scholarly journals Assessing Mitochondrial Energetics of Skeletal Muscle in the Study of Muscle Mobility and Aging (SOMMA)

2021 ◽  
Vol 5 (Supplement_1) ◽  
pp. 126-126
Author(s):  
Bret Goodpaster ◽  
Peggy Cawthon ◽  
Stephen Kritchevsky ◽  
Anne Newman ◽  
Russell Hepple ◽  
...  
Keyword(s):  
Skeletal Muscle ◽  
Ex Vivo ◽  
Complementary Information ◽  
Physiological Factors ◽  
Muscle Energetics ◽  
Age Related ◽  
Muscle Biopsies ◽  
Maximal Capacity ◽  
Permeabilized Muscle

Abstract Mitochondria produce energy as ATP that essential for muscle contraction and movement. We hypothesize that age-related decreases in the capacity to generate ATP in muscle plays a major role in loss of mobility with aging. In SOMMA, we use high-resolution respirometry to measure the activity of electron transport system (ETS) in permeabilized muscle fibers from muscle biopsies. This allows us to assay ETS function in a highly controlled ex vivo experiment at the myocellular level, removed from other potentially limiting physiological factors including supplies of substrates and oxygen. We are also measuring the maximal capacity to generate ATP (ATPmax) in vivo by 31PMRS. ATPmax reflects the rate of phosphocreatine replenishment via oxidative phosphorylation. Analysis from the first 113 participants indicates that ATPmax correlates with Maximal OXPHOS (r=0.27, P=0.005), and Maximal ETS capacity (r=0.17, P=0.08). This suggests that these approaches provide complementary information on skeletal muscle energetics.

scholarly journals HyPer2 imaging reveals temporal and heterogeneous hydrogen peroxide changes in denervated and aged skeletal muscle fibers in vivo

2019 ◽  
Vol 9 (1) ◽  
Author(s):  
C. A. Staunton ◽  
E. D. Owen ◽  
N. Pollock ◽  
A. Vasilaki ◽  
R. Barrett-Jolley ◽  
...  
Keyword(s):  
Skeletal Muscle ◽  
Hydrogen Peroxide ◽  
Ex Vivo ◽  
Redox Homeostasis ◽  
Muscle Fibers ◽  
Age Related ◽  
Resting Muscle ◽  
Anterior Tibialis

Abstract To determine the role of denervation and motor unit turnover in the age-related increase in skeletal muscle oxidative stress, the hydrogen peroxide (H2O2) specific, genetically-encoded, fluorescent cyto-HyPer2 probe was expressed in mouse anterior tibialis (AT) muscle and compared with ex vivo measurements of mitochondrial oxidant generation. Crush of the peroneal nerve induced increased mitochondrial peroxide generation, measured in permeabilised AT fibers ex vivo and intra vital confocal microscopy of cyto-HyPer2 fluorescence showed increased cytosolic H2O2 in a sub-set (~24%) of individual fibers associated with onset of fiber atrophy. In comparison, mitochondrial peroxide generation was also increased in resting muscle from old (26 month) mice compared with adult (6–8 month) mice, but no age effect on fiber cytosolic H2O2in vivo was seen. Thus ageing is associated with an increased ability of muscle fibers to maintain cytosolic redox homeostasis in the presence of denervation-induced increase in mitochondrial peroxide generation.

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

Cells ◽  
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.

scholarly journals Age-related changes in collagen synthesis and degradation in rat tissues. Importance of degradation of newly synthesized collagen in regulating collagen production

1991 ◽  
Vol 276 (2) ◽  
pp. 307-313 ◽  
Author(s):  
P K Mays ◽  
R J McAnulty ◽  
J S Campa ◽  
G J Laurent
Keyword(s):  
Skeletal Muscle ◽  
Collagen Synthesis ◽  
Rat Tissues ◽  
Age Related ◽  
Developmental Growth ◽  
Cross Links ◽  
Fractional Synthesis ◽  
Synthesis And Degradation ◽  
Age Related Changes

During developmental growth, collagens are believed to be continuously deposited into an extracellular matrix which is increasingly stabilized by the formation of covalent cross-links throughout life. However, the age-related changes in rates of synthetic and degradative processes are less well understood. In the present study we measured rates of collagen synthesis in vivo using a flooding dose of unlabelled proline given with [14C]proline and determining production of hydroxy[14C]proline. Degradation of newly synthesized collagen was estimated from the amount of free hydroxy [14C]proline in tissues 30 min after injection. Collagen fractional synthesis rates ranged from about 5%/day in skeletal muscle to 20%/day in hearts of rats aged 1 month. At 15 months of age, collagen fractional synthesis rates had decreased markedly in lung and skin, but in skeletal muscle and heart, rates were unchanged. At 24 months of age, synthesis rates had decreased by at least 10-fold in all tissues, compared with rates at 1 month. The proportion of newly synthesized collagen degraded ranged from 6.4 +/- 0.4% in skin to 61.6 +/- 5.0% in heart at 1 month of age. During aging the proportion degraded increased in all tissues to maximal values at 15 months, ranging from 56 +/- 7% in skin to 96 +/- 1% in heart. These data suggest that there are marked age-related changes in rates of collagen metabolism. They also indicate that synthesis is active even in old animals, where the bulk of collagens produced are destined to be degraded.

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

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.

scholarly journals Potential caveats of putative microglia-specific markers for assessment of age-related cerebrovascular neuroinflammation

2020 ◽  
Vol 17 (1) ◽  
Author(s):  
Pedram Honarpisheh ◽  
Juneyoung Lee ◽  
Anik Banerjee ◽  
Maria P. Blasco-Conesa ◽  
Parisa Honarpisheh ◽  
...  
Keyword(s):  
Flow Cytometry ◽  
Ex Vivo ◽  
Myeloid Cells ◽  
Amyloid Angiopathy ◽  
Future Studies ◽  
Age Related ◽  
In Vivo Animal Models ◽  
Intermediate Expression ◽  
The Brain

Abstract Background The ability to distinguish resident microglia from infiltrating myeloid cells by flow cytometry-based surface phenotyping is an important technique for examining age-related neuroinflammation. The most commonly used surface markers for the identification of microglia include CD45 (low-intermediate expression), CD11b, Tmem119, and P2RY12. Methods In this study, we examined changes in expression levels of these putative microglia markers in in vivo animal models of stroke, cerebral amyloid angiopathy (CAA), and aging as well as in an ex vivo LPS-induced inflammation model. Results We demonstrate that Tmem119 and P2RY12 expression is evident within both CD45int and CD45high myeloid populations in models of stroke, CAA, and aging. Interestingly, LPS stimulation of FACS-sorted adult microglia suggested that these brain-resident myeloid cells can upregulate CD45 and downregulate Tmem119 and P2RY12, making them indistinguishable from peripherally derived myeloid populations. Importantly, our findings show that these changes in the molecular signatures of microglia can occur without a contribution from the other brain-resident or peripherally sourced immune cells. Conclusion We recommend future studies approach microglia identification by flow cytometry with caution, particularly in the absence of the use of a combination of markers validated for the specific neuroinflammation model of interest. The subpopulation of resident microglia residing within the “infiltrating myeloid” population, albeit small, may be functionally important in maintaining immune vigilance in the brain thus should not be overlooked in neuroimmunological studies.

scholarly journals Telomere length and age-dependent telomere attrition: the blood-and-muscle model

2019 ◽  
Vol 97 (4) ◽  
pp. 328-334 ◽  
Author(s):  
Mirna N. Chahine ◽  
Simon Toupance ◽  
Sandy El-Hakim ◽  
Carlos Labat ◽  
Sylvie Gautier ◽  
...  
Keyword(s):  
Skeletal Muscle ◽  
Telomere Length ◽  
Cross Sectional Study ◽  
Muscle Model ◽  
Atherosclerotic Cardiovascular Disease ◽  
Cross Sectional ◽  
Telomere Attrition ◽  
Age Related ◽  
Age Dependent ◽  
Muscle Biopsies

Short telomere length (TL) is associated with atherosclerotic cardiovascular disease (ACVD) and other age-related diseases. It is unclear whether these associations originate from having inherently short TL or a faster TL attrition before or during disease development. We proposed the blood-and-muscle model to assess TL dynamics throughout life course. Our objective was to measure TL in leukocytes (LTL) and in skeletal muscle (MTL), which served as a proxy of TL at birth. The delta (MTL–LTL) represented life-long telomere attrition. Blood draws and skeletal muscle biopsies were performed on 35 Lebanese individuals undergoing surgery. Following DNA extraction, LTL and MTL were measured by Southern blot. In every individual aged between 30 and 85 years, MTL was longer than LTL. With age, MTL and LTL decreased, but the delta (MTL–LTL) increased by 14 bp/year. We validated the blood-and-muscle model that allowed us to identify TL, TL at birth, and lifelong TL attrition in a cross-sectional study. This model can be used in larger cross-sectional studies to evaluate the association of telomere dynamics with age-related diseases onset and progression.

scholarly journals Image-based modelling of skeletal muscle oxygenation

2017 ◽  
Vol 14 (127) ◽  
pp. 20160992 ◽  
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.

α7β1-Integrin regulates mechanotransduction and prevents skeletal muscle injury

2006 ◽  
Vol 290 (6) ◽  
pp. C1660-C1665 ◽  
Author(s):  
Marni D. Boppart ◽  
Dean J. Burkin ◽  
Stephen J. Kaufman
Keyword(s):  
Skeletal Muscle ◽  
Muscle Damage ◽  
Intracellular Signaling ◽  
Ex Vivo ◽  
Negative Regulator ◽  
Blue Dye ◽  
The Matrix ◽  
Mitogen Activated Protein ◽  
Exercise Induced

α7β1-Integrin links laminin in the extracellular matrix with the cell cytoskeleton and therein mediates transduction of mechanical forces into chemical signals. Muscle contraction and stretching ex vivo result in activation of intracellular signaling molecules that are integral to postexercise injury responses. Because α7β1-integrin stabilizes muscle and provides communication between the matrix and cytoskeleton, the role of this integrin in exercise-induced cell signaling and skeletal muscle damage was assessed in wild-type and transgenic mice overexpressing the α7BX2 chain. We report here that increasing α7β1-integrin inhibits phosphorylation of molecules associated with muscle damage, including the mitogen-activated protein kinases (JNK, p38, and ERK), following downhill running. Likewise, activation of molecules associated with hypertrophy (AKT, mTOR, and p70S6k) was diminished in mice overexpressing integrin. While exercise resulted in Evans blue dye-positive fibers, an index of muscle damage, increased integrin protected mice from injury. Moreover, exercise leads to an increase in α7β1 protein. These experiments provide the first evidence that α7β1-integrin is a negative regulator of mechanotransduction in vivo and provides resistance to exercise-induced muscle damage.

Effects of aging on cardiac and skeletal muscle AMPK activity: basal activity, allosteric activation, and response to in vivo hypoxemia in mice

2004 ◽  
Vol 287 (5) ◽  
pp. R1270-R1275 ◽  
Author(s):  
Asensio A. Gonzalez ◽  
Reetu Kumar ◽  
Jacob D. Mulligan ◽  
Ashley J. Davis ◽  
Kurt W. Saupe
Keyword(s):  
Skeletal Muscle ◽  
Ex Vivo ◽  
Allosteric Activation ◽  
Biochemical Basis ◽  
Hypoxic Tolerance ◽  
Ampk Activity ◽  
Effects Of Aging ◽  
Amp Activated Protein Kinase

Although a diminished ability of tissues and organisms to tolerate stress is a clinically important hallmark of normal aging, little is known regarding its biochemical basis. Our goal was to determine whether age-associated changes in AMP-activated protein kinase (AMPK), a key regulator of cellular metabolism during the stress response, might contribute to the poor stress tolerance of aged cardiac and skeletal muscle. Basal AMPK activity and the degree of activation of AMPK by AMP and by in vivo hypoxemia (arterial Po2 of 39 mmHg) were measured in cardiac and skeletal muscle (gastrocnemius) from 5- and 24-mo-old C57Bl/6 mice. In the heart, neither basal AMPK activity nor its allosteric activation by AMP was affected by age. However, after 10 min of hypoxemia, the activity of α2-AMPK, but not α1-AMPK, was significantly higher in the hearts from old than from young mice ( P < 0.005), this difference being due to differences in phosphorylation of α2-AMPK. Significant activation of AMPK in the young hearts did not occur until 30 min of hypoxemia ( P < 0.01), stress that was poorly tolerated by the old mice (mortality = 67%). In contrast, AMPK activity in gastrocnemius muscle was unaffected by age or hypoxemia. We conclude that the age-associated decline in hypoxic tolerance in cardiac and skeletal muscle is not caused by changes in basal AMPK activity or a blunted AMPK response to hypoxia. Activation of AMPK by in vivo hypoxia is slower and more modest than might be predicted from in vitro and ex vivo experiments.

scholarly journals MR imaging of model drug distribution in simulated vitreous

2015 ◽  
Vol 1 (1) ◽  
pp. 236-239 ◽  
Author(s):  
Sandra Stein ◽  
Christian Simroth-Loch ◽  
Sönke Langner ◽  
Stefan Hadlich ◽  
Oliver Stachs ◽  
...  
Keyword(s):  
Molecular Weight ◽  
Ex Vivo ◽  
Drug Distribution ◽  
Injection Technique ◽  
Innovative Therapy ◽  
Age Related ◽  
The Impact

AbstractThe in vitro and in vivo characterization of intravitreal injections plays an important role in developing innovative therapy approaches. Using the established vitreous model (VM) and eye movement system (EyeMoS) the distribution of contrast agents with different molecular weight was studied in vitro. The impact of the simulated age-related vitreal liquefaction (VL) on drug distribution in VM was examined either with injection through the gel phase or through the liquid phase. For comparison the distribution was studied ex vivo in the porcine vitreous. The studies were performed in a magnetic resonance (MR) scanner. As expected, with increasing molecular weight the diffusion velocity and the visual distribution of the injected substances decreased. Similar drug distribution was observed in VM and in porcine eye. VL causes enhanced convective flow and faster distribution in VM. Confirming the importance of the injection technique in progress of VL, injection through gelatinous phase caused faster distribution into peripheral regions of the VM than following injection through liquefied phase. VM and MR scanner in combination present a new approach for the in vitro characterization of drug release and distribution of intravitreal dosage forms.

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