Approaching Fatigue in Neuromuscular Diseases

Mimicking the Tendon Microenvironment to Enhance Skeletal Muscle Adhesion and Longevity in a Functional Microcantilever Platform

Microcantilever platforms are functional models for studying skeletal muscle force dynamics in vitro. However, the contractile force generated by the myotubes can cause them to detach from the cantilevers, especially during long-term experiments, thus impeding the chronic investigations of skeletal muscles for drug efficacy and toxicity. To improve the integration of myotubes with microcantilevers, we drew inspiration from the elastomeric proteins, elastin and resilin, that are present in the animal and insect worlds, respectively. The spring action of these proteins plays a critical role in force dampening in vivo. In animals, elastin is present in the collagenous matrix of the tendon which is the attachment point of muscles to bones. The tendon microenvironment consists of elastin, collagen, and an aqueous jelly-like mass of proteoglycans. In an attempt to mimic this tendon microenvironment, elastin, collagen, heparan sulfate proteoglycan, and hyaluronic acid were deposited on a positively charged silane substrate. This enabled the long-term survival of mechanically active myotubes on glass and silicon microcantilevers for over 28 days. The skeletal muscle cultures were derived from both primary and induced pluripotent stem cell (iPSC)-derived human skeletal muscles. Both types of myoblasts formed myotubes which survived for five weeks. Primary skeletal muscles and iPSC-derived skeletal muscles also showed a similar trend in fatigue index values. Upon integration with the microcantilever system, the primary muscle and iPSC-derived myotubes were tested successively over a one month period, thus paving the way for long-term chronic experiments on these systems for both drug efficacy and toxicity studies.

Non-Motor Features of Amyotrophic Lateral Sclerosis: A Clinic-based Study

Introduction:

Amyotrophic lateral sclerosis (ALS) is a progressive neurodegenerative disorder of motor neurons. Spread of pathology to other brain areas leads to development of non-motor symptoms (NMSs). These usually remain undiagnosed because of overwhelming motor problem and are responsible for significant distress to the patient. Our objective was to explore the burden of various NMSs of patients with ALS, compare between limb-onset and bulbar-onset patients, and to correlate with severity and duration of disease.

Methods:

Fifty patients with ALS diagnosed according to revised El Escorial Criteria and 50 healthy controls were included in this study. They were assessed with NMS Questionnaire, Beck's Depression Inventory, Center for Neurologic Study-Lability Scale, Drooling Frequency and Severity Scale, Epworth Sleepiness scale, Bengali Mental State Examination, and Frontal Assessment Battery and relevant statistical analyses were carried out.

Results:

The patients with ALS had significantly increased prevalence of almost all NMSs compared to controls. There was also significant increase in depression, suicidal ideation, pseudobulbar affect, and daytime sleepiness in patients with ALS. The bulbar onset subgroup had significantly increased daytime drooling, dysphagia, nausea and vomiting, whereas the limb onset subgroup reported increased frequency of leg swelling. Executive dysfunction was detected in 24% of patients with ALS and 9.8% had mild cognitive impairment. Weight loss, frequency of falling, insomnia, unpleasant nocturnal leg sensations, difficulty having sex, depression, and cognitive impairment increased significantly with an increase in severity of the disease.

Conclusion:

NMSs were significantly more prevalent in patients with ALS. Some NMSs worsened with advancement of the disease.

A Human-Based Functional NMJ System for Personalized ALS Modeling and Drug Testing

Loss of the neuromuscular junction (NMJ) is an early and critical hallmark in all forms of ALS. The study design was to develop a functional NMJ disease model by integrating motoneurons (MNs) differentiated from multiple ALS-patients' induced pluripotent stem cells (iPSCs) and primary human muscle into a chambered system. NMJ functionality was tested by recording myotube contractions while stimulating MNs by field electrodes and a set of clinically relevant parameters were defined to characterize the NMJ function. Three ALS lines were analyzed, 2 with SOD1 mutations and 1 with a FUS mutation. The ALS-MNs reproduced pathological phenotypes, including increased axonal varicosities, reduced axonal branching and elongation and increased excitability. These MNs formed functional NMJs with wild type muscle, but with significant deficits in NMJ quantity, fidelity and fatigue index. Furthermore, treatment with the Deana protocol was found to correct the NMJ deficits in all the ALS mutant lines tested. Quantitative analysis also revealed the variations inherent in each mutant lines. This functional NMJ system provides a platform for the study of both fALS and sALS and has the capability of being adapted into subtype-specific or patient-specific models for ALS etiological investigation and patient stratification for drug testing.

Assessment and management of fatigue in neuromuscular disease

Fatigue is a common and potentially debilitating symptom of neuromuscular disease (NMD). Studies show that patients with NMD subjectively report increased levels of fatigue. Laboratory testing has demonstrated that patients with NMD show objective physiological signs of increased fatigue, with both central and peripheral components. To date, no treatment has been proven to be truly effective through evidence-based medicine. Thus, the clinician must use a multimodality approach to treating fatigue in patients with NMD. Management interventions are generally based on a sequential approach including treatment of comorbid factors, with the goal of maximizing physical and psychological functioning. This might include low-intensity exercise training, cognitive therapy, treatment of associated depression, correction of risk factors such as obesity, poor nutrition, and inactivity (deconditioning). Optimizing cardiopulmonary function is also critical and measures such as noninvasive, positive pressure ventilation may reduce fatigue in patients with NMD. Novel medications such as modafinil, a nonamphetamine stimulant, may be a helpful pharmacological treatment. Nutraceutical agents, such as creatine monohydrate, coenzyme Q10 (CoQ10), and alpha-lipoic acid, may also improve neuromuscular function and reduce fatigue.

[Exercise therapy and myopathies]

Since the first consensus papers published early in the 2000s, a growing number of recent publications has shown that adapted physical activity is not only safe in the context of myopathy but also potentially effective as a therapeutic tool. After a short recall of the different exercise modalities, the mechanical strain they induce and the expected muscular benefits, the present paper reviews the different studies related to exercise therapy in myopathic patients and provides a critical analysis of the topic. Myopathies are rare diseases with many different etiologies and a large number of training modalities which could be useful for the different muscular challenges have been proposed. We have chosen to focus on several specific training modalities and to discuss the results from the most recent papers. The purpose of this review is to, firstly, update physical training guidelines for patients with myopathy and, secondly, highlight some common pitfalls associated with this strategy. This is particularly important for medical and allied professionals involved in prescribing and managing exercise therapy protocols.

Physical and mental fatigue in Parkinson's disease: epidemiology, pathophysiology and treatment

Fatigue is one of the most common non-motor complaints of Parkinson's disease (PD) patients and is associated with reduced activity and poorer quality of life. Fatigue can be experienced as a state of being tired or weary (subjective fatigue) or as a process of becoming tired or fatigued (fatigability). Subjective mental and physical fatigue are evaluated using self-report questionnaires such as the Multidimensional Fatigue Inventory. Physical fatigability is studied in a laboratory setting using physical exercise protocols and transcranial magnetic stimulation. Mental fatigability is evaluated by measuring attention over time using a reaction-time paradigm called the Attention Network Test (ANT). PD patients report more subjective physical and mental fatigue than controls on a variety of fatigue questionnaires. PD patients have increased physical fatigability in force generation and finger tapping. Levodopa and modafinil improve physical fatigability in PD subjects. Methylphenidate is useful for treating subjective physical fatigue. PD subjects have greater mental fatigability than control subjects and display abnormal performance in all three attention networks in the ANT. Therapies targeting the neurotransmitter systems involved in attention may be helpful for treating mental fatigability. Future fatigue research should focus on developing gold standards for fatigue measurement and developing treatments for fatigue and fatigability in PD.

Benefits of interval-training on fatigue and functional capacities in Charcot-Marie-Tooth disease

Exercise intolerance and undue fatigue are common complaints in patients with Charcot-Marie-Tooth (CMT) disease. Reduced physical ability is due directly to the disease, but it is also due to physical deconditioning. The aim of this study was to test whether 24 weeks of interval-training exercise (ITE) cycling can significantly improve physiological, neuromuscular, and functional capacities and alleviate fatigue in CMT patients. Eight CMT patients (4 CMT1A and 4 CMT2) participated in ITE for 3 nonconsecutive days per week. Cardiovascular fitness, muscle strength, fatigue resistance, and functional capacities were measured before and after 12 weeks of supervised hospital training and again after another 12 weeks of unsupervised home training. Training was well tolerated. There were significant improvements in cardiorespiratory capacities, isokinetic concentric strength, and functional ability measurements. All patients experienced an improvement in their self-reported visual analogic scale for fatigue and pain during training. However, there was no significant change in their isometric force production and indices of fatigue resistance after training. Although the improvement in exercise tolerance may be due in part to reversal of the deconditioning effect of their related sedentary lifestyle, this clinical trial suggests that ITE can benefit CMT patients especially in their functional performance and subjective perception of pain and fatigue. Moreover, the improvement observed at the end of the first supervised period ITE was maintained after the second unsupervised home period, although there was no further improvement in performance and tolerance.

Fatigue and neuromuscular diseases

PURPOSE

To identify the role of fatigue, its evaluation and its causes in the pathophysiology context of acquired or hereditary neuromuscular diseases of the spinal anterior horn cell, peripheral nerve, neuromuscular junction and muscle.

MATERIAL AND METHODS

A literature review has been done on Medline with the following keywords: neuromuscular disease, peripheral neuropathy, myopathy, fatigue assessment, exercise intolerance, force assessment, fatigue scale and questionnaire, then with the terms: Fatigue Severity Scale, Chalder Fatigue Scale, Fatigue Questionnaire, Piper Fatigue Scale, electromyography and the combination of the word Fatigue with the following terms: Amyotrophic Lateral Sclerosis (ALS), Post-Polio Syndrome (PPS), Guillain-Barre Syndrome, Immune Neuropathy, Charcot-Marie-Tooth Disease, Myasthenia Gravis (MG), Metabolic Myopathy, Mitochondrial Myopathy, Muscular Dystrophy, Facioscapulohumeral Dystrophy, Myotonic Dystrophy.

RESULTS

Fatigue is a symptom very frequently reported by patients. Fatigue is mainly evaluated by strength loss after an exercise, by change in electromyographic activity during a given exercise and by questionnaires that takes into account the subjective (psychological) part of fatigue. Due to the large diversity of motor disorders, there are multiple clinical expressions of fatigue that differ in their presentation, consequences and therapeutic approach.

CONCLUSION

This review shows that fatigue has to be taken into account in patients with neuromuscular diseases. In this context, pathophysiology of fatigue often implies the motor component but the disease evolution and the physical obligates of daily life also induce an important psychological component.

Fatigue and respiratory disorders

OBJECTIVES

To analyze the factors at the origin of fatigue in respiratory disorders. To assess fatigue and its functional impact on patients affected from respiratory diseases. To evaluate the results of comprehensive care on fatigue and functional capacity.

MATERIALS AND METHODS

We systematically reviewed the literature in Medline and the Cochrane Library, using the following keywords: fatigue, respiratory disorders, questionnaire, evaluation, assessment, randomized controlled trial, meta-analysis.

RESULTS

Fatigue is a high frequency symptom (90%) and takes an important place, as much as dyspnea, in the genesis of the respiratory induced handicap. Its assessment is varied, according to the studies. It originates from multiple causes, as shown from clinical and experimental studies. The main treatment consists in rehabilitation, using physical exercises. Its efficacy is demonstrated on physical endurance, but is not clear in terms of general fatigue.

CONCLUSION

Although fatigue is very frequent complaint, along with a major disabling condition, the comprehensive assessment of fatigue, in respiratory disorders, including its physical and cognitive components, is not still really codified. Rehabilitation is the main treatment. Its efficiency has been demonstrated on the physical and functional components of fatigue. Its results on perceived fatigue remains to be evaluated.