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Burke BI, Ismaeel A, McCarthy JJ. The utility of the rodent synergist ablation model in identifying molecular and cellular mechanisms of skeletal muscle hypertrophy. Am J Physiol Cell Physiol 2024; 327:C601-C606. [PMID: 39069822 DOI: 10.1152/ajpcell.00362.2024] [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: 05/29/2024] [Revised: 06/16/2024] [Accepted: 06/17/2024] [Indexed: 07/30/2024]
Abstract
Skeletal muscle exhibits remarkable plasticity to adapt to stimuli such as mechanical loading. The mechanisms that regulate skeletal muscle hypertrophy due to mechanical overload have been thoroughly studied. Remarkably, our understanding of many of the molecular and cellular mechanisms that regulate hypertrophic growth were first identified using the rodent synergist ablation (SA) model and subsequently corroborated in human resistance exercise training studies. To demonstrate the utility of the SA model, we briefly summarize the hypertrophic mechanisms identified using the model and the following translation of these mechanism to human skeletal muscle hypertrophy induced by resistance exercise training.
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Affiliation(s)
- Benjamin I Burke
- Department of Physiology, College of Medicine, University of Kentucky, Lexington, Kentucky, United States
- Center for Muscle Biology, University of Kentucky, Lexington, Kentucky, United States
| | - Ahmed Ismaeel
- Department of Physiology, College of Medicine, University of Kentucky, Lexington, Kentucky, United States
- Center for Muscle Biology, University of Kentucky, Lexington, Kentucky, United States
| | - John J McCarthy
- Department of Physiology, College of Medicine, University of Kentucky, Lexington, Kentucky, United States
- Center for Muscle Biology, University of Kentucky, Lexington, Kentucky, United States
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2
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Roberts MD, Hornberger TA, Phillips SM. The utility-and limitations-of the rodent synergist ablation model in examining mechanisms of skeletal muscle hypertrophy. Am J Physiol Cell Physiol 2024; 327:C607-C613. [PMID: 39069828 DOI: 10.1152/ajpcell.00405.2024] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/14/2024] [Accepted: 06/27/2024] [Indexed: 07/30/2024]
Abstract
In this issue, Burke et al. discuss the utility of the rodent synergist ablation (SA) model for examining mechanisms associated with skeletal muscle hypertrophy. In this invited perspective, we aim to complement their original perspective by discussing limitations to the model along with alternative mechanical overload models that have strengths and limitations.
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Affiliation(s)
- Michael D Roberts
- School of Kinesiology, Auburn University, Auburn, Alabama, United States
| | - Troy A Hornberger
- Department of Comparative Biosciences, University of Wisconsin-Madison, Madison, Wisconsin, United States
| | - Stuart M Phillips
- Department of Kinesiology, McMaster University, Hamilton, Ontario, Canada
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3
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Lin KH, Hibbert JE, Flynn CG, Lemens JL, Torbey MM, Steinert ND, Flejsierowicz PM, Melka KM, Lindley GT, Lares M, Setaluri V, Wagers AJ, Hornberger TA. Satellite cell-derived TRIM28 is pivotal for mechanical load- and injury-induced myogenesis. EMBO Rep 2024:10.1038/s44319-024-00227-1. [PMID: 39143258 DOI: 10.1038/s44319-024-00227-1] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/04/2024] [Revised: 07/19/2024] [Accepted: 07/26/2024] [Indexed: 08/16/2024] Open
Abstract
Satellite cells are skeletal muscle stem cells that contribute to postnatal muscle growth, and they endow skeletal muscle with the ability to regenerate after a severe injury. Here we discover that this myogenic potential of satellite cells requires a protein called tripartite motif-containing 28 (TRIM28). Interestingly, different from the role reported in a previous study based on C2C12 myoblasts, multiple lines of both in vitro and in vivo evidence reveal that the myogenic function of TRIM28 is not dependent on changes in the phosphorylation of its serine 473 residue. Moreover, the functions of TRIM28 are not mediated through the regulation of satellite cell proliferation or differentiation. Instead, our findings indicate that TRIM28 regulates the ability of satellite cells to progress through the process of fusion. Specifically, we discover that TRIM28 controls the expression of a fusogenic protein called myomixer and concomitant fusion pore formation. Collectively, the outcomes of this study expose the framework of a novel regulatory pathway that is essential for myogenesis.
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Affiliation(s)
- Kuan-Hung Lin
- Department of Comparative Biosciences, University of Wisconsin - Madison, Madison, WI, USA
- School of Veterinary Medicine, University of Wisconsin - Madison, Madison, WI, USA
- Department of Stem Cell and Regenerative Biology, Harvard University, Cambridge, MA, USA
| | - Jamie E Hibbert
- Department of Comparative Biosciences, University of Wisconsin - Madison, Madison, WI, USA
- School of Veterinary Medicine, University of Wisconsin - Madison, Madison, WI, USA
| | - Corey Gk Flynn
- Department of Comparative Biosciences, University of Wisconsin - Madison, Madison, WI, USA
- School of Veterinary Medicine, University of Wisconsin - Madison, Madison, WI, USA
| | - Jake L Lemens
- Department of Comparative Biosciences, University of Wisconsin - Madison, Madison, WI, USA
- School of Veterinary Medicine, University of Wisconsin - Madison, Madison, WI, USA
| | - Melissa M Torbey
- Department of Comparative Biosciences, University of Wisconsin - Madison, Madison, WI, USA
- School of Veterinary Medicine, University of Wisconsin - Madison, Madison, WI, USA
| | - Nathaniel D Steinert
- Department of Comparative Biosciences, University of Wisconsin - Madison, Madison, WI, USA
- School of Veterinary Medicine, University of Wisconsin - Madison, Madison, WI, USA
| | - Philip M Flejsierowicz
- Department of Comparative Biosciences, University of Wisconsin - Madison, Madison, WI, USA
- School of Veterinary Medicine, University of Wisconsin - Madison, Madison, WI, USA
| | - Kiley M Melka
- Department of Comparative Biosciences, University of Wisconsin - Madison, Madison, WI, USA
- School of Veterinary Medicine, University of Wisconsin - Madison, Madison, WI, USA
| | - Garrison T Lindley
- Department of Comparative Biosciences, University of Wisconsin - Madison, Madison, WI, USA
- School of Veterinary Medicine, University of Wisconsin - Madison, Madison, WI, USA
| | - Marcos Lares
- Department of Dermatology, University of Wisconsin - Madison, Madison, WI, USA
| | | | - Amy J Wagers
- Department of Stem Cell and Regenerative Biology, Harvard University, Cambridge, MA, USA
- Harvard Stem Cell Institute, Cambridge, MA, USA
- Joslin Diabetes Center, Boston, MA, USA
| | - Troy A Hornberger
- Department of Comparative Biosciences, University of Wisconsin - Madison, Madison, WI, USA.
- School of Veterinary Medicine, University of Wisconsin - Madison, Madison, WI, USA.
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4
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Meneses-Valdés R, Gallero S, Henríquez-Olguín C, Jensen TE. Exploring NADPH oxidases 2 and 4 in cardiac and skeletal muscle adaptations - A cross-tissue comparison. Free Radic Biol Med 2024; 223:296-305. [PMID: 39069268 DOI: 10.1016/j.freeradbiomed.2024.07.035] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 05/17/2024] [Revised: 07/23/2024] [Accepted: 07/24/2024] [Indexed: 07/30/2024]
Abstract
Striated muscle cells, encompassing cardiac myocytes and skeletal muscle fibers, are fundamental to athletic performance, facilitating blood circulation and coordinated movement through contraction. Despite their distinct functional roles, these muscle types exhibit similarities in cytoarchitecture, protein expression, and excitation-contraction coupling. Both muscle types also undergo molecular remodeling in energy metabolism and cell size in response to acute and repeated exercise stimuli to enhance exercise performance. Reactive oxygen species (ROS) produced by NADPH oxidase (NOX) isoforms 2 and 4 have emerged as signaling molecules that regulate exercise adaptations. This review systematically compares NOX2 and NOX4 expression, regulation, and roles in cardiac and skeletal muscle responses across exercise modalities. We highlight the many gaps in our knowledge and opportunities to let future skeletal muscle research into NOX-dependent mechanisms be inspired by cardiac muscle studies and vice versa. Understanding these processes could enhance the development of exercise routines to optimize human performance and health strategies that capitalize on the advantages of physical activity.
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Affiliation(s)
- Roberto Meneses-Valdés
- The August Krogh Section for Molecular Physiology, Department of Nutrition, Exercise and Sports, University of Copenhagen, Universitetsparken 13, Copenhagen, 2100, Denmark
| | - Samantha Gallero
- The August Krogh Section for Molecular Physiology, Department of Nutrition, Exercise and Sports, University of Copenhagen, Universitetsparken 13, Copenhagen, 2100, Denmark; Advanced Center for Chronic Diseases (ACCDiS) and Department of Biochemistry and Molecular Biology, Faculty of Chemical and Pharmaceutical Sciences, Universidad de Chile, Santiago, Chile
| | - Carlos Henríquez-Olguín
- The August Krogh Section for Molecular Physiology, Department of Nutrition, Exercise and Sports, University of Copenhagen, Universitetsparken 13, Copenhagen, 2100, Denmark; Center of Exercise Physiology and Metabolism, Department of Kinesiology, Faculty of Medicine, Universidad Finis Terrae, Santiago, Chile.
| | - Thomas E Jensen
- The August Krogh Section for Molecular Physiology, Department of Nutrition, Exercise and Sports, University of Copenhagen, Universitetsparken 13, Copenhagen, 2100, Denmark.
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5
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Millward DJ. Post-natal muscle growth and protein turnover: a narrative review of current understanding. Nutr Res Rev 2024; 37:141-168. [PMID: 37395180 DOI: 10.1017/s0954422423000124] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 07/04/2023]
Abstract
A model explaining the dietary-protein-driven post-natal skeletal muscle growth and protein turnover in the rat is updated, and the mechanisms involved are described, in this narrative review. Dietary protein controls both bone length and muscle growth, which are interrelated through mechanotransduction mechanisms with muscle growth induced both from stretching subsequent to bone length growth and from internal work against gravity. This induces satellite cell activation, myogenesis and remodelling of the extracellular matrix, establishing a growth capacity for myofibre length and cross-sectional area. Protein deposition within this capacity is enabled by adequate dietary protein and other key nutrients. After briefly reviewing the experimental animal origins of the growth model, key concepts and processes important for growth are reviewed. These include the growth in number and size of the myonuclear domain, satellite cell activity during post-natal development and the autocrine/paracrine action of IGF-1. Regulatory and signalling pathways reviewed include developmental mechanotransduction, signalling through the insulin/IGF-1-PI3K-Akt and the Ras-MAPK pathways in the myofibre and during mechanotransduction of satellite cells. Likely pathways activated by maximal-intensity muscle contractions are highlighted and the regulation of the capacity for protein synthesis in terms of ribosome assembly and the translational regulation of 5-TOPmRNA classes by mTORC1 and LARP1 are discussed. Evidence for and potential mechanisms by which volume limitation of muscle growth can occur which would limit protein deposition within the myofibre are reviewed. An understanding of how muscle growth is achieved allows better nutritional management of its growth in health and disease.
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Affiliation(s)
- D Joe Millward
- Department of Nutritional Sciences, School of Biosciences & Medicine, Faculty of Health and Medical Sciences, University of Surrey, Guildford, UK
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6
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Zhong R, Rua MT, Wei-LaPierre L. Targeting mitochondrial Ca 2+ uptake for the treatment of amyotrophic lateral sclerosis. J Physiol 2024; 602:1519-1549. [PMID: 38010626 PMCID: PMC11032238 DOI: 10.1113/jp284143] [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: 09/06/2023] [Accepted: 10/31/2023] [Indexed: 11/29/2023] Open
Abstract
Amyotrophic lateral sclerosis (ALS) is a rare adult-onset neurodegenerative disease characterized by progressive motor neuron (MN) loss, muscle denervation and paralysis. Over the past several decades, researchers have made tremendous efforts to understand the pathogenic mechanisms underpinning ALS, with much yet to be resolved. ALS is described as a non-cell autonomous condition with pathology detected in both MNs and non-neuronal cells, such as glial cells and skeletal muscle. Studies in ALS patient and animal models reveal ubiquitous abnormalities in mitochondrial structure and function, and disturbance of intracellular calcium homeostasis in various tissue types, suggesting a pivotal role of aberrant mitochondrial calcium uptake and dysfunctional calcium signalling cascades in ALS pathogenesis. Calcium signalling and mitochondrial dysfunction are intricately related to the manifestation of cell death contributing to MN loss and skeletal muscle dysfunction. In this review, we discuss the potential contribution of intracellular calcium signalling, particularly mitochondrial calcium uptake, in ALS pathogenesis. Functional consequences of excessive mitochondrial calcium uptake and possible therapeutic strategies targeting mitochondrial calcium uptake or the mitochondrial calcium uniporter, the main channel mediating mitochondrial calcium influx, are also discussed.
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Affiliation(s)
- Renjia Zhong
- Department of Applied Physiology and Kinesiology, College of Health and Human Performance, University of Florida, Gainesville, FL, 32611
- Department of Emergency Medicine, the First Affiliated Hospital of China Medical University, Shenyang, Liaoning, China, 110001
| | - Michael T. Rua
- Department of Applied Physiology and Kinesiology, College of Health and Human Performance, University of Florida, Gainesville, FL, 32611
| | - Lan Wei-LaPierre
- Department of Applied Physiology and Kinesiology, College of Health and Human Performance, University of Florida, Gainesville, FL, 32611
- Myology Institute, University of Florida, Gainesville, FL 32611
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7
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Jorgenson KW, Hibbert JE, Sayed RKA, Lange AN, Godwin JS, Mesquita PHC, Ruple BA, McIntosh MC, Kavazis AN, Roberts MD, Hornberger TA. A novel imaging method (FIM-ID) reveals that myofibrillogenesis plays a major role in the mechanically induced growth of skeletal muscle. eLife 2024; 12:RP92674. [PMID: 38466320 PMCID: PMC10928493 DOI: 10.7554/elife.92674] [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] [Indexed: 03/12/2024] Open
Abstract
An increase in mechanical loading, such as that which occurs during resistance exercise, induces radial growth of muscle fibers (i.e. an increase in cross-sectional area). Muscle fibers are largely composed of myofibrils, but whether radial growth is mediated by an increase in the size of the myofibrils (i.e. myofibril hypertrophy) and/or the number of myofibrils (i.e. myofibrillogenesis) is not known. Electron microscopy (EM) can provide images with the level of resolution that is needed to address this question, but the acquisition and subsequent analysis of EM images is a time- and cost-intensive process. To overcome this, we developed a novel method for visualizing myofibrils with a standard fluorescence microscope (fluorescence imaging of myofibrils with image deconvolution [FIM-ID]). Images from FIM-ID have a high degree of resolution and contrast, and these properties enabled us to develop pipelines for automated measurements of myofibril size and number. After extensively validating the automated measurements, we used both mouse and human models of increased mechanical loading to discover that the radial growth of muscle fibers is largely mediated by myofibrillogenesis. Collectively, the outcomes of this study offer insight into a fundamentally important topic in the field of muscle growth and provide future investigators with a time- and cost-effective means to study it.
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Affiliation(s)
- Kent W Jorgenson
- School of Veterinary Medicine and the Department of Comparative Biosciences, University of Wisconsin-MadisonMadisonUnited States
| | - Jamie E Hibbert
- School of Veterinary Medicine and the Department of Comparative Biosciences, University of Wisconsin-MadisonMadisonUnited States
| | - Ramy KA Sayed
- School of Veterinary Medicine and the Department of Comparative Biosciences, University of Wisconsin-MadisonMadisonUnited States
- Department of Anatomy and Embryology, Faculty of Veterinary Medicine, Sohag UniversitySohagEgypt
| | - Anthony N Lange
- School of Veterinary Medicine and the Department of Comparative Biosciences, University of Wisconsin-MadisonMadisonUnited States
| | | | | | | | | | | | | | - Troy A Hornberger
- School of Veterinary Medicine and the Department of Comparative Biosciences, University of Wisconsin-MadisonMadisonUnited States
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8
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Jorgenson KW, Hibbert JE, Sayed RKA, Lange AN, Godwin JS, Mesquita PHC, Ruple BA, McIntosh MC, Kavazis AN, Roberts MD, Hornberger TA. A Novel Imaging Method (FIM-ID) Reveals that Myofibrillogenesis Plays a Major Role in the Mechanically Induced Growth of Skeletal Muscle. BIORXIV : THE PREPRINT SERVER FOR BIOLOGY 2023:2023.09.13.557204. [PMID: 37745462 PMCID: PMC10515927 DOI: 10.1101/2023.09.13.557204] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 09/26/2023]
Abstract
An increase in mechanical loading, such as that which occurs during resistance exercise, induces radial growth of muscle fibers (i.e., an increase in cross-sectional area). Muscle fibers are largely composed of myofibrils, but whether radial growth is mediated by an increase in the size of the myofibrils (i.e., myofibril hypertrophy) and/or the number of myofibrils (i.e., myofibrillogenesis) is not known. Electron microscopy (EM) can provide images with the level of resolution that is needed to address this question, but the acquisition and subsequent analysis of EM images is a time- and cost-intensive process. To overcome this, we developed a novel method for visualizing myofibrils with a standard fluorescence microscope (FIM-ID). Images from FIM-ID have a high degree of resolution and contrast, and these properties enabled us to develop pipelines for automated measurements of myofibril size and number. After extensively validating the automated measurements, we used both mouse and human models of increased mechanical loading to discover that the radial growth of muscle fibers is largely mediated by myofibrillogenesis. Collectively, the outcomes of this study offer insight into a fundamentally important topic in the field of muscle growth and provide future investigators with a time- and cost-effective means to study it.
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9
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Trautman ME, Braucher LN, Elliehausen C, Zhu WG, Zelenovskiy E, Green M, Sonsalla MM, Yeh CY, Hornberger TA, Konopka AR, Lamming DW. Resistance exercise protects mice from protein-induced fat accretion. eLife 2023; 12:RP91007. [PMID: 38019262 PMCID: PMC10686620 DOI: 10.7554/elife.91007] [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] [Indexed: 11/30/2023] Open
Abstract
Low-protein (LP) diets extend the lifespan of diverse species and are associated with improved metabolic health in both rodents and humans. Paradoxically, many athletes and bodybuilders consume high-protein (HP) diets and protein supplements, yet are both fit and metabolically healthy. Here, we examine this paradox using weight pulling, a validated progressive resistance exercise training regimen, in mice fed either an LP diet or an isocaloric HP diet. We find that despite having lower food consumption than the LP group, HP-fed mice gain significantly more fat mass than LP-fed mice when not exercising, while weight pulling protected HP-fed mice from this excess fat accretion. The HP diet augmented exercise-induced hypertrophy of the forearm flexor complex, and weight pulling ability increased more rapidly in the exercised HP-fed mice. Surprisingly, exercise did not protect from HP-induced changes in glycemic control. Our results confirm that HP diets can augment muscle hypertrophy and accelerate strength gain induced by resistance exercise without negative effects on fat mass, and also demonstrate that LP diets may be advantageous in the sedentary. Our results highlight the need to consider both dietary composition and activity, not simply calories, when taking a precision nutrition approach to health.
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Affiliation(s)
- Michaela E Trautman
- Department of Medicine, University of Wisconsin-MadisonMadisonUnited States
- William S. Middleton Memorial Veterans HospitalMadisonUnited States
- Nutrition and Metabolism Graduate Program, University of Wisconsin- MadisonMadisonUnited States
| | - Leah N Braucher
- Department of Medicine, University of Wisconsin-MadisonMadisonUnited States
- William S. Middleton Memorial Veterans HospitalMadisonUnited States
| | - Christian Elliehausen
- Department of Medicine, University of Wisconsin-MadisonMadisonUnited States
- William S. Middleton Memorial Veterans HospitalMadisonUnited States
- Cellular and Molecular Biology Graduate Program, University of Wisconsin-MadisonMadisonUnited States
| | - Wenyuan G Zhu
- Department of Medicine, University of Wisconsin-MadisonMadisonUnited States
- William S. Middleton Memorial Veterans HospitalMadisonUnited States
- Comparative Biomedical Sciences Graduate Program, University of Wisconsin-MadisonMadisonUnited States
| | - Esther Zelenovskiy
- Department of Medicine, University of Wisconsin-MadisonMadisonUnited States
- William S. Middleton Memorial Veterans HospitalMadisonUnited States
| | - Madelyn Green
- Department of Medicine, University of Wisconsin-MadisonMadisonUnited States
- William S. Middleton Memorial Veterans HospitalMadisonUnited States
| | - Michelle M Sonsalla
- Department of Medicine, University of Wisconsin-MadisonMadisonUnited States
- William S. Middleton Memorial Veterans HospitalMadisonUnited States
- Comparative Biomedical Sciences Graduate Program, University of Wisconsin-MadisonMadisonUnited States
| | - Chung-Yang Yeh
- Department of Medicine, University of Wisconsin-MadisonMadisonUnited States
- William S. Middleton Memorial Veterans HospitalMadisonUnited States
| | - Troy A Hornberger
- Comparative Biomedical Sciences Graduate Program, University of Wisconsin-MadisonMadisonUnited States
- School of Veterinary Medicine, University of Wisconsin-MadisonMadisonUnited States
| | - Adam R Konopka
- Department of Medicine, University of Wisconsin-MadisonMadisonUnited States
- William S. Middleton Memorial Veterans HospitalMadisonUnited States
- Cellular and Molecular Biology Graduate Program, University of Wisconsin-MadisonMadisonUnited States
| | - Dudley W Lamming
- Department of Medicine, University of Wisconsin-MadisonMadisonUnited States
- William S. Middleton Memorial Veterans HospitalMadisonUnited States
- Nutrition and Metabolism Graduate Program, University of Wisconsin- MadisonMadisonUnited States
- Cellular and Molecular Biology Graduate Program, University of Wisconsin-MadisonMadisonUnited States
- Comparative Biomedical Sciences Graduate Program, University of Wisconsin-MadisonMadisonUnited States
- University of Wisconsin Carbone Cancer CenterMadisonUnited States
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10
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Roberts MD, McCarthy JJ, Hornberger TA, Phillips SM, Mackey AL, Nader GA, Boppart MD, Kavazis AN, Reidy PT, Ogasawara R, Libardi CA, Ugrinowitsch C, Booth FW, Esser KA. Mechanisms of mechanical overload-induced skeletal muscle hypertrophy: current understanding and future directions. Physiol Rev 2023; 103:2679-2757. [PMID: 37382939 PMCID: PMC10625844 DOI: 10.1152/physrev.00039.2022] [Citation(s) in RCA: 7] [Impact Index Per Article: 7.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/11/2023] [Revised: 06/12/2023] [Accepted: 06/21/2023] [Indexed: 06/30/2023] Open
Abstract
Mechanisms underlying mechanical overload-induced skeletal muscle hypertrophy have been extensively researched since the landmark report by Morpurgo (1897) of "work-induced hypertrophy" in dogs that were treadmill trained. Much of the preclinical rodent and human resistance training research to date supports that involved mechanisms include enhanced mammalian/mechanistic target of rapamycin complex 1 (mTORC1) signaling, an expansion in translational capacity through ribosome biogenesis, increased satellite cell abundance and myonuclear accretion, and postexercise elevations in muscle protein synthesis rates. However, several lines of past and emerging evidence suggest that additional mechanisms that feed into or are independent of these processes are also involved. This review first provides a historical account of how mechanistic research into skeletal muscle hypertrophy has progressed. A comprehensive list of mechanisms associated with skeletal muscle hypertrophy is then outlined, and areas of disagreement involving these mechanisms are presented. Finally, future research directions involving many of the discussed mechanisms are proposed.
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Affiliation(s)
- Michael D Roberts
- School of Kinesiology, Auburn University, Auburn, Alabama, United States
| | - John J McCarthy
- Department of Physiology, College of Medicine, University of Kentucky, Lexington, Kentucky, United States
| | - Troy A Hornberger
- Department of Comparative Biosciences, University of Wisconsin-Madison, Madison, Wisconsin, United States
| | - Stuart M Phillips
- Department of Kinesiology, McMaster University, Hamilton, Ontario, Canada
| | - Abigail L Mackey
- Institute of Sports Medicine Copenhagen, Department of Orthopedic Surgery, Copenhagen University Hospital-Bispebjerg and Frederiksberg, and Department of Clinical Medicine, University of Copenhagen, Copenhagen, Denmark
| | - Gustavo A Nader
- Department of Kinesiology and Huck Institutes of the Life Sciences, The Pennsylvania State University, University Park, Pennsylvania, United States
| | - Marni D Boppart
- Department of Kinesiology and Community Health, University of Illinois at Urbana-Champaign, Urbana, Illinois, United States
| | - Andreas N Kavazis
- School of Kinesiology, Auburn University, Auburn, Alabama, United States
| | - Paul T Reidy
- Department of Kinesiology, Nutrition and Health, Miami University, Oxford, Ohio, United States
| | - Riki Ogasawara
- Healthy Food Science Research Group, Cellular and Molecular Biotechnology Research Institute, National Institute of Advanced Industrial Science and Technology (AIST), Tsukuba, Japan
| | - Cleiton A Libardi
- MUSCULAB-Laboratory of Neuromuscular Adaptations to Resistance Training, Department of Physical Education, Federal University of São Carlos, São Carlos, Brazil
| | - Carlos Ugrinowitsch
- School of Physical Education and Sport, University of São Paulo, São Paulo, Brazil
| | - Frank W Booth
- Department of Biomedical Sciences, University of Missouri, Columbia, Missouri, United States
| | - Karyn A Esser
- Department of Physiology and Aging, College of Medicine, University of Florida, Gainesville, Florida, United States
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11
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Bagley JR, Denes LT, McCarthy JJ, Wang ET, Murach KA. The myonuclear domain in adult skeletal muscle fibres: past, present and future. J Physiol 2023; 601:723-741. [PMID: 36629254 PMCID: PMC9931674 DOI: 10.1113/jp283658] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/12/2022] [Accepted: 01/06/2023] [Indexed: 01/12/2023] Open
Abstract
Most cells in the body are mononuclear whereas skeletal muscle fibres are uniquely multinuclear. The nuclei of muscle fibres (myonuclei) are usually situated peripherally which complicates the equitable distribution of gene products. Myonuclear abundance can also change under conditions such as hypertrophy and atrophy. Specialised zones in muscle fibres have different functions and thus distinct synthetic demands from myonuclei. The complex structure and regulatory requirements of multinuclear muscle cells understandably led to the hypothesis that myonuclei govern defined 'domains' to maintain homeostasis and facilitate adaptation. The purpose of this review is to provide historical context for the myonuclear domain and evaluate its veracity with respect to mRNA and protein distribution resulting from myonuclear transcription. We synthesise insights from past and current in vitro and in vivo genetically modified models for studying the myonuclear domain under dynamic conditions. We also cover the most contemporary knowledge on mRNA and protein transport in muscle cells. Insights from emerging technologies such as single myonuclear RNA-sequencing further inform our discussion of the myonuclear domain. We broadly conclude: (1) the myonuclear domain can be flexible during muscle fibre growth and atrophy, (2) the mechanisms and role of myonuclear loss and motility deserve further consideration, (3) mRNA in muscle is actively transported via microtubules and locally restricted, but proteins may travel far from a myonucleus of origin and (4) myonuclear transcriptional specialisation extends beyond the classic neuromuscular and myotendinous populations. A deeper understanding of the myonuclear domain in muscle may promote effective therapies for ageing and disease.
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Affiliation(s)
- James R. Bagley
- Muscle Physiology Laboratory, Department of Kinesiology, San Francisco State University, San Francisco, California
| | | | - John J. McCarthy
- The Center for Muscle Biology, University of Kentucky, Lexington, Kentucky
- Department of Physiology, College of Medicine, University of Kentucky
| | - Eric T. Wang
- Department of Molecular Genetics and Microbiology, Center for NeuroGenetics, University of Florida, Gainesville, Florida
- Myology Institute, University of Florida
- Genetics Institute, University of Florida
| | - Kevin A. Murach
- Exercise Science Research Center, Department of Health, Human Performance, and Recreation, University of Arkansas, Fayetteville, Arkansas
- Cell and Molecular Biology Graduate Program, University of Arkansas
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12
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Going nuclear: Molecular adaptations to exercise mediated by myonuclei. SPORTS MEDICINE AND HEALTH SCIENCE 2022; 5:2-9. [PMID: 36994170 PMCID: PMC10040379 DOI: 10.1016/j.smhs.2022.11.005] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/17/2022] [Revised: 11/23/2022] [Accepted: 11/30/2022] [Indexed: 12/13/2022] Open
Abstract
Muscle fibers are multinucleated, and muscle fiber nuclei (myonuclei) are believed to be post-mitotic and are typically situated near the periphery of the myofiber. Due to the unique organization of muscle fibers and their nuclei, the cellular and molecular mechanisms regulating myofiber homeostasis in unstressed and stressed conditions (e.g., exercise) are unique. A key role myonuclei play in regulating muscle during exercise is gene transcription. Only recently have investigators had the capability to identify molecular changes at high resolution exclusively in myonuclei in response to perturbations in vivo. The purpose of this review is to describe how myonuclei modulate their transcriptome, epigenetic status, mobility and shape, and microRNA expression in response to exercise in vivo. Given the relative paucity of high-fidelity information on myonucleus-specific contributions to exercise adaptation, we identify specific gaps in knowledge and provide perspectives on future directions of research.
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Bernard C, Zavoriti A, Pucelle Q, Chazaud B, Gondin J. Role of macrophages during skeletal muscle regeneration and hypertrophy-Implications for immunomodulatory strategies. Physiol Rep 2022; 10:e15480. [PMID: 36200266 PMCID: PMC9535344 DOI: 10.14814/phy2.15480] [Citation(s) in RCA: 7] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/02/2022] [Accepted: 09/12/2022] [Indexed: 06/16/2023] Open
Abstract
Skeletal muscle is a plastic tissue that regenerates ad integrum after injury and adapts to raise mechanical loading/contractile activity by increasing its mass and/or myofiber size, a phenomenon commonly refers to as skeletal muscle hypertrophy. Both muscle regeneration and hypertrophy rely on the interactions between muscle stem cells and their neighborhood, which include inflammatory cells, and particularly macrophages. This review first summarizes the role of macrophages in muscle regeneration in various animal models of injury and in response to exercise-induced muscle damage in humans. Then, the potential contribution of macrophages to skeletal muscle hypertrophy is discussed on the basis of both animal and human experiments. We also present a brief comparative analysis of the role of macrophages during muscle regeneration versus hypertrophy. Finally, we summarize the current knowledge on the impact of different immunomodulatory strategies, such as heat therapy, cooling, massage, nonsteroidal anti-inflammatory drugs and resolvins, on skeletal muscle regeneration and their potential impact on muscle hypertrophy.
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Affiliation(s)
- Clara Bernard
- Institut NeuroMyoGène, Unité Physiopathologie et Génétique du Neurone et du MuscleUniversité Claude Bernard Lyon 1, CNRS UMR 5261, INSERM U1315, Université LyonLyonFrance
| | - Aliki Zavoriti
- Institut NeuroMyoGène, Unité Physiopathologie et Génétique du Neurone et du MuscleUniversité Claude Bernard Lyon 1, CNRS UMR 5261, INSERM U1315, Université LyonLyonFrance
| | - Quentin Pucelle
- Université de Versailles Saint‐Quentin‐En‐YvelinesVersaillesFrance
| | - Bénédicte Chazaud
- Institut NeuroMyoGène, Unité Physiopathologie et Génétique du Neurone et du MuscleUniversité Claude Bernard Lyon 1, CNRS UMR 5261, INSERM U1315, Université LyonLyonFrance
| | - Julien Gondin
- Institut NeuroMyoGène, Unité Physiopathologie et Génétique du Neurone et du MuscleUniversité Claude Bernard Lyon 1, CNRS UMR 5261, INSERM U1315, Université LyonLyonFrance
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14
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Hinks A, Jacob K, Mashouri P, Medak KD, Franchi MV, Wright DC, Brown SHM, Power GA. Influence of weighted downhill running training on serial sarcomere number and work loop performance in the rat soleus. Biol Open 2022; 11:276077. [PMID: 35876382 PMCID: PMC9346294 DOI: 10.1242/bio.059491] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/15/2022] [Accepted: 06/23/2022] [Indexed: 12/16/2022] Open
Abstract
Increased serial sarcomere number (SSN) has been observed in rats following downhill running training due to the emphasis on active lengthening contractions; however, little is known about the influence on dynamic contractile function. Therefore, we employed 4 weeks of weighted downhill running training in rats, then assessed soleus SSN and work loop performance. We hypothesised trained rats would produce greater net work output during work loops due to a greater SSN. Thirty-one Sprague-Dawley rats were assigned to a training or sedentary control group. Weight was added during downhill running via a custom-made vest, progressing from 5–15% body mass. Following sacrifice, the soleus was dissected, and a force-length relationship was constructed. Work loops (cyclic muscle length changes) were then performed about optimal muscle length (LO) at 1.5–3-Hz cycle frequencies and 1–7-mm length changes. Muscles were then fixed in formalin at LO. Fascicle lengths and sarcomere lengths were measured to calculate SSN. Intramuscular collagen content and crosslinking were quantified via a hydroxyproline content and pepsin-solubility assay. Trained rats had longer fascicle lengths (+13%), greater SSN (+8%), and a less steep passive force-length curve than controls (P<0.05). There were no differences in collagen parameters (P>0.05). Net work output was greater (+78–209%) in trained than control rats for the 1.5-Hz work loops at 1 and 3-mm length changes (P<0.05), however, net work output was more related to maximum specific force (R2=0.17-0.48, P<0.05) than SSN (R2=0.03-0.07, P=0.17-0.86). Therefore, contrary to our hypothesis, training-induced sarcomerogenesis likely contributed little to the improvements in work loop performance. This article has an associated First Person interview with the first author of the paper. Summary: An investigation of adaptations in mechanical function induced by a novel method of weighted downhill running training in rats, and the connections to adaptations in muscle architecture.
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Affiliation(s)
- Avery Hinks
- Department of Human Health and Nutritional Sciences, College of Biological Sciences, University of Guelph, 50 Stone Road East, Guelph, ON N1G 2W1, Canada
| | - Kaitlyn Jacob
- Department of Human Health and Nutritional Sciences, College of Biological Sciences, University of Guelph, 50 Stone Road East, Guelph, ON N1G 2W1, Canada
| | - Parastoo Mashouri
- Department of Human Health and Nutritional Sciences, College of Biological Sciences, University of Guelph, 50 Stone Road East, Guelph, ON N1G 2W1, Canada
| | - Kyle D Medak
- Department of Human Health and Nutritional Sciences, College of Biological Sciences, University of Guelph, 50 Stone Road East, Guelph, ON N1G 2W1, Canada
| | - Martino V Franchi
- Department of Biomedical Sciences, Neuromuscular Physiology Laboratory, University of Padua, Padua 35122, Italy
| | - David C Wright
- Department of Human Health and Nutritional Sciences, College of Biological Sciences, University of Guelph, 50 Stone Road East, Guelph, ON N1G 2W1, Canada.,School of Kinesiology, Faculty of Land and Food Systems, University of British Columbia, Vancouver, BC V6T 1Z4, Canada
| | - Stephen H M Brown
- Department of Human Health and Nutritional Sciences, College of Biological Sciences, University of Guelph, 50 Stone Road East, Guelph, ON N1G 2W1, Canada
| | - Geoffrey A Power
- Department of Human Health and Nutritional Sciences, College of Biological Sciences, University of Guelph, 50 Stone Road East, Guelph, ON N1G 2W1, Canada
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15
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Dungan CM, Brightwell CR, Wen Y, Zdunek CJ, Latham CM, Thomas NT, Zagzoog AM, Brightwell BD, Nolt GL, Keeble AR, Watowich SJ, Murach KA, Fry CS. Muscle-Specific Cellular and Molecular Adaptations to Late-Life Voluntary Concurrent Exercise. FUNCTION 2022; 3:zqac027. [PMID: 35774589 PMCID: PMC9233305 DOI: 10.1093/function/zqac027] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/30/2022] [Revised: 05/06/2022] [Accepted: 05/08/2022] [Indexed: 01/07/2023] Open
Abstract
Murine exercise models can provide information on factors that influence muscle adaptability with aging, but few translatable solutions exist. Progressive weighted wheel running (PoWeR) is a simple, voluntary, low-cost, high-volume endurance/resistance exercise approach for training young mice. In the current investigation, aged mice (22-mo-old) underwent a modified version of PoWeR for 8 wk. Muscle functional, cellular, biochemical, transcriptional, and myonuclear DNA methylation analyses provide an encompassing picture of how muscle from aged mice responds to high-volume combined training. Mice run 6-8 km/d, and relative to sedentary mice, PoWeR increases plantarflexor muscle strength. The oxidative soleus of aged mice responds to PoWeR similarly to young mice in every parameter measured in previous work; this includes muscle mass, glycolytic-to-oxidative fiber type transitioning, fiber size, satellite cell frequency, and myonuclear number. The oxidative/glycolytic plantaris adapts according to fiber type, but with modest overall changes in muscle mass. Capillarity increases markedly with PoWeR in both muscles, which may be permissive for adaptability in advanced age. Comparison to published PoWeR RNA-sequencing data in young mice identified conserved regulators of adaptability across age and muscles; this includes Aldh1l1 which associates with muscle vasculature. Agrn and Samd1 gene expression is upregulated after PoWeR simultaneous with a hypomethylated promoter CpG in myonuclear DNA, which could have implications for innervation and capillarization. A promoter CpG in Rbm10 is hypomethylated by late-life exercise in myonuclei, consistent with findings in muscle tissue. PoWeR and the data herein are a resource for uncovering cellular and molecular regulators of muscle adaptation with aging.
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Affiliation(s)
- Cory M Dungan
- Department of Physical Therapy, University of Kentucky, Lexington 40536, KY, USA
- Center for Muscle Biology, University of Kentucky, Lexington 40536, KY, USA
| | - Camille R Brightwell
- Center for Muscle Biology, University of Kentucky, Lexington 40536, KY, USA
- Department of Athletic Training and Clinical Nutrition, University of Kentucky, Lexington 40536, KY, USA
| | - Yuan Wen
- Department of Physical Therapy, University of Kentucky, Lexington 40536, KY, USA
- Center for Muscle Biology, University of Kentucky, Lexington 40536, KY, USA
| | | | - Christine M Latham
- Center for Muscle Biology, University of Kentucky, Lexington 40536, KY, USA
- Department of Athletic Training and Clinical Nutrition, University of Kentucky, Lexington 40536, KY, USA
| | - Nicholas T Thomas
- Center for Muscle Biology, University of Kentucky, Lexington 40536, KY, USA
- Department of Athletic Training and Clinical Nutrition, University of Kentucky, Lexington 40536, KY, USA
| | - Alyaa M Zagzoog
- Center for Muscle Biology, University of Kentucky, Lexington 40536, KY, USA
- Department of Athletic Training and Clinical Nutrition, University of Kentucky, Lexington 40536, KY, USA
| | - Benjamin D Brightwell
- Kinesiology and Health Promotion Graduate Program, University of Kentucky, Lexington 40536, KY, USA
| | - Georgia L Nolt
- Center for Muscle Biology, University of Kentucky, Lexington 40536, KY, USA
| | - Alexander R Keeble
- Center for Muscle Biology, University of Kentucky, Lexington 40536, KY, USA
- Department of Athletic Training and Clinical Nutrition, University of Kentucky, Lexington 40536, KY, USA
| | - Stanley J Watowich
- Department of Biochemistry and Molecular Biology, University of Texas Medical Branch, Galveston 77555, TX, USA
| | - Kevin A Murach
- Center for Muscle Biology, University of Kentucky, Lexington 40536, KY, USA
- Department of Health, Human Performance, and Recreation, University of Arkansas, Fayetteville 72701, AR, USA
- Cell and Molecular Biology Program, University of Arkansas, Fayetteville 72701, AR, USA
| | - Christopher S Fry
- Center for Muscle Biology, University of Kentucky, Lexington 40536, KY, USA
- Department of Athletic Training and Clinical Nutrition, University of Kentucky, Lexington 40536, KY, USA
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16
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Al-Sarraf H, Mouihate A. Muscle Hypertrophy in a Newly Developed Resistance Exercise Model for Rats. Front Physiol 2022; 13:851789. [PMID: 35634153 PMCID: PMC9136173 DOI: 10.3389/fphys.2022.851789] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/10/2022] [Accepted: 04/28/2022] [Indexed: 11/13/2022] Open
Abstract
Clinical evidence suggests that resistance exercise exerts health benefit. The mechanisms underlying such health benefits is largely explored in experimental animals. Available experimental models have several shortcomings such as the need for noxious stimuli that could affect the physiological readouts. In this study, we describe a simple-to-use experimental model of resistance exercise. In this resistance exercise, rats pull pre-determined weights using a tunnel and pulley system. We show that resistance-exercised rats developed a larger pulling strength when compared to those seen in either control rats or in rats subjected to traditional treadmill exercise. Histological examination revealed that resistance exercise led to a larger fiber cross-sectional area in the plantaris muscle, but not in the gastrocnemius or the soleus muscles. Similarly, the percentage of type-II muscle fibers in the plantaris was increased in resistance exercised rats when compared to those seen in plantaris muscles of either control or treadmill-exercised rat groups. Furthermore, this resistance exercise led to a significant increase in the expression levels of the phosphorylated protein kinase B; a marker of muscle hypertrophy in the plantaris muscle. Such effects were not seen in treadmill-trained rats. In conclusion, we developed an experimental model that can be amenable for experimental exploration of the mechanisms underlying the beneficial effects of resistance exercise. We further provide evidence that this resistance exercise model enhanced muscle strength and muscle hypertrophy.
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17
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Kalyuzhny AE. A Never-Ending Journey in Search for Novel Cell Biology Techniques. Cells 2022; 11:1393. [PMID: 35563699 PMCID: PMC9101893 DOI: 10.3390/cells11091393] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/29/2022] [Accepted: 04/15/2022] [Indexed: 02/01/2023] Open
Abstract
Cell techniques undergo rapid advancement across different areas of biomedical research [...].
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Affiliation(s)
- Alexander E Kalyuzhny
- Department of Neuroscience, University of Minnesota Twin Cities, 6-145 Jackson Hall, 321 Church St SE, Minneapolis, MN 55455, USA
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