title: Vitamin D and bone.
abstract: It is now well established that supraphysiological doses of 1alpha,25-dihydroxyvitamin D(3) [1alpha,25(OH)(2)D(3)] stimulate bone resorption. Recent studies have established that osteoblasts/stromal cells express receptor activator of NF-kappaB ligand (RANKL) in response to several bone-resorbing factors including 1alpha,25(OH)(2)D(3) to support osteoclast differentiation from their precursors. Osteoclast precursors which express receptor activator of NF-kappaB (RANK) recognize RANKL through cell-to-cell interaction with osteoblasts/stromal cells, and differentiate into osteoclasts in the presence of macrophage-colony stimulating factor (M-CSF). Osteoprotegerin (OPG) acts as a decoy receptor for RANKL. We also found that daily oral administration of 1alpha,25(OH)(2)D(3) for 14 days to normocalcemic thyroparathyroidectomized (TPTX) rats constantly infused with parathyroid hormone (PTH) inhibited the PTH-induced expression of RANKL and cathepsin K mRNA in bone. The inhibitory effect of 1alpha,25(OH)(2)D(3) on the PTH-induced expression of RANKL mRNA occurred only with physiological doses of the vitamin. Supraphysiological doses of 1alpha,25(OH)(2)D(3) increased serum Ca and expression of RANKL in vivo in the presence of PTH. These results suggest that the bone-resorbing activity of vitamin D does not occur at physiological dose levels in vivo. A certain range of physiological doses of 1alpha,25(OH)(2)D(3) rather suppress the PTH-induced bone resorption in vivo, supporting the concept that 1alpha,25(OH)(2)D(3) or its derivatives are useful for the treatment of various metabolic bone diseases such as osteoporosis and secondary hyperparathyroidism.
authors.affiliation: Research Center for Genomic Medicine, Saitama Medical School, Saitama 350-1241, Japan. tasuda@saitama-med.ac.jp
authors.forename: Tatsuo
authors.initials: T
authors.lastname: Suda
authors.forename: Yutaka
authors.initials: Y
authors.lastname: Ueno
authors.forename: Katsuyuki
authors.initials: K
authors.lastname: Fujii
authors.forename: Toshimasa
authors.initials: T
authors.lastname: Shinki
mesh_terms: D000818:Animals; D001846:Bone Development / Q000187:drug effects / Q000502:physiology; D001862:Bone Resorption / Q000378:metabolism*; D001842:Bone and Bones / Q000166:cytology / Q000502:physiology; D002113:Calcification, Physiologic / Q000187:drug effects / Q000502:physiology*; D002118:Calcium / Q000378:metabolism*; D002352:Carrier Proteins / Q000235:genetics / Q000378:metabolism; D002454:Cell Differentiation; D006801:Humans; D008562:Membrane Glycoproteins / Q000235:genetics / Q000378:metabolism; D010006:Osteoblasts / Q000166:cytology; D010010:Osteoclasts / Q000166:cytology; D010281:Parathyroid Hormone / Q000378:metabolism; D053245:RANK Ligand; D053246:Receptor Activator of Nuclear Factor-kappa B; D014807:Vitamin D / Q000378:metabolism* / Q000494:pharmacology
chemical_list: D002352:Carrier Proteins; D008562:Membrane Glycoproteins; D010281:Parathyroid Hormone; D053245:RANK Ligand; D053246:Receptor Activator of Nuclear Factor-kappa B; C505686:TNFRSF11A protein, human; C505688:TNFSF11 protein, human; D014807:Vitamin D; D002118:Calcium