Association of the CT gene (CA) polymorphism with BMD in osteoporotic mexican women

A comprehensive overview on osteoporosis and its risk factors

Osteoporosis is a bone disorder with remarkable changes in bone biologic material and consequent bone structural distraction, affecting millions of people around the world from different ethnic groups. Bone fragility is the worse outcome of the disease, which needs long term therapy and medical management, especially in the elderly. Many involved genes including environmental factors have been introduced as the disease risk factors so far, of which genes should be considered as effective early diagnosis biomarkers, especially for the individuals from high-risk families. In this review, a number of important criteria involved in osteoporosis are addressed and discussed.

JAG1, MEF2C and BDNF polymorphisms associated with bone mineral density in women from Northern México

Introduction: Osteoporosis is characterized by a low bone mineral density. Genetic composition is one of the most influential factors in determining bone mineral density (BMD). There are few studies on genes associated with BMD in the Mexican population. Objective: To investigate the association of eight single nucleotide polymorphisms (SNP) of JAG1, MEF2C and BDNF genes with BMD in women of Northern México. Materials and methods: This study involved 124 unrelated Mexican women between 40 and 80 years old. BMD was determined by dual X-ray absorptiometry. Genotyping was performed using allelic discrimination by real time PCR. We analyzed the SNP of JAG1 (rs6514116, rs2273061, rs2235811 and rs6040061), MEF2C (rs1366594, rs12521522 and rs11951031), and BDNF (rs6265) and the data using linear regression. Results: The JAG1 SNP rs2235811 was associated with the BMD of the total body under the dominant inheritance model (p=0,024). Although the other SNPs were not associated with BMD in any of the inheritance models studied, a trend was observed. Conclusion: Our results suggest that the SNP rs2235811 in the JAG1 gene might contribute to the variation in BMD in women from northern México.

Association of IL-6 G-174C polymorphism with bone mineral density

Functional polymorphisms in the promoter region of interleukin-6 (IL-6) are known to be involved in bone mineral density (BMD) and the development of osteoporosis, but the reported results have been inconsistent. Using the meta-analysis approach, the present study is designed to provide a relatively comprehensive picture of the relationship between bone mineral density (BMD) or osteoporosis and polymorphisms in the promoter region of IL-6 (rs1800795 and rs1800796). The difference of bone mineral density (BMD) values between genotypes was examined by mean difference and 95 % confidence intervals (CIs). Association between IL-6 polymorphism and clinical osteoporosis was evaluated by pooled odds ratios (ORs) and 95 % CIs. A total of 13 articles with 11,499 subjects were included in the present study. For -174 (rs1800795), we found that individuals with the G/G genotype had a significantly lower BMD value than those with C/C genotype at femoral neck (0.02 g/cm(2), 95 % CI 0.00-0.03) (p = 0.04) and distal radius (0.01 g/cm(2), 95 %CI 0.01-0.01) (p < 0.0001). However, we did not find a statistically significant difference of BMD at the spine. When analysis was limited to postmenopausal women, similar results were obtained. We further found that the C/C genotype was associated with a reduced risk of osteoporosis compared to G/G genotype, and the pooled OR was 0.72 (95 % CI 0.54-0.95, p = 0.02). In addition, a significant relationship was found between G-634C (rs1800796) polymorphism and distal radius BMD (CC vs. GG: 0.02 g/cm(2), 95 % CI 0.01-0.03; GC vs. GG: 0.02 g/cm(2), 95 % CI 0.00-0.03) in the Asian population. These findings suggest that the CC genotype of IL-6 G-174C polymorphism may be associated with high BMD at femoral neck and distal radius and decreased risk of osteoporosis in the Caucasian population whereas G-634C polymorphism was associated with distal radius BMD in Asians.

Association of LRP5 haplotypes with osteoporosis in Mexican women

Osteoporosis is a common health problem in Mexico, so it is essential to investigate the status of different gene polymorphisms that could serve as genetic susceptibility markers in the Mexican population. Genes with a role in bone metabolism are excellent candidates for association studies. In this study were determined the allelic and genotypic frequencies of four polymorphic markers (C/T rs3736228, G/A rs4988321, T/C rs627174 and T/C rs901824) in the low-density lipoprotein receptor-related protein 5 gene (LRP5) and their association with osteoporosis in 100 pos-menopausal osteoporotic Mexican women and their controls, using real time-PCR and TaqMan probes. Only the G/A polymorphism (rs4988321, Val667Met) showed significant differences (p = 0.039) when genotype frequencies were compared. However, when the haplotypes of these four polymorphisms were analyzed, interesting associations became evident. The CGTT haplotype showed significant association with low risk of osteoporosis (OR 0.629; p = 0.007; [95 % CI, 0.448-0.884]), whereas the TACT haplotype was significantly associated with a higher risk of osteoporosis (OR 7.965; p = 0.006; [95 % CI, 1.557-54.775]). Our results supported the association of LRP5 with osteoporosis and showed the potential value of LRP5 haplotypes to identify risk of osteoporosis in Mexican population.

Association study of calcitonin gene-related polypeptide-alpha (CALCA) gene polymorphism with migraine

Migraine is a neurological disorder that is associated with increased levels of calcitonin gene-related peptide (CGRP) in plasma. CGRP, being one of the mediators of neurogenic inflammation and a phenomenon implicated in the pathogenesis of migraine headache, is thus suggested to have an important role in migraine pathophysiology. Polymorphisms of the CALCA gene have been linked to Parkinson's disease, ovarian cancer and essential hypertension, suggesting a functional role for these polymorphisms. Given the strong evidence linking CGRP and migraine, it is hypothesised that polymorphisms in the CALCA gene may play a role in migraine pathogenesis. Seemingly non functional intronic polymorphisms are capable of disrupting normal RNA processing or introducing a splice site in the transcript. A 16bp deletion in the first intron of the CALCA gene has been reported to be a good match for the binding site for a transcription factor expressed strongly in neural crest derived cells, AP-2. This deletion also eliminates an intron splicing enhancer (ISE) that may potentially cause exon skipping. This study investigated the role of the 16bp intronic deletion in the CALCA gene in migraineurs and matched control individuals. Six hundred individuals were genotyped for the deletion by polymerase chain reaction followed by fragment analysis on the 3130 Genetic Analyser. The results of this study showed no significant association between the intronic 16bp deletion in the CALCA gene and migraine in the tested Australian Caucasian population. However, given the evidence linking CGRP and migraine, further investigation of variants with this gene may be warranted.

Association of the calcitonin gene (CA) polymorphism with osteoarthritis of the knee in a Mexican mestizo population

Osteoarthritis (OA) is the most common form of destructive joint disease that is characterized by the degeneration of the articular cartilage, synovial membrane, joint capsule, and subchondral bone. The knee is a joint commonly affected for OA. Calcitonin (CT) has been suggested to have chondroprotective effects; therefore, could play a role in the pathogenesis of OA of the knee. Genetic variations in or adjacent to the CT gene may be associated with primary OA development. We conducted a case-control association study in which we examined the correlation between a dinucleotide (cytosine-adenine, CA) repeat polymorphism at the CT locus and OA of the knee in 88 patients with OA and in 111 control subjects from the Mexican mestizo population. Allele A and genotype AG frequencies were significantly higher in patients with OA than in control subjects (56.3 vs. 43.2%; p<0.001 and 40.9 vs. 26.1%; p=0.027, respectively), and were associated with the presence of OA of the knee (odds ratio [OR], 2.62; 95% confidence interval [95% CI], 1.30-5.27, and OR, 1.93; 95% CI, 1.04-3.58, respectively) using a logistic regression model adjusted for gender, age and Body mass index (BMI). The GG genotype was associated with a lower risk of OA development of the knee; thus, it may constitute a protective factor against this disease (OR, 0.40; 95% CI, 0.16-0.98). In summary, we conclude that the dinucleotide CA polymorphism in the CT gene may become a useful marker for genetic studies of OA of the knee in Mexican population.

Association of interleukin-6 gene polymorphisms with bone mineral density in Mexican women

BACKGROUND

The interleukin-6 gene (IL-6) stimulates osteoclast development; therefore, it has been implicated in osteoporosis. In this study, the association of osteoporosis with three IL-6 gene markers (a CA dinucleotide repeat and two single nucleotide polymorphisms [SNPs]: G-174C and G-572C) was tested in the Mexican population.

METHODS

Population sample was comprised of 70 osteoporotic women, 70 non-osteoporotic women, and 500 subjects from the general population who were genotyped for the IL-6 markers. SNPs were analyzed by real-time PCR using the 5' exonuclease assay, whereas the CA dinucleotide polymorphism was evaluated by PCR and capillary electrophoresis. The allele-phenotype relationship was analyzed with the statistical method STRAT that considered population stratification and the results were adjusted with potential confounders for osteoporosis by a longitudinal multivariate model.

RESULTS

We found that the C allele of the G-174C SNP and the A3 allele of the CA polymorphism are associated with increased bone mineral density (BMD) (p<0.0001), whereas the G-572C SNP is not (p=0.19). In concordance, subjects heterozygous for the A3 allele have higher BMD and T score average values (90.75% and -0.87, respectively) than those who did not present any A3 allele (81.4% and -1.45, respectively). Likewise, subjects with the CC genotype of the G-174 SNP have higher BMD (96.5%) and T score average value (-0.33) than those bearing the CG or GG genotype (lumbar BMD, 88.5 and 79.98%, respectively; T score: -1.07 and -1.75, respectively).

CONCLUSIONS

The CA repeat and the G-174C SNP of the IL-6 gene may become useful markers for osteoporosis in the Mexican population.

Molecular genetic studies of gene identification for osteoporosis

This review comprehensively summarizes the most important and representative molecular genetics studies of gene identification for osteoporosis published up to the end of September 2007. It is intended to constitute a sequential update of our previously published reviews covering the available data up to the end of 2004. Evidence from candidate gene-association studies, genome-wide linkage and association studies, as well as functional genomic studies (including gene-expression microarray and proteomics) on osteogenesis and osteoporosis, are reviewed separately. Studies of transgenic and knockout mice models relevant to osteoporosis are summarized. The major results of all studies are tabulated for comparison and ease of reference. Comments are made on the most notable findings and representative studies for their potential influence and implications on our present understanding of genetics of osteoporosis. The format adopted by this review should be ideal for accommodating future new advances and studies.

Association of the estrogen receptor alpha gene polymorphisms with osteoporosis in the Mexican population

The estrogen receptor gene (ER alpha) has been implicated in the development of osteoporosis. In this study, the association of two ER alpha gene polymorphic markers (a TA dinucleotide repeat and a single nucleotide polymorphism, G2014A) with osteoporosis was tested in 70 osteoporotic women, 70 non-osteoporotic women and 500 subjects from the Mexican population. According to the genetic analysis of the Mexican population using eight unlinked polymorphic markers, we found that our population is structured into three subpopulations; therefore, the allele-phenotype relationship was analyzed with a statistical method that considered population stratification. We found that the G2014A polymorphism is associated with the presence of osteoporosis while the TA dinucleotide repeat is not. The G allele and the GG genotype frequencies of the G2014A marker were significantly higher in osteoporotic than in non-osteoporotic women. Likewise, subjects bearing the G allele in heterozygous or homozygous displayed lower values for lumbar bone mineral density and T score than those who did not present any G allele. The effect of confounders for osteoporosis on the association of G allele-osteoporosis was ruled out. In summary, we conclude that the G2014 polymorphism may become a useful marker for genetic studies of osteoporosis in the Mexican population.