1
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Zhang Q, Halle JL, Counts BR, Pi M, Carson JA. mTORC1 and BMP-Smad1/5 regulation of serum-stimulated myotube hypertrophy: a role for autophagy. Am J Physiol Cell Physiol 2024; 327:C124-C139. [PMID: 38766767 DOI: 10.1152/ajpcell.00237.2024] [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: 04/11/2024] [Revised: 05/14/2024] [Accepted: 05/14/2024] [Indexed: 05/22/2024]
Abstract
Protein synthesis regulation is critical for skeletal muscle hypertrophy, yet other established cellular processes are necessary for growth-related cellular remodeling. Autophagy has a well-acknowledged role in muscle quality control, but evidence for its role in myofiber hypertrophy remains equivocal. Both mammalian target of rapamycin complex I (mTORC1) and bone morphogenetic protein (BMP)-Smad1/5 (Sma and Mad proteins from Caenorhabditis elegans and Drosophila, respectively) signaling are reported regulators of myofiber hypertrophy; however, gaps remain in our understanding of how this regulation is integrated with growth processes and autophagy regulation. Therefore, we investigated the mTORC1 and Smad1/5 regulation of protein synthesis and autophagy flux during serum-stimulated myotube growth. Chronic serum stimulation experiments were performed on day 5 differentiated C2C12 myotubes incubated in differentiation medium [2% horse serum (HS)] or growth medium [5% fetal bovine serum (FBS)] for 48 h. Rapamycin or LDN193189 was dosed for 48 h to inhibit mTORC1 and BMP-Smad1/5 signaling, respectively. Acute serum stimulation was examined in day 7 differentiated myotubes. Protein synthesis was measured by puromycin incorporation. Bafilomycin A1 and immunoblotting for LC3B were used to assess autophagy flux. Chronic serum stimulation increased myotube diameter 22%, total protein 21%, total RNA 100%, and Smad1/5 phosphorylation 404% and suppressed autophagy flux. Rapamycin, but not LDN193189, blocked serum-induced myotube hypertrophy and the increase in total RNA. Acute serum stimulation increased protein synthesis 111%, Smad1/5 phosphorylation 559%, and rpS6 phosphorylation 117% and suppressed autophagy flux. Rapamycin increased autophagy flux during acute serum stimulation. These results provide evidence for mTORC1, but not BMP-Smad1/5, signaling being required for serum-induced myotube hypertrophy and autophagy flux by measuring LC3BII/I expression. Further investigation is warranted to examine the role of autophagy flux in myotube hypertrophy.NEW & NOTEWORTHY The present study demonstrates that myotube hypertrophy caused by chronic serum stimulation requires mammalian target of rapamycin complex 1 (mTORC1) signaling but not bone morphogenetic protein (BMP)-Smad1/5 signaling. The suppression of autophagy flux was associated with serum-induced myotube hypertrophy and mTORC1 regulation of autophagy flux by measuring LC3BII/I expression. Rapamycin is widely investigated for beneficial effects in aging skeletal muscle and sarcopenia; our results provide evidence that rapamycin can regulate autophagy-related signaling during myotube growth, which could benefit skeletal muscle functional and metabolic health.
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Affiliation(s)
- Quan Zhang
- Integrative Muscle Biology Laboratory, Division of Rehabilitation Sciences, College of Health ProfessionsUniversity of Tennessee Health Science Center, Memphis, Tennessee, United States
| | - Jessica L Halle
- Integrative Muscle Biology Laboratory, Division of Rehabilitation Sciences, College of Health ProfessionsUniversity of Tennessee Health Science Center, Memphis, Tennessee, United States
| | - Brittany R Counts
- Integrative Muscle Biology Laboratory, Division of Rehabilitation Sciences, College of Health ProfessionsUniversity of Tennessee Health Science Center, Memphis, Tennessee, United States
| | - Min Pi
- Department of Medicine, University of Tennessee Health Science Center, Memphis, Tennessee, United States
| | - James A Carson
- Huffines Institute for Sports Medicine & Human Performance, Department of Kinesiology & Sports Management , Texas A&M University, College Station, Texas, United States
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2
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Fowler A, Knaus KR, Khuu S, Khalilimeybodi A, Schenk S, Ward SR, Fry AC, Rangamani P, McCulloch AD. Network model of skeletal muscle cell signalling predicts differential responses to endurance and resistance exercise training. Exp Physiol 2024; 109:939-955. [PMID: 38643471 PMCID: PMC11140181 DOI: 10.1113/ep091712] [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: 12/06/2023] [Accepted: 03/20/2024] [Indexed: 04/22/2024]
Abstract
Exercise-induced muscle adaptations vary based on exercise modality and intensity. We constructed a signalling network model from 87 published studies of human or rodent skeletal muscle cell responses to endurance or resistance exercise in vivo or simulated exercise in vitro. The network comprises 259 signalling interactions between 120 nodes, representing eight membrane receptors and eight canonical signalling pathways regulating 14 transcriptional regulators, 28 target genes and 12 exercise-induced phenotypes. Using this network, we formulated a logic-based ordinary differential equation model predicting time-dependent molecular and phenotypic alterations following acute endurance and resistance exercises. Compared with nine independent studies, the model accurately predicted 18/21 (85%) acute responses to resistance exercise and 12/16 (75%) acute responses to endurance exercise. Detailed sensitivity analysis of differential phenotypic responses to resistance and endurance training showed that, in the model, exercise regulates cell growth and protein synthesis primarily by signalling via mechanistic target of rapamycin, which is activated by Akt and inhibited in endurance exercise by AMP-activated protein kinase. Endurance exercise preferentially activates inflammation via reactive oxygen species and nuclear factor κB signalling. Furthermore, the expected preferential activation of mitochondrial biogenesis by endurance exercise was counterbalanced in the model by protein kinase C in response to resistance training. This model provides a new tool for investigating cross-talk between skeletal muscle signalling pathways activated by endurance and resistance exercise, and the mechanisms of interactions such as the interference effects of endurance training on resistance exercise outcomes.
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Affiliation(s)
- Annabelle Fowler
- Department of BioengineeringUniversity of California SanDiegoLa JollaCaliforniaUSA
| | - Katherine R. Knaus
- Department of BioengineeringUniversity of California SanDiegoLa JollaCaliforniaUSA
| | - Stephanie Khuu
- Department of BioengineeringUniversity of California SanDiegoLa JollaCaliforniaUSA
| | - Ali Khalilimeybodi
- Department of Mechanical and Aerospace EngineeringUniversity of California San DiegoLa JollaCaliforniaUSA
| | - Simon Schenk
- Department of Orthopaedic SurgeryUniversity of California San DiegoLa JollaCaliforniaUSA
| | - Samuel R. Ward
- Department of Orthopaedic SurgeryUniversity of California San DiegoLa JollaCaliforniaUSA
| | - Andrew C. Fry
- Department of Health, Sport and Exercise SciencesUniversity of KansasLawrenceKansasUSA
| | - Padmini Rangamani
- Department of Mechanical and Aerospace EngineeringUniversity of California San DiegoLa JollaCaliforniaUSA
| | - Andrew D. McCulloch
- Department of BioengineeringUniversity of California SanDiegoLa JollaCaliforniaUSA
- Department of MedicineUniversity of California San DiegoLa JollaCaliforniaUSA
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3
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Ramachandran K, Futtner CR, Sommars MA, Quattrocelli M, Omura Y, Fruzyna E, Wang JC, Waldeck NJ, Senagolage MD, Telles CG, Demonbreun AR, Prendergast E, Lai N, Arango D, Bederman IR, McNally EM, Barish GD. Transcriptional programming of translation by BCL6 controls skeletal muscle proteostasis. Nat Metab 2024; 6:304-322. [PMID: 38337096 PMCID: PMC10949880 DOI: 10.1038/s42255-024-00983-3] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 04/02/2022] [Accepted: 01/09/2024] [Indexed: 02/12/2024]
Abstract
Skeletal muscle is dynamically controlled by the balance of protein synthesis and degradation. Here we discover an unexpected function for the transcriptional repressor B cell lymphoma 6 (BCL6) in muscle proteostasis and strength in mice. Skeletal muscle-specific Bcl6 ablation in utero or in adult mice results in over 30% decreased muscle mass and force production due to reduced protein synthesis and increased autophagy, while it promotes a shift to a slower myosin heavy chain fibre profile. Ribosome profiling reveals reduced overall translation efficiency in Bcl6-ablated muscles. Mechanistically, tandem chromatin immunoprecipitation, transcriptomic and translational analyses identify direct BCL6 repression of eukaryotic translation initiation factor 4E-binding protein 1 (Eif4ebp1) and activation of insulin-like growth factor 1 (Igf1) and androgen receptor (Ar). Together, these results uncover a bifunctional role for BCL6 in the transcriptional and translational control of muscle proteostasis.
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Affiliation(s)
- Krithika Ramachandran
- Division of Endocrinology, Metabolism, and Molecular Medicine, Department of Medicine, Feinberg School of Medicine, Northwestern University, Chicago, IL, USA
| | - Christopher R Futtner
- Division of Endocrinology, Metabolism, and Molecular Medicine, Department of Medicine, Feinberg School of Medicine, Northwestern University, Chicago, IL, USA
- Jesse Brown VA Medical Center, Chicago, IL, USA
| | - Meredith A Sommars
- Division of Endocrinology, Metabolism, and Molecular Medicine, Department of Medicine, Feinberg School of Medicine, Northwestern University, Chicago, IL, USA
| | - Mattia Quattrocelli
- Center for Genetic Medicine, Feinberg School of Medicine, Northwestern University, Chicago, IL, USA
- Division of Molecular Cardiovascular Biology, Heart Institute, Cincinnati Children's Hospital Medical Center, Cincinnati, OH, USA
- Department of Pediatrics, University of Cincinnati College of Medicine, Cincinnati, OH, USA
| | - Yasuhiro Omura
- Division of Endocrinology, Metabolism, and Molecular Medicine, Department of Medicine, Feinberg School of Medicine, Northwestern University, Chicago, IL, USA
- Jesse Brown VA Medical Center, Chicago, IL, USA
| | - Ellen Fruzyna
- Division of Endocrinology, Metabolism, and Molecular Medicine, Department of Medicine, Feinberg School of Medicine, Northwestern University, Chicago, IL, USA
| | - Janice C Wang
- Division of Endocrinology, Metabolism, and Molecular Medicine, Department of Medicine, Feinberg School of Medicine, Northwestern University, Chicago, IL, USA
| | - Nathan J Waldeck
- Division of Endocrinology, Metabolism, and Molecular Medicine, Department of Medicine, Feinberg School of Medicine, Northwestern University, Chicago, IL, USA
| | - Madhavi D Senagolage
- Division of Endocrinology, Metabolism, and Molecular Medicine, Department of Medicine, Feinberg School of Medicine, Northwestern University, Chicago, IL, USA
| | - Carmen G Telles
- Division of Endocrinology, Metabolism, and Molecular Medicine, Department of Medicine, Feinberg School of Medicine, Northwestern University, Chicago, IL, USA
| | - Alexis R Demonbreun
- Center for Genetic Medicine, Feinberg School of Medicine, Northwestern University, Chicago, IL, USA
| | - Erin Prendergast
- Department of Genetics and Genome Sciences, Case Western Reserve University, Cleveland, OH, USA
| | - Nicola Lai
- Department of Mechanical, Chemical, and Materials Engineering, University of Cagliari, Cagliari, Italy
| | - Daniel Arango
- Department of Pharmacology, Feinberg School of Medicine, Northwestern University, Chicago, IL, USA
| | - Ilya R Bederman
- Department of Genetics and Genome Sciences, Case Western Reserve University, Cleveland, OH, USA
| | - Elizabeth M McNally
- Center for Genetic Medicine, Feinberg School of Medicine, Northwestern University, Chicago, IL, USA
| | - Grant D Barish
- Division of Endocrinology, Metabolism, and Molecular Medicine, Department of Medicine, Feinberg School of Medicine, Northwestern University, Chicago, IL, USA.
- Jesse Brown VA Medical Center, Chicago, IL, USA.
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4
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Kataoka R, Hammert WB, Yamada Y, Song JS, Seffrin A, Kang A, Spitz RW, Wong V, Loenneke JP. The Plateau in Muscle Growth with Resistance Training: An Exploration of Possible Mechanisms. Sports Med 2024; 54:31-48. [PMID: 37787845 DOI: 10.1007/s40279-023-01932-y] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 09/01/2023] [Indexed: 10/04/2023]
Abstract
It is hypothesized that there is likely a finite ability for muscular adaptation. While it is difficult to distinguish between a true plateau following a long-term training period and short-term stalling in muscle growth, a plateau in muscle growth has been attributed to reaching a genetic potential, with limited discussion on what might physiologically contribute to this muscle growth plateau. The present paper explores potential physiological factors that may drive the decline in muscle growth after prolonged resistance training. Overall, with chronic training, the anabolic signaling pathways may become more refractory to loading. While measures of anabolic markers may have some predictive capabilities regarding muscle growth adaptation, they do not always demonstrate a clear connection. Catabolic processes may also constrain the ability to achieve further muscle growth, which is influenced by energy balance. Although speculative, muscle cells may also possess cell scaling mechanisms that sense and regulate their own size, along with molecular brakes that hinder growth rate over time. When considering muscle growth over the lifespan, there comes a point when the anabolic response is attenuated by aging, regardless of whether or not individuals approach their muscle growth potential. Our goal is that the current review opens avenues for future experimental studies to further elucidate potential mechanisms to explain why muscle growth may plateau.
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Affiliation(s)
- Ryo Kataoka
- Department of Health, Exercise Science, and Recreation Management, Kevser Ermin Applied Physiology Laboratory, The University of Mississippi, P.O. Box 1848, University, MS, 38677, USA
| | - William B Hammert
- Department of Health, Exercise Science, and Recreation Management, Kevser Ermin Applied Physiology Laboratory, The University of Mississippi, P.O. Box 1848, University, MS, 38677, USA
| | - Yujiro Yamada
- Department of Health, Exercise Science, and Recreation Management, Kevser Ermin Applied Physiology Laboratory, The University of Mississippi, P.O. Box 1848, University, MS, 38677, USA
| | - Jun Seob Song
- Department of Health, Exercise Science, and Recreation Management, Kevser Ermin Applied Physiology Laboratory, The University of Mississippi, P.O. Box 1848, University, MS, 38677, USA
| | - Aldo Seffrin
- Department of Health, Exercise Science, and Recreation Management, Kevser Ermin Applied Physiology Laboratory, The University of Mississippi, P.O. Box 1848, University, MS, 38677, USA
| | - Anna Kang
- Department of Health, Exercise Science, and Recreation Management, Kevser Ermin Applied Physiology Laboratory, The University of Mississippi, P.O. Box 1848, University, MS, 38677, USA
| | - Robert W Spitz
- Department of Health, Exercise Science, and Recreation Management, Kevser Ermin Applied Physiology Laboratory, The University of Mississippi, P.O. Box 1848, University, MS, 38677, USA
| | - Vickie Wong
- Department of Health, Exercise Science, and Recreation Management, Kevser Ermin Applied Physiology Laboratory, The University of Mississippi, P.O. Box 1848, University, MS, 38677, USA
| | - Jeremy P Loenneke
- Department of Health, Exercise Science, and Recreation Management, Kevser Ermin Applied Physiology Laboratory, The University of Mississippi, P.O. Box 1848, University, MS, 38677, USA.
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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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6
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Mechanotransduction for Muscle Protein Synthesis via Mechanically Activated Ion Channels. Life (Basel) 2023; 13:life13020341. [PMID: 36836698 PMCID: PMC9962945 DOI: 10.3390/life13020341] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/03/2023] [Revised: 01/24/2023] [Accepted: 01/26/2023] [Indexed: 02/03/2023] Open
Abstract
Cell mechanotransduction, the ability to detect physical forces and convert them into a series of biochemical events, is important for a wide range of physiological processes. Cells express an array of mechanosensors transducing physical forces into intracellular signaling cascades, including ion channels. Ion channels that can be directly activated by mechanical cues are known as mechanically activated (MA), or stretch-activated (SA), channels. In response to repeated exposures to mechanical stimulation in the form of resistance training, enhanced protein synthesis and fiber hypertrophy are elicited in skeletal muscle, whereas a lack of mechanical stimuli due to inactivity/mechanical unloading leads to reduced muscle protein synthesis and fiber atrophy. To date, the role of MA channels in the transduction of mechanical load to intracellular signaling pathways regulating muscle protein synthesis is poorly described. This review article will discuss MA channels in striated muscle, their regulation, and putative roles in the anabolic processes in muscle cells/fibers in response to mechanical stimuli.
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7
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Yoshihara T, Dobashi S, Takaragawa M, Naito H. Effect of losartan treatment on Smad signaling and recovery from hindlimb unloading-induced soleus muscle atrophy in female rats. Eur J Pharmacol 2022; 931:175223. [PMID: 35988789 DOI: 10.1016/j.ejphar.2022.175223] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/11/2022] [Revised: 08/08/2022] [Accepted: 08/16/2022] [Indexed: 11/29/2022]
Abstract
Losartan, an angiotensin II type 1 receptor blocker, exerts protective effect on soleus muscle atrophy in female rats. Thus, we aimed to examine the effect of losartan treatment on the recovery of atrophied soleus muscles. Female Wistar rats were subjected to hindlimb unloading for 7 d and then reloading for 7 d with either phosphate-buffered saline (PBS; n = 9) or losartan (40 mg/kg/day; n = 9). The soleus muscles were removed at rest (sedentary control [SED]; n = 9), after 7 d of hindlimb unloading (HU; n = 9), and after 7 d of reloading (HUR-PBS or HUR-LOS; n = 9 each). The absolute and relative weights, and fiber cross-sectional area (CSA) of the soleus muscles of rats in the HU group were significantly reduced as compared to those of the rats in the SED group at 7 d post-hindlimb unloading. Seven days of reloading significantly increased the muscle weights of rats in the HUR-PBS and HUR-LOS groups, with the recovery rate of the absolute muscle weight and type I fiber CSA being significantly higher in the HUR-LOS group (6.1% and 10.1%, respectively) than in the HUR-PBS group (4.7% and 5.2%, respectively) (p < 0.05). Moreover, the absolute and relative muscle weight in HUR-PBS were lower than SED; however, no significant difference was observed between the SED and HUR-LOS groups. CSAs of type I and IIa fiber were significantly higher in the HUR-LOS group than in the HU group. Losartan administration during reloading resulted in increased Smad1/5/8 and mTOR signaling and decreased Smad2/3 signaling and protein ubiquitination, facilitating the recovery of atrophied soleus muscle. Therefore, losartan administration-induced muscle recovery may partially be attributed to enhanced Smad1/5/8 and mTOR signaling activation, and reduced activation of canonical TGF-β signaling (Smad2/3) in the soleus muscle.
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Affiliation(s)
- Toshinori Yoshihara
- Graduate School of Health and Sports Science, Juntendo University, Chiba, Japan.
| | - Shohei Dobashi
- Institute of Health and Sports Science & Medicine, Juntendo University, Chiba, Japan
| | - Mizuki Takaragawa
- Graduate School of Health and Sports Science, Juntendo University, Chiba, Japan; Institute of Health and Sports Science & Medicine, Juntendo University, Chiba, Japan
| | - Hisashi Naito
- Graduate School of Health and Sports Science, Juntendo University, Chiba, Japan; Institute of Health and Sports Science & Medicine, Juntendo University, Chiba, Japan
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8
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Wen Y, Dungan CM, Mobley CB, Valentino T, von Walden F, Murach KA. Nucleus Type-Specific DNA Methylomics Reveals Epigenetic "Memory" of Prior Adaptation in Skeletal Muscle. FUNCTION (OXFORD, ENGLAND) 2021; 2:zqab038. [PMID: 34870208 PMCID: PMC8636928 DOI: 10.1093/function/zqab038] [Citation(s) in RCA: 29] [Impact Index Per Article: 9.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 06/14/2021] [Revised: 07/28/2021] [Accepted: 08/03/2021] [Indexed: 02/07/2023]
Abstract
Using a mouse model of conditional and inducible in vivo fluorescent myonuclear labeling (HSA-GFP), sorting purification of nuclei, low-input reduced representation bisulfite sequencing (RRBS), and a translatable and reversible model of exercise (progressive weighted wheel running, PoWeR), we provide the first nucleus type-specific epigenetic information on skeletal muscle adaptation and detraining. Adult (>4 mo) HSA-GFP mice performed PoWeR for 8 wk then detrained for 12 wk; age-matched untrained mice were used to control for the long duration of the study. Myonuclei and interstitial nuclei from plantaris muscles were isolated for RRBS. Relative to untrained, PoWeR caused similar myonuclear CpG hypo- and hyper-methylation of promoter regions and substantial hypomethylation in interstitial nuclear promoters. Over-representation analysis of promoters revealed a larger number of hyper- versus hypo-methylated pathways in both nuclear populations after training and evidence for reciprocal regulation of methylation between nucleus types, with hypomethylation of promoter regions in Wnt signaling-related genes in myonuclei and hypermethylation in interstitial nuclei. After 12 wk of detraining, promoter CpGs in documented muscle remodeling-associated genes and pathways that were differentially methylated immediately after PoWeR were persistently differentially methylated in myonuclei, along with long-term promoter hypomethylation in interstitial nuclei. No enduring gene expression changes in muscle tissue were observed using RNA-sequencing. Upon 4 wk of retraining, mice that trained previously grew more at the whole muscle and fiber type-specific cellular level than training naïve mice, with no difference in myonuclear number. Muscle nuclei have a methylation epi-memory of prior training that may augment muscle adaptability to retraining.
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Affiliation(s)
- Yuan Wen
- Department of Physiology, University of Kentucky, Lexington, KY 40508, USA,The Center for Muscle Biology, University of Kentucky, Lexington, KY 40536, USA
| | - Cory M Dungan
- The Center for Muscle Biology, University of Kentucky, Lexington, KY 40536, USA,College of Health Sciences, University of Kentucky, Lexington, KY 40536, USA
| | - C Brooks Mobley
- Department of Physiology, University of Kentucky, Lexington, KY 40508, USA,The Center for Muscle Biology, University of Kentucky, Lexington, KY 40536, USA
| | - Taylor Valentino
- Department of Physiology, University of Kentucky, Lexington, KY 40508, USA,The Center for Muscle Biology, University of Kentucky, Lexington, KY 40536, USA
| | - Ferdinand von Walden
- Division of Pediatric Neurology, Department of Women's and Children's Health, Karolinska Institutet, Stockholm 171 77, Sweden
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9
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Corbiere TF, Koh TJ. Local low-intensity vibration improves healing of muscle injury in mice. Physiol Rep 2021; 8:e14356. [PMID: 31981324 PMCID: PMC6981306 DOI: 10.14814/phy2.14356] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/16/2019] [Revised: 12/18/2019] [Accepted: 12/27/2019] [Indexed: 01/05/2023] Open
Abstract
Recovery from traumatic muscle injuries is typically prolonged and incomplete. Our previous study demonstrated that whole‐body low‐intensity vibration (LIV) enhances healing in a mouse laceration model. We sought to determine whether locally applied LIV (a) improves muscle repair following injury in mice and (b) is directly transduced by cultured muscle cells, via increased IGF‐1 activity. C57BL/6J mice were subjected to laceration of the gastrocnemius muscle and were treated with LIV applied directly to the lower leg for 30 min/day or non‐LIV sham treatment (controls) for 7 or 14 days. LIV was also applied to differentiating myotubes in culture for 30 min/day for 3 or 6 days. Compared with control mice, LIV increased myofiber cross‐sectional area, diameter, and percent area of peripherally nucleated fibers, and decreased percent damaged area after 14 days of treatment. In cultured myotubes, LIV increased fusion and diameter compared with controls after 6 days of treatment. These LIV‐induced effects were associated with increased total Akt on day 7 in injured muscle and on day 3 in myotubes, whereas phosphorylated‐to‐total Akt ratio increased on day 14 in injured muscle and on day 6 in myotubes but were not associated with increased IGF‐1 levels at any time point. These changes were also associated with LIV‐induced suppression of FOXO1 and Atrogin‐1 gene expression at day 7 in injured muscle. These findings demonstrate that muscle cells can directly transduce LIV signals into increased growth and differentiation, and this effect is associated with increased Akt signaling.
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Affiliation(s)
- Thomas F Corbiere
- Department of Kinesiology and Nutrition, University of Illinois at Chicago, Chicago, IL, USA
| | - Timothy J Koh
- Department of Kinesiology and Nutrition, University of Illinois at Chicago, Chicago, IL, USA
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10
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Benyamini H, Kling Y, Yakovlev L, Becker Cohen M, Nevo Y, Elgavish S, Harazi A, Argov Z, Sela I, Mitrani-Rosenbaum S. Upregulation of Hallmark Muscle Genes Protects GneM743T/M743T Mutated Knock-In Mice From Kidney and Muscle Phenotype. J Neuromuscul Dis 2020; 7:119-136. [PMID: 31985472 PMCID: PMC7175939 DOI: 10.3233/jnd-190461] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/22/2022]
Abstract
Background: Mutations in GNE cause a recessive, adult onset myopathy characterized by slowly progressive distal and proximal muscle weakness. Knock-in mice carrying the most frequent mutation in GNE myopathy patients, GneM743T/M743T, usually die few days after birth from severe renal failure, with no muscle phenotype. However, a spontaneous sub-colony remains healthy throughout a normal lifespan without any kidney or muscle pathology. Objective: We attempted to decipher the molecular mechanisms behind these phenotypic differences and to determine the mechanisms preventing the kidney and muscles from disease. Methods: We analyzed the transcriptome and proteome of kidneys and muscles of sick and healthy GneM743T/M743T mice. Results: The sick GneM743T/M743T kidney was characterized by up-regulation of extra-cellular matrix degradation related processes and by down-regulation of oxidative phosphorylation and respiratory electron chain pathway, that was also observed in the asymptomatic muscles. Surprisingly, the healthy kidneys of the GneM743T/M743T mice were characterized by up-regulation of hallmark muscle genes. In addition the asymptomatic muscles of the sick GneM743T/M743T mice showed upregulation of transcription and translation processes. Conclusions: Overexpression of muscle physiology genes in healthy GneM743T/M743T mice seems to define the protecting mechanism in these mice. Furthermore, the strong involvement of muscle related genes in kidney may bridge the apparent phenotypic gap between GNE myopathy and the knock-in GneM743T/M743T mouse model and provide new directions in the study of GNE function in health and disease.
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Affiliation(s)
- Hadar Benyamini
- Bioinformatics Unit of the I-CORE at the Hebrew University and Hadassah Medical Center, Jerusalem, Israel
| | - Yehuda Kling
- Goldyne Savad Institute of Gene Therapy, Hadassah Hebrew University Medical Center, Jerusalem, Israel
| | - Lena Yakovlev
- Goldyne Savad Institute of Gene Therapy, Hadassah Hebrew University Medical Center, Jerusalem, Israel
| | - Michal Becker Cohen
- Goldyne Savad Institute of Gene Therapy, Hadassah Hebrew University Medical Center, Jerusalem, Israel
| | - Yuval Nevo
- Bioinformatics Unit of the I-CORE at the Hebrew University and Hadassah Medical Center, Jerusalem, Israel
| | - Sharona Elgavish
- Bioinformatics Unit of the I-CORE at the Hebrew University and Hadassah Medical Center, Jerusalem, Israel
| | - Avi Harazi
- Goldyne Savad Institute of Gene Therapy, Hadassah Hebrew University Medical Center, Jerusalem, Israel
| | - Zohar Argov
- Department of Neurology, Hadassah Hebrew University Medical Center, Jerusalem, Israel
| | - Ilan Sela
- Goldyne Savad Institute of Gene Therapy, Hadassah Hebrew University Medical Center, Jerusalem, Israel
| | - Stella Mitrani-Rosenbaum
- Goldyne Savad Institute of Gene Therapy, Hadassah Hebrew University Medical Center, Jerusalem, Israel
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11
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Rimington RP, Capel AJ, Chaplin KF, Fleming JW, Bandulasena HCH, Bibb RJ, Christie SDR, Lewis MP. Differentiation of Bioengineered Skeletal Muscle within a 3D Printed Perfusion Bioreactor Reduces Atrophic and Inflammatory Gene Expression. ACS Biomater Sci Eng 2019; 5:5525-5538. [PMID: 33464072 DOI: 10.1021/acsbiomaterials.9b00975] [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] [Indexed: 12/25/2022]
Abstract
Bioengineered skeletal muscle tissues benefit from dynamic culture environments which facilitate the appropriate provision of nutrients and removal of cellular waste products. Biologically compatible perfusion systems hold the potential to enhance the physiological biomimicry of in vitro tissues via dynamic culture, in addition to providing technological advances in analytical testing and live cellular imaging for analysis of cellular development. To meet such diverse requirements, perfusion systems require the capacity and adaptability to incorporate multiple cell laden constructs of both monolayer and bioengineered tissues. This work reports perfusion systems produced using additive manufacturing technology for the in situ phenotypic development of myogenic precursor cells in monolayer and bioengineered tissue. Biocompatibility of systems 3D printed using stereolithography (SL), laser sintering (LS), and PolyJet outlined preferential morphological development within both SL and LS devices. When exposed to intermittent perfusion in the monolayer, delayed yet physiologically representative cellular proliferation, MyoD and myogenin transcription of C2C12 cells was evident. Long-term (8 days) intermittent perfusion of monolayer cultures outlined viable morphological and genetic in situ differentiation for the live cellular imaging of myogenic development. Continuous perfusion cultures (13 days) of bioengineered skeletal muscle tissues outlined in situ myogenic differentiation, forming mature multinucleated myotubes. Here, reductions in IL-1β and TNF-α inflammatory cytokines, myostatin, and MuRF-1 atrophic mRNA expression were observed. Comparable myosin heavy chain (MyHC) isoform transcription profiles were evident between conditions; however, total mRNA expression was reduced in perfusion conditions. Decreased transcription of MuRF1 and subsequent reduced ubiquitination of the MyHC protein allude to a decreased requirement for transcription of MyHC isoform transcripts. Together, these data appear to indicate that 3D printed perfusion systems elicit enhanced stability of the culture environment, resulting in a reduced basal requirement for MyHC gene expression within bioengineered skeletal muscle tissue.
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12
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Tényi Á, Cano I, Marabita F, Kiani N, Kalko SG, Barreiro E, de Atauri P, Cascante M, Gomez-Cabrero D, Roca J. Network modules uncover mechanisms of skeletal muscle dysfunction in COPD patients. J Transl Med 2018; 16:34. [PMID: 29463285 PMCID: PMC5819708 DOI: 10.1186/s12967-018-1405-y] [Citation(s) in RCA: 17] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/31/2017] [Accepted: 02/12/2018] [Indexed: 02/08/2023] Open
Abstract
Background Chronic obstructive pulmonary disease (COPD) patients often show skeletal muscle dysfunction that has a prominent negative impact on prognosis. The study aims to further explore underlying mechanisms of skeletal muscle dysfunction as a characteristic systemic effect of COPD, potentially modifiable with preventive interventions (i.e. muscle training). The research analyzes network module associated pathways and evaluates the findings using independent measurements. Methods We characterized the transcriptionally active network modules of interacting proteins in the vastus lateralis of COPD patients (n = 15, FEV1 46 ± 12% pred, age 68 ± 7 years) and healthy sedentary controls (n = 12, age 65 ± 9 years), at rest and after an 8-week endurance training program. Network modules were functionally evaluated using experimental data derived from the same study groups. Results At baseline, we identified four COPD specific network modules indicating abnormalities in creatinine metabolism, calcium homeostasis, oxidative stress and inflammatory responses, showing statistically significant associations with exercise capacity (VO2 peak, Watts peak, BODE index and blood lactate levels) (P < 0.05 each), but not with lung function (FEV1). Training-induced network modules displayed marked differences between COPD and controls. Healthy subjects specific training adaptations were significantly associated with cell bioenergetics (P < 0.05) which, in turn, showed strong relationships with training-induced plasma metabolomic changes; whereas, effects of training in COPD were constrained to muscle remodeling. Conclusion In summary, altered muscle bioenergetics appears as the most striking finding, potentially driving other abnormal skeletal muscle responses. Trial registration The study was based on a retrospectively registered trial (May 2017), ClinicalTrials.gov identifier: NCT03169270 Electronic supplementary material The online version of this article (10.1186/s12967-018-1405-y) contains supplementary material, which is available to authorized users.
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Affiliation(s)
- Ákos Tényi
- Hospital Clinic de Barcelona, Institut d'Investigacions Biomèdiques August Pi i Sunyer (IDIBAPS), Universitat de Barcelona, Barcelona, Spain. .,Center for Biomedical Network Research in Respiratory Diseases (CIBERES), Madrid, Spain.
| | - Isaac Cano
- Hospital Clinic de Barcelona, Institut d'Investigacions Biomèdiques August Pi i Sunyer (IDIBAPS), Universitat de Barcelona, Barcelona, Spain.,Center for Biomedical Network Research in Respiratory Diseases (CIBERES), Madrid, Spain
| | - Francesco Marabita
- Unit of Computational Medicine, Department of Medicine, Karolinska Institute, 171 77, Stockholm, Sweden.,Center for Molecular Medicine, Karolinska Institutet, 171 77, Stockholm, Sweden
| | - Narsis Kiani
- Unit of Computational Medicine, Department of Medicine, Karolinska Institute, 171 77, Stockholm, Sweden.,Center for Molecular Medicine, Karolinska Institutet, 171 77, Stockholm, Sweden
| | - Susana G Kalko
- Hospital Clinic de Barcelona, Institut d'Investigacions Biomèdiques August Pi i Sunyer (IDIBAPS), Universitat de Barcelona, Barcelona, Spain.,Center for Biomedical Network Research in Respiratory Diseases (CIBERES), Madrid, Spain.,Bioinformatics Core Facility, IDIBAPS-CEK, Hospital Clínic, University de Barcelona, Barcelona, Spain
| | - Esther Barreiro
- Center for Biomedical Network Research in Respiratory Diseases (CIBERES), Madrid, Spain.,Pulmonology Dept, Muscle and Respiratory System Research Unit, IMIM-Hospital del Mar, Universitat Pompeu Fabra, PRBB, Barcelona, Spain
| | - Pedro de Atauri
- Departament de Bioquimica i Biologia Molecular, Facultat de Biologia-IBUB, Universitat de Barcelona, 08028, Barcelona, Spain
| | - Marta Cascante
- Departament de Bioquimica i Biologia Molecular, Facultat de Biologia-IBUB, Universitat de Barcelona, 08028, Barcelona, Spain
| | - David Gomez-Cabrero
- Unit of Computational Medicine, Department of Medicine, Karolinska Institute, 171 77, Stockholm, Sweden.,Center for Molecular Medicine, Karolinska Institutet, 171 77, Stockholm, Sweden.,Mucosal and Salivary Biology Division, King's College London Dental Institute, London, SE1 9RT, UK
| | - Josep Roca
- Hospital Clinic de Barcelona, Institut d'Investigacions Biomèdiques August Pi i Sunyer (IDIBAPS), Universitat de Barcelona, Barcelona, Spain. .,Center for Biomedical Network Research in Respiratory Diseases (CIBERES), Madrid, Spain.
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13
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Neppl RL, Wu CL, Walsh K. lncRNA Chronos is an aging-induced inhibitor of muscle hypertrophy. J Cell Biol 2017; 216:3497-3507. [PMID: 28855249 PMCID: PMC5674882 DOI: 10.1083/jcb.201612100] [Citation(s) in RCA: 39] [Impact Index Per Article: 5.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/14/2016] [Revised: 06/28/2017] [Accepted: 08/03/2017] [Indexed: 02/07/2023] Open
Abstract
Neppl et al. identify a long noncoding RNA named Chronos whose expression increases with age and decreases in Akt-mediated growth. Inhibition of Chronos induces myofiber hypertrophy in vitro and in vivo, in part, through the epigenetic modulation of Bmp7 signaling. Skeletal muscle exhibits remarkable plasticity in its ability to modulate its mass in response to the physiologic changes associated with functional use, systemic disease, and aging. Although a gradual loss of muscle mass normally occurs with advancing age, its increasingly rapid progression results in sarcopenia in a subset of individuals. The identities of muscle-enriched, long noncoding RNAs that regulate this process are unknown. Here, we identify a long noncoding RNA, named Chronos, whose expression in muscle is positively regulated with advancing age and negatively regulated during Akt1-mediated growth. Inhibition of Chronos induces myofiber hypertrophy both in vitro and in vivo, in part, through the epigenetic modulation of Bmp7 signaling.
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Affiliation(s)
- Ronald L Neppl
- Molecular Cardiology, Whitaker Cardiovascular Institute, Boston University School of Medicine, Boston, MA .,Department of Orthopedic Surgery, Brigham and Women's Hospital, Harvard Medical School, Boston, MA
| | - Chia-Ling Wu
- Molecular Cardiology, Whitaker Cardiovascular Institute, Boston University School of Medicine, Boston, MA
| | - Kenneth Walsh
- Molecular Cardiology, Whitaker Cardiovascular Institute, Boston University School of Medicine, Boston, MA
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14
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Rossetti ML, Steiner JL, Gordon BS. Androgen-mediated regulation of skeletal muscle protein balance. Mol Cell Endocrinol 2017; 447:35-44. [PMID: 28237723 PMCID: PMC5407187 DOI: 10.1016/j.mce.2017.02.031] [Citation(s) in RCA: 58] [Impact Index Per Article: 8.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 01/06/2017] [Revised: 02/20/2017] [Accepted: 02/20/2017] [Indexed: 02/06/2023]
Abstract
Androgens significantly alter muscle mass in part by shifting protein balance in favor of net protein accretion. During various atrophic conditions, the clinical impact of decreased production or bioavailability of androgens (termed hypogonadism) is important as a loss of muscle mass is intimately linked with survival outcome. While androgen replacement therapy increases muscle mass in part by restoring protein balance, this is not a comprehensive treatment option due to potential side effects. Therefore, an understanding of the mechanisms by which androgens alter protein balance is needed for the development of androgen-independent therapies. While the data in humans suggest androgens alter protein balance (both synthesis and breakdown) in the fasted metabolic state, a predominant molecular mechanism(s) behind this observation is still lacking. This failure is likely due in part to inconsistent experimental design between studies including failure to control nutrient/feeding status, the method of altering androgens, and the model systems utilized.
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Affiliation(s)
- Michael L Rossetti
- The Institute of Exercise Physiology and Wellness, The University of Central Florida, PO Box 161250, Orlando, FL 32816, United States
| | - Jennifer L Steiner
- Department of Cellular and Molecular Physiology, The Pennsylvania State University College of Medicine, 500 University Drive, Hershey, PA 17033, United States
| | - Bradley S Gordon
- The Institute of Exercise Physiology and Wellness, The University of Central Florida, PO Box 161250, Orlando, FL 32816, United States.
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15
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Simon L, Jolley SE, Molina PE. Alcoholic Myopathy: Pathophysiologic Mechanisms and Clinical Implications. Alcohol Res 2017; 38:207-217. [PMID: 28988574 PMCID: PMC5513686] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022] Open
Abstract
Skeletal muscle dysfunction (i.e., myopathy) is common in patients with alcohol use disorder. However, few clinical studies have elucidated the significance, mechanisms, and therapeutic options of alcohol-related myopathy. Preclinical studies indicate that alcohol adversely affects both anabolic and catabolic pathways of muscle-mass maintenance and that an increased proinflammatory and oxidative milieu in the skeletal muscle is the primary contributing factor leading to alcohol-related skeletal muscle dysfunction. Decreased regenerative capacity of muscle progenitor cells is emerging as an additional mechanism that contributes to alcohol-induced loss in muscle mass and impairment in muscle growth. This review details the epidemiology of alcoholic myopathy, potential contributing pathophysiologic mechanisms, and emerging literature on novel therapeutic options.
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16
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Biressi S, Gopinath SD. The quasi-parallel lives of satellite cells and atrophying muscle. Front Aging Neurosci 2015; 7:140. [PMID: 26257645 PMCID: PMC4510774 DOI: 10.3389/fnagi.2015.00140] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/21/2015] [Accepted: 07/06/2015] [Indexed: 12/25/2022] Open
Abstract
Skeletal muscle atrophy or wasting accompanies various chronic illnesses and the aging process, thereby reducing muscle function. One of the most important components contributing to effective muscle repair in postnatal organisms, the satellite cells (SCs), have recently become the focus of several studies examining factors participating in the atrophic process. We critically examine here the experimental evidence linking SC function with muscle loss in connection with various diseases as well as aging, and in the subsequent recovery process. Several recent reports have investigated the changes in SCs in terms of their differentiation and proliferative capacity in response to various atrophic stimuli. In this regard, we review the molecular changes within SCs that contribute to their dysfunctional status in atrophy, with the intention of shedding light on novel potential pharmacological targets to counteract the loss of muscle mass.
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Affiliation(s)
- Stefano Biressi
- Dulbecco Telethon Institute and Centre for Integrative Biology (CIBIO), University of TrentoTrento, Italy
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17
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Steiner JL, Lang CH. Dysregulation of skeletal muscle protein metabolism by alcohol. Am J Physiol Endocrinol Metab 2015; 308:E699-712. [PMID: 25759394 PMCID: PMC4420901 DOI: 10.1152/ajpendo.00006.2015] [Citation(s) in RCA: 87] [Impact Index Per Article: 9.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 01/05/2015] [Accepted: 03/03/2015] [Indexed: 12/12/2022]
Abstract
Alcohol abuse, either by acute intoxication or prolonged excessive consumption, leads to pathological changes in many organs and tissues including skeletal muscle. As muscle protein serves not only a contractile function but also as a metabolic reserve for amino acids, which are used to support the energy needs of other tissues, its content is tightly regulated and dynamic. This review focuses on the etiology by which alcohol perturbs skeletal muscle protein balance and thereby over time produces muscle wasting and weakness. The preponderance of data suggest that alcohol primarily impairs global protein synthesis, under basal conditions as well as in response to several anabolic stimuli including growth factors, nutrients, and muscle contraction. This inhibitory effect of alcohol is mediated, at least in part, by a reduction in mTOR kinase activity via a mechanism that remains poorly defined but likely involves altered protein-protein interactions within mTOR complex 1. Furthermore, alcohol can exacerbate the decrement in mTOR and/or muscle protein synthesis present in other catabolic states. In contrast, alcohol-induced changes in muscle protein degradation, either global or via specific modulation of the ubiquitin-proteasome or autophagy pathways, are relatively inconsistent and may be model dependent. Herein, changes produced by acute intoxication versus chronic ingestion are contrasted in relation to skeletal muscle metabolism, and limitations as well as opportunities for future research are discussed. As the proportion of more economically developed countries ages and chronic illness becomes more prevalent, a better understanding of the etiology of biomedical consequences of alcohol use disorders is warranted.
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Affiliation(s)
- Jennifer L Steiner
- Department of Cellular and Molecular Physiology, Pennsylvania State College of Medicine, Hershey, Pennsylvania
| | - Charles H Lang
- Department of Cellular and Molecular Physiology, Pennsylvania State College of Medicine, Hershey, Pennsylvania
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