title: Action of 1,25-dihydroxyvitamin D3 on phospholipid metabolism of human bone cells in culture.
abstract: It has recently been proposed that the action of 1,25-dihydroxyvitamin D3 (1,25-(OH)2D3) on bone metabolism may be mediated by changes in phospholipid metabolism. The effects of vitamin D metabolites on the incorporation of radiolabelled precursors into corresponding phospholipid classes were investigated using cells arising from cultured explants of normal human bone with osteoblast-like characteristics. Treatment with 1,25-(OH)2D3 increased the incorporation of serine, measured as the ratio of [3H]serine in phosphatidylserine (PS) to [14C]ethanolamine in phosphatidylethanolamine (PE), in a time- and dose-dependent manner. The maximum effect on PS/PE of 141.6 +/- 5.9% over control (P = 0.022) was observed at a dose of 0.1 nmol 1,25-(OH)2D3/l, maintained for 24 h. Incubations with 25-hydroxyvitamin D3 (0.1 mumol/l) and 24,25-dihydroxyvitamin D3 (10 nmol/l) had no effect. Supraphysiological doses (0.1 mumol/l) of 1,24,25- and 1,25,26-trihydroxyvitamin D3 showed similar effects to those of 1,25-(OH)2D3, emphasizing the importance of 1 alpha-hydroxylation. Incorporation of [14C]choline into phosphatidylcholine, calculated as a ratio to PE, was not affected by treatment with vitamin D metabolites. However, [3H]inositol uptake into phosphatidylinositol was almost doubled when compared with control uptake within 2 h of treatment with 1,25-(OH)2D3 (0.1 mumol/l). This may be of relevance, considering the importance of phosphoinositide metabolism in influencing the intracellular calcium concentration. These results support a role for 1,25-(OH)2D3 in the modulation of phospholipid metabolism in human bone cells, which in turn may be involved in the action of 1,25-(OH)2D3 in bone mineralization.
mesh_terms: D001842:Bone and Bones / Q000166:cytology / Q000187:drug effects* / Q000378:metabolism; D002117:Calcitriol / Q000494:pharmacology*; D002478:Cells, Cultured; D002794:Choline / Q000378:metabolism; D006801:Humans; D010714:Phosphatidylethanolamines / Q000378:metabolism; D010718:Phosphatidylserines / Q000378:metabolism; D010743:Phospholipids / Q000378:metabolism*; D012694:Serine / Q000378:metabolism
chemical_list: D010714:Phosphatidylethanolamines; D010718:Phosphatidylserines; D010743:Phospholipids; D012694:Serine; D002117:Calcitriol; D002794:Choline