Effect of hyperthermia and acidosis on equine skeletal muscle mitochondrial oxygen consumption

The skeletal muscle of exercising horses develops pronounced hyperthermia and acidosis during strenuous or prolonged exercise, with very high tissue temperature and low pH associated with muscle fatigue or damage. The purpose of this study was to evaluate the individual effects of physiologically relevant hyperthermia and acidosis on equine skeletal muscle mitochondrial function, using ex vivo measurement of oxygen consumption to assess the function of different mitochondrial elements. Fresh triceps muscle biopsies from 6 healthy unfit Thoroughbred geldings were permeabilised to permit diffusion of small molecular weight substrates through the sarcolemma and analysed in a high resolution respirometer at 38, 40, 42, and 44 °C, and pH=7.1, 6.5, and 6.1. Oxygen consumption was measured under conditions of non-phosphorylating (leak) respiration and phosphorylating respiration through Complex I and Complex II. Data were analysed using a one-way repeated measures ANOVA and data are expressed as mean ± standard deviation. Leak respiration was ~3-fold higher at 44 °C compared to 38 °C regardless of electron source (Complex I: 22.88±3.05 vs 8.08±1.92 pmol O2/mg/s), P=0.002; Complex II: 79.14±23.72 vs 21.43±11.08 pmol O2/mg/s, P=0.022), resulting in a decrease in efficiency of oxidative phosphorylation. Acidosis had minimal effect on mitochondrial respiration at pH=6.5, but pH=6.1 resulted in a 50% decrease in mitochondrial oxygen consumption. These results suggest that skeletal muscle hyperthermia decreases the efficiency of oxidative phosphorylation through increased leak respiration, thus providing a specific biochemical basis for hyperthermia-induced muscle fatigue. The effect of myocellular acidosis on mitochondrial respiration was minimal under typical levels of acidosis, but atypically severe acidosis can lead to impairment of mitochondrial function.

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Abstract 355: Effect of Poloxamer 188 on Rat Brain Isolated Mitochondria After Exposure to Hydrogen Peroxide

Circulation ◽

10.1161/circ.140.suppl_2.355 ◽

2019 ◽

Vol 140 (Suppl_2) ◽

Author(s):

Johannes A Pille ◽

Michele M Salzman ◽

Anna A Sonju ◽

Felicia P Lotze ◽

Josephine E Hees ◽

...

Keyword(s):

Hydrogen Peroxide ◽

Oxygen Consumption ◽

Mitochondrial Function ◽

Complex I ◽

Room Temperature ◽

In Vitro Model ◽

Atp Synthesis ◽

Complex Ii ◽

Vitro Model

Introduction: In a pig model of myocardial infarction (MI), intracoronary delivered Poloxamer (P) 188 significantly reduces ischemia/reperfusion (IR) injury when given immediately upon reperfusion, with improved mitochondrial function as a predominant effect. As mitochondria are heavily damaged during IR, a direct effect of P188 on mitochondria may lead to better therapy options during reperfusion. To show not only a similar reduction of IR injury by P188 in the brain, but also a direct P188 effect on mitochondria, we established an in-vitro model of IR that consists of damaging isolated rat brain mitochondria with hydrogen peroxide (H 2 O 2 ), one component of ischemia, then applying P188, and analyzing mitochondrial function. Methods: Male Sprague-Dawley rat brains were removed, and the mitochondria isolated by differential centrifugation and Percoll gradients, then kept on ice to slow their bioenergetics prior to any experimental treatments. Mitochondria were exposed to 200 μM H 2 O 2 for 10 min at room temperature with slight agitation; controls received no H 2 O 2 . Samples were then diluted ½ with buffer ± P188 (250 μM after dilution) to simulate reperfusion and treatment, and kept at room temperature for 10 further minutes. ATP synthesis was measured in a luminometer using a luciferase enzymatic assay. Oxygen consumption was measured by closed cell respirometry with an oxygen meter. In both assays, Complex I and Complex II were examined; Complex I substrates glutamate and malate, Complex II substrate succinate plus the Complex I inhibitor rotenone. Statistics: Data are expressed as mean ± SEM. One-Way ANOVA, SNK-Test; Kruskal-Wallis-Test; α=0.05, * vs control. Results: In both Complex I and II, mitochondrial function was significantly impaired by H 2 O 2 , with ATP synthesis affected more at Complex I and oxygen consumption affected more at Complex II. Addition of P188 did not provide any significant improvement in mitochondrial function. Conclusions: Although P188 significantly reduced IR injury when given during reperfusion in a pig model of MI, it does not appear to provide direct protection to mitochondria in this in-vitro model. Whether the exposure to H 2 O 2 causes the appropriate injury for P188 to become effective remains to be elucidated.

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Abstract 15731: Sildenafil Improves Mitochondrial Function in Failing Single Ventricles

Circulation ◽

10.1161/circ.142.suppl_3.15731 ◽

2020 ◽

Vol 142 (Suppl_3) ◽

Author(s):

Anastacia M Garcia ◽

Carissa A Miyano ◽

Raleigh Joschner ◽

Matthew Stone ◽

Brian L Stauffer ◽

...

Keyword(s):

Oxygen Consumption ◽

Mitochondrial Function ◽

Complex I ◽

Molecular Mechanisms ◽

Ex Vivo ◽

Mitochondrial Oxygen Consumption ◽

Ventricular Tissue ◽

Substrate Inhibitor ◽

Phosphodiesterase 5 ◽

One Way Anova

Introduction: Heart failure (HF) remains a leading cause of death and indication for transplant in single ventricle congenital heart disease (SV). However, little is known regarding the molecular mechanisms leading to HF in SV. The purpose of this study was to characterize mitochondrial function in the myocardium of failing (SVHF) and non-failing (SVNF) SV patients compared to biventricular NF controls (BVNF). Furthermore, we investigated the effect of ex vivo treatment with the phosphodiesterase-5 inhibitor (PDE5i) sildenafil on mitochondrial function. Methods: Freshly explanted ventricular tissue was saponin permeabilized and mitochondrial oxygen consumption was measured sequentially throughout the electron transport system using SUbstrate-Inhibitor-Titration (“SUIT”) protocols and an Oroboros O2k high resolution respirometer. Permeabilized ventricular tissue was treated for 40 min with sildenafil [1μM] prior to measurement of oxygen consumption. A Western blot for PDE5 was performed in isolated mitochondrial proteins from SVHF subjects ± PDE5i. Results: Compared to BVNF (n=15) and SVNF (n=6), SVHF (n=8) hearts have decreased function of Complex I and Complex I and II (A, B), and decreased maximal respiration (C), all of which improve with acute ex vivo treatment with sildenafil in SVHF (SVHF+PDE5i, n=6). Importantly, mitochondrial function is impaired in BVNF+PDE5i (n=5) and SVNF+PDE5i hearts (n=5) (A-C, one-way Anova p<0.05). PDE5 protein is expressed in SVHF mitochondria, but expression is not affected by ex vivo PDE5i treatment (D). Conclusions: Our results indicate that mitochondrial function is impaired in SVHF, PDE5 protein is expressed in SVHF mitochondria, and PDE5i improves mitochondrial function in SVHF, but may be detrimental to mitochondrial function in SVNF and BVNF. Together these data suggest that mitochondrial PDE5 is a potential therapeutic target, but that indiscriminate use of PDE5i in SV patients may not be advisable.

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A new insight into the molecular hydrogen effect on coenzyme Q and mitochondrial function of rats

Canadian Journal of Physiology and Pharmacology ◽

10.1139/cjpp-2019-0281 ◽

2020 ◽

Vol 98 (1) ◽

pp. 29-34 ◽

Cited By ~ 4

Author(s):

Anna Gvozdjáková ◽

Jarmila Kucharská ◽

Branislav Kura ◽

Ol’ga Vančová ◽

Zuzana Rausová ◽

...

Keyword(s):

Oxidative Stress ◽

Oxidative Phosphorylation ◽

Respiratory Chain ◽

Mitochondrial Function ◽

Complex I ◽

Molecular Hydrogen ◽

Coenzyme Q ◽

Complex Ii ◽

Atp Production ◽

Q Cycle

Mitochondria are the major source of cellular energy metabolism. In the cardiac cells, mitochondria produce by way of the oxidative phosphorylation more than 90% of the energy supply in the form of ATP, which is utilized in many ATP-dependent processes, like cycling of the contractile proteins or maintaining ion gradients. Reactive oxygen species (ROS) are by-products of cellular metabolism and their levels are controlled by intracellular antioxidant systems. Imbalance between ROS and the antioxidant defense leads to oxidative stress and oxidative changes to cellular biomolecules. Molecular hydrogen (H2) has been proved as beneficial in the prevention and therapy of various diseases including cardiovascular disorders. It selectively scavenges hydroxyl radical and peroxynitrite, reduces oxidative stress, and has anti-inflammatory and anti-apoptotic effects. The effect of H2 on the myocardial mitochondrial function and coenzyme Q levels is not well known. In this paper, we demonstrated that consumption of H2-rich water (HRW) resulted in stimulated rat cardiac mitochondrial electron respiratory chain function and increased levels of ATP production by Complex I and Complex II substrates. Similarly, coenzyme Q9 levels in the rat plasma, myocardial tissue, and mitochondria were increased and malondialdehyde level in plasma was reduced after HRW administration. Based on obtained data, we hypothesize a new metabolic pathway of the H2 effect in mitochondria on the Q-cycle and in mitochondrial respiratory chain function. The Q-cycle contains three coenzyme Q forms: coenzyme Q in oxidized form (ubiquinone), radical form (semiquinone), or reduced form (ubiquinol). H2 may be a donor of both electron and proton in the Q-cycle and thus we can suppose stimulation of coenzyme Q production. When ubiquinone is reduced to ubiquinol, lipid peroxidation is reduced. Increased CoQ9 concentration can stimulate electron transport from Complex I and Complex II to Complex III and increase ATP production via mitochondrial oxidative phosphorylation. Our results indicate that H2 may function to prevent/treat disease states with disrupted myocardial mitochondrial function.

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Mitochondrial respiration of complex II is not lower than that of complex I in mouse skeletal muscle

Biochemistry and Biophysics Reports ◽

10.1016/j.bbrep.2019.100717 ◽

2020 ◽

Vol 21 ◽

pp. 100717 ◽

Cited By ~ 1

Author(s):

Satoshi Maekawa ◽

Shingo Takada ◽

Takaaki Furihata ◽

Arata Fukushima ◽

Takashi Yokota ◽

...

Keyword(s):

Skeletal Muscle ◽

Mitochondrial Respiration ◽

Complex I ◽

Complex Ii ◽

Mouse Skeletal Muscle

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Mitochondrial oxygen consumption in early postmortem permeabilized skeletal muscle fibers is influenced by cattle breed

Journal of Animal Science ◽

10.1093/jas/skaa044 ◽

2020 ◽

Vol 98 (3) ◽

Cited By ~ 3

Author(s):

Patricia M Ramos ◽

Chengcheng Li ◽

Mauricio A Elzo ◽

Stephanie E Wohlgemuth ◽

Tracy L Scheffler

Keyword(s):

Skeletal Muscle ◽

Oxygen Consumption ◽

Oxidative Phosphorylation ◽

Heat Tolerance ◽

Complex I ◽

Citrate Synthase ◽

Ex Vivo ◽

Muscle Fibers ◽

Cattle Breed ◽

Early Postmortem

Abstract Functional properties and integrity of skeletal muscle mitochondria (mt) during the early postmortem period may influence energy metabolism and pH decline, thereby impacting meat quality development. Angus typically produce more tender beef than Brahman, a Bos indicus breed known for heat tolerance. Thus, our objectives were to compare mt respiratory function in muscle collected early postmortem (1 h) from Angus and Brahman steers (n = 26); and to evaluate the effect of normal and elevated temperature on mt function ex vivo. We measured mt oxygen consumption rate (OCR) in fresh-permeabilized muscle fibers from Longissimus lumborum (LL) at 2 temperatures (38.5 and 40.0 °C) and determined citrate synthase (CS) activity and expression of several mt proteins. The main effects of breed, temperature, and their interaction were tested for mt respiration, and breed effect was tested for CS activity and protein expression. Breed, but not temperature (P > 0.40), influenced mt OCR (per tissue weight), with Brahman exhibiting greater complex I+II-mediated oxidative phosphorylation capacity (P = 0.05). Complex I- and complex II-mediated OCR also tended to be greater in Brahman (P = 0.07 and P = 0.09, respectively). Activity of CS was higher in LL from Brahman compared to Angus (P = 0.05). Expression of specific mt proteins did not differ between breeds, except for higher expression of adenosine triphosphate (ATP) synthase subunit 5 alpha in Brahman muscle (P = 0.04). Coupling control ratio differed between breeds (P = 0.05), revealing greater coupling between oxygen consumption and phosphorylation in Brahman. Our data demonstrate that both Angus and Brahman mt retained functional capacity and integrity 1-h postmortem; greater oxidative phosphorylation capacity and coupling in Brahman mt could be related to heat tolerance and impact early postmortem metabolism.

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Skeletal muscle mitochondrial function in polycystic ovarian syndrome

Acta Endocrinologica ◽

10.1530/eje-11-0419 ◽

2011 ◽

Vol 165 (4) ◽

pp. 631-637 ◽

Cited By ~ 14

Author(s):

Rasmus Rabøl ◽

Pernille F Svendsen ◽

Mette Skovbro ◽

Robert Boushel ◽

Peter Schjerling ◽

...

Keyword(s):

Skeletal Muscle ◽

Insulin Sensitivity ◽

High Resolution ◽

Mitochondrial Function ◽

Mitochondrial Respiration ◽

Complex I ◽

Polycystic Ovarian Syndrome ◽

Obese Women ◽

Mitochondrial Content ◽

Ovarian Syndrome

ObjectivePolycystic ovarian syndrome (PCOS) is associated with skeletal muscle insulin resistance (IR), which has been linked to decreased mitochondrial function. We measured mitochondrial respiration in lean and obese women with and without PCOS using high-resolution respirometry.MethodsHyperinsulinemic–euglycemic clamps (40 mU/min per m2) and muscle biopsies were performed on 23 women with PCOS (nine lean (body mass index (BMI) <25 kg/m2) and 14 obese (BMI >25 kg/m2)) and 17 age- and weight-matched controls (six lean and 11 obese). Western blotting and high-resolution respirometry was used to determine mitochondrial function.ResultsInsulin sensitivity decreased with PCOS and increasing body weight. Mitochondrial respiration with substrates for complex I and complex I+II were similar in all groups, and PCOS was not associated with a decrease in mitochondrial content as measured by mitochondrial DNA/genomic DNA. We found no correlation between mitochondrial function and indices of insulin sensitivity.ConclusionsIn contrast to previous reports, we found no evidence that skeletal muscle mitochondrial respiration is reduced in skeletal muscle of women with PCOS compared with control subjects. Furthermore, mitochondrial content did not differ between our control and PCOS groups. These results question the causal relationship between reduced mitochondrial function and skeletal muscle IR in PCOS.

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Polarographic determination of mitochondrial respiration in Gastrothylax crumenifer

Journal of Helminthology ◽

10.1017/s0022149x00009895 ◽

1987 ◽

Vol 61 (2) ◽

pp. 143-145

Author(s):

Jawed Siddiqui ◽

Ather H Siddiqi

Keyword(s):

Oxygen Consumption ◽

Oxidative Phosphorylation ◽

Oxidative Metabolism ◽

Mitochondrial Respiration ◽

Mitochondrial Atpase ◽

Mitochondrial Oxygen Consumption ◽

Salicylhydroxamic Acid ◽

Gastrothylax Crumenifer ◽

Mitochondrial Fractions

ABSTRACTThe oxidative metabolism of Gastrothylax crumenifer mitochondrial fractions was assayed polarographically at 30°C in the presence of various substrates. Succinate was most readily oxidized, malate and pyruvate were oxidized at subsantially lower retes. The spcific inhibitors such as malonate, KCN, NaN3, oxaloacetate, salicylhydroxamic acid and oligomycin effectively affected the mitochondrial oxygen consumption. The results indicate the presence of oxidative phosphorylation and cytochrome systems. Mitochondrial ATPase was found to be active.

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Cell-Permeable Succinate Rescues Mitochondrial Respiration in Cellular Models of Statin Toxicity

International Journal of Molecular Sciences ◽

10.3390/ijms22010424 ◽

2021 ◽

Vol 22 (1) ◽

pp. 424

Author(s):

Vlad F. Avram ◽

Imen Chamkha ◽

Eleonor Åsander-Frostner ◽

Johannes K. Ehinger ◽

Romulus Z. Timar ◽

...

Keyword(s):

Oxygen Consumption ◽

Mitochondrial Dysfunction ◽

Mitochondrial Respiration ◽

Complex I ◽

Ex Vivo ◽

Coupling Efficiency ◽

Human Platelets ◽

Lipid Lowering ◽

Lipid Lowering Therapy ◽

Cellular Models

Statins are the cornerstone of lipid-lowering therapy. Although generally well tolerated, statin-associated muscle symptoms (SAMS) represent the main reason for treatment discontinuation. Mitochondrial dysfunction of complex I has been implicated in the pathophysiology of SAMS. The present study proposed to assess the concentration-dependent ex vivo effects of three statins on mitochondrial respiration in viable human platelets and to investigate whether a cell-permeable prodrug of succinate (complex II substrate) can compensate for statin-induced mitochondrial dysfunction. Mitochondrial respiration was assessed by high-resolution respirometry in human platelets, acutely exposed to statins in the presence/absence of the prodrug NV118. Statins concentration-dependently inhibited mitochondrial respiration in both intact and permeabilized cells. Further, statins caused an increase in non-ATP generating oxygen consumption (uncoupling), severely limiting the OXPHOS coupling efficiency, a measure of the ATP generating capacity. Cerivastatin (commercially withdrawn due to muscle toxicity) displayed a similar inhibitory capacity compared with the widely prescribed and tolerable atorvastatin, but did not elicit direct complex I inhibition. NV118 increased succinate-supported mitochondrial oxygen consumption in atorvastatin/cerivastatin-exposed platelets leading to normalization of coupled (ATP generating) respiration. The results acquired in isolated human platelets were validated in a limited set of experiments using atorvastatin in HepG2 cells, reinforcing the generalizability of the findings.

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Dose Response of Endotoxin on Hepatocyte and Muscle Mitochondrial Respiration In Vitro

BioMed Research International ◽

10.1155/2015/353074 ◽

2015 ◽

Vol 2015 ◽

pp. 1-12 ◽

Cited By ~ 6

Author(s):

Victor Jeger ◽

Sebastian Brandt ◽

Francesca Porta ◽

Stephan M. Jakob ◽

Jukka Takala ◽

...

Keyword(s):

Skeletal Muscle ◽

Membrane Potential ◽

Mitochondrial Respiration ◽

Hepg2 Cells ◽

Human Hepatocytes ◽

Atp Content ◽

Muscle Mitochondria ◽

Complex Ii ◽

Skeletal Muscle Mitochondria ◽

Reduced Time

Introduction.Results on mitochondrial dysfunction in sepsis are controversial. We aimed to assess effects of LPS at wide dose and time ranges on hepatocytes and isolated skeletal muscle mitochondria.Methods.Human hepatocellular carcinoma cells (HepG2) were exposed to placebo or LPS (0.1, 1, and 10 μg/mL) for 4, 8, 16, and 24 hours and primary human hepatocytes to 1 μg/mL LPS or placebo (4, 8, and 16 hours). Mitochondria from porcine skeletal muscle samples were exposed to increasing doses of LPS (0.1–100 μg/mg) for 2 and 4 hours. Respiration rates of intact and permeabilized cells and isolated mitochondria were measured by high-resolution respirometry.Results.In HepG2 cells, LPS reduced mitochondrial membrane potential and cellular ATP content but did not modify basal respiration. Stimulated complex II respiration was reduced time-dependently using 1 μg/mL LPS. In primary human hepatocytes, stimulated mitochondrial complex II respiration was reduced time-dependently using 1 μg/mL LPS. In isolated porcine skeletal muscle mitochondria, stimulated respiration decreased at high doses (50 and 100 μg/mL LPS).Conclusion.LPS reduced cellular ATP content of HepG2 cells, most likely as a result of the induced decrease in membrane potential. LPS decreased cellular and isolated mitochondrial respiration in a time-dependent, dose-dependent and complex-dependent manner.

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