Neurodegeneration in the retina of motoneuron diseases: a longitudinal study in amyotrophic lateral sclerosis and Kennedy's disease

BACKGROUND

To what extent retinal atrophy in neurodegenerative diseases reflects the severity and/or the chronicity of brain pathology or is a local independent phenomenon remains to be clarified. Moreover, whether retinal atrophy has a clinical (diagnostic and prognostic) value in these diseases remains unclear.

OBJECTIVE

To add light on the pathological significance and clinical value of retinal atrophy in patients with amyotrophic lateral sclerosis (ALS) and Kennedy's disease (KD).

METHODS

Thirty-five ALS, thirty-seven KD, and forty-nine age-matched healthy controls (HC) were included in a one-year longitudinal study. Spectrum-domain optical coherence tomography (OCT) was performed at study entry (T0) and after 12 months (T1). Disease duration and functional rating scale (FRS) for ALS and KD patients were correlated to retinal thicknesses.

RESULTS

Compared to HC, peripapillary retinal nerve fiber layer (pRNFL) thickness was significantly thinner in both ALS (p = 0.034) and KD (p = 0.003). pRNFL was thinner in KD compared to ALS, but the difference was not significant. In KD, pRNFL atrophy significantly correlated with both disease severity (r = 0.296, p = 0.035) and disease duration (r = - 0.308, p = 0.013) while no significant correlation was found in ALS (disease severity: r = 0.147, p = 0.238; disease duration: r = - 0.093, p = 0.459). During the follow-up, pRNFL thickness remained stable in KD while significantly decreased in ALS (p = 0.043).

CONCLUSIONS

Our study provides evidence of retinal atrophy in both ALS and KD and suggests that retinal thinning is a primary local phenomenon in motoneuron diseases. The clinical value of pRNFL atrophy in KD is worthy of further investigation.

Using genetic testing to diagnose Kennedy's disease: a case report and literature review

Theoretical basis: Kennedy's disease (KD) is also known as spinal bulbar muscular dystrophy. Because the symptoms of KD are similar to most neuromuscular diseases, it is difficult to make a rapid clinical diagnosis. Patient case: We report the case of a 50-year-old man who was diagnosed with "lumbar disc herniation" five years ago because of progressive proximal limb weakness. After his initial diagnosis, his condition worsened gradually, and a muscle biopsy was performed 3 years ago, and he was then diagnosed with "motor neuron disease", but he had no such family history. His physical examination showed female breast development, erectile dysfunction, a weakness of the quadriceps femoris, a bilateral tendon reflex, and atrophy of the tongue muscle. One year ago, it was found that his blood sugar had increased, and when oral hypoglycemic drugs were given, his blood glucose control was not ideal. At the same time, it was found that his creatine kinase continued to increase significantly. He was admitted to the hospital again because of the aggravation of his walking difficulties. Diagnosis: A laboratory examination showed elevated creatine kinase, an impaired glucose tolerance, and abnormal lactate values. The diagnosis was confirmed using a genetic analysis, which showed a repeated amplification of CAG in the androgen receptor gene. Intervention measures and results: After this diagnosis, the patient had a good prognosis after receiving symptomatic treatment. Lesson: Genetic testing is the key to the diagnosis of KD. Clinicians should make a differential diagnosis, an early diagnosis, and provide treatment as soon as possible according to the patient's clinical manifestations and laboratory examination.

Kennedy's disease: an under-recognized motor neuron disorder

Kennedy's disease or spinal bulbar muscular atrophy is a rare, inherited and slowly progressive multisystem disease mostly manifesting with a motor neuron disease phenotype leading to disability. The slow progression, partial androgen insensitivity, electrophysiological evidence of sensory neuronopathy, and relatively spared central nervous system pathways help differentiate it from amyotrophic lateral sclerosis. To date, there is no treatment or cure with clinical care mainly focused on accurate diagnosis, symptom management, patient education, and genetic counselling.

Disorders of sleep in spinal and bulbar muscular atrophy (Kennedy's disease)

INTRODUCTION

Spinal and bulbar muscular atrophy (SBMA) is a progressive, X-linked lower motor neuron disorder exclusively affecting men. Since knowledge on sleep disorders in SBMA is scarce compared to other motoneuron diseases, this retrospective case-control study aimed to investigate sleep and sleep-related breathing in patients with SBMA.

METHODS

In 23 non-ventilated patients with SBMA (median age 52 years), clinical disease characteristics, forced vital capacity and diagnostic polysomnographies were retrospectively evaluated. In 16 patients, overnight transcutaneous capnometry was available. Twenty-three male control subjects with chronic insomnia were matched for age and body mass index.

RESULTS

In patients with SBMA obstructive sleep apnoea (OSA, apnoea-hypopnoea index/AHI > 5/h) was more frequent than in control subjects (14/23 or 61% vs. 6/23 or 26%, p = 0.02), and median AHI was significantly higher in patients (9.0/h vs. 3.4/h, p < 0.01). Among SBMA patients, the AHI was not related to age or body mass index. Alveolar hypoventilation as reflected by nocturnal hypercapnia was found in 3/16 patients. Rapid eye movement (REM) sleep without atonia was present in 44% of SBMA patients but only in 4% of controls (p < 0.01). During REM and non-REM sleep, no behavioural abnormalities were observed in either group. Periodic limb movements in sleep (index > 15/h) were frequent in SBMA patients but rarely disrupted sleep.

CONCLUSIONS

In patients with SBMA, sleep-disordered breathing may comprise both OSA and nocturnal hypoventilation. REM sleep without atonia may also be found, but its clinical significance remains unclear. In patients complaining of sleep-related symptoms, cardiorespiratory polysomnography and transcutaneous capnometry are recommended.

Exercise Intervention Leads to Functional Improvement in a Patient with Spinal and Bulbar Muscular Atrophy

Introduction

Spinal and bulbar muscular atrophy is a progressive neuromuscular disease that leads to muscle weakness and reduced physical function. Benefits of physical therapy for people with spinal and bulbar muscular atrophy have not been reported in the literature.

Case report

A 62-year-old male patient with spinal and bulbar muscular atrophy reported falling, difficulty walking and completing upright tasks, and showed clinical signs of low baseline function on examination. Transportation challenges made it difficult for this patient to attend frequent one-on-one physical therapy sessions.

Interventions and outcomes

A minimally supervised home-based exercise intervention was chosen with the goal of safely improving his functional capacity. The 5-visit clinical intervention, spread over 10 months, provided 3 exercise modules: seated-to-standing postural alignment and core muscle activation; upright functional and endurance training; and balance training and rhythmic walking. Post-intervention the patient had increased lower extremity muscle strength, improved balance, and reduced self-reported fatigue.

Conclusion

Home-based exercises were well tolerated with no increase in creatine kinase. Multiple clinical measures of strength and function improved, possibly related to the patients’ excellent motivation and compliance with the programme. Promising utilization of a minimally supervised home-based programme is described here.

Myoglobin: a new biomarker for spinal and bulbar muscular atrophy?

OBJECTIVES

There is a primary muscular affection in spinal and bulbar muscular atrophy (SBMA). Myoglobin (Myo) is mainly distributed in the myocardium and skeletal muscle. The purpose of the study was to explore the significance of serum Myo detection in the diagnosis and clinical evaluation of SBMA.

MATERIALS AND METHODS

In this study, serum creatine kinase (CK), Myo, and Troponin T (cTNT) levels were assessed in 80 patients with SBMA and were compared with those of 60 patients with amyotrophic lateral sclerosis (ALS). All measurement data were analyzed using the t-test and enumeration data using the χ2-test.

RESULTS

The rate of abnormal Myo levels in the SBMA group was 100%, however, none of the patients with ALS had an abnormal Myo level. There was no overlap between the two groups. The Myo levels in patients with SBMA were correlated with the course of the disease. Further, their CK level was significantly elevated compared with that in patients with ALS, however, there was an overlap between the two groups. The serum cTNT level in patients with SBMA was not significantly different from that in patients with ALS.

CONCLUSION

Myo, as a simple, inexpensive, and readily available biochemical indicator, is likely to be used for the differentiation between SBMA and ALS, and used as a new biomarker for the clinical evaluation of SBMA.

Disentangling balance impairments in spinal and bulbar muscular atrophy

Spinal and bulbar muscular atrophy (Kennedy's disease) has been associated with balance dysfunction and falls. However, postural control has not been studied quantitatively. Here, we quantified upright stance and aimed to disentangle the role of vestibular, proprioceptive and oculomotor deficits. Static balance was assessed in Kennedy patients (n = 7) during quiet stance on a force platform under different visual and proprioceptive feedback conditions. Vestibular function was assessed with the video head impulse test. Sural nerve neurography was employed to evaluate the severity of peripheral neuropathy. Also, horizontal saccades were recorded and quantified by the main sequence relationship. Posturographic analyses revealed significantly increased body sway, more pronounced in conditions with closed eyes, which was also reflected in the calculated Romberg indices. Horizontal vestibulo-ocular reflex gains were normal, i.e. > 0.75. In contrast, compound sensory nerve action potentials were markedly decreased in all patients (mean = 2.4 μV). Two patients showed slow saccades with increased exponential main sequence constants. We conclude that Kennedy patients exhibit severe deficits in quiet stance. Postural instability is greatest in conditions of absent vision with reduced proprioception being the main determinant of unsteadiness. Some patients show slowed saccadic eye movements suggesting a nuclear abducens neuronopathy.

Clinical manifestations and AR gene mutations in Kennedy's disease

Kennedy's disease, resulted from the expansion of a CAG repeat in exon 1 of androgen receptor (AR) gene, is a motor neuron degenerative disease in the brainstem and spinal cord with the slow development of facial, bulbar, and limb muscle degeneration. To investigate the clinical manifestations and gene mutations in Han Chinese patients with Kennedy's disease. The clinical manifestations of 5 male Han Chinese patients including 2 probands and their relatives from 2 families and 1 sporadic case were retrospectively studied. The CAG repeats in the first exon of AR were screened in 5 Han Chinese people including 2 probands and their healthy relatives from 2 families and 1 sporadic case by polymerase chain reaction (PCR) and direct sequencing. The average age at onset of Kennedy's disease was 48.20 ± 8.70 (mean ± SD) years and the average duration was 7.60 ± 5.32 years. All the patients showed slow onset and progressive weakness, wasting, and fasciculations of the whole body. Four patients demonstrated decreased fertility and 1 patient showed mild gynecomastia. Serum creatine kinase and testosterone levels were elevated mildly in 2 and 1 patients, respectively. The electromyogram showed neurogenic abnormalities. Muscle magnetic resonance demonstrated reduced muscle volume and fatty infiltration. Three different enlarged CAG domains were discovered in the 2 families and 1 sporadic patient with Kennedy's disease, and the CAG repeat number was 48, 43, and 44, respectively. The clinical manifestations of Kennedy's disease in Han Chinese middle-aged men were progressive weakness and atrophy in the bulbar and spinal muscles, occasionally demonstrating incomplete androgen insensitivity syndrome. These patients were also characterized with enlarged CAG repeat number in the first exon of AR, indicating that CAG number could be used in the diagnosis of Han Chinese patients with Kennedy's disease.

The metabolic and endocrine characteristics in spinal and bulbar muscular atrophy

OBJECTIVE

Spinal and bulbar muscular atrophy (SBMA) is caused by an abnormal expansion of the CAG repeat in the androgen receptor gene. This study aimed to systematically phenotype a German SBMA cohort (n = 80) based on laboratory markers for neuromuscular, metabolic, and endocrine status, and thus provide a basis for the selection of biomarkers for future therapeutic trials.

METHODS

We assessed a panel of 28 laboratory parameters. The clinical course and blood biomarkers were correlated with disease duration and CAG repeat length. A subset of 11 patients was evaluated with body fat MRI.

RESULTS

Almost all patients reported muscle weakness (99%), followed by dysphagia (77%), tremor (76%), and gynecomastia (75%) as major complaints. Creatine kinase was the most consistently elevated (94%) serum marker, which, however, did not relate with either the disease duration or the CAG repeat length. Paresis duration and CAG repeat length correlated with dehydroepiandrosterone sulfate after correction for body mass index and age. The androgen insensitivity index was elevated in nearly half of the participants (48%).

CONCLUSIONS

Metabolic alterations in glucose homeostasis (diabetes) and fat metabolism (combined hyperlipidemia), and sex hormone abnormalities (androgen insensitivity) could be observed among SBMA patients without association with the neuromuscular phenotype. Dehydroepiandrosterone sulfate was the only biomarker that correlated strongly with both weakness duration and the CAG repeat length after adjusting for age and BMI, indicating its potential as a biomarker for both disease severity and duration and, therefore, its possible use as a reliable outcome measure in future therapeutic studies.

Identification of neuron selective androgen receptor inhibitors

AIM

To identify neuron-selective androgen receptor (AR) signaling inhibitors, which could be useful in the treatment of spinal and bulbar muscular atrophy (SBMA), or Kennedy’s disease, a neuromuscular disorder in which deterioration of motor neurons leads to progressive muscle weakness.

METHODS

Cell lines representing prostate, kidney, neuron, adipose, and muscle tissue were developed that stably expressed the CFP-AR-YFP FRET reporter. We used these cells to screen a library of small molecules for cell type-selective AR inhibitors. Secondary screening in luciferase assays was used to identify the best cell-type specific AR inhibitors. The mechanism of action of a neuron-selective AR inhibitor was examined in vitro using luciferase reporter assays, immunofluorescence microscopy, and immunoprecipitations. Rats were treated with the most potent compound and tissue-selective AR inhibition was examined using RT-qPCR of AR-regulated genes and immunohistochemistry.

RESULTS

We identified the thiazole class of antibiotics as compounds able to inhibit AR signaling in a neuronal cell line but not a muscle cell line. One of these antibiotics, thiostrepton is able to inhibit the activity of both wild type and polyglutamine expanded AR in neuronal GT1-7 cells with nanomolar potency. The thiazole antibiotics are known to inhibit FOXM1 activity and accordingly, a novel FOXM1 inhibitor FDI-6 also inhibited AR activity in a neuron-selective fashion. The selective inhibition of AR is likely indirect as the varied structures of these compounds would not suggest that they are competitive antagonists. Indeed, we found that FOXM1 expression correlates with cell-type selectivity, FOXM1 co-localizes with AR in the nucleus, and that shRNA-mediated knock down of FOXM1 reduces AR activity and thiostrepton sensitivity in a neuronal cell line. Thiostrepton treatment reduces FOXM1 levels and the nuclear localization of beta-catenin, a known co-activator of both FOXM1 and AR, and reduces the association between beta-catenin and AR. Treatment of rats with thiostrepton demonstrated AR signaling inhibition in neurons, but not muscles.

CONCLUSION

Our results suggest that thiazole antibiotics, or other inhibitors of the AR-FOXM1 axis, can inhibit AR signaling selectively in motor neurons and may be useful in the treatment or prevention of SBMA symptoms.

Kennedy's disease 1234 scale: Preliminary design and test

Kennedy's disease (KD), also known as spinal and bulbar muscular atrophy (SBMA), is a rare x-linked genetic disorder which is characterized by muscle weakness and atrophy. In previous clinical trials, KD patients had been assessed using the ALSFRS scale, which was specifically designed for ALS patients. However, the progression of KD is very slow, and thus, the ALSFRS does not accurately reflect changes in the clinical condition of KD patient. Here, we developed the KD 1234 scale which designed specially for KD. We evaluated KD 1234 and ALSFRS in 81 KD patients and 100 healthy age-matched male participants. Of 81 cases, 52 were followed up after 32months. Scale reliability was assessed using inter-rater reliability, split-half reliability and internal consistency reliability (Cronbach's α coefficient). Scale validity was evaluated using content and structure validity. Longitudinal analysis was performed. The results showed the KD 1234 scale was simple and easy to operate, with good reliability, validity and reactivity. We think this new scale can quantitatively evaluate the clinical condition of KD patients and any changes in this condition, and is thus suitable for clinical studies.

Non-Cell-Autonomous Regulation of Retrograde Motoneuronal Axonal Transport in an SBMA Mouse Model

Defects in axonal transport are seen in motoneuronal diseases, but how that impairment comes about is not well understood. In spinal bulbar muscular atrophy (SBMA), a disorder linked to a CAG/polyglutamine repeat expansion in the androgen receptor (AR) gene, the disease-causing AR disrupts axonal transport by acting in both a cell-autonomous fashion in the motoneurons themselves, and in a non-cell-autonomous fashion in muscle. The non-cell-autonomous mechanism is suggested by data from a unique “myogenic” transgenic (TG) mouse model in which an AR transgene expressed exclusively in skeletal muscle fibers triggers an androgen-dependent SBMA phenotype, including defects in retrograde transport. However, motoneurons in this TG model retain the endogenous AR gene, leaving open the possibility that impairments in transport in this model also depend on ARs in the motoneurons themselves. To test whether non-cell-autonomous mechanisms alone can perturb retrograde transport, we generated male TG mice in which the endogenous AR allele has the testicular feminization mutation (Tfm) and, consequently, is nonfunctional. Males carrying the Tfm allele alone show no deficits in motor function or axonal transport, with or without testosterone treatment. However, when Tfm males carrying the myogenic transgene (Tfm/TG) are treated with testosterone, they develop impaired motor function and defects in retrograde transport, having fewer retrogradely labeled motoneurons and deficits in endosomal flux based on time-lapse video microscopy of living axons. These findings demonstrate that non-cell-autonomous disease mechanisms originating in muscle are sufficient to induce defects in retrograde transport in motoneurons.

Onset Manifestations of Spinal and Bulbar Muscular Atrophy (Kennedy's Disease)

Spinal and bulbar muscular atrophy (SBMA) is regarded as a disorder with adult onset between third and fifth decade of life. However, there is increasing evidence that SBMA may start already before adulthood. The present study investigated the following: (1) Which clinical manifestations have been described so far in the literature as initial manifestations? (2) Which was the age at onset of these manifestations? and (3) Is age at onset dependent on the CAG-repeat length if non-motor manifestations are additionally considered? Data for this review were identified by searches of MEDLINE using appropriate search terms. Onset manifestations in SBMA can be classified as frequent, rare, motor, non-motor, or questionable. Frequent are muscle weakness, cramps, fasciculations/twitching, tremor, dysarthria, dysphagia, or gynecomastia. Rare are myalgia, easy fatigability, exercise intolerance, polyneuropathy, hyper-CKemia, under-masculinized genitalia, scrotal hypospadias, microphallus, laryngospasm, or oligospermia. Questionable manifestations include sensory disturbances, cognitive impairment, increased pituitary volume, diabetes, reduced tongue pressure, elevated creatine-kinase, or low androgens/high estrogens. Age at onset is highly variable ranging from 4-76 years. Non-motor manifestations develop usually before motor manifestations. Age at onset depends on what is considered as an onset manifestation. Considering non-motor onset manifestations, age at onset is independent of the CAG-repeat size. In conclusion, age at onset of SBMA depends on what is regarded as onset manifestation. If non-motor manifestations are additionally considered, age at onset is independent of the CAG-repeat length. Since life expectancy is hardly reduced in SBMA, re-investigation of patients from published studies with regard to their initial disease profiles is recommended.

Mitochondrial dysfunction in Kennedy's disease: a new pharmacological target?

BACKGROUND

Mitochondrial impairment and elevated oxidative stress have been implicated in the pathogenesis of Kennedy's disease. However, there is still no study describing the mitochondrial nutrient management in patients with Kennedy's disease.

METHODS

We assessed the clinical and electrophysiological features in a patient with Kennedy's disease. This patient was diagnosed by genetic analysis. We also measured the plasma 8-hydroxydeoxyguanosine (8-OHdG) levels of the patient and his family members using commercial enzyme-linked immunosorbent assay (ELISA). Treatment with intravenous L-carnitine (2 g/day) for the patient was started on admission, followed by two weeks.

RESULTS

Routine laboratory tests revealed a severe elevation of creatine kinase (CK) (606.5 U/L; normal value: 15-170 U/L). Sequencing of the first exon of androgen receptor (AR) revealed an increased number of CAG repeat (50; the normal range from 10-36) in the patient. Plasma 8-OHdG level in the patient was relatively elevated (34.68±1.01 ng/mL) compared with the female carriers and non-carriers. Two weeks after L-carnitine treatment, we observed a reduction of approximately 40% in CK level (391 U/L) in the patient.

CONCLUSIONS

Oxidative stress resulting from mitochondrial dysfunction could be involved in Kennedy's disease. Targeting the mitochondrial dysfunction in Kennedy's disease may have significant therapeutic potential.

Brain MR diffusion tensor imaging in Kennedy's disease

INTRODUCTION

Kennedy's disease (KD) is a progressive degenerative disorder affecting lower motor neurons. We investigated the correlation between disease severity and whole brain white matter microstructure, including upper motor neuron tracts, by using diffusion-tensor imaging (DTI) in eight patients with KD in whom disease severity was evaluated using the Amyotrophic Lateral Sclerosis Functional Rating Scale (ALSFRS).

METHODS

From DTI acquisitions we obtained maps of fractional anisotropy (FA), mean diffusivity (MD), axial diffusivity (L1) and radial diffusivities (L2, L3). We then employed tract-based spatial statistics (TBSS) to investigate within-patient correlations of DTI invariants with ALSFRS and disease duration (DD).

RESULTS

We found a significant correlation between low ALSFRS and 1) low FA values in association commissural and projection fibers, and 2) high L3 values in commissural tracts and fronto-parietal white matter. Additionally, we found a significant association between longer DD and 1) low FA in the genu and body of corpus callosum, association fibers and midbrain and 2) high L1 in projection and association tracts.

CONCLUSIONS

The associations between clinical variables and white matter microstructural changes in areas thought to be spared by the disease process support the hypothesis of a multisystem involvement in the complex pathogenic mechanisms responsible for the clinical disability of these patients.

Early onset and novel features in a spinal and bulbar muscular atrophy patient with a 68 CAG repeat

Spinal and bulbar muscular atrophy (SBMA) is an X-linked neuromuscular disease caused by a trinucleotide (CAG) repeat expansion in the androgen receptor gene. Patients with SBMA have weakness, atrophy, and fasciculations in the bulbar and extremity muscles. Individuals with CAG repeat lengths greater than 62 have not previously been reported. We evaluated a 29year old SBMA patient with 68 CAGs who had unusually early onset and findings not seen in others with the disease. Analysis of the androgen receptor gene confirmed the repeat length of 68 CAGs in both peripheral blood and fibroblasts. Evaluation of muscle and sensory function showed deficits typical of SBMA, and in addition the patient had manifestations of autonomic dysfunction and abnormal sexual development. These findings extend the known phenotype associated with SBMA and shed new insight into the effects of the mutated androgen receptor.

Mechanisms mediating spinal and bulbar muscular atrophy: investigations into polyglutamine-expanded androgen receptor function and dysfunction

Spinal and bulbar muscular atrophy (SBMA, Kennedy’s disease), a late-onset neuromuscular disorder, is caused by expansion of the polymorphic polyglutamine tract in the androgen receptor (AR). The AR is a ligand-activated transcription factor, but plays roles in other cellular pathways. In SBMA, selective motor neuron degeneration occurs in the brainstem and spinal cord, thus the causes of neuronal dysfunction have been studied. However, pathogenic pathways in muscles may also be involved. Cultured cells, fly and mouse models are used to study the molecular mechanisms leading to SBMA. Both the structure of the polyglutamine-expanded AR (polyQ AR) and its interactions with other proteins are altered relative to the normal AR. The ligand-dependent translocation of the polyQ AR to the nucleus appears to be critical, as are interdomain interactions. The polyQ AR, or fragments thereof, can form nuclear inclusions, but their pathogenic or protective nature is unclear. Other data suggests soluble polyQ AR oligomers can be harmful. Post-translational modifications such as phosphorylation, acetylation, and ubiquitination influence AR function and modulate the deleterious effects of the polyQ AR. Transcriptional dysregulation is highly likely to be a factor in SBMA; deregulation of non-genomic AR signaling may also be involved. Studies on polyQ AR-protein degradation suggest inhibition of the ubiquitin proteasome system and changes to autophagic pathways may be relevant. Mitochondrial function and axonal transport may also be affected by the polyQ AR. Androgens, acting through the AR, can be neurotrophic and are important in muscle development; hence both loss of normal AR functions and gain of novel harmful functions by the polyQ AR can contribute to neurodegeneration and muscular atrophy. Thus investigations into polyQ AR function have shown that multiple complex mechanisms lead to the initiation and progression of SBMA.