Genetic influences on bone density: physiological correlates of vitamin D receptor gene alleles in premenopausal women

Evaluation of vitamin D receptor gene polymorphisms (Fok-I and Bsm-I) in T1DM Saudi children

BACKGROUND

Vitamin D deficiency conferred strongest susceptibility to pathogenesis of type 1 diabetes mellitus (T1DM). Altered gene expression and function have strong effect on VDR gene polymorphism.

OBJECTIVES

We aimed to check for the association of two single nucleotide polymorphisms (SNPs) in VDR gene (Fok-I and Bsm-I) with T1DM in Saudi children.

SUBJECTS AND METHODS

Cross-sectional study included 100 T1DM Saudi children, plus 102 unrelated healthy subjects. PCR technique was used for detection of Fok-I and Bsm-I SNPs in VDR gene.

RESULTS

Regarding the Fok-I polymorphisms, T1DM cases showed a significant increased frequency of the heterozygous genotype (Ff) than controls (33% vs 21%, OR = 1.9, 95% CI = 1.006-3.587, P = .04). In the meantime, they showed significantly lower frequency of the homozygous (ff) genotype (64% vs 79%, OR = 0.51, 95% CI = 0.28-0.96, P = .03). Cases showed also a significantly lower frequency of the (f) allele than controls (80.5% vs 87.7%, OR = 0.57, 95% CI = 0.33-0.995, P = .04). On the other hand, cases showed significantly higher frequency of the Bsm-I homozygous (bb) and heterozygous (Bb) genotypes (25% vs 11.8%, P = .01, OR = 2.5, 95% CI = 1.18-5.31) & (45% vs 27.5%, P = .0, OR = 2.1, 95 % CI = 1.20-3.89, respectively). Cases showed also significantly higher frequency of (b) allele compared to control (47.5% vs 25.5%, P = .0, OR = 2.6, 95% CI = 1.74-4.02). Haplotype analysis showed an increased risk with the fB and fb haplotypes.

CONCLUSION

This study emphasizes a positive association between SNPs (Fok-I and Bsm-I) and T1DM among Saudi children with increased risk with the Fok-I F and Bsm-I b alleles.

Vitamin D receptor gene polymorphisms in relation to the risk of colorectal cancer in the Polish population

The protective effect of vitamin D against several cancers including colorectal cancer is modulated by the vitamin D receptor (VDR) and its ligand, the active form of vitamin D. VDR response has been found to play a role in various genes encoding proteins involved in crucial cellular pathways. Single nucleotide polymorphisms (SNPs) of the VDR gene that modulate its activity are located in the promoter region, exons 2–9, and their vicinity and also in the 3′UTR region. Some of them have been previously studied in relation to cancer susceptibility and prognosis. The aim of our study was to investigate four polymorphisms, BsmI, ApaI, TaqI, and FokI, of the VDR gene in Polish patients with sporadic colorectal cancer and to evaluate their association with susceptibility to cancer. We found a significant association between the BsmI genotype and cancer (individuals with the bb genotype are more susceptible to cancer compared to those with other genotypes, p = 0.025, Fisher’s exact test for 2 × 2 table). Also, the TT genotype at TaqI and the AA genotype at ApaI are correlated with a higher risk of cancer (p = 0.00071 and p = 1.0 × 10⁻⁵, respectively). We found relatively strong linkage disequilibrium between the TaqI and ApaI loci (T with A and t with a, respectively). Both of these loci are associated with cancer. We do not observe any such association for the FokI polymorphism. In conclusion, a small modification in VDR expression may play a role in such a multipathway process as tumorigenesis.

Vitamin D and mammographic breast density: a systematic review

Studies suggest a protective relationship between Vitamin D and breast cancer risk. Several studies assessed the association of Vitamin D with mammographic breast density, a known and strong breast cancer risk factor. Understanding the potential role of Vitamin D in the modification of breast density might open new avenues in breast cancer prevention. This systematic review summarizes published studies that investigated the association between Vitamin D and mammographic breast density and offers suggestions for strategies to advance our scientific knowledge.

Influence of gene variants related to calcium homeostasis on biochemical parameters of women with polycystic ovary syndrome

PURPOSE

The purpose of this study was to evaluate the associations between polymorphisms in vitamin D receptor (VDR), parathyroid hormone (PTH), calcium sensing receptor (CASR), insulin receptor (INSR), and adiponectin (ADIPOQ) genes and biochemical characteristics of women with polycystic ovary syndrome (PCOS).

METHODS

Serum levels of LH, FSH, estradiol, testosterone, prolactin, SHBG, glucose, IGF-1, IGFBP-1, calcium, phosphorus, PTH, 25(OH)D, and 1,25(OH)(2) D were measured in 56 women with PCOS. Furthermore, genotyping five, one, one, two, and two polymorphisms of the VDR, PTH, CASR, INSR, and ADIPOQ genes, respectively, were performed.

RESULTS

The VDR TaqI "CC" genotype was associated with elevated serum levels of LH (p = 0.011). There were significant associations between decreased levels of SHBG and both VDR BsmI "GG" (p = 0.009) and ADIPOQ BsmI "CC" (p = 0.016) genotypes. Furthermore, patients with CaSR Hin1I "TG" genotype showed higher HoMA-IR (p = 0.008). All these associations remained significant after Bonferroni correction. In addition, phosphorus correlated negatively with estradiol (r =  -0.298, P = 0.026) and positively with glucose (r = 0.287, P = 0.032).

CONCLUSIONS

These data indicated for the first time that it is possible that the VDR and CASR gene variants through their effects on LH and SHBG levels, and insulin resistance are involved in pathogenesis of PCOS.

Pediatric Hodgkin lymphoma survivors at negligible risk for significant bone mineral density deficits

BACKGROUND

We hypothesized that pediatric Hodgkin lymphoma (HL) survivors would have bone mineral density (BMD) deficits compared to their peers because of osteotoxic chemotherapy during the time of greatest BMD accretion.

METHODS

We retrospectively reviewed records of HL survivors returning for follow-up between 1990 and 2002. Of the 133 eligible survivors, 109 who underwent quantitative computed tomography (QCT) comprised the study group. QCT-determined BMD Z-scores were correlated with patient characteristics and therapeutic exposures by Wilcoxon rank sum or Chi-square tests. Logistic regression models were used to explore risk factors for diminished BMD.

RESULTS

The study cohort was half male (50.5%) and 85.3% reported their race as white. Participants were representative of all survivors potentially eligible for study, except that more study participants were female, had hypothyroidism, and had received cyclophosphamide. Median age at diagnosis was 15.1 years (range, 3.1-20.7 years); median time between diagnosis and QCT was 7.5 years (range, 5.0-12.4 years). The proportion of HL survivors with BMD below the mean did not significantly differ from the general population (P = 0.503). However, those with BMD -1.5 SD and BMD -2.0 SD or lower (14.7% and 7.3%, respectively) exceeded that in the general population (6.7% and 2.3%, respectively; P < 0.001 for both degrees of severity). Males, diagnosed at 14 years or older, were at 6.5 times higher risk than females (OR 95% CI: 1.24-34.14; P = 0.027) for BMD deficits.

CONCLUSIONS

Overall, pediatric HL survivors had negligible BMD deficits. Male gender was associated with an increased risk of developing BMD deficits.

BsmI vitamin D receptor genotypes influence the efficacy of antiresorptive treatments in postmenopausal osteoporotic women. A 1-year multicenter, randomized and controlled trial

Vitamin D receptor (VDR) gene polymorphisms could be considered one of the factors influencing the efficacy of the anti-osteoporotic treatments. In this multicenter, prospective, randomized and controlled trial we evaluated whether BsmI vitamin D receptor (VDR) genotypes influence the efficacy of antiresorptive treatment regimes (administered alone or in combination) in postmenopausal osteoporotic women. Using restriction endonuclease, we identified the BsmI VDR polymorphism in 1,100 postmenopausal women with osteoporosis. The women were randomized, taking account of genotype, into five treatment groups: (1) alendronate (Aln, 10 mg/day) plus raloxifene (Rlx, 60 mg/day); (2) Aln plus hormone replacement therapy (HRT, 0.625 mg/day conjugated equine estrogens plus 2.5 mg/day medroxyprogesterone acetate); (3) Aln alone; (4) HRT alone; and (5) Rlx alone. Lumbar-spine bone mineral density (BMD) and bone turnover markers were measured at study entry and after 1 year of treatment. Using the general linear model (GLM) repeated-measures procedure, the means of BMD and bone turnover markers significantly differed from baseline after a period of treatment. In particular, the mean change from baseline for BMD was -0.034 (95% confidence interval [CI]: -0.037 to -0.031, P <0.001); for serum osteocalcin (OC) it was 1.369 (95% CI: 1.289 to 1.448, P <0.001); and for urinary deoxypyridinoline (DPD) it was 1.322 (95% CI: 1.242 to 1.401, P <0.001), indicating a considerable variation before and after treatment of these indicators. In all three cases these effects appeared significantly influenced by treatments, genotypes, and the treatments*genotypes interaction term (P <0.001 each, except for the BMD and genotype effect with P =0.02), and not by the investigational centers involved in the study. In conclusion, in postmenopausal osteoporotic women, BsmI VDR genotypes influence the efficacy of antiresorptive drugs particularly when used in combination.

The genetics of osteoporosis: vitamin D receptor gene polymorphisms and circulating osteocalcin in healthy Irish adults

BACKGROUND

A relationship between bone turnover and the vitamin D receptor (VDR) genotype is reported in Australian subjects of UK-Irish descent. There is conflicting evidence of linkage between the VDR genotype and differences in bone mineral density. No such study has been carried out on a resident Irish population.

AIMS

This study examined the relationship between serum osteocalcin (a marker of bone turnover) and VDR genotype in Irish adults.

METHODS

One hundred and eighteen healthy Irish adults aged between 19 and 67 were recruited and had two fasting blood samples taken. One sample was analysed for osteocalcin by enzyme immunoassay. The other was used to isolate genomic DNA and determine VDR genotype.

RESULTS

Tt was the most prevalent VDR genotype (53%) and tt (15%) the least prevalent in this group of healthy Irish adults. The tt VDR genotype was associated with significantly higher levels of serum osteocalcin (29% and 40%) than the Tt or TT VDR genotypes.

CONCLUSIONS

These findings suggest that healthy Irish adults with the tt VDR genotype have higher rates of bone turnover than those with Tt or TTVDR genotypes. They may have a higher risk of low bone mineral density and osteoporosis in later life.

Genetic markers of osteoarticular disorders: facts and hopes

Osteoarthritis and osteoporosis are the two most common age-related chronic disorders of articular joints and skeleton, representing a major public health problem in most developed countries. Apart from being influenced by environmental factors, both disorders have a strong genetic component, and there is now considerable evidence from large population studies that these two disorders are inversely related. Thus, an accurate analysis of the genetic component of one of these two multifactorial diseases may provide data of interest for the other. However, the existence of confounding factors must always be borne in mind in interpreting the genetic analysis. In addition, each patient must be given an accurate clinical evaluation, including family history, history of drug treatments, lifestyle, and environment, in order to reduce the background bias. Here, we review the impact of recent work in molecular genetics suggesting that powerful molecular biology techniques will soon make possible both a rapid accumulation of data on the genetics of both disorders and the development of novel diagnostic, prognostic, and therapeutic approaches.

Linkage of a gene causing high bone mass to human chromosome 11 (11q12-13)

The purpose of this paper is to report the linkage of a genetic locus (designated "HBM") in the human genome to a phenotype of very high spinal bone density, using a single extended pedigree. We measured spinal bone-mineral density, spinal Z(BMD), and collected blood from 22 members of this kindred. DNA was genotyped on an Applied Biosystems model 377 (ABI PRISM Linkage Mapping Sets; Perkin Elmer Applied Biosystems), by use of fluorescence-based marker sets that included 345 markers. Both two-point and multipoint linkage analyses were performed, by use of affected/unaffected and quantitative-trait models. Spinal Z(BMD) for affected individuals (N = 12) of the kindred was 5.54 +/- 1.40; and for unaffected individuals (N = 16) it was 0.41 +/- 0.81. The trait was present in affected individuals 18-86 years of age, suggesting that HBM influences peak bone mass. The only region of linkage was to a series of markers on chromosome 11 (11q12-13). The highest LOD score (5.21) obtained in two-point analysis, when a quantitative-trait model was used, was at D11S987. Multipoint analysis using a quantitative-trait model confirmed the linkage, with a LOD score of 5.74 near marker D11S987. HBM demonstrates the utility of spinal Z(BMD) as a quantitative bone phenotype that can be used for linkage analysis. Osteoporosis pseudoglioma syndrome also has been mapped to this region of chromosome 11. Identification of the causal gene for both traits will be required for determination of whether a single gene with different alleles that determine a wide range of peak bone densities exists in this region.