A pooled analysis of fall incidence from placebo‐controlled trials of denosumab

Recent studies suggest that the RANK/RANKL system impacts muscle function and/or mass. In the pivotal placebo‐controlled fracture trial of the RANKL inhibitor denosumab in women with postmenopausal osteoporosis, treatment was associated with a lower incidence of non‐fracture‐related falls (p = 0.02). This ad hoc exploratory analysis pooled data from five placebo‐controlled trials of denosumab to determine consistency across trials, if any, of the reduction of fall incidence. The analysis included trials in women with postmenopausal osteoporosis and low bone mass, men with osteoporosis, women receiving adjuvant aromatase inhibitors for breast cancer, and men receiving androgen deprivation therapy for prostate cancer. The analysis was stratified by trial, and only included data from the placebo‐controlled period of each trial. A time‐to‐event analysis of first fall and exposure‐adjusted subject incidence rates of falls were analyzed. Falls were reported and captured as adverse events. The analysis comprised 10,036 individuals; 5030 received denosumab 60 mg subcutaneously once every 6 months for 12 to 36 months and 5006 received placebo. Kaplan–Meier estimates showed an occurrence of falls in 6.5% of subjects in the placebo group compared with 5.2% of subjects in the denosumab group (hazard ratio = 0.79; 95% confidence interval 0.66–0.93; p = 0.0061). Heterogeneity in study designs did not permit overall assessment of association with fracture outcomes. In conclusion, denosumab may reduce the risk of falls in addition to its established fracture risk reduction by reducing bone resorption and increasing bone mass. These observations require further exploration and confirmation in studies with muscle function or falls as the primary outcome

miR‐24 and its target gene Prdx6 regulate viability and senescence of myogenic progenitors during aging

Satellite cell-dependent skeletal muscle regeneration declines during aging. Disruptions within the satellite cells and their niche, together with alterations in the myofibrillar environment, contribute to age-related dysfunction and defective muscle regeneration. In this study, we demonstrated an age-related decline in satellite cell viability and myogenic potential and an increase in ROS and cellular senescence. We detected a transient upregulation of miR-24 in regenerating muscle from adult mice and downregulation of miR-24 during muscle regeneration in old mice. FACS-sorted satellite cells were characterized by decreased levels of miR-24 and a concomitant increase in expression of its target: Prdx6. Using GFP reporter constructs, we demonstrated that miR-24 directly binds to its predicted site within Prdx6 mRNA. Subtle changes in Prdx6 levels following changes in miR-24 expression indicate miR-24 plays a role in fine-tuning Prdx6 expression. Changes in miR-24 and Prdx6 levels were associated with altered mitochondrial ROS generation, increase in the DNA damage marker: phosphorylated-H2Ax and changes in viability, senescence, and myogenic potential of myogenic progenitors from mice and humans. The effects of miR-24 were more pronounced in myogenic progenitors from old mice, suggesting a context-dependent role of miR-24 in these cells, with miR-24 downregulation likely a part of a compensatory response to declining satellite cell function during aging. We propose that downregulation of miR-24 and subsequent upregulation of Prdx6 in muscle of old mice following injury are an adaptive response to aging, to maintain satellite cell viability and myogenic potential through regulation of mitochondrial ROS and DNA damage pathways