Duchenne Muscular Dystrophy Subjects Research Articles

The Association Between Physical Activity/Heart Rate Variability Data Obtained Using a Wearable Device and Timed Motor Functional Tests in Patients with Duchenne Muscular Dystrophy: A Pilot Study.

Duchenne muscular dystrophy (DMD) is a devastating X-linked muscle disease. Clinical evaluation of DMD uses patient-intensive motor function tests, and the recent development of wearable devices allows the collection of a variety of biometric information, including physical activity. In this study, we examined differences in physical activity and heart rate variability (HRV) between patients with DMD and healthy subjects using a wearable device, and investigated any association between these parameters and motor function in patients with DMD. Participants were 7 patients with DMD and 8 healthy males, whose physical activity and HRV were provided by a wearable device. These data were used to investigate the relationship between both physical activity and HRV parameters and timed motor functional tests [Time to stand from supine, 10-meter walking time (10MWT), North Star Ambulatory Assessment (NSAA), and 6-minute walking test (6MWT)] in patients with DMD. Results of 24-hours physical activity, fat burning, total number of steps and active distance, average step rate, average exercise intensity during walking, exercise, degree of forward lean during walking, maximum heart rate, normalized low frequency power (LF norm), and maximum exercise intensity in patients with DMD were lower than those in control subjects. Physical activity and HRV parameters did not correlate with the time to stand from supine. The 10MWT positively correlated with average heart rate, while NSAA negatively correlated with average heart rate, total frequency power (TF), and very low frequency power (VLF) during arousal. The 6MWT negatively correlated with ratio LF/high frequency power (HF). Physical activity and HRV indices that differ from those of normal children and that correlate with motor function assessment may serve as digital biomarkers.

Rate of Change in Cardiac Magnetic Resonance Imaging Measures Is Associated With Death in Duchenne Muscular Dystrophy.

Cardiovascular disease is the leading cause of death among patients with Duchenne muscular dystrophy (DMD). Identifying patients at risk of early death could allow for increased monitoring and more intensive therapy. Measures that associate with death could serve as surrogate outcomes in clinical trials. Duchenne muscular dystrophy subjects prospectively enrolled in observational studies were included. Models using generalized least squares were used to assess the difference of cardiac magnetic resonance measurements between deceased and alive subjects. A total of 63 participants underwent multiple cardiac magnetic resonance imaging and were included in the analyses. Twelve subjects (19.1%) died over a median follow-up of 5 years (interquartile range, 3.1-7.0). Rate of decline in left ventricular ejection fraction was faster in deceased than alive subjects (P<0.0001). Rate of increase in indexed left ventricular end-diastolic (P=0.0132) and systolic (P<0.0001) volumes were higher in deceased subjects. Faster worsening in midcircumferential strain was seen in deceased subjects (P=0.049) while no difference in global circumferential strain was seen. The rate of increase in late gadolinium enhancement, base T1, and mid T1 did not differ between groups. Duchenne muscular dystrophy death is associated with the rate of change in left ventricular ejection fraction, midcircumferential strain, and ventricular volumes. Aggressive medical therapy to decrease the rate of progression may improve the mortality rate in this population. A decrease in the rate of progression may serve as a valid surrogate outcome for therapeutic trials.

Population longitudinal analysis of Gait Profile Score and North Star Ambulatory Assessment in children with Duchenne muscular dystrophy.

Duchenne muscular dystrophy (DMD) is a rare X-linked recessive disorder characterized by loss-of-function mutations in the gene encoding dystrophin. These mutations lead to progressive functional deterioration including muscle weakness, respiratory insufficiency, and musculoskeletal deformities. Three-dimensional gait analysis (3DGA) has been used as a tool to analyze gait pathology through the quantification of altered joint kinematics, kinetics, and muscle activity patterns. Among 3DGA indices, the Gait Profile Score (GPS), has been used as a sensitive overall measure to detect clinically relevant changes in gait patterns in children with DMD. To enhance our understanding of the clinical translation of 3DGA, we report here the development of a population nonlinear mixed-effect model that jointly describes the disease progression of the 3DGA index, GPS, and the functional endpoint, North Star Ambulatory Assessment (NSAA). The final model consists of a quadratic structure for GPS progression and a linear structure for GPS-NSAA correlation. Our model was able to capture the improvement in function in GPS and NSAA in younger subjects, as well as the decline of function in older subjects. Furthermore, the model predicted NSAA (CFB) at 1 year reasonably well for DMD subjects ≤7 years old at baseline. The model tended to slightly underpredict the decline in NSAA after 1 year for those >7 years old at baseline, but the prediction summary statistics were well maintained within the standard deviation of observed data. Quantitative models such as this may help answer clinically relevant questions to facilitate the development of novel therapies in DMD.

Electrocardiographic and Autonomic Nervous System Changes after Changes in the Posture of Children and Adolescents with Duchenne Muscular Dystrophy.

Duchenne Muscular Dystrophy (DMD) is a rare inherited neuromuscular disease. At first, cardiac involvement may be asymptomatic. Therefore, assessing patients using non-invasive methods can help detect any changes. Analyze the electrocardiogram (ECG) test and heart rate variability (HRV) of the DMD group and compare the information with that of the age-matched control group. A prospective study with 27 male patients with DMD (11.9 years old), who underwent clinical evaluation, ECG, echocardiogram, and Holter monitoring. ECG (200% increase) was assessed by two independent observers. HRV was measured over time (24 h) and in the frequency domain, in the supine and sitting positions. The healthy group consisted of nine patients (11.0 years old). A value of p < 0.05 was considered statistically significant. The mean ejection fraction (EF) was 60% (34 to 71%). The Kappa coefficient for ECG measurements ranged from 0.64 to 1.00. An increase in the R/S ratio in V1 was observed in 25.9% of the subjects, pathological Q wave in 29.6%, and fragmented QRS in 22.2% in inferior/high lateral regions, with a negative correlation with EF (p = 0.006). There was low HRV, without the influence of any variable, including treatment. With the change in position, there was an increase in HR (p = 0.004), but there was no change in HRV. The LF/HF ratio was 2.7 in the DMD group and 0.7 in the control group (p = 0.002). In DMD subjects, prominent R waves in V1 and changes in the inferior/high lateral regions occurred in almost 30% of the cases. Lower vagal tone was observed without the influence of the variables age, ejection fraction, QT dispersion, and treatment. Despite the increase in HR, there was no adequate HRV response to the change in position.

Utilization of Multi‐Parametric Quantitative Magnetic Resonance Imaging in the Early Diagnosis of Duchenne Muscular Dystrophy

BackgroundIt is challenging to diagnose suspected Duchenne muscular dystrophy (DMD) patients in the very early stage of the disease. More evidence is needed to demonstrate the potential of quantitative MRI (qMRI) in precisely identifying patients before substantial physical decline occurs.PurposeTo assess the early diagnostic performance of multi‐parametric qMRI for DMD patients, and the ability to identify DMD patients with mild functional decline.Study TypeProspective.SubjectsOne hundred and forty DMD subjects (9.0 ± 2.2 years old), 24 male healthy controls (HCs) (9.2 ± 2.5 years old).Field Strength/Sequence3.0 T/3‐point Dixon, T1‐mapping, and T2‐mapping.AssessmentqMRI measurements (fat fraction [FF], T1, and T2) of 11 thigh muscles (rectus femoris [RF], vastus lateralis [VL], vastus intermedius, vastus medialis, gracilis, sartorius, adductor longus, adductor magnus [AM], semitendinosus, semimembranosus, biceps femoris long head [BFLH]) on the right side were conducted. NorthStar ambulatory assessment (NSAA) score used to evaluate the function of DMD patients and divided them into three subgroups: mild (76–100 score), moderate (51–75 score), and severe (0–50 score) functional decline.Statistical TestsIndependent t‐test, ANOVA analysis, and receiver operating characteristic (ROC) curves. A P‐value &lt;0.05 was considered statistically significant.ResultsCompared with HCs, FF and T2 were significantly higher in the group of all DMD patients, while T1 was significantly lower. The combination of T1 and T2 in RF, VL, AM, and BFLH achieved excellent area under curve (AUCs) (0.967–0.992) in differentiating five DMD patients without abnormal fat infiltration from HCs. Overall, T2 reached higher AUCs than FF and T1 in distinguishing DMD with mild functional decline from HCs, whereas FF achieved higher AUCs than T1 and T2 in distinguishing three DMD subgroups with functional decline.Data ConclusionMulti‐parametric qMRI demonstrate effective diagnostic capabilities for DMD patients in the early stage of the disease, and can identify patients with mild physical decline.Level of Evidence2Technical EfficacyStage 3

Cognitive abnormalities in Becker muscular dystrophy: a mysterious link between dystrophin deficiency and executive functions

BackgroundDistrophinopathies are a heterogeneous group of neuromuscular disorders due to mutations in the DMD gene. Different isoforms of dystrophin are also expressed in the cerebral cortex and Purkinje cells. Despite cognitive abnormalities in Duchenne muscular dystrophy subjects that have been described in the literature, little is known about a comprehensive cognitive profile in Becker muscular dystrophy patients.AimThe aim of this study was to assess cognitive functioning in Becker muscular dystrophy patients by using an extensive neuropsychological battery. Our hypothesis is that the most impaired functions are the highly intentional and conscious ones, such as working memory functions, which require a prolonged state of cellular activation.MethodsWe performed an extensive neuropsychological assessment on 28 Becker muscular dystrophy patients from 18 to 65 years old. As control subjects, we selected 20 patients with limb-girdle muscular dystrophy, whose clinical picture was similar except for cognitive integrity. The evaluation, although extended to all areas, was focused on prefrontal control skills, with a distinction between inhibitory processes of selective attention and activating processes of working memory.Results and conclusionsSignificant underperformances were found exclusively in the Dual Task and PASAT tests, to demonstrate a selective impairment of working memory that, while not causing intellectual disability, reduces the intellectual potential of patients with Becker muscular dystrophy.

A highly sensitive and quantitative assay for dystrophin protein using Single Molecule Count Technology

Duchenne muscular dystrophy (DMD) is a genetic disease characterized by progressive muscle loss caused by mutations in dystrophin, resulting in decreased dystrophin levels. Dystrophin protein expression is a biomarker used to evaluate treatments that restore patient dystrophin levels. Currently, a semiquantitative assay using western blotting, which normalizes dystrophin expression to that of a control population, is used for regulatory filing. However, the current methods are limited in terms of sensitivity, quantification, and reproducibility. To address this, a highly sensitive and quantitative sandwich immune assay using Single Molecule Counting technology was established, with recombinant dystrophin protein as the calibrator. Capture and detection antibodies were selected to detect full-length dystrophin. Using this optimized assay, dystrophin levels in muscle samples from Myotonic Dystrophy (n = 9) and DMD (n = 8) subjects were 93.2 ± 31.9 (range: 49.4–145.3) and 14.5 ± 6.8 (range: 6.18–22.6) fmol/total protein mg, respectively. The lowest concentration of dystrophin measured in the DMD samples was 5 times higher than that in the lower limit of quantitation, a level not detected by western blotting. These data indicate that this assay accurately and sensitively measured dystrophin protein and may be useful in clinical trials assessing dystrophin restoration therapies.

Beneficial immune-modulatory effects of the N-163 strain of Aureobasidium pullulans-produced 1,3-1,6 Beta glucans in Duchenne muscular dystrophy: Results of an open-label, prospective, exploratory case-control clinical study

BackgroundThis exploratory case-control study is to evaluate the effects of supplementation of Aureobasidium pullulans-N-163 strain produced 1,3–1,− 6 beta glucan in young patients with Duchenne muscular dystrophy (DMD). MethodsTwenty-seven male subjects aged 5–19 years with DMD were included, nine in the control arm and 18 in the treatment arm to receive N-163 beta glucan along with conventional therapies for 45 days. While performing the analysis, steroid usage was also taken into consideration, those not administered steroids (Steroid -ve) (Control, n = 5; treatment, n = 9), those administered steroids (Steroid +ve) (Control, n = 4; treatment, n = 9). ResultsIL-6 showed a significant decrease in the treatment groups, especially the N-163 Steroid -ve group. IL-13 decreased in both treatment groups and TGF-β levels showed a significant decrease in the treatment groups, especially the N-163 Steroid –ve group, (p < 0.05). Dystrophin levels increased by up to 32% in the treatment groups compared to the control. Medical research council (MRC) grading showed slight improvement in muscle strength improvement in 12 out of 18 patients (67%) in the treatment group and four out of nine (44%) subjects in the control group. ConclusionSupplementation with the N-163 beta glucan food supplement produced beneficial effects: a significant decrease in inflammation and fibrosis markers, increase in serum dystrophin and slight improvement in muscle strength in DMD subjects over 45 days, thus making this a potential adjunct treatment for DMD after validation. Trial registrationThe study was registered in Clinical trials registry of India, CTRI/2021/05/033346. Registered on 5th May, 2021.

Duchenne Muscular Dystrophy Fatigue Trajectories.

Children with Duchenne muscular dystrophy (DMD) are at risk of experiencing fatigue that negatively impacts their health-related quality of life (HRQoL). This study aimed to assess the association between fatigue and HRQoL, by examining fatigue trajectories over 48 weeks, and assessing factors associated with these fatigue trajectories. The study sample consisted of 173 DMD subjects enrolled in a 48-week-long phase 2 clinical trial (NCT00592553) for a novel therapeutic who were between the ages of 5 and 16 years. The results of regression modeling show baseline fatigue and baseline HRQoL (R 2 = 0. 54 for child self-report and 0.51 for parent proxy report) and change in fatigue and HRQoL over 48 weeks (R 2 = 0.47 for child self-report and 0.36 for parent proxy report) were significantly associated with one another. Three unique fatigue trajectories using Latent Class Growth Models were identified for child and parent proxy reported fatigue. The risk of being in the high fatigue group as compared to the low fatigue group increased by 24% with each year increase in age and also with decreasing walking distance, as reported by children and parent proxy, respectively. This study identified fatigue trajectories and risk factors associated with greater fatigue, helping clinicians and researchers identify the profile of fatigue in DMD children.

Cardiovascular Measures of All-Cause Mortality in Duchenne Muscular Dystrophy.

Cardiopulmonary failure is the leading cause of death in Duchenne muscular dystrophy (DMD). Research into DMD-specific cardiovascular therapies is ongoing, but there are no Food and Drug Administration-approved cardiac end points. To adequately power a therapeutic trial, appropriate end points must be chosen and the rate of change for these end points reported. The objective of this study was to evaluate rate of change for cardiac magnetic resonance and blood biomarkers and to determine which measures associate with all-cause mortality in DMD. Seventy-eight DMD subjects underwent 211 cardiac magnetic resonance studies analyzed for left ventricular (LV) ejection fraction, indexed LV end diastolic and systolic volumes, circumferential strain, late gadolinium enhancement presence and severity (global severity score, and full width half maximum), native T1 mapping, T2 mapping, and extracellular volume. Blood samples were analyzed for BNP (brain natriuretic peptide), NT-proBNP (N-terminal pro-B-type natriuretic peptide), and troponin I. Cox proportional hazard regression modeling was performed with all-cause mortality as the outcome. Fifteen subjects (19%) died. LV ejection fraction, indexed end systolic volumes, global severity score, and full width half maximum worsened at 1 and 2 years while circumferential strain and indexed LV end diastolic volumes worsened at 2 years. LV ejection fraction, indexed LV end diastolic and systolic volumes, late gadolinium enhancement full width half maximum, and circumferential strain associated with all-cause mortality (P<0.05). NT-proBNP was the only blood biomarker that associated with all-cause mortality (P<0.05). LV ejection fraction, indexed LV volumes, circumferential strain, late gadolinium enhancement full width half maximum, and NT-proBNP are associated with all-cause mortality in DMD and may be the best end points for use in cardiovascular therapeutic trials. We also report change over time of cardiac magnetic resonance and blood biomarkers.

Abstract 14062: Longitudinal Rate of Change for Cardiac Magnetic Resonance Biomarkers Associates With Mortality in Duchenne Muscular Dystrophy

Introduction: Cardiomyopathy (CM) is the leading cause of death in Duchenne muscular dystrophy (DMD). Progression is variable. Multiple DMD-specific CM medications are in development, but there are no established outcome measures for therapeutic trials. Our prior work demonstrated an association between cardiac magnetic resonance (CMR) metrics and mortality, including left ventricular ejection fraction (LVEF), ventricular volumes, and native T1 mapping. The objective of this study was to determine whether longitudinal change in these metrics associates with all-cause mortality. Methods: Seventy-eight DMD subjects underwent 211 comprehensive CMR studies, including LVEF, indexed LV end diastolic and systolic volumes (LVESVi and LVEDVi), and native T1 mapping. To explore how the slope of CMR biomarkers affects mortality, multivariable linear regression was used to model age, mortality, and the interaction term of age and mortality on predictors of interest (LVEF, LVEDVi, LVESVi, native T1). Results: At baseline CMR, the median age was 12.5 years (range 7.4-27.5), and the median LVEF was 57%; 32 subjects (41%) had LVEF &lt; 55%. LGE was present in 54 subjects (71%). Fifteen subjects (19%) died over a median follow up of 5 years (IQR 3.1,7). The slope of LVEF decline differentiated between subjects with and without mortality (p&lt;0.001) ( Figure 1 ). A steeper increase in LVEDVi and LVESVi also associated with mortality (p&lt;0.001), while change in native T1 did not. Conclusions: DMD all-cause mortality is associated with the slope of progression of LVEF and ventricular volumes. Aggressive medical therapy to decrease the rate of progression may improve mortality in this patient population. In addition, a decrease in the rate of progression may serve as a valid surrogate outcome measure for therapeutic trials.

Novel Cardiac Imaging Risk Score for Mortality Prediction in Duchenne Muscular Dystrophy.

Cardiovascular disease is the leading cause of death in patients with Duchenne Muscular Dystrophy (DMD), but there is significant cardiomyopathy phenotypic variability. Some patients demonstrate rapidly progressive disease and die at a young age while others survive into the fourth decade. Criteria to identify DMD subjects at greatest risk for early mortality could allow for increased monitoring and more intensive therapy. A risk score was created describing the onset and progression of left ventricular dysfunction and late gadolinium enhancement in subjects with DMD. DMD subjects prospectively enrolled in ongoing observational studies (which included cardiac magnetic resonance [CMR]) were used to validate the risk score. A total of 69 subjects had calculable scores. During the study period, 12 (17%) died from complications of DMD. The median risk score was 3 (IQR [2,5]; range [0,9]). The overall risk score applied at the most recent imaging age was associated with mortality at a median age of 17years (IQR [16,20]) (HR 2.028, p < 0.001). There were no deaths in subjects with a score of less than two. Scores were stable over time. An imaging-based risk score allows risk stratification of subjects with DMD. This can be quickly calculated during a clinic visit to identify subjects at greatest risk of early death.

DUCHENNE MUSCULAR DYSTROPHY RESPIRATORY PROFILES FROM REAL-WORLD REGISTRY DATA: A RETROSPECTIVE LONGITUDINAL STUDY

DUCHENNE MUSCULAR DYSTROPHY RESPIRATORY PROFILES FROM REAL-WORLD REGISTRY DATA: A RETROSPECTIVE LONGITUDINAL STUDY

Autonomic Modulation in Duchenne Muscular Dystrophy During a Computer Task: A Prospective Transversal Controlled Trial Assessment by Non-linear Techniques.

Introduction: Due to functional and autonomic difficulties faced by individuals with Duchenne Muscular Dystrophy (DMD), the use of assistive technology is critical to provide or facilitate functional abilities. The key objective was to investigate acute cardiac autonomic responses, by application of Heart Rate Variability (HRV), during computer tasks in subjects with DMD via techniques based on non-linear dynamics.Method: HRV was attained via a Polar RS800CX. Then, was evaluated by Chaotic Global Techniques (CGT). Forty-five male subjects were included in the DMD group and age-matched with 45 in the healthy Typical Development (TD) control group. They were assessed for 20 min at rest sitting, and then 5 min whilst performing the maze task on a computer.Results: Both TD and DMD subjects exhibited a significantly reduced HRV measured by chaotic global combinations when undertaking the computer maze paradigm tests. DMD subjects presented decreased HRV during rest and computer task than TD subjects.Conclusion: While there is an impaired HRV in subjects with DMD, there remains an adaptation of the ANS during the computer tasks. The identification of autonomic impairment is critical, considering that the computer tasks in the DMD community may elevate their level of social inclusion, participation and independence.

Abstract 11387: Four-Dimensional Spatiotemporal Characterization of Cardiomyopathy in Duchenne Muscular Dystrophy Using Cardiac Magnetic Resonance Imaging

Introduction: Cardiomyopathy (CM) is the most common cause of mortality in Duchenne muscular dystrophy (DMD). Because CM progression is variable, there is a critical need for biomarkers to detect early onset or rapid progression. Our objective was to evaluate localized kinematic parameters that correlate with function utilizing spatiotemporal analysis of 4D (3D plus time) cardiac magnetic resonance (CMR). We hypothesized that novel regional strain metrics would correlate with left ventricular ejection fraction (LVEF), providing insight for future DMD CM characterization studies . Methods: Sequential short axis cine CMR images of DMD patients (n=10) with a range of CM severity were compiled into 4D sequences. Epi- and endocardial borders were then segmented across one cardiac cycle for kinematic analysis. We evaluated Green-Lagrange circumferential strain (ε cc ) at 60 equally spaced short axis slices and across 60 time points to generate a spatiotemporal map. We also evaluated a novel “hybrid strain index” combining basal ε cc with posterior free-wall longitudinal strain. Spearman’s rho was used to determine statistical correlation. Results: DMD subjects had a median age of 11 years (8-24); 3 had LVEF&lt;55% and 7 had late gadolinium enhancement. Regional peak averages of ε cc decreased with LVEF for basal ( rho =-0.94, p &lt;.001) and mid-LV ( rho =-0.84, p =.004) but not at the apex ( rho =-0.55, p =.106). The hybrid strain index also decreased with LVEF ( rho =0.89, p &lt;.001). Qualitative spatiotemporal ε cc maps of mild, moderate, and severe DMD cases demonstrate stark differences in regional wall motion (Figure 1). Conclusion: 4D spatiotemporal analysis of CMR images in DMD patients allows for robust comparison of regional kinematic parameters that correlate with LVEF. Figure 1: 4D CMR spatiotemporal analysis of DMD cardiomyopathy. A,B) Schematic of circumferential strain (ε cc ). C,D,E) Example mild, moderate, and severe patient spatiotemporal ε cc maps.

Abstract 9370: Myocardial Tissue Characterization of Pediatric Patients With Duchenne Muscular Dystrophy

Introduction: Cardiomyopathy (CM) is the leading cause of death in Duchenne muscular dystrophy (DMD). Cardiac magnetic resonance (CMR) parametric mapping sequences, Native T1, T2, and extracellular volume (ECV), can offer insights into disease pathophysiology. The objective of this abstract was to leverage parametric mapping sequences to define the tissue characteristics of DMD CM progression. We hypothesized DMD subjects could be categorized based on fibrosis, myocardial edema, and fat infiltration. Methods: DMD patients (n=52; median 12.1 years) underwent CMR including T1, T2, and ECV at the base, mid, and apex. Categories were defined as normal, early fibrosis (normal ECV, high T1, normal T2), fibrosis (high ECV, normal or high T1, normal T2), edema (normal or high ECV, normal or high T1, high T2), fat (normal ECV, low T1, high T2) or fibrofatty (high ECV, normal or low T1, high T2). Statistical analysis included Chi-square, Wilcoxon rank sum, Wilcoxon signed rank, and Spearman’s rho. Results: Median left ventricular ejection fraction (LVEF) was 59% and 15 (29%) had LVEF &lt; 55%; 18 subjects (35%) had normal LVEF and no late gadolinium enhancement. These subjects were younger (10.2 years [8.4,11.6] vs 14.7 [11.5,17.8], p&lt;0.001). Native T1 was elevated in at least one slice in 42 (81%). Patients with high T2 at any slice (n=13) were older (p=0.009) and had lower LVEF (p=0.009) compared with normal T2 (n=39). The most common stratifications (Figure 1) were early fibrosis (n=14) and fibrosis (n=21). Of the 13 with high T2, 9 were categorized as edema, 2 as fibrofatty, and 2 as fat. T2 at the base, mid, and apex increased from first to second CMR (all p&lt;0.05) and T2 at mid and apex correlated with age (rho=0.2 and rho=0.38, p&lt;0.05). Conclusion: Myocardial fibrosis is common in DMD. CM progresses with age and higher T2 suggesting fatty/fibrofatty infiltration. CMR parametric mapping sequences offer insights into disease pathophysiology, which should drive therapeutic innovation.

Profoundly lower muscle mass and rate of contractile protein synthesis in boys with Duchenne muscular dystrophy

Boys with Duchenne muscular dystrophy (DMD) experience a progressive loss of functional muscle mass, with fibrosis and lipid accumulation. Accurate evaluation of whole-body functional muscle mass (MM) in DMD patients has not previously been possible and the rate of synthesis of muscle proteins remains unexplored. We used non-invasive, stable isotope-based methods from plasma and urine to measure the fractional rate of muscle protein synthesis (FSR) functional muscle mass (MM), and fat free mass (FFM) in 10 DMD (6-17years) and 9 age-matched healthy subjects. An oral dose of D3 creatine in 70% 2 H2 O was administered to determine MM and FFM followed by daily 70% 2 H2 O to measure protein FSR. Functional MM was profoundly reduced in DMD subjects compared to controls (17% vs. 41% of body weight, P<0.0001), particularly in older, non-ambulant patients in whom functional MM was extraordinarily low (<13% body weight). We explored the urine proteome to measure FSR of skeletal muscle-derived proteins. Titin, myosin light chain and gelsolin FSRs were substantially lower in DMD subjects compared to controls (27%, 11% and 40% of control, respectively, P<0.0001) and were strongly correlated. There were no differences in muscle-derived sarcoplasmic proteins FSRs (creatine kinase M-type and carbonic anhydrase-3) measured in plasma. These data demonstrate that both functional MM, body composition and muscle protein synthesis rates can be quantified non-invasively and are markedly different between DMD and control subjects and suggest that the rate of contractile but not sarcoplasmic protein synthesis is affected by a lack of dystrophin. KEY POINTS: Duchenne muscular dystrophy (DMD) results in a progressive loss of functional skeletal muscle but total body functional muscle mass or rates of muscle protein synthesis have not previously been assessed in these patients. D3 -creatine dilution was used to measure total functional muscle mass and oral 2 H2 O was used to examine the rates of muscle protein synthesis non-invasively in boys with DMD and healthy controls using urine samples. Muscle mass was profoundly lower in DMD compared to control subjects, particularly in older, non-ambulant patients. The rates of contractile protein synthesis but not sarcoplasmic proteins were substantially lower in DMD. These results may provide non-invasive biomarkers for disease progression and therapeutic efficacy in DMD and other neuromuscular diseases.

Bone health in Duchenne muscular dystrophy: clinical and biochemical correlates.

An increased fracture risk is commonly reported in Duchenne muscular dystrophy (DMD). Our aim was to investigate bone mineral density (BMD) and bone turnover, including sclerostin, and their association with markers of cardiac and respiratory performance in a cohort of DMD subjects. In this single center, cross sectional observational study, lumbar spine (LS) BMD Z-scores, C-terminal telopeptide of procollagen type I (CTX) and osteocalcin (BGP), as bone resorption and formation markers, respectively, and sclerostin were assessed. Left ventricular ejection fraction (LVEF) and forced vital capacity (FVC) were evaluated. Clinical prevalent fractures were also recorded. Thirty-one patients [median age = 14 (12-21.5) years] were studied. Ambulant subjects had higher LS BMD Z-scores compared with non-ambulant ones and subjects with prevalent clinical fractures [n = 9 (29%)] showed lower LS BMD Z-scores compared with subjects without fractures. LS BMD Z-scores were positively correlated with FVC (r = 0.50; p = 0.01), but not with glucocorticoid use, and FVC was positively associated with BGP (r = 0.55; p = 0.02). In non-ambulant subjects, LS BMD Z-scores were associated with BMI (r = 0.54; p = 0.02) and sclerostin was associated with age (r = 0.44; p = 0.05). Age, BMI, FVC and sclerostin were independently associated with LS BMD Z-score in a stepwise multiple regression analysis. Older age, lower BMI, FVC and sclerostin were associated with lower LS BMD Z-scores. In a cohort of DMD patients, our data confirm low LS BMD Z-scores, mainly in non-ambulant subjects and irrespective of the glucocorticoid use, and suggest that FVC and sclerostin are independently associated with LS BMD Z-scores.

Duchenne muscular dystrophy patients: troponin leak in asymptomatic and implications for drug toxicity studies.

Cardiomyopathy is the leading cause of death in Duchenne muscular dystrophy (DMD), but studies suggest heart failure biomarkers correlate poorly with cardiomyopathy severity. DMD clinical trials have used troponin I (cTnI) as a biomarker of toxicity, but it is unclear if asymptomatic DMD patients have elevated cTnI. We longitudinally evaluated cTnI, brain natriuretic peptide (BNP), and N-terminal pro-BNP (NT-proBNP) in a DMD cohort. DMD patients were prospectively enrolled and followed for 3 years. Serum was drawn at the time of cardiac magnetic resonance (CMR). Normal biomarker values were derived from healthy subjects. Biomarkers were correlated with CMR markers. All subjects were asymptomatic at the time of enrollment. Several DMD subjects had transiently elevated cTnI. Those with elevated cTnI were more likely to have late gadolinium enhancement on baseline CMR. NT-proBNP correlated with indexed left ventricular end diastolic and maximum left atrial volumes. Otherwise, standard cardiac biomarkers did not correlate with CMR markers of cardiomyopathy. CTnI, BNP, and NT-proBNP do not correlate with CMR assessment of cardiomyopathy progression. A subset of DMD patients have asymptomatic cTnI leak of uncertain clinical significance, though of critical importance if cTnI is used to assess for cardiac toxicity in future drug trials. Asymptomatic patients with Duchenne muscular dystrophy (DMD) exhibit transient troponin I leak. NT-proBNP correlated with indexed left ventricular end diastolic volume and indexed maximum left atrial volume. Other cardiac biomarkers did not correlate with cardiac magnetic resonance (CMR) markers of cardiomyopathy.

Thoracoabdominal asynchrony and paradoxical motion in Duchenne muscular dystrophy and healthy subjects during cough: A case control study.

To assess thoracoabdominal asynchrony (TAA) and inspiratory paradoxical motion at different positionings in subjects with Duchenne muscular dystrophy (DMD) versus healthy subjects during quiet spontaneous breathing (QB) and cough. This is a case control study with a matched-pair design. We assessed 14 DMD subjects and 12 controls using optoelectronic plethysmography (OEP) during QB and spontaneous cough in 3 positions: supine, supine with headrest raised at 45°, and sitting with back support at 80°. The TAA was assessed using phase angle (θ) between upper (RCp) and lower rib cage (RCa) and abdomen (AB), as well as the percentage of inspiratory time the RCp (IPRCp ), RCa (IPRCa ), and AB (IPAB ) moved in opposite directions. During cough, DMD group showed higher RCp and RCa θ (p < .05), RCp and AB θ (p < .05) in supine and 45° positions, and higher RCp and Rca θ (p = .006) only in supine position compared with controls. Regarding the intragroup analysis, during cough, DMD group presented higher RCp and AB θ (p = .02) and RCa and AB θ (p = .002) in supine and higher RCa and AB θ (p = .002) in 45° position when compared to 80°. Receiver operating characteristic curve analyzes were able to discriminate TAA between controls and DMD in RCa supine position (area under the curve: 0.81, sensibility: 78.6% and specificity: 91.7%, p = .001). Subjects with DMD yields TAA with insufficient deflation of chest wall compartments and rib cage distortion during cough, by noninvasive assessment.