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Consequences of vitamin D receptor gene polymorphisms for growth inhibition of cultured human peripheral blood mononuclear cells by 1,25-dihydroxyvitamin D3

Authors


Dr J.P.T.M. van Leeuwen Department of Internal Medicine III, Dr Molewaterplein 40, 3015 GD Rotterdam, The Netherlands. Fax: + 31 10 463 3268; E-mail: vanleeuwen@ inw3.fgg.eur.nl

Abstract

OBJECTIVE

In the vitamin D receptor (VDR) gene a BsmI restriction fragment length polymorphism (RFLP) in intron 8 and a translational start-site polymorphism, identified as a FokI RFLP, have been described. Crucial for a proper interpretation of these polymorphisms in association studies is the knowledge whether they have direct consequences for 1,25-(OH)2D3 action at cellular level. The present study was designed to assess functional significance of the FokI and BsmI VDR gene polymorphisms in peripheral blood mononuclear cells (PBMC) with a natural occurring VDR genotype for cell growth inhibition by 1,25-(OH)2D3.

DESIGN

PBMC of women were isolated, VDR genotyped and in vitro inhibition by 1,25-(OH)2D3 of Phytohemagglutinin (PHA)-stimulated growth of PBMC was examined in relation to VDR genotype.

RESULTS

PHA-stimulated growth and maximal growth inhibition were independent of VDR genotype. However, the FF genotype had a significant lower ED50 than the Ff genotype corresponding to an allele dose effect of 0.32 nm per f allele copy (P = 0.0036). For BsmI genotypes no differences in ED50 were observed.

CONCLUSION

The present study demonstrates for the first time in cells with a natural VDR genotype a direct functional consequence of the VDR gene translational start-site polymorphism for the action of 1,25-(OH)2D3. Especially under conditions of vitamin D insufficiency these findings might have clinical implications.

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