Genotypes of the vitamin-D-receptor gene and bone mineral density in Caucasoid postmenopausal females

Bariatric Surgery and Vitamin D: Trends in Older Women and Association with Clinical Features and VDR Gene Polymorphisms

(1) Background: Obesity and its comorbidities can cause burdens and limitations. Bariatric surgery (BS) is indicated as a safe procedure to reduce body mass and improve present comorbidities. However, several complications were reported, such as vitamin D [25(OH)D] deficiency. We evaluated if 25(OH)D serum levels relate to clinical characteristics, symptoms, or habits in women after their BS, and whether the vitamin D receptor (VDR) gene's TaqI and FokI polymorphisms affected 25(OH)D levels and the total body bone mineral density (TBBMD). (2) Methods: This cohort cross-sectional comparative analytical prospective study consisted of 27 women, 61.6 ± 5.0 years, submitted to BS one year prior at a public reference hospital, DF-Brazil. All participants were asked to follow the physical and dietary activity recommendations and received vitamin D3 supplements. Their anthropometric, biochemical, and immunological measurements and blood samples were obtained. (3) Results: 73.3% of participants had low 25(OH)D levels, and their levels correlated positively with TBBMD and negatively with systolic pressure. VDR TaqI did not affect 25(OH)D levels, whereas VDR FokI's allele f presence correlated to a median rise in 25(OH)D levels. Neither polymorphism correlated to TBBMD. (4) Conclusions: 25(OH)D levels were positively correlated with TBBMD, negatively with systolic blood pressure, and were higher in those with the VDR FokI allele f.

Vitamin D status and vitamin D receptor gene polymorphism in Saudi children with acute lower respiratory tract infection

There is a significant association exists between vitamin D deficiencies, low respiratory tract infections, and certain types of VDR gene polymorphism. Various studies are being conducted to prove any such link between the different clinical conditions due to disturbed vitamin D regulation and VDR gene polymorphisms. The present study analyzed the presence of vitamin D receptor (VDR) gene polymorphisms (ApaI and TaqI) in Saudi pediatric patient suffering from acute lower respiratory tract infection (ALRTI) cases. Fifty children (50) with ALRTI admitted at King Saud University Medical City, Riyadh/Saudi Arabia were included in addition to seventy-three (73) apparently healthy children who were considered as the control group. Genomic DNA from whole blood was extracted and subjected to polymerase chain reaction (PCR) targeting TaqI and ApaI VDR polymorphisms. RFLP-PCR genotyping was performed to determine the allelic frequency within the VDR gene. In the whole sample, the allelic frequency of ApaI polymorphism in the VDR gene was 58.5%, 17.9%, and 23.6% for AA, Aa, and aa respectively (p = 0.11), while it was 48%, 19%, and 33% for TT, Tt, and tt respectively (p = 0.33) with regards to the frequency of TaqI polymorphism in the VDR gene. VDR ApaI Aa and aa genotypes and VDR TaqI Tt and tt genotypes were not associated with increased risk of ALRTI in children (OR 0.87, 95% CI 0.33-2.28, p = 0.77; OR 0.56, 95% CI 0.23-1.4, p = 0.21; OR 1.15, 95% CI 0.44-2.99, p = 0.77; OR 0.73, 95% CI 0.32-1.68, p = 0.46 respectively). To conclude, neither vitamin D status nor VDR gene polymorphisms such as ApaI and TaqI is associated with increased susceptibility to ALRTI. Linkage disequilibrium was not detected between ApaI and TaqI VDR gene polymorphisms as in the case of serum vitamin D status in ALRTI patients versus apparent healthy children.

Association between the vitamin D receptor gene polymorphism and osteoporosis

The influence of the vitamin D receptor (VDR) gene for the risk of osteoporosis remains to be elucidated. The aim of the present study was to understand the distribution of various single-nucleotide polymorphisms (SNPs) within the VDR gene and its association with the risk of osteoporosis. In total, 378 subjects without a genetic relationship were recruited to the study between January 2013 and July 2015. The subjects were divided into three groups, which were the normal (n=234), osteoporosis (n=65) and osteoporosis with osteoporotic fracture (n=79) groups. Three pertinent SNPs of the VDR gene rs17879735 (ApaI, Allele A/a, SNP C>A) were examined with polymerase chain reaction-restriction fragment length polymorphism. The bone mineral density (BMD) of the lumbar spine (L2-L4), femoral neck, Ward's and Tro was measured using dual-energy X-ray absorptiometry. The distributions of genotype frequencies aa, AA and Aa were 48.68, 42.86 and 8.46%, separately. Following analysis of each site, BMD, body mass index (BMI) and age, BMD for each site was negatively correlated with age (P<0.01) and positively correlated with BMI (P<0.01). Correction analysis revealed that there were significant differences in the Ward's triangle BMD among each genotype (P<0.05), in which the aa genotype exhibited the lower BMD (P<0.05). No significant difference was identified among the different genotypes in the occurrence of osteoporosis with osteoporotic fracture (P>0.05). In conclusion, these indicated that the VDR gene ApaI polymorphisms had an important role in the osteoporosis risk.

Vitamin D

Interest in vitamin D and the VDR gene is increasing as putative roles in human health and evolutionary processes are explored. This review looks beyond the classic biochemistry that links vitamin D to calcium homeostasis; it explores how vitamin D interacts with light in a broader perspective than simple skin photosynthesis. It examines how the vitamin influences circadian rhythm, and how it may have helped drive the evolution of skin pigmentation. To this end, the nutrient–nutrient relationship with folate is also explored. The VDR gene is additionally examined as a factor in the evolutionary selection of skin depigmentation at higher latitudes to allow vitamin D synthesis. Evidence is given to show that VDR polymorphisms exhibit a latitudinal gradient in allele prevalence consistent with such a paradigm. Overall, the review examines new evo-devo ideas that link light-sensitive vitamins to human health/phenotype, both within and across the lifecycle.

How genomics has informed our understanding of the pathogenesis of osteoporosis

Osteoporosis is a skeletal disorder characterized by compromised bone strength that predisposes a person to an increased risk of fracture. Osteoporosis is a complex trait that involves multiple genes, environmental factors, and gene-gene and gene-environment interactions. Twin and family studies have indicated that between 25% and 85% of the variation in bone mass and other skeletal phenotypes is heritable, but our knowledge of the underlying genes is limited. Bone mineral density is the most common assessment for diagnosing osteoporosis and is the most often used quantitative value in the design of genetic studies. In recent years, our understanding of the pathophysiology of osteoporosis has been greatly facilitated by advances brought about by the Human Genome Project. Genetic approaches ranging from family studies of monogenic traits to association studies with candidate genes, to whole-genome scans in both humans and animals have identified a small number of genes that contribute to the heritability of bone mass. Studies with transgenic and knockout mouse models have revealed major new insights into the biology of many of these identified genes, but much more needs to be learned. Ultimately, we hope that by revealing the underlying genetics and biology driving the pathophysiology of osteoporosis, new and effective treatment can be developed to combat and possibly cure this devastating disease. Here we review the rapidly evolving field of the genomics of osteoporosis with a focus on important gene discoveries, new biological/physiological paradigms that are emerging, and many of the unanswered questions and hurdles yet to be overcome in the field.

Haplotype analysis of VDR gene polymorphisms: a meta-analysis

INTRODUCTION

Although many studies have addressed the relationship between multiple individual polymorphisms in the vitamin D receptor (VDR) gene and bone health, few have analyzed this data in terms of haplotypes. We performed a meta-analysis of studies with data on the BsmI, ApaI, and TaqI polymorphisms in order to (a) estimate haplotype frequencies, (b) determine linkage disequilibrium (LD), and (c) estimate the magnitude of the association between haplotypes and osteoporosis/bone mineral density (BMD).

METHODS

Haplotypes were inferred using the expectation-maximization algorithm (EM); log-linear models were used to determine association with osteoporosis; and regression analysis with variance components was used to determine association with BMD.

RESULTS

Our results indicate that the most common haplotype for the VDR gene, regardless of ethnicity, is baT, followed by BAt and bAT in Caucasians, and bAT and BaT in Asians. This indicates strong LD between the BsmI and TaqI polymorphisms. We demonstrate a gain in power when considering the haplotypes rather than the individual polymorphisms separately, i.e., although BsmI, ApaI, and TaqI were not significantly associated with osteoporosis on their own, the haplotypes Bat and BAt were significantly associated, with an OR of approximately 4.

CONCLUSION

We have applied haplotype analysis to the VDR polymorphisms and bone measures. We also highlight a number of methodologic issues, including linkage disequilibrium, the robustness of the EM algorithm in this context, and the potential for exploring effect modification.

Association between Vitamin D receptor polymorphisms and the rate of bone loss in elderly women-importance of adjusting for dietary and lifestyle factors

The association between the restriction length polymorphisms of the Vitamin D receptor (VDR) gene and the bone mineral density (BMD) or the rate of bone loss is still under debate. In a longitudinal study of untreated postmenopausal elderly women, we evaluated the relationship between the VDR gene polymorphisms (BsmI, TaqI, ApaI, and FokI) and the rate of bone loss over a 3-year period. We also examined the effect of adjustments for dietary and lifestyle factors on these associations. Before adjustments, the rate of femoral neck bone loss was - 3.76 +/- 1.58% in women with BB genotype and 0.45 +/- 0.65% in women with bb genotype, which was not significantly different. Upon adjustment for dietary and lifestyle factors, statistically significant (P = 0.03) bone loss was observed at femoral neck in women with BB genotype (- 3.66 +/- 2.44%) compared to that of bb genotype (2.39 +/- 1.32%). Similar results were observed with TaqI genotypes. The rates of bone loss at other skeletal sites were not different between VDR genotypes defined by BsmI and TaqI. VDR gene polymorphisms defined by ApaI and FokI were not related to the rate of bone loss.

Meta-analysis of molecular association studies: vitamin D receptor gene polymorphisms and BMD as a case study

With the rise of molecular and genetic epidemiology, molecular association studies are increasingly common; however, meta-analysis of these studies has been a neglected area. This study performed a meta-analysis of the association of the vitamin D receptor (VDR) gene polymorphisms and BMD. We also highlight methodological issues that need to be resolved.

INTRODUCTION

With the rise of molecular and genetic epidemiology, molecular association studies are increasingly common; however, meta-analysis of these studies has been a neglected area. This study performed a meta-analysis of the association of vitamin D receptor (VDR) gene polymorphisms and BMD/osteoporosis and highlights methodological issues.

MATERIALS AND METHODS

Studies published from 1994 to 2001 were identified through Medline using PubMed software. The reference lists of the articles retrieved were also reviewed. Where eligible papers had insufficient information, we contacted authors by mail (up to three mailings) for additional information. Any observational study, which tested the association between VDR BsmI genotypes and either BMD or osteoporosis at the femoral neck or spine in adult women, was included in the review. Data were extracted independently by two reviewers (AT and JA) using a standardized data extraction form.

RESULTS

The B allele was significantly associated with BMD at the spine; it seemed to follow a recessive model, with the BB genotype having lower BMD than Bb/bb genotypes at baseline, which led to greater bone mineral loss over time. Highlighted methodological lessons included the need to check Hardy-Weinberg equilibrium and the importance of exploring heterogeneity, pooling data in a manner that is sensitive to genetic models, and avoiding multiple comparisons.

CONCLUSION

With the proliferation of molecular association studies, there will be an increased need to quantify the magnitude of the risk associated with genetic polymorphisms. This will likely entail meta-analytic methods, and this meta-analysis highlights some of the methodological issues that will need to be resolved.

Association of estrogen and vitamin D receptor gene polymorphisms with tooth loss and oral bone loss in Japanese postmenopausal women

OBJECTIVE

To investigate the relationship between estrogen receptor (ER) and vitamin D receptor (VDR) gene polymorphisms and tooth loss, oral bone loss, and postcranial bone mineral density (BMD) in Japanese postmenopausal women.

DESIGN

Polymorphisms at the ER PvuII and XbaI and VDR BsmI gene sites, number of teeth remaining, oral bone mass, and BMD of the lumbar spine and the hip were evaluated in 149 Japanese postmenopausal women.

RESULTS

The distribution of ER PvuII and XbaI and VDR BsmI restriction fragment length polymorphisms was as follows: pp, 30.2%; Pp, 49.7%; PP, 20.1%; xx, 71.8%; Xx, 22.5%; XX, 2.7%; bb, 76.5%; Bb, 22.2%; and BB, 1.3%. Analysis of covariance adjusted for confounding variables revealed that participants with pp allele had fewer teeth remaining than did those with P allele. There were no significant differences in oral bone mass and postcranial BMD among three alleles at the PvuII site. Participants with X and bb allele had less oral bone mass and lower postcranial BMD than did those with xx and B allele, respectively. We could not clarify the positive associations between XbaI and BsmI polymorphism and number of teeth.

CONCLUSIONS

PvuII polymorphism was associated with tooth loss, but not with oral bone mass and postcranial BMD. XbaI and BsmI polymorphisms may be associated with bone mass or density; however, PvuII polymorphism might contribute to another unknown pathway related to tooth loss.

Association of physical activity and bone: influence of vitamin D receptor genotype

PURPOSE

The aim of the study was to investigate the interaction between leisure physical activity and a BsmI polymorphism at the vitamin D receptor (VDR) gene on the modulation of bone mineral density (BMD).

METHODS

We studied 575 unrelated healthy postmenopausal women. Lumbar spine and femoral neck BMD were measured by dual-energy x-ray absorptiometry (DXA), and results were expressed as age-and-weight-adjusted (Z-score). VDR BsmI genotype was determined by polymerase reaction chain on peripheral blood leukocytes.

RESULTS

Overall, no significant association was found between the level of leisure physical activity or VDR genotypes and adjusted BMD at both bone sites. However, in active women, there was a trend for an association between VDR genotypes and adjusted BMD at the lumbar spine. Active women, who exercised three times or more a week, carrying the "bb" genotype had a lower BMD at the lumbar spine than active women carrying "BB" genotype (ANOVA; P = 0.04). No significant difference in crude or adjusted BMD at both bone sites was found between VDR genotypes in sedentary or moderately active women. Furthermore, classification of women according to the median-age of the sample (63.1 yr) revealed a significant interaction between the level of leisure physical activity and VDR genotype on adjusted lumbar spine BMD in the older active postmenopausal women (N = 137). Older active women carrying the "bb" genotype showed a lower adjusted BMD at the lumbar spine compared with active women carrying the "BB" genotype (P = 0.007).

CONCLUSION

These results suggested that gene-environment interactions such as leisure physical activity and VDR genotype may play a role in maintaining the BMD at the lumbar spine in active postmenopausal women, especially in older active women.

The association between heel ultrasound and hormone replacement therapy is modulated by a two-locus vitamin D and estrogen receptor genotype

Evidence supports the role of estrogen deprivation in the process of bone remodeling and increased risk of fracture in postmenopausal women but little is known about the genetic basis of individual differences in response to therapy. In a cross-sectional study, 425 ambulatory postmenopausal French-Canadian women from Quebec (age range, 42-85 years old) were genotyped for a common Bsm I polymorphism at the vitamin D receptor (VDR) gene as well as a Pvu II polymorphism in the estrogen receptor (ESR1) gene. Heel ultrasound was determined by right calcaneal quantitative ultrasound (QUS) and results were expressed as an age-and-weight-adjusted stiffness index (heel SI z score). Our aim was to investigate the interaction between hormone-replacement therapy (HRT) and receptor genotypes in an effect on heel SI. Notably, a two-locus genotype (VDR-bb/ESR-PP) present in 9.5% of women was responsible for over 30% of the total HRT-related heel SI difference in the whole sample. Women bearing this combined VDR/ESR1 genotype who received HRT for more than 5 years had a 21% (1.25 SD) greater heel SI (p = 0.002) than those bearing the same genotype but who received HRT for <5 years. This may translate into a 2- to 3-fold difference in the risk of fracture. Although follow-up studies are needed, our findings suggest that QUS of the heel in postmenopausal women taking HRT is affected by variation in VDR and ESR1 loci, jointly.

[Multiple genetic typing (vitamin D receptors and estrogens) in the assessment of the risk of fractures]

BACKGROUND

Several studies suggested that some vitamin D receptor (VDR) and estrogen receptor (ER) polymorphisms influence bone mass. However, others did not confirm these results. This study was undertaken to determine if the genotypes revealed by the combined analysis of VDR and ER polymorphisms are associated with clinically significant differences in peak bone mass and the risk of osteoporotic fractures.

PATIENTS AND METHODS

Restriction fragment length polymorphisms of VDR were determined with the enzymes Bsml, Apal, Taql, and Fokl. Enzymes Xbal and Pvull were used as polymorphic markers of the ER. The study group comprised 149 young control women (18-34 years), 66 postmenopausal controls, 99 women with hip fracture and 76 women with osteoporotic vertebral fractures. Bone mineral density (BMD) was measured by DEXA.

RESULTS

We did not find significant differences in lumbar spine or hip BMD among young women with different genotypes (determined with either single or multiple polymorphic markers). Likewise, there were no differences in the frequency distributions of VDR or ER alleles between control and fractured women. The study had a 77% power to detect a fracture odds ratio of 2 in case of genotypes present in at least 15% of the population.

CONCLUSIONS

These results suggest that the polymorphic markers used in this study do not have enough discriminant power to be clinically useful in the assessment of fracture risk.

Bone mineral density and its change in white women: estrogen and vitamin D receptor genotypes and their interaction

Low bone mineral density (BMD) is a major risk factor for development of osteoporosis; increasing evidence suggests that attainment and maintenance of peak bone mass as well as bone turnover and bone loss have strong genetic determinants. We examined the association of BMD levels and their change over a 3-year period, and polymorphisms of the estrogen receptor (ER), vitamin D receptor (VDR), type I collagen, osteonectin, osteopontin, and osteocalcin genes in pre- and perimenopausal women who were part of the Michigan Bone Health Study, a population-based longitudinal study of BMD. Body composition measurements, reproductive hormone profiles, bone-related serum protein measurements, and life-style characteristics were also available on each woman. Based on evaluation of women, ER genotypes (identified by PvuII [n = 253] and XbaI [n = 248]) were significantly predictive of both lumbar spine (p < 0.05) and total body BMD level, but not their change over the 3-year period examined. The VDR BsmI restriction fragment length polymorphism was not associated with baseline BMD, change in BMD over time, or any of the bone-related serum and body composition measurements in the 372 women in whom it was evaluated. Likewise, none of the other polymorphic markers was associated with BMD measurements. However, we identified a significant gene x gene interaction effect (p < 0.05) for the VDR locus and PvuII (p < 0.005) and XbaI (p < 0.05) polymorphisms, which impacted BMD levels. Women who had the (-/-) PvuII ER and bb VDR genotype combination had a very high average BMD, while individuals with the (-/-) PvuII ER and BB VDR genotype had significantly lower BMD levels. This contrast was not explained by differences in serum levels of osteocalcin, parathyroid hormone, 1,25-dihydroxyvitamin D, or 25-dihydroxyvitamin D. These data suggest that genetic variation at the ER locus, singly and in relation to the vitamin D receptor gene, influences attainment and maintenance of peak bone mass in younger women, which in turn may render some individuals more susceptible to osteoporosis than others.

Vitamin D receptor gene polymorphisms, bone turnover, and rates of bone loss in older African-American women

Bone mineral density (BMD) is under genetic control. Some studies in Caucasian and Asian women suggest that polymorphisms in the vitamin D receptor (VDR) gene are associated with BMD and the rate of postmenopausal bone loss. We determined if similar associations exist in 101 African-American women aged 65 years and older (71 +/- 5 years, mean +/- SD). We also examined the relation between VDR genotype and fractional 45Ca absorption and markers of bone formation (osteocalcin) and resorption (N-telopeptides) in these women. BMD was measured at the proximal femur and whole body at baseline and after 1.9 +/- 0.4 years (femur only) on a Hologic QDR-2000 densitometer using dual-energy X-ray absorptiometry. Calcaneal BMD was measured with single x-ray absorptiometry. VDR gene polymorphisms were defined by the endonucleases BsmI, ApaI, and TaqI. These polymorphisms were not associated with BMD at any skeletal site or with markers of bone turnover. There was a significant interaction between age and VDR genotype where the oldest women (> 70 years) with the TT genotype experienced greater hip bone loss than women with the TT genotype (-2.1%/year vs. -0.4%/year, respectively), whereas heterozygous women experienced an intermediate rate of bone loss (-1.3%/year). Women homozygous for the B allele had 14% lower fractional 45Ca absorption compared with women homozygous for the b allele, although this difference was not statistically significant (p = 0.08). We conclude that VDR gene polymorphisms are not associated with BMD or indices of bone turnover in this population of older African-American women. However, DNA sequence variation in the VDR gene or a nearby locus may influence intestinal calcium transport and the rate of postmenopausal bone loss in African-American women.

Are vitamin D receptor polymorphisms associated with bone mineral density? A meta-analysis

Vitamin D receptor (VDR) polymorphisms have been strongly associated with bone mineral density (BMD) in some studies but not in others. We used a meta-analytic approach to assess quantitatively the association between VDR and BMD and to examine the influence of specific study characteristics (e.g., skeletal site, mean age of subjects, menopausal status) on the reported results. Sixteen papers published in peer-reviewed journals through July 1996 were included. We calculated the mean difference, percent difference, and effect size (mean difference divided by standard deviation), comparing BMD between homozygous genotypes. At the hip, BMD in the BB genotype was lower than in the bb genotype (mean difference, -0.02 g/cm2; percent difference, -2.4% and effect size -0.18; p = 0.032). At the spine, the mean difference was -0.03 g/cm2; percent difference, -2.5%; and effect size, -0.19; p = 0.062. At the distal radius, the VDR effect was estimated as the mean difference, -0.01 g/cm2; percent difference, -1.7%; and effect size, -0.16; p = 0.078. The spine measurements exhibited the greatest between- and within-study variability. The difference in hip BMD between genotypes was larger (i.e., a more negative number) among the younger women and seemed to decrease with increasing age. However, statistical evidence for this trend was weak (p = 0.06). Data from the spine and the radius showed no evidence of a comparable interaction of the VDR effect with age. When we omitted data from the first report of an association between VDR polymorphisms and BMD, our analyses gave similar results, although the overall effect estimates were smaller. In the combined data from 29 study groups, the BB genotype frequency was 17.2, 4.9, and 2.3% in studies of whites, blacks, and Asians, respectively. VDR polymorphisms represent one genetic factor affecting BMD, but further research into the mechanisms, clinical significance, and its relation between other genetic and environmental factors is needed.