151
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Shi Y, Moon M, Dawood S, McManus B, Liu PP. Mechanisms and management of doxorubicin cardiotoxicity. Herz 2012; 36:296-305. [PMID: 21656050 DOI: 10.1007/s00059-011-3470-3] [Citation(s) in RCA: 146] [Impact Index Per Article: 12.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/04/2023]
Abstract
Doxorubicin is an effective anti-tumor agent with a cumulative dose-dependent cardiotoxicity. In addition to its principal toxic mechanisms involving iron and redox reactions, recent studies have described new mechanisms of doxorubicin-induced cell death, including abnormal protein processing, hyper-activated innate immune responses, inhibition of neuregulin-1 (NRG1)/ErbB(HER) signalling, impaired progenitor cell renewal/cardiac repair, and decreased vasculogenesis. Although multiple mechanisms involved in doxorubicin cardiotoxicity have been studied, there is presently no clinically proven treatment established for doxorubicin cardiomyopathy. Iron chelator dexrazoxane, angiotensin converting enzyme (ACE) inhibitors, and β-blockade have been proposed as potential preventive strategies for doxorubicin cardiotoxicity. Novel approaches such as anti-miR-146 or recombinant NRG1 to increase cardiomyocyte resistance to toxicity may be of interest in the future.
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Affiliation(s)
- Y Shi
- Division of Cardiology, Heart and Stroke/Richard Lewar Centre of Excellence, University Health Network, University of Toronto, Toronto General Hospital, Ontario, Canada
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152
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Abstract
PURPOSE OF REVIEW Therapeutic exercise may help maintain or slow down the rate of decline in muscle mass and physical function that occurs with cachexia. This review considers recent evidence in relation to patients with cachexia as regards the rationale for the use of exercise, the challenges in its clinical application and future developments. RECENT FINDINGS Exercise may attenuate the effects of cachexia by modulating muscle metabolism, insulin sensitivity and levels of inflammation. Studies targeting cachectic patients have demonstrated that even in advanced disease peripheral muscle has the capacity to respond to exercise training. Nonetheless, there are challenges in implementing the use of exercise, particularly once cachexia is established in which tolerance to even low levels of exercise is poor. Strategies to make exercise a more accessible therapy are required and could include offering exercise earlier on in the course of the disease, at lower intensities and in various forms, including more novel approaches. SUMMARY The use of therapeutic exercise has a sound rationale, even in patients with advanced disease and cachexia. Because of practical issues with its application, further study is required to examine if benefits achieved in small studies can be translated to a wider clinical population.
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153
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Powell SR, Herrmann J, Lerman A, Patterson C, Wang X. The ubiquitin-proteasome system and cardiovascular disease. PROGRESS IN MOLECULAR BIOLOGY AND TRANSLATIONAL SCIENCE 2012; 109:295-346. [PMID: 22727426 DOI: 10.1016/b978-0-12-397863-9.00009-2] [Citation(s) in RCA: 70] [Impact Index Per Article: 5.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/14/2022]
Abstract
Over the past decade, the role of the ubiquitin-proteasome system (UPS) has been the subject of numerous studies to elucidate its role in cardiovascular physiology and pathophysiology. There have been many advances in this field including the use of proteomics to achieve a better understanding of how the cardiac proteasome is regulated. Moreover, improved methods for the assessment of UPS function and the development of genetic models to study the role of the UPS have led to the realization that often the function of this system deviates from the norm in many cardiovascular pathologies. Hence, dysfunction has been described in atherosclerosis, familial cardiac proteinopathies, idiopathic dilated cardiomyopathies, and myocardial ischemia. This has led to numerous studies of the ubiquitin protein (E3) ligases and their roles in cardiac physiology and pathophysiology. This has also led to the controversial proposition of treating atherosclerosis, cardiac hypertrophy, and myocardial ischemia with proteasome inhibitors. Furthering our knowledge of this system may help in the development of new UPS-based therapeutic modalities for mitigation of cardiovascular disease.
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Affiliation(s)
- Saul R Powell
- Center for Heart and Lung Research, The Feinstein Institute for Medical Research, Manhasset, New York, USA
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154
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Protein metabolism and gene expression in skeletal muscle of critically ill patients with sepsis. Clin Sci (Lond) 2011; 122:133-42. [PMID: 21880013 DOI: 10.1042/cs20110233] [Citation(s) in RCA: 96] [Impact Index Per Article: 7.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/15/2023]
Abstract
Muscle wasting negatively affects morbidity and mortality in critically ill patients. This progressive wasting is accompanied by, in general, a normal muscle PS (protein synthesis) rate. In the present study, we investigated whether muscle protein degradation is increased in critically ill patients with sepsis and which proteolytic enzyme systems are involved in this degradation. Eight patients and seven healthy volunteers were studied. In vivo muscle protein kinetics was measured using arteriovenous balance techniques with stable isotope tracers. The activities of the major proteolytic enzyme systems were analysed in combination with mRNA expression of genes related to these proteolytic systems. Results show that critically ill patients with sepsis have a variable but normal muscle PS rate, whereas protein degradation rates are dramatically increased (up to 160%). Of the major proteolytic enzyme systems both the proteasome and the lysosomal systems had higher activities in the patients, whereas calpain and caspase activities were not changed. Gene expression of several genes related to the proteasome system was increased in the patients. mRNA levels of the two main lysosomal enzymes (cathepsin B and L) were not changed but, conversely, genes related to calpain and caspase had a higher expression in the muscles of the patients. In conclusion, the dramatic muscle wasting seen in critically ill patients with sepsis is due to increased protein degradation. This is facilitated by increased activities of both the proteasome and lysosomal proteolytic systems.
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155
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Paffett ML, Lucas SN, Campen MJ. Resveratrol reverses monocrotaline-induced pulmonary vascular and cardiac dysfunction: a potential role for atrogin-1 in smooth muscle. Vascul Pharmacol 2011; 56:64-73. [PMID: 22146233 DOI: 10.1016/j.vph.2011.11.002] [Citation(s) in RCA: 42] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/25/2011] [Revised: 10/31/2011] [Accepted: 11/20/2011] [Indexed: 12/19/2022]
Abstract
Arterial remodeling contributes to elevated pulmonary artery (PA) pressures and right ventricular hypertrophy seen in pulmonary hypertension (PH). Resveratrol, a sirtuin-1 (SIRT1) pathway activator, can prevent the development of PH in a commonly used animal model, but it is unclear whether it can reverse established PH pathophysiology. Furthermore, atrophic ubiquitin ligases, such as atrogin-1 and MuRF-1, are known to be induced by SIRT1 activators but have not been characterized in hypertrophic vascular disease. Therefore, we hypothesized that monocrotaline (MCT)-induced PH would attenuate atrophy pathways in the PA while, conversely, SIRT1 activation (resveratrol) would reverse indices of PH and restore atrophic gene expression. Thus, we injected Sprague-Dawley rats with MCT (50 mg/kg i.p.) or saline at Day 0, and then treated with oral resveratrol or sildenafil from days 28-42 post-MCT injection. Oral resveratrol attenuated established MCT-induced PH indices, including right ventricular systolic pressure, right ventricular hypertrophy, and medial thickening of intrapulmonary arteries. Resveratrol also normalized PA atrogin-1 mRNA expression, which was significantly reduced by MCT. In cultured human PA smooth muscle cells (hPASMC), resveratrol significantly inhibited PDGF-stimulated proliferation and cellular hypertrophy, which was also associated with improvements in atrogin-1 levels. In addition, SIRT1 inhibition augmented hPASMC proliferation, as assessed by DNA mass, and suppressed atrogin mRNA expression. These findings demonstrate an inverse relationship between indices of PH and PA atrogin expression that is SIRT1 dependent and may reflect a novel role for SIRT1 in PASMCs opposing cellular hypertrophy and proliferation.
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Affiliation(s)
- Michael L Paffett
- College of Pharmacy, Division of Pharmaceutical Sciences, University of New Mexico Health Sciences Center, Albuquerque, NM 87131-0001, USA
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156
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Vezzoli M, Castellani P, Corna G, Castiglioni A, Bosurgi L, Monno A, Brunelli S, Manfredi AA, Rubartelli A, Rovere-Querini P. High-mobility group box 1 release and redox regulation accompany regeneration and remodeling of skeletal muscle. Antioxid Redox Signal 2011; 15:2161-74. [PMID: 21294652 DOI: 10.1089/ars.2010.3341] [Citation(s) in RCA: 50] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/03/2023]
Abstract
High-mobility group box 1 (HMGB1), a damage-associated molecular pattern (DAMP) molecules, favors tissue regeneration via recruitment and activation of leukocytes and stem cells. Here we demonstrate, in a model of acute sterile muscle injury, that regeneration is accompanied by active reactive oxygen species (ROS) production counterbalanced and overcome by the generation of antioxidant moieties. Mitochondria are initially responsible for ROS formation. However, they undergo rapid disruption with almost complete disappearance. Twenty-four hours after injury, we observed a strong induction of MURF1 and atrogin-1 ubiquitin ligases, key signals in activation of the proteasome system and induction of muscle atrophy. At later time points, ROS generation is maintained by nonmitochondrial sources. The antioxidant response occurs in both regenerating fibers and leukocytes that express high levels of free thiols and antioxidant enzymes, such as superoxide dismutase 1 (SOD1) and thioredoxin. HMGB1, a protein thiol, weakly expressed in healthy muscles, increases during regeneration in parallel with the antioxidant response in both fibers and leukocytes. A reduced environment may be important to maintain HMGB1 bioactivity. Indeed, oxidation abrogates both muscle stem cell migration in response to HMGB1 and their ability to differentiate into myofibers in vitro. We propose that the early antioxidant response in regenerating muscle limits HMGB1 oxidation, thus allowing successful muscle regeneration.
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Affiliation(s)
- Michela Vezzoli
- Innate Immunity and Tissue Remodeling Unit, San Raffaele Scientific Institute, Via Olgettina 58, Milan, Italy
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157
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Gonnella P, Alamdari N, Tizio S, Aversa Z, Petkova V, Hasselgren PO. C/EBPβ regulates dexamethasone-induced muscle cell atrophy and expression of atrogin-1 and MuRF1. J Cell Biochem 2011; 112:1737-48. [PMID: 21381078 DOI: 10.1002/jcb.23093] [Citation(s) in RCA: 27] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/05/2023]
Abstract
Muscle wasting in catabolic patients is in part mediated by glucocorticoids and is associated with increased expression and activity of the transcription factor C/EBPβ. It is not known, however, if C/EBPβ is causally linked to glucocorticoid-induced muscle atrophy. We used dexamethasone-treated L6 myoblasts and myotubes to test the role of C/EBPβ in glucocorticoid-induced expression of the muscle-specific ubiquitin ligases atrogin-1 and MuRF1, protein degradation, and muscle atrophy by transfecting cells with C/EBPβ siRNA. In myoblasts, silencing C/EBPβ expression with siRNA inhibited dexamethasone-induced increase in protein degradation, atrogin-1 and MuRF1 expression, and muscle cell atrophy. Similar effects of C/EBPβ siRNA were seen in myotubes except that the dexamethasone-induced increase in MuRF1 expression was not affected by C/EBPβ siRNA in myotubes. In additional experiments, overexpressing C/EBPβ did not influence atrogin-1 or MuRF1 expression in myoblasts or myotubes. Taken together, our observations suggest that glucocorticoid-induced muscle wasting is at least in part regulated by C/EBPβ. Increased C/EBPβ expression alone, however, is not sufficient to upregulate atrogin-1 and MuRF1 expression.
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Affiliation(s)
- Patricia Gonnella
- Beth Israel Deaconess Medical Center, Department of Surgery, Harvard Medical School, Boston, Massachusetts 02215, USA
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158
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Pierno S, Liantonio A, Camerino GM, De Bellis M, Cannone M, Gramegna G, Scaramuzzi A, Simonetti S, Nicchia GP, Basco D, Svelto M, Desaphy JF, Camerino DC. Potential benefits of taurine in the prevention of skeletal muscle impairment induced by disuse in the hindlimb-unloaded rat. Amino Acids 2011; 43:431-45. [DOI: 10.1007/s00726-011-1099-4] [Citation(s) in RCA: 25] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/07/2011] [Accepted: 09/20/2011] [Indexed: 01/31/2023]
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159
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Garner TP, Strachan J, Shedden EC, Long JE, Cavey JR, Shaw B, Layfield R, Searle MS. Independent Interactions of Ubiquitin-Binding Domains in a Ubiquitin-Mediated Ternary Complex. Biochemistry 2011; 50:9076-87. [DOI: 10.1021/bi201137e] [Citation(s) in RCA: 32] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/22/2023]
Affiliation(s)
- Thomas P. Garner
- Centre for
Biomolecular Sciences,
School of Chemistry, University Park, University of Nottingham, Nottingham NG7 2RD, U.K
| | - Joanna Strachan
- School of Biomedical Sciences,
Queen's Medical Centre, University of Nottingham, Nottingham NG7 2UH, U.K
| | - Elizabeth C. Shedden
- Centre for
Biomolecular Sciences,
School of Chemistry, University Park, University of Nottingham, Nottingham NG7 2RD, U.K
| | - Jed E. Long
- Centre for
Biomolecular Sciences,
School of Chemistry, University Park, University of Nottingham, Nottingham NG7 2RD, U.K
| | - James R. Cavey
- School of Biomedical Sciences,
Queen's Medical Centre, University of Nottingham, Nottingham NG7 2UH, U.K
| | - Barry Shaw
- School of Biomedical Sciences,
Queen's Medical Centre, University of Nottingham, Nottingham NG7 2UH, U.K
| | - Robert Layfield
- School of Biomedical Sciences,
Queen's Medical Centre, University of Nottingham, Nottingham NG7 2UH, U.K
| | - Mark S. Searle
- Centre for
Biomolecular Sciences,
School of Chemistry, University Park, University of Nottingham, Nottingham NG7 2RD, U.K
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160
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Kim HJ, Jamart C, Deldicque L, An GL, Lee YH, Kim CK, Raymackers JM, Francaux M. Endoplasmic reticulum stress markers and ubiquitin–proteasome pathway activity in response to a 200-km run. Med Sci Sports Exerc 2011; 43:18-25. [PMID: 20473228 DOI: 10.1249/mss.0b013e3181e4c5d1] [Citation(s) in RCA: 60] [Impact Index Per Article: 4.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/30/2022]
Abstract
PURPOSE This study investigated whether a 200-km run modulates signaling pathways implicated in cellular stress in skeletal muscle, with special attention paid to the endoplasmic reticulum (ER) stress and to the activation of the ubiquitin-proteasome pathway. METHODS Eight men ran 200 km (28 h 03 min ± 2 h 01 min). Two muscle biopsies were obtained from the vastus lateralis muscle 2 wk before and 3 h after the race. Mitogen-activated protein kinase, ubiquitin-proteasome pathway, ER stress, inflammation, and oxidative stress markers were assayed by Western blot analysis or by quantitative real-time polymerase chain reaction. Chymotrypsin-like activity of the proteasome was measured by a fluorimetric assay. RESULTS Phosphorylation states of extracellular signal-related kinase 1/2 (+401% ± 173.8%, P = 0.027) and c-Jun N-terminal (+149% ± 61.9%, P = 0.023) increased after the race, whereas p38 phosphorylation remained unchanged. Increases in BiP (+235% ± 94.7%, P = 0.021) and in the messenger RNA level of total (+138% ± 31.2%, P = 0.002) and spliced X-box binding protein 1 (+241% ± 53.3%, P = 0.001) indicated the presence of ER stress. Transcripts of inflammatory markers interleukin-6 (+403% ± 96.1%, P = 0.002) and tumor necrosis factor-α (+233% ± 58.4%, P = 0.003) as well as oxidative stress markers metallothionein 1F (+519% ± 258.3%, P = 0.042), metallothionein 1H (+666% ± 157.5%, P = 0.002), and nicotinamide adenine dinucleotide phosphate-oxidase (NADPH oxidase) (+162% ± 60.5%, P = 0.016) were increased. The messenger RNA level of the ubiquitin ligases muscle-specific RING finger 1 (+583% ± 244.3%, P = 0.024) and muscle atrophy F-box (+249% ± 83.8%, P = 0.011) and the C2 proteasome subunit (+116% ± 40.6%, P = 0.012) also increased. Surprisingly, the amount of ubiquitin-conjugated proteins and the chymotrypsin-like activity of the proteasome were decreased by 20% ± 8.3% (P = 0.025) and 21% ± 4.4% (P = 0.001), respectively. The expression of ubiquitin-specific protease 28 deubiquitinase was increased (+81% ± 37.9%, P = 0.034). CONCLUSIONS In the skeletal muscle, a 200-km run activates the expression of ubiquitin ligases muscle-specific RING finger 1 and muscle atrophy F-box as well as various cellular stresses, among which are ER stress, oxidative stress, and inflammation. Meanwhile, compensatory mechanisms seem also triggered: the unfolded protein response is up-regulated, and the chymotrypsin-like activity of the proteasome is repressed.
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Affiliation(s)
- Hyo Jeong Kim
- Human Physiology, Korea National Sport University, Seoul, South Korea
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161
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Wing SS, Lecker SH, Jagoe RT. Proteolysis in illness-associated skeletal muscle atrophy: from pathways to networks. Crit Rev Clin Lab Sci 2011; 48:49-70. [PMID: 21699435 DOI: 10.3109/10408363.2011.586171] [Citation(s) in RCA: 58] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/07/2023]
Abstract
Improvements in health in the past decades have resulted in increased numbers of the elderly in both developed and developing regions of the world. Advances in therapy have also increased the prevalence of patients with chronic and degenerative diseases. Muscle wasting, a feature of most chronic diseases, is prominent in the elderly and contributes to both morbidity and mortality. A major research goal has been to identify the proteolytic system(s) that is responsible for the degradation of proteins that occurs in muscle atrophy. Findings over the past 20 years have clearly confirmed an important role of the ubiquitin proteasome system in mediating muscle proteolysis, particularly that of myofibrillar proteins. However, recent observations have provided evidence that autophagy, calpains and caspases also contribute to the turnover of muscle proteins in catabolic states, and furthermore, that these diverse proteolytic systems interact with each other at various levels. Importantly, a number of intracellular signaling pathways such as the IGF1/AKT, myostatin/Smad, PGC1, cytokine/NFκB, and AMPK pathways are now known to interact and can regulate some of these proteolytic systems in a coordinated manner. A number of loss of function studies have identified promising therapeutic approaches to the prevention and treatment of wasting. However, additional biomarkers and other approaches to improve early identification of patients who would benefit from such treatment need to be developed. The current data suggests a network of interacting proteolytic and signaling pathways in muscle. Future studies are needed to improve understanding of the nature and control of these interactions and how they work to preserve muscle function under various states of growth and atrophy.
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Affiliation(s)
- Simon S Wing
- Departments of Medicine, McGill University and McGill University Health Centre Research Institute, Montreal, Quebec, Canada.
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162
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Chen GQ, Mou CY, Yang YQ, Wang S, Zhao ZW. Exercise training has beneficial anti-atrophy effects by inhibiting oxidative stress-induced MuRF1 upregulation in rats with diabetes. Life Sci 2011; 89:44-9. [PMID: 21620866 DOI: 10.1016/j.lfs.2011.04.018] [Citation(s) in RCA: 24] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/07/2010] [Revised: 04/25/2011] [Accepted: 04/27/2011] [Indexed: 11/25/2022]
Abstract
AIMS MuRF1 E3 ubiquitin ligase has been identified as a mediator of skeletal muscle wasting in various skeletal muscle atrophy models, and its expression is upregulated by oxidative stress. Exercise training could decrease oxidative stress and restore the atrophied skeletal muscle. Here, our aim was to investigate whether exercise training has any effect on MuRF1 expression in rats with diabetes. MAIN METHODS Rats with streptozotocin-induced diabetes were subjected to exercise training, after which oxidative stress was determined, and MuRF1 expression was analyzed by immunohistochemistry, real-time RT-PCR and Western blot analysis. In addition, we analyzed C2C12 myotubes in an in vitro model to examine the effects of oxidative stress on the protein levels of MuRF1 and myosin heavy chain (MHC). KEY FINDINGS While oxidative stress and MuRF1 expression were increased in rats with diabetes, exercise training diminished the skeletal muscle wasting in diabetic rats by decreasing oxidative stress and inhibiting MuRF1 expression at both the mRNA and protein levels. In addition, oxidative stress-induced MuRF1 upregulation promoted proteasome dependent degradation of the myosin heavy chain (MHC) in C2C12 myotubes. SIGNIFICANCE Our study provides the first evidence that the beneficial anti-atrophy effects of exercise training on diabetes might be mediated by inhibiting oxidative stress-induced MuRF1 upregulation and preventing MuRF1-mediated degradation of MHC.
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Affiliation(s)
- Guo-Qing Chen
- Department of Health Science, Wuhan Institute of Physical Education, Luoyu Road No. 461, Wuhan City, Hubei Province, China
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163
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Jo C, Cho SJ, Jo SA. Mitogen-activated protein kinase kinase 1 (MEK1) stabilizes MyoD through direct phosphorylation at tyrosine 156 during myogenic differentiation. J Biol Chem 2011; 286:18903-13. [PMID: 21454680 DOI: 10.1074/jbc.m111.225128] [Citation(s) in RCA: 22] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Previously, we reported that mitogen-activated protein kinase kinase 1 (MEK1) activated in the mid-stage of skeletal muscle differentiation promotes myogenic differentiation. To elucidate the molecular mechanism, we investigated an activity of MEK1 for MyoD. Activated MEK1 associates with MyoD in the nucleus of differentiating myoblasts. In vitro kinase assay using active MEK1, a (32)P-labeled protein band corresponding to GST-MyoD was observed but not to mutant GST-MyoD-Y156F. Tyrosine phosphorylation of endogenous MyoD was detected with a specific anti-pMyoD-Y156 antibody; however, this response was blocked by PD184352, a MEK-specific inhibitor. These results indicate that activated MEK1 phosphorylates the MyoD-Y156 residue directly. Interestingly, the protein level of mutant MyoD-Y156F decreased compared with that of wild type but was recovered in the presence of lactacystin, a proteasome inhibitor. The protein level of MyoD-Y156E, which mimics phosphorylation at Tyr-156, was above that of wild type, indicating that the phosphorylation protects MyoD from the ubiquitin proteasome-mediated degradation. In addition, the low protein level of MyoD-Y156F was recovered over that of wild type by an additional mutation at Leu-164, a critical binding residue of MAFbx/AT-1, a Skp, Cullin, F-box (SCF) E3-ubiquitin ligase. The amount of MyoD co-precipitated with MAFbx/AT-1 also was reduced in the presence of active MEK1. Thus, these results suggested that the phosphorylation probably interrupts the binding of MAFbx/AT-1 to MyoD and thereby increases its stability. Collectively, our results suggest that MEK1 activated in differentiating myoblasts stimulates muscle differentiation by phosphorylating MyoD-Y156, which results in MyoD stabilization.
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Affiliation(s)
- Chulman Jo
- Division of Brain Disease, Center for Biomedical Science, National Institutes of Health, Korea Center for Disease Control and Prevention, 187 Osongsaengmyeong2-ro, Gangoe-myeon, Cheongwon-gun, Chungcheongbuk-do 363-951, South Korea
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164
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Gautel M. Cytoskeletal protein kinases: titin and its relations in mechanosensing. Pflugers Arch 2011; 462:119-34. [PMID: 21416260 PMCID: PMC3114093 DOI: 10.1007/s00424-011-0946-1] [Citation(s) in RCA: 102] [Impact Index Per Article: 7.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/04/2011] [Revised: 02/15/2011] [Accepted: 02/18/2011] [Indexed: 12/22/2022]
Abstract
Titin, the giant elastic ruler protein of striated muscle sarcomeres, contains a catalytic kinase domain related to a family of intrasterically regulated protein kinases. The most extensively studied member of this branch of the human kinome is the Ca2+–calmodulin (CaM)-regulated myosin light-chain kinases (MLCK). However, not all kinases of the MLCK branch are functional MLCKs, and about half lack a CaM binding site in their C-terminal autoinhibitory tail (AI). A unifying feature is their association with the cytoskeleton, mostly via actin and myosin filaments. Titin kinase, similar to its invertebrate analogue twitchin kinase and likely other “MLCKs”, is not Ca2+–calmodulin-activated. Recently, local protein unfolding of the C-terminal AI has emerged as a common mechanism in the activation of CaM kinases. Single-molecule data suggested that opening of the TK active site could also be achieved by mechanical unfolding of the AI. Mechanical modulation of catalytic activity might thus allow cytoskeletal signalling proteins to act as mechanosensors, creating feedback mechanisms between cytoskeletal tension and tension generation or cellular remodelling. Similar to other MLCK-like kinases like DRAK2 and DAPK1, TK is linked to protein turnover regulation via the autophagy/lysosomal system, suggesting the MLCK-like kinases have common functions beyond contraction regulation.
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Affiliation(s)
- Mathias Gautel
- King's College London BHF Centre of Research Excellence, Cardiovascular Division, London, SE1 1UL, UK.
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165
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Pellegrino MA, Desaphy JF, Brocca L, Pierno S, Camerino DC, Bottinelli R. Redox homeostasis, oxidative stress and disuse muscle atrophy. J Physiol 2011; 589:2147-60. [PMID: 21320887 DOI: 10.1113/jphysiol.2010.203232] [Citation(s) in RCA: 100] [Impact Index Per Article: 7.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/27/2022] Open
Abstract
A pivotal role has been ascribed to oxidative stress in determining the imbalance between protein synthesis and degradation leading to muscle atrophy in many pathological conditions and in disuse. However, a large variability in disuse-induced alteration of redox homeostasis through muscles, models and species emerges from the literature. Whereas the causal role of oxidative stress appears well established in the mechanical ventilation model, findings are less compelling in the hindlimb unloaded mice and very limited in humans. The mere coexistence of muscle atrophy, indirect indexes of increased reactive oxygen species (ROS) production and impairment of antioxidant defence systems, in fact, does not unequivocally support a causal role of oxidative stress in the phenomenon. We hypothesise that in some muscles, models and species only, due to a large redox imbalance, the leading phenomena are activation of proteolysis and massive oxidation of proteins, which would become more susceptible to degradation. In other conditions, due to a lower extent and variable time course of ROS production, different ROS-dependent, but also -independent intracellular pathways might dominate determining the variable extent of atrophy and even dispensable protein oxidation. The ROS production and removal are complex and finely tuned phenomena. They are indeed important intracellular signals and redox balance maintains normal muscle homeostasis and can underlie either positive or negative adaptations to exercise. A precise approach to determine the levels of ROS in living cells in various conditions appears to be of paramount importance to define and support such hypotheses.
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166
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Dysregulation and cellular mislocalization of specific miRNAs in myotonic dystrophy type 1. Neuromuscul Disord 2011; 21:81-8. [DOI: 10.1016/j.nmd.2010.11.012] [Citation(s) in RCA: 93] [Impact Index Per Article: 7.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/20/2010] [Revised: 11/15/2010] [Accepted: 11/22/2010] [Indexed: 12/23/2022]
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167
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Marimuthu K, Murton AJ, Greenhaff PL. Mechanisms regulating muscle mass during disuse atrophy and rehabilitation in humans. J Appl Physiol (1985) 2011; 110:555-60. [PMID: 21030670 DOI: 10.1152/japplphysiol.00962.2010] [Citation(s) in RCA: 70] [Impact Index Per Article: 5.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
Muscle mass loss accompanies periods of bedrest and limb immobilization in humans and requires rehabilitation exercise to effectively restore mass and function. Although recent evidence points to an early and transient rise in muscle protein breakdown contributing to this decline in muscle mass, the driving factor seems to be a reduction in muscle protein synthesis, not least in part due to the development of anabolic resistance to amino acid provision. Although the AKT signaling pathway has been identified in small animals as central to the regulation of muscle protein synthesis, several studies in humans have now demonstrated a disassociation between AKT signaling and muscle protein synthesis during feeding, exercise, and immobilization, suggesting that the mechanisms regulating protein synthesis in human skeletal muscle are more complex than initially thought (at least in non-inflammatory states). During rehabilitation, exercise-induced myogenesis may in part be responsible for the recovery of muscle mass. Rapid and sustained exercise-induced suppression of myostatin mRNA expression, that precedes any gain in muscle mass, points to this, along with other myogenic proteins, as being potential regulators of muscle regeneration during exercise rehabilitation in humans.
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Affiliation(s)
- Kanagaraj Marimuthu
- The School of Biomedical Sciences, The Univ. of Nottingham Medical School, Queen's Medical Centre, Nottingham, NG7 2UH, UK
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168
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Abstract
PURPOSE OF REVIEW The review summarizes and discusses the proposed new definitions for sarcopenia and cachexia. It also highlights the overlapping of both conditions and the fact that these conditions frequently occur in elderly patients. RECENT FINDINGS Sarcopenia is now recognized as a multifactorial geriatric syndrome. Cachexia is defined as a metabolic syndrome in which inflammation is the key feature and so cachexia can be an underlying condition of sarcopenia. Recently, cachexia has been defined as 'a complex metabolic syndrome associated with underlying illness and characterized by loss of muscle mass with or without loss of fat mass. The prominent clinical feature of cachexia is weight loss in adults'. Different recommendations have been proposed for the diagnosis of sarcopenia. At present, all definitions combine an assessment of muscle mass and muscle function (strength or physical performances such as gait speed). However, the relevance and the validation of these evolving definitions need to be assessed in future studies. SUMMARY Although the recent definitions of sarcopenia and cachexia boost research in the field and define distinct entities, the cause behind the loss of muscle mass (whether cachexia or sarcopenia) may, however, be indistinguishable in clinical practice. Therefore, new therapeutic approaches, alone or in combination, could be targeted on both conditions.
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Affiliation(s)
- Yves Rolland
- Inserm U558, University of Toulouse III, France.
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169
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Lin WS, Lu KM, Chung MH, Liu ST, Chen HH, Chang YL, Wang WM, Huang SM. The subcellular localization and protein stability of mouse alpha-actinin 2 is controlled by its nuclear receptor binding motif in C2C12 cells. Int J Biochem Cell Biol 2010; 42:2082-91. [DOI: 10.1016/j.biocel.2010.09.024] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/11/2010] [Revised: 09/09/2010] [Accepted: 09/30/2010] [Indexed: 01/10/2023]
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170
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Puthucheary Z, Montgomery H, Moxham J, Harridge S, Hart N. Structure to function: muscle failure in critically ill patients. J Physiol 2010; 588:4641-8. [PMID: 20961998 DOI: 10.1113/jphysiol.2010.197632] [Citation(s) in RCA: 64] [Impact Index Per Article: 4.6] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/13/2022] Open
Abstract
Impaired physical function and reduced physical activity are common findings in intensive care unit (ICU) survivors. More importantly, reduced muscle strength during critical illness is an independent predictor of survival. Skeletal muscle wasting as a direct consequence of critical illness has been suggested as the cause. However, data on the physiological processes regulating muscle mass, and function, in these critically ill patients are limited as this is not only a technically challenging research area, but also the heterogeneity of the patient group adds complexity to the interpretation of results. Despite this, clinical and research interest in this area is growing. This article highlights the issues involved in measurement of muscle function and mass in critically ill patients and the physiological complexities involved in studying these patients. Although the data are limited, this article reviews the animal and healthy human data providing a rational approach to the potential pathophysiological mechanisms involved in muscle mass regulation in critically ill patients, including the established muscle wasting 'risk factors' such as ageing, immobility and systemic inflammation, all of which are common findings in the general critical care population.
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Affiliation(s)
- Zudin Puthucheary
- Institute for Human Health and Performance, University College London and Division of Asthma Allergy and Lung Biology, Kings College London, London, UK.
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171
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Skeletal muscle dysfunction in critical care: Wasting, weakness, and rehabilitation strategies. Crit Care Med 2010; 38:S676-82. [DOI: 10.1097/ccm.0b013e3181f2458d] [Citation(s) in RCA: 74] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/13/2022]
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172
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Jones A, Hwang DJ, Narayanan R, Miller DD, Dalton JT. Effects of a novel selective androgen receptor modulator on dexamethasone-induced and hypogonadism-induced muscle atrophy. Endocrinology 2010; 151:3706-19. [PMID: 20534726 DOI: 10.1210/en.2010-0150] [Citation(s) in RCA: 48] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/12/2022]
Abstract
Glucocorticoids are the most widely used antiinflammatory drugs in the world. However, prolonged use of glucocorticoids results in undesirable side effects such as muscle wasting, osteoporosis, and diabetes. Skeletal muscle wasting, which currently has no approved therapy, is a debilitating condition resulting from either reduced muscle protein synthesis or increased degradation. The imbalance in protein synthesis could occur from increased expression and function of muscle-specific ubiquitin ligases, muscle atrophy F-box (MAFbx)/atrogin-1 and muscle ring finger 1 (MuRF1), or decreased function of the IGF-I and phosphatidylinositol-3 kinase/Akt kinase pathways. We examined the effects of a nonsteroidal tissue selective androgen receptor modulator (SARM) and testosterone on glucocorticoid-induced muscle atrophy and castration-induced muscle atrophy. The SARM and testosterone propionate blocked the dexamethasone-induced dephosphorylation of Akt and other proteins involved in protein synthesis, including Forkhead box O (FoxO). Dexamethasone caused a significant up-regulation in the expression of ubiquitin ligases, but testosterone propionate and SARM administration blocked this effect by phosphorylating FoxO. Castration induced rapid myopathy of the levator ani muscle, accompanied by up-regulation of MAFbx and MuRF1 and down-regulation of IGF-I, all of which was attenuated by a SARM. The results suggest that levator ani atrophy caused by hypogonadism may be the result of loss of IGF-I stimulation, whereas that caused by glucocorticoid treatment relies almost solely on up-regulation of MAFbx and MuRF1. Our studies provide the first evidence that glucocorticoid- and hypogonadism-induced muscle atrophy are mediated by distinct but overlapping mechanisms and that SARMs may provide a more effective and selective pharmacological approach to prevent glucocorticoid-induced muscle loss than steroidal androgen therapy.
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Affiliation(s)
- Amanda Jones
- Division of Pharmaceutics, College of Pharmacy, The Ohio State University, Columbus, Ohio 43210, USA
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173
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Disuse of the musculo-skeletal system in space and on earth. Eur J Appl Physiol 2010; 111:403-20. [PMID: 20617334 DOI: 10.1007/s00421-010-1556-x] [Citation(s) in RCA: 137] [Impact Index Per Article: 9.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 06/18/2010] [Indexed: 10/19/2022]
Abstract
Muscle mass and strength are well known to decline in response to actual and simulated microgravity exposure. However, despite the considerable knowledge gained on the physiological changes induced by spaceflight, the mechanisms of muscle atrophy and the effectiveness of in-flight countermeasures still need to be fully elucidated. The present review examines the effects and mechanisms of actual and simulated microgravity on single fibre and whole muscle structural and functional properties, protein metabolism, tendon mechanical properties, neural drive and reflex excitability. The effects of inflight countermeasures are also discussed in the light of recent advances in resistive loading techniques, in combined physical, pharmacological and nutritional interventions as well as in the development of artificial gravity systems. Emphasis has been given to the pioneering work of Pietro Enrico di Prampero in the development of artificial gravity systems and in the progress of knowledge on the limits of human muscular performance in space.
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174
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Lang CH, Frost RA, Bronson SK, Lynch CJ, Vary TC. Skeletal muscle protein balance in mTOR heterozygous mice in response to inflammation and leucine. Am J Physiol Endocrinol Metab 2010; 298:E1283-94. [PMID: 20388826 PMCID: PMC2886531 DOI: 10.1152/ajpendo.00676.2009] [Citation(s) in RCA: 48] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/22/2022]
Abstract
Sepsis and lipopolysaccharide (LPS) may decrease skeletal muscle protein synthesis by impairing mTOR (mammalian target of rapamycin) activity. The role of mTOR in regulating muscle protein synthesis was assessed in wild-type (WT) and mTOR heterozygous (+/-) mice under basal conditions and in response to LPS and/or leucine stimulation. No difference in body weight of mTOR(+/-) mice was observed compared with WT mice; whereas whole body lean body mass was reduced. Gastrocnemius weight was decreased in mTOR(+/-) mice, which was attributable in part to a reduced rate of basal protein synthesis. LPS decreased muscle protein synthesis in WT and mTOR(+/-) mice to the same extent. Reduced muscle protein synthesis in mTOR(+/-) mice under basal and LPS-stimulated conditions was associated with lower 4E-BP1 and S6K1 phosphorylation. LPS also decreased PRAS40 phosphorylation and increased phosphorylation of raptor and IRS-1 (Ser(307)) to the same extent in WT and mTOR(+/-) mice. Muscle atrogin-1 and MuRF1 mRNA content was elevated in mTOR(+/-) mice under basal conditions, implying increased ubiquitin-proteasome-mediated proteolysis, but the LPS-induced increase in these atrogenes was comparable between groups. Plasma insulin and IGF-I as well as tissue expression of TNFalpha, IL-6, or NOS2 did not differ between WT and mTOR(+/-) mice. Finally, whereas LPS impaired the ability of leucine to stimulate muscle protein synthesis and 4E-BP1 phosphorylation in WT mice, this inflammatory state rendered mTOR(+/-) mice leucine unresponsive. These data support the idea that the LPS-induced reduction in mTOR activity is relatively more important in regulating skeletal muscle mass in response to nutrient stimulation than under basal conditions.
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Affiliation(s)
- Charles H Lang
- Department of Cellular and Molecular Physiology, The Pennsylvania State University College of Medicine, Hershey, PA 17033, USA.
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175
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Abstract
PURPOSE OF REVIEW The purpose of this review is to discuss recent findings as they pertain to anabolic and catabolic-signaling pathways involved in the regulation of adult skeletal muscle mass. RECENT FINDINGS Research conducted over the past few years has continued to refine our understanding of the pathways that govern skeletal muscle mass, in particular the mTOR, FoxO and NF-kappaB pathways. Alternative signaling pathways have also emerged as important regulators of muscle mass such as the beta-catenin pathway. SUMMARY A better understanding of the anabolic and catabolic processes which regulate skeletal muscle mass is critical for the development of more effective therapeutics to prevent the loss of muscle with disuse, aging and disease.
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Affiliation(s)
| | - Karyn A. Esser
- Correspondence Karyn A. Esser Department of Physiology College of Medicine, University of Kentucky 800 S. Rose St. Lexington, KY 40536-0298 Tel: (859) 323-8107 Fax: 859-323-1070
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176
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Rusconi F, Mancinelli E, Colombo G, Cardani R, Da Riva L, Bongarzone I, Meola G, Zippel R. Proteome profile in Myotonic Dystrophy type 2 myotubes reveals dysfunction in protein processing and mitochondrial pathways. Neurobiol Dis 2010; 38:273-80. [DOI: 10.1016/j.nbd.2010.01.017] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/06/2009] [Revised: 01/19/2010] [Accepted: 01/27/2010] [Indexed: 02/07/2023] Open
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178
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Murton AJ, Greenhaff PL. Physiological control of muscle mass in humans during resistance exercise, disuse and rehabilitation. Curr Opin Clin Nutr Metab Care 2010; 13:249-54. [PMID: 20110809 DOI: 10.1097/mco.0b013e3283374d19] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/26/2022]
Abstract
PURPOSE OF REVIEW The preservation of skeletal muscle mass is central to maintaining mobility and quality of life with aging and also impacts on our capacity to recover from illness. However, our understanding of the processes that regulate muscle mass in humans during exercise, chronic disuse and rehabilitation remains unclear. This brief review aims to highlight some of the more recent and important findings concerning these physiological stimuli. RECENT FINDINGS Although several studies have detailed the molecular events that occur following an acute bout of resistance exercise, a paucity of data appears to remain concerning the molecular and signaling events that underpin resistance exercise training. Reports of increased transcripts for inflammatory proteins following eccentric but not concentric exercise could represent the stimulus for the instigation of structural adaptations that occur following intense muscle lengthening contractions. Studies investigating processes underlying disuse-induced muscle atrophy provide initial evidence to support the notion that transient increases in muscle protein degradation occur following the onset of muscle disuse in humans. SUMMARY The need for further studies to improve our basic understanding of muscle-associated processes in humans remains, particularly in relation to the temporal changes in muscle processes that occur during resistance training.
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Affiliation(s)
- Andrew J Murton
- School of Biomedical Sciences, The University of Nottingham, Queen's Medical Centre, Nottingham, UK.
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179
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Setsuie R, Suzuki M, Tsuchiya Y, Wada K. Skeletal muscles of Uchl3 knockout mice show polyubiquitinated protein accumulation and stress responses. Neurochem Int 2010; 56:911-8. [PMID: 20380862 DOI: 10.1016/j.neuint.2010.03.021] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/25/2009] [Revised: 03/27/2010] [Accepted: 03/31/2010] [Indexed: 10/19/2022]
Abstract
Ubiquitin C-terminal hydrolase (UCH)-L3 is an enzyme with a strongly suggested de-ubiquitinating function by in vitro studies, but has poorly been investigated in vivo. In this study, we show that skeletal muscles of Uchl3(-/-) mice exhibit the up-regulation of cleaved ATF6, Grp78, and PDI as well as HSP27, HSP70, HSP90 and HSP110, which indicate the induction of stress responses. The prominent accumulation of polyubiquitinated proteins, one of the factors reported to induce stress responses, was observed in the skeletal muscle of Uchl3(-/-) mice. Mouse embryonic fibroblasts (MEFs) from Uchl3(-/-) mice also showed an accumulation of polyubiquitinated proteins. Moreover, the polyubiquitinated protein accumulation in Uchl3(-/-) MEFs was attenuated by the exogenous expression of wild-type, but not hydrolase activity deficient, UCH-L3. In addition, wild-type, but not its hydrolase activity or ubiquitin binding activity deficient UCH-L3 showed the ability to cleave ubiquitin from polyubiquitinated lysozyme in vitro. These results suggest that UCH-L3 functions as a de-ubiquitinating enzyme in vivo where lack of its hydrolase activity may result in the prominent accumulation of ubiquitinated proteins and subsequent induction of stress responses in skeletal muscle.
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Affiliation(s)
- Rieko Setsuie
- Department of Degenerative Neurological Diseases, National Institute of Neuroscience, National Center of Neurology and Psychiatry, 4-1-1 Ogawahigashi, Kodaira, Tokyo 187-8502, Japan
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180
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Abstract
Doxorubicin (Dox) is a very potent anticancer agent, but its use is limited by its dose-dependent, irreversible cardiotoxicity. Despite intensive research efforts, the mechanism of Dox cardiotoxicity remains poorly understood, so very limited means are available for its prevention or effective management. Recent studies have revealed that a therapeutic dose of Dox can activate proteolysis in cardiomyocytes that is mediated by the ubiquitin-proteasome system (UPS), and that the UPS-mediated degradation of a number of pivotal cardiac transcription factors and/or survival factors is enhanced by Dox treatment. These findings suggest that Dox-induced UPS activation may represent a new mechanism underlying Dox cardiotoxicity. Notably, recent experimental studies suggest that proteasome activation promotes cardiac remodeling during hypertension. This review surveys the current literature on the impact of Dox on the UPS and the potential mechanisms by which UPS activation may compromise the heart during Dox therapy.
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181
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Abstract
Dysregulation of the UPS (ubiquitin-proteasome system) has been implicated in a wide range of pathologies including cancer, neurodegeneration and viral infection. Inhibiting the proteasome has been shown to be an effective therapeutic strategy in humans; however, toxicity with this target remains high. E3s (Ub-protein ligases) represent an alternative attractive therapeutic target in the UPS. In this paper, we will discuss current platforms that report on E3 ligase activity and can detect E3 inhibitors, and underline the advantages and disadvantages of each approach.
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182
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Abstract
Sarcopenia reflects a progressive withdrawal of anabolism and an increased catabolism, along with a reduced muscle regeneration capacity. Muscle force and power decline more than muscle dimensions: older muscle is intrinsically weak. Sarcopenic obesity (SO) among the elderly corroborates to the loss of muscle mass increasing the risk of metabolic syndrome development. Recent studies on the musculoskeletal adaptations with ageing and key papers on the mechanisms of muscle wasting, its functional repercussions and on SO are included. Neuropathic, hormonal, immunological, nutritional and physical activity factors contribute to sarcopenia. Selective fast fibre atrophy, loss of motor units and an increase in hybrid fibres are typical findings of ageing. Satellite cell number decreases reducing muscle regeneration capacity. SO promotes further muscle wasting and increases risk of metabolic syndrome development. The proportion of fast to slow fibres seems maintained in old age. In elderly humans, nuclear domain is maintained constant. Basal protein synthesis and breakdown show little changes in old age. Instead, blunting of the anabolic response to feeding and exercise and of the antiproteolytic effect of insulin is observed. Further understanding of the mechanisms of sarcopenia requires disentangling of the effects of ageing alone from those of disuse and disease. The causes of the greater anabolic resistance to feeding and exercise of elderly women need elucidating. The enhancement of muscle regeneration via satellite cell activation via the MAPK/notch molecular pathways seems particularly promising.
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Affiliation(s)
- Marco V Narici
- Faculty of Science and Engineering, Institute for Biomedical Research into Human Movement and Health, Manchester Metropolitan University, John Dalton Building, Chester Street, Manchester, UK.
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183
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A new role for sterol regulatory element binding protein 1 transcription factors in the regulation of muscle mass and muscle cell differentiation. Mol Cell Biol 2009; 30:1182-98. [PMID: 20028734 DOI: 10.1128/mcb.00690-09] [Citation(s) in RCA: 62] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
The role of the transcription factors sterol regulatory element binding protein 1a (SREBP-1a) and SREBP-1c in the regulation of cholesterol and fatty acid metabolism has been well studied; however, little is known about their specific function in muscle. In the present study, analysis of recent microarray data from muscle cells overexpressing SREBP1 suggested that they may play a role in the regulation of myogenesis. We then demonstrated that SREBP-1a and -1c inhibit myoblast-to-myotube differentiation and also induce in vivo and in vitro muscle atrophy. Furthermore, we have identified the transcriptional repressors BHLHB2 and BHLHB3 as mediators of these effects of SREBP-1a and -1c in muscle. Both repressors are SREBP-1 target genes, and they affect the expression of numerous genes involved in the myogenic program. Our findings identify a new role for SREBP-1 transcription factors in muscle, thus linking the control of muscle mass to metabolic pathways.
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184
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Op den Kamp CM, Langen RC, Haegens A, Schols AM. Muscle atrophy in cachexia: can dietary protein tip the balance? Curr Opin Clin Nutr Metab Care 2009; 12:611-6. [PMID: 19741519 DOI: 10.1097/mco.0b013e3283319399] [Citation(s) in RCA: 22] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/02/2023]
Abstract
PURPOSE OF REVIEW To review the efficacy of dietary protein supplementation in attenuating muscle atrophy in cachexia. RECENT FINDINGS Only very few recent randomized controlled trials have studied the effects of protein supplementation in clinical cachexia. It appears that supplementation of dietary protein (>1.5 g/kg per day) alone or in combination with other anabolic stimuli such as exercise training maintains or even improves muscle mass, but results on muscle function are controversial and no clinical studies have yet directly linked alterations in cellular signaling or metabolic signatures of protein intake-induced muscle anabolism to muscle weight gain. SUMMARY To elucidate the role of dietary protein supplementation in attenuating muscle atrophy in cachectic patients, randomized clinical trials are needed in adequately phenotyped patients using sensitive measures of muscle mass and function.
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Affiliation(s)
- Céline M Op den Kamp
- Department of Respiratory Medicine, NUTRIM School for Nutrition, Toxicology & Metabolism, Maastricht University Medical Centre +, NL-6202 AZ Maastricht, The Netherlands
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185
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186
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McGee SL, Hargreaves M. Histone modifications and skeletal muscle metabolic gene expression. Clin Exp Pharmacol Physiol 2009; 37:392-6. [PMID: 19793100 DOI: 10.1111/j.1440-1681.2009.05311.x] [Citation(s) in RCA: 36] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/13/2022]
Abstract
1. Skeletal muscle oxidative function and metabolic gene expression are co-ordinately downregulated in metabolic diseases such as insulin resistance, obesity and Type 2 diabetes. Altering skeletal muscle metabolic gene expression to favour enhanced energy expenditure is considered a potential therapy to combat these diseases. 2. Histone deacetylases (HDACs) are chromatin-remodelling enzymes that repress gene expression. It has been shown that HDAC4 and 5 co-operatively regulate a number of genes involved in various aspects of metabolism. Understanding how HDACs are regulated provides insights into the mechanisms regulating skeletal muscle metabolic gene expression. 3. Multiple kinases control phosphorylation-dependent nuclear export of HDACs, rendering them unable to repress transcription. We have found a major role for the AMP-activated protein kinase (AMPK) in response to energetic stress, yet metabolic gene expression is maintained in the absence of AMPK activity. Preliminary evidence suggests a potential role for protein kinase D, also a Class IIa HDAC kinase, in this response. 4. The HDACs are also regulated by ubiquitin-mediated proteasomal degradation, although the exact mediators of this process have not been identified. 5. Because HDACs appear to be critical regulators of skeletal muscle metabolic gene expression, HDAC inhibition could be an effective therapy to treat metabolic diseases. 6. Together, these data show that HDAC4 and 5 are critical regulators of metabolic gene expression and that understanding their regulation could provide a number of points of intervention for therapies designed to treat metabolic diseases, such as insulin resistance, obesity and Type 2 diabetes.
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Affiliation(s)
- Sean L McGee
- School of Medicine, Deakin University, Geelong, Vic., Australia.
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187
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Current world literature. Curr Opin Neurol 2009; 22:554-61. [PMID: 19755870 DOI: 10.1097/wco.0b013e3283313b14] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/25/2022]
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188
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Li W, Moylan JS, Chambers MA, Smith J, Reid MB. Interleukin-1 stimulates catabolism in C2C12 myotubes. Am J Physiol Cell Physiol 2009; 297:C706-14. [PMID: 19625606 DOI: 10.1152/ajpcell.00626.2008] [Citation(s) in RCA: 113] [Impact Index Per Article: 7.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/01/2023]
Abstract
Interleukin-1 (IL-1) is an inflammatory cytokine that has been linked to muscle catabolism, a process regulated by muscle-specific E3 proteins of the ubiquitin-proteasome pathway. To address cellular mechanism, we tested the hypothesis that IL-1 induces myofibrillar protein loss by acting directly on muscle to increase expression of two critical E3 proteins, atrogin1/muscle atrophy F-box (MAFbx) and muscle RING-finger 1 (MuRF1). Experiments were conducted using mature C2C12 myotubes to eliminate systemic cytokine effects and avoid paracrine signaling by nonmuscle cell types. Time-course protocols were used to define the sequence of cellular responses. We found that atrogin1/MAFbx mRNA and MuRF1 mRNA are elevated 60-120 min after myotube exposure to either IL-1alpha or IL-1beta. These responses are preceded by signaling events that promote E3 expression. Both IL-1 isoforms stimulate phosphorylation of p38 mitogen-activated protein kinase and stimulate nuclear factor-kappaB (NF-kappaB) signaling; I-kappaB levels fall and NF-kappaB DNA binding activity increases. Other regulators of E3 expression are unaffected by IL-1 [cytosolic oxidant activity, Forkhead-O (Foxo) activity] or respond paradoxically (AKT). Chronic exposure of C2C12 myotubes over 48 h resulted in reduced myotube width and loss of sarcomeric actin. We conclude that IL-1alpha and IL-1beta act via an oxidant- and AKT/Foxo-independent mechanism to activate p38 MAPK, stimulate NF-kappaB signaling, increase expression of atrogin1/MAFbx and MuRF1, and reduce myofibrillar protein in differentiated myotubes.
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Affiliation(s)
- Wei Li
- Department of Physiology, University of Kentucky, Lexington, Kentucky 40536-0298, USA
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189
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Puthucheary Z, Hart N. Intensive care unit acquired muscle weakness: when should we consider rehabilitation? CRITICAL CARE : THE OFFICIAL JOURNAL OF THE CRITICAL CARE FORUM 2009; 13:167. [PMID: 19664190 PMCID: PMC2750140 DOI: 10.1186/cc7937] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Subscribe] [Scholar Register] [Indexed: 12/15/2022]
Abstract
Muscle weakness is highly prevalent during acute critical illness, with the poor exercise performance that occurs after critical illness being recognized as a consequence of skeletal muscles weakness. Advanced techniques to measure peripheral muscle strength are available, but they have limited use in the clinical setting. Simple volitional methods to assess strength are limited because they rely on patient motivation, which can be problematic in the critical care setting. At present, the mechanisms that underlie skeletal muscle wasting and weakness are poorly understood, but use of rehabilitation early in critical illness appears to have beneficial effects on outcome. The future direction will be to determine the underlying mechanisms as well as developing rehabilitation programmes during both the acute and the post critical illness stages.
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Affiliation(s)
- Zudin Puthucheary
- Lane Fox Respiratory Unit, Department of Critical Care, Guy's & St Thomas' NHS Foundation Trust, Westminster Bridge Road, London SE1 7EH, UK
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190
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Rennie MJ, Selby A, Atherton P, Smith K, Kumar V, Glover EL, Philips SM. Facts, noise and wishful thinking: muscle protein turnover in aging and human disuse atrophy. Scand J Med Sci Sports 2009; 20:5-9. [PMID: 19558380 DOI: 10.1111/j.1600-0838.2009.00967.x] [Citation(s) in RCA: 94] [Impact Index Per Article: 6.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
Surprisingly little is known about the mechanisms of muscle atrophy with aging and disuse in human beings, in contrast to rodents, from which much has been extrapolated to explain the human condition. However, this extrapolation is likely unwarranted because the time course, extent of wasting, muscle fiber involvement and alterations of muscle protein turnover are all quite different in rodent and human muscle. Furthermore, there is little evidence that static indices of protein turnover represent dynamic changes and may be misleading. With disuse there are reductions in the rate of muscle protein synthesis (MPS) large enough to explain the atrophic loss of muscle protein without a concomitant increase in proteolysis. In aging, there is no evidence that there are marked alterations in basal muscle protein turnover in healthy individuals but instead the ability to maintain muscle after feeding is compromised. This anabolic resistance is evident with physical inactivity, which exacerbates the inability to maintain muscle mass with aging. The main conclusion of this review is that in uncomplicated, non-inflammatory disuse atrophy, the facilitative change causing loss of muscle mass is a depression of MPS, exacerbated by anabolic resistance during feeding, with possible adaptive depressions, rather than increases, of muscle proteolysis.
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Affiliation(s)
- M J Rennie
- School of Graduate Entry Medicine and Health, City Hospital, University of Nottingham, Derby, UK.
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191
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Jung R, Wendeler MW, Danevad M, Himmelbauer H, Geßner R. Phylogenetic origin of LI-cadherin revealed by protein and gene structure analysis. Cell Mol Life Sci 2004; 61:1157-66. [PMID: 15141301 PMCID: PMC11138757 DOI: 10.1007/s00018-004-3470-z] [Citation(s) in RCA: 18] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/04/2023]
Abstract
The intestine specific LI-cadherin differs in its overall structure from classical and desmosomal cadherins by the presence of seven instead of five cadherin repeats and a short cytoplasmic domain. Despite the low sequence similarity, a comparative protein structure analysis revealed that LI-cadherin may have originated from a five-repeat predecessor cadherin by a duplication of the first two aminoterminal repeats. To test this hypothesis, we cloned the murine LI-cadherin gene and compared its structure to that of other cadherins. The intron-exon organization, including the intron positions and phases, is perfectly conserved between repeats 3-7 of LI-cadherin and 1-5 of classical cadherins. Moreover, the genomic structure of the repeats 1-2 and 3-4 is identical for LI-cadherin and highly similar to that of the repeats 1-2 of classical cadherins. These findings strengthen our assumption that LI-cadherin originated from an ancestral cadherin with five domains by a partial gene duplication event.
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Affiliation(s)
- R. Jung
- Institute of Laboratory Medicine and Biochemistry, Virchow-Hospital of Charité Medical School, Humboldt University of Berlin, Augustenburger Platz 1, 13353 Berlin, Germany
- Schering AG, Müllerstr. 178, 13342 Berlin, Germany
| | - M. W. Wendeler
- Institute of Laboratory Medicine and Biochemistry, Virchow-Hospital of Charité Medical School, Humboldt University of Berlin, Augustenburger Platz 1, 13353 Berlin, Germany
| | - M. Danevad
- Institute of Laboratory Medicine and Biochemistry, Virchow-Hospital of Charité Medical School, Humboldt University of Berlin, Augustenburger Platz 1, 13353 Berlin, Germany
| | - H. Himmelbauer
- Max-Planck-Institute of Molecular Genetics, Ihnestr. 73, 14195 Berlin, Germany
| | - R. Geßner
- Institute of Laboratory Medicine and Biochemistry, Virchow-Hospital of Charité Medical School, Humboldt University of Berlin, Augustenburger Platz 1, 13353 Berlin, Germany
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