osteoprotegerin and Muscular-Dystrophy--Duchenne

Duchenne muscular dystrophy (DMD) is an X-linked inherited disorder. Patients present with decreased bone mineral density (BMD) due to glucocorticoid therapy and progressive muscle weakness. Bone remodeling allows bone volume and structure to be maintained and controlled by local and systemic factors. These include the receptor activator of the nuclear factor-kB (RANK)/RANK ligand (RANKL)/osteoprotegerin (OPG) system, a determining pathway in the balance between bone formation and resorption. Disruptions in this complex, caused by factors such as glucocorticoids, can affect bone metabolism. The extensive action of the RANK/RANKL/OPG pathway suggests an influence on dystrophic muscle pathophysiology. This review aimed to highlight some aspects of the RANK/RANKL/OPG system, the effect of glucocorticoids on this pathway, and the pathophysiology of the patient with DMD.. La distrofia muscular de Duchenne (DMD) es un trastorno hereditario ligado al cromosoma X. Los pacientes presentan una disminución de la densidad mineral ósea (DMO) debido a los efectos adversos del tratamiento con glucocorticoides y a la debilidad muscular progresiva. El remodelado óseo permite mantener el volumen y la estructura ósea, proceso controlado por factores locales y sistémicos. Entre ellos destaca el sistema del receptor activador del factor nuclear-kB (RANK), su ligando natural RANKL (RANKL) y la osteoprotegerina (OPG), una vía determinante en el equilibrio entre la resorción y formación ósea. Las alteraciones en este complejo, originadas por factores como los glucocorticoides, pueden afectar el metabolismo óseo. La amplia acción de RANKL y OPG ha sugerido una influencia en la fisiopatología de la DMD. El objetivo de esta revisión fue destacar algunos aspectos del sistema RANK/RANKL/OPG, el efecto de los glucocorticoides en esta vía y la fisiopatología del paciente con DMD.

Topics: Glucocorticoids; Humans; Muscular Dystrophy, Duchenne; Osteoprotegerin; RANK Ligand; Receptor Activator of Nuclear Factor-kappa B

In Duchenne muscular dystrophy (DMD), the progressive skeletal and cardiac muscle dysfunction and degeneration is accompanied by low bone mineral density and bone fragility. Glucocorticoids, which remain the standard of care for patients with DMD, increase the risk of developing osteoporosis. The scope of this review emphasizes the mutual cohesion and common signaling pathways between bone and skeletal muscle in DMD.. The muscle-bone interactions involve bone-derived osteokines, muscle-derived myokines, and dual-origin cytokines that trigger common signaling pathways leading to fibrosis, inflammation, or protein synthesis/degradation. In particular, the triad RANK/RANKL/OPG including receptor activator of NF-kB (RANK), its ligand (RANKL), along with osteoprotegerin (OPG), regulates bone matrix modeling and remodeling pathways and contributes to muscle pathophysiology in DMD. This review discusses the importance of the muscle-bone unit in DMD and covers recent research aimed at determining the muscle-bone interactions that may eventually lead to the development of multifunctional and effective drugs for treating muscle and bone disorders regardless of the underlying genetic mutations in DMD.

Topics: Bone and Bones; Bone Remodeling; Cytokines; Fibrosis; Humans; Muscle, Skeletal; Muscular Dystrophy, Duchenne; Osteoporosis; Osteoprotegerin; RANK Ligand; Receptor Activator of Nuclear Factor-kappa B; Signal Transduction

RANKL-OPG should be explored in DMD patients to potentially provide targeted therapy. We quantified RANKL and OPG levels in DMD patients compared with controls. RANKL, OPG, and RANKL:OPG significantly declined with age in DMD patients suggesting some bone turnover markers are difficult to assess or use as therapeutic indicators.. Osteoporosis in Duchenne muscular dystrophy (DMD) is multi-factorial in nature with high prevalence of fractures. RANKL-OPG should be explored to potentially provide targeted therapy for these patients. We quantified RANKL, OPG, and RANKL:OPG levels in DMD patients compared with controls and analyzed the influence of age, glucocorticoid use, ambulatory status, bone density, and fracture history.. DMD patients were enrolled at CHLA. Controls were recruited from general pediatric clinic and in collaboration with samples from a previously completed study. Free soluble RANKL and OPG levels were quantified using a sandwich ELISA.. Fifty DMD patients and 50 controls were enrolled. DMD patients had a significant decline in RANKL, OPG, and RANKL:OPG with age (p = < 0.0001, p = 0.026, and p = 0.002, respectively) while healthy controls showed no significant change. RANKL trended lower in patients on glucocorticoids (p = 0.05), attributed to the significantly older age in the treatment group. RANKL and RANKL:OPG levels were significantly lower in the non-ambulatory group compared with the ambulatory group (p = 0.010 and 0.036 respectively), again likely due to their older age. There was no correlation of RANKL, OPG, or RANKL:OPG with DXA Z-score or presence of vertebral fractures.. There was significant decline in RANKL, OPG, and RANKL:OPG with age in DMD patients compared with controls, potentially due to disease severity or worsening osteoblastic function. This suggests some bone turnover markers may be difficult to assess or use as therapeutic indicators in DMD patients. Larger studies are needed to evaluate the role of RANKL-OPG in DMD patients to provide better targeted therapy.

Topics: Absorptiometry, Photon; Biomarkers; Bone Density; Bone Remodeling; Case-Control Studies; Child; Cross-Sectional Studies; Enzyme-Linked Immunosorbent Assay; Female; Glucocorticoids; Humans; Male; Muscular Dystrophy, Duchenne; Osteoporosis; Osteoprotegerin; RANK Ligand; Spinal Fractures