFR ≤ 2.27 (AUC = 0.746; p < 0.001) were associated with the presence of HFpEF. In patients with HFpEF (n = 41) the values of gMFR were related to NYHA classes (p < 0.001) and the parameters of diastolic dysfunction (p < 0.001). The values of gMFR ≤ 2.27 may be used for the evaluation of microvascular changes in patients with HFpEF and non-obstructive CAD.

[Mechano-energetic defects in heart failure]

Heart failure is characterized by defects in excitation-contraction coupling, energetic deficit and oxidative stress. The energy for cardiac contraction and relaxation is provided in mitochondria, whose function is tightly regulated by excitation-contraction coupling in cardiac myocytes. In heart failure with reduced ejection fraction (HFrEF), alterations in the ion balance in cardiac myocytes impair mitochondrial Ca²⁺ uptake, which is required for activation of the Krebs cycle, causing an energetic deficit and oxidative stress in mitochondria. Recent clinical studies suggest that in heart failure with preserved ejection fraction (HFpEF), in stark contrast to HFrEF, hypercontractility often occurs as an attempt to compensate for a pathological increase in systemic and pulmonary vascular resistance. This hypercontractility increases cardiac energy and oxygen demands at rest and reduces the contractile, diastolic and coronary reserves, preventing an adequate increase in cardiac output during exercise. Moreover, increased contractility causes long-term maladaptive remodeling processes due to oxidative stress and redox-sensitive prohypertrophic signaling pathways. As overweight and diabetes, particularly in the interplay with hemodynamic stress, are important risk factors for the development of HFpEF, interventions targeting metabolism in particular could ameliorate the development and progression of HFpEF.

Diffuse Myocardial Fibrosis on Cardiac Magnetic Resonance Imaging Is Related to Galectin-3 and Predicts Outcome in Heart Failure

AIMS

Ongoing adverse remodeling is a hallmark of heart failure (HF), which might be reflected by either focal or diffuse myocardial fibrosis. Therefore, in (pre)clinical settings, we used immunohistochemistry or cardiac magnetic resonance imaging (CMR) to investigate the association of (focal or diffuse) fibrosis with cardiac biomarkers and adverse events in HF.

METHODS AND RESULTS

In C57Bl/6J mice, we determined the presence and extent of myocardial fibrosis 6 weeks post-myocardial infarction (MI). Furthermore, we studied 159 outpatient HF patients who underwent CMR, and determined focal and diffuse fibrosis by late gadolinium enhancement (LGE) and post-contrast T1 time of the non-LGE myocardium, respectively. HF patients were categorized based on the presence of LGE, and by the median post-contrast T1 time. Kaplan-Meier and Cox regression analyses were used to determine the association of fibrosis with HF hospitalization and all-cause mortality. LGE was detected in 61 (38%) patients. Cardiac biomarker levels were comparable between LGE-positive and LGE-negative patients. LGE-positive patients with a short T1 time had elevated levels of both NT-proBNP and galectin-3 (1611 vs. 453 ng/L, p = 0.026 and 20 vs. 15 μg/L, p = 0.004, respectively). This was not observed in LGE-negative patients. Furthermore, a short T1 time in LGE-positive patients was associated with a higher risk of adverse events (log-rank p = 0.01).

CONCLUSION

This study implies that cardiac biomarkers reflect active remodeling of the non-infarcted myocardium of patients with focal myocardial scarring. Diffuse fibrosis, in contrast to focal scarring, might have a higher prognostic value regarding adverse outcomes in HF patients.

Emerging epigenetic therapies of cardiac fibrosis and remodelling in heart failure: from basic mechanisms to early clinical development

Cardiovascular diseases and specifically heart failure (HF) impact global health and impose a significant economic burden on society. Despite current advances in standard of care, the risks for death and readmission of HF patients remain unacceptably high and new therapeutic strategies to limit HF progression are highly sought. In disease settings, persistent mechanical or neurohormonal stress to the myocardium triggers maladaptive cardiac remodelling, which alters cardiac function and structure at both the molecular and cellular levels. The progression and magnitude of maladaptive cardiac remodelling ultimately leads to the development of HF. Classical therapies for HF are largely protein-based and mostly are targeted to ameliorate the dysregulation of neuroendocrine pathways and halt adverse remodelling. More recently, investigation of novel molecular targets and the application of cellular therapies, epigenetic modifications, and regulatory RNAs has uncovered promising new avenues to address HF. In this review, we summarize the current knowledge on novel cellular and epigenetic therapies and focus on two non-coding RNA-based strategies that reached the phase of early clinical development to counteract cardiac remodelling and HF. The current status of the development of translating those novel therapies to clinical practice, limitations, and future perspectives are additionally discussed.

Periplocin Alleviates Cardiac Remodeling in DOCA-Salt-Induced Heart Failure Rats

Heart failure with preserved ejection fraction (HFpEF) is a common public health problem associated with increased morbidity and long-term mortality. However, effective treatment for HFpEF was not discovered yet. In the present study, we aimed to decipher the effects of Periplocin on DOCA-induced heart failure rats and explore the possible underlying mechanisms. We demonstrated that Periplocin could significantly attenuate cardiac structural remodeling and improve cardiac diastolic function. Of note, Periplocin significantly inhibited the recruitment of inflammatory and immune cells and decreased the expression of serum inflammatory cytokines. Meanwhile, Periplocin had the effect of cardiac glycosides to improve cardiomyocyte contractility and calcium transient amplitude. These findings indicate that Periplocin might be a potential medicine to treat HFpEF in patients.

The NO-cGMP-PKG Axis in HFpEF: From Pathological Mechanisms to Potential Therapies

Heart failure with preserved ejection fraction (HFpEF) accounts for almost half of all heart failure (HF) cases worldwide. Unfortunately, its incidence is expected to continue to rise, and effective therapy to improve clinical outcomes is lacking. Numerous efforts currently directed towards the pathophysiology of human HFpEF are uncovering signal transduction pathways and novel therapeutic targets. The nitric oxide-cyclic guanosine phosphate-protein kinase G (NO-cGMP-PKG) axis has been described as an important regulator of cardiac function. Suppression of the NO-cGMP-PKG signalling pathway is involved in the progression of HFpEF. Therefore, the NO-cGMP-PKG signalling pathway is a potential therapeutic target for HFpEF. In this review, we aim to explore the mechanism of NO-cGMP-PKG in the progression of HFpEF and to summarize potential therapeutic drugs that target this signalling pathway.

Heart failure with preserved ejection fraction: the role of microvascular dysfunction

Aim. To evaluate the relationship between coronary microvascular dysfunction (CMD), biomarkers of cardiac fibrosis and cardiac remodeling (soluble ST2 (sST2), fibroblast growth factor-23 (FGF-23), matrix metalloproteinase-9 (MMP-9), tissue inhibitor of metalloproteinase-1 (TIMP-1), and NT-proBNP), parameters of diastolic dysfunction (DD), and the presence of heart failure with preserved ejection fraction (HFpEF) in symptomatic patients.

Materials and methods. Study participants were 59 patients with non-obstructive coronary artery disease (CAD) and preserved left ventricular ejection fraction (LVEF) of 62 (56; 67) %. Non-obstructive CAD was verified by coronary computed tomography angiography. Stress-and rest-myocardial blood flow (MBF) and coronary flow reserve (CFR) parameters were evaluated by CZT SPECT. Serum levels of cardiac biomarkers were measured by the enzyme immunoassay. Two-dimensional transthoracic echocardiography was used to assess DD parameters.

Results. Decreased CFR was defined as CFR ≤ 2. Therefore, CMD was defined as the presence of decreased CFR in the absence of flow-limiting CAD. Distribution of patients was performed by CFR values: group 1 included patients with preserved CFR (>2, n = 35), and group 2 encompassed patients with decreased CFR (≤2, n = 24). In 87.5% of cases, patients with CMD were diagnosed with HFpEF, whereas in patients with preserved CFR, heart failure was diagnosed only in 51.4% of cases (p < 0.0001). CFR values were correlated with the left atrial volume (r = –0.527; p = 0.001), E / A ratio (r = –0.321, p = 0.012), and E / e’ (r = –0.307; p = 0.021). Following the ROC analysis, the levels of sST2 ≥ 31.304 ng / ml (AUС = 0.730; р = 0.004) and NT-proBNP ≥ 0.034 pg / ml (AUС = 0.815; р = 0.034) were identified as cut-off values for the presence of CMD in patients with non-obstructive CAD.

Conclusion. The obtained data suggest that CMD may play an essential role in HFpEF. The values of CFR were correlated with DD parameters, and decreased CFR was associated with overexpression of biomarkers of cardiac fibrosis and cardiac remodeling. Serum levels of sST2 and NT-proBNP were identified as cut-off values for the presence of CMD in patients with non-obstructive CAD.

Inhibition of Eicosanoid Degradation Mitigates Fibrosis of the Heart

BACKGROUND

Organ fibrosis due to excessive production of extracellular matrix by resident fibroblasts is estimated to contribute to >45% of deaths in the Western world, including those due to cardiovascular diseases such as heart failure. Here, we screened for small molecule inhibitors with a common ability to suppress activation of fibroblasts across organ systems.

METHODS

High-content imaging of cultured cardiac, pulmonary, and renal fibroblasts was used to identify nontoxic compounds that blocked induction of markers of activation in response to the profibrotic stimulus, transforming growth factor-β1. SW033291, which inhibits the eicosanoid-degrading enzyme, 15-hydroxyprostaglandin dehydrogenase, was chosen for follow-up studies with cultured adult rat ventricular fibroblasts and human cardiac fibroblasts (CF), and for evaluation in mouse models of cardiac fibrosis and diastolic dysfunction. Additional mechanistic studies were performed with CFs treated with exogenous eicosanoids.

RESULTS

Nine compounds, including SW033291, shared a common ability to suppress transforming growth factor-β1-mediated activation of cardiac, pulmonary, and renal fibroblasts. SW033291 dose-dependently inhibited transforming growth factor-β1-induced expression of activation markers (eg, α-smooth muscle actin and periostin) in adult rat ventricular fibroblasts and normal human CFs, and reduced contractile capacity of the cells. Remarkably, the 15-hydroxyprostaglandin dehydrogenase inhibitor also reversed constitutive activation of fibroblasts obtained from explanted hearts from patients with heart failure. SW033291 blocked cardiac fibrosis induced by angiotensin II infusion and ameliorated diastolic dysfunction in an alternative model of systemic hypertension driven by combined uninephrectomy and deoxycorticosterone acetate administration. Mechanistically, SW033291-mediated stimulation of extracellular signal-regulated kinase 1/2 mitogen-activated protein kinase signaling was required for the compound to block CF activation. Of the 12 exogenous eicosanoids that were tested, only 12(S)-hydroxyeicosatetraenoic acid, which signals through the G protein-coupled receptor, GPR31, recapitulated the suppressive effects of SW033291 on CF activation.

CONCLUSIONS

Inhibition of degradation of eicosanoids, arachidonic acid-derived fatty acids that signal through G protein-coupled receptors, is a potential therapeutic strategy for suppression of pathological organ fibrosis. In the heart, we propose that 15-hydroxyprostaglandin dehydrogenase inhibition triggers CF-derived autocrine/paracrine signaling by eicosanoids, including 12(S)-hydroxyeicosatetraenoic acid, to stimulate extracellular signal-regulated kinase 1/2 and block conversion of fibroblasts into activated cells that secrete excessive amounts of extracellular matrix and contribute to heart failure pathogenesis.

Tropoelastin Improves Post-Infarct Cardiac Function

BACKGROUND

Myocardial infarction (MI) is among the leading causes of death worldwide. Following MI, necrotic cardiomyocytes are replaced by a stiff collagen-rich scar. Compared to collagen, the extracellular matrix protein elastin has high elasticity and may have more favorable properties within the cardiac scar. We sought to improve post-MI healing by introducing tropoelastin, the soluble subunit of elastin, to alter scar mechanics early after MI.

METHODS AND RESULTS

We developed an ultrasound-guided direct intramyocardial injection method to administer tropoelastin directly into the left ventricular anterior wall of rats subjected to induced MI. Experimental groups included shams and infarcted rats injected with either PBS vehicle control or tropoelastin. Compared to vehicle treated controls, echocardiography assessments showed tropoelastin significantly improved left ventricular ejection fraction (64.7±4.4% versus 46.0±3.1% control) and reduced left ventricular dyssynchrony (11.4±3.5 ms versus 31.1±5.8 ms control) 28 days post-MI. Additionally, tropoelastin reduced post-MI scar size (8.9±1.5% versus 20.9±2.7% control) and increased scar elastin (22±5.8% versus 6.2±1.5% control) as determined by histological assessments. RNA sequencing (RNAseq) analyses of rat infarcts showed that tropoelastin injection increased genes associated with elastic fiber formation 7 days post-MI and reduced genes associated with immune response 11 days post-MI. To show translational relevance, we performed immunohistochemical analyses on human ischemic heart disease cardiac samples and showed an increase in tropoelastin within fibrotic areas. Using RNA-seq we also demonstrated the tropoelastin gene ELN is upregulated in human ischemic heart disease and during human cardiac fibroblast-myofibroblast differentiation. Furthermore, we showed by immunocytochemistry that human cardiac fibroblast synthesize increased elastin in direct response to tropoelastin treatment.

CONCLUSIONS

We demonstrate for the first time that purified human tropoelastin can significantly repair the infarcted heart in a rodent model of MI and that human cardiac fibroblast synthesize elastin. Since human cardiac fibroblasts are primarily responsible for post-MI scar synthesis, our findings suggest exciting future clinical translation options designed to therapeutically manipulate this synthesis.

The dynamic interplay between cardiac mitochondrial health and myocardial structural remodeling in metabolic heart disease, aging, and heart failure

This review provides a holistic perspective on the bi-directional relationship between cardiac mitochondrial dysfunction and myocardial structural remodeling in the context of metabolic heart disease, natural cardiac aging, and heart failure. First, a review of the physiologic and molecular drivers of cardiac mitochondrial dysfunction across a range of increasingly prevalent conditions such as metabolic syndrome and cardiac aging is presented, followed by a general review of the mechanisms of mitochondrial quality control (QC) in the heart. Several important mechanisms by which cardiac mitochondrial dysfunction triggers or contributes to structural remodeling of the heart are discussed: accumulated metabolic byproducts, oxidative damage, impaired mitochondrial QC, and mitochondrial-mediated cell death identified as substantial mechanistic contributors to cardiac structural remodeling such as hypertrophy and myocardial fibrosis. Subsequently, the less studied but nevertheless important reverse relationship is explored: the mechanisms by which cardiac structural remodeling feeds back to further alter mitochondrial bioenergetic function. We then provide a condensed pathogenesis of several increasingly important clinical conditions in which these relationships are central: diabetic cardiomyopathy, age-associated declines in cardiac function, and the progression to heart failure, with or without preserved ejection fraction. Finally, we identify promising therapeutic opportunities targeting mitochondrial function in these conditions.

In vitro bioreactor for mechanical control and characterization of tissue constructs

Cardiac fibrosis is a key contributor to the onset and progression of heart failure and occurs from extracellular matrix accumulation via activated cardiac fibroblasts. Cardiac fibroblasts activate in response to mechanical stress and have been studied in the past by applying forces and deformations to three-dimensional, cell-seeded gels and tissue constructs in vitro. Unfortunately, previous stretching platforms have traditionally not enabled mechanical property assessment to be performed with an efficient throughput, thereby limiting the full potential of in vitro mechanobiology studies. We have developed a novel in vitro platform to study cell-populated tissue constructs under dynamic mechanical stimulation while also performing repeatable, non-destructive stress-strain tests in living constructs. Additionally, this platform can perform these tests across all constructs in a multi-well plate simultaneously, providing exciting potential for direct, functional readouts in future screening applications. In our pilot application, we showed that cyclically stretching cell-populated tissue constructs composed of murine cardiac fibroblasts within a 3D fibrin matrix leads to collagen accumulation and increased tissue stiffness over a three-day time course. Results of this study validate our platform's ability to apply mechanical loads to tissues while performing live mechanical analyses to observe cell-mediated tissue remodeling.

New Opportunities in Heart Failure with Preserved Ejection Fraction: From Bench to Bedside… and Back

Heart failure with preserved ejection fraction (HFpEF) is a growing public health problem in nearly 50% of patients with heart failure. Therefore, research on new strategies for its diagnosis and management has become imperative in recent years. Few drugs have successfully improved clinical outcomes in this population. Therefore, numerous attempts are being made to find new pharmacological interventions that target the main mechanisms responsible for this disease. In recent years, pathological mechanisms such as cardiac fibrosis and inflammation, alterations in calcium handling, NO pathway disturbance, and neurohumoral or mechanic impairment have been evaluated as new pharmacological targets showing promising results in preliminary studies. This review aims to analyze the new strategies and mechanical devices, along with their initial results in pre-clinical and different phases of ongoing clinical trials for HFpEF patients. Understanding new mechanisms to generate interventions will allow us to create methods to prevent the adverse outcomes of this silent pandemic.

Impact of Myocardial Fibrosis on Cardiovascular Structure, Function and Functional Status in Heart Failure with Preserved Ejection Fraction

Myocardial fibrosis, measured using cardiovascular magnetic resonance extracellular volume (ECV), is associated with adverse outcome in heart failure with preserved ejection fraction, but the mechanisms by which myocardial fibrosis exerts this deleterious effect are unclear. We performed mediation analyses of data from the Pirfenidone in Patients with Heart Failure and Preserved Left Ventricular Ejection Fraction (PIROUETTE) trial to determine whether myocardial fibrotic regression causes changes in cardiovascular function and functional status following antifibrotic therapy. Regression of myocardial fibrosis correlated with improvements in 6-min walk test and KCCQ clinical summary score. The only outcome variable that demonstrated a treatment effect was an increase in left ventricular ejection fraction (LVEF). The estimated average causal mediation effects of myocardial ECV, absolute myocardial extracellular matrix volume and absolute myocardial cellular volume on LVEF were 6.1%, 21.5% and 13.7%, respectively, none of which was significant and therefore not mediated by myocardial fibrosis. (PIROUETTE; NCT02932566).

Inflamed adipose tissue: A culprit underlying obesity and heart failure with preserved ejection fraction

The incidence of heart failure with preserved ejection fraction is increasing in patients with obesity, diabetes, hypertension, and in the aging population. However, there is a lack of adequate clinical treatment. Patients with obesity-related heart failure with preserved ejection fraction display unique pathophysiological and phenotypic characteristics, suggesting that obesity could be one of its specific phenotypes. There has been an increasing recognition that overnutrition in obesity causes adipose tissue expansion and local and systemic inflammation, which consequently exacerbates cardiac remodeling and leads to the development of obese heart failure with preserved ejection fraction. Furthermore, overnutrition leads to cellular metabolic reprogramming and activates inflammatory signaling cascades in various cardiac cells, thereby promoting maladaptive cardiac remodeling. Growing evidence indicates that the innate immune response pathway from the NLRP3 inflammasome, to interleukin-1 to interleukin-6, is involved in the generation of obesity-related systemic inflammation and heart failure with preserved ejection fraction. This review established the existence of obese heart failure with preserved ejection fraction based on structural and functional changes, elaborated the inflammation mechanisms of obese heart failure with preserved ejection fraction, proposed that NLRP3 inflammasome activation may play an important role in adiposity-induced inflammation, and summarized the potential therapeutic approaches.

Scalable Generation of Nanovesicles from Human-Induced Pluripotent Stem Cells for Cardiac Repair

Extracellular vesicles (EVs) from stem cells have shown significant therapeutic potential to repair injured cardiac tissues and regulate pathological fibrosis. However, scalable generation of stem cells and derived EVs for clinical utility remains a huge technical challenge. Here, we report a rapid size-based extrusion strategy to generate EV-like membranous nanovesicles (NVs) from easily sourced human iPSCs in large quantities (yield 900× natural EVs). NVs isolated using density-gradient separation (buoyant density 1.13 g/mL) are spherical in shape and morphologically intact and readily internalised by human cardiomyocytes, primary cardiac fibroblasts, and endothelial cells. NVs captured the dynamic proteome of parental cells and include pluripotency markers (LIN28A, OCT4) and regulators of cardiac repair processes, including tissue repair (GJA1, HSP20/27/70, HMGB1), wound healing (FLNA, MYH9, ACTC1, ILK), stress response/translation initiation (eIF2S1/S2/S3/B4), hypoxia response (HMOX2, HSP90, GNB1), and extracellular matrix organization (ITGA6, MFGE8, ITGB1). Functionally, NVs significantly promoted tubule formation of endothelial cells (angiogenesis) (p < 0.05) and survival of cardiomyocytes exposed to low oxygen conditions (hypoxia) (p < 0.0001), as well as attenuated TGF-β mediated activation of cardiac fibroblasts (p < 0.0001). Quantitative proteome profiling of target cell proteome following NV treatments revealed upregulation of angiogenic proteins (MFGE8, MYH10, VDAC2) in endothelial cells and pro-survival proteins (CNN2, THBS1, IGF2R) in cardiomyocytes. In contrast, NVs attenuated TGF-β-driven extracellular matrix remodelling capacity in cardiac fibroblasts (ACTN1, COL1A1/2/4A2/12A1, ITGA1/11, THBS1). This study presents a scalable approach to generating functional NVs for cardiac repair.

Cardiac fibroblasts and mechanosensation in heart development, health and disease

The term 'mechanosensation' describes the capacity of cells to translate mechanical stimuli into the coordinated regulation of intracellular signals, cellular function, gene expression and epigenetic programming. This capacity is related not only to the sensitivity of the cells to tissue motion, but also to the decryption of tissue geometric arrangement and mechanical properties. The cardiac stroma, composed of fibroblasts, has been historically considered a mechanically passive component of the heart. However, the latest research suggests that the mechanical functions of these cells are an active and necessary component of the developmental biology programme of the heart that is involved in myocardial growth and homeostasis, and a crucial determinant of cardiac repair and disease. In this Review, we discuss the general concept of cell mechanosensation and force generation as potent regulators in heart development and pathology, and describe the integration of mechanical and biohumoral pathways predisposing the heart to fibrosis and failure. Next, we address the use of 3D culture systems to integrate tissue mechanics to mimic cardiac remodelling. Finally, we highlight the potential of mechanotherapeutic strategies, including pharmacological treatment and device-mediated left ventricular unloading, to reverse remodelling in the failing heart.

BmooMPα-I, a Metalloproteinase Isolated from Bothrops moojeni Venom, Reduces Blood Pressure, Reverses Left Ventricular Remodeling and Improves Cardiac Electrical Conduction in Rats with Renovascular Hypertension

BmooMPα-I has kininogenase activity, cleaving kininogen releasing bradykinin and can hydrolyze angiotensin I at post-proline and aspartic acid positions, generating an inactive peptide. We evaluated the antihypertensive activity of BmooMPα-I in a model of two-kidney, one-clip (2K1C). Wistar rats were divided into groups: Sham, who underwent sham surgery, and 2K1C, who suffered stenosis of the right renal artery. In the second week of hypertension, we started treatment (Vehicle, BmooMPα-I and Losartan) for two weeks. We performed an electrocardiogram and blood and heart collection in the fourth week of hypertension. The 2K1C BmooMPα-I showed a reduction in blood pressure (systolic pressure: 131 ± 2 mmHg; diastolic pressure: 84 ± 2 mmHg versus 174 ± 3 mmHg; 97 ± 4 mmHg, 2K1C Vehicle, p < 0.05), improvement in electrocardiographic parameters (Heart Rate: 297 ± 4 bpm; QRS: 42 ± 0.1 ms; QT: 92 ± 1 ms versus 332 ± 6 bpm; 48 ± 0.2 ms; 122 ± 1 ms, 2K1C Vehicle, p < 0.05), without changing the hematological profile (platelets: 758 ± 67; leukocytes: 3980 ± 326 versus 758 ± 75; 4400 ± 800, 2K1C Vehicle, p > 0.05), with reversal of hypertrophy (left ventricular area: 12.1 ± 0.3; left ventricle wall thickness: 2.5 ± 0.2; septum wall thickness: 2.3 ± 0.06 versus 10.5 ± 0.3; 2.7 ± 0.2; 2.5 ± 0.04, 2K1C Vehicle, p < 0.05) and fibrosis (3.9 ± 0.2 versus 7.4 ± 0.7, 2K1C Vehicle, p < 0.05). We concluded that BmooMPα-I improved blood pressure levels and cardiac remodeling, having a cardioprotective effect.

Arrhythmic Sudden Cardiac Death in Heart Failure With Preserved Ejection Fraction: Mechanisms, Genetics, and Future Directions

Heart failure with preserved ejection fraction (HFpEF) is an increasingly recognized disorder. Many clinical trials have failed to demonstrate benefit in patients with HFpEF but have recognized alarming rates of sudden cardiac death (SCD). Genetic testing has become standard in the workup of patients with otherwise unexplained cardiac arrest, but the genetic architecture of HFpEF, and the overlap of a genetic predisposition to HFpEF and arrhythmias, is poorly understood. An understanding of the genetics of HFpEF and related SCD has the potential to redefine and generate novel diagnostic, prognostic, and therapeutic tools. In this review, we examine recent pathophysiological and clinical advancements in our understanding of HFpEF, which reinforce the heterogeneity of the condition. We also discuss data describing SCD events in patients with HFpEF and review the current literature on genetic underpinnings of HFpEF. Mechanisms of arrhythmogenesis which may lead to SCD in this population are also explored. Lastly, we outline several areas of promise for experimentation and clinical trials that have the potential to further advance our understanding of and contribute to improved clinical care of this patient population.

Material property alterations for phenotypes of heart failure with preserved ejection fraction: A numerical study of subject-specific porcine models

A substantial proportion of heart failure patients have a preserved left ventricular (LV) ejection fraction (HFpEF). This condition carries a high burden of morbidity and mortality and has limited therapeutic options. left ventricular pressure overload leads to an increase in myocardial collagen content, causing left ventricular stiffening that contributes to the development of heart failure patients have a preserved left ventricular ejection fraction. Although several heart failure patients have a preserved left ventricular ejection fraction models have been developed in recent years to aid the investigation of mechanical alterations, none has investigated different phenotypes of the disease and evaluated the alterations in material properties. In this study, two similar healthy swine were subjected to progressive and prolonged pressure overload to induce diastolic heart failure characteristics, providing a preclinical model of heart failure patients have a preserved left ventricular ejection fraction. Cardiac magnetic resonance imaging (cMRI) scans and intracardiac pressures were recorded before and after induction. In both healthy and disease states, a corresponding finite element (FE) cardiac model was developed via mesh morphing of the Living Heart Porcine model. The material properties were derived by calibrating to its passive and active behavior. The change in the passive behavior was predominantly isotropic when comparing the geometries before and after induction. Myocardial thickening allowed for a steady transition in the passive properties while maintaining tissue incompressibility. This study highlights the importance of hypertrophy as an initial compensatory response and might also pave the way for assessing disease severity.

Acetylation and phosphorylation changes to cardiac proteins in experimental HFpEF due to metabolic risk reveal targets for treatment

AIMS

Despite the high prevalence of heart failure with preserved ejection fraction (HFpEF), the pathomechanisms remain elusive and specific therapy is lacking. Disease-causing factors include metabolic risk, notably obesity. However, proteomic changes in HFpEF are poorly understood, hampering therapeutic strategies. We sought to elucidate how metabolic syndrome affects cardiac protein expression, phosphorylation and acetylation in the Zucker diabetic fatty/Spontaneously hypertensive heart failure F1 (ZSF1) rat HFpEF model, and to evaluate changes regarding their potential for treatment.

MAIN METHODS

ZSF1 obese and lean rats were fed a Purina diet up to the onset of HFpEF in the obese animals. We quantified the proteome, phosphoproteome and acetylome of ZSF1 obese versus lean heart tissues by mass spectrometry and singled out targets for site-specific evaluation.

KEY FINDINGS

The acetylome of ZSF1 obese versus lean hearts was more severely altered (21 % of proteins changed) than the phosphoproteome (9 %) or proteome (3 %). Proteomic alterations, confirmed by immunoblotting, indicated low-grade systemic inflammation and endothelial remodeling in obese hearts, but low nitric oxide-dependent oxidative/nitrosative stress. Altered acetylation in ZSF1 obese hearts mainly affected pathways important for metabolism, energy production and mechanical function, including hypo-acetylation of mechanical proteins but hyper-acetylation of proteins regulating fatty acid metabolism. Hypo-acetylation and hypo-phosphorylation of elastic titin in ZSF1 obese hearts could explain myocardial stiffening.

SIGNIFICANCE

Cardiometabolic syndrome alters posttranslational modifications, notably acetylation, in experimental HFpEF. Pathway changes implicate a HFpEF signature of low-grade inflammation, endothelial dysfunction, metabolic and mechanical impairment, and suggest titin stiffness and mitochondrial metabolism as promising therapeutic targets.

NADPH Oxidases in Diastolic Dysfunction and Heart Failure with Preserved Ejection Fraction

Nicotinamide adenine dinucleotide phosphate (NADPH) oxidases regulate production of reactive oxygen species (ROS) that cause oxidative damage to cellular components but also regulate redox signaling in many cell types with essential functions in the cardiovascular system. Research over the past couple of decades has uncovered mechanisms by which NADPH oxidase (NOX) enzymes regulate oxidative stress and compartmentalize intracellular signaling in endothelial cells, smooth muscle cells, macrophages, cardiomyocytes, fibroblasts, and other cell types. NOX2 and NOX4, for example, regulate distinct redox signaling mechanisms in cardiac myocytes pertinent to the onset and progression of cardiac hypertrophy and heart failure. Heart failure with preserved ejection fraction (HFpEF), which accounts for at least half of all heart failure cases and has few effective treatments to date, is classically associated with ventricular diastolic dysfunction, i.e., defects in ventricular relaxation and/or filling. However, HFpEF afflicts multiple organ systems and is associated with systemic pathologies including inflammation, oxidative stress, arterial stiffening, cardiac fibrosis, and renal, adipose tissue, and skeletal muscle dysfunction. Basic science studies and clinical data suggest a role for systemic and myocardial oxidative stress in HFpEF, and evidence from animal models demonstrates the critical functions of NOX enzymes in diastolic function and several HFpEF-associated comorbidities. Here, we discuss the roles of NOX enzymes in cardiovascular cells that are pertinent to the development and progression of diastolic dysfunction and HFpEF and outline potential clinical implications.

Inorganic phosphate accelerates cardiac myofilament relaxation in response to lengthening

Myocardial relaxation in late systole is enhanced by increasing velocities of lengthening. Given that inorganic phosphate (Pi) can rebind to the force-producing myosin enzyme prior to MgADP release and hasten crossbridge detachment, we hypothesized that myocardial relaxation in late systole would be further enhanced by lengthening in the presence of Pi. Wistar rat left ventricular papillary muscles were attached to platinum clips, placed between a force transducer and a length motor at room temperature, and bathed in Krebs solution with 1.8 mM Ca²⁺ and varying Pi of 0, 1, 2, and 5 mM. Tension transients were elicited by electrical stimulation at 1 Hz. Peak tension was significantly enhanced by Pi: 0.593 ± 0.088 mN mm⁻² at 0 mM Pi and 0.817 ± 0.159 mN mm⁻² at 5 mM Pi (mean ± SEM, p < 0.01 by ANCOVA). All temporal characteristics of the force transient were significantly shortened with increasing Pi, e.g., time-to-50% recovery was shortened from 305 ± 14 ms at 0 mM Pi to 256 ± 10 ms at 5 mM Pi (p < 0.01). A 1% lengthening stretch with varying duration of 10–200 ms was applied at time-to-50% recovery during the descending phase of the force transient. Matching lengthening stretches were also applied when the muscle was not stimulated, thus providing a control for the passive viscoelastic response. After subtracting the passive from the active force response, the resulting myofilament response demonstrated features of faster myofilament relaxation in response to the stretch. For example, time-to-70% relaxation with 100 ms lengthening duration was shortened by 8.8 ± 6.8 ms at 0 Pi, 19.6 ± 4.8* ms at 1 mM Pi, 31.0 ± 5.6* ms at 2 Pi, and 25.6 ± 5.3* ms at 5 mM Pi (*p < 0.01 compared to no change). Using skinned myocardium, half maximally calcium-activated myofilaments underwent a 1% quick stretch, and the tension response was subjected to analysis for sensitivity of myosin detachment rate to stretch, g₁, at various Pi concentrations. The parameter g₁ was enhanced from 15.39 ± 0.35 at 0 Pi to 22.74 ± 1.31 s⁻¹/nm at 8 Pi (p < 0.01). Our findings suggest that increasing Pi at the myofilaments enhances lengthening-induced relaxation by elevating the sensitivity of myosin crossbridge detachment due to lengthening and thus speed the transition from late-systole to early-diastole.

Treatment of heart failure with preserved ejection fraction with SGLT2 inhibitors: new therapy standard?

Heart failure with preserved ejection fraction (HFpEF) is a common and difficult-to-treat heart disease. Approximately half of patients with heart failure suffer from this form, and mortality is between 5% and 7% per year. Previous therapeutic trials for the treatment of HFpEF have been disappointing. However, recent data on therapy with sodium-glucose cotransporter‑2 (SGLT2) inhibitors in HFpEF are encouraging. In addition to numerous experimental studies showing improvement in diastolic dysfunction parameters, the EMPEROR-Preserved study demonstrated for the first time clinically that therapy with the SGLT2 inhibitor empagliflozin significantly reduced hospitalization for heart failure. By contrast, cardiovascular mortality was not affected. Differences for patients with and without type 2 diabetes mellitus were not observed. Thus, for the first time, there is an evidence-based treatment option to reduce hospitalization and improve quality of life in these patients. Further studies will show to what extent these beneficial effects will also lead to an improvement in the prognosis of these patients.

Extracellular stiffness induces contractile dysfunction in adult cardiomyocytes via cell-autonomous and microtubule-dependent mechanisms

The mechanical environment of the myocardium has a potent effect on cardiomyocyte form and function, yet an understanding of the cardiomyocyte responses to extracellular stiffening remains incomplete. We therefore employed a cell culture substrate with tunable stiffness to define the cardiomyocyte responses to clinically relevant stiffness increments in the absence of cell-cell interactions. When cultured on substrates magnetically actuated to mimic the stiffness of diseased myocardium, isolated rat adult cardiomyocytes exhibited a time-dependent reduction of sarcomere shortening, characterized by slowed contraction and relaxation velocity, and alterations of the calcium transient. Cardiomyocytes cultured on stiff substrates developed increases in viscoelasticity and microtubule detyrosination in association with early increases in the α-tubulin detyrosinating enzyme vasohibin-2 (Vash2). We found that knockdown of Vash2 was sufficient to preserve contractile performance as well as calcium transient properties in the presence of extracellular substrate stiffening. Orthogonal prevention of detyrosination by overexpression of tubulin tyrosine ligase (TTL) was also able to preserve contractility and calcium homeostasis. These data demonstrate that a pathologic increment of extracellular stiffness induces early, cell-autonomous remodeling of adult cardiomyocytes that is dependent on detyrosination of α-tubulin.

Proteomic and phosphoproteomic profiling in heart failure with preserved ejection fraction (HFpEF)

Although the prevalence of heart failure with preserved ejection fraction (HFpEF) is increasing, evidence-based therapies for HFpEF remain limited, likely due to an incomplete understanding of this disease. This study sought to identify the cardiac-specific features of protein and phosphoprotein changes in a murine model of HFpEF using mass spectrometry. HFpEF mice demonstrated moderate hypertension, left ventricle (LV) hypertrophy, lung congestion and diastolic dysfunction. Proteomics analysis of the LV tissue showed that 897 proteins were differentially expressed between HFpEF and Sham mice. We observed abundant changes in sarcomeric proteins, mitochondrial-related proteins, and NAD-dependent protein deacetylase sirtuin-3 (SIRT3). Upregulated pathways by GSEA analysis were related to immune modulation and muscle contraction, while downregulated pathways were predominantly related to mitochondrial metabolism. Western blot analysis validated SIRT3 downregulated cardiac expression in HFpEF vs. Sham (0.8 ± 0.0 vs. 1.0 ± 0.0; P < 0.001). Phosphoproteomics analysis showed that 72 phosphosites were differentially regulated between HFpEF and Sham LV. Aberrant phosphorylation patterns mostly occurred in sarcomere proteins and nuclear-localized proteins associated with contractile dysfunction and cardiac hypertrophy. Seven aberrant phosphosites were observed at the z-disk binding region of titin. Additional agarose gel analysis showed that while total titin cardiac expression remained unaltered, its stiffer N2B isoform was significantly increased in HFpEF vs. Sham (0.144 ± 0.01 vs. 0.127 ± 0.01; P < 0.05). In summary, this study demonstrates marked changes in proteins related to mitochondrial metabolism and the cardiac contractile apparatus in HFpEF. We propose that SIRT3 may play a role in perpetuating these changes and may be a target for drug development in HFpEF.

Characteristics of Heart Failure With Preserved Ejection Fraction Across the Range of Left Ventricular Ejection Fraction

BACKGROUND

Recent trial data suggest that stratification of patients with heart failure with preserved ejection fraction (HFpEF) according to left ventricular ejection fraction (LVEF) provides a means for dissecting different treatment responses. However, the differential pathophysiologic considerations have rarely been described.

METHODS

This prospective, single-center study analyzed consecutive symptomatic patients with HFpEF diagnosed according to the 2016 European Society of Cardiology heart failure guidelines. Patients were grouped into LVEF 50% to 60% and LVEF >60% cohorts. All patients underwent cardiac magnetic resonance imaging. Transfemoral cardiac catheterization was performed to derive load-dependent and load-independent left ventricular (LV) properties on pressure-volume loop analyses.

RESULTS

Fifty-six patients with HFpEF were enrolled and divided into LVEF 50% to 60% (n=21) and LVEF >60% (n=35) cohorts. On cardiac magnetic resonance imaging, the LVEF >60% cohort showed lower LV end-diastolic volumes (P=0.019) and end-systolic volumes (P=0.001) than the LVEF 50% to 60% cohort; stroke volume (P=0.821) did not differ between the cohorts. Extracellular volume fraction was higher in the LVEF 50% to 60% cohort than in the LVEF >60% cohort (0.332 versus 0.309; P=0.018). Pressure-volume loop analyses demonstrated higher baseline LV contractility (end-systolic elastance, 1.85 vs 1.33 mm Hg/mL; P<0.001) and passive diastolic stiffness (β constant, 0.032 versus 0.018; P=0.004) in the LVEF >60% cohort. Ventriculo-arterial coupling (end-systolic elastance/arterial elastance) at rest was in the range of optimized stroke work in the LVEF >60% cohort but was impaired in the LVEF 50% to 60% cohort (1.01 versus 0.80; P=0.005). During handgrip exercise, patients with LVEF >60% had higher increases in end-systolic elastance (1.85 versus 0.82 mm Hg/mL; P=0.023), attenuated increases in indexed end-systolic volume (-1 versus 7 mL/m²; P<0.004), and more exaggerated increases in LV filling pressures (8 vs 5 mm Hg; P=0.023). LV stroke volume decreased in the LVEF >60% cohort (P=0.007) under exertion.

CONCLUSIONS

Patients with HFpEF in whom LVEF ranged from 50% to 60% demonstrated reduced contractility, impaired ventriculo-arterial coupling, and higher extracellular volume fraction. In contrast, patients with HFpEF and a LVEF >60% demonstrated a hypercontractile state with excessive LV afterload and diminished preload reserve. A LVEF-based stratification of patients with HFpEF identified distinct morphologic and pathophysiologic subphenotypes.

A Data Mining-Based Study on Medication Rules of Chinese Herbs to Treat Heart Failure with Preserved Ejection Fraction

OBJECTIVE

To summarize the medication rules of Chinese herbs to treat heart failure with preserved ejection fraction (HFPEF) based on data mining and to provide references for clinical utilization.

METHODS

The China National Knowledge Infrastructure (CNKI), Wanfang database (Wanfang), VIP database (VIP), Chinese Biomedical Literature (CBM), PubMed, Embase, and Cochrane Library databases were searched from inception to October 2021 to identify relevant literature on treating HFPEF with Chinese herbs. Microsoft Excel 2019 was used to set up a database, and then, association rule analysis and hierarchical cluster analysis were performed by using apriori algorithm and hclust function respectively in R-Studio (Version 4.0.3).

RESULTS

A total of 182 qualified papers were included, involving a total of 92 prescriptions, 130 Chinese herbs, and 872 individual herbs prescribed, with an average of 9.5 herbs per prescription. The six most frequently prescribed herbs were Astragali Radix (Huangqi), Salviae Miltiorrhizae Radix Et Rhizoma (Danshen), Poria (Fuling), Glycyrrhizae Radix Et Rhizoma (Gancao), Cinnamomi Ramulus (Guizhi), and Ginseng Radix Et Rhizoma (Renshen). There were 35 herbs used more than 5 times, involving 11 efficacy categories. The top three categories were deficiency-tonifying herbs, blood-activating and stasis-removing herbs, and dampness-draining diuretic herbs. The most commonly used herbs were mainly warm and sweet. The primary meridian tropisms were Lung Meridian, Heart Meridian and Spleen Meridian. Association rule analysis yielded 26 association rules, such as Astragali Radix (Huangqi) & Salviae Miltiorrhizae Radix Et Rhizoma (Danshen), Poria (Fuling), Cinnamomi Ramulus (Guizhi) & Atractylodis Macrocephalae Rhizoma (Baizhu). Hierarchical cluster analysis yielded four herb classes, and their functions were mainly qi-replenishing and yang-warming, blood-activating and diuresis-inducing.

CONCLUSIONS

HFPEF is the syndrome of root vacuity and tip repletion, and its core pathogenesis is "deficiency", "stasis", and "water", with "deficiency" being the most principal, which is closely related to Xin (heart), Fei (Lung), and Pi (Spleen). The treatment of this disease occurs by improving qi, warming yang, activating blood and inducing diuresis. Astragali Radix (Huangqi) with Salviae Miltiorrhizae Radix Et Rhizoma (Danshen) is the basic combination of herbs applied.

Current Understanding of Molecular Pathophysiology of Heart Failure With Preserved Ejection Fraction

Heart Failure (HF) is the most common cause of hospitalization in the Western societies. HF is a heterogeneous and complex syndrome that may result from any dysfunction of systolic or diastolic capacity. Abnormal diastolic left ventricular function with impaired relaxation and increased diastolic stiffness is characteristic of heart failure with preserved ejection fraction (HFpEF). HFpEF accounts for more than 50% of all cases of HF. The prevalence increases with age: from around 1% for those aged <55 years to >10% in those aged 70 years or over. Nearly 50% of HF patients have HFrEF and the other 50% have HFpEF/HFmrEF, mainly based on studies in hospitalized patients. The ESC Long-Term Registry, in the outpatient setting, reports that 60% have HFrEF, 24% have HFmrEF, and 16% have HFpEF. To some extent, more than 50% of HF patients are female. HFpEF is closely associated with co-morbidities, age, and gender. Epidemiological evidence suggests that HFpEF is highly represented in older obese women and proposed as 'obese female HFpEF phenotype'. While HFrEF phenotype is more a male phenotype. In addition, metabolic abnormalities and hemodynamic perturbations in obese HFpEF patients appear to have a greater impact in women then in men (Sorimachi et al., European J of Heart Fail, 2022, 22). To date, numerous clinical trials of HFpEF treatments have produced disappointing results. This outcome suggests that a "one size fits all" approach to HFpEF may be inappropriate and supports the use of tailored, personalized therapeutic strategies with specific treatments for distinct HFpEF phenotypes. The most important mediators of diastolic stiffness are the cardiomyocytes, endothelial cells, and extracellular matrix (ECM). The complex physiological signal transduction networks that respond to the dual challenges of inflammatory and oxidative stress are major factors that promote the development of HFpEF pathologies. These signalling networks contribute to the development of the diseases. Inhibition and/or attenuation of these signalling networks also delays the onset of disease. In this review, we discuss the molecular mechanisms associated with the physiological responses to inflammation and oxidative stress and emphasize the nature of the contribution of most important cells to the development of HFpEF via increased inflammation and oxidative stress.

Support Pressure Acting on the Epicardial Surface of a Rat Left Ventricle—A Computational Study

The present computational study investigates the effects of an epicardial support pressure mimicking a heart support system without direct blood contact. We chose restrictive cardiomyopathy as a model for a diseased heart. By changing one parameter representing the amount of fibrosis, this model allows us to investigate the impairment in a diseased left ventricle, both during diastole and systole. The aim of the study is to determine the temporal course and value of the support pressure that leads to a normalization of the cardiac parameters in diseased hearts. These are quantified via the end-diastolic pressure, end-diastolic volume, end-systolic volume, and ejection fraction. First, the amount of fibrosis is increased to model diseased hearts at different stages. Second, we determine the difference in the left ventricular pressure between a healthy and diseased heart during a cardiac cycle and apply for the epicardial support as the respective pressure difference. Third, an epicardial support pressure is applied in form of a piecewise constant step function. The support is provided only during diastole, only during systole, or during both phases. Finally, the support pressure is adjusted to reach the corresponding parameters in a healthy rat. Parameter normalization is not possible to achieve with solely diastolic or solely systolic support; for the modeled case with 50% fibrosis, the ejection fraction can be increased by 5% with purely diastolic support and 14% with purely systolic support. However, the ejection fraction reaches the value of the modeled healthy left ventricle (65.6%) using a combination of diastolic and systolic support. The end-diastolic pressure of 13.5 mmHg cannot be decreased with purely systolic support. However, the end-diastolic pressure reaches the value of the modeled healthy left ventricle (7.5 mmHg) with diastolic support as well as with the combination of the diastolic and systolic support. The resulting negative diastolic support pressure is −4.5 mmHg, and the positive systolic support pressure is 90 mmHg. We, thereby, conclude that ventricular support during both diastole and systole is beneficial for normalizing the left ventricular ejection fraction and the end-diastolic pressure, and thus it is a potentially interesting therapy for cardiac insufficiency.

Association of Pulmonary Function With Late-Life Cardiac Function and Heart Failure Risk: The ARIC Study

Background Pulmonary and cardiac functions decline with age, but the associations of pulmonary dysfunction with cardiac function and heart failure (HF) risk in late life is not known. We aimed to determine the associations of percent predicted forced vital capacity (ppFVC) and the ratio of forced expired volume in 1 second (FEV₁) to forced vital capacity (FVC; FEV₁/FVC) with cardiac function and incident HF with preserved or reduced ejection fraction in late life. Methods and Results Among 3854 HF-free participants in the ARIC (Atherosclerosis Risk in Communities) cohort study who underwent echocardiography and spirometry at the fifth study visit (2011-2013), associations of FEV₁/FVC and ppFVC with echocardiographic measures, cardiac biomarkers, and risk of HF, HF with preserved ejection fraction, and HF with reduced ejection fraction were assessed. Multivariable linear and Cox regression models adjusted for demographics, body mass index, coronary disease, atrial fibrillation, hypertension, and diabetes. Mean age was 75±5 years, 40% were men, 19% were Black, and 61% were ever smokers. Mean FEV₁/FVC was 72±8%, and ppFVC was 98±17%. In adjusted analyses, lower FEV₁/FVC and ppFVC were associated with higher NT-proBNP (N-terminal pro-B-type natriuretic peptide; both P<0.001) and pulmonary artery pressure (P<0.004). Lower ppFVC was also associated with higher left ventricular mass, left ventricular filling pressure, and high-sensitivity C-reactive protein (all P<0.01). Lower FEV₁/FVC was associated with a trend toward higher risk of incident HF with preserved ejection fraction (hazard ratio [HR] per 10-point decrease, 1.31; 95% CI, 0.98-1.74; P=0.07) and HF with reduced ejection fraction (HR per 10-point decrease, 1.24; 95% CI, 0.91-1.70; P=0.18), but these associations did not reach statistical significance. Lower ppFVC was associated with incident HF with preserved ejection fraction (HR per 10-unit decrease, 1.21; 95% CI, 1.04-1.41; P=0.013) but not with HF with reduced ejection fraction (HR per 10-unit decrease, 0.90; 95% CI, 0.76-1.07; P=0.24). Conclusions Subclinical reductions in FEV₁/FVC and ppFVC differentially associate with cardiac function and HF risk in late life.

Epoxyeicosatrienoic acid: A potential therapeutic target of heart failure with preserved ejection fraction

Heart failure with preserved ejection fraction (HFpEF) reduces the quality of life, costs substantial medical resources, and has a high mortality. However, we lack an effective therapy for HFpEF due to our limited knowledge of its mechanism. Therefore, it is crucial to explore novel therapeutics, such as those with endogenous protective roles, and seek new targeted therapies. Epoxyeicosatrienoic acids (EETs) are endogenous bioactive metabolites of arachidonic acids produced by cytochrome P450 (CYP) epoxygenases. EETs can function as endogenous cardioprotective factors with potent inhibitory roles in inflammation, endothelial dysfunction, cardiac remodeling, and fibrosis, which are the fundamental mechanisms of HFpEF. This suggests that EETs have the potential function to protect against HFpEF. Therefore, we present an overview of the ever-expanding world of EETs and how they might help alleviate the pathophysiology underlying HFpEF to provide new insights for research in this field.

Sex-specific Phenotypes in the Aging Mouse Heart and Consequences for Chronic Fibrosis

The incidence of diastolic dysfunction increases with age in both humans and mice. This is characterized by increased passive stiffness and slower relaxation of the left ventricle. The stiffness arises at least partially from progressively increased interstitial collagen deposition due to highly secretory fibroblasts. In the past, we demonstrated that AMPK activation via the drug Aicar in middle-aged mice reduced adverse remodeling after myocardial infarction. Therefore as an attempt to normalize the fibroblast phenotype, we used 21 month-old male and female mice and treated them with Aicar (0.166 mg/g of body weight) where each mouse was followed in a functional study over a 3-month period. We found sex-related differences in extracellular matrix (ECM) composition as well as heart function indices at baseline, which were further accentuated by Aicar treatment. Aicar attenuated the age-related increase in left atrial volume (LAV, an indicator of diastolic dysfunction) in female but not in male hearts which was associated with reduced collagen deposition in the old female heart, and reduced the transcription factor Gli1 expression in cardiac fibroblasts. We further demonstrated that collagen synthesis was dependent on Gli1, which is a target of AMPK-mediated degradation. By contrast, Aicar had a minor impact on cardiac fibroblasts in the old male heart due to blunted AMPK phosphorylation. Hence it did not significantly improve old male heart function indices. In conclusion, we demonstrated that male and female hearts are phenotypically different, and sex-specific differences need to be considered when analyzing the response to pharmacological intervention.