Genetic determinants of bone mass

Evaluation of the Association of VDR rs2228570 Polymorphism with Elite Track and Field Athletes' Competitive Performance

The present study aimed to examine the vitamin D receptor (VDR), rs2228570 polymorphism, and its effect on elite athletes' performance. A total of 60 elite athletes (31 sprint/power and 29 endurance) and 20 control/ physically inactive, aged 18-35, voluntarily participated in the study. The International Association of Athletics Federations (IAAF) score scale was used to determine the performance levels of the athletes' personal best (PB). Whole exome sequencing (WES) was performed by the genomic DNA isolated from the peripheral blood of the participants. Sports type, sex, and competitive performance were chosen as the parameters to compare within and between the groups by linear regression models. The results showed no statistically significant difference between the CC, TC, and TT genotypes within and between the groups (p > 0.05). Additionally, our results underlined that there were no statistically significant differences for the association of rs2228570 polymorphism with PBs within the groups of the (p > 0.05) athletes. The genetic profile in the selected gene was similar in elite endurance, sprint athletes, and in controls, suggesting that rs2228570 polymorphism does not determine competitive performance in the analyzed athlete cohort.

Estrogen increases the transcription of human α2-Heremans-Schmid-glycoprotein by an interplay of estrogen receptor α and activator protein-1

The expression of α2-Heremans-Schmid-glycoprotein (AHSG) was estrogen responsive in oophorectomized (OVX) osteopenic rats and HepG2 cells. Estrogen receptor α (ERα) interacted with the c-Jun/c-Fos heterodimer and indirectly associated with the -1488/-1482 activator protein-1 (AP-1) motif of the AHSG promoter. Estrogen increased c-Jun/c-Fos expression via the mitogen-activated protein kinase (MAPK) pathway.

INTRODUCTION

AHSG is a hepatic secretory protein implicated in the regulation of bone homeostasis. Serum AHSG in women has been reported to decrease after menopause and increase with estrogen therapy. The detailed regulatory mechanism of estrogen on AHSG is unclear.

METHODS

A postmenopausal osteoporosis model was generated in OVX rats. Skeletal parameters were determined by automatic biochemical analysis and dual X-ray absorptiometry. The expression of AHSG was evaluated by ELISA, real-time PCR, and Western blot. The 1.5-kb 5'-promoter region of AHSG was analyzed by serial truncation and luciferase assays. The putative -1488/-1482 AP-1 responsive element was identified by electrophoresis mobility shift assay (EMSA). Chromatin immunoprecipitation (ChIP), re-ChIP, and co-immunoprecipitation (Co-IP) were used to characterize the interaction of ERα and AP-1 at the -1488/-1482 AP-1 binding site. The MAPK pathway was evaluated using a specific inhibitor and active transfection.

RESULTS

The expression of AHSG was estrogen responsive in both OVX rats and estradiol (E2)/ERα-treated HepG2 cells. E2/ERα most prominently increased luciferase activity of a construct with a putative -1488/-1482 AP-1 binding element. ERα interacted with the c-Jun/c-Fos heterodimer and indirectly associated with the -1488/-1482 AP-1 motif of the AHSG promoter. c-Jun/c-Fos expression was increased via the MAPK pathway by E2/ERα.

CONCLUSION

Estrogen activated the transcription of AHSG through an indirect binding of ERα to the -1488/-1482 AP-1 binding element, with the c-Jun/c-Fos heterodimers.

Fracture, bone mineral density, and the effects of calcitonin receptor gene in postmenopausal Koreans

SUMMARY

In a candidate gene association study, we found that the variations of calcitonin receptor (CALCR) gene were related to the risk of vertebral fracture and increased bone mineral density (BMD).

INTRODUCTION

Calcitonins through calcitonin receptors inhibit osteoclast-mediated bone resorption and modulate calcium ion excretion by the kidney and also prevent vertebral bone loss in early menopause.

METHODS

To identify genetically susceptible factors of osteoporosis, we discovered the variations in CALCR gene, genotyped in Korean postmenopausal women (n = 729), and examined the potential involvement of seven single-nucleotide polymorphism (SNPs) and their haplotypes in linkage disequilibrium block (BL_hts).

RESULTS

The SNPs, +43147G > C (intron 7), +60644C > T (exon13, 3' untranslated region), and their haplotypes, BL2_ht1 and BL2_ht2, showed a significant association with risk of vertebral fracture (p = 0.048-0.004) and BL2_ht1 showed a highly significant protective effect. Moreover, the polymorphism +60644C > T showed a highly significant association with BMD at both lumbar spine and femoral neck. The subjects carrying CC and CT genotypes with the SNP, +60644C > T, had higher BMD values at the lumbar spine (p = 0.01-0.001) and femoral neck (p = 0.025-0.009).

CONCLUSION

These results indicate that the CALCR gene may regulate bone metabolism, and +60644C > T in the CALCR gene may genetically modulate bone phenotype.

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.

Sex-specific effect of Pirin gene on bone mineral density in a cohort of 4000 Chinese

BACKGROUND

Osteoporosis is a common condition among elderly. Genetic mapping studies repeatedly located the distal short arms of X-chromosome as the quantitative trait loci (QTL) for BMD in mice. Fine mapping of a syntenic segment on Xp22 in a Caucasian female population suggested a moderate association between lumbar spine (LS) BMD and 2 intronic SNPs in the Pirin (PIR) gene, which encodes an iron-binding nuclear protein. This study aimed to examine genetic variations in the PIR gene by a comprehensive tagging method and its sex-specific effects on BMD and osteoporotic risk.

METHODS

Two thousand men and 2000 women aged 65 or above were recruited from the community. BMDs at the LS, femoral neck, total hip and whole body were measured and followed up at 4-year. Genotyping was performed for tagSNPs of PIR gene including adjacent regions, and the PIR haplotypes were inferred using PHASE program.

RESULTS

Analysis by linear regression showed a significant association between SNP rs5935970 and LS-BMD, while haplotype T-T-A was significantly associated with BMD of all measured sites. However, none of such associations were found in men. Linear Mixed Model also confirmed the same sex-specific and site-specific effect for longitudinal BMD changes.

CONCLUSION

In addition to confirming the association between BMDs and the PIR gene, we also revealed that this finding is sex-specific, possibly due to an X-linked effect. This study demonstrated the importance of considering sex and genetic interactions in studies of disease predisposition and complex traits.

Gender and race/ethnicity differences in lead dose biomarkers

OBJECTIVES

We sought to identify predictors of lead concentrations in the blood, tibias, and patellae of older adults and to describe differences by gender, race/ethnicity, and other factors that can influence lead toxicokinetics and, thus modify health effects.

METHODS

Participants aged 50 to 70 years (N=1140) were randomly identified from selected neighborhoods in Baltimore, Maryland. We measured lead concentrations by anodic stripping voltammetry (in blood) and (109)Cd-induced K-shell x-ray fluorescence (in bone). We used multiple linear regression to identify predictors of lead concentrations.

RESULTS

Mean (SD) lead concentrations in blood, tibias, and patellae were 3.5 (2.4) mug/dL, 18.9 (12.5) mug/g, and 6.8 (18.1) mug/g, respectively. Tibia concentrations were 29% higher in African Americans than in Whites (P < .01). We observed effect modification by race/ethnicity on the association of gender and physical activity to blood lead concentrations and by gender on the association of age to tibia lead concentrations. Patella lead concentrations differed by gender; apolipoprotein E genotype modified this relation.

CONCLUSIONS

African Americans evidenced a prominent disparity in lifetime lead dose. Women may be at higher risk of release of lead from bone and consequent health effects because of increased bone demineralization with aging.

Polymorphisms in the low-density lipoprotein receptor-related protein 5 (LRP5) gene are associated with peak bone mass in non-sedentary men: results from the Odense androgen study

PURPOSE

To investigate the impact of the Ala1330Val (rs3736228, exon 18) and Val667Met (rs4988321, exon 9) polymorphisms of the low-density lipoprotein receptor-related protein 5 (LRP5) gene on peak bone mass in young men.

METHODS

The Odense Androgen Study (OAS) is a population-based study comprising 783 Caucasian men aged 20-30 years. Genotyping was performed using real-time polymerase chain reaction (PCR) or fluorescence polarization. Bone mineral density (BMD) measurements were performed using dual-energy X-ray absorptiometry.

RESULTS

The CC, CT, and TT genotypes in Ala1330Val were found in 75.6%, 21.8%, and 2.6% of the participants, respectively. Similarly, the GG, GA, and AA genotypes of Val667Met were found in 89.7%, 9.8%, and 0.5%, respectively. For the Ala1330Val polymorphism, no significant differences between the genotypes were found regarding BMD in the overall study population. However, when analysis was restricted to non-sedentary men (n = 589), a significant association between the number of T-alleles and BMD in the spine and whole body were found. Each copy of the T-allele changed the Z-score of the spine by (median and 95% confidence interval) -0.21 [95% CI: -0.40; -0.03] (p < 0.02). Analysis suggested an association between the AA genotype in the Val667Met polymorphism and increased body height and decreased BMD of the femoral neck; however, no significant gene-dose effect of the A-allele could be demonstrated in the whole population. When the analysis was restricted to non-sedentary subjects, however, each number of A-alleles was associated with a change in Z-score of -0.26 [95% CI: -0.51; -0.01] (p = 0.04). No further significant results emerged with haplotype analysis.

CONCLUSION

The Ala1330Val and Val667Met polymorphisms in the LRP5 gene are significantly associated with peak bone mass in physically active men.

Quantitative genetics of cortical bone mass in healthy 10-year-old children from the Fels Longitudinal Study

The genetic influences on bone mass likely change throughout the life span, but most genetic studies of bone mass regulation have focused on adults. There is, however, a growing awareness of the importance of genes influencing the acquisition of bone mass during childhood on lifelong bone health. The present investigation examines genetic influences on childhood bone mass by estimating the residual heritabilities of different measures of second metacarpal bone mass in a sample of 600 10-year-old participants from 144 families in the Fels Longitudinal Study. Bivariate quantitative genetic analyses were conducted to estimate genetic correlations between cortical bone mass measures, and measures of bone growth and development. Using a maximum likelihood-based variance components method for pedigree data, we found a residual heritability estimate of 0.71 for second metacarpal cortical index. Residual heritability estimates for individual measures of cortical bone (e.g., lateral cortical thickness, medial cortical thickness) ranged from 0.47 to 0.58, at this pre-pubertal childhood age. Low genetic correlations were found between cortical bone measures and both bone length and skeletal age. However, after Bonferonni adjustment for multiple testing, rho(G) was not significantly different from 0 for any of these pairs of traits. Results of this investigation provide evidence of significant genetic control over bone mass largely independent of maturation while bones are actively growing and before rapid accrual of bone that typically occurs during puberty.

Molecular genetic studies of gene identification for osteoporosis: a 2004 update

This review summarizes comprehensively the most important and representative molecular genetics studies of gene identification for osteoporosis published up to the end of December 2004. It is intended to constitute a sequential update of our previously published review covering the available data up to the end of 2002. Evidence from candidate gene association studies and genome-wide linkage studies in humans, as well as quantitative trait locus mapping animal models are reviewed separately. Studies of transgenic and knockout mice models relevant to osteoporosis are summarized. An important extension of this update is incorporation of functional genomic studies (including DNA microarrays and proteomics) on osteogenesis and osteoporosis, in light of the rapid advances and the promising prospects of the field. 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.

FokI and BsmI polymorphisms of the vitamin D receptor gene and bone mineral density in a random Bulgarian population sample

Numerous studies on vitamin D receptor (VDR) gene polymorphisms differ with conflicting data in various populations. We studied the association of FokI and BsmI polymorphisms in the gene encoding the vitamin D receptor with bone mineral density (BMD) in 219 persons of Bulgarian nationality. The calculated relative risk (RR) for low bone mineral density is higher for FokI marker (3.14) compared to BsmI marker (2.44). The etiological factor (EF), which shows association between polymorphisms investigated and illness on populational level, is defined as EF = 0.51 for FokI marker and EF = 0.42 for BsmI marker. Because of this we conclude that FokI and BsmI polymorphisms are closely related to low BMD at the forearm and lumbar spine. Both polymorphisms are useful genetic markers in determining BMD and osteoporosis risk. Further studies of larger cohorts and in ethnically diverse subgroups are necessary.

The BsmI vitamin D receptor gene polymorphism is associated with ulcerative colitis in Jewish Ashkenazi patients

Susceptibility to inflammatory bowel disease (IBD) has a strong genetic component. The vitamin D receptor (VDR) gene maps to a region on chromosome 12 shown to be associated with IBD in some studies. In this case-control study we determined the association between the BsmI VDR gene polymorphism and IBD in patients with Crohn's disease (CD) and ulcerative colits (UC). Three hundred seventy-nine Jewish Israeli patients with IBD, 228 with CD (129 Ashkenazi and 99 non-Ashkenazi), and 151 patients with UC (72 Ashkenazi, 79 non-Ashkenazi) were studied. The control group included 495 healthy blood donors (352 non-Ashkenazi and 143 Ashkenazi). All subjects were genotyped for the BsmI VDR gene polymorphism. The frequency of the BB genotype was higher in Ashkenazi patients with UC compared to Ashkenazi controls (0.21 vs. 0.11, p = 0.042, odds ratio 2.27, 95% confidence interval [CI] 1.06-4.9). There were no differences in the prevalence of the BB genotype or the B allele between ethnically matched patients with CD and UC. Nor were there differences in the BB genotype or B allele frequencies between CD patients and ethnically matched controls. The BsmI VDR gene polymorphism is associated with increased susceptibility to UC in Israeli Ashkenazi patients with UC.

The (GT)n polymorphism and haplotype of the COL1A2 gene, but not the (AAAG)n polymorphism of the PTHR1 gene, are associated with bone mineral density in Chinese

Collagen type I alpha2 (COL1A2) and parathyroid hormone (PTH)/PTH-related peptide receptor (PTHR1) are two prominent candidate genes for bone mineral density (BMD). To test their importance for BMD variation in Chinese, we recruited 388 nuclear families composed of both parents and at least one healthy daughter with a total of 1,220 individuals, and simultaneously analyzed population stratification, total-family association, and within-family association between BMD at the spine and hip and the (GT)n marker in the intron 1 of the COL1A2 gene and the (AAAG)n marker in the P3 promoter of PTHR1 gene. We also performed these association analyses with haplotypes of the MspI and (GT)n polymorphisms in the COL1A2 gene. Significant within-family association was found between the M(GT)12 haplotype and trochanter BMD (P<0.001). Individuals with this haplotype have, on average, 9.53% lower trochanter BMD than the non-carriers. Suggestive evidence of the within-family association was detected between the (GT)17 allele and BMD at the spine (P=0.012), hip (P=0.011), femoral neck (P=0.032), trochanter (P=0.023), and intertrochanter (P=0.034). The association was confirmed by subsequent permutation tests. For the association, the proportion of phenotypic variance explained by the detected markers ranged from 1.2 to 3.9%, with the highest 3.9% at the trochanter for the M(GT)12 haplotype. This association indicates that there is strong linkage disequilibrium between the polymorphisms (MspI and GT repeat polymorphism) in the COL1A2 gene and a nearby quantitative trait locus (QTL) underlying BMD variation in Chinese, or the markers themselves may have an important effect on the variation of BMD. On the other hand, no significant within-family association, population stratification and total-family association between the PTHR1 polymorphism and BMD were found in our Chinese population.

Areal bone mineral density of the lumbar spine in 80 premature newborns: a prospective and longitudinal study

BACKGROUND

Maximum bone mass accretion in the fetal skeleton is acquired during the third trimester of gestation, and may be compromised in premature newborns.

OBJECTIVE

To ascertain the incidence and evolution of osteopenia, a longitudinal study was performed to evaluate areal bone mineral density (aBMD) in the lumbar spine in premature newborns followed during the first 2 years of life.

METHODS

aBMD values were assessed in lumbar spine (L2-L4) by DEXA and expressed as grams hydroxyapatite/cm2 in 80 premature newborns, 41 boys and 39 girls, of gestational ages 24.5-35.7 weeks. aBMD values were evaluated at (mean+/-SD) 0.2+/-0.1 years (at discharge from the neonatal unit), 0.9+/-0.2 years and 2.0+/-0.5 years of postnatal age, and compared with those of age- and sex-matched full-term newborns with normal intrauterine and postnatal growth.

RESULTS

aBMD values recovered progressively from the first to the third evaluations, and were 0.139+/-0.06 g/cm2 (-2.4+/-1.4 SDS) at 0.2+/-0.1, 0.270+/-0.06 g/cm2 (-1.0+/-1.0 SDS) at 0.9+/-0.2 and 0.410 g/cm2 (-0.08+/-1.0 SDS) at 2.0+/-0.5 years.

CONCLUSIONS

Our data show a significant catch-up of aBMD, reaching values similar to those of full-term newborns at the age of 0.2+/-0.5 years, regardless of the gestational age at birth.

RUNX2 alleles associated with BMD in Scottish women; interaction of RUNX2 alleles with menopausal status and body mass index

Bone mineral density (BMD) is influenced by both environmental and genetic factors. We previously reported the association of the RUNX2 A allele with increased bone mineral density (BMD) and protection against a common form of osteoporotic fracture within a Geelong population. We genotyped 991 women from a Scottish cohort to decipher the role of RUNX2 alleles in regulating BMD. The alleles of RUNX2 within the glutamine-alanine repeat were determined by MspA1I restriction digest. Allele frequencies estimated from Scottish cohort were G allele, 0.87 +/- 0.01; A allele, 0.08 +/- 0.01; and 11Ala alanine deletion allele, 0.05 +/- 0.01. Analysis of covariance (ANCOVA) was used to adjust for the covariates weight and age for BMD at the femoral neck (FN). The A allele was associated with higher FN BMD (P = 0.035) within a postmenopausal subgroup of the population (n = 312). The effect of RUNX2 A alleles increased with increasing weight; A alleles were associated with FN BMD in those above the median BMI (BMI > 25), while no association was observed in thin/normal (BMI </= 25) postmenopausal women. Glutamine variants and an alanine insertion were identified within the group. These data suggest that the RUNX2 alleles are associated with BMD in a menopause- and weight-dependent manner.

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.

Association between polymorphisms of apolipoprotein E, bone mineral density of the lower forearm, quantitative ultrasound of the calcaneus and osteoporotic fractures in postmenopausal women with hip or lower forearm fracture

A genetic contribution to the development of osteoporosis is well documented. Although the association between the common allelic variation of apolipoprotein E (APOE), fracture risk, bone loss and bone mineral density (BMD) has been examined in several studies, the results of these investigations are contradictory. The aim of this study was to examine the association between polymorphisms of APOE, BMD of the lower forearm, quantitative ultrasound of the calcaneus and osteoporotic fractures in a population of postmenopausal women with hip or lower forearm fractures admitted to a department of orthopaedic surgery and age-matched controls from the population register. The APOE genotypes of 327 women were studied: 73 with lower forearm fractures, 43 with hip fractures and 211 age-matched controls. The participants were not receiving antiosteoporotic treatment. Polymerase chain reaction restriction fragment length polymorphism (PCR-RFLP) was used to detect the APOE genotypes. Quantitative ultrasound was measured at the calcaneus. Bone mineral density (BMD) of the lower forearm was measured with dual-energy X-ray absorptiometry. The distributions of genotype frequencies in this study were: E2/E2: 0.3%; E2/E3: 16.5%; E2/E4: 2.5%; E3/E3: 54.7%; E3/E4: 24.2%; E4/E4: 1.8%. All subpopulations were in Hardy-Weinburg equilibrium. There was no association between bone mass parameters and the APOE allele groups. Logistic regression analysis did not show any association between fractures and APOE allele groups. In conclusion, this study showed no association between bone mass parameters (BMD, speed of sound (SOS), broadband ultrasound attenuation (BUA)), hip or lower forearm fracture and APOE genotypes in a population of postmenopausal women and age-matched controls.

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.

Linkage and association of the CA repeat polymorphism of the IL6 gene, obesity-related phenotypes, and bone mineral density (BMD) in two independent Caucasian populations

Genetic factors play an important role in osteoporosis and obesity, two serious public health problems in the world. We investigated the relationships between obesity-related phenotypes, bone mineral density (BMD) and the CA repeat polymorphism of the IL6 gene in two large independent samples using the quantitative transmission disequilibrium test (QTDT). The first sample consisted of 1,816 individuals from 79 multigenerational pedigrees. Each pedigree was identified through a proband with BMD Z-scores </=-1.28 at the hip or spine. The second sample was a randomly ascertained set of 636 individuals from 157 nuclear families. Ten alleles containing 9-18 CA repeats were identified in our Caucasian populations. For body mass index (BMI), fat mass and percentage fat mass (PFM), highly significant (P<0.01) or significant (P<0.05) results were found for linkage in our sample of nuclear families and for association in the multigenerational pedigrees. We also observed weak evidence for linkage (P=0.069) with spine BMD and for association with hip BMD in the sample of multigenerational pedigrees. Our results suggest that genetic variation in or near the IL6 locus may be involved in the etiology of obesity and osteoporosis.

Relation of PvuII site polymorphism in the COL1A2 gene to the risk of fractures in prepubertal Finnish girls

Genetic susceptibility to fractures may be detectable in early childhood. We evaluated the associations between the polymorphic PvuII site of the COL1A2 gene and bone properties assessed by different modalities (dual-energy X-ray absorptiometry; peripheral quantitative computed tomography; gel coupling scanning quantitative ultrasonometry; ultrasound bone sonometry), bone turnover markers, and the occurrence of fractures in 244 prepubertal Finnish girls. Tanner stage and physical characteristics did not differ significantly among girls with different COL1A2 genotypes. The polymorphism was not significantly associated with different bone properties or any of the bone turnover markers when girls at Tanner stage I (prepuberty) and stage II (early puberty) were considered together, but there was a significant association with spine bone mineral content (BMC) and bone mineral density (BMD), as well as with speed of sound (SOS) (P < 0.05), when girls at Tanner stage I were considered separately, as a purpose to avoid the confounding effect that the pubertal growth spurt has on skeletal development. The distribution of fractures was different between the three genotype groups (P = 0.023). The P alleles were over-represented in girls who had been fractured at least once; 88% of them had at least one copy of the P allele (either PP or Pp). Girls with the PP genotype had 4.9 times higher relative risk for fractures than girls with the pp genotype (95% CI, 1.4 to 17.4; P = 0.015). No significant difference was found between fractured and nonfractured girls in anthropometric measurements, physical activity, or bone mass. However, BMD of the spine and SOS at the radius and tibia were significantly lower in the fractured girls. We conclude that the COL1A2 polymorphism is associated with nonosteoporotic fractures in prepubertal girls independently of bone density.

Differentiation of Caucasians and Chinese at bone mass candidate genes: implication for ethnic difference of bone mass

Bone mineral density (BMD) is an important risk factor for osteoporosis and has strong genetic determination. While average BMD differs among major ethnic groups, several important candidate genes have been shown to underlie BMD variation within populations of the same ethnicity. To investigate whether important candidate genes may contribute to ethnic differences in BMD, we studied the degree of genetic differentiation among several important candidate genes between two major ethnic groups: Caucasians and Chinese. The genetic variability of these two populations (1131 randomly selected individuals) was studied at six restriction sites exhibiting polymorphisms of five important candidate genes for BMD: the BsaHI polymorphism of the calcium-sensing receptor (CASR) gene, the SacI polymorphism of the alpha2HS-glycoprotein (AHSG) gene, the PvuII and XbaI polymorphisms of the estrogen receptor alpha (ESR1) gene, the ApaI polymorphism of the vitamin D receptor (VDR) gene, and the BstBI polymorphism of the parathyroid hormone (PTH) gene. The two ethnic groups showed significant allelic and genotypic differentiation of all the polymorphisms studied. The mean FST was 0.103, which significantly differed from zero (P < 0.01). The Chinese population had lower mean heterozygosity (0.331) than the Caucasian one (0.444); the CASR-BsaHI and PTH-BstBI polymorphisms contributed most significantly to this difference. Analysis of the intra- and inter-population variability suggests that various types of natural selection may affect the observed patterns of variation at some loci. If some of the candidate genes we studied indeed underlie variation in BMD, their population differentiation revealed here between ethnic groups may contribute to understanding ethnic difference in BMD.

Bone mineral density loss in patients with urolithiasis: a follow-up study

BACKGROUND

Recurrent calcium urolithiasis is often associated with disorders of calcium metabolism. The purpose of this investigation was to assess bone mineral content (BMC) and bone mineral density (BMD) over a period of 1 year in patients with urolithiasis and to determine the factors that could have influenced the changes in bone density during that period.

METHODS

The patient group comprised 34 men aged 41.2 plus minus 7.9 years with recurrent urolithiasis. A wide spectrum of biochemical measurements was performed. Bone mineral density (g/cm(2)), bone mineral content (BMC), and bone area (BA) were measured twice during a period of 1 year at the lumbar spine (L2-L4), femoral neck, Ward triangle, and trochanter, using dual energy absorptiometry. Patient results were compared to those obtained from 30 healthy male controls of a comparable age group.

RESULTS

Nine patients were hypercalciuric, while the majority of the remaining metabolic parameters were within the reference values. Bone mineral content and bone areas at all regions were lower in patients comparing to controls, but not significantly. The greatest annual reduction of BMD was noticed at Ward triangle (-5.70% in patients and -2.36% in controls), followed by femoral neck (-4.06% patients, -2.03% controls) and trochanter (-3.06% patients, -1.39% controls). There was no significant decrease of the BMD of the spine. Analyzing the influence of age, body mass index (BMI), metabolic parameters, and dietary calcium intake on the annual reduction of bone density, we found that age, hyperuricosuria, and calcium intake were significantly associated with bone loss in that time period.

CONCLUSIONS

Bone mass reduction in patients with urolithiasis over a 1-year period did not differ significantly from that in controls and was principally related to age, hyperuricosuria, and calcium dietary restriction but not to increased calcium excretion.

Fatores de risco da osteoporose: prevenção e detecção através do monitoramento clínico e genético

A osteoporose é uma doença sistêmica caracterizada pela baixa massa óssea e deterioração da micro arquitetura do tecido ósseo. Consequentemente existe um aumento na fragilidade do osso e suscetibilidade à fratura, que é considerada o efeito clínico mais importante deste processo. Muitos estudos que se utilizam de modelos em gêmeos ou pais e seus descendentes têm confirmado o papel da herança genética no pico de massa óssea, na verdade o maior fator de risco da fratura. Neste artigo de revisão, são enfocados os prováveis genes envolvidos no processo de osteoporose, ressaltando a importância das interações entre gene- gene e gene-ambiente. Concernente à influência isolada do ambiente, são abordados os hábitos relacionados ao estilo de vida, à nutrição e ao tabagismo envolvidos no aparecimento dessa doença. Durante os próximos anos, o conhecimento baseado na genética molecular elucidará o processo osteoporótico. Do mesmo modo, os estudos clínicos se expandirão, visando contribuir para a detecção precoce da doença, permitindo assim a aplicação de medidas preventivas e terapêuticas adequadas.

Role of genetics in osteoporosis

Osteoporosis is a disease characterized by fragile bones and high susceptibility to low-trauma fractures. It is a serious health problem, especially in elderly women. Bone mineral density (BMD) has been employed most commonly as the index for defining and studying osteoporosis. BMD has high genetic determination, with heritability ranging from 50 to 90%. Various gene-mapping approaches have been applied to identify specific genes underlying osteoporosis, largely using BMD as the study phenotype. We review here the genetic determination of osteoporosis as defined by BMD and discuss a fundamental issue we encounter in genetic research in osteoporosis: the choice of phenotype(s) to study. We briefly summarize and discuss advantages and disadvantages of various approaches used in genetic studies of osteoporosis. Finally, we review and discuss the current status for mapping and identification of genes for osteoporosis. We focus on linkage studies in humans and quantitative trait loci mapping in mice to supplement the already extensive reviews of association studies made by many investigators for candidate genes.

Association of collagen Ialpha 1 Sp1 polymorphism with the risk of prevalent fractures: a meta-analysis

Several studies have addressed the effect of the Spl polymorphism of the collagen Ialpha 1 (COLIA1) gene on the prevalence of fractures. The results are not in full agreement on whether this polymorphism is associated with fracture risk. To clarify this uncertainty, we performed a meta-analysis including 13 eligible studies with 3641 subjects. The COLIA1 Spl polymorphism showed a dose-response relationship with the prevalence of fractures. The risk was 1.25-fold (95% CI, 1.09-1.45) in Ss heterozygotes versus SS homozygotes, 1.68-fold (95% CI, 1.35-2.10) in ss homozygotes versus SS homozygotes, and 1.35 (95% CI, 1.04-1.75) for ss homozygotes versus Ss heterozygotes by random effects calculations. There was modest heterogeneity for these three effect estimates (p value for heterogeneity, 0.17, 0.16, and 0.08, respectively). The Sp1 polymorphism effects possibly were larger when the analysis was limited to studies considering only vertebral fractures (pooled risk ratios [RR], 1.30, 2.07, and 1.46, respectively). Conversely, the Spl polymorphism effects tended to be smaller in studies with mean patient age > or = 65 years than in studies with younger patients on average, but the differences were not formally significant. We estimated the total average attributable fraction (AF) of fractures due to the s allele in European/U.S. populations as 9.4%. The meta-analysis suggests an important role for the Spl polymorphism in the regulation of fracture risk; however, potential heterogeneity across ethnic groups, age groups, and skeletal sites may be important to clarify in future studies. Very large studies or meta-analyses are required to document subtle genetic differences in fracture risk.

Osteoporosis in children and adolescents: diagnosis, risk factors, and prevention

Bone mass acquired during childhood and adolescence is a key determinant of adult bone health. Peak bone mass, which is achieved in late adolescence, is a main determinant of osteoporosis in adulthood. Therefore, any factor adversely impacting on bone acquisition during childhood or adolescence can potentially have long-standing detrimental effects on bone health predisposing to osteoporosis and fracture risk. Thus, osteoporosis can well have its origin in childhood and adolescence. Pediatricians should be playing an active role in osteoporosis diagnosis and prevention. It is increasingly recognized that osteoporosis may occur in some disorders of children and adolescents. In this paper we review the diagnostic criteria of osteopenia/osteoporosis by densitometric assessment of bone mineral density, the contributing factors, and the mechanisms whereby several disorders may affect the acquisition of bone mass in children and adolescents. Finally, some recommendations to optimize peak bone mass in order to prevent osteopenia/osteoporosis are suggested.

Low Areal Bone Mineral Density Values in Adolescents and Young Adult Turner Syndrome Patients Increase after Long-Term Transdermal Estradiol Therapy

OBJECTIVE

To study the effects of long-term estradiol therapy on areal bone mineral density (aBMD) values in young adult Turner syndrome patients.

METHODS

The effects of 2-year transdermal estradiol administration on lumbar, L2-L4, aBMD values were evaluated in 12 Turner syndrome patients, 15.41-21.85 years old, who had reached adult height and had low aBMD values. Puberty was induced in all at a chronological age above 12 years and menarche appeared between 13.82 and 15.40 years. The patients were on oral estrogen/gestagen therapy from then until the start of the study. Adhesive patches of 17-beta-estradiol designed to be worn for 72 h and deliver 100 microg of estradiol per day, which results in a steady mean serum estradiol level of 75 pg/ml, were used for 21 days. From day 11 to day 21, 10 mg of oral didrogesterone were also added. Nutritional and physical activity habits were evaluated at the beginning, after 1 year and at the end of the study.

RESULTS

aBMD values significantly increased from 0.910 +/- 0.065 to 1.005 +/- 0.086 g/cm2 (10.06 +/- 3.37%) and the z-score from -2.38 +/- 0.63 to -1.54 +/- 0.71 (0.81 +/- 0.30 z-score). No significant differences were observed in body mass index, calcium intake and physical activity habits at the start, during and at the end of the study.

CONCLUSION

In summary, our results underline the importance of estrogens for bone mass peaking and suggest that this therapeutic protocol may be useful in the therapy of Turner syndrome patients with low bone mass.