Dynamic organization of mitochondria in human heart and in myocardial disease

Mitochondrial quality control: Biochemical mechanism of cardiovascular disease

Mitochondria play a key role in the regulation of energy homeostasis and ATP production in cardiac cells. Mitochondrial dysfunction can trigger several pathological events that contribute to the development and progression of cardiovascular diseases. These mechanisms include the induction of oxidative stress, dysregulation of intracellular calcium cycling, activation of the apoptotic pathway, and alteration of lipid metabolism. This review focuses on the role of mitochondria in intracellular signaling associated with cardiovascular diseases, emphasizing the contributions of reactive oxygen species production and mitochondrial dynamics. Indeed, mitochondrial dysfunction has been implicated in every aspect of cardiovascular disease and is currently being evaluated as a potential target for therapeutic interventions. To treat cardiovascular diseases and improve overall heart health, it is important to better understand these biochemical systems. These findings allow the achievement of targeted therapies and preventive measures. Therefore, this review investigates different studies that demonstrate how changes in mitochondrial dynamics like fusion, fission, and mitophagy contribute to the development or worsening of disorders related to heart diseases by summarizing current research on their role.

A novel super-resolution STED microscopy analysis approach to observe spatial MCU and MICU1 distribution dynamics in cells

The uptake of Ca2+ by mitochondria is an important and tightly controlled process in various tissues. Even small changes in the key proteins involved in this process can lead to significant cellular dysfunction and, ultimately, cell death. In this study, we used stimulated emission depletion (STED) microscopy and developed an unbiased approach to monitor the sub-mitochondrial distribution and dynamics of the mitochondrial calcium uniporter (MCU) and mitochondrial calcium uptake 1 (MICU1) under resting and stimulated conditions. To visualize the inner mitochondrial membrane, the STED-optimized dye called pkMitoRed was used. The study presented herein builds on the previously verified exclusive localization of MICU1 in the intermembrane space, and that MCU moves exclusively laterally along the inner mitochondrial membrane (IMM). We applied a multi-angled arrow histogram to analyze the distribution of proteins within mitochondria, providing a one-dimensional view of protein localization along a defined distance. Combining this with optimal transport colocalization enabled us to further predict submitochondrial protein distribution. Results indicate that in HeLa cells Ca2+ elevation yielded MCU translocation from the cristae membrane (CM) to the inner boundary membrane (IBM). In AC16 cardiomyocyte cell line, MCU is mainly located at the IBM under resting conditions, and it translocates to the CM upon rising Ca2+. Our data describe a novel unbiased super-resolution image analysis approach. Our showcase sheds light on differences in spatial distribution dynamics of MCU in cell lines with different MICU1:MCU abundance.

Identification of necroptosis-related diagnostic biomarkers in coronary heart disease

Background

The implication of necroptosis in cardiovascular disease was already recognized. However, the molecular mechanism of necroptosis has not been extensively studied in coronary heart disease (CHD).

Methods

The differentially expressed genes (DEGs) between CHD and control samples were acquired in the GSE20681 dataset downloaded from the GEO database. Key necroptosis-related DEGs were captured and ascertained by bioinformatics analysis techniques, including weighted gene co-expression network analysis (WGCNA) and two machine learning algorithms, while single-gene gene set enrichment analysis (GSEA) revealed their molecular mechanisms. The diagnostic biomarkers were selected via receiver operating characteristic (ROC) analysis. Moreover, an analysis of immune elements infiltration degree was carried out. Authentication of pivotal gene expression at the mRNA level was investigated in vitro utilizing quantitative real-time PCR (qRT-PCR).

Results

A total of 94 DE-NRGs were recognized here, among which, FAM166B, NEFL, POLDIP3, PRSS37, and ZNF594 were authenticated as necroptosis-related biomarkers, and the linear regression model based on them presented an acceptable ability to different sample types. Following regulatory analysis, the ascertained biomarkers were markedly abundant in functions pertinent to blood circulation, calcium ion homeostasis, and the MAPK/cAMP/Ras signaling pathway. Single-sample GSEA exhibited that APC co-stimulation and CCR were more abundant, and aDCs and B cells were relatively scarce in CHD patients. Consistent findings from bioinformatics and qRT-PCR analyses confirmed the upregulation of NEFL and the downregulation of FAM166B, POLDIP3, and PRSS37 in CHD.

Conclusion

Our current investigation identified 5 necroptosis-related genes that could be diagnostic markers for CHD and brought a novel comprehension of the latent molecular mechanisms of necroptosis in CHD.

Isoliquiritin can cause mitochondrial dysfunction and regulate Nrf2 to affect the development of mouse oocytes

IsoliQuirtigenin (ILG) has been widely studied in somatic cells and tissues, but less in reproductive development. It is a kind of widely used food additive. In this study, it was found that ILG could significantly increase the levels of ROS,GSH and MMP in mouse oocytes (P < 0.01). In order to explore the cause of this phenomenon, it was found that the abnormal distribution of mitochondria and ATP synthesis levels were significantly increased (P < 0.05). At this time, we made a reasonable hypothesis that ILG affected mitochondrial function. In subsequent studies, it was found that the endogenous ROS accumulation level in mitochondria was significantly increased. After continuous RT-PCR screening, it was found that the expression of Nrf2 was significantly inhibited (P < 0.01). Its upstream and downstream FOXO3 GPX1, CAT, SOD2, SIRT1 gene also appear different degree of significant change (P < 0.05), in which the lower expression of NADP + (P < 0.05) illustrates the mitochondrial ATP synthesis electronic chain were suppressed, it also has the reason, By inhibiting electron chain and ATP synthesis, ILG leads to oocyte apoptosis and initiation of autophagy, reducing oocyte and its subsequent developmental potential.

OPA1, a molecular regulator of dilated cardiomyopathy

Dilated cardiomyopathy (DCM) is a disease with no specific treatment, poor prognosis and high mortality. During DCM development, there is apoptosis, mitochondrial dynamics imbalance and changes in cristae structure. Optic atrophy 1 (OPA1) appears at high frequency in these three aspects. DCM LMNA (LaminA/C) gene mutation can activate TP53, and the study of P53 shows that P53 affects OPA1 through Bak/Bax and OMA1 (a metalloprotease). OPA1 can be considered the missing link between DCMp53 and DCM apoptosis, mitochondrial dynamics imbalance and changes in cristae structure. OPA1 regulates apoptosis by regulating the release of cytochrome c from the mitochondrial matrix through CJs (crisp linkages, located in the inner mitochondrial membrane) and unbalances mitochondrial fusion and fission by affecting mitochondrial inner membrane (IM) fusion. OPA1 is also associated with the formation and maintenance of mitochondrial cristae. OPA1 is not the root cause of DCM, but it is an essential mediator in P53 mediating the occurrence and development of DCM, so OPA1 also becomes a molecular regulator of DCM. This review discusses the implication of OPA1 for DCM from three aspects: apoptosis, mitochondrial dynamics and ridge structure.

Role of Mitochondrial Dynamics in Heart Diseases

Mitochondrial dynamics, including fission and fusion processes, are essential for heart health. Mitochondria, the powerhouses of cells, maintain their integrity through continuous cycles of biogenesis, fission, fusion, and degradation. Mitochondria are relatively immobile in the adult heart, but their morphological changes due to mitochondrial morphology factors are critical for cellular functions such as energy production, organelle integrity, and stress response. Mitochondrial fusion proteins, particularly Mfn1/2 and Opa1, play multiple roles beyond their pro-fusion effects, such as endoplasmic reticulum tethering, mitophagy, cristae remodeling, and apoptosis regulation. On the other hand, the fission process, regulated by proteins such as Drp1, Fis1, Mff and MiD49/51, is essential to eliminate damaged mitochondria via mitophagy and to ensure proper cell division. In the cardiac system, dysregulation of mitochondrial dynamics has been shown to cause cardiac hypertrophy, heart failure, ischemia/reperfusion injury, and various cardiac diseases, including metabolic and inherited cardiomyopathies. In addition, mitochondrial dysfunction associated with oxidative stress has been implicated in atherosclerosis, hypertension and pulmonary hypertension. Therefore, understanding and regulating mitochondrial dynamics is a promising therapeutic tool in cardiac diseases. This review summarizes the role of mitochondrial morphology in heart diseases for each mitochondrial morphology regulatory gene, and their potential as therapeutic targets to heart diseases.

Mitochondria as a therapeutic: a potential new frontier in driving the shift from tissue repair to regeneration

Fibrosis, or scar tissue development, is associated with numerous pathologies and is often considered a worst-case scenario in terms of wound healing or the implantation of a biomaterial. All that remains is a disorganized, densely packed and poorly vascularized bundle of connective tissue, which was once functional tissue. This creates a significant obstacle to the restoration of tissue function or integration with any biomaterial. Therefore, it is of paramount importance in tissue engineering and regenerative medicine to emphasize regeneration, the successful recovery of native tissue function, as opposed to repair, the replacement of the native tissue (often with scar tissue). A technique dubbed 'mitochondrial transplantation' is a burgeoning field of research that shows promise in in vitro, in vivo and various clinical applications in preventing cell death, reducing inflammation, restoring cell metabolism and proper oxidative balance, among other reported benefits. However, there is currently a lack of research regarding the potential for mitochondrial therapies within tissue engineering and regenerative biomaterials. Thus, this review explores these promising findings and outlines the potential for mitochondrial transplantation-based therapies as a new frontier of scientific research with respect to driving regeneration in wound healing and host-biomaterial interactions, the current successes of mitochondrial transplantation that warrant this potential and the critical questions and remaining obstacles that remain in the field.

Megamitochondria plasticity: function transition from adaption to disease

As the cell's energy factory and metabolic hub, mitochondria are critical for ATP synthesis to maintain cellular function. Mitochondria are highly dynamic organelles that continuously undergo fusion and fission to alter their size, shape, and position, with mitochondrial fusion and fission being interdependent to maintain the balance of mitochondrial morphological changes. However, in response to metabolic and functional damage, mitochondria can grow in size, resulting in a form of abnormal mitochondrial morphology known as megamitochondria. Megamitochondria are characterized by their considerably larger size, pale matrix, and marginal cristae structure and have been observed in various human diseases. In energy-intensive cells like hepatocytes or cardiomyocytes, the pathological process can lead to the growth of megamitochondria, which can further cause metabolic disorders, cell damage and aggravates the progression of the disease. Nonetheless, megamitochondria can also form in response to short-term environmental stimulation as a compensatory mechanism to support cell survival. However, extended stimulation can reverse the benefits of megamitochondria leading to adverse effects. In this review, we will focus on the findings of the different roles of megamitochondria, and their link to disease development to identify promising clinical therapeutic targets.

Exercise and Doxorubicin Modify Markers of Iron Overload and Cardiolipin Deficiency in Cardiac Mitochondria

Doxorubicin (DOX) is a chemotherapeutic agent highly effective at limiting cancer progression. Despite the efficacy of this anticancer drug, the clinical use of DOX is limited due to cardiotoxicity. The cardiac mitochondria are implicated as the primary target of DOX, resulting in inactivation of electron transport system complexes, oxidative stress, and iron overload. However, it is established that the cardiac mitochondrial subpopulations reveal differential responses to DOX exposure, with subsarcolemmal (SS) mitochondria demonstrating redox imbalance and the intermyofibrillar (IMF) mitochondria showing reduced respiration. In this regard, exercise training is an effective intervention to prevent DOX-induced cardiac dysfunction. Although it is clear that exercise confers mitochondrial protection, it is currently unknown if exercise training mitigates DOX cardiac mitochondrial toxicity by promoting beneficial adaptations to both the SS and IMF mitochondria. To test this, SS and IMF mitochondria were isolated from sedentary and exercise-preconditioned female Sprague Dawley rats exposed to acute DOX treatment. Our findings reveal a greater effect of exercise preconditioning on redox balance and iron handling in the SS mitochondria of DOX-treated rats compared to IMF, with rescue of cardiolipin synthase 1 expression in both subpopulations. These results demonstrate that exercise preconditioning improves mitochondrial homeostasis when combined with DOX treatment, and that the SS mitochondria display greater protection compared to the IMF mitochondria. These data provide important insights into the molecular mechanisms that are in part responsible for exercise-induced protection against DOX toxicity.

Age-Dependent Changes in Calcium Regulation after Myocardial Ischemia-Reperfusion Injury

During aging, heart structure and function gradually deteriorate, which subsequently increases susceptibility to ischemia-reperfusion (IR). Maintenance of Ca²⁺ homeostasis is critical for cardiac contractility. We used Langendorff's model to monitor the susceptibility of aging (6-, 15-, and 24-month-old) hearts to IR, with a specific focus on Ca²⁺-handling proteins. IR, but not aging itself, triggered left ventricular changes when the maximum rate of pressure development decreased in 24-month-olds, and the maximum rate of relaxation was most affected in 6-month-old hearts. Aging caused a deprivation of Ca²⁺-ATPase (SERCA2a), Na⁺/Ca²⁺ exchanger, mitochondrial Ca²⁺ uniporter, and ryanodine receptor contents. IR-induced damage to ryanodine receptor stimulates Ca²⁺ leakage in 6-month-old hearts and elevated phospholamban (PLN)-to-SERCA2a ratio can slow down Ca²⁺ reuptake seen at 2-5 μM Ca²⁺. Total and monomeric PLN mirrored the response of overexpressed SERCA2a after IR in 24-month-old hearts, resulting in stable Ca²⁺-ATPase activity. Upregulated PLN accelerated inhibition of Ca²⁺-ATPase activity at low free Ca²⁺ in 15-month-old after IR, and reduced SERCA2a content subsequently impairs the Ca²⁺-sequestering capacity. In conclusion, our study suggests that aging is associated with a significant decrease in the abundance and function of Ca²⁺-handling proteins. However, the IR-induced damage was not increased during aging.

Inner mitochondrial membrane structure and fusion dynamics are altered in senescent human iPSC-derived and primary rat cardiomyocytes

Dysfunction of the aging heart is a major cause of death in the human population. Amongst other tasks, mitochondria are pivotal to supply the working heart with ATP. The mitochondrial inner membrane (IMM) ultrastructure is tailored to meet these demands and to provide nano-compartments for specific tasks. Thus, function and morphology are closely coupled. Senescent cardiomyocytes from the mouse heart display alterations of the inner mitochondrial membrane. To study the relation between inner mitochondrial membrane architecture, dynamics and function is hardly possible in living organisms. Here, we present two cardiomyocyte senescence cell models that allow in cellular studies of mitochondrial performance. We show that doxorubicin treatment transforms human iPSC-derived cardiomyocytes and rat neonatal cardiomyocytes in an aged phenotype. The treated cardiomyocytes display double-strand breaks in the nDNA, have β-galactosidase activity, possess enlarged nuclei, and show p21 upregulation. Most importantly, they also display a compromised inner mitochondrial structure. This prompted us to test whether the dynamics of the inner membrane was also altered. We found that the exchange of IMM components after organelle fusion was faster in doxorubicin-treated cells than in control cells, with no change in mitochondrial fusion dynamics at the meso-scale. Such altered IMM morphology and dynamics may have important implications for local OXPHOS protein organization, exchange of damaged components, and eventually the mitochondrial bioenergetics function of the aged cardiomyocyte.

Kidney injury molecule-1 and podocalyxin dysregulation in an arginine vasopressin induced rodent model of preeclampsia

OBJECTIVE

To assess renal injury in an arginine vasopressin (AVP) rodent model of preeclampsia.

STUDY DESIGN

Urinary expression of kidney injury molecule-1 (KIM-1), urinary protein and creatinine was determined in rodents (n = 24; pregnant AVP, pregnant saline, non-pregnant AVP and non-pregnant saline), which received a continuous dose of either AVP or saline via subcutaneous mini osmotic pumps for 18 days, using a Multiplex kidney toxicity immunoassay. Renal morphology was assessed using haematoxylin and eosin staining and transmission electron microscopy. The immunolocalization of KIM-1 and podocalyxin was qualitatively evaluated using immunohistochemistry.

RESULTS

Urinary KIM-1 and urinary protein levels were significantly increased in treated vs. untreated rats on gestational days 8 (p < 0.05), 14 (p < 0.001) and 18 (p < 0.001). The pregnant rats displayed a lower trend of creatinine compared to the non-pregnant groups, albeit non-significantly. KIM-1 was immunolocalized in the proximal convoluted tubules in AVP treated vs. untreated groups. In contrast, podocalyxin was weakly immunostained within glomeruli of pregnant AVP treated vs. pregnant untreated rats. Histological evaluation revealed reduced Bowman's space, with some tubular and blood vessel necrosis in the pregnant treated group. Ultrastructural observations included effacement and fusion of podocyte foot processes, glomerular basement membrane abnormalities, podocyte nuclear crenations, mitochondrial oedema and cristae degeneration with cytoplasmic lysis within treated tissue.

CONCLUSION

Our findings demonstrate region-specific kidney injury particularly glomerular impairment and endothelial injury in AVP-treated rats. The findings highlight the utility of this model in studying the mechanisms driving renal damage in a rodent model of preeclampsia.

Football training as a non-pharmacological treatment of the global aging population-A topical review

In the present topical mini-review, the beneficial impact of small-sided game football training for the increasing elderly global population is presented. As a multicomponent type of physical activity, football training executed on small pitched with 4-6 players in each team is targeting a myriad of physiological systems and causes positive adaptations of relevance for several non-communicable diseases, of which the incidence increases with advancing age. There is strong scientific evidence that this type of football training promotes cardiovascular, metabolic and musculo-skeletal health in elderly individuals. These positive adaptations can prevent cardiovascular disease, type 2 diabetes, sarcopenia and osteoporosis, and lower the risk of falls. Also, football training has been proven an efficient part of the treatment of several patient groups including men with prostate cancer and women after breast cancer. Finally, regular football training has an anti-inflammatory effect and may slow the biological aging. Overall, there is a growing body of evidence suggesting that recreational football training can promote health in the elderly.

Maturation of induced pluripotent stem cell-derived cardiomyocytes and its therapeutic effect on myocardial infarction in mouse

Induced pluripotent stem cell-derived cardiomyocytes (iPSC-CMs) have an irreplaceable role in the treatment of myocardial infarction (MI), which can be injected into the transplanted area with new cardiomyocytes (Cardiomyocytes, CMs), and improve myocardial function. However, the immaturity of the structure and function of iPSC-CMs is the main bottleneck at present. Since collagen participates in the formation of extracellular matrix (ECM), we synthesized nano colloidal gelatin (Gel) with collagen as the main component, and confirmed that the biomaterial has good biocompatibility and is suitable for cellular in vitro growth. Subsequently, we combined the PI3K/AKT/mTOR pathway inhibitor BEZ-235 with Gel and found that the two combined increased the sarcomere length and action potential amplitude (APA) of iPSC-CMs, and improved the Ca²⁺ processing ability, the maturation of mitochondrial morphological structure and metabolic function. Not only that, Gel can also prolong the retention rate of iPSC-CMs in the myocardium and increase the expression of Cx43 and angiogenesis in the transplanted area of mature iPSC-CMs, which also provides a reliable basis for the subsequent treatment of mature iPSC-CMs.

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BEZ-235 + Gel promotes the maturation of sarcomere structure in iPSC-CMs.

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BEZ-235 + Gel promotes electrophysiological maturation of iPSC-CMs.

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BEZ-235 + Gel increases mitochondrial respiration in iPSC-CMs.

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Gel loaded with mature iPSC-CMs enhanced angiogenesis and gap junction formation at the injection site.

mtUPR Modulation as a Therapeutic Target for Primary and Secondary Mitochondrial Diseases

Mitochondrial dysfunction is a key pathological event in many diseases. Its role in energy production, calcium homeostasis, apoptosis regulation, and reactive oxygen species (ROS) balance render mitochondria essential for cell survival and fitness. However, there are no effective treatments for most primary and secondary mitochondrial diseases to this day. Therefore, new therapeutic approaches, such as the modulation of the mitochondrial unfolded protein response (mtUPR), are being explored. mtUPRs englobe several compensatory processes related to proteostasis and antioxidant system mechanisms. mtUPR activation, through an overcompensation for mild intracellular stress, promotes cell homeostasis and improves lifespan and disease alterations in biological models of mitochondrial dysfunction in age-related diseases, cardiopathies, metabolic disorders, and primary mitochondrial diseases. Although mtUPR activation is a promising therapeutic option for many pathological conditions, its activation could promote tumor progression in cancer patients, and its overactivation could lead to non-desired side effects, such as the increased heteroplasmy of mitochondrial DNA mutations. In this review, we present the most recent data about mtUPR modulation as a therapeutic approach, its role in diseases, and its potential negative consequences in specific pathological situations.

Heart Disease and Ageing: The Roles of Senescence, Mitochondria, and Telomerase in Cardiovascular Disease

During ageing molecular damage leads to the accumulation of several hallmarks of ageing including mitochondrial dysfunction, cellular senescence, genetic instability and chronic inflammation, which contribute to the development and progression of ageing-associated diseases including cardiovascular disease. Consequently, understanding how these hallmarks of biological ageing interact with the cardiovascular system and each other is fundamental to the pursuit of improving cardiovascular health globally. This review provides an overview of our current understanding of how candidate hallmarks contribute to cardiovascular diseases such as atherosclerosis, coronary artery disease and subsequent myocardial infarction, and age-related heart failure. Further, we consider the evidence that, even in the absence of chronological age, acute cellular stress leading to accelerated biological ageing expedites cardiovascular dysfunction and impacts on cardiovascular health. Finally, we consider the opportunities that modulating hallmarks of ageing offer for the development of novel cardiovascular therapeutics.

The Role of Mitochondrial Enzymes, Succinate-Coupled Signaling Pathways and Mitochondrial Ultrastructure in the Formation of Urgent Adaptation to Acute Hypoxia in the Myocardium

The effect of a single one-hour exposure to three modes of hypobaric hypoxia (HBH) differed in the content of O₂ in inhaled air (FiO₂-14%, 10%, 8%) in the development of mitochondrial-dependent adaptive processes in the myocardium was studied in vivo. The following parameters have been examined: (a) an urgent reaction of catalytic subunits of mitochondrial enzymes (NDUFV2, SDHA, Cyt b, COX2, ATP5A) in the myocardium as an indicator of the state of the respiratory chain electron transport function; (b) an urgent activation of signaling pathways dependent on GPR91, HIF-1α and VEGF, allowing us to assess their role in the formation of urgent mechanisms of adaptation to hypoxia in the myocardium; (c) changes in the ultrastructure of three subpopulations of myocardial mitochondria under these conditions. The studies were conducted on two rat phenotypes: rats with low resistance (LR) and high resistance (HR) to hypoxia. The adaptive and compensatory role of the mitochondrial complex II (MC II) in maintaining the electron transport and energy function of the myocardium in a wide range of reduced O₂ concentrations in the initial period of hypoxic exposure has been established. The features of urgent reciprocal regulatory interaction of NAD- and FAD-dependent oxidation pathways in myocardial mitochondria under these conditions have been revealed. The data indicating the participation of GPR91, HIF-1a and VEGF in this process have been obtained. The ultrastructure of the mitochondrial subpopulations in the myocardium of LR and HR rats differed in normoxic conditions and reacted differently to hypoxia of varying severity. The parameters studied together are highly informative indicators of the quality of cardiac activity and metabolic biomarkers of urgent adaptation in various hypoxic conditions.

The Effects of Exercise Training on Mitochondrial Function in Cardiovascular Diseases: A Systematic Review and Meta-Analysis

Mitochondria dysfunction is implicated in the pathogenesis of cardiovascular diseases (CVD). Exercise training is potentially an effective non-pharmacological strategy to restore mitochondrial health in CVD. However, how exercise modifies mitochondrial functionality is inconclusive. We conducted a systematic review using the PubMed; Scopus and Web of Science databases to investigate the effect of exercise training on mitochondrial function in CVD patients. Search terms included “mitochondria”, “exercise”, “aerobic capacity”, and “cardiovascular disease” in varied combination. The search yielded 821 records for abstract screening, of which 20 articles met the inclusion criteria. We summarized the effect of exercise training on mitochondrial morphology, biogenesis, dynamics, oxidative capacity, antioxidant capacity, and quality. Amongst these parameters, only oxidative capacity was suitable for a meta-analysis, which demonstrated a significant effect size of exercise in improving mitochondrial oxidative capacity in CVD patients (SMD = 4.78; CI = 2.99 to 6.57; p < 0.01), but with high heterogeneity among the studies (I2 = 75%, p = 0.003). Notably, aerobic exercise enhanced succinate-involved oxidative phosphorylation. The majority of the results suggested that exercise improves morphology and biogenesis, whereas findings on dynamic, antioxidant capacity, and quality, were inadequate or inconclusive. A further randomized controlled trial is clearly required to explain how exercise modifies the pathway of mitochondrial quantity and quality in CVD patients.

Ischemic Preconditioning and Postconditioning Protect the Heart by Preserving the Mitochondrial Network

Background

Mitochondria fuse to form elongated networks which are more tolerable to stress and injury. Ischemic pre- and postconditioning (IPC and IPost, respectively) are established cardioprotective strategies in the preclinical setting. Whether IPC and IPost modulates mitochondrial morphology is unknown. We hypothesize that the protective effects of IPC and IPost may be conferred via preservation of mitochondrial network.

Methods

IPC and IPost were applied to the H9c2 rat myoblast cells, isolated adult primary murine cardiomyocytes, and the Langendorff-isolated perfused rat hearts. The effects of IPC and IPost on cardiac cell death following ischemia-reperfusion injury (IRI), mitochondrial morphology, and gene expression of mitochondrial-shaping proteins were investigated.

Results

IPC and IPost successfully reduced cardiac cell death and myocardial infarct size. IPC and IPost maintained the mitochondrial network in both H9c2 and isolated adult primary murine cardiomyocytes. 2D-length measurement of the 3 mitochondrial subpopulations showed that IPC and IPost significantly increased the length of interfibrillar mitochondria (IFM). Gene expression of the pro-fusion protein, Mfn1, was significantly increased by IPC, while the pro-fission protein, Drp1, was significantly reduced by IPost in the H9c2 cells. In the primary cardiomyocytes, gene expression of both Mfn1 and Mfn2 were significantly upregulated by IPC and IPost, while Drp1 was significantly downregulated by IPost. In the Langendorff-isolated perfused heart, gene expression of Drp1 was significantly downregulated by both IPC and IPost.

Conclusion

IPC and IPost-mediated upregulation of pro-fusion proteins (Mfn1 and Mfn2) and downregulation of pro-fission (Drp1) promote maintenance of the interconnected mitochondrial network, ultimately conferring cardioprotection against IRI.

Human Induced Pluripotent Stem Cells for Studying Mitochondrial Diseases in the Heart

Mitochondrial dysfunction is known to contribute to a range of diseases, and primary mitochondrial defects strongly impact high-energy organs such as the heart. Platforms for high-throughput and human-relevant assessment of mitochondrial diseases are currently lacking, hindering the development of targeted therapies. In the past decade, human induced pluripotent stem cells (iPSCs) have become a promising technology for drug discovery in basic and clinical research. In particular, human iPSC-derived cardiomyocytes (iPSC-CMs) offer a unique tool to study a wide range of mitochondrial functions and possess the potential to become a key translational asset for mitochondrial drug development. This review summarizes mitochondrial functions and recent therapeutic discoveries, advancements, and limitations of using iPSC-CMs to study mitochondrial diseases of the heart with an emphasis on cardiac applications.

Cardiomyocyte Proliferation from Fetal- to Adult- and from Normal- to Hypertrophy and Failing Hearts

Simple Summary

Death from injury to the heart from a variety of causes remains a major cause of mortality worldwide. The cardiomyocyte, the major contracting cell of the heart, is responsible for pumping blood to the rest of the body. During fetal development, these immature cardiomyocytes are small and rapidly divide to complete development of the heart by birth when they develop structural and functional characteristics of mature cells which prevent further division. All further growth of the heart after birth is due to an increase in the size of cardiomyocytes, hypertrophy. Following the loss of functional cardiomyocytes due to coronary artery occlusion or other causes, the heart is unable to replace the lost cells. One of the significant research goals has been to induce adult cardiomyocytes to reactivate the cell cycle and repair cardiac injury. This review explores the developmental, structural, and functional changes of the growing cardiomyocyte, and particularly the sarcomere, responsible for force generation, from the early fetal period of reproductive cell growth through the neonatal period and on to adulthood, as well as during pathological response to different forms of myocardial diseases or injury. Multiple issues relative to cardiomyocyte cell-cycle regulation in normal or diseased conditions are discussed.

Abstract

The cardiomyocyte undergoes dramatic changes in structure, metabolism, and function from the early fetal stage of hyperplastic cell growth, through birth and the conversion to hypertrophic cell growth, continuing to the adult stage and responding to various forms of stress on the myocardium, often leading to myocardial failure. The fetal cell with incompletely formed sarcomeres and other cellular and extracellular components is actively undergoing mitosis, organelle dispersion, and formation of daughter cells. In the first few days of neonatal life, the heart is able to repair fully from injury, but not after conversion to hypertrophic growth. Structural and metabolic changes occur following conversion to hypertrophic growth which forms a barrier to further cardiomyocyte division, though interstitial components continue dividing to keep pace with cardiac growth. Both intra- and extracellular structural changes occur in the stressed myocardium which together with hemodynamic alterations lead to metabolic and functional alterations of myocardial failure. This review probes some of the questions regarding conditions that regulate normal and pathologic growth of the heart.

Structural Analysis of Mitochondrial Dynamics-From Cardiomyocytes to Osteoblasts: A Critical Review

Mitochondria play a crucial role in cell physiology and pathophysiology. In this context, mitochondrial dynamics and, subsequently, mitochondrial ultrastructure have increasingly become hot topics in modern research, with a focus on mitochondrial fission and fusion. Thus, the dynamics of mitochondria in several diseases have been intensively investigated, especially with a view to developing new promising treatment options. However, the majority of recent studies are performed in highly energy-dependent tissues, such as cardiac, hepatic, and neuronal tissues. In contrast, publications on mitochondrial dynamics from the orthopedic or trauma fields are quite rare, even if there are common cellular mechanisms in cardiovascular and bone tissue, especially regarding bone infection. The present report summarizes the spectrum of mitochondrial alterations in the cardiovascular system and compares it to the state of knowledge in the musculoskeletal system. The present paper summarizes recent knowledge regarding mitochondrial dynamics and gives a short, but not exhaustive, overview of its regulation via fission and fusion. Furthermore, the article highlights hypoxia and its accompanying increased mitochondrial fission as a possible link between cardiac ischemia and inflammatory diseases of the bone, such as osteomyelitis. This opens new innovative perspectives not only for the understanding of cellular pathomechanisms in osteomyelitis but also for potential new treatment options.

Effects of Treadmill Exercise on Mitochondrial DNA Damage and Cardiomyocyte Telomerase Activity in Aging Model Rats Based on Classical Apoptosis Signaling Pathway

In order to explore the effect of treadmill exercise on mitochondrial DNA damage and myocardial telomerase activity in aging model rats based on the classical apoptosis signaling pathway, a total of 36 clean-grade male SD rats are selected. After modeling, the rats are randomly divided into groups, namely, control and 3 times/w and 6 times/w exercise rats, with 12 rats in each group. After the rats of each group are modeled, the myocardial tissue and cells are collected, the apoptosis of myocardial cells is detected by TUNEL method, and the protein expressions of Bax and Bcl-2 in myocardial tissue are detected by western blotting. The mtDNA content of the control rats is the highest, which is significantly higher than that of the exercise group ( $P<0.05$ ); the expression of mtDNA content in the heart of the rats exercising 3 times/w is significantly higher than that of the rats exercising 6 times/w ( $P<0.05$ ); cardiomyocyte apoptosis AI value, Bcl-2, and Bax expressions of the control rats is the highest and significantly higher than those in the exercise group ( $P<0.05$ ); Bcl-2/Bax in the control rats is the lowest and is significantly lower than that in the exercise group ( $P<0.05$ ). The AI value, Bcl-2, and Bax expression of myocardial cell apoptosis in 3 times/w exercise rats are significantly higher than those in 6 times/w exercise rats ( $P<0.05$ ); Bcl-2/Bax of 3 times/w exercise rats is significantly lower than that in 6 times/w exercise rats ( $P<0.05$ ); by observing the rats that completed treadmill exercise, Akt2 protein of 3 times/w exercise rats and 6 times/w exercise rats is observed and analyzed. Compared with the control rats, the expressions of the two proteins are increased in 3 times/w exercise rats and 6 times/w exercise rats, and the upregulation in 6 times/w exercise rats is significantly increased and higher than that in 3 times/w exercise rats ( $P<0.05$ ). For aging rats, treadmill exercise can reduce the body Bcl-2 and Bax values, improve the mitochondrial DNA damage and myocardial cell telomerase activity in aging model rats, and slow down the aging process.

Mitochondrial Ca2+ Homeostasis: Emerging Roles and Clinical Significance in Cardiac Remodeling

Mitochondria are the sites of oxidative metabolism in eukaryotes where the metabolites of sugars, fats, and amino acids are oxidized to harvest energy. Notably, mitochondria store Ca²⁺ and work in synergy with organelles such as the endoplasmic reticulum and extracellular matrix to control the dynamic balance of Ca²⁺ concentration in cells. Mitochondria are the vital organelles in heart tissue. Mitochondrial Ca²⁺ homeostasis is particularly important for maintaining the physiological and pathological mechanisms of the heart. Mitochondrial Ca²⁺ homeostasis plays a key role in the regulation of cardiac energy metabolism, mechanisms of death, oxygen free radical production, and autophagy. The imbalance of mitochondrial Ca²⁺ balance is closely associated with cardiac remodeling. The mitochondrial Ca²⁺ uniporter (mtCU) protein complex is responsible for the uptake and release of mitochondrial Ca²⁺ and regulation of Ca²⁺ homeostasis in mitochondria and consequently, in cells. This review summarizes the mechanisms of mitochondrial Ca²⁺ homeostasis in physiological and pathological cardiac remodeling and the regulatory effects of the mitochondrial calcium regulatory complex on cardiac energy metabolism, cell death, and autophagy, and also provides the theoretical basis for mitochondrial Ca²⁺ as a novel target for the treatment of cardiovascular diseases.

Quantitative analysis of mitochondrial morphologies in human induced pluripotent stem cells for Leigh syndrome

Mitochondria are dynamic organelles with wide range of morphologies contributing to regulating different signaling pathways and several cellular functions. Leigh syndrome (LS) is a classic pediatric mitochondrial disorder characterized by complex and variable clinical pathologies, and primarily affects the nervous system during early development. It is important to understand the differences between mitochondrial morphologies in healthy and diseased states so that focused therapies can target the disease during its early stages. In this study, we performed a comprehensive analysis of mitochondrial dynamics in five patient-derived human induced pluripotent stem cells (hiPSCs) containing different mutations associated with LS. Our results suggest that subtle alterations in mitochondrial morphologies are specific to the mtDNA variant. Three out of the five LS-hiPSCs exhibited characteristics consistent with fused mitochondria. To our knowledge, this is the first comprehensive study that quantifies mitochondrial dynamics in hiPSCs specific to mitochondrial disorders. In addition, we observed an overall decrease in mitochondrial membrane potential in all five LS-hiPSCs. A more thorough analysis of the correlations between mitochondrial dynamics, membrane potential dysfunction caused by mutations in the mtDNA in hiPSCs and differentiated derivatives will aid in identifying unique morphological signatures of various mitochondrial disorders during early stages of embryonic development.

PHDs/CPT1B/VDAC1 axis regulates long-chain fatty acid oxidation in cardiomyocytes

Cardiac metabolism is a high-oxygen-consuming process, showing a preference for long-chain fatty acid (LCFA) as the fuel source under physiological conditions. However, a metabolic switch (favoring glucose instead of LCFA) is commonly reported in ischemic or late-stage failing hearts. The mechanism regulating this metabolic switch remains poorly understood. Here, we report that loss of PHD2/3, the cellular oxygen sensors, blocks LCFA mitochondria uptake and β-oxidation in cardiomyocytes. In high-fat-fed mice, PHD2/3 deficiency improves glucose metabolism but exacerbates the cardiac defects. Mechanistically, we find that PHD2/3 bind to CPT1B, a key enzyme of mitochondrial LCFA uptake, promoting CPT1B-P295 hydroxylation. Further, we show that CPT1B-P295 hydroxylation is indispensable for its interaction with VDAC1 and LCFA β-oxidation. Finally, we demonstrate that a CPT1B-P295A mutant constitutively binds to VDAC1 and rescues LCFA metabolism in PHD2/3-deficient cardiomyocytes. Together, our data identify an oxygen-sensitive regulatory axis involved in cardiac metabolism.

Glucose fluctuation accelerates cardiac injury of diabetic mice via sodium-dependent glucose cotransporter 1 (SGLT1)

Recent studies have shown that blood glucose fluctuation is associated with complications of diabetes mellitus (DM). SGLT1 (sodium-dependent glucose cotransporter 1), is highly expressed in pathological conditions of heart, and is expressed in cardiomyocytes induced by high glucose. Herein, we constructed a diabetic mouse model with glucose fluctuation to investigate whether SGLT1 is involved in glucose fluctuation-induced cardiac injury. Echocardiography, histology examination, and TUNEL staining were performed to evaluate cardiac dysfunction and damage. To assess glucose fluctuation-induced oxidative stress, reactive oxygen species (ROS), malondialdehyde (MDA), superoxide dismutase (SOD), catalase (CAT), and glutathione (GSH) levels were measured. To assess mitochondrial dysfunction, mitochondrial membrane potential (MMP), ATP content, mitochondrial respiratory chain complex activity, and expression of mitochondrial fusion and fission proteins were determined. The results indicated that diabetic mice with glucose fluctuation showed elevation of cardiac SGLT1 expression, left ventricular dysfunction, oxidative stress and mitochondrial dysfunction. Knockdown of SGLT1 could abrogate the effects of glucose fluctuation on cardiac injury. Thus, our study highlighted that SGLT1 plays an important role in glucose fluctuation induced cardiac injury through oxidative stress and mitochondrial dysfunction.

Metabolic Remodeling and Implicated Calcium and Signal Transduction Pathways in the Pathogenesis of Heart Failure

The heart is an organ with high-energy demands in which the mitochondria are most abundant. They are considered the powerhouse of the cell and occupy a central role in cellular metabolism. The intermyofibrillar mitochondria constitute the majority of the three-mitochondrial subpopulations in the heart. They are also considered to be the most important in terms of their ability to participate in calcium and cellular signaling, which are critical for the regulation of mitochondrial function and adenosine triphosphate (ATP) production. This is because they are located in very close proximity with the endoplasmic reticulum (ER), and for the presence of tethering complexes enabling interorganelle crosstalk via calcium signaling. Calcium is an important second messenger that regulates mitochondrial function. It promotes ATP production and cellular survival under physiological changes in cardiac energetic demand. This is accomplished in concert with signaling pathways that regulate both calcium cycling and mitochondrial function. Perturbations in mitochondrial homeostasis and metabolic remodeling occupy a central role in the pathogenesis of heart failure. In this review we will discuss perturbations in ER-mitochondrial crosstalk and touch on important signaling pathways and molecular mechanisms involved in the dysregulation of calcium homeostasis and mitochondrial function in heart failure.

Role of GTPase-Dependent Mitochondrial Dynamins in Heart Diseases

Heart function maintenance requires a large amount of energy, which is supplied by the mitochondria. In addition to providing energy to cardiomyocytes, mitochondria also play an important role in maintaining cell function and homeostasis. Although adult cardiomyocyte mitochondria appear as independent, low-static organelles, morphological changes have been observed in cardiomyocyte mitochondria under stress or pathological conditions. Indeed, cardiac mitochondrial fission and fusion are involved in the occurrence and development of heart diseases. As mitochondrial fission and fusion are primarily regulated by mitochondrial dynamins in a GTPase-dependent manner, GTPase-dependent mitochondrial fusion (MFN1, MFN2, and OPA1) and fission (DRP1) proteins, which are abundant in the adult heart, can also be regulated in heart diseases. In fact, these dynamic proteins have been shown to play important roles in specific diseases, including ischemia-reperfusion injury, heart failure, and metabolic cardiomyopathy. This article reviews the role of GTPase-dependent mitochondrial fusion and fission protein-mediated mitochondrial dynamics in the occurrence and development of heart diseases.

The interplay between mitochondria and store-operated Ca2+ entry: Emerging insights into cardiac diseases

Store‐operated Ca²⁺ entry (SOCE) machinery, including Orai channels, TRPCs, and STIM1, is key to cellular calcium homeostasis. The following characteristics of mitochondria are involved in the physiological and pathological regulation of cells: mitochondria mediate calcium uptake through calcium uniporters; mitochondria are regulated by mitochondrial dynamic related proteins (OPA1, MFN1/2, and DRP1) and form mitochondrial networks through continuous fission and fusion; mitochondria supply NADH to the electron transport chain through the Krebs cycle to produce ATP; under stress, mitochondria will produce excessive reactive oxygen species to regulate mitochondria‐endoplasmic reticulum interactions and the related signalling pathways. Both SOCE and mitochondria play critical roles in mediating cardiac hypertrophy, diabetic cardiomyopathy, and cardiac ischaemia‐reperfusion injury. All the mitochondrial characteristics mentioned above are determinants of SOCE activity, and vice versa. Ca²⁺ signalling dictates the reciprocal regulation between mitochondria and SOCE under the specific pathological conditions of cardiomyocytes. The coupling of mitochondria and SOCE is essential for various pathophysiological processes in the heart. Herein, we review the research focussing on the reciprocal regulation between mitochondria and SOCE and provide potential interplay patterns in cardiac diseases.

Multifactorial Basis and Therapeutic Strategies in Metabolism-Related Diseases

Throughout the 20th and 21st centuries, the incidence of non-communicable diseases (NCDs), also known as chronic diseases, has been increasing worldwide. Changes in dietary and physical activity patterns, along with genetic conditions, are the main factors that modulate the metabolism of individuals, leading to the development of NCDs. Obesity, diabetes, metabolic associated fatty liver disease (MAFLD), and cardiovascular diseases (CVDs) are classified in this group of chronic diseases. Therefore, understanding the underlying molecular mechanisms of these diseases leads us to develop more accurate and effective treatments to reduce or mitigate their prevalence in the population. Given the global relevance of NCDs and ongoing research progress, this article reviews the current understanding about NCDs and their related risk factors, with a focus on obesity, diabetes, MAFLD, and CVDs, summarizing the knowledge about their pathophysiology and highlighting the currently available and emerging therapeutic strategies, especially pharmacological interventions. All of these diseases play an important role in the contamination by the SARS-CoV-2 virus, as well as in the progression and severity of the symptoms of the coronavirus disease 2019 (COVID-19). Therefore, we briefly explore the relationship between NCDs and COVID-19.

FIsetin Preserves Interfibrillar Mitochondria to Protect Against Myocardial Ischemia-Reperfusion Injury

According to our previous study, fisetin (3,3',4',7-tetrahydroxyflavone), a bioactive phytochemical (flavonol), reportedly showed cardioprotection against ischemia-reperfusion injury (IRI) by reducing oxidative stress and inhibiting glycogen synthase kinase 3β (GSK3β) [1]. GSK3β is said to exert a non-mitochondrial mediated cardioprotection; therefore, distinct mechanisms of GSK3β on the regulatory effect of mitochondria need to be addressed. The two distinct mitochondrial subpopulations in the heart, namely interfibrillar mitochondria (IFM) and subsarcolemmal mitochondria (SSM), respond differently to disease states. The current study aimed to understand the effect of fisetin on the subpopulation-specific preservation of IFM and SSM while rendering cardioprotection against ischemia reperfusion (I/R). Rats were pre-treated with fisetin (20 mg/kg) intraperitoneally, and IRI was induced using Langendorff isolated heart perfusion technique. Hemodynamic parameters were recorded, and the cardiac injury was assessed using infarct size (IS), lactate dehydrogenase (LDH), and creatine kinase (CK) levels. Subpopulation-specific mitochondrial preservation was evaluated by electron transport chain (ETC), catalase, superoxide dismutase (SOD), and glutathione (GSH) activities. The bioavailability of fisetin in IFM and SSM was measured using the fluorescence method. The ability of fisetin to bind directly to the mitochondrial complex-1 and activating it through donating electrons to FMN was studied using molecular docking studies and further validated by in vitro rotenone sensitivity assay. Cardioprotective effects exhibited by fisetin were mainly mediated through IFM preservation. Mitochondrial bioavailability of fisetin is more in IFM than SSM in both ex vivo and in vitro conditions. Fisetin increased mitochondrial ATP production in I/R insult hearts by activating ETC complex 1. Inhibition of complex 1 prevents the ATP-producing capacity of fisetin. Our results provide evidence that fisetin plays a protective role in myocardial IRI, possibly by preserving the functional activities of IFM.

Protective Effects of Flavonoids Against Mitochondriopathies and Associated Pathologies: Focus on the Predictive Approach and Personalized Prevention

Multi-factorial mitochondrial damage exhibits a “vicious circle” that leads to a progression of mitochondrial dysfunction and multi-organ adverse effects. Mitochondrial impairments (mitochondriopathies) are associated with severe pathologies including but not restricted to cancers, cardiovascular diseases, and neurodegeneration. However, the type and level of cascading pathologies are highly individual. Consequently, patient stratification, risk assessment, and mitigating measures are instrumental for cost-effective individualized protection. Therefore, the paradigm shift from reactive to predictive, preventive, and personalized medicine (3PM) is unavoidable in advanced healthcare. Flavonoids demonstrate evident antioxidant and scavenging activity are of great therapeutic utility against mitochondrial damage and cascading pathologies. In the context of 3PM, this review focuses on preclinical and clinical research data evaluating the efficacy of flavonoids as a potent protector against mitochondriopathies and associated pathologies.

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.

Dioscin and diosgenin: Insights into their potential protective effects in cardiac diseases

BACKGROUND AND ETHNOPHARMACOLOGICAL RELEVANCE

Dioscin and diosgenin derived from plants of the genus Dioscoreaceae such as D. nipponica and D. panthaica Prain et Burk. Were utilized as the main active ingredients of traditional herbal medicinal products for coronary heart disease in the former Soviet Union and China since 1960s. A growing number of research showed that dioscin and diosgenin have a wide range of pharmacological activities in heart diseases.

AIM OF THE STUDY

To summarize the evidence of the effectiveness of dioscin and diosgenin in cardiac diseases, and to provide a basis and reference for future research into their clinical applications and drug development in the field of cardiac disease.

METHODS

Literatures in this review were searched in PubMed, ScienceDirect, Google Scholar, China National Knowledge Infrastructure (CNKI) and Web of Science. All eligible studies are analyzed and summarized in this review.

RESULTS

The pharmacological activities and therapeutic potentials of dioscin and diosgenin in cardiac diseases are similar, can effectively improve hypertrophic cardiomyopathy, arrhythmia, myocardial I/R injury and cardiotoxicity caused by doxorubicin. But the bioavailability of dioscin and diosgenin may be too low as a result of poor absorption and slow metabolism, which hinders their development and utilization.

CONCLUSION

Dioscin and diosgenin need further in-depth experimental research, clinical transformation and structural modification or research of new preparations before they can be expected to be developed into new therapeutic drugs in the field of cardiac disease.

Quantifying Mitochondrial Dynamics in Patient Fibroblasts with Multiple Developmental Defects and Mitochondrial Disorders

Mitochondria are dynamic organelles that undergo rounds of fission and fusion and exhibit a wide range of morphologies that contribute to the regulation of different signaling pathways and various cellular functions. It is important to understand the differences between mitochondrial structure in health and disease so that therapies can be developed to maintain the homeostatic balance of mitochondrial dynamics. Mitochondrial disorders are multisystemic and characterized by complex and variable clinical pathologies. The dynamics of mitochondria in mitochondrial disorders is thus worthy of investigation. Therefore, in this study, we performed a comprehensive analysis of mitochondrial dynamics in ten patient-derived fibroblasts containing different mutations and deletions associated with various mitochondrial disorders. Our results suggest that the most predominant morphological signature for mitochondria in the diseased state is fragmentation, with eight out of the ten cell lines exhibiting characteristics consistent with fragmented mitochondria. To our knowledge, this is the first comprehensive study that quantifies mitochondrial dynamics in cell lines with a wide array of developmental and mitochondrial disorders. A more thorough analysis of the correlations between mitochondrial dynamics, mitochondrial genome perturbations, and bioenergetic dysfunction will aid in identifying unique morphological signatures of various mitochondrial disorders in the future.

Mitochondrial Bioenergetics and Dynamism in the Failing Heart

The heart is responsible for pumping blood, nutrients, and oxygen from its cavities to the whole body through rhythmic and vigorous contractions. Heart function relies on a delicate balance between continuous energy consumption and generation that changes from birth to adulthood and depends on a very efficient oxidative metabolism and the ability to adapt to different conditions. In recent years, mitochondrial dysfunctions were recognized as the hallmark of the onset and development of manifold heart diseases (HDs), including heart failure (HF). HF is a severe condition for which there is currently no cure. In this condition, the failing heart is characterized by a disequilibrium in mitochondrial bioenergetics, which compromises the basal functions and includes the loss of oxygen and substrate availability, an altered metabolism, and inefficient energy production and utilization. This review concisely summarizes the bioenergetics and some other mitochondrial features in the heart with a focus on the features that become impaired in the failing heart.

Effect of crista morphology on mitochondrial ATP output: A computational study

Folding of the mitochondrial inner membrane (IM) into cristae greatly increases the ATP-generating surface area, S _IM, per unit volume but also creates diffusional bottlenecks that could limit reaction rates inside mitochondria. This study explores possible effects of inner membrane folding on mitochondrial ATP output, using a mathematical model for energy metabolism developed by the Jafri group and two- and three-dimensional spatial models for mitochondria, implemented on the Virtual Cell platform. Simulations demonstrate that cristae are micro-compartments functionally distinct from the cytosol. At physiological steady states, standing gradients of ADP form inside cristae that depend on the size and shape of the compartments, and reduce local flux (rate per unit area) of the adenine nucleotide translocase. This causes matrix ADP levels to drop, which in turn reduces the flux of ATP synthase. The adverse effects of membrane folding on reaction fluxes increase with crista length and are greater for lamellar than tubular crista. However, total ATP output per mitochondrion is the product of flux of ATP synthase and S _IM which can be two-fold greater for mitochondria with lamellar than tubular cristae, resulting in greater ATP output for the former. The simulations also demonstrate the crucial role played by intracristal kinases (adenylate kinase, creatine kinase) in maintaining the energy advantage of IM folding.

Aging-Related Changes in the Ultrastructure of Hepatocytes and Cardiomyocytes of Elderly Mice Are Enhanced in ApoE-Deficient Animals

Biological aging is associated with various morphological and functional changes, yet the mechanisms of these phenomena remain unclear in many tissues and organs. Hyperlipidemia is among the factors putatively involved in the aging of the liver and heart. Here, we analyzed morphological, ultrastructural, and biochemical features in adult (7-month-old) and elderly (17-month-old) mice, and then compared age-related features between wild type (C57Bl/6 strain) and ApoE-deficient (transgenic ApoE^−/−) animals. Increased numbers of damaged mitochondria, lysosomes, and lipid depositions were observed in the hepatocytes of elderly animals. Importantly, these aging-related changes were significantly stronger in hepatocytes from ApoE-deficient animals. An increased number of damaged mitochondria was observed in the cardiomyocytes of elderly animals. However, the difference between wild type and ApoE-deficient mice was expressed in the larger size of mitochondria detected in the transgenic animals. Moreover, a few aging-related differences were noted between wild type and ApoE-deficient mice at the level of plasma biochemical markers. Levels of cholesterol and HDL increased in the plasma of elderly ApoE^−/− mice and were markedly higher than in the plasma of elderly wild type animals. On the other hand, the activity of alanine transaminase (ALT) decreased in the plasma of elderly ApoE^−/− mice and was markedly lower than in the plasma of elderly wild type animals.

Mitochondrial Medicine: Genetic Underpinnings and Disease Modeling Using Induced Pluripotent Stem Cell Technology

Mitochondrial medicine is an exciting and rapidly evolving field. While the mitochondrial genome is small and differs from the nuclear genome in that it is circular and free of histones, it has been implicated in neurodegenerative diseases, type 2 diabetes, aging and cardiovascular disorders. Currently, there is a lack of efficient treatments for mitochondrial diseases. This has promoted the need for developing an appropriate platform to investigate and target the mitochondrial genome. However, developing these therapeutics requires a model system that enables rapid and effective studying of potential candidate therapeutics. In the past decade, induced pluripotent stem cells (iPSCs) have become a promising technology for applications in basic science and clinical trials, and have the potential to be transformative for mitochondrial drug development. Engineered iPSC-derived cardiomyocytes (iPSC-CM) offer a unique tool to model mitochondrial disorders. Additionally, these cellular models enable the discovery and testing of novel therapeutics and their impact on pathogenic mtDNA variants and dysfunctional mitochondria. Herein, we review recent advances in iPSC-CM models focused on mitochondrial dysfunction often causing cardiovascular diseases. The importance of mitochondrial disease systems biology coupled with genetically encoded NAD⁺/NADH sensors is addressed toward developing an in vitro translational approach to establish effective therapies.

Mechanisms underlying the pathophysiology of heart failure with preserved ejection fraction: the tip of the iceberg

Heart failure with preserved ejection fraction (HFpEF) is a multifaceted syndrome with a complex aetiology often associated with several comorbidities, such as left ventricle pressure overload, diabetes mellitus, obesity, and kidney disease. Its pathophysiology remains obscure mainly due to the complex phenotype induced by all these associated comorbidities and to the scarcity of animal models that adequately mimic HFpEF. Increased oxidative stress, inflammation, and endothelial dysfunction are currently accepted as key players in HFpEF pathophysiology. However, we have just started to unveil HFpEF complexity and the role of calcium handling, energetic metabolism, and mitochondrial function remain to clarify. Indeed, the enlightenment of such cellular and molecular mechanisms represents an opportunity to develop novel therapeutic approaches and thus to improve HFpEF treatment options. In the last decades, the number of research groups dedicated to studying HFpEF has increased, denoting the importance and the magnitude achieved by this syndrome. In the current technological and web world, the amount of information is overwhelming, driving us not only to compile the most relevant information about the theme but also to explore beyond the tip of the iceberg. Thus, this review aims to encompass the most recent knowledge related to HFpEF or HFpEF-associated comorbidities, focusing mainly on myocardial metabolism, oxidative stress, and energetic pathways.

Mitochondrial Membrane Intracellular Communication in Healthy and Diseased Myocardium

Research efforts in the twenty-first century have been paramount to the discovery and development of novel pharmacological treatments in a variety of diseases resulting in improved life expectancy. Yet, cardiac disease remains a leading cause of morbidity and mortality worldwide. Over time, there has been an expansion in conditions such as atrial fibrillation (AF) and heart failure (HF). Although past research has elucidated specific pathways that participate in the development of distinct cardiac pathologies, the exact mechanisms of action leading to disease remain to be fully characterized. Protein turnover and cellular bioenergetics are integral components of cardiac diseases, highlighting the importance of mitochondria and endoplasmic reticulum (ER) in driving cellular homeostasis. More specifically, the interactions between mitochondria and ER are crucial to calcium signaling, apoptosis induction, autophagy, and lipid biosynthesis. Here, we summarize mitochondrial and ER functions and physical interactions in healthy physiological states. We then transition to perturbations that occur in response to pathophysiological challenges and how this alters mitochondrial–ER and other intracellular organelle interactions. Finally, we discuss lifestyle interventions and innovative therapeutic targets that may be used to restore beneficial mitochondrial and ER interactions, thereby improving cardiac function.

The role of labile Zn2+ and Zn2+-transporters in the pathophysiology of mitochondria dysfunction in cardiomyocytes

An important energy supplier of cardiomyocytes is mitochondria, similar to other mammalian cells. Studies have demonstrated that any defect in the normal processes controlled by mitochondria can lead to abnormal ROS production, thereby high oxidative stress as well as lack of ATP. Taken into consideration, the relationship between mitochondrial dysfunction and overproduction of ROS as well as the relation between increased ROS and high-level release of intracellular labile Zn²⁺, those bring into consideration the importance of the events related with those stimuli in cardiomyocytes responsible from cellular Zn²⁺-homeostasis and responsible Zn²⁺-transporters associated with the Zn²⁺-homeostasis and Zn²⁺-signaling. Zn²⁺-signaling, controlled by cellular Zn²⁺-homeostatic mechanisms, is regulated with intracellular labile Zn²⁺ levels, which are controlled, especially, with the two Zn²⁺-transporter families; ZIPs and ZnTs. Our experimental studies in mammalian cardiomyocytes and human heart tissue showed that Zn²⁺-transporters localizes to mitochondria besides sarco(endo)plasmic reticulum and Golgi under physiological condition. The protein levels as well as functions of those transporters can re-distribute under pathological conditions, therefore, they can interplay among organelles in cardiomyocytes to adjust a proper intracellular labile Zn²⁺ level. In the present review, we aimed to summarize the already known Zn²⁺-transporters localize to mitochondria and function to stabilize not only the cellular Zn²⁺ level but also cellular oxidative stress status. In conclusion, one can propose that a detailed understanding of cellular Zn²⁺-homeostasis and Zn²⁺-signaling through mitochondria may emphasize the importance of new mitochondria-targeting agents for prevention and/or therapy of cardiovascular dysfunction in humans.

The Functional Impact of Mitochondrial Structure Across Subcellular Scales

Mitochondria are key determinants of cellular health. However, the functional role of mitochondria varies from cell to cell depending on the relative demands for energy distribution, metabolite biosynthesis, and/or signaling. In order to support the specific needs of different cell types, mitochondrial functional capacity can be optimized in part by modulating mitochondrial structure across several different spatial scales. Here we discuss the functional implications of altering mitochondrial structure with an emphasis on the physiological trade-offs associated with different mitochondrial configurations. Within a mitochondrion, increasing the amount of cristae in the inner membrane improves capacity for energy conversion and free radical-mediated signaling but may come at the expense of matrix space where enzymes critical for metabolite biosynthesis and signaling reside. Electrically isolating individual cristae could provide a protective mechanism to limit the spread of dysfunction within a mitochondrion but may also slow the response time to an increase in cellular energy demand. For individual mitochondria, those with relatively greater surface areas can facilitate interactions with the cytosol or other organelles but may be more costly to remove through mitophagy due to the need for larger phagophore membranes. At the network scale, a large, stable mitochondrial reticulum can provide a structural pathway for energy distribution and communication across long distances yet also enable rapid spreading of localized dysfunction. Highly dynamic mitochondrial networks allow for frequent content mixing and communication but require constant cellular remodeling to accommodate the movement of mitochondria. The formation of contact sites between mitochondria and several other organelles provides a mechanism for specialized communication and direct content transfer between organelles. However, increasing the number of contact sites between mitochondria and any given organelle reduces the mitochondrial surface area available for contact sites with other organelles as well as for metabolite exchange with cytosol. Though the precise mechanisms guiding the coordinated multi-scale mitochondrial configurations observed in different cell types have yet to be elucidated, it is clear that mitochondrial structure is tailored at every level to optimize mitochondrial function to meet specific cellular demands.

Regulation of energy metabolism by combination therapy attenuates cardiac metabolic remodeling in heart failure

Cardiac metabolic remodeling is recognized as an important hallmark of heart failure (HF), while strategies that target energy metabolism have therapeutic potential in treating HF. Shen-Fu formula (S-F) is a standardized herbal preparation frequently used in clinical practice and is a promising combinatorial therapy for HF-related metabolic remodeling. Herein, we performed an untargeted multi-omics analysis using transcriptomics, proteomics, and metabolomics on HF mice induced by transverse aortic constriction (TAC). Integrated and pathway-driven analyses were used to reveal the therapeutic targets associated with S-F treatment. The cardioprotective effect and potential mechanism of S-F were verified by the results from echocardiography, hemodynamics, histopathology, and biochemical assays. As a result, S-F significantly alleviated myocardial fibrosis and hypertrophy, thus reducing the loss of heart function during adverse cardiac remodeling in TAC mice. Integrated omics analysis showed that S-F synergistically mediated the metabolic flexibility of fatty acids and glucose in cardiac energy metabolism. These effects of S-F were confirmed by the activation of AMP-activated protein kinase (AMPK) and its downstream targets in the failing heart. Collectively, our results demonstrated that S-F suppressed cardiac metabolic remodeling through activating AMPK-related pathways via energy-dependent mechanisms.

Mitochondrial dysfunction in cardiovascular disease: Current status of translational research/clinical and therapeutic implications

Mitochondria provide energy to the cell during aerobic respiration by supplying ~95% of the adenosine triphosphate (ATP) molecules via oxidative phosphorylation. These organelles have various other functions, all carried out by numerous proteins, with the majority of them being encoded by nuclear DNA (nDNA). Mitochondria occupy ~1/3 of the volume of myocardial cells in adults, and function at levels of high-efficiency to promptly meet the energy requirements of the myocardial contractile units. Mitochondria have their own DNA (mtDNA), which contains 37 genes and is maternally inherited. Over the last several years, a variety of functions of these organelles have been discovered and this has led to a growing interest in their involvement in various diseases, including cardiovascular (CV) diseases. Mitochondrial dysfunction relates to the status where mitochondria cannot meet the demands of a cell for ATP and there is an enhanced formation of reactive-oxygen species. This dysfunction may occur as a result of mtDNA and/or nDNA mutations, but also as a response to aging and various disease and environmental stresses, leading to the development of cardiomyopathies and other CV diseases. Designing mitochondria-targeted therapeutic strategies aiming to maintain or restore mitochondrial function has been a great challenge as a result of variable responses according to the etiology of the disorder. There have been several preclinical data on such therapies, but clinical studies are scarce. A major challenge relates to the techniques needed to eclectically deliver the therapeutic agents to cardiac tissues and to damaged mitochondria for successful clinical outcomes. All these issues and progress made over the last several years are herein reviewed.

Maternal High Fat Diet and Diabetes Disrupts Transcriptomic Pathways That Regulate Cardiac Metabolism and Cell Fate in Newborn Rat Hearts

Background: Children born to diabetic or obese mothers have a higher risk of heart disease at birth and later in life. Using chromatin immunoprecipitation sequencing, we previously demonstrated that late-gestation diabetes, maternal high fat (HF) diet, and the combination causes distinct fuel-mediated epigenetic reprogramming of rat cardiac tissue during fetal cardiogenesis. The objective of the present study was to investigate the overall transcriptional signature of newborn offspring exposed to maternal diabetes and maternal H diet. Methods: Microarray gene expression profiling of hearts from diabetes exposed, HF diet exposed, and combination exposed newborn rats was compared to controls. Functional annotation, pathway and network analysis of differentially expressed genes were performed in combination exposed and control newborn rat hearts. Further downstream metabolic assessments included measurement of total and phosphorylated AKT2 and GSK3β, as well as quantification of glycolytic capacity by extracellular flux analysis and glycogen staining. Results: Transcriptional analysis identified significant fuel-mediated changes in offspring cardiac gene expression. Specifically, functional pathways analysis identified two key signaling cascades that were functionally prioritized in combination exposed offspring hearts: (1) downregulation of fibroblast growth factor (FGF) activated PI3K/AKT pathway and (2) upregulation of peroxisome proliferator-activated receptor gamma coactivator alpha (PGC1α) mitochondrial biogenesis signaling. Functional metabolic and histochemical assays supported these transcriptome changes, corroborating diabetes- and diet-induced cardiac transcriptome remodeling and cardiac metabolism in offspring. Conclusion: This study provides the first data accounting for the compounding effects of maternal hyperglycemia and hyperlipidemia on the developmental cardiac transcriptome, and elucidates nuanced and novel features of maternal diabetes and diet on regulation of heart health.

ER membranes associated with mitochondria: Possible therapeutic targets in heart-associated diseases

Cardiovascular system cell biology is tightly regulated and mitochondria play a relevant role in maintaining heart function. In recent decades, associations between such organelles and the sarco/endoplasmic reticulum (SR) have been raised great interest. Formally identified as mitochondria-associated SR membranes (MAMs), these structures regulate different cellular functions, including calcium management, lipid metabolism, autophagy, oxidative stress, and management of unfolded proteins. In this review, we highlight MAMs' alterations mainly in cardiomyocytes, linked with cardiovascular diseases, such as cardiac ischemia-reperfusion, heart failure, and dilated cardiomyopathy. We also describe proteins that are part of the MAMs' machinery, as the FUN14 domain containing 1 (FUNDC1), the sigma 1 receptor (Sig-1R) and others, which might be new molecular targets to preserve the function and structure of the heart in such diseases. Understanding the machinery of MAMs and its function demands our attention, as such knowledge might contribute to strengthen the role of these relative novel structures in heart diseases.

A novel homozygous missense SLC25A20 mutation in three CACT-deficient patients: clinical and autopsy data

Carnitine-acylcarnitine translocase (CACT) deficiency is a fatty acid ß-oxidation disorder of the carnitine shuttle in mitochondria, with a high mortality rate in childhood. We evaluated three patients, including two siblings, with neonatal-onset CACT deficiency and revealed identical homozygous missense mutations of p.Arg275Gln within the SLC25A20 gene. One patient died from hypoglycemia and arrhythmia at 26 months; his pathological autopsy revealed increased and enlarged mitochondria in the heart but not in the liver.