The vitamin D receptor start codon polymorphism (Fok1) and bone mineral density in premenopausal women in Taiwan

The Vitamin D receptor gene (VDRG) polymorphism as a factor of bone turnove r rate or bone mineral density (BMD) is a controversial issue, especially i n different ethnic populations. In addition to intron 8 (Bsm1, Taq1) and ex on 9 (Apa1), VDRG polymorphism is present at its translation initiation sit e on exon 2. The VDRG has two translation initiation sites. The first shows a thymine/cytosine polymorphism and can be detected by restriction fragmen t length polymorphism (RFLP) using the endonuclease Fok1. This start codon polymorphism (SCP) of the VDRG was detected by polymerase chain reaction an d then by RFLP with Fok1. While the f allele was assigned for the presence of the restriction site, the F allele was assigned for the absence of the r estriction site, and the encoded vitamin D receptor is shorter by three ami no acids. We examined the association between this SCP of the VDRG and bone turnover as well as BMD in 101 premenopausal Taiwanese women aged 40-53 ye ars. Total body bone mineral content and BMD of proximal femur and lumbar s pine were measured by dual-energy X-ray absorptiometry. We found a prevalen ce of 39.6% for the f allele of the VDRG. The frequencies of FF, Ff and ff genotypes were 35.6%, 49.5% and 14.9%, respectively. There was no statistic ally significant difference in BMD at any site or bone turnover markers amo ng the three Fok1 genotypes (FF, Ff and ff). The SCP is independent of Bsm1 , Apa1 or Taq1 polymorphisms of the VDRG at intron 8 and exon 9. In conclus ion, the SCP polymorphism detected by endonuclease Fok1 does not significan tly influence BMD or bone turnover in premenopausal women in Taiwan.