Atrophy and hypertrophy of skeletal muscles: structural and functional aspects

Concordance of Freehand 3D Ultrasound Muscle Measurements With Sarcopenia Parameters in a Geriatric Rehabilitation Ward

BACKGROUND

Sarcopenia is a devastating disease for older adults, but it lacks accessible and reliable tools for measuring total appendicular skeletal muscle mass (ASMM). Two-dimensional muscle ultrasound (US) has been developed for its bedside clinical advantages and feasibility but lacks standardization and prediction performance. We previously validated a new 3D-US technique to measure muscle volume (MV) at bedside and applied it in a geriatric rehabilitation setting. Objectives were to analyse the concordance between 3D-US MV and ASMM and compare concordance between 3D-US MV and 2D-US parameters with ASMM.

METHODS

Participants were recruited in a Geriatric rehabilitation ward in Nantes, France, from May to October 2022. Exclusion criteria were as follows: oedema in the lower limbs or recent history of unilateral lower limb damage or stroke. ASMM was measured with bioelectrical impedance analysis; 3D-US and 2D-US acquisitions were performed on three muscles of the right lower limb. Measures of strength (hand grip, knee extension and ankle dorsiflexion) were also recorded. Reliability of 3D-US MV measurements on 10 participants was high (ICC = 0.99). We used Lin's concordance correlation coefficients (CCC) and bias correction factor for agreement between variables and linear regression models for prediction equations.

RESULTS

Fifty-eight participants had an interpretable ASMM of whom 17 (29%) had a diagnosis of sarcopenia. Volumes of TA, RF and VL were all significantly concordant with ASMM measured by BIA (all p values < 0.001), with CCCs respectively of 0.72, 0.61 and 0.60. MV were all significantly concordant with isometric strength (p values < 0.001). Concordance and correlation with ASMM were higher with 3D-US than 2D-US measurements regardless of the muscle. Prediction of ASMM reached an adjusted R2 of 0.8 with tibialis anterior volume, biometrics and 2D measurements.

CONCLUSIONS

This study was the first to use 3D-US in a geriatric setting and develop a model to predict ASMM in very old hospitalized patients. MV measurements with 3D-US proved to be reliable and more concordant with appendicular muscle mass and strength than 2D parameters.

Non-Invasive and Quantitative Evaluation for Disuse Muscle Atrophy Caused by Immobilization After Limb Fracture Based on Surface Electromyography Analysis

BACKGROUND

The clinical evaluation for disuse muscle atrophy usually depends on qualitative rating indicators with subjective judgments of doctors and some invasive measurement methods such as needle electromyography. Surface electromyography, as a non-invasive method, has been widely used in the detection of muscular and neurological diseases in recent years. In this paper, we explore how to evaluate disuse muscle atrophy based on surface electromyography; Methods: Firstly, we conducted rat experiments using hind-limb suspension to create a model of disuse muscle atrophy. Five groups of rats were suspended for 0, 3, 7, 14, and 21 days, respectively. We induced leg electromyography of rats through electrical stimulation and used fluorescence staining to obtain the fiber-type composition of rats' leg muscles. We obtained the best-fitting frequency bands of power spectrum density of surface electromyography for type I and type II fibers in rats' leg muscles by changing the frequency band boundaries. Secondly, we conducted tests on the human body and collected the electromyography of the atrophied muscles of the subjects over a period of 21 days. The changes in muscle fiber composition were evaluated using the frequency bands of power spectrum density obtained from rat experiments. The method was to evaluate the changes in type I fibers by the changes in the area of the best-fitting frequency band of type I fibers and to evaluate the changes in type II fibers by the changes in the area of the best-fitting frequency band of type II fibers.

RESULTS

The results of rat experiments showed that type I fibers best fit the frequency band of 20-330 Hz and type II fibers best fit the frequency band of 176-500 Hz. The results of human testing showed that the atrophy of the two types of fibers was consistent with the changes in the areas of the corresponding best-fitting frequency bands.

CONCLUSIONS

The test results demonstrate the feasibility of using surface electromyography to evaluate muscle fiber-type composition and subsequently assess muscle atrophy. Further research may contribute to the diagnosis and treatment of disuse muscle atrophy.

Effects of Rehabilitative Exercise and Neuromuscular Electrical Stimulation on Muscle Morphology and Dynamic Balance in Individuals with Chronic Ankle Instability

Background and Objectives: Muscle atrophy caused by chronic ankle instability (CAI) can incur muscle weakness, altered movement patterns, and increased risk of injury. Previous studies have investigated the effects of rehabilitative exercises and neuromuscular electrical stimulation (NMES) on characteristics in CAI individuals, but few studies have examined their effects on foot and ankle muscle morphology. This study aimed to determine the effects of rehabilitative exercises and NMES on muscle morphology and dynamic balance in individuals with CAI. Materials and Methods: Participants with CAI (n = 47) were randomly divided into control (CG), rehabilitative exercise (REG), NMES (NG), and rehabilitative exercise and NMES combined (RNG) groups. The six-week intervention program consisting of rehabilitative exercises and NMES was applied to groups excluding CG. Muscle morphology and dynamic balance were evaluated using a portable wireless diagnostic ultrasound device and dynamic balance tests. For statistical analysis, an effect size with 95% confidence interval was calculated to assess mean differences according to intervention. Results: After six weeks, significant increases in morphology and dynamic balance were observed for all muscles except flexor hallucis longus (p > 0.05) in the intervention groups except for CG. However, no significant changes were observed in the CG (p > 0.05). Conclusions: These findings suggest that intervention programs may help prevent muscle atrophy and improve balance in CAI individuals.

Effects of thyroid hormones in skeletal muscle protein turnover

Thyroid hormones (THs) are critical regulators of muscle metabolism in both healthy and unhealthy conditions. Acting concurrently as powerful anabolic and catabolic factors, THs are endowed with a vital role in muscle mass maintenance. As a result, thyroid dysfunctions are the leading cause of a wide range of muscle pathologies, globally identified as myopathies. Whether muscle wasting is a common feature in patients with hyperthyroidism and is mainly caused by THs-dependent stimulation of muscle proteolysis, also muscle growth is often associated with hyperthyroid conditions, linked to THs-dependent stimulation of muscle protein synthesis. Noteworthy, also hypothyroid status negatively impacts on muscle physiology, causing muscle weakness and fatigue. Most of these symptoms are due to altered balance between muscle protein synthesis and breakdown. Thus, a comprehensive understanding of THs-dependent skeletal muscle protein turnover might facilitate the management of physical discomfort or weakness in conditions of thyroid disease. Herein, we describe the molecular mechanisms underlying the THs-dependent alteration of skeletal muscle structure and function associated with muscle atrophy and hypertrophy, thus providing new insights for targeted modulation of skeletal muscle dynamics.

Relationship between paraspinal muscle properties and bone mineral density based on QCT in patients with lumbar disc herniation

OBJECTIVE

Increasing research suggests that paraspinal muscle fat infiltration may be a potential biological marker for the assessment of osteoporosis. Our aim was to investigate the relationship between lumbar paraspinal muscle properties on MRI and volumetric bone mineral density (vBMD) based on QCT in patients with lumbar disc herniation (LDH).

METHODS

A total of 383 patients (aged 24-76 years, 193 females) with clinically and radiologically diagnosed LDH were enrolled in this retrospective study. The muscle cross-sectional area (CSA) and the proton density fat fraction (PDFF) were measured for the multifidus (MF), erector spinae (ES) and psoas major (PS) at the central level of L3/4, L4/5 and L5/S1 on lumbar MRI. QCT was used to measure the vBMD of two vertebral bodies at L1 and L2 levels. Patients were divided into three groups based on their vBMD values: normal bone density group (> 120 mg/cm3), osteopenia group (80 to 120 mg/cm3) and osteoporosis group (< 80 mg/cm3). The differences in paraspinal muscle properties among three vBMD groups were tested by one-way ANOVA with post hoc analysis. The relationships between paraspinal muscle properties and vBMD were analyzed using Pearson correlation coefficients. Furthermore, the association between vBMD and paraspinal muscle properties was further evaluated using multiple linear regression analysis, with age and sex also included as predictors.

RESULTS

Among the 383 LDH patients, 191 had normal bone density, 129 had osteopenia and 63 had osteoporosis. In LDH patients, compared to normal and osteopenia group, paraspinal muscle PDFF was significantly greater in osteoporosis group, while paraspinal muscle CSA was lower (p < 0.001). After adjusting for age and sex, it was found that MF PDFF and PS CSA were found to be independent factors influencing vBMD (p < 0.05).

CONCLUSION

In patients with LDH, paraspinal muscle properties measured by IDEAL-IQ sequence and lumbar MR scan were found to be related to vBMD. There was a correlation between the degree of paraspinal muscle PDFF and decreasing vBMD, as well as a decrease paraspinal muscle CSA with decreasing vBMD. These findings suggest that clinical management should consider offering tailored treatment options for patients with LDH based on these associations.

Validation of a scanning technique with minimal compression for measuring muscle volume with freehand 3D ultrasound

Freehand 3D ultrasound (3D-US) is a promising technique for measuring muscle volume but it requires gel pads or water tanks to limit probe compression on the skin which makes it hard to use in clinical applications. Our objectives were to measure the effect of different compressions on muscle volume in order to assess the clinical applicability of a minimal compression method for lower limb muscles. 4 muscles of the lower limb on 15 healthy volunteers were scanned with a new commercial freehand 3D-US setup accessible to clinical experimentators. Each muscle was scanned with 3 levels of compression: standard compression, minimal compression and gel pad (method validated against MRI). Volume was calculated using software segmentation tools. Acquisitions and segmentations were done by the same examiner. There was a significant impact of standard compression on volume measurements, but no difference between minimal compression and gel pad. Standard compression underestimated volume with a mean bias of 16 mL. For minimal compression, 75 % of measured differences were below the predefined clinically acceptable limits of 10 mL. Mean bias for this method was 1.1 mL. In conclusion, standard compression in freehand 3D-US induces a systematic bias in volume calculations. But, with a trained examiner and the necessary precautions to minimize compression, this bias could be abolished and become acceptable in clinical applications. When a high accuracy is required, gel pads could still be important to consider.

An electrical stimulation intervention protocol to prevent disuse atrophy and muscle strength decline: an experimental study in rat

BACKGROUND

Skeletal muscle is negatively impacted by conditions such as spaceflight or prolonged bed rest, resulting in a dramatic decline in muscle mass, maximum contractile force, and muscular endurance. Electrical stimulation (ES) is an essential tool in neurophysiotherapy and an effective means of preventing skeletal muscle atrophy and dysfunction. Historically, ES treatment protocols have used either low or high frequency electrical stimulation (LFES/HFES). However, our study tests the use of a combination of different frequencies in a single electrical stimulation intervention in order to determine a more effective protocol for improving both skeletal muscle strength and endurance.

METHODS

An adult male SD rat model of muscle atrophy was established through 4 weeks of tail suspension (TS). To investigate the effects of different frequency combinations, the experimental animals were treated with low (20 Hz) or high (100 Hz) frequency before TS for 6 weeks, and during TS for 4weeks. The maximum contraction force and fatigue resistance of skeletal muscle were then assessed before the animals were sacrificed. The muscle mass, fiber cross-sectional area (CSA), fiber type and related protein expression were examined and analyzed to gain insights into the mechanisms by which the ES intervention protocol used in this study regulates muscle strength and endurance.

RESULTS

After 4 weeks of unloading, the soleus muscle mass and fiber CSA decreased by 39% and 58% respectively, while the number of glycolytic muscle fibers increased by 21%. The gastrocnemius muscle fibers showed a 51% decrease in CSA, with a 44% decrease in single contractility and a 39% decrease in fatigue resistance. The number of glycolytic muscle fibers in the gastrocnemius also increased by 29%. However, the application of HFES either prior to or during unloading showed an improvement in muscle mass, fiber CSA, and oxidative muscle fibers. In the pre-unloading group, the soleus muscle mass increased by 62%, while the number of oxidative muscle fibers increased by 18%. In the during unloading group, the soleus muscle mass increased by 29% and the number of oxidative muscle fibers increased by 15%. In the gastrocnemius, the pre-unloading group showed a 38% increase in single contractile force and a 19% increase in fatigue resistance, while in the during unloading group, a 21% increase in single contractile force and a 29% increase in fatigue resistance was observed, along with a 37% and 26% increase in the number of oxidative muscle fibers, respectively. The combination of HFES before unloading and LFES during unloading resulted in a significant elevation of the soleus mass by 49% and CSA by 90%, with a 40% increase in the number of oxidative muscle fibers in the gastrocnemius. This combination also resulted in a 66% increase in single contractility and a 38% increase in fatigue resistance.

CONCLUSION

Our results indicated that using HFES before unloading can reduce the harmful effects of muscle unloading on the soleus and gastrocnemius muscles. Furthermore, we found that combining HFES before unloading with LFES during unloading was more effective in preventing muscle atrophy in the soleus and preserving the contractile function of the gastrocnemius muscle.

Mitochondrial Dysfunction as an Underlying Cause of Skeletal Muscle Disorders

Mitochondria are an important energy source in skeletal muscle. A main function of mitochondria is the generation of ATP for energy through oxidative phosphorylation (OXPHOS). Mitochondrial defects or abnormalities can lead to muscle disease or multisystem disease. Mitochondrial dysfunction can be caused by defective mitochondrial OXPHOS, mtDNA mutations, Ca2+ imbalances, mitochondrial-related proteins, mitochondrial chaperone proteins, and ultrastructural defects. In addition, an imbalance between mitochondrial fusion and fission, lysosomal dysfunction due to insufficient biosynthesis, and/or defects in mitophagy can result in mitochondrial damage. In this review, we explore the association between impaired mitochondrial function and skeletal muscle disorders. Furthermore, we emphasize the need for more research to determine the specific clinical benefits of mitochondrial therapy in the treatment of skeletal muscle disorders.

Adenosine monophosphate activated protein kinase contributes to skeletal muscle health through the control of mitochondrial function

Skeletal muscle is one of the largest organs in the body and the largest protein repository. Mitochondria are the main energy-producing organelles in cells and play an important role in skeletal muscle health and function. They participate in several biological processes related to skeletal muscle metabolism, growth, and regeneration. Adenosine monophosphate-activated protein kinase (AMPK) is a metabolic sensor and regulator of systemic energy balance. AMPK is involved in the control of energy metabolism by regulating many downstream targets. In this review, we propose that AMPK directly controls several facets of mitochondrial function, which in turn controls skeletal muscle metabolism and health. This review is divided into four parts. First, we summarize the properties of AMPK signal transduction and its upstream activators. Second, we discuss the role of mitochondria in myogenesis, muscle atrophy, regeneration post-injury of skeletal muscle cells. Third, we elaborate the effects of AMPK on mitochondrial biogenesis, fusion, fission and mitochondrial autophagy, and discuss how AMPK regulates the metabolism of skeletal muscle by regulating mitochondrial function. Finally, we discuss the effects of AMPK activators on muscle disease status. This review thus represents a foundation for understanding this biological process of mitochondrial dynamics regulated by AMPK in the metabolism of skeletal muscle. A better understanding of the role of AMPK on mitochondrial dynamic is essential to improve mitochondrial function, and hence promote skeletal muscle health and function.

Sports Elite Means Vaccine Elite? Concerns and Beliefs Related to COVID-19 Vaccines among Olympians and Elite Athletes

(1) Background: The purpose of this study was to investigate the concerns and beliefs of Olympians and elite athletes toward COVID-19 vaccination. (2) Methods: The study was framed by a quantitative method and was conducted using the PAPI (pen and paper interview) technique among 895 Polish elite athletes representing 34 sports. (3) Results: Three-quarters (76.3%) of the athletes were vaccinated against COVID-19; statistically participants were more likely to be women, and athletes who participated in the Olympic Games. Four in ten (39.2%) were in favor of vaccination. Athletes were mainly concerned that COVID-19 would exclude them from training/competition (19.3%) and could have a long-term impact on their health (17.2%). Athletes who were vaccinated reported much higher confidence in the composition of the vaccine and the doctors who recommended vaccination than unvaccinated athletes. Athletes who competed at the Olympic level were more likely than others to disbelieve that vaccines were produced too quickly and were not well tested. National-level athletes showed the highest degree of distrust in the government regarding COVID-19 vaccination, with one in six respondents distrusting doctors with respect to COVID-19 vaccination. Four in ten respondents said they were in favor of vaccination. (4) Conclusions: Athletes' attitudes toward COVID-19 vaccination were significantly influenced by their environment-especially coaches and relatives. The power of social norms with respect to the decision to vaccinate against COVID-19 was very strong. Therefore, it is essential to build awareness about preventive policies among athletes and their social environment.

Consequences of ankle joint immobilisation: insights from a morphometric analysis about fibre typification, intramuscular connective tissue, and muscle spindle in rats

Orthosis immobilisations are routinely used in orthopaedic procedures. This intervention is applicable in bone fractures, ligament injuries, and tendonitis, among other disorders of the musculoskeletal system. We aimed to evaluate the effects of ankle joint functional immobilisation on muscle fibre morphology, connective tissue, muscle spindle and fibre typification triggered by a novel metallic orthosis. We developed a rodent-proof experimental orthosis able to hold the tibiotalar joint in a functional position for short and long terms. The tibialis anterior muscles of free and immobilised legs were collected and stained by histology and histochemistry techniques to investigate general muscle morphology, connective tissue and muscle fibre typification. Morphometric analysis of muscle cross-section area, fibre type cross-section area, fibre type density, percentage of intramuscular connective tissue, and thickness of the muscle spindle capsule were obtained to gain insights into the experimental protocol. We found that short- and long-term immobilisation decreased the cross-section area of the muscles and induced centralisation of myonuclei. The connective tissue of immobilised muscle increased after 2 and 4 weeks mainly by deposition of type III and type I collagen fibres in the perimysium and endomysium, respectively, in addition to muscle spindle capsule thickening. Type IIB muscle fibre was severely affected in our study; the profile assumed odd shapes, and our data suggest interconversion of these fibre types within long-term immobilisation. In conclusion, our protocol has produced structural and histochemical changes in muscle biology. This method might be applied to various rodent models that enable genetic manipulation for the investigation of muscle degeneration/regeneration processes.

Covid-19 and the impact on young athletes

The Covid-19 pandemic has disrupted organised sport in the community as authorities cancelled, greatly modified or postponed sporting participation as part of a strategy to reduce transmission of the virus. This had a significant impact on young athletes and their families in relation to their psycho-social, physical and career progression considerations. The disruption is likely to continue for some years, considering the constraints of lockdowns, the need to overcome dysfunctional national logistics for delivery of medical care, fund and implement an efficacious vaccine programme locally, nationally and worldwide, develop sufficient herd immunity and create an environment of confidence in the safety of returning to sports for participants, coaches, umpires, administrators and observers. This article will consider the interim challenges regarding the physical and psychosocial importance of maintaining an active sporting programme for young athletes, reflect on safety measures for modifying sporting equipment and environmental protections to allow safest participation in training and competition and provide advice on protocols for a gradual return to sport for the young athlete after infection with Covid-19.

Psychological States and Training Habits during the COVID-19 Pandemic Lockdown in Spanish Basketball Athletes

The outbreak of the COVID-19 pandemic and the resulting restrictions designed to slow the spread of infection greatly disrupted people’s lives. The present study aimed to investigate the impact of lockdown on the psychology, training, and sleep habits of a cohort of basketball players. An online survey involving 169 professional and amateur athletes was conducted using four validated psychological questionnaires (WLEIS-S, POMS, BRS, SMS-II) and a Likert scale to measure the rating of perceived exertion (RPE) and training variables. Gender differences in fatigue (p = 0.022); friendships (p = 0.017); others’ emotional appraisal (p < 0.001); and resilience (p = 0.031) were apparent, with higher values for women in all categories bar resilience. Comparisons before and during the lockdown revealed that all participants reduced their RPE (p < 0.001); training days (p = 0.004); and training hours (p < 0.001), and experienced a decline in the quality of sleep (p < 0.001). Sleep hours (p < 0.001) increased during lockdown. The professionals and females maintained their training days (p > 0.05), while the non-professionals and males did not. Psychological states during lockdown were a predictor of the differences in training and recovery variables. In situations where training and competition are limited, it is important to develop plans to maintain physical activity, good quality sleep, and promote greater emotional management and understanding to control negative moods.

Understanding lower limb muscle volume adaptations to amputation

Amputation of a major limb, and the subsequent return to movement with a prosthesis, requires the development of compensatory strategies to account for the loss. Such strategies, over time, lead to regional muscle atrophy and hypertrophy through chronic under or overuse of muscles compared to uninjured individuals. The aim of this study was to quantify the lower limb muscle parameters of persons with transtibial and transfemoral amputations using high resolution MRI to ascertain muscle volume and to determine regression equations for predicting muscle volume using femur- and tibia-length, pelvic-width, height, and mass. Twelve persons with limb loss participated in this study and their data were compared to six matched control subjects. Subjects with unilateral transtibial amputation showed whole-limb muscle volume loss in the residual-limb, whereas minor volume changes in the intact limb were found, providing evidence for a compensation strategy that is dominated by the intact-limb. Subjects with bilateral-transfemoral amputations showed significant muscle volume increases in the short adductor muscles with an insertion not affected by the amputation, the hip flexors, and the gluteus medius, and significant volume decreases in the longer adductor muscles, rectus femoris, and hamstrings. This study presents a benchmark measure of muscle volume discrepancies in persons with limb-loss, and can be used to understand the compensation strategies of persons with limb-loss and the impact on muscle volume, thus enabling the development of optimised intervention protocols, conditioning therapies, surgical techniques, and prosthetic devices that promote and enhance functional capability within the population of persons with limb loss.

Radiotherapy before or during androgen-deprivation therapy does not blunt the exercise-induced body composition protective effects in prostate cancer patients: A secondary analysis of two randomized controlled trials

BACKGROUND

Androgen deprivation therapy (ADT) contributes to lean mass loss and adiposity increases in prostate cancer patients. Radiotherapy during ADT might act synergistically and further worsen body composition. Previous investigations have shown that resistance training is an effective method of preserving body composition during ADT, however, most have not accounted for direct or indirect effects of other therapies, such as radiotherapy. Therefore, the purpose of this study was to examine training adaptations of the tissue composition in patients receiving radiation therapy (RT) prior or during ADT.

METHODS

Analyses were performed by combining data from two previous trials for a total of 131 prostate cancer patients who underwent a combination of resistance and aerobic exercise training (N = 70, age: 68.9 ± 6.6y, RT-before: 13%, RT-during: 14%) or usual care (N = 61, age: 67.5 ± 7.9y, RT-before: 16%, RT-during: 20%) for 3 months upon ADT onset. Whole-body lean mass (LM), fat percentage and appendicular LM were determined by dual energy x-ray absorptiometry, and lower-leg muscle area and density by peripheral computed tomography at baseline (onset of ADT) and at 3 months post-intervention. Covariates included RT prior and during the intervention, demographic characteristics, physical symptoms, and chronic conditions.

RESULTS

Radiotherapy before or during the intervention did not affect body composition. Only the usual care group experienced a significant decrease in whole-body LM (-994 ± 150 g, P < 0.001) and appendicular LM (-126 ± 19 g, P < 0.001), and an increase in whole-body fat percentage (1% ± 0.1%, P < 0.001). There was no change in lower-leg muscle area or density in either group.

CONCLUSION

We suggest that radiation prior to and during ADT does not interfere with the beneficial effects of exercise training on body composition in men with prostate cancer.

Chrysanthemum zawadskil Herbich attenuates dexamethasone-induced muscle atrophy through the regulation of proteostasis and mitochondrial function

Chrysanthemum zawadskii Herbich (CZH) is used in traditional medicine to treat inflammatory diseases and diabetes. However, the effects of CZH on muscle wasting remains to be studied. Here, we investigated the effect of CZH on dexamethasone (DEX), a synthetic glucocorticoid, induced muscle atrophy. To examine the effect of CZH on muscle atrophy, C2C12 myotubes were co-treated with DEX and CZH for 24 h. The treatment with CZH prevented DEX-induced myotube atrophy in a dose-dependent manner. CZH inhibited the DEX-induced decrease of the MHC isoforms and the upregulation of atrogin-1 and MuRF1 in C2C12 differentiated cells. C57BL/6 mice were supplemented with 0.1 % CZH for 8 weeks, with DEX-induced muscle atrophy stimulated in the last 3 weeks. In the mice, CZH supplementation effectively reversed DEX-induced skeletal muscle atrophy and increased the exercise capacity of the mice through the inhibition of glucocorticoid receptor translocation. Additionally, we observed that DEX-evoked impaired proteostasis was ameliorated via the Akt/mTOR pathway. CZH also prevented the DEX-induced decrease in the mitochondrial respiration. HPLC analysis demonstrated the highest concentration of acacetin-7-O-β-d-rutinoside (AR) among 4 compounds. Moreover, AR, a functional compound of CZH, prevented DEX-evoked muscle atrophy. Thus, we suggest that CZH could be a potential therapeutic candidate against muscle atrophy and AR is the main functional compound of CZH.

Proteomic Characterization of Normal and Woody Breast Meat from Broilers of Five Genetic Strains

Woody breast (WB) is an emergent broiler myopathy that is macroscopically characterized by hardened areas of the Pectoralis major muscle. Five genetic strains (strains 1–5) of mixed-sex broilers were fed either a control or an amino acid (AA)-reduced diet (20% reduction of digestible lysine, total sulfur AAs, and threonine) for 8 wk. Differences between whole-muscle proteome profiles of normal breast (NB; n = 6 gels) and WB tissue (n = 6 gels) were characterized for (1) broiler strains 1–5 that were fed with a control diet and collected at 0 min; (2) strain 5 (control diet) that were collected at 15 min, 4 h, and 24 h; (3) strain 5 (0 min) that were fed with a control and an AA-reduced diet. Birds that yielded WB were heavier and had a greater pH at death (pH0min) than normal birds. Results indicated that 21 proteins were more abundant (P &lt; 0.05) and 3 proteins were less abundant (P &lt; 0.05) in WB compared with NB. The differentially abundant proteins in each comparison were consistently upregulated or downregulated in WB tissue although the different protein profiles were noticed for each comparison. Strains 2 and 5 had more protein profile differences between WB and NB meat than strains 1, 3, and 4, which potentially indicates a stronger genetic component for strains 2 and 5 with respect to WB formation. The proteins that were more abundant in WB compared to NB are involved in carbohydrate metabolism, oxidative stress, cytoskeleton structure, and transport and signaling. Ingenuity Pathway Analysis indicated that regulated pathways in WB were mainly related to carbohydrate metabolism, cellular repair, cellular organization and maintenance, and cell death and survival. The results support the potential causes of WB myopathy, including the presence of hypoxia, oxidative stress, increased apoptosis, misfolded proteins, and inflammation.

Strategies and Solutions for Team Sports Athletes in Isolation due to COVID-19

In December of 2019, there was an outbreak of a severe acute respiratory syndrome caused by the Coronavirus 2 (SARS-CoV-2 or COVID-19) in China. The virus rapidly spread into the whole World causing an unprecedented pandemic and forcing governments to impose a global quarantine, entering an extreme unknown situation. The organizational consequences of quarantine/isolation are: absence of organized training and competition, lack of communication among athletes and coaches, inability to move freely, lack of adequate sunlight exposure, inappropriate training conditions. Based on the current scientific, we strongly recommend encouraging the athlete to reset their mindset to understand quarantine as an opportunity for development, organizing appropriate guidance, educating and encourage athletes to apply appropriate preventive behavior and hygiene measures to promote immunity and ensuring good living isolation conditions. The athlete's living space should be equipped with cardio and resistance training equipment (portable bicycle or rowing ergometer). Some forms of body mass resistance circuit-based training could promote aerobic adaptation. Sports skills training should be organized based on the athlete's needs. Personalized conditioning training should be carried out with emphasis on neuromuscular performance. Athletes should also be educated about nutrition (Vitamin D and proteins) and hydration. Strategies should be developed to control body composition. Mental fatigue should be anticipated and mental controlled. Adequate methods of recovery should be provided. Daily monitoring should be established. This is an ideal situation in which to rethink personal life, understanding the situation, that can be promoted in these difficult times that affect practically the whole world.

Remarkable Homeostasis of Protein Sialylation in Skeletal Muscles of Hibernating Daurian Ground Squirrels (Spermophilus dauricus)

As the most common post-translational protein modification, glycosylation is intimately linked to muscle atrophy. This study aimed to investigate the performance of protein glycosylation in the soleus muscle (SOL) in Daurian ground squirrels (Spermophilus dauricus) and to determine the potential role of protein glycosylation in the mechanism underlying disuse muscle atrophy prevention. The results showed that (1) seven glycan structures comprising sialic acid α2-3 galactose (SAα2-3Gal) were altered during hibernation; (2) alterations in the SAα2-3Gal structure during hibernation were based on changes in the expression levels of beta-galactoside alpha-2 and 3-sialyltransferases; and (3) α2-3–linked sialylated modifications of heat shock cognate 70 and pyruvate kinase and expression of 14-3-3 epsilon protein were oscillatorily changed during hibernation. Our findings indicate that the skeletal muscles of hibernating Daurian ground squirrels maintain protein sialylation homeostasis by restoring sialylation modification during periodic interbout arousal, which might protect the skeletal muscles against disuse atrophy.

Skeletal muscle: A review of molecular structure and function, in health and disease

Decades of research in skeletal muscle physiology have provided multiscale insights into the structural and functional complexity of this important anatomical tissue, designed to accomplish the task of generating contraction, force and movement. Skeletal muscle can be viewed as a biomechanical device with various interacting components including the autonomic nerves for impulse transmission, vasculature for efficient oxygenation, and embedded regulatory and metabolic machinery for maintaining cellular homeostasis. The "omics" revolution has propelled a new era in muscle research, allowing us to discern minute details of molecular cross-talk required for effective coordination between the myriad interacting components for efficient muscle function. The objective of this review is to provide a systems-level, comprehensive mapping the molecular mechanisms underlying skeletal muscle structure and function, in health and disease. We begin this review with a focus on molecular mechanisms underlying muscle tissue development (myogenesis), with an emphasis on satellite cells and muscle regeneration. We next review the molecular structure and mechanisms underlying the many structural components of the muscle: neuromuscular junction, sarcomere, cytoskeleton, extracellular matrix, and vasculature surrounding muscle. We highlight aberrant molecular mechanisms and their possible clinical or pathophysiological relevance. We particularly emphasize the impact of environmental stressors (inflammation and oxidative stress) in contributing to muscle pathophysiology including atrophy, hypertrophy, and fibrosis. This article is categorized under: Physiology > Mammalian Physiology in Health and Disease Developmental Biology > Developmental Processes in Health and Disease Models of Systems Properties and Processes > Cellular Models.

O-GlcNAcylation as a regulator of the functional and structural properties of the sarcomere in skeletal muscle: An update review

Although the O-GlcNAcylation process was discovered in 1984, its potential role in the physiology and physiopathology of skeletal muscle only emerged 20 years later. An increasing number of publications strongly support a key role of O-GlcNAcylation in the modulation of important cellular processes which are essential for skeletal muscle functions. Indeed, over a thousand of O-GlcNAcylated proteins have been identified within skeletal muscle since 2004, which belong to various classes of proteins, including sarcomeric proteins. In this review, we focused on these myofibrillar proteins, including contractile and structural proteins. Because of the modification of motor and regulatory proteins, the regulatory myosin light chain (MLC2) is related to several reports that support a key role of O-GlcNAcylation in the fine modulation of calcium activation parameters of skeletal muscle fibres, depending on muscle phenotype and muscle work. In addition, another key function of O-GlcNAcylation has recently emerged in the regulation of organization and reorganization of the sarcomere. Altogether, this data support a key role of O-GlcNAcylation in the homeostasis of sarcomeric cytoskeleton, known to be disturbed in many related muscle disorders.

Transitional Hybrid Skeletal Muscle Fibers in Rat Soleus Development

Skeletal muscles comprise hundreds of individual muscle fibers, with each possessing specialized contractile properties. Skeletal muscles are recognized as being highly plastic, meaning that the physiological properties of single muscle fibers can change with appropriate use. During fiber type transitions, one myosin heavy chain isoform is exchanged for another and over time the fundamental nature of the fiber adapts to become a different fiber type. Within the rat triceps surae complex, the soleus muscle starts out as a muscle comprised of a mixture type IIA and type I fibers. As neonatal rats grow and mature, the soleus undergoes a near complete transition into a muscle with close to 100% type I fibers at maturity. We used immunohistochemistry and single fiber SDS-PAGE to track the transformation of type IIA into type I fibers. We found that transitioning fibers progressively incorporate new myofibrils containing type I myosin into existing type IIA fibers. During this exchange, distinct type I-containing myofibrils are segregated among IIA myofibrils. The individual myofibrils within existing muscle fibers thus appear to represent the functional unit that is exchanged during fiber type transitions that occur as part of normal muscle development.

Effects of a 6-week intrinsic foot muscle exercise program on the functions of intrinsic foot muscle and dynamic balance in patients with chronic ankle instability

We aimed to evaluate the effects of a 6-week intrinsic foot muscle exercise program on the activation of intrinsic foot muscle movement and dynamic balance in adults with chronic ankle stability. A total of 30 adults with chronic ankle instability were recruited. The participants were randomly assigned to a group performing intrinsic foot muscle exercises and a control group doing no exercises. We measured the activation rate and dynamic balance of the abductor hallucis, flexor digitorum brevis, flexor hallucis brevis, and quadratus plantae before and after the intervention. We found that the activation rate and dynamic balance significantly increased in all intrinsic foot muscles in the experimental group. These results suggest that intrinsic foot muscle exercise for patients with chronic ankle stability is an effective treatment for improving the functions and balance ability of the intrinsic foot muscles.

Changes in the macroscopic morphology of hip muscles in low back pain

Low back pain is a major health issue affecting the lumbopelvic muscles. Morphological changes in hip muscles, such as alterations in the muscle cross-sectional area and muscle volume, may occur in patients with low back pain. This systematic review was conducted to investigate whether patients with low back pain have macroscopic changes in their hip muscle morphology compared with asymptomatic, healthy individuals, based on current evidence. The electronic databases of PubMed/Medline, Ovid, Scopus, Embase^® , and Google Scholar were searched from the inception to August 31, 2018. We only included full texts of original studies regarding macroscopic morphological alterations, including atrophy and fat infiltration, in hip muscles of patients with low back pain compared with asymptomatic controls. The quality of the included studies was determined using an assessment tool based on the Newcastle-Ottawa Scale. The scale was modified for the purposes of this study. Sixteen comparative observational studies were found eligible to be included in this review. Eleven were classified as high quality and four as moderate quality. The morphological changes in the psoas major, gluteus maximus, gluteus medius, gluteus minimus, and piriformis muscles were assessed in the primary studies. All selected studies were considered B level of evidence studies. The strength of conclusions for the psoas major, gluteal, and piriformis muscles was moderate. The results revealed that there is substantial controversy about the morphological changes in hip muscles in patients with low back pain; however, the majority of high-quality studies concluded that atrophy of hip muscles is evident in patients with low back pain. The psoas major muscle was the most commonly investigated hip muscle for morphological changes. Major methodological limitations of the included studies were identified and discussed. The present systematic review does not include a formal meta-analysis because of very significant differences in the primary studies in terms of study populations and methodologies. Finally, in clinical practice, it is recommended that physical therapists develop exercise programs to improve hip muscle function in patients with low back pain.

Progressive resistance training for persons with intellectual disabilities and visual impairment

BACKGROUND

Knowledge concerning the feasibility and effects of progressive resistance training (PRT) for persons with intellectual disabilities and visual impairment who are categorized in Gross Motor Function Classification System (GMFCS) Level 1 is limited. The aim of our study was to evaluate feasibility and effect of PRT on participants' Quadriceps strength and personal goals.

METHODS

Eight Participants followed a PRT program for 10 weeks. Feasibility was determined by percentage of attendance and compliance. The effect of PRT was analyzed with a linear mixed model (p < 0.05) and by normalized bootstrap (95% CI).

RESULTS

Participants attended 87.8% of the sessions and trained according to the PRT program, indicating sufficient compliance. Quadriceps strength increased significantly by 69%, and participants' personal goals were achieved.

CONCLUSION

PRT is a feasible and potentially effective method for increasing Quadriceps strength as well as achieving personal goals in persons with intellectual disabilities and visual impairment with GMFCS Level 1.

Dual-Energy X-ray Absorptiometry and Bioelectrical Impedance Analysis are Beneficial Tools for Measuring the Trunk Muscle Mass of Patients with Low Back Pain

Introduction

Limb muscle mass measurement using dual-energy X-ray absorptiometry (DXA) is considered the gold standard for the diagnosis of sarcopenia. Moreover, bioelectrical impedance analysis (BIA) is also recognized as a beneficial tool considering its high correlation with DXA. However, it remains to be elucidated whether DXA and BIA can accurately measure trunk lean mass.

The aim of this study was to investigate the correlation between DXA and BIA measurements of trunk muscle mass and the cross-sectional area (CSA) of trunk muscles measured using magnetic resonance imaging (MRI) and to compare measures of trunk muscle mass obtained using DXA and BIA in patients with low back pain (LBP).

Methods

In total, 65 patients participated in the study. The correlation between DXA and BIA measurements and the CSA of trunk and paraspinal muscles at the L4-5 level were calculated. In addition, the correlation between DXA and BIA measurements of trunk muscle mass and the differences between these two measurements were determined.

Results

The correlation coefficient between DXA and BIA trunk muscle mass measurement and trunk muscle CSA was 0.74 and 0.56 for men and 0.69 and 0.44 for women, respectively. DXA and BIA measurement values showed a significantly moderate correlation with the CSA of the erector spinae (ES) and psoas major (PM). The multifidus (MF) CSA did not correlate with measurements of DXA and BIA in both men and women. Although DXA and BIA measurements were significantly correlated, a significant difference between these two measurements was found. BIA overestimated the trunk muscle mass significantly compared with DXA.

Conclusions

Trunk muscle mass measured with DXA and BIA was correlated with the CSA of most trunk muscles. Although the measurement of DXA and BIA showed a high correlation, BIA overestimated trunk muscle mass compared with DXA. Both DXA and BIA are beneficial for measuring trunk muscle mass.

da Silva F, Larina‐Neto R, Chadi G, Zanoteli E. Omega-3 multiple effects increasing glucocorticoid-induced muscle atrophy: autophagic, AMPK and UPS mechanisms

Muscle atrophy occurs in many conditions, including use of glucocorticoids. N-3 (omega-3) is widely consumed due its healthy properties; however, concomitant use with glucocorticoids can increase its side effects. We evaluated the influences of N-3 on glucocorticoid atrophy considering IGF-1, Myostatin, MEK/ERK, AMPK pathways besides the ubiquitin-proteasome system (UPS) and autophagic/lysosomal systems. Sixty animals constituted six groups: CT, N-3 (EPA 100 mg/kg/day for 40 days), DEXA 1.25 (DEXA 1.25 mg/kg/day for 10 days), DEXA 1.25 + N3 (EPA for 40 days + DEXA 1.25 mg/kg/day for the last 10 days), DEXA 2.5 (DEXA 2.5 mg/kg/day for 10 days), and DEXA 2.5 + N3 (EPA for 40 days + DEXA 2.5 mg/kg/day for 10 days). Results: N-3 associated with DEXA increases atrophy (fibers 1 and 2A), FOXO3a, P-SMAD2/3, Atrogin-1/MAFbx (mRNA) expression, and autophagic protein markers (LC3II, LC3II/LC3I, LAMP-1 and acid phosphatase). Additionally, N-3 supplementation alone decreased P-FOXO3a, PGC1-alpha, and type 1 muscle fiber area. Conclusion: N-3 supplementation increases muscle atrophy caused by DEXA in an autophagic, AMPK and UPS process.

Muscle Atrophy Induced by Mechanical Unloading: Mechanisms and Potential Countermeasures

Prolonged periods of skeletal muscle inactivity or mechanical unloading (bed rest, hindlimb unloading, immobilization, spaceflight and reduced step) can result in a significant loss of musculoskeletal mass, size and strength which ultimately lead to muscle atrophy. With advancement in understanding of the molecular and cellular mechanisms involved in disuse skeletal muscle atrophy, several different signaling pathways have been studied to understand their regulatory role in this process. However, substantial gaps exist in our understanding of the regulatory mechanisms involved, as well as their functional significance. This review aims to update the current state of knowledge and the underlying cellular mechanisms related to skeletal muscle loss during a variety of unloading conditions, both in humans and animals. Recent advancements in understanding of cellular and molecular mechanisms, including IGF1-Akt-mTOR, MuRF1/MAFbx, FOXO, and potential triggers of disuse atrophy, such as calcium overload and ROS overproduction, as well as their role in skeletal muscle protein adaptation to disuse is emphasized. We have also elaborated potential therapeutic countermeasures that have shown promising results in preventing and restoring disuse-induced muscle loss. Finally, identified are the key challenges in this field as well as some future prospectives.

TLR4-defective (C3H/HeJ) mice are not protected from cast immobilization-induced muscle atrophy

Recent studies have shown that activation of Toll‐like receptor (TLR)4 signaling may be an important factor in muscle atrophy and excessive inflammatory response associated with immobilization. To examine the role of TLR4 signaling on cast immobilization‐induced skeletal muscle atrophy, we tested the hypothesis that muscle atrophy and inflammation after cast immobilization is reduced in TLR4‐defective mice. TLR4‐defective (C3H/HeJ) and wild type (C3H/HeN) mice were divided into control and cast‐immobilization groups. Cast immobilization was imposed for 14 days. Cast immobilization increased TLR4 mRNA expression in the gastrocnemius and decreased muscle mass and cross‐sectional area (CSA) of the gastrocnemius fibers. However, there was no difference in the gastrocnemius muscle mass and CSA between TLR4‐defective and wild type mice. Cast immobilization‐induced increase in ubiquitin E3 ligases (MAFbx/Atrogin‐1 and MuRF1), inflammatory cytokines, and macrophage/monocyte marker mRNAs were unaffected by defective TLR4. Our findings in C3H/HeJ mice suggested that TLR4 signaling might not play an essential role in immobilization‐induced muscle atrophy.

Therapeutic effect of intra-articular injection of ribbon-type decoy oligonucleotides for hypoxia inducible factor-1 on joint contracture in an immobilized knee animal model

BACKGROUND

Limited range of motion (ROM) as a result of joint contracture in treatment associated with joint immobilization or motor paralysis is a critical issue. However, its molecular mechanism has not been fully clarified and a therapeutic approach is not yet established.

METHODS

In the present study, we investigated its molecular mechanism, focusing on the role of a transcription factor, hypoxia inducible factor-1 (HIF-1), which regulates the expression of connective tissue growth factor (CTGF) and vascular endothelial growth factor (VEGF), and evaluated the possibility of molecular therapy to inhibit HIF-1 activation by ribbon-type decoy oligonucleotides (ODNs) for HIF-1 using immobilized knee animal models.

RESULTS

In a mouse model, ROM of the immobilized knee significantly decreased in a time-dependent manner, accompanied by synovial hypertrophy. Immunohistochemical studies suggested that CTGF and VEGF are implicated in synovial hypertrophy with fibrosis. CTGF and VEGF were up-regulated at both the mRNA and protein levels at 1 and 2 weeks after immobilization, subsequent to up-regulation of HIF-1 mRNA and transcriptional activation of HIF-1. Of importance, intra-articular transfection of decoy ODNs for HIF-1 in a rat model successfully inhibited transcriptional activation of HIF-1, followed by suppression of expression of CTGF and VEGF, resulting in attenuation of restricted ROM, whereas transfection of scrambled decoy ODNs did not.

CONCLUSIONS

The present study demonstrates the important role of HIF-1 in the initial progression of immobilization-induced joint contracture, and indicates the possibility of molecular treatment to prevent the progression of joint contracture prior to intervention with physical therapy. Copyright © 2016 John Wiley & Sons, Ltd.

Analysis of correlation between degeneration of lower lumbar paraspinal muscles and spinopelvic alignment in patients with osteoporotic vertebral compression fracture

BACKGROUND

A few studies have pointed that trunk extensors may affect the spinopelvic alignment; however, little is known about the exact association between degeneration of lower lumbar paraspinal muscles and spinopelvic parameters.

OBJECTIVE

The study aimed to analyze the relationship between degeneration of lower lumbar paraspinal muscles and spinopelvic alignment in patients with osteoporotic vertebral compression fracture (OVCF).

METHODS

Thirty-nine OVCF patients were involved in this study. All patients underwent a standing lateral radiographs of the entire spine and pelvis 6 months after kyphoplasty. Pelvic incidence, pelvic tilt, lower lumbar lordosis (LLL) were measured. On the MRI images, the cross-sectional areas of the erector spinae (ES), multifidus (MF), vertebral body and the signal intensity of ES, MF, subcutaneous fat were measured. Pearson's correlation coefficients was applied to analyze the correlation between the muscular degeneration degree (muscular atrophy and fatty infiltration) and spinopelvic parameters.

RESULTS

The fatty change degree of ES at L4 inferior endplate level was positively correlated with pelvis retroversion (r= 0.480, p< 0.05). The grade of fat infiltration of ES plus MF at L5 level was negatively related to LLL (r=-0.446, p< 0.05). The fatty change of ES at L5 level, atrophy of ES at L4 and L5 level did not correlate with pelvis back tilt. The fat infiltration of ES plus MF at L4 level, the atrophy degree of ES plus MF at L4 and L5 level had no correlation with LLL.

CONCLUSIONS

With the increase of fatty infiltration of the erector spinae, the degree of pelvis retroversion increases; the lower lumbar lordosis decreases with the increase of intramuscular adipose tissue of the erector spinae plus multifidus. The atrophy degree of the erector spinae and multifidus is not correlated with pelvis back tilt and lower lumbar lordosis.

Remarkable plasticity of Na+, K+-ATPase, Ca2+-ATPase and SERCA contributes to muscle disuse atrophy resistance in hibernating Daurian ground squirrels

We investigated cytosolic calcium (Ca²⁺) and sarcoplasmic reticulum Ca²⁺ regulation in skeletal muscle fibers of hibernating Daurian ground squirrels (Spermophilus dauricus), non-hibernating hindlimb-unloaded (HLU) squirrels, and HLU rats to clarify the molecular mechanisms involved in preventing muscle atrophy in hibernators. The Na⁺, K⁺-ATPase and Ca²⁺-ATPase activities in the soleus muscle (SOL) of squirrels were maintained in hibernation, decreased during interbout arousal (IB-A), and increased to autumn/pre-hibernation (AUT/Pre-H) levels in torpor after interbout arousal (Post-IBA), whereas activities in the extensor digitorum longus muscle (EDL) were stable during hibernation, but increased during post-hibernation (Post-H). Activities increased in the SOL of HLU rats, but were stable in HLU squirrels. Sarco/endoplasmic reticulum Ca²⁺-ATPase (SERCA) activity in the SOL decreased in IB-A squirrels, but returned to AUT/Pre-H levels in the Post-IBA group; no significant changes were found in the EDL. SERCA activity increased in the EDL of HLU squirrels and SOL of HLU rats. Compared with AUT/Pre-H, SERCA type 2 protein expression increased in the SOL and EDL of IB-A and Post-IBA squirrels, but increased in the SOL only in HLU animals. We also describe the protein kinase A changes in this paper. Thus, hibernating ground squirrels displayed remarkable Na⁺, K⁺-ATPase, Ca²⁺-ATPase, and SERCA plasticity.

Comparison of morphological changes of muscle fibers in response to dynamic electrical muscle contraction and dynamic hydraulic stimulation in a rat hindlimb disuse model

This study attempted to compare the muscle fiber morphological responses to dynamic electrical muscle stimulation (DEMS) and dynamic hydraulic stimulation (DHS) in rats under hindlimb suspension (HLS). DEMS at 1 Hz, 50 Hz and 100 Hz for 10 min/day, 5 days/week were introduced to the animals' right quadriceps. Static and 2 Hz DHS were introduced to the right tibiae of other animal groups on a "10 min on - 5 min off - 10 min on" loading regime for 5 days/week. In the end of the 4-week experiments, histological changes in the corresponding soleus, gastrocnemius and quadriceps of the stimulated sites were examined. Compared to age-matched, HLS led to muscle atrophy and strongly reduced muscle wet weights and averaged cross-sectional fiber areas. Among the tested DEMS frequencies, the averaged cross-sectional quadriceps fiber area in the 50 Hz group was 29 % larger than the 100 Hz group. In contrast, difference in the muscle fiber response to the static and 2 Hz DHS was not observed in either soleus or gastrocnemius. Muscle fiber morphological responses to the active DEMS was in a load frequency dependent manner under disuse condition. Relatively passive compressions, either via static or 2Hz DHS, were unable to induce any difference in the muscle fiber responses under functional disuse.

The fatty degeneration of lumbar paraspinal muscles on computed tomography scan according to age and disc level

BACKGROUND CONTEXT

Spinal degeneration can occur not only in the bone and disc but also in muscles. Fatty infiltration (FI) and decreased volume have been described as characteristic changes that occur in muscle degeneration. Many studies about the lumbar paraspinal muscles have been conducted on patients with spine problems. However, the natural changes of age-dependent degeneration in the paraspinal muscles have not been studied properly.

PURPOSE

The purpose of this study is to investigate age- and level-dependent changes of the lumbar paraspinal muscles in the population without lumbar spinal symptoms.

STUDY DESIGN

This study is a retrospective case-control study.

PATIENT SAMPLE

A total of 887 patients who underwent computed tomography scan for abdomen and pelvis (APCT) between January 2013 and December 2013 were enrolled. After excluding 237 patients with medical history of spine surgery, low back pain, myopathy, muscular dystrophy, infectious disease, vertebral fracture, and deformity, 650 patients were finally subjected to this study.

OUTCOME MEASURE

The patients were divided into three age groups: young (20-39 years old), middle (40-59 years old), and old (60-89 years old). The degree of FI was checked twice for multifidus muscle (MF), erector spinae muscle (ES), and psoas muscle (PS) at each disc level from L1 to S1 on APCT by two investigators. The FI was measured as the Hounsfield unit, a mean density (MD) on CT.

METHODS

The age differences were compared with the data of the young group, and the level differences were compared with the data of the L1-L2 level. Student t test and intraclass correlation coefficient were checked for statistical analysis.

RESULTS

The gender ratio was not significantly different among the groups. Comparing with the young group, the MD of MF significantly decreased at L5-S1 in the middle group (p<.05), and at L3-L4-L5-S1 in the old group (p<.05). The MD of ES was significantly decreased at all levels in the old group (p<.05) but not significant in the middle group. Comparing with the L1-L2 level, the MD of MF significantly decreased at L5-S1 in the middle group (p<.05) and at L4-L5-S1 in the old group (p<.05). The MD of ES was significantly decreased at L5-S1 in the young and middle groups (p<.05) and at L4-L5-S1 in the old group (p<.01) compared with those at L1-L2. According to the age- and level-dependent changes of MD in the MF and ES, there was a tendency of progressive increase of FI in the muscles with age, which seemed to start from L5-S1 and spread to the upper levels. The age-dependent fatty degeneration appeared wider in the ES than the MF. The level-dependent FI of the ES showed a similar pattern with the MF, but the change of the ES seemed to start earlier in age than the MF at the L5-S1. There was no significant MD change in the PS according to age and level. Intraobserver and interobserver reliabilities were both high across all of the muscles (0.86-0.94 and 0.83-0.92).

CONCLUSIONS

As a result, the degree of intramuscular fat infiltration seems to be affected by age, disc level, and muscle type. It seems to be more prominent in the extensor muscles, extending from lower to upper levels.

Fatty Degeneration of the Paraspinal Muscle in Patients With Degenerative Lumbar Kyphosis: A New Evaluation Method of Quantitative Digital Analysis Using MRI and CT Scan

STUDY DESIGN

A comparative case-control study.

OBJECTIVE

The aim of this study was to quantify the degree of paraspinal muscle changes in degenerative lumbar kyphosis (DLK) patients using magnetic resonance imaging and computed tomography scanning.

SUMMARY OF BACKGROUND DATA

Although the pathophysiology of DLK is not completely understood, extensive degeneration and weakness of the lumbar extensor muscles are thought to underlie the condition in most patients. However, there is no ideal method to quantify the degree of fat infiltration and atrophy of the paraspinal muscles in patients with DLK.

MATERIALS AND METHODS

The study group comprised 20 patients with DLK and 20 healthy volunteers. The cross-sectional areas of the psoas, erector spinae (ES), multifidus (MF), quadratus lumborum, and vertebral body were measured. The ratio between the cross-sectional area of the muscle and the vertebral body was used to evaluate lumbar muscularity. The degree of fatty change was evaluated by measuring the ratio between the mean signal intensity of the muscle and that of the subcutaneous fat within regions of interest.

RESULTS

Muscularity in the MF and ES was not significantly different between the DLK and control groups at L1, L2, or L3, but was significantly different at L4 (ES, P=0.001; MF, P=0.001) and L5 (ES, P=0.001; MF, P=0.015). The mean signal intensities of the ES and MF were higher in the DLK group than in the control group at all levels. The degree of fatty change in the ES and MF was significantly higher in the DLK group than in the control group (P<0.05).

CONCLUSIONS

Quantitative analysis using magnetic resonance imaging and computed tomography scanning showed differences in paraspinal muscle volume and fatty degeneration between patients with DLK and healthy volunteers. This evaluation method may be useful for measuring the extent of paraspinal muscle degeneration.

Skeletal muscle mass and composition during mammalian hibernation

Hibernation is characterized by prolonged periods of inactivity with concomitantly low nutrient intake, conditions that would typically result in muscle atrophy combined with a loss of oxidative fibers. Yet, hibernators consistently emerge from winter with very little atrophy, frequently accompanied by a slight shift in fiber ratios to more oxidative fiber types. Preservation of muscle morphology is combined with down-regulation of glycolytic pathways and increased reliance on lipid metabolism instead. Furthermore, while rates of protein synthesis are reduced during hibernation, balance is maintained by correspondingly low rates of protein degradation. Proposed mechanisms include a number of signaling pathways and transcription factors that lead to increased oxidative fiber expression, enhanced protein synthesis and reduced protein degradation, ultimately resulting in minimal loss of skeletal muscle protein and oxidative capacity. The functional significance of these outcomes is maintenance of skeletal muscle strength and fatigue resistance, which enables hibernating animals to resume active behaviors such as predator avoidance, foraging and mating immediately following terminal arousal in the spring.

A pediatric animal model to evaluate the effects of disuse on musculoskeletal growth and development

Prolonged immobilization in hospitalized children can lead to fragility fractures and muscle contractures and atrophy. The purpose of this study was to develop a lower-extremity disuse rabbit model with musculoskeletal changes similar to those observed in children subjected to prolonged immobilization. Six-week-old rabbits were randomly assigned to control (CTRL, n=4) or bilateral sciatic and femoral neurectomy (bSFN, n=4) groups. Trans-axial helical CT scans of each rabbit׳s hind limbs were acquired after eight weeks. The rabbits were then euthanized and the tibiae and calcanea were harvested from each rabbit. μCT imaging was performed on the tibiae and calcanea mid-diaphysis. Four-point bending, gas pycnometry, and ashing were then performed on each tibia. All comparisons reflect the differences between the bSFN and CTRL rabbits. Significant decreases in tibiae bone mineral density (≥9.41%, p≤0.006), axial rigidity (≥50.47%, p≤0.02), and soft tissue mass (55.25%, p=0.006) were observed from the trans-axial helical CT scans. The μCT results indicated significant detriments in tibia and calcaneus cortical thickness and bone volume fraction (p≤0.011). Significant changes in stiffness, yield load, ultimate load, and ultimate displacement (≥30.05%, p≤0.025) were observed from mechanical testing. These data indicate that limb disuse at a time of rapid musculoskeletal growth severely impairs muscle and bone development, reflecting the musculoskeletal complications observed in children with chronic medical conditions causing immobilization. Interventions to reduce these musculoskeletal complications in children are urgently needed. This disuse rabbit model will be useful in pre-clinical studies evaluating novel interventions for improving pediatric musculoskeletal health.

Immobilization induces nuclear accumulation of HDAC4 in rat skeletal muscle

The study described herein aimed to examine changes in HDAC4 and its downstream targets in immobilization-induced rat skeletal muscle atrophy. Eleven male Wistar rats were used, and one hindlimb was immobilized in the plantar flexion position using a plaster cast. The contralateral, non-immobilized leg served as an internal control. After 10 days, the gastrocnemius muscles were removed from both hindlimbs. Ten days of immobilization resulted in a significant reduction (-27.3 %) in gastrocnemius muscle weight. A significant decrease in AMPK phosphorylation was also observed in nuclear fractions from immobilized legs relative to the controls. HDAC4 expression was significantly increased in immobilized legs in both the cytoplasmic and nuclear fractions. Moreover, Myogenin and MyoD mRNA levels were upregulated in immobilized legs, resulting in increased Atrogin-1 mRNA expression. Our data suggest that nuclear HDAC4 accumulation is partly related to immobilization-induced muscle atrophy.

Diminished Foot and Ankle Muscle Volumes in Young Adults With Chronic Ankle Instability

Background:

Patients with chronic ankle instability (CAI) have demonstrated altered neuromuscular function and decreased muscle strength when compared with healthy counterparts without a history of ankle sprain. Up to this point, muscle volumes have not been analyzed in patients with CAI to determine whether deficits in muscle size are present following recurrent sprain.

Purpose:

To analyze intrinsic and extrinsic foot and ankle muscle volumes and 4-way ankle strength in young adults with and without CAI.

Study Design:

Cross-sectional study; Level of evidence, 3.

Methods:

Five patients with CAI (mean age, 23.0 ± 4 years; 1 male, 4 females) and 5 healthy controls (mean age, 23.8 ± 4.5 years; 1 male, 4 females) volunteered for this study. Novel fast-acquisition magnetic resonance imaging (MRI) was used to scan from above the femoral condyles through the foot and ankle. The perimeter of each muscle was outlined on each axial slice and then the 2-dimensional area was multiplied by the slice thickness (5 mm) to calculate the muscle volume. Plantar flexion, dorsiflexion, inversion, and eversion isometric strength were measured using a handheld dynamometer. Patients with CAI were compared with healthy controls on all measures of muscle volume and strength. Extrinsic muscle volumes of patients with CAI were also compared with a normative database of healthy controls (n = 24) by calculating z scores for each muscle individually for each CAI subject.

Results:

The CAI group had smaller total shank, superficial posterior compartment, soleus, adductor hallucis obliqus, and flexor hallucis brevis muscle volumes compared with healthy controls as indicated by group means and associated 90% CIs that did not overlap. Cohen d effect sizes for the significant group differences were all large and ranged from 1.46 to 3.52, with 90% CIs that did not cross zero. The CAI group had lower eversion, dorsiflexion, and 4-way composite ankle strength, all with group means and associated 90% CIs that did not overlap. No other significant differences were identified.

Conclusion:

Patients with CAI demonstrate atrophy of intrinsic and extrinsic foot and ankle musculature accompanied by lower ankle strength.

Clinical Relevance:

Clinicians should be aware of the muscle atrophy and strength deficits when prescribing rehabilitation for patients with lateral ankle sprain or CAI.

O-GlcNAcylation is a key modulator of skeletal muscle sarcomeric morphometry associated to modulation of protein-protein interactions

BACKGROUND

The sarcomere structure of skeletal muscle is determined through multiple protein-protein interactions within an intricate sarcomeric cytoskeleton network. The molecular mechanisms involved in the regulation of this sarcomeric organization, essential to muscle function, remain unclear. O-GlcNAcylation, a post-translational modification modifying several key structural proteins and previously described as a modulator of the contractile activity, was never considered to date in the sarcomeric organization.

METHODS

C2C12 skeletal myotubes were treated with Thiamet-G (OGA inhibitor) in order to increase the global O-GlcNAcylation level.

RESULTS

Our data clearly showed a modulation of the O-GlcNAc level more sensitive and dynamic in the myofilament-enriched fraction than total proteome. This fine O-GlcNAc level modulation was closely related to changes of the sarcomeric morphometry. Indeed, the dark-band and M-line widths increased, while the I-band width and the sarcomere length decreased according to the myofilament O-GlcNAc level. Some structural proteins of the sarcomere such as desmin, αB-crystallin, α-actinin, moesin and filamin-C have been identified within modulated protein complexes through O-GlcNAc level variations. Their interactions seemed to be changed, especially for desmin and αB-crystallin.

CONCLUSIONS

For the first time, our findings clearly demonstrate that O-GlcNAcylation, through dynamic regulations of the structural interactome, could be an important modulator of the sarcomeric structure and may provide new insights in the understanding of molecular mechanisms of neuromuscular diseases characterized by a disorganization of the sarcomeric structure.

GENERAL SIGNIFICANCE

In the present study, we demonstrated a role of O-GlcNAcylation in the sarcomeric structure modulation.

Role of Active Contraction and Tropomodulins in Regulating Actin Filament Length and Sarcomere Structure in Developing Zebrafish Skeletal Muscle

Whilst it is recognized that contraction plays an important part in maintaining the structure and function of mature skeletal muscle, its role during development remains undefined. In this study the role of movement in skeletal muscle maturation was investigated in intact zebrafish embryos using a combination of genetic and pharmacological approaches. An immotile mutant line (cacnb1 (ts25) ) which lacks functional voltage-gated calcium channels (dihydropyridine receptors) in the muscle and pharmacological immobilization of embryos with a reversible anesthetic (Tricaine), allowed the study of paralysis (in mutants and anesthetized fish) and recovery of movement (reversal of anesthetic treatment). The effect of paralysis in early embryos (aged between 17 and 24 hours post-fertilization, hpf) on skeletal muscle structure at both myofibrillar and myofilament level was determined using both immunostaining with confocal microscopy and small angle X-ray diffraction. The consequences of paralysis and subsequent recovery on the localization of the actin capping proteins Tropomodulin 1 & 4 (Tmod) in fish aged from 17 hpf until 42 hpf was also assessed. The functional consequences of early paralysis were investigated by examining the mechanical properties of the larval muscle. The length-force relationship, active and passive tension, was measured in immotile, recovered and control skeletal muscle at 5 and 7 day post-fertilization (dpf). Recovery of muscle function was also assessed by examining swimming patterns in recovered and control fish. Inhibition of the initial embryonic movements (up to 24 hpf) resulted in an increase in myofibril length and a decrease in width followed by almost complete recovery in both moving and paralyzed fish by 42 hpf. In conclusion, myofibril organization is regulated by a dual mechanism involving movement-dependent and movement-independent processes. The initial contractile event itself drives the localization of Tmod1 to its sarcomeric position, capping the actin pointed ends and ultimately regulating actin length. This study demonstrates that both contraction and contractile-independent mechanisms are important for the regulation of myofibril organization, which in turn is necessary for establishing proper skeletal muscle structure and function during development in vivo in zebrafish.

Musculoskeletal architecture of the prey capture apparatus in salamandrid newts with multiphasic lifestyle: does anatomy change during the seasonal habitat switches?

Some newt species change seasonally between an aquatic and a terrestrial life as adults, and are therefore repeatedly faced with different physical circumstances that affect a wide range of functions of the organism. For example, it has been observed that seasonally habitat-changing newts display notable changes in skin texture and tail fin anatomy, allowing one to distinguish an aquatic and a terrestrial morphotype. One of the main functional challenges is the switch between efficient aquatic and terrestrial prey capture modes. Recent studies have shown that newts adapt quickly by showing a high degree of behavioral flexibility, using suction feeding in their aquatic stage and tongue prehension in their terrestrial stage. As suction feeding and tongue prehension place different functional demands on the prey capture apparatus, this behavioral flexibility may clearly benefit from an associated morphological plasticity. In this study, we provide a detailed morphological analysis of the musculoskeletal system of the prey capture apparatus in the two multiphasic newt species Ichthyosaura alpestris and Lissotriton vulgaris by using histological sections and micro-computed tomography. We then test for quantitative changes of the hyobranchial musculoskeletal system between aquatic and terrestrial morphotypes, The descriptive morphology of the cranio-cervical musculoskeletal system provides new insights on form and function of the prey capture apparatus in newts, and the quantitative approach shows hypertrophy of the hyolingual musculoskeletal system in the terrestrial morphotype of L. vulgaris but hypertrophy in the aquatic morphotype of I. alpestris. It was therefore concluded that the seasonal habitat shifts are accompanied by a species-dependent muscular plasticity of which the potential effect on multiphasic feeding performance in newts remains unclear.

Repeated exposure to heat stress results in a diaphragm phenotype that resists ventilator-induced diaphragm dysfunction

Controlled mechanical ventilation (CMV) is a life-saving intervention for patients in respiratory failure. Unfortunately, prolonged mechanical ventilation (MV) results in diaphragmatic atrophy and contractile dysfunction, both of which are predicted to contribute to problems in weaning patients from the ventilator. Therefore, developing a strategy to protect the diaphragm against ventilator-induced weakness is important. We tested the hypothesis that repeated bouts of heat stress result in diaphragm resistance against CMV-induced atrophy and contractile dysfunction. Male Wistar rats were randomly divided into six experimental groups: 1) control; 2) single bout of whole body heat stress; 3) repeated bouts of whole body heat stress; 4) 12 h CMV; 5) single bout of whole body heat stress 24 h before CMV; and 6) repeated bouts of whole body heat stress 1, 3, and 5 days before 12 h of CMV. Our results revealed that repeated bouts of heat stress resulted in increased levels of heat shock protein 72 in the diaphragm and protection against both CMV-induced diaphragmatic atrophy and contractile dysfunction at submaximal stimulation frequencies. The specific mechanisms responsible for this protection remain unclear: this heat stress-induced protection against CMV-induced diaphragmatic atrophy and weakness may be partially due to reduced diaphragmatic oxidative stress, diminished activation of signal transducer/transcriptional activator-3, lower caspase-3 activation, and decreased autophagy in the diaphragm.

Effects of occlusion on mandibular morphology and architecture in rats

BACKGROUND

A rodent occlusal hypofunction model has been widely established in jawbone-related studies. However, the effects of occlusal stimuli, with total elimination of molar contacts, and its rehabilitation on mandibular remodeling remain unclear.

MATERIALS AND METHODS

Forty-eight 5-wk-old Sprague-Dawley male rats were used. Twenty-four experimental rats underwent occlusal hypofunction by insertion of a bite-raising appliance. Twenty-four rats received no treatment (control group). Two weeks later, half the experimental rats (occlusal hypofunction group) were killed; the appliance was removed from the remaining experimental rats (recovery group) for two additional weeks before killing. Control animals were killed biweekly. Body weight and masseter muscle weight were measured, and the mandibles were subjected to micro-computed tomography to evaluate the mandibular morphology and cortical bone characteristics. The expressions of osteoblast- and osteoclast-related genes were evaluated with quantitative polymerase chain reaction.

RESULTS

No significant body weight differences were observed between the experimental and control rats. However, lighter masseter muscle, shorter mandibular incisor crown, mandibular body and ramus, and higher mandibular alveolar process and first molar fossae were observed in the occlusal hypofunction group. Moreover, the cortical bone characteristics associated with the expression of osteoblast- and osteoclast-related genes were remarkably different in the central and posterior mandible in the occlusal hypofunction group. At the 2-wk recovery time point after occlusal stimuli, the altered parameters in the masseter and mandible returned to normal levels.

CONCLUSIONS

Mandibular remodeling via bone turnover is region specific for altered occlusal stimuli. Normal occlusion is an important determinant of the mandibular morphology and architecture.

Seasonal oxidative capacity of skeletal muscles in hibernating Daurian ground squirrels (Spermophilus dauricus)

We investigated the mechanism of high oxidative capacity of skeletal muscles in hibernating Daurian ground squirrels (Spermophilus dauricus Brandt, 1843). Myoglobin (Mb) levels, as well as citrate synthase and lactate dehydrogenase (LDH) activities, were measured by spectrophotometry. Mb content in the soleus (SOL) muscle lasted from the beginning of hibernation to spring. Mb content in SOL was 87% higher in the hibernating group than in the summer group. Mb content in the extensor digitorum longus (EDL) muscle stayed at similar levels during the different periods of the year. Citrate synthase activity in SOL was 30% higher in the hibernating group than in the summer group. Meanwhile, citrate synthase activity in EDL did not change during hibernation. LDH activity in SOL was not different between the hibernating group and the summer active group, whereas LDH activity in EDL increased significantly (up to 11%) in the 2 days arousal after hibernation group compared with the hibernating group. We conclude that high oxidative capacity is provided by increased oxygen storage capacity of slow-twitch muscle fibers rather than from fast-twitch muscle fibers in hibernating animals.