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Watanabe D, Wada M. Glutathione depression alters cellular mechanisms of skeletal muscle fatigue in early stage of recovery and prolongs force depression in late stage of recovery. Am J Physiol Regul Integr Comp Physiol 2023; 325:R120-R132. [PMID: 37212553 DOI: 10.1152/ajpregu.00097.2022] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/06/2022] [Revised: 05/15/2023] [Accepted: 05/15/2023] [Indexed: 05/23/2023]
Abstract
The effects of reduced glutathione (GSH) on skeletal muscle fatigue were investigated. GSH was depressed by buthionine sulfoximine (BSO) (100 mg/kg body wt/day) treatment for 5 days, which decreased GSH content to ∼10%. Male Wistar rats were assigned to the control (N = 18) and BSO groups (N = 17). Twelve hours after BSO treatment, the plantar flexor muscles were subjected to fatiguing stimulation (FS). Eight control and seven BSO rats were rested for 0.5 h (early stage of recovery), and the remaining were rested for 6 h (late stage of recovery). Forces were measured before FS and after rest, and physiological functions were estimated using mechanically skinned fibers. The force at 40 Hz decreased to a similar extent in both groups in the early stage of recovery and was restored in the control but not in the BSO group in the late stage of recovery. In the early stage of recovery, sarcoplasmic reticulum (SR) Ca2+ release was decreased in the control greater than in the BSO group, whereas myofibrillar Ca2+ sensitivity was increased in the control but not in the BSO group. In the late stage of recovery, SR Ca2+ release decreased and SR Ca2+ leakage increased in the BSO group but not in the control group. These results indicate that GSH depression alters the cellular mechanism of muscle fatigue in the early stage and delays force recovery in the late stage of recovery, due at least in part, to the prolonged Ca2+ leakage from the SR.
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Affiliation(s)
- Daiki Watanabe
- Graduate School of Sport and Exercise Sciences, Osaka University of Health and Sport Sciences, Osaka, Japan
| | - Masanobu Wada
- Graduate School of Humanities and Social Sciences, Hiroshima University, Hiroshima, Japan
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Rader EP, Baker BA. Elevated muscle mass accompanied by transcriptional and nuclear alterations several months following cessation of resistance-type training in rats. Physiol Rep 2022; 10:e15476. [PMID: 36259109 PMCID: PMC9579736 DOI: 10.14814/phy2.15476] [Citation(s) in RCA: 4] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/29/2022] [Revised: 08/31/2022] [Accepted: 09/05/2022] [Indexed: 06/16/2023] Open
Abstract
Rodent studies investigating long-term effects following termination of hypertrophy-inducing loading have predominantly involved exposures such as synergist ablation and weighted wheel running or ladder climbing. This research yielded a spectrum of results regarding the extent of detraining in terms of muscle mass and myonuclei number. The studies were also limited in their lack of sensitive performance measures and indirect relatedness to resistance training. Our research group developed and validated a relevant rat model of resistance-type training that induces increased muscle mass and performance. The aim of the present study was to determine to what extent these features persist 3 months following the termination of this training. While performance returned to baseline, muscle mass remained elevated by 17% and a shift in distribution to larger muscle fibers persisted. A 16% greater total RNA and heightened mRNA levels of ribosomal protein S6 kinases implicated preserved transcriptional output and ribosomal content. Remodeling of muscle fiber nuclei was consistent with these findings - increased nuclear number and a distribution shift to a more circular nuclear shape. These findings indicate that muscle mass detrains at a slower rate than performance and implicates multiple forms of myonuclear remodeling in muscle memory.
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Affiliation(s)
- Erik P. Rader
- Centers for Disease Control and PreventionNational Institute for Occupational Safety and HealthMorgantownWest VirginiaUSA
| | - Brent A. Baker
- Centers for Disease Control and PreventionNational Institute for Occupational Safety and HealthMorgantownWest VirginiaUSA
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Rader EP, Naimo MA, Ensey J, Baker BA. Improved impedance to maladaptation and enhanced VCAM-1 upregulation with resistance-type training in the long-lived Snell dwarf ( Pit1dw/dw) mouse. Aging (Albany NY) 2022; 14:1157-1185. [PMID: 35113807 PMCID: PMC8876912 DOI: 10.18632/aging.203875] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/11/2019] [Accepted: 01/27/2022] [Indexed: 06/14/2023]
Abstract
Snell dwarf mice with the Pit1dw/dw mutation are deficient in growth hormone, prolactin, and thyroid stimulating hormone and exhibit >40% lifespan extension. This longevity is accompanied by compromised muscular performance. However, research regarding young (3-month-old) Snell dwarf mice demonstrate exceptional responsivity to resistance-type training especially in terms of a shifted fiber type distribution and increased protein levels of vascular cell adhesion molecule-1 (VCAM-1), a possible mediator of such remodeling. In the present study, we investigated whether this responsiveness persists at 12 months of age. Unlike 12-month-old control mice, age-matched Snell dwarf mice remained resistant to training-induced maladaptive decreases in performance and muscle mass. This was accompanied by retainment of the remodeling capacity in muscles of Snell dwarf mice to increase VCAM-1 protein levels and a shift in myosin heavy chain (MHC) isoform distribution with training. Even decreasing training frequency for control mice, an alteration which protected muscles from maladaptation at 12 months of age, did not result in the overt remodeling observed for Snell dwarf mice. The results demonstrate a distinct remodeling response to resistance-type exercise operative in the context of the Pit1dw/dw mutation of long-lived Snell dwarf mice.
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Affiliation(s)
- Erik P. Rader
- Centers for Disease Control and Prevention, National Institute for Occupational Safety and Health, Morgantown, WV 26505, USA
| | - Marshall A. Naimo
- Centers for Disease Control and Prevention, National Institute for Occupational Safety and Health, Morgantown, WV 26505, USA
- West Virginia School of Medicine, Division of Exercise Physiology, Morgantown, WV 26506, USA
| | - James Ensey
- Centers for Disease Control and Prevention, National Institute for Occupational Safety and Health, Morgantown, WV 26505, USA
| | - Brent A. Baker
- Centers for Disease Control and Prevention, National Institute for Occupational Safety and Health, Morgantown, WV 26505, USA
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4
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Naimo MA, Varanoske AN, Hughes JM, Pasiakos SM. Skeletal Muscle Quality: A Biomarker for Assessing Physical Performance Capabilities in Young Populations. Front Physiol 2021; 12:706699. [PMID: 34421645 PMCID: PMC8376973 DOI: 10.3389/fphys.2021.706699] [Citation(s) in RCA: 22] [Impact Index Per Article: 7.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/07/2021] [Accepted: 07/09/2021] [Indexed: 12/28/2022] Open
Abstract
Muscle quality (MQ), defined as the amount of strength and/or power per unit of muscle mass, is a novel index of functional capacity that is increasingly relied upon as a critical biomarker of muscle health in low functioning aging and pathophysiological adult populations. Understanding the phenotypical attributes of MQ and how to use it as an assessment tool to explore the efficacy of resistance exercise training interventions that prioritize functional enhancement over increases in muscle size may have implications for populations beyond compromised adults, including healthy young adults who routinely perform physically demanding tasks for competitive or occupational purposes. However, MQ has received far less attention in healthy young populations than it has in compromised adults. Researchers and practitioners continue to rely upon static measures of lean mass or isolated measures of strength and power, rather than using MQ, to assess integrated functional responses to resistance exercise training and physical stress. Therefore, this review will critically examine MQ and the evidence base to establish this metric as a practical and important biomarker for functional capacity and performance in healthy, young populations. Interventions that enhance MQ, such as high-intensity stretch shortening contraction resistance exercise training, will be highlighted. Finally, we will explore the potential to leverage MQ as a practical assessment tool to evaluate function and enhance performance in young populations in non-traditional research settings.
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Affiliation(s)
- Marshall A Naimo
- Military Performance Division, United States Army Research Institute of Environmental Medicine, Natick, MA, United States
| | - Alyssa N Varanoske
- Military Nutrition Division, United States Army Research Institute of Environmental Medicine, Natick, MA, United States.,Oak Ridge Institute for Science and Education, Oak Ridge, TN, United States
| | - Julie M Hughes
- Military Performance Division, United States Army Research Institute of Environmental Medicine, Natick, MA, United States
| | - Stefan M Pasiakos
- Military Nutrition Division, United States Army Research Institute of Environmental Medicine, Natick, MA, United States
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Rader EP, Baker BA. Age-dependent stress response DNA demethylation and gene upregulation accompany nuclear and skeletal muscle remodeling following acute resistance-type exercise in rats. Facets (Ott) 2020; 5:455-473. [PMID: 32775614 PMCID: PMC7413608 DOI: 10.1139/facets-2019-0060] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/15/2022] Open
Abstract
Efficacy of high-intensity resistance exercise becomes progressively compromised with aging. Previously, to investigate this, we developed a rodent model of high-intensity training consisting of stretch-shortening contractions (SSCs) and determined that following one month of training, young rats exhibit a robust stress response and 20% performance increase, whereas old rats display a muted stress response and 30% performance decrease. Whether these age-specific responses occur early in training and constitute primary factors in adaptation/maladaptation was not addressed. The aim of the present study was to characterize performance, remodeling, and stress response transcriptional profile 6–120 h following acute SSC exposure. For young rats, the stress response pathway was highly regulated (≥20 differentially expressed genes at each time point) and was accompanied by robust DNA demethylation, tissue remodeling, and isometric torque recovery. For old rats, a muted transcriptional profile (13 and 2 differentially expressed genes at 6 and 120 h, respectively) coincided with deficiencies in demethylation, muscle remodeling, and torque recovery. These findings occurred in the context of heightened chronic levels of stress response gene expression with aging. This demonstrates that age-related constitutive elevations in stress response gene expression was accompanied by diminished SSC-induced responsiveness in epigenomic regulation and tissue remodeling.
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Affiliation(s)
- Erik P Rader
- Centers for Disease Control and Prevention, National Institute for Occupational Safety and Health, Morgantown, WV 26505, USA
| | - Brent A Baker
- Centers for Disease Control and Prevention, National Institute for Occupational Safety and Health, Morgantown, WV 26505, USA
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Naimo MA, Rader EP, Ensey J, Kashon ML, Baker BA. Reduced frequency of resistance-type exercise training promotes adaptation of the aged skeletal muscle microenvironment. J Appl Physiol (1985) 2019; 126:1074-1087. [PMID: 30676867 DOI: 10.1152/japplphysiol.00582.2018] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/23/2022] Open
Abstract
The purpose of this study was to characterize the growth and remodeling molecular signaling response in aged skeletal muscle following 1 mo of "resistance-type exercise" training. Male Fischer 344 × Brown Norway hybrid rats aged 3 (young) and 30 mo (old) underwent stretch-shortening contraction (SSC) loading 2 or 3 days/wk; muscles were removed 72 h posttraining. Young rats SSC loaded 3 (Y3x) or 2 days/wk (Y2x) adapted via increased work performance. Old rats SSC loaded 3 days/wk (O3x) maladapted via decreased negative work; however, old rats SSC loaded 2 days/wk (O2x) adapted through improved negative and positive work. Y3x, Y2x, and O2x, but not O3x, displayed hypertrophy via larger fiber area and myonuclear domains. Y3x, Y2x, and O2x differentially expressed 19, 30, and 8 phosphatidylinositol 3-kinase-Akt genes, respectively, whereas O3x only expressed 2. Bioinformatics analysis revealed that rats in the adapting groups presented growth and remodeling processes (i.e., increased protein synthesis), whereas O3x demonstrated inflammatory signaling. In conclusion, reducing SSC-loading frequency in aged rodents positively influences the molecular signaling microenvironment, promoting muscle adaptation. NEW & NOTEWORTHY Decreasing resistance-type exercise training frequency in old rodents led to adaptation through enhancements in performance, fiber areas, and myonuclear domains. Modifying frequency influenced the molecular environment through improvements in phosphatidylinositol 3-kinase-Akt pathway-specific expression and bioinformatics indicating increased protein synthesis. Reducing training frequency may be appropriate in older individuals who respond unfavorably to higher frequencies (i.e., maladaptation); overall, modifying the parameters of the exercise prescription can affect the cellular environment, ultimately leading to adaptive or maladaptive outcomes.
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Affiliation(s)
- Marshall A Naimo
- Health Effects Laboratory Division, National Institute for Occupational Safety and Health, Centers for Disease Control and Prevention , Morgantown, West Virginia.,Division of Exercise Physiology, School of Medicine, West Virginia University , Morgantown, West Virginia
| | - Erik P Rader
- Health Effects Laboratory Division, National Institute for Occupational Safety and Health, Centers for Disease Control and Prevention , Morgantown, West Virginia
| | - James Ensey
- Health Effects Laboratory Division, National Institute for Occupational Safety and Health, Centers for Disease Control and Prevention , Morgantown, West Virginia
| | - Michael L Kashon
- Health Effects Laboratory Division, National Institute for Occupational Safety and Health, Centers for Disease Control and Prevention , Morgantown, West Virginia
| | - Brent A Baker
- Health Effects Laboratory Division, National Institute for Occupational Safety and Health, Centers for Disease Control and Prevention , Morgantown, West Virginia
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Rader EP, Naimo MA, Ensey J, Baker BA. VCAM-1 upregulation accompanies muscle remodeling following resistance-type exercise in Snell dwarf (Pit1 dw/dw ) mice. Aging Cell 2018; 17:e12816. [PMID: 29992743 PMCID: PMC6156491 DOI: 10.1111/acel.12816] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/25/2018] [Revised: 05/08/2018] [Accepted: 06/15/2018] [Indexed: 02/06/2023] Open
Abstract
Snell dwarf mice (Pit1dw/dw ) exhibit deficiencies in growth hormone, prolactin, and thyroid stimulating hormone. Besides being an experimental model of hypopituitarism, these mice are long-lived (>40% lifespan extension) and utilized as a model of slowed/delayed aging. Whether this longevity is accompanied by a compromised quality of life in terms of muscular performance has not yet been characterized. In this study, we investigated nontrained and trained muscles 1 month following a general validated resistance-type exercise protocol in 3-month-old Snell dwarf mice and control littermates. Nontrained Snell dwarf gastrocnemius muscles exhibited a 1.3-fold greater muscle mass to body weight ratio than control values although muscle quality, maximum isometric torque normalized to muscle mass, and fatigue recovery were compromised. For control mice, training increased isometric torque (17%) without altering muscle mass. For Snell dwarf mice, isometric torque was unaltered by training despite decreased muscle mass that rendered muscle mass to body weight ratio comparable to control values. Muscle quality and fatigue recovery improved twofold and threefold, respectively, for Snell dwarf mice. This accompanied a fourfold increase in levels of vascular cell adhesion molecule-1 (VCAM-1), a mediator of progenitor cell recruitment, and muscle remodeling in the form of increased number of central nuclei, additional muscle fibers per unit area, and altered fiber type distribution. These results reveal a trade-off between muscle quality and longevity in the context of anterior pituitary hormone deficiency and that resistance-type training can diminish this trade-off by improving muscle quality concomitant with VCAM-1 upregulation and muscle remodeling.
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Affiliation(s)
- Erik P. Rader
- Centers for Disease Control and Prevention; National Institute for Occupational Safety and Health; Morgantown West Virginia
| | - Marshall A. Naimo
- Centers for Disease Control and Prevention; National Institute for Occupational Safety and Health; Morgantown West Virginia
- Division of Exercise Physiology; West Virginia School of Medicine; Morgantown West Virginia
| | - James Ensey
- Centers for Disease Control and Prevention; National Institute for Occupational Safety and Health; Morgantown West Virginia
| | - Brent A. Baker
- Centers for Disease Control and Prevention; National Institute for Occupational Safety and Health; Morgantown West Virginia
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Rader EP, Naimo MA, Ensey J, Baker BA. High-intensity stretch-shortening contraction training modifies responsivity of skeletal muscle in old male rats. Exp Gerontol 2018; 104:118-126. [PMID: 29438735 DOI: 10.1016/j.exger.2018.02.009] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/30/2017] [Revised: 01/25/2018] [Accepted: 02/08/2018] [Indexed: 12/22/2022]
Abstract
Utilization of high-intensity resistance training to counter age-related sarcopenia is currently debated because of the potential for maladaptation when training design is inappropriate. Training design is problematic because the influence of various loading variables (e.g. contraction mode, repetition number, and training frequency) is still not well characterized at old age. To address this in a precisely controlled manner, we developed a rodent model of high-intensity training consisting of maximally-activated stretch-shortening contractions (SSCs), contractions typical during resistance training. With this model, we determined that at old age, high-repetition SSC training (80 SSCs: 8 sets of 10 repetitions) performed frequently (i.e. 3 days per week) for 4.5 weeks induced strength deficits with no muscle mass gain while decreasing frequency to 2 days per week promoted increases in muscle mass and muscle quality (i.e. performance normalized to muscle mass). This finding confirmed the popular notion that decreasing training frequency has a robust effect with age. Meanwhile, the influence of other loading variables remains contentious. The aim of the present study was to assess muscle adaptation following modulation of contraction mode and repetition number during high-intensity SSC training. Muscles of young (3 month old) and old (30 month old) male rats were exposed to 4.5 weeks of low-repetition static training of 4 (i.e. 4 sets of one repetition) isometric (ISO) contractions 3 days per week or a more moderate-repetition dynamic training of 40 SSCs (i.e. 4 sets of 10 repetitions) 3 days per week. For young rats, performance and muscle mass increased regardless of training protocol. For old rats, no muscle mass adaptation was observed for 4 ISO training while 40 SSC training induced muscle mass gain without improvement in muscle quality, an outcome distinct from modulating training frequency. Muscle mass gain for old rats was accompanied by decreased protein levels of tumor necrosis factor alpha, a mediator of age-related chronic inflammatory signaling, to young levels. These findings suggest that while dynamic high-intensity training with a moderate number of repetitions has a limited capacity for altering muscle quality, such training is a viable strategy for countering age-related inflammatory signaling and modifying muscle mass.
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Affiliation(s)
- Erik P Rader
- Centers for Disease Control and Prevention, National Institute for Occupational Safety and Health, Morgantown, WV 26505, United States.
| | - Marshall A Naimo
- Centers for Disease Control and Prevention, National Institute for Occupational Safety and Health, Morgantown, WV 26505, United States; West Virginia University School of Medicine, Division of Exercise Physiology, Morgantown, WV 26506, United States
| | - James Ensey
- Centers for Disease Control and Prevention, National Institute for Occupational Safety and Health, Morgantown, WV 26505, United States
| | - Brent A Baker
- Centers for Disease Control and Prevention, National Institute for Occupational Safety and Health, Morgantown, WV 26505, United States
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Rader EP, Naimo MA, Ensey J, Baker BA. Agonist muscle adaptation accompanied by antagonist muscle atrophy in the hindlimb of mice following stretch-shortening contraction training. BMC Musculoskelet Disord 2017; 18:60. [PMID: 28148306 PMCID: PMC5288976 DOI: 10.1186/s12891-017-1397-4] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 09/12/2016] [Accepted: 01/11/2017] [Indexed: 02/26/2023] Open
Abstract
Background The vast majority of dynamometer-based animal models for investigation of the response to chronic muscle contraction exposure has been limited to analysis of isometric, lengthening, or shortening contractions in isolation. An exception to this has been the utilization of a rat model to study stretch-shortening contractions (SSCs), a sequence of consecutive isometric, lengthening, and shortening contractions common during daily activity and resistance-type exercise. However, the availability of diverse genetic strains of rats is limited. Therefore, the purpose of the present study was to develop a dynamometer-based SSC training protocol to induce increased muscle mass and performance in plantarflexor muscles of mice. Methods Young (3 months old) C57BL/6 mice were subjected to 1 month of plantarflexion SSC training. Hindlimb muscles were analyzed for muscle mass, quantitative morphology, myogenesis/myopathy relevant gene expression, and fiber type distribution. Results The main aim of the research was achieved when training induced a 2-fold increase in plantarflexion peak torque output and a 19% increase in muscle mass for the agonist plantaris (PLT) muscle. In establishing this model, several outcomes emerged which raised the value of the model past that of being a mere recapitulation of the rat model. An increase in the number of muscle fibers per transverse muscle section accounted for the PLT muscle mass gain while the antagonist tibialis anterior (TA) muscle atrophied by 30% with preferential atrophy of type IIb and IIx fibers. These alterations were accompanied by distinct gene expression profiles. Conclusions The findings confirm the development of a stretch-shortening contraction training model for the PLT muscle of mice and demonstrate that increased cross-sectional fiber number can occur following high-intensity SSC training. Furthermore, the TA muscle atrophy provides direct evidence for the concept of muscle imbalance in phasic non-weight bearing muscles, a concept largely characterized based on clinical observation of patients. The susceptibility to this imbalance is demonstrated to be selective for the type IIb and IIx muscle fiber types. Overall, the study highlights the importance of considering muscle fiber number modulation and the effect of training on surrounding muscles in exercise comprised of SSCs. Electronic supplementary material The online version of this article (doi:10.1186/s12891-017-1397-4) contains supplementary material, which is available to authorized users.
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Affiliation(s)
- Erik P Rader
- Centers for Disease Control and Prevention, National Institute for Occupational Safety and Health, MS L3014, 1095 Willowdale Rd, Morgantown, West Virginia, 26505, USA.
| | - Marshall A Naimo
- Centers for Disease Control and Prevention, National Institute for Occupational Safety and Health, MS L3014, 1095 Willowdale Rd, Morgantown, West Virginia, 26505, USA.,West Virginia University School of Medicine, Division of Exercise Physiology, Morgantown, West Virginia, USA
| | - James Ensey
- Centers for Disease Control and Prevention, National Institute for Occupational Safety and Health, MS L3014, 1095 Willowdale Rd, Morgantown, West Virginia, 26505, USA
| | - Brent A Baker
- Centers for Disease Control and Prevention, National Institute for Occupational Safety and Health, MS L3014, 1095 Willowdale Rd, Morgantown, West Virginia, 26505, USA
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Abstract
Clinical Scenario: Even though chronological aging is an inevitable phenomenological consequence occurring in every living organism, it is biological aging that may be the most significant factor challenging our quality of life. Development of functional limitations, resulting from improper maintenance and restoration of various organ systems, ultimately leads to reduced health and independence. Skeletal muscle is an organ system that, when challenged, is often injured in response to varying stimuli. Overt muscle-strain injury can be traumatic, clinically diagnosable, properly managed, and a remarkably common event, yet our contemporary understanding of how age and environmental stressors affect the initial and subsequent induction of injury and how the biological processes resulting from this event are modifiable and, eventually, lead to functional restoration and healing of skeletal muscle and adjacent tissues is presently unclear. Even though the secondary injury response to and recovery from "contraction-induced" skeletal-muscle injury are impaired with aging, there is no scientific consensus as to the exact mechanism responsible for this event. Given the multitude of investigative approaches, particular consideration given to the appropriateness of the muscle-injury model, or research paradigm, is critical so that outcomes may be physiologically relevant and translational. In this case, methods implementing stretch-shortening contractions, the most common form of muscle movements used by all mammals during physical movement, work, and activity, are highlighted. CLINICAL RELEVANCE Understanding the fundamental evidence regarding how aging influences the responsivity of skeletal muscle to strain injury is vital for informing how clinicians approach and implement preventive strategies, as well as therapeutic interventions. From a practical perspective, maintaining or improving the overall health and tissue quality of skeletal muscle as one ages will positively affect skeletal muscle's safety threshold and responsivity, which may reduce incidence of injury, improve recovery time, and lessen overall fiscal burdens.
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Rader EP, Naimo MA, Layner KN, Triscuit AM, Chetlin RD, Ensey J, Baker BA. Enhancement of Skeletal Muscle in Aged Rats Following High-Intensity Stretch-Shortening Contraction Training. Rejuvenation Res 2016; 20:93-102. [PMID: 27378453 DOI: 10.1089/rej.2016.1816] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/21/2023] Open
Abstract
Exercise is the most accessible, efficacious, and multifactorial intervention to improve health and treat chronic disease. High-intensity resistance exercise, in particular, also maximizes skeletal muscle size and strength-outcomes crucial at advanced age. However, such training is capable of inducing muscle maladaptation when misapplied at old age. Therefore, characterization of parameters (e.g., mode and frequency) that foster adaptation is an active research area. To address this issue, we utilized a rodent model that allowed training at maximal intensity in terms of muscle activation and tested the hypothesis that muscles of old rats adapt to stretch-shortening contraction (SSC) training, provided the training frequency is sufficiently low. At termination of training, normalized muscle mass (i.e., muscle mass divided by tibia length) and muscle quality (isometric force divided by normalized muscle mass) were determined. For young rats, normalized muscle mass increased by ∼20% regardless of training frequency. No difference was observed for muscle quality values after 2 days versus 3 days per week training (0.65 ± 0.09 N/mg/mm vs. 0.59 ± 0.05 N/mg/mm, respectively). For old rats following 3 days per week training, normalized muscle mass was unaltered and muscle quality was 30% lower than young levels. Following 2 days per week training at old age, normalized muscle mass increased by 17% and muscle quality was restored to young levels. To investigate this enhanced response, oxidative stress was assessed by lipid peroxidation quantification. For young rats, lipid peroxidation levels were unaltered by training. With aging, baseline levels of lipid peroxidation increased by 1.5-fold. For old rats, only 2 days per week training decreased lipid peroxidation to levels indistinguishable from young values. These results imply that, appropriately scheduled high-intensity SSC training at old age is capable of restoring muscle to a younger phenotype in terms of lipid peroxidation levels and muscle quality.
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Affiliation(s)
- Erik P Rader
- 1 Centers for Disease Control and Prevention, National Institute for Occupational Safety and Health , Morgantown, West Virginia
| | - Marshall A Naimo
- 1 Centers for Disease Control and Prevention, National Institute for Occupational Safety and Health , Morgantown, West Virginia.,2 West Virginia School of Medicine , Division of Exercise Physiology, Morgantown, West Virginia
| | - Kayla N Layner
- 1 Centers for Disease Control and Prevention, National Institute for Occupational Safety and Health , Morgantown, West Virginia
| | - Alyssa M Triscuit
- 1 Centers for Disease Control and Prevention, National Institute for Occupational Safety and Health , Morgantown, West Virginia
| | - Robert D Chetlin
- 1 Centers for Disease Control and Prevention, National Institute for Occupational Safety and Health , Morgantown, West Virginia.,3 Department of Sports Medicine, Mercyhurst University , Erie, Pennsylvania
| | - James Ensey
- 1 Centers for Disease Control and Prevention, National Institute for Occupational Safety and Health , Morgantown, West Virginia
| | - Brent A Baker
- 1 Centers for Disease Control and Prevention, National Institute for Occupational Safety and Health , Morgantown, West Virginia
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Rader EP, Layner K, Triscuit AM, Chetlin RD, Ensey J, Baker BA. Age-dependent Muscle Adaptation after Chronic Stretch-shortening Contractions in Rats. Aging Dis 2016; 7:1-13. [PMID: 26816659 DOI: 10.14336/ad.2015.0920] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/05/2015] [Accepted: 09/20/2015] [Indexed: 11/01/2022] Open
Abstract
Age-related differences in contraction-induced adaptation have been well characterized especially for young and old rodent models but much less so at intermediate ages. Therefore, additional research is warranted to determine to what extent alterations in adaptation are due to maturation versus aging per se. The purpose of our study was to evaluate muscles of Fisher 344XBrown Norway rats of various ages following one month of exposure to stretch-shortening contractions (SSCs). With exposure, muscles mass increased by ~10% for 27 and 30 month old rats vs. ~20% for 3 and 6 month old rats (P < 0.05). For 3 month old rats, maximum isometric force and dynamic peak force increased by 22 ± 8% and 27 ± 10%, respectively (P < 0.05). For 6 month old rats, these forces were unaltered by exposure and positive work capacity diminished by 27 ± 2% (P = 0.006). By 30 months of age, age-related deficits in maximum isometric force, peak force, negative work, and positive work were apparent and SSC exposure was ineffective at counteracting such deficits. Recovery from fatigue was also tested and exposure-induced improvements in fatigue recovery were indicated for 6 month old rats and to a lesser extent for 3 month old rats whereas no such effect was observed for older rats. Alterations in fatigue recovery were accompanied by evidence of substantial type IIb to IIx fiber type shifting. These results highlight the exceptional adaptive capacity for strength at a young age, the inclination for adaptation in fatigue recovery at early adulthood, and diminished adaptation for muscle performance in general beginning at late adulthood. Such findings motivate careful investigation to determine appropriate SSC exposures at all stages of life.
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Affiliation(s)
- Erik P Rader
- 1Centers for Disease Control and Prevention, National Institute for Occupational Safety and Health, Morgantown, West Virginia 26505, USA
| | - KaylaN Layner
- 1Centers for Disease Control and Prevention, National Institute for Occupational Safety and Health, Morgantown, West Virginia 26505, USA
| | - Alyssa M Triscuit
- 1Centers for Disease Control and Prevention, National Institute for Occupational Safety and Health, Morgantown, West Virginia 26505, USA
| | - Robert D Chetlin
- 1Centers for Disease Control and Prevention, National Institute for Occupational Safety and Health, Morgantown, West Virginia 26505, USA; 2Mercyhurst University, Department of Sports Medicine, Erie, Pennsylvania 16546, USA
| | - James Ensey
- 1Centers for Disease Control and Prevention, National Institute for Occupational Safety and Health, Morgantown, West Virginia 26505, USA
| | - Brent A Baker
- 1Centers for Disease Control and Prevention, National Institute for Occupational Safety and Health, Morgantown, West Virginia 26505, USA
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Cutlip RG, Hollander MS, Johnson GA, Johnson BW, Friend SA, Baker BA. Magnetic resonance imaging of graded skeletal muscle injury in live rats. ENVIRONMENTAL HEALTH INSIGHTS 2014; 8:31-39. [PMID: 25525369 PMCID: PMC4241962 DOI: 10.4137/ehi.s15255] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 06/02/2014] [Revised: 09/12/2014] [Accepted: 09/22/2014] [Indexed: 06/04/2023]
Abstract
INTRODUCTION Increasing number of stretch-shortening contractions (SSCs) results in increased muscle injury. METHODS Fischer Hybrid rats were acutely exposed to an increasing number of SSCs in vivo using a custom-designed dynamometer. Magnetic resonance imaging (MRI) imaging was conducted 72 hours after exposure when rats were infused with Prohance and imaged using a 7T rodent MRI system (GE Epic 12.0). Images were acquired in the transverse plane with typically 60 total slices acquired covering the entire length of the hind legs. Rats were euthanized after MRI, the lower limbs removed, and tibialis anterior muscles were prepared for histology and quantified stereology. RESULTS Stereological analyses showed myofiber degeneration, and cellular infiltrates significantly increased following 70 and 150 SSC exposure compared to controls. MRI images revealed that the percent affected area significantly increased with exposure in all SSC groups in a graded fashion. Signal intensity also significantly increased with increasing SSC repetitions. DISCUSSION These results suggest that contrast-enhanced MRI has the sensitivity to differentiate specific degrees of skeletal muscle strain injury, and imaging data are specifically representative of cellular histopathology quantified via stereological analyses.
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Affiliation(s)
- Robert G Cutlip
- West Virginia University, School of Medicine, Morgantown, WV, USA
| | - Melinda S Hollander
- West Virginia University, Office of Research Integrity and Compliance Morgantown, WV, USA
| | | | | | - Sherri A Friend
- Centers for Disease Control, National Institute for Occupational Safety and Health (NIOSH/CDC), Morgantown, WV, USA
| | - Brent A Baker
- Centers for Disease Control, National Institute for Occupational Safety and Health (NIOSH/CDC), Morgantown, WV, USA
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Rader EP, Miller GR, Chetlin RD, Wirth O, Baker BA. Volitional Weight-Lifting in Rats Promotes Adaptation via Performance and Muscle Morphology prior to Gains in Muscle Mass. ENVIRONMENTAL HEALTH INSIGHTS 2014; 8:1-9. [PMID: 25392697 PMCID: PMC4216651 DOI: 10.4137/ehi.s15257] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 03/06/2014] [Revised: 04/15/2014] [Accepted: 04/16/2014] [Indexed: 06/04/2023]
Abstract
Investigation of volitional animal models of resistance training has been instrumental in our understanding of adaptive training. However, these studies have lacked reactive force measurements, a precise performance measure, and morphological analysis at a distinct phase of training - when initial strength gains precede muscle hypertrophy. Our aim was to expose rats to one month of training (70 or 700 g load) on a custom-designed weight-lifting apparatus for analysis of reactive forces and muscle morphology prior to muscle hypertrophy. Exclusively following 700 g load training, forces increased by 21% whereas muscle masses remained unaltered. For soleus (SOL) and tibialis anterior (TA) muscles, 700 g load training increased muscle fiber number per unit area by ∼20% and decreased muscle fiber area by ∼20%. Additionally, number of muscle fibers per section increased by 18% for SOL muscles. These results establish that distinct morphological alterations accompany early strength gains in a volitional animal model of load-dependent adaptive resistance training.
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Affiliation(s)
- Erik P Rader
- Centers for Disease Control and Prevention, National Institute for Occupational Safety and Health, Morgantown, WV, USA
| | - G Roger Miller
- Centers for Disease Control and Prevention, National Institute for Occupational Safety and Health, Morgantown, WV, USA
| | - Robert D Chetlin
- Centers for Disease Control and Prevention, National Institute for Occupational Safety and Health, Morgantown, WV, USA
- West Virginia University School of Medicine, Department of Neurology, WV, USA
| | - Oliver Wirth
- Centers for Disease Control and Prevention, National Institute for Occupational Safety and Health, Morgantown, WV, USA
| | - Brent A Baker
- Centers for Disease Control and Prevention, National Institute for Occupational Safety and Health, Morgantown, WV, USA
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Wheeler MW, Dunson DB, Pandalai SP, Baker BA, Herring AH. Mechanistic Hierarchical Gaussian Processes. J Am Stat Assoc 2014; 109:894-904. [PMID: 25541568 PMCID: PMC4273873 DOI: 10.1080/01621459.2014.899234] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/01/2013] [Revised: 01/01/2014] [Indexed: 10/25/2022]
Abstract
The statistics literature on functional data analysis focuses primarily on flexible black-box approaches, which are designed to allow individual curves to have essentially any shape while characterizing variability. Such methods typically cannot incorporate mechanistic information, which is commonly expressed in terms of differential equations. Motivated by studies of muscle activation, we propose a nonparametric Bayesian approach that takes into account mechanistic understanding of muscle physiology. A novel class of hierarchical Gaussian processes is defined that favors curves consistent with differential equations defined on motor, damper, spring systems. A Gibbs sampler is proposed to sample from the posterior distribution and applied to a study of rats exposed to non-injurious muscle activation protocols. Although motivated by muscle force data, a parallel approach can be used to include mechanistic information in broad functional data analysis applications.
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Affiliation(s)
- Matthew W. Wheeler
- National Institute for Occupational Safety and Health, 4676 Columbia Parkway, Cincinnati, Ohio 45226, MS C-15
| | | | - Sudha P. Pandalai
- National Institute for Occupational Safety and Health, 4676 Columbia Parkway, Cincinnati, Ohio 45226, MS C-15
| | - Brent A. Baker
- National Institute for Occupational Safety and Health, 4676 Columbia Parkway, Cincinnati, Ohio 45226, MS C-15
| | - Amy H. Herring
- Department of Biostatistics, University of North Carolina at Chapel Hill
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Alway SE, Cutlip RG. Resistance loading and signaling assays for oxidative stress in rodent skeletal muscle. Methods Mol Biol 2012; 798:185-211. [PMID: 22130838 DOI: 10.1007/978-1-61779-343-1_11] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 05/31/2023]
Abstract
Resistance loading provides an important tool for understanding skeletal muscle responses and adaptations to various perturbations. A model using anesthetized rodents provides the means to control the input parameters carefully, and to measure the output parameters of each muscle contraction. Unilateral models of anesthetized loading also provide the advantage of comparing an unloaded and loaded muscle from the same animal. Voluntary models for resistance loading arguably provide a more "physiological response" but it also introduces more variability in the input parameters, which can be affected by the stimulus used to motivate the animal to exercise. After either acute or chronic periods of muscle loading, the loaded muscles can be removed and various signaling proteins can be determined by sodium dodecyl sulfate polyacrylamide gel electrophoresis (SDS-PAGE) or enzyme assays. Several assays are described, which provide an indication of downstream markers for oxidative stress.
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Affiliation(s)
- Stephen E Alway
- Laboratory of Muscle Biology and Sarcopenia, Department of Exercise Physiology and Center for Cardiovascular and Respiratory Sciences, West Virginia University School of Medicine, Morgantown, WV, USA.
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