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The effects of methylmercury (MeHg) on exposed populations are a public health problem. In contrast to widely studied neurological damage, few cardiovascular changes have been described. Our group evaluated the cardiotoxicity of a cumulative dose of 70 mg.kg−1 fractioned over a 14-day exposure period in mice (MeHg70 group). The effects of MeHg on proteins relevant to cardiac mitochondrial function were also investigated. The results obtained showed a reduction in oxygen consumption in the two settings. In cardiac tissue samples in oxygraphy studies, this reduction was related to a lower efficiency of complexes II and V, which belong to the oxidative phosphorylation system. In vivo, mice in the MeHg70 group presented lower oxygen consumption and running tolerance, as shown by ergometric analyses. Cardiac stress was evident in the MeHg70 group, as indicated by a marked increase in the level of the mRNA encoding atrial natriuretic peptide. Electrocardiogram studies revealed a lower heart rate at rest in the animals from the MeHg70 group, as well as prolonged left ventricular depolarisation and repolarisation. Through echocardiographic analysis, reductions in the left ventricular ejection fraction and left ventricular wall thickness of approximately 10% and 20%, respectively, were detected. These results indicate that the oral intake of MeHg can decrease cardiac function and oxidative metabolism. This finding highlights the importance of monitoring MeHg levels in humans and animals in contaminated areas, as well as periodically carrying out cardiac function tests. [ABSTRACT FROM AUTHOR]

It is well known that in the heart and kidney mitochondria, more than 95% of ATP production is supported by the β-oxidation of long-chain fatty acids. However, the β-oxidation of fatty acids by mitochondria has been studied much less than the substrates formed during the catabolism of carbohydrates and amino acids. In the last few decades, several discoveries have been made that are directly related to fatty acid oxidation. In this review, we made an attempt to re-evaluate the β-oxidation of long-chain fatty acids from the perspectives of new discoveries. The single set of electron transporters of the cardiac mitochondrial respiratory chain is organized into three supercomplexes. Two of them contain complex I, a dimer of complex III, and two dimers of complex IV. The third, smaller supercomplex contains a dimer of complex III and two dimers of complex IV. We also considered other important discoveries. First, the enzymes of the β-oxidation of fatty acids are physically associated with the respirasome. Second, the β-oxidation of fatty acids creates the highest level of QH2 and reverses the flow of electrons from QH2 through complex II, reducing fumarate to succinate. Third, β-oxidation is greatly stimulated in the presence of succinate. We argue that the respirasome is uniquely adapted for the β-oxidation of fatty acids. The acyl-CoA dehydrogenase complex reduces the membrane's pool of ubiquinone to QH2, which is instantly oxidized by the smaller supercomplex, generating a high energization of mitochondria and reversing the electron flow through complex II, which reverses the electron flow through complex I, increasing the NADH/NAD+ ratio in the matrix. The mitochondrial nicotinamide nucleotide transhydrogenase catalyzes a hydride (H-, a proton plus two electrons) transfer across the inner mitochondrial membrane, reducing the cytosolic pool of NADP(H), thus providing the heart with ATP for muscle contraction and energy and reducing equivalents for the housekeeping processes. [ABSTRACT FROM AUTHOR]

Abstract Aims Impaired myocardial energy homeostasis plays an import role in the pathophysiology of heart failure with preserved ejection fraction (HFpEF). Left ventricular relaxation has a high energy demand, and left ventricular diastolic dysfunction has been related to impaired energy homeostasis. This study investigated whether trimetazidine, a fatty acid oxidation inhibitor, could improve myocardial energy homeostasis and consequently improve exercise haemodynamics in patients with HFpEF. Methods and results The DoPING‐HFpEF trial was a phase II single‐centre, double‐blind, placebo‐controlled, randomized cross‐over trial. Patients were randomized to trimetazidine treatment or placebo for 3 months and switched after a 2‐week wash‐out period. The primary endpoint was change in pulmonary capillary wedge pressure, measured with right heart catheterization at multiple stages of bicycling exercise. Secondary endpoint was change in myocardial phosphocreatine/adenosine triphosphate, an index of the myocardial energy status, measured with phosphorus‐31 magnetic resonance spectroscopy. The study included 25 patients (10/15 males/females; mean (standard deviation) age, 66 (10) years; body mass index, 29.8 (4.5) kg/m2); with the diagnosis of HFpEF confirmed with (exercise) right heart catheterization either before or during the trial. There was no effect of trimetazidine on the primary outcome pulmonary capillary wedge pressure at multiple levels of exercise (mean change 0 [95% confidence interval, 95% CI −2, 2] mmHg over multiple levels of exercise, P = 0.60). Myocardial phosphocreatine/adenosine triphosphate in the trimetazidine arm was similar to placebo (1.08 [0.76, 1.76] vs. 1.30 [0.95, 1.86], P = 0.08). There was no change by trimetazidine compared with placebo in the exploratory parameters: 6‐min walking distance (mean change of −6 [95% CI −18, 7] m vs. −5 [95% CI −22, 22] m, respectively, P = 0.93), N‐terminal pro‐B‐type natriuretic peptide (5 (−156, 166) ng/L vs. −13 (−172, 147) ng/L, P = 0.70), overall quality‐of‐life (KCCQ and EQ‐5D‐5L, P = 0.78 and P = 0.51, respectively), parameters for diastolic function measured with echocardiography and cardiac magnetic resonance, or metabolic parameters. Conclusions Trimetazidine did not improve myocardial energy homeostasis and did not improve exercise haemodynamics in patients with HFpEF.

The effects of methylmercury (MeHg) on exposed populations are a public health problem. In contrast to widely studied neurological damage, few cardiovascular changes have been described. Our group evaluated the cardiotoxicity of a cumulative dose of 70 mg.kg−1 fractioned over a 14-day exposure period in mice (MeHg70 group). The effects of MeHg on proteins relevant to cardiac mitochondrial function were also investigated. The results obtained showed a reduction in oxygen consumption in the two settings. In cardiac tissue samples in oxygraphy studies, this reduction was related to a lower efficiency of complexes II and V, which belong to the oxidative phosphorylation system. In vivo, mice in the MeHg70 group presented lower oxygen consumption and running tolerance, as shown by ergometric analyses. Cardiac stress was evident in the MeHg70 group, as indicated by a marked increase in the level of the mRNA encoding atrial natriuretic peptide. Electrocardiogram studies revealed a lower heart rate at rest in the animals from the MeHg70 group, as well as prolonged left ventricular depolarisation and repolarisation. Through echocardiographic analysis, reductions in the left ventricular ejection fraction and left ventricular wall thickness of approximately 10% and 20%, respectively, were detected. These results indicate that the oral intake of MeHg can decrease cardiac function and oxidative metabolism. This finding highlights the importance of monitoring MeHg levels in humans and animals in contaminated areas, as well as periodically carrying out cardiac function tests.

The work shows the effect of the metabolic modulator uridine on the functioning and ultrastructure of heart mitochondria in dystrophin-deficient mdx mice. Intraperitoneal administration of uridine (30 mg/kg/day for 28 days) improved K+ transport and increased its content in the heart mitochondria of mdx mice to the level of wild-type animals. This was accompanied by a significant decrease in the level of malondialdehyde and an increase in the number of mitochondria in the heart of mdx mice. At the same time, uridine did not affect the hyperfunctionality of mitochondria in mdx mice, which manifested in an increase in the calcium retention capacity. Nevertheless, we noted that uridine causes a significant decrease in the level of fibrosis in the heart of mdx mice, which attested to a positive effect of therapy. [ABSTRACT FROM AUTHOR]

Aims: Impaired myocardial energy homeostasis plays an import role in the pathophysiology of heart failure with preserved ejection fraction (HFpEF). Left ventricular relaxation has a high energy demand, and left ventricular diastolic dysfunction has been related to impaired energy homeostasis. This study investigated whether trimetazidine, a fatty acid oxidation inhibitor, could improve myocardial energy homeostasis and consequently improve exercise haemodynamics in patients with HFpEF. Methods and results: The DoPING‐HFpEF trial was a phase II single‐centre, double‐blind, placebo‐controlled, randomized cross‐over trial. Patients were randomized to trimetazidine treatment or placebo for 3 months and switched after a 2‐week wash‐out period. The primary endpoint was change in pulmonary capillary wedge pressure, measured with right heart catheterization at multiple stages of bicycling exercise. Secondary endpoint was change in myocardial phosphocreatine/adenosine triphosphate, an index of the myocardial energy status, measured with phosphorus‐31 magnetic resonance spectroscopy. The study included 25 patients (10/15 males/females; mean (standard deviation) age, 66 (10) years; body mass index, 29.8 (4.5) kg/m2); with the diagnosis of HFpEF confirmed with (exercise) right heart catheterization either before or during the trial. There was no effect of trimetazidine on the primary outcome pulmonary capillary wedge pressure at multiple levels of exercise (mean change 0 [95% confidence interval, 95% CI −2, 2] mmHg over multiple levels of exercise, P = 0.60). Myocardial phosphocreatine/adenosine triphosphate in the trimetazidine arm was similar to placebo (1.08 [0.76, 1.76] vs. 1.30 [0.95, 1.86], P = 0.08). There was no change by trimetazidine compared with placebo in the exploratory parameters: 6‐min walking distance (mean change of −6 [95% CI −18, 7] m vs. −5 [95% CI −22, 22] m, respectively, P = 0.93), N‐terminal pro‐B‐type natriuretic peptide (5 (−156, 166) ng/L vs. −13 (−172, 147) ng/L, P = 0.70), overall quality‐of‐life (KCCQ and EQ‐5D‐5L, P = 0.78 and P = 0.51, respectively), parameters for diastolic function measured with echocardiography and cardiac magnetic resonance, or metabolic parameters. Conclusions: Trimetazidine did not improve myocardial energy homeostasis and did not improve exercise haemodynamics in patients with HFpEF. [ABSTRACT FROM AUTHOR]

Optic atrophy-1 (OPA1) plays a crucial role in the regulation of mitochondria fusion and participates in maintaining the structural integrity of mitochondrial cristae. Here we elucidate the role of OPA1 cleavage induced by calcium swelling in the presence of Myls22 (an OPA1 GTPase activity inhibitor) and TPEN (an OMA1 inhibitor). The rate of ADP-stimulated respiration was found diminished by both inhibitors, and they did not prevent Ca2+-induced mitochondrial respiratory dysfunction, membrane depolarization, or swelling. L-OPA1 cleavage was stimulated at state 3 respiration; therefore, our data suggest that L-OPA1 cleavage produces S-OPA1 to maintain mitochondrial bioenergetics in response to stress. [ABSTRACT FROM AUTHOR]

Optic atrophy-1 (OPA1) plays a crucial role in the regulation of mitochondria fusion and participates in maintaining the structural integrity of mitochondrial cristae. Here we elucidate the role of OPA1 cleavage induced by calcium swelling in the presence of Myls22 (an OPA1 GTPase activity inhibitor) and TPEN (an OMA1 inhibitor). The rate of ADP-stimulated respiration was found diminished by both inhibitors, and they did not prevent Ca2+-induced mitochondrial respiratory dysfunction, membrane depolarization, or swelling. L-OPA1 cleavage was stimulated at state 3 respiration; therefore, our data suggest that L-OPA1 cleavage produces S-OPA1 to maintain mitochondrial bioenergetics in response to stress.

Type 2 diabetes mellitus is known to double mortality from cardiovascular diseases (CVD), in which oxidative stress plays an important role. It is suggested that the impact of diabetes on CVD risk may vary depending on gender. The aim of the study was to assess oxidative stress parameters in the heart of 12 weeks old male and female Wistar rats with type 2 diabetes mellitus (T2DM) induced by high-calorie diet followed by intraperitoneal streptozotocin injections. The level of advanced oxidation protein products, superoxide dismutase, glutathione reductase and glutathione peroxidase activity in the isolated heart mitochondria and NADPH-oxidase and xanthine oxidase activity in the post-mitochondrial supernatant fraction were determined. It was shown that T2DM induced more pronounced oxidative stress confirmed by the increased level of advanced oxidation protein products in the heart mitochondria of males than females. The data obtained indicate that the main reason of oxidative stress in the heart of diabetic males is the activation of non-mitochondrial sources of reactive oxygen species. While in the heart of diabetic female rats it is the decrease in antioxidant enzymes activity in mitochondria. These results justify the necessity of gender-specific therapy for the prevention and management of diabetic CVD.

• Cu reduces mitochondrial H 2 O 2 emission induced by Cd or Zn. • Binary mixtures of Cu, Cd, and Zn reduce mitochondrial H 2 O 2 consumption. • Cu, Cd, and Zn singly and in binary mixtures inhibit thioredoxin reductase. • Cu singly and as a mixture with Cd or Zn stimulates glutathione peroxidase. • Binary mixtures of Cu, Cd, and Zn act additively or antagonistically. For continuous pumping of blood, the heart needs a constant supply of energy (ATP) that is primarily met via oxidative phosphorylation in the mitochondria of cardiomyocytes. However, sustained high rates of electron transport for energy conversion redox reactions predisposes the heart to the production of reactive oxygen species (ROS) and oxidative stress. Mitochondrial ROS are fundamental drivers of responses to environmental stressors including metals but knowledge of how combinations of metals alter mitochondrial ROS homeodynamics remains sparse. We explored the effects and interactions of binary mixtures of copper (Cu), cadmium (Cd), and zinc (Zn), metals that are common contaminants of aquatic systems, on ROS (hydrogen peroxide, H 2 O 2) homeodynamics in rainbow trout (Oncorhynchus mykiss) heart mitochondria. Isolated mitochondria were energized with glutamate-malate or succinate and exposed to a range of concentrations of the metals singly and in equimolar binary concentrations. Speciation analysis revealed that Cu was highly complexed by glutamate or Tris resulting in Cu2+ concentrations in the picomolar to nanomolar range. The concentration of Cd2+ was 7.2–7.5 % of the total while Zn2+ was 15 % and 21 % of the total during glutamate-malate and succinate oxidation, respectively. The concentration-effect relationships for Cu and Cd on mitochondrial H 2 O 2 emission depended on the substrate while those for Zn were similar during glutamate-malate and succinate oxidation. Cu + Zn and Cu + Cd mixtures exhibited antagonistic interactions wherein Cu reduced the effects of both Cd and Zn, suggesting that Cu can mitigate oxidative distress caused by Cd or Zn. Binary combinations of the metals acted additively to reduce the rate constant and increase the half-life of H 2 O 2 consumption while concomitantly suppressing thioredoxin reductase and stimulating glutathione peroxidase activities. Collectively, our study indicates that binary mixtures of Cu, Zn, and Cd act additively or antagonistically to modulate H 2 O 2 homeodynamics in heart mitochondria. [ABSTRACT FROM AUTHOR]

Background: Calcium (Ca2+) is a key regulator of energy metabolism. Impaired Ca2+ homeostasis damages mitochondria, causing cardiomyocyte death, pathological hypertrophy, and heart failure. This study investigates the regulation and the role of the mitochondrial Ca2+ uniporter (MCU) in chronic stress-induced pathological cardiac remodeling.Methods: MCU knockout or transgenic mice were infused with isoproterenol (ISO; 10 mg/kg per day, 4 weeks). Cardiac hypertrophy and remodeling were evaluated by echocardiography and histology. Primary cultured rodent adult cardiomyocytes were treated with ISO (1 nmol/L, 48 hours). Intracellular Ca2+ handling and cell death pathways were monitored. Adenovirus-mediated gene manipulations were used in vitro.Results: Chronic administration of the β-adrenergic receptor agonist ISO increased the levels of the MCU and the MCU complex in cardiac mitochondria, raising mitochondrial Ca2+ concentrations, in vivo and in vitro. ISO also upregulated MCU without affecting its regulatory proteins in adult cardiomyocytes. It is interesting that ISO-induced cardiac hypertrophy, fibrosis, contractile dysfunction, and cardiomyocyte death were exacerbated in global MCU knockout mice. Cardiomyocytes from knockout mice or overexpressing a dominant negative MCU exhibited defective intracellular Ca2+ handling and activation of multiple cell death pathways. Conversely, cardiac-specific overexpression of MCU maintained intracellular Ca2+ homeostasis and contractility, suppressed cell death, and prevented ISO-induced heart hypertrophy. ISO upregulated MCU expression through activation of Ca2+/calmodulin kinase II δB (CaMKIIδB) and promotion of its nuclear translocation via calcineurin-mediated dephosphorylation at serine 332. Nuclear CaMKIIδB phosphorylated CREB (cAMP-response element binding protein), which bound the Mcu promoter to enhance Mcu gene transcription.Conclusions: The β-adrenergic receptor/CaMKIIδB/CREB pathway upregulates Mcu gene expression in the heart. MCU upregulation is a compensatory mechanism that counteracts stress-induced pathological cardiac remodeling by preserving Ca2+ homeostasis and cardiomyocyte viability. [ABSTRACT FROM AUTHOR]

Hypothermia provides an effective neuro and cardio-protection in clinical settings implying ischemia/reperfusion injury (I/R). At the onset of reperfusion, succinate-induced reactive oxygen species (ROS) production, impaired oxidative phosphorylation (OXPHOS), and decreased Ca2+ retention capacity (CRC) concur to mitochondrial damages. We explored the effects of temperature from 6 to 37 °C on OXPHOS, ROS production, and CRC, using isolated mitochondria from mouse brain and heart. Oxygen consumption and ROS production was gradually inhibited when cooling from 37 to 6 °C in brain mitochondria (BM) and heart mitochondria (HM). The decrease in ROS production was gradual in BM but steeper between 31 and 20 °C in HM. In respiring mitochondria, the gradual activation of complex II, in addition of complex I, dramatically enhanced ROS production at all temperatures without modifying respiration, likely because of ubiquinone over-reduction. Finally, CRC values were linearly increased by cooling in both BM and HM. In BM, the Ca2+ uptake rate by the mitochondrial calcium uniporter (MCU) decreased by 2.7-fold between 25 and 37 °C, but decreased by 5.7-fold between 25 and 37 °C in HM. In conclusion, mild cold (25–37 °C) exerts differential inhibitory effects by preventing ROS production, by reverse electron transfer (RET) in BM, and by reducing MCU-mediated Ca2+ uptake rate in BM and HM. [ABSTRACT FROM AUTHOR]

Fipronil (FPN) is an insecticide that is widely used agriculturally or in the veterinary for controlling a variety of pests. Little mechanistic information is available on the oxidative stress and mitochondrial damage caused by FPN in the heart. The aim of this research is to study the cardiotoxic effect of FPN by evaluating oxidative stress and mitochondrial damage in the heart tissue using the isolated mitochondria. Results showed that FPN induced oxidative stress and mitochondrial dysfunction via an increase in mitochondrial reactive oxygen species (ROS) generation, lipid peroxidation (LPO), mitochondrial membrane potential (MMP) collapse, mitochondrial swelling, and cytochrome c release. According to the result, we suggest that FPN is capable to induce cardiotoxicity through mitochondrial damage and increased mitochondrial ROS generation in cardiomyocyte. [ABSTRACT FROM AUTHOR]

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Hypothermia provides an effective neuro and cardio-protection in clinical settings implying ischemia/reperfusion injury (I/R). At the onset of reperfusion, succinate-induced reactive oxygen species (ROS) production, impaired oxidative phosphorylation (OXPHOS), and decreased Ca2+ retention capacity (CRC) concur to mitochondrial damages. We explored the effects of temperature from 6 to 37 °C on OXPHOS, ROS production, and CRC, using isolated mitochondria from mouse brain and heart. Oxygen consumption and ROS production was gradually inhibited when cooling from 37 to 6 °C in brain mitochondria (BM) and heart mitochondria (HM). The decrease in ROS production was gradual in BM but steeper between 31 and 20 °C in HM. In respiring mitochondria, the gradual activation of complex II, in addition of complex I, dramatically enhanced ROS production at all temperatures without modifying respiration, likely because of ubiquinone over-reduction. Finally, CRC values were linearly increased by cooling in both BM and HM. In BM, the Ca2+ uptake rate by the mitochondrial calcium uniporter (MCU) decreased by 2.7-fold between 25 and 37 °C, but decreased by 5.7-fold between 25 and 37 °C in HM. In conclusion, mild cold (25–37 °C) exerts differential inhibitory effects by preventing ROS production, by reverse electron transfer (RET) in BM, and by reducing MCU-mediated Ca2+ uptake rate in BM and HM.

The current study investigated the protective effect of Hertia cheirifolia L. n-butanol extract on oxidative stress in vitro by measuring lipid peroxidation (MDA) level and superoxide anion (O2•-) production in liver and heart mitochondria of rat. In addition, the antioxidant potential of H. cheirifolia n-butanol extract was evaluated by using five methods: ABTS•+, O2•-, Bleaching of β-carotene in linoleic acid, CUPRAC and Ferric reducing power. The results indicated that n-butanol extract contained large amounts of total phenolics (203.52±1.81 mg GAE/g) and flavonoids (104.86±0.57 mg QE/g), and had an interesting antioxidant activity and protective effect on mitochondrial oxidative stress. Therefore, H. cheirifolia n-butanol extract may serve as potential source of natural antioxidant for pharmaceutical applications. [ABSTRACT FROM AUTHOR]

High energy demand for continuous mechanical work and large number of mitochondria predispose the heart to excessive reactive oxygen species (ROS) production that may precipitate oxidative stress and heart failure. While mitochondria have been proposed as a unifying cellular target and driver of adverse effects induced by diverse stressful states, there is limited understanding of how heart mitochondrial ROS homeostasis is affected by combinations of stress factors. Thus, we probed the effect of copper (Cu) and thermal stress on ROS (as hydrogen peroxide, H 2 O 2) emission and elucidated the effects of Cu on ROS production sites in rainbow trout heart mitochondria using the Amplex UltraRed-horseradish peroxidase detection system optimized for our model. Mitochondria oxidizing malate-glutamate or succinate were incubated at 4, 11 (control) and 23 °C and exposed to a range (1–100 μM) of Cu concentrations. We found that the rates and patterns of H 2 O 2 emission depended on substrate type, Cu concentration and temperature. In mitochondria oxidizing malate-glutamate, Cu increased the rate of H 2 O 2 emission with a spike at 1 μM while temperature had no effect. In contrast, both temperature and Cu increased the rate of H 2 O 2 emission in mitochondria oxidizing succinate with a prominent spike at 25 μM Cu. The rates of H 2 O 2 emission at the three temperatures during the spike imposed by 25 μM Cu were of the order 11 > 23 > 4 °C. Interestingly, 5 μM Cu supressed H 2 O 2 emission in mitochondria oxidizing succinate or malate-glutamate suggesting a common mechanism of action independent of substrate type. In the absence of Cu, the site-specific capacities of H 2 O 2 emission were: complex III outer ubiquinone binding site (site III Qo) > complex II flavin site (site II F) ≥ complex I flavin site (site I F) > complex I ubiquinone-binding site (site I Q). Rotenone marginally increased succinate-driven H 2 O 2 emission suggesting either the absence of reverse electron transport (RET)-driven ROS production at site I Q or masking of the expected rotenone response (reduction) by H 2 O 2 produced from other sites. Cu acted at multiple sites in the electron transport system resulting in different site-specific H 2 O 2 emission responses depending on the concentration. Specifically, site I F H 2 O 2 emission was suppressed by Cu concentration-dependently while H 2 O 2 emission by site II F was inhibited and stimulated by low and high concentrations of Cu, respectively. Additionally, emission from site III Qo was stimulated by low and inhibited by high Cu concentrations. Overall, our study unveiled distinctive effects and sites of modulation of mitochondrial ROS production by Cu with implications for cardiac redox signaling networks and development of mitochondria-targeted Cu-based drugs. Image 1 • Optimized Amplex UltraRed-HRP detection system improves accuracy of mitochondrial H 2 O 2 emission measurement. • Effect of Cu on H 2 O 2 emission in heart mitochondria depends on substrate type, metal concentration and temperature. • Cu acts promiscuously to alter H 2 O 2 emission at multiple sites in the electron transport system. • Cu at 25 µM alone or combined with atpenin A5 induces a prominent surge in mitochondrial H 2 O 2 emission. [ABSTRACT FROM AUTHOR]

The biological mechanisms linking nutrition and antioxidants content of the diet with cardiovascular protection are subject of intense investigation. It has been demonstrated that dietary supplementation with cow, donkey or human milk, characterized by distinct nutritional properties, triggers significant differences in the metabolic and inflammatory status through the modulation of hepatic and skeletal muscle mitochondrial functions. Cardiac mitochondria play a key role for energy-demanding heart functions, and their disfunctions is leading to pathologies. Indeed, an altered heart mitochondrial function and the consequent increased reactive oxygen species (ROS) production and inflammatory state, is linked to several cardiac diseases such as hypertension and heart failure. In this work it was investigated the impact of the milk consumption on heart mitochondrial functions, inflammation and oxidative stress. In addition, it was underlined the crosstalk between mitochondrial metabolic flexibility, lipid storage and redox status as control mechanisms for the maintenance of cardiovascular health.

Abstract Background Ocean acidification and warming are happening fast in the Arctic but little is known about the effects of ocean acidification and warming on the physiological performance and survival of Arctic fish. Results In this study we investigated the metabolic background of performance through analyses of cardiac mitochondrial function in response to control and elevated water temperatures and PCO2 of two gadoid fish species, Polar cod (Boreogadus saida), an endemic Arctic species, and Atlantic cod (Gadus morhua), which is a temperate to cold eurytherm and currently expanding into Arctic waters in the wake of ocean warming. We studied their responses to the above-mentioned drivers and their acclimation potential through analysing the cardiac mitochondrial function in permeabilised cardiac muscle fibres after 4 months of incubation at different temperatures (Polar cod: 0, 3, 6, 8 °C and Atlantic cod: 3, 8, 12, 16 °C), combined with exposure to present (400μatm) and year 2100 (1170μatm) levels of CO2. OXPHOS, proton leak and ATP production efficiency in Polar cod were similar in the groups acclimated at 400μatm and 1170μatm of CO2, while incubation at 8 °C evoked increased proton leak resulting in decreased ATP production efficiency and decreased Complex IV capacity. In contrast, OXPHOS of Atlantic cod increased with temperature without compromising the ATP production efficiency, whereas the combination of high temperature and high PCO2 depressed OXPHOS and ATP production efficiency. Conclusions Polar cod mitochondrial efficiency decreased at 8 °C while Atlantic cod mitochondria were more resilient to elevated temperature; however, this resilience was constrained by high PCO2. In line with its lower habitat temperature and higher degree of stenothermy, Polar cod has a lower acclimation potential to warming than Atlantic cod.

Abstract Impaired tissue oxygenation is the key pathomechanism in the development of organ dysfunction in shock; mitochondrial impairment can aggravate the condition. However, measuring tissue oxygenation directly and non-invasively still poses a clinical challenge. A novel device (COMET) allows the assessment of mitochondrial oxygen metabolism using the Protoporphyrin IX Triplet State Lifetime Technique (PpIX-TSLT). Critically ill patients, especially in sepsis, often exhibit oedema which may interfere with the COMET measurement. Furthermore, patients' physical activity level differs significantly before and during hospitalisation. Thus, the aim of this study was to identify the effects of physical activity and body composition on mitochondrial oxygen tension (mitoPO 2) and consumption (mitoVO 2) in healthy controls (N = 40). Furthermore, the study tested the repeatability of the COMET variables and identified covariates. Multiple COMET measurements were performed before (T 1 , T 2), during and after (T 3 , T 4) ergometry. Body composition was assessed by bioimpedance analysis. Physiological variables (blood pressure, heart rate, oxygen saturation) were recorded. In the analytical sample (n = 26), physical activity significantly decreased mitoVO 2 ; other COMET variables remained unchanged between T 2 and T 3. During ergometry, mitoPO 2 increased significantly. The distribution of body water significantly influenced mitoVO 2. In our setting, the method demonstrated moderate repeatability. Variables of fitness (heart rate recovery, phase angle and physical activity level), signal quality and duration of exposure to 5-aminolevulinic acid (obligatory for PpIX-TSLT) were identified as significant covariates of mitoVO 2. Mitochondrial oxygen delivery (mitoDO 2) was established as a new variable of COMET analysis. Results of this pilot study should be validated in future studies. Highlights • First non-invasive analysis of mitochondrial oxygen metabolism during exercise • Cellular oxygen metabolism measurement (COMET) proved re-test reliable. • Variables of fitness and body water distribution influenced COMET measurements. • Proposal of an alternative fitting method for COMET analysis • Introduction of the new variable mitochondrial oxygen delivery (mitoDO 2) [ABSTRACT FROM AUTHOR]

Abstract Mitochondria play an essential role in the energy metabolism of the heart. Many of the essential functions are associated with mitochondrial membranes and oxidative phosphorylation driven by the respiratory chain. Mitochondrial membranes are unique in the cell as they contain the phospholipid cardiolipin. The important role of cardiolipin in cardiovascular health is highlighted by several cardiac diseases, in which cardiolipin plays a fundamental role. Barth syndrome, Sengers syndrome, and Dilated cardiomyopathy with ataxia (DCMA) are genetic disorders, which affect cardiolipin biosynthesis. Other cardiovascular diseases including ischemia/reperfusion injury and heart failure are also associated with changes in the cardiolipin pool. Here, we summarize molecular functions of cardiolipin in mitochondrial biogenesis and morphology. We highlight the role of cardiolipin for the respiratory chain, metabolite carriers, and mitochondrial metabolism and describe links to apoptosis and mitochondria specific autophagy (mitophagy) with possible implications in cardiac disease. Highlights • Tafazzin mediates remodeling of the phospholipid Cardiolipin in mitochondrial membranes. • Cardiolipin is required for mitochondrial respiration, providing 95% of the cardiac energy demand. • Other functions of Cardiolipin include morphology, mitophagy and apoptosis. • Changes in Cardiolipin pool are associated with cardiomyopathy in Barth syndrome (BTHS), and Sengers disease. [ABSTRACT FROM AUTHOR]

Abstract Ischemic conditioning induces cardioprotection; the final infarct size following a myocardial ischemic event is reduced. However, whether ischemic conditioning has long-term beneficial effects on myocardial contractile function following such an ischemic event needs further elucidation. To date, ex vivo studies have shown that ischemic conditioning improves the contractile recovery of isolated ventricular papillary muscle or atrial trabeculae following simulated ischemia. However, in vivo animal studies and studies in patients undergoing elective cardiac surgery show conflicting results. At the subcellular level, it is known that ischemic conditioning improved energy metabolism, preserved mitochondrial respiration, ATP production, and Ca2+ homeostasis in isolated mitochondria from the myocardium. Ischemic conditioning also presents with post-translational modifications of proteins in the contractile machinery of the myocardium. The beneficial effects on myocardial contractile function need further elucidation. This article is part of a Special Issue entitled: The power of metabolism: Linking energy supply and demand to contractile function edited by Torsten Doenst, Michael Schwarzer and Christine Des Rosiers. Highlights • Ischemic conditioning improves contractile recovery of ventricular muscle or atrial trabeculae in vitro. • Ischemic conditioning improves mitochondrial respiration, ATP production, and Ca2+ homeostasis. • Ischemic conditioning is associated with post‐translational modifications of contractile proteins. [ABSTRACT FROM AUTHOR]

Abstract 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. Highlights • Mitochondrial quality control in the heart: • Relies on multiple overlapping mechanisms • Depends on developmental stage, physiological state, and pathological state • Proteases and MDVs constitute baseline/early stress response mechanisms. • Mitophagy appears mostly important for large scale clearance of organelles during development and stress. [ABSTRACT FROM AUTHOR]

Abstract Sepsis is defined as a life-threatening organ dysfunction caused by a dysregulated host response to infection. Myocardial dysfunction, often termed sepsis-induced cardiomyopathy, is a frequent complication and is associated with worse outcomes. Numerous mechanisms contribute to sepsis-induced cardiomyopathy and a growing body of evidence suggests that bioenergetic and metabolic derangements play a central role in its development; however, there are significant discrepancies in the literature, perhaps reflecting variability in the experimental models employed or in the host response to sepsis. The condition is characterised by lack of significant cell death, normal tissue oxygen levels and, in survivors, reversibility of organ dysfunction. The functional changes observed in cardiac tissue may represent an adaptive response to prolonged stress that limits cell death, improving the potential for recovery. In this review, we describe our current understanding of the pathophysiology underlying myocardial dysfunction in sepsis, with a focus on disrupted mitochondrial processes. Highlights • Sepsis-induced cardiomyopathy (SIC) is common in septic patients and affects outcome. • Mitochondrial dysfunction is likely to play a central role in SIC pathogenesis. • Mitochondrial dysfunction could be a protective mechanism similar to myocardial hibernation. [ABSTRACT FROM AUTHOR]

Abstract The heart is composed of cardiomyocytes that require large amounts of energy to sustain contraction. Mitochondria are distinctive organelles of bacterial origin that generate most of the energy for the heart via oxidative phosphorylation. To ensure a healthy population of mitochondria that efficiently produce ATP, myocytes quickly eliminate any unhealthy or unwanted mitochondria via a process known as mitochondrial autophagy, or mitophagy. It is especially important to selectively remove damaged or aged mitochondria since they can become excessive producers of reactive oxygen species and release pro-death proteins. Because this is such a crucial cellular process, cells have several mechanisms in place to deal with potentially harmful mitochondria. Here, we review the various pathways identified to date and how they are regulated. We also discuss the importance of these canonical and non-canonical pathways in the heart and their link to cardiovascular health, disease and aging. Highlights • Mitophagy is vital in maintaining a healthy population of mitochondria in cells. • Multiple mechanism and pathways exist to facilitate mitochondrial clearance. • Altered mitophagy contributes to development of cardiovascular disease and aging. [ABSTRACT FROM AUTHOR]

Since mitochondria are the main cellular source of reactive oxygen species, it is important to study the effect of dietary phenolic compounds on the level of ROS in these organelles. Using the EPR spectroscopy and TIRON probe, the ability of the investigated phenols (quercetin, rutin, caffeic acid, curcumin, and resveratrol) to scavenge superoxide anion radicals generated by isolated heart mitochondria of Wistar rats under variable oxygen partial pressure was studied. It was shown that during a 10 min incubation, caffeic acid in concentrations of 10-500 μM most effectively scavenged superoxide radicals formed in the complex III of the mitochondrial respiratory chain. A comparable antioxidant effect of rutin under these experimental conditions was observed at higher concentrations of 1-10 mM. The antioxidant activity of quercetin in the concentration range of 10-500 μM during the first minutes of incubation was higher than that of caffeic acid. Of the phenolic compounds studied, curcumin had the least effect on the superoxide radicals. [ABSTRACT FROM AUTHOR]

Abstract We investigated the effects of thyroid state on the mechanisms underlying rat heart mitochondrial capacity to remove H 2 O 2 produced by an exogenous source. The removal rates were higher in the presence of respiratory substrates independently from thyroid state and were higher in hyperthyroid than in hypothyroid preparations. The thyroid state-linked changes in H 2 O 2 removal rates, mirrored those in H 2 O 2 release rates, showing that endogenous and exogenous H 2 O 2 do not compete for the removing system. Mitochondrial content of coenzyme Q9 and Q10 was lower in hypothyroidism and higher in hyperthyroidism suggesting that the thyroid state-linked changes in the rates of H 2 O 2 production are due to changes in the ubiquinone mitochondrial content. The rates of H 2 O 2 removal in the presence of antioxidant enzyme inhibitors indicated that the contribution of each antioxidant is dependent on the thyroid state. This was supported by enzymatic activity measurements. Pharmacological inhibition also showed that the overall percentage contribution of the enzymatic processes, as well as that of non-enzymatic processes, is not affected by thyroid state. Cytochrome levels, inferred by light emission measurements, and western blot determination of cytochrome c, were lower in hypothyroid and higher in hyperthyroid preparations supporting the idea that the levels of reducing compounds were modified in opposite way by the changes in thyroid state. Further support was obtained showing that the whole antioxidant capacity, which provides an evaluation of capacity of the systems, different from cytochromes, assigned to H 2 O 2 scavenging, was lower in hyperthyroid than in hypothyroid state. Highlights • H 2 O 2 removal (HR)is higher in hyper than in hypothyroid heart mitochondria. • T3 increase both enzymatic and non-enzymatic H 2 O 2 removal systems. • Respiratory substrates increase HR sustaining antioxidant enzyme activities. • The contribution of each antioxidant enzyme is dependent on the thyroid state. • Non-enzymatic HR is mainly due to T3 induced changes in cytochromes levels. [ABSTRACT FROM AUTHOR]

Abstract Aims Our earlier studies revealed the cardio-protective effects of oleic acid, a monounsaturated fatty acid, against adrenaline induced myocardial injury. Moreover, it has been found to possess antioxidant properties. Thus, in the present study we have investigated the protective role of oleic acid on adrenaline induced mitochondrial dysfunction in vitro in rat heart mitochondria. Main methods Isolated rat cardiac mitochondria was incubated in vitro with adrenaline-bitartrate alone and with graded doses of oleic acid. Biomarkers of oxidative stress, mitochondrial Krebs cycle enzymes and respiratory chain enzymes along with mitochondrial morphology, membrane potential as well as intactness were analyzed. Isothermal titration calorimetric studies with pure adrenaline and oleic acid was also carried out. Key findings Incubation with adrenaline, in vitro, showed elevated levels of lipid peroxidation and protein carbonylation of mitochondrial membrane, a reduced level of glutathione content along with an altered profile of mitochondrial enzymes, morphology, membrane potential as well as intactness. All these changes were found to be ameliorated when cardiac mitochondria were co-incubated with adrenaline and oleic acid, in vitro. Significance Our earlier studies demonstrated the antioxidant properties of oleic acid. This study suggests that oleic acid binds adrenaline with high affinity gradual saturation of the binding sites of adrenaline. This prevents the generation of ROS and finally providing consequent protection of the cardiac mitochondria and ameliorating adrenaline induced mitochondrial dysfunction. Hence, oleic acid may be considered as a potent future cardio-protective antioxidant. Highlights • Reactive oxygen species (ROS) is the primary cause of myocardial ischemia induced mitochondrial dysfunction • Oleic acid can protect rat cardiac mitochondria, in vitro , from adrenaline induced oxidative damage • Oleic acid can effectively scavenge ROS through its antioxidant activity • Isothermal titration calorimetry study indicated very strong and high affinity binding with gradual saturation. [ABSTRACT FROM AUTHOR]

Diabetes mellitus (DM) constitutes one of the public health problems today. It is characterized by hyperglycemia through a defect in the β-cells function and/or decreased insulin sensitivity. Apocynin has been tasted acting directly as an NADPH oxidase inhibitor and reactive oxygen species (ROS) scavenger, exhibiting beneficial effects against diabetic complications. Hence, the present study’s goal was to dissect the possible mechanisms by which apocynin could mediate its cardioprotective effect against DM-induced oxidative stress. Male Wistar rats were assigned into 4 groups: Control (C), control + apocynin (C+A), diabetes (D), diabetes + apocynin (D+A). DM was induced with streptozotocin. Apocynin treatment (3 mg/kg/day) was applied for 5 weeks. Treatment significantly decreased blood glucose levels and insulin resistance in diabetic rats. In cardiac tissue, ROS levels were higher, and catalase enzyme activity was reduced in the D group compared to the C group; the apocynin treatment significantly attenuated these responses. In heart mitochondria, Complexes I and II of the electron transport chain (ETC) were significantly enhanced in the D+A group. Total glutathione, the level of reduced glutathione (GSH) and the GSH/ oxidized glutathione (GSSG) ratio were increased in the D+A group. Superoxide dismutase (SOD) and the glutathione peroxidase (GSH-Px) activities were without change. Apocynin enhances glucose uptake and insulin sensitivity, preserving the antioxidant defense and mitochondrial function.

Recent electron microscopy data have revealed that cardiac mitochondria are not arranged in crystalline columns but are organised with several mitochondria aggregated into columns of varying sizes often spanning the cell cross-section. This raises the question—how does the mitochondrial arrangement affect the metabolite distributions within cardiomyocytes and their impact on force dynamics? Here we employed finite element modelling of cardiac bioenergetics, using computational meshes derived from electron microscope images, to address this question. Our results indicate that heterogeneous mitochondrial distributions can lead to significant spatial variation across the cell in concentrations of inorganic phosphate, creatine (Cr) and creatine phosphate (PCr). However, our model predicts that sufficient activity of the creatine kinase (CK) system, coupled with rapid diffusion of Cr and PCr, maintains near uniform ATP and ADP ratios across the cell cross sections. This homogenous distribution of ATP and ADP should also evenly distribute force production and twitch duration with contraction. These results suggest that the PCr shuttle, and associated enzymatic reactions, act to maintain uniform force dynamics in the cell despite the heterogeneous mitochondrial organization. However, our model also predicts that under hypoxia—activity of mitochondrial CK enzyme and diffusion of high-energy phosphate compounds may be insufficient to sustain uniform ATP/ADP distribution and hence force generation. [ABSTRACT FROM AUTHOR]

1. Mephedrone, a new and popular amphetamine drug, is widely abused and is still legal in some parts around the world. Little data on mechanisms involved in mephedrone induced cardiotoxicity are available. 2. Therefore, we decided to explain the mechanisms of mephedrone cardiotoxicity by using mitochondria isolated from rat heart. The isolated heart mitochondria were incubated with different concentrations of mephedrone (5, 10 and 20 µM). 3. Results showed that mephedrone induced mitochondrial dysfunction via an increase in mitochondrial reactive oxygen species (ROS) production, mitochondrial membrane potential (MMP) collapse, mitochondrial swelling and damage in the mitochondrial outer membrane (MOM) which is associated with the cytochrome c release. Our results showed that decrease of ATP levels is an indicator of disturbance in oxidative phosphorylation. Also, mephedrone increased the caspase-3 activity. 4. According to the results, we suggest that mephedrone induced cardiotoxicity is the result of a disruptive effect on the mitochondrial respiratory chain and induction of ROS-mediated apoptosis signaling in heart cardiomyocytes. [ABSTRACT FROM AUTHOR]

Ascertaining the structure and functions of mitochondrial respiratory chain complexes is essential to understanding the biological mechanisms of energy conversion; therefore, numerous studies have examined these complexes. A fundamental part of that research involves devising a method for purifying samples with good reproducibility; the samples obtained need to be stable and their constituents need to retain the same structure and functions they possess when in mitochondrial membranes. Submitochondrial bovine heart particles were isolated using differential centrifugation to adjust to a membrane concentration of 46.0% (w/v) or 31.5% (w/v) based on weight. After 0.7% (w/v) deoxycholic acid, 0.4% (w/v) decyl maltoside, and 7.2% (w/v) potassium chloride were added to the mitochondrial membranes, those membranes were solubilized. At a membrane concentration of 46%, complex V was selectively solubilized, whereas at a concentration of 31.5% (w/v), complexes I and III were solubilized. Two steps—sucrose density gradient centrifugation and anion-exchange chromatography on a POROS HQ 20 μm column—enabled selective purification of samples that retained their structure and functions. These two steps enabled complexes I, III, and V to be purified in two days with a high yield. Complexes I, III, and V were stabilized with n-decyl-β-D-maltoside. A total of 200 mg–300 mg of those complexes from one bovine heart (1.1 kg muscle) was purified with good reproducibility, and the complexes retained the same functions they possessed while in mitochondrial membranes. [ABSTRACT FROM AUTHOR]

Intrinsic cardioprotective mechanisms become activated in the early diabetes mellitus (DM) and this may protect the heart from ischemia/reperfusion (I/R) similarly as in case of ischemic preconditioning. However, this protection may by blunted in the presence of cardiovascular risk factors. Assuming that hypercholesterolemia (HCH) frequently accompanies DM, this study extends findings from separate models of DM and HCH by investigation the impact of HCH on DM-induced changes, including those of compensatory nature, in rat heart and its mitochondria. We used a factorial design with all combinations of treatment factors DM and HCH: control rats (C) and streptozotocin-treated rats (DM), both on standard chow (C and DM) and fed fat-cholesterol diet (HCH and DM-HCH). Isolated, Langendorff perfused hearts were subjected to 30 min global ischemia followed by reperfusion. Significantly increased levels of cholesterol in DM-HCH after I/R injury abrogated compensatory fluidization characteristic of DM mitochondria membranes. Concomitantly, the mitochondrial Mg2+-ATPase activity in DM-HCH was depressed. In comparison with DM, which showed significantly reduced size of myocardial infarction with simultaneously improved recovery of contractile function due to conditioning, DM-HCH hearts exhibited attenuated resistance to I/R injury. Taken together, cholesterol-enriched diet was associated with inflicting damage and has been implicated in the mechanisms leading to suppression of cardiac protection presented in diabetic group. Apparently, DM and HCH are factors which are not additive in their effects, therefore, caution should be exercised, when interpreting findings from studies considering these factors in isolation. Our findings suggest that this complex condition could accelerate the development of late diabetic complications. [ABSTRACT FROM AUTHOR]

The purpose of this study is to demonstrate the presence of three more receptors in mitochondria. Two N-methyl- d -aspartate receptor (NMDAR) subunits (NR1 and NR2B) are found by protein immunoblot and immunogold labeling in mitochondria fraction isolated from rat heart. These data allow supposing NMDAR presence and functioning in the inner mitochondrial membrane. There are no signs of receptor presence obtained in heart tissue lysate, that indicates the receptor localization exactly in mitochondria. The possible receptor functions discussed are its participation in calcium transport and in excitation-metabolism coupling. Besides, preliminary evidence is obtained of GABA A and GABA B receptors presence in heart mitochondria. One can surmise their role in metabolism regulation and their possible co-operation with NMDAR just as in the nervous system. [ABSTRACT FROM AUTHOR]

Background: Mitochondria hold crucial importance in organs with high energy demand especially the heart. We investigated whether chronic kidney disease (CKD), which eventually culminates in cardiorenal syndrome, could affect cardiac mitochondria and assessed the potential involvement of angiotensin II (AngII) in the process. Methods: Male Lewis rats underwent 5/6 nephrectomy allowing CKD development for eight months or for eleven weeks. Short-term CKD rats were administered with AngII receptor blocker (ARB). Cardiac function was assessed by echocardiography and cardiac sections were evaluated for interstitial fibrosis and cardiomyocytes’ hypertrophy. Electron microscopy was used to explore the spatial organization of the cardiomyocytes. Expression levels of mitochondrial content and activity markers were tested in order to delineate the underlying mechanisms for mitochondrial pathology in the CKD setting with or without ARB administration. Results: CKD per-se resulted in induced cardiac interstitial fibrosis and cardiomyocytes’ hypertrophy combined with a marked disruption of the mitochondrial structure. Moreover, CKD led to enhanced cytochrome C leakage to the cytosol and to enhanced PARP-1 cleavage which are associated with cellular apoptosis. ARB treatment did not improve kidney function but markedly reduced left ventricular mass, cardiomyocytes’ hypertrophy and interstitial fibrosis. Interestingly, ARB administration improved the spatial organization of cardiac mitochondria and reduced their increased volume compared to untreated CKD animals. Nevertheless, ARB did not improve mitochondrial content, mitochondrial biogenesis or the respiratory enzyme activity. ARB mildly upregulated protein levels of mitochondrial fusion-related proteins. Conclusions: CKD results in cardiac pathological changes combined with mitochondrial damage and elevated apoptotic markers. We anticipate that the increased mitochondrial volume mainly represents mitochondrial swelling that occurs during the pathological process of cardiac hypertrophy. Chronic administration of ARB may improve the pathological appearance of the heart. Further recognition of the molecular pathways leading to mitochondrial insult and appropriate intervention is of crucial importance. [ABSTRACT FROM AUTHOR]

Aims Mitochondrial creatine kinase (MtCK) couples ATP production via oxidative phosphorylation to phosphocreatine in the cytosol, which acts as a mobile energy store available for regeneration of ATP at times of high demand. We hypothesized that elevating MtCK would be beneficial in ischaemia--reperfusion (I/R) injury. Methods and results Mice were created over-expressing the sarcomeric MtCK gene with αMHC promoter at the Rosa26 locus (MtCK-OE) and compared with wild-type (WT) littermates. MtCK activity was 27% higher than WT, with no change in other CK isoenzymes or creatine levels. Electron microscopy confirmed normal mitochondrial cell density and mitochondrial localization of transgenic protein. Respiration in isolated mitochondria was unaltered and metabolomic analysis by ¹H-NMR suggests that cellular metabolism was not grossly affected by transgene expression. There were no significant differences in cardiac structure or function under baseline conditions by cine-MRI or LV haemodynamics. In Langendorff-perfused hearts subjected to 20 min ischaemia and 30 min reperfusion, MtCK-OE exhibited less ischaemic contracture, and improved functional recovery (Rate pressure product 58% above WT; P < 0.001). These hearts had reduced myocardial infarct size, which was confirmed in vivo: 55 ± 4% in WT vs. 29 ± 4% in MtCK-OE; P < 0.0001). Isolated cardiomyocytes from MtCK-OE hearts exhibited delayed opening of the mitochondrial permeability transition pore (mPTP) compared to WT, which was confirmed by reduced mitochondrial swelling in response to calcium. There was no detectable change in the structural integrity of the mitochondrial membrane. Conclusions Modest elevation of MtCK activity in the heart does not adversely affect cellular metabolism, mitochondrial or in vivo cardiac function, but modifies mPTP opening to protect against I/R injury and improve functional recovery. Our findings support MtCK as a prime therapeutic target in myocardial ischaemia. [ABSTRACT FROM AUTHOR]

Abstract: Mitochondria are widely known as a major source of reactive oxygen and nitrogen species for the cardiovascular system. Numerous studies established that superoxide anion radical production by heart mitochondria is only slightly suppressed under conditions of deep hypoxia, but is completely blocked under anoxia. It was found also that dinitrosyl iron complexes (DNIC) compare favourably with other physiologically active derivatives of nitric oxide (NO). DNIC with glutathione effectively scavenge superoxide radicals generated by mitochondria at different partial pressures of oxygen. Under conditions of simulated hypoxia, the synthesis of thiol‐containing DNIC takes place in mitochondria and is concomitant with a significant decrease in the concentration of NO metabolites at the reoxygenation step. Free NO required for DNIC synthesis is generated in the reaction of S‐nitrosothiols with superoxide or during single‐electron oxidation of the nitroxyl radical (HNO) by coenzyme Q. Plausible mechanisms of antiradical effects of DNIC and their protective role in oxidative stress induced by hypoxia/reoxygenation of myocardial tissues are considered. © 2018 BioFactors, 44(3):237–244, 2018 [ABSTRACT FROM AUTHOR]

Cardiac mitochondrial oxidative stress causes mitochondrial damage that plays an important role in the pathology of myocardial infarction. The preventive effects of diosmin on cardiac mitochondrial oxidative stress in isoproterenol-induced myocardial infarcted rats were evaluated. Rats were pretreated with diosmin (10 mg/kg body weight) daily for 10 days. Myocardial infarction was induced in rats by isoproterenol (100 mg/kg body weight) injection twice at an interval of 24 h (on 11th and 12th day). Isoproterenol-induced myocardial infarcted rats showed a significant increase in the levels of cardiac diagnostic markers, heart mitochondrial lipid peroxidation, calcium ion, and a significant decrease in the levels of heart mitochondrial glutathione peroxidase, reduced glutathione, glutathione-S-transferase, isocitrate, malate, α-ketoglutarate, and succinate dehydrogenases. Transmission electron microscopic findings revealed damaged mitochondria with loss of cristae, swelling, and vacuolation in isoproterenol-induced rats’ heart. Diosmin pretreatment showed significant preventive effects on all the biochemical parameters, and the structure of mitochondria was evaluated. Furthermore, the transmission electron microscopic study confirms the biochemical findings. The antioxidant and negative inotropic effects of diosmin inhibited cardiac mitochondrial oxidative stress and prevented mitochondrial damage in myocardial infarcted rats. [ABSTRACT FROM AUTHOR]

The incidence of cardiovascular disease and metabolic syndrome increases after the onset of menopause, suggesting estrogen has a vital role in their prevention. Mitochondrial dynamics are known to play an important role in the maintenance of cardiac physiological function. However, the effects of estrogen deprivation on cardiometabolic status and cardiac mitochondrial dynamics under conditions of obese-insulin resistance have never been investigated. We hypothesized that estrogen deprivation aggravates cardiac dysfunction through increased cardiac mitochondrial fission in obese-insulin resistant rats. Female rats were fed on either a high fat (HFD, 57.60% fat) or normal (ND, 19.77% fat) diet for 13 weeks. The rats were then divided into 4 groups. Two sham groups (HFS and NDS) and 2 operated or ovariectomized (HFO and NDO) groups ( n  = 8/group). Six weeks after surgery, metabolic status, heart rate variability (HRV), left ventricular (LV) function, cardiac mitochondrial function and dynamics, and metabolic parameters were determined. Insulin resistance developed in NDO, HFS and HFO rats as indicated by increased plasma insulin and HOMA index. Although rats in both NDO and HFS groups had markedly impaired LV function indicated by reduced %LVFS and impaired cardiac mitochondrial function, rats in the HFO group had the most severe impairments. Moreover, the estrogen deprived rats (NDO and HFO) had increased cardiac mitochondrial fission through activation of phosphorylation of Drp-1 at serine 616. Our findings indicated that estrogen deprivation caused the worsening of LV dysfunction through increased cardiac mitochondrial fission in obese-insulin resistant rats. [ABSTRACT FROM AUTHOR]

Myocardial infarction is one of the clinical manifestations of coronary heart disease. In some cases, the cause of myocardial infarction may be atherosclerotic plaques which occurred in the human aorta. The association of mtDNA mutations with atherosclerotic lesions in human arteries was previously detected by our research group. In this study, we used samples of white blood cells collected from 225 patients with myocardial infarction and 239 control persons with no health complaints. DNA was isolated from the blood leukocyte samples. Then, PCR fragments of DNA were obtained. They contained the investigated regions of 11 mitochondrial genome mutations (m.5178C>A, m.3336T>C, m.652delG, m.12315G>A, m.14459G>A, m.652insG, m.14846G>A, m.13513G>A, m.1555A>G, m.15059G>A, m.3256C>T). According to the obtained results, three mutations of the human mitochondrial genome correlated with myocardial infarction. A positive correlation was observed for mutation m.5178C>A. At the same time, a highly significant negative correlation with myocardial infarction was observed for mutation m.14846G>A. One single-nucleotide substitution of m.12315G>A had a trend towards negative correlation. These mutations can potentially be useful for creating molecular/cellular models for studying the mechanisms of myocardial infarction and designing novel therapies. Moreover, these mutations can possibly be used for diagnostic purposes. [ABSTRACT FROM AUTHOR]

Freshwater turtles (Trachemys scripta) are among the very few vertebrates capable of tolerating severe hypoxia and reoxygenation without suffering from damage to the heart. As myocardial ischemia and reperfusion causes a burst of mitochondrial reactive oxygen species (ROS) in mammals, the question arises as to whether, and if so how, this ROS burst is prevented in the turtle heart. We find here that heart mitochondria isolated from turtles acclimated to anoxia produce less ROS than mitochondria from normoxic turtles when consuming succinate. As succinate accumulates in the hypoxic heart and is oxidised when oxygen returns this suggest an adaptation to lessen ROS production. Specific S-nitrosation of complex I can lower ROS in mammals and here we show that turtle complex I activity and ROS production can also be strongly depressed in vitro by S-nitrosation. While we can detect in vivo endogenous S-nitrosated complex I in turtle heart mitochondria, these levels are unaffected upon anoxia acclimation. Thus while heart mitochondria from anoxia-acclimated turtles generate less ROS and have a lower aerobic capacity than those from normoxic turtles, this is not due to decreases in complex I activity or expression levels. Interestingly, in-gel activity staining reveals that most complex I of heart mitochondria from normoxic and anoxic turtles forms stable supercomplexes with other respiratory enzymes and, in contrast to mammals, these are not disrupted by dodecyl maltoside. Taken together, these results show that, although S-nitrosation of complex I is a potent mechanism to prevent ROS formation upon reoxygenation after anoxia in vitro, this is not a major cause of the suppression of ROS production by anoxic turtle heart mitochondria. [ABSTRACT FROM AUTHOR]

The cross-tolerance effect of exercise against heart mitochondrial-mediated quality control, remodeling and death-related mechanisms associated with sub-chronic Doxorubicin (DOX) treatment is yet unknown. We therefore analyzed the effects of two distinct chronic exercise models (endurance treadmill training-TM and voluntary free wheel activity-FW) performed during the course of the sub-chronic DOX treatment on mitochondrial susceptibility to permeability transition pore (mPTP), apoptotic and autophagic signaling and mitochondrial dynamics. Male Sprague-Dawley rats were divided into six groups ( n = 6 per group): saline sedentary (SAL + SED), SAL + TM (12-weeks treadmill), SAL + FW (12-weeks voluntary free-wheel), DOX + SED [7-weeks sub-chronic DOX treatment (2 mg kg week)], DOX + TM and DOX + FW. Apoptotic signaling and mPTP regulation were followed by measuring caspase 3, 8 and 9 activities, Bax, Bcl2, CypD, ANT, and cophilin expression. Mitochondrial dynamics (Mfn1, Mfn2, OPA1 and DRP1) and auto(mito)phagy (LC3, Beclin1, Pink1, Parkin and p62)-related proteins were semi-quantified. DOX treatment results in augmented mPTP susceptibility and apoptotic signaling (caspases 3, 8 and 9 and Bax/Bcl2 ratio). Moreover, DOX decreased the expression of fusion-related proteins (Mfn1, Mfn2, OPA1), increased DRP1 and the activation of auto(mito)phagy signaling. TM and FW prevented DOX-increased mPTP susceptibility and apoptotic signaling, alterations in mitochondrial dynamics and inhibits DOX-induced increases in auto(mito)phagy signaling. Collectively, our results suggest that both used chronic exercise models performed before and during the course of sub-chronic DOX treatment limit cardiac mitochondrial-driven apoptotic signaling and regulate alterations in mitochondrial dynamics and auto(mito)phagy in DOX-treated animals. [ABSTRACT FROM AUTHOR]

Cardiac mitochondrial phospholipid acyl chains regulate respiratory enzymatic activity. In several diseases, the rodent cardiac phospholipidome is extensively rearranged; however, whether specific acyl chains impair respiratory enzyme function is unknown. One unique remodeling event in the myocardium of obese and diabetic rodents is an increase in docosahexaenoic acid (DHA) levels. Here, we first confirmed that cardiac DHA levels are elevated in diabetic humans relative to controls. We then used dietary supplementation of a Western diet with DHA as a tool to promote cardiac acyl chain remodeling and to study its influence on respiratory enzyme function. DHA extensively remodeled the acyl chains of cardiolipin (CL), monolyso-CL, phosphatidylcholine, and phosphatidylethanolamine. Moreover, DHAlowered enzyme activities of respiratory complexes I, IV, V, and I + III. Mechanistically, the reduction in enzymatic activities was not driven by a dramatic reduction in the abundance of supercomplexes. Instead, replacement of tetralinoleoyl-CL with tetradocosahexaenoyl-CL in biomimetic membranes prevented formation of phospholipid domains that regulate enzyme activity. Tetradocosahexaenoyl-CL inhibited domain organization due to favorable Gibbs free energy of phospholipid mixing. Furthermore, in vitro substitution of tetralinoleoyl- CL with tetradocosahexaenoyl-CL blocked complex IV binding. Finally, reintroduction of linoleic acid, via fusion of phospholipid vesicles to mitochondria isolated from DHA-fed mice, rescued the major losses in the mitochondrial phospholipidome and complexes I, IV, and V activities. Altogether, our results show that replacing linoleic acid with DHA lowers select cardiac enzyme activities by potentially targeting domain organization and phospholipid-protein binding, which has implications for the ongoing debate about. [ABSTRACT FROM AUTHOR]

Cardio-protective effect of hydrogen sulfide (H 2 S) against myocardial ischemia reperfusion injury (I/R) via preservation of mitochondria is well documented. But the distinct role of exogenous and endogenous H 2 S in cardio-protection and its dependency on functional cardiac mitochondria is not understood. The present study was designed to investigate the role of exogenous H 2 S preconditioning on cardiac mitochondrial subpopulation namely interfibrillar (IFM) and subsarcolemmal (SSM), in attenuating I/R injury in an isolated rat heart model in the absence of endogenous H 2 S production. The well-known inhibitor of endogenous H 2 S production DL-propargylglycine (cystathionine gamma lyase inhibitor) used for this purpose. Our previous studies revealed that NaSH (a H 2 S donor) preconditioning at a dose of 20 μM significantly reduced the infarct size and preserved the functional activities of IFM. However, this protective effect significantly declined, when the heart preconditioned with NaSH in the presence of PAG. Apparently, cardiac recovery was improved hemodynamically to a minimal level by increased concentration of NaSH (40 μM). The rat heart perfused with 2, 4 dinitrophenol a mitochondrial uncoupler, before NaSH preconditioning to understand the mitochondrial dependency of exogenous NaSH, we found that cardio-protective effect of NaSH was negated even with higher concentration of H 2 S. The result indicates that exogenous NaSH mediated cardio protection depends on functional cardiac mitochondria. However, no functional difference between the subpopulation i.e., interfibrillar and subsarcolemmal mitochondria observed with NaSH preconditioning in the presence of PAG. [ABSTRACT FROM AUTHOR]

Doxorubicin – basic drug for the neoplastic diseases treatment, it’s main adverse effect is cardiotoxicity. The development of this complication is connected with the energy metabolism, prooxidant-antioxidant homeostasis, disturbances and influence on the genetic apparatus. The aim of the study – to state the succin acid’ derivatives – yakton and mexicor influence on indicators of glycolysis, glyconeogenesis and energoproduct function of mitochondria in the rats’ myocardium in the conditions of doxorubicin cardiomyopathy. Results. In was found that myocardial pyruvate, malate, isocitrate, glycogen, glucose-6-phosphate level and malatdegidrogenase activity were decreased in rats with doxorubicin cardiomyopathy. In comparison lactate lactate level increased. Conclusion. Succin acid’ derivatives – yakton and mexicor, administering with doxorubicin, protect glycolysis, glyconeogenesis and energoproduct function of mitochondria in the rats’ myocardium.

In mitochondria, the sirtuin SIRT5 is an NAD+-dependent protein deacylase that controls several metabolic pathways. Although a wide range of SIRT5 targets have been identified, the overall function of SIRT5 in organismal metabolic homeostasis remains unclear. Given that SIRT5 expression is highest in the heart and that sirtuins are commonly stress-response proteins, we used an established model of pressure overload-induced heart muscle hypertrophy caused by transverse aortic constriction (TAC) to determine SIRT5's role in cardiac stress responses. Remarkably, SIRT5KO mice had reduced survival upon TAC compared with wild-type mice but exhibited no mortality when undergoing a sham control operation. The increased mortality with TAC was associated with increased pathological hypertrophy and with key abnormalities in both cardiac performance and ventricular compliance. By combining high-resolution MS-based metabolomic and proteomic analyses of cardiac tissues from wild-type and SIRT5KO mice, we found several biochemical abnormalities exacerbated in the SIRT5KO mice, including apparent decreases in fatty acid oxidation and glucose oxidation as well as an overall decrease in mitochondrial NAD+/NADH. Together, these abnormalities suggest that SIRT5 deacylates protein substrates involved in cellular oxidative metabolism to maintain mitochondrial energy production. Overall, the functional and metabolic results presented here suggest an accelerated development of cardiac dysfunction in SIRT5KO mice in response to TAC, explaining increased mortality upon cardiac stress. Our findings reveal a key role for SIRT5 in maintaining cardiac oxidative metabolism under pressure overload to ensure survival. [ABSTRACT FROM AUTHOR]

This study, in an experimental model of type I Diabetes Mellitus in rats, deals with the mitochondrial production rates and steady-state concentrations of H 2 O 2 and NO, and ATP levels as part of a network of signaling molecules involved in heart mitochondrial biogenesis. Sustained hyperglycemia leads to a cardiac compromise against a work overload, in the absence of changes in resting cardiac performance and of heart hypertrophy. Diabetes was induced in male Wistar rats by a single dose of Streptozotocin (STZ, 60 mg × kg -1 , ip. ). After 28 days of STZ-injection, rats were sacrificed and hearts were isolated. The mitochondrial mass (mg mitochondrial protein × g heart -1 ), determined through cytochrome oxidase activity ratio, was 47% higher in heart from diabetic than from control animals. Stereological analysis of cardiac tissue microphotographs showed an increase in the cytosolic volume occupied by mitochondria (30%) and in the number of mitochondria per unit area (52%), and a decrease in the mean area of each mitochondrion (23%) in diabetic respect to control rats. Additionally, an enhancement (76%) in PGC-1α expression was observed in cardiac tissue of diabetic animals. Moreover, heart mitochondrial H 2 O 2 (127%) and NO (23%) productions and mtNOS expression (132%) were higher, while mitochondrial ATP production rate was lower (~ 40%), concomitantly with a partial-mitochondrial depolarization, in diabetic than in control rats. Changes in mitochondrial H 2 O 2 and NO steady-state concentrations and an imbalance between cellular energy demand and mitochondrial energy transduction could be involved in the signaling pathways that lead to the novo synthesis of mitochondria. However, this compensatory mechanism triggered to restore the mitochondrial and tissue normal activities, did not lead to competent mitochondria capable of supplying the energetic demands in diabetic pathological conditions. [ABSTRACT FROM AUTHOR]