Intermittent glucocorticoid regimes for younger boys with duchenne muscular dystrophy: Balancing efficacy with side effects

Use of the experience sampling method in adolescents with Duchenne muscular dystrophy: a feasibility study

Experience sampling methods (ESM) using mobile health (mHealth) technology with a smartphone application are increasingly used in clinical practice and research. Still, recommendations are limited in young people, and adaptations may be necessary. Patients with Duchenne muscular dystrophy (DMD) are chronically treated with steroids from a young age. However, the impact of intermittent treatment schedules on fluctuations in somatic, cognitive and behavioural symptoms is poorly investigated. Existing studies are often cross-sectional and occur in controlled clinical settings, which do not provide sufficiently detailed insights into possible correlations. ESM might alleviate these problems. ESM innovates data collection with a smartphone application, which repeatedly assesses specific symptoms and contextual factors at random moments in daily life. We aimed to evaluate its feasibility in adolescents with DMD. In three (without/with/without steroids) 4-day periods of ESM, that were nested in 10/10 or 11/9 day on/off-medication periods, we evaluated its user-friendliness and compliance, and explored its ability to objectify fluctuations in somatic, cognitive and behavioural symptom severity and their relationship with contextual factors in seven DMD patients (age range 12-18 years) using intermittent corticosteroid treatment (dosage range 0.3-0.6 mg/kg/day). Patients reported that ESM was convenient and user-friendly. We were able to capture extensive intra-individual symptom fluctuations during intermittent corticosteroid treatment that were not revealed by routine clinical assessment. Implementing ESM to evaluate symptom fluctuation patterns in relation to treatment effects shows promise in adolescents with DMD. Optimization in further research is needed.

A transcriptomics-based drug repositioning approach to identify drugs with similar activities for the treatment of muscle pathologies in spinal muscular atrophy (SMA) models

Spinal muscular atrophy (SMA) is a genetic neuromuscular disorder caused by the reduction of survival of motor neuron (SMN) protein levels. Although three SMN-augmentation therapies are clinically approved that significantly slow down disease progression, they are unfortunately not cures. Thus, complementary SMN-independent therapies that can target key SMA pathologies and that can support the clinically approved SMN-dependent drugs are the forefront of therapeutic development. We have previously demonstrated that prednisolone, a synthetic glucocorticoid (GC) improved muscle health and survival in severe Smn-/-;SMN2 and intermediate Smn2B/- SMA mice. However, long-term administration of prednisolone can promote myopathy. We thus wanted to identify genes and pathways targeted by prednisolone in skeletal muscle to discover clinically approved drugs that are predicted to emulate prednisolone's activities. Using an RNA-sequencing, bioinformatics, and drug repositioning pipeline on skeletal muscle from symptomatic prednisolone-treated and untreated Smn-/-; SMN2 SMA and Smn+/-; SMN2 healthy mice, we identified molecular targets linked to prednisolone's ameliorative effects and a list of 580 drug candidates with similar predicted activities. Two of these candidates, metformin and oxandrolone, were further investigated in SMA cellular and animal models, which highlighted that these compounds do not have the same ameliorative effects on SMA phenotypes as prednisolone; however, a number of other important drug targets remain. Overall, our work further supports the usefulness of prednisolone's potential as a second-generation therapy for SMA, identifies a list of potential SMA drug treatments and highlights improvements for future transcriptomic-based drug repositioning studies in SMA.

Alteration of STIM1/Orai1-Mediated SOCE in Skeletal Muscle: Impact in Genetic Muscle Diseases and Beyond

Intracellular Ca2+ ions represent a signaling mediator that plays a critical role in regulating different muscular cellular processes. Ca2+ homeostasis preservation is essential for maintaining skeletal muscle structure and function. Store-operated Ca2+ entry (SOCE), a Ca2+-entry process activated by depletion of intracellular stores contributing to the regulation of various function in many cell types, is pivotal to ensure a proper Ca2+ homeostasis in muscle fibers. It is coordinated by STIM1, the main Ca2+ sensor located in the sarcoplasmic reticulum, and ORAI1 protein, a Ca2+-permeable channel located on transverse tubules. It is commonly accepted that Ca2+ entry via SOCE has the crucial role in short- and long-term muscle function, regulating and adapting many cellular processes including muscle contractility, postnatal development, myofiber phenotype and plasticity. Lack or mutations of STIM1 and/or Orai1 and the consequent SOCE alteration have been associated with serious consequences for muscle function. Importantly, evidence suggests that SOCE alteration can trigger a change of intracellular Ca2+ signaling in skeletal muscle, participating in the pathogenesis of different progressive muscle diseases such as tubular aggregate myopathy, muscular dystrophy, cachexia, and sarcopenia. This review provides a brief overview of the molecular mechanisms underlying STIM1/Orai1-dependent SOCE in skeletal muscle, focusing on how SOCE alteration could contribute to skeletal muscle wasting disorders and on how SOCE components could represent pharmacological targets with high therapeutic potential.