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Wang N, Wang H, Shen L, Liu X, Ma Y, Wang C. Aging-Related Rotator Cuff Tears: Molecular Mechanisms and Implications for Clinical Management. Adv Biol (Weinh) 2024; 8:e2300331. [PMID: 38295015 DOI: 10.1002/adbi.202300331] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/12/2023] [Revised: 11/15/2023] [Indexed: 02/02/2024]
Abstract
Shoulder pain and disabilities are prevalent issues among the elderly population, with rotator cuff tear (RCT) being one of the leading causes. Although surgical treatment has shown some success, high postoperative retear rates remain a great challenge, particularly in elderly patients. Aging-related degeneration of muscle, tendon, tendon-to-bone enthesis, and bone plays a critical role in the development and prognosis of RCT. Studies have demonstrated that aging worsens muscle atrophy and fatty infiltration, alters tendon structure and biomechanical properties, exacerbates enthesis degeneration, and reduces bone density. Although recent researches have contributed to understanding the pathophysiological mechanisms of aging-related RCT, a comprehensive systematic review of this topic is still lacking. Therefore, this article aims to present a review of the pathophysiological changes and their clinical significance, as well as the molecular mechanisms underlying aging-related RCT, with the goal of shedding light on new therapeutic approaches to reduce the occurrence of aging-related RCT and improve postoperative prognosis in elderly patients.
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Affiliation(s)
- Ni Wang
- Department of Rehabilitation Medicine, Shanghai Sixth People's Hospital Affiliated to Shanghai Jiao Tong University School of Medicine, Shanghai, 200233, China
| | - Haoyuan Wang
- Department of Orthopedics, Shanghai Sixth People's Hospital Affiliated to Shanghai Jiao Tong University School of Medicine, Shanghai, 200233, China
| | - Longxiang Shen
- Department of Orthopedics, Shanghai Sixth People's Hospital Affiliated to Shanghai Jiao Tong University School of Medicine, Shanghai, 200233, China
| | - Xudong Liu
- Department of Orthopedics, Shanghai Sixth People's Hospital Affiliated to Shanghai Jiao Tong University School of Medicine, Shanghai, 200233, China
| | - Yanhong Ma
- Department of Rehabilitation Medicine, Shanghai Sixth People's Hospital Affiliated to Shanghai Jiao Tong University School of Medicine, Shanghai, 200233, China
| | - Chongyang Wang
- Department of Orthopedics, Shanghai Sixth People's Hospital Affiliated to Shanghai Jiao Tong University School of Medicine, Shanghai, 200233, China
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2
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Chaillou T, Montiel-Rojas D. Does the blunted stimulation of skeletal muscle protein synthesis by aging in response to mechanical load result from impaired ribosome biogenesis? FRONTIERS IN AGING 2023; 4:1171850. [PMID: 37256189 PMCID: PMC10225510 DOI: 10.3389/fragi.2023.1171850] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 02/22/2023] [Accepted: 05/04/2023] [Indexed: 06/01/2023]
Abstract
Age-related loss of skeletal muscle mass leads to a reduction of strength. It is likely due to an inadequate stimulation of muscle protein synthesis (MPS) in response to anabolic stimuli, such as mechanical load. Ribosome biogenesis is a major determinant of translational capacity and is essential for the control of muscle mass. This mini-review aims to put forth the hypothesis that ribosome biogenesis is impaired by aging in response to mechanical load, which could contribute to the age-related anabolic resistance and progressive muscle atrophy. Recent animal studies indicate that aging impedes muscle hypertrophic response to mechanical overload. This is associated with an impaired transcription of ribosomal DNA (rDNA) by RNA polymerase I (Pol I), a limited increase in total RNA concentration, a blunted activation of AKT/mTOR pathway, and an increased phosphorylation of AMPK. In contrast, an age-mediated impairment of ribosome biogenesis is unlikely in response to electrical stimulations. In human, the hypertrophic response to resistance exercise training is diminished with age. This is accompanied by a deficit in long-term MPS and an absence of increased total RNA concentration. The results addressing the acute response to resistance exercise suggest an impaired Pol I-mediated rDNA transcription and attenuated activation/expression of several upstream regulators of ribosome biogenesis in muscles from aged individuals. Altogether, emerging evidence indicates that impaired ribosome biogenesis could partly explain age-related anabolic resistance to mechanical load, which may ultimately contribute to progressive muscle atrophy. Future research should develop more advanced molecular tools to provide in-depth analysis of muscle ribosome biogenesis.
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3
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Passive repetitive stretching is associated with greater muscle mass and cross-sectional area in the sarcopenic muscle. Sci Rep 2021; 11:15302. [PMID: 34315961 PMCID: PMC8316451 DOI: 10.1038/s41598-021-94709-0] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/12/2021] [Accepted: 07/15/2021] [Indexed: 11/09/2022] Open
Abstract
Mechanical stimulation has benefits for muscle mass and function. Passive stretching is widely performed in clinical rehabilitation medicine. However, the hypertrophic effects of passive repetitive stretching on senescent skeletal muscles against muscle atrophy remain unknown. We used senescence-accelerated model SAM-P8 mice. The gastrocnemius muscle was passively repetitive stretched by manual ankle dorsiflexion for 15 min, 5 days a week for 2 weeks under deep anesthesia. We examined the effects of passive stretching on muscle mass, myofiber cross-sectional area, muscle fiber type composition, satellite cell and myonuclei content, signaling pathways involved in muscle protein synthesis, and myogenic regulatory factors. The gastrocnemius muscle weight and fiber cross-sectional area of the stretched side was found greater compared with that of the unstretched side. Passive repetitive stretching increased the mRNA expression level of Akt, p70S6K, 4E-BP1, Myf5, myogenin, MuRF1.The phosphorylation level of p70S6K significantly increased in the stretched muscles, whereas of Akt and 4E-BP1 remained unchanged, compared to the unstretched side. The Pax7+ cells and myonuclei content did not differ between the stretched and unstretched muscles. These findings suggest that the hypertrophic or suppressed atrophic observation in the stretched muscles are mainly attributable to the protein turnover provoked by stretching. These findings are applicable to clinical muscle strengthening and sarcopenia prevention.
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Lawrence MM, Van Pelt DW, Confides AL, Hettinger ZR, Hunt ER, Reid JJ, Laurin JL, Peelor FF, Butterfield TA, Miller BF, Dupont-Versteegden EE. Muscle from aged rats is resistant to mechanotherapy during atrophy and reloading. GeroScience 2021; 43:65-83. [PMID: 32588343 PMCID: PMC8050124 DOI: 10.1007/s11357-020-00215-y] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/15/2020] [Accepted: 06/09/2020] [Indexed: 12/22/2022] Open
Abstract
Massage is a viable mechanotherapy to improve protein turnover during disuse atrophy and improve muscle regrowth during recovery from disuse atrophy in adult muscle. Therefore, we investigated whether massage can cause beneficial adaptations in skeletal muscle from aged rats during normal weight-bearing (WB) conditions, hindlimb suspension (HS), or reloading (RE) following HS. Aged (30 months) male Fischer 344/Brown Norway rats were divided into two experiments: (1) WB for 7 days (WB, n = 8), WB with massage (WBM, n = 8), HS for 7 days (HS7, n = 8), or HS with massage (HSM, n = 8), and (2) WB for 14 days (WB14, n = 8), HS for 14 days (HS14, n = 8), reloading (RE, n = 10), or reloading with massage (REM, n = 10) for 7 days following HS. Deuterium oxide (D2O) labeling was used to assess dynamic protein and ribosome turnover in each group and anabolic signaling pathways were assessed. Massage did have an anabolic benefit during RE or WB. In contrast, massage during HS enhanced myofibrillar protein turnover in both the massaged limb and contralateral non-massaged limb compared with HS, but this did not prevent muscle loss. Overall, the data demonstrate that massage is not an effective mechanotherapy for prevention of atrophy during muscle disuse or recovery of muscle mass during reloading in aged rats.
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Affiliation(s)
- Marcus M Lawrence
- Aging and Metabolism Research Program, Oklahoma Medical Research Foundation, Oklahoma City, OK, 73104, USA
| | - Douglas W Van Pelt
- Department of Physical Therapy, University of Kentucky, Lexington, KY, 40536, USA
- Center for Muscle Biology, University of Kentucky, Lexington, KY, 40536, USA
| | - Amy L Confides
- Department of Physical Therapy, University of Kentucky, Lexington, KY, 40536, USA
- Center for Muscle Biology, University of Kentucky, Lexington, KY, 40536, USA
| | - Zachary R Hettinger
- Department of Physical Therapy, University of Kentucky, Lexington, KY, 40536, USA
- Center for Muscle Biology, University of Kentucky, Lexington, KY, 40536, USA
| | - Emily R Hunt
- Department of Physical Therapy, University of Kentucky, Lexington, KY, 40536, USA
- Center for Muscle Biology, University of Kentucky, Lexington, KY, 40536, USA
| | - Justin J Reid
- Aging and Metabolism Research Program, Oklahoma Medical Research Foundation, Oklahoma City, OK, 73104, USA
| | - Jaime L Laurin
- Aging and Metabolism Research Program, Oklahoma Medical Research Foundation, Oklahoma City, OK, 73104, USA
| | - Frederick F Peelor
- Aging and Metabolism Research Program, Oklahoma Medical Research Foundation, Oklahoma City, OK, 73104, USA
| | - Timothy A Butterfield
- Center for Muscle Biology, University of Kentucky, Lexington, KY, 40536, USA
- Department of Athletic Training and Clinical Nutrition, University of Kentucky, Lexington, KY, 40536, USA
| | - Benjamin F Miller
- Aging and Metabolism Research Program, Oklahoma Medical Research Foundation, Oklahoma City, OK, 73104, USA
| | - Esther E Dupont-Versteegden
- Department of Physical Therapy, University of Kentucky, Lexington, KY, 40536, USA.
- Center for Muscle Biology, University of Kentucky, Lexington, KY, 40536, USA.
- College of Health Sciences, University of Kentucky, 900 S. Limestone CTW210E, Lexington, KY, 40536-0200, USA.
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5
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MacDonald TL, Pattamaprapanont P, Pathak P, Fernandez N, Freitas EC, Hafida S, Mitri J, Britton SL, Koch LG, Lessard SJ. Hyperglycaemia is associated with impaired muscle signalling and aerobic adaptation to exercise. Nat Metab 2020; 2:902-917. [PMID: 32694831 PMCID: PMC8278496 DOI: 10.1038/s42255-020-0240-7] [Citation(s) in RCA: 28] [Impact Index Per Article: 7.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 11/12/2019] [Accepted: 06/12/2020] [Indexed: 12/11/2022]
Abstract
Increased aerobic exercise capacity, as a result of exercise training, has important health benefits. However, some individuals are resistant to improvements in exercise capacity, probably due to undetermined genetic and environmental factors. Here, we show that exercise-induced improvements in aerobic capacity are blunted and aerobic remodelling of skeletal muscle is impaired in several animal models associated with chronic hyperglycaemia. Our data point to chronic hyperglycaemia as a potential negative regulator of aerobic adaptation, in part, via glucose-mediated modifications of the extracellular matrix, impaired vascularization and aberrant mechanical signalling in muscle. We also observe low exercise capacity and enhanced c-Jun N-terminal kinase activation in response to exercise in humans with impaired glucose tolerance. Our work indicates that current shifts in dietary and metabolic health, associated with increasing incidence of hyperglycaemia, might impair muscular and organismal adaptations to exercise training, including aerobic capacity as one of its key health outcomes.
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Affiliation(s)
- Tara L MacDonald
- Research Division, Joslin Diabetes Center, Boston, MA, USA
- Harvard Medical School, Harvard University, Boston, MA, USA
- Department of Medicine, Brigham and Women's Hospital, Boston, MA, USA
| | - Pattarawan Pattamaprapanont
- Research Division, Joslin Diabetes Center, Boston, MA, USA
- Harvard Medical School, Harvard University, Boston, MA, USA
- Department of Medicine, Brigham and Women's Hospital, Boston, MA, USA
| | - Prerana Pathak
- Research Division, Joslin Diabetes Center, Boston, MA, USA
| | | | - Ellen C Freitas
- School of Physical Education and Sport, University of São Paulo, Ribeirão Preto, Brazil
| | - Samar Hafida
- Research Division, Joslin Diabetes Center, Boston, MA, USA
- Department of Medicine, Brigham and Women's Hospital, Boston, MA, USA
| | - Joanna Mitri
- Research Division, Joslin Diabetes Center, Boston, MA, USA
- Department of Medicine, Brigham and Women's Hospital, Boston, MA, USA
| | - Steven L Britton
- Department of Molecular and Integrative Physiology, and Department of Anesthesiology, University of Michigan, Ann Arbor, MI, USA
| | - Lauren G Koch
- Department of Physiology and Pharmacology, The University of Toledo, Toledo, OH, USA
| | - Sarah J Lessard
- Research Division, Joslin Diabetes Center, Boston, MA, USA.
- Harvard Medical School, Harvard University, Boston, MA, USA.
- Department of Medicine, Brigham and Women's Hospital, Boston, MA, USA.
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6
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Biglari S, Afousi AG, Mafi F, Shabkhiz F. High-intensity interval training-induced hypertrophy in gastrocnemius muscle via improved IGF-I/Akt/FoxO and myostatin/Smad signaling pathways in rats. Physiol Int 2020; 107:220-230. [PMID: 32644938 DOI: 10.1556/2060.2020.00020] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/26/2019] [Accepted: 04/04/2020] [Indexed: 12/17/2022]
Abstract
Objective It has been shown that high-intensity interval training (HIIT) leads to skeletal muscle hypertrophy; however, its mechanisms of cellular and molecular regulation are still unclear. The purpose of this study was to investigate the effect of HIIT on muscle hypertrophy and major signal transduction pathways. Design 12 male rats were randomly divided into two groups: control and HIIT. The exercise group performed 30-min HIIT in each session (5 × 4-min intervals running at 85-95% VO2max separated by 2-min active rest at 55-60% VO2max), 3 days/week for 8 weeks. Muscle fiber cross-sectional area (CSA) and the expression of signal transduction pathway proteins were determined in the gastrocnemius muscle. Results In the HIIT group, the expression of IGF-I, IGF-IR Akt, p-Akt, AMPKα, p-AMPKα and follistatin increased significantly, whereas a significant decrease was observed in the expression of FoxO1, p-FoxO1, myostatin, ActRIIB, Smad2/3 and p-Smad2/3 (P < 0.05). However, there were no significant differences between the HIIT and control groups in the expression of mTOR, p-mTOR, P70S6K, and p-P70S6K (P > 0.05). In addition, CSA and gastrocnemius muscle weight increased significantly in the HIIT group (P < 0.05). Conclusions HIIT induced muscle hypertrophy by improving IGF-I/Akt/FoxO and myostatin/Smad signal transduction pathways.
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Affiliation(s)
- Soheil Biglari
- Department of Exercise Physiology, Faculty of Physical Education and Exercise Sciences, University of Tehran, Tehran, Islamic Republic of Iran
| | - Alireza Ghardashi Afousi
- Department of Exercise Physiology, Faculty of Physical Education and Exercise Sciences, University of Tehran, Tehran, Islamic Republic of Iran
| | - Farnoosh Mafi
- Department of Exercise Physiology, Faculty of Physical Education and Exercise Sciences, University of Tehran, Tehran, Islamic Republic of Iran
| | - Fatemeh Shabkhiz
- Department of Exercise Physiology, Faculty of Physical Education and Exercise Sciences, University of Tehran, Tehran, Islamic Republic of Iran
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7
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Estrada-Bonilla YC, Castro PATS, Luna GLF, Souza ABA, Santos GS, Salvini TF, Leal AMO, Russo TL. Reaching task performance is associated to neuromuscular junction adaptations in rats with induced diabetes mellitus. ACTA ACUST UNITED AC 2020; 53:e8763. [PMID: 32520205 PMCID: PMC7279698 DOI: 10.1590/1414-431x20208763] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/16/2019] [Accepted: 02/13/2020] [Indexed: 11/22/2022]
Abstract
Upper limb performance is affected by diabetes mellitus (DM). Neuromuscular junction (NMJ) is a key structure to understand the relationship between performance and morphology in DM. The aim of the study was to analyze NMJ plasticity due to DM in an animal model and its relationship with the function of forelimbs in rats. Twelve Wistar rats were divided into control (C) and DM groups. Animals were trained to perform a grasping task, following procedures of habituation, shaping, and reaching task. DM was induced using streptozotocin. Forelimb neuromuscular performance for dexterity was evaluated one day before DM induction and five weeks following induction. After that, biceps, triceps, and finger flexors and extensors were removed. Connective tissue and muscle fiber cross-sectional area (CSA) were measured. NMJ was assessed by its morphometric characteristics (area, perimeter, and maximum diameter), using ImageJ software. Motor performance analyses were made using single pellet retrieval task performance test. Student’s t-test was used for comparisons between groups. A significant decrease in all NMJ morphometric parameters was observed in the DM group compared with the C group. Results showed that DM generated NMJ retraction in muscles involved in a reaching task. These alterations are related to signs of muscular atrophy and to poor reaching task performance. In conclusion, induced DM caused NMJ retraction and muscular atrophy in muscles involved in reaching task performance. Induced DM caused significantly lower motor performance, especially in the final moments of evaluation, when DM compromised the tropism of the muscular tissue.
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Affiliation(s)
- Y C Estrada-Bonilla
- Departamento de Fisioterapia, Universidade Federal de São Carlos, São Carlos, SP, Brasil.,Body, Subject and Education Research Group, Universidad Santo Tomás de Aquino, Bogotá, D.C., Colombia
| | - P A T S Castro
- Departamento de Fisioterapia, Universidade Federal de São Carlos, São Carlos, SP, Brasil
| | - G L F Luna
- Departamento de Fisioterapia, Universidade Federal de São Carlos, São Carlos, SP, Brasil
| | - A B A Souza
- Departamento de Fisioterapia, Universidade Federal de São Carlos, São Carlos, SP, Brasil
| | - G S Santos
- Departamento de Fisioterapia, Universidade Federal de São Carlos, São Carlos, SP, Brasil
| | - T F Salvini
- Departamento de Fisioterapia, Universidade Federal de São Carlos, São Carlos, SP, Brasil
| | - A M O Leal
- Departamento de Medicina, Universidade Federal de São Carlos, São Carlos, SP, Brasil
| | - T L Russo
- Departamento de Fisioterapia, Universidade Federal de São Carlos, São Carlos, SP, Brasil
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8
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Van Pelt DW, Confides AL, Abshire SM, Hunt ER, Dupont-Versteegden EE, Butterfield TA. Age-related responses to a bout of mechanotherapy in skeletal muscle of rats. J Appl Physiol (1985) 2019; 127:1782-1791. [PMID: 31670600 PMCID: PMC6962605 DOI: 10.1152/japplphysiol.00641.2019] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/11/2019] [Revised: 10/14/2019] [Accepted: 10/24/2019] [Indexed: 12/25/2022] Open
Abstract
Cyclic compressive loading (CCL) is a massage mimetic that improves muscle regrowth from atrophy in adult rats. Therefore, we tested if a single bout of CCL increases anabolic signaling and protein synthesis in muscle during normal, weight-bearing conditions in gastrocnemius muscle from adult and aged rats. Male Brown Norway/F344 rats at 10 (adult) and 30 (aged) months of age were assigned control or CCL (receiving a single bout of CCL). Twenty-four hours following a single bout of CCL there was no change in protein synthesis, Akt, or GSK3β signaling at either age, despite adult rats having higher abundance and activation of mechanosensitive pathways (integrins and integrin-linked kinase). Murf1 was elevated in response to CCL in both age groups, potentially indicating muscle remodeling. Muscle from aged rats exhibited an increase in heat shock protein (HSP) 25 and HSP70 and in the cold shock protein RNA-binding motif 3 (RBM3), demonstrating a unique stress response to CCL in aged muscle only. Finally, muscle from aged rats exhibited higher basal protein synthesis that was corroborated by elevated eIF2Bε and rpS6 signaling, without an additional effect of CCL. In summary, a single bout of CCL does not have anabolic effects on skeletal muscle during normal, weight-bearing conditions, even though it has previously been shown to improve regrowth from atrophy. These data demonstrate that interventions that may help recover from atrophy do not necessarily induce muscle hypertrophy in unperturbed conditions.NEW & NOTEWORTHY Massage has been demonstrated to be an effective mechanotherapy to improve recovery from atrophy in adult skeletal muscle; however, this study shows that a single bout of massage fails to increase protein synthesis or anabolic signaling in adult or aged skeletal muscle during normal, weight-bearing conditions. Altogether, our data suggest massage is a useful mechanotherapy for preserving skeletal muscle when combined with other interventions but is not an anabolic stimulus on its own.
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Affiliation(s)
- Douglas W Van Pelt
- Department of Physical Therapy, University of Kentucky, Lexington, Kentucky
- Center for Muscle Biology, University of Kentucky, Lexington, Kentucky
| | - Amy L Confides
- Department of Physical Therapy, University of Kentucky, Lexington, Kentucky
- Center for Muscle Biology, University of Kentucky, Lexington, Kentucky
| | - Sarah M Abshire
- Center for Muscle Biology, University of Kentucky, Lexington, Kentucky
- Department of Athletic Training and Clinical Nutrition, University of Kentucky, Lexington, Kentucky
| | - Emily R Hunt
- Center for Muscle Biology, University of Kentucky, Lexington, Kentucky
- Rehabilitation Sciences PhD Program, University of Kentucky, Lexington, Kentucky
| | - Esther E Dupont-Versteegden
- Department of Physical Therapy, University of Kentucky, Lexington, Kentucky
- Center for Muscle Biology, University of Kentucky, Lexington, Kentucky
| | - Timothy A Butterfield
- Center for Muscle Biology, University of Kentucky, Lexington, Kentucky
- Department of Athletic Training and Clinical Nutrition, University of Kentucky, Lexington, Kentucky
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9
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Kirby TJ. Mechanosensitive pathways controlling translation regulatory processes in skeletal muscle and implications for adaptation. J Appl Physiol (1985) 2019; 127:608-618. [PMID: 31295035 DOI: 10.1152/japplphysiol.01031.2018] [Citation(s) in RCA: 23] [Impact Index Per Article: 4.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
The ability of myofibers to sense and respond appropriately to mechanical signals is one of the primary determinants of the skeletal muscle phenotype. In response to a change in mechanical load, muscle cells alter their protein metabolism, primarily through the regulation of protein synthesis rate. Protein synthesis rates are determined by both translation efficiency and translational capacity within the muscle. Translational capacity is strongly determined by the ribosome content of the muscle; thus the regulation of ribosomal biogenesis by mechanical inputs has been an area of recent interest. Despite the clear association between mechanical signals and changes in protein metabolism, the molecular pathways that link these events are still not fully elucidated. This review focuses on recent studies looking at how mechanosignaling impacts translational events. The role of impaired mechanotransduction in aging is discussed, as is the connection between age-dependent signaling defects and compromised ribosomal biogenesis during mechanical overload. Finally, emerging evidence suggests that the nucleus can act as a mechanosensitive element and that this mode of mechanotransduction may have an important role in skeletal muscle physiology and adaptation.
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Affiliation(s)
- Tyler J Kirby
- Nancy E. and Peter C. Meinig School of Biomedical Engineering, Cornell University, Ithaca, New York.,Weill Institute for Cell and Molecular Biology, Cornell University, Ithaca, New York
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10
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The Role of AMPK in the Regulation of Skeletal Muscle Size, Hypertrophy, and Regeneration. Int J Mol Sci 2018; 19:ijms19103125. [PMID: 30314396 PMCID: PMC6212977 DOI: 10.3390/ijms19103125] [Citation(s) in RCA: 127] [Impact Index Per Article: 21.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/28/2018] [Revised: 10/08/2018] [Accepted: 10/09/2018] [Indexed: 12/22/2022] Open
Abstract
AMPK (5’-adenosine monophosphate-activated protein kinase) is heavily involved in skeletal muscle metabolic control through its regulation of many downstream targets. Because of their effects on anabolic and catabolic cellular processes, AMPK plays an important role in the control of skeletal muscle development and growth. In this review, the effects of AMPK signaling, and those of its upstream activator, liver kinase B1 (LKB1), on skeletal muscle growth and atrophy are reviewed. The effect of AMPK activity on satellite cell-mediated muscle growth and regeneration after injury is also reviewed. Together, the current data indicate that AMPK does play an important role in regulating muscle mass and regeneration, with AMPKα1 playing a prominent role in stimulating anabolism and in regulating satellite cell dynamics during regeneration, and AMPKα2 playing a potentially more important role in regulating muscle degradation during atrophy.
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11
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Hulston CJ, Woods RM, Dewhurst‐Trigg R, Parry SA, Gagnon S, Baker L, James LJ, Markey O, Martin NRW, Ferguson RA, van Hall G. Resistance exercise stimulates mixed muscle protein synthesis in lean and obese young adults. Physiol Rep 2018; 6:e13799. [PMID: 30009507 PMCID: PMC6046643 DOI: 10.14814/phy2.13799] [Citation(s) in RCA: 14] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/24/2018] [Revised: 06/26/2018] [Accepted: 06/27/2018] [Indexed: 12/16/2022] Open
Abstract
Obese individuals exhibit a diminished muscle protein synthesis response to nutrient stimulation when compared with their lean counterparts. However, the effect of obesity on exercise-stimulated muscle protein synthesis remains unknown. Nine lean (23.5 ± 0.6 kg/m2 ) and 8 obese (33.6 ± 1.2 kg/m2 ) physically active young adults participated in a study that determined muscle protein synthesis and intracellular signaling at rest and following an acute bout of resistance exercise. Mixed muscle protein synthesis was determined by combining stable isotope tracer ([13 C6 ]phenylalanine) infusion with serial biopsies of the vastus lateralis. A unilateral leg resistance exercise model was adopted so that resting and postexercise measurements of muscle protein synthesis could be obtained simultaneously. Obesity was associated with higher basal levels of serum insulin (P < 0.05), plasma triacylglycerol (P < 0.01), plasma cholesterol (P < 0.01), and plasma CRP (P < 0.01), as well as increased insulin resistance determined by HOMA-IR (P < 0.05). However, resting and postexercise rates of muscle protein synthesis were not significantly different between lean and obese participants (P = 0.644). Furthermore, resistance exercise stimulated muscle protein synthesis (~50% increase) in both groups (P < 0.001), with no difference between lean and obese (P = 0.809). Temporal increases in the phosphorylation of intracellular signaling proteins (AKT/4EBP1/p70S6K) were observed within the exercised leg (P < 0.05), with no differences between lean and obese. These findings suggest a normal anabolic response to muscle loading in obese young adults.
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Affiliation(s)
- Carl J. Hulston
- School of Sport, Exercise & Health SciencesLoughborough UniversityLoughboroughLeicestershireUnited Kingdom
| | - Rachel M. Woods
- School of Sport, Exercise & Health SciencesLoughborough UniversityLoughboroughLeicestershireUnited Kingdom
| | - Rebecca Dewhurst‐Trigg
- School of Sport, Exercise & Health SciencesLoughborough UniversityLoughboroughLeicestershireUnited Kingdom
| | - Sion A. Parry
- School of Sport, Exercise & Health SciencesLoughborough UniversityLoughboroughLeicestershireUnited Kingdom
- Present address:
Sion A. Parry Oxford Centre for Diabetes, Endocrinology and MetabolismUniversity of OxfordChurchill HospitalOxfordUnited Kingdom
| | - Stephanie Gagnon
- School of Sport, Exercise & Health SciencesLoughborough UniversityLoughboroughLeicestershireUnited Kingdom
| | - Luke Baker
- School of Sport, Exercise & Health SciencesLoughborough UniversityLoughboroughLeicestershireUnited Kingdom
| | - Lewis J. James
- School of Sport, Exercise & Health SciencesLoughborough UniversityLoughboroughLeicestershireUnited Kingdom
| | - Oonagh Markey
- School of Sport, Exercise & Health SciencesLoughborough UniversityLoughboroughLeicestershireUnited Kingdom
| | - Neil R. W. Martin
- School of Sport, Exercise & Health SciencesLoughborough UniversityLoughboroughLeicestershireUnited Kingdom
| | - Richard A. Ferguson
- School of Sport, Exercise & Health SciencesLoughborough UniversityLoughboroughLeicestershireUnited Kingdom
| | - Gerrit van Hall
- Clinical Metabolomics Core FacilityDepartment of Clinical BiochemistryRigshospitaletDepartment of Biomedical SciencesUniversity of CopenhagenCopenhagenDenmark
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12
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Margolis LM, Carbone JW, Berryman CE, Carrigan CT, Murphy NE, Ferrando AA, Young AJ, Pasiakos SM. Severe energy deficit at high altitude inhibits skeletal muscle mTORC1-mediated anabolic signaling without increased ubiquitin proteasome activity. FASEB J 2018; 32:fj201800163RR. [PMID: 29878853 DOI: 10.1096/fj.201800163rr] [Citation(s) in RCA: 17] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/15/2022]
Abstract
Muscle loss at high altitude (HA) is attributable to energy deficit and a potential dysregulation of anabolic signaling. Exercise and protein ingestion can attenuate the effects of energy deficit on muscle at sea level (SL). Whether these effects are observed when energy deficit occurs at HA is unknown. To address this, muscle obtained from lowlanders ( n = 8 males) at SL, acute HA (3 h, 4300 m), and chronic HA (21 d, -1766 kcal/d energy balance) before [baseline (Base)] and after 80 min of aerobic exercise followed by a 2-mile time trial [postexercise (Post)] and 3 h into recovery (Rec) after ingesting whey protein (25 g) were analyzed using standard molecular techniques. At SL, Post, and REC, p-mechanistic target of rapamycin (mTOR)Ser2448, p-p70 ribosomal protein S6 kinase (p70S6K)Ser424/421, and p-ribosomal protein S6 (rpS6)Ser235/236 were similar and higher ( P < 0.05) than Base. At acute HA, Post p-mTORSer2448 and Post and REC p-p70S6KSer424/421 were not different from Base and lower than SL ( P < 0.05). At chronic HA, Post and Rec p-mTORSer2448 and p-p70S6KSer424/421 were not different from Base and lower than SL, and, independent of time, p-rpS6Ser235/236 was lower than SL ( P < 0.05). Post proteasome activity was lower ( P < 0.05) than Base and Rec, independent of phase. Our findings suggest that HA exposure induces muscle anabolic resistance that is exacerbated by energy deficit during acclimatization, with no change in proteolysis.-Margolis, L. M., Carbone, J. W., Berryman, C. E., Carrigan, C. T., Murphy, N. E., Ferrando, A. A., Young, A. J., Pasiakos, S. M. Severe energy deficit at high altitude inhibits skeletal muscle mTORC1-mediated anabolic signaling without increased ubiquitin proteasome activity.
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Affiliation(s)
- Lee M Margolis
- Military Nutrition Division, U.S. Army Research Institute of Environmental Medicine, Natick, Massachusetts, USA
- Oak Ridge Institute of Science and Education, Oak Ridge, Tennessee, USA
| | - John W Carbone
- Oak Ridge Institute of Science and Education, Oak Ridge, Tennessee, USA
- School of Health Sciences, Eastern Michigan University, Ypsilanti, Michigan, USA
| | - Claire E Berryman
- Military Nutrition Division, U.S. Army Research Institute of Environmental Medicine, Natick, Massachusetts, USA
- Oak Ridge Institute of Science and Education, Oak Ridge, Tennessee, USA
| | - Christopher T Carrigan
- Military Nutrition Division, U.S. Army Research Institute of Environmental Medicine, Natick, Massachusetts, USA
| | - Nancy E Murphy
- Military Nutrition Division, U.S. Army Research Institute of Environmental Medicine, Natick, Massachusetts, USA
| | - Arny A Ferrando
- Department of Geriatrics, The Center for Translational Research in Aging and Longevity, Donald W. Reynolds Institute of Aging, University of Arkansas for Medical Sciences, Little Rock, Arkansas, USA
| | - Andrew J Young
- Military Nutrition Division, U.S. Army Research Institute of Environmental Medicine, Natick, Massachusetts, USA
- Oak Ridge Institute of Science and Education, Oak Ridge, Tennessee, USA
| | - Stefan M Pasiakos
- Military Nutrition Division, U.S. Army Research Institute of Environmental Medicine, Natick, Massachusetts, USA
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13
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Fortes MAS, Scervino MVM, Marzuca-Nassr GN, Vitzel KF, da Justa Pinheiro CH, Curi R. Hypertrophy Stimulation at the Onset of Type I Diabetes Maintains the Soleus but Not the EDL Muscle Mass in Wistar Rats. Front Physiol 2017; 8:830. [PMID: 29123487 PMCID: PMC5662641 DOI: 10.3389/fphys.2017.00830] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/07/2017] [Accepted: 10/06/2017] [Indexed: 12/17/2022] Open
Abstract
Diabetes mellitus induces a reduction in skeletal muscle mass and strength. Strength training is prescribed as part of treatment since it improves glycemic control and promotes increase of skeletal muscle mass. The mechanisms involved in overload-induced muscle hypertrophy elicited at the establishment of the type I diabetic state was investigated in Wistar rats. The purpose was to examine whether the overload-induced hypertrophy can counteract the hypotrophy associated to the diabetic state. The experiments were performed in oxidative (soleus) or glycolytic (EDL) muscles. PI3K/Akt/mTOR protein synthesis pathway was evaluated 7 days after overload-induced hypertrophy of soleus and of EDL muscles. The mRNA expression of genes associated with different signaling pathways that control muscle hypertrophy was also evaluated: mechanotransduction (FAK), Wnt/β-catenin, myostatin, and follistatin. The soleus and EDL muscles when submitted to overload had similar hypertrophic responses in control and diabetic animals. The increase of absolute and specific twitch and tetanic forces had the same magnitude as muscle hypertrophic response. Hypertrophy of the EDL muscle from diabetic animals mostly involved mechanical loading-stimulated PI3K/Akt/mTOR pathway besides the reduced activation of AMP-activated protein kinase (AMPK) and decrease of myostatin expression. Hypertrophy was more pronounced in the soleus muscle of diabetic animals due to a more potent activation of rpS6 and increased mRNA expression of insulin-like growth factor-1 (IGF-1), mechano-growth factor (MGF) and follistatin, and decrease of myostatin, MuRF-1 and atrogin-1 contents. The signaling changes enabled the soleus muscle mass and force of the diabetic rats to reach the values of the control group.
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Affiliation(s)
- Marco A S Fortes
- Department of Physiology and Biophysics, Institute of Biomedical Sciences, University of São Paulo, São Paulo, Brazil
| | - Maria V M Scervino
- Department of Physiology and Biophysics, Institute of Biomedical Sciences, University of São Paulo, São Paulo, Brazil
| | - Gabriel N Marzuca-Nassr
- Department of Physiology and Biophysics, Institute of Biomedical Sciences, University of São Paulo, São Paulo, Brazil.,Department of Internal Medicine, Faculty of Medicine, Universidad de La Frontera, Temuco, Chile
| | - Kaio F Vitzel
- School of Health Sciences, College of Health, Massey University, Albany, New Zealand
| | - Carlos H da Justa Pinheiro
- Department of Physiology and Biophysics, Institute of Biomedical Sciences, University of São Paulo, São Paulo, Brazil
| | - Rui Curi
- Department of Physiology and Biophysics, Institute of Biomedical Sciences, University of São Paulo, São Paulo, Brazil.,Interdisciplinary Post-Graduate Program in Health Sciences, Cruzeiro do Sul University, São Paulo, Brazil
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14
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Figueiredo VC, Markworth JF, Cameron-Smith D. Considerations on mTOR regulation at serine 2448: implications for muscle metabolism studies. Cell Mol Life Sci 2017; 74:2537-2545. [PMID: 28220207 PMCID: PMC11107628 DOI: 10.1007/s00018-017-2481-5] [Citation(s) in RCA: 49] [Impact Index Per Article: 7.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/20/2016] [Revised: 01/27/2017] [Accepted: 01/30/2017] [Indexed: 02/03/2023]
Abstract
The mammalian target of rapamycin (mTOR) complex exerts a pivotal role in protein anabolism and cell growth. Despite its importance, few studies adequately address the complexity of phosphorylation of the mTOR protein itself to enable conclusions to be drawn on the extent of kinase activation following this event. In particular, a large number of studies in the skeletal muscle biology field have measured Serine 2448 (Ser2448) phosphorylation as a proxy of mTOR kinase activity. However, the evidence to be described is that Ser2448 is not a measure of mTOR kinase activity nor is a target of AKT activity and instead has inhibitory effects on the kinase that is targeted by the downstream effector p70S6K in a negative feedback loop mechanism, which is evident when revisiting muscle research studies. It is proposed that this residue modification acts as a fine-tuning mechanism that has been gained during vertebrate evolution. In conclusion, it is recommended that Ser2448 is an inadequate measure and that preferential analysis of mTORC1 activation should focus on the downstream and effector proteins, including p70S6K and 4E-BP1, along mTOR protein partners that bind to mTOR protein to form the active complexes 1 and 2.
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Affiliation(s)
- Vandré Casagrande Figueiredo
- The Liggins Institute, University of Auckland, 85 Park Road, Grafton, Private Bag 92019, Auckland, 1023, New Zealand
| | - James F Markworth
- The Liggins Institute, University of Auckland, 85 Park Road, Grafton, Private Bag 92019, Auckland, 1023, New Zealand
| | - David Cameron-Smith
- The Liggins Institute, University of Auckland, 85 Park Road, Grafton, Private Bag 92019, Auckland, 1023, New Zealand.
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15
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Moore TM, Mortensen XM, Ashby CK, Harris AM, Kump KJ, Laird DW, Adams AJ, Bray JK, Chen T, Thomson DM. The effect of caffeine on skeletal muscle anabolic signaling and hypertrophy. Appl Physiol Nutr Metab 2017; 42:621-629. [DOI: 10.1139/apnm-2016-0547] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
Caffeine is a widely consumed stimulant with the potential to enhance physical performance through multiple mechanisms. However, recent in vitro findings have suggested that caffeine may block skeletal muscle anabolic signaling through AMP-activated protein kinase (AMPK)-mediated inhibition of mechanistic target of rapamycin (mTOR) signaling pathway. This could negatively affect protein synthesis and the capacity for muscle growth. The primary purpose of this study was to assess the effect of caffeine on in vivo AMPK and mTOR pathway signaling, protein synthesis, and muscle growth. In cultured C2C12 muscle cells, physiological levels of caffeine failed to impact mTOR activation or myoblast proliferation or differentiation. We found that caffeine administration to mice did not significantly enhance the phosphorylation of AMPK or inhibit signaling proteins downstream of mTOR (p70S6k, S6, or 4EBP1) or protein synthesis after a bout of electrically stimulated contractions. Skeletal muscle-specific knockout of LKB1, the primary AMPK activator in skeletal muscle, on the other hand, eliminated AMPK activation by contractions and enhanced S6k, S6, and 4EBP1 activation before and after contractions. In rats, the addition of caffeine did not affect plantaris hypertrophy induced by the tenotomy of the gastrocnemius and soleus muscles. In conclusion, caffeine administration does not impair skeletal muscle load-induced mTOR signaling, protein synthesis, or muscle hypertrophy.
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Affiliation(s)
- Timothy M. Moore
- Department of Physiology and Developmental Biology, 4005 LSB, Brigham Young University, Provo, UT 84602, USA
- Department of Physiology and Developmental Biology, 4005 LSB, Brigham Young University, Provo, UT 84602, USA
| | - Xavier M. Mortensen
- Department of Physiology and Developmental Biology, 4005 LSB, Brigham Young University, Provo, UT 84602, USA
- Department of Physiology and Developmental Biology, 4005 LSB, Brigham Young University, Provo, UT 84602, USA
| | - Conrad K. Ashby
- Department of Physiology and Developmental Biology, 4005 LSB, Brigham Young University, Provo, UT 84602, USA
- Department of Physiology and Developmental Biology, 4005 LSB, Brigham Young University, Provo, UT 84602, USA
| | - Alexander M. Harris
- Department of Physiology and Developmental Biology, 4005 LSB, Brigham Young University, Provo, UT 84602, USA
- Department of Physiology and Developmental Biology, 4005 LSB, Brigham Young University, Provo, UT 84602, USA
| | - Karson J. Kump
- Department of Physiology and Developmental Biology, 4005 LSB, Brigham Young University, Provo, UT 84602, USA
- Department of Physiology and Developmental Biology, 4005 LSB, Brigham Young University, Provo, UT 84602, USA
| | - David W. Laird
- Department of Physiology and Developmental Biology, 4005 LSB, Brigham Young University, Provo, UT 84602, USA
- Department of Physiology and Developmental Biology, 4005 LSB, Brigham Young University, Provo, UT 84602, USA
| | - Aaron J. Adams
- Department of Physiology and Developmental Biology, 4005 LSB, Brigham Young University, Provo, UT 84602, USA
- Department of Physiology and Developmental Biology, 4005 LSB, Brigham Young University, Provo, UT 84602, USA
| | - Jeremy K. Bray
- Department of Physiology and Developmental Biology, 4005 LSB, Brigham Young University, Provo, UT 84602, USA
- Department of Physiology and Developmental Biology, 4005 LSB, Brigham Young University, Provo, UT 84602, USA
| | - Ting Chen
- Department of Physiology and Developmental Biology, 4005 LSB, Brigham Young University, Provo, UT 84602, USA
- Department of Physiology and Developmental Biology, 4005 LSB, Brigham Young University, Provo, UT 84602, USA
| | - David M. Thomson
- Department of Physiology and Developmental Biology, 4005 LSB, Brigham Young University, Provo, UT 84602, USA
- Department of Physiology and Developmental Biology, 4005 LSB, Brigham Young University, Provo, UT 84602, USA
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16
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Sakuma K, Aoi W, Yamaguchi A. Molecular mechanism of sarcopenia and cachexia: recent research advances. Pflugers Arch 2017; 469:573-591. [PMID: 28101649 DOI: 10.1007/s00424-016-1933-3] [Citation(s) in RCA: 99] [Impact Index Per Article: 14.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/12/2016] [Revised: 12/28/2016] [Accepted: 12/29/2016] [Indexed: 12/17/2022]
Abstract
Skeletal muscle provides a fundamental basis for human function, enabling locomotion and respiration. Muscle loss occurs as a consequence of several chronic diseases (cachexia) and normal aging (sarcopenia). Although many negative regulators (atrogin-1, muscle ring finger-1, nuclear factor-kappaB (NF-κB), myostatin, etc.) have been proposed to enhance protein degradation during both sarcopenia and cachexia, the adaptation of these mediators markedly differs within both conditions. Sarcopenia and cachectic muscles have been demonstrated to be abundant in myostatin-linked molecules. The ubiquitin-proteasome system (UPS) is activated during rapid atrophy model (cancer cachexia), but few mediators of the UPS change during sarcopenia. NF-κB signaling is activated in cachectic, but not in sarcopenic, muscle. Recent studies have indicated the age-related defect of autophagy signaling in skeletal muscle, whereas autophagic activation occurs in cachectic muscle. This review provides recent research advances dealing with molecular mediators modulating muscle mass in both sarcopenia and cachexia.
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Affiliation(s)
- Kunihiro Sakuma
- Institute for Liberal Arts, Environment and Society, Tokyo Institute of Technology, 2-12-1 Ookayama, Meguro-ku, Tokyo, 152-8550, Japan.
| | - Wataru Aoi
- Laboratory of Health Science, Graduate School of Life and Environmental Sciences, Kyoto Prefectural University, 1-5 Hangi-cho Shimogamo, Sakyo-ku, Kyoto, 606-8522, Japan
| | - Akihiko Yamaguchi
- Department of Physical Therapy, Health Sciences University of Hokkaido, Kanazawa, Ishikari-Tobetsu, Hokkaido, 061-0293, Japan
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17
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Russ DW, Acksel C, McCorkle KW, Edens NK, Garvey SM. Effects of Running Wheel Activity and Dietary HMB and β-alanine Co-Supplementation on Muscle Quality in Aged Male Rats. J Nutr Health Aging 2017; 21:554-561. [PMID: 28448086 DOI: 10.1007/s12603-016-0810-2] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/06/2023]
Abstract
OBJECTIVE Loss of skeletal muscle function is linked to increased risk for loss of health and independence in older adults. Dietary interventions that can enhance aging muscle function, alone or in combination with exercise, may offer an effective way to reduce these risks. The goal of this study was to evaluate the muscular effects of beta-hydroxy-beta-methylbutyrate (HMB) and beta-alanine (β-Ala) co-supplementation in aged Sprague-Dawley rats with voluntary access to running wheels (RW). METHODS Aged (20 months) rats were housed with ad libitum access to RW while on a purified diet for 4 weeks, then balanced for RW activity and assigned to either a control or an experimental diet (control + HMB and β-Ala) for the next 4 weeks (n = 10/group). At the end of the study, we assessed muscle size, in situ force and fatigability in the medial gastrocnemius muscles, as well as an array of protein markers related to various age- and activity-responsive signaling pathways. RESULTS Dietary HMB+β-Ala did not improve muscle force or fatigue resistance, but a trend for increased muscle cross-sectional area (CSA) was observed (P = 0.077). As a result, rats on the experimental diet exhibited reduced muscle quality (force/CSA; P = 0.032). Dietary HMB+β-Ala reduced both the abundance of PGC1-α (P = 0.050) and the ratio of the lipidated to non-lipidated forms of microtubule-associated protein 1 light chain 3 beta (P = 0.004), markers of mitochondrial biogenesis and autophagy, respectively. Some alterations in myostatin signaling also occurred in the dietary HMB+β-Ala group. There was an unexpected difference (P = 0.046) in RW activity, which increased throughout the study in the animals on the control diet, but not in animals on the experimental diet. CONCLUSIONS These data suggest that the short-term addition of dietary HMB+β-Ala to modest physical activity provided little enhancement of muscle function in this model of uncomplicated aging.
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Affiliation(s)
- D W Russ
- David W. Russ, PT, Ph.D. Associate Professor, Division of Physical Therapy , School of Rehab and Communication Sciences, Ohio University, W279 Grover Center, Athens, OH 45701, (ph.)740-566-0022, (fax)740-593-0293,
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18
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Age-related deficits in skeletal muscle recovery following disuse are associated with neuromuscular junction instability and ER stress, not impaired protein synthesis. Aging (Albany NY) 2016; 8:127-46. [PMID: 26826670 PMCID: PMC4761718 DOI: 10.18632/aging.100879] [Citation(s) in RCA: 138] [Impact Index Per Article: 17.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/05/2023]
Abstract
Age-related loss of muscle mass and strength can be accelerated by impaired recovery of muscle mass following a transient atrophic stimulus. The aim of this study was to identify the mechanisms underlying the attenuated recovery of muscle mass and strength in old rats following disuse-induced atrophy. Adult (9 month) and old (29 month) male F344BN rats underwent hindlimb unloading (HU) followed by reloading. HU induced significant atrophy of the hindlimb muscles in both adult (17-38%) and old (8-29%) rats, but only the adult rats exhibited full recovery of muscle mass and strength upon reloading. Upon reloading, total RNA and protein synthesis increased to a similar extent in adult and old muscles. At baseline and upon reloading, however, proteasome-mediated degradation was suppressed leading to an accumulation of ubiquitin-tagged proteins and p62. Further, ER stress, as measured by CHOP expression, was elevated at baseline and upon reloading in old rats. Analysis of mRNA expression revealed increases in HDAC4, Runx1, myogenin, Gadd45a, and the AChRs in old rats, suggesting neuromuscular junction instability/denervation. Collectively, our data suggests that with aging, impaired neuromuscular transmission and deficits in the proteostasis network contribute to defects in muscle fiber remodeling and functional recovery of muscle mass and strength.
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19
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Margolis LM, Rivas DA, Berrone M, Ezzyat Y, Young AJ, McClung JP, Fielding RA, Pasiakos SM. Prolonged Calorie Restriction Downregulates Skeletal Muscle mTORC1 Signaling Independent of Dietary Protein Intake and Associated microRNA Expression. Front Physiol 2016; 7:445. [PMID: 27761114 PMCID: PMC5050214 DOI: 10.3389/fphys.2016.00445] [Citation(s) in RCA: 26] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/26/2016] [Accepted: 09/20/2016] [Indexed: 01/18/2023] Open
Abstract
Short-term (5-10 days) calorie restriction (CR) downregulates muscle protein synthesis, with consumption of a high protein-based diet attenuating this decline. Benefit of increase protein intake is believed to be due to maintenance of amino acid-mediated anabolic signaling through the mechanistic target of rapamycin complex 1 (mTORC1), however, there is limited evidence to support this contention. The purpose of this investigation was to determine the effects of prolonged CR and high protein diets on skeletal muscle mTORC1 signaling and expression of associated microRNA (miR). Twelve-week old male Sprague Dawley rats consumed ad libitum (AL) or calorie restricted (CR; 40%) adequate (10%, AIN-93M) or high (32%) protein milk-based diets for 16 weeks. Body composition was determined using dual energy X-ray absorptiometry and muscle protein content was calculated from muscle homogenate protein concentrations expressed relative to fat-free mass to estimate protein content. Western blot and RT-qPCR were used to determine mTORC1 signaling and mRNA and miR expression in fasted mixed gastrocnemius. Independent of dietary protein intake, muscle protein content was 38% lower (P < 0.05) in CR compared to AL. Phosphorylation and total Akt, mTOR, rpS6, and p70S6K were lower (P < 0.05) in CR vs. AL, and total rpS6 was associated with muscle protein content (r = 0.64, r2 = 0.36). Skeletal muscle miR expression was not altered by either energy or protein intake. This study provides evidence that chronic CR attenuates muscle protein content by downregulating mTORC1 signaling. This response is independent of skeletal muscle miR and dietary protein.
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Affiliation(s)
- Lee M Margolis
- Nutrition, Exercise, Physiology, and Sarcopenia Laboratory, U.S. Department of Agriculture Jean Mayer Human Nutrition Research Center on Aging, Tufts UniversityBoston, MA, USA; Military Nutrition Division, US Army Research Institute of Environmental MedicineNatick, MA, USA
| | - Donato A Rivas
- Nutrition, Exercise, Physiology, and Sarcopenia Laboratory, U.S. Department of Agriculture Jean Mayer Human Nutrition Research Center on Aging, Tufts University Boston, MA, USA
| | - Maria Berrone
- Nutrition, Exercise, Physiology, and Sarcopenia Laboratory, U.S. Department of Agriculture Jean Mayer Human Nutrition Research Center on Aging, Tufts University Boston, MA, USA
| | - Yassine Ezzyat
- Nutrition, Exercise, Physiology, and Sarcopenia Laboratory, U.S. Department of Agriculture Jean Mayer Human Nutrition Research Center on Aging, Tufts University Boston, MA, USA
| | - Andrew J Young
- Military Nutrition Division, US Army Research Institute of Environmental Medicine Natick, MA, USA
| | - James P McClung
- Military Nutrition Division, US Army Research Institute of Environmental Medicine Natick, MA, USA
| | - Roger A Fielding
- Nutrition, Exercise, Physiology, and Sarcopenia Laboratory, U.S. Department of Agriculture Jean Mayer Human Nutrition Research Center on Aging, Tufts University Boston, MA, USA
| | - Stefan M Pasiakos
- Military Nutrition Division, US Army Research Institute of Environmental Medicine Natick, MA, USA
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20
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Fortes MAS, Marzuca-Nassr GN, Vitzel KF, da Justa Pinheiro CH, Newsholme P, Curi R. Housekeeping proteins: How useful are they in skeletal muscle diabetes studies and muscle hypertrophy models? Anal Biochem 2016; 504:38-40. [PMID: 27060530 DOI: 10.1016/j.ab.2016.03.023] [Citation(s) in RCA: 49] [Impact Index Per Article: 6.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/25/2016] [Revised: 03/28/2016] [Accepted: 03/29/2016] [Indexed: 12/15/2022]
Abstract
The use of Western blot analysis is of great importance in research, and the measurement of housekeeping proteins is commonly used for loading controls. However, Ponceau S staining has been shown to be an alternative to analysis of housekeeping protein levels as loading controls in some conditions. In the current study, housekeeping protein levels were measured in skeletal muscle hypertrophy and streptozotocin-induced diabetes experimental models. The following housekeeping proteins were investigated: glyceraldehyde-3-phosphate dehydrogenase (GAPDH), β-actin, α-tubulin, γ-tubulin, and α-actinin. Evidence is presented that Ponceau S is more reliable than housekeeping protein levels for specific protein quantifications in Western blot analysis.
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Affiliation(s)
- Marco Aurélio Salomão Fortes
- Department of Physiology and Biophysics, Institute of Biomedical Sciences, University of São Paulo, Butantã, São Paulo 05508-900, Brazil.
| | - Gabriel Nasri Marzuca-Nassr
- Department of Physiology and Biophysics, Institute of Biomedical Sciences, University of São Paulo, Butantã, São Paulo 05508-900, Brazil
| | - Kaio Fernando Vitzel
- Department of Physiology and Biophysics, Institute of Biomedical Sciences, University of São Paulo, Butantã, São Paulo 05508-900, Brazil
| | - Carlos Hermano da Justa Pinheiro
- Department of Physiology and Biophysics, Institute of Biomedical Sciences, University of São Paulo, Butantã, São Paulo 05508-900, Brazil
| | - Philip Newsholme
- School of Biomedical Sciences, Curtin Health Innovation Research Institute (CHIRI) Biosciences, Curtin University, Bentley, Perth, Western Australia 6102, Australia
| | - Rui Curi
- Department of Physiology and Biophysics, Institute of Biomedical Sciences, University of São Paulo, Butantã, São Paulo 05508-900, Brazil
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21
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Vigelsø A, Gram M, Dybboe R, Kuhlman AB, Prats C, Greenhaff PL, Constantin-Teodosiu D, Birk JB, Wojtaszewski JFP, Dela F, Helge JW. The effect of age and unilateral leg immobilization for 2 weeks on substrate utilization during moderate-intensity exercise in human skeletal muscle. J Physiol 2016; 594:2339-58. [PMID: 26801521 DOI: 10.1113/jp271712] [Citation(s) in RCA: 17] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/08/2015] [Accepted: 01/15/2016] [Indexed: 11/08/2022] Open
Abstract
KEY POINTS This study aimed to provide molecular insight into the differential effects of age and physical inactivity on the regulation of substrate metabolism during moderate-intensity exercise. Using the arteriovenous balance technique, we studied the effect of immobilization of one leg for 2 weeks on leg substrate utilization in young and older men during two-legged dynamic knee-extensor moderate-intensity exercise, as well as changes in key proteins in muscle metabolism before and after exercise. Age and immobilization did not affect relative carbohydrate and fat utilization during exercise, but the older men had higher uptake of exogenous fatty acids, whereas the young men relied more on endogenous fatty acids during exercise. Using a combined whole-leg and molecular approach, we provide evidence that both age and physical inactivity result in intramuscular lipid accumulation, but this occurs only in part through the same mechanisms. ABSTRACT Age and inactivity have been associated with intramuscular triglyceride (IMTG) accumulation. Here, we attempt to disentangle these factors by studying the effect of 2 weeks of unilateral leg immobilization on substrate utilization across the legs during moderate-intensity exercise in young (n = 17; 23 ± 1 years old) and older men (n = 15; 68 ± 1 years old), while the contralateral leg served as the control. After immobilization, the participants performed two-legged isolated knee-extensor exercise at 20 ± 1 W (∼50% maximal work capacity) for 45 min with catheters inserted in the brachial artery and both femoral veins. Biopsy samples obtained from vastus lateralis muscles of both legs before and after exercise were used for analysis of substrates, protein content and enzyme activities. During exercise, leg substrate utilization (respiratory quotient) did not differ between groups or legs. Leg fatty acid uptake was greater in older than in young men, and although young men demonstrated net leg glycerol release during exercise, older men showed net glycerol uptake. At baseline, IMTG, muscle pyruvate dehydrogenase complex activity and the protein content of adipose triglyceride lipase, acetyl-CoA carboxylase 2 and AMP-activated protein kinase (AMPK)γ3 were higher in young than in older men. Furthermore, adipose triglyceride lipase, plasma membrane-associated fatty acid binding protein and AMPKγ3 subunit protein contents were lower and IMTG was higher in the immobilized than the contralateral leg in young and older men. Thus, immobilization and age did not affect substrate choice (respiratory quotient) during moderate exercise, but the whole-leg and molecular differences in fatty acid mobilization could explain the age- and immobilization-induced IMTG accumulation.
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Affiliation(s)
- A Vigelsø
- XLAB, Center for Healthy Aging, Department of Biomedical Sciences, University of Copenhagen, Copenhagen, Denmark
| | - M Gram
- XLAB, Center for Healthy Aging, Department of Biomedical Sciences, University of Copenhagen, Copenhagen, Denmark
| | - R Dybboe
- XLAB, Center for Healthy Aging, Department of Biomedical Sciences, University of Copenhagen, Copenhagen, Denmark.,Section of Molecular Physiology, The August Krogh Centre, Department of Nutrition, Exercise and Sports, University of Copenhagen, Copenhagen, Denmark
| | - A B Kuhlman
- XLAB, Center for Healthy Aging, Department of Biomedical Sciences, University of Copenhagen, Copenhagen, Denmark
| | - C Prats
- XLAB, Center for Healthy Aging, Department of Biomedical Sciences, University of Copenhagen, Copenhagen, Denmark
| | - P L Greenhaff
- MRC/Arthritis Research UK Centre for Musculoskeletal Ageing Research, Arthritis Research UK Centre for Sport, Exercise and Osteoarthritis, School of Life Sciences, The Medical School, University of Nottingham, Nottingham, UK
| | - D Constantin-Teodosiu
- MRC/Arthritis Research UK Centre for Musculoskeletal Ageing Research, Arthritis Research UK Centre for Sport, Exercise and Osteoarthritis, School of Life Sciences, The Medical School, University of Nottingham, Nottingham, UK
| | - J B Birk
- Section of Molecular Physiology, The August Krogh Centre, Department of Nutrition, Exercise and Sports, University of Copenhagen, Copenhagen, Denmark
| | - J F P Wojtaszewski
- Section of Molecular Physiology, The August Krogh Centre, Department of Nutrition, Exercise and Sports, University of Copenhagen, Copenhagen, Denmark
| | - F Dela
- XLAB, Center for Healthy Aging, Department of Biomedical Sciences, University of Copenhagen, Copenhagen, Denmark
| | - J W Helge
- XLAB, Center for Healthy Aging, Department of Biomedical Sciences, University of Copenhagen, Copenhagen, Denmark
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Impaired Ribosome Biogenesis and Skeletal Muscle Growth in a Murine Model of Inflammatory Bowel Disease. Inflamm Bowel Dis 2016; 22:268-78. [PMID: 26588088 DOI: 10.1097/mib.0000000000000616] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/27/2023]
Abstract
BACKGROUND Inflammation is a factor potentially underpinning skeletal muscle mass. Intestinal-derived inflammation in inflammatory bowel disease (IBD) results in loss of muscle mass; however, the underlying mechanism is unclear. The interleukin 10 gene-deficient (Il10-/-) mouse is a genetically modified animal model of IBD that can be used to study the effect of intestinal-derived inflammation on muscles. METHODS Il10-/- and C57BL/6 wild-type (WT) mice were inoculated with intestinal bacteria to induce colon inflammation at the fifth week of age. Skeletal muscles were collected between 7 and 14 weeks of age for analysis of muscle weight, myofiber cross-sectional area (CSA), and molecular markers of inflammation and anabolism pathways, with a focus on ribosome biogenesis. RESULTS Il10-/- animals that developed colon inflammation had a marked increase in muscle immunoglobulin G (IgG) compared with WT. Inflamed Il10-/- animals had impaired muscle mass gain and smaller myofiber CSA. Intramuscular IgG deposition negatively correlated with muscle mass. After the onset of muscle inflammation, Il10-/- mice had decreased levels of total and ribosomal RNAs (45S, 28S, 18S, and 5.8S rRNAs). Inflammation inversely correlated with muscle levels of total RNA and 28S rRNA which in turn positively correlated with muscle mass. The abundance of growth-related proteins (p70S6K and upstream binding factor, UBF) was decreased in Il10-/- mice. CONCLUSIONS Muscle inflammation and associated decline of ribosome biogenesis lead to muscle growth impairment in Il10-/- mice. This may have implications for maintenance of muscle mass in conditions associated with chronic intestinal-derived inflammation.
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Dungan CM, Li Z, Wright DC, Williamson DL. Hyperactive mTORC1 signaling is unaffected by metformin treatment in aged skeletal muscle. Muscle Nerve 2015; 53:107-17. [PMID: 25926238 DOI: 10.1002/mus.24698] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/09/2014] [Revised: 04/22/2015] [Accepted: 04/28/2015] [Indexed: 01/04/2023]
Abstract
INTRODUCTION Appropriate activation of growth signaling pathways, specifically mammalian target of rapamycin complex 1 (mTORC1), is central to muscle mass and metabolism. The goal of these studies was to examine the effects of metformin on mTORC1 signaling in aged skeletal muscle in an attempt to normalize growth signaling. METHODS Aged (23m) and young (3m) male mice were fed a low fat diet without or with 0.5% metformin for up to 8 weeks, then mTORC1-related signaling was examined in the plantar flexor complex. RESULTS Metformin had no significant effect on lowering body weight or muscle mass in aged animals, nor altered p70 S6 Kinase 1 (S6K1) and 4E-binding protein 1 (4E-BP1) phosphorylation. However, it significantly (P < 0.05) reduced body weight and lowered S6K1 and rpS6 phosphorylation in the young. CONCLUSIONS Collectively, these data suggest metformin is ineffective at normalizing growth signaling in aged skeletal muscle.
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Affiliation(s)
- Cory M Dungan
- Department of Exercise and Nutrition Sciences, School of Public Health and Health Professions, University at Buffalo, Buffalo, New York, USA
| | - Zhuyun Li
- Department of Exercise and Nutrition Sciences, School of Public Health and Health Professions, University at Buffalo, Buffalo, New York, USA
| | - David C Wright
- Department of Human Health and Nutritional Sciences, University of Guelph, Ontario, Canada
| | - David L Williamson
- Department of Exercise and Nutrition Sciences, School of Public Health and Health Professions, University at Buffalo, Buffalo, New York, USA
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Russ DW, Acksel C, Boyd IM, Maynard J, McCorkle KW, Edens NK, Garvey SM. Dietary HMB and β-alanine co-supplementation does not improve in situ muscle function in sedentary, aged male rats. Appl Physiol Nutr Metab 2015; 40:1294-301. [PMID: 26579948 DOI: 10.1139/apnm-2015-0391] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/16/2023]
Abstract
This study evaluated the effects of dietary β-hydroxy-β-methylbutyrate (HMB) combined with β-alanine (β-Ala) in sedentary, aged male rats. It has been suggested that dietary HMB or β-Ala supplementation may mitigate age-related declines in muscle strength and fatigue resistance. A total of 20 aged Sprague-Dawley rats were studied. At age 20 months, 10 rats were administered a control, purified diet and 10 rats were administered a purified diet supplemented with both HMB and β-Ala (HMB+β-Ala) for 8 weeks (approximately equivalent to 3 and 2.4 g per day human dose). We measured medial gastrocnemius (MG) size, force, fatigability, and myosin composition. We also evaluated an array of protein markers related to muscle mitochondria, protein synthesis and breakdown, and autophagy. HMB+β-Ala had no significant effects on body weight, MG mass, force or fatigability, myosin composition, or muscle quality. Compared with control rats, those fed HMB+β-Ala exhibited a reduced (41%, P = 0.039) expression of muscle RING-finger protein 1 (MURF1), a common marker of protein degradation. Muscle from rats fed HMB+β-Ala also exhibited a 45% reduction (P = 0.023) in p70s6K phosphorylation following fatiguing stimulation. These data suggest that HMB+β-Ala at the dose studied may reduce muscle protein breakdown by reducing MURF1 expression, but has minimal effects on muscle function in this model of uncomplicated aging. They do not, however, rule out potential benefits of HMB+β-Ala co-supplementation at other doses or durations of supplementation in combination with exercise or in situations where extreme muscle protein breakdown and loss of mass occur (e.g., bedrest, cachexia, failure-to-thrive).
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Affiliation(s)
- David W Russ
- a Laboratory for Integrative Muscle Biology, Division of Physical Therapy, School of Rehabilitation and Communication Sciences, Ohio University, Athens, OH 45701, USA.,b Ohio Musculoskeletal and Neurological Institute (OMNI), Heritage College of Osteopathic Medicine, Athens, OH 45701, USA
| | - Cara Acksel
- a Laboratory for Integrative Muscle Biology, Division of Physical Therapy, School of Rehabilitation and Communication Sciences, Ohio University, Athens, OH 45701, USA.,c Division of Nutrition, School of Applied Health Sciences and Wellness, Ohio University, Athens, OH 45701, USA
| | - Iva M Boyd
- a Laboratory for Integrative Muscle Biology, Division of Physical Therapy, School of Rehabilitation and Communication Sciences, Ohio University, Athens, OH 45701, USA
| | - John Maynard
- a Laboratory for Integrative Muscle Biology, Division of Physical Therapy, School of Rehabilitation and Communication Sciences, Ohio University, Athens, OH 45701, USA
| | - Katherine W McCorkle
- a Laboratory for Integrative Muscle Biology, Division of Physical Therapy, School of Rehabilitation and Communication Sciences, Ohio University, Athens, OH 45701, USA
| | - Neile K Edens
- d Abbott Nutrition R&D, 3300 Stelzer Road, Columbus, OH 43219, USA
| | - Sean M Garvey
- d Abbott Nutrition R&D, 3300 Stelzer Road, Columbus, OH 43219, USA
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25
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Fortes MAS, Pinheiro CHJ, Guimarães-Ferreira L, Vitzel KF, Vasconcelos DAA, Curi R. Overload-induced skeletal muscle hypertrophy is not impaired in STZ-diabetic rats. Physiol Rep 2015. [PMID: 26197932 PMCID: PMC4552534 DOI: 10.14814/phy2.12457] [Citation(s) in RCA: 18] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/17/2022] Open
Abstract
The aim of this study was to evaluate the effect of overload-induced hypertrophy on extensor digitorum longus (EDL) and soleus muscles of streptozotocin-induced diabetic rats. The overload-induced hypertrophy and absolute tetanic and twitch forces increases in EDL and soleus muscles were not different between diabetic and control rats. Phospho-Akt and rpS6 contents were increased in EDL muscle after 7 days of overload and returned to the pre-overload values after 30 days. In the soleus muscle, the contents of total and phospho-Akt and total rpS6 were increased in both groups after 7 days. The contents of total Akt in controls and total rpS6 and phospho-Akt in the diabetic rats remained increased after 30 days. mRNA expression after 7 days of overload in the EDL muscle of control and diabetic animals showed an increase in MGF and follistatin and a decrease in myostatin and Axin2. The expression of FAK was increased and of MuRF-1 and atrogin-1 decreased only in the control group, whereas Ankrd2 expression was enhanced only in diabetic rats. In the soleus muscle caused similar changes in both groups: increase in FAK and MGF and decrease in Wnt7a, MuRF-1, atrogin-1, and myostatin. Differences between groups were observed only in the increased expression of follistatin in diabetic animals and decreased Ankrd2 expression in the control group. So, insulin deficiency does not impair the overload-induced hypertrophic response in soleus and EDL muscles. However, different mechanisms seem to be involved in the comparable hypertrophic responses of skeletal muscle in control and diabetic animals.
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Affiliation(s)
- Marco Aurélio S Fortes
- Department of Physiology and Biophysics, Institute of Biomedical Sciences, University of São Paulo, São Paulo, Brazil
| | - Carlos Hermano J Pinheiro
- Department of Physiology and Biophysics, Institute of Biomedical Sciences, University of São Paulo, São Paulo, Brazil
| | - Lucas Guimarães-Ferreira
- Department of Physiology and Biophysics, Institute of Biomedical Sciences, University of São Paulo, São Paulo, Brazil Exercise Metabolism Research Group, Center of Physical Education and Sports, Federal University of Espírito Santo, Vitória, Brazil
| | - Kaio F Vitzel
- Department of Physiology and Biophysics, Institute of Biomedical Sciences, University of São Paulo, São Paulo, Brazil
| | - Diogo A A Vasconcelos
- Department of Physiology and Biophysics, Institute of Biomedical Sciences, University of São Paulo, São Paulo, Brazil
| | - Rui Curi
- Department of Physiology and Biophysics, Institute of Biomedical Sciences, University of São Paulo, São Paulo, Brazil
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26
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Kirby TJ, Lee JD, England JH, Chaillou T, Esser KA, McCarthy JJ. Blunted hypertrophic response in aged skeletal muscle is associated with decreased ribosome biogenesis. J Appl Physiol (1985) 2015; 119:321-7. [PMID: 26048973 DOI: 10.1152/japplphysiol.00296.2015] [Citation(s) in RCA: 63] [Impact Index Per Article: 7.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/20/2015] [Accepted: 06/02/2015] [Indexed: 12/19/2022] Open
Abstract
The ability of skeletal muscle to hypertrophy in response to a growth stimulus is known to be compromised in older individuals. We hypothesized that a change in the expression of protein-encoding genes in response to a hypertrophic stimulus contributes to the blunted hypertrophy observed with aging. To test this hypothesis, we determined gene expression by microarray analysis of plantaris muscle from 5- and 25-mo-old mice subjected to 1, 3, 5, 7, 10, and 14 days of synergist ablation to induce hypertrophy. Overall, 1,607 genes were identified as being differentially expressed across the time course between young and old groups; however, the difference in gene expression was modest, with cluster analysis showing a similar pattern of expression between the two groups. Despite ribosome protein gene expression being higher in the aged group, ribosome biogenesis was significantly blunted in the skeletal muscle of aged mice compared with mice young in response to the hypertrophic stimulus (50% vs. 2.5-fold, respectively). The failure to upregulate pre-47S ribosomal RNA (rRNA) expression in muscle undergoing hypertrophy of old mice indicated that rDNA transcription by RNA polymerase I was impaired. Contrary to our hypothesis, the findings of the study suggest that impaired ribosome biogenesis was a primary factor underlying the blunted hypertrophic response observed in skeletal muscle of old mice rather than dramatic differences in the expression of protein-encoding genes. The diminished increase in total RNA, pre-47S rRNA, and 28S rRNA expression in aged muscle suggest that the primary dysfunction in ribosome biogenesis occurs at the level of rRNA transcription and processing.
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Affiliation(s)
- Tyler J Kirby
- Center for Muscle Biology, University of Kentucky, Lexington, Kentucky; Department of Physiology, College of Medicine, University of Kentucky, Lexington, Kentucky
| | - Jonah D Lee
- Center for Muscle Biology, University of Kentucky, Lexington, Kentucky; Department of Rehabilitation Sciences, College of Health Sciences, University of Kentucky, Lexington, Kentucky; Department of Molecular and Integrative Physiology, Medical School, University of Michigan, Ann Arbor, Michigan; and
| | - Jonathan H England
- Department of Physiology, College of Medicine, University of Kentucky, Lexington, Kentucky
| | - Thomas Chaillou
- Center for Muscle Biology, University of Kentucky, Lexington, Kentucky; Department of Physiology, College of Medicine, University of Kentucky, Lexington, Kentucky; Department of Physiology and Pharmacology, Karolinska Institutet, Stockholm, Sweden
| | - Karyn A Esser
- Center for Muscle Biology, University of Kentucky, Lexington, Kentucky; Department of Physiology, College of Medicine, University of Kentucky, Lexington, Kentucky
| | - John J McCarthy
- Center for Muscle Biology, University of Kentucky, Lexington, Kentucky; Department of Physiology, College of Medicine, University of Kentucky, Lexington, Kentucky;
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27
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White JR, Confides AL, Moore-Reed S, Hoch JM, Dupont-Versteegden EE. Regrowth after skeletal muscle atrophy is impaired in aged rats, despite similar responses in signaling pathways. Exp Gerontol 2015; 64:17-32. [PMID: 25681639 DOI: 10.1016/j.exger.2015.02.007] [Citation(s) in RCA: 37] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/14/2014] [Revised: 01/14/2015] [Accepted: 02/10/2015] [Indexed: 01/07/2023]
Abstract
Skeletal muscle regrowth after atrophy is impaired in the aged and in this study we hypothesized that this can be explained by a blunted response of signaling pathways and cellular processes during reloading after hind limb suspension in muscles from old rats. Male Brown Norway Fisher 344 rats at 6 (young) and 32 (old) months of age were subjected to normal ambulatory conditions (amb), hind limb suspension for 14 days (HS), and HS followed by reloading through normal ambulation for 14 days (RE); soleus muscles were used for analysis of intracellular signaling pathways and cellular processes. Soleus muscle regrowth was blunted in old compared to young rats which coincided with a recovery of serum IGF-1 and IGFBP-3 levels in young but not old. However, the response to reloading for p-Akt, p-p70s6k and p-GSK3β protein abundance was similar between muscles from young and old rats, even though main effects for age indicate an increase in activation of this protein synthesis pathway in the aged. Similarly, MAFbx mRNA levels in soleus muscle from old rats recovered to the same extent as in the young, while Murf-1 was unchanged. mRNA abundance of autophagy markers Atg5 and Atg7 showed an identical response in muscle from old compared to young rats, but beclin did not. Autophagic flux was not changed at either age at the measured time point. Apoptosis was elevated in soleus muscle from old rats particularly with HS, but recovered in HSRE and these changes were not associated with differences in caspase-3, -8 or -9 activity in any group. Protein abundance of apoptosis repressor with caspase-recruitment domain (ARC), cytosolic EndoG, as well as cytosolic and nuclear apoptosis inducing factor (AIF) were lower in muscle from old rats, and there was no age-related difference in the response to atrophy or regrowth. Soleus muscles from old rats had a higher number of ED2 positive macrophages in all groups and these decreased with HS, but recovered in HSRE in the old, while no changes were observed in the young. Pro-inflammatory cytokines in serum did not show a differential response with age to different loading conditions. Results indicate that at the measured time point the impaired skeletal muscle regrowth after atrophy in aged animals is not associated with a general lack of responsiveness to changes in loading conditions.
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Affiliation(s)
- Jena R White
- Department of Rehabilitation Sciences, College of Health Sciences, University of Kentucky, 900 S Limestone, Lexington, KY 40536-0200, USA
| | - Amy L Confides
- Department of Rehabilitation Sciences, College of Health Sciences, University of Kentucky, 900 S Limestone, Lexington, KY 40536-0200, USA
| | - Stephanie Moore-Reed
- Department of Rehabilitation Sciences, College of Health Sciences, University of Kentucky, 900 S Limestone, Lexington, KY 40536-0200, USA
| | - Johanna M Hoch
- Department of Rehabilitation Sciences, College of Health Sciences, University of Kentucky, 900 S Limestone, Lexington, KY 40536-0200, USA
| | - Esther E Dupont-Versteegden
- Department of Rehabilitation Sciences, College of Health Sciences, University of Kentucky, 900 S Limestone, Lexington, KY 40536-0200, USA.
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28
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Chaillou T, Kirby TJ, McCarthy JJ. Ribosome biogenesis: emerging evidence for a central role in the regulation of skeletal muscle mass. J Cell Physiol 2014; 229:1584-94. [PMID: 24604615 DOI: 10.1002/jcp.24604] [Citation(s) in RCA: 127] [Impact Index Per Article: 12.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/01/2014] [Accepted: 03/04/2014] [Indexed: 12/17/2022]
Abstract
The ribosome is a supramolecular ribonucleoprotein complex that functions at the heart of the translation machinery to convert mRNA into protein. Ribosome biogenesis is the primary determinant of translational capacity of the cell and accordingly has an essential role in the control of cell growth in eukaryotes. Cumulative evidence supports the hypothesis that ribosome biogenesis has an important role in the regulation of skeletal muscle mass. The purpose of this review is to, first, summarize the main mechanisms known to regulate ribosome biogenesis and, second, put forth the hypothesis that ribosome biogenesis is a central mechanism used by skeletal muscle to regulate protein synthesis and control skeletal muscle mass in response to anabolic and catabolic stimuli. The mTORC1 and Wnt/β-catenin/c-myc signaling pathways are discussed as the major pathways that work in concert with each of the three RNA polymerases (RNA Pol I, II, and III) in regulating ribosome biogenesis. Consistent with our hypothesis, activation of these two pathways has been shown to be associated with ribosome biogenesis during skeletal muscle hypertrophy. Although further study is required, the finding that ribosome biogenesis is altered under catabolic states, in particular during disuse atrophy, suggests that its activation represents a novel therapeutic target to reduce or prevent muscle atrophy. Lastly, the emerging field of ribosome specialization is discussed and its potential role in the regulation of gene expression during periods of skeletal muscle plasticity.
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Affiliation(s)
- Thomas Chaillou
- Center for Muscle Biology, University of Kentucky, Lexington, Kentucky; Department of Physiology, College of Medicine, University of Kentucky, Lexington, Kentucky
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29
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Sakuma K, Aoi W, Yamaguchi A. The intriguing regulators of muscle mass in sarcopenia and muscular dystrophy. Front Aging Neurosci 2014; 6:230. [PMID: 25221510 PMCID: PMC4148637 DOI: 10.3389/fnagi.2014.00230] [Citation(s) in RCA: 43] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/05/2014] [Accepted: 08/10/2014] [Indexed: 12/25/2022] Open
Abstract
Recent advances in our understanding of the biology of muscle have led to new interest in the pharmacological treatment of muscle wasting. Loss of muscle mass and increased intramuscular fibrosis occur in both sarcopenia and muscular dystrophy. Several regulators (mammalian target of rapamycin, serum response factor, atrogin-1, myostatin, etc.) seem to modulate protein synthesis and degradation or transcription of muscle-specific genes during both sarcopenia and muscular dystrophy. This review provides an overview of the adaptive changes in several regulators of muscle mass in both sarcopenia and muscular dystrophy.
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Affiliation(s)
- Kunihiro Sakuma
- Research Center for Physical Fitness, Sports and Health, Toyohashi University of Technology, Toyohashi, Japan
| | - Wataru Aoi
- Laboratory of Health Science, Graduate School of Life and Environmental Sciences, Kyoto Prefectural University, Kyoto, Japan
| | - Akihiko Yamaguchi
- Department of Physical Therapy, Health Sciences University of Hokkaido, Kanazawa, Japan
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30
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Martin TD, Dennis MD, Gordon BS, Kimball SR, Jefferson LS. mTORC1 and JNK coordinate phosphorylation of the p70S6K1 autoinhibitory domain in skeletal muscle following functional overloading. Am J Physiol Endocrinol Metab 2014; 306:E1397-405. [PMID: 24801387 PMCID: PMC4059989 DOI: 10.1152/ajpendo.00064.2014] [Citation(s) in RCA: 30] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
The present project was designed to investigate phosphorylation of p70S6K1 in an animal model of skeletal muscle overload. Within 24 h of male Sprague-Dawley rats undergoing unilateral tenotomy to induce functional overloading of the plantaris muscle, phosphorylation of the Thr³⁸⁹ and Thr⁴²¹/Ser⁴²⁴ sites on p70S6K1 was significantly elevated. Since the Thr⁴²¹/Ser⁴²⁴ sites are purportedly mammalian target of rapamycin complex 1 (mTORC1) independent, we sought to identify the kinase(s) responsible for their phosphorylation. Initially, we used IGF-I treatment of serum-deprived HEK-293E cells as an in vitro model system, because IGF-I promotes phosphorylation of p70S6K1 on both the Thr³⁸⁹ and Thr⁴²¹/Ser⁴²⁴ sites in skeletal muscle and in cells in culture. We found that, whereas the mTOR inhibitor TORIN2 prevented the IGF-I-induced phosphorylation of the Thr⁴²¹/Ser⁴²⁴ sites, it surprisingly enhanced phosphorylation of these sites during serum deprivation. JNK inhibition with SP600125 attenuated phosphorylation of the Thr⁴²¹/Ser⁴²⁴ sites, and in combination with TORIN2 both the effect of IGF-I and the enhanced Thr⁴²¹/Ser⁴²⁴ phosphorylation during serum deprivation were ablated. In contrast, both JNK activation with anisomycin and knockdown of the mTORC2 subunit rictor specifically stimulated phosphorylation of the Thr⁴²¹/Ser⁴²⁴ sites, suggesting that mTORC2 represses JNK-mediated phosphorylation of these sites. The role of JNK in mediating p70S6K1 phosphorylation was confirmed in the animal model noted above, where rats treated with SP600125 exhibited attenuated Thr⁴²¹/Ser⁴²⁴ phosphorylation. Overall, the results provide evidence that the mTORC1 and JNK signaling pathways coordinate the site-specific phosphorylation of p70S6K1. They also identify a novel role for mTORC1 and mTORC2 in the inhibition of JNK.
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Affiliation(s)
- Tony D Martin
- Department of Cellular and Molecular Physiology, The Pennsylvania State University College of Medicine, Hershey, Pennsylvania
| | - Michael D Dennis
- Department of Cellular and Molecular Physiology, The Pennsylvania State University College of Medicine, Hershey, Pennsylvania
| | - Bradley S Gordon
- Department of Cellular and Molecular Physiology, The Pennsylvania State University College of Medicine, Hershey, Pennsylvania
| | - Scot R Kimball
- Department of Cellular and Molecular Physiology, The Pennsylvania State University College of Medicine, Hershey, Pennsylvania
| | - Leonard S Jefferson
- Department of Cellular and Molecular Physiology, The Pennsylvania State University College of Medicine, Hershey, Pennsylvania
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31
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Washington TA, Healey JM, Thompson RW, Lowe LL, Carson JA. Lactate dehydrogenase regulation in aged skeletal muscle: Regulation by anabolic steroids and functional overload. Exp Gerontol 2014; 57:66-74. [PMID: 24835193 DOI: 10.1016/j.exger.2014.05.003] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/19/2013] [Revised: 04/23/2014] [Accepted: 05/05/2014] [Indexed: 12/17/2022]
Abstract
Aging alters the skeletal muscle response to overload-induced growth. The onset of functional overload is characterized by increased myoblast proliferation and an altered muscle metabolic profile. The onset of functional overload is associated with increased energy demands that are met through the interconversion of lactate and pyruvate via the activity of lactate dehydrogenase (LDH). Testosterone targets many of the processes activated at the onset of functional overload. However, the effect of aging on this metabolic plasticity at the onset of functional overload and how anabolic steroid administration modulates this response is not well understood. The purpose of this study was to determine if aging would alter overload-induced LDH activity and expression at the onset of functional overload and whether anabolic steroid administration would modulate this response. Five-month and 25-month male Fischer 344xF1 BRN were given nandrolone decanoate (ND) or sham injections for 14days and then the plantaris was functionally overloaded (OV) for 3days by synergist ablation. Aging reduced muscle LDH-A & LDH-B activity 70% (p<0.05). Aging also reduced LDH-A mRNA abundance, however there was no age effect on LDH-B mRNA abundance. In 5-month muscle, both ND and OV decreased LDH-A and LDH-B activity. However, there was no synergistic or additive effect. In 5-month muscle, ND and OV decreased LDH-A mRNA expression with no change in LDH-B expression. In 25-month muscle, ND and OV increased LDH-A and LDH-B activity. LDH-A mRNA expression was not altered by ND or OV in aged muscle. However, there was a main effect of OV to decrease LDH-B mRNA expression. There was also an age-induced LDH isoform shift. ND and OV treatment increased the "fast" LDH isoforms in aged muscle, whereas ND and OV increased the "slow" isoforms in young muscle. Our study provides evidence that aging alters aspects of skeletal muscle metabolic plasticity normally induced by overload and anabolic steroid administration.
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Affiliation(s)
- Tyrone A Washington
- Exercise Muscle Biology Laboratory, Human Performance Laboratory, Department of Health, Human Performance and Recreation, University of Arkansas, Fayetteville AR 72701, United States; Integrative Muscle Biology Laboratory, Exercise Science Department, Norman J. Arnold School of Public Health, University of South Carolina, Columbia, SC 29208, United States.
| | - Julie M Healey
- Integrative Muscle Biology Laboratory, Exercise Science Department, Norman J. Arnold School of Public Health, University of South Carolina, Columbia, SC 29208, United States
| | - Raymond W Thompson
- Integrative Muscle Biology Laboratory, Exercise Science Department, Norman J. Arnold School of Public Health, University of South Carolina, Columbia, SC 29208, United States
| | - Larry L Lowe
- Department of Biological and Physical Sciences, Benedict College, Columbia, SC 29208, United States
| | - James A Carson
- Integrative Muscle Biology Laboratory, Exercise Science Department, Norman J. Arnold School of Public Health, University of South Carolina, Columbia, SC 29208, United States
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32
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Current understanding of sarcopenia: possible candidates modulating muscle mass. Pflugers Arch 2014; 467:213-29. [PMID: 24797147 DOI: 10.1007/s00424-014-1527-x] [Citation(s) in RCA: 60] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/03/2014] [Revised: 04/21/2014] [Accepted: 04/22/2014] [Indexed: 12/17/2022]
Abstract
The world's elderly population is expanding rapidly, and we are now faced with the significant challenge of maintaining or improving physical activity, independence, and quality of life in the elderly. Sarcopenia, the age-related loss of skeletal muscle mass, is characterized by a deterioration of muscle quantity and quality leading to a gradual slowing of movement, a decline in strength and power, increased risk of fall-related injury, and often, frailty. Since sarcopenia is largely attributed to various molecular mediators affecting fiber size, mitochondrial homeostasis, and apoptosis, the mechanisms responsible for these deleterious changes present numerous therapeutic targets for drug discovery. Muscle loss has been linked with several proteolytic systems, including the ubuiquitin-proteasome, lysosome-autophagy, and tumor necrosis factor (TNF)-α/nuclear factor-kappaB (NF-κB) systems. Although many factors are considered to regulate age-dependent muscle loss, this gentle atrophy is not affected by factors known to enhance rapid atrophy (denervation, hindlimb suspension, etc.). In addition, defects in Akt-mammalian target of rapamycin (mTOR) and serum response factor (SRF)-dependent signaling have been found in sarcopenic muscle. Intriguingly, more recent studies indicated an apparent functional defect in autophagy- and myostatin-dependent signaling in sarcopenic muscle. In this review, we summarize the current understanding of the adaptation of many regulators in sarcopenia.
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Hardman SE, Hall DE, Cabrera AJ, Hancock CR, Thomson DM. The effects of age and muscle contraction on AMPK activity and heterotrimer composition. Exp Gerontol 2014; 55:120-8. [PMID: 24747582 DOI: 10.1016/j.exger.2014.04.007] [Citation(s) in RCA: 28] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/26/2013] [Revised: 03/05/2014] [Accepted: 04/10/2014] [Indexed: 01/06/2023]
Abstract
Sarcopenia is characterized by increased skeletal muscle atrophy due in part to alterations in muscle metabolism. AMP-activated protein kinase (AMPK) is a master regulator of skeletal muscle metabolic pathways which regulate many cellular processes that are disrupted in old-age. Functional AMPK is a heterotrimer composed of α, β and γ subunits, and each subunit can be represented in the heterotrimer by one of two (α1/α2, β1/β2) or three (γ1/γ2/γ3) isoforms. Altered isoform composition affects AMPK localization and function. Previous work has shown that overall AMPK activation with endurance-type exercise is blunted in old vs. young skeletal muscle. However, details regarding the activation of the specific isoforms of AMPK, as well as the heterotrimeric composition of AMPK in old skeletal muscle, are unknown. Our purpose here, therefore, was to determine the effect of old-age on 1) the activation of the α1 and α2 catalytic subunits of AMPK in skeletal muscle by a continuous contraction bout, and 2) the heterotrimeric composition of skeletal muscle AMPK. We studied gastrocnemius (GAST) and tibialis anterior (TA) muscles from young adult (YA; 8months old) and old (O; 30months old) male Fischer344×Brown Norway F1 hybrid rats after an in situ bout of endurance-type contractions produced via electrical stimulation of the sciatic nerve (STIM). AMPKα phosphorylation and AMPKα1 and α2 activities were unaffected by age at rest. However, AMPKα phosphorylation and AMPKα2 protein content and activity were lower in O vs. YA after STIM. Conversely, AMPKα1 content was greater in O vs. YA muscle, and α1 activity increased with STIM in O but not YA muscles. AMPKγ3 overall concentration and its association with AMPKα1 and α2 were lower in O vs. YA GAST. We conclude that activation of AMPKα1 is enhanced, while activation of α2 is suppressed immediately after repeated skeletal muscle contractions in O vs. YA skeletal muscle. These changes are associated with changes in the AMPK heterotrimer composition. Given the known roles of AMPK α1, α2 and γ3, this may contribute to sarcopenia and associated muscle metabolic dysfunction.
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Affiliation(s)
- Shalene E Hardman
- Department of Physiology and Developmental Biology, Brigham Young University, Provo, UT, 84602, USA
| | - Derrick E Hall
- Department of Physiology and Developmental Biology, Brigham Young University, Provo, UT, 84602, USA
| | - Alyssa J Cabrera
- Department of Physiology and Developmental Biology, Brigham Young University, Provo, UT, 84602, USA
| | - Chad R Hancock
- Department of Physiology and Developmental Biology, Brigham Young University, Provo, UT, 84602, USA
| | - David M Thomson
- Department of Physiology and Developmental Biology, Brigham Young University, Provo, UT, 84602, USA.
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Hwee DT, Baehr LM, Philp A, Baar K, Bodine SC. Maintenance of muscle mass and load-induced growth in Muscle RING Finger 1 null mice with age. Aging Cell 2014; 13:92-101. [PMID: 23941502 PMCID: PMC3947038 DOI: 10.1111/acel.12150] [Citation(s) in RCA: 82] [Impact Index Per Article: 8.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 08/08/2013] [Indexed: 12/18/2022] Open
Abstract
Age-related loss of muscle mass occurs to varying degrees in all individuals and has a detrimental effect on morbidity and mortality. Muscle RING Finger 1 (MuRF1), a muscle-specific E3 ubiquitin ligase, is believed to mediate muscle atrophy through the ubiquitin proteasome system (UPS). Deletion of MuRF1 (KO) in mice attenuates the loss of muscle mass following denervation, disuse, and glucocorticoid treatment; however, its role in age-related muscle loss is unknown. In this study, skeletal muscle from male wild-type (WT) and MuRF1 KO mice was studied up to the age of 24 months. Muscle mass and fiber cross-sectional area decreased significantly with age in WT, but not in KO mice. In aged WT muscle, significant decreases in proteasome activities, especially 20S and 26S β5 (20–40% decrease), were measured and were associated with significant increases in the maladaptive endoplasmic reticulum (ER) stress marker, CHOP. Conversely, in aged MuRF1 KO mice, 20S or 26S β5 proteasome activity was maintained or decreased to a lesser extent than in WT mice, and no increase in CHOP expression was measured. Examination of the growth response of older (18 months) mice to functional overload revealed that old WT mice had significantly less growth relative to young mice (1.37- vs. 1.83-fold), whereas old MuRF1 KO mice had a normal growth response (1.74- vs. 1.90-fold). These data collectively suggest that with age, MuRF1 plays an important role in the control of skeletal muscle mass and growth capacity through the regulation of cellular stress.
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Affiliation(s)
- Darren T. Hwee
- Departments of Neurobiology, Physiology, and Behavior; University of California Davis; Davis CA 95616 USA
- Molecular, Cellular and Integrative Physiology Graduate Group; University of California Davis; Davis CA 95616 USA
| | - Leslie M. Baehr
- Physiology and Membrane Biology; University of California Davis; Davis CA 95616 USA
| | - Andrew Philp
- Departments of Neurobiology, Physiology, and Behavior; University of California Davis; Davis CA 95616 USA
| | - Keith Baar
- Departments of Neurobiology, Physiology, and Behavior; University of California Davis; Davis CA 95616 USA
- Physiology and Membrane Biology; University of California Davis; Davis CA 95616 USA
| | - Sue C. Bodine
- Departments of Neurobiology, Physiology, and Behavior; University of California Davis; Davis CA 95616 USA
- Physiology and Membrane Biology; University of California Davis; Davis CA 95616 USA
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Adams GR, Bamman MM. Characterization and regulation of mechanical loading-induced compensatory muscle hypertrophy. Compr Physiol 2013; 2:2829-70. [PMID: 23720267 DOI: 10.1002/cphy.c110066] [Citation(s) in RCA: 67] [Impact Index Per Article: 6.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/05/2023]
Abstract
In mammalian systems, skeletal muscle exists in a dynamic state that monitors and regulates the physiological investment in muscle size to meet the current level of functional demand. This review attempts to consolidate current knowledge concerning development of the compensatory hypertrophy that occurs in response to a sustained increase in the mechanical loading of skeletal muscle. Topics covered include: defining and measuring compensatory hypertrophy, experimental models, loading stimulus parameters, acute responses to increased loading, hyperplasia, myofiber-type adaptations, the involvement of satellite cells, mRNA translational control, mechanotransduction, and endocrinology. The authors conclude with their impressions of current knowledge gaps in the field that are ripe for future study.
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Affiliation(s)
- Gregory R Adams
- Department of Physiology and Biophysics, University of California Irvine, Irvine, California, USA.
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Bodine SC. Disuse-induced muscle wasting. Int J Biochem Cell Biol 2013; 45:2200-8. [PMID: 23800384 DOI: 10.1016/j.biocel.2013.06.011] [Citation(s) in RCA: 245] [Impact Index Per Article: 22.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/20/2013] [Revised: 06/11/2013] [Accepted: 06/12/2013] [Indexed: 12/17/2022]
Abstract
Loss of skeletal muscle mass occurs frequently in clinical settings in response to joint immobilization and bed rest, and is induced by a combination of unloading and inactivity. Disuse-induced atrophy will likely affect every person in his or her lifetime, and can be debilitating especially in the elderly. Currently there are no good therapies to treat disuse-induced muscle atrophy, in part, due to a lack of understanding of the cellular and molecular mechanisms responsible for the induction and maintenance of muscle atrophy. Our current understanding of disuse atrophy comes from the investigation of a variety of models (joint immobilization, hindlimb unloading, bed rest, spinal cord injury) in both animals and humans. Under conditions of unloading, it is widely accepted that there is a decrease in protein synthesis, however, the role of protein degradation, especially in humans, is debated. This review will examine the current understanding of the molecular and cellular mechanisms regulating muscle loss under disuse conditions, discussing the similarities and areas of dispute between the animal and human literature. This article is part of a Directed Issue entitled: Molecular basis of muscle wasting.
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Affiliation(s)
- Sue C Bodine
- Department of Neurobiology, Physiology and Behavior, University of California, Davis, One Shields Avenue, Davis, CA 95616, United States.
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Luo L, Lu AM, Wang Y, Hong A, Chen Y, Hu J, Li X, Qin ZH. Chronic resistance training activates autophagy and reduces apoptosis of muscle cells by modulating IGF-1 and its receptors, Akt/mTOR and Akt/FOXO3a signaling in aged rats. Exp Gerontol 2013; 48:427-36. [PMID: 23419688 DOI: 10.1016/j.exger.2013.02.009] [Citation(s) in RCA: 117] [Impact Index Per Article: 10.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/26/2012] [Revised: 01/09/2013] [Accepted: 02/04/2013] [Indexed: 11/16/2022]
Abstract
Resistance exercise training (RET) remains the most effective treatment for the loss of muscle mass and strength in elderly people. However, the underlying cellular and molecular mechanisms are not well understood. Recent evidence suggests that autophagic signaling is altered in aged skeletal muscles. This study aimed to investigate if RET affects IGF-1 and its receptors, the Akt/mTOR, and Akt/FOXO3a signaling pathways and regulates autophagy and apoptosis in the gastrocnemius muscles of 18-20 month old rats. The results showed that 9 weeks of RET prevented the loss of muscle mass and improved muscle strength, accompanied by reduced LC3-II/LC3-I ratio, reduced p62 protein levels, and increased levels of autophagy regulatory proteins, including Beclin 1, Atg5/12, Atg7, and the lysosomal enzyme cathepsin L. RET also reduced cytochrome c level in the cytosol but increased its level in mitochondrial fraction, and inhibited cleaved caspase 3 production and apoptosis. Furthermore, RET upregulated the expression of IGF-1 and its receptors but downregulated the phosphorylation of Akt and mTOR. In addition, RET upregulated the expression of total AMPK, phosphorylated AMPK, and FOXO3a. Taken together, these results suggest that the benefits of RET are associated with increased autophagy activity and reduced apoptosis of muscle cells by modulating IGF-1 and its receptors, the Akt/mTOR and Akt/FOXO3a signaling pathways in aged skeletal muscles.
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Affiliation(s)
- Li Luo
- School of Physical Education and Sports Science, Soochow University, Suzhou 215021, China
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The role of mTORC1 in regulating protein synthesis and skeletal muscle mass in response to various mechanical stimuli. Rev Physiol Biochem Pharmacol 2013; 166:43-95. [PMID: 24442322 DOI: 10.1007/112_2013_17] [Citation(s) in RCA: 91] [Impact Index Per Article: 8.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/13/2022]
Abstract
Skeletal muscle plays a fundamental role in mobility, disease prevention, and quality of life. Skeletal muscle mass is, in part, determined by the rates of protein synthesis, and mechanical loading is a major regulator of protein synthesis and skeletal muscle mass. The mammalian/mechanistic target of rapamycin (mTOR), found in the multi-protein complex, mTORC1, is proposed to play an essential role in the regulation of protein synthesis and skeletal muscle mass. The purpose of this review is to examine the function of mTORC1 in relation to protein synthesis and cell growth, the current evidence from rodent and human studies for the activation of mTORC1 signaling by different types of mechanical stimuli, whether mTORC1 signaling is necessary for changes in protein synthesis and skeletal muscle mass that occur in response to different types of mechanical stimuli, and the proposed molecular signaling mechanisms that may be responsible for the mechanical activation of mTORC1 signaling.
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Rivas DA, Morris EP, Haran PH, Pasha EP, Morais MDS, Dolnikowski GG, Phillips EM, Fielding RA. Increased ceramide content and NFκB signaling may contribute to the attenuation of anabolic signaling after resistance exercise in aged males. J Appl Physiol (1985) 2012; 113:1727-36. [PMID: 23042913 DOI: 10.1152/japplphysiol.00412.2012] [Citation(s) in RCA: 74] [Impact Index Per Article: 6.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/12/2022] Open
Abstract
One of the most fundamental adaptive physiological events is the response of skeletal muscle to high-intensity resistance exercise, resulting in increased protein synthesis and ultimately larger muscle mass. However, muscle growth in response to contraction is attenuated in older humans. Impaired contractile-induced muscle growth may contribute to sarcopenia: the age-associated loss of muscle mass and function that is manifested by loss of strength, contractile capacity, and endurance. We hypothesized that the storage of ceramide would be increased in older individuals and this would be associated with increases in NFκB signaling and a decreased anabolic response to exercise. To test this hypothesis we measured ceramides at rest and anabolic and NFκB signaling after an acute bout of high-intensity resistance exercise in young and older males. Using lipidomics analysis we show there was a 156% increase in the accumulation of C16:0-ceramide (P < 0.05) and a 30% increase in C20:0-ceramide (P < 0.05) in skeletal muscle with aging, although there was no observable difference in total ceramide. C16:0-ceramide content was negatively correlated (P = 0.008) with lower leg lean mass. Aging was associated with a ~60% increase in the phosphorylation of the proinflammatory transcription factor NFκB in the total and nuclear cell fractions (P < 0.05). Furthermore, there was an attenuated activation of anabolic signaling molecules such as Akt (P < 0.05), FOXO1 (P < 0.05), and S6K1 (P < 0.05) after an acute bout of high-intensity resistance exercise in older males. We conclude that ceramide may have a significant role in the attenuation of contractile-induced skeletal muscle adaptations and atrophy that is observed with aging.
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Affiliation(s)
- Donato A Rivas
- Nutrition, Exercise Physiology and Sarcopenia Laboratory, Jean Mayer USDA Human Nutrition Research Center on Aging, Tufts University, Boston, MA 02111, USA
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Haran PH, Rivas DA, Fielding RA. Role and potential mechanisms of anabolic resistance in sarcopenia. J Cachexia Sarcopenia Muscle 2012; 3:157-62. [PMID: 22589021 PMCID: PMC3424190 DOI: 10.1007/s13539-012-0068-4] [Citation(s) in RCA: 104] [Impact Index Per Article: 8.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 09/17/2011] [Accepted: 04/11/2012] [Indexed: 01/06/2023] Open
Abstract
There is pressing need to understand the aging process to better cope with its associated physical and societal costs. The age-related muscle wasting known as sarcopenia is a major contributor to the problems faced by the elderly. By hindering mobility and reducing strength, it greatly diminishes independence and quality of life. In studying the factors that contribute to the development of sarcopenia, the focus is shifting to the study of disordered muscle anabolism. The abnormal response of muscle to previously well-established anabolic stimuli is known as anabolic resistance, and may be a key factor in the development and progression of sarcopenia. Factors such as age, obesity, inflammation, and lipotoxicity contribute to anabolic resistance, and have been studied either directly or indirectly in cell systems and whole animals. Understanding the physiologic and mechanistic basis of anabolic resistance could be the key to formulating new and targeted interventions that would ease the burden currently borne by the world's aged population.
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Affiliation(s)
- Prashanth H Haran
- Nutrition, Exercise Physiology, and Sarcopenia Laboratory, Jean Mayer USDA Human Nutrition Research Center on Aging, Tufts University, 711 Washington Street, Boston, MA, 02111, USA
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Wagner AL, Urschel KL. Developmental regulation of the activation of translation initiation factors of skeletal muscle in response to feeding in horses. Am J Vet Res 2012; 73:1241-51. [DOI: 10.2460/ajvr.73.8.1241] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
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Sakuma K, Yamaguchi A. Sarcopenia and cachexia: the adaptations of negative regulators of skeletal muscle mass. J Cachexia Sarcopenia Muscle 2012; 3:77-94. [PMID: 22476916 PMCID: PMC3374017 DOI: 10.1007/s13539-011-0052-4] [Citation(s) in RCA: 92] [Impact Index Per Article: 7.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 05/13/2011] [Accepted: 11/08/2011] [Indexed: 12/25/2022] Open
Abstract
Recent advances in our understanding of the biology of muscle, and how anabolic and catabolic stimuli interact to control muscle mass and function, have led to new interest in the pharmacological treatment of muscle wasting. Loss of muscle occurs as a consequence of several chronic diseases (cachexia) as well as normal aging (sarcopenia). Although many negative regulators [Atrogin-1, muscle ring finger-1, nuclear factor-kappaB (NF-κB), myostatin, etc.] have been proposed to enhance protein degradation during both sarcopenia and cachexia, the adaptation of mediators markedly differs among these conditions. Sarcopenic and cachectic muscles have been demonstrated to be abundant in myostatin- and apoptosis-linked molecules. The ubiquitin-proteasome system (UPS) is activated during many different types of cachexia (cancer cachexia, cardiac heart failure, chronic obstructive pulmonary disease), but not many mediators of the UPS change during sarcopenia. NF-κB signaling is activated in cachectic, but not in sarcopenic, muscle. Some studies have indicated a change of autophagic signaling during both sarcopenia and cachexia, but the adaptation remains to be elucidated. This review provides an overview of the adaptive changes in negative regulators of muscle mass in both sarcopenia and cachexia.
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Affiliation(s)
- Kunihiro Sakuma
- Research Center for Physical Fitness, Sports and Health, Toyohashi University of Technology, 1-1 Hibarigaoka, Tenpaku-cho, Toyohashi, 441-8580, Japan,
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Norrby M, Evertsson K, Fjällström AK, Svensson A, Tågerud S. Akt (protein kinase B) isoform phosphorylation and signaling downstream of mTOR (mammalian target of rapamycin) in denervated atrophic and hypertrophic mouse skeletal muscle. J Mol Signal 2012; 7:7. [PMID: 22657251 PMCID: PMC3406959 DOI: 10.1186/1750-2187-7-7] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/17/2011] [Accepted: 06/01/2012] [Indexed: 11/10/2022] Open
Abstract
BACKGROUND The present study examines the hypothesis that Akt (protein kinase B)/mTOR (mammalian target of rapamycin) signaling is increased in hypertrophic and decreased in atrophic denervated muscle. Protein expression and phosphorylation of Akt1, Akt2, glycogen synthase kinase-3beta (GSK-3beta), eukaryotic initiation factor 4E binding protein 1 (4EBP1), 70 kD ribosomal protein S6 kinase (p70S6K1) and ribosomal protein S6 (rpS6) were examined in six-days denervated mouse anterior tibial (atrophic) and hemidiaphragm (hypertrophic) muscles. RESULTS In denervated hypertrophic muscle expression of total Akt1, Akt2, GSK-3beta, p70S6K1 and rpS6 proteins increased 2-10 fold whereas total 4EBP1 protein remained unaltered. In denervated atrophic muscle Akt1 and Akt2 total protein increased 2-16 fold. A small increase in expression of total rpS6 protein was also observed with no apparent changes in levels of total GSK-3beta, 4EBP1 or p70S6K1 proteins. The level of phosphorylated proteins increased 3-13 fold for all the proteins in hypertrophic denervated muscle. No significant changes in phosphorylated Akt1 or GSK-3beta were detected in atrophic denervated muscle. The phosphorylation levels of Akt2, 4EBP1, p70S6K1 and rpS6 were increased 2-18 fold in atrophic denervated muscle. CONCLUSIONS The results are consistent with increased Akt/mTOR signaling in hypertrophic skeletal muscle. Decreased levels of phosphorylated Akt (S473/S474) were not observed in denervated atrophic muscle and results downstream of mTOR indicate increased protein synthesis in denervated atrophic anterior tibial muscle as well as in denervated hypertrophic hemidiaphragm muscle. Increased protein degradation, rather than decreased protein synthesis, is likely to be responsible for the loss of muscle mass in denervated atrophic muscles.
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Affiliation(s)
- Marlene Norrby
- School of Natural Sciences, Linnaeus University, SE-391 82, Kalmar, Sweden.
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Sakuma K, Yamaguchi A. Sarcopenia and age-related endocrine function. Int J Endocrinol 2012; 2012:127362. [PMID: 22690213 PMCID: PMC3368374 DOI: 10.1155/2012/127362] [Citation(s) in RCA: 111] [Impact Index Per Article: 9.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 12/01/2011] [Accepted: 02/22/2012] [Indexed: 02/06/2023] Open
Abstract
Sarcopenia, the age-related loss of skeletal muscle, is characterized by a deterioration of muscle quantity and quality leading to a gradual slowing of movement, a decline in strength and power, and an increased risk of fall-related injuries. Since sarcopenia is largely attributed to various molecular mediators affecting fiber size, mitochondrial homeostasis, and apoptosis, numerous targets exist for drug discovery. In this paper, we summarize the current understanding of the endocrine contribution to sarcopenia and provide an update on hormonal intervention to try to improve endocrine defects. Myostatin inhibition seems to be the most interesting strategy for attenuating sarcopenia other than resistance training with amino acid supplementation. Testosterone supplementation in large amounts and at low frequency improves muscle defects with aging but has several side effects. Although IGF-I is a potent regulator of muscle mass, its therapeutic use has not had a positive effect probably due to local IGF-I resistance. Treatment with ghrelin may ameliorate the muscle atrophy elicited by age-dependent decreases in growth hormone. Ghrelin is an interesting candidate because it is orally active, avoiding the need for injections. A more comprehensive knowledge of vitamin-D-related mechanisms is needed to utilize this nutrient to prevent sarcopenia.
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Affiliation(s)
- Kunihiro Sakuma
- Research Center for Physical Fitness, Sports and Health, Toyohashi University of Technology, 1-1 Hibarigaoka, Tenpaku-cho, Toyohashi 441-8580, Japan
- *Kunihiro Sakuma:
| | - Akihiko Yamaguchi
- School of Dentistry, Health Sciences University of Hokkaido, Kanazawa, Ishikari-Tobetsu, Hokkaido 061-0293, Japan
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Goodman CA, Mayhew DL, Hornberger TA. Recent progress toward understanding the molecular mechanisms that regulate skeletal muscle mass. Cell Signal 2011; 23:1896-906. [PMID: 21821120 PMCID: PMC3744211 DOI: 10.1016/j.cellsig.2011.07.013] [Citation(s) in RCA: 116] [Impact Index Per Article: 8.9] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/01/2011] [Accepted: 07/15/2011] [Indexed: 01/30/2023]
Abstract
The maintenance of muscle mass is critical for health and issues associated with the quality of life. Over the last decade, extensive progress has been made with regard to our understanding of the molecules that regulate skeletal muscle mass. Not surprisingly, many of these molecules are intimately involved in the regulation of protein synthesis and protein degradation [e.g. the mammalian target of rapamycin (mTOR), eukaryotic initiation factor 2B (eIF2B), eukaryotic initiation factor 3f (eIF3f) and the forkhead box O (FoxO) transcription factors]. It is also becoming apparent that molecules which sense, or control, the energetic status of the cell play a key role in the regulation of muscle mass [e.g. AMP-activated protein kinase (AMPK) and peroxisome proliferator-activated receptor gamma coactivator-1 α (PGC1α)]. In this review we will attempt to summarize the current knowledge of how these molecules regulate skeletal muscle mass.
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Affiliation(s)
- Craig A Goodman
- Department of Comparative Biosciences, School of Veterinary Medicine, University of Wisconsin Madison, Madison, WI 53706, USA.
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Conte TC, Silva LH, Silva MT, Hirabara SM, Oliveira AC, Curi R, Moriscot AS, Aoki MS, Miyabara EH. The β2-adrenoceptor agonist formoterol improves structural and functional regenerative capacity of skeletal muscles from aged rat at the early stages of postinjury. J Gerontol A Biol Sci Med Sci 2011; 67:443-55. [PMID: 22113942 DOI: 10.1093/gerona/glr195] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/04/2023] Open
Abstract
Skeletal muscles from old rats fail to completely regenerate following injury. This study investigated whether pharmacological stimulation of β2-adrenoceptors in aged muscles following injury could improve their regenerative capacity, focusing on myofiber size recovery. Young and aged rats were treated with a subcutaneous injection of β2-adrenergic agonist formoterol (2 μg/kg/d) up to 10 and 21 days after soleus muscle injury. Formoterol-treated muscles from old rats evaluated at 10 and 21 days postinjury showed reduced inflammation and connective tissue but a similar number of regenerating myofibers of greater caliber when compared with their injured controls. Formoterol minimized the decrease in tetanic force and increased protein synthesis and mammalian target of rapamycin phosphorylation in old muscles at 10 days postinjury. Our results suggest that formoterol improves structural and functional regenerative capacity of regenerating skeletal muscles from aged rats by increasing protein synthesis via mammalian target of rapamycin activation. Furthermore, formoterol may have therapeutic benefits in recovery following muscle damage in senescent individuals.
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Affiliation(s)
- Talita C Conte
- Department of Anatomy, Institute of Biomedical Sciences, University of Sao Paulo, São Paulo, Brazil
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Ljubicic V, Khogali S, Renaud JM, Jasmin BJ. Chronic AMPK stimulation attenuates adaptive signaling in dystrophic skeletal muscle. Am J Physiol Cell Physiol 2011; 302:C110-21. [PMID: 21940670 DOI: 10.1152/ajpcell.00183.2011] [Citation(s) in RCA: 41] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
In the present study, we evaluated how a pharmacologically induced phenotype shift in dystrophic skeletal muscle would affect subsequent intracellular signaling in response to a complementary, adaptive physiological stimulus. mdx mice were treated with the AMP-activated protein kinase (AMPK) activator 5-aminoimidazole-4-carboxamide-1-β-D-ribofuranoside (AICAR; 500 mg·kg(-1)·day(-1)) for 30 days, and then one-half of the animals were subjected to a bout of treadmill running to induce acute AMPK and p38 MAPK signaling. The mRNA levels of phenotypic modifiers, including peroxisome proliferator-activated receptor-δ (PPARδ), PPARγ coactivator-1α (PGC-1α), receptor interacting protein 140 (RIP 140), and silent information regulator two ortholog 1 (SIRT1) were assessed in skeletal muscle, as well as the expression of the protein arginine methyltransferase genes PRMT1 and CARM1. We found unique AMPK and p38 phosphorylation and expression signatures between dystrophic and healthy muscle. In dystrophic skeletal muscle, treadmill running induced PPARδ, PGC-1α, and SIRT1 mRNAs, three molecules that promote the slow, oxidative myogenic program. In the mdx animals that received the chronic AICAR treatment, running-elicited AMPK and p38 phosphorylation was attenuated compared with vehicle-treated mice. Similarly, acute stress-evoked expression of PPARδ, PGC-1α, and SIRT1 was also blunted by chronic pharmacological AMPK stimulation. Skeletal muscle PRMT1 and CARM1 protein contents were higher in mdx mice compared with wild-type littermates. The acute running-evoked induction of PRMT1 and CARM1 mRNAs was also attenuated by the AICAR treatment. Our data demonstrate that prior pharmacological conditioning is a salient determinant in how dystrophic muscle adapts to subsequent complementary, acute physiological stress stimuli. These results provide insight into possible therapeutic applications of synthetic agonists in neuromuscular diseases, such as during chronic administration to Duchenne muscular dystrophy patients.
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Affiliation(s)
- Vladimir Ljubicic
- Department of Cellular and Molecular Medicine, Faculty of Medicine, and Center for Neuromuscular Disease, University of Ottawa, Ottawa, Ontario, Canada.
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Rivas DA, Morris EP, Fielding RA. Lipogenic regulators are elevated with age and chronic overload in rat skeletal muscle. Acta Physiol (Oxf) 2011; 202:691-701. [PMID: 21439027 DOI: 10.1111/j.1748-1716.2011.02289.x] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
AIM Both muscle mass and strength decline with ageing, but the loss of strength far surpasses what is projected based on the decline in mass. Interestingly, the accumulation of fat mass has been shown to be a strong predictor of functional loss and disability. Furthermore, there is a known attenuated hypertrophic response to skeletal muscle overload with ageing. The purpose of this study was to determine the effect of 28 days of overload on the storage of intramuscular triglycerides (IMTG) and metabolic regulators of lipid synthesis in young and old skeletal muscle. METHODS The phosphorylation and expression of essential lipogenic regulators were determined in the plantaris of young (YNG; 6-month-old) and aged (OLD; 30-month-old) rats subjected to bilateral synergist ablation (SA) of two-thirds of the gastrocnemius muscle or sham surgery. RESULTS We demonstrate that age-induced increases in IMTG are associated with enhancements in the expression of lipogenic regulators in muscle. We also show that the phosphorylation and concentration of the 5'AMP-activated protein kinase (AMPK) isoforms are altered in OLD. We observed increases in the expression of lipogenic regulators and AMPK signalling after SA in YNG, despite no increase in IMTG. Markers of oxidative capacity were increased in YNG after SA. These overload-induced effects were blunted in OLD. CONCLUSION These data suggest that lipid metabolism may be altered in ageing skeletal muscle and is unaffected by mechanical overload via SA. By determining the role of increased lipid storage on skeletal muscle mass during ageing, possible gene targets for the treatment of sarcopenia may be identified.
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Affiliation(s)
- D A Rivas
- Nutrition, Exercise Physiology and Sarcopenia Laboratory, Jean Mayer USDA Human Nutrition Research Center on Aging, Tufts University, Boston, MA, USA
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Murakami T, Hasegawa K, Yoshinaga M. Rapid induction of REDD1 expression by endurance exercise in rat skeletal muscle. Biochem Biophys Res Commun 2011; 405:615-9. [DOI: 10.1016/j.bbrc.2011.01.078] [Citation(s) in RCA: 33] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/19/2011] [Accepted: 01/21/2011] [Indexed: 02/02/2023]
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Rahnert JA, Luo Q, Balog EM, Sokoloff AJ, Burkholder TJ. Changes in growth-related kinases in head, neck and limb muscles with age. Exp Gerontol 2010; 46:282-91. [PMID: 21095226 DOI: 10.1016/j.exger.2010.11.004] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/12/2010] [Revised: 10/20/2010] [Accepted: 11/07/2010] [Indexed: 12/21/2022]
Abstract
Sarcopenia coincides with declines in several systemic processes that signal through the MAP kinase and Akt-mTOR-p70S6k cascades typically associated with muscle growth. Effects of aging on these pathways have primarily been examined in limb muscles, which experience substantial activity and neural changes in addition to systemic hormonal and metabolic changes. Head and neck muscles are reported to undergo reduced sarcopenia and disuse with age relative to limb muscles, suggesting muscle activity may contribute to maintaining mass with age. However many head and neck muscles derive from embryonic branchial arches, rather than the somites from which limb muscles originate, suggesting that developmental origin may be important. This study compares the expression and phosphorylation of MAP kinase and mTOR networks in head, neck, tongue, and limb muscles from 8- and 26-month old F344 rats to test the hypothesis that physical activity and developmental origin contribute to preservation of muscle mass with age. Phosphorylation of p38 was exaggerated in aged branchial arch muscles. Phosphorylation of ERK and p70S6k T421/S424 declined with age only in the biceps brachii. Expression of p70S6k declined in all head and neck, tongue and limb muscles although no change in phosphorylation of p70S6k on T389 could be resolved. A systemic change that results in a loss of p70S6k protein expression may reduce the capacity to respond to acute hypertrophic stimuli, while the exaggerated p38 signaling in branchial arch muscles may reflect more active muscle remodeling.
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Affiliation(s)
- Jill A Rahnert
- School of Applied Physiology, Georgia Institute of Technology, Atlanta, GA 30332, USA
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