Intermittent glucocorticoid steroid dosing enhances muscle repair without eliciting muscle atrophy
Mattia Quattrocelli, … , Alexis R. Demonbreun, Elizabeth M. McNally
Mattia Quattrocelli, … , Alexis R. Demonbreun, Elizabeth M. McNally
Published May 8, 2017
Citation Information: J Clin Invest. 2017;127(6):2418-2432. https://doi.org/10.1172/JCI91445.
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Research Article Metabolism Muscle biology

Intermittent glucocorticoid steroid dosing enhances muscle repair without eliciting muscle atrophy

Abstract

Glucocorticoid steroids such as prednisone are prescribed for chronic muscle conditions such as Duchenne muscular dystrophy, where their use is associated with prolonged ambulation. The positive effects of chronic steroid treatment in muscular dystrophy are paradoxical because these steroids are also known to trigger muscle atrophy. Chronic steroid use usually involves once-daily dosing, although weekly dosing in children has been suggested for its reduced side effects on behavior. In this work, we tested steroid dosing in mice and found that a single pulse of glucocorticoid steroids improved sarcolemmal repair through increased expression of annexins A1 and A6, which mediate myofiber repair. This increased expression was dependent on glucocorticoid response elements upstream of annexins and was reinforced by the expression of forkhead box O1 (FOXO1). We compared weekly versus daily steroid treatment in mouse models of acute muscle injury and in muscular dystrophy and determined that both regimens provided comparable benefits in terms of annexin gene expression and muscle repair. However, daily dosing activated atrophic pathways, including F-box protein 32 (Fbxo32), which encodes atrogin-1. Conversely, weekly steroid treatment in mdx mice improved muscle function and histopathology and concomitantly induced the ergogenic transcription factor Krüppel-like factor 15 (Klf15) while decreasing Fbxo32. These findings suggest that intermittent, rather than daily, glucocorticoid steroid regimen promotes sarcolemmal repair and muscle recovery from injury while limiting atrophic remodeling.

Authors

Mattia Quattrocelli, David Y. Barefield, James L. Warner, Andy H. Vo, Michele Hadhazy, Judy U. Earley, Alexis R. Demonbreun, Elizabeth M. McNally

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Figure 3

miR-383 contributes to GC-associated Anxa6 regulation.

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miR-383 contributes to GC-associated Anxa6 regulation. (A) Model of path...
(A) Model of pathway linking GC uptake in muscle to regulation of miR-383 and Anxa6 expression. Solid lines, reported interactions; dashed lines, interrogated interactions. (B) Nr0b1 and miR-383 were upregulated and downregulated, respectively, in GC–pulse dosed skeletal muscle (quadriceps) and primary myoblasts. (C) Electroporation directly into muscle with targeting oligonucleotides altered miR-383 and Anxa6 levels. (D) miR-383 mimic correlated with worse sarcolemmal injury, whereas anti–miR-383 correlated with smaller injury. (Left) Z-stack rendering of laser-injured sarcolemmal sites at 300 seconds after injury; (center) quantitation of FM4-64 dye accumulation at sarcolemmal site after laser injury; (right) end-point area of injury. (E) Luciferase assay to validate GC-dependent regulation of Anxa6-3′ UTR targeting by miR-383 in skeletal muscle. Diagram depicting experimental design after introducing 3′ UTR reporter constructs into muscle followed by ex vivo Fluc measurement. miR-383 reduced luminescence, while 3′ UTR without the miR-383–binding site (Δ miR-383) increased luminescence. n = 5 mice/group (B); n = 3 mice (30 myofibers)/group (C–E). *P < 0.05 vs. vehicle, 1-way ANOVA test with Bonferroni’s multiple comparison; #P < 0.05 vs. vehicle, 2-way ANOVA test with Bonferroni’s multiple comparison.