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ABSTRACT: Spinal and bulbar muscular atrophy (SBMA) is an hereditary, adult-onset, lower motor neuron disease caused by an aberrant elongation of a trinucleotide CAG repeat, which encodes the polyglutamine tract, in the first exon of the androgen receptor (AR) gene. The main symptoms are slowly progressive muscle weakness and atrophy of bulbar, facial and limb muscles. The cardinal histopathological findings of SBMA are an extensive loss of lower motor neurons in the anterior horn of the spinal cord as well as in brainstem motor nuclei and intranuclear accumulations of mutant AR protein in the residual motor neurons. Androgen deprivation therapy rescues neuronal dysfunction in animal models of SBMA, suggesting that the molecular basis for motor neuron degeneration in this disorder is testosterone-dependent nuclear accumulation of the mutant AR. Suppression of disease progression by leuprorelin acetate has also been demonstrated in a phase 2 clinical trial. In addition, the clarification of pathophysiology leads to appearance of candidate drugs to treat this devastating disease: heat shock protein (HSP) inducer, Hsp90 inhibitor, and histone deacetylase inhibitor. Advances in basic and clinical research on SBMA are now paving the way for clinical application of pathogenesis-targeting therapeutics.
Neuropathology 06/2009; 29(4):509-16. · 2.02 Impact Factor
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ABSTRACT: Spinal and bulbar muscular atrophy (SBMA) is a hereditary motor neuron disease caused by the expansion of a polyglutamine tract in the androgen receptor (AR). The histopathological finding in SBMA is loss of lower motor neurons in the anterior horn of the spinal cord as well as in the brainstem motor nuclei. Animal studies have revealed that the pathogenesis of SBMA depends on the level of serum testosterone, and that androgen deprivation mitigates neurodegeneration through inhibition of nuclear accumulation of the pathogenic AR. Heat shock proteins, ubiquitin-proteasome system and transcriptional regulation are also potential targets of therapy development for SBMA.
International Journal of Molecular Sciences 04/2009; 10(3):1000-12. · 2.60 Impact Factor
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Haruhiko Banno,
Masahisa Katsuno, Keisuke Suzuki,
Yu Takeuchi,
Motoshi Kawashima,
Noriaki Suga,
Motoko Takamori,
Mizuki Ito,
Tomohiko Nakamura,
Koji Matsuo, [......],
Hiroaki Adachi,
Makoto Minamiyama,
Masahiro Waza,
Naoki Atsuta,
Hirohisa Watanabe,
Yasushi Fujimoto,
Tsutomu Nakashima,
Fumiaki Tanaka,
Manabu Doyu,
Gen Sobue
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ABSTRACT: Spinal and bulbar muscular atrophy (SBMA) is a hereditary motor neuron disease caused by the expansion of a polyglutamine tract in the androgen receptor (AR). Animal studies have shown that the pathogenesis of SBMA is dependent on serum testosterone level. This study is aimed at evaluating the efficacy and safety of androgen deprivation by leuprorelin acetate in patients with SBMA.
Fifty SBMA patients underwent subcutaneous injections of leuprorelin acetate or placebo in a randomized, placebo-controlled trial for 48 weeks, followed by an open-label trial for an additional 96 weeks, in which 19 patients of the leuprorelin group and 15 of the placebo group received leuprorelin acetate. The patients who did not participate in the open-label trial were also followed up for the 96-week period (UMIN000000474).
Leuprorelin acetate significantly extended the duration of cricopharyngeal opening in videofluorography and decreased mutant AR accumulation in scrotal skin biopsy. The patients treated with leuprorelin acetate for 144 weeks exhibited significantly greater functional scores and better swallowing parameters than those who received placebo. Autopsy of one patient who received leuprorelin acetate for 118 weeks suggested that androgen deprivation inhibits the nuclear accumulation or stabilization, or both, of mutant AR in the motor neurons of the spinal cord and brainstem.
These observations suggest that administration of leuprorelin acetate suppresses the deterioration of neuromuscular impairment in SBMA by inhibiting the toxic accumulation of mutant AR. The results of this phase 2 trial support the start of large-scale clinical trials of androgen deprivation for SBMA.
Annals of Neurology 03/2009; 65(2):140-50. · 11.09 Impact Factor
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ABSTRACT: Spinal and bulbar muscular atrophy (SBMA) is an adult-onset motor neuron disease caused by a CAG repeat expansion in the androgen receptor gene. Because the progression of SBMA is slow, it is plausible to identify biomarkers that monitor disease course for therapeutic development. To verify whether the 6-min walk test (6MWT) is a biomarker of SBMA, we performed the 6MWT in 35 genetically confirmed patients and in 29 age-matched healthy controls. The walk distance covered within 6 min (6MWD) was significantly less in SBMA than it was in controls (323.3 +/- 143.9 m and 637.6 +/- 94.2 m, respectively; P < 0.001). In test-retest analysis, the intraclass correlation coefficient for the 6MWD was high in SBMA patients (r = 0.982). In a 1-year follow-up the 6MWD significantly decreased at a rate of 11.3% per year. Our observations suggest that the 6MWT is a biomarker that can be used to monitor progression of motor impairment in SBMA.
Muscle & Nerve 08/2008; 38(2):964-71. · 2.37 Impact Factor
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ABSTRACT: Polyglutamine diseases are hereditary neurodegenerative disorders caused by an abnormal expansion of a trinucleotide CAG repeat, which encodes a polyglutamine tract. To date, nine polyglutamine diseases are known: Huntington's disease (HD), spinal and bulbar muscular atrophy (SBMA), dentatorubral-pallidoluysian atrophy (DRPLA) and six forms of spinocerebellar ataxia (SCA). The diseases are inherited in an autosomal dominant fashion except for SBMA, which shows an X-linked pattern of inheritance. Although the causative gene varies with each disorder, polyglutamine diseases share salient genetic features as well as molecular pathogenesis. CAG repeat size correlates well with the age of onset in each disease, shows both somatic and germline instability, and has a strong tendency to further expand in successive generations. Aggregation of the mutant protein followed by the disruption of cellular functions, such as transcription and axonal transport, has been implicated in the etiology of neurodegeneration in polyglutamine diseases. Although animal studies have provided promising therapeutic strategies for polyglutamine diseases, it remains difficult to translate these disease-modifying therapies to the clinic. To optimize "proof of concept", the process for testing candidate therapies in humans, it is of importance to identify biomarkers which can be used as surrogate endpoints in clinical trials for polyglutamine diseases.
Current Molecular Medicine 06/2008; 8(3):221-34. · 5.10 Impact Factor
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Keisuke Suzuki,
Masahisa Katsuno,
Haruhiko Banno,
Yu Takeuchi,
Naoki Atsuta,
Mizuki Ito,
Hirohisa Watanabe,
Fumitada Yamashita,
Norio Hori,
Tomohiko Nakamura,
Masaaki Hirayama,
Fumiaki Tanaka,
Gen Sobue
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ABSTRACT: Spinal and bulbar muscular atrophy (SBMA) is an adult-onset, lower motor neuron disease caused by an aberrant elongation of a CAG repeat in the androgen receptor (AR) gene. The main symptoms are weakness and atrophy of bulbar, facial and limb muscles, but sensory disturbances are frequently found in SBMA patients. Motor symptoms have been attributed to the accumulation of mutant AR in the nucleus of lower motor neurons, which is more profound in patients with a longer CAG repeat. We examined nerve conduction properties including F-waves in a total of 106 patients with genetically confirmed SBMA (mean age at data collection = 53.8 years; range = 31-75 years) and 85 control subjects. Motor conduction velocities (MCV), compound muscle action potentials (CMAP), sensory conduction velocities (SCV) and sensory nerve action potentials (SNAP) were significantly decreased in all nerves examined in the SBMA patients compared with that in the normal controls, indicating that axonal degeneration is the primary process in both motor and sensory nerves. More profound abnormalities were observed in the nerves of the upper limbs than in those of the lower limbs. F-waves in the median nerve were absent in 30 of 106 cases (28.3%), but no cases of absent F-waves were observed in the tibial nerve. From an analysis of the relationship between CMAPs and SNAPs, patients were identified with different electrophysiological phenotypes: motor-dominant, sensory-dominant and non-dominant phenotypes. The CAG repeat size and the age at onset were significantly different among the patients with motor- and sensory-dominant phenotypes, indicating that a longer CAG repeat is more closely linked to the motor-dominant phenotype and a shorter CAG repeat is more closely linked to the sensory-dominant phenotype. Furthermore, when we classified the patients by CAG repeat size, CMAP values showed a tendency to be decreased in patients with a longer CAG repeat (> or =47), while SNAPs were significantly decreased in patients with a shorter CAG repeat (<47). In addition, we found that the frequency of aggregation in the sensory neuron cytoplasm tended to inversely correlate with the CAG repeat size in the autopsy study, supporting the view that the CAG repeat size differentially correlates with motor- and sensory-dominant phenotypes. In conclusion, our results suggest that there are unequivocal electrophysiological phenotypes influenced by CAG repeat size in SBMA.
Brain 01/2008; 131(Pt 1):229-39. · 9.46 Impact Factor
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ABSTRACT: Neurodegenerative diseases have been construed as incurable disorders. However, therapeutic development for these diseases is now facing a turning point: analyses of cellular and animal models have provided insights into pathogenesis of neurodegenerative diseases, and have indicated rational therapeutic approaches to them. Therefore, how to design clinical trials for neurodegenerative diseases is becoming one of the most challenging issues in the clinical neurology. Given a small number of patients and a slow progression of symptoms, it is important to carry out effective trials using surrogate endpoints or historical control data, if necessary. In particular, pathogenesis-based disease-modifying therapy should be carefully evaluated in clinical trials, because its effect is likely to be suppression of neurodegenerative processes, but not symptom relief. The development of androgen deprivation therapy for spinal and bulbar muscular atrophy (SBMA) is a representative study in this field. SBMA is a hereditary neurodegenerative disease caused by expansion of a trinucleotide CAG repeat, which encodes the polyglutamine tract, in the first exon of the androgen receptor (AR) gene. Animal models carrying human mutant AR gene recapitulate polyglutamine-mediated motor neuron degeneration, providing insights into the pathogenesis of SBMA. There is increasing evidence that testosterone, the ligand of AR, plays a pivotal role in the neurodegeneration in SBMA. The striking success of androgen deprivation therapy in SBMA mouse models has been translated into phase 2, and then phase 3, clinical trials.
Brain and nerve = Shinkei kenkyū no shinpo 05/2007; 59(4):367-74.
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Masahisa Katsuno,
Hiroaki Adachi,
Makoto Minamiyama,
Masahiro Waza,
Keisuke Tokui,
Haruhiko Banno, Keisuke Suzuki,
Yu Onoda,
Fumiaki Tanaka,
Manabu Doyu,
Gen Sobue
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ABSTRACT: Spinal and bulbar muscular atrophy (SBMA) is a hereditary neurodegenerative disease caused by an expansion of a trinucleotide CAG repeat encoding the polyglutamine tract in the androgen receptor (AR) gene. To elucidate the pathogenesis of polyglutamine-mediated motor neuron dysfunction, we investigated histopathological and biological alterations in a transgenic mouse model of SBMA carrying human pathogenic AR. In affected mice, neurofilaments and synaptophysin accumulated at the distal motor axon. A similar intramuscular accumulation of neurofilament was detected in the skeletal muscle of SBMA patients. Fluoro-gold labeling and sciatic nerve ligation demonstrated an impaired retrograde axonal transport in the transgenic mice. The mRNA level of dynactin 1, an axon motor for retrograde transport, was significantly reduced in the SBMA mice resulting from pathogenic AR-induced transcriptional dysregulation. These pathological events were observed before the onset of neurological symptoms, but were reversed by castration, which prevents nuclear accumulation of pathogenic AR. Overexpression of dynactin 1 mitigated neuronal toxicity of the pathogenic AR in a cell culture model of SBMA. These observations indicate that polyglutamine-dependent transcriptional dysregulation of dynactin 1 plays a crucial role in the reversible neuronal dysfunction in the early stage of SBMA.
Journal of Neuroscience 12/2006; 26(47):12106-17. · 7.11 Impact Factor
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ABSTRACT: Spinal and bulbar muscular atrophy (SBMA) is a hereditary neurodegenerative disease characterized by slowly progressive muscle weakness and atrophy of bulbar, facial, and limb muscles. The cause of SBMA is expansion of a trinucleotide CAG repeat, which encodes the polyglutamine tract, in the first exon of the androgen receptor (AR) gene. SBMA chiefly occurs in adult males, whereas neurological symptoms are rarely detected in females having mutant AR gene. The cardinal histopathological finding of SBMA is loss of lower motor neurons in the anterior horn of spinal cord as well as in brainstem motor nuclei. Animal models carrying human mutant AR gene recapitulate polyglutamine-mediated motor neuron degeneration, providing clues to the pathogenesis of SBMA. There is increasing evidence that testosterone, the ligand of AR, plays a pivotal role in the pathogenesis of neurodegeneration in SBMA. The striking success of androgen deprivation therapy in SBMA mouse models has been translated into clinical trials. In addition, elucidation of pathophysiology using animal models leads to emergence of candidate drugs to treat this devastating disease: HSP inducer, Hsp90 inhibitor, and histone deacetylase inhibitor. Utilizing biomarkers such as scrotal skin biopsy would improve efficacy of clinical trials to verify the results from animal studies. Advances in basic and clinical researches on SBMA are now paving the way for clinical application of potential therapeutics.
Experimental Neurology 08/2006; 200(1):8-18. · 4.70 Impact Factor
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ABSTRACT: Spinal and bulbar muscular atrophy (SBMA) is an adult-onset motoneuron disease caused by a CAG-repeat expansion in the androgen receptor (AR) gene and for which no curative therapy exists. However, since recent research may provide opportunities for medical treatment, information concerning the natural history of SBMA would be beneficial in planning future clinical trials. We investigated the natural course of SBMA as assessed by nine activities of daily living (ADL) milestones in 223 Japanese SBMA patients (mean age at data collection = 55.2 years; range = 30-87 years) followed from 1 to 20 years. All the patients were diagnosed by genetic analysis. Hand tremor was an early event that was noticed at a median age of 33 years. Muscular weakness occurred predominantly in the lower limbs, and was noticed at a median age of 44 years, followed by the requirement of a handrail to ascend stairs at 49, dysarthria at 50, dysphagia at 54, use of a cane at 59 and a wheelchair at 61 years. Twenty-one of the patients developed pneumonia at a median age of 62 and 15 of them died at a median age of 65 years. The most common cause of death in these cases was pneumonia and respiratory failure. The ages at onset of each ADL milestone were strongly correlated with the length of CAG repeats in the AR gene. However CAG-repeat length did not correlate with the time intervals between each ADL milestone, suggesting that although the onset age of each ADL milestone depends on the CAG-repeat length in the AR gene, the rate of disease progression does not. The levels of serum testosterone, an important triggering factor for polyglutamine-mediated motoneuron degeneration, were maintained at relatively high levels even at advanced ages. These results provide beneficial information for future clinical therapeutic trials, although further detailed prospective studies are also needed.
Brain 07/2006; 129(Pt 6):1446-55. · 9.46 Impact Factor
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ABSTRACT: Spinal and bulbar muscular atrophy (SBMA) is a hereditary motor neuron disease caused by the expansion of a polyglutamine tract in the androgen receptor (AR). The nuclear accumulation of mutant AR is central to the pathogenesis of SBMA. Androgen deprivation with leuprorelin inhibits mutant AR accumulation, resulting in rescue of neuronal dysfunction in a mouse model of SBMA. This study aimed to investigate whether mutant AR accumulation in the scrotal skin is an appropriate biomarker of SBMA.
Immunohistochemistry of both scrotal skin and the spinal cord was performed on five autopsied SBMA cases. Neurological severity and scrotal skin findings were studied in another 13 patients. Five other patients received subcutaneous injections of leuprorelin and underwent scrotal skin biopsy.
The degree of mutant AR accumulation in scrotal skin epithelial cells tended to be correlated with that in the spinal motor neurons in autopsy specimens, and it was well correlated with CAG repeat length and inversely correlated with the amyotrophic lateral sclerosis functional scale. Leuprorelin treatment inhibited mutant AR protein accumulation in the scrotal skin of SBMA patients.
These observations suggest that scrotal skin biopsy findings are a potent pathogenic marker of SBMA and can be a surrogate end point in therapeutic trials.
Annals of Neurology 04/2006; 59(3):520-6. · 11.09 Impact Factor
