Vitamin D receptor alleles predict growth and bone density in girls

Single Nucleotide Polymorphisms in Vitamin D Receptor Gene Affect Birth Weight and the Risk of Preterm Birth: Results From the "Mamma & Bambino" Cohort and A Meta-Analysis

The effect of vitamin D receptor gene (VDR) polymorphisms on adverse pregnancy outcomes—including preterm birth (PTB), low birth weight and small for gestational age—is currently under debate. We investigated 187 mother-child pairs from the Italian “Mamma & Bambino” cohort to evaluate the association of maternal VDR polymorphisms—BsmI, ApaI, FokI and TaqI—with neonatal anthropometric measures and the risk of PTB. To corroborate our results, we conducted a meta-analysis of observational studies. For the FokI polymorphism, we showed that gestational duration and birth weight decreased with increasing number of A allele (p = 0.040 and p = 0.010, respectively). Compared to the GG and GA genotypes, mothers who carried the AA genotype exhibited higher PTB risk (OR = 12.049; 95% CI = 2.606–55.709; p = 0.001) after adjusting for covariates. The meta-analysis confirmed this association under the recessive model (OR = 3.67, 95%CI 1.18–11.43), and also pointed out the protective effect of BsmI polymorphism against the risk of PTB under the allelic (A vs. G: OR = 0.74; 95%CI 0.59–0.93) and recessive (AA vs. GG + AG: OR = 0.62; 95%CI 0.43–0.89) models. Our results suggest the association between some maternal VDR polymorphisms with neonatal anthropometric measures and the risk of PTB.

Genetic Determinants of Prepubertal and Pubertal Growth and Development

This article surveys the current general understanding of genetic influences on within- and between-population variation in growth and development in the context of establishing an International Growth Standard for Preadolescent and Adolescent Children. Traditional genetic epidemiologic analysis methods are reviewed, and evidence from family studies for genetic effects on different measures of growth and development is then presented. Findings from linkage and association studies seeking to identify specific genomic locations and allelic variants of genes influencing variation in growth and maturation are then summarized. Special mention is made of the need to study the interactions between genes and environments. At present, specific genes and polymorphisms contributing to variation in growth and maturation are only beginning to be identified. Larger genetic epidemiologic studies are needed in different parts of the world to better explore population differences in gene frequencies and gene—environment interactions. As advances continue to be made in molecular and statistical genetic methods, the genetic architecture of complex processes, including those of growth and development, will become better elucidated. For now, it can only be concluded that although the fundamental genetic underpinnings of the growth and development of children worldwide are likely to be essentially the same, there are also likely to be differences between populations in the frequencies of allelic gene variants that influence growth and maturation and in the nature of gene–environment interactions. This does not necessarily preclude an international growth reference, but it does have important implications for the form that such a reference might ultimately take.

Pediatric data for dual X-ray absorptiometric measures of normal lumbar bone mineral density in children under 5 years of age using the lunar prodigy densitometer

OBJECTIVES

Knowledge of physiological variations of bone mineral density (BMD) in newborns and infants is necessary to evaluate pathological changes associated with fractures. Limited reference data for children under 5 years old are available. This study provides normative data of lumbar BMD for the Lunar Prodigy in young children under 5 years old.

SUBJECTS AND METHODS

We assessed cross-sectionally 155 healthy children (77 boys, 80% Caucasian), ranging in age from newborn to the age of 5 years. Lumbar bone mineral content (BMC) and areal BMD were measured by dual-energy X-ray absorptiometry using a Lunar Prodigy absorptiometer. Volumetric BMD was calculated using the Kroeger and Carter methods.

RESULTS

BMC and areal BMD increased from birth to 5 years (p<0.001). Volumetric BMD did not change with age. BMD and BMC correlated with age, weight and height (R(2)≥0.85 for all), with a maximum gain between the ages of 1 and 4 years, which did not follow the same pattern as height velocity. We did not find significant sex difference for any of the three measured parameters.

CONCLUSION

This study provides normative data for lumbar spine densitometry of infants and young children using the Lunar Prodigy DXA system.

Association between Vitamin D Receptor Gene BsmI Polymorphism and Bone Mineral Density in A Population of 146 Iranian Women

OBJECTIVE

Osteoporosis is a bone disorder that reduces bone mineral density (BMD) and leads to bone fracture. In addition to different factors, gene polymorphisms have been revealed to be associated with osteoporosis. In this study, we investigated the association between the BsmI polymorphism of vitamin D receptor (VDR) gene (rs1544410) and BMD in a population of Iranian women.

MATERIALS AND METHODS

In this case control study, clinical risk factors for osteoporosis were obtained from the participants through a questionnaire for a case-control study. The World Health Organisation (WHO) criteria were applied for the diagnosis of the disease. Peripheral blood samples were obtained from 146 pre- and or postmenopausal Iranian women aged between 35 and 71 years (53.53 ± 9.8). The study population was classified for BMD into normal and osteoporotic groups, who matched for age, pregnancy status, menstrual condition, and body mass index (BMI). The BMD of the lumbar spine (L1-4) and femoral neck was measured. Polymerase chain reactionrestriction fragment length polymorphism (PCR-RFLP) was performed to detect and analyze the genotype.

RESULTS

The frequencies of AA and GG were significantly different between the two groups (p value<0.05), with the first genotype being higher in the patients and the second being higher in the normal group. The GG genotype was significantly associated with increased BMD in the lumbar spine (p value<0.05) but non-significant in the femoral neck (p value>0.05).

CONCLUSION

BsmI polymorphism of VDR gene has a significant association with BMD in the lumbar spine and may have a minor effect on the proximal femur BMD in Iranian women.

Selected risk factors of fractures in children — own observation

Bone fractures may depend on Vitamin D Receptor Gene (VDR), bone mineral density, bone turnover markers. Patients and methods. 161 patients were recruited and underwent: skeletal densitometry (DXA) method and bone turnover studies (Osteocalcin and Ntx).The study group was evaluated using restriction enzyme digestion at BsmI (rs1544410), FokI (rs2228570), ApaI (rs7975232) and TaqI (rs731236), polymorphic sites of the VDR gene. Multivariate logistic regression was used to assess factor significance. The model included variables with sex- and age-standardized parameters, VDR genotypes, and bone metabolism marker levels. Results. Factors associated with fractures were: osteocalcin concentration and Z-score BMDt. Odds Ratio (OR) values equaled: 1.01 (95%Confidence Interval (95%CI) 1.00–1.02) for osteocalcin (p=0.006), and 0.66 (95%CI 0.42-1.03; p=0.07) for Z-score BMDt. In patients with reduced bone mass, factors related to fractures were: osteocalcin (0.04) and carriage of BsmI b (0.07) or ApaI a alleles (0.08). ORs were 1.01 (95%CI 1.00–1.02) for OC, 0.29 (95%CI 0.07–1.14) for BsmI, and 2.13 (95%CI 0.91–4.99) for ApaI polymorphic allele carriage. Conclusions. Carriage of BsmI b allele reduces, while carriage of ApaI a allele and heightened osteoclacin level increase the risk of fractures in study children with reduced bone mass. VDR polymorphism, bone mineral density and bone formation’s marker — osteocalcin maybe considered as risk factor for fracure in children from Lodz region.

The relationship between vitamin D receptor gene polymorphisms and bone density, osteocalcin level and growth in adolescents

BACKGROUND/OBJECTIVE

The relationship between vitamin D receptor gene polymorphisms and bone density, osteocalcin and growth was investigated.

SUBJECTS

Eighty eight adolescents aged between 8-15, with no history of illness influencing the level of bone parameters, were examined in our study.

METHODS

Areal BMD for lumbar spine (L1-4) was assessed by dual energy X-ray absorptiometry (DEXA). Height and weight were measured on the day of the DEXA scans. Serum osteocalcin level was determined by using ELISA method. DNA was extracted from white blood cells, amplified by the polymerase chain reaction (PCR) and the polymorphic sites were analyzed by using ApaI, TaqI and FokI restriction enzymes.

RESULTS

The most frequent genotypes were FF (% 54.6), Aa (% 53.4) and Tt (% 48.8). No significant relationship was found between VDR genotypes and areal BMD, osteocalcin level or growth in either sex. But there was a strong tendency for a higher BMD at the lumbar spine of TT and AA genotypes compared to tt and Aa genotypes. The children with TT genotype were taller and heavier than the children with tt genotype

CONCLUSION

Our results suggest that VDR gene TaqI polymorphism may be associated with body weight and bone mass, but more studies with larger groups should be conducted.

Vitamin D receptor gene polymorphisms modulate the skeletal response to vitamin D supplementation in healthy girls

OBJECTIVES

Vitamin D receptor (VDR) gene plays an important role in bone mass regulation. We have previously shown a beneficial effect of vitamin D supplementation on bone mass in girls. This study investigated whether the musculo-skeletal response to Vitamin D was modulated by polymorphisms in VDR gene.

DESIGN

Randomized placebo-controlled trial.

METHODS

179 girls (10-17 years), were randomly assigned to placebo or Vitamin D3 for one year. VDR genotypes were determined in 167 girls using BsmI, TaqI and ApaI restriction enzymes. Bone mass at the spine, hip, forearm and total body, and lean mass were measured by DXA at baseline and at one year.

RESULTS

After one year, VDR gene polymorphisms using Bsm1 and TaqI restriction enzymes were associated with percent changes in bone area, BMC and BMD at multiple skeletal sites in the Vitamin D3 group but not in the placebo group. The least increments were observed in the BB and tt genotypes. No similar effect was observed with ApaI enzyme. This relationship between VDR genotypes and changes in BMD and BMC remained significant after adjustment for puberty, changes in lean mass, height and bone area.

CONCLUSION

VDR gene polymorphisms influence the skeletal response to vitamin D supplementation in healthy adolescent girls.

Preliminary findings: 25(OH)D levels and PTH are indicators of rapid bone accrual in pubertal children

OBJECTIVE

The objective of this study was to evaluate the role of serum levels of 25(OH)D and PTH on the accumulation of whole body bone mass in a cohort of children.

METHODS

This was a longitudinal study (1.98 +/- 0.07 y) of sixty-nine children (89% Caucasian, 44% male) enrolled in a calcium supplementation trial. Bone area, bone mineral content (BMC) and density (BMD) of the whole body and radius were assessed using a QDR 2000 (Hologic, Inc) dual energy x-ray absorptiometer. Serum PTH and 25(OH)D were measured using radioimmunoassays.

RESULTS

Vitamin D stores were inversely related gain in bone area (p < 0.002), BMC (p < 0.002) BMD (p < 0.027), as well as to PTH levels (p < 0.0001). Compared to those with adequate vitamin D stores (>34 ng/ml), those who had consistently low vitamin D stores (18 ng/ml) had a 8% larger gain in bone area (p < 0.05); 11% in BMC (p < 0.05) and no differences in gain in BMD; after adjusting for baseline bone measurements, race, gender, season measured, Tanner stage, and calcium intake.

CONCLUSIONS

High normal PTH with low-normal 25(OH)D stores and moderate to high calcium intake may be beneficial to accruing larger bone size and BMC during puberty.

Bone mass pharmacogenetics and ethnic health implications

Osteoporosis is a common skeletal disease with a strong genetic component characterized by reduced bone mass and increased risk of fragility fractures. Bone mineral density (BMD) is considered the best established risk factor for osteoporotic fractures.Over the last years a large number of studies have pointed to the variability in many target genes and their relation with BMD and other determinants of fracture risk such as ultrasound bone properties, skeletal geometry and bone turnover markers. The importance of genetic factors in the bone quality is substantial, but no consensus exists yet on the genes that are involved.Although osteoporosis is world healthy problem, there are many differences in human ethnics regarding both disease morbidity and drug treatment efficacy. Heterogeneity in drug response may reflect varying responsiveness to osteoporosis treatments due to allele variation in signaling pathway genes such as vitamin D receptor (VDR) or estrogen receptor α (ERα). Polymorphisms of VDR and ERαloci appear genetic determinants of their corresponding hormonal treatment response such as vitamin D and estrogens. Because of their specific ethnic distribution, polymorphisms of VDR and ERαgenes may be involved in reported human differences of osteoporosis treatment responses.Knowledge of the molecular and functional consequences of the gene polymorphisms is crucial to fully appreciate their significance and understand their potential clinical implications. Future studies and preventive strategies to management osteoporosis need to take in account these genetic factors.

A genetic approach to fracture epidemiology in childhood

The purpose of this report is to provide a review of both childhood fracture epidemiology and known heritable causes for fracture predisposition to the Medical Geneticist, who is frequently consulted to assess children with multiple or unexplained fractures for a physiologic etiology. A detailed knowledge of the clinical and laboratory evaluation for osteogenesis imperfecta (OI) and other single-gene disorders is obviously essential to complete a useful evaluation of such children. The experienced clinician will immediately recognize that single gene disorders represent only a small fraction of these patients. In infants, non-accidental trauma (NAT) unfortunately is the likely explanation for the fracture pattern, but in some infants, and certainly in older children with recurrent fractures, no medical explanations can be found. Recent studies in which bone mineral density (BMD) has been associated with genetic variation at a number of candidate genes are promising but these studies are too premature yet to be used clinically. Nonetheless, we do expect that in the future whole-genome approaches in conjunction with key clinical and epidemiological variables may be combined through an informatics approach to create better predictors of fracture susceptibility for these populations of patients.

Evidence for involvement of the vitamin D receptor gene in idiopathic short stature via a genome-wide linkage study and subsequent association studies

Stature is a highly heritable trait under both polygenic and major gene control. We aimed to identify genetic regions linked to idiopathic short stature (ISS) in childhood, through a whole genome scan in 92 families each with two affected children with ISS, including constitutional delay of growth and puberty and familial short stature. Linkage analysis was performed for ISS, height and bone age retardation. Chromosome 12q11 showed significant evidence of linkage to ISS and height (maximum non-parametric multipoint LOD scores 3.18 and 2.31 at 55-58 cM, between D12S1301 and D12S1048), especially in sister-sister pairs (LOD score of 1.9 for ISS in 22 pairs). These traits were also linked to chromosomes 1q12 and 2q36. The region on chromosome 12q11 had previously shown significant linkage to adult stature in several genome scans and harbors the vitamin D receptor gene, which has been associated with variation in height. A single nucleotide polymorphism (SNP) (rs10735810, FokI), which leads to a functionally relevant alteration at the protein level, showed preferential transmission of the transcriptionally more active G-allele to affected children (P=0.04) and seems to be responsible for the observed linkage (P=0.05, GIST test). Bone age retardation showed moderate linkage to chromosomes 19p11-q11 and 7p14 (LOD scores 1.69 at 57 cM and 1.42 at 50 cM), but there was no clear overlap with linkage regions for stature. In conclusion, we identified significant linkage, which might be due to a functional SNP in the vitamin D receptor (VDR) gene and could be responsible for up to 34% of ISS cases in the population.

Bone mineral density-affecting genes in Africans

BACKGROUND

We have recently reported the role of environmental exposure in the ethnic diversity of bone mineral density (BMD). Potential genetic difference has not been adequately assessed.

PURPOSE

To determine allele frequencies of BMD-affecting genes and their association with BMD in Africans.

METHODS

Allele frequencies at 18 polymorphic sites in 13 genes that affect BMD in Asians and/or Caucasians were determined in 143 recent immigrants (55 men and 88 women, 18-51 years of age) from sub-Saharan Sudan to the United States. Genetic association studies were performed.

RESULTS

Among the 14 single-nucleotide polymorphisms (SNPs), 10 were significantly different in allele frequency between Sudanese and Asians, and 10 between Sudanese and Caucasians. Only the osteocalcin gene was not significantly different in allele frequency among Sudanese, Asians and Caucasians. Allele frequencies in the TGFB, COL1A1 and CSR genes were extremely low (<0.04) in the Sudanese. Frequencies of microsatellite alleles in four genes were significantly different among Sudanese, Asians and Caucasians. SNPs in the VDR and ERalpha genes were associated with BMD and/or BMC (bone mineral content) at several bone sites.

CONCLUSIONS

Genetic difference may play a role in the ethnic diversity in BMD and/or BMC.

Association of estrogen receptor gene polymorphisms with susceptibility to adolescent idiopathic scoliosis

STUDY DESIGN

A case-control study is presented.

OBJECTIVE

To investigate the association of estrogen receptor gene polymorphisms with adolescent idiopathic scoliosis (AIS) risk.

SUMMARY OF BACKGROUND DATA

Previous studies have shown that genetic factors are important in the pathogenesis of idiopathic scoliosis. Only 1 publication suggested that XbaI site polymorphism was associated with curve severity of idiopathic scoliosis. However, to our knowledge, the relationship of estrogen receptor gene polymorphisms and the individual susceptibility to idiopathic scoliosis has not been studied.

METHODS

This study included 202 patients with AIS and 174 healthy controls. Height, menarche status, curve pattern, Cobb angle, and Risser sign in female patients were recorded. There were 2 polymorphic loci, PvuII and XbaI locus, of estrogen receptor analyzed by restriction fragment length polymorphisms.

RESULTS

The frequency of XX genotype was significantly higher in patients than that in controls (P = 0.005). The X allele appeared to be overrepresented in patients compared with controls (P = 0.001). Furthermore, the frequencies of XX genotype in female patients whose height was > or = 160 cm and Cobb angle > or = 40 degrees were higher than those whose height was <160 cm and Cobb angle <40 degrees (P = 0.001 and P < 0.001, respectively).

CONCLUSIONS

The XbaI site polymorphism of estrogen receptor gene may be associated with a risk of AIS.

Vitamin D receptor gene polymorphisms are linked to and associated with adult height

BACKGROUND

The vitamin D receptor (VDR) gene is important to human stature, as it mediates metabolic pathways, calcium homeostasis, and phosphate homeostasis, which influence growth.

METHODS

We examined the relationship between VDR and adult height in 1873 white subjects from 406 nuclear families. Four SNPs, namely -4817A/G at intron 1, FokI C/T at exon 2 start codon, BsmI A/G at intron 8, and TaqI T/C at exon 9 in VDR were tested for linkage and association with adult height variation by the program QTDT (quantitative transmission disequilibrium test). The bT haplotype of the BsmI and TaqI loci was further tested for its association with height in unrelated samples randomly chosen from the 406 nuclear families by traditional population association methods.

RESULTS

All four tested SNPs were linked to adult height. Within family associations with height were detected at BsmI and TaqI loci (p = 0.048 and 0.039, respectively). Analyses based on BsmI/TaqI haplotypes also revealed evidence for linkage (p = 0.05) and association (p = 0.001) with height. The bT haplotype was significantly associated with higher adult height (p = 0.033, within family association test). Such an association might be female specific and influenced by menstrual status.

CONCLUSIONS

Our results strongly suggest that VDR may be linked to and associated with adult height variation in white populations.

Vitamin D and estrogen receptor-alpha genotype and indices of bone mass and bone turnover in Danish girls

Peak bone mass is a major determinant of osteoporosis risk in later life. It is under strong genetic control; however, little is known about the identity of the genes involved. In the present study, we investigated the relationship between polymorphisms in the genes encoding the vitamin D receptor (VDR) (FokI, TaqI) and estrogen receptor-alpha (ERalpha) (PvuII, XbaI), and bone mineral density (BMD), bone mineral content (BMC), and markers of bone turnover in 224 Danish girls aged 11-12 years. BMD and BMC were measured by dual-energy X-ray absorptiometry. Serum osteocalcin, 25(OH)D, and parathyroid hormone (PTH) were measured by ELISA assays and urinary pyridinium cross-links by HPLC. Physical activity, dietary calcium, and Tanner stage were assessed by questionnaire. In general, there were no significant differences in anthropometrical variables, physical activity, dietary calcium, serum 25(OH)D, or PTH among genotype groups. BMD or BMC of lumbar spine or whole body (adjusted for body and bone size and pubertal status) were not associated with VDR or ERalpha genotypes or the combination of these genotypes. This lack of association remained even after adjustment for dietary and environmental factors. VDR genotypes had no effect on bone turnover markers. XX and PP ERalpha genotypes were associated (P < 0.05) with reduced levels of urinary pyridinium cross-links, whereas serum osteocalcin was similar among genotypes. These findings suggest that the rate of bone resorption was influenced by ERalpha genotypes, even though these biochemical differences were not evident in bone mass indices.

Two single-nucleotide polymorphisms in the human vitamin D receptor promoter change protein–DNA complex formation and are associated with height and vitamin D status in adolescent girls

Numerous association studies have dealt with single-nucleotide polymorphisms (SNPs) in coding and intronic regions of the human vitamin D receptor (hVDR) gene. We have hypothesized that phenotypic traits may also be associated with variations in VDR expression due to the presence of SNPs in promoter regions. In this work, we have studied two SNPs located 1521 bp (G/C) and 1012 bp (A/G) upstream of the transcriptional start site of the main human VDR gene promoter. One base-change in any of the two variant sites led to a dramatic change in protein-DNA complex formation using nuclear extracts from HEK293, Caco-2 and COS-7 cells. Genetic analysis of 185 healthy adolescent girls evidenced two major haplotypes: 1521G/1012A and 1521C/1012G and three main genotypes: homozygous for 1521G/1012A (21.1%), homozygous for 1521C/1012G (17.3%) and heterozygous 1521CG/1012GA (57.3%). On the basis of transfection data, promoter activity was nearly 2-fold higher with the 1521G/1012A haplotype, when compared with the 1521C/1012G haplotype. Clinical and biological association study in the adolescent cohort showed that girls with a CC/GG genotype had (i) lower circulating levels of 25-dihydroxyvitamin D, with no detectable consequence on calcium metabolism, (ii) lower serum IGF-1 levels and (iii) smaller height from 11 years of age up to adult height.

Insulin-Like Growth Factor Pathway Polymorphisms Associated with Body Size in Hispanic and Non-Hispanic White Women

Polymorphisms affecting insulin-like growth factors (IGF), their binding proteins (IGFBP), insulin receptor substrates (IRS), and other IGF regulatory molecules may affect growth, obesity, and obesity-related diseases, including cancer. The objective of this study was to better describe the associations between several IGF pathway variants and body size. Hispanic (n = 462) and non-Hispanic White (n = 1,702) women were recruited as controls in collaborative population-based case-control studies in Arizona, New Mexico, Colorado, Utah, and California. Body size measurements were taken by trained interviewers; genotypes were determined for the IGF1 CA repeat, the IGFBP3 -202 C > A substitution, the IRS1 G972R and IRS2 G1057D substitutions, and the vitamin D receptor (VDR) BsmI and FokI polymorphisms. Two associations were observed that were consistent in both Hispanics and non-Hispanic Whites: IGF1 CA repeat alleles of length other than 19 were associated with higher mean waist-to-hip ratios (WHR), P = 0.01, and women who carried an IGFBP3 A allele, compared with women with the CC genotype, more often reported high birthweight (odds ratio, 1.9; 95% confidence interval, 1.1-3.2). We observed trends for associations between IGFBP3 A allele and taller height, IRS1R allele, and smaller WHR, and VDR FokI ff genotype and larger WHR; each of these trends was present in only one ethnic group, and heterogeneity of effect by ethnicity was detected. These results provide evidence that IGF pathway polymorphisms have functional effects on growth and central obesity and indicate that genotype-phenotype relationships are ethnic specific.

The VDR, COL1A1, PTH, and PTHR1 gene polymorphisms are not associated with bone size and height in Chinese nuclear families

We tested the relationship of the ApaI, Eco31I, BstBI, and (AAAG)n polymorphisms in the vitamin D receptor (VDR), collagen type I alpha-1 (COL1A1), parathyroid hormone (PTH), and parathyroid hormone (PTH)/PTH-related peptide receptor (PTHR1) genes with variations in bone size (BS) and height. Population stratification, total-family association, and within-family association were used to test these relationships in 400 Chinese nuclear families with a total of 1256 individuals. The BS at hip and spine was measured using a Hologic QDR 2000 dual-energy X-ray absorptiometry (DXA) scanner. The minor allele frequencies were 29.2%, 36.0%, and 14.0% for the VDR-ApaI, COL1A1-Eco31I, and PTH-BstBI markers, respectively. (AAAG)5 and (AAAG)6 of the PTHR1 gene are two major alleles in the Chinese people. Significant population stratification was found between the spine BS and PTHR1-(AAAG)5 (P = 0.048) and PTHR1-(AAAG)6 (P = 0.023), as well as between PTHR1-(AAAG)5 and height (P = 0.048), but we did not detect any significant within-family association or total-family association between the VDR, COL1A1, PTH, and PTHR1 gene polymorphisms and the variations in BS and height in our sample. Our results do not support that the VDR, COL1A1, PTH, and PTHR1 genes have an important influence on the variation in BS and height in our Chinese population.

Association of vitamin D receptor gene polymorphisms with childhood and adult asthma

Vitamin D receptor (VDR) polymorphisms have been associated with several immune-related diseases, and VDR and vitamin D itself modulate T cell differentiation. VDR maps to chromosome 12q, near a region commonly linked to asthma. We evaluated VDR as part of a 12q positional candidate survey, and in response to observations of VDR polymorphism associations with asthma and atopy in a founder population of Quebec. Twenty-eight loci in 7 positional candidates (7 in VDR) were genotyped in 582 families. Whereas other candidates demonstrated no association, the VDR ApaI polymorphism demonstrated significant transmission distortion, with undertransmission of the C allele in a ratio of 4:5 (p = 0.01). This association was most prominent in girls, in whom distortion was more marked (p = 0.009). Sex-specific associations between multiple VDR polymorphisms and immunoglobulin E levels were also observed (p = 0.006-0.01). Asthma associations were replicated in a second cohort (517 females with asthma and 519 matched control subjects): 4 of 6 VDR variants demonstrated significant association (p = 0.02-0.04). The direction of association in this second cohort was opposite to the effects seen in the trios, but similar to findings in the Quebec study. These results suggest that VDR influences asthma and allergy susceptibility in a complex manner.

Current limitations of SNP data from the public domain for studies of complex disorders: a test for ten candidate genes for obesity and osteoporosis

BACKGROUND

Public SNP databases are frequently used to choose SNPs for candidate genes in the association and linkage studies of complex disorders. However, their utility for such studies of diseases with ethnic-dependent background has never been evaluated.

RESULTS

To estimate the accuracy and completeness of SNP public databases, we analyzed the allele frequencies of 41 SNPs in 10 candidate genes for obesity and/or osteoporosis in a large American-Caucasian sample (1,873 individuals from 405 nuclear families) by PCR-invader assay. We compared our results with those from the databases and other published studies. Of the 41 SNPs, 8 were monomorphic in our sample. Twelve were reported for the first time for Caucasians and the other 29 SNPs in our sample essentially confirmed the respective allele frequencies for Caucasians in the databases and previous studies. The comparison of our data with other ethnic groups showed significant differentiation between the three major world ethnic groups at some SNPs (Caucasians and Africans differed at 3 of the 18 shared SNPs, and Caucasians and Asians differed at 13 of the 22 shared SNPs). This genetic differentiation may have an important implication for studying the well-known ethnic differences in the prevalence of obesity and osteoporosis, and complex disorders in general.

CONCLUSION

A comparative analysis of the SNP data of the candidate genes obtained in the present study, as well as those retrieved from the public domain, suggests that the databases may currently have serious limitations for studying complex disorders with an ethnic-dependent background due to the incomplete and uneven representation of the candidate SNPs in the databases for the major ethnic groups. This conclusion attests to the imperative necessity of large-scale and accurate characterization of these SNPs in different ethnic groups.

Analysis of polymorphisms of the vitamin D receptor, estrogen receptor, and collagen Ialpha1 genes and their relationship with height in children with bone cancer

PURPOSE

The authors' objectives were to compare height at diagnosis of children with bone tumors with that of Spanish reference children; to analyze the frequency of the genotypes for the polymorphisms of the vitamin D receptor (VDR), estrogen receptor (ER), and collagen Ialpha1 (COLIalpha1) genes in patients and in healthy controls; and to test the relationship between the genetic markers and height.

PATIENTS AND METHODS

Height and weight at diagnosis were measured in 58 osteosarcoma and 36 Ewing sarcoma patients and compared with standards published for Spanish reference children according to sex and age. For the molecular analysis, genetic polymorphisms of the VDR (Fok I, Apa I, and TaqI), ER (Pvu II and XbaI), and COLIalpha1 (Msc I) genes were characterized in 72 osteosarcoma and 53 Ewing sarcomas and in a group of 143 healthy matched children.

RESULTS

Osteosarcoma and Ewing sarcoma patients were significantly taller than Spanish reference children. Osteosarcoma patients showed a significantly higher frequency of the Ff genotype for the Fok I polymorphism (VDR gene) than the control group. The odds ratio for this genotype was 1.78, with an increased relative risk of 78% for heterozygous Ff carriers. Among Ewing sarcoma patients, this same genotype was significantly associated with lower height than homozygotes (FF or ff).

CONCLUSIONS

Children with bone cancer are significantly taller than the reference population, which may be influenced by the genotype for the Fok I polymorphism of the VDR gene.

Vitamin D receptor gene polymorphism and bone metabolism during low-dose oral contraceptive use in young women

With the aim to determine whether bone metabolism in young women using low-dose oral contraception is influenced by vitamin D receptor (VDR) genotype, we designed the prospective clinical study of 41 healthy women aged 20-27 years. Twenty-one women of the study group were prescribed an oral contraceptive (30 microg ethynyl estradiol and 150 microg levonorgestrel) and 20 women of the control group a nonhormonal contraceptive or none. Biochemical markers of bone metabolism (bone-specific alkaline phosphatase, osteocalcin, deoxypyridinoline) and VDR genotype, using BsmI endonuclease, were determined. After 3 months in the study group, the BB genotype subgroup showed significantly decreased osteocalcin (p = 0.010), in the Bb genotype subgroup bone-specific alkaline phosphatase (p = 0.043) and osteocalcin (p = 0.006) decreased, and in the bb genotype subgroup no changes were observed. In the control group, there were no significant changes in markers of bone metabolism regarding VDR genotype. In conclusion, our study shows that in young women VDR gene polymorphism could influence bone metabolism during low-dose oral contraceptive use.

Association of polymorphisms of the estrogen receptor alpha gene with bone mineral density and fracture risk in women: a meta-analysis

The contribution of genetic polymorphisms to bone mineral density (BMD) and fracture risk in women is a controversial topic. We evaluated the effect of the XbaI and PvuII polymorphisms of the estrogen receptor a to BMD and fracture risk in a meta-analysis, including published data and additional information from investigators. Five thousand eight hundred thirty-four women from 30 study groups were analyzed with fixed and random effects models. The PvuII polymorphism was not associated with BMD at any skeletal site examined and 95% CIs exclude effects over 0.015 g/cm2 for both the femoral neck and the lumbar spine. Conversely, XX homozygotes (women carrying two copies of the gene variant without an XbaI restriction site) consistently had higher BMD than other subjects. The magnitude of the effect was similar in the femoral neck and lumbar spine (0.014 g/cm2 [95% CI, 0.003-0.025] and 0.015 g/cm2 [95% CI, 0.000-0.030], respectively; no between-study heterogeneity for either). Total body BMD was also significantly higher in XX homozygotes (by 0.039 g/cm2 and 0.029 g/cm2 compared with Xx and xx, respectively). Available data on fractures suggested a protective effect for XX (odds ratio [OR], 0.66 [95% CI, 0.47-0.93] among 1591 women), but not PP (OR, 0.93 [95% CI, 0.72-1.18] among 2,229 women). In summary, we have found that XX homozygotes may have higher BMD and also a decreased risk of fractures when compared with carriers of the x allele, whereas the PvuII polymorphism is not associated with either BMD or fracture risk.

Association between estrogen receptor gene polymorphisms and curve severity of idiopathic scoliosis

STUDY DESIGN

Analysis of the estrogen receptor gene of girls with idiopathic scoliosis.

OBJECTIVES

To determine whether estrogen receptor gene polymorphisms correlate with curve severity of adolescent idiopathic scoliosis.

SUMMARY OF BACKGROUND DATA

Studies suggest that idiopathic scoliosis is a familial condition and that curve progression is related to genetically determined factors, such as skeletal and sexual growth.

METHODS

A total of 304 girls with idiopathic scoliosis were followed until growth maturation. Height, arm span, menarcheal age, and age at growth maturation were recorded, and curve severity was measured using Cobb's method. The estrogen receptor gene, which contains polymorphic PvuII and XbaI sites, was amplified from lymphocyte deoxyribonucleic acid by polymerase chain reaction.

RESULTS

The mean maximum Cobb measurements for patients with genotypes XX and Xx were greater than for those with genotype xx (P = 0.002). The risk of curve progression, defined as progression of >5 degrees from initial evaluation, was higher with genotype Xx than with xx (P = 0.03). Patients with genotypes XX and Xx had a significantly higher risk for operative treatment than those with genotype xx (21.4%, 24.7% vs. 7.6%, P< 0.001). Growth examination around the time of the growth spurt revealed that the XbaI site polymorphism was also related to the age of growth maturation. The frequency of patients with growth maturation at >or=16 years was higher for genotypes XX and Xx than for genotype xx (33.3%, 29.9% vs. 16.8%, P= 0.013).

CONCLUSION

Our results suggest that the XbaI site polymorphism is associated with curve severity. DNA analysis may predict curve progression.

Genetics of osteoporosis: role of steroid hormone receptor gene polymorphisms

Osteoporosis is a common skeletal disease characterized by low bone mass and microarchitectural deterioration of bone tissue with a consequent increase in bone fragility and susceptibility to fracture. In the past years, twin and family study have shown that this disease recognizes a strong genetic component and that genetic factors play an important role in regulating bone mineral density (BMD). While in few isolate conditions osteoporosis can be inherited in a simple Mendelian pattern, due to single gene mutations, in the majority of cases has to be considered a multifactorial polygenic disease in which genetic determinants are modulated by hormonal, environmental and nutritional factors. Given the important role that steroid hormones play in bone cell development and in the maintenance of normal bone architecture, polymorphisms at receptor of the steroid/thyroid hormone receptor superfamily, such as estrogen receptor alpha (ERalpha) and Vitamin D receptor (VDR) have been thoroughly investigated in the last years and appeared to represent important candidate genes. The individual contribution of these genetic polymorphisms to the pathogenesis of osteoporosis remains to be universally confirmed and an important aim in future work will be to define their functional molecular consequences and how these polymorphisms interact with each other and with the environment to cause the osteoporotic phenotype. A further promising application of genetic studies in osteoporosis comes from their pharmacogenomic implications, with the possibility to give a better guidance for therapeutic agents commonly used to treat this invalidating disorder or to identify target molecules for new therapeutic agents.

Effect of VDR polymorphisms on growth and bone mineral density in homozygous beta thalassaemia

We examined the effect of vitamin D receptor (VDR) polymorphisms at exon 2 (FokI) and intron 8 (BsmI) on the stature and bone mineral density at femoral neck (FBMD) and lumbar spine (LBMD) in 108 prepubertal and pubertal homozygous beta thalassaemic patients, regularly treated. We found significantly shorter stature and lower LBMD and FBMD in all patients with CC VDR genotype, and significant shorter height and lower LBMD in prepubertal and pubertal female patients with BB VDR genotype. Because homozygous CC and BB VDR genotypes influence Vitamin D activity, they can be considered additional risk factors for bone disease in beta thalassaemia.

Genetic determinants of bone mineral content in premature infants

Genetic determinants of bone mineral content in prematurely born children at 3 months and 9-11 years of age were studied. The findings suggest that multiple genes are involved in the regulation of site specific bone mass accumulation during childhood.

The relative contribution of diet and genotype to bone development

The present review addresses the relative contribution of diet and genotype to variability in human bone growth and mineralisation in the context of the aetiology of osteoporosis. Heritability studies indicate that 60-70 % of the variability in bone mineral mass or bone mineral density (BMD) can be accounted for by genetic variation. Cross-trait analyses suggest that a proportion of this variation reflects genetic influences on bone and body size, such as height and lean body mass. Candidate-gene studies have demonstrated associations between several genetic polymorphisms and bone mineral mass but, as yet, genotype determinations have proved unhelpful in identifying individuals at increased risk of osteoporosis. Variations in diet and other environmental factors contribute 30-40 % to total phenotypic variance in bone mineral mass or BMD. Correlations between intakes of individual nutrients and BMD have been reported, but these relationships are subject to confounding due to size. However, no specific dietary factor has been identified from prospective and twin studies as making a significant contribution to environmental variability in BMD or bone loss. This finding may reflect the difficulties in quantifying environmental exposures. both current and over a lifetime. In addition, the influence of diet on bone health may depend on the genotype of the individual. Optimisation of nutrition and lifestyle remains an attractive strategy for the reduction of fracture risk, but more research is required to fully define optimal dietary requirements.

Genetic susceptibility to lead poisoning

Major strides have been taken in the regulation of lead intoxication in the general population, but studies using genetic markers of susceptibility to environmental toxicants raise the question of whether genes can make certain individuals more vulnerable to environmental toxins such as lead. At least three polymorphic genes have been identified that potentially can influence the bioaccumulation and toxicokinetics of lead in humans. The first gene to be discussed in this review is the gene coding for delta-aminolevulinic acid dehydratase (ALAD), an enzyme of heme biosynthesis, that exists in two polymorphic forms. The resulting isozymes have been shown to affect the blood and bone lead levels in human populations. The effects of ALAD in lead intoxication have also been studied in laboratory mice that differ in the genetic dose for this enzyme. The second gene reviewed here is the vitamin D receptor (VDR) gene. The VDR is involved in calcium absorption through the gut and into calcium-rich tissues such as bone. Recent findings suggest that VDR polymorphism may influence the accumulation of lead in bone. Finally, the third gene to be discussed here that may influence the absorption of lead is the hemochromatosis gene coding for the HFE protein. The presence of mutations in the HFE gene leads to hemochromatosis in homozygotic individuals. Because of the associations between iron and lead transport, it is possible that polymorphisms in the HFE gene may also influence the absorption of lead, but this has not yet been studied. More studies will be needed to define the role of these genes in lead intoxication.

Genetic susceptibility to lead poisoning

Major strides have been taken in the regulation of lead intoxication in the general population, but studies using genetic markers of susceptibility to environmental toxicants raise the question of whether genes can make certain individuals more vulnerable to environmental toxins such as lead. At least three polymorphic genes have been identified that potentially can influence the bioaccumulation and toxicokinetics of lead in humans. The first gene to be discussed in this review is the gene coding for delta-aminolevulinic acid dehydratase (ALAD), an enzyme of heme biosynthesis, that exists in two polymorphic forms. The resulting isozymes have been shown to affect the blood and bone lead levels in human populations. The effects of ALAD in lead intoxication have also been studied in laboratory mice that differ in the genetic dose for this enzyme. The second gene reviewed here is the vitamin D receptor (VDR) gene. The VDR is involved in calcium absorption through the gut and into calcium-rich tissues such as bone. Recent findings suggest that VDR polymorphism may influence the accumulation of lead in bone. Finally, the third gene to be discussed here that may influence the absorption of lead is the hemochromatosis gene coding for the HFE protein. The presence of mutations in the HFE gene leads to hemochromatosis in homozygotic individuals. Because of the associations between iron and lead transport, it is possible that polymorphisms in the HFE gene may also influence the absorption of lead, but this has not yet been studied. More studies will be needed to define the role of these genes in lead intoxication.