Fig. 2. Pathways of circadian clock genes and miRNAs regulating bone metabolism, modified from the study of Smith et al. (2016) and Tang et al. (2020) . ATF4: activating transcription factor 4; BMAL1: brain and muscle aryl hydrocarbon receptor nuclear translocator (ARNT)-like 1; CLOCK: circadian locomotor output cycles kaput; CRY2: cryptochrome 2; DUSP1: dual specificity phosphatase 1; GR: glucocorticoid receptor; GRE: glucocorticoid receptor element; Noct: Nocturnin; Osx: osterix; OCN: osteocalcin; PER2: period 2; REV-ERBα/β: nuclear receptor subfamily 1 group D 1/2 (NR1D1/2); RISC: RNA-induced silencing complex; Runx2: Runt-related transcription factor 2.↑ ↑ : up-regulated;↓ ↓ : down-regulated.