REDD1 (regulated in development and DNA damage response 1) expression in skeletal muscle as a surrogate biomarker of the efficiency of glucocorticoid receptor blockade

► Glucocorticoids upregulate REDD1 mRNA expression in skeletal muscle. ► The upregulation is robust, reproducible, and model independent. ► The upregulation is blocked by the glucocorticoid receptor antagonist RU-486. ► Upregulated REDD1 expression correlates with decreased mTORC1 signaling. ► Changes in REDD1 expression represent a surrogate biomarker for RU-486 effectiveness.