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.

Blood Flow Restriction Combined with Electrical Stimulation Attenuates Thigh Muscle Disuse Atrophy

PURPOSE

This study aimed to investigate the effects of blood flow restriction (BFR) combined with electrical muscle stimulation (EMS) on skeletal muscle mass and strength during a period of limb disuse.

METHODS

Thirty healthy participants (22 ± 3 yr; 23 ± 3 kg·m-2) were randomly assigned to control (CON; n = 10), BFR alone (BFR; n = 10), or BFR combined with EMS (BFR + EMS; n = 10). All participants completed unloading of a single leg for 14 d, with no treatment (CON), or while treated with either BFR or BFR + EMS (twice daily, 5 d·wk-1). BFR treatment involved arterial three cycles of 5-min occlusion using suprasystolic pressure, each separated by 5 min of reperfusion. EMS (6 s on, 15 s off; 200 μs; 60 Hz; 15% maximal voluntary contraction [MVC]) was applied continuously throughout the three BFR cycles. Quadriceps muscle mass (whole-thigh lean mass via dual-energy x-ray absorptiometry and vastus lateralis [VL] muscle thickness via ultrasound) and strength (via knee extension MVC) were assessed before and after the 14-d unloading period.

RESULTS

After limb unloading, whole-thigh lean mass decreased in the control group (-4% ± 1%, P < 0.001) and BFR group (-3% ± 2%, P = 0.001), but not in the BFR + EMS group (-0.3% ± 3%, P = 0.8). VL muscle thickness decreased in the control group (-4% ± 4%, P = 0.005) and was trending toward a decrease in the BFR group (-8% ± 11%, P = 0.07) and increase in the BFR + EMS group (+5% ± 10%, P = 0.07). Knee extension MVC decreased over time (P < 0.005) in the control group (-18% ± 15%), BFR group (-10% ± 13%), and BFR + EMS group (-18% ± 15%), with no difference between groups (P > 0.5).

CONCLUSION

Unlike BFR performed in isolation, BFR + EMS represents an effective interventional strategy to attenuate the loss of muscle mass during limb disuse, but it does not demonstrate preservation of strength.

Nutritional Strategies to Offset Disuse-Induced Skeletal Muscle Atrophy and Anabolic Resistance in Older Adults: From Whole-Foods to Isolated Ingredients

Preserving skeletal muscle mass and functional capacity is essential for healthy ageing. Transient periods of disuse and/or inactivity in combination with sub-optimal dietary intake have been shown to accelerate the age-related loss of muscle mass and strength, predisposing to disability and metabolic disease. Mechanisms underlying disuse and/or inactivity-related muscle deterioration in the older adults, whilst multifaceted, ultimately manifest in an imbalance between rates of muscle protein synthesis and breakdown, resulting in net muscle loss. To date, the most potent intervention to mitigate disuse-induced muscle deterioration is mechanical loading in the form of resistance exercise. However, the feasibility of older individuals performing resistance exercise during disuse and inactivity has been questioned, particularly as illness and injury may affect adherence and safety, as well as accessibility to appropriate equipment and physical therapists. Therefore, optimising nutritional intake during disuse events, through the introduction of protein-rich whole-foods, isolated proteins and nutrient compounds with purported pro-anabolic and anti-catabolic properties could offset impairments in muscle protein turnover and, ultimately, the degree of muscle atrophy and recovery upon re-ambulation. The current review therefore aims to provide an overview of nutritional countermeasures to disuse atrophy and anabolic resistance in older individuals.

Increasing myosin light chain 3f (MLC3f) protects against a decline in contractile velocity

Disuse induces adaptations in skeletal muscle, which lead to muscle deterioration. Hindlimb-unloading (HU) is a well-established model to investigate cellular mechanisms responsible for disuse-induced skeletal muscle dysfunction. In myosin heavy chain (MHC) type IIB fibers HU induces a reduction in contraction speed (Vo) and a reduction in the relative myosin light chain 3f (MLC3f) protein content compared with myosin light chain 1f (MLC1f) protein. This study tested the hypothesis that increasing the relative MLC3f protein content via rAd-MLC3f vector delivery would attenuate the HU-induced decline in Vo in single MHC type IIB fibers. Fischer-344 rats were randomly assigned to one of three groups: control, HU for 7 days, and HU for 7 days plus rAd-MLC3f. The semimembranosus muscles were injected with rAd-MLC3f (3.75 x 10¹¹–5 x 10¹¹ ifu/ml) at four days after the initiation of HU. In single MHC type IIB fibers the relative MLC3f content decreased by 25% (12.00±0.60% to 9.06±0.66%) and Vo was reduced by 29% (3.22±0.14fl/s vs. 2.27±0.08fl/s) with HU compared to the control group. The rAd-MLC3f injection resulted in an increase in the relative MLC3f content (12.26±1.19%) and a concomitant increase in Vo (2.90±0.15fl/s) of MHC type IIB fibers. A positive relationship was observed between the percent of MLC3f content and Vo. Maximal isometric force and specific tension were reduced with HU by 49% (741.45±44.24μN to 379.09±23.77μN) and 33% (97.58±4.25kN/m² to 65.05±2.71kN/m²), respectively compared to the control group. The rAd-MLC3f injection did not change the HU-induced decline in force or specific tension. Collectively, these results indicate that rAd-MLC3f injection rescues hindlimb unloading-induced decline in Vo in MHC type IIB single muscle fibers.

Resveratrol Improves Muscle Atrophy by Modulating Mitochondrial Quality Control in STZ-Induced Diabetic Mice

SCOPE

In this study, we aim to determine the effects of resveratrol (RSV) on muscle atrophy in streptozocin-induced diabetic mice and to explore mitochondrial quality control (MQC) as a possible mechanism.

METHODS AND RESULTS

The experimental mice were fed either a control diet or an identical diet containing 0.04% RSV for 8 weeks. Examinations were subsequently carried out, including the effects of RSV on muscle atrophy and muscle function, as well as on the signaling pathways related to protein degradation and MQC processes. The results show that RSV supplementation improves muscle atrophy and muscle function, attenuates the increase in ubiquitin and muscle RING-finger protein-1 (MuRF-1), and simultaneously attenuates LC3-II and cleaved caspase-3 in the skeletal muscle of diabetic mice. Moreover, RSV treatment of diabetic mice results in an increase in mitochondrial biogenesis and inhibition of the activation of mitophagy in skeletal muscle. RSV also protects skeletal muscle against excess mitochondrial fusion and fission in the diabetic mice.

CONCLUSION

The results suggest that RSV ameliorates diabetes-induced skeletal muscle atrophy by modulating MQC.

Skeletal muscle PGC-1β signaling is sufficient to drive an endurance exercise phenotype and to counteract components of detraining in mice

Peroxisome proliferator-activated receptor-γ coactivator (PGC)-1α and -1β serve as master transcriptional regulators of muscle mitochondrial functional capacity and are capable of enhancing muscle endurance when overexpressed in mice. We sought to determine whether muscle-specific transgenic overexpression of PGC-1β affects the detraining response following endurance training. First, we established and validated a mouse exercise-training-detraining protocol. Second, using multiple physiological and gene expression end points, we found that PGC-1β overexpression in skeletal muscle of sedentary mice fully recapitulated the training response. Lastly, PGC-1β overexpression during the detraining period resulted in partial prevention of the detraining response. Specifically, an increase in the plateau at which O₂ uptake (V̇o₂) did not change from baseline with increasing treadmill speed [peak V̇o₂ (ΔV̇o_2max)] was maintained in trained mice with PGC-1β overexpression in muscle 6 wk after cessation of training. However, other detraining responses, including changes in running performance and in situ half relaxation time (a measure of contractility), were not affected by PGC-1β overexpression. We conclude that while activation of muscle PGC-1β is sufficient to drive the complete endurance phenotype in sedentary mice, it only partially prevents the detraining response following exercise training, suggesting that the process of endurance detraining involves mechanisms beyond the reversal of muscle autonomous mechanisms involved in endurance fitness. In addition, the protocol described here should be useful for assessing early-stage proof-of-concept interventions in preclinical models of muscle disuse atrophy.

Additive effect of PTH (1-34) and zoledronate in the prevention of disuse osteopenia in rats

Immobilization is known to cause a rapid bone loss due to increased osteoclastic bone resorption and decreased osteoblastic bone formation. Zoledronate (Zln) is a potent anti-resorptive pharmaceutical, while intermittent PTH is a potent bone anabolic agent. The aim of the present study was to investigate whether PTH or Zln alone or in combination could prevent immobilization-induced osteopenia. Immobilization was achieved by injecting 4IU Botox (BTX) into the right hind limb musculature. Seventy-two 16-week-old female Wistar rats were randomized into 6 groups; baseline (Base), control (Ctrl), BTX, BTX+PTH, BTX+Zln, and BTX+PTH+Zln. PTH (1-34) (80μg/kg) was given 5days/week and Zln (100μg/kg) was given once at study start. The animals were killed after 4weeks of treatment. The bone properties were evaluated using DEXA, μCT, dynamic bone histomorphometry, and mechanical testing. BTX resulted in lower femoral trabecular bone volume fraction (BV/TV) (-25%, p<0.05), lower tibial trabecular bone formation rate (BFR/BS) (-29%, p<0.05), and lower bone strength (Fmax) at the distal femur (-19%, p<0.001) compared with Ctrl. BTX+PTH resulted in higher femoral BV/TV (+31%, p<0.05), higher tibial trabecular BFR/BS (+297%, p<0.05), and higher Fmax at the distal femur (+11%, p<0.05) compared with BTX. BTX+Zln resulted in higher femoral BV/TV (+36%, p<0.05), lower tibial trabecular BFR/BS (-93%, p<0.05), and higher Fmax at the distal femur (+10%, p<0.05) compared with BTX. BTX+PTH+Zln resulted in higher femoral BV/TV (+70%, p<0.001), higher tibial trabecular BFR/BS (+59%, p<0.05), and higher Fmax at the distal femur (+32%, p<0.001) compared with BTX. In conclusion, BTX-induced immobilization led to lower BV/TV, BFR/BS, and Fmax. In general, PTH or Zln alone prevented the BTX-induced osteopenia, whereas PTH and Zln given in combination not only prevented, but also increased BV/TV and BFR/BS, and maintained Fmax at the distal femoral metaphysis compared with Ctrl.

The non-thermal effects of pulsed ultrasound irradiation on the development of disuse muscle atrophy in rat gastrocnemius muscle

This study examined the effects of therapeutic pulsed ultrasound (US) on the development of disuse muscle atrophy in rat gastrocnemius muscle. Male Wistar rats were randomly distributed into control, immobilization (Im), sham US, and US groups. In the Im, sham US and US groups, the bilateral ankle joints of each rat were immobilized in full plantar flexion with a plaster cast for a 4-wk period. The pulsed US (frequency, 1 MHz; intensity, 1.0 W/cm(2); pulsed mode 1:4; 15 min) was irradiated to the gastrocnemius muscle in the US group over a 4-wk immobilization period. The pulsed US irradiation delivered only non-thermal effects to the muscle. In conjunction with US irradiation, 5-bromo-2'-deoxyuridine (BrdU) was injected subcutaneously to label the nuclei of proliferating satellite cells 1 h before each pulsed US irradiation. Immobilization resulted in significant decreases in the mean diameters of type I, IIA and IIB muscle fibers of the gastrocnemius muscle in the Im, sham US and US groups compared with the control group. However, the degrees of muscle fiber atrophy for all types were significantly lower in the US group compared with the Im and sham US groups. Although the number of capillaries and the concentrations of insulin-like growth factor and basic fibroblast growth factor did not change in the muscle, the number of BrdU-positive nuclei in the muscle was significantly increased by pulsed US irradiation in the US group. The results of this study suggest that pulsed US irradiation inhibits the development of disuse muscle atrophy partly via activation of satellite cells.

Dynamic skeletal muscle stimulation and its potential in bone adaptation

To identify mechanotransductive signals for combating musculoskeletal deterioration, it is essential to determine the components and mechanisms critical to the anabolic processes of musculoskeletal tissues. It is hypothesized that the interaction between bone and muscle may depend on fluid exchange in these tissues by mechanical loading. It has been shown that intramedullary pressure (ImP) and low-level bone strain induced by muscle stimulation (MS) has the potential to mitigate bone loss induced by disuse osteopenia. Optimized MS signals, i.e., low-intensity and high frequency, may be critical in maintaining bone mass and mitigating muscle atrophy. The objectives for this review are to discuss the potential for MS to induce ImP and strains on bone, to regulate bone adaptation, and to identify optimized stimulation frequency in the loading regimen. The potential for MS to regulate blood and fluid flow will also be discussed. The results suggest that oscillatory MS regulates fluid dynamics with minimal mechanical strain in bone. The response was shown to be dependent on loading frequency, serving as a critical mediator in mitigating bone loss. A specific regimen of dynamic MS may be optimized in vivo to attenuate disuse osteopenia and serve as a biomechanical intervention in the clinical setting.

Knee extensor fatigability after bedrest for 8 weeks with and without countermeasure

We analyzed the effects of gravitational unloading on muscular fatigability and the effectiveness of resistive vibration exercise to counteract these changes. Changes in knee extensor fatigability as a consequence of 8 weeks of horizontal bedrest with or without daily resistive vibration exercise were evaluated in 17 healthy male volunteers. Bedrest increased fatigability (% decrease in maximal voluntary isometric torque per minute exercise) from -7.2 +/- 0.5 to -10.2 +/- 1.0%/min (P < 0.05), which was accompanied by a decline (of 52.0 +/- 3.7%, P < 0.05) in muscle blood flow. Daily resistive vibration exercise training during bedrest prevented increases in fatigability (from -10.8 +/- 1.8 to -8.4 +/- 1.6%/min, P < 0.05), and mitigated the reduction in blood flow (decline of 26.1 +/- 5.1%, P < 0.05). Daily resistive exercise may thus be suggested as an effective countermeasure during spaceflight and illness-related prolonged bedrest to combat the detrimental changes in muscle endurance that result from gravitational unloading.

Polyglutamine-mediated neurodegeneration: use of chaperones as prevention strategy

Polyglutamine diseases are a class of inherited neurodegenerative disorders caused by the expansion of a polyglutamine tract within the respective proteins. Clinical studies have revealed that the forming of neuronal intranuclear inclusions by the disease protein is a common pathological feature of polyglutamine diseases. Although there has been considerable progress in understanding polyglutamine diseases, many questions regarding their mechanism are still unanswered. The finding that molecular chaperones are associated with ubiquitinated intranuclear inclusions clearly indicates a crucial role of molecular chaperones in the generation of these fatal diseases. Molecular and chemical chaperones have been found to be a good agent for suppressing many polyglutamine diseases in several animal models. In this review, I discuss the roles of the ubiquitin-proteasome pathway and molecular chaperones in the development of polyglutamine diseases and probable approach for the prevention of many of these fatal disorders using molecular chaperones as a therapeutic agent. Newly found chemical chaperones have been demonstrated to be potentially useful and could be used as a therapeutic strategy in preventing many versions of polyglutamine diseases.

Force steadiness, muscle activity, and maximal muscle strength in subjects with subacromial impingement syndrome

We investigated the effects of the subacromial impingement syndrome (SIS) on shoulder sensory-motor control and maximal shoulder muscle strength. It was hypothesized that both would be impaired due to chronic shoulder pain associated with the syndrome. Nine subjects with unilateral SIS who remained physically active in spite of shoulder pain and nine healthy matched controls were examined to determine isometric and isokinetic submaximal shoulder-abduction force steadiness at target forces corresponding to 20%, 27.5%, and 35% of the maximal shoulder abductor torque, and maximal shoulder muscle strength (MVC). Electromyographic (EMG) activity was assessed using surface and intramuscular recordings from eight shoulder muscles. Force steadiness was impaired in SIS subjects during concentric contractions at the highest target force level only, with muscle activity largely unaffected. No between-group differences in shoulder MVC were observed. The present data suggest that shoulder sensory-motor control is only mildly impaired in subjects with SIS who are able to continue with upper body physical activity in spite of shoulder pain. Thus, physical activity should be continued by patients with SIS, if possible, to avoid the loss in neural and muscle functions associated with inactivity.

Continuous Muscle Stretch Prevents Disuse Muscle Atrophy and Deterioration of Its Oxidative Capacity in Rat Tail–Suspension Models

OBJECTIVE

The purpose of this study was to evaluate the effect of continuous muscle stretch on disuse-atrophied muscles.

DESIGN

Sprague-Dawley rats were used and divided into five groups: control group, hind limb suspended for 3 and 7 days, and hind-limb suspension plus strenuous continuous muscle stretch for 3 and 7 days. In the hind-limb suspension plus strenuous continuous muscle stretch groups, the gastrocnemius-plantaris-soleus muscles were stretched using a plastic plate that immobilized the ankle joint at the maximum dorsal flexed position during the hind-limb suspension period. The intracellular energy metabolism of the working muscle during electric stimulation was evaluated by phosphorus-31 magnetic resonance spectroscopy in vivo. Changes in phosphocreatine, inorganic phosphate, and the intracellular pH were monitored to evaluate intramuscular oxidative capacity. Maximum tension and muscle wet mass were also measured.

RESULTS

The oxidative capacity, muscle wet weight, and maximum tension decreased after hind-limb suspension. The muscle oxidative capacity at control levels was maintained during the first 3 days in muscles subjected to continuous strenuous stretch. It was also effective to prevent the decrease in muscle mass and maximum twitch tension during the initial 3 days. However, the effects did not persist.

CONCLUSION

Continuous strenuous stretch was effective to prevent disuse muscle atrophy and its functional deterioration; however, its effects did not last long.

Spaceflight and hindlimb suspension disuse models in mice

Osteoporosis is a disease characterized by low bone mass and structural deterioration of bone tissue, leading to bone fragility and increased susceptibility to fractures. The microgravity of space creates an extreme environment that provides a model for osteoporosis in humans. This greatly accelerated form of osteopenia results in a 0.5-2% loss of bone mass per month. Rat models for this osteoporosis have been examined on many occasions, but STS-108 was the first Space Shuttle flight to use mice. Data reported to date indicate that spaceflight experiments with mice hold promise in predicting some spaceflight effects on humans. Due to the cost and infrequency of flights, ground-based models have been developed to mimic the deleterious effects of the microgravity environment. Hindlimb suspension is one such localized model. This model removes gravitational loading from the hindlimbs by suspending the animal by its tail to a guy wire that runs lengthwise across the cage. Because mice had not flown before STS-108, a direct comparison of this model's ability to predict spaceflight results has not been examined. The objective of this research is to closely repeat the STS-108 profile, with hindlimb suspension replacing spaceflight. This includes examining the ability of the protein osteoprotegerin, an osteoclast-inhibiting therapeutic, to mitigate the deleterious effects of skeletal unloading. It is expected that the results will lead to better understanding of the mechanisms of mineralization and bone remodeling to aid in development of countermeasures to prevent spaceflight induced osteoporosis and aid the treatment of osteoporosis here on earth.

Prevention of muscle disuse atrophy by low-frequency electrical stimulation in rats

When muscles lose neural drive, they atrophy rapidly. Neuromuscular electrical stimulation (NMS) has been used in attempts to prevent or reverse the atrophy, but optimal stimulation programs and parameters are not well defined. In this study, we investigated the effects of four different stimulation patterns on disuse atrophy produced in the tibialis anterior, lateral gastrocnemius, and soleus muscles of rats paralyzed with tetrodotoxin for seven days. Stimulation paradigms differed from one another by their stimulation frequency (2 or 10 pulses/s) and by their stimulation period (2 or 10 h a day). Results showed that stimulation with 2 pulses/s, paradigms were more effective at preventing disuse muscle atrophy than higher-frequency stimulation. The most marked difference was in the slow soleus muscle, which had only 10% mean atrophy when stimulated at 2 pulses/s for 10 h, compared to 26% atrophy when stimulated at 10 pulses/s for either 2 or 10 h and 32% atrophy in unstimulated, paralyzed controls. The level of atrophic change was not correlated with the levels of serum creatine kinase, used as an index of muscle damage. Results suggest that remediation of disuse atrophy may be accomplished using unphysiologically low rates of motor-unit activation despite the relatively low force produced by such unfused contractions. This may have significant implications for the design of therapies for muscle paralysis consequent to upper-motoneuron lesions.

Cancer rehabilitation: particularly with aspects on physical impairments

Cancer can cause multiple impairments, activity limitations and participation restrictions. According to individual case findings and needs, rehabilitation treatment is varied. The review mainly focuses on specific problems. Because of functional deficits cancer patients suffer from persistent emotional and social distress and a reduced quality of life (QOL). QOL encompasses at least the four dimensions of physical, emotional, social and cognitive function, which may be positively influenced by physical exercise. Physical exercise also has been shown to prevent or minimise inactivity/ disuse problems and to reduce fatigue. The management of sexuality dysfunction has to begin with a thorough history taking and a consequent sexuality counselling. The goals of rehabilitation procedures under palliative care are not only to control physical pain but also to help with mental, social and spiritual pain, together with other symptoms. Rehabilitation problems in head and neck cancer, sexuality, lung cancer, prostate cancer, breast cancer and lymphedema can be improved by rehabilitation. The review mainly focuses on impairment and activity limitation. Social, psychological and vocational aspects are left aside in this review.

Electrical stimulation prevents deterioration of the oxidative capacity of disuse-atrophied muscles in rats

INTRODUCTION

The purpose of this study was to evaluate the effects of electrical stimulation on disuse-atrophied muscles.

METHODS

Sprague-Dawley rats were used and divided into three groups: control (C), hind-limb suspended for 7 d (HS), and HS plus transcutaneous electrical stimulation for 7 d (ES). In the ES group, transcutaneous electrical stimulation was induced at 1 Hz for 1 h every day to condition the gastrocnemius-plantaris-soleus muscles. Muscle oxidative capacity was evaluated by 31P-MRS in vivo. Maximum tension and muscle wet mass were also measured.

RESULTS

Muscle oxidative capacity decreased within 1 wk in HS; however, it was maintained when electric stimulation was applied to the suspended limb. The maximum twitch tension in HS was significantly smaller than that in C (p < 0.05), while in ES it did not differ from that in C. The muscle mass was significantly smaller in the HS and ES groups compared to C (p < 0.05).

CONCLUSION

These data indicated that twitch electrical stimulation was effective in preventing deterioration of muscle functions, such as maximum tension and oxidative capacity, induced by 1 wk of disuse.

L-Carnitine: a potential treatment for blocking apoptosis and preventing skeletal muscle myopathy in heart failure

Skeletal muscle in congestive heart failure is responsible for increased fatigability and decreased exercise capacity. A specific myopathy with increased expression of fast-type myosins, myocyte atrophy, secondary to myocyte apoptosis triggered by high levels of circulating tumor necrosis factor-alpha (TNF-alpha) has been described. In an animal model of heart failure, the monocrotaline-treated rat, we have observed an increase of apoptotic skeletal muscle nuclei. Proapoptotic agents, caspase-3 and -9, were increased, as well as serum levels of TNF-alpha and its second messenger sphingosine. Treatment of rats with L-carnitine, known for its protective effect on muscle metabolism injuries, was found to inhibit caspases and to decrease the levels of TNF-alpha and sphingosine, as well as the number of apoptotic myonuclei. Staurosporine was used in in vitro experiments to induce apoptosis in skeletal muscle cells in culture. When L-carnitine was applied to skeletal muscle cells, before staurosporine treatment, we observed a reduction in apoptosis. These findings show that L-carnitine can prevent apoptosis of skeletal muscles cells and has a role in the treatment of congestive heart failure-associated myopathy.