Mitochondrial adaptations to physiological vs. pathological cardiac hypertrophy

RNA-mediated epigenetic regulation in exercised heart: Mechanisms and opportunities for intervention

Physical exercise has been widely acknowledged as a beneficial lifestyle alteration and a potent non-pharmacological treatment for heart disease. Extensive investigations have revealed the beneficial effects of exercise on the heart and the underlying mechanisms involved. Exercise is considered one of the key factors that can lead to epigenetic alterations. The increasing number of identified molecules in the exercised heart has led to many studies in recent years that have explored the cellular function of ncRNAs and RNA modifications in the heart. Investigating the regulatory role of RNA-mediated epigenetic regulation in exercised hearts will contribute to the development of therapeutic strategies for the management of heart diseases. This review aims to summarize the positive impact of exercise on cardiac health. We will first provide an overview of the mechanisms through which exercise offers protection to the heart. Subsequently, we will delve into the current understanding of ncRNAs, specifically miRNAs, lncRNAs, and circRNAs, as well as RNA modification, focusing on RNA m6A and RNA A-to-I editing, and how they contribute to exercise-induced benefits for the heart. Lastly, we will explore the emerging therapeutic strategies that utilize exercise-mediated RNA epigenetic regulation in the treatment of heart diseases, while also addressing the challenges faced in this field.

Metabolic mechanisms in physiological and pathological cardiac hypertrophy: new paradigms and challenges

Cardiac metabolism is vital for heart function. Given that cardiac contraction requires a continuous supply of ATP in large quantities, the role of fuel metabolism in the heart has been mostly considered from the perspective of energy production. However, the consequence of metabolic remodelling in the failing heart is not limited to a compromised energy supply. The rewired metabolic network generates metabolites that can directly regulate signalling cascades, protein function, gene transcription and epigenetic modifications, thereby affecting the overall stress response of the heart. In addition, metabolic changes in both cardiomyocytes and non-cardiomyocytes contribute to the development of cardiac pathologies. In this Review, we first summarize how energy metabolism is altered in cardiac hypertrophy and heart failure of different aetiologies, followed by a discussion of emerging concepts in cardiac metabolic remodelling, that is, the non-energy-generating function of metabolism. We highlight challenges and open questions in these areas and finish with a brief perspective on how mechanistic research can be translated into therapies for heart failure.

AMPK activator-treated human cardiac spheres enhance maturation and enable pathological modeling

BACKGROUND

Cardiac pathological outcome of metabolic remodeling is difficult to model using cardiomyocytes derived from human-induced pluripotent stem cells (hiPSC-CMs) due to low metabolic maturation.

METHODS

hiPSC-CM spheres were treated with AMP-activated protein kinase (AMPK) activators and examined for hiPSC-CM maturation features, molecular changes and the response to pathological stimuli.

RESULTS

Treatment of hiPSC-CMs with AMPK activators increased ATP content, mitochondrial membrane potential and content, mitochondrial DNA, mitochondrial function and fatty acid uptake, indicating increased metabolic maturation. Conversely, the knockdown of AMPK inhibited mitochondrial maturation of hiPSC-CMs. In addition, AMPK activator-treated hiPSC-CMs had improved structural development and functional features-including enhanced Ca2+ transient kinetics and increased contraction. Transcriptomic, proteomic and metabolomic profiling identified differential levels of expression of genes, proteins and metabolites associated with a molecular signature of mature cardiomyocytes in AMPK activator-treated hiPSC-CMs. In response to pathological stimuli, AMPK activator-treated hiPSC-CMs had increased glycolysis, and other pathological outcomes compared to untreated cells.

CONCLUSION

AMPK activator-treated cardiac spheres could serve as a valuable model to gain novel insights into cardiac diseases.

Status of Mitochondrial Oxidative Phosphorylation during the Development of Heart Failure

Mitochondria are specialized organelles, which serve as the "Power House" to generate energy for maintaining heart function. These organelles contain various enzymes for the oxidation of different substrates as well as the electron transport chain in the form of Complexes I to V for producing ATP through the process of oxidative phosphorylation (OXPHOS). Several studies have shown depressed OXPHOS activity due to defects in one or more components of the substrate oxidation and electron transport systems which leads to the depletion of myocardial high-energy phosphates (both creatine phosphate and ATP). Such changes in the mitochondria appear to be due to the development of oxidative stress, inflammation, and Ca2+-handling abnormalities in the failing heart. Although some investigations have failed to detect any changes in the OXPHOS activity in the failing heart, such results appear to be due to a loss of Ca2+ during the mitochondrial isolation procedure. There is ample evidence to suggest that mitochondrial Ca2+-overload occurs, which is associated with impaired mitochondrial OXPHOS activity in the failing heart. The depression in mitochondrial OXPHOS activity may also be due to the increased level of reactive oxygen species, which are formed as a consequence of defects in the electron transport complexes in the failing heart. Various metabolic interventions which promote the generation of ATP have been reported to be beneficial for the therapy of heart failure. Accordingly, it is suggested that depression in mitochondrial OXPHOS activity plays an important role in the development of heart failure.

Epicardial adipose tissue and cardiac lipotoxicity: A review

Epicardial adipose tissue (EAT) has morphological and physiological contiguity with the myocardium and coronary arteries, making it a visceral fat deposit with some unique properties. Under normal circumstances, EAT exhibits biochemical, mechanical, and thermogenic cardioprotective characteristics. Under clinical processes, epicardial fat can directly impact the heart and coronary arteries by secreting proinflammatory cytokines via vasocrine or paracrine mechanisms. It is still not apparent what factors affect this equilibrium. Returning epicardial fat to its physiological purpose may be possible by enhanced local vascularization, weight loss, and focused pharmacological therapies. This review centers on EAT's developing physiological and pathophysiological dimensions and its various and pioneering clinical utilities.

Proteomic profiling of sudden cardiac death with acquired cardiac hypertrophy

BACKGROUND

Cardiac hypertrophy, which develops in middle-aged and older individuals as a consequence of hypertension and obesity, is an established risk factor for sudden cardiac death (SCD). However, it is sometimes difficult to differentiate SCD with acquired cardiac hypertrophy (SCH) from compensated cardiac hypertrophy (CCH), at autopsy. We aimed to elucidate the proteomic alteration in SCH, which can be a guideline for future postmortem diagnosis.

METHODS

Cardiac tissues were sampled at autopsy. SCH group consisted of ischemic heart failure, hypertensive heart failure, and aortic stenosis. CCH group included cases of non-cardiac death with cardiac hypertrophy. The control group comprised cases of non-cardiac death without cardiac hypertrophy. All patients were aged > 40 years, and hypertrophic cardiomyopathy was not included in this study. We performed histological examination and shotgun proteomic analysis, followed by quantitative polymerase chain reaction analysis.

RESULTS

Significant obesity and myocardial hypertrophy, and mild myocardial fibrosis were comparable in SCH and CCH cases compared to control cases. The proteomic profile of SCH cases was distinguishable from those of CCH and control cases, and many sarcomere proteins were increased in SCH cases. Especially, the protein and mRNA levels of MYH7 and MYL3 were significantly increased in SCH cases.

CONCLUSION

This is the first report of cardiac proteomic analysis in SCH and CCH cases. The stepwise upregulation of sarcomere proteins may increase the risk for SCD in acquired cardiac hypertrophy before cardiac fibrosis progresses significantly. These findings can possibly aid in the postmortem diagnosis of SCH in middle-aged and older individuals.

Comparative Metabolomics in Single Ventricle Patients after Fontan Palliation: A Strong Case for a Targeted Metabolic Therapy

Most studies on single ventricle (SV) circulation take a physiological or anatomical approach. Although there is a tight coupling between cardiac contractility and metabolism, the metabolic perspective on this patient population is very recent. Early findings point to major metabolic disturbances, with both impaired glucose and fatty acid oxidation in the cardiomyocytes. Additionally, Fontan patients have systemic metabolic derangements such as abnormal glucose metabolism and hypocholesterolemia. Our literature review compares the metabolism of patients with a SV circulation after Fontan palliation with that of patients with a healthy biventricular (BV) heart, or different subtypes of a failing BV heart, by Pubmed review of the literature on cardiac metabolism, Fontan failure, heart failure (HF), ketosis, metabolism published in English from 1939 to 2023. Early evidence demonstrates that SV circulation is not only a hemodynamic burden requiring staged palliation, but also a metabolic issue with alterations similar to what is known for HF in a BV circulation. Alterations of fatty acid and glucose oxidation were found, resulting in metabolic instability and impaired energy production. As reported for patients with BV HF, stimulating ketone oxidation may be an effective treatment strategy for HF in these patients. Few but promising clinical trials have been conducted thus far to evaluate therapeutic ketosis with HF using a variety of instruments, including ketogenic diet, ketone esters, and sodium-glucose co-transporter-2 (SGLT2) inhibitors. An initial trial on a small cohort demonstrated favorable outcomes for Fontan patients treated with SGLT2 inhibitors. Therapeutic ketosis is worth considering in the treatment of Fontan patients, as ketones positively affect not only the myocardial energy metabolism, but also the global Fontan physiopathology. Induced ketosis seems promising as a concerted therapeutic strategy.

Exercise, exerkines, and cardiometabolic health: from individual players to a team sport

Exercise confers numerous salutary effects that extend beyond individual organ systems to provide systemic health benefits. Here, we discuss the role of exercise in cardiovascular health. We summarize major findings from human exercise studies in cardiometabolic disease. We next describe our current understanding of cardiac-specific substrate metabolism that occurs with acute exercise and in response to exercise training. We subsequently focus on exercise-stimulated circulating biochemicals ("exerkines") as a paradigm for understanding the global health circuitry of exercise, and discuss important concepts in this emerging field before highlighting exerkines relevant in cardiovascular health and disease. Finally, this Review identifies gaps that remain in the field of exercise science and opportunities that exist to translate biologic insights into human health improvement.

A defect in mitochondrial protein translation influences mitonuclear communication in the heart

The regulation of the informational flow from the mitochondria to the nucleus (mitonuclear communication) is not fully characterized in the heart. We have determined that mitochondrial ribosomal protein S5 (MRPS5/uS5m) can regulate cardiac function and key pathways to coordinate this process during cardiac stress. We demonstrate that loss of Mrps5 in the developing heart leads to cardiac defects and embryonic lethality while postnatal loss induces cardiac hypertrophy and heart failure. The structure and function of mitochondria is disrupted in Mrps5 mutant cardiomyocytes, impairing mitochondrial protein translation and OXPHOS. We identify Klf15 as a Mrps5 downstream target and demonstrate that exogenous Klf15 is able to rescue the overt defects and re-balance the cardiac metabolome. We further show that Mrps5 represses Klf15 expression through c-myc, together with the metabolite L-phenylalanine. This critical role for Mrps5 in cardiac metabolism and mitonuclear communication highlights its potential as a target for heart failure therapies.

Prohibitin1 maintains mitochondrial quality in isoproterenol-induced cardiac hypertrophy in H9C2 cells

BACKGROUND INFORMATION

Various types of stress initially induce a state of cardiac hypertrophy (CH) in the heart. But, persistent escalation of cardiac stress leads to progression from an adaptive physiological to a maladaptive pathological state. So, elucidating molecular mechanisms that can attenuate CH is imperative in developing cardiac therapies. Previously, we showed that Prohibitin1 (PHB1) has a protective role in CH-induced oxidative stress. Nevertheless, it is unclear how PHB1, a mitochondrial protein, has a protective role in CH. Therefore, we hypothesized that PHB1 maintains mitochondrial quality in CH. To test this hypothesis, we used Isoproterenol (ISO) to induce CH in H9C2 cells overexpressing PHB1 and elucidated mitochondrial quality control pathways.

RESULTS

We found that overexpressing PHB1 attenuates ISO-induced CH and restores mitochondrial morphology in H9C2 cells. In addition, PHB1 blocks the pro-hypertrophic IGF1R/AKT pathway and restores the mitochondrial membrane polarization in ISO-treated cells. We observed that overexpressing PHB1 promotes mitochondrial biogenesis, improves mitochondrial respiratory capacity, and triggers mitophagy.

CONCLUSION

We conclude that PHB1 maintains mitochondrial quality in ISO-induced CH in H9C2 cells.

SIGNIFICANCE

Based on our results, we suggest that small molecules that induce PHB1 in cardiac cells may prove beneficial in developing cardiac therapies.

Sodium-glucose Cotransporter 2 Inhibitors and Pathological Myocardial Hypertrophy

Sodium-glucose cotransporter 2 (SGLT2) inhibitors are a new type of oral hypoglycemic drugs that exert a hypoglycemic effect by blocking the reabsorption of glucose in the proximal renal tubules, thus promoting the excretion of glucose from urine. Their hypoglycemic effect is not dependent on insulin. Increasing data shows that SGLT2 inhibitors improve cardiovascular outcomes in patients with type 2 diabetes. Previous studies have demonstrated that SGLT2 inhibitors can reduce pathological myocardial hypertrophy with or without diabetes, but the exact mechanism remains to be elucidated. To clarify the relationship between SGLT2 inhibitors and pathological myocardial hypertrophy, with a view to providing a reference for the future treatment thereof, this study reviewed the possible mechanisms of SGLT2 inhibitors in attenuating pathological myocardial hypertrophy. We focused specifically on the mechanisms in terms of inflammation, oxidative stress, myocardial fibrosis, mitochondrial function, epicardial lipids, endothelial function, insulin resistance, cardiac hydrogen and sodium exchange, and autophagy.

Extracellular vesicles DJ-1 derived from hypoxia-conditioned hMSCs alleviate cardiac hypertrophy by suppressing mitochondria dysfunction and preventing ATRAP degradation

BACKGROUND

As a pathological myocardial remodeling process in a variety of cardiovascular diseases, cardiac hypertrophy still has no effective treatment. Human mesenchymal stem cells (hMSCs) derived extracellular vesicles (EVs) has been recognized as a promising treatment strategy for cardiac disease.

METHODS

In this study, the inhibitory effects on cardiac hypertrophy are compared between normoxia-conditioned hMSC-derived EVs (Nor-EVs) and hypoxia-conditioned hMSC-derived EVs (Hypo-EVs) in neonatal rat cardiomyocytes (NRCMs) after angiotensin II (Ang II) stimulation and in a mouse model of transverse aortic constriction (TAC).

RESULTS

We demonstrate that Hypo-EVs exert an increased inhibitory effect on cardiac hypertrophy compared with Nor-EVs. Parkinson disease protein 7 (PARK7/DJ-1) is identify as a differential protein between Nor-EVs and Hypo-EVs by quantitative proteomics analysis. Results show that DJ-1, which is rich in Hypo-EVs, alleviates mitochondrial dysfunction and excessive mitochondrial reactive oxygen species (mtROS) production as an antioxidant. Mechanistic studies demonstrate for the first time that DJ-1 may suppress cardiac hypertrophy by inhibiting the activity of proteasome subunit beta type 10 (PSMB10) through a direct physical interaction. This interaction can inhibit angiotensin II type 1 receptor (AT1R)-mediated signaling pathways resulting in cardiac hypertrophy through alleviating ubiquitination degradation of AT1R-associated protein (ATRAP).

CONCLUSIONS

When taken together, our study suggests that Hypo-EVs have significant potential as a novel therapeutic agent for the treatment of cardiac hypertrophy.

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.

Iron Deficiency and Deranged Myocardial Energetics in Heart Failure

Among different pathomechanisms involved in the development of heart failure, adverse metabolic myocardial remodeling closely related to ineffective energy production, constitutes the fundamental feature of the disease and translates into further progression of both cardiac dysfunction and maladaptations occurring within other organs. Being the component of key enzymatic machineries, iron plays a vital role in energy generation and utilization, hence the interest in whether, by correcting systemic and/or cellular deficiency of this micronutrient, we can influence the energetic efficiency of tissues, including the heart. In this review we summarize current knowledge on disturbed energy metabolism in failing hearts as well as we analyze experimental evidence linking iron deficiency with deranged myocardial energetics.

Monoamine Oxidase (MAO) Is Expressed at the Level of Mitral Valve with Severe Regurgitation in Hypertrophic Obstructive Cardiomyopathy: A Case Report

Hypertrophic obstructive cardiomyopathy (HOCM) is one of the most common hereditary heart diseases. The severely hypertrophied interventricular septum combined with the systolic anterior movement (SAM) of the mitral valve (MV) frequently cause a significant pressure gradient in the left ventricular outflow tract associated with varying degrees of mitral regurgitation (MR). We present the case of a 64-year-old female patient who was diagnosed with HOCM two years ago and was admitted to the Institute of Cardiovascular Disease with exertion dyspnea and fatigue. Transthoracic echocardiography revealed concentric, asymmetrical left ventricular hypertrophy, an elongated anterior mitral leaflet (AML) and a significant SAM causing severe regurgitation, with indication for valvular replacement Monoamine oxidase (MAO), a mitochondrial enzyme, with 2 isoforms, MAO-A and B, has emerged as an important source of reactive oxygen species (ROS) in the cardiovascular system, but literature data on its expression in valvular tissue is scarce. Therefore, we assessed MAO-A and B gene (qPCR) and protein (immune fluorescence) expression as well as ROS production (spectrophotometry and confocal microscopy) and in the explanted MV harvested during replacement surgery. MAO expression and ROS production (assessed by both methods) were further augmented following ex vivo incubation with angiotensin II, an effect that was reversed in the presence of either MAO-A (clorgyline) or B (selegiline) inhibitor, respectively. In conclusion, MAO isoforms are expressed at the level of severely impaired mitral valve in the setting of HOCM and can be induced in conditions that mimic the activation of renin-angiotensin-aldosterone system. The observation that the enzyme can be modulated by MAO inhibitors warrants further investigation in a patient cohort.

Hypertrophic cardiomyopathy: Mutations to mechanisms to therapies

Hypertrophic cardiomyopathy (HCM) affects more than 1 in 500 people in the general population with an extensive burden of morbidity in the form of arrhythmia, heart failure, and sudden death. More than 25 years since the discovery of the genetic underpinnings of HCM, the field has unveiled significant insights into the primary effects of these genetic mutations, especially for the myosin heavy chain gene, which is one of the most commonly mutated genes. Our group has studied the molecular effects of HCM mutations on human β-cardiac myosin heavy chain using state-of-the-art biochemical and biophysical tools for the past 10 years, combining insights from clinical genetics and structural analyses of cardiac myosin. The overarching hypothesis is that HCM-causing mutations in sarcomere proteins cause hypercontractility at the sarcomere level, and we have shown that an increase in the number of myosin molecules available for interaction with actin is a primary driver. Recently, two pharmaceutical companies have developed small molecule inhibitors of human cardiac myosin to counteract the molecular consequences of HCM pathogenesis. One of these inhibitors (mavacamten) has recently been approved by the FDA after completing a successful phase III trial in HCM patients, and the other (aficamten) is currently being evaluated in a phase III trial. Myosin inhibitors will be the first class of medication used to treat HCM that has both robust clinical trial evidence of efficacy and that targets the fundamental mechanism of HCM pathogenesis. The success of myosin inhibitors in HCM opens the door to finding other new drugs that target the sarcomere directly, as we learn more about the genetics and fundamental mechanisms of this disease.

Exercise training maintains cardiovascular health: signaling pathways involved and potential therapeutics

Exercise training has been widely recognized as a healthy lifestyle as well as an effective non-drug therapeutic strategy for cardiovascular diseases (CVD). Functional and mechanistic studies that employ animal exercise models as well as observational and interventional cohort studies with human participants, have contributed considerably in delineating the essential signaling pathways by which exercise promotes cardiovascular fitness and health. First, this review summarizes the beneficial impact of exercise on multiple aspects of cardiovascular health. We then discuss in detail the signaling pathways mediating exercise's benefits for cardiovascular health. The exercise-regulated signaling cascades have been shown to confer myocardial protection and drive systemic adaptations. The signaling molecules that are necessary for exercise-induced physiological cardiac hypertrophy have the potential to attenuate myocardial injury and reverse cardiac remodeling. Exercise-regulated noncoding RNAs and their associated signaling pathways are also discussed in detail for their roles and mechanisms in exercise-induced cardioprotective effects. Moreover, we address the exercise-mediated signaling pathways and molecules that can serve as potential therapeutic targets ranging from pharmacological approaches to gene therapies in CVD. We also discuss multiple factors that influence exercise's effect and highlight the importance and need for further investigations regarding the exercise-regulated molecules as therapeutic targets and biomarkers for CVD as well as the cross talk between the heart and other tissues or organs during exercise. We conclude that a deep understanding of the signaling pathways involved in exercise's benefits for cardiovascular health will undoubtedly contribute to the identification and development of novel therapeutic targets and strategies for CVD.

Regulation of the Keap1-Nrf2 Signaling Axis by Glycyrrhetinic Acid Promoted Oxidative Stress-Induced H9C2 Cell Apoptosis

Excessive reactive oxygen species (ROS) could interfere with the physiological capacities of H₉C₂ cells and cause cardiomyocyte apoptosis. Glycyrrhetinic acid (GA), one of the main medicinal component of Glycyrrhetinic Radix et Rhizoma, shows toxic and adverse side effects in the clinic setting. In particular, some studies have reported that GA exerts toxic effects on H₉C₂ cells. The purpose of this study is to assess the effect of GA-induced oxidative stress on cultured H₉C₂ cells and reveal the relevant signaling pathways. LDH assay was used to assess cell damage. Apoptosis was detected using Hoechst 33242 and a propidium iodide (PI) assay. An Annexin V-fluorescein isothiocyanate/PI double-staining assay was utilized to investigate GA-induced apoptosis in H₉C₂ cells. The expression level of specific genes/proteins was evaluated by RT-qPCR and Western blotting. Flow cytometry and DCFH-DA fluorescent testing were used to determine the ROS levels of H₉C₂ cells. The potential mechanism of GA-induced cardiomyocyte injury was also investigated. GA treatment increased ROS generation and mitochondrial membrane depolarization and triggered caspase-3/9 activation and apoptosis. GA treatment also caused the nuclear translocation of NF-E2-related factor 2 after its dissociation from Keap1. This change was accompanied by a dose-dependent decline in the expression of the downstream target gene heme oxygenase-1. The findings demonstrated that GA could regulate the Keap1-Nrf2 signaling axis and induce oxidative stress to promote the apoptosis of H₉C₂ cells.

High Exogenous Antioxidant, Restorative Treatment (Heart) for Prevention of the Six Stages of Heart Failure: The Heart Diet

The exact pathophysiology of heart failure (HF) is not yet known. Western diet, characterized by highly sweetened foods, as well as being rich in fat, fried foods, red meat and processed meat, eggs, and sweet beverages, may cause inflammation, leading to oxidative dysfunction in the cardiac ultra-structure. Oxidative function of the myocardium and how oxidative dysfunction causes physio-pathological remodeling, leading to HF, is not well known. Antioxidants, such as polyphenolics and flavonoids, omega-3 fatty acids, and other micronutrients that are rich in Indo-Mediterranean-type diets, could be protective in sustaining the oxidative functions of the heart. The cardiomyocytes use glucose and fatty acids for the physiological functions depending upon the metabolic requirements of the heart. Apart from toxicity due to glucose, lipotoxicity also adversely affects the cardiomyocytes, which worsen in the presence of deficiency of endogenous antioxidants and deficiency of exogenous antioxidant nutrients in the diet. The high-sugar-and-high-fat-induced production of ceramide, advanced glycation end products (AGE) and triamino-methyl-N-oxide (TMAO) can predispose individuals to oxidative dysfunction and Ca-overloading. The alteration in the biology may start with normal cardiac cell remodeling to biological remodeling due to inflammation. An increase in the fat content of a diet in combination with inducible nitric oxide synthase (NOSi) via N-arginine methyl ester has been found to preserve the ejection fraction in HF. It is proposed that a greater intake of high exogenous antioxidant restorative treatment (HEART) diet, polyphenolics and flavonoids, as well as cessation of red meat intake and egg, can cause improvement in the oxidative function of the heart, by inhibiting oxidative damage to lipids, proteins and DNA in the cell, resulting in beneficial effects in the early stage of the Six Stages of HF. There is an unmet need to conduct cohort studies and randomized, controlled studies to demonstrate the role of the HEART diet in the treatment of HF.

Mitochondria in Pathological Cardiac Hypertrophy Research and Therapy

Cardiac hypertrophy, a stereotypic cardiac response to increased workload, ultimately progresses to severe contractile dysfunction and uncompensated heart failure without appropriate intervention. Sustained cardiac overload inevitably results in high energy consumption, thus breaking the balance between mitochondrial energy supply and cardiac energy demand. In recent years, accumulating evidence has indicated that mitochondrial dysfunction is implicated in pathological cardiac hypertrophy. The significant alterations in mitochondrial energetics and mitochondrial proteome composition, as well as the altered expression of transcripts that have an impact on mitochondrial structure and function, may contribute to the initiation and progression of cardiac hypertrophy. This article presents a summary review of the morphological and functional changes of mitochondria during the hypertrophic response, followed by an overview of the latest research progress on the significant modulatory roles of mitochondria in cardiac hypertrophy. Our article is also to summarize the strategies of mitochondria-targeting as therapeutic targets to treat cardiac hypertrophy.

Multiparametric MRI identifies subtle adaptations for demarcation of disease transition in murine aortic valve stenosis

Aortic valve stenosis (AS) is the most frequent valve disease with relevant prognostic impact. Experimental model systems for AS are scarce and comprehensive imaging techniques to simultaneously quantify function and morphology in disease progression are lacking. Therefore, we refined an acute murine AS model to closely mimic human disease characteristics and developed a high-resolution magnetic resonance imaging (MRI) approach for simultaneous in-depth analysis of valvular, myocardial as well as aortic morphology/pathophysiology to identify early changes in tissue texture and critical transition points in the adaptive process to AS. AS was induced by wire injury of the aortic valve. Four weeks after surgery, cine loops, velocity, and relaxometry maps were acquired at 9.4 T to monitor structural/functional alterations in valve, aorta, and left ventricle (LV). In vivo MRI data were subsequently validated by histology and compared to echocardiography. AS mice exhibited impaired valve opening accompanied by significant valve thickening due to fibrotic remodelling. While control mice showed bell-shaped flow profiles, AS resulted not only in higher peak flow velocities, but also in fragmented turbulent flow patterns associated with enhanced circumferential strain and an increase in wall thickness of the aortic root. AS mice presented with a mild hypertrophy but unaffected global LV function. Cardiac MR relaxometry revealed reduced values for both T1 and T2 in AS reflecting subtle myocardial tissue remodelling with early alterations in mitochondrial function in response to the enhanced afterload. Concomitantly, incipient impairments of coronary flow reserve and myocardial tissue integrity get apparent accompanied by early troponin release. With this, we identified a premature transition point with still compensated cardiac function but beginning textural changes. This will allow interventional studies to explore early disease pathophysiology and novel therapeutic targets.

Targeting the NLRP3 inflammasome in cardiovascular diseases

The NACHT, leucine-rich repeat (LRR), and pyrin domain (PYD)-containing protein 3 (NLRP3) inflammasome is an intracellular sensing protein complex that plays a major role in innate immunity. Following tissue injury, activation of the NLRP3 inflammasome results in cytokine production, primarily interleukin(IL)-1β and IL-18, and, eventually, inflammatory cell death - pyroptosis. While a balanced inflammatory response favors damage resolution and tissue healing, excessive NLRP3 activation causes detrimental effects. A key involvement of the NLRP3 inflammasome has been reported across a wide range of cardiovascular diseases (CVDs). Several pharmacological agents selectively targeting the NLRP3 inflammasome system have been developed and tested in animals and early phase human studies with overall promising results. While the NLRP3 inhibitors are in clinical development, multiple randomized trials have demonstrated the safety and efficacy of IL-1 blockade in atherothrombosis, heart failure and recurrent pericarditis. Furthermore, the non-selective NLRP3 inhibitor colchicine has been recently shown to significantly reduce cardiovascular events in patients with chronic coronary disease. In this review, we will outline the mechanisms driving NLRP3 assembly and activation, and discuss the pathogenetic role of the NLRP3 inflammasome in CVDs, providing an overview of the current and future therapeutic approaches targeting the NLRP3 inflammasome.

Circ_nuclear factor I X (circNfix) attenuates pressure overload-induced cardiac hypertrophy via regulating miR-145-5p/ATF3 axis

Cardiac hypertrophy can cause heart failure. However, the mechanisms underlying the progression of cardiac hypertrophy remain unclear. Emerging evidence suggests that circular RNAs (circRNAs) play a critical role in cardiac hypertrophy. However, the association between circ_nuclear factor I X (circNfix) and cardiac hypertrophy remain largely unknown. Therefore, the aim of the present study was to explore the role of circNfix in cardiac hypertrophy. In order to detect the function of circNfix in cardiac hypertrophy, cardiomyocytes were stimulated with angiotensin II (Ang II) to mimic the pathogenesis of the disease. In addition, pressure overload-induced cardiac hypertrophy in a mouse model was established using transverse aortic constriction (TAC) surgery. The mechanism via which circNfix regulated cardiac hypertrophy was investigated using RNA pull-down and luciferase reporter assays, and fluorescence in situ hybridization (FISH). circNfix was downregulated in Ang II-treated cardiomyocytes. Similarly, circNfix expression was markedly downregulated in mice following TAC surgery. In addition, circNfix overexpression significantly prevented the progression of cardiac hypertrophy in TAC-treated mice. Luciferase activity and RNA pull-down assays indicated that circNfix could indirectly target activating transcription factor 3 (ATF3) by binding with microRNA (miR)-145-5p in cardiomyocytes. miR-145-5p overexpression or ATF3 knockdown could reverse the effects of circNfix in Ang II-treated mouse cardiomyocytes. circNfix attenuated pressure overload-induced cardiac hypertrophy by regulating the miR-145-5p/ATF3 axis. Therefore, circNfix may serve as a molecular target for cardiac hypertrophy treatment.

New Insights into Molecular Mechanisms Mediating Adaptation to Exercise; A Review Focusing on Mitochondrial Biogenesis, Mitochondrial Function, Mitophagy and Autophagy

Exercise itself is fundamental for good health, and when practiced regularly confers a myriad of metabolic benefits in a range of tissues. These benefits are mediated by a range of adaptive responses in a coordinated, multi-organ manner. The continued understanding of the molecular mechanisms of action which confer beneficial effects of exercise on the body will identify more specific pathways which can be manipulated by therapeutic intervention in order to prevent or treat various metabolism-associated diseases. This is particularly important as exercise is not an available option to all and so novel methods must be identified to confer the beneficial effects of exercise in a therapeutic manner. This review will focus on key emerging molecular mechanisms of mitochondrial biogenesis, autophagy and mitophagy in selected, highly metabolic tissues, describing their regulation and contribution to beneficial adaptations to exercise.

Did giraffe cardiovascular evolution solve the problem of heart failure with preserved ejection fraction?

The evolved adaptations of other species can be a source of insight for novel biomedical innovation. Limitations of traditional animal models for the study of some pathologies are fueling efforts to find new approaches to biomedical investigation. One emerging approach recognizes the evolved adaptations in other species as possible solutions to human pathology. The giraffe heart, for example, appears resistant to pathology related to heart failure with preserved ejection fraction (HFpEF)—a leading form of hypertension-associated cardiovascular disease in humans. Here, we postulate that the physiological pressure-induced left ventricular thickening in giraffes does not result in the pathological cardiovascular changes observed in humans with hypertension. The mechanisms underlying this cardiovascular adaptation to high blood pressure in the giraffe may be a bioinspired roadmap for preventive and therapeutic strategies for human HFpEF.

Molecular Signature of HFpEF: Systems Biology in a Cardiac-Centric Large Animal Model

In this study the authors used systems biology to define progressive changes in metabolism and transcription in a large animal model of heart failure with preserved ejection fraction (HFpEF). Transcriptomic analysis of cardiac tissue, 1-month post-banding, revealed loss of electron transport chain components, and this was supported by changes in metabolism and mitochondrial function, altogether signifying alterations in oxidative metabolism. Established HFpEF, 4 months post-banding, resulted in changes in intermediary metabolism with normalized mitochondrial function. Mitochondrial dysfunction and energetic deficiencies were noted in skeletal muscle at early and late phases of disease, suggesting cardiac-derived signaling contributes to peripheral tissue maladaptation in HFpEF. Collectively, these results provide insights into the cellular biology underlying HFpEF progression.

The Role of Mitochondrial Dysfunction in Atrial Fibrillation: Translation to Druggable Target and Biomarker Discovery

Atrial fibrillation (AF) is the most prevalent and progressive cardiac arrhythmia worldwide and is associated with serious complications such as heart failure and ischemic stroke. Current treatment modalities attenuate AF symptoms and are only moderately effective in halting the arrhythmia. Therefore, there is an urgent need to dissect molecular mechanisms that drive AF. As AF is characterized by a rapid atrial activation rate, which requires a high energy metabolism, a role of mitochondrial dysfunction in AF pathophysiology is plausible. It is well known that mitochondria play a central role in cardiomyocyte function, as they produce energy to support the mechanical and electrical function of the heart. Details on the molecular mechanisms underlying mitochondrial dysfunction are increasingly being uncovered as a contributing factor in the loss of cardiomyocyte function and AF. Considering the high prevalence of AF, investigating the role of mitochondrial impairment in AF may guide the path towards new therapeutic and diagnostic targets. In this review, the latest evidence on the role of mitochondria dysfunction in AF is presented. We highlight the key modulators of mitochondrial dysfunction that drive AF and discuss whether they represent potential targets for therapeutic interventions and diagnostics in clinical AF.

Functional genomics meta-analysis to identify gene set enrichment networks in cardiac hypertrophy

In order to take advantage of the continuously increasing number of transcriptome studies, it is important to develop strategies that integrate multiple expression datasets addressing the same biological question to allow a robust analysis. Here, we propose a meta-analysis framework that integrates enriched pathways identified through the Gene Set Enrichment Analysis (GSEA) approach and calculates for each meta-pathway an empirical p-value. Validation of our approach on benchmark datasets showed comparable or even better performance than existing methods and an increase in robustness with increasing number of integrated datasets. We then applied the meta-analysis framework to 15 functional genomics datasets of physiological and pathological cardiac hypertrophy. Within these datasets we grouped expression sets measured at time points that represent the same hallmarks of heart tissue remodeling ('aggregated time points') and performed meta-analysis on the expression sets assigned to each aggregated time point. To facilitate biological interpretation, results were visualized as gene set enrichment networks. Here, our meta-analysis framework identified well-known biological mechanisms associated with pathological cardiac hypertrophy (e.g., cardiomyocyte apoptosis, cardiac contractile dysfunction, and alteration in energy metabolism). In addition, results highlighted novel, potentially cardioprotective mechanisms in physiological cardiac hypertrophy involving the down-regulation of immune cell response, which are worth further investigation.

Lactoferrin ameliorates pathological cardiac hypertrophy related to mitochondrial quality control in aged mice

Pathological myocardial hypertrophy, which lacks effective prevention and treatment strategies, makes the elderly susceptible to various cardiovascular diseases. Based on the beneficial attributes of lactoferrin in aging-related diseases, we aimed to investigate whether lactoferrin could exert protection against aging-related cardiac hypertrophy and further explore the underlying mechanisms. Here, we assessed the effects of lactoferrin on myocardial pathology, apoptotic proteins, mitochondrial morphology, kinetics, autophagy, and aging-related markers, including lipofuscin deposition, overloaded iron, and oxidative stress, which are known to destabilize the mitochondrial-lysosomal axis in aged mice. Upon the administration of lactoferrin, aged hearts showed amelioration of pathological cardiac hypertrophy, which was associated with decreased apoptosis, improved morphology, rearrangement of mitochondrial dynamics, increased lysosome-dependent autophagy, and inhibition of factors detrimental to the mitochondrial-lysosomal axis. In conclusion, lactoferrin ameliorated pathological cardiac hypertrophy, potentially by improving the mitochondrial quality related to mitochondrial dynamics and the mitochondrial-lysosomal axis, thus reducing mitochondria-dependent apoptosis, which is the pivotal factor for cardiac hypertrophy in aged mice.

Physical Exercise and Cardiac Repair: The Potential Role of Nitric Oxide in Boosting Stem Cell Regenerative Biology

Over the years strong evidence has been accumulated showing that aerobic physical exercise exerts beneficial effects on the prevention and reduction of cardiovascular risk. Exercise in healthy subjects fosters physiological remodeling of the adult heart. Concurrently, physical training can significantly slow-down or even reverse the maladaptive pathologic cardiac remodeling in cardiac diseases, improving heart function. The underlying cellular and molecular mechanisms of the beneficial effects of physical exercise on the heart are still a subject of intensive study. Aerobic activity increases cardiovascular nitric oxide (NO) released mainly through nitric oxidase synthase 3 activity, promoting endothelium-dependent vasodilation, reducing vascular resistance, and lowering blood pressure. On the reverse, an imbalance between increasing free radical production and decreased NO generation characterizes pathologic remodeling, which has been termed the "nitroso-redox imbalance". Besides these classical evidence on the role of NO in cardiac physiology and pathology, accumulating data show that NO regulate different aspects of stem cell biology, including survival, proliferation, migration, differentiation, and secretion of pro-regenerative factors. Concurrently, it has been shown that physical exercise generates physiological remodeling while antagonizes pathologic remodeling also by fostering cardiac regeneration, including new cardiomyocyte formation. This review is therefore focused on the possible link between physical exercise, NO, and stem cell biology in the cardiac regenerative/reparative response to physiological or pathological load. Cellular and molecular mechanisms that generate an exercise-induced cardioprotective phenotype are discussed in regards with myocardial repair and regeneration. Aerobic training can benefit cells implicated in cardiovascular homeostasis and response to damage by NO-mediated pathways that protect stem cells in the hostile environment, enhance their activation and differentiation and, in turn, translate to more efficient myocardial tissue regeneration. Moreover, stem cell preconditioning by and/or local potentiation of NO signaling can be envisioned as promising approaches to improve the post-transplantation stem cell survival and the efficacy of cardiac stem cell therapy.

Differences in molecular phenotype in mouse and human hypertrophic cardiomyopathy

Hypertrophic cardiomyopathy (HCM) is characterized by phenotypic heterogeneity. We investigated the molecular basis of the cardiac phenotype in two mouse models at established disease stage (mouse-HCM), and human myectomy tissue (human-HCM). We analyzed the transcriptome in 2 mouse models with non-obstructive HCM (R403Q-MyHC, R92W-TnT)/littermate-control hearts at 24 weeks of age, and in myectomy tissue of patients with obstructive HCM/control hearts (GSE36961, GSE36946). Additionally, we examined myocyte redox, cardiac mitochondrial DNA copy number (mtDNA-CN), mt-respiration, mt-ROS generation/scavenging and mt-Ca²⁺ handling in mice. We identified distinct allele-specific gene expression in mouse-HCM, and marked differences between mouse-HCM and human-HCM. Only two genes (CASQ1, GPT1) were similarly dysregulated in both mutant mice and human-HCM. No signaling pathway or transcription factor was predicted to be similarly dysregulated (by Ingenuity Pathway Analysis) in both mutant mice and human-HCM. Losartan was a predicted therapy only in TnT-mutant mice. KEGG pathway analysis revealed enrichment for several metabolic pathways, but only pyruvate metabolism was enriched in both mutant mice and human-HCM. Both mutant mouse myocytes demonstrated evidence of an oxidized redox environment. Mitochondrial complex I RCR was lower in both mutant mice compared to controls. MyHC-mutant mice had similar mtDNA-CN and mt-Ca²⁺ handling, but TnT-mutant mice exhibited lower mtDNA-CN and impaired mt-Ca²⁺ handling, compared to littermate-controls. Molecular profiling reveals differences in gene expression, transcriptional regulation, intracellular signaling and mt-number/function in 2 mouse models at established disease stage. Further studies are needed to confirm differences in gene expression between mouse and human-HCM, and to examine whether cardiac phenotype, genotype and/or species differences underlie the divergence in molecular profiles.

Generation of mature compact ventricular cardiomyocytes from human pluripotent stem cells

Compact cardiomyocytes that make up the ventricular wall of the adult heart represent an important therapeutic target population for modeling and treating cardiovascular diseases. Here, we established a differentiation strategy that promotes the specification, proliferation and maturation of compact ventricular cardiomyocytes from human pluripotent stem cells (hPSCs). The cardiomyocytes generated under these conditions display the ability to use fatty acids as an energy source, a high mitochondrial mass, well-defined sarcomere structures and enhanced contraction force. These ventricular cells undergo metabolic changes indicative of those associated with heart failure when challenged in vitro with pathological stimuli and were found to generate grafts consisting of more mature cells than those derived from immature cardiomyocytes following transplantation into infarcted rat hearts. hPSC-derived atrial cardiomyocytes also responded to the maturation cues identified in this study, indicating that the approach is broadly applicable to different subtypes of the heart. Collectively, these findings highlight the power of recapitulating key aspects of embryonic and postnatal development for generating therapeutically relevant cell types from hPSCs.

Cardiomyocytes of heart ventricles consist of subpopulations of trabecular and compact subtypes. Here the authors describe the generation of structurally, metabolically and functionally mature compact ventricular cardiomyocytes as well as mature atrial cardiomyocytes from human pluripotent stem cells.

Does Transient Receptor Potential Vanilloid Type 1 Alleviate or Aggravate Pathological Myocardial Hypertrophy?

Transient receptor potential vanilloid type 1 (TRPV1) is a non-selective cation channel, which is involved in the endogenous stress adaptation mechanism for protection of the heart as well as the occurrence and development of some heart diseases. Although the effect of activation of the TRPV1 channel on different types of non-neural cells in the heart remains unclear, most data show that stimulation of sensory nerves expressing TRPV1 or stimulation/overexpression of the TRPV1 channel has a beneficial role in heart disease. Some studies have proven that TRPV1 has an important relationship with pathological myocardial hypertrophy, but the specific mechanism and effect are not clear. In order to help researchers better understand the relationship between TRPV1 and pathological myocardial hypertrophy, this paper aims to summarize the effect of TRPV1 and the related mechanism in the occurrence and development of pathological myocardial hypertrophy from the following three points of view: 1) role of TRPV1 in alleviation of pathological myocardial hypertrophy; 2) role of TRPV1 in aggravation of pathological myocardial hypertrophy; and 3) the point of view of our team of researchers. It is expected that new therapies can provide potential targets for pathological myocardial hypertrophy.

Physical Exercise: A Novel Tool to Protect Mitochondrial Health

Mitochondrial dysfunction is a crucial contributor to heart diseases. Alterations in energetic metabolism affect crucial homeostatic processes, such asATP production, the generation of reactive oxygen species, and the release of pro-apoptotic factors, associated with metabolic abnormalities. In response to energetic deficiency, the cardiomyocytes activate the Mitochondrial Quality Control (MQC), a critical process in maintaining mitochondrial health. This process is compromised in cardiovascular diseases depending on the pathology's severity and represents, therefore, a potential therapeutic target. Several potential targeting molecules within this process have been identified in the last years, and therapeutic strategies have been proposed to ameliorate mitochondria monitoring and function. In this context, physical exercise is considered a non-pharmacological strategy to protect mitochondrial health. Physical exercise regulates MQC allowing the repair/elimination of damaged mitochondria and synthesizing new ones, thus recovering the metabolic state. In this review, we will deal with the effect of physical exercise on cardiac mitochondrial function tracing its ability to modulate specific steps in MQC both in physiologic and pathologic conditions.

Exercise promotes heart regeneration in aged rats by increasing regenerative factors in myocardial tissue

Exercise-induced stem cell activation is implicated in cardiovascular regeneration. However, ageing limits the capacity of cellular and molecular remodelling of the heart. It has been shown that exercise improves structure regeneration and function in the process of ageing. Aged male Wistar rats (n = 24) were divided into three groups: Control (CO), High-intensity interval training (HIIT) (80-100% of the maximum speed), and continuous endurance training (CET) (60-70% of the maximum speed) groups. Training groups were trained for 6 weeks. The expression of the Nkx2.5 gene was determined by real-time (RT-PCRs) analysis. Immunohistochemical staining was performed to assess the C-kit positive cardiac progenitor and Ki67 positive cells. The mRNA level of Nkx2.5 was significantly increased in the CET and HIIT groups (P < 0.05). Also, cardiac progenitor cells positive for C-kit were increased in both the CET and HIIT groups (P < 0.05). Exercise training improved the ejection fraction and fractional shortening in both training groups (P < 0.05). This study indicated that training initiates the activation of cardiac progenitor cells, leading to the generation of new myocardial cells (R = 0.737, P = 0.001). It seems that C-kit positive cells in training groups showed an increase in the expression of some transcription factors (Nkx2.5 gene), representing an increased regenerative capacity of cardiomyocytes during the training period. These findings suggest that the endogenous regenerative capacity of the adult heart, mediated by cardiac stem cells, would be increased in response to exercise.

The pyruvate-lactate axis modulates cardiac hypertrophy and heart failure

The metabolic rewiring of cardiomyocytes is a widely accepted hallmark of heart failure (HF). These metabolic changes include a decrease in mitochondrial pyruvate oxidation and an increased export of lactate. We identify the mitochondrial pyruvate carrier (MPC) and the cellular lactate exporter monocarboxylate transporter 4 (MCT4) as pivotal nodes in this metabolic axis. We observed that cardiac assist device-induced myocardial recovery in chronic HF patients was coincident with increased myocardial expression of the MPC. Moreover, the genetic ablation of the MPC in cultured cardiomyocytes and in adult murine hearts was sufficient to induce hypertrophy and HF. Conversely, MPC overexpression attenuated drug-induced hypertrophy in a cell-autonomous manner. We also introduced a novel, highly potent MCT4 inhibitor that mitigated hypertrophy in cultured cardiomyocytes and in mice. Together, we find that alteration of the pyruvate-lactate axis is a fundamental and early feature of cardiac hypertrophy and failure.

Testosterone activates glucose metabolism through AMPK and androgen signaling in cardiomyocyte hypertrophy

Background

Testosterone regulates nutrient and energy balance to maintain protein synthesis and metabolism in cardiomyocytes, but supraphysiological concentrations induce cardiac hypertrophy. Previously, we determined that testosterone increased glucose uptake—via AMP-activated protein kinase (AMPK)—after acute treatment in cardiomyocytes. However, whether elevated glucose uptake is involved in long-term changes of glucose metabolism or is required during cardiomyocyte growth remained unknown. In this study, we hypothesized that glucose uptake and glycolysis increase in testosterone-treated cardiomyocytes through AMPK and androgen receptor (AR).

Methods

Cultured cardiomyocytes were stimulated with 100 nM testosterone for 24 h, and hypertrophy was verified by increased cell size and mRNA levels of β-myosin heavy chain (β-mhc). Glucose uptake was assessed by 2-NBDG. Glycolysis and glycolytic capacity were determined by measuring extracellular acidification rate (ECAR).

Results

Testosterone induced cardiomyocyte hypertrophy that was accompanied by increased glucose uptake, glycolysis enhancement and upregulated mRNA expression of hexokinase 2. In addition, testosterone increased AMPK phosphorylation (Thr172), while inhibition of both AMPK and AR blocked glycolysis and cardiomyocyte hypertrophy induced by testosterone. Moreover, testosterone supplementation in adult male rats by 5 weeks induced cardiac hypertrophy and upregulated β-mhc, Hk2 and Pfk2 mRNA levels.

Conclusion

These results indicate that testosterone stimulates glucose metabolism by activation of AMPK and AR signaling which are critical to induce cardiomyocyte hypertrophy.

Supplementary Information

The online version contains supplementary material available at 10.1186/s40659-021-00328-4.

β-Catenin Regulates Cardiac Energy Metabolism in Sedentary and Trained Mice

The role of canonical Wnt signaling in metabolic regulation and development of physiological cardiac hypertrophy remains largely unknown. To explore the function of β-catenin in the regulation of cardiac metabolism and physiological cardiac hypertrophy development, we used mice heterozygous for cardiac-specific β-catenin knockout that were subjected to a swimming training model. β-Catenin haploinsufficient mice subjected to endurance training displayed a decreased β-catenin transcriptional activity, attenuated cardiomyocytes hypertrophic growth, and enhanced activation of AMP-activated protein kinase (AMPK), phosphoinositide-3-kinase-Akt (Pi3K-Akt), and mitogen-activated protein kinase/extracellular signal-regulated kinases 1/2 (MAPK/Erk1/2) signaling pathways compared to trained wild type mice. We further observed an increased level of proteins involved in glucose aerobic metabolism and β-oxidation along with perturbed activity of mitochondrial oxidative phosphorylation complexes (OXPHOS) in trained β-catenin haploinsufficient mice. Taken together, Wnt/β-catenin signaling appears to govern metabolic regulatory programs, sustaining metabolic plasticity in adult hearts during the adaptation to endurance training.

WY14643 improves left ventricular myocardial mitochondrial and systolic functions in obese rats under chronic persistent hypoxia via the PPARα pathway

AIMS

Peroxisome proliferator-activated receptor (PPAR) α, a key regulator of lipid metabolism, plays a role in maintaining the homeostasis of myocardial energy metabolism. Both hypoxia and obesity inhibit the expression of PPARα in the myocardium. In this study, we verified the inhibitory effects of hypoxia and obesity on PPARα and examined whether WY14643 (4-chloro-6-(2,3-xylidino)-2-pyrimidinylthioacetic acid), an agonist of PPARα, ameliorates myocardial mitochondrial dysfunction and protects cardiac function in obese rats under chronic persistent hypoxia.

MAIN METHODS

Sprague-Dawley rats were randomly divided into six groups: a control group (normal chow diet, normal oxygen), a high-fat diet (HFD) group (normal oxygen), a chronic persistent hypoxia normal chow diet group, a chronic persistent hypoxia HFD group, a chronic persistent hypoxia HFD group with WY14643 treatment, and a chronic persistent hypoxia HFD group with vehicle treatment.

KEY FINDINGS

Hypoxia and obesity increased myocardial lipid accumulation, mitochondrial dysfunction, and left ventricular systolic dysfunction. Myocardial lipid metabolism-related genes, including those encoding PPARα, PPARγ coactivator 1α (PGC1α), and carnitine palmitoyl transferase 1α (CPT1α), were downregulated, while acetyl-CoA carboxylase 2 (ACC2) was upregulated under a combination of hypoxia and obesity. WY14643 upregulated PPARα, PGC1α, and CPT1α, and downregulated ACC2. WY14643 alleviated hypoxia- and obesity-induced myocardial lipid accumulation and improved mitochondrial and left ventricular systolic functions.

SIGNIFICANCE

WY14643 improved myocardial mitochondrial and left ventricular systolic functions in obese rats under chronic persistent hypoxia. Thus, WY14643 possibly exerts its effects by regulating the PPARα pathway and shows potential as a therapeutic target for cardiovascular diseases associated with obesity and hypoxia.

Thiopental sodium loaded solid lipid nano-particles attenuates obesity-induced cardiac dysfunction and cardiac hypertrophy via inactivation of inflammatory pathway

This work evaluates solid lipid nanoparticles of thiopental sodium against obesity-induced cardiac dysfunction and hypertrophy and explores the possible mechanism of action. TS loaded SLNs were formulated by hot-homogenization and solvent diffusion method. TS-SLNs were scrutinized for entrapment efficiency, drug loading capacity, gastric stability, particle size, in vitro drug release. Mice were feed with the normal chow or high-fat diet for 08 weeks to induce obesity and primary cardiomyocytes. The therapeutic effects of thiopental sodium in the high fat diet (HFD) induced cardiac hypertrophy. Systolic blood pressure (SBP) was estimated at a regular time interval. At the end of the experimental study, systolic pressure left ventricular, LV end-diastolic pressure and rate of increase of LV pressure and antioxidant, apoptosis, cytokines and inflammatory scrutinized. HFD induced group mice exhibited a reduction in the body weight and enhancement of cardiac hypertrophy marker and dose-dependent treatment of thiopental sodium up-regulation the body weight and down-regulated the cardiac hypertrophy. Thiopental sodium significantly (p < .001) dose-dependently altered the antioxidant, biochemical, cardiac parameters and remodeling. Thiopental sodium significantly (p < .001) dose-dependently reduced the SBP. Thiopental sodium altered the apoptosis marker, pro-inflammatory cytokines, inflammatory parameters along with reduced the p38-MAPK level. The cardiac protective effect of thiopental sodium shed light on future therapeutic interventions in obesity and related cardiovascular complications via inflammatory pathway.

The role of CD36 in cardiovascular disease

CD36, also known as the scavenger receptor B2, is a multifunctional receptor widely expressed in various organs. CD36 plays a crucial role in the uptake of long-chain fatty acids, the main metabolic substrate in myocardial tissue. The maturation and transportation of CD36 is regulated by post-translational modifications, including phosphorylation, ubiquitination, glycosylation, and palmitoylation. CD36 is decreased in pathological cardiac hypertrophy caused by ischaemia-reperfusion and pressure overload, and increased in diabetic cardiomyopathy and atherosclerosis. Deficiency of CD36 alleviates diabetic cardiomyopathy and atherosclerosis, while overexpression of CD36 eliminates ischaemia-reperfusion damage, together suggesting that CD36 is closely associated with the progression of cardiovascular diseases and may be a new therapeutic target. This review summarizes the regulation and post-translational modifications of CD36 and evaluates its role in cardiovascular diseases and its potential as a therapeutic target.

tRNA-Derived Small RNAs and Their Potential Roles in Cardiac Hypertrophy

Transfer RNAs (tRNAs) are abundantly expressed, small non-coding RNAs that have long been recognized as essential components of the protein translation machinery. The tRNA-derived small RNAs (tsRNAs), including tRNA halves (tiRNAs), and tRNA fragments (tRFs), were unexpectedly discovered and have been implicated in a variety of important biological functions such as cell proliferation, cell differentiation, and apoptosis. Mechanistically, tsRNAs regulate mRNA destabilization and translation, as well as retro-element reverse transcriptional and post-transcriptional processes. Emerging evidence has shown that tsRNAs are expressed in the heart, and their expression can be induced by pathological stress, such as hypertrophy. Interestingly, cardiac pathophysiological conditions, such as oxidative stress, aging, and metabolic disorders can be viewed as inducers of tsRNA biogenesis, which further highlights the potential involvement of tsRNAs in these conditions. There is increasing enthusiasm for investigating the molecular and biological functions of tsRNAs in the heart and their role in cardiovascular disease. It is anticipated that this new class of small non-coding RNAs will offer new perspectives in understanding disease mechanisms and may provide new therapeutic targets to treat cardiovascular disease.

Exercise training delays cardiac remodeling in a mouse model of cancer cachexia

AIMS

We aimed to investigate the impact of cancer cachexia and previous aerobic exercise training (AET) on cardiac function and structure in tumor bearing mice.

MAIN METHODS

Colon adenocarcinoma cells 26 (CT26) were subcutaneously injected in BALB/c mice to establish robust cancer cachexia model. AET was performed on a treadmill during 45 days, 60 min/5 days per week. Cardiac function was evaluated by echocardiography and cardiac morphology was assessed by light microscopy. The protein expression levels of mitochondrial complex were analyzed by Western blotting. The mRNA levels of genes related to cardiac remodeling and autophagy were analyzed by quantitative Real-Time PCR.

KEY FINDINGS

Our data confirms CT26 tumor bearing mice as a well-characterized and robust model of cancer cachexia. CT26 mice exhibited cardiac remodeling and dysfunction characterized by cardiac atrophy and impaired left ventricle ejection fraction paralleled by cardiac necrosis, inflammation and fibrosis. AET partially reversed the left ventricle ejection fraction and led to significant anti-cardiac remodeling effect associated reduced necrosis, inflammation and cardiac collagen deposition in CT26 mice. Reduced TGF-β1 mRNA levels, increased mitochondrial complex IV protein levels and partial recovery of BNIP3 mRNA levels in cardiac tissue were associated with the cardiac effects of AET in CT26 mice. Thus, we suggest AET as a powerful regulator of key pathways involved in cardiac tissue homeostasis in cancer cachexia.

SIGNIFICANCE

Our study provides a robust model of cancer cachexia, as well as highlights the potential and integrative effects of AET as a preventive strategy for reducing cardiac damage in cancer cachexia.

Energy Metabolism in Exercise-Induced Physiologic Cardiac Hypertrophy

Physiologic hypertrophy of the heart preserves or enhances systolic function without interstitial fibrosis or cell death. As a unique form of physiological stress, regular exercise training can trigger the adaptation of cardiac muscle to cause physiological hypertrophy, partly due to its ability to improve cardiac metabolism. In heart failure (HF), cardiac dysfunction is closely associated with early initiation of maladaptive metabolic remodeling. A large amount of clinical and experimental evidence shows that metabolic homeostasis plays an important role in exercise training, which is conducive to the treatment and recovery of cardiovascular diseases. Potential mechanistic targets for modulation of cardiac metabolism have become a hot topic at present. Thus, exploring the energy metabolism mechanism in exercise-induced physiologic cardiac hypertrophy may produce new therapeutic targets, which will be helpful to design novel effective strategies. In this review, we summarize the changes of myocardial metabolism (fatty acid metabolism, carbohydrate metabolism, and mitochondrial adaptation), metabolically-related signaling molecules, and probable regulatory mechanism of energy metabolism during exercise-induced physiological cardiac hypertrophy.

Cardiomyocyte Proteome Remodeling due to Isoproterenol-Induced Cardiac Hypertrophy during the Compensated Phase

PURPOSE

Although the pathophysiological response of cardiac tissue to pro-hypertrophic stimulus is well characterized, a comprehensive characterization of the molecular events underlying the pathological hypertrophy in cardiomyocytes during the early compensated cardiac hypertrophy is currently lacking.

EXPERIMENTAL DESIGN

A quantitative label-free proteomic analysis of cardiomyocytes isolated was conducted from mice treated subcutaneously with isoproterenol (ISO) during 7 days in comparison with cardiomyocytes from control animals (CT).

RESULTS

Canonical pathway analysis of dysregulated proteins indicated that ISO-hypertrophy drives the activation of actin cytoskeleton and integrin-linked kinase (ILK) signaling, and inhibition of the sirtuin signaling. Alteration in cardiac contractile function and calcium signaling are predicted as downstream effects of ISO-hypertrophy probably due to the upregulation of key elements such as myosin-7 (MYH7). Confocal microscopy corroborated that indeed ISO-treatment led to increased abundance of MYH7. Potential early markers for cardiac hypertrophy as APBB1, GOLGA4, HOOK1, KATNA1, KIFBP, MAN2B2, and SLC16A1 are also reported.

CONCLUSIONS AND CLINICAL RELEVANCE

The data consist in a complete molecular mapping of ISO-induced compensated cardiac hypertrophy model at cardiomyocyte level. Marker candidates reported may assist early diagnosis of cardiac hypertrophy and ultimately heart failure.

MicroRNA-27 attenuates pressure overload-Induced cardiac hypertrophy and dysfunction by targeting galectin-3

Cardiac hypertrophy is an adaptive response to hemodynamic stress to compensate for cardiac dysfunction. MicroRNAs can regulate cardiac function and play a vital role in the regulation of cardiac hypertrophy. In the current study, in vivo and vitro hypertrophy models are established to explore the role of miR-27b and to elucidate the underlying mechanism in cardiac hypertrophy. Expression of miR-27b was down-regulated in mice with cardiac hypertrophy. The cardiac function of the mice with cardiac hypertrophy could be restored with the overexpression of miR-27b, this is observed in terms of decreasing LVEDd, LVESd, and increasing LVFS, LVEF. This study also predicted and confirmed that galectin-3 is a target gene of miR-27b. Depletion of galectin-3 significantly attenuated hypertrophy of hearts in both in vitro and in vivo tests. In conclusion, MiR-27b be used to exert a protective role against cardiac dysfunction and hypertrophy by decreasing the expression level of galectin-3. The methodology suggested in this study provides a novel therapeutic strategy against cardiac hypertrophy.

Re-balancing cellular energy substrate metabolism to mend the failing heart

Fatty acids and glucose are the main substrates for myocardial energy provision. Under physiologic conditions, there is a distinct and finely tuned balance between the utilization of these substrates. Using the non-ischemic heart as an example, we discuss that upon stress this substrate balance is upset resulting in an over-reliance on either fatty acids or glucose, and that chronic fuel shifts towards a single type of substrate appear to be linked with cardiac dysfunction. These observations suggest that interventions aimed at re-balancing a tilted substrate preference towards an appropriate mix of substrates may result in restoration of cardiac contractile performance. Examples of manipulating cellular substrate uptake as a means to re-balance fuel supply, being associated with mended cardiac function underscore this concept. We also address the molecular mechanisms underlying the apparent need for a fatty acid-glucose fuel balance. We propose that re-balancing cellular fuel supply, in particular with respect to fatty acids and glucose, may be an effective strategy to treat the failing heart.

Metabolism, Epigenetics, and Causal Inference in Heart Failure

Eukaryotes must balance the metabolic and cell death actions of mitochondria via control of gene expression and cell fate by chromatin, thereby functionally binding the metabolome and epigenome. This interaction has far-reaching implications for chronic diseases in humans, the most common of which are those of the cardiovascular system. The most devastating consequence of cardiovascular disease, heart failure, is not a single disease, diagnosis, or endpoint. Human and animal studies have revealed that, regardless of etiology and symptoms, heart failure is universally associated with abnormal metabolism and gene expression - to frame this as cause or consequence, however, may be to wrongfoot the question. This essay aims to challenge current thinking on metabolic-epigenetic crosstalk in heart failure, presenting hypotheses for how chronic diseases arise, take hold, and persist. We unpack assumptions about the order of operations for gene expression and metabolism, exploring recent findings in noncardiac systems that link metabolic intermediates directly to chromatin remodeling. Lastly, we discuss potential mechanisms by which chromatin may serve as a substrate for metabolic memory, and how changes in cellular transcriptomes (and hence in cellular behavior) in response to stress correspond to global changes in chromatin accessibility and structure.

Cardiac ketone body metabolism

The ketone bodies, d-β-hydroxybutyrate and acetoacetate, are soluble 4-carbon compounds derived principally from fatty acids, that can be metabolised by many oxidative tissues, including heart, in carbohydrate-depleted conditions as glucose-sparing energy substrates. They also have important signalling functions, acting through G-protein coupled receptors and histone deacetylases to regulate metabolism and gene expression including that associated with anti-oxidant activity. Their concentration, and hence availability, increases in diabetes mellitus and heart failure. Whilst known to be substrates for ATP production, especially in starvation, their role(s) in the heart, and in heart disease, is uncertain. Recent evidence, reviewed here, indicates that increased ketone body metabolism is a feature of heart failure, and is accompanied by other changes in substrate selection. Whether the change in myocardial ketone body metabolism is adaptive or maladaptive is unknown, but it offers the possibility of using exogenous ketones to treat the failing heart.