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Background: Duchenne's muscular dystrophy (DMD) is a severe type of hereditary, neuromuscular disorder caused by a mutation in the dystrophin gene resulting in the absence or production of truncated dystrophin protein. Conventionally, clinical descriptions of the disorder focus principally on striated muscle defects; however, DMD manifestations involving gastrointestinal (GI) smooth muscle have been reported, even if not rigorously studied. Purpose: The objective of the present review is to offer a comprehensive perspective on the existing knowledge concerning GI manifestations in DMD, focusing the attention on evidence in DMD patients and mdx mice. This includes an assessment of symptomatology, etiological pathways, and potential corrective approaches. This paper could provide helpful information about DMD gastrointestinal implications that could serve as a valuable orientation for prospective research endeavors in this field. This manuscript emphasizes the effectiveness of mdx mice, a DMD animal model, in unraveling mechanistic insights and exploring the pathological alterations in the GI tract. The gastrointestinal consequences evident in patients with DMD and the mdx mice models are a significant area of focus for researchers. The exploration of this area in depth could facilitate the development of more efficient therapeutic approaches and improve the well‐being of individuals impacted by the condition. [ABSTRACT FROM AUTHOR]

Duchenne muscular dystrophy (DMD) is an X-linked neuromuscular disease caused by a deficiency in dystrophin – a structural protein which stabilises muscle during contraction. Dystrophin deficiency adversely affects the respiratory system leading to sleep-disordered breathing, hypoventilation, and weakness of the expiratory and inspiratory musculature, which culminate in severe respiratory dysfunction. Muscle degeneration-associated respiratory impairment in neuromuscular disease is a result of disruptions at multiple sites of the respiratory control network, including sensory and motor pathways. As a result of this pathology, respiratory failure is a leading cause of premature death in DMD patients. Currently available treatments for DMD respiratory insufficiency attenuate respiratory symptoms without completely reversing the underlying pathophysiology. This underscores the need to develop curative therapies to improve quality of life and longevity of DMD patients. This review summarises research findings on the pathophysiology of respiratory insufficiencies in DMD disease in humans and animal models, the clinical interventions available to ameliorate symptoms, and gene-based therapeutic strategies uncovered by preclinical animal studies. [ABSTRACT FROM AUTHOR]

Exposure‐response relationships of vamorolone, a novel dissociative steroidal anti‐inflammatory drug, were investigated in clinical trials in boys with Duchenne muscular dystrophy. Variables were clinical outcome measures, Fridericia‐corrected QT (QTcF) duration, and pharmacodynamic (PD) biomarkers. Exposure metrics were area under the plasma concentration time curve (AUC) and maximum plasma concentration (Cmax), with a sigmoid Emax model applied. Significant improvement in clinical efficacy outcomes was observed after 24 weeks of daily dosing. The primary outcome, time to stand from supine velocity, exhibited the highest sensitivity to vamorolone, with the lowest AUC value providing 50% of maximum effect (E50 = 186 ng·h/mL), followed by time to climb 4 stairs (E50 = 478 ng·h/mL), time to run/walk 10 m (E50 = 1220 ng·h/mL), and 6‐minute walk test (E50 = 1770 ng·h/mL). Week 2 changes of proinflammatory PD biomarkers showed exposure‐dependent decreases. The E50 was 260 ng·h/mL for insulin‐like growth factor‐binding protein 2, 1200 ng·h/mL for matrix metalloproteinase 12, 1260 ng·h/mL for lymphotoxin α1/β2, 1340 ng·h/mL for CD23, 1420 ng·h/mL for interleukin‐22‐binding protein, and 1600 ng·h/mL for macrophage‐derived chemokine/C‐C motif chemokine 22. No relationship was found between QTcF interval changes from baseline and Cmax in week 2 or 24. This analysis showed that improvements in clinical efficacy end points in week 24 and PD biomarkers in week 2 were achieved at typical vamorolone exposure of 2 mg/kg daily dose with a median AUC dose of 6 mg/kg (3651 ng·h/mL), corresponding to approximately 95% of maximum effects for most response variables. [ABSTRACT FROM AUTHOR]

Duchenne muscular dystrophy (DMD) is the most common muscular dystrophy seen in children. In addition to skeletal muscle, DMD also has a significant impact on bone. The pathogenesis of bone abnormalities in DMD is still unknown. Recently, we have identified a novel bone‐regulating cytokine, fibroblast growth factor‐21 (FGF‐21), which is dramatically upregulated in skeletal muscles from DMD animal models. We hypothesize that muscle‐derived FGF‐21 negatively affects bone homeostasis in DMD. Dystrophin/utrophin double‐knockout (dKO) mice were used in this study. We found that the levels of circulating FGF‐21 were significantly higher in dKO mice than in age‐matched WT controls. Further tests on FGF‐21 expressing tissues revealed that both FGF‐21 mRNA and protein expression were dramatically upregulated in dystrophic skeletal muscles, whereas FGF‐21 mRNA expression was downregulated in liver and white adipose tissue (WAT) compared to WT controls. Neutralization of circulating FGF‐21 by i.p. injection of anti‐FGF‐21 antibody significantly alleviated progressive bone loss in weight‐bearing (vertebra, femur, and tibia) and non–weight bearing bones (parietal bones) in dKO mice. We also found that FGF‐21 directly promoted RANKL‐induced osteoclastogenesis from bone marrow macrophages (BMMs), as well as promoted adipogenesis while concomitantly inhibiting osteogenesis of bone marrow mesenchymal stem cells (BMMSCs). Furthermore, fibroblast growth factor receptors (FGFRs) and co‐receptor β‐klotho (KLB) were expressed in bone cells (BMM‐derived osteoclasts and BMMSCs) and bone tissues. KLB knockdown by small interfering RNAs (siRNAs) significantly inhibited the effects of FGF21 on osteoclast formation of BMMs and on adipogenic differentiation of BMMSCs, indicating that FGF‐21 may directly affect dystrophic bone via the FGFRs‐β‐klotho complex. In conclusion, this study shows that dystrophic skeletal muscles express and secrete significant levels of FGF‐21, which negatively regulates bone homeostasis and represents an important pathological factor for the development of bone abnormalities in DMD. The current study highlights the importance of muscle/bone cross‐talk via muscle‐derived factors (myokines) in the pathogenesis of bone abnormalities in DMD. © 2019 American Society for Bone and Mineral Research. [ABSTRACT FROM AUTHOR]

Background: Duchenne muscular dystrophy (DMD) is characterized by progressive weakness and wasting of skeletal, cardiac, and respiratory muscles, with consequent cardiopulmonary failure as the main cause of death. Reliable outcome measures able to demonstrate specific trends over disease progression are essential.Purpose: To investigate MRI as a noninvasive imaging modality to assess diaphragm impairment in DMD. In particular, we sought to correlate MRI measurement of diaphragm structure and function with pulmonary function tests and with the abdominal volumes (VAB ) measured by optoelectronic plethysmography, being an index of the action of the diaphragm.Study Type: Cross-sectional study.Population: Twenty-six DMD patients (17.9 ± 6.2 years) and 12 age-matched controls (17.8 ± 5.9 years).Field Strength/sequence: 3-Point gradient echo Dixon sequence at 3T.Assessment: Images were acquired in breath-hold at full-expiration (EXP) and full-inspiration (INSP). INSP and EXP lung volumes were segmented and the diaphragm surface was reconstructed as the bottom surface of the left and the right lung. The inspiratory and the expiratory diaphragm surfaces were aligned by a nonrigid iterative closest point algorithm. On MRI we measured: 1) craniocaudal diaphragmatic excursion; 2) diaphragm fatty infiltration.Statistical Tests: Three-parameter sigmoid regression, one-way analysis of variance (ANOVA), Spearman's correlation.Results: In patients, diaphragm excursion decreased with age (r2 = 0.68, P < 0.0001) and fat fraction increased (r2 = 0.51, P = 0.0002). In healthy subjects, diaphragm excursion and fat fraction had no relationship with age. Diaphragm excursion decreased with decreasing FEV1 %pred (r = 0.78, P < 0.0001) and FVC %pred (r = 0.76, P < 0.0001) and correlated with VAB (r = 0.60, P = 0.0002). Fatty infiltration increased with decreasing FEV1 %pred (r = -0.88, P < 0.0001) and FVC %pred (r = -0.88, P < 0.0001).Data Conclusion: The progressive structural and functional diaphragm impairment is highly related to pulmonary function tests and to VAB . The results suggest that MRI might represent a new and noninvasive tool for the functional and structural assessment of the diaphragm.Level Of Evidence: 2 Technical Efficacy: Stage 5 J. Magn. Reson. Imaging 2020;51:461-471. [ABSTRACT FROM AUTHOR]

Ezutromid (SMT C1100) is a small‐molecule utrophin modulator that was developed to treat Duchenne muscular dystrophy (DMD). Previous clinical trials of this agent revealed lower exposure in DMD patients compared with healthy volunteers, which may reflect differences in diet. This study evaluated the pharmacokinetics of ezutromid in patients with DMD who followed a balanced diet. This was a multicenter, double‐blind, placebo‐controlled, ascending single and multiple oral dose study. Twelve pediatric patients were randomly allocated to 1 of 3 treatment sequences within which were 3 treatment periods of 2 weeks each. Each patient received, in a dose‐escalating fashion, 1250 mg and 2500 mg twice daily (BID) of ezutromid administered orally as a microfluidized suspension (F3) with placebo in the other treatment period. Throughout the study, patients followed a balanced diet including recommended proportions of major food groups and administration of drug accompanied with 100 mL of full‐fat milk. This approach improved the absorption of ezutromid, resulting in higher systemic exposure, with considerable variability in exposure between patients at each dose level. Single and multiple oral doses of 1250 mg and 2500 mg BID were considered safe and well tolerated. No severe or serious adverse events and no study discontinuations due to adverse events were reported. This study provides assurance that, with the formulation tested (F3) and instructions regarding food (balanced diet and whole‐fat milk), 2500 mg BID of ezutromid achieves plasma concentrations that, based on preclinical studies, should be able to modulate utrophin expression in future clinical trials. [ABSTRACT FROM AUTHOR]

Duchenne muscular dystrophy (DMD) is an inherited neuromuscular disorder occurring in boys and caused by mutations in the dystrophin gene. Vamorolone is a first‐generation delta‐9,11 compound that has favorable efficacy and side effect profiles relative to classical glucocorticoids. The pharmacokinetics (PK) of oral vamorolone were assessed in parallel‐group studies in healthy men (phase 1, n = 86) and boys with DMD (phase 2a, n = 48) during 14 days of once‐daily dosing with a range of doses. Vamorolone exhibited moderate variability in PK, with the maximum plasma concentration usually occurring at 2‐4 hours and a half‐life of approximately 2 hours for all doses and days examined. Population PK modeling of all data together indicated that the PK of vamorolone can be well described by a 1‐compartment model with zero‐order absorption. Both men and boys showed a dose‐linearity of PK parameters for the doses examined, with no accumulation of the drug during daily dosing. Ingestion with food resulted in markedly enhanced absorption of the drug, as tested in healthy men. There were similar PK of vamorolone in healthy men and DMD boys with apparent clearance averaging 2.0 L/h/kg in men and 1.7 L/h/kg in boys. Overall, vamorolone exhibited well‐behaved linear PK, with similar profiles in healthy men and boys with DMD, moderate variability in PK parameters, and absorption and disposition profiles similar to those of classical glucocorticoids. [ABSTRACT FROM AUTHOR]

Quantitative NMRI and 31P NMRS indices are reported in the forearms of 24 patients with Duchenne muscular dystrophy (DMD) (6-18 years, 14 non-ambulant) amenable to exon 53 skipping therapy and in 12 age-matched male controls (CONT). Examinations carried out at 3 T comprised multi-slice 17-echo measurements of muscle water T2 and heterogeneity, three-point Dixon imaging of fat fraction in flexor and extensor muscles (FLEX, EXT), and non-localised spectroscopy of phosphate metabolites. We studied four imaging indices, eight metabolic ratios combining ATP, phosphocreatine, phosphomonoesters and phosphodiesters, the cytosolic inorganic phosphate (Pia) and an alkaline (Pib) pool present in dystrophic muscle, and average pH. All indices differed between DMD and CONT, except for muscle water T2. Measurements were outside the 95th percentile of age-matched CONT values in over 65% of cases for percentage fat signal (%F), and in 78-100% of cases for all spectroscopic indices. T2 was elevated in one-third of FLEX measurements, whereas %pixels > 39 ms and T2 heterogeneity were abnormal in one-half of the examinations. The FLEX muscles had higher fat infiltration and T2 than EXT muscle groups. All indices, except pH, correlated with patient age, although the correlation was negative for T2. However, in non-ambulant patients, the correlation with years since loss of ambulation was stronger than the correlation with age, and the slope of evolution per year was steeper after loss of ambulation. All indices except Pi/gATP differed between ambulant and non-ambulant patients; however, T2 and %pixels > 39 ms were highest in ambulant patients, possibly owing to the greater extent of inflammatory processes earlier in the disease. All other indices were worse in non-ambulant subjects. Quantitative measurements obtained from patients at different disease stages covered a broad range of abnormalities that evolved with the disease, and metabolic indices were up to 10-fold above normal from the onset, thus establishing a variety of potential markers for future therapy. Copyright © 2015 John Wiley & Sons, Ltd. [ABSTRACT FROM AUTHOR]

Duchenne muscular dystrophy (DMD) is a genetic disease that occurs due to the deficiency of the dystrophin protein. Although dystrophin is deficient in all muscles, it is unclear why degeneration progresses differently across muscles in DMD. We hypothesized that each muscle undergoes a different degree of eccentric contraction during gait, which could contribute to the selective degeneration in lower limb muscle, as indicated by various amounts of fatty infiltration. By comparing eccentric contractions quantified from a previous multibody dynamic musculoskeletal gait simulation and fat fractions quantified in a recent imaging study, our preliminary analyses show a strong correlation between eccentric contractions during gait and lower limb muscle fat fractions, supporting our hypothesis. This knowledge is critical for developing safe exercise regimens for the DMD population. This study also provides supportive evidence for using multiscale modeling and simulation of the musculoskeletal system in future DMD research. [ABSTRACT FROM AUTHOR]

As part of an international consortium, case-parent trios were collected for a genome-wide association study of isolated, non-syndromic oral clefts, including cleft lip (CL), cleft palate (CP): and cleft lip and palate (CLP). Non-syndromic oral clefts have a complex and heterogeneous etiology. Risk is influenced by genes and environmental factors, and differs markedly by gender. Family-based association tests (FBAT) were used on 14,486 single nucleotide polymorphisms (SNPs) spanning the X chromosome, stratified by type of cleft and racial group. Significant results, even after multiple-comparisons correction, were obtained for the Duchenne muscular dystrophy (DMD) gene, the largest single gene in the human genome, among CL/P (i.e. both CL and CLP combined) trios. When stratified into groups of European and Asian ancestry, stronger signals were obtained for Asian subjects. Although conventional sliding-window haplotype analysis showed no increase in significance, selected combinations of the 25 most significant SNPs in the DMD gene identified four SNPs together that attained genome-wide significance among Asian CL/P trios, raising the possibility of interaction between distant SNPs within the DMD gene [ABSTRACT FROM AUTHOR]

Duchenne muscular dystrophy (DMD) is a lethal muscle disorder caused by mutations in the DMD gene for which no mutation-targeted therapy has been available thus far. However, exon-skipping mediated by antisense oligonucleotides (AOs), which are short single-strand DNAs, has considerable potential for DMD therapy, and clinical trials in DMD patients are currently underway. This exon-skipping therapy changes an out-of-frame mutation into an in-frame mutation, aiming at conversion of a severe DMD phenotype into a mild phenotype by restoration of truncated dystrophin expression. Recently, stable and less-toxic AOs have been developed, and their higher efficacy was confirmed in mice and dog models of DMD. In this review, we briefly summarize the genetic basis of DMD and the potential and perspectives of exon skipping as a promising therapy for this disease. [ABSTRACT FROM AUTHOR]

Duchenne Muscular Dystrophy (DMD) is a fatal X‐linked genetic disorder. In DMD, the absence of the dystrophin protein causes decreased sarcolemmal integrity resulting in progressive replacement of muscle with fibrofatty tissue. The effects of lacking dystrophin on muscle and systemic metabolism are still unclear. Therefore, to determine the impact of the absence of dystrophin on metabolism, we investigated the metabolic and lipid profile at two different, well‐defined stages of muscle damage and stabilization in mdx mice. We measured NMR‐detectable metabolite and lipid profiles in the serum and muscles of mdx mice at 6 and 24 weeks of age. Metabolites were determined in muscle in vivo using 1H MRI/MRS, in isolated muscles using 1H‐HR‐MAS NMR, and in serum using high resolution 1H/13C NMR. Dystrophic mice were found to have a unique lipid saturation profile compared with control mice, revealing an age‐related metabolic change. In the 6‐week‐old mdx mice, serum lipids were increased and the degree of lipid saturation changed between 6 and 24 weeks. The serum taurine‐creatine ratio increased over the life span of mdx, but not in control mice. Furthermore, the saturation index of lipids increased in the serum but decreased in the tissue over time. Finally, we demonstrated associations between MRI‐T2, a strong indicator of inflammation/edema, with tissue and serum lipid profiles. These results indicate the complex temporal changes of metabolites in the tissue and serum during repetitive bouts of muscle damage and regeneration that occur in dystrophic muscle. [ABSTRACT FROM AUTHOR]