Aerobic exercise-mediated changes in the expression of glucocorticoid responsive genes in skeletal muscle differ across the day

Glucocorticoids are released in by acute aerobic exercise. The objective was to define changes in the expression of glucocorticoid target genes in skeletal muscle in response to acute aerobic exercise at different times of day. We identified glucocorticoid target genes altered in skeletal muscle by acute exercise by comparing data sets from rodents subjected to acute aerobic exercise in the light or dark cycles to data sets from C2C12 myotubes treated with glucocorticoids. The role of glucocorticoid receptor signaling and REDD1 protein in mediating gene expression was assessed in exercised mice. Changes to expression of glucocorticoid genes were greater when exercise occurred in the dark cycle. REDD1 was required for the induction of genes induced at both times of day. In all, the time of day at which aerobic exercise is conducted dictates changes to the expression of glucocorticoid target genes in skeletal muscle with REDD1 contributing to those changes. • Short-term exposure to glucocorticoids alters muscle gene expression. • Glucocorticoids are transiently increased in response to acute aerobic exercise. • Concurrent signals at the time of glucocorticoid exposure regulate gene expression. • Aerobic exercise alters glucocorticoid gene expression differently by time of day. • REDD1 is a concurrent signal regulating time of day differences in gene expression.