Models Of Muscle Atrophy Research Articles

Extracts of Aurantiochytrium alga improves symptoms in knee osteoarthritis and muscle atrophy models

Extracts of <i>Aurantiochytrium</i> alga improves symptoms in knee osteoarthritis and muscle atrophy models

Effects of neuromuscular electrical stimulation on pulmonary alveola and cytokines in chronic obstructive pulmonary disease (COPD) and skeletal muscle atrophy model mice.

[Purpose] It has been reported that exercise affects skeletal muscle in the chronic obstructive pulmonary disease (COPD) disease model. In this study, we examined the effects of neuromuscular electrical stimulation (NMES) in skeletal muscle on alveoli and cytokines. [Materials and Methods] We used twenty wild-type mice, randomly divided into three groups: Group A: Control (non-COPD, non-amyotrophia, non-NMES), Group B: COPD, amyotrophia with NMES and Group C: COPD, amyotrophia without NMES. Among those, a group of mice with ages from 12 to 14 weeks were used to create a chronic obstructive pulmonary disease (COPD) model, a group of mice with ages from 15 to 16 weeks was used to create a disuse syndrome by hind limb suspension, and a group of mice with ages from 17 to 28 weeks (12 weeks) were used to implement NMES. In this study, we used the real-time PCR method to assess the mRNA expression levels. We also conducted morphological analysis, assessed macrophage expression level by staining (general staining and immunostaining), and employed spirometry. [Results] Our study results showed significant decreases in Interleukin-6 (IL-6) levels in the lungs and muscle RING-finger protein-1 (MuRF1) in the muscles. Moreover, the pulmonary stromal macrophage marker (F4/80) and the protease marker (MMP12) showed significantly decreased expression, while no change was observed in the morphological of the alveolar spaces (mean linear intercept). [Conclusion] On the basis of these findings, our study reveals that NMES affects cytokines and macrophages in COPD skeletal muscle atrophy.

Inhibitory effects of curcuminoids on dexamethasone-induced muscle atrophy in differentiation of C2C12 cells

BackgroundSarcopenia is a disease of progressive loss of muscle mass due to the imbalance of protein synthesis and proteolysis, and tends to emerge with ageing. Currently its treatment consists of non-drug therapies and drug therapies, but some medications can have various side effects. Therefore, it is important to search for effective herbal medicines that can modulate muscle mass. PurposeIn this study, we investigated the inhibition effects of Cu, De, Bis, CRE, CRE-SD, CRE-Bin, and CRE-Ter on dexamethasone-induced muscle atrophy in differentiation of C2C12 cells. MethodsC2C12 cells were cultured and treated with various concentrations of curcuminoids including, Cu, De, Bis, CRE, CRE-SD, CRE-Bin, and CRE-Ter. The inhibitory effects were studied using various methods, including MTT and LDH assays for cell viability and cell cytotoxicity, RT-qPCR for gene expression analysis, and Western blots for protein analysis. In this study, dexamethasone-treated C2C12 myotubes (Dex) are the positive drug control and used as in vitro models of muscle atrophy. ResultsThe results revealed that treating differentiated C2C12 cells with Cu, CRE, CRE-Bin, and CRE-Ter reduced Atrogin-1 and MuRF-1 expression, whereas CRE-SD reduced only MuRF-1 expression. The Western blot analysis results show that Cu, CRE, CRE-Bin, CRE-Ter, and CRE-SD upregulated the phosphorylation level of Akt, which is an important protein in the mTOR signaling pathway. ConclusionOur results show that Cu, CRE, CRE-Bin, CRE-SD, and CRE-Ter tend to inhibit muscle atrophy by decreasing expression of Atrogin-1 and MuRF-1 inhibiting protein degradation, and to upregulate Phospho-Akt to stimulate protein synthesis. These results provide corroborating evidence of therapeutic potential to treat sarcopenia patients.

Polyamine pathway is associated with muscle anabolic effects by androgen receptor ligand

AbstractBackgroundMuscle wasting is a common condition concomitant with aging. Androgens significantly increase skeletal muscle mass, but the role of the androgen receptor (AR) in skeletal muscle is not well established. TEI‐SARM2, a novel selective androgen receptor modulator (SARM), was developed as a pharmaceutical candidate for the treatment of muscle wasting diseases.MethodsThe efficacy and specificity of TEI‐SARM2 were analysed in vitro assays, and efficacy was also evaluated in vivo using orchiectomized male rats, rat tail‐suspension, rat and mice cancer‐induced muscle atrophy models, and female cynomolgus monkeys. Male myofibre‐specific AR‐knockout (mARKO) mice were orchiectomized to investigate the role of AR in muscle using TEI‐SARM2. RNA‐seq analysis of bulbocavernosus muscle was performed. The effects of spermidine were evaluated in C2C12 myoblasts.ResultsSelective, potent anabolic effects of TEI‐SARM2 in muscle were detected in rats and monkeys. TEI‐SARM2 inhibited muscle loss and promoted muscle recovery in a model of muscle disuse and prevented muscle wasting and improved survival rate in cancer models. In vivo and RNA‐seq analyses revealed that AR regulates skeletal muscle mass in myofibres and extra‐myofibres, both directly and indirectly. Among them, polyamine synthesis‐related genes were focused, and spermidine treatment could induce C2C12 cell proliferation.ConclusionsTEI‐SARM2 exhibited potent and selective anabolic effects in muscles, as well as tissue specificity in various animal models. The results support that TEI‐SARM2 is a promising drug candidate for muscle wasting diseases. TEI‐SARM2 induced anabolic effects on skeletal muscle via AR in myofibres as well as other androgen target cells.

Theaflavins decrease skeletal muscle wasting in disuse atrophy induced by hindlimb suspension in mice.

We previously found that a single dose of theaflavins induced skeletal muscle metabolic changes. In this study, we examined the effect of theaflavins on disuse muscle atrophy model mice by hindlimb suspension. Mice were assigned to 4 groups; ground-vehicle, ground-theaflavins, suspension-vehicle, and suspension-theaflavins, dosed with theaflavins (250 mg/kg/day) for 2 weeks. The peak of myotube size of cross sectional area was significantly moved to the smaller side in the suspension-vehicle group compared with the ground-vehicle group, and these shifts were significantly reduced by the treatment with theaflavins in both soleus and extensor digitorum longus. The level of phosphorylated eukaryotic translation initiation factor 4E-binding protein (4EBP)-1, located downstream of the Akt/mTOR pathway, was significantly different between suspension-vehicle and suspension-theaflavins in soleus. The ratio of forkhead box O (FoxO) 3a to phosphorylated FoxO3a significantly increased in soleus or tended to rise in extensor digitorum longus of suspension-vehicle group compared with ground-vehicle. In contrast, these changes were not observed in suspension-theaflavins group. These results suggested that theaflavins inhibited the progress of disuse muscle atrophy through modulation of protein metabolism.

The body region specificity in murine models of muscle regeneration and atrophy.

AimSkeletal muscles are distributed throughout the body, presenting a variety of sizes, shapes and functions. Here, we examined whether muscle regeneration and atrophy occurred homogeneously throughout the body in mouse models.MethodsAcute muscle regeneration was induced by a single intramuscular injection of cardiotoxin in adult mice. Chronic muscle regeneration was assessed in mdx mice. Muscle atrophy in different muscles was evaluated by cancer cachexia, ageing and castration mouse models.ResultsWe found that, in the cardiotoxin‐injected acute muscle injury model, head muscles slowly regenerated, while limb muscles exhibited a rapid regeneration and even overgrowth. This overgrowth was also observed in limb muscles alone (but not in head muscles) in mdx mice as chronic injury models. We described the body region–specific decline in the muscle mass in muscle atrophy models: cancer cachexia‐induced, aged and castrated mice. The positional identities, including gene expression profiles and hormone sensitivity, were robustly preserved in the ectopically engrafted satellite cell‐derived muscles in the castrated model.ConclusionOur results indicate that positional identities in muscles should be considered for the development of efficient regenerative therapies for muscle weakness, such as muscular dystrophy and age‐related sarcopenia.

Targeting cPLA2 derived lipid hydroperoxides as a potential intervention for sarcopenia

Defects in neuromuscular innervation contribute significantly to the age-related decline in muscle mass and function (sarcopenia). Our previous studies demonstrated that denervation induces muscle mitochondrial hydroperoxide production (H2O2 and lipid hydroperoxides (LOOHs)). Here we define the relative contribution of mitochondrial electron transport chain (ETC) derived H2O2 versus cytosolic phospholipase A2 (cPLA2) derived LOOHs in neurogenic muscle atrophy. We show that denervation increases muscle cPLA2 protein content, activity, and metabolites downstream of cPLA2 including LOOHs. Increased scavenging of mitochondrial H2O2 does not protect against denervation atrophy, suggesting ETC generated H2O2 is not a critical player. In contrast, inhibition of cPLA2 in vivo mitigates LOOH production and muscle atrophy and maintains individual muscle fiber size while decreasing oxidative damage. Overall, we show that loss of innervation in several muscle atrophy models including aging induces generation of LOOHs produced by arachidonic acid metabolism in the cPLA2 pathway contributing to loss of muscle mass.

Determining Maximal Muscle Strength in Mice: Validity and Reliability of an Adapted Swimming Incremental Overload Test.

Gouvêa, AL, Martinez, CG, and Kurtenbach, E. Determining maximal muscle strength in mice: validity and reliability of an adapted swimming incremental overload test. J Strength Cond Res 34(8): 2360-2368, 2020-At present, there are no reliable methods to determine maximal muscle strength in small rodents. Here, we established an adapted swimming incremental overload test (SIOT) as an instrument for this purpose. First, to validate the test, BALB/c mice received 20 mg·kg·d of dexamethasone (DEXA group) or water (control group). After 14 days, with a cumulative dose of 120 mg·kg of dexamethasone, the SIOT could detect a decrease of approximately 7% in muscle strength. In addition, this decrease was consistent with a significant reduction in body (above 13.5%) and muscle (approximately 15%) weight in DEXA atrophic animals. To establish the SIOT reliability, another group of animals was evaluated for 5 consecutive days. In this second protocol, the SIOT was executed with an initial load corresponding to 12% of the mouse body weight (BW) fixed to the tail. Increments between 1 and 5% of the BW were added during each attempt to obtain the highest load that was tolerated for a time interval of 5-7 seconds. On the last day, the SIOT reliability test was performed by 2 different raters to obtain the inter-rater reproducibility. The adapted SIOT was shown to be reliable when measured by the same rater (intraclass correlation coefficient [ICC] = 0.939) and by 2 different raters (ICC = 0.830). The Bland-Altman graphical representation did not demonstrate heteroscedastic errors. Therefore, the SIOT proved to be a sensitive and reliable method to measure muscle strength, and it can be applied to small animals in different models of muscle atrophy.

20(S)-ginsenoside Rg3 promotes myoblast differentiation and protects against myotube atrophy via regulation of the Akt/mTOR/FoxO3 pathway

We previously found that 20(S)-ginsenoside Rg3 (S-Rg3) promotes myoblast differentiation via an unknown mechanism. Here we measured levels of myosin heavy chain (MHC) and myogenin, markers of myoblast differentiation, using Western blot analysis and immunofluorescence staining. Notably, S-Rg3 treatment of C2C12 myoblasts led to increased muscle differentiation and protection from muscle atrophy in a dexamethasone (DEX)-treated C2C12 myotube-based muscle atrophy model. This effect was likely caused by S-Rg3 treatment-induced promotion of Akt/mTOR phosphorylation and inhibition of FoxO3 nuclear transcription. Additionally, S-Rg3 treatment also led to increased fruit fly climbing distances (Drosophila melanogaster) and prevented muscle atrophy in aged fruit flies. Our study provides a mechanistic framework for understanding how S-Rg3 enhances myoblast differentiation and inhibits myotube atrophy through activation of the Akt/mTOR/FoxO3 signaling pathway, as demonstrated in vitro in C2C12 cells and in vivo in fruit flies.

NeuroHeal Reduces Muscle Atrophy and Modulates Associated Autophagy.

Muscle wasting is an unmet medical need which leads to a reduction of myofiber diameter and a negative impact on the functional performance of daily activities. We previously found that a new neuroprotective drug called NeuroHeal reduced muscle atrophy produced by transient denervation. Aiming to decipher whether NeuroHeal has a direct role in muscle biology, we used herein different models of muscle atrophy: one caused by chronic denervation, another caused by hindlimb immobilization, and lastly, an in vitro model of myotube atrophy with Tumor Necrosis Factor-α (TNFα). In all these models, we observed that NeuroHeal reduced muscle atrophy and that SIRT1 activation seems to be required for that. The treatment downregulated some critical markers of protein degradation: Muscle Ring Finger 1 (MuRF1), K48 poly-Ub chains, and p62/SQSTM1. Moreover, it seems to restore the autophagy flux associated with denervation. Hence, we envisage a prospective use of NeuroHeal at clinics for different myopathies.

Gene-Metabolite Network Linked to Inhibited Bioenergetics in Association With Spaceflight-Induced Loss of Male Mouse Quadriceps Muscle.

ABSTRACTProlonged residence of mice in spaceflight is a scientifically robust and ethically ratified model of muscle atrophy caused by continued unloading. Under the Rodent Research Program of the National Aeronautics and Space Administration (NASA), we assayed the large‐scale mRNA and metabolomic perturbations in the quadriceps of C57BL/6j male mice that lived in spaceflight (FLT) or on the ground (control or CTR) for approximately 4 weeks. The wet weights of the quadriceps were significantly reduced in FLT mice. Next‐generation sequencing and untargeted mass spectroscopic assays interrogated the gene‐metabolite landscape of the quadriceps. A majority of top‐ranked differentially suppressed genes in FLT encoded proteins from the myosin or troponin families, suggesting sarcomere alterations in space. Significantly enriched gene‐metabolite networks were found linked to sarcomeric integrity, immune fitness, and oxidative stress response; all inhibited in space as per in silico prediction. A significant loss of mitochondrial DNA copy numbers in FLT mice underlined the energy deprivation associated with spaceflight‐induced stress. This hypothesis was reinforced by the transcriptomic sequencing–metabolomics integrative analysis that showed inhibited networks related to protein, lipid, and carbohydrate metabolism, and adenosine triphosphate (ATP) synthesis and hydrolysis. Finally, we discovered important upstream regulators, which could be targeted for next‐generation therapeutic intervention for chronic disuse of the musculoskeletal system. © 2020 The Authors. Journal of Bone and Mineral Research published by American Society for Bone and Mineral Research.

The concept of skeletal muscle memory: Evidence from animal and human studies.

Within the current paradigm of the myonuclear domain theory, it is postulated that a linear relationship exists between muscle fibre size and myonuclear content. The myonuclear domain is kept (relatively) constant by adding additional nuclei (supplied by muscle satellite cells) during muscle fibre hypertrophy and nuclear loss (by apoptosis) during muscle fibre atrophy. However, data from recent animal studies suggest that myonuclei that are added to support muscle fibre hypertrophy are not lost within various muscle atrophy models. Such myonuclear permanence has been suggested to constitute a mechanism allowing the muscle fibre to (re)grow more efficiently during retraining, a phenomenon referred to as “muscle memory.” The concept of “muscle memory by myonuclear permanence” has mainly been based on data attained from rodent experimental models. Whether the postulated mechanism also holds true in humans remains largely ambiguous. Nevertheless, there are several studies in humans that provide evidence to potentially support or contradict (parts of) the muscle memory hypothesis. The goal of the present review was to discuss the evidence for the existence of “muscle memory” in both animal and human models of muscle fibre hypertrophy as well as atrophy. Furthermore, to provide additional insight in the potential presence of muscle memory by myonuclear permanence in humans, we present new data on previously performed exercise training studies. Finally, suggestions for future research are provided to establish whether muscle memory really exists in humans.

MP30-13 USE OF UNIFORMLY SIZED MUSCLE FIBER FRAGMENTS FOR THE TREATMENT OF URINARY INCONTINENCE

You have accessJournal of UrologyUrodynamics/Lower Urinary Tract Dysfunction/Female Pelvic Medicine: Female Incontinence: Therapy I (MP30)1 Apr 2020MP30-13 USE OF UNIFORMLY SIZED MUSCLE FIBER FRAGMENTS FOR THE TREATMENT OF URINARY INCONTINENCE In Kap Ko, Eun Sang Yoo, Sang Mi Park, Bu-Kyu Lee, John Jackson*, Ji Hyun Kim, James Yoo, and Anthony Atala In Kap KoIn Kap Ko More articles by this author , Eun Sang YooEun Sang Yoo More articles by this author , Sang Mi ParkSang Mi Park More articles by this author , Bu-Kyu LeeBu-Kyu Lee More articles by this author , John Jackson*John Jackson* More articles by this author , Ji Hyun KimJi Hyun Kim More articles by this author , James YooJames Yoo More articles by this author , and Anthony AtalaAnthony Atala More articles by this author View All Author Informationhttps://doi.org/10.1097/JU.0000000000000869.013AboutPDF ToolsAdd to favoritesDownload CitationsTrack CitationsPermissionsReprints ShareFacebookLinked InTwitterEmail Abstract INTRODUCTION AND OBJECTIVE: Treatment of muscle function loss due to traumatic injury, congenital defects, or tumor ablations is clinically challenging. The current treatment standard is grafting of autologous muscle flaps, however significant donor site morbidity and graft tissue availability remain a problem. Alternatively, muscle fiber therapy has been attempted to treat muscle injury by transplanting single fibers into the defect site. However, irregularly organized long fibers resulted in low survivability due to delay in vascular and neural integration, thus limiting the therapeutic efficacy. Therefore, no effective method is available to permanently restore extensive muscle injuries. To address the current limitations, we developed a novel method that produces uniformly sized native muscle fiber fragments (MFFs) for muscle transplantation. We hypothesized that fragmentation of muscle fibers into small and uniformly sized fragments would allow for rapid reassembly and efficient engraftment within the defect site, resulting in accelerated recovery of muscle function. In this study, we applied autologous MFFs to restore sphincteric muscle anatomy and function for the treatment of urinary incontinence. METHODS: We developed an MFF processing method that produces uniformly sized fragments (approximately 100 μm in width and length) with intact muscle cells on the fiber surface. To test the therapeutic effects of the MFF technology, we created several rodent muscle injury models, including 1) a muscle atrophy model using toxin treatment such as barium chloride (BaCl2), 2) a volumetric muscle defect model by surgical ablation, and 3) urinary incontinence (UI) model by damaging the external sphincter of urethra. The effectiveness of the MFF therapy was determined by structural and functional recovery of muscle tissues in these models. RESULTS: The processed MFFs have a dimension of approximately 100 μm and contain living muscle cells on extracellular matrices (ECM). In preclinical animal studies using muscle atrophy, volumetric defect, and urinary incontinence models, histological and functional analyses confirmed that the transplanted MFFs into the injury sites were able to effectively integrate with host muscle tissue, vascular, and neural systems, which resulted in significant improvement of muscle function and mass. CONCLUSIONS: These results indicate that the MFF technology platform is a promising therapeutic option for the restoration of muscle function in several muscle defect models, including the urinary incontinence. The ease of preparation and short processing time makes this technology readily usable as a point of care procedure in the operating room. Source of Funding: Departmental funding © 2020 by American Urological Association Education and Research, Inc.FiguresReferencesRelatedDetails Volume 203Issue Supplement 4April 2020Page: e443-e443 Advertisement Copyright & Permissions© 2020 by American Urological Association Education and Research, Inc.MetricsAuthor Information In Kap Ko More articles by this author Eun Sang Yoo More articles by this author Sang Mi Park More articles by this author Bu-Kyu Lee More articles by this author John Jackson* More articles by this author Ji Hyun Kim More articles by this author James Yoo More articles by this author Anthony Atala More articles by this author Expand All Advertisement PDF downloadLoading ...

Developing of a Muscle Atrophy Model

Muscle atrophy is one of the most important and frequent problems observed in patients in Intensive Care Units following a surgery, immobilization, extended periods of bed rest as well as in sports medicine. All of these involves loss of muscle mass and decreased muscle strength which increases the risk for future health problems. Immobilization changes the function as well as structure of the peripheral neuromuscular system, and alters both protein degradation and synthesis. Therefore, effective therapeutic strategies to treat muscle wasting induced by immobilization are urgently required but first is necessary to validate and standardize the immobilization technique. In this work we develop a reproducible well‐characterized injury model using a modified Thomas‐ splint validated with mechanical force measurements, histology (H&amp;E and NADH), morphology and ultrasound imaging. Forty young Wistar male rats were divided into two groups: 1) Control‐ no immobilized extremities (CON; n=10) and 2) Unilateral right hindlimb immobilization at 3, 7 or 14 days (Im 3, Im 7, Im 14; n=10 for each group). Results showed a significant increment in body weight for Im 7 and Im 14 compared to CON. Experiments performed in tibialis anterior (TA) of Im muscle showed morphological changes in muscle weight and muscle diameter compared to CON confirmed by Ultrasound imaging. These changes were accompanied with a decrement in peak isometric tetanic force (Po) of immobilized muscles of 20%, 41% and 28% at 3, 7 and 14 days post injury, respectively. Fatigue time for all Im muscles was higher than CON ones (Im 3= 23%, Im 7=33% and Im 14=42%). Metabolic changes using NADH technique denoted an early increase of oxidative fibers and a decrement of glycolytic fibers at 7 days post‐injury compared to CON. In here, we developed, standardized and characterized an immobilization technique that can be used as a first approach to use effective therapeutic strategies to avoid muscle atrophy.Support or Funding InformationSupported partially by UNAM ‐PAPIIT RA207818 and CONACyT AI‐S‐17636 to KPGP.

Expression Levels of Long Non-Coding RNAs Change in Models of Altered Muscle Activity and Muscle Mass.

Skeletal muscle is a highly plastic organ that is necessary for homeostasis and health of the human body. The size of skeletal muscle changes in response to intrinsic and extrinsic stimuli. Although protein-coding RNAs including myostatin, NF-κβ, and insulin-like growth factor-1 (IGF-1), have pivotal roles in determining the skeletal muscle mass, the role of long non-coding RNAs (lncRNAs) in the regulation of skeletal muscle mass remains to be elucidated. Here, we performed expression profiling of nine skeletal muscle differentiation-related lncRNAs (DRR, DUM1, linc-MD1, linc-YY1, LncMyod, Neat1, Myoparr, Malat1, and SRA) and three genomic imprinting-related lncRNAs (Gtl2, H19, and IG-DMR) in mouse skeletal muscle. The expression levels of these lncRNAs were examined by quantitative RT-PCR in six skeletal muscle atrophy models (denervation, casting, tail suspension, dexamethasone-administration, cancer cachexia, and fasting) and two skeletal muscle hypertrophy models (mechanical overload and deficiency of the myostatin gene). Cluster analyses of these lncRNA expression levels were successfully used to categorize the muscle atrophy models into two sub-groups. In addition, the expression of Gtl2, IG-DMR, and DUM1 was altered along with changes in the skeletal muscle size. The overview of the expression levels of lncRNAs in multiple muscle atrophy and hypertrophy models provides a novel insight into the role of lncRNAs in determining the skeletal muscle mass.

Tinospora cordifolia protects from skeletal muscle atrophy by alleviating oxidative stress and inflammation induced by sciatic denervation

Ethanopharmacological relevanceTinospora cordifolia (TC) is widely being used as immunomodulatory and re-juvenile drug and well described in Indian Ayurveda system of medicine. Rejuvenation also means the fine tuning of the skeletal muscles. Skeletal muscle related disorder, i.e. atrophy is major problem which arise due to cachexia, sarcopenia and immobilization. However, despite of the great efforts, there is scarcity of FDA approved drugs in the market to treat skeletal muscle atrophy. Aim of the studyThe current study was aimed to explore the in-vitro and in-vivo efficacy and mechanism of TC in myogenic differentiation and skeletal muscle atrophy to establish the possibility of its usage to counteract skeletal muscle atrophy. Materials and methodsC2C12 cell lines were used to determine myogenic potential and anti-atrophic effects of T. cordifolia water extract (TCE). Its in-vitro efficacy was re-validated in vivo by supplementation of TCE at a dose of 200 mg/kg/p.o. for 30 days in denervated mice model of skeletal muscle atrophy. Effects of TCE administration on levels of oxidative stress, inflammatory markers and proteolysis were determined. ResultsTCE supplementation displayed increased lymphocyte proliferation and induced myogenic differentiation of C2C12 myoblasts by significantly increasing myocytes length and thickness, in comparison to control (p < 0.05). TCE supplementation decreased oxidative stress and inflammatory response by significantly modulating activities of catalase, glutathione peroxidase, lipid peroxidase, superoxide dismutase and β-glucuronidase (p < 0.05). It increased MF-20c expression and ameliorated degradation of muscle protein by down-regulating MuRF-1 and calpain activity. ConclusionTCE supplementation promotes myogenic differentiation in C2C12 cell lines and prevents denervation induced skeletal muscle atrophy by antagonizing the proteolytic systems (calpain and UPS) and maintaining the oxidative defense mechanism of the cell. Hence, TCE can be used as a protective agent against muscle atrophy.

Corticotropin releasing factor-overexpressing mouse is a model of chronic stress-induced muscle atrophy.

Chronic stress and continually high glucocorticoid levels can induce muscle atrophy. Unfortunately, there is a lack of appropriate animal models for stress-induced muscle atrophy research. Corticotropin releasing factor-overexpressing (CRF-OE) mice are a transgenic model of chronic stress that exhibit increased plasma corticosterone levels and Cushing’s syndrome; however, the skeletal muscle pathology of the CRF-OE mouse has not been well studied. We observed that male, 19-week-old CRF-OE mice had significantly lower skeletal muscle mass, average cross-sectional myofiber area, and total muscle protein content than their wild type (WT) littermates. Muscle function determined by grip strength, wire-hang, and open field tests showed that 19-week-old male CRF-OE mice had impaired physical ability. Additionally, the skeletal muscles of CRF-mice exhibited decreased expression of factors involved in the IGF-1/AKT/mTOR protein synthesis pathway and increased ubiquitin proteasome pathway activity compared to the WT control mice. In conclusion, 19-week-old CRF-OE mice display numerous features of muscle atrophy and thus serve as a model for investigating stress-induced muscle atrophy and interventions to target the deleterious effects of stress on skeletal muscle.

Age-related degeneration of the lumbar paravertebral muscles: Systematic review and three-level meta-regression.

Morphological changes of the lumbar spine muscles are not well characterised with ageing. To further the understanding of age-related degeneration of the lumbar spine musculature, normative morphological changes that occur within the paravertebral muscles must first be established. A systematic review and meta-regressions were conducted adhering to PRISMA guidelines. Searches for published and unpublished data were completed in June 2019. Searches returned 4781 articles. 34 articles were included in the quantitative analysis. Three-level meta-analyses showed age-related atrophy (r=-0.26; 95% CI: -0.33, -0.17) and fat infiltration (r=0.39; 95% CI: 0.28, 0.50) in the lumbar paravertebral muscles. Degenerative changes were muscle-specific and men (r=-0.32; 95% CI: -0.61, 0.01) exhibited significantly greater muscle atrophy than women (r=-0.24; 95% CI: -0.47, 0.03). Imaging modality, specifically ultrasound, also influenced age-related muscle atrophy. Measurements taken across all lumbar levels revealed the greatest fat infiltration with ageing (r=0.58, 95% CI: 0.35, 0.74). Moderators explained a large proportion of between-study variance in true effects for muscle atrophy (72.6%) and fat infiltration (79.8%) models. Lumbar paravertebral muscles undergo age-related degeneration in healthy adults with muscle, lumbar level and sex-specific responses. Future studies should use high-resolution imaging modalities to quantify muscle atrophy and fat infiltration.

Resistance exercise with anti-inflammatory foods attenuates skeletal muscle atrophy induced by chronic inflammation.

Chronic inflammation (CI) can contribute to muscle atrophy and sarcopenia. Resistance exercise (RE) promotes increased and/or maintenance of skeletal muscle mass, but the effects of RE in the presence of CI are unclear. In this study, we developed a novel animal model of CI-induced muscle atrophy and examined the effect of acute or chronic RE by electrical stimulation. CI was induced in young female Lewis rats by injection with peptidoglycan-polysaccharide (PG-PS). Extracellular signal-regulated kinase (ERK), p70S6 kinase (p70S6K), 4E binding protein 1 (4E-BP1), Akt, and Forkhead box O1 (FOXO1) phosphorylation levels increased in gastrocnemius (Gas) muscle from normal rats subjected to acute RE. After acute RE in CI rats, increased levels of phosphorylated ERK, p70S6K, and 4E-BP1, but not Akt or FOXO1, were observed. Chronic RE significantly increased the Gas weight in the exercised limb relative to the nontrained opposing limb in CI rats. Dietary supplementation with anti-inflammatory agents, eicosapentaenoic/docosahexaenoic acid and α-lactalbumin attenuated CI-induced muscle atrophy in the untrained Gas and could promote RE-induced inhibition of atrophy in the trained Gas. In the trained leg, significant negative correlations (r ≤ -0.80) were seen between Gas weights and CI indices, including proinflammatory cytokines and white blood cell count. These results indicated that the anabolic effects of RE are effective for preventing CI-induced muscle atrophy but are partially attenuated by inflammatory molecules. The findings also suggested that anti-inflammatory treatment together with RE is an effective intervention for muscle atrophy induced by CI. Taken together, we conclude that systemic inflammation levels are associated with skeletal muscle protein metabolism and plasticity.NEW & NOTEWORTHY This study developed a novel chronic inflammation (CI) model rat demonstrating that resistance exercise (RE) induced activation of protein synthesis signaling pathways and mitigated skeletal muscle atrophy. These anabolic effects were partially abrogated likely through attenuation of Akt/Forkhead box O1 axis activity. The degree of skeletal muscle atrophy was related to inflammatory responses. Dietary supplementation with anti-inflammatory agents could enhance the anabolic effect of RE. Our findings provide insight for development of countermeasures for CI-related muscle atrophy, especially secondary sarcopenia.

Long acting GLP-1 analog liraglutide ameliorates skeletal muscle atrophy in rodents

BackgroundSkeletal muscle atrophy is characterized by muscle wasting with partial or complete functional loss. Skeletal muscle atrophy severely affects the quality of life and currently, there is no available therapy except for spinal muscular atrophy. ObjectiveDrug repositioning is a promising strategy that reduces cost and time due to prior availability of safety and toxicity details. Here we investigated myogenic and anti-atrophy effects of glucagon-like peptide-1 (GLP-1) analog liraglutide. MethodsWe used several in vitro atrophy models in C2C12 cells and in vivo models in Sprague Dawley rats to study Liraglutide's efficacy. Western blotting was used to assess cAMP-dependent signaling pathways specifically activated by liraglutide. Therapeutic efficacy of liraglutide was investigated by histological analysis of transverse muscle sections followed by morphometry. Myogenic capacity was investigated by immunoblotting for myogenic factors. ResultsLiraglutide induced myogenesis in C2C12 myoblasts through GLP-1 receptor via a cAMP-dependent complex network of signaling events involving protein kinase A, phosphoinositide 3-kinase/protein kinase B, p38 mitogen-activated protein kinase and extracellular signal-regulated kinase. Liraglutide imparted protection against freeze injury, denervation, and dexamethasone -induced skeletal muscle atrophy and improved muscular function in all these models. In a therapeutic model, liraglutide restored myofibrillar architecture in ovariectomy-induced atrophy. Anti-atrophy actions of liraglutide involved suppression of atrogene expression and enhancement in expression of myogenic factors. ConclusionLiraglutide imparted protection and restored myofibrillar architecture in diverse models of muscle atrophy. Given its potent anti-atrophy, and recently reported osteoanabolic effects, we propose liraglutide's clinical evaluation in skeletal muscle atrophy and musculoskeletal disorders associated with diverse pathologies.