Chronobiology and clock genes in bone and mineral metabolism

Rhythmicity in cellular processes and organ function is controlled by internal circadian clocks found in all cell types investigated, including osteoblasts, osteoclasts, and osteocytes, as well as cell types with implications for bone health: cartilage, parathyroid, intestine, and muscle. Accumulating evidence from human and animal studies points to a detrimental effect of chrono-disruption on bone health, such as that induced by rotating shift work or chronic jet lag. The current chapter introduces the circadian clock system and covers the current knowledge on the chronobiology of bone and the functions of the circadian clock in cell types important in bone biology and mineral metabolism. Implications for bone health of chrono-disruption by sleep disturbance are discussed, and the emerging principle of chronotherapy is introduced.