[Wnt signaling and glucocorticoid-induced osteoporosis]

Wnt signaling plays an important role not only in development and morphogenesis of embryos but in pathogenesis of various disorders including cancers. Analyses of the mutations in LDL receptor-related protein 5 (LRP5), a Wnt co-receptor, revealed that the Wnt signaling pathway is important for bone formation. Glucocorticoids suppress the canonical Wnt signaling pathway by such mechanisms as the enhancement the expression of dickkopf-1 (Dkk-1) and secreted frizzled-related protein 1 (sFRP1), and activation of the glycogen synthase kinase-3beta (GSK-3beta) activity. The inhibition of the canonical Wnt signal by glucocorticoid may be involved in the pathogenesis of glucocorticoid-induced osteoporosis.