Mitochondrial centrality in heart failure

Chia seeds ameliorate cardiac disease risk factors via alleviating oxidative stress and inflammation in rats fed high-fat diet

Obesity upsurges the risk of developing cardiovascular disease, primarily heart failure and coronary heart disease. Chia seeds have a high concentration of dietary fiber and increased concentrations of anti-inflammatoryand antioxidant compounds. They are used for weight loss plus enhancing blood glucose and lipid profile. The current perspective was commenced to examine the protective influence of chia seeds ingestion on cardiovascular disease risk factors in high-fat diet-fed rats. Forty male albino rats (with an initial body weight of 180-200 g) were used in this study. Rats were randomly and equally divided into 4 groups: Group I was the control group and group II was a control group with chia seeds supplementation. Group III was a high-fat diet group (HFD) that received HFD for 10 weeks and group IV was fed on HFD plus chia seeds for 10 weeks. In all groups Echocardiographic measurements were performed, initial and final BMI, serum glucose, AC/TC ratio, lipid profile, insulin (with a computed HOMA-IR), creatinine phosphokinase-muscle/brain (CPK-MB), CRP, and cardiac troponin I (cTnI) and MAP were estimated. Whole heart weight (WHW) was calculated, and then WHW/body weight (BW) ratio was estimated. Eventually, a histopathological picture of cardiac tissues was performed to assess the changes in the structure of the heart under Haematoxylin and Eosin and Crossmon's trichrome stain. Ingestion of a high diet for 10 weeks induced a clear elevation in BMI, AC/ TC, insulin resistance, hyperlipidemia, CRP, CPK-MB, and cTnI in all HFD groups. Moreover, there was a significant increase in MAP, left ventricular end diastolic diameter (LVEDD), and left ventricular end systolic diameter (LVESD). Furthermore, histological cardiac examination showed structural alteration of the normal structure of the heart tissue with an increase in collagen deposition. Also, the Bcl-2 expression in the heart muscle was significantly lower, but Bax expression was significantly higher. Chia seeds ingestion combined with HFD noticeably ameliorated the previously-recorded biochemical biomarkers, hemodynamic and echocardiography measures, and histopathological changes. Outcomes of this report reveal that obesity is a hazard factor for cardiovascular disease and chia seeds could be a good candidate for cardiovascular system protection.

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.

Acute myocardial infarction in a patient with MELAS syndrome: a possible link?

The mitochondrial encephalomyopathy, lactic acidosis, and stroke (MELAS) syndrome is a mitochondrial disorder, commonly caused by m.3243A>G mutation in the MT-TL1 gene. It encodes for the mitochondrial leucine transfer RNA (tRNA Leu [UUR]), implicated in the translation of proteins involved in the assembly and function of mitochondrial complexes in the electron transport chain. The m.3243A>G mutation determines complex I (CI) deficiency, ultimately leading to NADH accumulation, higher rates of glycolysis in order to compensate for the reduced ATP production and increase in lactates, the end-product of glycolysis. Disruption of the oxidative phosphorylation function with an inability to produce sufficient energy results in multi-organ dysfunction, with high energy demanding cells, such as myocytes and neurons, being the most affected ones. Therefore, MELAS syndrome is characterized by a heterogeneous clinical spectrum. Here we report on a case of a 55-year-old man affected by MELA syndrome with no cardiovascular risk factors. He was admitted to our department because of a non ST-segment elevation myocardial infarction (NSTEMI). A coronary angioplasty of the posterior descending artery and of the left anterior descending artery was realized. Transthoracic echocardiography showed inferior and anterior left ventricular wall hypokinesis together with a moderate left ventricle hypertrophy. Cardiac involvement is reported in about a third of the patients and left ventricular hypertrophy (LVH) is the most common phenotype, with possible dilated cardiomyopathy in end-stage disease; brady- arrhythmias and tachy-arrhythmias are also frequently reported as well as Wolff- Parkinson-White (WPW) syndrome. Organ impairment and clinical manifestations depend on the heteroplasmy level of mutant DNA in cells that can differ among individuals, explaining why some patients present a more severe disease. A clear relationship between MELAS syndrome and atherosclerosis has never been established, however recently advocated. In vitro studies in MELAS patients have shown that higher mitochondrial ROS levels and increased expression of oxidative stress-related genes, as a consequence of complex I deficiency and disrupted electron transport, allow circulating LDL to be promptly oxidized into ox-LDL, contributing to endothelial dysfunction and atherosclerosis plaque formation. In light of the recent evidence suggesting a possible link between mitochondrial disorders and atherosclerosis, we speculate that MELAS syndrome may have played a role in the pathogenesis of coronary artery disease in our patient. Further investigations are needed to confirm a pathogenetic link.

Temporal evolution of the heart failure phenotype in Barth syndrome and treatment with elamipretide

Barth syndrome (BTHS) is a rare genetic disorder caused by pathogenic variants in TAFAZZIN leading to reduced remodeled cardiolipin (CL), a phospholipid essential to mitochondrial function and structure. Cardiomyopathy presents in most patients with BTHS, typically appearing as dilated cardiomyopathy (DCM) in infancy and evolving to hypertrophic cardiomyopathy (HCM) resembling heart failure (HF) with preserved ejection fraction (HFpEF) in some patients ≥12 years. Elamipretide localizes to the inner mitochondrial membrane where it associates with CL, improving mitochondrial function, structure and bioenergetics, including ATP synthesis. Numerous preclinical and clinical studies in BTHS and other forms of HF have demonstrated that elamipretide improves left ventricular relaxation by ameliorating mitochondrial dysfunction, making it well suited for therapeutic use in adolescent and adult patients with BTHS.

Myocardial Infarction as a Consequence of Mitochondrial Dysfunction

Acute myocardial infarction is an event of myocardial necrosis caused by unstable ischemic syndrome. Myocardial infarction (MI) occurs when blood stops flowing to the cardiac tissue or myocardium and the heart muscle gets damaged due to poor perfusion and reduced oxygen supply. Mitochondria can serve as the arbiter of cell fate in response to stress. Oxidative metabolism is the function of mitochondria within the cell. Cardiac cells being highly oxidative tissue generates about 90% of their energy through oxidative metabolism. In this review, we focused on the role of mitochondria in energy generation in myocytes as well as its consequences on heart cells causing cell damage. The role of mitochondrial dysfunction due to oxidative stress, production of reactive oxygen species, and anaerobic production of lactate as a failure of oxidative metabolism are also discussed.

Interplay between cardiovascular and thyroid dysfunctions: A review of clinical implications and management strategies

Cardiovascular diseases (CVD) and thyroid dysfunction are two of the most prevailing disorders in the world that are closely interlinked. Actions of thyroid hormones are mediated via thyroid receptors present in the myocardium and the vascular tissue. Primary mechanism that links thyroid dysfunction with CVD is the modification of cardiovascular risk factors (dyslipidemia, blood pressure, coagulation parameters, etc.) resulting in endothelial and left ventricular systolic and diastolic dysfunction.

Both overt and subclinical hyperthyroidism and hypothyroidism may cause adverse alterations in cardiac function. Hyperthyroidism gives rise to palpitation, atrial fibrillation, systolic hypertension, and heart failure, whereas hypothyroidism increases diastolic hypertension, pericardial effusion, and the risk of ischemic heart disease via altering lipid and coagulation parameters. Early recognition and treatment of thyroid dysfunction may prevent adverse cardiovascular events in patients with or without pre-existing CVD.

Certain cardiac conditions and medications can cause alterations in thyroid function that may predispose an individual to higher morbidity and mortality. In certain situations, thyroid dysfunction treatment may have cardiovascular benefits. This study deals with the interplay between cardiovascular and thyroid dysfunctions associated with clinical implications and management strategies.

Nicotinamide riboside kinase-2 inhibits JNK pathway and limits dilated cardiomyopathy in mice with chronic pressure overload

Nicotinamide riboside kinase-2 (NRK-2) has recently emerged as a critical regulator of cardiac remodeling however, underlying molecular mechanisms is largely unknown. To explore the same, NRK2 knockout (KO) and littermate control mice were subjected to trans-aortic constriction (TAC) or sham surgeries and cardiac function was assessed by serial M-mode echocardiography. A mild cardiac contractile dysfunction was observed in the KOs at the early adaptive phase of remodeling followed by a significant deterioration during the maladaptive cardiac remodeling phase. Consistently, NRK2 KO hearts displayed increased cardiac hypertrophy and heart failure reflected by morphometric parameters as well as increased fetal genes ANP and BNP expressions. Histological assessment revealed an extensive left ventricular (LV) chamber dilatation accompanied by elevated cardiomyopathy and fibrosis in the KO hearts post-TAC. In a gain-of-function model, NRK-2 overexpressing in AC16 cardiomyocytes displayed significantly attenuated fetal genes ANP and BNP expression. Consistently, NRK-2 overexpression attenuated angiotensin II- induced cardiomyocyte death. Mechanistically, we identified NRK-2 as a regulator of JNK MAP kinase and mitochondrial function where NRK-2 overexpression in human cardiomyocytes markedly suppressed the angiotensin II- induced JNK activation and mitochondrial depolarization. Thus, our results demonstrate that NRK-2 plays protective roles in pressure overload- induced dilatative cardiac remodeling and, genetic ablation exacerbates dilated cardiomyopathy, interstitial collagen deposition, and cardiac dysfunction post-TAC due, in part, to increased JNK activation and mitochondrial dysfunction.

Somatic Mutations in Cardiovascular Disease

Advances in population-scale genomic sequencing have greatly expanded the understanding of the inherited basis of cardiovascular disease (CVD). Reanalysis of these genomic datasets identified an unexpected risk factor for CVD, somatically acquired DNA mutations. In this review, we provide an overview of somatic mutations and their contributions to CVD. We focus on the most common and well-described manifestation, clonal hematopoiesis of indeterminate potential. We also review the currently available data regarding how somatic mutations lead to tissue mosaicism in various forms of CVD, including atrial fibrillation and aortic aneurism associated with Marfan Syndrome. Finally, we highlight future research directions given current knowledge gaps and consider how technological advances will enhance the discovery of somatic mutations in CVD and management of patients with somatic mutations.

Regulation of Mitochondrial Function by Noncoding RNAs in Heart Failure and Its Application in Diagnosis and Treatment

ABSTRACT

Heart failure (HF) is the terminal stage of multiple cardiovascular diseases. However, the pathogenesis of HF remains unclear and prompt; appropriate diagnosis and treatment of HF are crucial. Cardiomyocytes isolated from HF subjects frequently present mitochondrial impairment and dysfunction. Many studies have suggested that the regulation by noncoding RNAs (ncRNAs) of mitochondria can affect the occurrence and progression of HF. The regulation by ncRNAs of myocardial mitochondria during HF and the recent applications of ncRNAs in the diagnosis and treatment of HF are summarized in this review that is intended to gain keen insights into the mechanisms of HF and more effective treatments.

Barth syndrome cardiomyopathy: targeting the mitochondria with elamipretide

Barth syndrome (BTHS) is a rare, X-linked recessive, infantile-onset debilitating disorder characterized by early-onset cardiomyopathy, skeletal muscle myopathy, growth delay, and neutropenia, with a worldwide incidence of 1/300,000-400,000 live births. The high mortality rate throughout infancy in BTHS patients is related primarily to progressive cardiomyopathy and a weakened immune system. BTHS is caused by defects in the TAZ gene that encodes tafazzin, a transacylase responsible for the remodeling and maturation of the mitochondrial phospholipid cardiolipin (CL), which is critical to normal mitochondrial structure and function (i.e., ATP generation). A deficiency in tafazzin results in up to a 95% reduction in levels of structurally mature CL. Because the heart is the most metabolically active organ in the body, with the highest mitochondrial content of any tissue, mitochondrial dysfunction plays a key role in the development of heart failure in patients with BTHS. Changes in mitochondrial oxidative phosphorylation reduce the ability of mitochondria to meet the ATP demands of the human heart as well as skeletal muscle, namely ATP synthesis does not match the rate of ATP consumption. The presence of several cardiomyopathic phenotypes have been described in BTHS, including dilated cardiomyopathy, left ventricular noncompaction, either alone or in conjunction with other cardiomyopathic phenotypes, endocardial fibroelastosis, hypertrophic cardiomyopathy, and an apical form of hypertrophic cardiomyopathy, among others, all of which can be directly attributed to the lack of CL synthesis, remodeling, and maturation with subsequent mitochondrial dysfunction. Several mechanisms by which these cardiomyopathic phenotypes exist have been proposed, thereby identifying potential targets for treatment. Dysfunction of the sarcoplasmic reticulum Ca2+-ATPase pump and inflammation potentially triggered by circulating mitochondrial components have been identified. Currently, treatment modalities are aimed at addressing symptomatology of HF in BTHS, but do not address the underlying pathology. One novel therapeutic approach includes elamipretide, which crosses the mitochondrial outer membrane to localize to the inner membrane where it associates with cardiolipin to enhance ATP synthesis in several organs, including the heart. Encouraging clinical results of the use of elamipretide in treating patients with BTHS support the potential use of this drug for management of this rare disease.

Dilated cardiomyopathy impairs mitochondrial biogenesis and promotes inflammation in an age- and sex-dependent manner

Dilated cardiomyopathy (DCM) belongs to the myocardial diseases associated with a severe impairment of cardiac function, but the question of how sex and age affect this pathology has not been fully explored. Impaired energy homeostasis, mitochondrial dysfunction, and systemic inflammation are well-described phenomena associated with aging. In this study, we investigated if DCM affects these phenomena in a sex- and age-related manner. We analyzed the expression of mitochondrial and antioxidant proteins and the inflammatory state in DCM heart tissue from younger and older women and men. A significant downregulation of Sirt1 expression was detected in older DCM patients. Sex-related differences were observed in the phosphorylation of AMPK that only appeared in older males with DCM, possibly due to an alternative Sirt1 regulation mechanism. Furthermore, reduced expression of several mitochondrial proteins (TOM40, TIM23, Sirt3, and SOD2) and genes (cox1, nd4) was only detected in old DCM patients, suggesting that age has a greater effect than DCM on these alterations. Finally, an increased expression of inflammatory markers in older, failing hearts, with a stronger pro-inflammatory response in men, was observed. Together, these findings indicate that age- and sex-related increased inflammation and disturbance of mitochondrial homeostasis occurs in male individuals with DCM.

Metabolic Alterations Caused by Defective Cardiolipin Remodeling in Inherited Cardiomyopathies

The heart is the most energy-consuming organ in the human body. In heart failure, the homeostasis of energy supply and demand is endangered by an increase in cardiomyocyte workload, or by an insufficiency in energy-providing processes. Energy metabolism is directly associated with mitochondrial redox homeostasis. The production of toxic reactive oxygen species (ROS) may overwhelm mitochondrial and cellular ROS defense mechanisms in case of heart failure. Mitochondria are essential cell organelles and provide 95% of the required energy in the heart. Metabolic remodeling, changes in mitochondrial structure or function, and alterations in mitochondrial calcium signaling diminish mitochondrial energy provision in many forms of cardiomyopathy. The mitochondrial respiratory chain creates a proton gradient across the inner mitochondrial membrane, which couples respiration with oxidative phosphorylation and the preservation of energy in the chemical bonds of ATP. Akin to other mitochondrial enzymes, the respiratory chain is integrated into the inner mitochondrial membrane. The tight association with the mitochondrial phospholipid cardiolipin (CL) ensures its structural integrity and coordinates enzymatic activity. This review focuses on how changes in mitochondrial CL may be associated with heart failure. Dysfunctional CL has been found in diabetic cardiomyopathy, ischemia reperfusion injury and the aging heart. Barth syndrome (BTHS) is caused by an inherited defect in the biosynthesis of cardiolipin. Moreover, a dysfunctional CL pool causes other types of rare inherited cardiomyopathies, such as Sengers syndrome and Dilated Cardiomyopathy with Ataxia (DCMA). Here we review the impact of cardiolipin deficiency on mitochondrial functions in cellular and animal models. We describe the molecular mechanisms concerning mitochondrial dysfunction as an incitement of cardiomyopathy and discuss potential therapeutic strategies.

Nicotinamide Riboside-The Current State of Research and Therapeutic Uses

Nicotinamide riboside (NR) has recently become one of the most studied nicotinamide adenine dinucleotide (NAD+) precursors, due to its numerous potential health benefits mediated via elevated NAD+ content in the body. NAD+ is an essential coenzyme that plays important roles in various metabolic pathways and increasing its overall content has been confirmed as a valuable strategy for treating a wide variety of pathophysiological conditions. Accumulating evidence on NRs' health benefits has validated its efficiency across numerous animal and human studies for the treatment of a number of cardiovascular, neurodegenerative, and metabolic disorders. As the prevalence and morbidity of these conditions increases in modern society, the great necessity has arisen for a rapid translation of NR to therapeutic use and further establishment of its availability as a nutritional supplement. Here, we summarize currently available data on NR effects on metabolism, and several neurodegenerative and cardiovascular disorders, through to its application as a treatment for specific pathophysiological conditions. In addition, we have reviewed newly published research on the application of NR as a potential therapy against infections with several pathogens, including SARS-CoV-2. Additionally, to support rapid NR translation to therapeutics, the challenges related to its bioavailability and safety are addressed, together with the advantages of NR to other NAD+ precursors.

High-fat diet affects skeletal muscle mitochondria comparable to pressure overload-induced heart failure

In heart failure, high-fat diet (HFD) may exert beneficial effects on cardiac mitochondria and contractility. Skeletal muscle mitochondrial dysfunction in heart failure is associated with myopathy. However, it is not clear if HFD affects skeletal muscle mitochondria in heart failure as well. To induce heart failure, we used pressure overload (PO) in rats fed normal chow or HFD. Interfibrillar mitochondria (IFM) and subsarcolemmal mitochondria (SSM) from gastrocnemius were isolated and functionally characterized. With PO heart failure, maximal respiratory capacity was impaired in IFM but increased in SSM of gastrocnemius. Unexpectedly, HFD affected mitochondria comparably to PO. In combination, PO and HFD showed additive effects on mitochondrial subpopulations which were reflected by isolated complex activities. While PO impaired diastolic as well as systolic cardiac function and increased glucose tolerance, HFD did not affect cardiac function but decreased glucose tolerance. We conclude that HFD and PO heart failure have comparable effects leading to more severe impairment of IFM. Glucose tolerance seems not causally related to skeletal muscle mitochondrial dysfunction. The additive effects of HFD and PO may suggest accelerated skeletal muscle mitochondrial dysfunction when heart failure is accompanied with a diet containing high fat.

Analysis of mitochondrial enzymatic activity in blood lymphomonocyte fractions during infection with different Trypanosoma cruzi strains

Proinflammatory and inflammatory mediators induced by Trypanosoma cruzi infection increase the oxidative stress, generating toxicity for cells targeting mitochondria of different tissues. We studied the activity of citrate synthase and complexes I-IV of respiratory chain in mitochondria of blood lymphomonocyte fraction, from albino Swiss mice infected with different isolates of T. cruzi, during Chagas disease evolution. Complexes I-IV were modified in infected groups (p<0.05) in all the stages, and an inflammatory process of different magnitudes was detected in the heart and skeletal muscle according to the isolate. The citrate synthase activity presented modifications in the SGO Z12 and the Tulahuen group (p<0.05). Hearts showed fiber fragmentation and fibrosis; skeletal muscle presented inflammatory infiltrates and in the Tulahuen infected group, there were also amastigote nests. The inflammatory processes produced an oxidative stress that induced different alterations of mitochondrial enzymes activities in the lymphomonocyte fraction that can be detected by a simple blood extraction, suggesting that they could be used as disease markers, especially in the indeterminate phase of Chagas disease.

Targeting the Mitochondria in Heart Failure: A Translational Perspective

The burden of heart failure (HF) in terms of health care expenditures, hospitalizations, and mortality is substantial and growing. The failing heart has been described as "energy-deprived" and mitochondrial dysfunction is a driving force associated with this energy supply-demand imbalance. Existing HF therapies provide symptomatic and longevity benefit by reducing cardiac workload through heart rate reduction and reduction of preload and afterload but do not address the underlying causes of abnormal myocardial energetic nor directly target mitochondrial abnormalities. Numerous studies in animal models of HF as well as myocardial tissue from explanted failed human hearts have shown that the failing heart manifests abnormalities of mitochondrial structure, dynamics, and function that lead to a marked increase in the formation of damaging reactive oxygen species and a marked reduction in on demand adenosine triphosphate synthesis. Correcting mitochondrial dysfunction therefore offers considerable potential as a new therapeutic approach to improve overall cardiac function, quality of life, and survival for patients with HF.

Fetal Programming and Sexual Dimorphism of Mitochondrial Protein Expression and Activity of Hearts of Prenatally Hypoxic Guinea Pig Offspring

Chronic intrauterine hypoxia is a programming stimulus of cardiovascular dysfunction. While the fetal heart adapts to the reduced oxygenation, the offspring heart becomes vulnerable to subsequent metabolic challenges as an adult. Cardiac mitochondria are key organelles responsible for an efficient energy supply but are subject to damage under hypoxic conditions. We propose that intrauterine hypoxia alters mitochondrial function as an underlying programming mechanism of contractile dysfunction in the offspring. Indices of mitochondrial function such as mitochondrial DNA content, Complex (C) I-V expression, and CI/CIV enzyme activity were measured in hearts of male and female offspring at 90 days old exposed to prenatal hypoxia (10.5% O2) for 14 d prior to term (65 d). Both left ventricular tissue and cardiomyocytes exhibited decreased mitochondrial DNA content, expression of CIV, and CI/CIV activity in male hearts. In female cardiomyocytes, hypoxia had no effect on protein expression of CI-CV nor on CI/CIV activity. This study suggests that chronic intrauterine hypoxia alters the intrinsic properties of select respiratory complexes as a programming mechanism of cardiac dysfunction in the offspring. Sex differences in mitochondrial function may underlie the increased vulnerability of age-matched males compared to females in cardiovascular disease and heart failure.

The impact of thyroid hormone dysfunction on ischemic heart disease

Thyroid hormones have a central role in cardiovascular homeostasis. In myocardium, these hormones stimulate both diastolic myocardial relaxation and systolic myocardial contraction, have a pro-angiogenic effect and an important role in extracellular matrix maintenance. Thyroid hormones modulate cardiac mitochondrial function. Dysfunction of thyroid axis impairs myocardial bioenergetic status. Both overt and subclinical hypothyroidism are associated with a higher incidence of coronary events and an increased risk of heart failure progression. Endothelial function is also impaired in hypothyroid state, with decreased nitric oxide-mediated vascular relaxation. In heart disease, particularly in ischemic heart disease, abnormalities in thyroid hormone levels are common and are an important factor to be considered. In fact, low thyroid hormone levels should be interpreted as a cardiovascular risk factor. Regarding ischemic heart disease, during the late post-myocardial infarction period, thyroid hormones modulate left ventricular structure, function and geometry. Dysfunction of thyroid axis might even be more prevalent in the referred condition since there is an upregulation of type 3 deiodinase in myocardium, producing a state of local cardiac hypothyroidism. In this focused review, we summarize the central pathophysiological and clinical links between altered thyroid function and ischemic heart disease. Finally, we highlight the potential benefits of thyroid hormone supplementation as a therapeutic target in ischemic heart disease.

Telomerase Deficiency Predisposes to Heart Failure and Ischemia-Reperfusion Injury

Introduction: Elevated levels of mitochondrial reactive oxygen species (ROS) contribute to the development of numerous cardiovascular diseases. TERT, the catalytic subunit of telomerase, has been shown to translocate to mitochondria to suppress ROS while promoting ATP production. Acute overexpression of TERT increases survival and decreases infarct size in a mouse model of myocardial infarct, while decreased telomerase activity predisposes to mitochondrial defects and heart failure. In the present study, we examined the role of TERT on cardiac structure and function under basal conditions and conditions of acute or prolonged stress in a novel rat model of TERT deficiency. Methods: Cardiac structure and function were evaluated via transthoracic echocardiogram. Langendorff preparations were used to test the effects of acute global ischemia reperfusion injury on cardiac function and infarction. Coronary flow and left ventricular pressure were measured during and after ischemia/reperfusion (I/R). Mitochondrial DNA integrity was measured by PCR and mitochondrial respiration was assessed in isolated mitochondria using an Oxygraph. Angiotensin II infusion was used as an established model of systemic stress. Results: No structural changes (echocardiogram) or coronary flow/left ventricle pressure (isolated hearts) were observed in TERT^-/- rats at baseline; however, after I/R, coronary flow was significantly reduced in TERT^-/- compared to wild type (WT) rats, while diastolic Left Ventricle Pressure was significantly elevated (n = 6 in each group; p < 0.05) in the TERT^-/-. Interestingly, infarct size was less in TERT^-/- rats compared to WT rats, while mitochondrial respiratory control index decreased and mitochondrial DNA lesions increased in TERT^-/- compared to WT. Angiotensin II treatment did not alter cardiac structure or function; however, it augmented the infarct size significantly more in TERT^-/- compared to the WT. Conclusion: Absence of TERT activity increases susceptibility to stress like cardiac injury. These results suggest a critical role of telomerase in chronic heart disease.

Cobalt chloride toxicity elicited hypertension and cardiac complication via induction of oxidative stress and upregulation of COX-2/Bax signaling pathway

Cobalt is a ferromagnetic metal with extensive industrial and biological applications. To assess the toxic effects of, and mechanisms involved in cobalt chloride (CoCl₂)-induced cardio-renal dysfunctions. Male Wistar rats were exposed orally, daily through drinking water to 0 ppm (control), 150 ppm, 300 ppm, and 600 ppm of CoCl₂, respectively. Following exposure, results revealed significant ( p < 0.05) rise in markers of oxidative stress, but decreased activities of catalase, glutathione peroxidase, glutathione-S-transferase, and reduced glutathione content in cardiac and renal tissues. There were significant increases in systolic, diastolic, and mean arterial blood pressure at the 300- and 600-ppm level of CoCl₂-exposed rats relative to the control. Prolongation of QT and QTc intervals was observed in CoCl₂ alone treated rats. Also, there were significant increases in the heart rates, and reduction in P wave, and PR duration of rats administered CoCl₂. Histopathology of the kidney revealed peritubular and periglomerular inflammation, focal glomerular necrosis following CoCl₂ exposure. Further, cyclooxygenase-2 and B-cell associated protein X expressions were upregulated in the cardiac and renal tissues of CoCl₂-exposed rats relative to the control. Combining all, results from this study implicated oxidative stress, inflammation, and apoptosis as pathologic mechanisms in CoCl₂-induced hypertension and cardiovascular complications of rats.

Mitochondrial quality control in the cardiac system: An integrative view

Recent studies have led to the discovery of multiple mitochondrial quality control (mQC) processes that operate at various scales, ranging from the degradation of proteins by mitochondrial proteases to the degradation of selected cargos or entire organelles in lysosomes. While the mechanisms governing these mQC processes are progressively being delineated, their role and importance remain unclear. Converging evidence however point to a complex system whereby multiple and partly overlapping processes are recruited to orchestrate a cell type specific mQC response that is adapted to the physiological state and level of stress encountered. Knowledge gained from basic model systems of mQC therefore need to be integrated within organ-specific (patho)physiological frameworks. Building on this notion, this article focuses on mQC in the heart, where developmental metabolic reprogramming, sustained contraction, and multiple pathophysiological conditions pose broadly different constraints. We provide an overview of current knowledge of mQC processes, and discuss their implication in cardiac mQC under normal and diseased conditions.

Cardioprotection and thyroid hormones

The evolution of cardiac disease after an acute ischemic event depends on a complex and dynamic network of mechanisms alternating from ischemic damage due to acute coronary occlusion to reperfusion injury due to the adverse effects of coronary revascularization till post-ischemic remodeling. Cardioprotection is a new purpose of the therapeutic interventions in cardiology with the goal to reduce infarct size and thus prevent the progression toward heart failure after an acute ischemic event. In a complex biological system such as the human one, an effective cardioprotective strategy should diachronically target the network of cross-talking pathways underlying the disease progression. Thyroid system is strictly interconnected with heart homeostasis, and recent studies highlighted its role in cardioprotection, in particular through the preservation of mitochondrial function and morphology, the antifibrotic and proangiogenetic effect and also to the potential induction of cell regeneration and growth. The objective of this review was to highlight the cardioprotective role of triiodothyronine in the complexity of post-ischemic disease evolution.

An open-label, non-randomized study of the pharmacokinetics of the nutritional supplement nicotinamide riboside (NR) and its effects on blood NAD+ levels in healthy volunteers

Objectives

The co-primary objectives of this study were to determine the human pharmacokinetics (PK) of oral NR and the effect of NR on whole blood nicotinamide adenine dinucleotide (NAD+) levels.

Background

Though mitochondrial dysfunction plays a critical role in the development and progression of heart failure, no mitochondria-targeted therapies have been translated into clinical practice. Recent murine studies have reported associations between imbalances in the NADH/NAD+ ratio with mitochondrial dysfunction in multiple tissues, including myocardium. Moreover, an NAD+ precursor, nicotinamide mononucleotide, improved cardiac function, while another NAD+ precursor, nicotinamide riboside (NR), improved mitochondrial function in muscle, liver and brown adipose. Thus, PK studies of NR in humans is critical for future clinical trials.

Methods

In this non-randomized, open-label PK study of 8 healthy volunteers, 250 mg NR was orally administered on Days 1 and 2, then uptitrated to peak dose of 1000 mg twice daily on Days 7 and 8. On the morning of Day 9, subjects completed a 24-hour PK study after receiving 1000 mg NR at t = 0. Whole-blood levels of NR, clinical blood chemistry, and NAD+ levels were analyzed.

Results

Oral NR was well tolerated with no adverse events. Significant increases comparing baseline to mean concentrations at steady state (C_ave,ss) were observed for both NR (p = 0.03) and NAD+ (p = 0.001); the latter increased by 100%. Absolute changes from baseline to Day 9 in NR and NAD+ levels correlated highly (R² = 0.72, p = 0.008).

Conclusions

Because NR increases circulating NAD+ in humans, NR may have potential as a therapy in patients with mitochondrial dysfunction due to genetic and/or acquired diseases.

Correlation Between Mitochondrial DNA Content Measured in Myocardium and Peripheral Blood of Patients with Non-Ischemic Heart Failure

BACKGROUND/OBJECTIVES

Heart failure (HF) is associated with disturbances in mitochondrial energy production. This mitochondrial dysfunction is reflected by depletion of mitochondrial DNA (mtDNA) in different tissues. Our aims were to determine if there was a correlation between mtDNA content measured in myocardial tissue and the easily accessible peripheral blood cells of patients with non-ischemic HF; and to determine if there was a correlation between myocardial mtDNA and left ventricular (LV) ejection fraction.

METHODS

We prospectively collected paired myocardial tissue and peripheral blood samples from 13 consecutive end-stage non-ischemic HF patients undergoing cardiac transplantation. mtDNA content was assessed with real-time quantitative PCR by calculating the relative ratio of two specific mitochondrial sequences and one nuclear control gene sequence.

RESULTS

HF patients with lower myocardial mtDNA content had a significantly lower LV ejection fraction (r = 0.65, p = 0.016). Peripheral blood mtDNA content correlated positively with right ventricular myocardial mtDNA content (r = 0.63, p = 0.021). We also observed that averaged myocardial DNA content tended to correlate with peripheral blood mtDNA content (r = 0.53, p = 0.061).

CONCLUSIONS

In non-ischemic HF patients, myocardial mtDNA content is positively correlated with peripheral blood mtDNA content and LV function as assessed by echocardiography.

Depleted Leukocyte Mitochondrial DNA Copy Number Correlates With Unfavorable Left Ventricular Volumetric and Spherical Shape Remodeling in Acute Myocardial Infarction After Primary Angioplasty

BACKGROUND

Left ventricular (LV) shape influences LV systolic function. It is possible to assess LV shape using 3-D echocardiography sphericity index (SI). Maintaining mitochondrial DNA copy number (MCN) is important for preserving mitochondrial function and LV systolic function after acute myocardial infarction (AMI). Information is limited, however, regarding the relationship between leukocyte MCN and the subsequent change in LV shape after AMI.Methods and Results:Fifty-five AMI patients undergoing primary angioplasty were recruited. Plasma MCN was measured before primary angioplasty using quantitative polymerase chain reaction. 3-D echocardiography measurement of SI was performed at baseline, and at 1-, 3-, and 6-month follow-up. AMI subjects with MCN lower than the median had a higher 6-month SI and LV volume compared with those with higher MCN. Baseline echocardiographic parameters were similar between the 2 groups. MCN was negatively correlated with 3- and 6-month SI, and 3- and 6-month LV volume. On multiple linear regression analysis, baseline plasma MCN could predict LV SI and LV volume at 6 months after primary angioplasty for AMI, even after adjusting for traditional prognostic factors.

CONCLUSIONS

In AMI patients, higher plasma leukocyte MCN at baseline was associated with favorable LV shape and remodeling at 6-month follow-up. Plasma leukocyte MCN may provide a novel prognostic biomarker for LV remodeling after AMI.

ALDH2 Glu504Lys Confers Susceptibility to Schizophrenia and Impacts Hippocampal-Prefrontal Functional Connectivity

Although previous evidence suggested that ALDH2 is a candidate gene for schizophrenia, the association and underlying mechanisms have never been investigated. Therefore, we investigated ALDH2 as a susceptibility gene for schizophrenia and explored the effect of its polymorphisms on brain functions. In the discovery stage, we detected a positive association between a dominant-negative mutant, Glu504Lys, and schizophrenia (P= 8.01E-5, OR = 1.34, 95% CI = 1.16-1.55). This association was confirmed in the validation stage (P= 3.48E-6, OR = 1.28, 95% CI = 1.15-1.42). The combined P reached a genome-wide significance (Pcombined= 1.32E-9, OR = 1.30, 95% CI = 1.20-1.42). To investigate the neural mechanism linking Glu504Lys to schizophrenia, we calculated the functional connectivity (FC) and applied an imaging genetics strategy using resting-state fMRI data. The imaging analysis revealed a significant interaction of diagnostic group by genotype for FC between the left hippocampus and the prefrontal cortex. In the Glu homozygotes, hippocampal-prefrontal FC correlated inversely with memory performance in the healthy controls and with the PANSS negative score in the schizophrenia patients. Our results supported a role for ALDH2 in the pathophysiology of schizophrenia. Moreover, variation at Glu504Lys disrupts hippocampal-prefrontal FC, which might be the neural mechanism linking it to the disease.

Combined Inhibition of the Renin-Angiotensin System and Neprilysin Positively Influences Complex Mitochondrial Adaptations in Progressive Experimental Heart Failure

BACKGROUND

Inhibitors of the renin angiotensin system and neprilysin (RAS-/NEP-inhibitors) proved to be extraordinarily beneficial in systolic heart failure. Furthermore, compelling evidence exists that impaired mitochondrial pathways are causatively involved in progressive left ventricular (LV) dysfunction. Consequently, we aimed to assess whether RAS-/NEP-inhibition can attenuate mitochondrial adaptations in experimental heart failure (HF).

METHODS AND RESULTS

By progressive right ventricular pacing, distinct HF stages were induced in 15 rabbits, and 6 animals served as controls (CTRL). Six animals with manifest HF (CHF) were treated with the RAS-/NEP-inhibitor omapatrilat. Echocardiographic studies and invasive blood pressure measurements were undertaken during HF progression. Mitochondria were isolated from LV tissue, respectively, and further worked up for proteomic analysis using the SWATH technique. Enzymatic activities of citrate synthase and the electron transfer chain (ETC) complexes I, II, and IV were assessed. Ultrastructural analyses were performed by transmission electron microscopy. During progression to overt HF, intricate expression changes were mainly detected for proteins belonging to the tricarboxylic acid cycle, glucose and fat metabolism, and the ETC complexes, even though ETC complex I, II, or IV enzymatic activities were not significantly influenced. Treatment with a RAS-/NEP-inhibitor then reversed some maladaptive metabolic adaptations, positively influenced the decline of citrate synthase activity, and altered the composition of each respiratory chain complex, even though this was again not accompanied by altered ETC complex enzymatic activities. Finally, ultrastructural evidence pointed to a reduction of autophagolytic and degenerative processes with omapatrilat-treatment.

CONCLUSIONS

This study describes complex adaptations of the mitochondrial proteome in experimental tachycardia-induced heart failure and shows that a combined RAS-/NEP-inhibition can beneficially influence mitochondrial key pathways.

Mitochondrial involvement in myocyte death and heart failure

As the heart is an energy-demanding organ, impaired cardiac energy metabolism and mitochondrial function have been inexorably linked to cardiac dysfunction. There is a growing recognition that mitochondrial dysfunction contributes to impaired myocardial energetics and increased oxidative stress in cardiomyopathies, cardiac ischemic damage and heart failure (HF), and mitochondrial permeability transition pore opening has been reported a critical trigger of myocyte death and myocardial remodeling. It is well established that mitochondria play pivotal roles in intracellular signaling in both cell death as well as in cardioprotective pathways. Moreover, recent studies have shown that defects in mitochondrial dynamics affecting biogenesis and turnover are linked to cardiac senescence and HF. Accordingly, there has been an increasing interest in targeting mitochondria for HF therapy. This article reviews the background and recent evidence of mitochondrial involvement in several types of cell death (apoptosis, necrosis and autophagy) occurring in HF. In addition, potential strategies for targeting mitochondria are examined, and their utility in HF therapy considered.

Mitochondrial structure and function are not different between nonfailing donor and end-stage failing human hearts

During human heart failure, the balance of cardiac energy use switches from predominantly fatty acids (FAs) to glucose. We hypothesized that this substrate shift was the result of mitochondrial degeneration; therefore, we examined mitochondrial oxidation and ultrastructure in the failing human heart by using respirometry, transmission electron microscopy, and gene expression studies of demographically matched donor and failing human heart left ventricular (LV) tissues. Surprisingly, respiratory capacities for failing LV isolated mitochondria (n = 9) were not significantly diminished compared with donor LV isolated mitochondria (n = 7) for glycolysis (pyruvate + malate)- or FA (palmitoylcarnitine)-derived substrates, and mitochondrial densities, assessed via citrate synthase activity, were consistent between groups. Transmission electron microscopy images also showed no ultrastructural remodeling for failing vs. donor mitochondria; however, the fraction of lipid droplets (LDs) in direct contact with a mitochondrion was reduced, and the average distance between an LD and its nearest neighboring mitochondrion was increased. Analysis of FA processing gene expression between donor and failing LVs revealed 0.64-fold reduced transcript levels for the mitochondrial-LD tether, perilipin 5, in the failing myocardium (P = 0.003). Thus, reduced FA use in heart failure may result from improper delivery, potentially via decreased perilipin 5 expression and mitochondrial-LD tethering, and not from intrinsic mitochondrial dysfunction.-Holzem, K. M., Vinnakota, K. C., Ravikumar, V. K., Madden, E. J., Ewald, G. A., Dikranian, K., Beard, D. A., Efimov, I. R. Mitochondrial structure and function are not different between nonfailing donor and end-stage failing human hearts.

Diseases caused by defects of energy level and loss of coherence in living cells

Human and animal diseases are brought about by pathological alterations of production, composition, and conformation of macromolecules and structures in cells. Additional contributing factors include changes in physiological states caused by disturbances of energy supply, energy transduction, energy dissipation in moving or oscillating parts, and parasitic energy consumption. Disturbances of energy states may endanger existence of the system. The cell-mediated immunity (CMI) response of T lymphocytes correlating with their adherence properties was examined using antigen prepared from the serum of inbred laboratory mice strain C3H H(2k) infected with lactate dehydrogenase elevating (LDH) virus. LDH virus is a parasite on the cellular energy system. Significant CMI response was elicited in T lymphocytes prepared from the blood of patients with cancer of different phenotypes, acute myocardial infarctions, schizophrenia, and recurrent spontaneous abortions in early pregnancy from unknown reasons. The CMI response is assumed to monitor transferred information about decreased levels of energy states and decoherence in the cells caused by mitochondrial malfunction, parasitic consumption, production of lactate, and possibly other disturbances. The LDH virus infection or similar pathological processes caused by different agents might be connected with the diseases and monitored by the examined CMI response. A large amount of mitoses with chromosome defects in aborted fetuses suggest increased mutability of genomes caused by defective energy states.

Association of left ventricular structure and function with peripheral blood mitochondrial DNA content in a general population

BACKGROUND/OBJECTIVES

mtDNA content might be an important biomarker in heart disease prediction and to date no population studies are available on the association of mtDNA content with cardiac structure and function. We, therefore, investigated in a general population in cross-sectional and longitudinal studies whether echocardiographic indexes of LV structure and function are associated with mtDNA content measured in peripheral blood cells.

METHODS

At baseline we performed echocardiography in 701 randomly selected individuals (50.9% women, mean age, 53.2years) from a Flemish population. Relative mtDNA copy number compared to nuclear DNA was measured by quantitative real-time PCR in peripheral blood cells.

RESULTS

With adjustments applied, we observed significant inverse association of LV diastolic and systolic diameters (P≤0.028) and volumes (P=0.013) with mtDNA content. Moreover, for a 1-SD increment in mtDNA (0.37), we found an increase in Tissue Doppler s' velocity by 0.093cm/s (P=0.019) and a decrease in E/e' ratio by 0.18 (P=0.008). In 223 subjects with available echocardiography and mtDNA content at baseline and follow-up, we observed that higher baseline mtDNA content was associated with less increase in 2D LV diastolic volume (P=0.0003), M-mode LV diameter (P=0.046) and LV mass (P=0.003) during the follow-up period.

CONCLUSIONS

In the general population, higher mtDNA content was associated with smaller LV diastolic and systolic diameters and volumes and better LV systolic and diastolic function. Moreover, we observed that baseline mtDNA content was a significant predictor of longitudinal changes of LV diastolic volume and dimension, and LV mass.

Age Related Bioenergetics Profiles in Isolated Rat Cardiomyocytes Using Extracellular Flux Analyses

Mitochondrial dysfunction is increasingly recognized and studied as a mediator of heart disease. Extracellular flux analysis (XF) has emerged as a powerful tool to investigate cellular bioenergetics in the context of cardiac health and disease, however its use and interpretation requires improved understanding of the normal metabolic differences in cardiomyocytes (CM) at various stages of maturation. This study standardized XF analyses methods (mitochondrial stress test, glycolytic stress test and palmitate oxidation test) and established age related differences in bioenergetics profiles of healthy CMs at newborn (NB1), weaning (3WK), adult (10WK) and aged (12–18MO) time points. Findings show that immature CMs demonstrate a more robust and sustained glycolytic capacity and a relative inability to oxidize fatty acids when compared to older CMs. The study also highlights the need to recognize the contribution of CO₂ from the Krebs cycle as well as lactate from anaerobic glycolysis to the proton production rate before interpreting glycolytic capacity in CMs. Overall, this study demonstrates that caution should be taken to assure that translatable developmental time points are used to investigate mitochondrial dysfunction as a cause of cardiac disease. Specifically, XF analysis of newborn CMs should be reserved to study fetal/neonatal disease and older CMs (≥10 weeks) should be used to investigate adult disease pathogenesis. Knowledge gained will aid in improved investigation of developmentally programmed heart disease and stress the importance of discerning maturational differences in bioenergetics when developing mitochondrial targeted preventative and therapeutic strategies for cardiac disease.

Role of the Thyroid System in the Dynamic Complex Network of Cardioprotection

Cardioprotection is a common goal of new therapeutic strategies in patients with coronary artery disease and/or left ventricular dysfunction. Myocardial damage following ischaemia/reperfusion injury lead to left ventricular adverse remodelling through many mechanisms arising from different cell types in different myocardial districts, namely the border and remote zone. Cardioprotection must face this complex, dynamic network of cooperating units. In this scenario, thyroid hormones can represent an effective therapeutic strategy due to the numerous actions and regulating mechanisms carried out at the level of the myocytes, interstitium and the vasculature, as well as to the activation of different pro-survival intracellular pathways involved in cardioprotection.

Low T3 State Is Correlated with Cardiac Mitochondrial Impairments after Ischemia Reperfusion Injury: Evidence from a Proteomic Approach

Mitochondria are major determinants of cell fate in ischemia/reperfusion injury (IR) and common effectors of cardio-protective strategies in cardiac ischemic disease. Thyroid hormone homeostasis critically affects mitochondrial function and energy production. Since a low T3 state (LT3S) is frequently observed in the post infarction setting, the study was aimed to investigate the relationship between 72 h post IR T3 levels and both the cardiac function and the mitochondrial proteome in a rat model of IR. The low T3 group exhibits the most compromised cardiac performance along with the worst mitochondrial activity. Accordingly, our results show a different remodeling of the mitochondrial proteome in the presence or absence of a LT3S, with alterations in groups of proteins that play a key role in energy metabolism, quality control and regulation of cell death pathways. Overall, our findings highlight a relationship between LT3S in the early post IR and poor cardiac and mitochondrial outcomes, and suggest a potential implication of thyroid hormone in the cardio-protection and tissue remodeling in ischemic disease.

Mitochondrial transcription factor A regulation of mitochondrial degeneration in experimental diabetic neuropathy

Oxidative stress-induced mitochondrial dysfunction and mitochondrial DNA (mtDNA) damage in peripheral neurons is considered to be important in the development of diabetic neuropathy. Mitochondrial transcription factor A (TFAM) wraps mtDNA and promotes mtDNA replication and transcription. We studied whether overexpression of TFAM reverses experimental peripheral diabetic neuropathy using TFAM transgenic mice (TFAM Tg) that express human TFAM (hTFAM). Levels of mouse mtDNA and the total TFAM (mouse TFAM + hTFAM) in the dorsal root ganglion (DRG) increased by approximately twofold in the TFAM Tg mice compared with control (WT) mice. WT and TFAM Tg mice were made diabetic by the administration of streptozotocin. Neuropathy end points were motor and sensory nerve conduction velocities, mechanical allodynia, thermal nociception, and intraepidermal nerve fiber density (IENFD). In the DRG neurons, mtDNA copy number and damage to mtDNA were quantified by qPCR, and TFAM levels were measured by Western blot. Mice with 16-wk duration of diabetes developed motor and sensory nerve conduction deficits, behavioral deficits, and intraepidermal nerve fiber loss. All of these changes were mostly prevented in diabetic TFAM Tg mice and were independent of changes in blood parameters. Mice with 16 wk of diabetes had a 40% decrease in mtDNA copy number compared with nondiabetic mice (P < 0.01). Importantly, the mtDNA copy number in diabetic TFAM Tg mice reached the same level as that of WT nondiabetic mice. In comparison, there was upregulation of mtDNA and TFAM in 6-wk diabetic mice, suggesting that TFAM activation could be a therapeutic strategy to treat peripheral neuropathy.

Mitochondrial dysfunction in skeletal muscle during experimental Chagas disease

Trypanosoma cruzi invasion and replication in cardiomyocytes and other tissues induce cellular injuries and cytotoxic reactions, with the production of inflammatory cytokines and nitric oxide, both sources of reactive oxygen species. The myocyte response to oxidative stress involves the progression of cellular changes primarily targeting mitochondria. Similar alterations could be taking place in mitochondria from the skeletal muscle; if that is the case, a simple skeletal muscle biopsy would give information about the cardiac energetic production that could be used as a predictor of the chagasic cardiopathy evolution. Therefore, in the present paper we studied skeletal muscle mitochondrial structure and the enzymatic activity of citrate synthase and respiratory chain complexes I to IV (CI-CIV), in Albino Swiss mice infected with T. cruzi, Tulahuen strain and SGO Z12 and Lucky isolates, along the infection. Changes in the mitochondrial structure were detected in 100% of the mitochondria analyzed from the infected groups: they all presented at least 1 significant abnormality such as increase in their matrix or disorganization of their cristae, which are probably related to the enzymatic dysfunction. When we studied the Krebs cycle functionality through the measurement of the specific citrate synthase activity, we found it to be significantly diminished during the acute phase of the infection in Tulahuen and SGO Z12 infected groups with respect to the control one; citrate synthase activity from the Lucky group was significantly increased (p<0.05). The activity of this enzyme was reduced in all the infected groups during the chronic asymptomatic phase (p<0.001) and return to normal values (Tulahuen and SGO Z12) or increased its activity (Lucky) by day 365 post-infection (p.i.). When the mitochondrial respiratory chain was analyzed from the acute to the chronic phase of the infection through the measurement of the activity of complexes I to IV, the activity of CI remained similar to control in Tulahuen and Lucky groups, but was significantly augmented in the SGO Z12 one in the acute and chronic phases (p<0.05). CII increased its activity in Tulahuen and Lucky groups by day 75 p.i. and in SGO Z12 by day 365 p.i. (p<0.05). CIII showed a similar behavior in the 3 infected groups, remaining similar to control values in the first two stages of the infection and significantly increasing later on (p<0.0001). CIV showed an increase in its activity in Lucky throughout all stages of infection (p<0.0001) and an increase in Tulahuen by day 365days p.i. (p<0.0001); SGO Z12 on the other hand, showed a decreased CIV activity at the same time. The structural changes in skeletal muscle mitochondria and their altered enzyme activity began in the acute phase of infection, probably modifying the ability of mitochondria to generate energy; these changes were not compensated in the rest of the phases of the infection. Chagas is a systemic disease, which produces not only heart damage but also permanent skeletal muscle alterations.

Mitochondria as key targets of cardioprotection in cardiac ischemic disease: role of thyroid hormone triiodothyronine

Ischemic heart disease is the major cause of mortality and morbidity worldwide. Early reperfusion after acute myocardial ischemia has reduced short-term mortality, but it is also responsible for additional myocardial damage, which in the long run favors adverse cardiac remodeling and heart failure evolution. A growing body of experimental and clinical evidence show that the mitochondrion is an essential end effector of ischemia/reperfusion injury and a major trigger of cell death in the acute ischemic phase (up to 48–72 h after the insult), the subacute phase (from 72 h to 7–10 days) and chronic stage (from 10–14 days to one month after the insult). As such, in recent years scientific efforts have focused on mitochondria as a target for cardioprotective strategies in ischemic heart disease and cardiomyopathy. The present review discusses recent advances in this field, with special emphasis on the emerging role of the biologically active thyroid hormone triiodothyronine (T3).

Mitochondrial integrity in a neonatal bovine model of right ventricular dysfunction

Right ventricular (RV) function is a key determinant of survival in patients with both RV and left ventricular (LV) failure, yet the mechanisms of RV failure are poorly understood. Recent studies suggest cardiac metabolism is altered in RV failure in pulmonary hypertension (PH). Accordingly, we assessed mitochondrial content, dynamics, and function in hearts from neonatal calves exposed to hypobaric hypoxia (HH). This model develops severe PH with concomitant RV hypertrophy, dilation, and dysfunction. After 2 wk of HH, pieces of RV and LV were obtained along with samples from age-matched controls. Comparison with control assesses the effect of hypoxia, whereas comparison between the LV and RV in HH assesses the additional impact of RV overload. Mitochondrial DNA was unchanged in HH, as was mitochondrial content as assessed by electron microscopy. Immunoblotting for electron transport chain subunits revealed a small increase in mitochondrial content in HH in both ventricles. Mitochondrial dynamics were largely unchanged. Activity of individual respiratory chain complexes was reduced (complex I) or unchanged (complex V) in HH. Key enzymes in the glycolysis pathway were upregulated in both HH ventricles, alongside upregulation of hypoxia-inducible factor-1α protein. Importantly, none of the changes in expression or activity were different between ventricles, suggesting the changes are in response to HH and not RV overload. Upregulation of glycolytic modulators without chamber-specific mitochondrial dysfunction suggests that mitochondrial capacity and activity are maintained at the onset of PH, and the early RV dysfunction in this model results from mechanisms independent of the mitochondria.

Triiodothyronine prevents cardiac ischemia/reperfusion mitochondrial impairment and cell loss by regulating miR30a/p53 axis

Mitochondrial dysfunctions critically affect cardiomyocyte survival during ischemia/reperfusion (I/R) injury. In this scenario p53 activates multiple signaling pathways that impair cardiac mitochondria and promote cell death. p53 is a validated target of miR-30 whose levels fall under ischemic conditions. Although triiodothyronine (T3) rescues post-ischemic mitochondrial activity and cell viability, no data are available on its role in the modulation of p53 signaling in I/R. Here we test the hypothesis that early T3 supplementation in rats inhibits the post I/R activation of p53 pro-death cascade through the maintenance of miRNA 30a expression. In our model, T3 infusion improves the recovery of post-ischemic cardiac performance. At the molecular level, the beneficial effect of T3 is associated with restored levels of miR-30a expression in the area at risk (AAR) that correspond to p53 mRNA downregulation. The concomitant decrease in p53 protein content reduces Bax expression and limits mitochondrial membrane depolarization resulting in preserved mitochondrial function and decreased apoptosis and necrosis extent in the AAR. Also in primary cardiomyocyte culture of neonatal rats, T3 prevents both miR-30a downregulation and p53 raise induced by hypoxia. The regulatory effect of T3 is greatly suppressed by miR-30a knockdown. Overall these data suggest a new mechanism of T3-mediated cardioprotection that is targeted to mitochondria and acts, at least in part, through the regulation of miR-30a/p53 axis.