Richard T. Moxley

A call for transparent reporting to optimize the predictive value of preclinical research

The US National Institute of Neurological Disorders and Stroke convened major stakeholders in June 2012 to discuss how to improve the methodological reporting of animal studies in grant applications and publications. The main workshop recommendation is that at a minimum studies should report on sample-size estimation, whether and how animals were randomized, whether investigators were blind to the treatment, and the handling of data. We recognize that achieving a meaningful improvement in the quality of reporting will require a concerted effort by investigators, reviewers, funding agencies and journal editors. Requiring better reporting of animal studies will raise awareness of the importance of rigorous study design to accelerate scientific progress.

Expanded CUG Repeats Trigger Aberrant Splicing of ClC-1 Chloride Channel Pre-mRNA and Hyperexcitability of Skeletal Muscle in Myotonic Dystrophy

In myotonic dystrophy (dystrophia myotonica, DM), expression of RNAs that contain expanded CUG or CCUG repeats is associated with degeneration and repetitive action potentials (myotonia) in skeletal muscle. Using skeletal muscle from a transgenic mouse model of DM, we show that expression of expanded CUG repeats reduces the transmembrane chloride conductance to levels well below those expected to cause myotonia. The expanded CUG repeats trigger aberrant splicing of pre-mRNA for ClC-1, the main chloride channel in muscle, resulting in loss of ClC-1 protein from the surface membrane. We also have identified a similar defect in ClC-1 splicing and expression in two types of human DM. We propose that a transdominant effect of mutant RNA on RNA processing leads to chloride channelopathy and membrane hyperexcitability in DM.

Randomized, Double-Blind Six-Month Trial of Prednisone in Duchenne's Muscular Dystrophy

We performed a randomized, double-blind, controlled six-month trial of prednisone in 103 boys with Duchennes muscular dystrophy (age, 5 to 15 years). The patients were assigned to one of three regimens: prednisone, 0.75 mg per kilogram of body weight per day (n = 33); prednisone, 1.5 mg per kilogram per day (n = 34); or placebo (n = 36). The groups were initially comparable in all measures of muscle function. Both prednisone groups had significant improvement of similar degree in the summary scores of muscle strength and function. Improvement began as early as one month and peaked by three months. At six months the high-dose prednisone group, as compared with the placebo group, had improvement in the time needed to rise from a supine to a standing position (3.4 vs. 6.2 seconds), to walk 9 m (7.0 vs. 9.7 seconds), and to climb four stairs (4.0 vs. 7.1 seconds), in lifting a weight (2.1 vs. 1.2 kg), and in forced vital capacity (1.7 vs. 1.5 liters) (P less than 0.001 for all comparisons). There was an increase in urinary creatinine excretion (261 vs. 190 mg per 24 hours), which suggested an increase in total muscle mass. However, the prednisone-treated patients who had required long-leg braces (n = 5) or wheelchairs (n = 11) continued to require them. The most frequent side effects were weight gain, cushingoid appearance, and excessive hair growth. We conclude from this six-month study that prednisone improves the strength and function of patients with Duchennes muscular dystrophy. However, further research is required to identify the mechanisms responsible for these improvements and to determine whether prolonged treatment with corticosteroids may be warranted despite their side effects.

Duchenne muscular dystrophy: Patterns of clinical progression and effects of supportive therapy

Two-hundred eighty-three boys with Duchenne dystrophy and 10 with Becker dystrophy have been followed for up to 10 years in a protocol that accurately measured their function, strength, contractures, and back curvature. Clinical heterogeneity is noted. Patients whose muscles were stronger were more likely to die from a cardiomyopathy. Weaker patients died from respiratory failure. A series of milestones is defined, which is of use in following the illness in an individual patient. This approach permits a scoring system that allows the severity of the disease to be defined in an individual boy. Evaluation of physical therapy and surgical intervention shows that night splints and scoliosis surgery are effective forms of treatment.

Practice Parameter: Corticosteroid treatment of Duchenne dystrophy Report of the Quality Standards Subcommittee of the American Academy of Neurology and the Practice Committee of the Child Neurology Society

Background: The Quality Standards Subcommittee of the American Academy of Neurology and the Practice Committee of the Child Neurology Society develop practice parameters as strategies for patient management based on analysis of evidence. Objective: To review available evidence on corticosteroid treatment of boys with Duchenne dystrophy. Methods: Relevant literature was reviewed, abstracted, and classified. Recommendations were based on a four-tiered scheme of evidence classification, and areas for future research are defined. Results: Seven class I studies and numerous less rigorous trials all demonstrated that corticosteroid treatment for 6 months with prednisone (0.75 or 1.5 mg/kg/day) increased muscle strength, performance, and pulmonary function and significantly slowed the progression of weakness. Two class I trials examined the effect of lower dosage of prednisone (0.30 and 0.35 mg/kg/day), demonstrated lesser but similar benefits, and showed a lower frequency of side effects (e.g., weight gain). The only significant side effects in all class I trials were weight gain and development of a cushingoid facial appearance. One longer-term trial of daily prednisone (0.3 to 0.7 mg/kg/day), a class III study, showed prolongation of functional ability and slower progression of weakness in patients during 3 years of treatment. One class IV, open trial of alternate-day prednisone (2 mg/kg for 2 months, then two-thirds dose every other day) extended ambulation by approximately 2 years in treated compared with untreated patients. Deflazacort, a corticosteroid similar in structure to prednisone, produced similar improvement in muscle strength and function with a similar side effect profile. Conclusions: Prednisone has been demonstrated to have a beneficial effect on muscle strength and function in boys with Duchenne dystrophy and should be offered (at a dose of 0.75 mg/kg/day) as treatment. If side effects require a decrease in prednisone, tapering to dosages as low as 0.3 mg/kg/day gives less robust but significant improvement. Deflazacort (0.9 mg/kg/day) can also be used for the treatment of Duchenne dystrophy in countries in which it is available. Benefits and side effects of corticosteroid therapy need to be monitored. The offer of treatment with corticosteroids should include a balanced discussion of potential risks.

Distribution of insulin receptor-like immunoreactivity in the rat forebrain

Previous studies have suggested that insulin may play a role in the hormonal regulation of neurotransmitter metabolisms within the central nervous system. In order to provide additional information to support this hypothesis, we examined the distribution of insulin receptors within the forebrain of adult male rats. Insulin receptors were localized by immunocytochemistry, using an antibody directed against the carboxy-terminus of the beta-subunit of the insulin receptor. The antibody specificity was tested by immunoprecipitation of brain insulin receptors with antiserum and the purity of the receptor-antibody preparation was determined using hormone binding-assays with radiolabeled insulin and insulin-like growth factor-l. Insulin receptor-like immunoreactivity was found in a widespread, but selective, distribution on neurons throughout the rat forebrain. Double-labeling with glial fibrillary acidic protein did not demonstrate any detectable insulin receptor-like immunoreactivity on glial cells. Areas with the highest density of insulin receptor-like immunoreactivity were found in the olfactory bulbs, hypothalamus and median eminence, medial habenula, subthalamic nucleus, subfornical organ, CA 1/2 pyramidal cell layer of the hippocampus and piriform cortex. Double-staining of hypothalamic sections with somatostatin and vasopressin antisera revealed insulin receptor-like immunoreactivity on a subpopulation of somatostatin neurons in the periventricular region and on vasopressin neurons in the supraoptic nucleus. A moderately dense insulin receptor-like immunoreactivity was observed in layers II-IV of cerebral cortex, medial amygdala, reticular thalamic nucleus, zona incerta, and preoptic and septal regions, whereas a low density of insulin receptor-like immunoreactive neurons was found in basolateral amygdala and most thalamic regions. The basal ganglia and most parts of the thalamus were almost devoid of insulin receptor-like immunoreactivity. Our findings provide morphological support for a direct action of insulin on selected regions of the rat forebrain and suggest that the insulin receptor may modulate synaptic transmission or the release of neurotransmitters and peptide hormones in the CNS.

Proximal myotonic myopathy: A new dominant disorder with myotonia, muscle weakness, and cataracts

We describe three families with a dominantly inherited disorder. Affected individuals have myotonia, proximal muscle weakness, and cataracts. There was no abnormal CTG repeat expansion of the myotonic dystrophy (DM) gene in DNA from blood and muscle. The structure of the three families permitted linkage analysis, and there is no linkage to the gene loci for DM or to the loci for the muscle chloride channel disorders or muscle sodium channel disorders. The collection of symptoms in these three families seems to represent a new disorder.

Long‐term benefit from prednisone therapy in Duchenne muscular dystrophy

Two successive, 6-month, randomized, double-blind, controlled trials of prednisone showed that 0.75 ing/kg/d was the optimal dose to improve strength in boys with Duchenne muscular dystrophy (DMD). We attempted to maintain 93 boys on that dose for an additional 2 years. During the 3 years of observation, the decline in average muscle strength scores of all boys taking prednisone was 0.072 units/yr, as compared with an expected decline of 0.341 units/yr from natural history controls. The occurrence of side effects in some boys prevented maintenance of the full dose, which may have lessened the response. At the time of last visit, dosages ranged from 0.15 mg/kg to 0.75 mg/kg. In addition to maintaining their strength, several of the boys actually improved their performance in lifting kilogram weights and in some timed function tests. Treatment of DMD with prednisone significantly slows the progression of weakness and loss of function for at least 3 years.

Executive dysfunction and avoidant personality trait in myotonic dystrophy type 1 (DM-1) and in proximal myotonic myopathy (PROMM/DM-2)

A previous study in proximal myotonic myopathy (PROMM/DM-2) and myotonic dystrophy type 1 (DM-1) using brain positron emission tomography demonstrated a reduced cerebral blood flow in the frontal and temporal regions associated with cognitive impairment. The objective was to investigate further cognitive and behavioural aspects in a new series of patients with DM-1 and PROMM/DM-2. Nineteen patients with genetically determined PROMM/DM-2 and 21 patients with moderately severe DM-1 underwent neuropsychological testing and neuropsychiatric interviews. DM-1 and PROMM/DM-2 patients had significantly lower scores on tests of frontal lobe function compared to controls. Neuropsychiatric interviews demonstrated an avoidant trait personality disorder in both patient groups. Brain single photon emission computed tomography showed frontal and parieto-occipital hypoperfusion. The results suggest that there is a specific cognitive and behavioural profile in PROMM/DM-2 and in DM-1, and that this profile is associated with hypoperfusion in frontal and parieto-occipital regions of the brain.

Duchenne dystrophy: randomized, controlled trial of prednisone (18 months) and azathioprine (12 months)

Prednisone has been shown to improve strength in Duchenne dystrophy. Azathioprine often benefits corticosteroid-responsive diseases and can reduce the dose of prednisone needed. The present study reports a randomized, controlled trial of prednisone and azathioprine designed to assess the longer-term effects of prednisone and to determine whether azathioprine alone, or in combination with prednisone, improves strength. Ninety-nine boys (aged five to 15 years) with Duchenne dystrophy were randomized to one of three groups: (I) placebo; (II) prednisone 0.3 mg/kg/d; or (III) prednisone 0.75 mg/kg/d. After 6 months, azathioprine 2 to 2.5 mg/kg/d was added in groups I and II and placebo added in group III. The study showed that the beneficial effect of prednisone (0.75 mg/kg/d) is maintained for at least 18 months and is associated with a 36% increase in muscle mass. There was weight gain, growth retardation, and other side effects. Azathioprine did not have a beneficial effect. This study suggests that prednisones beneficial effect is not due to immunosuppression.