Mitochondrial energy metabolism in heart failure: a question of balance

SIRT6 in Regulation of Mitochondrial Damage and Associated Cardiac Dysfunctions: A Possible Therapeutic Target for CVDs

Cardiovascular diseases (CVDs) can be described as a global health emergency imploring possible prevention strategies. Although the pathogenesis of CVDs has been extensively studied, the role of mitochondrial dysfunction in CVD development has yet to be investigated. Diabetic cardiomyopathy, ischemic-reperfusion injury, and heart failure are some of the CVDs resulting from mitochondrial dysfunction Recent evidence from the research states that any dysfunction of mitochondria has an impact on metabolic alteration, eventually causes the death of a healthy cell and therefore, progressively directing to the predisposition of disease. Cardiovascular research investigating the targets that both protect and treat mitochondrial damage will help reduce the risk and increase the quality of life of patients suffering from various CVDs. One such target, i.e., nuclear sirtuin SIRT6 is strongly associated with cardiac function. However, the link between mitochondrial dysfunction and SIRT6 concerning cardiovascular pathologies remains poorly understood. Although the Role of SIRT6 in skeletal muscles and cardiomyocytes through mitochondrial regulation has been well understood, its specific role in mitochondrial maintenance in cardiomyocytes is poorly determined. The review aims to explore the domain-specific function of SIRT6 in cardiomyocytes and is an effort to know how SIRT6, mitochondria, and CVDs are related.

Senegenin Attenuates Pulmonary Fibrosis by Inhibiting Oxidative-Stress-Induced Epithelial Cell Senescence through Activation of the Sirt1/Pgc-1α Signaling Pathway

Idiopathic pulmonary fibrosis is a fatal interstitial lung disease for which effective drug therapies are lacking. Senegenin, an effective active compound from the traditional Chinese herb Polygala tenuifolia Willd, has been shown to have a wide range of pharmacological effects. In this study, we investigated the therapeutic effects of senegenin on pulmonary fibrosis and their associated mechanisms of action. We found that senegenin inhibited the senescence of epithelial cells and thus exerted anti-pulmonary-fibrosis effects by inhibiting oxidative stress. In addition, we found that senegenin promoted the expression of Sirt1 and Pgc-1α and that the antioxidative and antisenescent effects of senegenin were suppressed by specific silencing of the Sirt1 and Pgc-1α genes, respectively. Moreover, the senegenin-induced effects of antioxidation, antisenescence of epithelial cells, and antifibrosis were inhibited by treatment with Sirt1 inhibitors in vivo. Thus, the Sirt1/Pgc-1α pathway exerts its antifibrotic effect on lung fibrosis by mediating the antioxidative and antisenescent effects of senegenin.

Pathological Changes and Metabolic Adaptation in the Myocardium of Rats in Response to Chronic Variable Mild Stress

Chronic variable mild stress (CVS) in rats is a well-established paradigm for inducing depressive-like behaviors and has been utilized extensively to explore potential therapeutic interventions for depression. While the behavioral and neurobiological effects of CVS have been extensively studied, its impact on myocardial function remains largely unexplored. To induce the CVS model, rats were exposed to various stressors over 40 days. Behavioral assessments confirmed depressive-like behavior. Biochemical analyses revealed alterations in myocardial metabolism, including changes in NAD+ and NADP+, and NADPH concentrations. Free amino acid analysis indicated disturbances in myocardial amino acid metabolism. Evaluation of oxidative DNA damage demonstrated an increased number of abasic sites in the DNA of rats exposed to CVS. Molecular analysis showed significant changes in gene expression associated with glucose metabolism, oxidative stress, and cardiac remodeling pathways. Histological staining revealed minor morphological changes in the myocardium of CVS-exposed rats, including increased acidophilicity of cells, collagen deposition surrounding blood vessels, and glycogen accumulation. This study provides novel insights into the impact of chronic stress on myocardial function and metabolism, highlighting potential mechanisms linking depression and cardiovascular diseases. Understanding these mechanisms may aid in the development of targeted therapeutic strategies to mitigate the adverse cardiovascular effects of depression.

Pathophysiology and Advances in the Therapy of Cardiomyopathy in Patients with Diabetes Mellitus

Diabetes mellitus (DM) is known as the first non-communicable global epidemic. It is estimated that 537 million people have DM, but the condition has been properly diagnosed in less than half of these patients. Despite numerous preventive measures, the number of DM cases is steadily increasing. The state of chronic hyperglycaemia in the body leads to numerous complications, including diabetic cardiomyopathy (DCM). A number of pathophysiological mechanisms are behind the development and progression of cardiomyopathy, including increased oxidative stress, chronic inflammation, increased synthesis of advanced glycation products and overexpression of the biosynthetic pathway of certain compounds, such as hexosamine. There is extensive research on the treatment of DCM, and there are a number of therapies that can stop the development of this complication. Among the compounds used to treat DCM are antiglycaemic drugs, hypoglycaemic drugs and drugs used to treat myocardial failure. An important element in combating DCM that should be kept in mind is a healthy lifestyle-a well-balanced diet and physical activity. There is also a group of compounds-including coenzyme Q10, antioxidants and modulators of signalling pathways and inflammatory processes, among others-that are being researched continuously, and their introduction into routine therapies is likely to result in greater control and more effective treatment of DM in the future. This paper summarises the latest recommendations for lifestyle and pharmacological treatment of cardiomyopathy in patients with DM.

Charge-Reversal NaCl/G-Quartets for Aggregation-Induced Mitochondrial MicroRNA Imaging and Ion-Interference Therapy

Mitochondrial therapy is a promising new strategy that offers the potential to achieve precise disease diagnosis or maximum therapeutic response. However, versatile mitochondrial theranostic platforms that integrate biomarker detection and therapy have rarely been exploited. Here, we report a charge-reversal nanomedicine activated by an acidic microenvironment for mitochondrial microRNA (mitomiR) detection and ion-interference therapy. The transporter liposome (DD-DC) was constructed from a pH-responsive polymer and a positively charged phospholipid, encapsulating NaCl nanoparticles with coloading of the aggregation-induced emission (AIE) fluorogens AIEgen-DNA/G-quadruplexes precursor and brequinar (NAB@DD-DC). The negatively charged nanomedicine ensured good blood stability and high tumor accumulation, while the charge-reversal to positive in response to the acidic pH in the tumor microenvironment (TME) and lysosomes enhanced the uptake by tumor cells and lysosome escape, achieving accumulation in mitochondria. The subsequently released Na+ in mitochondria not only contributed to the formation of mitomiR-494 induced G-quadruplexes for AIE imaging diagnosis but also led to an osmolarity surge that was enhanced by brequinar to achieve effective ion-interference therapy.

Uncovering the link between diabetes and cardiovascular diseases: insights from adipose-derived stem cells

Cardiovascular diseases (CVDs) are the leading causes of morbidity and mortality worldwide. The escalating global occurrence of obesity and diabetes mellitus (DM) has led to a significant upsurge in individuals afflicted with CVDs. As the prevalence of CVDs continues to rise, it is becoming increasingly important to identify the underlying cellular and molecular mechanisms that contribute to their development and progression, which will help discover novel therapeutic avenues. Adipose tissue (AT) is a connective tissue that plays a crucial role in maintaining lipid and glucose homeostasis. However, when AT is exposed to diseased conditions, such as DM, this tissue will alter its phenotype to become dysfunctional. AT is now recognized as a critical contributor to CVDs, especially in patients with DM. AT is comprised of a heterogeneous cellular population, which includes adipose-derived stem cells (ADSCs). ADSCs resident in AT are believed to regulate physiological cardiac function and have potential cardioprotective roles. However, recent studies have also shown that ADSCs from various adipose tissue depots become pro-apoptotic, pro-inflammatory, less angiogenic, and lose their ability to differentiate into various cell lineages upon exposure to diabetic conditions. This review aims to summarize the current understanding of the physiological roles of ADSCs, the impact of DM on ADSC phenotypic changes, and how these alterations may contribute to the pathogenesis of CVDs.

From Beats to Metabolism: the Heart at the Core of Interorgan Metabolic Cross Talk

The heart, once considered a mere blood pump, is now recognized as a multifunctional metabolic and endocrine organ. Its function is tightly regulated by various metabolic processes, at the same time it serves as an endocrine organ, secreting bioactive molecules that impact systemic metabolism. In recent years, research has shed light on the intricate interplay between the heart and other metabolic organs, such as adipose tissue, liver, and skeletal muscle. The metabolic flexibility of the heart and its ability to switch between different energy substrates play a crucial role in maintaining cardiac function and overall metabolic homeostasis. Gaining a comprehensive understanding of how metabolic disorders disrupt cardiac metabolism is crucial, as it plays a pivotal role in the development and progression of cardiac diseases. The emerging understanding of the heart as a metabolic and endocrine organ highlights its essential contribution to whole body metabolic regulation and offers new insights into the pathogenesis of metabolic diseases, such as obesity, diabetes, and cardiovascular disorders. In this review, we provide an in-depth exploration of the heart's metabolic and endocrine functions, emphasizing its role in systemic metabolism and the interplay between the heart and other metabolic organs. Furthermore, emerging evidence suggests a correlation between heart disease and other conditions such as aging and cancer, indicating that the metabolic dysfunction observed in these conditions may share common underlying mechanisms. By unraveling the complex mechanisms underlying cardiac metabolism, we aim to contribute to the development of novel therapeutic strategies for metabolic diseases and improve overall cardiovascular health.

Mitochondrial density in skeletal and cardiac muscle

Kubat et al. provide a review on the role Mitochondrial density in skeletal and cardiac muscle of mitochondrial dysfunction in muscle atrophy. They stress mitochondria's pivotal function, citing a 52 % density in skeletal muscle. However, the reference to Park et al.'s work misinterprets their findings. Park et al. report citrate synthase (CS) activity, indicating mitochondrial density as 222 ± 13 μmol.min-1.mg-1 for cardiac muscle and 115 ± 2 μmol.min-1.mg-1 for skeletal muscle. Thus, the authors should clarify that skeletal muscle density is approximately 52 % of cardiac muscle, not an absolute 52 %. Mitochondrial volume density assessment, predominantly through TEM, establishes cardiomyocytes at 25-30 % and untrained skeletal muscle at 2-6 %, increasing to 11 % in trained athletes. However, this remains modest compared to myofibrils' 75 %-85 % of muscle fiber volume. Although the utility of CS activity is evident, TEM and other novel approaches such as three-dimensional focused ion beam scanning electron microscopy are likely superior for assessing mitochondrial volume density and morphology.

Exposure of the inner mitochondrial membrane triggers apoptotic mitophagy

During apoptosis mediated by the intrinsic pathway, BAX/BAK triggers mitochondrial permeabilization and the release of cytochrome-c, followed by a dramatic remodelling of the mitochondrial network that results in mitochondrial herniation and the subsequent release of pro-inflammatory mitochondrial components. Here, we show that mitochondrial herniation and subsequent exposure of the inner mitochondrial membrane (IMM) to the cytoplasm, initiates a unique form of mitophagy to deliver these damaged organelles to lysosomes. IMM-induced mitophagy occurs independently of canonical PINK1/Parkin signalling and is driven by ubiquitination of the IMM. Our data suggest IMM-induced mitophagy is an additional safety mechanism that cells can deploy to contain damaged mitochondria. It may have particular relevance in situations where caspase activation is incomplete or inhibited, and in contexts where PINK1/Parkin-mitophagy is impaired or overwhelmed.

Metabolic remodeling in cardiac hypertrophy and heart failure with reduced ejection fraction occurs independent of transcription factor EB in mice

Background

A metabolic shift from fatty acid (FAO) to glucose oxidation (GO) occurs during cardiac hypertrophy (LVH) and heart failure with reduced ejection fraction (HFrEF), which is mediated by PGC-1α and PPARα. While the transcription factor EB (TFEB) regulates the expression of both PPARGC1A/PGC-1α and PPARA/PPARα, its contribution to metabolic remodeling is uncertain.

Methods

Luciferase assays were performed to verify that TFEB regulates PPARGC1A expression. Cardiomyocyte-specific Tfeb knockout (cKO) and wildtype (WT) male mice were subjected to 27G transverse aortic constriction or sham surgery for 21 and 56 days, respectively, to induce LVH and HFrEF. Echocardiographic, morphological, and histological analyses were performed. Changes in markers of cardiac stress and remodeling, metabolic shift and oxidative phosphorylation were investigated by Western blot analyses, mass spectrometry, qRT-PCR, and citrate synthase and complex II activity measurements.

Results

Luciferase assays revealed that TFEB increases PPARGC1A/PGC-1α expression, which was inhibited by class IIa histone deacetylases and derepressed by protein kinase D. At baseline, cKO mice exhibited a reduced cardiac function, elevated stress markers and a decrease in FAO and GO gene expression compared to WT mice. LVH resulted in increased cardiac remodeling and a decreased expression of FAO and GO genes, but a comparable decline in cardiac function in cKO compared to WT mice. In HFrEF, cKO mice showed an improved cardiac function, lower heart weights, smaller myocytes and a reduction in cardiac remodeling compared to WT mice. Proteomic analysis revealed a comparable decrease in FAO- and increase in GO-related proteins in both genotypes. A significant reduction in mitochondrial quality control genes and a decreased citrate synthase and complex II activities was observed in hearts of WT but not cKO HFrEF mice.

Conclusions

TFEB affects the baseline expression of metabolic and mitochondrial quality control genes in the heart, but has only minor effects on the metabolic shift in LVH and HFrEF in mice. Deletion of TFEB plays a protective role in HFrEF but does not affect the course of LVH. Further studies are needed to elucidate if TFEB affects the metabolic flux in stressed cardiomyocytes.

Improved integration of single-cell transcriptome data demonstrates common and unique signatures of heart failure in mice and humans

BACKGROUND

Cardiovascular research heavily relies on mouse (Mus musculus) models to study disease mechanisms and to test novel biomarkers and medications. Yet, applying these results to patients remains a major challenge and often results in noneffective drugs. Therefore, it is an open challenge of translational science to develop models with high similarities and predictive value. This requires a comparison of disease models in mice with diseased tissue derived from humans.

RESULTS

To compare the transcriptional signatures at single-cell resolution, we implemented an integration pipeline called OrthoIntegrate, which uniquely assigns orthologs and therewith merges single-cell RNA sequencing (scRNA-seq) RNA of different species. The pipeline has been designed to be as easy to use and is fully integrable in the standard Seurat workflow.We applied OrthoIntegrate on scRNA-seq from cardiac tissue of heart failure patients with reduced ejection fraction (HFrEF) and scRNA-seq from the mice after chronic infarction, which is a commonly used mouse model to mimic HFrEF. We discovered shared and distinct regulatory pathways between human HFrEF patients and the corresponding mouse model. Overall, 54% of genes were commonly regulated, including major changes in cardiomyocyte energy metabolism. However, several regulatory pathways (e.g., angiogenesis) were specifically regulated in humans.

CONCLUSIONS

The demonstration of unique pathways occurring in humans indicates limitations on the comparability between mice models and human HFrEF and shows that results from the mice model should be validated carefully. OrthoIntegrate is publicly accessible (https://github.com/MarianoRuzJurado/OrthoIntegrate) and can be used to integrate other large datasets to provide a general comparison of models with patient data.

Complex II ambiguities-FADH2 in the electron transfer system

The prevailing notion that reduced cofactors NADH and FADH2 transfer electrons from the tricarboxylic acid cycle to the mitochondrial electron transfer system creates ambiguities regarding respiratory Complex II (CII). CII is the only membrane-bound enzyme in the tricarboxylic acid cycle and is part of the electron transfer system of the mitochondrial inner membrane feeding electrons into the coenzyme Q-junction. The succinate dehydrogenase subunit SDHA of CII oxidizes succinate and reduces the covalently bound prosthetic group FAD to FADH2 in the canonical forward tricarboxylic acid cycle. However, several graphical representations of the electron transfer system depict FADH2 in the mitochondrial matrix as a substrate to be oxidized by CII. This leads to the false conclusion that FADH2 from the β-oxidation cycle in fatty acid oxidation feeds electrons into CII. In reality, dehydrogenases of fatty acid oxidation channel electrons to the Q-junction but not through CII. The ambiguities surrounding Complex II in the literature and educational resources call for quality control, to secure scientific standards in current communications of bioenergetics, and ultimately support adequate clinical applications. This review aims to raise awareness of the inherent ambiguity crisis, complementing efforts to address the well-acknowledged issues of credibility and reproducibility.

Revisiting Skeletal Muscle Dysfunction and Exercise in Chronic Obstructive Pulmonary Disease: Emerging Significance of Myokines

Skeletal muscle dysfunction (SMD) is the most significant extrapulmonary complication and an independent prognostic indicator in patients with chronic obstructive pulmonary disease (COPD). Myokines, such as interleukin (IL)-6, IL-15, myostatin, irisin, and insulin-like growth factor (IGF)-1, play important roles in skeletal muscle mitochondrial function, protein synthesis and breakdown balance, and regeneration of skeletal muscles in COPD. As the main component of pulmonary rehabilitation, exercise can improve muscle strength, muscle endurance, and exercise capacity in patients with COPD, as well as improve the prognosis of SMD and COPD by regulating the expression levels of myokines. The mechanisms by which exercise regulates myokine levels are related to microRNAs. IGF-1 expression is upregulated by decreasing the expression of miR-1 or miR-29b. Myostatin downregulation and irisin upregulation are associated with increased miR-27a expression and decreased miR-696 expression, respectively. These findings suggest that myokines are potential targets for the prevention and treatment of SMD in COPD. A comprehensive analysis of the role and regulatory mechanisms of myokines can facilitate the development of new exercise-based therapeutic approaches for patients with COPD.

Keeping the Heart Healthy: The Role of Exercise in Cardiac Repair and Regeneration

Significance: Heart failure is often accompanied by a decrease in the number of cardiomyocytes. Although the adult mammalian hearts have limited regenerative capacity, the rate of regeneration is extremely low and decreases with age. Exercise is an effective means to improve cardiovascular function and prevent cardiovascular diseases. However, the molecular mechanisms of how exercise acts on cardiomyocytes are still not fully elucidated. Therefore, it is important to explore the role of exercise in cardiomyocytes and cardiac regeneration. Recent Advances: Recent advances have shown that the effects of exercise on cardiomyocytes are critical for cardiac repair and regeneration. Exercise can induce cardiomyocyte growth by increasing the size and number. It can induce physiological cardiomyocyte hypertrophy, inhibit cardiomyocyte apoptosis, and promote cardiomyocyte proliferation. In this review, we have discussed the molecular mechanisms and recent studies of exercise-induced cardiac regeneration, with a focus on its effects on cardiomyocytes. Critical Issues: There is no effective way to promote cardiac regeneration. Moderate exercise can keep the heart healthy by encouraging adult cardiomyocytes to survive and regenerate. Therefore, exercise could be a promising tool for stimulating the regenerative capability of the heart and keeping the heart healthy. Future Directions: Although exercise is an important measure to promote cardiomyocyte growth and subsequent cardiac regeneration, more studies are needed on how to do beneficial exercise and what factors are involved in cardiac repair and regeneration. Thus, it is important to clarify the mechanisms, pathways, and other critical factors involved in the exercise-mediated cardiac repair and regeneration. Antioxid. Redox Signal. 39, 1088-1107.

Inhibition of OAT1/3 and CMPF uptake attenuates myocardial ischemia-induced chronic heart failure via decreasing fatty acid oxidation and the therapeutic effects of ruscogenin

Chronic heart failure (CHF) as a long-term disease is highly prevalent in elder people worldwide. Early diagnosis and treatments are crucial for preventing the development of CHF. Herein, we aimed to identify novel diagnostic biomarker, therapeutic target and drug for CHF. Untargeted metabolomic analysis has been used to characterize the different metabolomic profile between CHF patients and healthy people. Meanwhile, the targeted metabolomic study demonstrated the elevation of 3-carboxy-4-methyl-5-propyl-2-furanpropanoic acid (CMPF) in the serum of CHF patients and coronary artery ligation-induced CHF mice. Subsequently, we firstly observed that elevation of CMPF impaired cardiac function and aggravated myocardial injury by enhancing fatty acid oxidation (FAO). Interestingly, inhibition of responsible transporters organic anion transporter 1/3 (OAT1/3) has been found to decrease the CMPF level, and suppress FAO-related key protein expressions including peroxisome proliferator-activated receptor alpha, peroxisome proliferative activated receptor-α, carnitine palmitoyl transferase 1, and malonyl CoA decarboxylase in coronary artery ligation-induced CHF mice. Meanwhile, the inhibitor of OAT1/3 presented an excellent improvement in cardiac function and histological injury. Based on the above findings, molecular docking was adopted to screen the potential therapeutic drug targeting OAT1/3, and ruscogenin (RUS) exhibited a great binding affinity with OAT1 and OAT3. Next, it was verified that RUS could remarkedly decrease the expression of OAT1/3 and CMPF levels in heart tissue of CHF mice, as well as suppress the expression of FAO-related proteins. What's more, RUS can effectively improve cardiac function, myocardial fibrosis and morphological damage. Collectively, this study provided a potential metabolic marker CMPF and novel target OAT1/3 for CHF, which were demonstrated to be involved in FAO. And RUS was identified as a potential anti-FAO drug for CHF by regulating OAT1/3.

Clinical Approaches for Mitochondrial Diseases

Mitochondria are subcontractors dedicated to energy production within cells. In human mitochondria, almost all mitochondrial proteins originate from the nucleus, except for 13 subunit proteins that make up the crucial system required to perform 'oxidative phosphorylation (OX PHOS)', which are expressed by the mitochondria's self-contained DNA. Mitochondrial DNA (mtDNA) also encodes 2 rRNA and 22 tRNA species. Mitochondrial DNA replicates almost autonomously, independent of the nucleus, and its heredity follows a non-Mendelian pattern, exclusively passing from mother to children. Numerous studies have identified mtDNA mutation-related genetic diseases. The consequences of various types of mtDNA mutations, including insertions, deletions, and single base-pair mutations, are studied to reveal their relationship to mitochondrial diseases. Most mitochondrial diseases exhibit fatal symptoms, leading to ongoing therapeutic research with diverse approaches such as stimulating the defective OXPHOS system, mitochondrial replacement, and allotropic expression of defective enzymes. This review provides detailed information on two topics: (1) mitochondrial diseases caused by mtDNA mutations, and (2) the mechanisms of current treatments for mitochondrial diseases and clinical trials.

Epigenetics in Heart Failure: Role of DNA Methylation in Potential Pathways Leading to Heart Failure with Preserved Ejection Fraction

This review will focus on epigenetic modifications utilizing the DNA methylation mechanism, which is potentially involved in the pathogenesis of heart failure with preserved ejection fraction (HFpEF). The putative pathways of HFpEF will be discussed, specifically myocardial fibrosis, myocardial inflammation, sarcoplasmic reticulum Ca2+-ATPase, oxidative-nitrosative stress, mitochondrial and metabolic defects, as well as obesity. The relationship of HFpEF to aging and atrial fibrillation will be examined from the perspective of DNA methylation.

Metabolic switch from fatty acid oxidation to glycolysis in knock-in mouse model of Barth syndrome

Mitochondria are central for cellular metabolism and energy supply. Barth syndrome (BTHS) is a severe disorder, due to dysfunction of the mitochondrial cardiolipin acyl transferase tafazzin. Altered cardiolipin remodeling affects mitochondrial inner membrane organization and function of membrane proteins such as transporters and the oxidative phosphorylation (OXPHOS) system. Here, we describe a mouse model that carries a G197V exchange in tafazzin, corresponding to BTHS patients. TAZG197V mice recapitulate disease-specific pathology including cardiac dysfunction and reduced oxidative phosphorylation. We show that mutant mitochondria display defective fatty acid-driven oxidative phosphorylation due to reduced levels of carnitine palmitoyl transferases. A metabolic switch in ATP production from OXPHOS to glycolysis is apparent in mouse heart and patient iPSC cell-derived cardiomyocytes. An increase in glycolytic ATP production inactivates AMPK causing altered metabolic signaling in TAZG197V . Treatment of mutant cells with AMPK activator reestablishes fatty acid-driven OXPHOS and protects mice against cardiac dysfunction.

Loss of Ptpmt1 limits mitochondrial utilization of carbohydrates and leads to muscle atrophy and heart failure in tissue-specific knockout mice

While mitochondria in different tissues have distinct preferences for energy sources, they are flexible in utilizing competing substrates for metabolism according to physiological and nutritional circumstances. However, the regulatory mechanisms and significance of metabolic flexibility are not completely understood. Here, we report that the deletion of Ptpmt1, a mitochondria-based phosphatase, critically alters mitochondrial fuel selection - the utilization of pyruvate, a key mitochondrial substrate derived from glucose (the major simple carbohydrate), is inhibited, whereas the fatty acid utilization is enhanced. Ptpmt1 knockout does not impact the development of the skeletal muscle or heart. However, the metabolic inflexibility ultimately leads to muscular atrophy, heart failure, and sudden death. Mechanistic analyses reveal that the prolonged substrate shift from carbohydrates to lipids causes oxidative stress and mitochondrial destruction, which in turn results in marked accumulation of lipids and profound damage in the knockout muscle cells and cardiomyocytes. Interestingly, Ptpmt1 deletion from the liver or adipose tissue does not generate any local or systemic defects. These findings suggest that Ptpmt1 plays an important role in maintaining mitochondrial flexibility and that their balanced utilization of carbohydrates and lipids is essential for both the skeletal muscle and the heart despite the two tissues having different preferred energy sources.

Dynamic defence? Intertidal triplefin species show better maintenance of mitochondrial membrane potential than subtidal species at low oxygen pressures

Oxygen is essential for most eukaryotic lifeforms, as it supports mitochondrial oxidative phosphorylation to supply ∼90% of cellular adenosine triphosphate (ATP). Fluctuations in O2 present a major stressor, with hypoxia leading to a cascade of detrimental physiological changes that alter cell operations and ultimately induce death. Nonetheless, some species episodically tolerate near-anoxic environments, and have evolved mechanisms to sustain function even during extended hypoxic periods. While mitochondria are pivotal in central metabolism, their role in hypoxia tolerance remains ill defined. Given the vulnerability of the brain to hypoxia, mitochondrial function was tested in brain homogenates of three closely related triplefin species with varying degrees of hypoxia tolerance (Bellapiscis medius, Forsterygion lapillum and Forsterygion varium). High-resolution respirometry coupled with fluorometric measurements of mitochondrial membrane potential (mtMP) permitted assessment of differences in mitochondrial function and integrity in response to intermittent hypoxia and anoxia. Traditional steady-state measures of respiratory flux and mtMP showed no differences among species. However, in the transition into anoxia, the tolerant species B. medius and F. lapillum maintained mtMP at O2 pressures 7- and 4.4-fold lower, respectively, than that of the hypoxia-sensitive F. varium and exhibited slower rates of membrane depolarisation. The results indicate that dynamic oxic-hypoxic mitochondria transitions underlie hypoxia tolerance in these intertidal fish.

Improving mitochondrial function in preclinical models of heart failure: therapeutic targets for future clinical therapies?

INTRODUCTION

Heart failure is a complex clinical syndrome resulting from the unsuccessful compensation of symptoms of myocardial damage. Mitochondrial dysfunction is a process that occurs because of an attempt to adapt to the disruption of metabolic and energetic pathways occurring in the myocardium. This, in turn, leads to further dysfunction in cardiomyocyte processes. Currently, many therapeutic strategies have been implemented to improve mitochondrial function, but their effectiveness varies widely.

AREAS COVERED

This review focuses on new models of therapeutic strategies targeting mitochondrial function in the treatment of heart failure.

EXPERT OPINION

Therapeutic strategies targeting mitochondria appear to be a valuable option for treating heart failure. Currently, the greatest challenge is to develop new research models that could restore the disrupted metabolic processes in mitochondria as comprehensively as possible. Only the development of therapies that focus on improving as many dysregulated mitochondrial processes as possible in patients with heart failure will be able to bring the expected clinical improvement, along with inhibition of disease progression. Combined strategies involving the reduction of the effects of oxidative stress and mitochondrial dysfunction, appear to be a promising possibility for developing new therapies for a complex and multifactorial disease such as heart failure.

IFN-γ and androgens disrupt mitochondrial function in murine myocytes

The effect of cytokines on non-traditional immunological targets under conditions of chronic inflammation is an ongoing subject of study. Fatigue is a symptom often associated with autoimmune diseases. Chronic inflammatory response and activated cell-mediated immunity are associated with cardiovascular myopathies which can be driven by muscle weakness and fatigue. Thus, we hypothesize that immune dysfunction-driven changes in myocyte mitochondria may play a critical role in fatigue-related pathogenesis. We show that persistent low-level expression of IFN-γ in designated IFN-γ AU-Rich Element deletion mice (ARE mice) under androgen exposure resulted in mitochondrial and metabolic deficiencies in myocytes from male or castrated ARE mice. Most notably, echocardiography unveiled that low ejection fraction in the left ventricle post-stress correlated with mitochondrial deficiencies, explaining how heart function decreases under stress. We report that inefficiencies and structural changes in mitochondria, with changes to expression of mitochondrial genes, are linked to male-biased fatigue and acute cardiomyopathy under stress. Our work highlights how male androgen hormone backgrounds and active autoimmunity reduce mitochondrial function and the ability to cope with stress and how pharmacological blockade of stress signal protects heart function. These studies provide new insight into the diverse actions of IFN-γ in fatigue, energy metabolism, and autoimmunity. © 2023 The Pathological Society of Great Britain and Ireland. This article has been contributed to by U.S. Government employees and their work is in the public domain in the USA.

Nrf2-Mediated Antioxidant Defense and Thyroid Hormone Signaling: A Focus on Cardioprotective Effects

Thyroid hormones (TH) perform a plethora of actions in numerous tissues and induce an overall increase in metabolism, with an augmentation in energy demand and oxygen expenditure. Oxidants are required for normal thyroid-cell proliferation, as well as for the synthesis of the main hormones secreted by the thyroid gland, triiodothyronine (T3) and thyroxine (T4). However, an uncontrolled excess of oxidants can cause oxidative stress, a major trigger in the pathogenesis of a broad spectrum of diseases, including inflammation and cancer. In particular, oxidative stress is implicated in both hypo- and hyper-thyroid diseases. Furthermore, it is important for the TH system to rely on efficient antioxidant defense, to maintain balance, despite sustained tissue exposure to oxidants. One of the main endogenous antioxidant responses is the pathway centered on the nuclear factor erythroid 2-related factor (Nrf2). The aim of the present review is to explore the multiple links between Nrf2-related pathways and various TH-associated conditions. The main aspect of TH signaling is described and the role of Nrf2 in oxidant-antioxidant homeostasis in the TH system is evaluated. Next, the antioxidant function of Nrf2 associated with oxidative stress induced by TH pathological excess is discussed and, subsequently, particular attention is given to the cardioprotective role of TH, which also acts through the mediation of Nrf2. In conclusion, the interaction between Nrf2 and most common natural antioxidant agents in altered states of TH is briefly evaluated.

Structure and Functions of HMGB2 Protein

High-Mobility Group (HMG) chromosomal proteins are the most numerous nuclear non-histone proteins. HMGB domain proteins are the most abundant and well-studied HMG proteins. They are involved in variety of biological processes. HMGB1 and HMGB2 were the first members of HMGB-family to be discovered and are found in all studied eukaryotes. Despite the high degree of homology, HMGB1 and HMGB2 proteins differ from each other both in structure and functions. In contrast to HMGB2, there is a large pool of works devoted to the HMGB1 protein whose structure-function properties have been described in detail in our previous review in 2020. In this review, we attempted to bring together diverse data about the structure and functions of the HMGB2 protein. The review also describes post-translational modifications of the HMGB2 protein and its role in the development of a number of diseases. Particular attention is paid to its interaction with various targets, including DNA and protein partners. The influence of the level of HMGB2 expression on various processes associated with cell differentiation and aging and its ability to mediate the differentiation of embryonic and adult stem cells are also discussed.

An Adjuvant Stem Cell Patch with Coronary Artery Bypass Graft Surgery Improves Diastolic Recovery in Porcine Hibernating Myocardium

Diastolic dysfunction persists despite coronary artery bypass graft surgery (CABG) in patients with hibernating myocardium (HIB). We studied whether the adjunctive use of a mesenchymal stem cells (MSCs) patch during CABG improves diastolic function by reducing inflammation and fibrosis. HIB was induced in juvenile swine by placing a constrictor on the left anterior descending (LAD) artery, causing myocardial ischemia without infarction. At 12 weeks, CABG was performed using the left-internal-mammary-artery (LIMA)-to-LAD graft with or without placement of an epicardial vicryl patch embedded with MSCs, followed by four weeks of recovery. The animals underwent cardiac magnetic resonance imaging (MRI) prior to sacrifice, and tissue from septal and LAD regions were collected to assess for fibrosis and analyze mitochondrial and nuclear isolates. During low-dose dobutamine infusion, diastolic function was significantly reduced in HIB compared to the control, with significant improvement after CABG + MSC treatment. In HIB, we observed increased inflammation and fibrosis without transmural scarring, along with decreased peroxisome proliferator-activated receptor-gamma coactivator (PGC1α), which could be a possible mechanism underlying diastolic dysfunction. Improvement in PGC1α and diastolic function was noted with revascularization and MSCs, along with decreased inflammatory signaling and fibrosis. These findings suggest that adjuvant cell-based therapy during CABG may recover diastolic function by reducing oxidant stress–inflammatory signaling and myofibroblast presence in the myocardial tissue.

Calcium and Reactive Oxygen Species Signaling Interplays in Cardiac Physiology and Pathologies

Mitochondria are key players in energy production, critical activity for the smooth functioning of energy-demanding organs such as the muscles, brain, and heart. Therefore, dysregulation or alterations in mitochondrial bioenergetics primarily perturb these organs. Within the cell, mitochondria are the major site of reactive oxygen species (ROS) production through the activity of different enzymes since it is one of the organelles with the major availability of oxygen. ROS can act as signaling molecules in a number of different pathways by modulating calcium (Ca²⁺) signaling. Interactions among ROS and calcium signaling can be considered bidirectional, with ROS regulating cellular Ca²⁺ signaling, whereas Ca²⁺ signaling is essential for ROS production. In particular, we will discuss how alterations in the crosstalk between ROS and Ca²⁺ can lead to mitochondrial bioenergetics dysfunctions and the consequent damage to tissues at high energy demand, such as the heart. Changes in Ca²⁺ can induce mitochondrial alterations associated with reduced ATP production and increased production of ROS. These changes in Ca²⁺ levels and ROS generation completely paralyze cardiac contractility. Thus, ROS can hinder the excitation-contraction coupling, inducing arrhythmias, hypertrophy, apoptosis, or necrosis of cardiac cells. These interplays in the cardiovascular system are the focus of this review.

Role of mitochondrial metabolism in immune checkpoint inhibitors-related myocarditis

Background

Immune checkpoint inhibitor-related myocarditis is the deadliest complication of immunotherapy. However, the underlying pathophysiological mechanisms of its occurrence and development remain unclear. Due to the long-term lack of effective early diagnosis and treatment options, it is of great significance to understand the pathophysiological mechanism of immune checkpoint inhibitor-related myocarditis.

Methods

Tissue samples from three patients with immune checkpoint inhibitor-related myocarditis and three control tissue samples were collected for protein analysis. Differentially expressed proteins were screened out using quantitative proteomics technology based on TMT markers. Protein-protein interaction (PPI) and Gene Ontology (GO) functional enrichment analyses of cross-factors were subsequently performed. Combined with the PD-L1 subcellular organelle- level protein interaction network, we searched for hub proteins involved in immune checkpoint inhibitor-related myocarditis and explored potential drug sensitivity and disease correlation.

Results

A total of 306 differentially expressed proteins were identified in immune checkpoint inhibitor-related myocarditis. Enrichment analysis showed that the differentially expressed proteins were closely related to mitochondrial metabolism. By analyzing mitochondria-related proteins and PD-L1-related proteins, we found four hub proteins, mammalian target of rapamycin (mTOR), Glycogen synthase kinase 3β (GSK3β), Protein tyrosine phosphatase non-receptor type 11 (PTPN11), and Mitofusin 2 (MFN2), indicating that they are closely related to immune checkpoint inhibitor-related myocarditis. Finally, we explored potential drugs for the treatment of immune checkpoint inhibitor-related myocarditis.

Conclusion

Mitochondrial metabolism is involved in the process of immune checkpoint inhibitor-related myocarditis, and we identified four hub proteins, which may become new biomarkers for the early diagnosis and treatment of immune checkpoint inhibitor-related myocarditis.

Dysregulated energy metabolism impairs chondrocyte function in osteoarthritis

OBJECTIVES

Metabolic pathways are a series of chemical reactions by which cells take in nutrient substrates for energy and building blocks needed to maintain critical cellular processes. Details of chondrocyte metabolism and how it rewires during the progression of osteoarthritis (OA) are unknown. This research aims to identify what changes in the energy metabolic state occur in OA cartilage.

METHODS

Patient matched OA and non-OA cartilage specimens were harvested from total knee replacement patients. Cartilage was first collected for metabolomics, proteomics, and transcriptomics analyses to study global alterations in OA metabolism. We then determined the metabolic routes by tracking [U-¹³C] isotope with liquid chromatography-mass spectrometry (LC-MS). We further evaluated cellular bioenergetic profiles by measuring oxygen consumption rate (OCR) and extracellular acidification rate (ECAR) and investigated the effects of low-dose and short-term effects of 2-deoxyglucose (2DG) on chondrocytes.

RESULTS

OA chondrocytes showed increased basal ECAR and more lactate production compared to non-OA chondrocytes. [U-¹³C] glucose labelling revealed that less glucose-derived carbon entered the tricarboxylic acid (TCA) cycle. On the other hand, mitochondrial respiratory rates were markedly decreased in the OA chondrocytes compared to non-OA chondrocytes. These changes were accompanied by decreased cellular ATP production, mitochondrial membrane potential and disrupted mitochondrial morphology. We further demonstrated in vitro that short-term inhibition of glycolysis suppressed matrix degeneration gene expression in chondrocytes and bovine cartilage explants cultured under inflammatory conditions.

CONCLUSION

This study represents the first comprehensive comparative analysis of metabolism in OA chondrocytes and lays the groundwork for therapeutic targeting of metabolism in OA.

Novel Therapeutic Approaches Enhance PGC1-alpha to Reduce Oxidant Stress-Inflammatory Signaling and Improve Functional Recovery in Hibernating Myocardium

Ischemic heart disease affects millions of people around the world. Current treatment options, including coronary artery bypass grafting, do not result in full functional recovery, highlighting the need for novel adjunctive therapeutic approaches. Hibernation describes the myocardial response to prolonged ischemia and involves a set of complex cytoprotective metabolic and functional adaptations. PGC1-alpha, a key regulator of mitochondrial energy metabolism and inhibitor of oxidant-stress-inflammatory signaling, is known to be downregulated in hibernating myocardium. PGC1-alpha is a critical component of cellular stress responses and links cellular metabolism with inflammation in the ischemic heart. While beneficial in the acute setting, a chronic state of hibernation can be associated with self-perpetuating oxidant stress-inflammatory signaling which leads to tissue injury. It is likely that incomplete functional recovery following revascularization of chronically ischemic myocardium is due to persistence of metabolic changes as well as prooxidant and proinflammatory signaling. Enhancement of PGC1-alpha signaling has been proposed as a possible way to improve functional recovery in patients with ischemic heart disease. Adjunctive mesenchymal stem cell therapy has been shown to induce PGC1-alpha signaling in hibernating myocardium and could help improve clinical outcomes for patients undergoing bypass surgery.

Estrogen signaling as a bridge between the nucleus and mitochondria in cardiovascular diseases

Cardiovascular diseases (CVDs) are the leading cause of morbidity and mortality worldwide. Epidemiological studies indicate that pre-menopausal women are more protected against the development of CVDs compared to men of the same age. This effect is attributed to the action/effects of sex steroid hormones on the cardiovascular system. In this context, estrogen modulates cardiovascular function in physiological and pathological conditions, being one of the main physiological cardioprotective agents. Here we describe the common pathways and mechanisms by which estrogens modulate the retrograde and anterograde communication between the nucleus and mitochondria, highlighting the role of genomic and non-genomic pathways mediated by estrogen receptors. Additionally, we discuss the presumable role of bromodomain-containing protein 4 (BRD4) in enhancing mitochondrial biogenesis and function in different CVD models and how this protein could act as a master regulator of estrogen protective activity. Altogether, this review focuses on estrogenic control in gene expression and molecular pathways, how this activity governs nucleus-mitochondria communication, and its projection for a future generation of strategies in CVDs treatment.

Novel Targets for a Combination of Mechanical Unloading with Pharmacotherapy in Advanced Heart Failure

LVAD therapy is an effective rescue in acute and especially chronic cardiac failure. In several scenarios, it provides a platform for regeneration and sustained myocardial recovery. While unloading seems to be a key element, pharmacotherapy may provide powerful tools to enhance effective cardiac regeneration. The synergy between LVAD support and medical agents may ensure satisfying outcomes on cardiomyocyte recovery followed by improved quality and quantity of patient life. This review summarizes the previous and contemporary strategies for combining LVAD with pharmacotherapy and proposes new therapeutic targets. Regulation of metabolic pathways, enhancing mitochondrial biogenesis and function, immunomodulating treatment, and stem-cell therapies represent therapeutic areas that require further experimental and clinical studies on their effectiveness in combination with mechanical unloading.

Circulating amino acids and acylcarnitines correlated with different CAC score ranges in diabetic postmenopausal women using LC-MS/MS based metabolomics approach

BACKGROUND

Diabetes mellitus (DM) and its cardiovascular disease (CVD) complication are among the most frequent causes of death worldwide. However, the metabolites linking up diabetes and CVD are less understood. In this study, we aimed to evaluate serum acylcarnitines and amino acids in postmenopausal women suffering from diabetes with different severity of CVD and compared them with healthy controls.

METHODS

Through a cross-sectional study, samples were collected from postmenopausal women without diabetes and CVD as controls (n = 20), patients with diabetes and without CVD (n = 16), diabetes with low risk of CVD (n = 11), and diabetes with a high risk of CVD (n = 21) referred for CT angiography for any reason. Metabolites were detected by a targeted approach using LC-MS/MS and metabolic -alterations were assessed by applying multivariate statistical analysis. The diagnostic ability of discovered metabolites based on multivariate statistical analysis was evaluated by ROC curve analysis.

RESULTS

The study included women aged from 50-80 years with 5-30 years of menopause. The relative concentration of C14:1, C14:2, C16:1, C18:1, and C18:2OH acylcarnitines decreased and C18 acylcarnitine and serine increased in diabetic patients compared to control. Besides, C16:1 and C18:2OH acylcarnitines increased in high-risk CVD diabetic patients compared to no CVD risk diabetic patients.

CONCLUSION

Dysregulation of serum acylcarnitines and amino acids profile correlated with different CAC score ranges in diabetic postmenopausal women. (Ethic approval No: IR.TUMS.EMRI.REC.1399.062).

Riociguat attenuates left ventricular proteome and microRNA profile changes after experimental aortic stenosis in mice

BACKGROUND AND PURPOSE

Development and progression of heart failure (HF) involve endothelial and myocardial dysfunction as well as a dysregulation of the nitric oxide - soluble guanylyl cyclase - cyclic guanosine monophosphate (NO-sGC-cGMP) signalling pathway. Recently, we reported that the sGC stimulator riociguat (RIO) has beneficial effects on cardiac remodelling and progression of HF in response to chronic pressure overload. Here, we examined if these favourable RIO effects are also reflected in alterations of the myocardial proteome and microRNA profiles.

EXPERIMENTAL APPROACH

Male C57BL/6N mice underwent transverse aortic constriction (TAC) and sham operated mice served as controls. TAC and sham animals were randomised and treated with either RIO or vehicle for five weeks, starting three weeks post-surgery when cardiac hypertrophy was established. Afterwards we performed mass spectrometric proteome analyses and microRNA sequencing of proteins and RNAs, respectively, isolated from left ventricles (LV).

KEY RESULTS

TAC-induced changes of the LV proteome were significantly reduced by RIO treatment. Bioinformatics analyses revealed that RIO improved TAC-induced cardiovascular disease related pathways, metabolism and energy production, e.g. reversed alterations in the levels of myosin heavy chain 7 (MYH7), cardiac phospholamban (PLN), and ankyrin repeat domain-containing protein 1 (ANKRD1). RIO also attenuated TAC-induced changes of microRNA levels in the LV.

CONCLUSION AND IMPLICATIONS

The sGC stimulator RIO has beneficial effects on cardiac structure and function during pressure overload, which is accompanied by a reversal of TAC-induced changes of the cardiac proteome and microRNA profile. Our data support the potential of RIO as a novel HF therapeutic.

PGC-1α-Mediated Mitochondrial Quality Control: Molecular Mechanisms and Implications for Heart Failure

Mitochondria with structural and functional integrity are essential for maintaining mitochondrial function and cardiac homeostasis. It is involved in the pathogenesis of many diseases. Peroxisome proliferator-activated receptor γ coactivator 1 α (PGC-1α), acted as a transcriptional cofactor, is abundant in the heart, which modulates mitochondrial biogenesis and mitochondrial dynamics and mitophagy to sustain a steady-state of mitochondria. Cumulative evidence suggests that dysregulation of PGC-1α is closely related to the onset and progression of heart failure. PGC-1α deficient-mice can lead to worse cardiac function under pressure overload compared to sham. Here, this review mainly focuses on what is known about its regulation in mitochondrial functions, as well as its crucial role in heart failure.

ULK1 mediated mitophagy prevents pathological cardiac remodelling and heart failure

The defects in mitochondrial clearance mechanisms can trigger adverse cardiac remodeling and severely impair cardiac performance. A new study identifies Ulk1/Rab9 mediated alternative mitophagy to be important for mitochondrial clearance in heart under pressure overload conditions. Moreover, the defects in ULK1 mediated alternative mitophagy resulted in accumulation of damaged mitochondria, severe hypertrophy, fibrosis, and cardiac dysfunction in response to TAC induced pressure overload. The findings highlight Ulk1/Rab9 mediated alternative mitophagy as a prominent mode of mitophagy and quality control in response to pressure overload hypertrophy.

Mitochondrial Dynamics and Mitophagy in Cardiometabolic Disease

Mitochondria play a key role in cellular metabolism. Mitochondrial dynamics (fusion and fission) and mitophagy, are critical to mitochondrial function. Fusion allows organelles to share metabolites, proteins, and mitochondrial DNA, promoting complementarity between damaged mitochondria. Fission increases the number of mitochondria to ensure that they are passed on to their offspring during mitosis. Mitophagy is a process of selective removal of excess or damaged mitochondria that helps improve energy metabolism. Cardiometabolic disease is characterized by mitochondrial dysfunction, high production of reactive oxygen species, increased inflammatory response, and low levels of ATP. Cardiometabolic disease is closely related to mitochondrial dynamics and mitophagy. This paper reviewed the mechanisms of mitochondrial dynamics and mitophagy (focus on MFN1, MFN2, OPA1, DRP1, and PINK1 proteins) and their roles in diabetic cardiomyopathy, myocardial infarction, cardiac hypertrophy, heart failure, atherosclerosis, and obesity.

Animal Models of Dysregulated Cardiac Metabolism

As a muscular pump that contracts incessantly throughout life, the heart must constantly generate cellular energy to support contractile function and fuel ionic pumps to maintain electrical homeostasis. Thus, mitochondrial metabolism of multiple metabolic substrates such as fatty acids, glucose, ketones, and lactate is essential to ensuring an uninterrupted supply of ATP. Multiple metabolic pathways converge to maintain myocardial energy homeostasis. The regulation of these cardiac metabolic pathways has been intensely studied for many decades. Rapid adaptation of these pathways is essential for mediating the myocardial adaptation to stress, and dysregulation of these pathways contributes to myocardial pathophysiology as occurs in heart failure and in metabolic disorders such as diabetes. The regulation of these pathways reflects the complex interactions of cell-specific regulatory pathways, neurohumoral signals, and changes in substrate availability in the circulation. Significant advances have been made in the ability to study metabolic regulation in the heart, and animal models have played a central role in contributing to this knowledge. This review will summarize metabolic pathways in the heart and describe their contribution to maintaining myocardial contractile function in health and disease. The review will summarize lessons learned from animal models with altered systemic metabolism and those in which specific metabolic regulatory pathways have been genetically altered within the heart. The relationship between intrinsic and extrinsic regulators of cardiac metabolism and the pathophysiology of heart failure and how these have been informed by animal models will be discussed.

The Cardiac Dysfunction Caused by Metabolic Alterations in Alzheimer's Disease

A progressive defect in the energy generation pathway is implicated in multiple aging-related diseases, including cardiovascular conditions and Alzheimer's Disease (AD). However, evidence of the pathogenesis of cardiac dysfunction in AD and the associations between the two organ diseases need further elucidation. This study aims to characterize cellular defects resulting in decreased cardiac function in AD-model. 5XFAD mice, a strain expressing five mutations in human APP and PS1 that shows robust Aβ production with visible plaques at 2 months and were used in this study as a model of AD. 5XFAD mice and wild-type (WT) counterparts were subjected to echocardiography at 2-, 4-, and 6-month, and 5XFAD had a significant reduction in cardiac fractional shortening and ejection fraction compared to WT. Additionally, 5XFAD mice had decreased observed electrical signals demonstrated as decreased R, P, T wave amplitudes. In isolated cardiomyocytes, 5XFAD mice showed decreased fraction shortening, rate of shortening, as well as the degree of transient calcium influx. To reveal the mechanism by which AD leads to cardiac systolic dysfunction, the immunoblotting analysis showed increased activation of AMP-activated protein kinase (AMPK) in 5XFAD left ventricular and brain tissue, indicating altered energy metabolism. Mito Stress Assays examining mitochondrial function revealed decreased basal and maximal oxygen consumption rate, as well as defective pyruvate dehydrogenase activity in the 5XFAD heart and brain. Cellular inflammation was provoked in the 5XFAD heart and brain marked by the increase of reactive oxygen species accumulation and upregulation of inflammatory mediator activities. Finally, AD pathological phenotype with increased deposition of Aβ and defective cognitive function was observed in 6-month 5XFAD mice. In addition, elevated fibrosis was observed in the 6-month 5XFAD heart. The results implicated that AD led to defective mitochondrial function, and increased inflammation which caused the decrease in contractility of the heart.

The dual role of the hexosamine biosynthetic pathway in cardiac physiology and pathophysiology

The heart is a highly metabolic organ with extensive energy demands and hence relies on numerous fuel substrates including fatty acids and glucose. However, oxidative stress is a natural by-product of metabolism that, in excess, can contribute towards DNA damage and poly-ADP-ribose polymerase activation. This activation inhibits key glycolytic enzymes, subsequently shunting glycolytic intermediates into non-oxidative glucose pathways such as the hexosamine biosynthetic pathway (HBP). In this review we provide evidence supporting the dual role of the HBP, i.e. playing a unique role in cardiac physiology and pathophysiology where acute upregulation confers cardioprotection while chronic activation contributes to the onset and progression of cardio-metabolic diseases such as diabetes, hypertrophy, ischemic heart disease, and heart failure. Thus although the HBP has emerged as a novel therapeutic target for such conditions, proposed interventions need to be applied in a context- and pathology-specific manner to avoid any potential drawbacks of relatively low cardiac HBP activity.

Milrinone effects on cardiac mitochondria, hemodynamics, and death in catecholamine-infused rats

BACKGROUND

Catecholamine-storm is considered the major cause of enterovirus 71-associated cardiopulmonary death. To elucidate the effect of milrinone on cardiac mitochondria and death, a rat model of catecholamine-induced heart failure was investigated.

METHODS

Young male Spray-Dawley rats received a continuous intravenous infusion of norepinephrine then followed by co-treatment with and without milrinone or esmolol. Vital signs were monitored and echocardiography was performed at indicated time points. At the end of experiments, hearts were extracted to study mitochondrial function, biogenesis, and DNA copy numbers.

RESULTS

Hypernorepinephrinemia induced persistent tachycardia, hypertension, and high mortality and significantly impaired the activities of the electron transport chain and suppressed mitochondrial DNA copy number, mitochondrial transcription factor A and peroxisome proliferator-activated receptor-gamma coactivator 1-α. Norepinephrine-induced hypertension could be significantly suppressed by milrinone and esmolol. Milrinone improved but esmolol deteriorated the survival rate. The left ventricle was significantly enlarged shortly after norepinephrine infusion but later gradually reduced in size by milrinone. The impairment and suppression of mitochondrial function could be significantly reversed by milrinone but not by esmolol.

CONCLUSIONS

Milrinone may protect the heart via maintaining mitochondrial function from hypernorepinephrinemia. This study warrants the importance of milrinone and the preservation of mitochondrial function in the treatment of catecholamine-induced death.

IMPACT

Milrinone may protect the heart from hypernorepinephrinemia-induced death via maintaining myocardial mitochondrial activity, function, and copy number. Maintenance of cardiac mitochondrial function may be a potential therapeutic strategy in such catecholamine-induced heart failure.

Modelling Metabolic Shifts during Cardiomyocyte Differentiation, Iron Deficiency and Transferrin Rescue Using Human Pluripotent Stem Cells

Cardiomyocytes rely on specialised metabolism to meet the high energy demand of the heart. During heart development, metabolism matures and shifts from the predominant utilisation of glycolysis and glutamine oxidation towards lactate and fatty acid oxidation. Iron deficiency (ID) leads to cellular metabolism perturbations. However, the exact alterations in substrate metabolism during ID are poorly defined. Using human induced pluripotent stem cell-derived cardiomyocytes (hiPSC-CM), the present study investigated changes in major metabolic substrate utilisation in the context of ID or upon transferrin rescue. Typically, during hiPSC-CM differentiation, the greatest increase in total metabolic output and rate was seen in fatty acid metabolism. When ID was induced, hiPSC-CMs displayed increased reliance on glycolytic metabolism, and six TCA cycle, five amino acid, and four fatty acid substrates were significantly impaired. Transferrin rescue was able to improve TCA cycle substrate metabolism, but the amino acid and fatty acid metabolism remained perturbed. Replenishing iron stores partially reverses the adverse metabolic changes that occur during ID. Understanding the changes in metabolic substrate utilisation and their modification may provide potential for discovery of new biomarkers and therapeutic targets in cardiovascular diseases.

Light Emitting Diodes Photobiomodulation Improves Cardiac Function by Promoting ATP Synthesis in Mice With Heart Failure

Heart failure (HF) is the common consequences of various cardiovascular diseases, often leading to severe cardiac output deficits with a high morbidity and mortality. In recent years, light emitting diodes-based therapy (LEDT) has been widely used in multiple cardiac diseases, while its modulatory effects on cardiac function with HF still remain unclear. Therefore, the objective of this study was to investigate the effects of LED-Red irradiation on cardiac function in mice with HF and to reveal its mechanisms. In this study, we constructed a mouse model of HF. We found that LED-Red (630 nm) was an effective wavelength for the treatment of HF. Meanwhile, the application of LED-Red therapy to treat HF mice improved cardiac function, ameliorate heart morphology, reduced pulmonary edema, as well as inhibited collagen deposition. Moreover, LED-Red therapy attenuated the extent of perivascular fibrosis. Besides, LED-Red irradiation promoted calcium transients in cardiomyocytes as well as upregulated ATP synthesis, which may have positive implications for contractile function in mice with HF. Collectively, we identified that LED-Red exerts beneficial effects on cardiac function in HF mice possibly by promoting the synthesis of ATP.

Altered cardiac mitochondrial dynamics and biogenesis in rat after short-term cocaine administration

Abuse of the potent psychostimulant cocaine is widely established to have cardiovascular consequences. The cardiotoxicity of cocaine is mainly associated with oxidative stress and mitochondrial dysfunction. Mitochondrial dynamics and biogenesis, as well as the mitochondrial unfolded protein response (UPRmt), guarantee cardiac mitochondrial homeostasis. Collectively, these mechanisms act to protect against stress, injury, and the detrimental effects of chemicals on mitochondria. In this study, we examined the effects of cocaine on cardiac mitochondrial dynamics, biogenesis, and UPRmt in vivo. Rats administered cocaine via the tail vein at a dose of 20 mg/kg/day for 7 days showed no structural changes in the myocardium, but electron microscopy revealed a significant increase in the number of cardiac mitochondria. Correspondingly, the expressions of the mitochondrial fission gene and mitochondrial biogenesis were increased after cocaine administration. Significant increase in the expression and nuclear translocation of activating transcription factor 5, the major active regulator of UPRmt, were observed after cocaine administration. Accordingly, our findings show that before any structural changes are observable in the myocardium, cocaine alters mitochondrial dynamics, elevates mitochondrial biogenesis, and induces the activation of UPRmt. These alterations might reflect cardiac mitochondrial compensation to protect against the cardiotoxicity of cocaine.

Relevance of mitochondrial dysfunction in heart disease associated with insulin resistance conditions

Insulin resistance plays a key role in the development and progression of obesity, diabetes, and their complications. Moreover, insulin resistance is considered the principal link between metabolic diseases and cardiovascular diseases. Heart disease associated with insulin resistance is one of the most important consequences of both obesity and diabetes, and it is characterized by impaired cardiac energetics, diastolic dysfunction, and finally heart failure. Mitochondrion plays a key role in cell energy homeostasis and is the main source of reactive oxygen species. Obesity and diabetes are associated with alterations in mitochondrial function and dynamics. Mitochondrial dysfunction is characterized by changes in mitochondrial respiratory chain with reduced ATP production and elevated reactive oxygen species production. These mitochondrial alterations together with inflammation contribute to the development and progression of heart disease under insulin resistance conditions. Finally, numerous miRNAs participate in the regulation of energy substrate metabolism, reactive oxygen species production, and apoptotic pathways within the mitochondria. This notion supports the relevance of interactions between miRNAs and mitochondrial dysfunction in the pathophysiology of metabolic heart disease.

Computational drug repurposing of bethanidine for SENP1 inhibition in cardiovascular diseases treatment

AIMS

Bethanidine (BW467C60) is a newly presented strong adrenergic neuron blocking factor which has a hypotensive operation in man. SENPs are essential for maintaining a balance between SUMOylation and deSUMOylation which can be disturbed by changing the expression of (sentrin-specific proteases) SENPs. SENP1 is the most studied isoform of SENPs. Hypertrophic stimuli can increase SENP1 expression using calcium/calcineurin-NFAT3 signaling in heart. Moreover, SENP1 expression may positively relate to the expression of mitochondrial genes of the heart, and can cause the heart and mitochondrial dysfunction.

MATERIALS AND METHODS

In order to inhibit SENP1 using Bethanidine, molecular docking and molecular dynamics (MD) simulation of SENP1 with Bethanidine were performed. Molecular docking showed that Bethanidine can inhibit SENP1.

KEY FINDINGS

MD Simulation showed that Bethanidine constitutes a stable complex with SENP1 as was evident from RMSD, RMSF, H-bond and DSSP plots. Free binding energy and the interaction patterns were obtained from molecular docking, and MD trajectory exhibited Bethanidine can be a potential drug candidate for SENP1 inhibition.

SIGNIFICANCE

This study supplies enough evidences that Bethanidine is a potential inhibitor of SENP1 and can be applied for the treatment of cardiovascular diseases.

Energy metabolism design of the striated muscle cell

The design of the energy metabolism system in striated muscle remains a major area of investigation. Here, we review our current understanding and emerging hypotheses regarding the metabolic support of muscle contraction. Maintenance of ATP free energy, so called energy homeostasis, via mitochondrial oxidative phosphorylation is critical to sustained contractile activity, and this major design criterion is the focus of this review. Cell volume invested in mitochondria reduces the space available for generating contractile force, and this spatial balance between mitochondria acontractile elements to meet the varying sustained power demands across muscle types is another important design criterion. This is accomplished with remarkably similar mass-specific mitochondrial protein composition across muscle types, implying that it is the organization of mitochondria within the muscle cell that is critical to supporting sustained muscle function. Beyond the production of ATP, ubiquitous distribution of ATPases throughout the muscle requires rapid distribution of potential energy across these large cells. Distribution of potential energy has long been thought to occur primarily through facilitated metabolite diffusion, but recent analysis has questioned the importance of this process under normal physiological conditions. Recent structural and functional studies have supported the hypothesis that the mitochondrial reticulum provides a rapid energy distribution system via the conduction of the mitochondrial membrane potential to maintain metabolic homeostasis during contractile activity. We extensively review this aspect of the energy metabolism design contrasting it with metabolite diffusion models and how mitochondrial structure can play a role in the delivery of energy in the striated muscle.

Inhibition of calpain reduces cell apoptosis by suppressing mitochondrial fission in acute viral myocarditis

Cardiomyocyte apoptosis is critical for the development of viral myocarditis (VMC), which is one of the leading causes of cardiac sudden death in young adults. Our previous studies have demonstrated that elevated calpain activity is involved in the pathogenesis of VMC. This study aimed to further explore the underlying mechanisms. Neonatal rat cardiomyocytes (NRCMs) and transgenic mice overexpressing calpastatin were infected with coxsackievirus B3 (CVB3) to establish a VMC model. Apoptosis was detected with flow cytometry, TUNEL staining, and western blotting. Cardiac function was measured using echocardiography. Mitochondrial function was measured using ATP assays, JC-1, and MitoSOX. Mitochondrial morphology was observed using MitoTracker staining and transmission electron microscopy. Colocalization of dynamin-related protein 1 (Drp-1) in mitochondria was examined using immunofluorescence. Phosphorylation levels of Drp-1 at Ser637 site were determined using western blotting analysis. We found that CVB3 infection impaired mitochondrial function as evidenced by increased mitochondrial ROS production, decreased ATP production and mitochondrial membrane potential, induced myocardial apoptosis and damage, and decreased myocardial function. These effects of CVB3 infection were attenuated by inhibition of calpain both by PD150606 treatment and calpastatin overexpression. Furthermore, CVB3-induced mitochondrial dysfunction was associated with the accumulation of Drp-1 in the outer membrane of mitochondria and subsequent increase in mitochondrial fission. Mechanistically, calpain cleaved and activated calcineurin A, which dephosphorylated Drp-1 at Ser637 site and promoted its accumulation in the mitochondria, leading to mitochondrial fission and dysfunction. In summary, calpain inhibition attenuated CVB3-induced myocarditis by reducing mitochondrial fission, thereby inhibiting cardiomyocyte apoptosis.