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Rozhkov SV, Sharlo KA, Shenkman BS, Mirzoev TM. Inhibition of mTORC1 differentially affects ribosome biogenesis in rat soleus muscle at the early and later stages of hindlimb unloading. Arch Biochem Biophys 2022; 730:109411. [PMID: 36155780 DOI: 10.1016/j.abb.2022.109411] [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: 06/21/2022] [Revised: 07/29/2022] [Accepted: 09/19/2022] [Indexed: 11/02/2022]
Abstract
Prolonged inactivity of skeletal muscles due to limb immobilization, bedrest, and exposure to microgravity results in a significant muscle atrophy. Inactivity-induced muscle atrophy is caused by a downregulation of protein synthesis (PS) and increased proteolysis. Mechanistic target of rapamycin complex 1 (mTORC1) is considered to be one of the main regulators of translational capacity (quantity of ribosomes), a key determinant of PS. Using a specific mTORC1 inhibitor (rapamycin) we aimed to determine if mTORC1 activity would influence ribosome biogenesis in rat soleus muscle at both early and later stages of mechanical unloading. Wistar rats were subjected to 1- and 7-day hindlimb suspension (HS) with and without rapamycin injections (1.5 mg/kg) and compared to weight-bearing control animals. The key markers of ribosome biogenesis were assessed by RT-PCR or agarose gel electrophoresis. The rate of PS was measured by SUnSET method. Both 1-day and 7-day HS resulted in a significant downregulation of ribosome biogenesis markers (c-Myc, 47S pre-rRNA, 18S + 28S rRNAs) and the rate of PS. Rapamycin administration during 1-day HS fully prevented a decrease in 47S pre-rRNA expression and amount of 18S + 28S rRNAs (without affecting c-Myc mRNA expression) and partially attenuated a decline in PS. Rapamycin treatment during 7-day HS significantly decreased p70S6K phosphorylation but failed to rescue a reduction in both the markers of ribosome biogenesis and the rate of PS. All together, our results suggest that mTORC1 inhibition at the initial (1 day), but not later (7 days) stage of HS can be beneficial for the maintenance of translational capacity (ribosome biogenesis) and the rate of PS in rat soleus muscle.
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Affiliation(s)
- Sergey V Rozhkov
- Myology Laboratory, Institute of Biomedical Problems RAS, 123007, 76A Khoroshevskoe shosse, Moscow, Russia
| | - Kristina A Sharlo
- Myology Laboratory, Institute of Biomedical Problems RAS, 123007, 76A Khoroshevskoe shosse, Moscow, Russia
| | - Boris S Shenkman
- Myology Laboratory, Institute of Biomedical Problems RAS, 123007, 76A Khoroshevskoe shosse, Moscow, Russia
| | - Timur M Mirzoev
- Myology Laboratory, Institute of Biomedical Problems RAS, 123007, 76A Khoroshevskoe shosse, Moscow, Russia.
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2
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Belova SP, Tyganov SA, Mochalova EP, Shenkman BS. Restricted Activity and Protein Synthesis
in Postural and Locomotor Muscles. J EVOL BIOCHEM PHYS+ 2021. [DOI: 10.1134/s0022093021030194] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/30/2023]
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3
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Mirzoev TM, Shenkman BS. Regulation of Protein Synthesis in Inactivated Skeletal Muscle: Signal Inputs, Protein Kinase Cascades, and Ribosome Biogenesis. BIOCHEMISTRY (MOSCOW) 2018; 83:1299-1317. [PMID: 30482143 DOI: 10.1134/s0006297918110020] [Citation(s) in RCA: 14] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/16/2022]
Abstract
Disuse atrophy of skeletal muscles is characterized by a significant decrease in the mass and size of muscle fibers. Disuse atrophy develops as a result of prolonged reduction in the muscle functional activity caused by bed rest, limb immobilization, and real or simulated microgravity. Disuse atrophy is associated with the downregulation of protein biosynthesis and simultaneous activation of protein degradation. This review is focused on the key molecular mechanisms regulating the rate of protein synthesis in mammalian skeletal muscles during functional unloading.
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Affiliation(s)
- T M Mirzoev
- Institute of Biomedical Problems, Russian Academy of Sciences, Moscow, 123007, Russia.
| | - B S Shenkman
- Institute of Biomedical Problems, Russian Academy of Sciences, Moscow, 123007, Russia
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4
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Mitrou GI, Sakkas GK, Poulianiti KP, Karioti A, Tepetes K, Christodoulidis G, Giakas G, Stefanidis I, Geeves MA, Koutedakis Y, Karatzaferi C. Evidence of functional deficits at the single muscle fiber level in experimentally-induced renal insufficiency. J Biomech 2018; 82:259-265. [PMID: 30447801 DOI: 10.1016/j.jbiomech.2018.10.035] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/28/2016] [Revised: 10/27/2018] [Accepted: 10/30/2018] [Indexed: 11/27/2022]
Abstract
Chronic kidney disease patients present with metabolic and functional muscle abnormalities, called uremic myopathy, whose mechanisms have not yet been fully elucidated. We investigated whether chronic renal insufficiency (CRI) affects skeletal muscle contractile properties at the cellular level. CRI was induced surgically in New Zealand rabbits (UREM), with sham-operation for controls (CON), and samples were collected at 3 months post-surgery, following euthanasia. All protocols had University Ethics approval following national and European guidelines. Sample treatments and evaluations were blinded. Maximal isometric force was assessed in 382 permeabilized psoas fibers (CON, n = 142, UREM, n = 240) initially at pH7, 10 °C ('standard' conditions), in subsets of fibers in acidic conditions (pH6.2, 10 °C) but also at near physiological temperature (pH7, 30 °C and pH6.2, 30 °C). CRI resulted in significant smaller average cross sectional areas (CSAs) by ∼11% for UREM muscle fibers (vs CON, P < 0.01). At standard conditions, UREM fibers produced lower absolute and specific forces (i.e. normalized force per fiber CSA) (vs CON, P < 0.01); force increased in 30 °C for both groups (P < 0.01), but the disparity between UREM and CON remained significant. Acidosis significantly reduced force (vs pH7, 10 °C P < 0.01), similarly in both groups (in UREM by -48% and in CON by -43%, P > 0.05). For the first time, we give evidence that CRI can induce significant impairments in single psoas muscle fibers force generation, only partly explained by fiber atrophy, thus affecting muscle mechanics at the cellular level.
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Affiliation(s)
- Georgia I Mitrou
- Muscle Physiology & Mechanics Group, CREHP, DPESS, University of Thessaly, Trikala, Greece; Faculty of Sport and Health Sciences, University of St Mark and St John (Marjon), Plymouth, United Kingdom
| | - Giorgos K Sakkas
- Muscle Physiology & Mechanics Group, CREHP, DPESS, University of Thessaly, Trikala, Greece; Institute for Research and Technology Thessaly-CERTH, Trikala, Greece; Faculty of Sport and Health Sciences, University of St Mark and St John (Marjon), Plymouth, United Kingdom
| | | | - Aggeliki Karioti
- Muscle Physiology & Mechanics Group, CREHP, DPESS, University of Thessaly, Trikala, Greece
| | - Konstantinos Tepetes
- Department of Surgery, Faculty of Medicine, University of Thessaly, Larissa, Greece
| | | | - Giannis Giakas
- Institute for Research and Technology Thessaly-CERTH, Trikala, Greece; Human Performance Group, CREHP, DPESS, University of Thessaly, Trikala, Greece
| | - Ioannis Stefanidis
- Department of Nephrology, Faculty of Medicine, University of Thessaly, Larissa, Greece
| | | | - Yiannis Koutedakis
- Human Performance Group, CREHP, DPESS, University of Thessaly, Trikala, Greece; Institute for Research and Technology Thessaly-CERTH, Trikala, Greece; School of Sport, Performing Arts and Leisure, Wolverhampton University, United Kingdom
| | - Christina Karatzaferi
- Muscle Physiology & Mechanics Group, CREHP, DPESS, University of Thessaly, Trikala, Greece; Institute for Research and Technology Thessaly-CERTH, Trikala, Greece; Faculty of Sport and Health Sciences, University of St Mark and St John (Marjon), Plymouth, United Kingdom.
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5
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Pierre N, Appriou Z, Gratas-Delamarche A, Derbré F. From physical inactivity to immobilization: Dissecting the role of oxidative stress in skeletal muscle insulin resistance and atrophy. Free Radic Biol Med 2016; 98:197-207. [PMID: 26744239 DOI: 10.1016/j.freeradbiomed.2015.12.028] [Citation(s) in RCA: 20] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 10/31/2015] [Revised: 12/23/2015] [Accepted: 12/24/2015] [Indexed: 12/16/2022]
Abstract
In the literature, the terms physical inactivity and immobilization are largely used as synonyms. The present review emphasizes the need to establish a clear distinction between these two situations. Physical inactivity is a behavior characterized by a lack of physical activity, whereas immobilization is a deprivation of movement for medical purpose. In agreement with these definitions, appropriate models exist to study either physical inactivity or immobilization, leading thereby to distinct conclusions. In this review, we examine the involvement of oxidative stress in skeletal muscle insulin resistance and atrophy induced by, respectively, physical inactivity and immobilization. A large body of evidence demonstrates that immobilization-induced atrophy depends on the chronic overproduction of reactive oxygen and nitrogen species (RONS). On the other hand, the involvement of RONS in physical inactivity-induced insulin resistance has not been investigated. This observation outlines the need to elucidate the mechanism by which physical inactivity promotes insulin resistance.
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Affiliation(s)
- Nicolas Pierre
- EA1274 Laboratory "Movement, Sport and Health Sciences" M2S, Rennes 2 University - ENS Rennes, Bruz, France
| | - Zephyra Appriou
- EA1274 Laboratory "Movement, Sport and Health Sciences" M2S, Rennes 2 University - ENS Rennes, Bruz, France
| | - Arlette Gratas-Delamarche
- EA1274 Laboratory "Movement, Sport and Health Sciences" M2S, Rennes 2 University - ENS Rennes, Bruz, France
| | - Frédéric Derbré
- EA1274 Laboratory "Movement, Sport and Health Sciences" M2S, Rennes 2 University - ENS Rennes, Bruz, France.
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Ryder DJ, Judge SM, Beharry AW, Farnsworth CL, Silva JC, Judge AR. Identification of the Acetylation and Ubiquitin-Modified Proteome during the Progression of Skeletal Muscle Atrophy. PLoS One 2015; 10:e0136247. [PMID: 26302492 PMCID: PMC4547751 DOI: 10.1371/journal.pone.0136247] [Citation(s) in RCA: 32] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/29/2015] [Accepted: 07/31/2015] [Indexed: 02/07/2023] Open
Abstract
Skeletal muscle atrophy is a consequence of several physiological and pathophysiological conditions including muscle disuse, aging and diseases such as cancer and heart failure. In each of these conditions, the predominant mechanism contributing to the loss of skeletal muscle mass is increased protein turnover. Two important mechanisms which regulate protein stability and degradation are lysine acetylation and ubiquitination, respectively. However our understanding of the skeletal muscle proteins regulated through acetylation and ubiquitination during muscle atrophy is limited. Therefore, the purpose of the current study was to conduct an unbiased assessment of the acetylation and ubiquitin-modified proteome in skeletal muscle during a physiological condition of muscle atrophy. To induce progressive, physiologically relevant, muscle atrophy, rats were cast immobilized for 0, 2, 4 or 6 days and muscles harvested. Acetylated and ubiquitinated peptides were identified via a peptide IP proteomic approach using an anti-acetyl lysine antibody or a ubiquitin remnant motif antibody followed by mass spectrometry. In control skeletal muscle we identified and mapped the acetylation of 1,326 lysine residues to 425 different proteins and the ubiquitination of 4,948 lysine residues to 1,131 different proteins. Of these proteins 43, 47 and 50 proteins were differentially acetylated and 183, 227 and 172 were differentially ubiquitinated following 2, 4 and 6 days of disuse, respectively. Bioinformatics analysis identified contractile proteins as being enriched among proteins decreased in acetylation and increased in ubiquitination, whereas histone proteins were enriched among proteins increased in acetylation and decreased in ubiquitination. These findings provide the first proteome-wide identification of skeletal muscle proteins exhibiting changes in lysine acetylation and ubiquitination during any atrophy condition, and provide a basis for future mechanistic studies into how the acetylation and ubiquitination status of these identified proteins regulates the muscle atrophy phenotype.
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Affiliation(s)
- Daniel J. Ryder
- Department of Physical Therapy, University of Florida, Gainesville, FL, United States of America
| | - Sarah M. Judge
- Department of Physical Therapy, University of Florida, Gainesville, FL, United States of America
| | - Adam W. Beharry
- Department of Physical Therapy, University of Florida, Gainesville, FL, United States of America
| | | | - Jeffrey C. Silva
- Cell Signaling Technology, Danvers, MA, United States of America
| | - Andrew R. Judge
- Department of Physical Therapy, University of Florida, Gainesville, FL, United States of America
- * E-mail:
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7
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Hanna JS. Sarcopenia and critical illness: a deadly combination in the elderly. JPEN J Parenter Enteral Nutr 2015; 39:273-81. [PMID: 25591973 DOI: 10.1177/0148607114567710] [Citation(s) in RCA: 52] [Impact Index Per Article: 5.8] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/21/2022]
Abstract
Sarcopenia is the age-associated loss of lean skeletal muscle mass. It is the result of multiple physiologic derangements, ultimately resulting in an insidious functional decline. Frailty, the clinical manifestation of sarcopenia and physical infirmity, is associated with significant morbidity and mortality in the elderly population. The underlying pathology results in a disruption of the individual's ability to tolerate internal and external stressors such as injury or illness. This infirmity results in a markedly increased risk of falls and subsequent morbidity and mortality from the resulting traumatic injury, as well as an inability to recover from medical insults, resulting in critical illness. The increasing prevalence of sarcopenia and critical illness in the elderly has resulted in a deadly intersection of disease processes. The lethality of this combination appears to be the result of altered muscle metabolism, decreased mitochondrial energetics needed to survive critical illness, and a chronically activated catabolic state likely mediated by tumor necrosis factor-α. Furthermore, these underlying derangements are independently associated with an increased incidence of critical illness, resulting in a progressive downward spiral. Considerable evidence has been gathered supporting the role of aggressive nutrition support and physical therapy in improving outcomes. Critical care practitioners must consider sarcopenia and the resulting frailty phenotype a comorbid condition so that the targeted interventions can be instituted and research efforts focused.
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Affiliation(s)
- Joseph S Hanna
- Department of Surgery, Division of Acute Care Surgery, Rutgers-Robert Wood Johnson Medical School, New Brunswick, New Jersey
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8
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Sun S, Henriksen K, Karsdal MA, Armbrecht G, Belavý DL, Felsenberg D, Rittweger J, Wang Y, Zheng Q, Nedergaard AF. Measurement of a MMP-2 degraded Titin fragment in serum reflects changes in muscle turnover induced by atrophy. Exp Gerontol 2014; 58:83-9. [PMID: 25077715 DOI: 10.1016/j.exger.2014.07.016] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/26/2014] [Revised: 06/30/2014] [Accepted: 07/27/2014] [Indexed: 11/17/2022]
Abstract
PURPOSE In this study we sought to determine whether a Titin peptide fragment can serve as a clinical biomarker for changes in muscle mass. METHODS Mass spectrometry was used to identify Titin fragment in urine. An antibody against this Titin sequence was raised and used to develop a competitive ELISA assay for measurement in serum. Rat tissue extractions in the presence or absence of a series of proteases of interest were used to identify its enzymatic origin. A rat model of dexamethasone (DEX) induced muscle atrophy and a human 56-day bed rest study with and without vibration therapy were used to assess biological and clinical relevance. RESULTS A technically robust ELISA measuring the Titin fragment was developed against a Titin peptide fragment identified in human urine. The fragment was shown to be produced primarily by MMP-2 cleavage of Titin. In the rat muscle DEX induced atrophy model, Titin-MMP2 fragment was decreased in the beginning of DEX treatment, and then significantly increased later on during DEX administration. In the human bed rest study, the Titin-MMP2 fragment was initially decreased 11.9 (±3.7) % after 1day of bed rest, and then gradually increased ending up at a 16.4 (±4.6) % increase at day 47. CONCLUSIONS We developed a robust ELISA measuring a muscle derived MMP-2 generated Titin degradation fragment in rat and human serum. Importantly, the fragment can be measured in serum and that these levels are related to induction of skeletal muscle atrophy.
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Affiliation(s)
- S Sun
- Nordic Bioscience Biomarkers and Research, Herlev, Denmark.
| | - K Henriksen
- Nordic Bioscience Biomarkers and Research, Herlev, Denmark
| | - M A Karsdal
- Nordic Bioscience Biomarkers and Research, Herlev, Denmark
| | - G Armbrecht
- Center for Muscle and Bone Research, Charite Campus Benjamin Franklin, Free University and Humboldt-University Berlin, Berlin, Germany
| | - D L Belavý
- Center for Muscle and Bone Research, Charite Campus Benjamin Franklin, Free University and Humboldt-University Berlin, Berlin, Germany
| | - D Felsenberg
- Center for Muscle and Bone Research, Charite Campus Benjamin Franklin, Free University and Humboldt-University Berlin, Berlin, Germany
| | - J Rittweger
- Institute of Aerospace Medicine, German Aerospace Center (DLR), Cologne, Germany
| | - Y Wang
- Nordic Bioscience Biomarkers and Research, Beijing, China
| | - Q Zheng
- Nordic Bioscience Biomarkers and Research, Beijing, China
| | - A F Nedergaard
- Nordic Bioscience Biomarkers and Research, Herlev, Denmark; Institute of Sports Medicine Copenhagen, Bispebjerg Hospital, Copenhagen, Denmark
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9
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Fielding RA. Protein nutrition mediates lean body mass homeostasis in the aging warfighter. J Nutr 2013; 143:1857S-1861S. [PMID: 24027178 DOI: 10.3945/jn.113.176768] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/07/2023] Open
Abstract
The demographic shift of the average age in the United States and worldwide mandates that careful attention be paid to the nutritional and health needs of all segments of our older adult population. Well-defined changes in body composition occur in aging animals and humans. Characteristic of this change is the age-associated decline in skeletal muscle mass, sarcopenia. Data from observational studies of dietary intake and body composition suggest that a substantial proportion of adults over the age of 60 y consume less than the U.S.-recommended dietary allowance for protein and that greater dietary protein intake appears to reduce the decline in lean/muscle mass with aging. Studies of acute ingestion of high-quality dietary protein in healthy older adults suggest that the age-related blunting of protein synthetic capacity can be overcome with increased dietary protein intake. However, studies on chronic administration of high-quality protein supplements in cohorts of older adults are more equivocal with respect to improving or preserving muscle mass. This review highlights selective aspects of protein supplementation in older adults.
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Affiliation(s)
- Roger A Fielding
- Nutrition, Exercise Physiology, and Sarcopenia Laboratory, Jean Mayer Human Nutrition Research Center on Aging at Tufts University, Boston, MA
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10
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Nutritional strategies to counteract muscle atrophy caused by disuse and to improve recovery. Nutr Res Rev 2013; 26:149-65. [PMID: 23930668 DOI: 10.1017/s0954422413000115] [Citation(s) in RCA: 53] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/06/2023]
Abstract
Periods of immobilisation are often associated with pathologies and/or ageing. These periods of muscle disuse induce muscle atrophy which could worsen the pathology or elderly frailty. If muscle mass loss has positive effects in the short term, a sustained/uncontrolled muscle mass loss is deleterious for health. Muscle mass recovery following immobilisation-induced atrophy could be critical, particularly when it is uncompleted as observed during ageing. Exercise, the best way to recover muscle mass, is not always applicable. So, other approaches such as nutritional strategies are needed to limit muscle wasting and to improve muscle mass recovery in such situations. The present review discusses mechanisms involved in muscle atrophy following disuse and during recovery and emphasises the effect of age in these mechanisms. In addition, the efficiency of nutritional strategies proposed to limit muscle mass loss during disuse and to improve protein gain during recovery (leucine supplementation, whey proteins, antioxidants and anti-inflammatory compounds, energy intake) is also discussed.
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11
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An extract of Artemisia dracunculus L. inhibits ubiquitin-proteasome activity and preserves skeletal muscle mass in a murine model of diabetes. PLoS One 2013; 8:e57112. [PMID: 23437325 PMCID: PMC3577785 DOI: 10.1371/journal.pone.0057112] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/12/2012] [Accepted: 01/17/2013] [Indexed: 12/20/2022] Open
Abstract
Impaired insulin signaling is a key feature of type 2 diabetes and is associated with increased ubiquitin-proteasome-dependent protein degradation in skeletal muscle. An extract of Artemisia dracunculus L. (termed PMI5011) improves insulin action by increasing insulin signaling in skeletal muscle. We sought to determine if the effect of PMI5011 on insulin signaling extends to regulation of the ubiquitin-proteasome system. C2C12 myotubes and the KK-Ay murine model of type 2 diabetes were used to evaluate the effect of PMI5011 on steady-state levels of ubiquitylation, proteasome activity and expression of Atrogin-1 and MuRF-1, muscle-specific ubiquitin ligases that are upregulated with impaired insulin signaling. Our results show that PMI5011 inhibits proteasome activity and steady-state ubiquitylation levels in vitro and in vivo. The effect of PMI5011 is mediated by PI3K/Akt signaling and correlates with decreased expression of Atrogin-1 and MuRF-1. Under in vitro conditions of hormonal or fatty acid-induced insulin resistance, PMI5011 improves insulin signaling and reduces Atrogin-1 and MuRF-1 protein levels. In the KK-Ay murine model of type 2 diabetes, skeletal muscle ubiquitylation and proteasome activity is inhibited and Atrogin-1 and MuRF-1 expression is decreased by PMI5011. PMI5011-mediated changes in the ubiquitin-proteasome system in vivo correlate with increased phosphorylation of Akt and FoxO3a and increased myofiber size. The changes in Atrogin-1 and MuRF-1 expression, ubiquitin-proteasome activity and myofiber size modulated by PMI5011 in the presence of insulin resistance indicate the botanical extract PMI5011 may have therapeutic potential in the preservation of muscle mass in type 2 diabetes.
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12
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Powers SK, Wiggs MP, Duarte JA, Zergeroglu AM, Demirel HA. Mitochondrial signaling contributes to disuse muscle atrophy. Am J Physiol Endocrinol Metab 2012; 303:E31-9. [PMID: 22395111 PMCID: PMC3404565 DOI: 10.1152/ajpendo.00609.2011] [Citation(s) in RCA: 164] [Impact Index Per Article: 13.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/12/2023]
Abstract
It is well established that long durations of bed rest, limb immobilization, or reduced activity in respiratory muscles during mechanical ventilation results in skeletal muscle atrophy in humans and other animals. The idea that mitochondrial damage/dysfunction contributes to disuse muscle atrophy originated over 40 years ago. These early studies were largely descriptive and did not provide unequivocal evidence that mitochondria play a primary role in disuse muscle atrophy. However, recent experiments have provided direct evidence connecting mitochondrial dysfunction to muscle atrophy. Numerous studies have described changes in mitochondria shape, number, and function in skeletal muscles exposed to prolonged periods of inactivity. Furthermore, recent evidence indicates that increased mitochondrial ROS production plays a key signaling role in both immobilization-induced limb muscle atrophy and diaphragmatic atrophy occurring during prolonged mechanical ventilation. Moreover, new evidence reveals that, during denervation-induced muscle atrophy, increased mitochondrial fragmentation due to fission is a required signaling event that activates the AMPK-FoxO3 signaling axis, which induces the expression of atrophy genes, protein breakdown, and ultimately muscle atrophy. Collectively, these findings highlight the importance of future research to better understand the mitochondrial signaling mechanisms that contribute to disuse muscle atrophy and to develop novel therapeutic interventions for prevention of inactivity-induced skeletal muscle atrophy.
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Affiliation(s)
- Scott K Powers
- Department of Applied Physiology and Kinesiology, University of Florida, Gainesville, FL 32611, USA.
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13
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Verhees KJP, Schols AMWJ, Kelders MCJM, Op den Kamp CMH, van der Velden JLJ, Langen RCJ. Glycogen synthase kinase-3β is required for the induction of skeletal muscle atrophy. Am J Physiol Cell Physiol 2011; 301:C995-C1007. [DOI: 10.1152/ajpcell.00520.2010] [Citation(s) in RCA: 60] [Impact Index Per Article: 4.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
Skeletal muscle atrophy commonly occurs in acute and chronic disease. The expression of the muscle-specific E3 ligases atrogin-1 (MAFbx) and muscle RING finger 1 (MuRF1) is induced by atrophy stimuli such as glucocorticoids or absence of IGF-I/insulin and subsequent Akt signaling. We investigated whether glycogen synthase kinase-3β (GSK-3β), a downstream molecule in IGF-I/Akt signaling, is required for basal and atrophy stimulus-induced expression of atrogin-1 and MuRF1, and myofibrillar protein loss in C2C12 skeletal myotubes. Abrogation of basal IGF-I signaling, using LY294002, resulted in a prominent induction of atrogin-1 and MuRF1 mRNA and was accompanied by a loss of myosin heavy chain fast (MyHC-f) and myosin light chains 1 (MyLC-1) and -3 (MyLC-3). The synthetic glucocorticoid dexamethasone (Dex) also induced the expression of both atrogenes and likewise resulted in the loss of myosin protein abundance. Genetic ablation of GSK-3β using small interfering RNA resulted in specific sparing of MyHC-f, MyLC-1, and MyLC-3 protein levels after Dex treatment or impaired IGF-I/Akt signaling. Interestingly, loss of endogenous GSK-3β suppressed both basal and atrophy stimulus-induced atrogin-1 and MuRF1 expression, whereas pharmacological GSK-3β inhibition, using CHIR99021 or LiCl, only reduced atrogin-1 mRNA levels in response to LY294002 or Dex. In conclusion, our data reveal that myotube atrophy and myofibrillar protein loss are GSK-3β dependent, and demonstrate for the first time that basal and atrophy stimulus-induced atrogin-1 mRNA expression requires GSK-3β enzymatic activity, whereas MuRF1 expression depends solely on the physical presence of GSK-3β.
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Affiliation(s)
- Koen J. P. Verhees
- Department of Respiratory Medicine, School for Nutrition, Toxicology and Metabolism (NUTRIM), Maastricht University Medical Centre (MUMC+), Maastricht, the Netherlands
| | - Annemie M. W. J. Schols
- Department of Respiratory Medicine, School for Nutrition, Toxicology and Metabolism (NUTRIM), Maastricht University Medical Centre (MUMC+), Maastricht, the Netherlands
| | - Marco C. J. M. Kelders
- Department of Respiratory Medicine, School for Nutrition, Toxicology and Metabolism (NUTRIM), Maastricht University Medical Centre (MUMC+), Maastricht, the Netherlands
| | - Céline M. H. Op den Kamp
- Department of Respiratory Medicine, School for Nutrition, Toxicology and Metabolism (NUTRIM), Maastricht University Medical Centre (MUMC+), Maastricht, the Netherlands
| | - Jos L. J. van der Velden
- Department of Respiratory Medicine, School for Nutrition, Toxicology and Metabolism (NUTRIM), Maastricht University Medical Centre (MUMC+), Maastricht, the Netherlands
| | - Ramon C. J. Langen
- Department of Respiratory Medicine, School for Nutrition, Toxicology and Metabolism (NUTRIM), Maastricht University Medical Centre (MUMC+), Maastricht, the Netherlands
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14
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You JS, Park MN, Song W, Lee YS. Dietary fish oil alleviates soleus atrophy during immobilization in association with Akt signaling to p70s6k and E3 ubiquitin ligases in rats. Appl Physiol Nutr Metab 2010; 35:310-8. [PMID: 20555375 DOI: 10.1139/h10-022] [Citation(s) in RCA: 70] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/10/2023]
Abstract
Reduced muscle activity leads to impaired insulin signaling, which leads to loss of contractile proteins and muscle mass via the Akt pathway. Dietary fish oil rich in long chain n-3 polyunsaturated fatty acids has been shown to prevent insulin signaling resistance in skeletal muscle. This study was conducted to elucidate the protective effect of dietary fish oil on disuse-induced perturbations in insulin signaling and soleus muscle atrophy. To accomplish this, rats were fed a corn-oil- (control) or fish-oil-based diet for 2 weeks, and then subjected to hindlimb immobilization while still receiving the same diets. After 10 days of immobilization, the soleus muscle mass and myosin heavy chain level had markedly decreased; however, these losses were significantly suppressed in rats fed dietary fish oil, compared with the control group. Dietary fish oil nearly completely attenuated the disturbances in activation of the Akt and p70 S6 kinase proteins, as well as the gene expression of muscle-specific E3 ubiquitin ligases (muscle atrophy F-box and muscle RING finger 1). However, insulin receptor substrate 1 associated with the p85 subunit of phosphoinositide 3-kinase was not altered during immobilization. Dietary fish oil also inhibited alterations in the gene expression of cyclooxygenase-2 and inducible nitric oxide synthase, with no additional observation of oxidative stress. Collectively, these findings indicate that dietary fish oil prior to and during immobilization may alleviate the immobilization-induced soleus muscle atrophy, at least in part, via the Akt pathway through E3 ubiquitin ligases and p70s6k.
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Affiliation(s)
- Jae-Sung You
- Department of Food and Nutrition, Seoul National University, Seoul 151-742, Korea
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15
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Cohen S, Brault JJ, Gygi SP, Glass DJ, Valenzuela DM, Gartner C, Latres E, Goldberg AL. During muscle atrophy, thick, but not thin, filament components are degraded by MuRF1-dependent ubiquitylation. ACTA ACUST UNITED AC 2009; 185:1083-95. [PMID: 19506036 PMCID: PMC2711608 DOI: 10.1083/jcb.200901052] [Citation(s) in RCA: 450] [Impact Index Per Article: 30.0] [Reference Citation Analysis] [Abstract] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
Loss of myofibrillar proteins is a hallmark of atrophying muscle. Expression of muscle RING-finger 1 (MuRF1), a ubiquitin ligase, is markedly induced during atrophy, and MuRF1 deletion attenuates muscle wasting. We generated mice expressing a Ring-deletion mutant MuRF1, which binds but cannot ubiquitylate substrates. Mass spectrometry of the bound proteins in denervated muscle identified many myofibrillar components. Upon denervation or fasting, atrophying muscles show a loss of myosin-binding protein C (MyBP-C) and myosin light chains 1 and 2 (MyLC1 and MyLC2) from the myofibril, before any measurable decrease in myosin heavy chain (MyHC). Their selective loss requires MuRF1. MyHC is protected from ubiquitylation in myofibrils by associated proteins, but eventually undergoes MuRF1-dependent degradation. In contrast, MuRF1 ubiquitylates MyBP-C, MyLC1, and MyLC2, even in myofibrils. Because these proteins stabilize the thick filament, their selective ubiquitylation may facilitate thick filament disassembly. However, the thin filament components decreased by a mechanism not requiring MuRF1.
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Affiliation(s)
- Shenhav Cohen
- Department of Cell Biology, Harvard Medical School, Boston, MA 02115, USA
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16
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Strasser EM, Wessner B, Roth E. [Cellular regulation of anabolism and catabolism in skeletal muscle during immobilisation, aging and critical illness]. Wien Klin Wochenschr 2007; 119:337-48. [PMID: 17634890 DOI: 10.1007/s00508-007-0817-0] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/07/2007] [Accepted: 05/16/2007] [Indexed: 12/13/2022]
Abstract
Skeletal muscle atrophy is associated with situations of acute and chronical illness, such as sepsis, surgery, trauma and immobility. Additionally, it is a common problem during the physiological process of aging. The myofibrillar proteins myosin and actin, which are essential for muscle contraction, are the major targets during the process of protein degradation. This leads to a general loss of muscle mass, muscle strength and to increased muscle fatigue. In critically ill or immobile patients skeletal muscle atrophy is accompanied by enhanced inflammation, reduced wound healing, weaning complications and difficulties in mobilisation. During aging it results in falls, fractures, physical injuries and loss of mobility. Relating to the primary stimulators - hormones, muscle lengthening, stress, inflammation, neuronal activity - research is now focusing on the investigation of the signal transduction pathways, which influence protein synthesis and protein degradation during skeletal muscle atrophy.
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Affiliation(s)
- Eva-Maria Strasser
- Chirurgische Forschungslaboratorien, Medizinische Universität Wien, Wien, Austria
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17
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Gomes ARS, Cornachione A, Salvini TF, Mattiello-Sverzut AC. Morphological effects of two protocols of passive stretch over the immobilized rat soleus muscle. J Anat 2007; 210:328-35. [PMID: 17331181 PMCID: PMC2100284 DOI: 10.1111/j.1469-7580.2007.00697.x] [Citation(s) in RCA: 25] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022] Open
Abstract
This study evaluated two different stretching protocols employed during a period of hind-limb immobilization in terms of their effects on muscle morphology. Quantitative data regarding the soleus muscle were obtained based on the clinical hypothesis that a high frequency of this exercise would improve the recovery of muscle structure. Twenty-four male Wistar rats were divided into four groups (n = 6 each): the control group (C); the immobilized group, in which the left hind limb was immobilized in order to maintain the soleus muscle in a fully shortened position for 3 weeks (I); the 'immobilized and stretched every 3 days' group, in which the left hind limb was immobilized as in the immobilized group, but with the soleus muscle stretched every 3 days for 40 min (Ist3); and the 'immobilized (as in the immobilized group) and stretched every 7 days' group (ISt7). All soleus muscles were excised 21 days after the beginning of the experiment, and were processed for (1) haematoxylin and eosin and myosin ATPase to evaluate muscle morphology and cross-sectional area and the proportions of the different fibre types, and (2) ultrastructural analysis. The cross-sectional area was found to have decreased in all fibre types (I, II and C), mainly in ISt7, when compared with the C group and ISt3 group. The proportion of the different fibre types did not show statistical difference between groups. Light and electron microscopy examination revealed signs of cell degeneration that was more intense in the group immobilized and stretched three times a week. In conclusion, sessions of passive stretching applied to the soleus during immobilization induce muscle fibre injury, suggesting that this therapeutic tool should be applied carefully to disused muscles.
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Affiliation(s)
- Anna R S Gomes
- Unit of Skeletal Muscle Plasticity, Physical Therapy Department, Federal University of São CarlosBrazil
| | - Anabelle Cornachione
- Department of Biomechanics, Medicine and Rehabilitation of the Locomotor Apparatus, Ribeirão Preto School of Medicine, University of São PauloSP, Brazil
| | - Tania F Salvini
- Unit of Skeletal Muscle Plasticity, Physical Therapy Department, Federal University of São CarlosBrazil
| | - Ana Cláudia Mattiello-Sverzut
- Department of Biomechanics, Medicine and Rehabilitation of the Locomotor Apparatus, Ribeirão Preto School of Medicine, University of São PauloSP, Brazil
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18
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Enns DL, Raastad T, Ugelstad I, Belcastro AN. Calpain/calpastatin activities and substrate depletion patterns during hindlimb unweighting and reweighting in skeletal muscle. Eur J Appl Physiol 2007; 100:445-55. [PMID: 17429681 DOI: 10.1007/s00421-007-0445-4] [Citation(s) in RCA: 60] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 03/09/2007] [Indexed: 11/29/2022]
Abstract
Unloading of skeletal muscle by hindlimb unweighting (HU) is characterized by atrophy, protein loss, and an elevation in intracellular Ca(2+) levels that may be sufficient to activate Ca(2+)-dependent proteases (calpains). In this study, we investigated the time course of calpain activation and the depletion pattern of a specific structural protein (desmin) with unloading and subsequent reweighting. Rats underwent 12 h, 24 h, 72 h or 9 days of HU, followed by reweighting for either 0, 12 or 24 h. Total calpain-like activity was elevated with HU in skeletal muscle (P < 0.05) and was further enhanced with reweighting (P < 0.05). The increases in calpain-like activity were associated with a proportional increase in activity of the particulate fraction (P < 0.05). Activity of the mu-calpain isoform was elevated with 12 and 24 h of HU (P < 0.05) and returned to control levels thereafter. With reweighting, activities of mu-calpain were elevated above control levels for all HU groups except 9 days (P < 0.05). In contrast, minimal changes in m-calpain and calpastatin activity were observed with HU and reweighting. Although desmin depletion levels did not reach statistical significance, a significant inverse relationship was found between the mu-calpain/calpastatin ratio and the amount of desmin in isolated myofibrils (R = -0.83, P < 0.001). The results suggest that calpain activation is an early event during unloading in skeletal muscle, and that the majority of the increase in calpain activity can be attributed to the micro-isoform.
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Affiliation(s)
- Deborah L Enns
- School of Kinesiology, The University of Western Ontario, London, ON, N6A 3K7, Canada
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19
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Vermaelen M, Sirvent P, Raynaud F, Astier C, Mercier J, Lacampagne A, Cazorla O. Differential localization of autolyzed calpains 1 and 2 in slow and fast skeletal muscles in the early phase of atrophy. Am J Physiol Cell Physiol 2006; 292:C1723-31. [PMID: 17182728 DOI: 10.1152/ajpcell.00398.2006] [Citation(s) in RCA: 26] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
Calpains have been proposed to be involved in the cytoskeletal remodeling and wasting of skeletal muscle. However, limited data are available about the specific involvement of each calpain in the early stages of muscle atrophy. The aims of this study were to determine whether calpains 1 and 2 are autolyzed after a short period of muscle disuse, and, if so, where in the myofibers the autolyzed products are localized. In the rat soleus muscle, 5 days of immobilization increased autolyzed calpain 1 in the particulate and not the soluble fraction. Conversely, autolyzed calpain 2 was not found in the particulate fraction, whereas it was increased in the soluble fraction after immobilization. In the less atrophied plantaris muscle, no difference was noted between the control and immobilized groups whatever the fraction or calpain. Other proteolytic pathways were also investigated. The ubiquitin-proteasome pathway was activated in both skeletal muscles, and caspase 3 was activated only in the soleus muscle. Taken together, our data suggest that calpains 1 and 2 are involved in atrophy development in slow type muscle exclusively and that they have different regulation and protein targets. Moreover, the activation of proteolytic pathways appears to differ in slow and fast muscles, and the proteolytic mechanisms involved in fast-type muscle atrophy remain unclear.
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Affiliation(s)
- Marianne Vermaelen
- INSERM, ERI 25, Hôpitol Arnaud de Villneuve, 34295 Montpellier Cedex 5, France.
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20
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Enns DL, Belcastro AN. Early activation and redistribution of calpain activity in skeletal muscle during hindlimb unweighting and reweighting. Can J Physiol Pharmacol 2006; 84:601-9. [PMID: 16900244 DOI: 10.1139/y06-013] [Citation(s) in RCA: 41] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
The aims of this study were the following: (i) to determine whether activation of the Ca2+-activated protease, calpain, is an early event during hindlimb unweighting (HU) in skeletal muscle; and (ii) to assess whether calpain activity is greater during reweighting compared with HU alone. Rats were exposed to 12, 24, and 72 h, or 9 d of HU, followed by reweighting for 0, 12, or 24 h. Calpain activities were assayed for total, soluble, and particulate fractions. Total calpain activity was increased in the soleus at all HU time points, whereas activities were elevated in the gastrocnemius only after 9 d of HU. With reweighting, calpain activity remained elevated at all time points for both muscles. In general, reweighting the gastrocnemius increased its calpain activity more than during HU only, whereas reweighting the soleus did not produce additional increases in its calpain activity. The increases in calpain activity were associated with a proportional increase in activity of the particulate (membrane- and protein-associated) fraction. The results suggest that calpain activation is an early event during HU in the soleus, and that the increases in calpain activity in both muscles are associated with a redistribution of activity from cytosolic to particulate fractions.
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Affiliation(s)
- Deborah L Enns
- School of Kinesiology, The University of Western ON, London, ON, N6A 3K7, Canada.
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21
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Bajotto G, Shimomura Y. Determinants of Disuse-Induced Skeletal Muscle Atrophy: Exercise and Nutrition Countermeasures to Prevent Protein Loss. J Nutr Sci Vitaminol (Tokyo) 2006; 52:233-47. [PMID: 17087049 DOI: 10.3177/jnsv.52.233] [Citation(s) in RCA: 39] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/27/2022]
Abstract
Muscle atrophy results from a variety of conditions such as disease states, neuromuscular injuries, disuse, and aging. Absence of gravitational loading during spaceflight or long-term bed rest predisposes humans to undergo substantial loss of muscle mass and, consequently, become unfit and/or unhealthy. Disuse- or inactivity-induced skeletal muscle protein loss takes place by differential modulation of proteolytic and synthetic systems. Transcriptional, translational, and posttranslational events are involved in the regulation of protein synthesis and degradation in myofibers, and these regulatory events are known to be responsive to contractile activity. However, regardless of the numerous studies which have been performed, the intracellular signals that mediate skeletal muscle wasting due to muscular disuse are not completely comprehended. Understanding the triggers of atrophy and the mechanisms that regulate protein loss in unloaded muscles may lead to the development of effective countermeasures such as exercise and dietary intervention. The objective of the present review is to provide a window into the molecular processes that underlie skeletal muscle remodeling and to examine what we know about exercise and nutrition countermeasures designed to minimize muscle atrophy.
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Affiliation(s)
- Gustavo Bajotto
- Department of Materials Science and Engineering, Shikumi College, Nagoya Institute of' Technology, Gokiso-cho, Showa-ku, Nagoya 466-8 555, Japan
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22
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Vermaelen M, Marini JF, Chopard A, Benyamin Y, Mercier J, Astier C. Ubiquitin targeting of rat muscle proteins during short periods of unloading. ACTA ACUST UNITED AC 2005; 185:33-40. [PMID: 16128695 DOI: 10.1111/j.1365-201x.2005.01446.x] [Citation(s) in RCA: 30] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
AIM The ubiquitin-proteasome system is known to be involved in many situations leading to skeletal muscle atrophy. However, the cellular mechanisms triggering the atrophic process initiation are still poorly understood. For short periods of rat hindlimb unloading, we assessed the specific ubiquitin targeting of sarcoplasmic or myofibrillar proteins in slow and fast rat muscle types. METHODS Adult Sprague Dawley rats were randomly assigned to three groups: control, hindlimb-unloaded for 4 days (HU4) and hindlimb-unloaded for 8 days (HU8). In fractionated extracts from soleus (SOL) and Extensor Digitorum Longus (EDL) muscles, the relative contents of free and conjugated ubiquitin were quantified by immunoblotting. RESULTS Hindlimb unloading of short durations resulted in a preferential atrophy of slow-twitch fibres and bound ubiquitin levels were increased by 37 and 68% in the soleus myofibrillar fraction after respectively 4 and 8 days. The ubiquitin conjugation was shown to principally affect the high molecular weight proteins. Free and conjugated ubiquitin levels remained unchanged in sarcoplasmic fraction from SOL muscle after 8 days HU. For the fast muscle (EDL), ubiquitin contents were approximately twofold lower in control conditions, and did not significantly change during the hindlimb unloading periods considered. CONCLUSION The postural SOL muscle was shown to contain higher constitutive sarcoplasmic ubiquitin levels than the phasic EDL. The high response to unloading of the slow twitch fibres rich SOL muscle was accompanied by a specific conjugation of its myofibrillar proteins that may participate in the initiation of skeletal muscle remodelling consequent to disuse.
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Affiliation(s)
- M Vermaelen
- EA 701, Muscle et pathologies chroniques, Institut de Biologie, 34060 Montpellier, France
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23
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Abstract
Skeletal muscle atrophy attributable to muscular inactivity has significant adverse functional consequences. While the initiating physiological event leading to atrophy seems to be the loss of muscle tension and a good deal of the physiology of muscle atrophy has been characterized, little is known about the triggers or the molecular signaling events underlying this process. Decreases in protein synthesis and increases in protein degradation both have been shown to contribute to muscle protein loss due to disuse, and recent work has delineated elements of both synthetic and proteolytic processes underlying muscle atrophy. It is also becoming evident that interactions among known proteolytic pathways (ubiquitin-proteasome, lysosomal, and calpain) are involved in muscle proteolysis during atrophy. Factors such as TNF-alpha, glucocorticoids, myostatin, and reactive oxygen species can induce muscle protein loss under specified conditions. Also, it is now apparent that the transcription factor NF-kappaB is a key intracellular signal transducer in disuse atrophy. Transcriptional profiles of atrophying muscle show both up- and downregulation of various genes over time, thus providing further evidence that there are multiple concurrent processes involved in muscle atrophy. The purpose of this review is to synthesize our current understanding of the molecular regulation of muscle atrophy. We also discuss how ongoing work should uncover more about the molecular underpinnings of muscle wasting, particularly that due to disuse.
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Affiliation(s)
- Robert W Jackman
- Boston University, Department of Health Sciences, 635 Commonwealth Ave., Rm. 443, Boston, MA 02215, USA
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24
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Fiorotto ML, Davis TA, Reeds PJ, Burrin DG. Nonnutritive factors in colostrum enhance myofibrillar protein synthesis in the newborn Pig. Pediatr Res 2000; 48:511-7. [PMID: 11004243 DOI: 10.1203/00006450-200010000-00015] [Citation(s) in RCA: 22] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/06/2022]
Abstract
Colostrum is a complex source of nutrients, immune factors, and bioactive substances consumed by newborn mammals. In previous work, we observed that protein synthesis in the skeletal muscle of newborn piglets is enhanced when they are fed colostrum rather than a nutrient-matched formula devoid of growth factors. To elucidate the mechanisms responsible for this response, we contrasted the fractional rates of sarcoplasmic and myofibrillar protein synthesis of newborn piglets that received only water with those fed for 24 h with colostrum, a nutrient-matched formula, or mature sow's milk. Compared with water, feeding resulted in a 2.5- to 3-fold increase in total skeletal muscle protein synthesis, and this increase was 28% greater in the colostrum-fed than either the formula- or mature milk-fed piglets. Feeding also stimulated muscle ribosome and total polyadenylated RNA accretion. Ribosomal translational efficiency, however, was similar across all fed groups. The greater stimulation of protein synthesis in colostrum-fed pigs was restricted entirely to the myofibrillar protein compartment and was associated with higher ribosome and myosin heavy chain mRNA abundance. Taken together, these data suggest that nonnutritive factors in colostrum enhance ribosomal accretion and muscle-specific gene transcription that, in turn, stimulate specifically the synthesis of myofibrillar proteins in the skeletal musculature of the newborn.
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Affiliation(s)
- M L Fiorotto
- USDA/ARS Children's Nutrition Research Center, Department of Pediatrics, Baylor College of Medicine, Houston, Texas 77030, USA
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25
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Fiorotto ML, Davis TA, Reeds PJ. Regulation of myofibrillar protein turnover during maturation in normal and undernourished rat pups. Am J Physiol Regul Integr Comp Physiol 2000; 278:R845-54. [PMID: 10749771 DOI: 10.1152/ajpregu.2000.278.4.r845] [Citation(s) in RCA: 25] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
The study tested the hypothesis that a higher rate of myofibrillar than sarcoplasmic protein synthesis is responsible for the rapid postdifferentiation accumulation of myofibrils and that an inadequate nutrient intake will compromise primarily myofibrillar protein synthesis. Myofibrillar (total and individual) and sarcoplasmic protein synthesis, accretion, and degradation rates were measured in vivo in well-nourished (C) rat pups at 6, 15, and 28 days of age and compared at 6 and 15 days of age with pups undernourished (UN) from birth. In 6-day-old C pups, a higher myofibrillar than sarcoplasmic protein synthesis rate accounted for the greater deposition of myofibrillar than sarcoplasmic proteins. The fractional synthesis rates of both protein compartments decreased with age, but to a greater degree for myofibrillar proteins (-54 vs. -42%). These decreases in synthesis rates were partially offset by reductions in degradation rates, and from 15 days, myofibrillar and sarcoplasmic proteins were deposited in constant proportion to one another. Undernutrition reduced both myofibrillar and sarcoplasmic protein synthesis rates, and the effect was greater at 6 (-25%) than 15 days (-15%). Decreases in their respective degradation rates minimized the effect of undernutrition on sarcoplasmic protein accretion from 4 to 8 days and on myofibrillar proteins from 13 to 17 days. Although these adaptations in protein turnover reduced overall growth of muscle mass, they mitigated the effects of undernutrition on the normal maturational changes in myofibrillar protein concentration.
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Affiliation(s)
- M L Fiorotto
- United States Department of Agriculture/Agricultural Research Service Children's Nutrition Research Center, Department of Pediatrics, Baylor College of Medicine, Houston, Texas 77030, USA.
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26
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27
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Tischler ME, Satarug S, Aannestad A, Munoz KA, Henriksen EJ. Insulin attenuates atrophy of unweighted soleus muscle by amplified inhibition of protein degradation. Metabolism 1997; 46:673-9. [PMID: 9186304 DOI: 10.1016/s0026-0495(97)90012-3] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 02/04/2023]
Abstract
Unweighting atrophy of immature soleus muscle occurs rapidly over the first several days, followed by slower atrophy coinciding with increased sensitivity to insulin of in vitro protein metabolism. This study determined whether this increased sensitivity might account for the diminution of atrophy after 3 days of tall-cast hindlimb suspension. The physiological significance of the increased response to insulin in unweighted muscle was evaluated by analyzing in vivo protein metabolism for day 3 (48 to 72 hours) and day 4 (72 to 96 hours) of unweighting in diabetic animals either injected with insulin or not treated. Soleus from nontreated diabetic animals showed a similar loss of protein during day 3 (-16.2%) and day 4 (-14.5%) of unweighting, whereas muscle from insulin-treated animals showed rapid atrophy (-14.5%) during day 3 only, declining to just -3.1% the next day. Since fractional protein synthesis was similar for both day 3 (8.6%/d) and day 4 (7.0%/d) of unweighting in insulin-treated animals, the reduction in protein loss must be accounted for by a slowing of protein degradation due to circulating insulin. Intramuscular (IM) injection of insulin (600 nmol/L) stimulated in situ protein synthesis similarly in 4-day unweighted (+56%) and weight-bearing (+90%) soleus, even though unweighted muscle showed a greater in situ response of 2-deoxy-[3H]glucose uptake to IM injection of either insulin (133 nmol/L) or insulin-like growth factor-I (IGF-I) (200 nmol/L) than control muscle. These findings suggest that unweighted muscle is selectively more responsive in vivo to insulin, and that the slower atrophy after 3 days of unweighting was due to an increased effect of insulin on inhibiting protein degradation.
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Affiliation(s)
- M E Tischler
- Department of Biochemistry, University of Arizona, Tucson, USA
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28
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Abstract
Unweighting the hindlimbs by tail suspension of juvenile rats leads to atrophy of the soleus muscle, especially during the third day of unweighting. Although a previous study using adrenalectomized animals suggested a minimal role of glucocorticoids in this atrophy, the inability of adrenalectomized animals to release other adrenal hormones could have been important. Therefore, the influence of oral administration of RU38486 [11-beta-(4-dimethylaminophenyl) 17-beta-hydroxy 17-alpha(prop-1-ynyl) estra 4,9-dien 3-one], a selective glucocorticoid antagonist, on protein metabolism in the unweighted soleus was studied. The effectiveness of RU38486 treatment was demonstrated in hindlimb-suspended rats as the drug abolished the increase in soleus glutamine synthetase activity shown previously to be caused by elevated circulating glucocorticoids. The slower weight gain of suspended rats was unaffected by the drug. After 3 days of unweighting, the difference in protein content from weighted soleus muscle was not diminished significantly by RU38486 (-25%, vehicle only; -18%, RU38486-treated). However, in both weight-bearing and suspended animals, RU38486 seemed to promote protein accretion between days 2 and 3 of the experiment; ie, unweighted muscle seemed to lose less protein. All suspended animals showed slower (-58% to -64%) fractional in vivo rates of synthesis. RU38486 did not affect these percent differences in fractional protein synthesis after either 2 or 3 days of unweighting. The apparent improvement in protein balance likely resulted from a decline in protein degradation in both the weight-bearing (-26%) and unweighted (-35%) soleus.(ABSTRACT TRUNCATED AT 250 WORDS)
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Affiliation(s)
- M E Tischler
- Department of Biochemistry, University of Arizona Health Sciences Center, Tucson
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29
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Munoz KA, Aannestad A, Tischler ME, Henriksen EJ. Skeletal muscle protein content and synthesis after voluntary running and subsequent unweighting. Metabolism 1994; 43:994-9. [PMID: 8052157 DOI: 10.1016/0026-0495(94)90179-1] [Citation(s) in RCA: 20] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/28/2023]
Abstract
The effects of exercise training with or without subsequent unweighting on wet weight, protein content, and in vivo fractional protein synthesis were studied in soleus and plantaris muscles of juvenile female Sprague-Dawley rats under the following four conditions: normal weight bearing (N), voluntary-activity wheel running (WR) for up to 4 weeks, mechanical unweighting for 7 days via hindlimb suspension (HS), or wheel running followed by 7 days of hindlimb suspension (WR-HS). Fractional protein synthesis was determined by the 3H-phenylalanine flooding method. Increases (P < .05) in wet weight and protein content were detected in the soleus after just 1 week of running, with no increase in fractional protein synthesis. Two weeks of running were required for an increase in protein synthesis in this muscle. Significant increases in these parameters were first observed in the plantaris after 2 weeks of running. Maximal increases occurred by 3 weeks in both muscles. Reductions (P < .05) in soleus and plantaris parameters were observed in both HS and WR-HS groups compared with N and WR groups, respectively. However, protein content and fractional synthesis were maintained at significantly higher levels in WR-HS muscles compared with HS muscles. These results indicate that (1) wheel training represents a noninvasive method for inducing rapid hypertrophy of the skeletal muscles studied, in part by increasing fractional protein synthesis; (2) unweighting decreases protein content and synthesis to the same extent whether the muscles are trained; and (3) previously hypertrophied muscles display higher protein contents and fractional protein synthesis following unweighting compared with unweighted muscles of untrained animals.
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Affiliation(s)
- K A Munoz
- Department of Biochemistry, University of Arizona, Tucson
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