Stretching and electrical stimulation reduce the accumulation of MyoD, myostatin and atrogin-1 in denervated rat skeletal muscle

Short and long-term outcomes of multidimensional physiotherapy in cases with acute compartment syndrome secondary to carbon monoxide poisoning with prolonged forearm compression

BACKGROUND

Compartment syndrome following carbon monoxide (CO) poisoning and compression, can have a devastating impact on neuromuscular structures, depending on a time-based dosage.

PURPOSE

To investigate multidimensional physiotherapy's short-term and long-term outcomes in identical twin cases who developed compartment syndrome due to CO poisoning and prolonged compression.

STUDY DESIGN

Case report.

METHODS

This study was conducted with two male cases, a 21-year-old identical twin. The loss of consciousness due to CO poisoning lasted for 15 hours. Case one had compartment syndrome that caused damage to the median and ulnar nerves in the right forearm, while Case two had compartment syndrome that caused damage to the radial nerve in the left forearm. No surgical intervention was performed (Fasciotomy etc).

RESULTS

The disability, dexterity, hand health status, sensory-motor function, and edema were evaluated. Initial evaluations showed severe sensory and motor dysfunction, disability, and edema. Treatment included Complex decongestive physiotherapy, electrical stimulation, therapeutic ultrasound, orthotics, and exercises. On the 144th day (discharge day), both cases still exhibited weakness in functional strength and sensory loss compared to the uninjured side. At the ninth month, all parameters except strength were similar to the uninjured side in both cases. By the 53rd month, strength also reached normal values.

CONCLUSIONS

Multidimensional physiotherapy effectively manages edema, improves sensory-motor function, and enhances hand function in the short and long term.

Skeletal Muscle Electrical Stimulation Prevents Progression of Disuse Muscle Atrophy via Forkhead Box O Dynamics Mediated by Phosphorylated Protein Kinase B and Peroxisome Proliferator-Activated Receptor gamma Coactivator-1alpha

Although electrical muscle stimulation (EMS) of skeletal muscle effectively prevents muscle atrophy, its effect on the breakdown of muscle component proteins is unknown. In this study, we investigated the biological mechanisms by which EMS-induced muscle contraction inhibits disuse muscle atrophy progression. Experimental animals were divided into a control group and three experimental groups: immobilized (Im; immobilization treatment), low-frequency (LF; immobilization treatment and low-frequency muscle contraction exercise), and high-frequency (HF; immobilization treatment and high-frequency muscle contraction exercise). Following the experimental period, bilateral soleus muscles were collected and analyzed. Atrogin-1 and Muscle RING finger 1 (MuRF-1) mRNA expression levels were significantly higher for the experimental groups than for the control group but were significantly lower for the HF group than for the Im group. Peroxisome proliferator-activated receptor gamma coactivator-1alpha (PGC-1alpha) mRNA and protein expression levels in the HF group were significantly higher than those in the Im group, with no significant differences compared to the Con group. Both the Forkhead box O (FoxO)/phosphorylated FoxO and protein kinase B (AKT)/phosphorylated AKT ratios were significantly lower for the Im group than for the control group and significantly higher for the HF group than for the Im group. These results, the suppression of atrogin-1 and MuRF-1 expression for the HF group may be due to decreased nuclear expression of FoxO by AKT phosphorylation and suppression of FoxO transcriptional activity by PGC-1alpha. Furthermore, the number of muscle contractions might be important for effective EMS.

Belt electrode tetanus muscle stimulation reduces denervation-induced atrophy of rat multiple skeletal muscle groups

Belt electrode-skeletal muscle electrical stimulation (B-SES) involves the use of belt-shaped electrodes to contract multiple muscle groups simultaneously. Twitch contractions have been demonstrated to protect against denervation-induced muscle atrophy in rats, possibly through mitochondrial biosynthesis. This study examined whether inducing tetanus contractions with B-SES suppresses muscle atrophy and identified the underlying molecular mechanisms. We evaluated the effects of acute (60 Hz, 5 min) and chronic (60 Hz, 5 min, every alternate day for one week) B-SES on the tibialis anterior (TA) and gastrocnemius (GAS) muscles in Sprague-Dawley rats using belt electrodes attached to both ankle joints. After acute stimulation, a significant decrease in the glycogen content was observed in the left and right TA and GAS, suggesting that B-SES causes simultaneous contractions in multiple muscle groups. B-SES enhanced p70S6K phosphorylation, an indicator of the mechanistic target of rapamycin complex 1 activity. During chronic stimulations, rats were divided into control (CONT), denervation-induced atrophy (DEN), and DEN + electrically stimulated with B-SES (DEN + ES) groups. After seven days of treatment, the wet weight (n = 8-11 for each group) and muscle fiber cross-sectional area (CSA, n = 6 for each group) of the TA and GAS muscles were reduced in the DEN and DEN + ES groups compared with that in the CON group. The DEN + ES group showed significantly higher muscle weight and CSA than those in the DEN group. Although RNA-seq and pathway analysis suggested that mitochondrial biogenesis is a critical event in this phenomenon, mitochondrial content showed no difference. In contrast, ribosomal RNA 28S and 18S (n = 6) levels in the DEN + ES group were higher than those in the DEN group, even though RNA-seq showed that the ribosome biogenesis pathway was reduced by electrical stimulation. The mRNA levels of the muscle proteolytic molecules atrogin-1 and MuRF1 were significantly higher in DEN than those in CONT. However, they were more suppressed in DEN + ES than those in DEN. In conclusion, tetanic electrical stimulation of both ankles using belt electrodes effectively reduced denervation-induced atrophy in multiple muscle groups. Furthermore, ribosomal biosynthesis plays a vital role in this phenomenon.

Impacts of whole-body vibration on denervated skeletal-muscle atrophy in rats

Whole-body vibration has been considered as a countermeasure against muscle atrophy. However, its effects on muscle atrophy are poorly understood. We evaluated the effects of whole-body vibration on denervated skeletal muscle atrophy. Whole-body vibration was performed on rats from Day 15 to 28 after denervation injury. Motor performance was evaluated using an inclined-plane test. Compound muscle action potentials of the tibial nerve were examined. Muscle wet weight and muscle fiber cross-sectional area were measured. Myosin heavy chain isoforms were analyzed in both muscle homogenates and single myofibers. Whole-body vibration resulted in a significantly decreased inclination angle and muscle weight, but not muscle fiber cross-sectional area of fast-twitch gastrocnemius compared to denervation only. In denervated gastrocnemius, a fast-to-slow shift was observed in myosin heavy chain isoform composition following whole-body vibration. There were no significant changes in muscle weight, muscle fiber cross-sectional area, and myosin heavy chain isoform composition in denervated slow-twitch soleus. These results imply that whole-body vibration does not promote recovery of denervation-induced muscle atrophy.

Inhibiting myostatin signaling partially mitigates structural and functional adaptations to hindlimb suspension in mice

Novel treatments for muscle wasting are of significant value to patients with disease states that result in muscle weakness, injury recovery after immobilization and bed rest, and for astronauts participating in long-duration spaceflight. We utilized an anti-myostatin peptibody to evaluate how myostatin signaling contributes to muscle loss in hindlimb suspension. Male C57BL/6 mice were left non-suspended (NS) or were hindlimb suspended (HS) for 14 days and treated with a placebo vehicle (P) or anti-myostatin peptibody (D). Hindlimb suspension (HS-P) resulted in rapid and significantly decreased body mass (-5.6% by day 13) with hindlimb skeletal muscle mass losses between -11.2% and -22.5% and treatment with myostatin inhibitor (HS-D) partially attenuated these losses. Myostatin inhibition increased hindlimb strength with no effect on soleus tetanic strength. Soleus mass and fiber CSA were reduced with suspension and did not increase with myostatin inhibition. In contrast, the gastrocnemius showed histological evidence of wasting with suspension that was partially mitigated with myostatin inhibition. While expression of genes related to protein degradation (Atrogin-1 and Murf-1) in the tibialis anterior increased with suspension, these atrogenes were not significantly reduced by myostatin inhibition despite a modest activation of the Akt/mTOR pathway. Taken together, these findings suggest that myostatin is important in hindlimb suspension but also motivates the study of other factors that contribute to disuse muscle wasting. Myostatin inhibition benefitted skeletal muscle size and function, which suggests therapeutic potential for both spaceflight and terrestrial applications.

The roles of Runx1 in skeletal development and osteoarthritis: A concise review

Runt-related transcription factor-1 (Runx1) is well known for its functions in hematopoiesis and leukemia but recent research has focused on its role in skeletal development and osteoarthritis (OA). Deficiency of the Runx1 gene is fatal in early embryonic development, and specific knockout of Runx1 in cell lineages of cartilage and bone leads to delayed cartilage formation and impaired bone calcification. Runx1 can regulate genes including collagen type II (Col2a1) and X (Col10a1), SRY-box transcription factor 9 (Sox9), aggrecan (Acan) and matrix metalloproteinase 13 (MMP-13), and the up-regulation of Runx1 improves the homeostasis of the whole joint, even in the pathological state. Moreover, Runx1 is activated as a response to mechanical compression, but impaired in the joint with the pathological progress associated with osteoarthritis. Therefore, interpretation about the role of Runx1 could enlarge our understanding of key marker genes in the skeletal development and an increased understanding of Runx1 could be helpful to identify treatments for osteoarthritis. This review provides the most up-to-date advances in the roles and bio-mechanisms of Runx1 in healthy joints and osteoarthritis from all currently published articles and gives novel insights in therapeutic approaches to OA based on Runx1.

Transcription and proteome changes involved in re-innervation muscle following nerve crush in rats

Severe peripheral nerve injury leads to the irreparable disruption of nerve fibers. This leads to disruption of synapses with the designated muscle, which consequently go through progressive atrophy and damage of muscle function. The molecular mechanism that underlies the re-innervation process has yet to be evaluated using proteomics or transcriptomics. In the present study, multi-dimensional data were therefore integrated with transcriptome and proteome profiles in order to investigate the mechanism of re-innervation in muscles. Two simulated nerve injury muscle models in the rat tibial nerve were compared: the nerve was either cut (denervated, DN group) or crushed but with the nerve sheath intact (re-innervated, RN group). The control group had a preserved and intact tibial nerve. At 4 weeks, the RN group showed better tibial nerve function and recovery of muscle atrophy compared to the DN group. As the high expression of Myh3, Postn, Col6a1 and Cfi, the RN group demonstrated superior re-innervation as well. Both differentially expressed genes (DEGs) and proteins (DEPs) were enriched in the peroxisome proliferator-activated receptors (PPARs) signaling pathway, as well as the energy metabolism. This study provides basic information regarding DEGs and DEPs during re-innervation-induced muscle atrophy. Furthermore, the crucial genes and proteins can be detected as possible treatment targets in the future.

A Collagen Hydrolysate Containing Tripeptides Ameliorates Sarcopenia in Middle-Aged Mice

Collagen peptide (CP) and collagen tripeptide (CTP) are supplementary health foods that exhibit several biological effects. However, the effects of collagen on age-associated sarcopenia and its underlying mechanisms are unclear. C57BL/6J mice (n = 24, 12 months old) were divided into three dietary groups and administered AIN93G (aging control, AC; JA BIO, Suwon, Korea), AIN93G plus 0.2% CP, and AING93G plus 0.2% CTP supplement for 12 weeks. The results indicated that the CP and CTP supplements significantly increased the weight of the quadriceps tibialis anterior and gastrocnemius muscles and reduced body fat. A morphological analysis revealed that the spaces within the muscle cells were tight with attenuated fibrosis following CP and CTP supplementation. Immunohistochemistry was applied and a Western blot analysis was performed to determine the underlying mechanisms. The CTP supplement increased the expression of IGF-1, PI3K/AKT, and mTOR, whereas the CP supplement increased the expression of IGF-1 and AMPK in the gastrocnemius of aging mice. CP and CTP ameliorate age-associated sarcopenia through different mechanisms.

Efficacy of passive repetitive stretching of skeletal muscle on myofiber hypertrophy and genetic suppression on MAFbx, MuRF1, and myostatin

Skeletal muscles undergo adaptations in response to mechanical stimuli such as stretching. However, there is limited evidence regarding the hypertrophic effects of passive repetitive stretching in vivo. We examined the effect of passive repetitive stretching on skeletal muscle myofiber morphology, satellite cell content, and messenger RNA expression of myogenic regulatory factors and signaling molecules involved in muscle protein synthesis and degradation. The gastrocnemius muscles of mice were stretched 15 times/min by manual ankle dorsiflexion for 15 min, 5 days a week for 2 weeks. We found that passive repetitive stretching significantly increased myofiber cross-sectional area. In stretched gastrocnemius muscles, the messenger RNA expression of p70S6K and myogenin was upregulated, whereas MuRF1, MAFbx, myostatin, and 4E-BP1 were downregulated. The phosphorylation level of p70S6K was significantly increased in stretched muscles. The number of Pax7+ cells was unaffected. Passive repetitive stretching induces muscle hypertrophy by regulating signaling pathways involved in muscle protein turnover. These findings are applicable to clinical muscle strengthening and for the maintenance of skeletal muscle mass and function in patients who are unconscious or paralyzed.

Preventive effect and possible mechanisms of ultrashort wave diathermy on myogenic contracture in a rabbit model

The purpose of this study was to determine the preventive effect of ultrashort wave diathermy on immobilization-induced myogenic contracture and to explore its underlying mechanisms. Forty-two rabbits were randomly assigned into control (Group C), immobilization (Group I, which was further divided into one week, Group I-1; two weeks, Group I-2; and four weeks, Group I-4, subgroups by the length of immobilization) and ultrashort wave prevention (Group U, which was further divided into one week, Group U-1; two weeks, Group U-2; and four weeks, Group U-4, by time of treatment) groups. Intervention effects were assessed by evaluating rectus femoris cross-sectional area (CSA), knee range of motion, and the protein levels for myogenic differentiation (MyoD) and muscle atrophy F-box (MAFbx-1) in the rectus femoris. Compared with those of Group C, in Groups I and U, total contracture, myogenic contracture, MyoD and MAFbx-1 levels were significantly elevated, and CSA was significantly smaller (p < 0.05). Compared with those of Group I at each time point, MyoD levels were significantly elevated, MAFbx-1 levels were significantly lower, CSA was significantly larger, and myogenic contracture was significantly alleviated in Group U (p < 0.05). In the early stages of contracture, ultrashort wave diathermy reduces muscle atrophy and delays the process of myogenic contracture during joint immobilization; the mechanism of this may be explained as increased expression of MyoD triggered by suppression of the MAFbx-1-mediated ubiquitin-proteasome pathway.

Passive repetitive stretching is associated with greater muscle mass and cross-sectional area in the sarcopenic muscle

Mechanical stimulation has benefits for muscle mass and function. Passive stretching is widely performed in clinical rehabilitation medicine. However, the hypertrophic effects of passive repetitive stretching on senescent skeletal muscles against muscle atrophy remain unknown. We used senescence-accelerated model SAM-P8 mice. The gastrocnemius muscle was passively repetitive stretched by manual ankle dorsiflexion for 15 min, 5 days a week for 2 weeks under deep anesthesia. We examined the effects of passive stretching on muscle mass, myofiber cross-sectional area, muscle fiber type composition, satellite cell and myonuclei content, signaling pathways involved in muscle protein synthesis, and myogenic regulatory factors. The gastrocnemius muscle weight and fiber cross-sectional area of the stretched side was found greater compared with that of the unstretched side. Passive repetitive stretching increased the mRNA expression level of Akt, p70S6K, 4E-BP1, Myf5, myogenin, MuRF1.The phosphorylation level of p70S6K significantly increased in the stretched muscles, whereas of Akt and 4E-BP1 remained unchanged, compared to the unstretched side. The Pax7+ cells and myonuclei content did not differ between the stretched and unstretched muscles. These findings suggest that the hypertrophic or suppressed atrophic observation in the stretched muscles are mainly attributable to the protein turnover provoked by stretching. These findings are applicable to clinical muscle strengthening and sarcopenia prevention.

Physiological Ca2+ Transients Versus Pathological Steady-State Ca2+ Elevation, Who Flips the ROS Coin in Skeletal Muscle Mitochondria

Mitochondria are both the primary provider of ATP and the pivotal regulator of cell death, which are essential for physiological muscle activities. Ca²⁺ plays a multifaceted role in mitochondrial function. During muscle contraction, Ca²⁺ influx into mitochondria activates multiple enzymes related to tricarboxylic acid (TCA) cycle and oxidative phosphorylation, resulting in increased ATP synthesis to meet the energy demand. Pathophysiological conditions such as skeletal muscle denervation or unloading also lead to elevated Ca²⁺ levels inside mitochondria. However, the outcomes of this steady-state elevation of mitochondrial Ca²⁺ level include exacerbated reactive oxygen species (ROS) generation, sensitized opening of mitochondrial permeability transition pore (mPTP), induction of programmed cell death, and ultimately muscle atrophy. Previously, both acute and long-term endurance exercises have been reported to activate certain signaling pathways to counteract ROS production. Meanwhile, electrical stimulation is known to help prevent apoptosis and alleviate muscle atrophy in denervated animal models and patients with motor impairment. There are various mechanistic studies that focus on the excitation-transcription coupling framework to understand the beneficial role of exercise and electrical stimulation. Interestingly, a recent study has revealed an unexpected role of rapid mitochondrial Ca²⁺ transients in keeping mPTP at a closed state with reduced mitochondrial ROS production. This discovery motivated us to contribute this review article to inspire further discussion about the potential mechanisms underlying differential outcomes of physiological mitochondrial Ca²⁺ transients and pathological mitochondrial Ca²⁺ elevation in skeletal muscle ROS production.

Fast repetitive stretch suppresses denervation-induced muscle fibrosis

BACKGROUND

We aimed to examine the influence of different speeds of stretching on denervation-induced skeletal muscle fibrosis.

METHODS

Stretching was passively applied to rat plantaris muscle denervated by sciatic nerve excision in three different cycles of 0.5, 3, or 12 cycles/min, for 20 min/d for 2 weeks.

RESULTS

Gene analysis results showed greater expression of fibrosis-related factors with fast stretching compared with non-stretched muscle. Laser Doppler blood flow analysis indicated reduced intramuscular blood flow during stretching. Histological analysis demonstrated fibrotic area decreases in 12 cycles/min stretched muscle compared with non-stretched muscle.

CONCLUSIONS

Slower stretching induced greater mRNA expression of collagen and fibroblasts and greater decrement of blood flow. Histologically, faster stretching suppressed fibrosis. These results suggest that fast repetitive stretching of denervated muscle might suppress processes of muscle fibrosis.

RUNX1: an emerging therapeutic target for cardiovascular disease

Runt-related transcription factor-1 (RUNX1), also known as acute myeloid leukaemia 1 protein (AML1), is a member of the core-binding factor family of transcription factors which modulate cell proliferation, differentiation, and survival in multiple systems. It is a master-regulator transcription factor, which has been implicated in diverse signalling pathways and cellular mechanisms during normal development and disease. RUNX1 is best characterized for its indispensable role for definitive haematopoiesis and its involvement in haematological malignancies. However, more recently RUNX1 has been identified as a key regulator of adverse cardiac remodelling following myocardial infarction. This review discusses the role RUNX1 plays in the heart and highlights its therapeutic potential as a target to limit the progression of adverse cardiac remodelling and heart failure.

Effects of mesenchymal stromal cells on motor function and collagen in the skeletal muscles of rats with type I diabetes

The present study aimed to evaluate the effects of mesenchymal stromal cell (MSC) transplantation on motor function and collagen organization in the muscles of rats with type 1 diabetes mellitus. Male Wistar rats were randomly assigned to three groups: control (C), diabetic (DM) and diabetic treated with MSCs (DM-MSCs). Diabetes was induced by streptozotocin (50 µg/kg). Bone marrow cells were isolated from the tibia and femur. After 10 weeks of DM induction, the DM-MSC rats received four i.p. injections of MSCs (1 × 106). Ten weeks after MSC transplantation, motor performance was evaluated by the rotarod test and the anterior tibial (TA) muscles were collected for morphometric and quantification of collagen birefringence by polarizing microscopy analysis. Motor performance of the DM group was significantly reduced when compared to the C group and increased significantly in the DM + MSC group. The TA muscle mass was significantly reduced in the DM and DM + MSC groups compared to the C group. The connective tissue increased in the DM group compared to the C group and decreased in the DM + MSC group. The percentage collagen birefringence decreased significantly in the DM group when compared to the C group and increased in the DM + MSC group. Motor performance was positively correlated with collagen birefringence and negatively correlated with percentage of connective tissue. The results indicate that MSC transplantation improves both motor function and the collagen macromolecular organization in type 1 DM.

Changes in Pre- and Post-Electroconvulsive Therapy Serum Myostatin Levels in Patients with Treatment Resistant Depression

Objective

Methods

Results

Conclusion

Effects of mesenchymal stromal cells on type 1 diabetes mellitus rat muscles

INTRODUCTION

Type 1 diabetes mellitus (DM) causes marked skeletal muscle atrophy. Mesenchymal stromal cells (MSC) are an attractive therapy to avoid diabetic complications because of their ability to modify the microenvironment at sites of tissue injury. The objective of this study was to evaluate the effects of MSC transplantation on muscle adaptation caused by diabetes.

METHODS

DM was induced by streptozotocin (STZ), and the diabetic animals received systemic MSC transplantation. The von Frey test and footprint analysis were used to assess sensation and sensory motor performance, respectively. Tibialis anterior muscles were investigated by morphology; molecular markers atrogin-1/muscle RING-finger protein-1, nuclear factor κB/p38 mitogen-activated protein kinase, tumor necrosis-like weak inducer of apoptosis/fibroblast growth factor-inducible 14, myostatin, myogenic differentiation 1, and insulin-like growth factor 1 were also assessed.

RESULTS

MSC transplantation improved sensation and walking performance and also decreased muscle fibrosis in DM rats by modulating atrogenes but did not prevent muscle atrophy.

DISCUSSION

MSCs can reduce muscle and functional complications that result from type 1 DM in rats. Muscle Nerve 58: 583-591, 2018.

Regulation of extracellular matrix elements and sarcomerogenesis in response to different periods of passive stretching in the soleus muscle of rats

Stretching is a common method used to prevent muscle shortening and improve limited mobility. However, the effect of different time periods on stretching-induced adaptation of the extracellular matrix and its regulatory elements have yet to be investigated. We aimed to evaluate the expression of fibrillar collagens, sarcomerogenesis, metalloproteinase (MMP) activity and gene expression of the extracellular matrix (ECM) regulators in the soleus (SOL) muscle of rats submitted to different stretching periods. The soleus muscles were submitted to 10 sets of passive stretching over 10 (St 10d) or 15 days (St 15d) (1 min per set, with 30 seconds' rest between sets). Sarcomerogenesis, muscle cross-sectional area (CSA), and MMP activity and mRNA levels in collagen (type I, III and IV), connective tissue growth factor (CTGF), growth factor-beta (TGF-β), and lysyl oxidase (LOX) were analyzed. Passive stretching over both time periods mitigated COL-I deposition in the SOL muscle of rats. Paradoxically, 10 days of passive stretching induced COL-I and COL-III synthesis, with concomitant upregulation of TGF-β1 and CTGF at a transcriptional level. These responses may be associated with lower LOX mRNA levels in SOL muscles submitted to 10 passive stretching sessions. Moreover, sarcomerogenesis was observed after 15 days of stretching, suggesting that stretching-induced muscle adaptations are time-dependent responses.

Insulin treatment reverses the increase in atrogin-1 expression in atrophied skeletal muscles of diabetic rats with acute joint inflammation

Background

The aim of this study was to evaluate the changes in biomarkers of skeletal muscle proteolysis (atrogin-1, muscle RING finger-1 protein [MuRF-1]) and inflammation (nuclear factor kappa-B) in skeletal muscles of rats under two catabolic conditions, diabetes mellitus (DM) and acute joint inflammation, and the effects of insulin therapy.

Materials and methods

Male Wistar rats were divided into groups without diabetes – normal (N), saline (NS), or ι-carrageenan (NCa) injection into the tibiotarsal joint – and groups with diabetes – diabetes (D), plus insulin (DI), saline (DS), or ι-carrageenan (DCa) injection into the tibiotarsal joint, or ι-carrageenan injection and treatment with insulin (DCaI). Three days after ι-carrageenan injection (17 days after diabetes induction), tibialis anterior (TA) and soleus (SO) skeletal muscles were used for analysis.

Results

DM alone caused a significant decrease in the mass of TA and SO muscles, even with low levels of atrogenes (atrogin-1, MuRF-1), which could be interpreted as an adaptive mechanism to spare muscle proteins under this catabolic condition. The loss of muscle mass was exacerbated when ι-carrageenan was administered in the joints of diabetic rats, in association with increased expression of atrogin-1, MuRF-1, and nuclear factor kappa-B. Treatment with insulin prevented the increase in atrogin-1 (TA, SO) and the loss of muscle mass (SO) in diabetic-carrageenan rats; in comparison with TA, SO muscle was more responsive to the anabolic actions of insulin.

Conclusion

Acute joint inflammation overcame the adaptive mechanism in diabetic rats to prevent excessive loss of muscle mass, worsening the catabolic state. The treatment of diabetic-carrageenan rats with insulin prevented the loss of skeletal muscle mass mainly via atrogin-1 inhibition. Under the condition of DM and inflammation, muscles with the prevalence of slow-twitch, type 1 fibers were more responsive to insulin treatment, recovering the ability to grow.

Genome-wide association study identifies novel susceptible loci and highlights Wnt/beta-catenin pathway in the development of adolescent idiopathic scoliosis

The genetic architecture of adolescent idiopathic scoliosis (AIS) remains poorly understood. Here we present the result of a 4-stage genome-wide association study composed of 5,953 AIS patients and 8,137 controls. Overall, we identified three novel susceptible loci including rs7593846 at 2p14 near MEIS1 (Pcombined = 1.19 × 10-13, OR = 1.21, 95% CI = 1.10-1.32), rs7633294 at 3p14.1 near MAGI1 (Pcombined = 1.85 × 10-12, OR = 1.20, 95% CI = 1.09-1.32), and rs9810566 at 3q26.2 near TNIK (Pcombined = 1.14 × 10-11, OR = 1.19, 95% CI = 1.08-1.32). We also confirmed a recently reported region associated with AIS at 20p11.22 (Pcombined = 1.61 × 10-15, OR = 1.22, 95% CI = 1.12-1.34). Furthermore, we observed significantly asymmetric expression of Wnt/beta-catenin pathway in the bilateral paraspinal muscle of AIS patients, including beta-catenin, TNIK, and LBX1. This is the first study that unveils the potential role of Wnt/beta-catenin pathway in the development of AIS, and our findings may shed new light on the etiopathogenesis of AIS.

Electrical stimulation delays reinnervation in denervated rat muscle

INTRODUCTION

It is not clear if electrical stimulation (ES) can affect muscle reinnervation. This study aimed to verify if ES affects neuromuscular recovery after nerve crush injury in rats.

METHODS

Denervated muscles were electrically stimulated daily for 6 or 14 days. Neuromuscular performance and excitability, and muscle morphology were determined. Muscle trophism markers (atrogin-1, MuRF-1, and myoD), as well as neuromuscular junction (NMJ) organization (muscle-specific receptor tyrosine kinase [MuSK], cytoplasmic protein downstream of kinase-7 [Dok-7], nicotinic ACh receptor [nAChR], and neural cell adhesion molecule [N-CAM]) were assessed.

RESULTS

ES impaired neuromuscular recovery at day 14 postdenervation. Muscle hypoexcitability was accentuated by ES at 6 and 14 days postdenervation. Although ES reduced the accumulation of atrogin-1, MuRF1, and myoD mRNAs, it increased muscle atrophy. Gene expression of MuSK, Dok-7, nAChR, and the content of N-CAM protein were altered by ES.

DISCUSSION

ES can delay the reinnervation process by modulating factors related to NMJ stability and organization, and inducing dysfunction, hypoexcitability, and muscle atrophy. Muscle Nerve 56: E108-E118, 2017.

Safety and feasibility of a neuromuscular electrical stimulation chronaxie-based protocol in critical ill patients: A prospective observational study

PURPOSE

The aim of this study was to evaluate the safety and feasibility of a neuromuscular electrical stimulation (NMES) protocol based on neuromuscular excitability and applied in numerous muscle groups of critical ill patients.

MATERIALS AND METHODS

We performed a prospective observational study using an NMES applied daily and bilaterally into 5 muscle groups in lower limbs for 3 consecutive days. The characteristics of NMES were 90 contractions per muscle, pulse width equal to chronaxie, and a pulse frequency of 100 Hz. We assessed safety with central venous oxygen saturation, serum lactate, and creatine phosphokinase measurements. To evaluate feasibility, we recorded the time spent for the entire NMES protocol and the number of NMES sessions completed.

RESULTS

Eleven male patients finished the study. There were no significant changes observed in creatine phosphokinase from baseline up to 96 hours: 470(±270) IU/L and 455(±240) IU/L (P>.99). Central venous oxygen saturation and serum lactate had the same pattern with no significant variations (P=.23 and P=.8, respectively). The time spent during the whole procedure and the number of complete NMES sessions performed were 107±24 minutes and 84 sessions (85%), respectively.

CONCLUSIONS

We demonstrated that NMES chronaxie-based protocol is safe and feasible.

Serum myostatin levels are independently associated with skeletal muscle wasting in patients with heart failure

BACKGROUND

It has been reported that skeletal muscle mass and strength are decreased in patients with heart failure (HF), and HF is associated with both reduced exercise capacity and adverse clinical outcomes. Myostatin has been known as a negative regulator of muscle growth, follistatin as the myostatin antagonist, maintaining tissue homeostasis. We thus determined serum myostatin levels in HF patients and whether they are associated with skeletal muscle wasting.

METHODS AND RESULTS

Forty one consecutive HF patients (58±15years old, New York Heart Association class I-III) and 30 age-matched healthy subjects as controls (53±8years old) were studied. Serum myostatin levels were significantly lower in HF patients than controls (18.7±7.4 vs. 23.6±5.2ng/mL, P<0.001). Circumference of the thickest part of the right thigh was significantly small (468±72 vs. 559±37mm, P=0.001) and lower extremity muscular strength was lower in patients with HF (129±55 vs. 219±52N×m, P<0.001). Fourteen HF patients (34%) had muscle wasting. By univariate analysis, higher age, higher serum follistatin, and lower serum myostatin were significantly associated with the presence of muscle wasting. By multivariate analysis, serum myostatin levels were independently associated with muscle wasting (OR=0.77, 95% CI [0.58, 0.93], P=0.02).

CONCLUSION

Serum myostatin levels were significantly decreased in HF patients and associated with lower extremity muscle wasting, suggesting that myostatin may be an important factor for maintaining skeletal muscle mass and strength in HF.

Intermittent stretching induces fibrosis in denervated rat muscle

INTRODUCTION

Stretching (St) has been used for treating denervated muscles. However, its effectiveness and safety claims require further study.

METHODS

Rats were divided into: (1) those with denervated (D) muscles, evaluated 7 or 15 days after sciatic nerve crush injury; (2) those with D muscles submitted to St during 7 or 15 days; and (3) those with normal muscles. Muscle fiber cross-sectional area, serial sarcomere number, sarcomere length, and connective tissue density were measured. MMP-2, MMP-9, TIMP-1, TGF-β1, and myostatin mRNAs were determined by real-time polymerase chain reaction. MMP-2 and MMP-9 activity was evaluated by zymography. Collagen I was localized using immunofluorescence.

RESULTS

St did not prevent muscle atrophy due to denervation, but it increased fibrosis and collagen I deposition at day 15. St also upregulated MMP-9 and TGF-β1 gene expressions at day 7, and myostatin at day 15.

CONCLUSIONS

Stretching denervated muscle does not prevent atrophy, but it increases fibrosis via temporal modulation of TGF-β1/myostatin and MMP-9 cascades.

Optimizing stimulation parameters in functional electrical stimulation of denervated muscles: a cross-sectional study

Background

To counteract denervation atrophy long-term electrical stimulation with a high number of muscle contractions has to be applied. This may lead to discomfort of the patient and negative side effects like burns. A functional effective muscle contraction induced by the lowest possible stimulation intensity is desirable. In clinical practice a selective stimulation of denervated muscles with triangular pulses is used.

The aim of the study was to evaluate the influence of polarity and pulse duration on the stimulation intensity of triangular pulses in denervated muscles in patients with peripheral nerve lesions.

Methods

Twenty-four patients with denervated extensor digitorum communis muscle and twenty-four patients with denervated tibialis anterior muscle due to peripheral nerve lesions were included. Four different combinations of triangular pulses with various duration and polarity were delivered randomly to the denervated muscles. The threshold intensity to induce a functional effective muscle contraction was noted. One-way within subject ANOVA was used to assess changes in intensity. An alpha level of p less than or equal to 0.05 was the criterion for statistical significance.

Results

Patients with a denervated tibialis anterior muscle presented significant lower intensities inducing a functional effective muscle contraction in favor of the stimulation with a duration of 200 ms and a polarity with the cathode proximally applied. No significant differences could be shown between the different stimulation protocols in case of denervated extensor digitorum communis muscle.

Conclusions

We recommend electrical stimulation of the denervated tibialis anterior muscle with triangular current with a duration of 200 ms and a polarity with the cathode proximally applied.

Modulation of satellite cells activity and MyoD in rat thyroarytenoid muscle after reinnervation

OBJECTIVES/HYPOTHESIS

To examine modulation of M-cadherin, a marker for satellite cells (SCs); and MyoD, which may indicate the myogenic activity following recurrent laryngeal nerve (RLN) denervation and immediate reinnervation; and to elucidate the correlation between their modulations and establishment of neuromuscular junctions (NMJs) in the reinnervated rat thyroarytenoid (TA) muscle.

STUDY DESIGN

Quantitative real-time polymerase chain reaction qPCR and histologic assessment of the TA muscle following RLN transection and anastomosis.

METHODS

Rats were divided into three groups: 1) denervation alone (DNV) (n = 60), 2) denervation with anastomosis (ANS) (n = 60), and 3) sham-operated controls (n = 12). Animals were sacrificed at 3 days and 1, 3, and 5 weeks after treatment. TA muscles harvested from 40 animals from each DNV and ANS group; all of sham group were subjected to qPCR for assessment of the modulation of M-cadherin and MyoD; and the remaining larynges of DNV and ANS group were used for histologic analysis.

RESULTS

The expression levels of messenger RNAs (mRNAs) encoding M-cadherin and MyoD in the TA muscle of the DNV group were significantly higher (P < 0.05) than in the control throughout the study period. These mRNA levels in the ANS group were significantly higher (P < 0.05) at ≤ 1 week than in the controls but fell to control levels at ≥ 3 weeks. In the ANS group, recovery of muscle area and NMJs structure occurred by 3 weeks.

CONCLUSION

These data suggested that NMJ formation following reinnervation might prompt recovery of M-cadherin and MyoD mRNA expression to the quiescent level of SCs.

Electrical stimulation influences satellite cell differentiation after sciatic nerve crush injury in rats

INTRODUCTION

Electrical stimulation is often used to prevent muscle atrophy and preserve contractile function, but its effects on the satellite cell population after nerve injury are not well understood. In this study we aimed to determine whether satellite cell differentiation is affected by electrical stimulation after nerve crush.

METHODS

The sciatic nerves of Sprague-Dawley (SD) rats were crushed. Half of the injured rats received daily electrical stimulation of the gastrocnemius muscle, and the others did not. Tests for detecting paired box protein 7 (Pax7), myogenic differentiation antigen (MyoD), embryonic myosin heavy chain (eMyHC), and force production were performed 2, 4, and 6 weeks after injury.

RESULTS

More Pax7+/MyoD+ nuclei in stimulated muscles were observed than in non-stimulated muscles. eMyHC expression was elevated in stimulated muscles and correlated positively with enhanced force production.

CONCLUSIONS

Increased satellite cell differentiation is correlated with preserved muscle function in response to electrical stimulation after nerve injury.

Skeletal muscle wasting with disuse atrophy is multi-dimensional: the response and interaction of myonuclei, satellite cells and signaling pathways

Maintenance of skeletal muscle is essential for health and survival. There are marked losses of skeletal muscle mass as well as strength and physiological function under conditions of low mechanical load, such as space flight, as well as ground based models such as bed rest, immobilization, disuse, and various animal models. Disuse atrophy is caused by mechanical unloading of muscle and this leads to reduced muscle mass without fiber attrition. Skeletal muscle stem cells (satellite cells) and myonuclei are integrally involved in skeletal muscle responses to environmental changes that induce atrophy. Myonuclear domain size is influenced differently in fast and slow twitch muscle, but also by different models of muscle wasting, a factor that is not yet understood. Although the myonuclear domain is 3-dimensional this is rarely considered. Apoptosis as a mechanism for myonuclear loss with atrophy is controversial, whereas cell death of satellite cells has not been considered. Molecular signals such as myostatin/SMAD pathway, MAFbx, and MuRF1 E3 ligases of the ubiquitin proteasome pathway and IGF1-AKT-mTOR pathway are 3 distinctly different contributors to skeletal muscle protein adaptation to disuse. Molecular signaling pathways activated in muscle fibers by disuse are rarely considered within satellite cells themselves despite similar exposure to unloading or low mechanical load. These molecular pathways interact with each other during atrophy and also when various interventions are applied that could alleviate atrophy. Re-applying mechanical load is an obvious method to restore muscle mass, however how nutrient supplementation (e.g., amino acids) may further enhance recovery (or reduce atrophy despite unloading or ageing) is currently of great interest. Satellite cells are particularly responsive to myostatin and to growth factors. Recently, the hibernating squirrel has been identified as an innovative model to study resistance to atrophy.

Efeito da eletroestimulação no músculo desnervado de animais: revisão sistemática

INTRODUÇÃO: A recuperação funcional após a lesão nervosa periférica está relacionada a fatores intrínsecos e extrínsecos ao sistema nervoso periférico, tais como a gravidade da lesão e a condição dos órgãos-alvo. A atrofia constitui uma das principais alterações do músculo após a lesão nervosa e, uma vez instalada, atua como barreira ao crescimento axonal durante a reinervação muscular. O uso da eletroestimulação é rotineiro no campo da fisioterapia e tem o objetivo de minimizar ou impedir a atrofia muscular e, assim, favorecer a recuperação da lesão nervosa periférica. OBJETIVO: Avaliar os efeitos da eletroestimulação sobre as características tróficas do músculo desnervado. MÉTODOS: Artigos publicados entre 1990 e 2010 e indexados aos bancos de dados da PUBMED foram selecionados utilizando os seguintes descritores: "muscle denervation AND electric stimulation" e "muscular atrophy AND electric stimulation". Foram considerados como critério de inclusão os estudos experimentais em animais (ratos) que utilizassem a lesão nervosa periférica como modelo de desnervação e que avaliassem o efeito da eletroestimulação muscular sobre a área de secção transversa e/ou a massa muscular de músculos desnervados. RESULTADOS: Nove artigos foram selecionados para a revisão. CONCLUSÕES: O efeito da eletroestimulação está diretamente relacionado à característica do protocolo de intervenção, que, quando aplicado de maneira adequada, apresenta o efeito de retardar e, em alguns casos, impedir a atrofia do músculo desnervado.

Acupuncture ameliorated skeletal muscle atrophy induced by hindlimb suspension in mice

Preventing skeletal muscle atrophy is critical for maintaining quality of life, but it is often a challenging goal for the elderly and patients with severe conditions. We hypothesized that acupuncture in place of exercise training is an alternative non-pharmacological intervention that can help to prevent muscle atrophy. To elucidate the effects of acupuncture on skeletal muscle atrophy caused by hindlimb suspension (HS), we performed acupuncture on mice according to two different methods: acupuncture with electrical stimulation (EA: electroacupuncture) and without electrical stimulation (MA: manual acupuncture). A needle was retained in the gastrocnemius muscle for 30 min every day for 2 weeks in the EA and MA groups. In the EA group, 30 min of repetitive electrical stimulation (1 Hz, 1 ms pulse width, 6.5 mA intensity) was also applied. HS significantly reduced muscle mass and the cross-sectional area of the soleus muscles. This HS-induced reduction was significantly improved in the EA group, although the level of improvement remained insufficient when compared with the control group. We found that the mRNA expression levels of atrogin-1 and MuRF1, which play a principal role in muscle-specific degradation as E3 ubiquitin ligases, were significantly increased in the HS group compared to the control group. EA and MA reduced the HS-induced upregulation of atrogin-1 (p<0.01 in EA and MA) and MuRF1 (p<0.01 in EA) mRNAs. We also found that the expression levels of PI3K, Akt1, TRPV4, adenosine A1 receptor, myostatin, and SIRT1 mRNAs tended to be increased by HS. EA and MA further increased the HS-induced upregulation of Akt1 (p<0.05 in MA) and TRPV4 (p<0.05 in MA) mRNAs. We concluded that acupuncture partially prevented skeletal muscle atrophy. This effect might be due to an increase in protein synthesis and a decrease in protein degradation.

Electrostimulation during hindlimb unloading modulates PI3K-AKT downstream targets without preventing soleus atrophy and restores slow phenotype through ERK

Our aim was to analyze the role of phosphatidylinositol 3-kinase (PI3K)-AKT and MAPK signaling pathways in the regulation of muscle mass and slow-to-fast phenotype transition during hindlimb unloading (HU). For that purpose, we studied, in rat slow soleus and fast extensor digitorum longus muscles, the time course of anabolic PI3K-AKT-mammalian target of rapamycin, catabolic PI3K-AKT-forkhead box O (FOXO), and MAPK signaling pathway activation after 7, 14, and 28 days of HU. Moreover, we performed chronic low-frequency soleus electrostimulation during HU to maintain exclusively contractile phenotype and so to determine more precisely the role of these signaling pathways in the modulation of muscle mass. HU induced a downregulation of the anabolic AKT, mammalian target of rapamycin, 70-kDa ribosomal protein S6 kinase, 4E-binding protein 1, and glycogen synthase kinase-3β targets, and an upregulation of the catabolic FOXO1 and muscle-specific RING finger protein-1 targets correlated with soleus muscle atrophy. Unexpectedly, soleus electrostimulation maintained 70-kDa ribosomal protein S6 kinase, 4E-binding protein 1, FOXO1, and muscle-specific RING finger protein-1 to control levels, but failed to reduce muscle atrophy. HU decreased ERK phosphorylation, while electrostimulation enabled the maintenance of ERK phosphorylation similar to control level. Moreover, slow-to-fast myosin heavy chain phenotype transition and upregulated glycolytic metabolism were prevented by soleus electrostimulation during HU. Taken together, our data demonstrated that the processes responsible for gradual disuse muscle plasticity in HU conditions involved both PI3-AKT and MAPK pathways. Moreover, electrostimulation during HU restored PI3K-AKT activation without counteracting soleus atrophy, suggesting the involvement of other signaling pathways. Finally, electrostimulation maintained initial contractile and metabolism properties in parallel to ERK activation, reinforcing the idea of a predominant role of ERK in the regulation of muscle slow phenotype.