Mitochondrial dysfunction in heart failure

Intravenous iron in patients with iron deficiency and heart failure: a review of modern evidence

PURPOSE OF REVIEW

Iron deficiency is common in patients with heart failure, affecting up to half of ambulatory patients and an even greater percentage of patients admitted for acute decompensation. Iron deficiency in this population is also associated with poor outcomes, including worse quality of life in addition to increased hospitalizations for heart failure and mortality. Evidence suggests that patients with iron deficiency in heart failure may benefit from repletion with IV iron.

RECENT FINDINGS

In this review, we outline the etiology and pathophysiology of iron deficiency in heart failure as well as various iron formulations available. We discuss evidence for intravenous iron repletion with a particular focus on recent studies that have evaluated its effects on hospitalizations and mortality. Finally, we discuss areas of uncertainty and future study and provide practical guidance for iron repletion.

SUMMARY

In summary, there is overwhelming evidence that intravenous iron repletion in patients with iron deficiency in heart failure is both beneficial and safe. However, further evidence is needed to better identify which patients would most benefit from iron repletion as well as the ideal repletion strategy.

Mitochondria: A source of potential biomarkers for non-communicable diseases

Mitochondria, as an endosymbiont of eukaryotic cells, controls multiple cellular activities, including respiration, reactive oxygen species production, fatty acid synthesis, and death. Though the majority of functional mitochondrial proteins are translated through a nucleus-controlled process, very few of them (∼10%) are translated within mitochondria through their own machinery. Germline and somatic mutations in mitochondrial and nuclear DNA significantly impact mitochondrial homeostasis and function. Such modifications disturbing mitochondrial biogenesis, metabolism, or mitophagy eventually resulted in cellular pathophysiology. In this chapter, we discussed the impact of mitochondria and its dysfunction on several non-communicable diseases like cancer, diabetes, neurodegenerative, and cardiovascular problems. Mitochondrial dysfunction and its outcome could be screened by currently available omics-based techniques, flow cytometry, and high-resolution imaging. Such characterization could be evaluated as potential biomarkers to assess the disease burden and prognosis.

Mitochondrial Dysfunction in Heart Failure: From Pathophysiological Mechanisms to Therapeutic Opportunities

Mitochondrial dysfunction, a feature of heart failure, leads to a progressive decline in bioenergetic reserve capacity, consisting in a shift of energy production from mitochondrial fatty acid oxidation to glycolytic pathways. This adaptive process of cardiomyocytes does not represent an effective strategy to increase the energy supply and to restore the energy homeostasis in heart failure, thus contributing to a vicious circle and to disease progression. The increased oxidative stress causes cardiomyocyte apoptosis, dysregulation of calcium homeostasis, damage of proteins and lipids, leakage of mitochondrial DNA, and inflammatory responses, finally stimulating different signaling pathways which lead to cardiac remodeling and failure. Furthermore, the parallel neurohormonal dysregulation with angiotensin II, endothelin-1, and sympatho-adrenergic overactivation, which occurs in heart failure, stimulates ventricular cardiomyocyte hypertrophy and aggravates the cellular damage. In this review, we will discuss the pathophysiological mechanisms related to mitochondrial dysfunction, which are mainly dependent on increased oxidative stress and perturbation of the dynamics of membrane potential and are associated with heart failure development and progression. We will also provide an overview of the potential implication of mitochondria as an attractive therapeutic target in the management and recovery process in heart failure.

Molecular mechanisms underlying sarcopenia in heart failure

The loss of skeletal muscle, also known as sarcopenia, is an aging-associated muscle disorder that is disproportionately present in heart failure (HF) patients. HF patients with sarcopenia have poor outcomes compared to the overall HF patient population. The prevalence of sarcopenia in HF is only expected to grow as the global population ages, and novel treatment strategies are needed to improve outcomes in this cohort. Multiple mechanistic pathways have emerged that may explain the increased prevalence of sarcopenia in the HF population, and a better understanding of these pathways may lead to the development of therapies to prevent muscle loss. This review article aims to explore the molecular mechanisms linking sarcopenia and HF, and to discuss treatment strategies aimed at addressing such molecular signals.

Asiatic acid protects against pressure overload-induced heart failure in mice by inhibiting mitochondria-dependent apoptosis

BACKGROUND

Mitochondrial dysfunction and subsequent cardiomyocyte apoptosis significantly contribute to pressure overload-induced heart failure (HF). A highly oxidative environment leads to mitochondrial damage, further exacerbating this condition. Asiatic acid (AA), a proven antioxidant and anti-hypertrophic agent, might provide a solution, but its role and mechanisms in chronic pressure overload-induced HF remain largely unexplored.

METHODS

We induced pressure overload in mice using transverse aortic constriction (TAC) and treated them with AA (100 mg/kg/day) or vehicle daily by oral gavage for 8 weeks. The effects of AA on mitochondrial dysfunction, oxidative stress-associated signaling pathways, and overall survival were evaluated. Additionally, an in vitro model using hydrogen peroxide-exposed neonatal rat cardiomyocytes was established to further investigate the role of AA in oxidative stress-induced mitochondrial apoptosis.

RESULTS

AA treatment significantly improved survival and alleviated cardiac dysfunction in TAC-induced HF mice. It preserved mitochondrial structure, reduced the LVW/BW ratio by 20.24%, mitigated TAC-induced mitochondrial-dependent apoptosis by significantly lowering the Bax/Bcl-2 ratio and cleaved caspase-9/3 levels, and attenuated oxidative stress. AA treatment protected cardiomyocytes from hydrogen peroxide-induced apoptosis, with concurrent modulation of mitochondrial-dependent apoptosis pathway-related proteins and the JNK pathway.

CONCLUSIONS

Our findings suggest that AA effectively combats chronic TAC-induced and hydrogen peroxide-induced cardiomyocyte apoptosis through a mitochondria-dependent mechanism. AA reduces cellular levels of oxidative stress and inhibits the activation of the JNK pathway, highlighting its potential therapeutic value in the treatment of HF.

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.

The Impact of Pharmacotherapy for Heart Failure on Oxidative Stress-Role of New Drugs, Flozins

Heart failure (HF) is a multifactorial clinical syndrome involving many complex processes. The causes may be related to abnormal heart structure and/or function. Changes in the renin-angiotensin-aldosterone system, the sympathetic nervous system, and the natriuretic peptide system are important in the pathophysiology of HF. Dysregulation or overexpression of these processes leads to changes in cardiac preload and afterload, changes in the vascular system, peripheral vascular dysfunction and remodeling, and endothelial dysfunction. One of the important factors responsible for the development of heart failure at the cellular level is oxidative stress. This condition leads to deleterious cellular effects as increased levels of free radicals gradually disrupt the state of equilibrium, and, as a consequence, the internal antioxidant defense system is damaged. This review focuses on pharmacotherapy for chronic heart failure with regard to oxidation-reduction metabolism, with special attention paid to the latest group of drugs, SGLT2 inhibitors-an integral part of HF treatment. These drugs have been shown to have beneficial effects by protecting the antioxidant system at the cellular level.

Sex and age differences in AMPK phosphorylation, mitochondrial homeostasis, and inflammation in hearts from inflammatory cardiomyopathy patients

Linked to exacerbated inflammation, myocarditis is a cardiovascular disease, which may lead to dilated cardiomyopathy. Although sex and age differences in the development of chronic myocarditis have been postulated, underlying cellular mechanisms remain poorly understood. In the current study, we aimed to investigate sex and age differences in mitochondrial homeostasis, inflammation, and cellular senescence. Cardiac tissue samples from younger and older patients with inflammatory dilated cardiomyopathy (DCMI) were used. The expression of Sirt1, phosphorylated AMPK, PGC-1α, Sirt3, acetylated SOD2, catalase, and several mitochondrial genes was analyzed to assess mitochondrial homeostasis. The expression of NF-κB, TLR4, and interleukins was used to examine the inflammatory state in the heart. Finally, several senescence markers and telomere length were investigated. Cardiac AMPK expression and phosphorylation were significantly elevated in male DCMI patients, whereas Sirt1 expression remained unchanged in all groups investigated. AMPK upregulation was accompanied by a preserved expression of all mitochondrial proteins/genes investigated in older male DCMI patients, whereas the expression of TOM40, TIM23, and the mitochondrial oxidative phosphorylation genes was significantly reduced in older female patients. Mitochondrial homeostasis in older male patients was further supported by the reduced acetylation of mitochondrial proteins as indicated by acetylated SOD2. The inflammatory markers NF-κB and TLR4 were downregulated in older male DCMI patients, whereas the expression of IL-18 was increased in older female patients. This was accompanied by progressed senescence in older DCMI hearts. In conclusion, older women experience more dramatic immunometabolic disorders on the cellular level than older men.

Atrial natriuretic peptide stimulates autophagy/mitophagy and improves mitochondrial function in chronic heart failure

Mitochondrial dysfunction, causing increased reactive oxygen species (ROS) production, is a molecular feature of heart failure (HF). A defective antioxidant response and mitophagic flux were reported in circulating leucocytes of patients with chronic HF and reduced ejection fraction (HFrEF). Atrial natriuretic peptide (ANP) exerts many cardiac beneficial effects, including the ability to protect cardiomyocytes by promoting autophagy. We tested the impact of ANP on autophagy/mitophagy, altered mitochondrial structure and function and increased oxidative stress in HFrEF patients by both ex vivo and in vivo approaches. The ex vivo study included thirteen HFrEF patients whose peripheral blood mononuclear cells (PBMCs) were isolated and treated with αANP (10^-11 M) for 4 h. The in vivo study included six HFrEF patients who received sacubitril/valsartan for two months. PBMCs were characterized before and after treatment. Both approaches analyzed mitochondrial structure and functionality. We found that levels of αANP increased upon sacubitril/valsartan, whereas levels of NT-proBNP decreased. Both the ex vivo direct exposure to αANP and the higher αANP level upon in vivo treatment with sacubitril/valsartan caused: (i) improvement of mitochondrial membrane potential; (ii) stimulation of the autophagic process; (iii) significant reduction of mitochondrial mass-index of mitophagy stimulation-and upregulation of mitophagy-related genes; (iv) reduction of mitochondrial damage with increased inner mitochondrial membrane (IMM)/outer mitochondrial membrane (OMM) index and reduced ROS generation. Herein we demonstrate that αANP stimulates both autophagy and mitophagy responses, counteracts mitochondrial dysfunction, and damages ultimately reducing mitochondrial oxidative stress generation in PBMCs from chronic HF patients. These properties were confirmed upon sacubitril/valsartan administration, a pivotal drug in HFrEF treatment.

A conditional knockout rat resource of mitochondrial protein-coding genes via a DdCBE-induced premature stop codon

Hundreds of pathogenic variants of mitochondrial DNA (mtDNA) have been reported to cause mitochondrial diseases, which still lack effective treatments. It is a huge challenge to install these mutations one by one. We repurposed the DddA-derived cytosine base editor to incorporate a premature stop codon in the mtProtein-coding genes to ablate mitochondrial proteins encoded in the mtDNA (mtProteins) instead of installing pathogenic variants and generated a library of both cell and rat resources with mtProtein depletion. In vitro, we depleted 12 of 13 mtProtein-coding genes with high efficiency and specificity, resulting in decreased mtProtein levels and impaired oxidative phosphorylation. Moreover, we generated six conditional knockout rat strains to ablate mtProteins using Cre/loxP system. Mitochondrially encoded ATP synthase membrane subunit 8 and NADH:ubiquinone oxidoreductase core subunit 1 were specifically depleted in heart cells or neurons, resulting in heart failure or abnormal brain development. Our work provides cell and rat resources for studying the function of mtProtein-coding genes and therapeutic strategies.

Emerging role of mitophagy in heart failure: from molecular mechanism to targeted therapy

Heart failure is defined as a drop in heart's pump function, accounting for reduced blood output and venous stasis, and constitutes the end stage of various cardiovascular diseases. Although mild mitochondrial dysfunction may hinder cardiomyocyte metabolism and impair myocardial function, severe mitochondrial injury is accompanied by cardiomyocyte apoptosis, leading to irreversible damage of the heart. Selective autophagy of mitochondria, or mitophagy, serves to rapidly remove dysfunctional mitochondria and restore the health of the mitochondrial population within cells by allowing reutilization of degradative substrates such as amino acids, fatty acids, and nucleotides. Although mitophagy represents a protective program that prevents the accumulation of poorly structured or damaged mitochondria, excessive mitophagy leads to mitochondrial population decline, impaired oxidative phosphorylation, and decreased ATP production. In this review, we first discuss the molecular underpinnings of mitophagy and the roles of different mitophagy adaptors. Then, the multiple and complex influence of mitophagy on heart failure is summarized. Finally, novel pharmacological strategies targeting mitophagy to relieve heart failure are briefly summarized.

Proteomics as a Tool for the Study of Mitochondrial Proteome, Its Dysfunctionality and Pathological Consequences in Cardiovascular Diseases

The focus of this review is on the proteomic approaches applied to the study of the qualitative/quantitative changes in mitochondrial proteins that are related to impaired mitochondrial function and consequently different types of pathologies. Proteomic techniques developed in recent years have created a powerful tool for the characterization of both static and dynamic proteomes. They can detect protein-protein interactions and a broad repertoire of post-translation modifications that play pivotal roles in mitochondrial regulation, maintenance and proper function. Based on accumulated proteomic data, conclusions can be derived on how to proceed in disease prevention and treatment. In addition, this article will present an overview of the recently published proteomic papers that deal with the regulatory roles of post-translational modifications of mitochondrial proteins and specifically with cardiovascular diseases connected to mitochondrial dysfunction.

Hazard-based risk grouping effectively stratifying breast cancer patients in post-irradiation long-term heart diseases: a population-based cohort study

Background

Even though advanced radiotherapy techniques provide a better protective effect on surrounding normal tissues, the late sequelae from radiation exposure to the heart are still considerable in breast cancer patients. The present population-based study explored the role of cox-regression-based hazard risk grouping and intended to stratify patients with post-irradiation long-term heart diseases.

Materials and methods

The present study investigated the Taiwan National Health Insurance (TNHI) database. From 2000 to 2017, we identified 158,798 breast cancer patients. Using a propensity score match of 1:1, we included 21,123 patients in each left and right breast irradiation cohort. Heart diseases, including heart failure (HF), ischemic heart disease (IHD), and other heart diseases (OHD), and anticancer agents, including epirubicin, doxorubicin, and trastuzumab, were included for analysis.

Results

Patients received left breast irradiation demonstrated increased risks on IHD (aHR, 1.16; 95% CI, 1.06-1.26; p < 0.01) and OHD (aHR, 1.08; 95% CI, 1.01-1.15; p < 0.05), but not HF (aHR, 1.11; 95% CI, 0.96-1.28; p = 0.14), when compared with patients received right breast irradiation. In patients who received left breast irradiation dose of >6,040 cGy, subsequent epirubicin might have a trend to increase the risk of heart failure (aHR, 1.53; 95% CI, 0.98-2.39; p = 0.058), while doxorubicin (aHR, 0.59; 95% CI, 0.26-1.32; p = 0.19) and trastuzumab (aHR, 0.93; 95% CI, 0.33-2.62; p = 0.89) did not. Older age was the highest independent risk factor for post-irradiation long-term heart diseases.

Conclusion

Generally, systemic anticancer agents are safe in conjunction with radiotherapy for managing post-operative breast cancer patients. Hazard-based risk grouping may help stratify breast cancer patients associated with post-irradiation long-term heart diseases. Notably, radiotherapy should be performed cautiously for elderly left breast cancer patients who received epirubicin. Limited irradiation dose to the heart should be critically considered. Regular monitoring of potential signs of heart failure may be conducted.

Resistin impairs mitochondrial homeostasis via cyclase-associated protein 1-mediated fission, leading to obesity-induced metabolic diseases

OBJECTIVE

One of the suggested mechanisms of obesity-induced insulin resistance is mitochondrial dysfunction in target tissues such as skeletal muscle. In our study, we examined whether resistin, an adipokine associated with obesity-mediated insulin resistance, induced metabolic disorders by impairing mitochondrial homeostasis.

METHODS

The morphology and function of mitochondria of skeletal muscle were examined in resistin-knockout and humanized resistin mice that were subjected to high-fat diet for 3 months. Morphology was examined by transmission electron microscopy. Mitochondria bioenergetics of skeletal muscle were evaluated using a Seahorse XF96 analyzer. Human skeletal myoblasts were used for in vitro studies on signaling mechanisms in responses to resistin.

RESULTS

A high-fat diet in humanized resistin mice increased fragmented and shorter mitochondria in the skeletal muscle, whereas resistin-knockout mice had healthy normal mitochondria. In vitro studies showed that human resistin treatment impaired mitochondrial homeostasis by inducing mitochondrial fission, leading to a decrease in ATP production and mitochondrial dysfunction. Induction of mitochondrial fission by resistin was accompanied by increased formation of mitochondria-associated ER membranes (MAM). At the same time, resistin induced up-regulation of the protein kinase A (PKA) pathway. This activation of PKA induced phosphorylation of Drp1 at serine 616, leading to Drp1 activation and subsequent induction of mitochondrial fission. The key molecule that mediated human resistin-induced mitochondrial fission was adenylyl cyclase-associated protein 1 (CAP1), which was reported as a bona fide receptor for human resistin. Moreover, our newly developed biomimetic selective blocking peptide could repress human resistin-mediated mitochondrial dysfunction. High-fat diet-fed mice showed lower exercise capacity and higher insulin resistance, which was prevented by a novel peptide to block the binding of resistin to CAP1 or in the CAP1-knockdown mice.

CONCLUSIONS

Our study demonstrated that human resistin induces mitochondrial dysfunction by inducing abnormal mitochondrial fission. This result suggests that the resistin-CAP1 complex could be a potential therapeutic target for the treatment of obesity-related metabolic diseases such as diabetes and cardiometabolic diseases.

The complex pathophysiology of cardiac cachexia: A review of current pathophysiology and implications for clinical practice

Cardiac cachexia is a muscle wasting process that often develops in those with chronic heart failure resulting in weight loss, low levels of physical activity, reduced quality of life, and is associated with a poor prognosis. The pathology of cardiac cachexia is complex with new evidence emerging that implicates several body systems. This review describes the pathophysiology associated with cardiac cachexia and addresses: 1) hormonal changes- neurohormonal abnormalities and metabolic hormone imbalance; 2) mechanisms of muscle wasting in cardiac cachexia, and the integral mechanisms between changed hormones due to cardiac cachexia and muscle wasting processes, and 3) associated abnormalities of gastrointestinal system that contribute to cardiac cachexia. These pleiotropic mechanisms demonstrate the intricate interplay between the affected systems and account for why cardiac cachexia is difficult to manage clinically. This review summarises current pathophysiology of cardiac cachexia and highlights symptoms of cardiac cachexia, implications for clinical practice and research gaps.

Metformin Acutely Mitigates Oxidative Stress in Human Atrial Tissue: A Pilot Study in Overweight Non-Diabetic Cardiac Patients

Metformin, the first-line drug in type 2 diabetes mellitus, elicits cardiovascular protection also in obese patients via pleiotropic effects, among which the anti-oxidant is one of the most investigated. The aim of the present study was to assess whether metformin can acutely mitigate oxidative stress in atrial tissue harvested from overweight non-diabetic patients. Right atrial appendage samples were harvested during open-heart surgery and used for the evaluation of reactive oxygen species (ROS) production by means of confocal microscopy (superoxide anion) and spectrophotometry (hydrogen peroxide). Experiments were performed after acute incubation with metformin (10 µM) in the presence vs. absence of angiotensin II (AII, 100 nM), lipopolysaccharide (LPS, 1 μg/mL), and high glucose (Gluc, 400 mg/dL). Stimulation with AII, LPS, and high Gluc increased ROS production. The magnitude of oxidative stress correlated with several echocardiographic parameters. Metformin applied in the lowest therapeutic concentration (10 µM) was able to decrease ROS generation in stimulated but also non-stimulated atrial samples. In conclusion, in a pilot group of overweight non-diabetic cardiac patients, acute incubation with metformin at a clinically relevant dose alleviated oxidative stress both in basal conditions and conditions that mimicked the activation of the renin-angiotensin-aldosterone system, acute inflammation, and uncontrolled hyperglycemia.

Inositol 1,4,5-trisphosphate receptors in cardiomyocyte physiology and disease

The contraction of cardiac muscle underlying the pumping action of the heart is mediated by the process of excitation-contraction coupling (ECC). While triggered by Ca²⁺ entry across the sarcolemma during the action potential, it is the release of Ca²⁺ from the sarcoplasmic reticulum (SR) intracellular Ca²⁺ store via ryanodine receptors (RyRs) that plays the major role in induction of contraction. Ca²⁺ also acts as a key intracellular messenger regulating transcription underlying hypertrophic growth. Although Ca²⁺ release via RyRs is by far the greatest contributor to the generation of Ca²⁺ transients in the cardiomyocyte, Ca²⁺ is also released from the SR via inositol 1,4,5-trisphosphate (InsP₃) receptors (InsP₃Rs). This InsP₃-induced Ca²⁺ release modifies Ca²⁺ transients during ECC, participates in directing Ca²⁺ to the mitochondria, and stimulates the transcription of genes underlying hypertrophic growth. Central to these specific actions of InsP₃Rs is their localization to responsible signalling microdomains, the dyad, the SR-mitochondrial interface and the nucleus. In this review, the various roles of InsP₃R in cardiac (patho)physiology and the mechanisms by which InsP₃ signalling selectively influences the different cardiomyocyte cell processes in which it is involved will be presented.

This article is part of the theme issue ‘The cardiomyocyte: new revelations on the interplay between architecture and function in growth, health, and disease’.

Training programs in preclinical studies. The example of pulmonary hypertension. Systematic review and meta-analysis

Background

Exercise and cardiopulmonary exercise testing are essential in the evaluation of physiological, biochemical, and molecular responses in the experimental studies on chronic diseases such as diabetes, heart failure and hypertension. The exercise tolerance and seem to be a valuable contribution to the experiments that are performed in animal models of pulmonary hypertension (PH), as well. The current survey uses detailed quantitative analyses to assess the advantages of exercise training programs performed in preclinical studies based on outcomes such as exercise capacity, cardiopulmonary hemodynamics, and mortality.

Methods

Articles were identified through search engines in the online electronic databases Pubmed/Medline, Web of Science following the PRISMA Protocol. Studies conducted between 1991 and 2022 without language restrictions were included in this study. Heterogeneity was assessed using the Cochrane Q-test and I2 test statistics. Subgroup analysis was employed with evidence of heterogeneity. Quality assessment was carried out using SYRCLE’s risk of bias tool for animal studies. Publication bias across studies was determined using the funnel plot and Egger’s regression test statistic.

Results

The available protocols typically included treadmill running, swimming, and voluntary wheel running with a different series of intensities, times and durations; these were also used in studies examining the efficacy of chronic training programs. In 66 interventions, PH induction reduced exercise endurance by half compared to healthy subjects, while exposure to tested medical agents normalized exercise capacity. The other 58 interventions demonstrated the advantages of various exercise training programs for PH. Induction of PH reduced exercise endurance by half compared to healthy subjects (R = 0.52; 0.48 − 0.55 95%CI; P<0.0001; I2 = 98.9%), while the exposure to tested medical agents normalized exercise capacity (R = 1.75; 1.61 − 1.91 95%CI; P<0.0001; I2 = 97.8%).

Conclusion

Despite a wide spectrum of study protocols to measure exercise endurance in animals with PH, there is a significant correlation between worsening of exercise-related parameters and PH development, manifested by alterations in haemodynamic and remodeling parameters. Familiarization with exercise, training program schedule, method used for PH induction, or detailed training parameters such as slope, exercise intensity or individualization, can influence the final outcome. This in turn can impact on the diversity and reproducibility of results being obtained in particular experimental studies.

Surrogate markers of gut dysfunction are related to heart failure severity and outcome-from the BIOSTAT-CHF consortium

BACKGROUND

The contribution of gut dysfunction to heart failure (HF) pathophysiology is not routinely assessed. We sought to investigate whether biomarkers of gut dysfunction would be useful in assessment of HF (eg, severity, adverse outcomes) and risk stratification.

METHODS

A panel of gut-related biomarkers including metabolites of the choline/carnitine- pathway (acetyl-L-carnitine, betaine, choline, γ-butyrobetaine, L-carnitine and trimethylamine-N-oxide [TMAO]) and the gut peptide, Trefoil factor-3 (TFF-3), were investigated in 1,783 patients with worsening HF enrolled in the systems BIOlogy Study to TAilored Treatment in Chronic Heart Failure (BIOSTAT-CHF) cohort and associations with HF severity and outcomes, and use in risk stratification were assessed.

RESULTS

Metabolites of the carnitine-TMAO pathway (acetyl-L-carnitine, γ-butyrobetaine, L-carnitine, and TMAO) and TFF-3 were associated with the composite outcome of HF hospitalization or all-cause mortality at 3 years (hazards ratio [HR] 2.04-2.93 [95% confidence interval {CI} 1.30-4.71] P≤ .002). Combining the carnitine-TMAO metabolites with TFF-3, as a gut dysfunction panel, showed a graded association; a greater number of elevated markers was associated with higher New York Heart Association class (P< .001), higher plasma concentrations of B-type natriuretic peptide (P< .001), and worse outcome (HR 1.90-4.58 [95% CI 1.19-6.74] P≤ 0.008). Addition of gut dysfunction biomarkers to the contemporary BIOSTAT HF risk model also improved prediction for the aforementioned composite outcome (C-statistics P≤ .011, NRI 13.5-21.1 [95% CI 2.7-31.9] P≤ .014).

CONCLUSIONS

A panel of biomarkers of gut dysfunction showed graded association with severity of HF and adverse outcomes. Biomarkers as surrogate markers are potentially useful for assessment of gut dysfunction to HF pathophysiology and in risk stratification.

Predictive Model for Acute Heart Failure in Patients with Acute Myocardial Infarction and Type 2 Diabetes Mellitus Based on Energy and Adipokine Metabolism Indicators

BACKGROUND: Acute heart failure (AHF) is one of the early complications of acute myocardial infarction (AMI) in diabetic patients. Evaluation of biomarkers of energy and adipokine metabolism can help in the early identification of diabetic patients at risk of AHF. AIM: The present study is aimed to predict the development of AHF in diabetic patients with AMI based on energy and adipokine metabolism parameters. METHODS: A total of 74 diabetic patients with AMI were examined between September 1, 2018, and December 31, 2020. Serum adropin, irisin, and C1q/TNF-related protein 3 (CTRP3) levels were measured by enzyme-linked immunosorbent assay. To predict AHF development in AMI patients, generalized linear mixed model (GLMM) was applied. RESULTS: The serum concentrations of adropin, irisin, and CTRP3 have been found to be reduced in diabetic patients with AMI and AHF. The accuracy of predicting AHF Killip Class 1 was 96.7%, and the accuracy of prediction for AHF Killip Class 2 was 57.1%, that is, the model was poorly sensitive to this level of complications. The prediction accuracy for AHF Killip Class 3 was 80%, that is, the model was highly sensitive to complications of this level, and for AHF Killip Class 4 – 100% being the maximum level of the model sensitivity. CONCLUSIONS: Low serum concentrations of adropin, irisin, and CTRP3 indicate an imbalance in energy and adipokine homeostasis. The constructed model predicts the probability of AHF development with high accuracy of 91.9% in diabetic patients with AMI.

Studies on Anemone nemorosa L. extracts; polyphenols profile, antioxidant activity, and effects on Caco-2 cells by in vitro and in silico studies

In this study, two polar extracts (aqueous and ethanolic) from the aerial part of Anemone nemorosa L. (dried plant) were assessed to reveal their polyphenols profile, antioxidant activity, cytotoxic, and antiproliferative activity on Caco-2 (ATCC-HTB-37) cell line. In silico studies on two key compounds, protoanemonin and anemonin, on four molecular targets – cyclooxygenase-1 and cyclooxygenase-2, and human tankyrase 1 and human tankyrase 2 in relation to human colon cancer cell development have also been achieved. The results are as follows: caffeic acid esters and quercetin glycosides, including (iso)rhamnetin derivates, are the major polyphenol compounds in wood anemone polar extracts; the two polar extracts indicated very strong antioxidant activity in the interval from 0.1 to 5 µg [GAE] per 1 mL sample (IC50 < 0.290 µg GAE/mL), and in vitro studies on Caco-2 cells have revealed their simultaneous stimulatory and protective activity exactly in the concentration area with the strongest antioxidant activity. In silico studies have revealed moderate inhibitory activity of the two key compounds, anemonin and protoanemonin, on the four molecular targets studied; it was concluded having particular benefits of the wood anemone polar extracts in managing postoperative intestinal recovery, and generally in regenerative medicine.

Hypoxia Acclimation Protects against Heart Failure Postacute Myocardial Infarction via Fundc1-Mediated Mitophagy

Mitochondrial dysfunction is the main cause of heart failure (HF) postacute myocardial infarction (AMI). Hypoxia acclimation (HA) reduces efficiently the area of AMI caused by ischemia and/or reperfusion and delays HF. Here, we examined whether HA improves mitochondrial structure and function through the hypoxic autophagy receptor FUNDC1 to prevent HF post-AMI. Male adult mice were acclimated in a low-pressure hypoxic animal chamber (11% oxygen (O2)) for 8 h/day for 28 days, and then, an induced HF post-AMI model via left anterior descending (LAD) artery ligation was structured to explore the efficacy and mechanism of HA. Our results showed that HA exposure can improve cardiac structure and function in mice with HF post-AMI and protected myocardial mitochondrial morphology and function. Further studies showed that HA increased the expression of Fundc1 protein and its associated mitophagy protein LC3 in myocardial tissue after infarction. We then established a cellular model of oxygen glucose deprivation (OGD) in vitro, and knockdown of FUNDC1 attenuated the protective effect of HA exposed on cardiomyocyte mitochondria and increased cardiomyocyte apoptosis. In conclusion, the protective effect of HA on HF post-AMI is achieved by regulating Fundc1-mediated mitophagy in myocardial tissue. FUNDC1-mediated mitophagy could be a promising strategy to treat cardiovascular diseases, including HF.

Myocardial Cytoskeletal Adaptations in Advanced Kidney Disease

Background The myocardial cytoskeleton functions as the fundamental framework critical for organelle function, bioenergetics and myocardial remodeling. To date, impairment of the myocardial cytoskeleton occurring in the failing heart in patients with advanced chronic kidney disease has been largely undescribed. Methods and Results We conducted a 3-arm cross-sectional cohort study of explanted human heart tissues from patients who are dependent on hemodialysis (n=19), hypertension (n=10) with preserved renal function, and healthy controls (n=21). Left ventricular tissues were subjected to pathologic examination and next-generation RNA sequencing. Mechanistic and interference RNA studies utilizing in vitro human cardiac fibroblast models were performed. Left ventricular tissues from patients undergoing hemodialysis exhibited increased myocardial wall thickness and significantly greater fibrosis compared with hypertension patients (P<0.05) and control (P<0.01). Transcriptomic analysis revealed that the focal adhesion pathway was significantly enriched in hearts from patients undergoing hemodialysis. Hearts from patients undergoing hemodialysis exhibited dysregulated components of the focal adhesion pathway including reduced β-actin (P<0.01), β-tubulin (P<0.01), vimentin (P<0.05), and increased expression of vinculin (P<0.05) compared with controls. Cytoskeletal adaptations in hearts from the hemodialysis group were associated with impaired mitochondrial bioenergetics, including dysregulated mitochondrial dynamics and fusion, and loss of cell survival pathways. Mechanistic studies revealed that cytoskeletal changes can be driven by uremic and metabolic abnormalities of chronic kidney disease, in vitro. Furthermore, focal adhesion kinase silencing via interference RNA suppressed major cytoskeletal proteins synergistically with mineral stressors found in chronic kidney disease in vitro. Conclusions Myocardial failure in advanced chronic kidney disease is characterized by impairment of the cytoskeleton involving disruption of the focal adhesion pathway, mitochondrial failure, and loss of cell survival pathways.

Mitochondrial Determinants of Anti-Cancer Drug-Induced Cardiotoxicity

Mitochondria are key organelles for the maintenance of myocardial tissue homeostasis, playing a pivotal role in adenosine triphosphate (ATP) production, calcium signaling, redox homeostasis, and thermogenesis, as well as in the regulation of crucial pathways involved in cell survival. On this basis, it is not surprising that structural and functional impairments of mitochondria can lead to contractile dysfunction, and have been widely implicated in the onset of diverse cardiovascular diseases, including ischemic cardiomyopathy, heart failure, and stroke. Several studies support mitochondrial targets as major determinants of the cardiotoxic effects triggered by an increasing number of chemotherapeutic agents used for both solid and hematological tumors. Mitochondrial toxicity induced by such anticancer therapeutics is due to different mechanisms, generally altering the mitochondrial respiratory chain, energy production, and mitochondrial dynamics, or inducing mitochondrial oxidative/nitrative stress, eventually culminating in cell death. The present review summarizes key mitochondrial processes mediating the cardiotoxic effects of anti-neoplastic drugs, with a specific focus on anthracyclines (ANTs), receptor tyrosine kinase inhibitors (RTKIs) and proteasome inhibitors (PIs).

Role of Creatine Supplementation in Conditions Involving Mitochondrial Dysfunction: A Narrative Review

Creatine monohydrate (CrM) is one of the most widely used nutritional supplements among active individuals and athletes to improve high-intensity exercise performance and training adaptations. However, research suggests that CrM supplementation may also serve as a therapeutic tool in the management of some chronic and traumatic diseases. Creatine supplementation has been reported to improve high-energy phosphate availability as well as have antioxidative, neuroprotective, anti-lactatic, and calcium-homoeostatic effects. These characteristics may have a direct impact on mitochondrion's survival and health particularly during stressful conditions such as ischemia and injury. This narrative review discusses current scientific evidence for use or supplemental CrM as a therapeutic agent during conditions associated with mitochondrial dysfunction. Based on this analysis, it appears that CrM supplementation may have a role in improving cellular bioenergetics in several mitochondrial dysfunction-related diseases, ischemic conditions, and injury pathology and thereby could provide therapeutic benefit in the management of these conditions. However, larger clinical trials are needed to explore these potential therapeutic applications before definitive conclusions can be drawn.

The Emerging Role of FUNDC1-Mediated Mitophagy in Cardiovascular Diseases

Mitochondria are highly dynamic organelles and play essential role in ATP synthase, ROS production, innate immunity, and apoptosis. Mitochondria quality control is critical for maintaining the cellular function in response to cellular stress, growth, and differentiation Signals. Damaged or unwanted mitochondria are selectively removed by mitophagy, which is a crucial determinant of cell viability. Mitochondria-associated Endoplasmic Reticulum Membranes (MAMs) are the cellular structures that connect the ER and mitochondria and are involved in calcium signaling, lipid transfer, mitochondrial dynamic, and mitophagy. Abnormal mitochondrial quality induced by mitophagy impairment and MAMs dysfunction is associated with many diseases, including cardiovascular diseases (CVDs), metabolic syndrome, and neurodegenerative diseases. As a mitophagy receptor, FUNDC1 plays pivotal role in mitochondrial quality control through regulation of mitophagy and MAMs and is closely related to the occurrence of several types of CVDs. This review covers the regulation mechanism of FUNDC1-mediated mitophagy and MAMs formation, with a particular focus on its role in CVDs.

Mitochondrial proteins that connected with calcium: do their pathways changes in PAH?

Calcium can be regulated by mitochondria and also plays a significant role in mitochondrial pathways. Recent study showed mitochondrial protein changes in the right ventricle in pulmonary arterial hypertension, which affects calcium network at the same time. The specific objective of this study is to assess the pathway of calcium transport by permeable pore in mitochondria and investigate the regulation of mitochondrial proteins in order to find the connection between mitochondrial proteins and right ventricular dysfunction in PAH (pulmonary arterial hypertension). This literature-based review came out by searching articles in Pubmed and Science Direct. And the related flow chart is expressed by the form of PRISMA. There is a network between mitochondria and calcium through the transport chain called mitochondria permeability transition pore (MPTP) as well as different kinds of proteins that are located in the mitochondria. MPTP is a kind of mitochondria pore and can have conformational changes after protein phosphorylation or reaction between mitochondrial proteins to activate the apoptosis capase cascade process in cell death. In addition, MPTP can be activated by other mitochondrial protein like signal transducer activator of transcription3 (STAT3) to activate cytochrome c in pro-apoptosis to initiate cell death at the same time. The most obvious finding from this study is the role of calcium regulation in therapeutic treatment in PAH patients, which suggest an imaginable role for calcium transporter like mitochondria calcium uniporter (MCU) promoting bio-markers in cardiovascular disease resulting from mitochondrial dysfunction. In addition, right ventricle is a target of PAH in which mitochondria in RV would play an essential role in pathways such as ATP production via mitochondria metabolism.

RBFOX2 is critical for maintaining alternative polyadenylation patterns and mitochondrial health in rat myoblasts

RBFOX2, which has a well-established role in alternative splicing, is linked to heart diseases. However, it is unclear whether RBFOX2 has other roles in RNA processing that can influence gene expression in muscle cells, contributing to heart disease. Here, we employ both 3'-end and nanopore cDNA sequencing to reveal a previously unrecognized role for RBFOX2 in maintaining alternative polyadenylation (APA) signatures in myoblasts. RBFOX2-mediated APA modulates mRNA levels and/or isoform expression of a collection of genes, including contractile and mitochondrial genes. Depletion of RBFOX2 adversely affects mitochondrial health in myoblasts, correlating with disrupted APA of mitochondrial gene Slc25a4. Mechanistically, RBFOX2 regulation of Slc25a4 APA is mediated through consensus RBFOX2 binding motifs near the distal polyadenylation site, enforcing the use of the proximal polyadenylation site. In sum, our results unveil a role for RBFOX2 in fine-tuning expression of mitochondrial and contractile genes via APA in myoblasts relevant to heart diseases.

Reciprocal organ interactions during heart failure: a position paper from the ESC Working Group on Myocardial Function

Heart failure-either with reduced or preserved ejection fraction (HFrEF/HFpEF)-is a clinical syndrome of multifactorial and gender-dependent aetiology, indicating the insufficiency of the heart to pump blood adequately to maintain blood flow to meet the body's needs. Typical symptoms commonly include shortness of breath, excessive fatigue with impaired exercise capacity, and peripheral oedema, thereby alluding to the fact that heart failure is a syndrome that affects multiple organ systems. Patients suffering from progressed heart failure have a very limited life expectancy, lower than that of numerous cancer types. In this position paper, we provide an overview regarding interactions between the heart and other organ systems, the clinical evidence, underlying mechanisms, potential available or yet-to-establish animal models to study such interactions and finally discuss potential new drug interventions to be developed in the future. Our working group suggests that more experimental research is required to understand the individual molecular mechanisms underlying heart failure and reinforces the urgency for tailored therapeutic interventions that target not only the heart but also other related affected organ systems to effectively treat heart failure as a clinical syndrome that affects and involves multiple organs.

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.

Insulin Resistance in Skeletal Muscle Selectively Protects the Heart in Response to Metabolic Stress

Obesity and type 2 diabetes mellitus (T2DM) are the leading causes of cardiovascular morbidity and mortality. Although insulin resistance is believed to underlie these disorders, anecdotal evidence contradicts this common belief. Accordingly, obese patients with cardiovascular disease have better prognoses relative to leaner patients with the same diagnoses, whereas treatment of T2DM patients with thiazolidinedione, one of the popular insulin-sensitizer drugs, significantly increases the risk of heart failure. Using mice with skeletal musclespecific ablation of the insulin receptor gene (MIRKO), we addressed this paradox by demonstrating that insulin signaling in skeletal muscles specifically mediated cross talk with the heart, but not other metabolic tissues, to prevent cardiac dysfunction in response to metabolic stress. Despite severe hyperinsulinemia and aggregating obesity, MIRKO mice were protected from myocardial insulin resistance, mitochondrial dysfunction, and metabolic reprogramming in response to diet-induced obesity. Consequently, the MIRKO mice were also protected from myocardial inflammation, cardiomyopathy, and left ventricle dysfunction. Together, our findings suggest that insulin resistance in skeletal muscle functions as a double-edged sword in metabolic diseases.

Effects of SGLT2 Inhibitors on Ion Homeostasis and Oxidative Stress associated Mechanisms in Heart Failure

Sodium-glucose cotransporter 2 (SGLT2) inhibitors present a class of antidiabetic drugs, which inhibit renal glucose reabsorption resulting in the elevation of urinary glucose levels. Within the past years, SGLT2 inhibitors have become increasingly relevant due to their effects beyond glycemic control in patients with type 2 diabetes (T2DM). Although dedicated large trials demonstrated cardioprotective effects of SGLT2 inhibitors, the exact mechanisms responsible for those benefits have not been fully identified. Alterations in Ca²⁺ signaling and oxidative stress accompanied by excessive reactive oxygen species (ROS) production, fibrosis and inflammatory processes form cornerstones of potential molecular targets for SGLT2 inhibitors. This review focused on three hypotheses for SGLT2 inhibitor-mediated cardioprotection: ion homeostasis, oxidative stress and endothelial dysfunction.

Role of Irisin in Myocardial Infarction, Heart Failure, and Cardiac Hypertrophy

Irisin is a myokine derived from the cleavage of fibronectin type III domain-containing 5. Irisin regulates mitochondrial energy, glucose metabolism, fatty acid oxidation, and fat browning. Skeletal muscle and cardiomyocytes produce irisin and affect various cardiovascular functions. In the early phase of acute myocardial infarction, an increasing irisin level can reduce endothelial damage by inhibiting inflammation and oxidative stress. By contrast, higher levels of irisin in the later phase of myocardial infarction are associated with more cardiovascular events. During different stages of heart failure, irisin has various influences on mitochondrial dysfunction, oxidative stress, metabolic imbalance, energy expenditure, and heart failure prognosis. Irisin affects blood pressure and controls hypertension through modulating vasodilatation. Moreover, irisin can enhance vasoconstriction via the hypothalamus. Because of these dual effects of irisin on cardiovascular physiology, irisin can be a critical therapeutic target in cardiovascular diseases. This review focuses on the complex functions of irisin in myocardial ischemia, heart failure, and cardiac hypertrophy.

Superiority of focused ion beam-scanning electron microscope tomography of cardiomyocytes over standard 2D analyses highlighted by unmasking mitochondrial heterogeneity

BACKGROUND

Cardioprotection by preventing or repairing mitochondrial damage is an unmet therapeutic need. To understand the role of cardiomyocyte mitochondria in physiopathology, the reliable characterization of the mitochondrial morphology and compartment is pivotal. Previous studies mostly relied on two-dimensional (2D) routine transmission electron microscopy (TEM), thereby neglecting the real three-dimensional (3D) mitochondrial organization. This study aimed to determine whether classical 2D TEM analysis of the cardiomyocyte ultrastructure is sufficient to comprehensively describe the mitochondrial compartment and to reflect mitochondrial number, size, dispersion, distribution, and morphology.

METHODS

Spatial distribution of the complex mitochondrial network and morphology, number, and size heterogeneity of cardiac mitochondria in isolated adult mouse cardiomyocytes and adult wild-type left ventricular tissues (C57BL/6) were assessed using a comparative 3D imaging system based on focused ion beam-scanning electron microscopy (FIB-SEM) nanotomography. For comparison of 2D vs. 3D data sets, analytical strategies and mathematical comparative approaches were performed. To confirm the value of 3D data for mitochondrial changes, we compared the obtained values for number, coverage area, size heterogeneity, and complexity of wild-type cardiomyocyte mitochondria with data sets from mice lacking the cytosolic and mitochondrial protein BNIP3 (BCL-2/adenovirus E1B 19-kDa interacting protein 3; Bnip3^-/- ) using FIB-SEM. Mitochondrial respiration was assessed on isolated mitochondria using the Seahorse XF analyser. A cardiac biopsy was obtained from a male patient (48 years) suffering from myocarditis.

RESULTS

The FIB-SEM nanotomographic analysis revealed that no linear relationship exists for mitochondrial number (r = 0.02; P = 0.9511), dispersion (r = -0.03; P = 0.9188), and shape (roundness: r = 0.15, P = 0.6397; elongation: r = -0.09, P = 0.7804) between 3D and 2D results. Cumulative frequency distribution analysis showed a diverse abundance of mitochondria with different sizes in 3D and 2D. Qualitatively, 2D data could not reflect mitochondrial distribution and dynamics existing in 3D tissue. 3D analyses enabled the discovery that BNIP3 deletion resulted in more smaller, less complex cardiomyocyte mitochondria (number: P < 0.01; heterogeneity: C.V. wild-type 89% vs. Bnip3^-/- 68%; complexity: P < 0.001) forming large myofibril-distorting clusters, as seen in human myocarditis with disturbed mitochondrial dynamics. Bnip3^-/- mice also show a higher respiration rate (P < 0.01).

CONCLUSIONS

Here, we demonstrate the need of 3D analyses for the characterization of mitochondrial features in cardiac tissue samples. Hence, we observed that BNIP3 deletion physiologically acts as a molecular brake on mitochondrial number, suggesting a role in mitochondrial fusion/fission processes and thereby regulating the homeostasis of cardiac bioenergetics.

Sex differences in the impact of parental obesity on offspring cardiac SIRT3 expression, mitochondrial efficiency, and diastolic function early in life

Previous studies suggest that parental obesity may adversely impact long-term metabolic health of the offspring. We tested the hypothesis that parental (paternal + maternal) obesity impairs cardiac function in the offspring early in life. Within 1-3 days after weaning, offspring from obese rats fed a high-fat diet (HFD-Offs) and age-matched offspring from lean rats (ND-Offs) were submitted to echocardiography and cardiac catheterization for assessment of pressure-volume relationships. Then, hearts were digested and isolated cardiomyocytes were used to determine contractile function, calcium transients, proteins related to calcium signaling, and mitochondrial bioenergetics. Female and male HFD-Offs were heavier (72 ± 2 and 61 ± 4 g vs. 57 ± 2 and 49 ± 1 g), hyperglycemic (112 ± 8 and 115 ± 12 mg/dL vs. 92 ± 10 and 96 ± 8 mg/dL) with higher plasma insulin and leptin concentrations compared with female and male ND-Offs. When compared with male controls, male HFD-Offs exhibited similar systolic function but impaired diastolic function as indicated by increased IVRT (22 ± 1 vs. 17 ± 1 ms), E/E' ratio (29 ± 2 vs. 23 ± 1), and tau (5.7 ± 0.2 vs. 4.8 ± 0.2). The impaired diastolic function was associated with reduced resting free Ca²⁺ levels and phospholamban protein expression, increased activated matrix metalloproteinase 2, and reduced SIRT3 protein expression, mitochondrial ATP reserve, and ATP-linked respiration. These results indicate that male and female Offs from obese parents have multiple metabolic abnormalities early in life (1-3 days after weaning) and that male, but not female, Offs have impaired diastolic function as well as reductions in cardiac SIRT3, resting free Ca²⁺ levels, and mitochondrial biogenesis.NEW & NOTEWORTHY Parental obesity contributes to diastolic dysfunction in young offspring (1-3 days after weaning) in a sex-dependent manner, as well as reduced cardiac SIRT3 expression and altered mitochondrial bioenergetics, resting Ca²⁺ levels, and reduced phospholamban protein levels.

TMEM135 is a Novel Regulator of Mitochondrial Dynamics and Physiology with Implications for Human Health Conditions

Transmembrane proteins (TMEMs) are integral proteins that span biological membranes. TMEMs function as cellular membrane gates by modifying their conformation to control the influx and efflux of signals and molecules. TMEMs also reside in and interact with the membranes of various intracellular organelles. Despite much knowledge about the biological importance of TMEMs, their role in metabolic regulation is poorly understood. This review highlights the role of a single TMEM, transmembrane protein 135 (TMEM135). TMEM135 is thought to regulate the balance between mitochondrial fusion and fission and plays a role in regulating lipid droplet formation/tethering, fatty acid metabolism, and peroxisomal function. This review highlights our current understanding of the various roles of TMEM135 in cellular processes, organelle function, calcium dynamics, and metabolism.

Consuming oxidative frying oil impairs cardiac energy production and calcium recycling, causing cardiac hypertrophy, fibrosis and diastolic dysfunction in male Sprague Dawley rats

With regards to cardiovascular health, frequent consumption of fried foods is discouraged, despite a lack of clear evidence of a direct link between eating oxidative frying oil (OFO) and cardiovascular diseases. In this study, male Sprague Dawley rats were exposed to diets containing fresh or fried soybean oil (groups C and O, respectively) from in utero to 28 weeks of age. A subset of rats in group O was supplemented with vitamin E (500 mg/kg of DL-α-tocopherol acetate; group OE) from 8 week of age onward to mitigate oxidative stress associated with OFO ingestion. Echocardiography, cardiac histology and indices associated with ATP production and calcium cycling in cardiac tissues were measured. Compared to group C, there was cardiac hypertrophy, fibrosis and diastolic dysfunction, in groups O and OE, with no differences between the latter two groups. Although cardiac mRNA levels of genes associated with mitochondrial biogenesis and function were increased, there were lower ATP concentrations and higher transcripts of uncoupling proteins in groups O and OE than in group C. In addition, decreases in phosphorylation of phospholamban and Ca²⁺/calmodulin-dependent protein kinase II activity, plus increased protein phosphatase 2A activity in groups O and OE, implied calcium cycling required for cardiac function was disrupted by OFO consumption. We concluded that long-term OFO exposure resulted in cardiac hypertrophy, fibrosis and diastolic dysfunction that was not mitigated by vitamin E supplementation. Underlying mechanisms were partly attributed to inefficient energy production via uncoupled phosphorylation and disrupted calcium cycling.

Skeletal Muscle Mitochondria Dysfunction in Genetic Neuromuscular Disorders with Cardiac Phenotype

Mitochondrial dysfunction is considered the major contributor to skeletal muscle wasting in different conditions. Genetically determined neuromuscular disorders occur as a result of mutations in the structural proteins of striated muscle cells and therefore are often combined with cardiac phenotype, which most often manifests as a cardiomyopathy. The specific roles played by mitochondria and mitochondrial energetic metabolism in skeletal muscle under muscle-wasting conditions in cardiomyopathies have not yet been investigated in detail, and this aspect of genetic muscle diseases remains poorly characterized. This review will highlight dysregulation of mitochondrial representation and bioenergetics in specific skeletal muscle disorders caused by mutations that disrupt the structural and functional integrity of muscle cells.

Impact of Aldosterone on the Failing Myocardium: Insights from Mitochondria and Adrenergic Receptors Signaling and Function

The mineralocorticoid aldosterone regulates electrolyte and blood volume homeostasis, but it also adversely modulates the structure and function of the chronically failing heart, through its elevated production in chronic human post-myocardial infarction (MI) heart failure (HF). By activating the mineralocorticoid receptor (MR), a ligand-regulated transcription factor, aldosterone promotes inflammation and fibrosis of the heart, while increasing oxidative stress, ultimately induding mitochondrial dysfunction in the failing myocardium. To reduce morbidity and mortality in advanced stage HF, MR antagonist drugs, such as spironolactone and eplerenone, are used. In addition to the MR, aldosterone can bind and stimulate other receptors, such as the plasma membrane-residing G protein-coupled estrogen receptor (GPER), further complicating it signaling properties in the myocardium. Given the salient role that adrenergic receptor (ARs)—particularly βARs—play in cardiac physiology and pathology, unsurprisingly, that part of the impact of aldosterone on the failing heart is mediated by its effects on the signaling and function of these receptors. Aldosterone can significantly precipitate the well-documented derangement of cardiac AR signaling and impairment of AR function, critically underlying chronic human HF. One of the main consequences of HF in mammalian models at the cellular level is the presence of mitochondrial dysfunction. As such, preventing mitochondrial dysfunction could be a valid pharmacological target in this condition. This review summarizes the current experimental evidence for this aldosterone/AR crosstalk in both the healthy and failing heart, and the impact of mitochondrial dysfunction in HF. Recent findings from signaling studies focusing on MR and AR crosstalk via non-conventional signaling of molecules that normally terminate the signaling of ARs in the heart, i.e., the G protein-coupled receptor-kinases (GRKs), are also highlighted.

LACTATE CAN BE A MARKER OF METABOLIC SYNDROME IN SEVERE OBESITY?

Background:

In the last decades, numerous studies have confirmed the importance of lactate - by-product to the nutrient signal of the intracellular redox state - to regulatory functions in energy metabolism.

Aim:

To evaluate changes in blood lactate in patients with severe obesity and its correlation with body composition and metabolic profile.

Methods:

Twenty-four people with severe obesity (BMI=40 kg/m²) were evaluated in a prospective case-control study before and six months after Roux-in-Y gastric bypass. The blood lactate, total cholesterol, and fractions, C-reactive protein and HOMA-IR were analyzed after 12 h fasting. Body mass composition was evaluated by bioelectrical impedance and respiratory quotient was measured by indirect calorimetry.

Results:

The initial lactate level was 2.5±1.1 mmol/l and returned to normal level (1.9±3.6 mmol/l, p=0.0018) after surgery. This reduction was positively correlated with a decrease in BMI (p=0.0001), % free fat mass (p=0,001), % fat mass (p=0.001) and HOMA-IR (p=0.01). There was normalization of lactatemia in 70% of patients. There was no correlation between lactatemia and C-reactive protein.

Conclusions:

There was a significant improvement of metabolic parameters, normalization of blood lactate, fat mass loss, although these individuals remained with a high BMI.

Both Traditional and Stair Climbing-based HIIT Cardiac Rehabilitation Induce Beneficial Muscle Adaptations

PURPOSE

There is a lack of knowledge as to how different exercise-based cardiac rehabilitation programming affects skeletal muscle adaptations in coronary artery disease (CAD) patients. We first characterized the skeletal muscle from adults with CAD compared with a group of age- and sex-matched healthy adults. We then determined the effects of a traditional moderate-intensity continuous exercise program (TRAD) or a stair climbing-based high-intensity interval training program (STAIR) on skeletal muscle metabolism in CAD.

METHODS

Sixteen adults (n = 16, 61 ± 7 yr), who had undergone recent treatment for CAD, were randomized to perform (3 d·wk-1) either TRAD (n = 7, 30 min at 60%-80% of peak heart rate) or STAIR (n = 9, 3 × 6 flights) for 12 wk. Muscle biopsies were collected at baseline in both CAD and healthy controls (n = 9), and at 4 and 12 wk after exercise training in CAD patients undertaking TRAD or STAIR.

RESULTS

We found that CAD had a lower capillary-to-fiber ratio (C/Fi, 35% ± 25%, P = 0.06) and capillary-to-fiber perimeter exchange (CFPE) index (23% ± 29%, P = 0.034) in Type II fibers compared with healthy controls. However, 12 wk of cardiac rehabilitation with either TRAD or STAIR increased C/Fi (Type II, 23% ± 14%, P < 0.001) and CFPE (Type I, 10% ± 23%, P < 0.01; Type II, 18% ± 22%, P = 0.002).

CONCLUSION

Cardiac rehabilitation via TRAD or STAIR exercise training improved the compromised skeletal muscle microvascular phenotype observed in CAD patients.

In vitro model of ischemic heart failure using human induced pluripotent stem cell-derived cardiomyocytes

Human induced pluripotent stem cell-derived cardiomyocytes (hiPSC-CMs) have been used extensively to model inherited heart diseases, but hiPSC-CM models of ischemic heart disease are lacking. Here, our objective was to generate an hiPSC-CM model of ischemic heart disease. To this end, hiPSCs were differentiated into functional hiPSC-CMs and then purified using either a simulated ischemia media or by using magnetic antibody-based purification targeting the nonmyocyte population for depletion from the cell population. Flow cytometry analysis confirmed that each purification approach generated hiPSC-CM cultures that had more than 94% cTnT+ cells. After purification, hiPSC-CMs were replated as confluent syncytial monolayers for electrophysiological phenotype analysis and protein expression by Western blotting. The phenotype of metabolic stress-selected hiPSC-CM monolayers recapitulated many of the functional and structural hallmarks of ischemic CMs, including elevated diastolic calcium, diminished calcium transient amplitude, prolonged action potential duration, depolarized resting membrane potential, hypersensitivity to chemotherapy-induced cardiotoxicity, depolarized mitochondrial membrane potential, depressed SERCA2a expression, reduced maximal oxygen consumption rate, and abnormal response to β1-adrenergic receptor stimulation. These findings indicate that metabolic selection of hiPSC-CMs generated cell populations with phenotype similar to what is well known to occur in the setting of ischemic heart failure and thus provide a opportunity for study of human ischemic heart disease.

Preparation and biological evaluation of radioiodine-labeled triphenylphosphine derivatives as mitochondrial targeting probes

The positive-charged lipophilic triphenylphosphonium cations (TPPs⁺ ) have been served as mitochondrial targeting vehicles for the delivery of various probes. In this study, we developed a new method for the preparation of radioiodine-labeled TPPs⁺ . Four ¹²⁵ I-labeled TPPs⁺ , [¹²⁵ I] 9-[¹²⁵ I] 12, were prepared from the corresponding triphenylphosphine phenylborate precursors of B 5-B 8 via an optimized copper-catalyzed one-step procedure in high radiochemical yield (>95%). After radio-HPLC purification, the final products could be obtained with high specific activity. Their physicochemical properties, in vitro cellular uptake, and ex vivo mice biodistribution were investigated. The results suggested the ¹²⁵ I-labeled TPPs⁺ were lipophilic and could specifically accumulate in the mitochondrial-rich myocardial cells through the mitochondrial membrane potential.

Cognitive impairment in myocardial infarction and heart failure

Myocardial infarction (MI) occurs when coronary blood flow is decreased due to an obstruction/occlusion of the vessels, leading to myocardial death and progression to heart failure (HF). Cognitive impairment, anxiety, depression and memory loss are the most frequent mental health problems among patients with HF. The most common cause of cognitive decline is cardiac systolic dysfunction, which leads to reduced cerebral perfusion. Several in vivo and clinical studies provide information regarding the underlying mechanisms of HF in brain pathology. Neurohormonal activation, oxidative stress, inflammation, glial activation, dendritic spine loss and brain programmed cell death are all proposed as contributors of cognitive impairment in HF. Furthermore, several investigations into the effects of various medications on brain pathology utilizing MI models have been reported. In this review, potential mechanisms involving HF-associated cognitive impairment, as well as neuroprotective interventions in HF models, are discussed and summarized. In addition, gaps in the surrounding knowledge, including the types of brain cell death and the effects of cell death inhibitors in HF, are presented and discussed. This review provides valuable information that will suggest the potential therapeutic strategies for cognitive impairment in patients with HF.

Association of gut-related metabolites with outcome in acute heart failure

BACKGROUND

Trimethylamine N-oxide (TMAO), a gut-related metabolite, is associated with heart failure (HF) outcomes. However, TMAO is the final product of a complex metabolic pathway (ie, choline/carnitine) that has never been entirely investigated in HF. The present study investigates a panel of metabolites involved in the TMAO-choline/carnitine metabolic pathway for their associations with outcome in acute HF patients.

METHODS

In total, 806 plasma samples from acute HF patients were analyzed for TMAO, trimethyllysine, L-carnitine, acetyl-L-carnitine, γ-butyrobetaine, crotonobetaine, trimethylamine, betaine aldehyde, choline, and betaine using a developed liquid chromatography-tandem mass spectrometry method. Associations with outcome of all-cause mortality (death) and a composite of all-cause mortality and/or rehospitalization caused by HF (death/HF) at 30 days and 1 year were investigated.

RESULTS

TMAO, trimethyllysine, L-carnitine, acetyl-L-carnitine, and γ-butyrobetaine were associated with death and death/HF at 30 days (short term; hazard ratio 1.30-1.49, P≤ .021) and at 1 year (long term; hazard ratio 1.15-1.25, P≤ .026) when adjusted for cardiac risk factors. L-carnitine and acetyl-L-carnitine were superior for short-term outcomes whereas TMAO was the superior metabolite for association with long-term outcomes. Furthermore, acetyl-L-carnitine and L-carnitine were superior for in-hospital mortality and improved risk stratification when combined with current clinical risk scores (ie, Acute Decompensated HEart Failure National REgistry, Organized Program To Initiate Lifesaving Treatment In Hospitalized Patients With Heart Failure, and Get With The Guidelines-Heart Failure; odds ratio (OR) ≥ 1.52, P≤ .020).

CONCLUSIONS

Carnitine-related metabolites show associations with adverse outcomes in acute HF, in particular L-carnitine and acetyl-L-carnitine for short-term outcomes, and TMAO for long-term outcomes. Further studies are warranted to investigate the role and implications of carnitine metabolites including intervention in the pathogenesis of HF.

Mitochondrial functional resilience after TFAM ablation in the adult heart

The nuclear genome-encoded mitochondrial DNA (mtDNA) transcription factor A (TFAM) is indispensable for mitochondrial energy production in the developing and postnatal heart; a similar role for TFAM is inferred in adult heart. Here, we provide evidence that challenges this long-standing paradigm. Unexpectedly, conditional Tfam ablation in vivo in adult mouse cardiomyocytes resulted in a prolonged period of functional resilience characterized by preserved mtDNA content, mitochondrial function, and cardiac function, despite mitochondrial structural alterations and decreased transcript abundance. Remarkably, TFAM protein levels did not directly dictate mtDNA content in the adult heart, and mitochondrial translation was preserved with acute TFAM inactivation, suggesting maintenance of respiratory chain assembly/function. Long-term Tfam inactivation, however, downregulated the core mtDNA transcription and replication machinery, leading to mitochondrial dysfunction and cardiomyopathy. Collectively, in contrast to the developing heart, these data reveal a striking resilience of the differentiated adult heart to acute insults to mtDNA regulation.

Real-time in situ monitoring of Lon and Caspase-3 for assessing the state of cardiomyocytes under hypoxic conditions via a novel Au-Se fluorescent nanoprobe

Myocardial dysfunction caused by cardiomyocyte apoptosis under ischemic and hypoxic conditions is the pathological basis of most cardiovascular diseases. Current diagnosis of myocardial dysfunction still focuses on the symptomatic stage, usually after the occurrence of the irreversible remodelling and functional impairment. Thus, early stage identification of the apoptotic cardiomyocytes induced by hypoxia is highly significant for preventing the onset and delaying the progression of myocardial dysfunction. Herein, a novel Au-Se nanoprobe with strong anti-interference capability was developed for simultaneous real-time in situ monitoring the expression of Lon protease (Lon) and Caspase-3 with high-fidelity in living cardiomyocytes. As Lon upregulation plays a major role in the initiation of hypoxia-induced apoptosis and Caspase-3 is a marker protein for apoptosis, the nanoprobe has been successfully applied for imaging the activation of Lon-Caspase-3 apoptotic signalling pathway and assessing the state of cardiomyocytes under hypoxic conditions. Furthermore, combining with mitochondrial H₂O₂ probe-MitoPY1, the nanoprobe was also used to confirm the synergistic effect of Lon and ROS on hypoxia-induced apoptosis of cardiomyocytes and evaluate the function of ROS scavenger on attenuating such apoptosis. This work proposed a promising strategy for early diagnosis, prevention and treatment of hypoxic-ischemic myocardial dysfunction.

Modulation of Mitochondrial Quality Control Processes by BGP-15 in Oxidative Stress Scenarios: From Cell Culture to Heart Failure

Heart failure (HF) is a complex chronic clinical disease characterized by among others the damage of the mitochondrial network. The disruption of the mitochondrial quality control and the imbalance in fusion-fission processes lead to a lack of energy supply and, finally, to cell death. BGP-15 (O-[3-piperidino-2-hydroxy-1-propyl]-nicotinic acid amidoxime dihydrochloride) is an insulin sensitizer molecule and has a cytoprotective effect in a wide variety of experimental models. In our recent work, we aimed to clarify the mitochondrial protective effects of BGP-15 in a hypertension-induced heart failure model and "in vitro." Spontaneously hypertensive rats (SHRs) received BGP-15 or placebo for 18 weeks. BGP-15 treatment preserved the normal mitochondrial ultrastructure and enhanced the mitochondrial fusion. Neonatal rat cardiomyocytes (NRCMs) were stressed by hydrogen-peroxide. BGP-15 treatment inhibited the mitochondrial fission processes, promoted mitochondrial fusion, maintained the integrity of the mitochondrial genome, and moreover enhanced the de novo biogenesis of the mitochondria. As a result of these effects, BGP-15 treatment also supports the maintenance of mitochondrial function through the preservation of the mitochondrial structure during hydrogen peroxide-induced oxidative stress as well as in an "in vivo" heart failure model. It offers the possibility, which pharmacological modulation of mitochondrial quality control under oxidative stress could be a novel therapeutic approach in heart failure.

Simulating cardiac Ca2+ release units: effects of RyR cluster size and Ca2+ buffers on diastolic Ca2+ leak

Leak of Ca²⁺ out of the cardiac sarcoplasmic reticulum (SR) via ryanodine receptors (RyRs) during diastole is vital to regulate SR Ca²⁺ levels. This leak can become deleterious when large spontaneous RyR-mediated Ca²⁺ release events evoke proarrhythmic Ca²⁺ waves that can lead to delayed after-depolarizations. Here, we model diastolic SR Ca²⁺ leak at individual SR Ca²⁺ release sites using computer simulations of RyR arrays like those in the dyadic cleft. The results show that RyR arrays size has a significant effect on SR Ca²⁺ leak, with bigger arrays producing larger and more frequent Ca²⁺ release events. Moreover, big RyR arrays are more susceptible to small changes in the levels of dyadic Ca²⁺ buffers. Such changes in buffering shift Ca²⁺ leak from small Ca²⁺ release events (involving few open RyRs) to larger events (with many open RyRs). Moreover, by analyzing a large parameter space of possible buffering and SR Ca²⁺ loads, we find further evidence for the hypothesis that SR Ca²⁺ leak by RyR arrays can undergo a sudden phase transition.