Caffeine decreases vitamin D receptor protein expression and 1,25(OH)2D3 stimulated alkaline phosphatase activity in human osteoblast cells

Prema B. Rapuri, J. C. Gallagher, Zafar Nawaz

Research output: Contribution to journalArticlepeer-review

47 Scopus citations

Abstract

Of the various risk factors contributing to osteoporosis, dietary/lifestyle factors are important. In a clinical study we reported that women with caffeine intakes >300 mg/day had higher bone loss and women with vitamin D receptor (VDR) variant, tt were at a greater risk for this deleterious effect of caffeine. However, the mechanism of how caffeine effects bone metabolism is not clear. 1,25-Dihydroxy vitamin D3 (1,25(OH)2D3) plays a critical role in regulating bone metabolism. The receptor for 1,25(OH)2D3, VDR has been demonstrated in osteoblast cells and it belongs to the superfamily of nuclear hormone receptors. To understand the molecular mechanism of the role of caffeine in relation to bone, we tested the effect of caffeine on VDR expression and 1,25(OH)2D3 mediated actions in bone. We therefore examined the effect of different doses of caffeine (0.2, 0.5, 1.0 and 10 mM) on 1,25(OH)2D3 induced VDR protein expression in human osteoblast cells. We also tested the effect of different doses of caffeine on 1,25(OH)2D3 induced alkaline phosphatase (ALP) activity, a widely used marker of osteoblastic activity. Caffeine dose dependently decreased the 1,25(OH)2D3 induced VDR expression and at concentrations of 1 and 10 mM, VDR expression was decreased by about 50-70%, respectively. In addition, the 1,25(OH)2D3 induced alkaline phosphatase activity was also reduced at similar doses thus affecting the osteoblastic function. The basal ALP activity was not affected with increasing doses of caffeine. Overall, our results suggest that caffeine affects 1,25(OH)2D3 stimulated VDR protein expression and 1,25(OH)2D3 mediated actions in human osteoblast cells.

Original languageEnglish (US)
Pages (from-to)368-371
Number of pages4
JournalJournal of Steroid Biochemistry and Molecular Biology
Volume103
Issue number3-5
DOIs
StatePublished - Mar 1 2007

Keywords

  • 1,25(OH)D
  • Osteoblast cells
  • vitamin D

ASJC Scopus subject areas

  • Biochemistry
  • Endocrinology

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