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OP0115 Polymorphism at the type i collagen (colia1) and relative risk of osteoporosis and vertebral fractures in postmenopausal women
  1. J Fernández-Melón1,
  2. M Bernad1,
  3. ML Gonzalez2,
  4. C Gonzalez3,
  5. MV Garces4,
  6. E Martin-Mola1,
  7. ME Martinez5
  1. 1Rheumatology
  2. 2Biochemistry Service, Hospital Gomez Ulla, Madrid, Spain
  3. 3Rheumatology, Hospital Gregorio Marañón
  4. 4Research, Hospital La Paz
  5. 5Biochemistry Service

Abstract

Background Twin and family studies have demonstrated that an important degree of the population variance in bone mineral density (BMD) is attributable to genetic factors.

Objectives A polymorphism in the collagen type I alpha 1 (COLIA1) gene has recently been associated with low bone mass and fracture incidence.

Methods We analysed the relationship between COLIA1 gene polymorphism, lumbar spine and hip BMD, T-score and fracture incidence in a population of 319 postmenopausical women classified by WHO standards: 98 non-osteoporotic women (NOPW) (57.4 ± 6.2 yrs), 146 osteoporotic women without fracture (OPW without fracture: OPWnF)(60.0 ± 5.2) and 75 osteoporotic women with fracture (OPW with fracture: OPWwF) (61.2 ± 6.3 yrs). The COLIA1 genotype was assessed by polymerase chain reaction and Bal I endonuclease digestion. Genotype frequencies for the total group were 49.2% “SS” homozygotes, 39.5% “Ss” heterozygotes and 11.3% “ss” homozygotes.

Results We found significant differences in the percentage of homozygous “ss” between NOPW and OPW (6.1% and 13.6% respectively). However, the incidence of genotype “ss” in OPWnF was 6.2% and 28% in OPWwF. We observed no associations between the COLIA1 genotype and lumbar and hip BMD. However, the lumbar spine T-scores were lower in the “ss” group than in the “Ss” and “ss” group. The incidence of fractures (64 vertebral and 11 colles) varied significantly by genotype: “SS” 21.7%; “Ss” 15.9%; and “ss” 58.3% (chi-square = 15.43; p < 0.0001); this resulted in a fracture odds ratio of 5.96 (95% confidence interval 2.26–15.69). Logistic regression analysis of fracture prevalence showed that for prevalent fractures, the women with “ss” group had 4.17 times risk of the woman “SS”+ “Ss” groups. When prevalence was adjusted for BMD and T-scores, the respective fracture risk was 2.6 and 2.94 for the “ss” group versus the other genotypes (SS+Ss).

Conclusion A slight association was found between lumbar T-score and gene COLIA1 polymorphism. Expression of the “ss” allele seems to be related with a higher incidence of fracture in postmenopausical women and was independent of bone mineral density.

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