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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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Burke BI, Ismaeel A, von Walden F, Murach KA, McCarthy JJ. Skeletal muscle hypertrophy: cell growth is cell growth. Am J Physiol Cell Physiol 2024; 327:C614-C618. [PMID: 39069829 DOI: 10.1152/ajpcell.00418.2024] [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: 06/20/2024] [Accepted: 07/05/2024] [Indexed: 07/30/2024]
Abstract
Roberts et al. have provided an insightful counterpoint to our review article on the utility of the synergist ablation model. The purpose of this review is to provide some further dialogue regarding the strengths and weaknesses of the synergist ablation model. Specifically, we highlight that the robustness of the model overshadows surgical limitations. We also compare the transcriptomic responses to synergist ablation in mice and resistance exercise in humans to identify common pathways. We conclude that "cell growth is cell growth" and that the mechanisms available to cells to accumulate biomass and increase in size are similar across cell types and independent of the rate of growth.
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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
| | - Ferdinand von Walden
- Department of Women's and Children's Health, Karolinska Institutet, Solna, Sweden
| | - Kevin A Murach
- Department Health, Human Performance, and Recreation, University of Arkansas, Fayetteville, Arkansas, 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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4
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Ismaeel A, Thomas NT, McCashland M, Vechetti IJ, Edman S, Lanner JT, Figueiredo VC, Fry CS, McCarthy JJ, Wen Y, Murach KA, von Walden F. Coordinated Regulation of Myonuclear DNA Methylation, mRNA, and miRNA Levels Associates With the Metabolic Response to Rapid Synergist Ablation-Induced Skeletal Muscle Hypertrophy in Female Mice. FUNCTION 2023; 5:zqad062. [PMID: 38020067 PMCID: PMC10666992 DOI: 10.1093/function/zqad062] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/18/2023] [Revised: 10/16/2023] [Accepted: 11/01/2023] [Indexed: 12/01/2023] Open
Abstract
The central dogma of molecular biology dictates the general flow of molecular information from DNA that leads to a functional cellular outcome. In skeletal muscle fibers, the extent to which global myonuclear transcriptional alterations, accounting for epigenetic and post-transcriptional influences, contribute to an adaptive stress response is not clearly defined. In this investigation, we leveraged an integrated analysis of the myonucleus-specific DNA methylome and transcriptome, as well as myonuclear small RNA profiling to molecularly define the early phase of skeletal muscle fiber hypertrophy. The analysis of myonucleus-specific mature microRNA and other small RNA species provides new directions for exploring muscle adaptation and complemented the methylation and transcriptional information. Our integrated multi-omics interrogation revealed a coordinated myonuclear molecular landscape during muscle loading that coincides with an acute and rapid reduction of oxidative metabolism. This response may favor a biosynthesis-oriented metabolic program that supports rapid hypertrophic growth.
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Affiliation(s)
- Ahmed Ismaeel
- Department of Physiology, College of Medicine, University of Kentucky, Lexington, KY 40508, USA
- Center for Muscle Biology, University of Kentucky, Lexington, KY 40536, USA
| | - Nicholas T Thomas
- Center for Muscle Biology, University of Kentucky, Lexington, KY 40536, USA
- Department of Athletic Training and Clinical Nutrition, College of Health Sciences, University of Kentucky, Lexington, KY 40536, USA
| | - Mariah McCashland
- Department of Nutrition and Health Sciences, University of Nebraska–Lincoln, Lincoln, NE 68583, USA
| | - Ivan J Vechetti
- Department of Nutrition and Health Sciences, University of Nebraska–Lincoln, Lincoln, NE 68583, USA
| | - Sebastian Edman
- Department of Women’s and Children’s Health, Karolinska Institutet, Solna 17177, Sweden
| | - Johanna T Lanner
- Department of Physiology and Pharmacology, Karolinska Institutet, Solna 17177, Sweden
| | - Vandré C Figueiredo
- Department of Biological Sciences, Oakland University, Rochester, MI 48309, USA
| | - Christopher S Fry
- Center for Muscle Biology, University of Kentucky, Lexington, KY 40536, USA
- Department of Athletic Training and Clinical Nutrition, College of Health Sciences, University of Kentucky, Lexington, KY 40536, USA
| | - John J McCarthy
- Department of Physiology, College of Medicine, University of Kentucky, Lexington, KY 40508, USA
- Center for Muscle Biology, University of Kentucky, Lexington, KY 40536, USA
| | - Yuan Wen
- Department of Physiology, College of Medicine, University of Kentucky, Lexington, KY 40508, USA
- Center for Muscle Biology, University of Kentucky, Lexington, KY 40536, USA
- Division of Biomedical Informatics, Department of Internal Medicine, College of Medicine, University of Kentucky, Lexington, KY 40536, USA
| | - Kevin A Murach
- Department of Health, Human Performance, and Recreation, Exercise Science Research Center, University of Arkansas, Fayetteville, AR 72701, USA
| | - Ferdinand von Walden
- Department of Women’s and Children’s Health, Karolinska Institutet, Solna 17177, Sweden
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5
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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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Scervino MVM, Fortes MAS, Vitzel KF, de Souza DR, Murata GM, Santana GO, da Silva EB, Levada‐Pires AC, Kuwabara WMT, Loureiro TCA, Curi R. Autophagy signaling in hypertrophied muscles of diabetic and control rats. FEBS Open Bio 2023; 13:1709-1722. [PMID: 37470707 PMCID: PMC10476571 DOI: 10.1002/2211-5463.13677] [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: 12/21/2022] [Revised: 07/05/2023] [Accepted: 07/19/2023] [Indexed: 07/21/2023] Open
Abstract
Autophagy plays a vital role in cell homeostasis by eliminating nonfunctional components and promoting cell survival. Here, we examined the levels of autophagy signaling proteins after 7 days of overload hypertrophy in the extensor digitorum longus (EDL) and soleus muscles of control and diabetic rats. We compared control and 3-day streptozotocin-induced diabetic rats, an experimental model for type 1 diabetes mellitus (T1DM). EDL muscles showed increased levels of basal autophagy signaling proteins. The diabetic state did not affect the extent of overload-induced hypertrophy or the levels of autophagy signaling proteins (p-ULK1, Beclin-1, Atg5, Atg12-5, Atg7, Atg3, LC3-I and II, and p62) in either muscle. The p-ULK-1, Beclin-1, and p62 protein expression levels were higher in the EDL muscle than in the soleus before the hypertrophic stimulus. On the contrary, the soleus muscle exhibited increased autophagic signaling after overload-induced hypertrophy, with increases in Beclin-1, Atg5, Atg12-5, Atg7, Atg3, and LC3-I expression in the control and diabetic groups, in addition to p-ULK-1 in the control groups. After hypertrophy, Beclin-1 and Atg5 levels increased in the EDL muscle of both groups, while p-ULK1 and LC3-I increased in the control group. In conclusion, the baseline EDL muscle exhibited higher autophagy than the soleus muscle. Although TDM1 promotes skeletal muscle mass loss and strength reduction, it did not significantly alter the extent of overload-induced hypertrophy and autophagy signaling proteins in EDL and soleus muscles, with the two groups exhibiting different patterns of autophagy activation.
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Affiliation(s)
- Maria V. M. Scervino
- Instituto de Ciências da Atividade Física e Esporte (ICAFE)Universidade Cruzeiro do SulSão PauloBrazil
- Departmento de Fisiologia e Biofísica, Instituto de Ciências BiomédicasUniversidade de São PauloBrazil
| | - Marco A. S. Fortes
- Departmento de Fisiologia e Biofísica, Instituto de Ciências BiomédicasUniversidade de São PauloBrazil
- Departmento de NutriçãoCentro Universitário AvantisBalneário CamburiúBrazil
| | - Kaio F. Vitzel
- School of Health Sciences, College of HealthMassey UniversityAucklandNew Zealand
| | - Diego R. de Souza
- Instituto de Ciências da Atividade Física e Esporte (ICAFE)Universidade Cruzeiro do SulSão PauloBrazil
- Departamento de Projetos de Pesquisa e EnsinoEscola de Educação Física da Polícia Militar do Estado de São PauloBrazil
| | - Gilson M. Murata
- Departmento de Fisiologia e Biofísica, Instituto de Ciências BiomédicasUniversidade de São PauloBrazil
| | - Giovanna O. Santana
- Instituto de Ciências da Atividade Física e Esporte (ICAFE)Universidade Cruzeiro do SulSão PauloBrazil
| | - Eliane B. da Silva
- Instituto de Ciências da Atividade Física e Esporte (ICAFE)Universidade Cruzeiro do SulSão PauloBrazil
| | - Adriana C. Levada‐Pires
- Instituto de Ciências da Atividade Física e Esporte (ICAFE)Universidade Cruzeiro do SulSão PauloBrazil
| | - Wilson M. T. Kuwabara
- Departmento de Fisiologia e Biofísica, Instituto de Ciências BiomédicasUniversidade de São PauloBrazil
| | - Tatiana C. A. Loureiro
- Departmento de Fisiologia e Biofísica, Instituto de Ciências BiomédicasUniversidade de São PauloBrazil
| | - Rui Curi
- Instituto de Ciências da Atividade Física e Esporte (ICAFE)Universidade Cruzeiro do SulSão PauloBrazil
- Departmento de Fisiologia e Biofísica, Instituto de Ciências BiomédicasUniversidade de São PauloBrazil
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Bloom ET, Lin LM, Locke RC, Giordani A, Krassan E, Peloquin JM, Silbernagel KG, Parreno J, Santare MH, Killian ML, Elliott DM. Overload in a Rat In Vivo Model of Synergist Ablation Induces Tendon Multiscale Structural and Functional Degeneration. J Biomech Eng 2023; 145:081003. [PMID: 37184932 PMCID: PMC10782872 DOI: 10.1115/1.4062523] [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: 11/21/2022] [Revised: 05/02/2023] [Accepted: 05/04/2023] [Indexed: 05/16/2023]
Abstract
Tendon degeneration is typically described as an overuse injury with little distinction made between magnitude of load (overload) and number of cycles (overuse). Further, in vivo, animal models of tendon degeneration are mostly overuse models, where tendon damage is caused by a high number of load cycles. As a result, there is a lack of knowledge of how isolated overload leads to degeneration in tendons. A surgical model of synergist ablation (SynAb) overloads the target tendon, plantaris, by ablating its synergist tendon, Achilles. The objective of this study was to evaluate the structural and functional changes that occur following overload of plantaris tendon in a rat SynAb model. Tendon cross-sectional area (CSA) and shape changes were evaluated by longitudinal MR imaging up to 8 weeks postsurgery. Tissue-scale structural changes were evaluated by semiquantified histology and second harmonic generation microscopy. Fibril level changes were evaluated with serial block face scanning electron microscopy (SBF-SEM). Functional changes were evaluated using tension tests at the tissue and microscale using a custom testing system allowing both video and microscopy imaging. At 8 weeks, overloaded plantaris tendons exhibited degenerative changes including increases in CSA, cell density, collagen damage area fraction (DAF), and fibril diameter, and decreases in collagen alignment, modulus, and yield stress. To interpret the differences between overload and overuse in tendon, we introduce a new framework for tendon remodeling and degeneration that differentiates between the inputs of overload and overuse. In summary, isolated overload induces multiscale degenerative structural and functional changes in plantaris tendon.
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Affiliation(s)
- Ellen T Bloom
- Department of Biomedical Engineering, University of Delaware, Newark, DE 19716
| | - Lily M Lin
- Department of Biomedical Engineering, University of Delaware, Newark, DE 19716
| | - Ryan C Locke
- Department of Orthopaedic Surgery, University of Pennsylvania, Philadelphia, PA 19104; Translational Musculoskeletal Research Center, CMCVAMC, Philadelphia, PA 19104
| | - Alyssa Giordani
- Department of Biomedical Engineering, University of Delaware, Newark, DE 19716
| | - Erin Krassan
- Department of Biomedical Engineering, University of Delaware, Newark, DE 19716
| | - John M Peloquin
- Department of Biomedical Engineering, University of Delaware, Newark, DE 19716
| | | | - Justin Parreno
- Department of Biological Sciences, University of Delaware, Newark, DE 19716
| | - Michael H Santare
- Department of Mechanical Engineering, University of Delaware, Newark, DE 19716
| | - Megan L Killian
- Department of Orthopaedic Surgery, University of Michigan, Ann Arbor, MI 48104
| | - Dawn M Elliott
- Department of Biomedical Engineering, University of Delaware, Newark, DE 19716
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Martinelli A, Andreo L, Dos Santos Malavazzi TC, Terena SML, da Cruz Tobelem D, Bussadori SK, Fernandes KPS, Mesquita-Ferrari RA. Vascular photobiomodulation increases muscle fiber diameter and improves the gait during compensatory hypertrophy of plantar muscle in rats. JOURNAL OF BIOPHOTONICS 2022; 15:e202200192. [PMID: 36054438 DOI: 10.1002/jbio.202200192] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/23/2022] [Revised: 08/18/2022] [Accepted: 08/19/2022] [Indexed: 06/15/2023]
Abstract
The local photobiomodulation (LPBM) has demonstrated positive effects during compensatory hypertrophy (CH) in skeletal muscle as a response to an overload. The aim was to compare the effects of the transcutaneous vascular photobiomodulation (VPBM) and the LPBM on muscle fiber size, gait functionality, and on mechanical sensitivity during the CH model in rats. VPBM was administered over the rat's main tail vein and LPBM was applied over the plantar muscle region. VPBM induced an increase in muscle fiber diameter and cross-sectional area (CSA) after 7 days. At 14 days, an increase in the fiber diameter was found in both irradiated groups. The VPBM and LPBM promoted the reestablishment of normal gait evaluated by the sciatic functional index after 14 days. No changes were found in the mechanical (nociceptive) sensitivity in VPBM and LPBM groups in comparison to the CH group but there was an increase in the nociceptive sensitivity in the CH groups in comparison to the control after 7 and 14 days. In conclusion, both PBM, vascular and local, were able to improve the muscle size and gait during the CH process with more pronounced effects when irradiation was performed systemically (VPBM).
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Affiliation(s)
- Andréia Martinelli
- Postgraduate Program in Rehabilitation Sciences, Universidade Nove de Julho (UNINOVE), São Paulo, Brazil
| | - Lucas Andreo
- Postgraduate Program in Biophotonics Applied to the Health Sciences, Universidade Nove de Julho (UNINOVE), São Paulo, Brazil
| | | | - Stella Maris Lins Terena
- Postgraduate Program in Biophotonics Applied to the Health Sciences, Universidade Nove de Julho (UNINOVE), São Paulo, Brazil
| | - Daysi da Cruz Tobelem
- Postgraduate Program in Biophotonics Applied to the Health Sciences, Universidade Nove de Julho (UNINOVE), São Paulo, Brazil
| | - Sandra Kalil Bussadori
- Postgraduate Program in Rehabilitation Sciences, Universidade Nove de Julho (UNINOVE), São Paulo, Brazil
- Postgraduate Program in Biophotonics Applied to the Health Sciences, Universidade Nove de Julho (UNINOVE), São Paulo, Brazil
| | | | - Raquel Agnelli Mesquita-Ferrari
- Postgraduate Program in Rehabilitation Sciences, Universidade Nove de Julho (UNINOVE), São Paulo, Brazil
- Postgraduate Program in Biophotonics Applied to the Health Sciences, Universidade Nove de Julho (UNINOVE), São Paulo, Brazil
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Dungan CM, Figueiredo VC, Wen Y, VonLehmden GL, Zdunek CJ, Thomas NT, Mobley CB, Murach KA, Brightwell CR, Long DE, Fry CS, Kern PA, McCarthy JJ, Peterson CA. Senolytic treatment rescues blunted muscle hypertrophy in old mice. GeroScience 2022; 44:1925-1940. [PMID: 35325353 PMCID: PMC9616988 DOI: 10.1007/s11357-022-00542-2] [Citation(s) in RCA: 21] [Impact Index Per Article: 10.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/24/2021] [Accepted: 03/06/2022] [Indexed: 01/07/2023] Open
Abstract
With aging, skeletal muscle plasticity is attenuated in response to exercise. Here, we report that senescent cells, identified using senescence-associated β-galactosidase (SA β-Gal) activity and p21 immunohistochemistry, are very infrequent in resting muscle, but emerge approximately 2 weeks after a bout of resistance exercise in humans. We hypothesized that these cells contribute to blunted hypertrophic potential in old age. Using synergist ablation-induced mechanical overload (MOV) of the plantaris muscle to model resistance training in adult (5-6-month) and old (23-24-month) male C57BL/6 J mice, we found increased senescent cells in both age groups during hypertrophy. Consistent with the human data, there were negligible senescent cells in plantaris muscle from adult and old sham controls, but old mice had significantly more senescent cells 7 and 14 days following MOV relative to young. Old mice had blunted whole-muscle hypertrophy when compared to adult mice, along with smaller muscle fibers, specifically glycolytic type 2x + 2b fibers. To ablate senescent cells using a hit-and-run approach, old mice were treated with vehicle or a senolytic cocktail consisting of 5 mg/kg dasatinib and 50 mg/kg quercetin (D + Q) on days 7 and 10 during 14 days of MOV; control mice underwent sham surgery with or without senolytic treatment. Old mice given D + Q had larger muscles and muscle fibers after 14 days of MOV, fewer senescent cells when compared to vehicle-treated old mice, and changes in the expression of genes (i.e., Igf1, Ddit4, Mmp14) that are associated with hypertrophic growth. Our data collectively show that senescent cells emerge in human and mouse skeletal muscle following a hypertrophic stimulus and that D + Q improves muscle growth in old mice.
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Affiliation(s)
- Cory M Dungan
- Center for Muscle Biology, University of Kentucky, Lexington, KY, USA.
- Department of Physical Therapy, University of Kentucky, Lexington, KY, USA.
- College of Health Sciences, University of Kentucky, 900 S. Limestone, CTW 445, Lexington, KY, 40536, USA.
| | | | - Yuan Wen
- Center for Muscle Biology, University of Kentucky, Lexington, KY, USA
- Department of Physical Therapy, University of Kentucky, Lexington, KY, USA
| | | | | | - Nicholas T Thomas
- Center for Muscle Biology, University of Kentucky, Lexington, KY, USA
- Department of Athletic Training and Clinical Nutrition, University of Kentucky, Lexington, KY, USA
| | - C Brooks Mobley
- Center for Muscle Biology, University of Kentucky, Lexington, KY, USA
- Department of Physiology, University of Kentucky, Lexington, KY, USA
- School of Kinesiology, Auburn University, Auburn, AL, USA
| | - Kevin A Murach
- Center for Muscle Biology, University of Kentucky, Lexington, KY, USA
- Department of Health, Human Performance, and Recreation, University of Arkansas, Fayetteville, AR, USA
| | - Camille R Brightwell
- Center for Muscle Biology, University of Kentucky, Lexington, KY, USA
- Department of Athletic Training and Clinical Nutrition, University of Kentucky, Lexington, KY, USA
| | - Douglas E Long
- Center for Muscle Biology, University of Kentucky, Lexington, KY, USA
- Department of Physical Therapy, University of Kentucky, Lexington, KY, USA
| | - Christopher S Fry
- Center for Muscle Biology, University of Kentucky, Lexington, KY, USA
- Department of Athletic Training and Clinical Nutrition, University of Kentucky, Lexington, KY, USA
| | - Philip A Kern
- Department of Internal Medicine, Division of Endocrinology, University of Kentucky, Lexington, KY, USA
| | - John J McCarthy
- Center for Muscle Biology, University of Kentucky, Lexington, KY, USA
- Department of Physiology, University of Kentucky, Lexington, KY, USA
| | - Charlotte A Peterson
- Center for Muscle Biology, University of Kentucky, Lexington, KY, USA
- Department of Physical Therapy, University of Kentucky, Lexington, KY, USA
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10
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Improved Electrical Stimulation-Based Exercise Model to Induce Mice Tibialis Anterior Muscle Hypertrophy and Function. APPLIED SCIENCES-BASEL 2022. [DOI: 10.3390/app12157673] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 02/01/2023]
Abstract
Efficient and suitable animal models directed to skeletal muscle hypertrophy are highly needed; nevertheless, the currently available models have limitations, such as restricted hypertrophy outcome and prolonged protocols; thus, additional research is required. In this study, we developed an improved muscle training protocol for mice by directly stimulating the tibialis anterior (TA) muscle motor point using electrical stimulation. C57BL/6 adult male mice were separated into four groups: CTR (control groups for one and two weeks), ES1 (electrical stimulation for one week), and ES2 (electrical stimulation for two weeks). Following muscle training, TA was taken for further examination. The results demonstrated a steady increase in the fiber cross-sectional area as a result of muscle training (ES1, 14.6% and ES2, 28.9%, p < 0.0001). Two weeks of muscle training enhanced muscle mass and maximal tetanic force by 18 (p = 0.0205) and 30%, respectively (p = 0.0260). To assess the tissue remodeling response in this model, we evaluated satellite cell activity and observed an increase in the number of Pax-7-positive nuclei after one and two weeks of muscle training (both >2-fold, p < 0.0001). In addition, we observed an increase in the number of positive nuclei for MyoD after two weeks (2.6-fold, p = 0.0057) without fiber damage. Accordingly, phosphorylation of mTOR and p70 increased following two weeks of muscle training (17%, p = 0.0215 and 66%, p = 0.0364, respectively). The results indicate that this muscle training strategy is appropriate for promoting quick and intense hypertrophy.
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11
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Müller A, Forterre F, Vidondo B, Stoffel MH, Hernández-Guerra Á, Plessas IN, Schmidt MJ, Precht C. Evaluation of Paraspinal Musculature in Small Breed Dogs with and without Atlantoaxial Instability Using Computed Tomography. Vet Comp Orthop Traumatol 2022; 35:305-313. [PMID: 35672019 PMCID: PMC9578766 DOI: 10.1055/s-0042-1748860] [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] [Indexed: 10/30/2022]
Abstract
OBJECTIVE The aim of this study was to evaluate differences in paraspinal musculature between dogs with and without atlantoaxial instability (AAI) using computed tomography scans. STUDY DESIGN Retrospective multicentre study evaluating transverse reconstructed computed tomography scans of 83 small breed dogs (34 with and 49 without AAI) for the cross-sectional paraspinal musculature area at three levels (Occiput/C1, mid-C1, mid-C2). Ratio of moments, dorsal-to-ventral muscle-area ratios (d-v-ratio) and ratios of the dorsal and ventral musculature to C2 height (d-C2-ratio and v-C2-ratio) were evaluated for differences between groups using multivariate analysis of variance (p < 0.05) taking the head-neck position into account. RESULTS Dogs with AAI showed a significantly lower d-v-ratio at levels 2 and 3, d-C2-ratio at level 2 and ratio of moments at all levels. When head-neck positions were analysed separately, ratio of moments was significantly lower in affected dogs at level 1 and 2. Also lower was d-C2-ratio at level 2, but only in flexed positioning. The head-neck position had a significant influence on ratio of moments and d-v-ratio at all three levels and on d-C2-ratio at level 1. CONCLUSION Significant changes in muscle area were observed only for the hypaxial muscles at the C1 level, indicating a limited role of muscular adaption in AAI patients. Our results confirm an altered ratio of moments in dogs with AAI. The head-neck position has a significant impact and should be taken into account when evaluating spinal musculature.
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Affiliation(s)
- Annina Müller
- Tierarztpraxis Emmevet AG, Hasle-Rüegsau, Switzerland.,Division of Small Animal Surgery, Department of Clinical Veterinary Medicine, Vetsuisse Faculty, University of Bern, Bern, Switzerland
| | - Franck Forterre
- Division of Small Animal Surgery, Department of Clinical Veterinary Medicine, Vetsuisse Faculty, University of Bern, Bern, Switzerland
| | - Beatriz Vidondo
- Department of Clinical Research and Veterinary Public Health, Veterinary Public Health Institute, Vetsuisse Faculty, University of Bern, Liebefeld, Switzerland
| | - Michael H Stoffel
- Division of Veterinary Anatomy, Vetsuisse Faculty, University of Bern, Bern, Switzerland
| | - Ángel Hernández-Guerra
- Department of Veterinary Medicine and Surgery, Universidad Cardenal Herrera-CEU, CEU Universities, Valencia, Spain
| | - Ioannis N Plessas
- Davies Veterinary Specialists Limited, Manor Farm Business Park, Higham Gobion, Herts, United Kingdom
| | - Martin J Schmidt
- Clinic for Small Animals, Department of Veterinary Clinical Sciences, Justus-Liebig-University Giessen, Giessen, Germany
| | - Christina Precht
- Division of Clinical Radiology, Department of Clinical Veterinary Medicine, Vetsuisse Faculty, University of Bern, Bern, Switzerland
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12
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Nakano D, Machida S. Mitochondrial fusion- and fission-related protein expression in the regulation of skeletal muscle mass. Physiol Rep 2022; 10:e15281. [PMID: 35439362 PMCID: PMC9017976 DOI: 10.14814/phy2.15281] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/05/2021] [Revised: 03/01/2022] [Accepted: 03/29/2022] [Indexed: 06/14/2023] Open
Abstract
Mitochondria in the skeletal muscle are essential for maintaining metabolic plasticity and function. Mitochondrial quality control encompasses the dynamics of the biogenesis and remodeling of mitochondria, characterized by the constant fission and fusion of mitochondria in response to metabolic stressors. However, the roles of mitochondrial fission or fusion in muscle hypertrophy and atrophy remain unclear. The aim of this study was to determine whether mitochondrial fusion and fission events are influenced by muscle hypertrophy or atrophy stimulation. Twenty-six male F344 rats were randomly assigned to a control group or were subjected to up to 14 days of either plantaris overload (via tenotomy of the gastrocnemius and soleus muscles; hypertrophy group) or hindlimb cast immobilization (atrophy group). After 14 days of treatment, plantaris muscle samples were collected to determine the expression levels of mitochondrial fusion- and fission-related proteins. Muscle weight and total muscle protein content increased following plantaris overload in the hypertrophy group, but decreased following immobilization for 14 days in the atrophy group. In the hypertrophied muscle, the level of activated dynamin-related protein 1 (Drp1), phosphorylated at Ser616, significantly increased by 25.8% (p = 0.014). Moreover, the protein expression level of mitochondrial fission factor significantly decreased by 36.5% in the hypertrophy group compared with that of the control group (p = 0.017). In contrast, total Drp1 level significantly decreased in the atrophied plantaris muscle (p = 0.011). Our data suggest that mitochondrial fission events may be influenced by both muscle hypertrophy and atrophy stimulation, and that mitochondrial fission- related protein Drp1 plays an important role in the regulation of skeletal muscle in response to mechanical stimulation.
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Affiliation(s)
- Daiki Nakano
- Ritsumeikan UniversityKusatsuJapan
- Graduate School of Health and Sports ScienceJuntendo UniversityInzaiJapan
| | - Shuichi Machida
- Graduate School of Health and Sports ScienceJuntendo UniversityInzaiJapan
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13
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Valentino T, Figueiredo VC, Mobley CB, McCarthy JJ, Vechetti IJ. Evidence of myomiR regulation of the pentose phosphate pathway during mechanical load-induced hypertrophy. Physiol Rep 2021; 9:e15137. [PMID: 34889054 PMCID: PMC8661100 DOI: 10.14814/phy2.15137] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/13/2021] [Revised: 10/13/2021] [Accepted: 11/10/2021] [Indexed: 12/29/2022] Open
Abstract
Many of the molecular and cellular mechanisms discovered to regulate skeletal muscle hypertrophy were first identified using the rodent synergist ablation model. This model reveals the intrinsic capability and necessary pathways of skeletal muscle growth in response to mechanical overload (MOV). Reminiscent of the rapid cellular growth observed with cancer, we hypothesized that in response to MOV, skeletal muscle would undergo metabolic programming to sustain increased demands to support hypertrophy. To test this hypothesis, we analyzed the gene expression of specific metabolic pathways taken from transcriptomic microarray data of a MOV time course. We found an upregulation of genes involved in the oxidative branch of the pentose phosphate pathways (PPP) and mitochondrial branch of the folate cycle suggesting an increase in the production of NADPH. In addition, we sought to determine the potential role of skeletal muscle-enriched microRNA (myomiRs) and satellite cells in the regulation of the metabolic pathways that changed during MOV. We observed an inverse pattern in gene expression between muscle-enriched myomiR-1 and its known target gene glucose-6-phosphate dehydrogenase, G6pdx, suggesting myomiR regulation of PPP activation in response to MOV. Satellite cell fusion had a significant but modest impact on PPP gene expression. These transcriptomic findings suggest the robust muscle hypertrophy induced by MOV requires enhanced redox metabolism via PPP production of NADPH which is potentially regulated by a myomiR network.
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Affiliation(s)
- Taylor Valentino
- Department of PhysiologyCollege of MedicineLexingtonKentuckyUSA
- Center for Muscle BiologyUniversity of KentuckyLexingtonKentuckyUSA
| | - Vandre C. Figueiredo
- Center for Muscle BiologyUniversity of KentuckyLexingtonKentuckyUSA
- Department of Physical TherapyCollege of Health SciencesUniversity of KentuckyLexingtonKentuckyUSA
| | | | - John J. McCarthy
- Department of PhysiologyCollege of MedicineLexingtonKentuckyUSA
- Center for Muscle BiologyUniversity of KentuckyLexingtonKentuckyUSA
| | - Ivan J. Vechetti
- Department of Nutrition and Health SciencesCollege of Education and Human SciencesUniversity of Nebraska‐LincolnLincolnNebraskaUSA
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14
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Aoyama S, Kim HK, Hirooka R, Tanaka M, Shimoda T, Chijiki H, Kojima S, Sasaki K, Takahashi K, Makino S, Takizawa M, Takahashi M, Tahara Y, Shimba S, Shinohara K, Shibata S. Distribution of dietary protein intake in daily meals influences skeletal muscle hypertrophy via the muscle clock. Cell Rep 2021; 36:109336. [PMID: 34233179 DOI: 10.1016/j.celrep.2021.109336] [Citation(s) in RCA: 26] [Impact Index Per Article: 8.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/08/2019] [Revised: 03/20/2021] [Accepted: 06/11/2021] [Indexed: 01/25/2023] Open
Abstract
The meal distribution of proteins throughout the day is usually skewed. However, its physiological implications and the effects of better protein distribution on muscle volume are largely unknown. Here, using the two-meals-per-day feeding model, we find that protein intake at the early active phase promotes overloading-induced muscle hypertrophy, in a manner dependent on the local muscle clock. Mice fed branched-chain amino acid (BCAA)-supplemented diets at the early active phase demonstrate skeletal muscle hypertrophy. However, distribution-dependent effects are not observed in ClockΔ19 or muscle-specific Bmal1 knockout mice. Additionally, we examined the relationship between the distribution of proteins in meals and muscle functions, such as skeletal muscle index and grip strength in humans. Higher muscle functions were observed in subjects who ingested dietary proteins mainly at breakfast than at dinner. These data suggest that protein intake at breakfast may be better for the maintenance of skeletal muscle mass.
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Affiliation(s)
- Shinya Aoyama
- Laboratory of Physiology and Pharmacology, School of Advanced Science and Engineering, Waseda University, Tokyo 162-8480, Japan; Organization for University Research Initiatives, Waseda University, Tokyo 162-8480, Japan; Department of Neurobiology & Behavior, Graduate School of Biomedical Sciences, Nagasaki University, Nagasaki 852-8523, Japan
| | - Hyeon-Ki Kim
- Laboratory of Physiology and Pharmacology, School of Advanced Science and Engineering, Waseda University, Tokyo 162-8480, Japan; Organization for University Research Initiatives, Waseda University, Tokyo 162-8480, Japan
| | - Rina Hirooka
- Laboratory of Physiology and Pharmacology, School of Advanced Science and Engineering, Waseda University, Tokyo 162-8480, Japan
| | - Mizuho Tanaka
- Laboratory of Physiology and Pharmacology, School of Advanced Science and Engineering, Waseda University, Tokyo 162-8480, Japan
| | - Takeru Shimoda
- Laboratory of Physiology and Pharmacology, School of Advanced Science and Engineering, Waseda University, Tokyo 162-8480, Japan
| | - Hanako Chijiki
- Laboratory of Physiology and Pharmacology, School of Advanced Science and Engineering, Waseda University, Tokyo 162-8480, Japan
| | - Shuichi Kojima
- Laboratory of Physiology and Pharmacology, School of Advanced Science and Engineering, Waseda University, Tokyo 162-8480, Japan
| | - Keisuke Sasaki
- Laboratory of Physiology and Pharmacology, School of Advanced Science and Engineering, Waseda University, Tokyo 162-8480, Japan
| | - Kengo Takahashi
- Laboratory of Physiology and Pharmacology, School of Advanced Science and Engineering, Waseda University, Tokyo 162-8480, Japan
| | - Saneyuki Makino
- Laboratory of Physiology and Pharmacology, School of Advanced Science and Engineering, Waseda University, Tokyo 162-8480, Japan
| | - Miku Takizawa
- Laboratory of Physiology and Pharmacology, School of Advanced Science and Engineering, Waseda University, Tokyo 162-8480, Japan
| | - Masaki Takahashi
- Institute for Liberal Arts, Tokyo Institute of Technology, Tokyo 152-8550, Japan
| | - Yu Tahara
- Laboratory of Physiology and Pharmacology, School of Advanced Science and Engineering, Waseda University, Tokyo 162-8480, Japan
| | - Shigeki Shimba
- Department of Health Science, School of Pharmacy, Nihon University, Chiba 274-8555, Japan
| | - Kazuyuki Shinohara
- Department of Neurobiology & Behavior, Graduate School of Biomedical Sciences, Nagasaki University, Nagasaki 852-8523, Japan
| | - Shigenobu Shibata
- Laboratory of Physiology and Pharmacology, School of Advanced Science and Engineering, Waseda University, Tokyo 162-8480, Japan.
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15
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West DWD, Doering TM, Thompson JLM, Budiono BP, Lessard SJ, Koch LG, Britton SL, Steck R, Byrne NM, Brown MA, Peake JM, Ashton KJ, Coffey VG. Low responders to endurance training exhibit impaired hypertrophy and divergent biological process responses in rat skeletal muscle. Exp Physiol 2021; 106:714-725. [PMID: 33486778 DOI: 10.1113/ep089301] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/26/2020] [Accepted: 01/19/2021] [Indexed: 12/11/2022]
Abstract
NEW FINDINGS What is the central question of this study? The extent to which genetics determines adaptation to endurance versus resistance exercise is unclear. Previously, a divergent selective breeding rat model showed that genetic factors play a major role in the response to aerobic training. Here, we asked: do genetic factors that underpin poor adaptation to endurance training affect adaptation to functional overload? What is the main finding and its importance? Our data show that heritable factors in low responders to endurance training generated differential gene expression that was associated with impaired skeletal muscle hypertrophy. A maladaptive genotype to endurance exercise appears to dysregulate biological processes responsible for mediating exercise adaptation, irrespective of the mode of contraction stimulus. ABSTRACT Divergent skeletal muscle phenotypes result from chronic resistance-type versus endurance-type contraction, reflecting the principle of training specificity. Our aim was to determine whether there is a common set of genetic factors that influence skeletal muscle adaptation to divergent contractile stimuli. Female rats were obtained from a genetically heterogeneous rat population and were selectively bred from high responders to endurance training (HRT) or low responders to endurance training (LRT; n = 6/group; generation 19). Both groups underwent 14 days of synergist ablation to induce functional overload of the plantaris muscle before comparison to non-overloaded controls of the same phenotype. RNA sequencing was performed to identify Gene Ontology biological processes with differential (LRT vs. HRT) gene set enrichment. We found that running distance, determined in advance of synergist ablation, increased in response to aerobic training in HRT but not LRT (65 ± 26 vs. -6 ± 18%, mean ± SD, P < 0.0001). The hypertrophy response to functional overload was attenuated in LRT versus HRT (20.1 ± 5.6 vs. 41.6 ± 16.1%, P = 0.015). Between-group differences were observed in the magnitude of response of 96 upregulated and 101 downregulated pathways. A further 27 pathways showed contrasting upregulation or downregulation in LRT versus HRT in response to functional overload. In conclusion, low responders to aerobic endurance training were also low responders for compensatory hypertrophy, and attenuated hypertrophy was associated with differential gene set regulation. Our findings suggest that genetic factors that underpin aerobic training maladaptation might also dysregulate the transcriptional regulation of biological processes that contribute to adaptation to mechanical overload.
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Affiliation(s)
- Daniel W D West
- Department of Physiology and Membrane Biology, University of California Davis, Davis, California, USA.,Toronto Rehabilitation Institute, Toronto, Ontario, Canada.,Faculty of Kinesiology and Physical Education, University of Toronto, Toronto, Ontario, Canada
| | - Thomas M Doering
- Faculty of Health Sciences and Medicine, Bond University, Robina, Gold Coast, Queensland, Australia.,School of Health, Medical and Applied Sciences, Central Queensland University, Rockhampton, Queensland, Australia
| | - Jamie-Lee M Thompson
- Faculty of Health Sciences and Medicine, Bond University, Robina, Gold Coast, Queensland, Australia
| | - Boris P Budiono
- School of Community Health, Charles Sturt University, Port Macquarie, New South Wales, Australia
| | - Sarah J Lessard
- Research Division, Joslin Diabetes Center, Boston, Massachusetts, USA.,Department of Medicine, Brigham and Women's Hospital and Harvard Medical School, Boston, Massachusetts, USA
| | - Lauren G Koch
- Department of Physiology and Pharmacology, University of Toledo, Toledo, Ohio, USA
| | - Steven L Britton
- Department of Anesthesiology, University of Michigan, Ann Arbor, Michigan, USA
| | - Roland Steck
- Institute of Health and Biomedical Innovation, Queensland University of Technology, Brisbane, Queensland, Australia
| | - Nuala M Byrne
- School of Health Sciences, University of Tasmania, Launceston, Tasmania, Australia
| | - Matthew A Brown
- Guy's & St Thomas' NHS Foundation Trust and King's College London NIHR Biomedical Research Centre, London, UK
| | - Jonathan M Peake
- Institute of Health and Biomedical Innovation, Queensland University of Technology, Brisbane, Queensland, Australia
| | - Kevin J Ashton
- Faculty of Health Sciences and Medicine, Bond University, Robina, Gold Coast, Queensland, Australia
| | - Vernon G Coffey
- Faculty of Health Sciences and Medicine, Bond University, Robina, Gold Coast, Queensland, Australia
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16
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Jorgenson KW, Phillips SM, Hornberger TA. Identifying the Structural Adaptations that Drive the Mechanical Load-Induced Growth of Skeletal Muscle: A Scoping Review. Cells 2020; 9:cells9071658. [PMID: 32660165 PMCID: PMC7408414 DOI: 10.3390/cells9071658] [Citation(s) in RCA: 52] [Impact Index Per Article: 13.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/23/2020] [Revised: 07/06/2020] [Accepted: 07/07/2020] [Indexed: 12/21/2022] Open
Abstract
The maintenance of skeletal muscle mass plays a critical role in health and quality of life. One of the most potent regulators of skeletal muscle mass is mechanical loading, and numerous studies have led to a reasonably clear understanding of the macroscopic and microscopic changes that occur when the mechanical environment is altered. For instance, an increase in mechanical loading induces a growth response that is mediated, at least in part, by an increase in the cross-sectional area of the myofibers (i.e., myofiber hypertrophy). However, very little is known about the ultrastructural adaptations that drive this response. Even the most basic questions, such as whether mechanical load-induced myofiber hypertrophy is mediated by an increase in the size of the pre-existing myofibrils and/or an increase in the number myofibrils, have not been resolved. In this review, we thoroughly summarize what is currently known about the macroscopic, microscopic and ultrastructural changes that drive mechanical load-induced growth and highlight the critical gaps in knowledge that need to be filled.
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Affiliation(s)
- Kent W. Jorgenson
- School of Veterinary Medicine and the Department of Comparative Biosciences, University of Wisconsin, Madison, WI 53706, USA;
| | - Stuart M. Phillips
- Department of Kinesiology, McMaster University, Hamilton, ON L8S 4K1, Canada;
| | - Troy A. Hornberger
- School of Veterinary Medicine and the Department of Comparative Biosciences, University of Wisconsin, Madison, WI 53706, USA;
- Correspondence:
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17
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Martinelli A, Andreo L, Alves AN, Terena SML, Santos TC, Bussadori SK, Fernandes KPS, Mesquita-Ferrari RA. Photobiomodulation modulates the expression of inflammatory cytokines during the compensatory hypertrophy process in skeletal muscle. Lasers Med Sci 2020; 36:791-802. [PMID: 32638240 DOI: 10.1007/s10103-020-03095-y] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/30/2019] [Accepted: 07/01/2020] [Indexed: 02/06/2023]
Abstract
Compensatory hypertrophy (CH) occurs due to excessive mechanical load on a muscle, promoting an increase in the size of muscle fibers. In clinical practice, situations such as partial nerve injuries, denervation, and muscle imbalance caused by trauma to muscles and nerves or diseases that promote the loss of nerve conduction can induce CH in muscle fibers. Photobiomodulation (PBM) has demonstrated beneficial effects on muscle tissue during CH. The aim of the present study was to evaluate the effect of PBM on the inflammatory cytokines interleukin-6 (IL-6) and tumor necrosis factor alpha (TNF-α) as well as type 2 metalloproteinases (MMP-2) during the process of CH due to excessive load on the plantaris muscle in rats. Forty-five Wistar rats weighing 250 g were divided into three groups: control group (n = 10), hypertrophy (H) group (n = 40), and H + PBM group (n = 40). CH was induced through the ablation of synergist muscles of the plantaris muscle. The tendons of the gastrocnemius and soleus muscles were isolated and sectioned to enable the partial removal of each of muscle. The preserved plantaris muscle below the removed muscles was submitted to excessive functional load. PBM was performed with low-level laser (AsGaAl, λ = 780 nm; 40 mW; energy density: 10 J/cm2; 10 s on each point, 8 points; 3.2 J). Animals from each group were euthanized after 7 and 14 days. The plantaris muscles were carefully removed and sent for analysis of the gene and protein expression of IL-6 and TNF-α using qPCR and ELISA, respectively. MMP-2 activity was analyzed using zymography. The results were submitted to statistical analysis (ANOVA + Tukey's test, p < 0.05). The protein expression analysis revealed an increase in IL-6 levels in the H + PBM group compared to the H group and a reduction in the H group compared to the control group. A reduction in TNF-α was found in the H and H + PBM groups compared to the control group at 7 days. The gene expression analysis revealed an increase in IL-6 in the H + PBM group compared to the H group at 14 days as well as an increase in TNF-α in the H + PBM group compared to the H group at 7 days. Increases in MMP-2 were found in the H and H + PBM groups compared to the control group at both 7 and 14 days. Based on findings in the present study, it is concluded that PBM was able to modulate pro-inflammatory cytokines that are essential for the compensatory hypertrophy process. However, it has not shown a modulation effect directly in MMP-2 activity during the same period evaluated.
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Affiliation(s)
- A Martinelli
- Postgraduate Program in Rehabilitation Sciences, Universidade Nove de Julho (UNINOVE), Rua Vergueiro, 349, São Paulo, SP, 01504001, Brazil
| | - L Andreo
- Postgraduate Program in Biophotonics Applied to Health Sciences, Universidade Nove de Julho (UNINOVE), Rua Vergueiro, 349, São Paulo, SP, 01504001, Brazil
| | - A N Alves
- Postgraduate Program in Biophotonics Applied to Health Sciences, Universidade Nove de Julho (UNINOVE), Rua Vergueiro, 349, São Paulo, SP, 01504001, Brazil
| | - S M L Terena
- Postgraduate Program in Biophotonics Applied to Health Sciences, Universidade Nove de Julho (UNINOVE), Rua Vergueiro, 349, São Paulo, SP, 01504001, Brazil
| | - T C Santos
- Postgraduate Program in Biophotonics Applied to Health Sciences, Universidade Nove de Julho (UNINOVE), Rua Vergueiro, 349, São Paulo, SP, 01504001, Brazil
| | - S K Bussadori
- Postgraduate Program in Rehabilitation Sciences, Universidade Nove de Julho (UNINOVE), Rua Vergueiro, 349, São Paulo, SP, 01504001, Brazil.,Postgraduate Program in Biophotonics Applied to Health Sciences, Universidade Nove de Julho (UNINOVE), Rua Vergueiro, 349, São Paulo, SP, 01504001, Brazil
| | - K P S Fernandes
- Postgraduate Program in Biophotonics Applied to Health Sciences, Universidade Nove de Julho (UNINOVE), Rua Vergueiro, 349, São Paulo, SP, 01504001, Brazil
| | - Raquel Agnelli Mesquita-Ferrari
- Postgraduate Program in Rehabilitation Sciences, Universidade Nove de Julho (UNINOVE), Rua Vergueiro, 349, São Paulo, SP, 01504001, Brazil. .,Postgraduate Program in Biophotonics Applied to Health Sciences, Universidade Nove de Julho (UNINOVE), Rua Vergueiro, 349, São Paulo, SP, 01504001, Brazil.
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18
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Roberts MD, Mobley CB, Vann CG, Haun CT, Schoenfeld BJ, Young KC, Kavazis AN. Synergist ablation-induced hypertrophy occurs more rapidly in the plantaris than soleus muscle in rats due to different molecular mechanisms. Am J Physiol Regul Integr Comp Physiol 2019; 318:R360-R368. [PMID: 31850817 DOI: 10.1152/ajpregu.00304.2019] [Citation(s) in RCA: 12] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
We examined molecular mechanisms that were altered during rapid soleus (type I fiber-dominant) and plantaris (type II fiber-dominant) hypertrophy in rats. Twelve Wistar rats (3.5 mo old; 6 female, 6 male) were subjected to surgical right-leg soleus and plantaris dual overload [synergist ablation (SA)], and sham surgeries were performed on left legs (CTL). At 14 days after surgery, the muscles were dissected. Plantaris mass was 27% greater in the SA than CTL leg (P < 0.001), soleus mass was 13% greater in the SA than CTL leg (P < 0.001), and plantaris mass was higher than soleus mass in the SA leg (P = 0.001). Plantaris total RNA concentrations and estimated total RNA levels (suggestive of ribosome density) were 19% and 47% greater in the SA than CTL leg (P < 0.05), protein synthesis levels were 64% greater in the SA than CTL leg (P = 0.038), and satellite cell number per fiber was 60% greater in the SA than CTL leg (P = 0.003); no differences in these metrics were observed between soleus SA and CTL legs. Plantaris, as well as soleus, 20S proteasome activity was lower in the SA than CTL leg (P < 0.05), although the degree of downregulation was greater in the plantaris than soleus muscle (-63% vs. -20%, P = 0.001). These data suggest that early-phase plantaris hypertrophy occurs more rapidly than soleus hypertrophy, which coincided with greater increases in ribosome biogenesis, protein synthesis, and satellite cell density, as well as greater decrements in 20S proteasome activity, in the plantaris muscle.
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Affiliation(s)
- Michael D Roberts
- School of Kinesiology, Auburn University, Auburn, Alabama.,Department of Cell Biology and Physiology, Edward Via College of Veterinary Medicine, Auburn, Alabama
| | - Christopher B Mobley
- Department of Physiology, College of Medicine, University of Kentucky, Lexington, Kentucky.,Center for Muscle Biology, University of Kentucky, Lexington, Kentucky
| | | | - Cody T Haun
- Department of Exercise Science, LaGrange College, LaGrange, Georgia
| | - Brad J Schoenfeld
- Department of Health Sciences, City University of New York Lehman College, Bronx, New York
| | - Kaelin C Young
- School of Kinesiology, Auburn University, Auburn, Alabama.,Department of Cell Biology and Physiology, Edward Via College of Veterinary Medicine, Auburn, Alabama
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19
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Musclin, A Myokine Induced by Aerobic Exercise, Retards Muscle Atrophy During Cancer Cachexia in Mice. Cancers (Basel) 2019; 11:cancers11101541. [PMID: 31614775 PMCID: PMC6826436 DOI: 10.3390/cancers11101541] [Citation(s) in RCA: 43] [Impact Index Per Article: 8.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/07/2019] [Revised: 09/20/2019] [Accepted: 10/09/2019] [Indexed: 12/14/2022] Open
Abstract
Physical activity improves the prognosis of cancer patients, partly by contrasting the associated muscle wasting (cachexia), through still unknown mechanisms. We asked whether aerobic exercise causes secretion by skeletal muscles of proteins (myokines) that may contrast cachexia. Media conditioned by peroxisome proliferator-activated receptor γ coactivator 1α (PGC1α)-expressing myotubes, reproducing some metabolic adaptations of aerobic exercise, as increased mitochondrial biogenesis and oxidative phosphorylation, restrained constitutively active Forkhead box-containing subfamily O3 (caFoxO3)-induced proteolysis. Microarray analysis identified amphiregulin (AREG), natriuretic peptide precursor B (NppB), musclin and fibroblast growth factor 18 (FGF18) as myokines highly induced by PGC1α. Notably, only musclin tended to be low in muscle of mice with a rare human renal carcinoma; it was reduced in plasma and in muscles of C26-bearing mice and in atrophying myotubes, where PGC1α expression is impaired. Therefore, we electroporated the Tibialis Anterior (TA) of C26-bearing mice with musclin or (its receptor) natriuretic peptide receptor 3 (Npr3)-encoding plasmids and found a preserved fiber area, as a result of restrained proteolysis. Musclin knockout (KO) mice lose more muscle tissue during growth of two distinct cachexia-causing tumors. Running protected C26-bearing mice from cachexia, not changing tumor growth, and rescued the C26-induced downregulation of musclin in muscles and plasma. Musclin expression did not change in overloaded plantaris of mice, recapitulating partially muscle adaptations to anaerobic exercise. Musclin might, therefore, be beneficial to cancer patients who cannot exercise and are at risk of cachexia and may help to explain how aerobic exercise alleviates cancer-induced muscle wasting.
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20
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Effect of different sources of dietary protein on muscle hypertrophy in functionally overloaded mice. Biochem Biophys Rep 2019; 20:100686. [PMID: 31528720 PMCID: PMC6742840 DOI: 10.1016/j.bbrep.2019.100686] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/11/2019] [Revised: 09/05/2019] [Accepted: 09/06/2019] [Indexed: 01/10/2023] Open
Abstract
Dietary protein intake is important for skeletal muscle protein synthesis. In this study, we investigated the differential effect of protein sources on hypertrophy of plantaris muscle induced by surgical ablation of gastrocnemius and soleus muscles. Six-week old mice were fed diets containing caseinate, whey, or soy as protein sources for 2 weeks. Plantaris muscle hypertrophy was induced by a unilateral ablation of synergistic muscles after a week. Food intake of soy protein-fed mice was higher than that of caseinate and whey-fed mice, resulting in higher body and fat weights. Plantaris muscle weight in sham-operated mice was not different across the groups. Overload-operated plantaris muscle weight and increased ratio of overloaded muscle to sham-operated muscle weights were higher in caseinate-fed mice than in whey- and soy protein-fed mice, suggesting caseinate as a promising protein source for muscle hypertrophy. Type of dietary protein source affects functionally overloaded muscle hypertrophy. Caseinate intake induces higher muscle hypertrophy compared to whey and soy protein. Dietary protein sources have no effect on non-overloaded muscle weight. There is no effect of dietary protein sources on locomotor activity.
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Severo JS, Morais JB, Beserra JB, de Farias LM, dos Santos LR, de Sousa Melo SR, do Nascimento Nogueira N, do Nascimento Marreiro D. Effect of Zinc Supplementation on Lipid Profile in Obese People: A Systematic Review. CURRENT NUTRITION & FOOD SCIENCE 2019. [DOI: 10.2174/1573401314666180420094522] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
Background:
Many studies have investigated the influence of minerals on the control of
changes in lipid metabolism in obese individuals. The objective of this study was to describe, in a systematic
review, the clinical trial outcomes of zinc supplementation and lipid profiles of obese participants.
Methods:
This review was conducted in accordance with Preferred Reporting Items for Systematic
Reviews and Meta-Analyses (PRISMA) recommendations. A survey was conducted for selecting clinical
trials related to the effects of zinc supplementation on lipid profiles in obese people, using the following
databases: PubMed, SciVerse ScienceDirect and Cochrane.
Results:
After the selection process, five articles were identified as eligible for this review and it was
observed that the clinical trials included adults and children of both sexes, in three different countries,
and with zinc supplementation doses ranging from 20 to 100 mg/day. None of the studies observed
changes in High-Density Lipoprotein (HDL-c) with zinc supplementation. On the other hand, three
studies observed a positive effect of zinc supplementation on triglycerides, and two found an effect on
Low-Density Lipoprotein (LDL-c) and total cholesterol.
Conclusion:
The results of this systematic review provide evidence on the benefits of zinc supplementation
on lipid profiles in obese individuals. However, new intervention studies are needed to elucidate
the function of the nutrient in protection against disorders related to lipid metabolism, as well as the
standardization of the type, dose, and time of zinc supplementation.
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Affiliation(s)
- Juliana S. Severo
- Department of Nutrition, Federal University of Piaui, Campus Minister Petrônio Portela, Ininga, Teresina, Piaui, Brazil
| | - Jennifer B.S. Morais
- Department of Nutrition, Federal University of Piaui, Campus Minister Petrônio Portela, Ininga, Teresina, Piaui, Brazil
| | - Jessica B. Beserra
- Department of Nutrition, Federal University of Piaui, Campus Minister Petrônio Portela, Ininga, Teresina, Piaui, Brazil
| | - Luciana M. de Farias
- Department of Nutrition, Federal University of Piaui, Campus Minister Petrônio Portela, Ininga, Teresina, Piaui, Brazil
| | - Loanne R. dos Santos
- Department of Nutrition, Federal University of Piaui, Campus Minister Petrônio Portela, Ininga, Teresina, Piaui, Brazil
| | - Stéfany R. de Sousa Melo
- Department of Nutrition, Federal University of Piaui, Campus Minister Petrônio Portela, Ininga, Teresina, Piaui, Brazil
| | - Nadir do Nascimento Nogueira
- Department of Nutrition, Federal University of Piaui, Campus Minister Petrônio Portela, Ininga, Teresina, Piaui, Brazil
| | - Dilina do Nascimento Marreiro
- Department of Nutrition, Federal University of Piaui, Campus Minister Petrônio Portela, Ininga, Teresina, Piaui, Brazil
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You JS, McNally RM, Jacobs BL, Privett RE, Gundermann DM, Lin KH, Steinert ND, Goodman CA, Hornberger TA. The role of raptor in the mechanical load-induced regulation of mTOR signaling, protein synthesis, and skeletal muscle hypertrophy. FASEB J 2019; 33:4021-4034. [PMID: 30509128 PMCID: PMC6404572 DOI: 10.1096/fj.201801653rr] [Citation(s) in RCA: 90] [Impact Index Per Article: 18.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/15/2018] [Accepted: 11/05/2018] [Indexed: 12/21/2022]
Abstract
It is well known that an increase in mechanical loading can induce skeletal muscle hypertrophy, and a long standing model in the field indicates that mechanical loads induce hypertrophy via a mechanism that requires signaling through the mechanistic target of rapamycin complex 1 (mTORC1). Specifically, it has been widely proposed that mechanical loads activate signaling through mTORC1 and that this, in turn, promotes an increase in the rate of protein synthesis and the subsequent hypertrophic response. However, this model is based on a number of important assumptions that have not been rigorously tested. In this study, we created skeletal muscle specific and inducible raptor knockout mice to eliminate signaling by mTORC1, and with these mice we were able to directly demonstrate that mechanical stimuli can activate signaling by mTORC1, and that mTORC1 is necessary for mechanical load-induced hypertrophy. Surprisingly, however, we also obtained multiple lines of evidence that indicate that mTORC1 is not required for a mechanical load-induced increase in the rate of protein synthesis. This observation highlights an important shortcoming in our understanding of how mechanical loads induce hypertrophy and illustrates that additional mTORC1-independent mechanisms play a critical role in this process.-You, J.-S., McNally, R. M., Jacobs, B. L., Privett, R. E., Gundermann, D. M., Lin, K.-H., Steinert, N. D., Goodman, C. A., Hornberger, T. A. The role of raptor in the mechanical load-induced regulation of mTOR signaling, protein synthesis, and skeletal muscle hypertrophy.
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Affiliation(s)
- Jae-Sung You
- Department of Comparative Biosciences, University of Wisconsin–Madison, Madison, Wisconsin, USA
- School of Veterinary Medicine, University of Wisconsin–Madison, Madison, Wisconsin, USA
| | - Rachel M. McNally
- Department of Comparative Biosciences, University of Wisconsin–Madison, Madison, Wisconsin, USA
- School of Veterinary Medicine, University of Wisconsin–Madison, Madison, Wisconsin, USA
| | - Brittany L. Jacobs
- Department of Comparative Biosciences, University of Wisconsin–Madison, Madison, Wisconsin, USA
- School of Veterinary Medicine, University of Wisconsin–Madison, Madison, Wisconsin, USA
| | - Rachel E. Privett
- Department of Comparative Biosciences, University of Wisconsin–Madison, Madison, Wisconsin, USA
- School of Veterinary Medicine, University of Wisconsin–Madison, Madison, Wisconsin, USA
| | - David M. Gundermann
- Department of Comparative Biosciences, University of Wisconsin–Madison, Madison, Wisconsin, USA
- School of Veterinary Medicine, University of Wisconsin–Madison, Madison, Wisconsin, USA
| | - Kuan-Hung Lin
- Department of Comparative Biosciences, University of Wisconsin–Madison, Madison, Wisconsin, USA
- School of Veterinary Medicine, University of Wisconsin–Madison, Madison, Wisconsin, USA
| | - Nate D. Steinert
- Department of Comparative Biosciences, University of Wisconsin–Madison, Madison, Wisconsin, USA
- School of Veterinary Medicine, University of Wisconsin–Madison, Madison, Wisconsin, USA
| | - Craig A. Goodman
- Department of Comparative Biosciences, University of Wisconsin–Madison, Madison, Wisconsin, USA
- School of Veterinary Medicine, University of Wisconsin–Madison, Madison, Wisconsin, USA
- Institute of Health and Sport, Victoria University, Melbourne, Victoria, Australia
- Australian Institute for Musculoskeletal Science, Victoria University, St. Albans, Victoria, Australia
| | - Troy A. Hornberger
- Department of Comparative Biosciences, University of Wisconsin–Madison, Madison, Wisconsin, USA
- School of Veterinary Medicine, University of Wisconsin–Madison, Madison, Wisconsin, USA
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Buratti P, Covatti C, Centenaro LA, Brancalhão RMC, Torrejais MM. Morphofunctional characteristics of skeletal muscle in rats with cerebral palsy. Int J Exp Pathol 2019; 100:49-59. [PMID: 30773727 DOI: 10.1111/iep.12304] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/10/2018] [Revised: 10/24/2018] [Accepted: 12/27/2018] [Indexed: 01/10/2023] Open
Abstract
Knowledge of skeletal muscle adaptations is important to understand the functional deficits in cerebral palsy (CP). This study aimed to investigate the morphofunctional characteristics of skeletal muscle in a CP animal model. Initially, pregnant Wistar rats were injected intraperitoneally with saline or lipopolysaccharide over the last five days of pregnancy. The control group (n = 8) consisted of male pups born to females injected with saline. The CP group (n = 8) consisted of male pups born to females injected with lipopolysaccharide, which were submitted to perinatal anoxia [day of birth, postnatal day 0 (P0)] and sensorimotor restriction (P1-P30). The open-field test was undertaken on P29 and P45. On P48, the animals were weighed, and the plantaris muscle was collected and its weight and length were measured. Transverse sections were stained with haematoxylin-eosin, NADH-TR, Masson's trichrome and non-specific esterase reaction for analysis. and transmission electron microscopy was performed. In the CP group, reductions were observed in mobility time, number of crossings and rearing frequency, body weight, muscle weight and length, and nucleus-to-fibre and capillary-to-fibre ratios. There was a statistically significant increase in the percentage area of the muscle section occupied by collagen; reduction in the area and increase in the number of type I muscle fibres; increase in myofibrillar disorganization and Z-line disorganization and dissolution; and reduction in the area and largest and smallest diameters of neuromuscular junctions. Thus this animal model of CP produced morphofunctional alterations in skeletal muscle, that were associated with evidence of motor deficits as demonstrated by the open-field test.
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Affiliation(s)
- Pâmela Buratti
- Programa de Pós-Graduação em Biociências e Saúde, Universidade Estadual do Oeste do Paraná - UNIOESTE, Cascavel, Paraná, Brazil
| | - Caroline Covatti
- Programa de Pós-Graduação em Biociências e Saúde, Universidade Estadual do Oeste do Paraná - UNIOESTE, Cascavel, Paraná, Brazil
| | - Lígia Aline Centenaro
- Centro de Ciências Médicas e Farmacêuticas, Universidade Estadual do Oeste do Paraná - UNIOESTE, Cascavel, Paraná, Brazil
| | - Rose Meire Costa Brancalhão
- Programa de Pós-Graduação em Biociências e Saúde, Universidade Estadual do Oeste do Paraná - UNIOESTE, Cascavel, Paraná, Brazil
| | - Marcia Miranda Torrejais
- Programa de Pós-Graduação em Biociências e Saúde, Universidade Estadual do Oeste do Paraná - UNIOESTE, Cascavel, Paraná, Brazil
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Lee AH, Elliott DM. Comparative multi-scale hierarchical structure of the tail, plantaris, and Achilles tendons in the rat. J Anat 2019; 234:252-262. [PMID: 30484871 PMCID: PMC6326909 DOI: 10.1111/joa.12913] [Citation(s) in RCA: 30] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 10/18/2018] [Indexed: 12/19/2022] Open
Abstract
Rodent tendons are widely used to study human pathologies such as tendinopathy and repair, and to address fundamental physiological questions about development, growth, and remodeling. However, how the gross morphology and multi-scale hierarchical structure of rat tendons, such as the tail, plantaris, and Achilles tendons, compare with that of human tendons are unknown. In addition, there remains disagreement about terminology and definitions. Specifically, the definitions of fascicle and fiber are often dependent on diameter sizes, not their characteristic features, and these definitions impair the ability to compare hierarchical structure across species, where the sizes of the fiber and fascicle may change with animal size and tendon function. Thus, the objective of the study was to select a single species that is commonly used for tendon research (rat) and tendons with varying mechanical functions (tail, plantaris, Achilles) to evaluate the hierarchical structure at multiple length scales using histology, SEM, and confocal imaging. With the exception of the specialized rat tail tendon, we confirmed that in rat tendons there are no fascicles and the fiber is the largest subunit. In addition, we provided a structurally based definition of a fiber as a bundle of collagen fibrils that is surrounded by elongated cells, and this definition was supported by both histologically processed and unprocessed samples. In all rat tendons studied, the fiber diameters were consistently between 10 and 50 μm, and this diameter range appears to be conserved across larger species. Specific recommendations were made highlighting the strengths and limitations of each rat tendon as a research model. Understanding the hierarchical structure of tendon can advance the design and interpretation of experiments and development of tissue-engineered constructs.
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Affiliation(s)
- Andrea H. Lee
- Department of Biomedical EngineeringUniversity of DelawareNewarkUSA
| | - Dawn M. Elliott
- Department of Biomedical EngineeringUniversity of DelawareNewarkUSA
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Huey KA. Potential Roles of Vascular Endothelial Growth Factor During Skeletal Muscle Hypertrophy. Exerc Sport Sci Rev 2018; 46:195-202. [PMID: 29652692 DOI: 10.1249/jes.0000000000000152] [Citation(s) in RCA: 16] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
Vascular endothelial growth factor (VEGF) deletion in adult mouse muscle fibers contributes to impaired contractile and muscular adaptations to a hypertrophic stimulus suggesting a critical role in adult muscle growth. This review explores the hypothesis that VEGF is essential for adult muscle growth by impacting inflammatory processes, satellite-endothelial cell interactions, and contractile protein accumulation by functioning within known hypertrophic signaling pathways including insulin-like growth factor-1 (IGF-1-Akt) and Wnt-ß-catenin.
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Affiliation(s)
- Kimberly A Huey
- College of Pharmacy and Health Sciences, Drake University, Des Moines, IA
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