Bone mineral density, osteoporosis, and osteoporotic fractures: a genome-wide association study

Abstract

Background: Osteoporosis is diagnosed by the measurement of bone mineral density, which is a highly heritable and multifactorial trait. We aimed to identify genetic loci that are associated with bone mineral density.

Methods: In this genome-wide association study, we identified the most promising of 314 075 single nucleotide polymorphisms (SNPs) in 2094 women in a UK study. We then tested these SNPs for replication in 6463 people from three other cohorts in western Europe. We also investigated allelic expression in lymphoblast cell lines. We tested the association between the replicated SNPs and osteoporotic fractures with data from two studies.

Findings: We identified genome-wide evidence for an association between bone mineral density and two SNPs (p<5x10(-8)). The SNPs were rs4355801, on chromosome 8, near to the TNFRSF11B (osteoprotegerin) gene, and rs3736228, on chromosome 11 in the LRP5 (lipoprotein-receptor-related protein) gene. A non-synonymous SNP in the LRP5 gene was associated with decreased bone mineral density (rs3736228, p=6.3x10(-12) for lumbar spine and p=1.9x10(-4) for femoral neck) and an increased risk of both osteoporotic fractures (odds ratio [OR] 1.3, 95% CI 1.09-1.52, p=0.002) and osteoporosis (OR 1.3, 1.08-1.63, p=0.008). Three SNPs near the TNFRSF11B gene were associated with decreased bone mineral density (top SNP, rs4355801: p=7.6x10(-10) for lumbar spine and p=3.3x10(-8) for femoral neck) and increased risk of osteoporosis (OR 1.2, 95% CI 1.01-1.42, p=0.038). For carriers of the risk allele at rs4355801, expression of TNFRSF11B in lymphoblast cell lines was halved (p=3.0x10(-6)). 1883 (22%) of 8557 people were at least heterozygous for these risk alleles, and these alleles had a cumulative association with bone mineral density (trend p=2.3x10(-17)). The presence of both risk alleles increased the risk of osteoporotic fractures (OR 1.3, 1.08-1.63, p=0.006) and this effect was independent of bone mineral density.

Interpretation: Two gene variants of key biological proteins increase the risk of osteoporosis and osteoporotic fracture. The combined effect of these risk alleles on fractures is similar to that of most well-replicated environmental risk factors, and they are present in more than one in five white people, suggesting a potential role in screening.

Figure 1

Study design SNP=single nucleotide polymorphism. *TwinsUK Discovery cohort. †Subsample of the Rotterdam cohort. ‡TwinsUK replication cohort, Chingford cohort, and the remainder of the Rotterdam cohort. §Rotterdam fracture cohort. ¶Chingford fracture cohort.

Figure 2

Association of single nucleotide polymorphisms at LRP5 with bone mineral density in the lumbar spine (A) Negative log p values for associations between the SNP, rs3736228, and bone mineral density are plotted against chromosomal position. (B) Annotated reference sequence genes by chromosomal position (according to the US National Centre for Biotechnology Information). (C) Linkage disequilibrium in GOLD heatmap Haploview 4.0 colour scheme. SNP rs3736228 represents data from all cohorts. Details of all SNPs are in webtable 3.

Figure 3

Association of single nucleotide polymorphisms near the osteoprotegerin gene (TNFRSF11B) and bone mineral density at lumbar spine (A) Negative log p values for associations between the SNP, rs4355801, and bone mineral density are plotted against chromosomal position. (B) Annotated reference sequence genes by chromosomal position (according to the US National Center for Biotechnology Information). (C) Linkage disequilibrium in GOLD heatmap Haploview 4.0 colour scheme. SNPs rs4355801, rs6469792, and rs6469804 represent data from all cohorts. Details of all SNPs in this figure are in webtable 3.

Figure 4

Bone mineral density and number of risk alleles at TNFRSF11B (rs6469792) and LRP5 (rs3736228) Bone mineral density at (A) lumbar spine and (B) femoral neck. Vertical bars represent standard errors. p value is from the non-parametric trend test. The data represent all cohorts studied.