Tests of linkage and association of the COL1A2 gene with bone phenotypes' variation in Chinese nuclear families

LGR4 Gene Polymorphisms Are Associated With Bone and Obesity Phenotypes in Chinese Female Nuclear Families

OBJECTIVE

The current study was conducted to determine whether peak bone mineral density (BMD) and obesity phenotypes are associated with certain LGR4 gene polymorphisms found in Chinese nuclear families with female children.

METHODS

A total of 22 single nucleotide polymorphisms (SNPs) located in and around the LGR4 gene were identified in 1,300 subjects who were members of 390 Chinese nuclear families with female children. Then, BMD readings of the femoral neck, total hip, and lumbar spine as well as measurements of the total lean mass (TLM), total fat mass (TFM), and trunk fat mass were obtained via dual-energy X-ray absorptiometry. The quantitative transmission disequilibrium test was used to analyze the associations between specific SNPs and LGR4 haplotypes and peak BMD as well as between LGR4 haplotypes and TLM, percent lean mass, TFM, percent fat mass, trunk fat mass, and body mass index (BMI).

RESULTS

Here, rs7936621 was significantly associated with the BMD values for the total hip and lumbar spine, while rs10835171 and rs6484295 were associated with the trunk fat mass and BMI, respectively. Regarding the haplotypes, we found significant associations between GAA in block 2 and trunk fat mass and BMI, between AGCGT in block 3 and total hip BMD, between TGCTCC in block 5 and femoral neck BMD, and between TACTTC in block 5 and both lumbar spine and femoral neck BMD (all P-values < 0.05).

CONCLUSION

Genetic variations of the LGR4 gene are related to peak BMD, BMI, and trunk fat mass.

Association between SNPs and haplotypes in the METTL21C gene and peak bone mineral density and body composition in Chinese male nuclear families

The methyltransferase-like 21C gene (METTL21C), which is mainly expressed in muscle, can promote the differentiation of myoblasts to myotubes and reduce glucocorticoid-induced apoptosis of osteocytes. The purpose of this study was to explore the association between single nucleotide polymorphisms of METTL21C and peak bone mineral density (BMD), body mass index, total fat mass (TFM), and total lean mass (TLM) in Chinese young men. Fifteen tagging single nucleotide polymorphisms were genotyped, and haplotype blocks were derived in 400 Chinese male nuclear families. The peak BMD of the lumbar and hip, TFM, and TLM were measured by dual-energy X-ray absorptiometry. The association analyses were performed by a quantitative transmission disequilibrium test. Both TLM and TFM had a significant positive effect on peak BMD, but the positive regulation of TLM was stronger than that of TFM. After 1000 permutations, significant within-family associations were found between rs9585961 and lumbar spine BMD and femoral neck BMD, rs9518810 and femoral neck BMD, and rs599976 and body mass index, TFM, and percentage fat mass (all P < 0.05). The association analyses with haplotypes showed that haplotype AG in block 1 was significantly associated with TFM (P = 0.031) and haplotype CAG in block 2 was significantly associated with lumbar spine BMD (P = 0.020). Our study, for the first time, demonstrates that the polymorphisms and haplotypes of METTL21C contribute to the peak BMD and TFM in Chinese males, which suggests that as a quantitative trait locus with potential pleiotropy it may have an influence on osteoporosis and obesity.

Contribution of myostatin gene polymorphisms to normal variation in lean mass, fat mass and peak BMD in Chinese male offspring

AIM

Myostatin gene is a member of the transforming growth factor-β (TGF-β) family that negatively regulates skeletal muscle growth. Genetic polymorphisms in Myostatin were found to be associated with the peak bone mineral density (BMD) in Chinese women. The purpose of this study was to investigate whether myostatin played a role in the normal variation in peak BMD, lean mass (LM), and fat mass (FM) of Chinese men.

METHODS

Four hundred male-offspring nuclear families of Chinese Han ethnic group were recruited. Anthropometric measurements, including the peak BMD, body LM and FM were measured using dual-energy X-ray absorptiometry (DXA). The single nucleotide polymorphisms (SNPs) studied were tag-SNPs selected by sequencing. Both rs2293284 and +2278GA were genotyped using TaqMan assay, and rs3791783 was genotyped with PCR-restriction fragment length polymorphism (RFLP) analysis. The associations of the SNPs with anthropometric variations were analyzed using the quantitative transmission disequilibrium test (QTDT).

RESULTS

Using QTDT to detect within-family associations, neither single SNP nor haplotype was found to be associated with peak BMD at any bone site. However, rs3791783 was found to be significantly associated with fat mass of the trunk (P<0.001). Moreover, for within-family associations, haplotypes AGG, AAA, and TGG were found to be significantly associated with the trunk fat mass (all P<0.001).

CONCLUSION

Our results suggest that genetic variation within myostatin may play a role in regulating the variation in fat mass in Chinese males. Additionally, the myostatin gene may be a candidate that determines body fat mass in Chinese men.

Contribution of the sclerostin domain-containing protein 1 (SOSTDC1) gene to normal variation of peak bone mineral density in Chinese women and men

A genome-wide linkage analysis in Chinese families revealed a significant quantitative trait loci on chromosome 7p21.1 for femoral neck bone mineral density (BMD) (LOD = 3.68), and a potential candidate gene, sclerostin domain-containing protein 1 (SOSTDC1), is located in this region. SOSTDC1 belongs to a class of bone morphogenetic protein (BMP) antagonists that bind BMPs and regulate their signaling. We therefore genotyped 6 tag single nucleotide polymorphisms (tag-SNPs) in SOSTDC1 gene using allele-specific PCR method and investigated the association between SOSTDC1 gene polymorphisms and peak BMD variation in 401 Chinese female-offspring nuclear families (including 1260 subjects) and 400 Chinese male-offspring nuclear families (including 1215 subjects), respectively. Using both family-based (quantitative transmission disequilibrium test) and population-based (ANOVA) methods of analyses, BMD values were adjusted for age, height and weight. In female-offspring nuclear families, we found a significant within family association between rs16878759 and the lumbar spine peak BMD (P = 0.003) and rs16878759 accounted for 1.4% of the lumbar spine peak BMD variation. Moreover, haplotype CCC (containing rs12699800, rs16878759, and rs17619769) had a significant within family association with the lumbar spine peak BMD (P = 0.001) and accounted for 1.9% of the peak BMD variation at this bone site. However, in the male-offspring nuclear families, we failed to detect any significant association between any SNP or haplotype and peak BMD at any bone site. In conclusion, our results indicate for the first time that the genetic polymorphisms in SOSTDC1 have an effect on attainment and maintenance of peak bone mass in Chinese women.

No association between polymorphisms of peroxisome [corrected] proliferator-activated receptor-gamma gene and peak bone mineral density variation in Chinese nuclear families

Association between SNPs in polymorphism in peroxisome [corrected] proliferator-activated receptor-gamma (PPARG) and peak bone mineral density (BMD) variation of women was measured in 401 Chinese nuclear families using quantitative transmission disequilibrium test (QTDT). The peak BMD variation was not attributable to PPARG in our sample.

INTRODUCTION

The purpose of this study is to test whether genetic PPARG might play a role in normal variation in peak BMD.

METHODS

We genotyped 10 tagging SNPs in PPARG using allele-specific polymerase chain reaction and further test whether these SNPs were associated with peak BMD variation at the lumbar spine and femoral neck of women in 401 Chinese nuclear families using QTDT. Furthermore, the association between these SNPs in PPARG and BMD in 710 postmenopausal Chinese women was measured.

RESULTS

Using QTDT for within-family association, we failed to find that single SNP and haplotype were significantly associated with peak BMD at the lumbar spine and femoral neck. Meanwhile, we found that only rs1801282 was significantly associated with BMD at the lumbar spine in postmenopausal women (P = 0.013).

CONCLUSIONS

Our present results suggest, for the first time, that the genetic polymorphism in PPARG is not a major contributor to the observed variability in peak BMD at the lumbar spine and femoral neck in Chinese women.

Association between VDR and ESR1 gene polymorphisms with bone and obesity phenotypes in Chinese male nuclear families

AIM

The goal of this study was to determine whether polymorphisms in the vitamin D receptor (VDR) and estrogen receptor alpha (ESR1) genes are associated with variations of peak bone mineral density (BMD) and obesity phenotypes in young Chinese men.

METHODS

A total of 1215 subjects from 400 Chinese nuclear families were genotyped by polymerase chain reaction-restriction fragment length polymorphism (PCR-RFLP) and allele-specific multiple PCR (ASM-PCR) analysis at the ApaI, FokI, and CDX2 sites in the VDR gene and the PvuII and XbaI sites in the ESR1 gene. BMD at the lumbar spine and hip, total fat mass, and total lean mass were measured using dual energy X-ray absorptiometry. The associations between VDR and ESR1 gene polymorphisms with peak BMD, body mass index (BMI), total fat mass, total lean mass, and percentage fat mass (PFM) were determined using quantitative transmission disequilibrium tests (QTDTs).

RESULTS

Using QTDTs, no significant within-family associations were obtained between genotypes or haplotypes of the VDR and ESR1 genes and peak BMD. For the obesity phenotypes, the within-family associations were significant between CDX2 genotypes and BMI (P=0.046), fat mass (P=0.004), and PFM (P=0.020). Further, PvuII was significantly associated with the variation of fat mass and PFM (P=0.002 and P=0.039, respectively). A subsequent 1000 permutations were in agreement with these within-family association results.

CONCLUSION

Our findings showed that VDR and ESR1 polymorphisms were associated with total fat mass in young Chinese men, but we failed to find a significant association between VDR and ESR1 genotypes and peak BMD. These findings suggested that the VDR and ESR1 genes are quantitative trait loci (QTL) underlying fat mass variation in young Chinese men.

Family-based mapping of quantitative trait loci in plant breeding populations with resistance to Fusarium head blight in wheat as an illustration

Traditional quantitative trait loci (QTL) mapping approaches are typically based on early or advanced generation analysis of bi-parental populations. A limitation associated with this methodology is the fact that mapping populations rarely give rise to new cultivars. Additionally, markers linked to the QTL of interest are often not immediately available for use in breeding and they may not be useful within diverse genetic backgrounds. Use of breeding populations for simultaneous QTL mapping, marker validation, marker assisted selection (MAS), and cultivar release has recently caught the attention of plant breeders to circumvent the weaknesses of conventional QTL mapping. The first objective of this study was to test the feasibility of using family-pedigree based QTL mapping techniques generally used with humans and animals within plant breeding populations (PBPs). The second objective was to evaluate two methods (linkage and association) to detect marker-QTL associations. The techniques described in this study were applied to map the well characterized QTL, Fhb1 for Fusarium head blight resistance in wheat (Triticum aestivum L.). The experimental populations consisted of 82 families and 793 individuals. The QTL was mapped using both linkage (variance component and pedigree-wide regression) and association (using quantitative transmission disequilibrium test, QTDT) approaches developed for extended family-pedigrees. Each approach successfully identified the known QTL location with a high probability value. Markers linked to the QTL explained 40-50% of the phenotypic variation. These results show the usefulness of a human genetics approach to detect QTL in PBPs and subsequent use in MAS.

Association between myostatin gene polymorphisms and peak BMD variation in Chinese nuclear families

We identified 17 polymorphisms in myostatin by sequencing, and three informative single nucleotide polymorphisms (SNPs) were selected for further observation for their association with peak BMD of women in 401 Chinese nuclear families. Our results suggest that genetic polymorphisms in myostatin likely play a role in attainment of peak BMD in Chinese women.

INTRODUCTION

Myostatin is a TGF-beta family member that is a negative regulator of skeletal muscle growth.

MATERIALS AND METHODS

We identified SNPs in myostatin by direct sequencing. Furthermore, using a quantitative transmission disequilibrium test (QTDT). we tested and further test whether SNPs were associated with peak bone mineral density (BMD) variation at the spines and hips of 401 Chinese nuclear families. We identified 17 polymorphisms in myostatin by sequencing. Next, we selected three informative SNPs for further observation of an association with peak BMD of premenopausal women in 401 Chinese nuclear families.

RESULTS

Using QTDT for the within-family association, we found significant association between rs2293284 and total hip, femoral neck, and trochanter BMD (all p < 0.05), while rs7570532 was associated with total hip and trochanter BMD (p = 0.034 and p = 0.035, respectively). The within-family association was significant between BMI and +2278G > A (p = 0.022). Subsequent permutations were in agreement with these significant within-family association results. Moreover, analyses of the haplotypes confer further evidence for association of rs2293284 and rs7570532 with hip peak BMD variation.

CONCLUSIONS

These results suggest, for the first time, the genetic polymorphisms in myostatin likely play a role in attainment of peak BMD in Chinese women.

Evaluating the correlation and prediction of trunk fat mass with five anthropometric indices in Chinese females aged 20-40 years

BACKGROUND AND AIMS

Obesity is a worldwide problem, and excess trunk fat mass (FM(trunk)) has been associated with an increased risk of diseases. The early measurement of FM(trunk) has potential importance to evaluate trunk obesity. We sought to evaluate the correlation and predication of FM(trunk) with five anthropometric indices in Chinese females.

METHODS AND RESULTS

A sample of 850 China females aged 20-40 years were recruited and divided into four age groups with a 5-year range in each group. Five anthropometric indices were measured or calculated. FM(trunk) in kg was measured using a dual-energy X-ray absorptiometry scanner. Principal component analysis (PCA) and multiple regression analysis were performed to develop prediction equations. There was an increasing trend of FM(trunk) and five anthropometric indices in successively older age groups. Four formed principal components (PCs) interpreted over 99% of the total variation of five relative anthropometric indices in all age groups. Regression analyses showed that four PCs combined explained a greater variance (R(2)=45.2-81.6%) in FM(trunk) than did each of the five indices alone (R(2)=2.4-72.2%).

CONCLUSIONS

Our results suggested that there is an increasing trend of FM(trunk) and five anthropometric indices with aging; that age obviously influences the relationship of FM(trunk) and the anthropometric indices studied; and that the accuracy of predicting the FM(trunk) using five anthropometric indices combined is greater than using the five indices alone.

Association between SNP and haplotypes in PPARGC1 and adiponectin genes and bone mineral density in Chinese nuclear families

AIM

To assess the contribution of single nucleotide polymorphisms (SNP) and haplotypes in the peroxisome proliferators-activated receptor-gamma co-activator-1 (PPARGC1) and adiponectin genes to normal bone mineral density (BMD) variation in healthy Chinese women and men.

METHODS

We performed population-based (ANOVA) and family-based (quantitative trait locus transmission disequilibrium test) association studies of PPARGC1 and adiponectin genes. SNP in the 2 genes were genotyped. BMD was measured using dual-energy X-ray absorptiometry in the lumbar spine and hip in 401 nuclear families with a total of 1260 subjects, including 458 premenopausal women, 20-40 years of age; 401 postmenopausal women (mothers), 43-74 years of age; and 401 men (fathers), 49-76 years of age.

RESULTS

Significant within-family association was found between the Thr394Thr polymorphism in the PPGAGC1 gene and peak BMD in the femoral neck (P=0.026). Subsequent permutations were in agreement with this significant within-family association result (P=0.016), but Thr394Thr SNP only accounted for 0.7% of the variation in femoral neck peak BMD. However, no significant within-family association was detected between each SNP in the adiponectin gene and peak BMD. Although no significant association was found between BMD and SNP in the PPARGC1 and adiponectin genes in both men and postmenopausal women, haplotype 2 (T-T) in the adiponectin gene was associated with lumbar spine BMD in postmenopausal women (P=0.019).

CONCLUSION

Our findings suggest that Thr394Thr SNP in the PPARGC1 gene was associated with peak BMD in the femoral neck in Chinese women. Confirmation of our results is needed in other populations and with more functional markers within and flanking the PPARGC1 or adiponectin genes region.

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.

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.

Strong association between polymorphisms in ANKH locus and skeletal size traits

Loss of bone strength is the main determinant of bone fragility. Bone strength is directly dependent on bone size (BS). A substantial portion of BS variation is attributable to genetic effects. However, the list of genes and allelic variants involved in the determination of BS variation is far from being complete. Polymorphisms in the ANKH gene have been shown to be associated with radiographic hand BS-related phenotypes. The present study examined the possible association of the ANKH gene with skeletal size and shape in order to test the universality of the ANKH effect on BS traits. Our sample consisted of a total of 212 ethnically homogeneous nuclear families (743 individuals) of European origin. Each individual was measured for body height, weight, and several other anthropometrical measurements, and genotyped for nine polymorphic markers (the average heterozygosity level was 0.4). We observed significant associations with practically all the anthropometrical phenotypes studied. More specifically, we found associations with body weight and height, limb length (P</=0.001; promoter region). After adjustment for body height, we demonstrated the substantial association increase for biacromial breadth (P=0.0012; some 140 kb downstream from ANKH) and vertebral column length (P=0.0008; exons 2-7 region). The majority of the observed associations persisted even after correction for multiple testing. For the first time the reliable evidence in support of universality of ANKH gene polymorphisms effect on bone size was provided.

Variation in femoral length is associated with polymorphisms in RUNX2 gene

INTRODUCTION

Bone size is an important determinant of bone strength. Although it is well established that bone size traits are under the strong genetic control, genes involved in their determination are poorly characterized. The major objective of the present study was to test hypothesis of possible association between three RUNX2 SNP polymorphisms (rs2819858, rs1406846, rs2819854) and anthropometrical femoral length (FEML). In addition, the possibility of association between anthropometrical tibial length (TIBL) and stature and chosen RUNX2 polymorphisms was tested.

MATERIALS AND METHODS

The study was conducted on 265 nuclear families comprised of a total of 904 individuals. DNA samples were available for 705 individuals, belonging to 212 nuclear families. Three different transmission disequilibrium tests (TDTs), population-based and pedigree-based (PDT) association analyses were implemented in order to test the working hypothesis.

RESULTS

The results unambiguously and consistently demonstrated significant association for FEML regardless of the specific polymorphism tested and type of analysis implemented. The P values obtained by TDTs ranged between 0.0155 and 0.0007. The effect of RUNX2 polymorphisms was estimated to explain 1.9% of the total FEML variation after adjustment for sex and age. The data suggested that the strength of association between RUNX2 polymorphisms and FEML may be higher in females (P = 0.007) than in males (P = 0.046), according to PDT. Conversely, no reliable evidence of association between RUNX2 polymorphisms and either TIBL or stature was found.

CONCLUSIONS

For the first time, the evidence of association between RUNX2 polymorphisms and FEML was provided. The results of the present research contribute to the deeper understanding of the genetic architecture of femoral size and introduce the issues of site and sex dependency of the extent of RUNX2 effect. Further studies are required to confirm our findings, specifically focused on clinically oriented sites of skeleton, like femoral neck.

Genetic determination and correlation of body weight and body mass index (BMI) and cross-sectional geometric parameters of the femoral neck

INTRODUCTION

This study aimed to examine the genetic determination of body weight, body mass index (BMI) and cross-sectional geometric parameters of the femoral neck including cross-sectional area (CSA), cortical thickness (CT), sectional modulus (Z), and buckling ratio (BR), and to test the genetic correlation between body weight/BMI and the femoral neck geometric parameters.

METHODS

A total of 929 healthy subjects from 292 Chinese nuclear families was included. Femoral neck geometric parameters were estimated from bone mineral density (BMD) and bone area which were measured by dual energy X-ray absorptiometry (DXA).

RESULTS

The heritability (h(2)) estimate values were 0.643, 0.626, 0.626, 0.674, 0.405, and 0.615 for body weight, BMI, CSA, CT, Z, and BR, respectively. Body weight was significantly correlated with bone geometric parameters (p</=0.001) with genetic correlation (rho(G)) values of 0.551, 0.457, 0.571, and -0.385, and bivariate heritability (rho2G) values of 0.304, 0.209, 0.326, and 0.148 for CSA, CT, Z, and BR, respectively. Similar correlations (p</=0.001) were observed between BMI and bone geometric parameters, with rho(G) values of 0.446, 0.432, 0.334, and -0.362, and (rho2G) values of 0.199, 0.187, 0.112, and 0.131 for CSA, CT, Z, and BR, respectively.

CONCLUSION

In summary, our study suggested that body weight, BMI, and femoral neck geometry were under strong genetic determination. The strong genetic correlations suggested that the genetic factors of bone geometry may be overlapped with those of body weight and BMI.

Genetic determination and correlation of body mass index and bone mineral density at the spine and hip in Chinese Han ethnicity

The purpose of the present study was to evaluate the magnitude of genetic determination of spine and hip bone mineral density (BMD) and body mass index (BMI), and to explore the genetic, environmental, and phenotypic correlations among the above phenotypes in Chinese Han ethnicity. The sample was composed of at least 217 complete nuclear families in Chinese Han ethnicity. BMD at the spine and hip was measured using a dual-energy X-ray absorptiometry scanner. The heritability (h2) of BMI and BMD at the spine and hip, the genetic correlation (rhoG) and environmental correlation (rhoE) among the three phenotypes were evaluated via variance analysis, with age, sex, and age-by-sex interaction as covariates. The phenotypic correlation (rhoP) and the bivariate heritability rhoG2 were also calculated. The heritability for BMD and BMI was approximately 0.70 and approximately 0.50, respectively (p<0.0001). The common environment shared by household members (household effect) is significant for BMI variation (p=0.0004). Significant genetic, environmental, and phenotypic correlation was observed. The rhoG2 values were 0.13 for BMI/spine BMD, 0.18 for BMI/hip BMD, and 0.58 for the spine BMD/hip BMD. While BMD at the spine and hip have significant genetic determination, BMI is more likely to be affected by environmental factors than BMD. In addition, BMD at the spine and hip shares more genetic effect (pleiotropy) than BMI and BMD do in Chinese Han ethnicity, though the effects are significant for both.

Relationship of total body fatness and five anthropometric indices in Chinese aged 20–40 years: different effects of age and gender

OBJECTIVES

We aim to evaluate the ethnic-specific relationship of total fat mass and anthropometric indices in Chinese.

DESIGN

Cross-section study.

SETTING

This study was performed at the College of Life Sciences, Hunan Normal University, P.R. China.

SUBJECTS AND METHOD

To increase our understanding of the relationship of total fat mass and anthropometric indices in Chinese, 793 females and 1091 males aged 20-40 years were randomly recruited from Changsha city of P. R. China. Hip circumference (HC) and waist circumference (WC) were measured using standardized equipments, and other three anthropometric indices of body mass index (BMI), waist-to-hip ratio (WHR), and conicity index (CI) were calculated using weight, height, HC and WC. Total body fatness (TBF) in kg was measured using a Hologic QDR 4500 W dual-energy X-ray absorptiometry (DEXA) scanner.

RESULTS

There was an increasing trend of TBF, %TBF (percent total body fatness) and the five anthropometric indices in successively older age groups. Compared with females, males generally had high average BMI, WC, HC, WHR and CI, but had low average TBF and %TBF. Except for some correlations in 25-29 years age groups, TBF and %TBF were significantly correlated with five anthropometric indices with the Pearson's correlation coefficients ranging from 0.07 to 0.87. Principal component analysis (PCA) was performed to form four principal components (PCs) that interpreted over 99% of the total variation of the five related anthropometric indices in all age groups, with over 53% of the total variation accounted for by the PC1. Multiple regression analyses showed that four PCs combined explained a greater variance (R (2)=55.2-80.8%) in TBF than did BMI alone (R (2)=40-74.9%).

CONCLUSION

Our results suggest that there is an increasing trend of total fat mass and five anthropometric indices with aging; that age and sex have the important effects on influencing the correlations of TBF and the studied anthropometric indices; and that the accuracy of predicting the TBF using five anthropometric indices is higher than using BMI alone.

Association and haplotype analyses of the COL1A2 and ER-alpha gene polymorphisms with bone size and height in Chinese

Bone size (BS) is another risk factor of fracture independent of BMD in determining bone strength, and height is highly related with BS. To test the effect of the estrogen receptor-alpha (ER-alpha) and collagen type I alpha 2 (COL1A2) genes on the variation of BS and height, we genotyped the PvuII and XbaI polymorphisms in the intron 1 of the ER-alpha gene and the MspI and (GT)n markers in the intron 47 and intron 1 of the COL1A2 gene in 400 Chinese nuclear families with a total of 1256 individuals. The BS at the hip and spine was measured using a Hologic QDR 2000 dual-energy X-ray absorptiometry (DXA) scanner. Population stratification, total-family association, and within-family association were used to test the relationship of BS (at the spine and hip) and height with the four polymorphisms. We also performed these association analyses with the haplotypes of the MspI and (GT)n polymorphisms in the COL1A2 gene, and with the haplotypes of the PvuII and XbaI markers in the ER-alpha gene. Weak within-family association was found between the COL1A2-MspI (P = 0.05) and the femoral neck BS, between the ER-alpha-PX (P = 0.04) and the intertrochanter BS, and between the COL1A2-(GT)(17) (P = 0.02), COL1A2-m(GT)(17) (P = 0.009) and height. Subsequent permutation tests generally confirmed the suggestive within-family association. For the weak within-family association, the proportions of phenotypic variance accounted by the COL1A2-MspI, ER-alpha-PX, COL1A2-(GT)(17), COL1A2-m(GT)(17) markers were 1.50%, 1.51%, 2.15%, and 2.43% for the corresponding phenotypes. The association results indicate that the (GT)n and MspI markers of COL1A2 gene may have some influence on the variation of both BS and height, and the XbaI and PvuII markers of ER-alpha gene may have some effect on the variation of height in Chinese but not on the variation of BS.

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.

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.