Large-scale analysis of association between polymorphisms in the transforming growth factor beta 1 gene (TGFB1) and osteoporosis: the GENOMOS study.

INTRODUCTION: The TGFB1 gene which encodes transforming growth factor beta 1, is a strong candidate for susceptibility to osteoporosis and several studies have reported associations between bone mineral density (BMD), osteoporotic fractures and polymorphisms of TGFB1, although these studies have yielded conflicting results. METHODS: We investigated associations between TGFB1 polymorphisms and BMD and fracture in the GENOMOS study: a prospective multicenter study involving 10 European research studies including a total of 28,924 participants. Genotyping was conducted for known TGFB1 polymorphisms at the following sites: G-1639-A (G-800-A, rs1800468), C-1348-T (C-509-T, rs1800469), T29-C (Leu10Pro, rs1982073), G74-C (Arg25Pro, rs1800471) and C788-T (Thr263Ile, rs1800472). These polymorphisms were genotyped prospectively and methodology was standardized across research centers. Genotypes and haplotypes were related to BMD at the lumbar sine and femoral neck and fractures. RESULTS: There were no significant differences in either women or men at either skeletal site for any of the examined polymorphisms with the possible exception of a weak association with reduced BMD (-12 mg/cm2) in men with the T-1348 allele (p<0.05). None of the haplotypes was associated with BMD and none of the polymorphisms or haplotypes significantly affected overall risk of fractures, however, the odds ratio for incident vertebral fracture in carriers of the rare T788 allele was 1.64 (95% CI: 1.09-2.64), p<0.05. CONCLUSIONS: This study indicates that polymorphic variation in the TGFB1 gene does not play a major role in regulating BMD or susceptibility to fractures. The weak associations we observed between the C-1348-T and lumbar spine BMD in men and between C788-T and risk of incident vertebral fractures are of interest but could be chance findings and will need replication in future studies.

Large-scale population-based study shows no association between common polymorphisms of the TGFB1 gene and BMD in women.

UNLABELLED: The TGFB1 gene is a strong functional candidate for regulating genetic susceptibility to osteoporosis. We studied five common polymorphisms of TGFB1 in relation to osteoporosis-related phenotypes in a population-based cohort of 2975 British women, but found no significant association with bone mass, bone loss, bone markers, or fracture. INTRODUCTION: The gene encoding TGFB1 is a strong functional candidate for genetic susceptibility to osteoporosis. Several polymorphisms have been identified in TGFB1, and previous work has suggested that allelic variants of TGFB1 may regulate BMD and susceptibility to osteoporotic fracture. MATERIALS AND METHODS: We studied the relationship between common polymorphisms of TGFB1 and several osteoporosis-related phenotypes including BMD at the lumbar spine and femoral neck, measured by DXA; bone loss over a 6-year period; biochemical markers of bone turnover (urinary free deoxypyridinoline and free pyridinoline/creatinine ratio and serum N-terminal propeptide of type 1 collagen), and fractures in a population-based study of 2975 women from the United Kingdom. Participants were genotyped for single nucleotide polymorphisms (SNPs) in the TGFB1 promoter (G-800A; rs1800468; C-509T; rs1800469), exon 1 (T29C; rs1982073 and G74C; rs1982073); and exon 5 (C788T; rs1800471) on PCR-generated fragments of genomic DNA. Haplotypes were constructed from genotype data using the PHASE software program, and genotypes and haplotypes were related to the phenotypes of interest using general linear model ANOVA, with correction for confounding factors including age, height, weight, menopausal status, hormone replacement therapy (HRT) use, physical activity score, and dietary calcium intake. RESULTS: The polymorphisms were in strong linkage disequilibrium, and four common haplotypes accounted for >95% of alleles at the locus. There was no association between individual SNPs and BMD, bone loss, or biochemical markers of bone turnover. Haplotype analysis showed a nominally significant association with femoral neck BMD (p = 0.042) and with incident osteoporotic fracture (p = 0.013), but these were not significant after correcting for multiple testing. CONCLUSIONS: Common polymorphic variants of the TGFB1 gene did not influence BMD or bone loss in this population.

The association between common vitamin D receptor gene variations and osteoporosis: a participant-level meta-analysis.

BACKGROUND: Polymorphisms of the vitamin D receptor (VDR) gene have been implicated in the genetic regulation of bone mineral density (BMD). However, the clinical impact of these variants remains unclear. OBJECTIVE: To evaluate the relation between VDR polymorphisms, BMD, and fractures. DESIGN: Prospective multicenter large-scale association study. SETTING: The Genetic Markers for Osteoporosis consortium, involving 9 European research teams. PARTICIPANTS: 26,242 participants (18,405 women). MEASUREMENTS: Cdx2 promoter, FokI, BsmI, ApaI, and TaqI polymorphisms; BMD at the femoral neck and the lumbar spine by dual x-ray absorptiometry; and fractures. RESULTS: Comparisons of BMD at the lumbar spine and femoral neck showed nonsignificant differences less than 0.011 g/cm2 for any genotype with or without adjustments. A total of 6067 participants reported a history of fracture, and 2088 had vertebral fractures. For all VDR alleles, odds ratios for fractures were very close to 1.00 (range, 0.98 to 1.02) and collectively the 95% CIs ranged from 0.94 (lowest) to 1.07 (highest). For vertebral fractures, we observed a 9% (95% CI, 0% to 18%; P = 0.039) risk reduction for the Cdx2 A-allele (13% risk reduction in a dominant model). LIMITATIONS: The authors analyzed only selected VDR polymorphisms. Heterogeneity was detected in some analyses and may reflect some differences in collection of fracture data across cohorts. Not all fractures were related to osteoporosis. CONCLUSIONS: The FokI, BsmI, ApaI, and TaqI VDR polymorphisms are not associated with BMD or with fractures, but the Cdx2 polymorphism may be associated with risk for vertebral fractures.

Haplotypes defined by promoter and intron 1 polymorphisms of the COLIA1 gene regulate bone mineral density in women.

CONTEXT: The COLIA1 gene is a strong candidate for susceptibility to osteoporosis. The causal genetic variants are currently unclear, but the most likely are functional polymorphisms in the promoter and intron 1 of COLIA1. OBJECTIVE: The objective of the study was to determine whether promoter and intron 1 polymorphisms of COLIA1 or haplotypes defined by these polymorphisms regulate bone mineral density (BMD) in women. DESIGN: This was a population-based association study involving 3270 women from the United Kingdom who took part in a regional osteoporosis screening program. MAIN OUTCOME MEASURES: BMD at the lumbar spine (LS-BMD) and femoral neck (FN-BMD) was measured on two occasions approximately 6 yr apart, in relation to polymorphisms and haplotypes defined by polymorphisms within the COLIA1 intron 1 (+1245G/T; rs1800012) and promoter (-1997G/T; rs1107946; -1663IndelT; rs2412298). RESULTS: The polymorphisms were in strong linkage disequilibrium, and three haplotypes accounted for more than 95% of alleles at the COLIA1 locus. The individual polymorphisms were associated with BMD, but the most consistent associations were with haplotypes defined by all three polymorphisms. Homozygote carriers of haplotype 2 (-1997G/-1663delT/+1245T) had reduced BMD at baseline (P = 0.007 for LS-BMD; P = 0.008 for FN-BMD), whereas homozygotes for haplotype 3 (-1997T/-1663insT/+1245G) had increased BMD (P = 0.007 for LS-BMD). Similar associations were observed at follow-up for haplotype 3, but the association with haplotype 2 was weaker due to increased uptake of hormone replacement therapy in homozygotes for this haplotype. CONCLUSIONS: Two haplotypes defined by polymorphisms in the 5' flank of the COLIA1 regulate BMD in a bidirectional manner in women.