Skeletal muscle ex vivo mitochondrial respiration parallels decline in vivo oxidative capacity, cardiorespiratory fitness, and muscle strength: The Baltimore Longitudinal Study of Aging

Abstract Resting metabolic rate (RMR) tends to decline with aging. The age-trajectory of decline in RMR is similar to changes that occur in muscle mass, muscle strength, and fitness, but while the decline in these phenotypes has been related to changes of mitochondrial function and oxidative capacity, whether lower RMR is associated with poorer mitochondrial oxidative capacity is unknown. In 619 participants of the Baltimore Longitudinal Study of Aging, we analyzed the cross-sectional association between RMR (kcal/day), assessed by indirect calorimetry, and skeletal muscle maximal oxidative phosphorylation capacity, assessed as postexercise phosphocreatine recovery time constant (τ PCr), by phosphorous magnetic resonance spectroscopy. Linear regression models were used to evaluate the relationship between τ PCr and RMR, adjusting for potential confounders. Independent of age, sex, lean body mass, muscle density, and fat mass, higher RMR was significantly associated with shorter τ PCr, indicating greater mitochondrial oxidative capacity. Higher RMR is associated with a higher mitochondrial oxidative capacity in skeletal muscle. This association may reflect a relationship between better muscle quality and greater mitochondrial health.

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Consequences of SUR2[A478V] Mutation in Skeletal Muscle of Murine Model of Cantu Syndrome

Cells ◽

10.3390/cells10071791 ◽

2021 ◽

Vol 10 (7) ◽

pp. 1791

Author(s):

Rosa Scala ◽

Fatima Maqoud ◽

Nicola Zizzo ◽

Giuseppe Passantino ◽

Antonietta Mele ◽

...

Keyword(s):

Skeletal Muscle ◽

Katp Channel ◽

Ex Vivo ◽

Channel Modulation ◽

Flexor Digitorum Brevis ◽

Inflammatory Edema ◽

Flexor Digitorum ◽

Channel Currents

(1) Background: Cantu syndrome (CS) arises from gain-of-function (GOF) mutations in the ABCC9 and KCNJ8 genes, which encode ATP-sensitive K+ (KATP) channel subunits SUR2 and Kir6.1, respectively. Most CS patients have mutations in SUR2, the major component of skeletal muscle KATP, but the consequences of SUR2 GOF in skeletal muscle are unknown. (2) Methods: We performed in vivo and ex vivo characterization of skeletal muscle in heterozygous SUR2[A478V] (SUR2wt/AV) and homozygous SUR2[A478V] (SUR2AV/AV) CS mice. (3) Results: In SUR2wt/AV and SUR2AV/AV mice, forelimb strength and diaphragm amplitude movement were reduced; muscle echodensity was enhanced. KATP channel currents recorded in Flexor digitorum brevis fibers showed reduced MgATP-sensitivity in SUR2wt/AV, dramatically so in SUR2AV/AV mice; IC50 for MgATP inhibition of KATP currents were 1.9 ± 0.5 × 10−5 M in SUR2wt/AV and 8.6 ± 0.4 × 10−6 M in WT mice and was not measurable in SUR2AV/AV. A slight rightward shift of sensitivity to inhibition by glibenclamide was detected in SUR2AV/AV mice. Histopathological and qPCR analysis revealed atrophy of soleus and tibialis anterior muscles and up-regulation of atrogin-1 and MuRF1 mRNA in CS mice. (4) Conclusions: SUR2[A478V] “knock-in” mutation in mice impairs KATP channel modulation by MgATP, markedly so in SUR2AV/AV, with atrophy and non-inflammatory edema in different skeletal muscle phenotypes.

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Ex Vivo Mitochondrial Respiration Parallels Biochemical Response to Ibrutinib in CLL Cells

Cancers ◽

10.3390/cancers13020354 ◽

2021 ◽

Vol 13 (2) ◽

pp. 354

Author(s):

Subir Roy Chowdhury ◽

Cheryl Peltier ◽

Sen Hou ◽

Amandeep Singh ◽

James B. Johnston ◽

...

Keyword(s):

Mitochondrial Respiration ◽

Ex Vivo ◽

Standard Dose ◽

Cell Receptor ◽

Lymphocytic Leukemia ◽

Clinical Tool ◽

Potential Biomarker ◽

Apoptotic Pathways ◽

The Impact

Mitochondrial respiration is becoming more commonly used as a preclinical tool and potential biomarker for chronic lymphocytic leukemia (CLL) and activated B-cell receptor (BCR) signaling. However, respiration parameters have not been evaluated with respect to dose of ibrutinib given in clinical practice or the effect of progression on ibrutinib treatment on respiration of CLL cells. We evaluated the impact of low and standard dose ibrutinib on CLL cells from patients treated in vivo on mitochondrial respiration using Oroboros oxygraph. Cytokines CCL3 and CCL4 were evaluated using the Mesoscale. Western blot analysis was used to evaluate the BCR and apoptotic pathways. We observed no difference in the mitochondrial respiration rates or levels of plasma chemokine (C-C motif) ligands 3 and 4 (CCL3/CCL4), β-2 microglobulin (β-2 M) and lactate dehydrogenase (LDH) between low and standard doses of ibrutinib. This may confirm why clinical observations of the safety and efficacy of low dose ibrutinib are observed in practice. Of interest, we also observed that the mitochondrial respiration of CLL cells paralleled the increase in β-2 M and LDH at progression. Our study further supports mitochondrial respiration as a biomarker for response and progression on ibrutinib in CLL cells and a valuable pre-clinical tool.

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Skeletal muscle phenotype signaling with ex vivo endurance-type dynamic contractions in rat muscle

Journal of Applied Physiology ◽

10.1152/japplphysiol.00107.2021 ◽

2021 ◽

Author(s):

Jesper Emil Jakobsgaard ◽

Jacob Andresen ◽

Frank V. de Paoli ◽

Kristian Vissing

Keyword(s):

Skeletal Muscle ◽

Translation Initiation ◽

Ex Vivo ◽

Contractile Activity ◽

Specific Protein ◽

Signaling Proteins ◽

Dependent Manner ◽

Metabolic Signaling ◽

Dynamic Endurance

Skeletal muscle phenotype may influence the response sensitivity of myocellular regulatory mechanisms to contractile activity. To examine this, we employed an ex vivo endurance-type dynamic contraction model to evaluate skeletal muscle phenotype-specific protein signaling responses in rat skeletal muscle. Preparations of slow-twitch soleus and fast-twitch extensor digitorum longus skeletal muscle from 4-wk old female Wistar rats were exposed to an identical ex vivo dynamic endurance-type contraction paradigm consisting of 40 minutes of stretch-shortening contractions under simultaneous low-frequency electrostimulation delivered in an intermittent pattern. Phosphorylation of proteins involved in metabolic signaling and signaling for translation initiation was evaluated at 0, 1, and 4 hours after stimulation by immunoblotting. For both muscle phenotypes, signaling related to metabolic events was upregulated immediately after stimulation, with concomitant absence of signaling for translation-initiation. Signaling for translation-initiation was then activated in both muscle phenotypes at 1-4 hours after stimulation, coinciding with attenuated metabolic signaling. The recognizable pattern of signaling responses support how our ex vivo dynamic muscle contraction model can be utilized to infer a stretch-shortening contraction pattern resembling stretch-shortening contraction of in vivo endurance exercise. Moreover, using this model, we observed that some specific signaling proteins adhering to metabolic events or to translation initation exhibited phosphorylation changes in a phenotype-dependent manner, whereas other signaling proteins exhibited phenotype-independent changes. These findings may aid the interpretation of myocellular signaling outcomes adhering to mixed muscle samples collected during human experimental trials.

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The vitamin D receptor regulates mitochondrial function in C2C12 myoblasts

AJP Cell Physiology ◽

10.1152/ajpcell.00568.2019 ◽

2020 ◽

Vol 318 (3) ◽

pp. C536-C541 ◽

Cited By ~ 6

Author(s):

Stephen P. Ashcroft ◽

Joseph J. Bass ◽

Abid A. Kazi ◽

Philip J. Atherton ◽

Andrew Philp

Keyword(s):

Skeletal Muscle ◽

Vitamin D ◽

Protein Content ◽

Vitamin D Receptor ◽

Mitochondrial Function ◽

Mitochondrial Respiration ◽

Oxidative Capacity ◽

C2c12 Myoblasts

Vitamin D deficiency has been linked to a reduction in skeletal muscle function and oxidative capacity; however, the mechanistic bases of these impairments are poorly understood. The biological actions of vitamin D are carried out via the binding of 1α,25-dihydroxyvitamin D3 (1α,25(OH)2D3) to the vitamin D receptor (VDR). Recent evidence has linked 1α,25(OH)2D3 to the regulation of skeletal muscle mitochondrial function in vitro; however, little is known with regard to the role of the VDR in this process. To examine the regulatory role of the VDR in skeletal muscle mitochondrial function, we used lentivirus-mediated shRNA silencing of the VDR in C2C12 myoblasts (VDR-KD) and examined mitochondrial respiration and protein content compared with an shRNA scrambled control. VDR protein content was reduced by ~95% in myoblasts and myotubes ( P < 0.001). VDR-KD myoblasts displayed a 30%, 30%, and 36% reduction in basal, coupled, and maximal respiration, respectively ( P < 0.05). This phenotype was maintained in VDR-KD myotubes, displaying a 34%, 33%, and 48% reduction in basal, coupled, and maximal respiration ( P < 0.05). Furthermore, ATP production derived from oxidative phosphorylation (ATPOx) was reduced by 20%, suggesting intrinsic impairments within the mitochondria following VDR-KD. However, despite the observed functional decrements, mitochondrial protein content, as well as markers of mitochondrial fission were unchanged. In summary, we highlight a direct role for the VDR in regulating skeletal muscle mitochondrial respiration in vitro, providing a potential mechanism as to how vitamin D deficiency might impact upon skeletal muscle oxidative capacity.

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Combined Training Enhances Skeletal Muscle Mitochondrial Oxidative Capacity Independent of Age

The Journal of Clinical Endocrinology & Metabolism ◽

10.1210/jc.2014-3081 ◽

2015 ◽

Vol 100 (4) ◽

pp. 1654-1663 ◽

Cited By ~ 53

Author(s):

Brian A. Irving ◽

Ian R. Lanza ◽

Gregory C. Henderson ◽

Rajesh R. Rao ◽

Bruce M. Spiegelman ◽

...

Keyword(s):

Older Adults ◽

Skeletal Muscle ◽

Body Composition ◽

Transcription Factors ◽

Muscle Strength ◽

Oxidative Capacity ◽

Physical Characteristics ◽

Mitochondrial Proteins ◽

Combined Training ◽

Skeletal Muscle Strength

Context: Skeletal muscle from sedentary older adults exhibits reduced mitochondrial abundance and oxidative capacity. Objective: The primary objective was to determine whether 8 weeks of combined training (CT) has a more robust effect than endurance training (ET) or resistance training (RT) on mitochondrial physiology in healthy young (18–30 years) and older (≥65 years) adults. Intervention: Thirty-four young and 31 older adults were randomly assigned to 8 weeks of ET, RT, and control/CT. Control subjects completed 8 weeks of no exercise (control) followed by 8 weeks of CT. Body composition, skeletal muscle strength, and peak oxygen uptake were measured before and after the intervention. Vastus lateralis muscle biopsy samples were obtained before and 48 hours after the intervention. Mitochondrial physiology was evaluated by high-resolution respirometry and expression of mitochondrial proteins and transcription factors by quantitative PCR and immunoblotting. Results: ET and CT significantly increased oxidative capacity and expression of mitochondrial proteins and transcription factors. All training modalities improved body composition, cardiorespiratory fitness, and skeletal muscle strength. CT induced the most robust improvements in mitochondria-related outcomes and physical characteristics despite lower training volumes for the ET and RT components. Importantly, most of the adaptations to training occurred independent of age. Conclusion: Collectively, these results demonstrate that both ET and CT increase muscle mitochondrial abundance and capacity although CT induced the most robust improvements in the outcomes measured. In conclusion, CT provides a robust exercise regimen to improve muscle mitochondrial outcomes and physical characteristics independent of age.

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Separate and combined effects of a 10-d exposure to hypoxia and inactivity on oxidative function in vivo and mitochondrial respiration ex vivo in humans

Journal of Applied Physiology ◽

10.1152/japplphysiol.00832.2015 ◽

2016 ◽

Vol 121 (1) ◽

pp. 154-163 ◽

Cited By ~ 17

Author(s):

Desy Salvadego ◽

Michail E. Keramidas ◽

Lorenza Brocca ◽

Rossana Domenis ◽

Irene Mavelli ◽

...

Keyword(s):

Mitochondrial Respiration ◽

Ex Vivo ◽

Combined Effects ◽

Oxidative Function

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Image-based modelling of skeletal muscle oxygenation

Journal of The Royal Society Interface ◽

10.1098/rsif.2016.0992 ◽

2017 ◽

Vol 14 (127) ◽

pp. 20160992 ◽

Cited By ~ 7

Author(s):

B. Zeller-Plumhoff ◽

T. Roose ◽

G. F. Clough ◽

P. Schneider

Keyword(s):

Skeletal Muscle ◽

Blood Vessel ◽

Ex Vivo ◽

Imaging Techniques ◽

Muscle Oxygenation ◽

Skeletal Muscle Oxygenation ◽

Health And Disease ◽

Vessel Networks

The supply of oxygen in sufficient quantity is vital for the correct functioning of all organs in the human body, in particular for skeletal muscle during exercise. Disease is often associated with both an inhibition of the microvascular supply capability and is thought to relate to changes in the structure of blood vessel networks. Different methods exist to investigate the influence of the microvascular structure on tissue oxygenation, varying over a range of application areas, i.e. biological in vivo and in vitro experiments, imaging and mathematical modelling. Ideally, all of these methods should be combined within the same framework in order to fully understand the processes involved. This review discusses the mathematical models of skeletal muscle oxygenation currently available that are based upon images taken of the muscle microvasculature in vivo and ex vivo . Imaging systems suitable for capturing the blood vessel networks are discussed and respective contrasting methods presented. The review further informs the association between anatomical characteristics in health and disease. With this review we give the reader a tool to understand and establish the workflow of developing an image-based model of skeletal muscle oxygenation. Finally, we give an outlook for improvements needed for measurements and imaging techniques to adequately investigate the microvascular capability for oxygen exchange.

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Long-term Enrollment in Cardiac Rehabilitation Benefits Cardiorespiratory Fitness and Skeletal Muscle Strength in Men With Cardiovascular Disease

Canadian Journal of Cardiology ◽

10.1016/j.cjca.2019.05.018 ◽

2019 ◽

Vol 35 (10) ◽

pp. 1359-1365 ◽

Cited By ~ 2

Author(s):

Mike Pryzbek ◽

Maureen MacDonald ◽

Paul Stratford ◽

Angelica McQuarrie ◽

Julie Richardson ◽

...

Keyword(s):

Cardiovascular Disease ◽

Skeletal Muscle ◽

Muscle Strength ◽

Cardiac Rehabilitation ◽

Cardiorespiratory Fitness ◽

Skeletal Muscle Strength

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Opposing effects of nitric oxide and prostaglandin inhibition on muscle mitochondrial V̇o2 during exercise

AJP Regulatory Integrative and Comparative Physiology ◽

10.1152/ajpregu.00044.2012 ◽

2012 ◽

Vol 303 (1) ◽

pp. R94-R100 ◽

Cited By ~ 13

Author(s):

Robert Boushel ◽

Teresa Fuentes ◽

Ylva Hellsten ◽

Bengt Saltin

Keyword(s):

Nitric Oxide ◽

Blood Flow ◽

Mitochondrial Respiration ◽

Complex I ◽

Ex Vivo ◽

Knee Extension ◽

Physiological Effect ◽

Dependent Manner ◽

Concentration Dependent Manner

Nitric oxide (NO) and prostaglandins (PG) together play a role in regulating blood flow during exercise. NO also regulates mitochondrial oxygen consumption through competitive binding to cytochrome- c oxidase. Indomethacin uncouples and inhibits the electron transport chain in a concentration-dependent manner, and thus, inhibition of NO and PG synthesis may regulate both muscle oxygen delivery and utilization. The purpose of this study was to examine the independent and combined effects of NO and PG synthesis blockade (l-NMMA and indomethacin, respectively) on mitochondrial respiration in human muscle following knee extension exercise (KEE). Specifically, this study examined the physiological effect of NO, and the pharmacological effect of indomethacin, on muscle mitochondrial function. Consistent with their mechanism of action, we hypothesized that inhibition of nitric oxide synthase (NOS) and PG synthesis would have opposite effects on muscle mitochondrial respiration. Mitochondrial respiration was measured ex vivo by high-resolution respirometry in saponin-permeabilized fibers following 6 min KEE in control (CON; n = 8), arterial infusion of NG-monomethyl-l-arginine (l-NMMA; n = 4) and Indo ( n = 4) followed by combined inhibition of NOS and PG synthesis (l-NMMA + Indo, n = 8). ADP-stimulated state 3 respiration (OXPHOS) with substrates for complex I (glutamate, malate) was reduced 50% by Indo. State 3 O2 flux with complex I and II substrates was reduced less with both Indo (20%) and l-NMMA + Indo (15%) compared with CON. The results indicate that indomethacin reduces state 3 mitochondrial respiration primarily at complex I of the respiratory chain, while blockade of NOS by l-NMMA counteracts the inhibition by Indo. This effect on muscle mitochondria, in concert with a reduction of blood flow accounts for in vivo changes in muscle O2 consumption during combined blockade of NOS and PG synthesis.

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