Association of a single-nucleotide variation (A1330V) in the low-density lipoprotein receptor-related protein 5 gene (LRP5) with bone mineral density in adult Japanese women

Low-density lipoprotein receptor-related protein 5 (LRP5), a co-receptor of Wnt signaling, is an important regulator of bone development and maintenance. Recently we identified correlation between an intronic single-nucleotide polymorphism (SNP) in the LRP5 gene and vertebral bone mineral density (BMD), indicating that a genetic ground exists at this locus for determination of BMD. In the study reported here, we searched for nucleotide variation(s) that might confer susceptibility to osteoporosis among an extended panel of 387 healthy subjects recruited from the same hospital (Group-A), as well as among 384 subjects from the general population in eastern Japan (Group-B). We basically focused on two potentially functional variations, Q89R (c.266A > G) and A1330V (c.3989C > T), whose functional effects by the amino-acid changes were estimated by the SIFT software program; it predicted the 1330 V allele as deleterious ("intolerant") although the minor allele of Q89R was questionable. By analyzing associations between the variant alleles and the BMD, reproducible association of the minor variant of A1330V to lower adjusted BMD levels was detected; i.e., In Group-A subjects 1330-V significantly associated with the spinal BMD Z-score (P = 0.034), and in Group-B it associated with low radial BMD (P = 0.019). From haplotype and linkage disequilibrium (LD) analysis for 29 SNPs, we detected two separate LD blocks within the entire 137-kb LRP5 locus, basically consistent with a previous report on Caucasians. One of the second block haplotype significantly associated with adjusted BMD (r = 0.15, P = 0.004). Possible combined effect of Q89R and A1330V belonging to different LD blocks was denied by multiple regression analyses. Our results indicate that genetic variations in LRP5 are important factors affecting BMD in adult women and that 1330 V may contribute to osteoporosis susceptibility, at least in Japanese.     

Association of a single-nucleotide polymorphism in low-density lipoprotein receptor-related protein 5 gene with bone mineral density

Low-density lipoprotein receptor-related protein 5 (LRP5) is an important regulator of osteoblast growth and differentiation, affecting peak bone mass in vertebrates. Here, we analyzed whether the LRP5 gene was involved in the etiology of postmenopausal osteoporosis, using association analysis between bone mineral density (BMD) and an LRP5 gene single-nucleotide polymorphism (SNP). Association of an SNP in the LRP5 gene at IVS17-1677C > A (intron 17) with BMD was examined in 308 postmenopausal Japanese women (65.2 ± 9.6 years; mean ± SD). The subjects bearing at least one variant A allele (CA + AA; n = 142) had significantly lower Z scores for total body and lumbar BMD than the subjects with no A allele (CC; n = 166) (total body, 0.08 ± 1.09 versus 0.50 ± 1.03; P = 0.0022; lumbar spine, –0.42 ± 1.43 versus –0.02 ± 1.42; P = 0.013). These findings suggest that the LRP5 gene is a candidate for the genetic determinants of BMD in postmenopausal women, and this SNP could be useful as a genetic marker for predicting the risk of osteoporosis.     

Low-density lipoprotein receptor-related protein 5 (LRP5) gene polymorphisms are associated with bone mass in both Chinese and whites.

In this study, the associations of novel LRP5 variants with BMD variation were detected and some replicated in the two ethnic groups of Chinese and white origins, respectively. These data support the concept that LRP5 variation can contribute to minor and major variation in bone structure. INTRODUCTION: Mutations in the low-density lipoprotein receptor-related protein 5 (LRP5) gene have been shown to cause both high and low bone mass. However, it is still controversial whether LRP5 is associated with normal BMD variation. This study explored the association of LRP5 with BMD phenotypes at three clinically important skeletal sites-the spine, hip, and ultradistal radius (UD)-in two independent populations of Chinese and white ethnicities, respectively. MATERIALS AND METHODS: The Chinese sample consisted of 733 unrelated subjects. The white sample was made up of 1873 subjects from 405 nuclear families. High-density single nucleotide polymorphisms (SNPs) across the whole LRP5 gene were genotyped and analyzed in both samples. RESULTS: Linkage disequilibrium (LD) analyses showed that the haplotype structures of LRP5 between Chinese and whites were in good agreement. Association tests showed that polymorphisms in block 5 spanning intron 7 to intron 19 of LRP5 significantly associated with spine BMD variation in both samples. Particularly, the significant association of SNP rs491347 in intron 7 with spine BMD in the Chinese sample (p=0.002) was replicated in whites, even after adjusting for multiple testing (p=0.005). Its strongly associated SNP rs1784235 could cause the loss of an estrogen receptor alpha (ERalpha) binding site in LRP5, which could partially explain the above replicated association. However, we did not observe any significant replication with BMD variation at the hip and UD. After accounting for multiple testing, associations with BMD variation at these two sites were mainly found in Chinese. Sex-stratified analyses further revealed that the LRP5 associations with BMD in Chinese and whites were driven by male and female subjects, respectively. CONCLUSIONS: Our work supported LRP5 genetic variants as possible susceptibility factors for osteoporosis and fractures in humans. Especially, the SNP rs491347 and its strongly associated SNPs (e.g., rs1784235) could be important to human osteoporosis phenotypes.     

Genetic variation at the low-density lipoprotein receptor-related protein 5 (LRP5) locus modulates Wnt signaling and the relationship of physical activity with bone mineral density in men

Polymorphisms in the LRP5 gene have been associated with bone mineral density (BMD) in men and/or women. However, the functional basis for this association remains obscure. We hypothesized that LRP5 alleles could modulate Wnt signaling and the relationship between physical activity and BMD. This genetic association study was performed in the population-based Framingham Study Offspring Cohort, and included a subset of 1797 unrelated individuals who provided blood samples for DNA and who had BMD measurements of the hip and spine. Ten single-nucleotide polymorphisms (SNPs) spanning the LRP5 gene were genotyped and used for association and interaction analyses with BMD by regression methods. LRP5 haplotypes were transiently co-expressed with Wnt3a, MesD and Dkk1 in HEK293 cells and their activity evaluated by the TCF-Lef reporter assay. Six out of ten SNPs in LRP5 were associated with one or more of the femur or spine BMDs in men or women after adjustment for covariates, and these associations differed between genders. In men< or =age 60 years, 3 SNPs were significantly associated with BMD: rs2306862 on Exon 10 with femoral neck BMD (p=0.01) and Ward's BMD (p=0.01); rs4988321/p. V667M with Ward's BMD (p=0.02); and intronic rs901825 with trochanter BMD (p=0.03). In women, 3 SNPs in intron 2 were significantly associated with BMD: rs4988330 for trochanter (p=0.01) and spine BMD (p=0.003); rs312778 with femoral neck BMD (p=0.05); and rs4988331 with spine BMD (p=0.04). For each additional rare allele, BMD changed by 3-5% in males and 2-4% in females. Moreover, there was a significant interaction between physical activity and rs2306862 in exon 10 (p for interaction=0.02) and rs3736228/p. A1330V in exon 18 (p for interaction=0.05) on spine BMD in men. In both cases, the TT genotype was associated with lower BMD in men with higher physical activity scores, conversely with higher BMD in men with lower physical activity scores. In vitro, TCF-Lef activity in presence of Wnt3a was significantly reduced in cells expressing LRP5 haplotypes carrying the T allele of exon 10 and 18 compared to the wild-type allele, whereas co-expression of Dkk1 completely inhibited Wnt3a response through all LRP5 haplotypes. In summary, genetic variation in exons 10 and 18 of the LRP5 gene modulates Wnt signaling and the relationship between physical activity and BMD in men. These observations suggest that Wnt-LRP5 may play a role in the adaptation of bone to mechanical load in humans, and may explain some gender-related differences in bone mass.     

LRP5基因A1330V、Q89R位点多态性、突变与绝经后T2DM骨质疏松症的关系

目的研究低密度脂蛋白受体相关蛋白5(LRP5)基因A1330V、Q89R位点多态性及突变与绝经后2型糖尿病(T2DM)伴骨质疏松症(OP)的关系。方法选取我院门诊81例绝经后T2DM患者,根据是否伴OP分为T2DM伴OP组39例,T2DM组42例,单纯OP组40例,同期体检中心绝经后健康女性40例为对照组,应用基因测序技术检测LRP5基因A1330V、Q89R位点多态性。结果 T2DM伴OP组Hb AIC、FINS高于对照组,腰L2-4BMD、股骨颈BMD低于对照组; T2DM组Hb AIC、FINS高于对照组,差异有统计学意义(P0.05)。T2DM伴OP组、T2DM组和OP组LRP5基因A1330V位点AA型、AV型、VV型构成与对照组比较差异有统计学意义(P0.05)。各组LRP5基因Q89R位点基因型分布差异无统计学意义(P 0.05)。T2DM伴OP组LRP5基因A1330V位点AA型、AV型、VV型Hb AIC、腰L_(2-4)BMD、股骨颈BMD差异均有统计学意义(P 0.05)。AA型、AV型、VV型TRACP-5b、BALP、FINS比较差异均无统计学意义(P 0.05)。结论 LRP5基因可能是绝经后女性T2DM和OP的易感基因,A1330V位点多态性、突变对绝经后女性T2DM和OP的发生有影响。     

Early smoking is associated with peak bone mass and prevalent fractures in young,healthy men

Smoking is associated with lower areal bone mineral density (aBMD) and higher fracture risk, although most evidence has been derived from studies in elderly subjects. This study investigates smoking habits in relation to areal and volumetric bone parameters and fracture prevalence in young, healthy males at peak bone mass. Healthy male siblings (n = 677) at the age of peak bone mass (25 to 45 years) were recruited in a cross‐sectional population‐based study. Trabecular and cortical bone parameters of the radius and cortical bone parameters of the tibia were assessed using peripheral quantitative computed tomography (pQCT). Areal bone mass was determined using dual energy X‐ray absorptiometry (DXA). Sex steroids and bone markers were determined using immunoassays. Prevalent fractures and smoking habits were assessed using questionnaires. Self‐reported fractures were more prevalent in the current and early smokers than in the never smokers (p < .05), with a fracture prevalence odds ratio for early smokers of 1.96 (95% confidence interval 1.18–3.24) after adjustment for age, weight, educational level, and alcohol use and exclusion of childhood fractures. Current smoking was associated with a larger endosteal circumference (β = 0.027 ± 0.009, p = .016) and a decreased cortical thickness (β = ?0.034 ± 0.01, p = .020) at the tibia. In particular, early smokers (≤16 years) had a high fracture risk and lower areal BMD, together with a lower cortical bone area at the tibia and lower trabecular and cortical bone density at the radius. An interaction between free estradiol and current smoking was observed in statistical models predicting cortical area and thickness (β = 0.29 ± 0.11, p = .01). In conclusion, smoking at a young age is associated with unfavorable bone geometry and density and is associated with increased fracture prevalence, providing arguments for a disturbed acquisition of peak bone mass during puberty by smoking, possibly owing to an interaction with sex steroid action. © 2010 American Society for Bone and Mineral Research     

Heterozygous mutations in the LDL receptor-related protein 5 (LRP5) gene are associated with primary osteoporosis in children.

Three of 20 patients with juvenile osteoporosis were found to have a heterozygous mutation in the LRP5 gene. No mutations were found in the type I collagen genes. Mutations in the other family members with similar bone phenotype confirmed that LRP5 has a role in both juvenile and adult osteoporosis. INTRODUCTION: The gene encoding the low-density lipoprotein receptor-related protein 5 (LRP5) gene has recently been shown to affect bone mass accrual during growth and to be involved in osteoporosis-pseudoglioma syndrome and a high bone mass phenotype. Mutations in the type I collagen genes (COL1A1 and COL1A2) are known to cause osteogenesis imperfecta, characterized by increased bone fragility. MATERIALS AND METHODS: Here we analyzed COL1A1, COL1A2, and LRP5 for mutations in 20 pediatric patients with primary osteoporosis characterized by low BMD, recurrent fractures, and absent extraskeletal manifestations. RESULTS AND CONCLUSIONS: No mutations were detected in the type I collagen genes, but two missense mutations (A29T and R1036Q) and one frameshift mutation (C913fs) were found in the LRP5 gene in three of the patients. The frameshift mutation was also seen in the proband's father and brother, who both were found to have significant osteoporosis. R1036Q was observed in the proband's mother and two brothers, who all had osteoporosis. These results indicate that heterozygous mutations in the LRP5 gene can cause osteoporosis in both children and adults.     

Prevalent fractures are related to cortical bone geometry in young healthy men at age of peak bone mass

Low areal bone mass is a risk factor for fractures in men. Limited data are available on fractures and bone geometry in men, and the relation with sex steroids is incompletely understood. We investigated prevalent fractures in relation to peak bone mass, bone geometry, and sex steroids in healthy young men. Healthy male siblings (n = 677) at the age of peak bone mass (25 to 45 years) were recruited in a cross‐sectional population‐based study. Trabecular and cortical bone parameters of the radius and cortical bone parameters of the tibia were assessed using peripheral quantitative computed tomography (pQCT). Areal bone mineral density (aBMD) was determined using dual‐energy X‐ray absorptiometry (DXA). Sex steroids were determined using immunoassays, and fracture prevalence was assessed using questionnaires. Fractures in young men were associated with a longer limb length, shorter trunk, lower trabecular BMD, smaller cortical bone area, and smaller cortical thickness (p < .005) but not with bone‐size‐adjusted volumetic BMD (vBMD). With decreasing cortical thickness [odds ratio (OR) 1.4/SD, p ≤ .001] and decreasing cortical area (OR 1.5/SD, p ≤ .001), fracture odds ratios increased. No association between sex steroid concentrations and prevalent fractures was observed. Childhood fractures (≤15 years) were associated with a thinner bone cortex (?5%, p ≤ .005) and smaller periosteal size (?3%, p ≤ .005). Fractures occurring later than 15 years of age were associated with a thinner bone cortex (?3%, p ≤ .05) and larger endosteal circumference (+3%, p ≤ .05) without differences in periosteal bone size. In conclusion, prevalent fractures in healthy young men are associated with unfavorable bone geometry and not with cortical vBMD when adjusting for bone size. Moreover, the data suggest different mechanisms of childhood fractures and fractures during adult life. © 2010 American Society for Bone and Mineral Research     

The relation of the Xbal and Pvull polymorphisms of the estrogen receptor gene and the CAG repeat polymorphism of the androgen receptor gene to peak bone mass and bone turnover rate among young healthy men

The genes coding for estrogen receptor- (ER-) and androgen receptors (AR) are potential candidates for the regulation of bone mass and turnover, which may contribute to both the achievement of peak bone mass and bone loss after completion of growth. The present study was aimed at elucidating the role of two restriction fragment lengths (XbaI and PvuII) polymorphisms of the ER gene and the CAG repeat polymorphism of the AR gene as determinants of peak bone mass in men; special attention was paid to the interaction between serum free estradiol (E₂) levels and the XbaI and PvuII genotypes. A cross-sectional study, with data on lifestyle factors collected retrospectively, was performed in 234 young men, aged 18.3 to 20.6 years. Of the men, 184 were recruits of the Finnish Army and 50 were men of similar age who had postponed their military service for reasons not related to health. Bone mineral content (BMC), density (BMD) and scan area were measured in the lumbar spine and upper femur by dual-energy X-ray absorptiometry (DXA). The bone turnover rate was assessed by measuring serum type I procollagen aminoterminal propeptide (PINP) and tartrate-resistant acid phosphatase 5b (TRACP5b) as well as urinary excretion of type I collagen aminoterminal telopeptide (NTX). After adjusting for age, height, weight, exercise, smoking, calcium and alcohol intake, BMC, scan area and BMD at all measurement sites were similar for the different XbaI and PvuII genotypes of the ER and independent of the number of the CAG repeats of the AR gene. No association was found between free E₂ levels and bone parameters among any genotype group of the XbaI and PvuII polymorphisms. Except for urinary NTX, which showed a tendency to higher values for the xx ( P =0.08) and pp ( P =0.10) genotypes of the ER, bone turnover markers were not related to the genotypes studied. Our study does not support the view that the XbaI and PvuII polymorphisms of the ER gene and the CAG polymorphism of the AR gene would have a substantial impact on the development of peak bone mass in young Finnish men.     

Common genetic variation of the low-density lipoprotein receptor-related protein 5 and 6 genes determines fracture risk in elderly white men.

Both LRP5 and LRP6 genes have been implicated to play a role in bone metabolism. In a large population-based study, we related common variation in both genes to bone parameters and fractures. LRP5 variation was associated to both BMD and frame size, whereas both LRP5 and 6 variations were associated with an increased fracture risk in males. INTRODUCTION: The low-density lipoprotein receptor-related protein 5 (LRP5) gene has a clear role in rare BMD traits and also in normal variation in peak BMD. We examined whether common variation in LRP5 and its close homolog, LRP6, plays a role in BMD in old age and fractures, the main clinical endpoint of osteoporosis. MATERIALS AND METHODS: We analyzed four variants of LRP5 and one amino acid variant of the LRP6 gene in a large prospective population-based cohort study of elderly subjects. RESULTS AND CONCLUSIONS: In men, the LRP5 1330-valine variant was associated with decreased BMD at the lumbar spine and the femoral neck with evidence for an allele-dose effect (p = 0.001 and 0.01, respectively). The Val allele was also associated with decreased vertebral body size and femoral neck width. Haplotype analysis of studied polymorphisms did not improve the association found and suggested that the 1330 variant was driving the association. We observed a borderline significant association of the LRP6 Ile1062Val polymorphism with height and vertebral body size in males. Male carriers of the LRP5 1330-valine variant had a 60% increased risk for fragility fractures, and the LRP6 1062-valine allele also conferred a 60% higher risk. Carriers of both the risk alleles of LRP5 and 6 had a 140% (p = 0.004) higher risk compared with noncarriers of both risk alleles and accounted for 10% of the fractures in males. The fracture risks were independent of age, height, weight, and BMD. In women, all of these associations were weaker and less consistent compared with men. The polymorphisms that were found associated were both situated in potentially important domains of the receptor and show considerable evolutionary conservation, which is evidence for functional importance of these residues.     

A DNA polymorphism in the human low-density lipoprotein receptor gene

A new restriction fragment length polymorphism (RFLP) in the low-density lipoprotein receptor gene is described using the Stu I restriction endonuclease and a cDNA probe. The frequency of the two RFLP alleles was determined in 60 unrelated white subjects and 11.7% of them were found to be heterozygous for the polymorphism. Mendelian segregation of the RFLP was found in 3 informative families. The possible use of the RFLP in the diagnosis of familial hypercholesterolaemia in South Africa is discussed.     

Physical activity is the strongest predictor of calcaneal peak bone mass in young Swedish men

Summary  

In a highly representative sample of young adult Swedish men (n = 2,384), we demonstrate that physical activity during childhood and adolescence was the strongest predictor of calcaneal bone mineral density (BMD), and that peak bone mass was reached at this site at the age of 18 years.     

东亚人群LRPS基因A1330V位点多态性与骨密度相关性的M eta分析

目的 利用Meta分析的方法,综合评价LRPS基因A1330V位点多态性与东亚人群骨密度(BMD )的相关性。方法 计算机检索Pubmed , Embase、中国生物医学文献数据库和万方数据库数据库等,并手工检索相关杂志,收集有关东亚人群LRPS基因A1330V位点多态性的基因型频率与BMD相关性的研究。检索时间截止至2012年11月。在评价纳人研究质量,提取有效数据后,采用Stata 12.0软件进行Meta分析。结果 共11项研究符合既定的纳人和排除标准,合计5906名研究对象。Meta分析结果显示:AA基因型较AV/VV基因型腰椎BMD高,且差异有统计学意义[SMD =0.107, 95% CI (0.044,0. 171)。在股骨颈BMD方面,AA基因型高于AV/VV基因型[ SMD =0. 190, 95% CI (0. 034, 0. 346) ]。 AA基因型的挠骨、全身BMD也高于AV/VV基因型。但是,AA基因型群体的转子间BMD与AV/VV基因型的差异无统计学意义[SMD =0. 090, 95% CI(-0.029, 1. 143)]。除腰椎、转子间BMD以外,AA基因型群体的股骨颈、挠骨以及全身BMD高于VV基因型,但此基因型间比较的纳人研究数量过少,证据尚不充分。结论 本Meta分析结果提示,东亚人群中LRPS基因A1330V位点的突变可能与骨密度的变化具有相关性,尤其AA基因型人群在股骨颈、腰椎部位有比AV/VV或VV基因型人群更高的骨密度值。但目前的结论尚需进一步大样本、高质量的研究去验证。     

LRP5 coding polymorphisms influence the variation of peak bone mass in a normal population of French-Canadian women

INTRODUCTION: Bone mineral density has a strong genetic component but it is also influenced by environmental factors making it a complex trait to study. LRP5 gene was previously shown to be involved in rare diseases affecting bone mass. Mutations associated with gain-of-function were described as well as loss-of-function mutations. Following this discovery, many frequent LRP5 polymorphisms were tested against the variation of BMD in the normal population. MATERIALS AND METHODS: Heel bone parameters (SOS, BUA) were measured by right calcaneal QUS in 5021 healthy French-Canadian women and for 2104 women, BMD evaluated by DXA at two sites was available (femoral neck (FN) and lumbar spine (LS)). Among women with QUS measures and those with DXA measures, 26.5% and 32.8% respectively were premenopausal, 9.2% and 10.7% were perimenopausal and 64.2% and 56.5% were postmenopausal. About a third of the peri- and postmenopausal women never received hormone therapy. Two single nucleotide coding polymorphisms (Val667Met and Ala1330Val) in LRP5 gene were genotyped by allele-specific PCR. All bone measures were tested individually for associations with each polymorphism by analysis of covariance with adjustment for non genetic risk factors. Furthermore, haplotype analysis was performed to take into account the strong linkage disequilibrium between the two polymorphisms. RESULTS AND CONCLUSION: The two LRP5 polymorphisms were found to be associated with all five bone measures (L2L4 and femoral neck DXA as well as heel SOS, BUA and stiffness index) in the whole sample. Premenopausal women drove the association as expected from the proposed role of LRP5 in peak bone mass. Our results suggest that the Val667Met polymorphism is the causative variant but this remains to be functionally proven.     

健康中青年男性体检者骨密度现状研究

目的 研究上海及周边地区健康中青年男性骨密度现状.方法 2007年4月至8月对上海及周边地区来我院健康体检的304名中青年男性进行双能x线骨密度仪检测,对其结果尤其是中青年的骨密度测定结果进行分析研究.结果 体检健康男性腰椎骨密度峰值出现在60～69岁(0.992±0.121 g/cm2),其余各部分骨密度峰值均出现在20～29岁[总髋骨(0.979±0.149)g/cm2、股骨颈(0.890±0.172)g/cm2、大转子(0.712±0.123)g/cm2、Ward氏区(0.742±0.159)g/cm2];参照世界卫生组织的骨质疏松诊断标准,该研究发现30～39岁骨质疏松患病率为11.27%,40～49岁为7.34%,50～59岁为17.65%.参照最新文献报道的三组(上海、长沙、香港)国内男性骨密度峰值分别得出的骨质疏松和骨量减少比例仍然较高,即使在骨量减少最少的一组数据(上海)中,其所占比例也分别高达26.67%(20～29岁),21.13%(30～39岁),22.02%(40～49岁)和25.88%(50～59岁).结论 本研究对象为上海及周边地区男性公司职员或私营企业主,其各年龄段骨质疏松患病率均高于国内其他各地的报道,而且30～39岁和40～49岁年龄组都有半数骨密度不正常.吸烟、饮酒、疲劳熬夜等不良生活习惯对现代中青年人骨密度的严重影响不容忽视.     

Smoking is associated with impaired bone mass development in young adult men: A 5-year longitudinal study

It has previously been shown that smoking is associated with reduced bone mass and increased fracture risk, but no longitudinal studies have been published investigating altered smoking behavior at the time of bone mass acquisition. The aim of this study was to investigate the development of bone density and geometry according to alterations in smoking behavior in a 5‐year, longitudinal, population‐based study of 833 young men, age 18 to 20 years (baseline). Furthermore, we aimed to examine the cross‐sectional, associations between current smoking and parameters of trabecular microarchitecture of the radius and tibia, using high‐resolution peripheral quantitative computed tomography (HR‐pQCT), in young men aged 23 to 25 years (5‐year follow‐up). Men who had started to smoke since baseline had considerably smaller increases in areal bone mineral density (aBMD) at the total body (mean ± SD, 0.020 ± 0.047 mg/cm² versus 0.043 ± 0.040 mg/cm², p < 0.01) and lumbar spine (0.027 ± 0.062 mg/cm² versus 0.052 ± 0.065 mg/cm², p = 0.04), and substantially greater decreases in aBMD at the total hip (?0.055 ± 0.058 mg/cm² versus ?0.021 ± 0.062 mg/cm², p < 0.01) and femoral neck (?0.077 ± 0.059 mg/cm² versus ?0.042 ± 0.070 mg/cm², p < 0.01) than men who were nonsmokers at both the baseline and follow‐up visits. At the tibia, subjects who had started to smoke had a smaller increment of the cortical cross‐sectional area (CSA) than nonsmokers (8.1 ± 4.3 mm² versus 11.5 ± 8.9 mm², p = 0.03), and a larger decrement of trabecular volumetric BMD (vBMD) than nonsmokers (?13.9 ± 20.5 mg/mm³ versus ?4.1 ± 13.9 mg/mm³, p < 0.001). In the cross‐sectional analysis at follow‐up (23–25 years of age), smokers had significantly lower trabecular vBMD at the tibia (7.0%, p < 0.01) due to reduced trabecular thickness (8.9%, p < 0.001), as assessed using HR‐pQCT, than nonsmokers. In conclusion, this study is the first to report that men who start to smoke in young adulthood have poorer development of their aBMD at clinically important sites such as the spine and hip than nonsmokers, possibly due to augmented loss of trabecular density and impaired growth of cortical cross‐sectional area. © 2012 American Society for Bone and Mineral Research.     

Low‐density lipoprotein receptor‐related protein 5 (LRP5) expression in human osteoarthritic chondrocytes

The aim of this study was to investigate the activation of the Wnt/β‐catenin pathway in osteoarthritis and the role of low‐density lipoprotein receptor‐related protein 5 (LRP5) in human osteoarthritic chondrocytes. The influence of 1,25(OH)₂D₃ on the expression of the LRP5 gene in human chondrocytes was also assessed. Human cartilage was obtained from 11 patients with primary osteoarthritis (OA) undergoing total knee replacement surgery. Normal cartilage was obtained from five healthy individuals. Beta‐catenin and LRP5 mRNA levels were investigated using real‐time PCR and LRP5 protein expression using Western blot analysis. Furthermore, we evaluated the effect of 1,25(OH)₂D₃ on LRP5 mRNA expression levels in osteoarthritic chondrocytes. Blocking LRP5 expression was performed using small interfering RNA (siRNA) against LRP5, and subsequent MMP‐13 mRNA and protein levels were evaluated by real‐time PCR and Western blot analysis, respectively. We confirmed the activation of the Wnt/β‐catenin pathway in OA, as we observed significant up‐regulation of β‐catenin mRNA expression in osteoarthritic chondrocytes. We also observed that LRP5 mRNA and protein expression were significantly up‐regulated in osteoarthritic cartilage compared to normal cartilage, and LRP5 mRNA expression was further increased by vitamin D. Also, blocking LRP5 expression using siRNA against LRP5 resulted in a significant decrease in MMP‐13 mRNA and protein expressions. Our findings suggest the catabolic role of LRP5 is mediated by the Wnt/β‐catenin pathway in human osteoarthritis. © 2009 Orthopaedic Research Society. Published by Wiley Periodicals, Inc. J Orthop Res 28:348–353, 2010     

Smaller low-density lipoprotein size as a possible risk factor for the prevalence of coronary artery diseases in haemodialysis patients: associations of cholesteryl ester transfer protein and the hepatic lipase gene polymorphism with low-density lipoprotein size

Aim: Smaller low‐density lipoprotein (LDL) size has recently been reported as a non‐traditional lipid risk factor for coronary artery disease (CAD). Cholesteryl ester transfer protein (CETP) and the C/T hepatic lipase (HL) gene polymorphism may promote LDL size reduction via the CETP‐mediated exchange of CE for triglyceride (TG) and subsequent HL‐mediated TG hydrolysis in LDL. However, little is known about LDL size status and its relationship with CAD prevalence in haemodialysis (HD) patients who are at high risk for atherosclerosis. Methods: CETP levels, HL genotypes and LDL size were determined, and the determinants of LDL size and its association with CAD prevalence in HD patients (n = 236) aged over 30 years were investigated. Results: The HD patients had a similar LDL size to the healthy subjects. In the HD group, high‐density lipoprotein cholesterol was an independent positive determinant of LDL size, while log₁₀ (TG) was an independent negative determinant in the high (≥2.1 µg/mL) but not low (<2.1 µg/mL) CETP group. In the patients with hypertriglyceridemia, the high CETP group had a significantly smaller LDL size than the low CETP group. Among the patients with above‐median TG levels, the CC genotype and CETP were independent negative determinants of LDL size. In the whole group and the high CETP group, the patients with CAD had a significantly smaller LDL size than those without CAD. Finally, DM and smaller LDL size were identified as independent risk factors for CAD prevalence. Conclusion: These suggest that a smaller LDL size, which is associated with higher levels of TG and CETP and the HL/CC genotype, may serve as a risk factor for CAD in HD patients.