Vitamin D receptor polymorphism may protect against osteoporosis

By Helen Albert, Senior medwireNews Reporter

A polymorphism in the vitamin D receptor gene (VDR) significantly influences risk for osteoporosis, suggest results from a meta-analysis of 26 studies.

The researchers found that people with two copies of the recessive b allele (bb genotype) for the VDR rs1544410 single nucleotide polymorphism (SNP) were a significant 39% less likely to develop osteoporosis than those with two copies of the wild type, dominant allele B (BB genotype).

In 1992, the rs1544410 or BsmI SNP was shown to influence variation in bone mineral density and circulating osteocalcin levels.

"Subsequently, a large number of epidemiological studies have been carried out to evaluate the association between [rs1544410] and individual susceptibility to osteoporosis. However, the results were inconclusive rather than conclusive," write Bai-Lian Liu, Ying Xiong (Kunming Medical University, Yunnan, China) and colleagues.

To investigate further, Liu and team carried out a meta-analysis of 26 published studies involving 2274 people with osteoporosis and 3150 controls. To be included in the analysis the studies had to be case-control in nature, assess the association between the rs1544410 SNP and osteoporosis, include enough information and data to calculate odds ratios, and be published in English.

As reported in Genetic Testing and Molecular Biomarkers, the team confirmed previous research suggesting that the bb genotype of rs1544410 may be protective. In addition to being significantly protective when compared with the BB genotype, people with the bb genotype had a significant 30% reduction in risk for osteoporosis when compared with people with BB and Bb genotypes.

When the researchers restricted their analysis to postmenopausal women, they observed a similar significant osteoporosis risk reduction of 32% when those with the bb genotype were compared with those with a BB or Bb genotype.

When the pooled cohort was divided according to ethnicity, Liu and co-workers found that the reduction in risk for osteoporosis could be explained by a significantly reduced risk associated with carriage of the b allele (82% reduced risk for Bb or bb genotypes compared with BB genotype) in African people, but not in Asian, Caucasian, or Turkish populations.

"This meta-analysis provides a pathway to help determine the likelihood that a person may develop osteoporosis and is a good example for the potential application of genetics to clinical medicine," commented independent genetics expert Kenneth Berns (University of Florida's Genetics Institute, Gainesville, USA).

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