Figure 2.

Schematic diagram illustrating the effects of some molecules generated by bone on systemic homeostasis. (A) Some molecules secreted by osteoblasts, osteocytes and osteoclasts such as CXCL12, CTSK, G-CSF, MMP-9, IL-7 and IL-9 play very important roles in regulating HSCs maintenance, expansion or mobilization, and thus influence the hematopoietic and immune systems such as lymphopoiesis and megakaryopoiesis. (B) FGF23 inhibits phosphate reabsorption and promotes calcium and sodium reabsorption in the kidney. (C) GluOC and LCN2 induce insulin production and improve insulin sensitivity and then regulate energy expenditure. Sclerostin secreted by osteocytes regulates insulin sensitivity and metabolism of adipocytes. (D) GluOC promotes brain development and cognitive function. (E) GluOC can regulate male fertility by promoting testosterone production and inhibiting the apoptosis of Leydig cells in testes. (F) Bone regulates muscle mass and exercise capacity through secretion of GluOC, PGE2, VEGF, and others.