The ClC-1 chloride channel inhibitor NMD670 improves skeletal muscle function in rat models and patients with myasthenia gravis

Myasthenia gravis (MG) is a neuromuscular disease that results in compromised transmission of electrical signals at the neuromuscular junction (NMJ) from motor neurons to skeletal muscle fibers. As a result, patients with MG have reduced skeletal muscle function and present with symptoms of severe muscle weakness and fatigue. ClC-1 is a skeletal muscle specific chloride (Cl-) ion channel that plays important roles in regulating neuromuscular transmission and muscle fiber excitability during intense exercise. Here, we show that partial inhibition of ClC-1 with an orally bioavailable small molecule (NMD670) can restore muscle function in rat models of MG and in patients with MG. In severely affected MG rats, ClC-1 inhibition enhanced neuromuscular transmission, restored muscle function, and improved mobility after both single and prolonged administrations of NMD670. On this basis, NMD670 was progressed through nonclinical safety pharmacology and toxicology studies, leading to approval for testing in clinical studies. After successfully completing phase 1 single ascending dose in healthy volunteers, NMD670 was tested in patients with MG in a randomized, placebo-controlled, single-dose, three-way crossover clinical trial. The clinical trial evaluated safety, pharmacokinetics, and pharmacodynamics of NMD670 in 12 patients with mild MG. NMD670 had a favorable safety profile and led to clinically relevant improvements in the quantitative myasthenia gravis (QMG) total score. This translational study spanning from single muscle fiber recordings to patients provides proof of mechanism for ClC-1 inhibition as a potential therapeutic approach in MG and supports further development of NMD670.

Biological aging of CNS-resident cells alters the clinical course and immunopathology of autoimmune demyelinating disease

Biological aging is the strongest factor associated with the clinical phenotype of multiple sclerosis (MS). Relapsing-remitting MS typically presents in the third or fourth decade, whereas the mean age of presentation of progressive MS (PMS) is 45 years old. Here, we show that experimental autoimmune encephalomyelitis (EAE), induced by the adoptive transfer of encephalitogenic CD4⁺ Th17 cells, was more severe, and less likely to remit, in middle-aged compared with young adult mice. Donor T cells and neutrophils were more abundant, while B cells were relatively sparse, in CNS infiltrates of the older mice. Experiments with reciprocal bone marrow chimeras demonstrated that radio-resistant, nonhematopoietic cells played a dominant role in shaping age-dependent features of the neuroinflammatory response, as well as the clinical course, during EAE. Reminiscent of PMS, EAE in middle-aged adoptive transfer recipients was characterized by widespread microglial activation. Microglia from older mice expressed a distinctive transcriptomic profile suggestive of enhanced chemokine synthesis and antigen presentation. Collectively, our findings suggest that drugs that suppress microglial activation, and acquisition or expression of aging-associated properties, may be beneficial in the treatment of progressive forms of inflammatory demyelinating disease.

An uncommon cause of headache and dizziness after cruise travel: case report of Mal De Debarquement syndrome

Mal de Debarquement syndrome (MdDS), also known as disembarkment syndrome, is a benign neurological condition characterized by a feeling of rocking, bobbing, or swaying, usually presenting after an individual has been exposed to passive motion as from being on a cruise, long drive, turbulent air travel, or train. Clinical awareness about this condition is limited, as is research; thus, many patients go undiagnosed. In this case report, the authors describe a case of a severe headache as a major presenting symptom of MdDS in a 46-year-old woman who eventually attained full resolution of symptoms. This report aims to highlight this unique presentation and make practitioners more aware of the cardinal clinical features, to assist in prompt diagnosis of this disorder.

Fingerstick Precision and Total Error of a Point-of-Care HbA1c Test

BACKGROUND

Point-of-care (POC) HbA1c tests hold the promise of reducing the rates of undiagnosed diabetes, provided they exhibit acceptable analytical performance. The precision and total error of the POC (Afinion™ HbA1c Dx) test were investigated using whole blood samples obtained by fingerstick and venipuncture.

METHODS

Fingerstick samples spanning the assay range were collected from 61 subjects at three representative POC sites. At each site, six fingerstick samples were obtained from each subject and tested on the POC test across two (Afinion AS100) instruments. Repeatability, between-operator, and between-instrument components of variance were calculated using analysis of variance (ANOVA). Four venous samples (low, threshold, medium, and high HbA1c) were measured in duplicate across three instruments using three reagent lots, twice per day over 20-days. Repeatability, between-run, between-day, between-lot, and between-instrument components of variance were calculated. These fingerstick and venous blood results, combined with estimates of imprecision and bias from a prior investigation, allowed for the calculation of the total coefficient of variation (CV) and total error of the POC test using fingerstick and venous whole blood samples.

RESULTS

The total imprecision ranged from 1.30% to 2.03% CV using fingerstick samples and from 1.31% to 1.64% CV using venous samples. The total error ranged from 2.87% to 4.75% using fingerstick samples and from 2.93% to 3.80% using venous samples.

CONCLUSIONS

The POC test evaluated here is precise across its measuring range using both fingerstick and venous whole blood. The calculated total error of the test is well under the accepted quality requirement of ≤6%.

Accuracy and Precision of a Point-of-Care HbA1c Test

BACKGROUND

Point-of-care (POC) hemoglobin A1c (HbA1c) testing has advantages over laboratory testing, but some questions have remained regarding the accuracy and precision of these methods. The accuracy and the precision of the POC Afinion™ HbA1c Dx test were investigated.

METHODS

Samples spanning the assay range were collected from prospectively enrolled subjects at three clinical sites. The accuracy of the POC test using fingerstick and venous whole blood samples was estimated via correlation and bias with respect to values obtained by an NGSP secondary reference laboratory (SRL). The precision of the POC test using fingerstick samples was estimated from duplicate results by calculating the coefficient of variation (CV) and standard deviation (SD), and separated into its components using analysis of variance (ANOVA). The precision of the POC test using venous blood was evaluated from samples run in four replicates on each of three test cartridge lots, twice per day for 10 consecutive days. The SD and CV by study site and overall were calculated.

RESULTS

Across the assay range, POC test results from fingerstick and venous whole blood samples were highly correlated with results from the NGSP SRL (r = .99). The mean bias was -0.021% HbA1c (-0.346% relative) using fingerstick samples and -0.005% HbA1c (-0.093% relative) using venous samples. Imprecision ranged from 0.62% to 1.93% CV for fingerstick samples and 1.11% to 1.69% CV for venous samples.

CONCLUSIONS

The results indicate that the POC test evaluated here is accurate and precise using both fingerstick and venous whole blood.

Early-onset aging and mitochondrial defects associated with loss of histone acetyltransferase 1 (Hat1)

Histone acetyltransferase 1 (Hat1) is responsible for the acetylation of newly synthesized histone H4 on lysines 5 and 12 during the process of chromatin assembly. To understand the broader biological role of Hat1, we have generated a conditional mouse knockout model of this enzyme. We previously reported that Hat1 is required for viability and important for mammalian development and genome stability. In this study, we show that haploinsufficiency of Hat1 results in a significant decrease in lifespan. Defects observed in Hat1^+/− mice are consistent with an early‐onset aging phenotype. These include lordokyphosis (hunchback), muscle atrophy, minor growth retardation, reduced subcutaneous fat, cancer, and paralysis. In addition, the expression of Hat1 is linked to the normal aging process as Hat1 mRNA and protein becomes undetectable in many tissues in old mice. At the cellular level, fibroblasts from Hat1 haploinsufficient embryos undergo early senescence and accumulate high levels of p21. Hat1^+/− mouse embryonic fibroblasts (MEFs) display modest increases in endogenous DNA damage but have significantly higher levels of reactive oxygen species (ROS). Consistently, further studies show that Hat1^−/− MEFs exhibit mitochondrial defects suggesting a critical role for Hat1 in mitochondrial function. Taken together, these data show that loss of Hat1 induces multiple hallmarks of early‐onset aging.

Hyperexcitability precedes motoneuron loss in the Smn2B/- mouse model of spinal muscular atrophy

Spinal motoneuron dysfunction and loss are pathological hallmarks of the neuromuscular disease spinal muscular atrophy (SMA). Changes in motoneuron physiological function precede cell death, but how these alterations vary with disease severity and motoneuron maturational state is unknown. To address this question, we assessed the electrophysiology and morphology of spinal motoneurons of presymptomatic Smn^2B/- mice older than 1 wk of age and tracked the timing of motor unit loss in this model using motor unit number estimation (MUNE). In contrast to other commonly used SMA mouse models, Smn^2B/- mice exhibit more typical postnatal development until postnatal day (P)11 or 12 and have longer survival (~3 wk of age). We demonstrate that Smn^2B/- motoneuron hyperexcitability, marked by hyperpolarization of the threshold voltage for action potential firing, was present at P9-10 and preceded the loss of motor units. Using MUNE studies, we determined that motor unit loss in this mouse model occurred 2 wk after birth. Smn^2B/- motoneurons were also larger in size, which may reflect compensatory changes taking place during postnatal development. This work suggests that motoneuron hyperexcitability, marked by a reduced threshold for action potential firing, is a pathological change preceding motoneuron loss that is common to multiple models of severe SMA with different motoneuron maturational states. Our results indicate voltage-gated sodium channel activity may be altered in the disease process.NEW & NOTEWORTHY Changes in spinal motoneuron physiologic function precede cell death in spinal muscular atrophy (SMA), but how they vary with maturational state and disease severity remains unknown. This study characterized motoneuron and neuromuscular electrophysiology from the Smn^2B/- model of SMA. Motoneurons were hyperexcitable at postnatal day (P)9-10, and specific electrophysiological changes in Smn^2B/- motoneurons preceded functional motor unit loss at P14, as determined by motor unit number estimation studies.

Myocardial fibrosis by late gadolinium enhancement cardiovascular magnetic resonance in myotonic muscular dystrophy type 1: highly prevalent but not associated with surface conduction abnormality

BACKGROUND

Conduction disease and arrhythmias represent a major cause of mortality in myotonic muscular dystrophy type 1 (MMD1). Permanent pacemaker (PPM) implantation is the cornerstone of therapy to reduce cardiovascular mortality in MMD1. Cardiovascular magnetic resonance (CMR) studies demonstrate a high prevalence of myocardial fibrosis in MMD1, however the association between CMR myocardial fibrosis with late gadolinium enhancement (CMR-LGE) and surface conduction abnormality is not well established in MMD1. We investigated whether myocardial fibrosis by CMR-LGE is associated with surface conduction abnormalities meeting criteria for PPM implantation according to current guidelines in a cohort of patients with genetically confirmed MMD1.

METHODS

Patients with genetically confirmed MMD1 were retrospectively evaluated. 12-lead electrocardiography (ECG) performed within 6 months of CMR was necessary for inclusion. The severity and extent of MMD1 was quantified using a validated Muscular Impairment Rating Scale (MIRS). Based on current guidelines for device-based therapy of cardiac rhythm abnormalities, we defined surface conduction abnormality as the presence of ECG alterations meeting criteria for PPM implant (class I or II indications): PR interval > 200 ms (type I atrioventricular (AV) block) and/or mono or bifascicular block (QRS > 120 ms), or evidence of advanced AV block. Balanced steady-state free precession sequences (bSSFP) were used for assessment of left ventricular (LV) volumes and ejection fraction. MOdified Look-Locker Inversion Recovery (MOLLI) acquisition schemes were used to acquire T1 maps. Patients' charts were reviewed up to 12 months post-CMR for occurrence of PPM implantation.

RESULTS

Fifty-two patients (38% male, 41 ± 14 years) were included. Overall, 31 (60%) patients had a surface conduction abnormality and 22 (42%) demonstrated midwall myocardial fibrosis by CMR-LGE. After a median of 57 days from CMR exam, 15 patients (29%) underwent PPM implantation. Subjects with vs. without surface conduction abnormality had significantly longer disease length (15.5 vs. 7.8 years, p = 0.015) and higher disease severity on the MIRS scale (p = 0.041). High prevalence of myocardial fibrosis by CMR-LGE was detected in subjects with and without surface conduction abnormality with no significant difference between the two cohorts (42% vs. 43%, p = 0.999). By multivariate logistic regression analysis, disease length was the only independent variable associated with surface conduction abnormality (OR 1.071, 95%CI 1.003-1.144, p = 0.040); while CMR-LGE was not associated with conduction abnormality (ρ = - 0.009, p = 0.949).

CONCLUSIONS

Myocardial fibrosis by CMR-LGE is highly prevalent in MMD1 but not related to surface conduction abnormality meeting current guideline criteria for PPM implantation .

A comparison of three electrophysiological methods for the assessment of disease status in a mild spinal muscular atrophy mouse model

Objectives

There is a need for better, noninvasive quantitative biomarkers for assessing the rate of progression and possible response to therapy in spinal muscular atrophy (SMA). In this study, we compared three electrophysiological measures: compound muscle action potential (CMAP) amplitude, motor unit number estimate (MUNE), and electrical impedance myography (EIM) 50 kHz phase values in a mild mouse model of spinal muscular atrophy, the Smn1^c/c mouse.

Methods

Smn1^c/c mice (N = 11) and wild type (WT) animals (−/−, N = 13) were measured on average triweekly until approximately 1 year of age. Measurements included CMAP, EIM, and MUNE of the gastrocnemius muscle as well as weight and front paw grip strength. At the time of sacrifice at one year, additional analyses were performed on the animals including serum survival motor neuron (SMN) protein levels and muscle fiber size.

Results

Both EIM 50 kHz phase and CMAP showed strong differences between WT and SMA animals (repeated measures 2-way ANOVA, P<0.0001 for both) whereas MUNE did not. Both body weight and EIM showed differences in the trajectory over time (p<0.001 and p = 0.005, respectively). At the time of sacrifice at one year, EIM values correlated to motor neuron counts in the spinal cord and SMN levels across both groups of animals (r = 0.41, p = 0.047 and r = 0.57, p  = 0.003, respectively), while CMAP did not. Motor neuron number in Smn1^c/c mice was not significantly reduced compared to WT animals.

Conclusions

EIM appears sensitive to muscle status in this mild animal model of SMA. The lack of a reduction in MUNE or motor neuron number but reduced EIM and CMAP values support that much of the pathology in these animals is distal to the cell body, likely at the neuromuscular junction or the muscle itself.

Comparative effectiveness of antinociceptive gene therapies in animal models of diabetic neuropathic pain

Peripheral neuropathic pain is one of the most common and debilitating complications of diabetes. Several genes have been shown to be effective in reducing neuropathic pain in animal models of diabetes after transfer to the dorsal root ganglion using replication-defective herpes simplex virus (HSV)1-based vectors, yet there has never been a comparative analysis of their efficacy. We compared four different HSV1-based vectors engineered to produce one of two opioid receptor agonists (enkephalin or endomorphin), or one of two isoforms of glutamic acid decarboxylase (GAD65 or GAD67), alone and in combination, in the streptozotocin-induced diabetic rat and mouse models. Our results indicate that a single subcutaneous hindpaw inoculation of vectors expressing GAD65 or GAD67 reduced diabetes-induced mechanical allodynia to a degree that was greater than daily injections of gabapentin in rats. Diabetic mice that developed thermal hyperalgesia also responded to GAD65 or endomorphin gene delivery. The results suggest that either GAD65 or GAD67 vectors are the most effective in the treatment of diabetic pain. The vector combinations, GAD67+endomorphin, GAD67+enkephalin or endomorphin+enkephalin also produced a significant antinociceptive effect but the combination did not appear to be superior to single gene treatment. These findings provide further justification for the clinical development of antinociceptive gene therapies for the treatment of diabetic peripheral neuropathies.

The WAP four-disulfide core domain protein HE4: a novel biomarker for heart failure

OBJECTIVES

This study investigated clinical determinants and added prognostic value of HE4 as a biomarker not previously described in heart failure (HF).

BACKGROUND

Identification of plasma biomarkers that help to risk stratify HF patients may help to improve treatment.

METHODS

Plasma HE4 levels were determined in 567 participants of the COACH (Coordinating study evaluating outcomes of Advising and Counseling in Heart failure). Patients had been hospitalized for HF and were followed for 18 months. The primary endpoint of this study was a composite of all-cause mortality and HF hospitalization.

RESULTS

HE4 showed a strong correlation with HF severity, according to New York Heart Association functional class and brain natriuretic peptide (BNP) levels (p < 0.001). HE4 also showed a positive correlation with GDF15 (p < 0.001) and, in addition, correlated with kidney function (estimated glomerular filtration rate [eGFR]; p < 0.001). Cox regression analysis revealed that a doubling of HE4 levels was associated with a hazard ratio (HR) of 1.73 (95% confidence interval [CI]: 1.53 to 1.95) for the primary outcome (p < 0.001). After correction for age, gender, BNP, and eGFR, the HR was 1.46 (95% CI: 1.23 to 1.72; p < 0.001), and after additional adjustment for GDF15, the HR lowered to 1.30 (95% CI: 1.07 to 1.59; p = 0.009). The area under the curve in the receiver-operating characteristic curve analysis increased from 0.727 to 0.752 when HE4 was included in the clinical evaluation (p = 0.051). The integrated discrimination improvement and net reclassification index for reclassification showed significant improvements when HE4 was added to the clinical model, and this remained significant after BNP inclusion in the model.

CONCLUSIONS

HE4 plasma levels are correlated with markers of HF severity, show prognostic value, and can improve risk assessment in HF.

Mutant small heat shock protein B3 causes motor neuropathy: utility of a candidate gene approach

OBJECTIVE

Idiopathic peripheral neuropathy is common and likely due to genetic factors that are not detectable using standard linkage analysis. We initiated a candidate gene approach to study the genetic influence of the small heat shock protein (sHSP) gene family on an axonal motor and motor/sensory neuropathy patient population.

METHODS

The promoter region and all exonic and intronic sequences of the 10 sHSP genes (HSPB1-HSPB10) were screened in a cohort of presumed nonacquired, axonal motor and motor/sensory neuropathy patients seen at the Ohio State University Neuromuscular Clinic.

RESULTS

A missense mutation in the gene encoding small heat shock protein B3 (HSPB3, also called HSP27, protein 3) was discovered in 2 siblings with an asymmetric axonal motor neuropathy. Electrophysiologic studies revealed an axonal, predominantly motor, length-dependent neuropathy. The mutation, HSPB3(R7S), is located in the N-terminal domain and involves the loss of a conserved arginine.

CONCLUSIONS

The discovery of an HSPB3 mutation associated with an axonal motor neuropathy using a candidate gene approach supports the notion that the small heat shock protein gene family coordinately plays an important role in motor neuron viability.

Small molecule affinity fingerprinting. A tool for enzyme family subclassification, target identification, and inhibitor design

Classifying proteins into functionally distinct families based only on primary sequence information remains a difficult task. We describe here a method to generate a large data set of small molecule affinity fingerprints for a group of closely related enzymes, the papain family of cysteine proteases. Binding data was generated for a library of inhibitors based on the ability of each compound to block active-site labeling of the target proteases by a covalent activity based probe (ABP). Clustering algorithms were used to automatically classify a reference group of proteases into subfamilies based on their small molecule affinity fingerprints. This approach was also used to identify cysteine protease targets modified by the ABP in complex proteomes by direct comparison of target affinity fingerprints with those of the reference library of proteases. Finally, experimental data were used to guide the development of a computational method that predicts small molecule inhibitors based on reported crystal structures. This method could ultimately be used with large enzyme families to aid in the design of selective inhibitors of targets based on limited structural/function information.

The bowel management tube: an effective means for controlling fecal incontinence

Regular bowel washout enemas have been used as a method of management of fecal incontinence. The effective administration of a washout enema to a child with weak anal sphincters is often a problem. Using a new silastic balloon-tipped enema catheter (bowel management tube [BMT]) of our design, we prospectively studied its effectiveness in a group of children who suffered fecal incontinence. Thirty-one children were studied over a 1-year period. Their diagnoses included meningomyelocele (19), postoperative Hirschsprung's disease or imperforate anus (10), and other (2). Before and after starting the BMT enema system, clinical assessment and a diary, which graded the degree of fecal incontinence and satisfaction with the system, were completed. Five patients failed to benefit because of noncompliance (3) or balloon extrusion (2). Three more patients discontinued the use of the tube system. Twenty-three patients achieved successful results with this system as evidenced by a significant amelioration in their fecal incontinence and their unwillingness to give up the use of the BMT. We conclude that the use of a regular washout enemas with BMT can be an effective method for control of fecal incontinence in children.

The effect of early weight-bearing on the stability of femoral neck fractures treated with Knowles pins

I compared the effects of early weight-bearing on the stability of femoral neck fractures following Knowles-pin fixation with data on a similar group of patients who were studied ten years previously, in which weight-bearing had been delayed until radiographic evidence of fracture-healing was apparent. The results concerning stability were essentially comparable, indicating that early weight-bearing did not adversely affect the stability of a properly reduced and pinned displaced fracture of the femoral neck. Factors that did adversely affect stability following fixation with Knowles pins included the degree of initial displacement of the fracture (Garden Type IV), failure to adequately reduce or fix the fracture, and severe demineralizing bone disease as measured in an iliac-crest biopsy specimen obtained at the time of surgery.

Untreated congenital hip dysplasia in the Navajo

Congenital hip dysplasia without dislocation was identified in 18 Navajo Indian children. Treatment had been declined and the children presented a unique opportunity to observe the natural course of hip dysplasia. In a follow-up period of three to 19 years (average, 11.2 years), none of the dysplastic hips were observed to progress to dislocation. In 15 of the children with dysplastic hips, the condition became roentgenographically normal in the course of normal growth and development. The other three children continued to show roentgenographic signs of hip dysplasia.

Simultaneous fractures of both femoral necks: review of the literature and report of two cases

Simultaneous fracture of both femoral necks is extremely rare. Delay in diagnosis may be avoided by noting the association of these fractures with two conditions: violent skeletal trauma and major motor seizures. Treatment of two patients is reported in addition to a review of seven cases previously reported. The author's experience indicates that accurate reduction and percutaneous Knowles pinning provide adequate fixation and permit early weight-bearing.

Haemophilic arthropathy in the joints of the hands and feet

Radiographs of the hands and feet of 72 haemophilic patients were reviewed for peripheral joint involvement. Fifty patients or 69% had changes in the small joints of their hands and/or feet with a total of 160 abnormal joints. In the hands the metacarpo-phalangeal joints were predominantly involved (42 of 50 joints), and in the feet, the metatarso-phalangeal joints (68 of 110 abnormal joints), as well as the posterior subtalar joint (36 of 110 joints). Röntgen abnormalities were characterized by irregularity and/or flattening of the articular cortices. The involvement of the small peripheral joint in haemophilic patients has not been a primary consideration in previous clinical and radiographic studies because of the more common and more debilitating changes in the large joints. The recognition of involvement of the small joints is described to avoid misinterpretation of the röntgen findings and to appreciate the incidence of involvement, especially with the increased availability of replacement therapy.

Osteoid osteomas in siblings. Case reports

Osteoid osteomas occurred in siblings with a nearly simultaneous onset of symptoms, and with some unusual neoplastic characteristics. The combination of simultaneous occurrence and neoplastic change suggests that a viral or other infectious etiology is possible.

Fractures in thalassemia

Fractures occur frequently in patients with homozygous beta-thalassemia. A study was made of the fractures noted in a group of patients who were followed at the Thalassemia Clinic at The New York Hospital-Cornell Medical Center. Results indicate that these patients often sustain fractures which are multiple and which frequently heal with resultant deformities.

PRIMARY AND SECONDARY DISLOCATION OF THE SCAPHOID BONE

1. Nine cases of disturbance of the relationship between the scaphoid and the radius and between the scaphoid and the lunate bones are described.

2. Persistent dislocation of the scaphoid bone may follow reduction of perilunar dislocations or of other dislocations of the proximal row of the carpus. It may be obvious, as in waist-deep dislocation, or may be solely a rotational dislocation which may be difficult to diagnose.

3. Uncorrected rotational dislocation of the scaphoid bone caused significant disability in six of seven cases.

4. Aids to the diagnosis of this condition are described and a vigorous approach to the problem of correction is advocated.

5. The experience of other workers in this field is reviewed and discussed.