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Casolo A, Maeo S, Balshaw TG, Lanza MB, Martin NRW, Nuccio S, Moro T, Paoli A, Felici F, Maffulli N, Eskofier B, Kinfe TM, Folland JP, Farina D, Vecchio AD. Non-invasive estimation of muscle fibre size from high-density electromyography. J Physiol 2023; 601:1831-1850. [PMID: 36929484 DOI: 10.1113/jp284170] [Citation(s) in RCA: 3] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/25/2022] [Accepted: 03/13/2023] [Indexed: 03/18/2023] Open
Abstract
Because of the biophysical relation between muscle fibre diameter and the propagation velocity of action potentials along the muscle fibres, motor unit conduction velocity could be a non-invasive index of muscle fibre size in humans. However, the relation between motor unit conduction velocity and fibre size has been only assessed indirectly in animal models and in human patients with invasive intramuscular EMG recordings, or it has been mathematically derived from computer simulations. By combining advanced non-invasive techniques to record motor unit activity in vivo, i.e. high-density surface EMG, with the gold standard technique for muscle tissue sampling, i.e. muscle biopsy, here we investigated the relation between the conduction velocity of populations of motor units identified from the biceps brachii muscle, and muscle fibre diameter. We demonstrate the possibility of predicting muscle fibre diameter (R2 = 0.66) and cross-sectional area (R2 = 0.65) from conduction velocity estimates with low systematic bias (∼2% and ∼4% respectively) and a relatively low margin of individual error (∼8% and ∼16%, respectively). The proposed neuromuscular interface opens new perspectives in the use of high-density EMG as a non-invasive tool to estimate muscle fibre size without the need of surgical biopsy sampling. The non-invasive nature of high-density surface EMG for the assessment of muscle fibre size may be useful in studies monitoring child development, ageing, space and exercise physiology, although the applicability and validity of the proposed methodology need to be more directly assessed in these specific populations by future studies. KEY POINTS: Because of the biophysical relation between muscle fibre size and the propagation velocity of action potentials along the sarcolemma, motor unit conduction velocity could represent a potential non-invasive candidate for estimating muscle fibre size in vivo. This relation has been previously assessed in animal models and humans with invasive techniques, or it has been mathematically derived from simulations. By combining high-density surface EMG with muscle biopsy, here we explored the relation between the conduction velocity of populations of motor units and muscle fibre size in healthy individuals. Our results confirmed that motor unit conduction velocity can be considered as a novel biomarker of fibre size, which can be adopted to predict muscle fibre diameter and cross-sectional area with low systematic bias and margin of individual error. The proposed neuromuscular interface opens new perspectives in the use of high-density EMG as a non-invasive tool to estimate muscle fibre size without the need of surgical biopsy sampling.
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Affiliation(s)
- Andrea Casolo
- Department of Biomedical Sciences, University of Padova, Padua, Italy
| | - Sumiaki Maeo
- Faculty of Sport and Health Science, Ritsumeikan University, Kusatsu, Shiga, Japan
- School of Sport, Exercise & Health Sciences, Loughborough University, Loughborough, UK
| | - Thomas G Balshaw
- School of Sport, Exercise & Health Sciences, Loughborough University, Loughborough, UK
- Versus Arthritis Centre for Sport, Exercise and Osteoarthritis Research, Loughborough University, Leicestershire, UK
| | - Marcel B Lanza
- Department of Physical Therapy and Rehabilitation Science, University of Maryland, Baltimore, MD, USA
| | - Neil R W Martin
- Versus Arthritis Centre for Sport, Exercise and Osteoarthritis Research, Loughborough University, Leicestershire, UK
| | - Stefano Nuccio
- Department of Movement, Human and Health Sciences, University of Rome 'Foro Italico', Rome, Italy
| | - Tatiana Moro
- Department of Biomedical Sciences, University of Padova, Padua, Italy
| | - Antonio Paoli
- Department of Biomedical Sciences, University of Padova, Padua, Italy
| | - Francesco Felici
- Department of Movement, Human and Health Sciences, University of Rome 'Foro Italico', Rome, Italy
| | - Nicola Maffulli
- Department of Trauma and Orthopaedic Surgery, School Medicine, Surgery and Dentistry, University of Salerno, Salerno, Italy
- School of Pharmacy and Bioengineering, Keele University School of Medicine, Stoke on Trent, UK
- Queen Mary University of London, Barts and the London School of Medicine and Dentistry, Centre for Sports and Exercise Medicine, Mile End Hospital, London, UK
| | - Bjoern Eskofier
- Department Artificial Intelligence in Biomedical Engineering, Friedrich-Alexander University Erlangen-Nürnberg, Erlangen, Germany
| | - Thomas M Kinfe
- Department Artificial Intelligence in Biomedical Engineering, Friedrich-Alexander University Erlangen-Nürnberg, Erlangen, Germany
| | - Jonathan P Folland
- School of Sport, Exercise & Health Sciences, Loughborough University, Loughborough, UK
- Versus Arthritis Centre for Sport, Exercise and Osteoarthritis Research, Loughborough University, Leicestershire, UK
| | - Dario Farina
- Department of Bioengineering, Imperial College London, London, UK
| | - Alessandro Del Vecchio
- Department Artificial Intelligence in Biomedical Engineering, Friedrich-Alexander University Erlangen-Nürnberg, Erlangen, Germany
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Aldahhan RA, Motawei KH, Al-Hariri MT. Lipotoxicity-related sarcopenia: a review. J Med Life 2022; 15:1334-1339. [PMID: 36567835 PMCID: PMC9762358 DOI: 10.25122/jml-2022-0157] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/27/2022] [Accepted: 07/27/2022] [Indexed: 12/27/2022] Open
Abstract
A body of literature supports the postulation that a persistent lipid metabolic imbalance causes lipotoxicity, "an abnormal fat storage in the peripheral organs". Hence, lipotoxicity could somewhat explain the process of sarcopenia, an aging-related, gradual, and involuntary decline in skeletal muscle strength and mass associated with several health complications. This review focuses on the recent mechanisms underlying lipotoxicity-related sarcopenia. A vicious cycle occurs between sarcopenia and ectopic fat storage via a complex interplay of mitochondrial dysfunction, pro-inflammatory cytokine production, oxidative stress, collagen deposition, extracellular matrix remodeling, and life habits. The repercussions of lipotoxicity exacerbation of sarcopenia can include increased disability, morbidity, and mortality. This suggests that appropriate lipotoxicity management should be considered the primary target for the prevention and/or treatment of chronic musculoskeletal and other aging-related disorders. Further advanced research is needed to understand the molecular details of lipotoxicity and its consequences for sarcopenia and sarcopenia-related comorbidities.
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Affiliation(s)
| | - Kamaluddin Hasan Motawei
- Department of Anatomy, College of Medicine, Imam Abdulrahman Bin Faisal University, Dammam, Saudi Arabia
| | - Mohammed Taha Al-Hariri
- Department of Physiology, College of Medicine, Imam Abdulrahman Bin Faisal University, Dammam, Saudi Arabia,Corresponding Author: Mohammed Taha Al-Hariri, Department of Physiology, College of Medicine, Imam Abdulrahman Bin Faisal University, Dammam, Saudi Arabia. E-mail:
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Davis LA, Fogarty MJ, Brown A, Sieck GC. Structure and Function of the Mammalian Neuromuscular Junction. Compr Physiol 2022; 12:3731-3766. [PMID: 35950651 PMCID: PMC10461538 DOI: 10.1002/cphy.c210022] [Citation(s) in RCA: 5] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022]
Abstract
The mammalian neuromuscular junction (NMJ) comprises a presynaptic terminal, a postsynaptic receptor region on the muscle fiber (endplate), and the perisynaptic (terminal) Schwann cell. As with any synapse, the purpose of the NMJ is to transmit signals from the nervous system to muscle fibers. This neural control of muscle fibers is organized as motor units, which display distinct structural and functional phenotypes including differences in pre- and postsynaptic elements of NMJs. Motor units vary considerably in the frequency of their activation (both motor neuron discharge rate and duration/duty cycle), force generation, and susceptibility to fatigue. For earlier and more frequently recruited motor units, the structure and function of the activated NMJs must have high fidelity to ensure consistent activation and continued contractile response to sustain vital motor behaviors (e.g., breathing and postural balance). Similarly, for higher force less frequent behaviors (e.g., coughing and jumping), the structure and function of recruited NMJs must ensure short-term reliable activation but not activation sustained for a prolonged period in which fatigue may occur. The NMJ is highly plastic, changing structurally and functionally throughout the life span from embryonic development to old age. The NMJ also changes under pathological conditions including acute and chronic disease. Such neuroplasticity often varies across motor unit types. © 2022 American Physiological Society. Compr Physiol 12:1-36, 2022.
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Affiliation(s)
- Leah A. Davis
- Department of Physiology & Biomedical Engineering, Mayo Clinic, Rochester, Minnesota, USA
| | - Matthew J. Fogarty
- Department of Physiology & Biomedical Engineering, Mayo Clinic, Rochester, Minnesota, USA
| | - Alyssa Brown
- Department of Physiology & Biomedical Engineering, Mayo Clinic, Rochester, Minnesota, USA
| | - Gary C. Sieck
- Department of Physiology & Biomedical Engineering, Mayo Clinic, Rochester, Minnesota, USA
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Excess Accumulation of Lipid Impairs Insulin Sensitivity in Skeletal Muscle. Int J Mol Sci 2020; 21:ijms21061949. [PMID: 32178449 PMCID: PMC7139950 DOI: 10.3390/ijms21061949] [Citation(s) in RCA: 32] [Impact Index Per Article: 8.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/18/2020] [Revised: 03/09/2020] [Accepted: 03/10/2020] [Indexed: 12/12/2022] Open
Abstract
Both glucose and free fatty acids (FFAs) are used as fuel sources for energy production in a living organism. Compelling evidence supports a role for excess fatty acids synthesized in intramuscular space or dietary intermediates in the regulation of skeletal muscle function. Excess FFA and lipid droplets leads to intramuscular accumulation of lipid intermediates. The resulting downregulation of the insulin signaling cascade prevents the translocation of glucose transporter to the plasma membrane and glucose uptake into skeletal muscle, leading to metabolic disorders such as type 2 diabetes. The mechanisms underlining metabolic dysfunction in skeletal muscle include accumulation of intracellular lipid derivatives from elevated plasma FFAs. This paper provides a review of the molecular mechanisms underlying insulin-related signaling pathways after excess accumulation of lipids.
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Altarawneh MM, Hanson ED, Betik AC, Petersen AC, Hayes A, McKenna MJ. Effects of testosterone suppression, hindlimb immobilization, and recovery on [ 3H]ouabain binding site content and Na +, K +-ATPase isoforms in rat soleus muscle. J Appl Physiol (1985) 2020; 128:501-513. [PMID: 31854248 DOI: 10.1152/japplphysiol.01077.2018] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
We investigated the effects of testosterone suppression, hindlimb immobilization, and recovery on skeletal muscle Na+,K+-ATPase (NKA), measured via [3H]ouabain binding site content (OB) and NKA isoform abundances (α1-3, β1-2). Male rats underwent castration or sham surgery plus 7 days of rest, 10 days of unilateral immobilization (cast), and 14 days of recovery, with soleus muscles obtained at each time from cast and noncast legs. Testosterone reduction did not modify OB or NKA isoforms in nonimmobilized control muscles. With sham surgery, OB was lower after immobilization in the cast leg than in both the noncast leg (-26%, P = 0.023) and the nonimmobilized control (-34%, P = 0.001), but OB subsequently recovered. With castration, OB was lower after immobilization in the cast leg than in the nonimmobilized control (-34%, P = 0.001), and remained depressed at recovery (-34%, P = 0.001). NKA isoforms did not differ after immobilization or recovery in the sham group. After castration, α2 in the cast leg was ~60% lower than in the noncast leg (P = 0.004) and nonimmobilized control (P = 0.004) and after recovery remained lower than the nonimmobilized control (-42%, P = 0.039). After immobilization, β1 was lower in the cast than the noncast leg (-26%, P = 0.018), with β2 lower in the cast leg than in the noncast leg (-71%, P = 0.004) and nonimmobilized control (-65%, P = 0.012). No differences existed for α1 or α3. Thus, both OB and α2 decreased after immobilization and recovery in the castration group, with α2, β1, and β2 isoform abundances decreased with immobilization compared with the sham group. Therefore, testosterone suppression in rats impaired restoration of immobilization-induced lowered number of functional NKA and α2 isoforms in soleus muscle.NEW & NOTEWORTHY: The Na+,K+-ATPase (NKA) is vital in muscle excitability and function. In rats, immobilization depressed soleus muscle NKA, with declines in [3H]ouabain binding, which was restored after 14 days recovery. After testosterone suppression by castration, immobilization depressed [3H]ouabain binding, depressed α2, β1, and β2 isoforms, and abolished subsequent recovery in [3H]ouabain binding and α2 isoforms. This may have implications for functional recovery for inactive men with lowered testosterone levels, such as in prostate cancer or aging.
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Affiliation(s)
- Muath M Altarawneh
- Institute for Health and Sport, Victoria University, Melbourne, Australia
| | - Erik D Hanson
- Institute for Health and Sport, Victoria University, Melbourne, Australia.,Department of Exercise and Sport Science, University of North Carolina at Chapel Hill, North Carolina
| | - Andrew C Betik
- Institute for Health and Sport, Victoria University, Melbourne, Australia.,Institute for Physical Activity and Nutrition, School of Exercise and Nutrition Sciences, Deakin University, Geelong, Australia
| | - Aaron C Petersen
- Institute for Health and Sport, Victoria University, Melbourne, Australia
| | - Alan Hayes
- Institute for Health and Sport, Victoria University, Melbourne, Australia.,Australian Institute for Musculoskeletal Science, Victoria University, Melbourne, Australia
| | - Michael J McKenna
- Institute for Health and Sport, Victoria University, Melbourne, Australia
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CASOLO ANDREA, FARINA DARIO, FALLA DEBORAH, BAZZUCCHI ILENIA, FELICI FRANCESCO, DEL VECCHIO ALESSANDRO. Strength Training Increases Conduction Velocity of High-Threshold Motor Units. Med Sci Sports Exerc 2019; 52:955-967. [DOI: 10.1249/mss.0000000000002196] [Citation(s) in RCA: 14] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
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7
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Lipotoxicity, aging, and muscle contractility: does fiber type matter? GeroScience 2019; 41:297-308. [PMID: 31227962 DOI: 10.1007/s11357-019-00077-z] [Citation(s) in RCA: 25] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/01/2019] [Accepted: 06/05/2019] [Indexed: 12/18/2022] Open
Abstract
Sarcopenia is a universal characteristic of the aging process and is often accompanied by increases in whole-body adiposity. These changes in body composition have important clinical implications, given that loss of muscle and gain of fat mass are both significantly and independently associated with declining physical performance as well as an increased risk for disability, hospitalizations, and mortality in older individuals. This increased fat mass is not exclusively stored in adipose depots but may become deposited in non-adipose tissues, such as skeletal muscle, when the oxidative capacity of the adipose tissue itself is exceeded. The redistributed adipose tissue is thought to exert detrimental local effects on the muscle environment given the close proximity. Thus, sarcopenia observed with aging may be better defined in the context of loss of muscle quality rather than loss of muscle quantity per se. In this perspective, we briefly review the age-related physiological changes in cellularity, secretory profiles, and inflammatory status of adipose tissue which drive lipotoxicity (spillover) of skeletal muscle and then provide evidence of how this may affect specific fiber type contractility. We focus on biological contributors (cellular machinery) to contractility for which there is some evidence of vulnerability to lipid stress distinguishing between fiber types.
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Methenitis S, Stasinaki AN, Zaras N, Spengos K, Karandreas N, Terzis G. Intramuscular fibre conduction velocity and muscle fascicle length in human vastus lateralis. Appl Physiol Nutr Metab 2018; 44:133-138. [PMID: 30011376 DOI: 10.1139/apnm-2018-0081] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
Muscle fascicle length and muscle fibre conduction velocity (MFCV) are thought to be important parameters for power performance. It might be expected that faster muscle fibre conduction velocities would compensate for longer fascicle lengths to increase the speed of action potential propagation along the elongated fibres. However, the relationship between muscle fascicle length and MFCV remains unknown. The aim of the present study was to explore the relationship between average vastus lateralis MFCV and average fascicle length. In 17 moderately trained, healthy, male, physical education students (age, 23.4 ± 3.1 years; body height, 178 ± 5.5 cm; body mass, 82.7 ± 6.9 kg; body mass index, 24.6 ± 1.5 kg·m-2) resting MFCV was measured with intramuscular microelectrodes while muscle architecture was evaluated with ultrasonography. Fascicle length was highly correlated with total MFCV (r = 0.923, p = 0.000), maximum MFCV (r = 0.949, p = 0.000), and MFCV of the fastest (r = 0.709, p = 0.001), but not of the slowest fibres (r = 0.131, p = 0.616). No significant correlations were also found between vastus lateralis thickness or fascicle angle with any of MFCV parameters (r = 0.145-0.430; R2 < 0.130; p > 0.05). These data indicate that average MFCV is associated with average fascicle length in vastus lateralis muscle in different individuals. It seems that participants with longer fascicle lengths have also higher MFCVs.
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Affiliation(s)
- Spyridon Methenitis
- a Sports Performance Laboratory, School of Physical Education and Sports Science, National and Kapodistrian University of Athens, Ethnikis Antistassis 41, 172 37, Daphne, Athens, Greece
| | - Angeliki-Nikoletta Stasinaki
- a Sports Performance Laboratory, School of Physical Education and Sports Science, National and Kapodistrian University of Athens, Ethnikis Antistassis 41, 172 37, Daphne, Athens, Greece
| | - Nikolaos Zaras
- a Sports Performance Laboratory, School of Physical Education and Sports Science, National and Kapodistrian University of Athens, Ethnikis Antistassis 41, 172 37, Daphne, Athens, Greece
| | - Konstantinos Spengos
- b A' Neurology Clinic, Aiginition Hospital, Medical School, National and Kapodistrian University of Athens, Ethnikis Antistassis 41, 172 37, Daphne, Athens, Greece
| | - Nikolaos Karandreas
- b A' Neurology Clinic, Aiginition Hospital, Medical School, National and Kapodistrian University of Athens, Ethnikis Antistassis 41, 172 37, Daphne, Athens, Greece
| | - Gerasimos Terzis
- a Sports Performance Laboratory, School of Physical Education and Sports Science, National and Kapodistrian University of Athens, Ethnikis Antistassis 41, 172 37, Daphne, Athens, Greece
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Methenitis S, Karandreas N, Spengos K, Zaras N, Stasinaki AN, Terzis G. Muscle Fiber Conduction Velocity, Muscle Fiber Composition, and Power Performance. Med Sci Sports Exerc 2017; 48:1761-71. [PMID: 27128672 DOI: 10.1249/mss.0000000000000954] [Citation(s) in RCA: 48] [Impact Index Per Article: 6.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
PURPOSE The aim of this study was to explore the relationship between muscle fiber conduction velocity (MFCV), fiber type composition, and power performance in participants with different training background. METHODS Thirty-eight young males with different training background participated: sedentary (n = 10), endurance runners (n = 9), power trained (n = 10), and strength trained (n = 9). They performed maximal countermovement jumps (CMJ) and maximal isometric leg press for the measurement of the rate of force development (RFD). Resting vastus lateralis MFCV was measured with intramuscular microelectrodes on a different occasion, whereas muscle fiber type and cross-sectional area (CSA) of vastus lateralis were evaluated through muscle biopsies 1wk later. RESULTS MFCV, CMJ power, RFD, and % CSA of type II and type IIx fibers were higher for the power-trained group (P < 0.001). No difference was found between sedentary participants and endurance runners in these variables, but both of these groups performed worse than strength/power participants. Close correlations were found between MFCV and fiber CSA as well as the % CSA of all fiber types as well as with RFD and CMJ power (r = 0.712-0.943, P < 0.005). Partial correlations revealed that the % CSA of IIx fibers dictates a large part of the correlation between MFCV and RFD, power performance. Significant models for the prediction of the % CSA of type IIa and type II as well as the CSA of all muscle fibers based upon MFCV, RFD, and CMJ were revealed (P = 0.000). CONCLUSION MFCV is closely associated with muscle fiber % CSA. RFD and jumping power are associated with the propagation of the action potentials along the muscle fibers. This link is regulated by the size and the distribution of type II, and especially type IIx muscle fibers.
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Affiliation(s)
- Spyridon Methenitis
- 1Athletics Laboratory, School of Physical Education and Sports Science, National and Kapodistrian University of Athens, Athens, GREECE; and 2Neurology Clinic, Aiginition Hospital, Medical School, National and Kapodistrian University of Athens, Athens, GREECE
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Wyckelsma VL, McKenna MJ. Effects of Age on Na(+),K(+)-ATPase Expression in Human and Rodent Skeletal Muscle. Front Physiol 2016; 7:316. [PMID: 27531982 PMCID: PMC4969555 DOI: 10.3389/fphys.2016.00316] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/25/2016] [Accepted: 07/13/2016] [Indexed: 12/30/2022] Open
Abstract
The maintenance of transmembrane Na(+) and K(+) concentration gradients and membrane potential is vital for the production of force in skeletal muscle. In aging an inability to maintain ion regulation and membrane potential would have adverse consequences on the capacity for performing repeated muscle contractions, which are critical for everyday activities and functional independence. This short review focusses on the effects of aging on one major and vital component affecting muscle Na(+) and K(+) concentrations, membrane potential and excitability in skeletal muscle, the Na(+),K(+)-ATPase (Na(+),K(+)-pump, NKA) protein. The review examines the effects of age on NKA in both human and rodent models and highlights a distant lack of research in NKA with aging. In rodents, the muscle NKA measured by [(3)H]ouabain binding site content, declines with advanced age from peak values in early life. In human skeletal muscle, however, there appears to be no age effect on [(3)H]ouabain binding site content in physically active older adults between 55 and 76 years compared to those aged between 18 and 30 years of age. Analysis of the NKA isoforms reveal differential changes with age in fiber-types in both rat and humans. The data show considerable disparities, suggesting different regulation of NKA isoforms between rodents and humans. Finally we review the importance of physical activity on NKA content in older humans. Findings suggest that physical activity levels of an individual may have a greater effect on regulating the NKA content in skeletal muscle rather than aging per se, at least up until 80 years of age.
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Affiliation(s)
- Victoria L Wyckelsma
- Clinical Exercise Science Program, Institute of Sport Exercise and Active Living, Victoria University Melbourne, VIC, Australia
| | - Michael J McKenna
- Clinical Exercise Science Program, Institute of Sport Exercise and Active Living, Victoria University Melbourne, VIC, Australia
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Pirkmajer S, Chibalin AV. Na,K-ATPase regulation in skeletal muscle. Am J Physiol Endocrinol Metab 2016; 311:E1-E31. [PMID: 27166285 DOI: 10.1152/ajpendo.00539.2015] [Citation(s) in RCA: 70] [Impact Index Per Article: 8.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 12/31/2015] [Accepted: 05/02/2016] [Indexed: 12/17/2022]
Abstract
Skeletal muscle contains one of the largest and the most dynamic pools of Na,K-ATPase (NKA) in the body. Under resting conditions, NKA in skeletal muscle operates at only a fraction of maximal pumping capacity, but it can be markedly activated when demands for ion transport increase, such as during exercise or following food intake. Given the size, capacity, and dynamic range of the NKA pool in skeletal muscle, its tight regulation is essential to maintain whole body homeostasis as well as muscle function. To reconcile functional needs of systemic homeostasis with those of skeletal muscle, NKA is regulated in a coordinated manner by extrinsic stimuli, such as hormones and nerve-derived factors, as well as by local stimuli arising in skeletal muscle fibers, such as contractions and muscle energy status. These stimuli regulate NKA acutely by controlling its enzymatic activity and/or its distribution between the plasma membrane and the intracellular storage compartment. They also regulate NKA chronically by controlling NKA gene expression, thus determining total NKA content in skeletal muscle and its maximal pumping capacity. This review focuses on molecular mechanisms that underlie regulation of NKA in skeletal muscle by major extrinsic and local stimuli. Special emphasis is given to stimuli and mechanisms linking regulation of NKA and energy metabolism in skeletal muscle, such as insulin and the energy-sensing AMP-activated protein kinase. Finally, the recently uncovered roles for glutathionylation, nitric oxide, and extracellular K(+) in the regulation of NKA in skeletal muscle are highlighted.
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Affiliation(s)
- Sergej Pirkmajer
- Institute of Pathophysiology, Faculty of Medicine, University of Ljubljana, Ljubljana, Slovenia; and
| | - Alexander V Chibalin
- Department of Molecular Medicine and Surgery, Karolinska Institutet, Stockholm, Sweden
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Abstract
The vital gradients of Na+ and K+ across the plasma membrane of animal cells are maintained by the Na,K-ATPase, an αβ enzyme complex, whose α subunit carries out the ion transport and ATP hydrolysis. The specific roles of the β subunit isoforms are less clear, though β2 is essential for motor physiology in mammals. Here, we show that compared to β1 and β3, β2 stabilizes the Na+-occluded E1P state relative to the outward-open E2P state, and that the effect is mediated by its transmembrane domain. Molecular dynamics simulations further demonstrate that the tilt angle of the β transmembrane helix correlates with its functional effect, suggesting that the relative orientation of β modulates ion binding at the α subunit. β2 is primarily expressed in granule neurons and glomeruli in the cerebellum, and we propose that its unique functional characteristics are important to respond appropriately to the cerebellar Na+ and K+ gradients.
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13
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Wyckelsma VL, McKenna MJ, Levinger I, Petersen AC, Lamboley CR, Murphy RM. Cell specific differences in the protein abundances of GAPDH and Na(+),K(+)-ATPase in skeletal muscle from aged individuals. Exp Gerontol 2015; 75:8-15. [PMID: 26747222 DOI: 10.1016/j.exger.2015.12.010] [Citation(s) in RCA: 19] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/13/2015] [Revised: 12/12/2015] [Accepted: 12/27/2015] [Indexed: 10/22/2022]
Abstract
Na(+), K(+)-ATPase (NKA) isoforms (α1,α2,α3,β1,β2,β3) are involved in the maintenance of membrane potential and hence are important regulators of cellular homeostasis. Given the age-related decline in skeletal muscle function, we investigated whether the natural physiological process of aging is associated with altered abundance of NKA isoforms (α1,α2,α3,β1,β2,β3) or of the commonly used control protein, glyceraldehyde-3-phosphate dehydrogenase (GAPDH). Importantly, measurements were made in both whole muscle or specific fiber types obtained from skeletal muscle biopsies. Seventeen healthy older (AGED, 69.4 ± 3.5 years, mean ± SD) and 14 younger (YOUNG, 25.5 ± 2.8 years) adults underwent a muscle biopsy for biochemical analyses. Comparing homogenates from AGED and YOUNG individuals revealed higher β3 isoform (p<0.05) and lower GAPDH (p<0.05). Analysis of individual fibers in muscle from YOUNG individuals, showed greater α3 and β2 isoforms, and more GAPDH in Type II compared with Type I fibers (p<0.05). In the AGED, GAPDH was higher in Type II compared with Type I fibers (p<0.05), there were no fiber type differences in the NKA isoforms (p>0.05). Compared with the same fiber type in YOUNG, α1 was greater (Type I) and α3 lower (Type II), while in both fiber types, β2 was lower, β3 greater and GAPDH lower, in muscle from AGED individuals (all p<0.05). Overall, we demonstrate that (i) GAPDH is an inappropriate choice of protein for normalization in all skeletal muscle research and (ii) full understanding of the role of NKA isoforms in human skeletal muscle requires consideration of age and muscle fiber type.
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Affiliation(s)
- Victoria L Wyckelsma
- Institute of Sport, Exercise and Active Living (ISEAL), Victoria University, Victoria, Australia; Department of Biochemistry and Genetics, La Trobe Institute for Molecular Science, La Trobe University, Melbourne, Victoria, Australia
| | - Michael J McKenna
- Institute of Sport, Exercise and Active Living (ISEAL), Victoria University, Victoria, Australia
| | - Itamar Levinger
- Institute of Sport, Exercise and Active Living (ISEAL), Victoria University, Victoria, Australia
| | - Aaron C Petersen
- Institute of Sport, Exercise and Active Living (ISEAL), Victoria University, Victoria, Australia
| | - Cedric R Lamboley
- Institute of Sport, Exercise and Active Living (ISEAL), Victoria University, Victoria, Australia
| | - Robyn M Murphy
- Department of Biochemistry and Genetics, La Trobe Institute for Molecular Science, La Trobe University, Melbourne, Victoria, Australia.
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DiFranco M, Hakimjavadi H, Lingrel JB, Heiny JA. Na,K-ATPase α2 activity in mammalian skeletal muscle T-tubules is acutely stimulated by extracellular K+. ACTA ACUST UNITED AC 2015; 146:281-94. [PMID: 26371210 PMCID: PMC4586590 DOI: 10.1085/jgp.201511407] [Citation(s) in RCA: 56] [Impact Index Per Article: 6.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/11/2015] [Accepted: 08/21/2015] [Indexed: 11/20/2022]
Abstract
The K+ affinity of the Na,K-ATPase α2 isoform matches its activity to the range of extracellular K+ concentrations in the T-tubules at rest and during contraction, maintaining the excitability of active muscle. The Na,K-ATPase α2 isoform is the predominant Na,K-ATPase in adult skeletal muscle and the sole Na,K-ATPase in the transverse tubules (T-tubules). In quiescent muscles, the α2 isozyme operates substantially below its maximal transport capacity. Unlike the α1 isoform, the α2 isoform is not required for maintaining resting ion gradients or the resting membrane potential, canonical roles of the Na,K-ATPase in most other cells. However, α2 activity is stimulated immediately upon the start of contraction and, in working muscles, its contribution is crucial to maintaining excitation and resisting fatigue. Here, we show that α2 activity is determined in part by the K+ concentration in the T-tubules, through its K+ substrate affinity. Apparent K+ affinity was determined from measurements of the K1/2 for K+ activation of pump current in intact, voltage-clamped mouse flexor digitorum brevis muscle fibers. Pump current generated by the α2 Na,K-ATPase, Ip, was identified as the outward current activated by K+ and inhibited by micromolar ouabain. Ip was outward at all potentials studied (−90 to −30 mV) and increased with depolarization in the subthreshold range, −90 to −50 mV. The Q10 was 2.1 over the range of 22–37°C. The K1/2,K of Ip was 4.3 ± 0.3 mM at −90 mV and was relatively voltage independent. This K+ affinity is lower than that reported for other cell types but closely matches the dynamic range of extracellular K+ concentrations in the T-tubules. During muscle contraction, T-tubule luminal K+ increases in proportion to the frequency and duration of action potential firing. This K1/2,K predicts a low fractional occupancy of K+ substrate sites at the resting extracellular K+ concentration, with occupancy increasing in proportion to the frequency of membrane excitation. The stimulation of preexisting pumps by greater K+ site occupancy thus provides a rapid mechanism for increasing α2 activity in working muscles.
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Affiliation(s)
- Marino DiFranco
- Department of Physiology, David Geffen School of Medicine, University of California, Los Angeles, Los Angeles, CA 90095
| | - Hesamedin Hakimjavadi
- Department of Molecular and Cellular Physiology, University of Cincinnati College of Medicine, Cincinnati, OH 45267
| | - Jerry B Lingrel
- Department of Molecular and Cellular Physiology, University of Cincinnati College of Medicine, Cincinnati, OH 45267
| | - Judith A Heiny
- Department of Molecular and Cellular Physiology, University of Cincinnati College of Medicine, Cincinnati, OH 45267
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15
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Barrientos G, Llanos P, Hidalgo J, Bolaños P, Caputo C, Riquelme A, Sánchez G, Quest AFG, Hidalgo C. Cholesterol removal from adult skeletal muscle impairs excitation-contraction coupling and aging reduces caveolin-3 and alters the expression of other triadic proteins. Front Physiol 2015; 6:105. [PMID: 25914646 PMCID: PMC4392612 DOI: 10.3389/fphys.2015.00105] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/31/2015] [Accepted: 03/16/2015] [Indexed: 12/30/2022] Open
Abstract
Cholesterol and caveolin are integral membrane components that modulate the function/location of many cellular proteins. Skeletal muscle fibers, which have unusually high cholesterol levels in transverse tubules, express the caveolin-3 isoform but its association with transverse tubules remains contentious. Cholesterol removal impairs excitation–contraction (E–C) coupling in amphibian and mammalian fetal skeletal muscle fibers. Here, we show that treating single muscle fibers from adult mice with the cholesterol removing agent methyl-β-cyclodextrin decreased fiber cholesterol by 26%, altered the location pattern of caveolin-3 and of the voltage dependent calcium channel Cav1.1, and suppressed or reduced electrically evoked Ca2+ transients without affecting membrane integrity or causing sarcoplasmic reticulum (SR) calcium depletion. We found that transverse tubules from adult muscle and triad fractions that contain ~10% attached transverse tubules, but not SR membranes, contained caveolin-3 and Cav1.1; both proteins partitioned into detergent-resistant membrane fractions highly enriched in cholesterol. Aging entails significant deterioration of skeletal muscle function. We found that triad fractions from aged rats had similar cholesterol and RyR1 protein levels compared to triads from young rats, but had lower caveolin-3 and glyceraldehyde 3-phosphate dehydrogenase and increased Na+/K+-ATPase protein levels. Both triad fractions had comparable NADPH oxidase (NOX) activity and protein content of NOX2 subunits (p47phox and gp91phox), implying that NOX activity does not increase during aging. These findings show that partial cholesterol removal impairs E–C coupling and alters caveolin-3 and Cav1.1 location pattern, and that aging reduces caveolin-3 protein content and modifies the expression of other triadic proteins. We discuss the possible implications of these findings for skeletal muscle function in young and aged animals.
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Affiliation(s)
- Genaro Barrientos
- Physiology and Biophysics Program, Institute of Biomedical Sciences, School of Medicine, University of Chile Santiago, Chile
| | - Paola Llanos
- Institute for Research in Dental Sciences, Faculty of Dentistry, University of Chile Santiago, Chile
| | - Jorge Hidalgo
- Physiology and Biophysics Program, Institute of Biomedical Sciences, School of Medicine, University of Chile Santiago, Chile
| | - Pura Bolaños
- Centre of Biophysics and Biochemistry, Venezuelan Institute for Scientific Research Caracas, Venezuela
| | - Carlo Caputo
- Centre of Biophysics and Biochemistry, Venezuelan Institute for Scientific Research Caracas, Venezuela
| | - Alexander Riquelme
- Biomedical Neuroscience Institute, School of Medicine, University of Chile Santiago, Chile
| | - Gina Sánchez
- Biomedical Neuroscience Institute, School of Medicine, University of Chile Santiago, Chile ; Pathophysiology Program, Institute of Biomedical Sciences, School of Medicine, University of Chile Santiago, Chile ; Center for Molecular Studies of the Cell, School of Medicine, University of Chile Santiago, Chile
| | - Andrew F G Quest
- Center for Molecular Studies of the Cell, School of Medicine, University of Chile Santiago, Chile ; Laboratory of Cell Communication, Program in Cell and Molecular Biology, Institute of Biomedical Sciences, School of Medicine, University of Chile Santiago, Chile ; Advanced Center for Chronic Diseases and Network for Metabolic Stress Signaling, University of Chile Santiago, Chile
| | - Cecilia Hidalgo
- Physiology and Biophysics Program, Institute of Biomedical Sciences, School of Medicine, University of Chile Santiago, Chile ; Biomedical Neuroscience Institute, School of Medicine, University of Chile Santiago, Chile ; Center for Molecular Studies of the Cell, School of Medicine, University of Chile Santiago, Chile
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16
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Thomassen M, Murphy RM, Bangsbo J. Fibre type-specific change in FXYD1 phosphorylation during acute intense exercise in humans. J Physiol 2013; 591:1523-33. [PMID: 23359667 DOI: 10.1113/jphysiol.2012.247312] [Citation(s) in RCA: 30] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/22/2022] Open
Abstract
The aim of the present study was to examine fibre type-specific Na(+)-K(+) pump subunit expression and exercise-induced alterations in phospholemman (FXYD1) phosphorylation in humans. Segments of human skeletal muscle fibres were dissected and fibre typed, and protein expression was determined by Western blotting. The protein expression of the Na(+)-K(+) pump α2 isoform was lower in type I than in type II fibres (0.63 ± 0.04 a.u. vs. 1.00 ± 0.07 a.u., P < 0.001), while protein expression of the Na(+)-K(+) pump α1 and β1 isoforms was not different. Protein expression of the ATP-dependent potassium channel Kir6.2 was higher in type I compared with type II fibres. In both type I (P < 0.01) and type II fibres (P < 0.001) the AB_FXYD1 signal was lower after exercise compared with rest, indicating an increase in unspecific FXYD1 phosphorylation. The FXYD1 serine 68 phosphorylation was higher (P < 0.001) after exercise compared with rest in type II fibres (1.90 ± 0.25 vs. 1.00 ± 0.08) and not changed in type I fibres. Total FXYD1 was not expressed in a fibre type-specific manner. Expression of phosphofructokinase was lower (P < 0.001) in type I than in type II fibres, whereas citrate synthase and 3-hydroxyacyl-CoA dehydrogenase were more abundant (P < 0.001) in type I fibres. In conclusion, FXYD1 phosphorylation at serine 68 increased after an acute bout of intense exercise in human type II fibres, while AB_FXYD1 signal intensity was lower in both type I and type II fibres, indicating fibre type-specific differences in FXYD1 phosphorylation on serine 63, serine 68 and threonine 69. This, together with the observation of a higher abundance of the Na(+)-K(+) pump α2 isoform protein in type II fibres, is likely to have importance for the exercise-induced human Na(+)-K(+) pump activity in the different fibre types.
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Affiliation(s)
- Martin Thomassen
- Department of Nutrition, Exercise and Sports, Section of Integrated Physiology, University of Copenhagen, August Krogh Building, Universitetsparken 13, 2. sal, 2100 Copenhagen, Denmark
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17
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McKenna MJ, Perry BD, Serpiello FR, Caldow MK, Levinger P, Cameron-Smith D, Levinger I. Unchanged [3H]ouabain binding site content but reduced Na+-K+ pump α2-protein abundance in skeletal muscle in older adults. J Appl Physiol (1985) 2012; 113:1505-11. [DOI: 10.1152/japplphysiol.01032.2011] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
Aging is associated with reduced muscle mass, weakness, and increased fatigability. In skeletal muscle, the Na+-K+ pump (NKA) is important in regulating Na+-K+ gradients, membrane excitability, and thus contractility, but the effects of aging on muscle NKA are unclear. We investigated whether aging is linked with reduced muscle NKA by contrasting muscle NKA isoform gene expression and protein abundance, and NKA total content in 17 Elderly (66.8 ± 6.4 yr, mean ± SD) and 16 Young adults (23.9 ± 2.2 yr). Participants underwent peak oxygen consumption assessment and a vastus lateralis muscle biopsy, which was analyzed for NKA α1-, α2-, α3-, β1-, β2-, and β3-isoform gene expression (real-time RT-PCR), protein abundance (immunoblotting), and NKA total content ([3H]ouabain binding sites). The Elderly had lower peak oxygen consumption (−36.7%, P = 0.000), strength (−36.3%, P = 0.001), NKA α2- (−24.4%, 11.9 ± 4.4 vs. 9.0 ± 2.7 arbitrary units, P = 0.049), and NKA β3-protein abundance (−23.0%, P = 0.041) than Young. The β3-mRNA was higher in Elderly compared with Young ( P = 0.011). No differences were observed between groups for other NKA isoform mRNA or protein abundance, or for [3H]ouabain binding site content. Thus skeletal muscle in elderly individuals was characterized by decreased NKA α2- and β3-protein abundance, but unchanged α1 abundance and [3H]ouabain binding. The latter was likely caused by reduced α2 abundance with aging, preventing an otherwise higher [3H]ouabain binding that might occur with a greater membrane density in smaller muscle fibers. Further study is required to verify reduced muscle NKA α2 with aging and possible contributions to impaired exercise capability and daily living activities.
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Affiliation(s)
- Michael J. McKenna
- Institute of Sport, Exercise and Active Living (ISEAL), Muscle, Ions and Exercise Group, Victoria University, Melbourne, Victoria, Australia
| | - Ben D. Perry
- Institute of Sport, Exercise and Active Living (ISEAL), Muscle, Ions and Exercise Group, Victoria University, Melbourne, Victoria, Australia
- School of Sport and Exercise Science, Muscle, Ions and Exercise Group, Victoria University, Melbourne, Victoria, Australia
| | - Fabio R. Serpiello
- Institute of Sport, Exercise and Active Living (ISEAL), Muscle, Ions and Exercise Group, Victoria University, Melbourne, Victoria, Australia
- School of Sport and Exercise Science, Muscle, Ions and Exercise Group, Victoria University, Melbourne, Victoria, Australia
- Facolta' di Scienze Motorie, Universita' degli Studi di Verona, Verona, Italy
| | - Marissa K. Caldow
- School of Exercise and Nutrition Sciences, Deakin University, Melbourne, Victoria, Australia; and
| | - Pazit Levinger
- Institute of Sport, Exercise and Active Living (ISEAL), Muscle, Ions and Exercise Group, Victoria University, Melbourne, Victoria, Australia
| | | | - Itamar Levinger
- Institute of Sport, Exercise and Active Living (ISEAL), Muscle, Ions and Exercise Group, Victoria University, Melbourne, Victoria, Australia
- School of Sport and Exercise Science, Muscle, Ions and Exercise Group, Victoria University, Melbourne, Victoria, Australia
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18
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Benziane B, Widegren U, Pirkmajer S, Henriksson J, Stepto NK, Chibalin AV. Effect of exercise and training on phospholemman phosphorylation in human skeletal muscle. Am J Physiol Endocrinol Metab 2011; 301:E456-66. [PMID: 21653224 DOI: 10.1152/ajpendo.00533.2010] [Citation(s) in RCA: 29] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/05/2023]
Abstract
Phospholemman (PLM, FXYD1) is a partner protein and regulator of the Na(+)-K(+)-ATPase (Na(+)-K(+) pump). We explored the impact of acute and short-term training exercise on PLM physiology in human skeletal muscle. A group of moderately trained males (n = 8) performed a 1-h acute bout of exercise by utilizing a one-legged cycling protocol. Muscle biopsies were taken from vastus lateralis at 0 and 63 min (non-exercised leg) and 30 and 60 min (exercised leg). In a group of sedentary males (n = 9), we determined the effect of a 10-day intense aerobic cycle training on Na(+)-K(+)-ATPase subunit expression, PLM phosphorylation, and total PLM expression as well as PLM phosphorylation in response to acute exercise (1 h at ∼72% Vo(2peak)). Biopsies were taken at rest, immediately following, and 3 h after an acute exercise bout before and at the conclusion of the 10-day training study. PLM phosphorylation was increased both at Ser(63) and Ser(68) immediately after acute exercise (75%, P < 0.05, and 30%, P < 0.05, respectively). Short-term training had no adaptive effect on PLM phosphorylation at Ser(63) and Ser(68), nor was the total amount of PLM altered posttraining. The protein expressions of α(1)-, α(2)-,and β(1)-subunits of Na(+)-K(+)-ATPase were increased after training (113%, P < 0.05, 49%, P < 0.05, and 27%, P < 0.05, respectively). Whereas an acute bout of exercise increased the phosphorylation of PKCα/βII on Thr(638/641) pre- and posttraining, phosphorylation of PKCζ/λ on Thr(403/410) was increased in response to acute exercise only after the 10-day training. In conclusion, we show that only acute exercise, and not short-term training, increases phosphorylation of PLM on Ser(63) and Ser(68), and data from one-legged cycling indicate that this effect of exercise on PLM phosphorylation is not due to systemic factors. Our results provide evidence that phosphorylation of PLM may play a role in the acute regulation of the Na(+)-K(+)-ATPase response to exercise.
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Affiliation(s)
- Boubacar Benziane
- Dept. of Molecular Medicine and Surgery, Integrative Physiology, Karolinska Institutet, Stockholm, Sweden
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19
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Kristensen M, Juel C. Potassium-transporting proteins in skeletal muscle: cellular location and fibre-type differences. Acta Physiol (Oxf) 2010; 198:105-23. [PMID: 19769637 DOI: 10.1111/j.1748-1716.2009.02043.x] [Citation(s) in RCA: 37] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
Abstract Potassium (K(+)) displacement in skeletal muscle may be an important factor in the development of muscle fatigue during intense exercise. It has been shown in vitro that an increase in the extracellular K(+) concentration ([K(+)](e)) to values higher than approx. 10 mm significantly reduce force development in unfatigued skeletal muscle. Several in vivo studies have shown that [K(+)](e) increases progressively with increasing work intensity, reaching values higher than 10 mm. This increase in [K(+)](e) is expected to be even higher in the transverse (T)-tubules than the concentration reached in the interstitium. Besides the voltage-sensitive K(+) (K(v)) channels that generate the action potential (AP) it is suggested that the big-conductance Ca(2+)-dependent K(+) (K(Ca)1.1) channel contributes significantly to the K(+) release into the T-tubules. Also the ATP-dependent K(+) (K(ATP)) channel participates, but is suggested primarily to participate in K(+) release to the interstitium. Because there is restricted diffusion of K(+) to the interstitium, K(+) released to the T-tubules during AP propagation will be removed primarily by reuptake mediated by transport proteins located in the T-tubule membrane. The most important protein that mediates K(+) reuptake in the T-tubules is the Na(+),K(+)-ATPase alpha(2) dimers, but a significant contribution of the strong inward rectifier K(+) (Kir2.1) channel is also suggested. The Na(+), K(+), 2Cl(-) 1 (NKCC1) cotransporter also participates in K(+) reuptake but probably mainly from the interstitium. The relative content of the different K(+)-transporting proteins differs in oxidative and glycolytic muscles, and might explain the different [K(+)](e) tolerance observed.
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Affiliation(s)
- M Kristensen
- Department of Biology, University of Copenhagen, Universitetsparken 13, DK-2200, Copenhagen N, Denmark.
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20
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Peretich AL, Abbott LL, Andrews FM, Dhar MS. Age-dependent regulation of sodium-potassium adenosinetriphosphatase and sodium-hydrogen exchanger mRNAs in equine nonglandular mucosa. Am J Vet Res 2009; 70:1124-8. [DOI: 10.2460/ajvr.70.9.1124] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
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21
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Rigoard P, Chaillou M, Fares M, Sottejeau Y, Giot JP, Honfo-Ga C, Rohan J, Lapierre F, Maixent JM. [Energetic applications: Na+/K+-ATPase and neuromuscular transmission]. Neurochirurgie 2009; 55 Suppl 1:S92-103. [PMID: 19230940 DOI: 10.1016/j.neuchi.2008.06.005] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/29/2008] [Accepted: 06/05/2008] [Indexed: 11/29/2022]
Abstract
Na/K-ATPase electrogenic activity and its indispensable role in maintaining gradients suggest that the modifications in isoform distribution and the functioning of the sodium pump have a major influence on both the neuronal functions, including excitability, and motor efficiency. This article proposes to clarify the involvement of Na/K-ATPase in the transmission of nerve influx within the peripheral nerve and then in the genesis, the maintenance, and the physiology of muscle contraction by comparing the data found in the literature with our work on neuron and muscle characterization of Na/K-ATPase activity and isoforms.
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Affiliation(s)
- P Rigoard
- Service de neurochirurgie, CHU La Milétrie, 2, rue de La Milétrie, BP 577, 86021 Poitiers cedex, France.
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22
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Zhang L, Ng YC. Fiber specific differential phosphorylation of the alpha1-subunit of the Na(+),K (+)-ATPase in rat skeletal muscle: the effect of aging. Mol Cell Biochem 2007; 303:231-7. [PMID: 17457517 DOI: 10.1007/s11010-007-9479-5] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/16/2007] [Accepted: 04/03/2007] [Indexed: 11/29/2022]
Abstract
In skeletal muscle, the Na(+),K(+)-ATPase maintains the Na(+) and K(+) gradients and modulates contractile functions. The different fibers of the skeletal muscle possess diverse properties and functions, and thus, the demands for the Na-pump activity might be different. Because phosphorylation of the alpha1-subunit of the Na(+),K(+)-ATPase appears to serve a regulatory role in the activity of Na(+),K(+)-ATPase, we postulated that a difference in the phosphorylation of the alpha1-subunit may be found among the fibers. We utilized two well-characterized specific antibodies for the alpha1-subunit, namely the McK1 and alpha6F, to determine, by immunofluorescence, if the alpha1-subunit in rat skeletal muscle fiber is differentially phosphorylated. McK1 has the unique property that its binding to the alpha1-subunit is greatly reduced when Ser-18 is phosphorylated. Our data show that, in red gastrocnemius muscle, only a small number of the fibers were stained on the sarcolemmal membrane by McK1, while other fibers were almost completely devoid of any staining. By contrast, the staining pattern by McK1 in the white gastrocnemius muscle was mostly uniform. Immunostaining of serial sections using the alpha6F antibody showed that the alpha1-subunit is expressed in all fibers. Dephosphorylation of the tissue sections by phosphatase partially restored immunostaining of the alpha1-subunit by McK1. Fiber typing results showed that, in red gastrocnemius, those fibers stained positive for alpha1-subunit by McK1 are the Type I fibers, whereas those stained negative are the Type IIA, IID, and IIB fibers. With age, the number of fibers in red gastrocnemius stained positive for McK1 increased markedly in 30-month old rats compared to 6-month old rats. In conclusion, our result suggests that, in rats, the alpha1-subunit of the Na(+),K(+)-ATPase is differentially phosphorylated in the fibers of the red gastrocnemius muscle. Furthermore, advanced age is associated with an apparent decrease in the phosphorylation of the alpha1-subunit, in addition to the previously demonstrated increase in the levels of expression of the subunit.
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Affiliation(s)
- Lianqin Zhang
- Department of Pharmacology, The Milton S Hershey Medical Center, College of Medicine, The Pennsylvania State University, Hershey, PA 17033, USA
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23
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Bretag A. Too much hype, not enough hope: Are balanced reporting and proper controls too much to expect from therapeutic studies in animal models of neuromuscular diseases that presage clinical trials in humans? Neuromuscul Disord 2007; 17:203-5. [PMID: 17324571 DOI: 10.1016/j.nmd.2007.02.001] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/07/2007] [Accepted: 02/07/2007] [Indexed: 11/24/2022]
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