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Spinal and bulbar muscular atrophy (SBMA) is a hereditary neuromuscular disorder caused by CAG trinucleotide expansion in the gene encoding the androgen receptor (AR). In the central nervous system, lower motor neurons are selectively affected, whereas pathology of patients and animal models also indicates involvement of skeletal muscle including loss of fast-twitch type 2 fibres and increased slow-twitch type 1 fibres, together with a glycolytic-to-oxidative metabolic switch. Evaluation of muscle and fat using MRI, in addition to biochemical indices such as serum creatinine level, are promising biomarkers to track the disease progression. The serum level of creatinine starts to decrease before the onset of muscle weakness, followed by the emergence of hand tremor, a prodromal sign of the disease. Androgen-dependent nuclear accumulation of the polyglutamine-expanded AR is an essential step in the pathogenesis, providing therapeutic opportunities via hormonal manipulation and gene silencing with antisense oligonucleotides. Animal studies also suggest that hyperactivation of Src, alteration of autophagy and a mitochondrial deficit underlie the neuromuscular degeneration in SBMA and provide alternative therapeutic targets.

Spinal and bulbar muscular atrophy (SBMA) is an X-linked neuromuscular disorder primarily affecting adult males due to the expansion of CAG repeats in the androgen receptor gene. It manifests as progressive lower motor neuropathy and androgen deficiency. A Japanese man in his late 50s presented with gradually progressive muscle weakness over 6 years. Examination revealed muscle weakness and atrophy in upper and lower limbs, decreased deep tendon reflexes, involuntary facial movements, bilateral finger tremors, tongue atrophy, fasciculations and bilateral gynaecomastia. Blood tests indicated elevated creatine kinase and mild hepatic dysfunction. Nerve conduction studies showed decreased sensory nerve action potentials, and electromyography demonstrated neurogenic changes. Genetic testing confirmed SBMA with 47 CAG repeats despite no family history. Treatment included leuprorelin acetate and rehabilitation using a wearable cyborg hybrid-assistive limb. As SBMA progresses slowly and symptoms like hand tremors and decreased serum creatinine precede significant weakness, early recognition is critical for diagnosis.

Spinal and bulbar muscular atrophy (SBMA), also known as Kennedy’s disease, is a rare, X-linked hereditary lower motor neuron disease, characterized by progressive muscular weakness. An expanded trinucleotide repeat (CAG > 37) in the androgen receptor gene (AR), encoding glutamine, is the mutation responsible for Kennedy’s disease. Toxicity of this mutant protein affects both motor neurons and muscles. In this review, we provide a comprehensive, clinically oriented overview of the current literature regarding Kennedy’s disease, highlighting gaps in our knowledge that remain to be addressed in further research. Kennedy’s disease mimics are also discussed, as are ongoing and recently completed therapeutic endeavours.

As autophony can be accompanied by several conditions, it is important to find co-morbidities. This paper reports a patient with Kennedy's disease (spinobulbar muscular atrophy, an X-linked, hereditary, lower motor neuron disease) having autophony as the first symptom. A 62-year-old male presented to the otorhinolaryngology department with autophony that began 2 years previously and worsened after losing weight 3 months prior to presentation. Otoscopic examination demonstrated inward and outward movement of the tympanic membrane, synchronised with respiration. Although he had no other symptoms, facial twitching was found on physical examination. In the neurology department, lower motor neuron disease, with subtle weakness of the tongue, face and upper limbs, and gynaecomastia, were confirmed. He was diagnosed with Kennedy's disease based on genetic analysis. Autophonia was presumed to be attributed to bulbofacial muscle weakness due to Kennedy's disease, and worsened by recent weight loss. Patients with autophony require a thorough history-taking and complete physical examination to assess the nasopharynx and the integrity of lower cranial function.

Spinal and bulbar muscular atrophy (SBMA) is a neuromuscular disease caused by an expanded CAG repeat in the androgen receptor (AR) gene. Here, we perform a comprehensive analysis of signaling pathways in a mouse model of SBMA (AR-97Q mice) utilizing a phosphoprotein assay. We measure the levels of 17 phosphorylated proteins in spinal cord and skeletal muscle of AR-97Q mice at three stages. The level of phosphorylated Src (p-Src) is markedly increased in the spinal cords and skeletal muscles of AR-97Q mice prior to the onset. Intraperitoneal administration of a Src kinase inhibitor improves the behavioral and histopathological phenotypes of the transgenic mice. We identify p130Cas as an effector molecule of Src and show that the phosphorylated p130Cas is elevated in murine and cellular models of SBMA. These results suggest that Src kinase inhibition is a potential therapy for SBMA. Spinal and bulbar muscular atrophy is a neuromuscular disease caused by an expanded CAG repeat in the androgen receptor gene. Here the authors show that Src kinase signaling is activated in a mouse model of the disease, and that Src inhibition improves pathology and behavioral symptoms in mice.

Background Spinal and bulbar muscular atrophy (SBMA) is a hereditary neuromuscular disorder linked to androgen receptor gene mutations, often associated with metabolic abnormalities. We aimed to investigate the incidence of fragility fractures and the underlying mechanisms in SBMA. Methods Consecutive genetically confirmed SBMA patients and healthy controls (HC) were enrolled. We surveyed fracture history and assessed motor function, bone metabolism markers, and bone mineral density (BMD) using dual‐energy X‐ray absorptiometry. Longitudinal BMD changes were also analyzed between SBMA patients and HC. Results A total of 109 SBMA patients and 21 HC were included. Fragility fractures in SBMA patients were mainly observed in cortical bone‐dominant regions. Their lower limb BMD was significantly reduced (SBMA 1.10 g/cm, HC 1.19 g/cm; p < 0.05) and further decreased overtime. Despite low bone resorption markers, bone formation markers showed no difference between the groups, suggesting that SBMA patients exhibit characteristics of low turnover osteoporosis. Serum 25‐hydroxyvitamin D levels were lower in SBMA patients than in HC (15.4 ng/mL vs. 19.4 ng/mL; p < 0.01). Longitudinal analysis revealed that SBMA patients had a higher incidence of fragility fractures than HC (log‐rank test, p < 0.05), with the first fragility fracture occurring 10 years after the onset of muscle weakness. Low baseline BMD was a predictor of fragility fractures (adjusted OR = 0.32; 95% CI: 0.17–0.60; p < 0.05). Conclusions SBMA patients have a high fragility fracture incidence, particularly in cortical bone, with a progressive BMD decrease. Low bone turnover and vitamin D deficiency are associated with these fractures. SBMA patients had a 39% fragility fracture incidence versus 14% in controls, with fractures occurring predominantly in cortical bone regions (foot/toe, knee/leg, ribs). They also showed a progressive decline of lower limb BMD, characterized by low bone turnover despite preserved formation markers, along with a high prevalence of vitamin D deficiency.

Spinal and bulbar muscular atrophy (SBMA) is a neuromuscular disease caused by a polyglutamine (polyQ) expansion in the androgen receptor (AR). Despite the fact that the monogenic cause of SBMA has been known for nearly 3 decades, there is no effective treatment for this disease, underscoring the complexity of the pathogenic mechanisms that lead to a loss of motor neurons and muscle in SBMA patients. In the current review, we provide an overview of the system-wide clinical features of SBMA, summarize the structure and function of the AR, discuss both gain-of-function and loss-of-function mechanisms of toxicity caused by polyQ-expanded AR, and describe the cell and animal models utilized in the study of SBMA. Additionally, we summarize previously conducted clinical trials which, despite being based on positive results from preclinical studies, proved to be largely ineffective in the treatment of SBMA; nonetheless, these studies provide important insights as researchers develop the next generation of therapies.

Polyglutamine (polyQ) diseases are devastating, slowly progressing neurodegenerative conditions caused by expansion of polyQ-encoding CAG repeats within the coding regions of distinct, unrelated genes. In spinal and bulbar muscular atrophy (SBMA), polyQ expansion within the androgen receptor (AR) causes progressive neuromuscular toxicity, the molecular basis of which is unclear. Using quantitative proteomics, we identified changes in the AR interactome caused by polyQ expansion. We found that the deubiquitinase USP7 preferentially interacts with polyQ-expanded AR and that lowering USP7 levels reduced mutant AR aggregation and cytotoxicity in cell models of SBMA. Moreover, USP7 knockdown suppressed disease phenotypes in SBMA and spinocerebellar ataxia type 3 (SCA3) fly models, and monoallelic knockout of Usp7 ameliorated several motor deficiencies in transgenic SBMA mice. USP7 overexpression resulted in reduced AR ubiquitination, indicating the direct action of USP7 on AR. Using quantitative proteomics, we identified the ubiquitinated lysine residues on mutant AR that are regulated by USP7. Finally, we found that USP7 also differentially interacts with mutant Huntingtin (HTT) protein in striatum and frontal cortex of a knockin mouse model of Huntington's disease. Taken together, our findings reveal a critical role for USP7 in the pathophysiology of SBMA and suggest a similar role in SCA3 and Huntington's disease.

Spinal and bulbar muscular atrophy is an X-linked neuromuscular disease caused by CAG repeat expansion in the androgen receptor gene. Patients with this disease have low concentrations of insulin-like growth factor-1 (IGF-1), and studies of overexpression and administration of IGF-1 showed benefit in a transgenic model; thus the IGF-1 pathway presents as a potential treatment target. We assessed safety, tolerability, and preliminary efficacy of BVS857, an IGF-1 mimetic, in patients with spinal and bulbar muscular atrophy. In this randomised, double-blind, placebo-controlled trial, we recruited patients from neuromuscular centres in Denmark (Copenhagen), Germany (Ulm), Italy (Padova), and three sites within the USA (Bethesda, MD; Irvine, CA; and Columbus, OH). Eligible patients were 18 years or older with a confirmed genetic diagnosis of spinal and bulbar muscular atrophy, were ambulatory, had symptomatic weakness, and had serum IGF-1 concentrations of 170 ng/mL or lower. Patients were randomly assigned (2:1) to study drug or placebo by a number scheme. Patients, investigators, and study personnel were masked to treatment assignment. After a safety and tolerability assessment with eight patients, BVS857 was administered once a week (0·06 mg/kg intravenously) for 12 weeks. Primary outcome measures were safety, tolerability, and the effects of BVS857 on thigh muscle volume (TMV) measured by MRI. The ratio of TMV at day 85 to baseline was analysed with ANCOVA per protocol. Secondary outcomes of muscle strength and function were measured with the Adult Myopathy Assessment Tool, lean body mass through dual energy x-ray absorptiometry, and BVS857 pharmacokinetics. This trial was registered with ClinicalTrials.gov, NCT02024932. 31 patients were assessed for eligibility, 27 of whom were randomly assigned to either BVS857 treatment (n=18) or placebo (n=9), and 24 were included in the preliminary efficacy analysis (BVS857 group, n=15; placebo group, n=9). BVS857 was generally safe with no serious adverse events. No significant differences were found in adverse events between the BVS857 and placebo groups. Immunogenicity was detected in 13 (72%) of 18 patients in the BVS857 group, including crossreacting antibodies with neutralising capacity to endogenous IGF-1 in five patients. TMV decreased from baseline to day 85 in the placebo group (–3·4% [–110 cm3]) but not in the BVS857 group (0% [2 cm3]). A significant difference in change in TMV was observed in the BVS857 group versus the placebo group (geometric-mean ratio 1·04 [90% CI 1·01–1·07]; p=0·02). There were no differences between groups in measures of muscle strength and function. TMV remained stable in patients with spinal and bulbar muscular atrophy after being given BVS857 for 12 weeks. The intervention was associated with high incidence of immunogenicity and did not improve muscle strength or function. Additional studies might be needed to assess the efficacy of activating the IGF-1 pathway in this disease. Novartis Pharmaceuticals and the US National Institutes of Health.

This study aimed to develop a functional measurement that combines quantitative motor evaluation index of various body regions in patients with spinal and bulbar muscular atrophy (SBMA). We assessed subjects with SBMA and healthy controls with quantitative muscle strength measurements and functional scales. We selected tongue pressure, grip power, % peak expiratory flow (%PEF), timed walking test, and % forced vital capacity (%FVC) as components. By combining these values with Z-score, we created a functional composite (SBMA functional composite: SBMAFC). We also calculated the standardized response mean to compare the sensitivity of SBMAFC with that of existing measurements. A total of 97 genetically confirmed patients with SBMA and 36 age- and sex-matched healthy controls were enrolled. In the longitudinal analysis, the standardized response mean of SBMAFC was larger than that of existing rating scales. Receiver operating characteristic (ROC) analysis demonstrated that the SBMAFC is capable of distinguishing between subjects with early-stage SBMA and healthy controls. SBMAFC is more sensitive to disease progression than existing functional rating scales and is a potential outcome measure in clinical trials of SBMA.