Motoneuron survival is promoted by specific exercise in a mouse model of amyotrophic lateral sclerosis

The analysis of the skeletal muscle metabolism is crucial for designing optimal exercise paradigms in type 2 diabetes mellitus

BACKGROUND

Type 2 diabetes mellitus (T2DM) is a chronic metabolic disease that commonly results from a high-calorie diet and sedentary lifestyle, leading to insulin resistance and glucose homeostasis perturbation. Physical activity is recommended as one first-line treatment in T2DM, but it leads to contrasted results. We hypothesized that, instead of applying standard exercise protocols, the prescription of personalized exercise programs specifically designed to reverse the potential metabolic alterations in skeletal muscle could result in better results.

METHODS

To test this hypothesis, we drew the metabolic signature of the fast-twitch quadriceps muscle, based on a combined unbiased NMR spectroscopy and RT-qPCR study, in several T2DM mouse models of different genetic background (129S1/SvImJ, C57Bl/6J), sex and aetiology (high-fat diet (HFD) or HFD/Streptozotocin (STZ) induction or transgenic MKR (FVB-Tg Ckm-IGF1R*K1003R)1Dlr/J) mice. Three selected mouse models with unique muscular metabolic signatures were submitted to three different swimming-based programs, designed to address each metabolic specificity.

RESULTS

We found that depending on the genetic background, the sex, and the mode of T2DM induction, specific muscular adaptations occurred, including depressed glycolysis associated with elevated PDK4 expression, shift to β-oxidation, or deregulation of amino-acid homeostasis. Interestingly, dedicated swimming-based exercises designed to restore specific metabolic alterations in muscle were found optimal in improving systemic T2DM hallmarks, including a significant reduction in insulin resistance, the improvement of glucose homeostasis, and a delay in sensorimotor function alterations.

CONCLUSION

The muscle metabolism constitutes an important clue for the design of precision exercises with potential clinical implications for T2DM patients.

Targeting mitochondrial Ca2+ uptake for the treatment of amyotrophic lateral sclerosis

Amyotrophic lateral sclerosis (ALS) is a rare adult-onset neurodegenerative disease characterized by progressive motor neuron (MN) loss, muscle denervation and paralysis. Over the past several decades, researchers have made tremendous efforts to understand the pathogenic mechanisms underpinning ALS, with much yet to be resolved. ALS is described as a non-cell autonomous condition with pathology detected in both MNs and non-neuronal cells, such as glial cells and skeletal muscle. Studies in ALS patient and animal models reveal ubiquitous abnormalities in mitochondrial structure and function, and disturbance of intracellular calcium homeostasis in various tissue types, suggesting a pivotal role of aberrant mitochondrial calcium uptake and dysfunctional calcium signalling cascades in ALS pathogenesis. Calcium signalling and mitochondrial dysfunction are intricately related to the manifestation of cell death contributing to MN loss and skeletal muscle dysfunction. In this review, we discuss the potential contribution of intracellular calcium signalling, particularly mitochondrial calcium uptake, in ALS pathogenesis. Functional consequences of excessive mitochondrial calcium uptake and possible therapeutic strategies targeting mitochondrial calcium uptake or the mitochondrial calcium uniporter, the main channel mediating mitochondrial calcium influx, are also discussed.

Spinal cord abnormal autophagy and mitochondria energy metabolism are modified by swim training in SOD1-G93A mice

Amyotrophic lateral sclerosis (ALS) may result from the dysfunctions of various mechanisms such as protein accumulation, mitophagy, and biogenesis of mitochondria. The purpose of the study was to evaluate the molecular mechanisms in ALS development and the impact of swim training on these processes. In the present study, an animal model of ALS, SOD1-G93A mice, was used with the wild-type mice as controls. Mice swam five times per week for 30 min. Mice were analyzed before ALS onset (70 days old), at ALS 1 disease onset (116 days old), and at the terminal stage of the disease ALS (130 days old), and compared with the corresponding ALS untrained groups and normalized to the wild-type group. Enzyme activity and protein content were analyzed in the spinal cord homogenates. The results show autophagy disruptions causing accumulation of p62 accompanied by low PGC-1α and IGF-1 content in the spinal cord of SOD1-G93A mice. Swim training triggered a neuroprotective effect, attenuation of NF-l degradation, less accumulated p62, and lower autophagy initiation. The IGF-1 pathway induces pathophysiological adaptation to maintain energy demands through anaerobic metabolism and mitochondrial protection. KEY MESSAGES: The increased protein content of p62 in the spinal cord of SOD1-G93A mice suggests that autophagic clearance and transportation are disrupted. Swim training attenuates neurofilament light destruction in the spinal cord of SOD1-G93A mice. Swim training reducing OGDH provokes suppression of ATP-consuming anabolic pathways. Swim training induces energy metabolic changes and mitochondria protection through the IGF-1 signaling pathway.

Amyotrophic lateral sclerosis associated disturbance of iron metabolism is blunted by swim training-role of AKT signaling pathway

Swim training has increased the life span of the transgenic animal model of amyotrophic lateral sclerosis (ALS). Conversely, the progress of the disease is associated with the impairment of iron metabolism and insulin signaling. We used transgenic hmSOD1 G93A (ALS model) and non-transgenic mice in the present study. The study was performed on the muscles taken from trained (ONSET and TERMINAL) and untrained animals at three stages of the disease: BEFORE, ONSET, and TERMINAL. In order to study the molecular mechanism of changes in iron metabolism, we used SH-SY5Y and C2C12 cell lines expression vector pcDNA3.1 and transiently transfected with specific siRNAs. The progress of ALS resulted in decreased P-Akt/Akt ratio, which is associated with increased proteins responsible for iron storage ferritin L, ferritin H, PCBP1, and skeletal muscle iron at ONSET. Conversely, proteins responsible for iron export- TAU significantly decrease. The training partially reverses changes in proteins responsible for iron metabolism. AKT silencing in the SH-SY5Y cell line decreased PCBP2 and ferroportin and increased ferritin L, H, PCBP1, TAU, transferrin receptor 1, and APP. Moreover, silencing APP led to an increase in ferritin L and H. Our data suggest that swim training in the mice ALS model is associated with significant changes in iron metabolism related to AKT activity. Down-regulation of AKT mainly upregulates proteins involved in iron import and storage but decreases proteins involved in iron export.

Muscle Involvement in Amyotrophic Lateral Sclerosis: Understanding the Pathogenesis and Advancing Therapeutics

Amyotrophic lateral sclerosis (ALS) is a fatal condition characterized by the selective loss of motor neurons in the motor cortex, brainstem, and spinal cord. Muscle involvement, muscle atrophy, and subsequent paralysis are among the main features of this disease, which is defined as a neuromuscular disorder. ALS is a persistently progressive disease, and as motor neurons continue to degenerate, individuals with ALS experience a gradual decline in their ability to perform daily activities. Ultimately, muscle function loss may result in paralysis, presenting significant challenges in mobility, communication, and self-care. While the majority of ALS research has traditionally focused on pathogenic pathways in the central nervous system, there has been a great interest in muscle research. These studies were carried out on patients and animal models in order to better understand the molecular mechanisms involved and to develop therapies aimed at improving muscle function. This review summarizes the features of ALS and discusses the role of muscle, as well as examines recent studies in the development of treatments.

TrkB signaling is correlated with muscular fatigue resistance and less vulnerability to neurodegeneration

At the neuromuscular junction (NMJ), motor neurons and myocytes maintain a bidirectional communication that guarantees adequate functionality. Thus, motor neurons' firing pattern, which is influenced by retrograde muscle-derived neurotrophic factors, modulates myocyte contractibility. Myocytes can be fast-twitch fibers and become easily fatigued or slow-twitch fibers and resistant to fatigue. Extraocular muscles (EOM) show mixed properties that guarantee fast contraction speed and resistance to fatigue and the degeneration caused by Amyotrophic lateral sclerosis (ALS) disease. The TrkB signaling is an activity-dependent pathway implicated in the NMJ well-functioning. Therefore, it could mediate the differences between fast and slow myocytes' resistance to fatigue. The present study elucidates a specific protein expression profile concerning the TrkB signaling that correlates with higher resistance to fatigue and better neuroprotective capacity through time. The results unveil that Extra-ocular muscles (EOM) express lower levels of NT-4 that extend TrkB signaling, differential PKC expression, and a higher abundance of phosphorylated synaptic proteins that correlate with continuous neurotransmission requirements. Furthermore, common molecular features between EOM and slow soleus muscles including higher neurotrophic consumption and classic and novel PKC isoforms balance correlate with better preservation of these two muscles in ALS. Altogether, higher resistance of Soleus and EOM to fatigue and ALS seems to be associated with specific protein levels concerning the TrkB neurotrophic signaling.

Multi-omics studies reveal ameliorating effects of physical exercise on neurodegenerative diseases

INTRODUCTION

Neurodegenerative diseases such as Alzheimer's disease, Parkinson's disease, amyotrophic lateral sclerosis, and Huntington's disease, are heavy burdens to global health and economic development worldwide. Mounting evidence suggests that exercise, a type of non-invasive intervention, has a positive impact on the life quality of elderly with neurodegenerative diseases. X-omics are powerful tools for mapping global biochemical changes in disease and treatment.

METHOD

Three major databases were searched related to current studies in exercise intervention on neurodegenerative diseases using omics tools, including metabolomics, metagenomics, genomics, transcriptomics, and proteomics.

RESULT

We summarized the omics features and potential mechanisms associated with exercise and neurodegenerative diseases in the current studies. Three main mechanisms by which exercise affects neurodegenerative diseases were summed up, including adult neurogenesis, brain-derived neurotrophic factor (BDNF) signaling, and short-chain fatty acids (SCFAs) metabolism.

CONCLUSION

Overall, there is compelling evidence that exercise intervention is a feasible way of preventing the onset and alleviating the severity of neurodegenerative diseases. These studies highlight the importance of exercise as a complementary approach to the treatment and intervention of neurodegenerative diseases in addition to traditional treatments. More mechanisms on exercise interventions for neurodegenerative diseases, the specification of exercise prescriptions, and differentiated exercise programs should be explored so that they can actually be applied to the clinic.

Swim Training Affects on Muscle Lactate Metabolism, Nicotinamide Adenine Dinucleotides Concentration, and the Activity of NADH Shuttle Enzymes in a Mouse Model of Amyotrophic Lateral Sclerosis

In this study, we aim to verify whether swim training can improve lactate metabolism, NAD+ and NADH levels, as well as modify the activity of glycolytic and NADH shuttle enzymes and monocarboxylate transporters (MCTs) in skeletal muscle of amyotrophic lateral sclerosis (ALS) mice. ALS mice (SOD1G93A) (n = 7 per group) were analyzed before the onset of ALS, at first disease symptoms (trained and untrained), and the last stage of disease (trained and untrained), and then compared with a wild-type (WT) group of mice. The blood lactate and the skeletal muscle concentration of lactate, NAD+ and NADH, MCT1 and MCT4 protein levels, as well as lactate dehydrogenase (LDH) and malate dehydrogenase (MDH) activities in skeletal muscle were determined by fluorometric, Western blotting, liquid chromatography-MS3 spectrometry, and spectrometric methods. In the untrained terminal ALS group, there were decreased blood lactate levels (p < 0.001) and increased skeletal muscle lactate levels (p < 0.05) as compared with a WT group of mice. The amount of nicotinamide adenine dinucleotides in the ALS groups were also significantly reduced as well as LDH activity and the level of MCT1. Swim training increased lactate levels in the blood (p < 0.05 vs. ALS TERMINAL untrained). In addition, cytosolic MDH activity and the cMDH/LDH 2.1 ratio were significantly higher in trained vs. untrained mice (p < 0.05). The data indicate significant dysfunction of lactate metabolism in ALS mice, associated with a reduction in muscle anaerobic metabolism and NADH transporting enzymes, as well as swim-induced compensation of energy demands in the ALS mice.

BDNF-dependent modulation of axonal transport is selectively impaired in ALS

Axonal transport ensures long-range delivery of essential cargoes between proximal and distal compartments, and is needed for neuronal development, function, and survival. Deficits in axonal transport have been detected at pre-symptomatic stages in the SOD1^G93A and TDP-43^M337V mouse models of amyotrophic lateral sclerosis (ALS), suggesting that impairments in this critical process are fundamental for disease pathogenesis. Strikingly, in ALS, fast motor neurons (FMNs) degenerate first whereas slow motor neurons (SMNs) are more resistant, and this is a currently unexplained phenomenon. The main aim of this investigation was to determine the effects of brain-derived neurotrophic factor (BDNF) on in vivo axonal transport in different α-motor neuron (MN) subtypes in wild-type (WT) and SOD1^G93A mice. We report that despite displaying similar basal transport speeds, stimulation of wild-type MNs with BDNF enhances in vivo trafficking of signalling endosomes specifically in FMNs. This BDNF-mediated enhancement of transport was also observed in primary ventral horn neuronal cultures. However, FMNs display selective impairment of axonal transport in vivo in symptomatic SOD1^G93A mice, and are refractory to BDNF stimulation, a phenotype that was also observed in primary embryonic SOD1^G93A neurons. Furthermore, symptomatic SOD1^G93A mice display upregulation of the classical non-pro-survival truncated TrkB and p75^NTR receptors in muscles, sciatic nerves, and Schwann cells. Altogether, these data indicate that cell- and non-cell autonomous BDNF signalling is impaired in SOD1^G93A MNs, thus identifying a new key deficit in ALS.

Use and subjective experience of the impact of motor-assisted movement exercisers in people with amyotrophic lateral sclerosis: a multicenter observational study

Motor-assisted movement exercisers (MME) are devices that assist with physical therapy in domestic settings for people living with ALS. This observational cross-sectional study assesses the subjective experience of the therapy and analyzes users' likelihood of recommending treatment with MME. The study was implemented in ten ALS centers between February 2019 and October 2020, and was coordinated by the research platform Ambulanzpartner. Participants assessed symptom severity, documented frequency of MME use and rated the subjective benefits of therapy on a numerical scale (NRS, 0 to 10 points, with 10 being the highest). The Net Promotor Score (NPS) determined the likelihood of a participant recommending MME. Data for 144 participants were analyzed. Weekly MME use ranged from 1 to 4 times for 41% of participants, 5 to 7 times for 42%, and over 7 times for 17%. Particularly positive results were recorded in the following domains: amplification of a sense of achievement (67%), diminution of the feeling of having rigid limbs (63%), diminution of the feeling of being immobile (61%), improvement of general wellbeing (55%) and reduction of muscle stiffness (52%). Participants with more pronounced self-reported muscle weakness were more likely to note a beneficial effect on the preservation and improvement of muscle strength during MME treatment (p < 0.05). Overall, the NPS for MME was high (+ 61). High-frequency MME-assisted treatment (defined as a minimum of five sessions a week) was administered in the majority of participants (59%) in addition to physical therapy. Most patients reported having achieved their individual therapeutic objectives, as evidenced by a high level of satisfaction with MME therapy. The results bolster the justification for extended MME treatment as part of a holistic approach to ALS care.

Effects of Skin Stimulation on Sensory-Motor Networks Excitability: Possible Implications for Physical Training in Amyotrophic Lateral Sclerosis

Background

Many different trials were assessed for rehabilitation of patients with amyotrophic lateral sclerosis (ALS), with non-unique results. Beside the effects on muscle trophism, some of the encouraging results of physical training could be ascribed to the modulation of cortical excitability, which was found hyperexcited in ALS.

Objective

The effects of tactile skin stimulation in the modulation of the sensory-motor integrative networks in healthy subjects were assayed through the paired associative stimulation (PAS) protocol.

Methods

In total, 15 healthy subjects were enrolled. In the standard PAS session, the average amplitude of the motor evoked potential (MEP) after 10 stimuli of transcranial magnetic stimulation (TMS) was measured at the baseline and after the PAS protocol (0, 10, 20, 30, and 60 min). In the skin stimulation session, the average amplitude of the MEP was measured before and after 10 min of skin stimulation over the hand. Subsequently, each subject underwent the PAS stimulation and the measure of the average amplitude of the MEP (0, 10, 20, 30, and 60 min).

Results

The tactile skin stimulation on healthy subjects increases the PAS-induced sensory-motor network hyperexcitability in healthy subjects.

Conclusion

Skin stimulation should be avoided in the physiotherapeutic approaches for patients with ALS, given the possible hyperexciting effects on the already upmodulated sensory-motor networks. They can be taken into account for diseases characterized by downregulation of cortical and transcortical networks.

Alteration of the Neuromuscular Junction and Modifications of Muscle Metabolism in Response to Neuron-Restricted Expression of the CHMP2Bintron5 Mutant in a Mouse Model of ALS-FTD Syndrome

CHMP2B is a protein that coordinates membrane scission events as a core component of the ESCRT machinery. Mutations in CHMP2B are an uncommon cause of amyotrophic lateral sclerosis (ALS) and frontotemporal dementia (FTD), two neurodegenerative diseases with clinical, genetic, and pathological overlap. Different mutations have now been identified across the ALS-FTD spectrum. Disruption of the neuromuscular junction is an early pathogenic event in ALS. Currently, the links between neuromuscular junction functionality and ALS-associated genes, such as CHMP2B, remain poorly understood. We have previously shown that CHMP2B transgenic mice expressing the CHMP2B^intron5 mutant specifically in neurons develop a progressive motor phenotype reminiscent of ALS. In this study, we used complementary approaches (behavior, histology, electroneuromyography, and biochemistry) to determine the extent to which neuron-specific expression of CHMP2B^intron5 could impact the skeletal muscle characteristics. We show that neuronal expression of the CHMP2B^intron5 mutant is sufficient to trigger progressive gait impairment associated with structural and functional changes in the neuromuscular junction. Indeed, CHMP2B^intron5 alters the pre-synaptic terminal organization and the synaptic transmission that ultimately lead to a switch of fast-twitch glycolytic muscle fibers to more oxidative slow-twitch muscle fibers. Taken together these data indicate that neuronal expression of CHMP2B^intron5 is sufficient to induce a synaptopathy with molecular and functional changes in the motor unit reminiscent of those found in ALS patients.

Motor Learning and Physical Exercise in Adaptive Myelination and Remyelination

The idea that myelination is driven by both intrinsic and extrinsic cues has gained much traction in recent years. Studies have demonstrated that myelination occurs in an intrinsic manner during early development and continues through adulthood in an activity-dependent manner called adaptive myelination. Motor learning, the gradual acquisition of a specific novel motor skill, promotes adaptive myelination in both the healthy and demyelinated central nervous system (CNS). On the other hand, exercise, a physical activity that involves planned, structured and repetitive bodily movements that expend energy and benefits one's fitness, promotes remyelination in pathology, but it is less clear whether it promotes adaptive myelination in healthy subjects. Studies on these topics have also investigated whether the timing of motor learning or physical exercise is important for successful addition of myelin. Here we review our current understanding of the relationship of motor skill learning and physical exercise on myelination.

Swim Training Ameliorates Hyperlocomotion of ALS Mice and Increases Glutathione Peroxidase Activity in the Spinal Cord

(1) Background: Amyotrophic lateral sclerosis (ALS) is an incurable, neurodegenerative disease. In some cases, ALS causes behavioral disturbances and cognitive dysfunction. Swimming has revealed a neuroprotective influence on the motor neurons in ALS. (2) Methods: In the present study, a SOD1-G93A mice model of ALS were used, with wild-type B6SJL mice as controls. ALS mice were analyzed before ALS onset (10th week of life), at ALS 1 onset (first symptoms of the disease, ALS 1 onset, and ALS 1 onset SWIM), and at terminal ALS (last stage of the disease, ALS TER, and ALS TER SWIM), and compared with wild-type mice. Swim training was applied 5 times per week for 30 min. All mice underwent behavioral tests. The spinal cord was analyzed for the enzyme activities and oxidative stress markers. (3) Results: Pre-symptomatic ALS mice showed increased locomotor activity versus control mice; the swim training reduced these symptoms. The metabolic changes in the spinal cord were present at the pre-symptomatic stage of the disease with a shift towards glycolytic processes at the terminal stage of ALS. Swim training caused an adaptation, resulting in higher glutathione peroxidase (GPx) and protection against oxidative stress. (4) Conclusion: Therapeutic aquatic activity might slow down the progression of ALS.

Swim training affects Akt signaling and ameliorates loss of skeletal muscle mass in a mouse model of amyotrophic lateral sclerosis

We tested the hypothesis that swim training reverses the impairment of Akt/FOXO3a signaling, ameliorating muscle atrophy in ALS mice. Transgenic male mice B6SJL-Tg (SOD1^G93A) 1Gur/J were used as the ALS model (n = 35), with wild-type B6SJL (WT) mice as controls (n = 7). ALS mice were analyzed before ALS onset, at ALS onset, and at terminal ALS. Levels of insulin/Akt signaling pathway proteins were determined, and the body and tibialis anterior muscle mass and plasma creatine kinase. Significantly increased levels of FOXO3a in ALS groups (from about 13 to 21-fold) compared to WT mice were observed. MuRF1 levels in the ONSET untrained group (12.0 ± 1.7 AU) were significantly higher than in WT mice (1.12 ± 0.2 AU) and in the BEFORE ALS group (3.7 ± 0.9 AU). This was associated with body mass and skeletal muscle mass reduction. Swim training significantly ameliorated the reduction of skeletal muscle mass in both TERMINAL groups (p < 0.001) and partially reversed changes in the levels of Akt signaling pathway proteins. These findings shed light on the swimming-induced attenuation of skeletal muscle atrophy in ALS with possible practical implications for anti-cachexia approaches.

Mobility Improvements After a High-cadence Dynamic Cycling Intervention in an Individual with Motor Neuron Disease: A Case Study

Previous exercise studies in individuals with motor neuron disease have shown some positive benefits but the stress of regular exercise could result in overuse weakness in this population. The purpose of this case study is to determine the efficacy, and tolerability of a high-cadence dynamic cycling intervention in an individual with motor neuron disease. A 67-year-old male with significant lower extremity weakness and a diagnosis of idiopathic motor neuron disease completed six 30-minute sessions of high cadence dynamic cycling over a two-week period using a custom-built motorized ergometer with the motor speed set at 80 revolutions per minute. This intervention resulted in an 80.4 m increase in walking distance during the six-minute walk test (21% increase), with a lower rating of perceived exertion than at baseline. Amyotrophic Lateral Sclerosis Functional Rating Scale-Revised scores improved slightly (2.4%) suggesting that the intervention was tolerated, and it did not compromise the participant's physical function. These data show that this intervention can improve mobility, is well-tolerated and minimizes the risk of overuse weakness in an individual with motor neuron disease.

Skeletal Muscle Metabolism: Origin or Prognostic Factor for Amyotrophic Lateral Sclerosis (ALS) Development?

Amyotrophic lateral sclerosis (ALS) is a fatal neurodegenerative disease characterized by progressive and selective loss of motor neurons, amyotrophy and skeletal muscle paralysis usually leading to death due to respiratory failure. While generally considered an intrinsic motor neuron disease, data obtained in recent years, including our own, suggest that motor neuron protection is not sufficient to counter the disease. The dismantling of the neuromuscular junction is closely linked to chronic energy deficit found throughout the body. Metabolic (hypermetabolism and dyslipidemia) and mitochondrial alterations described in patients and murine models of ALS are associated with the development and progression of disease pathology and they appear long before motor neurons die. It is clear that these metabolic changes participate in the pathology of the disease. In this review, we summarize these changes seen throughout the course of the disease, and the subsequent impact of glucose–fatty acid oxidation imbalance on disease progression. We also highlight studies that show that correcting this loss of metabolic flexibility should now be considered a major goal for the treatment of ALS.

Skeletal Muscle in ALS: An Unappreciated Therapeutic Opportunity?

Amyotrophic lateral sclerosis (ALS) is a neurodegenerative disorder characterized by the selective degeneration of upper and lower motor neurons and by the progressive weakness and paralysis of voluntary muscles. Despite intense research efforts and numerous clinical trials, it is still an incurable disease. ALS had long been considered a pure motor neuron disease; however, recent studies have shown that motor neuron protection is not sufficient to prevent the course of the disease since the dismantlement of neuromuscular junctions occurs before motor neuron degeneration. Skeletal muscle alterations have been described in the early stages of the disease, and they seem to be mainly involved in the “dying back” phenomenon of motor neurons and metabolic dysfunctions. In recent years, skeletal muscles have been considered crucial not only for the etiology of ALS but also for its treatment. Here, we review clinical and preclinical studies that targeted skeletal muscles and discuss the different approaches, including pharmacological interventions, supplements or diets, genetic modifications, and training programs.

Delayed Onset Muscle Soreness (DOMS): The Repeated Bout Effect and Chemotherapy-Induced Axonopathy May Help Explain the Dying-Back Mechanism in Amyotrophic Lateral Sclerosis and Other Neurodegenerative Diseases

Delayed onset muscle soreness (DOMS) is hypothesized to be caused by glutamate excitotoxicity-induced acute compression axonopathy of the sensory afferents in the muscle spindle. Degeneration of the same sensory afferents is implicated in the disease onset and progression of amyotrophic lateral sclerosis (ALS). A series of “silent” acute compression proprioceptive axonopathies with underlying genetic/environmental factors, damaging eccentric contractions and the non-resolving neuroinflammatory process of aging could lead to ALS disease progression. Since the sensory terminals in the muscle spindle could not regenerate from the micro-damage in ALS, unlike in DOMS, the induced protective microcircuits and their long-term functional plasticity (the equivalent of the repeated bout effect in DOMS) will be dysfunctional. The acute stress invoking osteocalcin, bradykinin, COX1, COX2, GDNF, PGE2, NGF, glutamate and N-methyl-D-aspartate (NMDA) receptors are suggested to be the critical signalers of this theory. The repeated bout effect of DOMS and the dysfunctional microcircuits in ALS are suggested to involve several dimensions of memory and learning, like pain memory, inflammation, working and episodic memory. The spatial encoding of these memory dimensions is compromised in ALS due to blunt position sense from the degenerating proprioceptive axon terminals of the affected muscle spindles. Dysfunctional microcircuits progressively and irreversibly interfere with postural control, with motor command and locomotor circuits, deplete the neuroenergetic system, and ultimately interfere with life-sustaining central pattern generators in ALS. The activated NMDA receptor is suggested to serve the “gate control” function in DOMS and ALS in line with the gate control theory of pain. Circumvention of muscle spindle-loading could be a choice of exercise therapy in muscle spindle-affected neurodegenerative diseases.

What skeletal muscle has to say in amyotrophic lateral sclerosis: Implications for therapy

Amyotrophic lateral sclerosis (ALS) is an adult onset disorder characterized by progressive neuromuscular junction (NMJ) dismantling and degeneration of motor neurons leading to atrophy and paralysis of voluntary muscles responsible for motion and breathing. Except for a minority of patients harbouring genetic mutations, the origin of most ALS cases remains elusive. Peripheral tissues, and particularly skeletal muscle, have lately demonstrated an active contribution to disease pathology attracting a growing interest for these tissues as therapeutic targets in ALS. In this sense, molecular mechanisms essential for cell and tissue homeostasis have been shown to be deregulated in the disease. These include muscle metabolism and mitochondrial activity, RNA processing, tissue-resident stem cell function responsible for muscle regeneration, and proteostasis that regulates muscle mass in adulthood. This review aims to compile scientific evidence that demonstrates the role of skeletal muscle in ALS pathology and serves as reference for development of novel therapeutic strategies targeting this tissue to delay disease onset and progression. LINKED ARTICLES: This article is part of a themed issue on Neurochemistry in Japan. To view the other articles in this section visit http://onlinelibrary.wiley.com/doi/10.1111/bph.v178.6/issuetoc.

Androgen Therapy in Neurodegenerative Diseases

Neurodegenerative diseases, including Alzheimer disease (AD), Parkinson disease (PD), multiple sclerosis (MS), amyotrophic lateral sclerosis (ALS), and Huntington disease, are characterized by the loss of neurons as well as neuronal function in multiple regions of the central and peripheral nervous systems. Several studies in animal models have shown that androgens have neuroprotective effects in the brain and stimulate axonal regeneration. The presence of neuronal androgen receptors in the peripheral and central nervous system suggests that androgen therapy might be useful in the treatment of neurodegenerative diseases. To illustrate, androgen therapy reduced inflammation, amyloid-β deposition, and cognitive impairment in patients with AD. As well, improvements in remyelination in MS have been reported; by comparison, only variable results are observed in androgen treatment of PD. In ALS, androgen administration stimulated motoneuron recovery from progressive damage and regenerated both axons and dendrites. Only a few clinical studies are available in human individuals despite the safety and low cost of androgen therapy. Clinical evaluations of the effects of androgen therapy on these devastating diseases using large populations of patients are strongly needed.

Running and swimming prevent the deregulation of the BDNF/TrkB neurotrophic signalling at the neuromuscular junction in mice with amyotrophic lateral sclerosis

Nerve-induced muscle contraction regulates the BDNF/TrkB neurotrophic signalling to retrogradely modulate neurotransmission and protect the neuromuscular junctions and motoneurons. In muscles with amyotrophic lateral sclerosis, this pathway is strongly misbalanced and neuromuscular junctions are destabilized, which may directly cause the motoneuron degeneration and muscular atrophy observed in this disease. Here, we sought to demonstrate (1) that physical exercise, whose recommendation has been controversial in amyotrophic lateral sclerosis, would be a good option for its therapy, because it normalizes and improves the altered neurotrophin pathway and (2) a plausible molecular mechanism underlying its positive effect. SOD1-G93A mice were trained following either running or swimming-based protocols since the beginning of the symptomatic phase (day 70 of age) until day 115. Next, the full BDNF pathway, including receptors, downstream kinases and proteins related with neurotransmission, was characterized and motoneuron survival was analysed. The results establish that amyotrophic lateral sclerosis-induced damaging molecular changes in the BDNF/TrkB pathway are reduced, prevented or even overcompensated by precisely defined exercise protocols that modulate TrkB isoforms and neurotransmission regulatory proteins and reduce motoneuron death. Altogether, the maintenance of the BDNF/TrkB signalling and the downstream pathway, particularly after the swimming protocol, adds new molecular evidence of the benefits of physical exercise to reduce the impact of amyotrophic lateral sclerosis. These results are encouraging since they reveal an improvement even starting the therapy after the onset of the disease.

Swimming Exercise Ameliorates Symptoms of MOG-Induced Experimental Autoimmune Encephalomyelitis by Inhibiting Inflammation and Demyelination in Rats

Purpose

Multiple sclerosis is an autoimmune disease that affects the central nerve system, resulting in cumulative loss of motor function. Multiple sclerosis is induced through multiple mechanisms and is caused by inflammation and demyelination. This study aims to evaluate the neuroprotective effect of swimming exercise in experimental autoimmune encephalomyelitis (EAE) rats, an animal model of multiple sclerosis.

Methods

EAE was induced by an intradermal injection of 50-μg purified myelin oligodendrocyte glycoprotein 33–55 (MOG_33-55) dissolved in 200-μL saline at the base of the tail. The rats in the swimming exercise group were made to swim for 30 minutes once pert a day for 26 consecutive days, starting 5 days after induction of EAE. To compare the effect of swimming exercise with interferon-β, a drug for multiple sclerosis, interferon-β was injected intraperitoneally into rats of the EAE-induced and interferon-β-treated group during the exercise period.

Results

Injection of MOG_33-55 caused weight loss, decreased clinical disability score, and increased level of pro-inflammatory cytokines and inflammatory mediators in the lumbar spinal cord. Loss of motor function and weakness increased demyelination score. Swimming exercise suppressed demyelination and expression of pro-inflammatory cytokines and inflammatory mediators. These changes promoted recovery of EAE symptoms such as body weight loss, motor dysfunction, and weakness. Swimming exercise caused the same level of improvement as interferon-β treatment.

Conclusions

The results of this experiment suggest the possibility of swimming exercise in urological diseases that are difficult to treat. Swimming exercises can be considered for relief of symptom in incurable multiple sclerosis.

Potential Preventive Strategies for Amyotrophic Lateral Sclerosis

It may seem useless to propose preventive measures for a disease without established pathogenesis and successful therapy, such as amyotrophic lateral sclerosis (ALS). However, we will show that ALS shares essential molecular mechanisms with aging and that established anti-aging strategies, such as healthy diet or individually adjusted exercise, may be successfully applied to ameliorate the condition of ALS patients. These strategies might be applied for prevention if persons at ALS risk could be identified early enough. Recent research advances indicate that this may happen soon.

Effects of Physical Activity on Amyotrophic Lateral Sclerosis

Amyotrophic lateral sclerosis (ALS) is a heterogeneous neurodegenerative disease characterized by the loss of upper and lower motor neurons. To date, no resolutive cure is available, and only two Food and Drug Administration-approved drugs are used to treat ALS without a resolutive outcome. In recent years, the study of the beneficial effects of physical activity on health has acquired special relevance. However, the relationship between ALS progression and physical exercise is still a hotly debated topic in medicine. Some studies have suggested higher risks to develop the disease that are associated with practicing intense physical activity, as seen in professional soccer or football players, for example. On the contrary, moderate training has been shown to exert several benefits in ALS-affected patients. Overall, more studies are needed to clarify whether physical activity is helpful or harmful for developing ALS.

The influence of metallothionein treatment and treadmill running exercise on disease onset and survival in SOD1G93A amyotrophic lateral sclerosis mice

Amyotrophic lateral sclerosis (ALS) is a fatal neurodegenerative disease, characterised by the degeneration of motor neurons innervating skeletal muscle. The mechanisms underlying neurodegeneration in ALS are not yet fully elucidated, and with current therapeutics only able to extend lifespan by a matter of months there is a clear need for novel therapies to increase lifespan and patient quality of life. Here, we evaluated whether moderate-intensity treadmill exercise and/or treatment with metallothionein-2 (MT2), a neuroprotective protein, could improve survival, behavioural or neuropathological outcomes in SOD1^G93A familial ALS mice. Six-week-old female SOD1^G93A mice were allocated to one of four treatment groups: MT2 injection, i.m.; moderate treadmill exercise; neither MT2 nor exercise; or both MT2 and exercise. MT2-treated mice survived around 3% longer than vehicle-treated mice, with this mild effect reaching statistical significance in Cox proportional hazards analysis once adjusted for potential confounders. Mixed model body weight trajectories over time indicated that MT2-treated mice, with or without exercise, reached maximum body weight at a later age, suggesting a delay in disease onset of around 4% compared to saline-treated mice. Exercise alone did not significantly increase survival or delay disease onset, and neither exercise nor MT2 substantially ameliorated gait abnormalities or muscle strength loss. We conclude that neither exercise nor MT2 treatment was detrimental in female SOD1^G93A mice, and further study could determine whether the mild effect of peripheral MT2 administration on disease onset and survival could be improved via direct administration of MT2 to the central nervous system.

The Impact of Kinases in Amyotrophic Lateral Sclerosis at the Neuromuscular Synapse: Insights into BDNF/TrkB and PKC Signaling

Brain-derived neurotrophic factor (BDNF) promotes neuron survival in adulthood in the central nervous system. In the peripheral nervous system, BDNF is a contraction-inducible protein that, through its binding to tropomyosin-related kinase B receptor (TrkB), contributes to the retrograde neuroprotective control done by muscles, which is necessary for motor neuron function. BDNF/TrkB triggers downstream presynaptic pathways, involving protein kinase C, essential for synaptic function and maintenance. Undeniably, this reciprocally regulated system exemplifies the tight communication between nerve terminals and myocytes to promote synaptic function and reveals a new view about the complementary and essential role of pre and postsynaptic interplay in keeping the synapse healthy and strong. This signaling at the neuromuscular junction (NMJ) could establish new intervention targets across neuromuscular diseases characterized by deficits in presynaptic activity and muscle contractility and by the interruption of the connection between nervous and muscular tissues, such as amyotrophic lateral sclerosis (ALS). Indeed, exercise and other therapies that modulate kinases are effective at delaying ALS progression, preserving NMJs and maintaining motor function to increase the life quality of patients. Altogether, we review synaptic activity modulation of the BDNF/TrkB/PKC signaling to sustain NMJ function, its and other kinases’ disturbances in ALS and physical and molecular mechanisms to delay disease progression.

Low-Intensity Running and High-Intensity Swimming Exercises Differentially Improve Energy Metabolism in Mice With Mild Spinal Muscular Atrophy

Spinal Muscular Atrophy (SMA), an autosomal recessive neurodegenerative disease characterized by the loss of spinal-cord motor-neurons, is caused by mutations on Survival-of-Motor Neuron (SMN)-1 gene. The expression of SMN2, a SMN1 gene copy, partially compensates for SMN1 disruption due to exon-7 excision in 90% of transcripts subsequently explaining the strong clinical heterogeneity. Several alterations in energy metabolism, like glucose intolerance and hyperlipidemia, have been reported in SMA at both systemic and cellular level, prompting questions about the potential role of energy homeostasis and/or production involvement in disease progression. In this context, we have recently reported the tolerance of mild SMA-like mice (Smn^Δ7/Δ7; huSMN2^+/+) to 10 months of low-intensity running or high-intensity swimming exercise programs, respectively involving aerobic and a mix aerobic/anaerobic muscular metabolic pathways. Here, we investigated whether those exercise-induced benefits were associated with an improvement in metabolic status in mild SMA-like mice. We showed that untrained SMA-like mice exhibited a dysregulation of lipid metabolism with an enhancement of lipogenesis and adipocyte deposits when compared to control mice. Moreover, they displayed a high oxygen consumption and energy expenditure through β-oxidation increase yet for the same levels of spontaneous activity. Interestingly, both exercises significantly improved lipid metabolism and glucose homeostasis in SMA-like mice, and enhanced oxygen consumption efficiency with the maintenance of a high oxygen consumption for higher levels of spontaneous activity. Surprisingly, more significant effects were obtained with the high-intensity swimming protocol with the maintenance of high lipid oxidation. Finally, when combining electron microscopy, respiratory chain complexes expression and enzymatic activity measurements in muscle mitochondria, we found that (1) a muscle-specific decreased in enzymatic activity of respiratory chain I, II, and IV complexes for equal amount of mitochondria and complexes expression and (2) a significant decline in mitochondrial maximal oxygen consumption, were reduced by both exercise programs. Most of the beneficial effects were obtained with the high-intensity swimming protocol. Taking together, our data support the hypothesis that active physical exercise, including high-intensity protocols, induces metabolic adaptations at both systemic and cellular levels, providing further evidence for its use in association with SMN-overexpressing therapies, in the long-term care of SMA patients.

The Role of Exercise as a Non-pharmacological Therapeutic Approach for Amyotrophic Lateral Sclerosis: Beneficial or Detrimental?

Amyotrophic lateral sclerosis (ALS), a fatal neurodegenerative disease, involves the rapid deterioration of motor neurons resulting in severe muscle atrophy and respiratory insufficiency. It is considered a "multisystemic" disease with many potential mechanisms responsible for its pathology. Currently, there is no cure for ALS. Exercise training is suggested as a potential approach to reduce ALS pathology, but its beneficial role remains controversial. This review provides an overview of the effects of exercise training in ALS-affected mice and patients. It will compare the intensity, duration, and type of exercise on the health of SOD1^G93A mice, a mouse model of familial ALS, and review clinical studies involving ALS patients undergoing both endurance and resistance training. In summary, mild-to-moderate swimming-based endurance training appears the most advantageous mode of exercise in SOD1^G93A mice, improving animal survival, and delaying the onset and progression of disease. Furthermore, clinical studies show that both endurance and resistance training have an advantageous impact on the quality of life of ALS patients without extending life expectancy. However, small sample sizes, non-representative control populations, heterogeneous disease stage of patients, and the presence of confounders often exist in the exercise studies conducted with ALS patients. This raises concerns about the interpretation of these findings and, therefore, these results should be considered with caution. While promising, more pre-clinical and clinical studies with improved experimental design and fewer limitations are still necessary to confirm the impact of exercise training on the health of ALS patients.

Overview of Impaired BDNF Signaling, Their Coupled Downstream Serine-Threonine Kinases and SNARE/SM Complex in the Neuromuscular Junction of the Amyotrophic Lateral Sclerosis Model SOD1-G93A Mice

Amyotrophic lateral sclerosis (ALS) is a chronic neurodegenerative disease characterized by progressive motor weakness. It is accepted that it is caused by motoneuron degeneration leading to a decrease in muscle stimulation. However, ALS is being redefined as a distal axonopathy, in that neuromuscular junction dysfunction precedes and may even influence motoneuron loss. In this synapse, several metabotropic receptor-mediated signaling pathways converge on effector kinases that phosphorylate targets that are crucial for synaptic stability and neurotransmission quality. We have previously shown that, in physiological conditions, nerve-induced muscle contraction regulates the brain-derived neurotrophic factor/tropomyosin-related kinase B (BDNF/TrkB) signaling to retrogradely modulate presynaptic protein kinases PKC and PKA, which are directly involved in the modulation of acetylcholine release. In ALS patients, the alteration of this signaling may significantly contribute to a motor impairment. Here, we investigate whether BDNF/TrkB signaling, the downstream PKC (cPKCβI, cPKCα, and nPKCε isoforms), and PKA (regulatory and catalytic subunits) and some SNARE/SM exocytotic machinery proteins (Munc18-1 and SNAP-25) are altered in the skeletal muscle of pre- and symptomatic SOD1-G93A mice. We found that this pathway is strongly affected in symptomatic ALS mice muscles including an unbalance between (I) BDNF and TrkB isoforms, (II) PKC isoforms and PKA subunits, and (III) Munc18-1 and SNAP-25 phosphorylation ratios. Changes in TrkB.T1 and cPKCβI are precociously observed in presymptomatic mice. Altogether, several of these molecular alterations can be partly associated with the known fast-to-slow motor unit transition during the disease process but others can be related with the initial disease pathogenesis.

Iron Metabolism of the Skeletal Muscle and Neurodegeneration

Recent studies clearly indicate that the endocrine function of the skeletal muscle is essential for a long and healthy life. Regular exercise, which has been shown to stimulate the release of myokines, lowers the risk of many diseases, including Alzheimer’s and Parkinson’s disease, emphasizing the role of skeletal muscle in proper functioning of other tissues. In addition, exercise increases insulin sensitivity, which may also impact iron metabolism. Even though the role of iron in neurodegeneration is well established, the exact mechanisms of iron toxicity are not known. Interestingly, exercise has been shown to modulate iron metabolism, mainly by reducing body iron stores. Insulin signaling and iron metabolism are interconnected, as high tissue iron stores are associated with insulin resistance, and conversely, impaired insulin signaling may lead to iron accumulation in an affected tissue. Excess iron accumulation in tissue triggers iron-dependent oxidative stress. Further, iron overload in the skeletal muscle not only negatively affects muscle contractility but also might impact its endocrine function, thus possibly affecting the clinical outcome of diseases, including neurodegenerative diseases. In this review, we discuss possible mechanisms of iron dependent oxidative stress in skeletal muscle, its impact on muscle mass and endocrine function, as well as on neurodegeneration processes.

Recumbent stepping aerobic exercise in amyotrophic lateral sclerosis: a pilot study

OBJECTIVES

Aerobic exercise can promote neuroplastic responses in the healthy and injured brain. Although the role of exercise in amyotrophic lateral sclerosis (ALS) is debated, new evidence suggests that exercise may reduce disease progression. While common exercise modalities such as the treadmill and cycle ergometer have been explored in ALS, the safety and feasibility of a total body recumbent stepper have not been investigated. Additionally, the functional and neurophysiological effects of recumbent stepping in ALS are still unknown. Here, we investigated the safety and feasibility of a 4-week recumbent stepping program to slow disease progression in ALS and possibly facilitate neuroplasticity.

METHOD

Nine individuals with ALS performed moderate intensity recumbent stepping for four weeks. Outcomes included participation satisfaction questionnaire, ALS Functional Rating Scale Revised (ALSFRS-R), clinical tests of walking and endurance, fatigue severity scale, Beck depression inventory, SF-12, and transcranial magnetic stimulation-induced motor evoked potentials (MEPs). All measurements were collected at baseline, post-intervention, and at the 1-month follow-up.

RESULTS

Eight participants completed the study without any adverse events. The ALSFRS-R scores were similar at the end of the study and at follow-up. No significant differences were noted for any of the clinical outcomes. MEPs were present only in two participants and changes in corticomotor excitability after exercise were minimal.

CONCLUSIONS

Results from this preliminary study support the safety and feasibility of 12 sessions of total body recumbent stepping in individuals with ALS.

Swim Training Modulates Mouse Skeletal Muscle Energy Metabolism and Ameliorates Reduction in Grip Strength in a Mouse Model of Amyotrophic Lateral Sclerosis

Metabolic reprogramming in skeletal muscles in the human and animal models of amyotrophic lateral sclerosis (ALS) may be an important factor in the diseases progression. We hypothesized that swim training, a modulator of cellular metabolism via changes in muscle bioenergetics and oxidative stress, ameliorates the reduction in muscle strength in ALS mice. In this study, we used transgenic male mice with the G93A human SOD1 mutation B6SJL-Tg (SOD1^G93A) 1Gur/J and wild type B6SJL (WT) mice. Mice were subjected to a grip strength test and isolated skeletal muscle mitochondria were used to perform high-resolution respirometry. Moreover, the activities of enzymes involved in the oxidative energy metabolism and total sulfhydryl groups (as an oxidative stress marker) were evaluated in skeletal muscle. ALS reduces muscle strength (-70% between 11 and 15 weeks, p < 0.05), modulates muscle metabolism through lowering citrate synthase (CS) (-30% vs. WT, p = 0.0007) and increasing cytochrome c oxidase and malate dehydrogenase activities, and elevates oxidative stress markers in skeletal muscle. Swim training slows the reduction in muscle strength (-5% between 11 and 15 weeks) and increases CS activity (+26% vs. ALS I, p = 0.0048). Our findings indicate that swim training is a modulator of skeletal muscle energy metabolism with concomitant improvement of skeletal muscle function in ALS mice.

Effects of moderate- versus high- intensity swimming training on inflammatory and CD4+ T cell subset profiles in experimental autoimmune encephalomyelitis mice

Multiple sclerosis (MS) is an inflammatory neurodegenerative disease of the central nervous system (CNS). Evidence about experimental autoimmune encephalomyelitis (EAE), a mouse model of MS, has been shown to modulate disease parameters within exercise intervention. However, these initial studies weren't carried out intensity of exercise in mice. This study explored the impacts of different-intensity swimming training on EAE mice. Female mice were given access to swimming with predetermined weight (moderated-intensity (ME) group is 0% body weight; high-intensity (HE) group is 4% body weight) for 6 weeks, were immunized to induce EAE and then continued swimming until sacrificed. Compared to non-exercise mice, ME training didn't affect EAE clinical symptoms and neuropathology. However, HE swimming attenuated EAE clinical scores, reduced infiltrating cells and demyelination of spinal cords. Analysis of CD4⁺ T cell subsets from CNS of EAE showed the reduction of Th1 and Th17 populations and an increase of Treg in HE, not ME mice. Accordingly, HE training lead to a decrease of IFN-γ and IL-17 and an increase of IL-10 and TGF-β. Of note, HE, not ME, swimming induced an increase of brain derived neurotrophic factor in the CNS of EAE. Moreover, HE training upregulated Treg and downregualted antigen-specific T cell proliferation and Th1 and Th17 populations from draining lymph node cells. These results suggest that HE swimming training might have benefits on attenuating the progression and pathological hallmarks of EAE, thus representing an important non-pharmacological intervention for improvement of chronic inflammation or T-cell mediated autoimmunity.

Is edaravone harmful? (A placebo is not a control)

Edaravone is delivered by long-term daily intravenous infusions, yet the risk of infusion was not considered in the design or analysis of studies examining the efficacy of edaravone in ALS. A reappraisal of the pivotal edaravone study (Study 19) on which claims of efficacy are based suggests that this risk cannot be dismissed, that the efficacy of edaravone may be over-estimated, and that some differences between edaravone and placebo may not implicate the ALS disease process. When trial conditions may be harmful to both arms of a placebo-controlled trial, not only is it necessary that treatment prove superior to placebo, but also that treatment is better than no intervention. In Study 19, edaravone performed better than placebo, but both placebo and edaravone likely did worse than no intervention, an interpretation more in keeping with previous trial experience of drugs with similar mechanisms of action, and with previous trial experience with edaravone. Edaravone, as presently delivered, may be both ineffective and harmful.

hmSOD1 gene mutation-induced disturbance in iron metabolism is mediated by impairment of Akt signalling pathway

BACKGROUND

Recently, skeletal muscle atrophy, impairment of iron metabolism, and insulin signalling have been reported in rats suffering from amyotrophic lateral sclerosis (ALS). However, the interrelationship between these changes has not been studied. We hypothesize that an impaired Akt-FOXO3a signalling pathway triggers changes in the iron metabolism in the muscles of transgenic animals.

METHODS

In the present study, we used transgenic rats bearing the G93A hmSOD1 gene and their non-transgenic littermates. The study was performed on the muscles taken from animals at three different stages of the disease: asymptomatic (ALS I), the onset of the disease (ALS II), and the terminal stage of the disease (ALS III). In order to study the molecular mechanism of changes in iron metabolism, we used SH-SY5Y and C2C12 cell lines stably transfected with pcDNA3.1, SOD1 WT and SOD1 G93A, or FOXO3a TM-ER.

RESULTS

A significant decrease in P-Akt level and changes in iron metabolism were observed even in the group of ALS I animals. This was accompanied by an increase in the active form of FOXO3a, up-regulation of atrogin-1, and catalase. However, significant muscle atrophy was observed in ALS II animals. An increase in ferritin L and H was accompanied by a rise in PCBP1 and APP protein levels. In SH-SY5Y cells stably expressing SOD1 or SOD1 G93A, we observed elevated levels of ferritin L and H and non-haem iron. Interestingly, insulin treatment significantly down-regulated ferritin L and H proteins in the cell. Conversely, cells transfected with small interfering RNA against Akt 1, 2, 3, respectively, showed a significant increase in the ferritin and FOXO3a levels. In order to assess the role of FOXO3a in the ferritin expression, we constructed a line of SH-SY5Y cells that expressed a fusion protein made of FOXO3a fused at the C-terminus with the ligand-binding domain of the oestrogen receptor (TM-ER) being activated by 4-hydroxytamoxifen. Treatment of the cells with 4-hydroxytamoxifen significantly up-regulated ferritin L and H proteins level.

CONCLUSIONS

Our data suggest that impairment of insulin signalling and iron metabolism in the skeletal muscle precedes muscle atrophy and is mediated by changes in Akt/FOXO3a signalling pathways.

Swim Training Modulates Skeletal Muscle Energy Metabolism, Oxidative Stress, and Mitochondrial Cholesterol Content in Amyotrophic Lateral Sclerosis Mice

Recently, in terms of amyotrophic lateral sclerosis (ALS), much attention has been paid to the cell structures formed by the mitochondria and the endoplasmic reticulum membranes (MAMs) that are involved in the regulation of Ca²⁺ signaling, mitochondrial bioenergetics, apoptosis, and oxidative stress. We assumed that remodeling of these structures via swim training may accompany the prolongation of the ALS lifespan. In the present study, we used transgenic mice with the G93A hmSOD1 gene mutation. We examined muscle energy metabolism, oxidative stress parameters, and markers of MAMs (Caveolin-1 protein level and cholesterol content in crude mitochondrial fraction) in groups of mice divided according to disease progression and training status. The progression of ALS was related to the lowering of Caveolin-1 protein levels and the accumulation of cholesterol in a crude mitochondrial fraction. These changes were associated with aerobic and anaerobic energy metabolism dysfunction and higher oxidative stress. Our data indicated that swim training prolonged the lifespan of ALS mice with accompanying changes in MAM components. Swim training also maintained mitochondrial function and lowered oxidative stress. These data suggest that modification of MAMs might play a crucial role in the exercise-induced deceleration of ALS development.

Effects of combined endurance and resistance training in Amyotrophic Lateral Sclerosis: A pilot, randomized, controlled study

Based on available evidence, muscle strengthening and cardiovascular exercises can help maintain function and not adversely affect the progression of disease in patients with ALS. However, this evidence is not sufficiently detailed to recommend a specific exercise prescription. The purpose of this project was to assess clinical outcomes of a combined exercise programme to increase knowledge of rehabilitation in ALS patients. 38 ALS patients were assigned randomly to two groups: one group underwent a specific exercise programme (ALS-EP) based on a moderate aerobic workout and isometric contractions, and the second group followed a standard neuromotor rehabilitation treatment. Objective evaluation consisted of cardiovascular measures, muscle strength and fatigue. Some positive effects of physical activity on ALS patients were found. Among the benefits, an overall improvement of functional independence in all patients, independently of the type of exercise conducted was seen. In addition, improvements in muscle power, oxygen consumption and fatigue were specifically observed in the ALS-EP group, all hallmarks of a training effect for the specific exercises. In conclusion, moderate intensity exercise is beneficial in ALS, helping in avoiding deconditioning and muscle atrophy resulting from progressive inactivity.

Pathogenic commonalities between spinal muscular atrophy and amyotrophic lateral sclerosis: Converging roads to therapeutic development

Spinal muscular atrophy (SMA) and amyotrophic lateral sclerosis (ALS) are the two most common motoneuron disorders, which share typical pathological hallmarks while remaining genetically distinct. Indeed, SMA is caused by deletions or mutations in the survival motor neuron 1 (SMN1) gene whilst ALS, albeit being mostly sporadic, can also be caused by mutations within genes, including superoxide dismutase 1 (SOD1), Fused in Sarcoma (FUS), TAR DNA-binding protein 43 (TDP-43) and chromosome 9 open reading frame 72 (C9ORF72). However, it has come to light that these two diseases may be more interlinked than previously thought. Indeed, it has recently been found that FUS directly interacts with an Smn-containing complex, mutant SOD1 perturbs Smn localization, Smn depletion aggravates disease progression of ALS mice, overexpression of SMN in ALS mice significantly improves their phenotype and lifespan, and duplications of SMN1 have been linked to sporadic ALS. Beyond genetic interactions, accumulating evidence further suggests that both diseases share common pathological identities such as intrinsic muscle defects, neuroinflammation, immune organ dysfunction, metabolic perturbations, defects in neuron excitability and selective motoneuron vulnerability. Identifying common molecular effectors that mediate shared pathologies in SMA and ALS would allow for the development of therapeutic strategies and targeted gene therapies that could potentially alleviate symptoms and be equally beneficial in both disorders. In the present review, we will examine our current knowledge of pathogenic commonalities between SMA and ALS, and discuss how furthering this understanding can lead to the establishment of novel therapeutic approaches with wide-reaching impact on multiple motoneuron diseases.

Specific Physical Exercise Improves Energetic Metabolism in the Skeletal Muscle of Amyotrophic-Lateral- Sclerosis Mice

Amyotrophic Lateral Sclerosis is an adult-onset neurodegenerative disease characterized by the specific loss of motor neurons, leading to muscle paralysis and death. Although the cellular mechanisms underlying amyotrophic lateral sclerosis (ALS)-induced toxicity for motor neurons remain poorly understood, growing evidence suggest a defective energetic metabolism in skeletal muscles participating in ALS-induced motor neuron death ultimately destabilizing neuromuscular junctions. In the present study, we report that a specific exercise paradigm, based on a high intensity and amplitude swimming exercise, significantly improves glucose metabolism in ALS mice. Using physiological tests and a biophysics approach based on nuclear magnetic resonance (NMR), we unexpectedly found that SOD1(G93A) ALS mice suffered from severe glucose intolerance, which was counteracted by high intensity swimming but not moderate intensity running exercise. Furthermore, swimming exercise restored the highly ALS-sensitive tibialis muscle through an autophagy-linked mechanism involving the expression of key glucose transporters and metabolic enzymes, including GLUT4 and glyceraldehyde-3-phosphate dehydrogenase (GAPDH). Importantly, GLUT4 and GAPDH expression defects were also found in muscles from ALS patients. Moreover, we report that swimming exercise induced a triglyceride accumulation in ALS tibialis, likely resulting from an increase in the expression levels of lipid transporters and biosynthesis enzymes, notably DGAT1 and related proteins. All these data provide the first molecular basis for the differential effects of specific exercise type and intensity in ALS, calling for the use of physical exercise as an appropriate intervention to alleviate symptoms in this debilitating disease.

Comprehensive catwalk gait analysis in a chronic model of multiple sclerosis subjected to treadmill exercise training

BACKGROUND

Multiple sclerosis (MS) is a demyelinating disease with a wide range of symptoms including walking impairment and neuropathic pain mainly represented by mechanical allodynia. Noteworthy, exercise preconditioning may affect both walking impairment and mechanical allodynia. Most of MS symptoms can be reproduced in the animal model named experimental autoimmune encephalomyelitis (EAE). Usually, neurological deficits of EAE are recorded using a clinical scale based on the development of disease severity that characterizes tail and limb paralysis. Following paralysis recovery, subtle motor alterations and even mechanical allodynia investigation are difficult to record, representing sequels of peak disease. The aim of the present study was to investigate the walking dysfunction by the catwalk system (CT) in exercised and non-exercised C57BL/6 mice submitted to EAE with MOG35-55 up to 42 days post-induction (dpi).

METHODS

Twenty-four C57BL/6 female mice were randomly assigned to unexercised (n = 12) or exercised (n = 12) groups. The MOG35-55 induced EAE model has been performed at the beginning of the fifth week of the physical exercise training protocol. In order to characterize the gait parameters, we used the CT system software version XT 10.1 (Noldus Inc., The Netherlands) from a basal time point (before induction) to 42 days post induction (dpi). Statistical analyses were performed with GraphPad Prisma 4.0 software.

RESULTS

Data show dynamic gait changes in EAE mice including differential front (FP) and hind paw (HP) contact latency. Such findings are hypothesized as related to an attempt to maintain balance and posture similar to what has been observed in patients with MS. Importantly, pre-exercised mice show differences in the mentioned gait compensation, particularly at the propulsion sub-phase of HP stand. Besides, we observed reduced intensity of the paw prints as well as reduced print area in EAE subjects, suggestive of a development of chronic mechanical allodynia in spite of being previously exercised.

CONCLUSIONS

Our data suggest that Catwalk system is a useful tool to investigate subtle motor impairment and mechanical allodynia at chronic time points of the EAE model, improving the functional investigation of gait abnormalities and demyelination sequelae.

ALS-Associated Endoplasmic Reticulum Proteins in Denervated Skeletal Muscle: Implications for Motor Neuron Disease Pathology

Alpha-motoneurons and muscle fibres are structurally and functionally interdependent. Both cell types particularly rely on endoplasmic reticulum (ER/SR) functions. Mutations of the ER proteins VAPB, SigR1 and HSP27 lead to hereditary motor neuron diseases (MNDs). Here, we determined the expression profile and localization of these ER proteins/chaperons by immunohistochemistry and immunoblotting in biopsy and autopsy muscle tissue of patients with amyotrophic lateral sclerosis (ALS) and other neurogenic muscular atrophies (NMAs) and compared these patterns to mouse models of neurogenic muscular atrophy. Postsynaptic neuromuscular junction staining for VAPB was intense in normal human and mouse muscle and decreased in denervated Nmd^2J mouse muscle fibres. In contrast, VAPB levels together with other chaperones and autophagy markers were increased in extrasynaptic regions of denervated muscle fibres of patients with MNDs and other NMAs, especially at sites of focal myofibrillar disintegration (targets). These findings did not differ between NMAs due to ALS and other causes. G93A-SOD1 mouse muscle fibres showed a similar pattern of protein level increases in denervated muscle fibres. In addition, they showed globular VAPB-immunoreactive structures together with misfolded SOD1 protein accumulations, suggesting a primary myopathic change. Our findings indicate that altered expression and localization of these ER proteins and autophagy markers are part of the dynamic response of muscle fibres to denervation. The ER is particularly prominent and vulnerable in both muscle fibres and alpha-motoneurons. Thus, ER pathology could contribute to the selective build-up of degenerative changes in the neuromuscular axis in MNDs.

Neuroprotective Effects of Exercise Treatments After Injury: The Dual Role of Neurotrophic Factors

BACKGROUND

Shared connections between physical activity and neuroprotection have been studied for decades, but the mechanisms underlying this effect of specific exercise were only recently brought to light. Several evidences suggest that physical activity may be a reasonable and beneficial method to improve functional recovery in both peripheral and central nerve injuries and to delay functional decay in neurodegenerative diseases. In addition to improving cardiac and immune functions, physical activity may represent a multifunctional approach not only to improve cardiocirculatory and immune functions, but potentially modulating trophic factors signaling and, in turn, neuronal function and structure at times that may be critical for neurodegeneration and regeneration.

METHODS

Research content related to the effects of physical activity and specific exercise programs in normal and injured nervous system have been reviewed.

RESULTS

Sustained exercise, particularly if applied at moderate intensity and early after injury, exerts anti-inflammatory and pro-regenerative effects, and may boost cognitive and motor functions in aging and neurological disorders. However, newest studies show that exercise modalities can differently affect the production and function of brain-derived neurotrophic factor and other neurotrophins involved in the generation of neuropathic conditions. These findings suggest the possibility that new exercise strategies can be directed to nerve injuries with therapeutical benefits.

CONCLUSION

Considering the growing burden of illness worldwide, understanding of how modulation of neurotrophic factors contributes to exercise-induced neuroprotection and regeneration after peripheral nerve and spinal cord injuries is a relevant topic for research, and represents the beginning of a new non-pharmacological therapeutic approach for better rehabilitation of neural disorders.

Effect of physical exercise and anabolic steroid treatment on spinal motoneurons and surrounding glia of wild-type and ALS mice

Motoneuron degeneration is the hallmark of amyotrophic lateral sclerosis (ALS). The cause and predisposing factors for sporadic ALS are still unknown. Exposure to a specific environmental risk factors in subjects with a susceptibility genotype may increase the risk of the disease. The role of physical activity and the use of anabolic steroids are still debated in epidemiological studies on patients and murine models of ALS. To assess at the cellular level the role (beneficial or detrimental) of physical exercise and the use of anabolic steroid, we here investigated, in SOD1(G93A) (mSOD1) mice and wild-type littermates, changes in the ventral horn after regular exercise, treatment with the anabolic androgenic steroid 19-nortestosterone (nandrolone), and their combination, compared with matched control sedentary mice. The experiments were pursued for several weeks until symptom onset in mSOD1 mice. Lumbar motoneurons, astrocytes and microglia were analyzed. In wild-type mice, cytological alterations of motoneurons were observed especially after nandrolone treatment. The following main findings were observed in treated mSOD1 mice versus untreated ones: i) nandrolone treatment markedly enhanced motoneuron loss; this detrimental effect was reverted by the combination with exercise, resulting in increased motoneuron survival; ii) astrocytic activation was most marked after nandrolone treatment when motoneuron damage was most severe; iii) microglia activation was most marked after physical exercise when motoneuron damage was less severe. The results indicate a vulnerability of mSOD1 motoneurons to nandrolone treatment, a potential neuroprotective effect of physical exercise, and a modulation by glial cells in the ALS murine model in the examined paradigms.

Impact of expiratory strength training in amyotrophic lateral sclerosis

INTRODUCTION

We evaluated the feasibility and impact of expiratory muscle strength training (EMST) on respiratory and bulbar function in persons with amyotrophic lateral sclerosis (ALS).

METHODS

Twenty-five ALS patients participated in this delayed intervention open-label clinical trial. Following a lead-in period, patients completed a 5-week EMST protocol. Outcome measures included: maximum expiratory pressure (MEP); physiologic measures of swallow and cough; and penetration-aspiration scale (PAS) scores.

RESULTS

Of participants who entered the active phase of the study (n = 15), EMST was well tolerated and led to significant increases in MEPs and maximum hyoid displacement during swallowing post-EMST (P < 0.05). No significant differences were observed for PAS scores or cough spirometry measures.

CONCLUSIONS

EMST was feasible and well tolerated in this small cohort of ALS patients and led to improvements in expiratory force-generating pressures and swallow kinematics. Further investigation is warranted to confirm these preliminary findings. Muscle Nerve 54: 48-53, 2016.

Long-term exercise-specific neuroprotection in spinal muscular atrophy-like mice

KEY POINTS

The real impact of physical exercise parameters, i.e. intensity, type of contraction and solicited energetic metabolism, on neuroprotection in the specific context of neurodegeneration remains poorly explored. In this study behavioural, biochemical and cellular analyses were conducted to compare the effects of two different long-term exercise protocols, high intensity swimming and low intensity running, on motor units of a type 3 spinal muscular atrophy (SMA)-like mouse model. Our data revealed a preferential SMA-induced death of intermediate and fast motor neurons which was limited by the swimming protocol only, suggesting a close relationship between neuron-specific protection and their activation levels by specific exercise. The exercise-induced neuroprotection was independent of SMN protein expression and associated with specific metabolic and behavioural adaptations with notably a swimming-induced reduction of muscle fatigability. Our results provide new insight into the motor units' adaptations to different physical exercise parameters and will contribute to the design of new active physiotherapy protocols for patient care.

ABSTRACT

Spinal muscular atrophy (SMA) is a group of autosomal recessive neurodegenerative diseases differing in their clinical outcome, characterized by the specific loss of spinal motor neurons, caused by insufficient level of expression of the protein survival of motor neuron (SMN). No cure is at present available for SMA. While physical exercise might represent a promising approach for alleviating SMA symptoms, the lack of data dealing with the effects of different exercise types on diseased motor units still precludes the use of active physiotherapy in SMA patients. In the present study, we have evaluated the efficiency of two long-term physical exercise paradigms, based on either high intensity swimming or low intensity running, in alleviating SMA symptoms in a mild type 3 SMA-like mouse model. We found that 10 months' physical training induced significant benefits in terms of resistance to muscle damage, energetic metabolism, muscle fatigue and motor behaviour. Both exercise types significantly enhanced motor neuron survival, independently of SMN expression, leading to the maintenance of neuromuscular junctions and skeletal muscle phenotypes, particularly in the soleus, plantaris and tibialis of trained mice. Most importantly, both exercises significantly improved neuromuscular excitability properties. Further, all these training-induced benefits were quantitatively and qualitatively related to the specific characteristics of each exercise, suggesting that the related neuroprotection is strongly dependent on the specific activation of some motor neuron subpopulations. Taken together, the present data show significant long-term exercise benefits in type 3 SMA-like mice providing important clues for designing rehabilitation programmes in patients.