Abstract
Objectives
Both genetic and lifestyle factors have been shown to influence bone mineral density (BMD). We investigated the correlations between BMD and low-density lipoprotein receptor-related protein 5 (LRP5) A1330V (rs3736228) polymorphism, exercise, smoking, and alcohol intake in Japanese male workers.
Methods
The subjects were 829 male employees (aged 20–59 years) of a large-scale integrated manufacturing facility in Japan. BMD was measured at the nondominant radius by dual-energy X-ray absorptiometry. Lifestyle information was obtained by a questionnaire at the same time, and genomic DNA was isolated from peripheral leukocytes.
Results
Mean ± standard deviation (SD) BMD was 0.557 ± 0.059 g/cm2. The genotype frequencies of LRP5 gene polymorphism were 51, 42, and 7% for AA, AV, and VV, respectively. Analysis of variance and post hoc Tukey test indicated that mean BMD was significantly lower in subjects with VV genotype than in those with AA genotype (0.540 ± 0.048 versus 0.562 ± 0.062 g/cm2). According to multiple linear regression analysis, LRP5 A1330V polymorphism was an independent determinant of BMD, after adjusting for age, body mass index (BMI), and lifestyle variables. Exercise (past or current) also influenced BMD.
Conclusions
These findings suggest that LRP5 A1330V polymorphism and exercise may influence BMD in Japanese male workers.
Keywords: Bone mineral density, Genetic polymorphism, Low-density lipoprotein receptor-related protein 5 gene
Introduction
Osteoporosis is usually considered to be a typical problem of postmenopausal or elderly women, but it is also prevalent in men. In fact, approximately 30% of hip fractures occur in men [1], and the mortality associated with fracture is considerably higher in men than in women [2]. Recently, the American College of Physicians recommended that physicians should assess risk factors for osteoporosis in older men and measure the bone mineral density (BMD) of men at increased risk for osteoporosis [3]. Thus, male osteoporosis has now been recognized as an important public health issue. Because of the long-term emphasis on osteoporosis in women, however, the cellular and molecular basis of male osteoporosis is still poorly understood [4]. Since osteoporosis is clinically silent until fracture occurs [5], men at risk of osteoporosis and those with the disease need to be identified.
Diagnosis of osteoporosis is based on assessment of BMD, which is influenced by both genetic and lifestyle factors (exercise, smoking, alcohol, etc.) [6]. Low BMD is an important risk factor for osteoporosis and has high heritability [7]. In recent years, genomewide association studies have emerged as a powerful tool for identifying genes related to many common human disorders and phenotypes. A recent multicenter collaborative genomewide association study on 314,075 single-nucleotide polymorphisms (SNPs) in 8,557 individuals showed that rs3736228 (A1330V) in the low-density lipoprotein receptor-related protein 5 (LRP5) gene on chromosome 11 was strongly associated with the BMD of women and men in Europe, since the expression of the risk allele decreased the BMD by 0.13 SD [8]. Other studies [9–16] have also suggested that LRP5 A1330V polymorphism is associated with BMD, and that individuals with the AV or VV genotype have lower BMD than those with the AA genotype. Better understanding of the relation between BMD and LRP5 A1330V polymorphism, as well as the influence of lifestyle factors, may allow us to identify a high-risk group for osteoporosis and lead to more effective prevention of this condition and improvement of public health. The purpose of the present cross-sectional study is to investigate the correlations among BMD, LRP5 A1330V polymorphism, and lifestyle factors (exercise, smoking, and alcohol intake) in Japanese male workers.
Methods
Subjects and methods
The subjects were 829 male employees aged 20–59 years (mean 37.8 ± 6.7 years) who worked at a large-scale integrated manufacturing facility in Japan (Table 1). The criteria for entry into this study were no previous diagnosis of osteoporosis, no systemic diseases, and no medications known to influence bone or calcium metabolism. Height, weight, BMD, urinary deoxypyridinoline (DPD), and serum bone alkaline phosphatase (BAP) were measured during a comprehensive health check. Body mass index (BMI) was calculated as weight in kilograms divided by height in meters squared. Lifestyle information, such as past history of exercise, current exercise, smoking status, and alcohol intake, was obtained with a self-reporting questionnaire [17]. Each lifestyle factor was divided into 2 categories as follows: past history of exercise (regular exercise until the age of 20 years): no versus yes; current exercise: ≤2 days/week versus ≥3 days/week; smoking status: no versus yes; and alcohol intake: no versus yes. The study protocol was approved by the ethics committee of Kumamoto University, and all subjects provided written informed consent.
Table 1.
Profile of the subjects (829 men)
| Age (years)a | 37.8 ± 6.7 |
| Height (cm)a | 169.9 ± 6.0 |
| Weight (kg)a | 67.8 ± 10.1 |
| BMI (kg/m2)a | 23.4 ± 3.1 |
| BMD (g/m2)a | 0.557 ± 0.059 |
| Bone metabolism markers | |
| DPD (nmol/mmol Cr)b | 3.5 (10.0) |
| BAP (U/L)b | 24.3 (80.7) |
| Lifestyle | |
| Past history of exercise (%) | |
| Yes | 80.0 |
| No | 20.0 |
| Current exercise (%) | |
| ≤2 days/week | 89.9 |
| ≥3 days/week | 10.1 |
| Smoking status (%) | |
| Yes | 58.1 |
| No | 41.9 |
| Alcohol intake (%) | |
| Yes | 68.1 |
| No | 31.9 |
Past history of exercise was determined from exercise habits until the age of 20 years
BMI body mass index, BMD bone mineral density, DPD deoxypyridinoline, BAP bone alkaline phosphatase
aValues are mean ± SD
bValues are median (interquartile range)
Bone metabolism markers
BAP levels were measured using an Alkaphase B kit (enzyme immunoassay; Metra Biosystems). Urinary DPD levels were determined using commercially available pyridinium cross-links with a high-performance liquid chromatography (HPLC) kit (enzyme immunoassay; Metra Biosystems, Mountain View, CA, USA). Urinary concentrations of creatinine were determined using a colorimetric assay performed with a creatinine test kit (Wako, Osaka, Japan). DPD excretion was expressed as a ratio of urinary creatinine concentration. DPD has been validated as a useful marker of bone resorption, while BAP is a marker of bone formation [18].
Measurement of bone mineral density
BMD was measured at the distal 1/3 site of the radius on the nondominant side by dual-energy X-ray absorptiometry (DXA, Osteometer DTX200) according to the manufacturer’s protocol [coefficient of variation (CV) for precision error <1.0% in vivo]. Quality control was carried out in accordance with the manufacturer’s instructions.
DNA extraction and genotyping
Genomic DNA was extracted from peripheral blood leukocytes using a DNA Extractor WB Kit (Wako Pure Chemical Industries, Osaka, Japan) according to the manufacturer’s instructions.
A real-time quantitative polymerase chain reaction assay was performed using a Step One Sequence Detector (Applied Biosystems). LRP5 A1330V (rs3736228) polymorphism was genotyped with a Custom TaqMan Genotyping Assay (Applied Biosystems) according to the manufacturer’s protocol.
Statistical analysis
Statistical analysis was performed with SPSS 18.0 software, and the results are presented as mean ± standard deviation (SD) or median (interquartile range) as appropriate. The chi-square test was employed to verify Hardy–Weinberg equilibrium of genotype frequencies. DPD and BAP values did not show a normal distribution in the Kolmogorov–Smirnov test. Pearson’s correlation analysis was used to examine the influence of age, height, weight, and BMI on BMD. Spearman’s rank correlation analysis was used to examine the influence of DPD and BAP levels on BMD. Analysis of variance (ANOVA) and the post hoc Tukey test were used to assess the differences in the mean values of age, height, weight, BMI, and BMD among subjects with different polymorphisms. Kruskal–Wallis test was used to examine the differences in DPD, BAP, past history of exercise, current exercise, smoking status, and alcohol intake among subjects with different polymorphisms. The stepwise method of multiple linear regression analysis was performed to detect variables with an independent influence on BMD. To examine multicollinearity of the regression model, we calculated the variance inflation factor. (A variance inflation factor exceeding 10 was defined as indicating that collinearity was problematic.) Age, BMI, LRP5 A1330V polymorphism, past history of exercise, current exercise, smoking status, and alcohol intake were selected among subjects with variance inflation factor <10, i.e., height and weight were excluded. Statistical significance was accepted at P < 0.05.
Results
Table 1 presents a profile of the subjects. Mean age was 37.8 ± 6.7 years, and mean BMD was 0.557 ± 0.059 g/cm2 (Table 1).
Correlations were analyzed to investigate factors with an influence on BMD. As a result, BMD was positively correlated with age (r = 0.08, P < 0.05), height (r = 0.10, P < 0.001), weight (r = 0.38, P < 0.001), and BMI (r = 0.38, P < 0.001), but was negatively correlated with DPD (r = −0.08, P < 0.05) and BAP (r = −0.14, P < 0.001) (Table 2).
Table 2.
Correlation between various parameters and bone mineral density among 829 men
| r | P | |
|---|---|---|
| Age (years)a | 0.08 | <0.05 |
| Height (cm)a | 0.10 | <0.001 |
| Weight (kg)a | 0.38 | <0.001 |
| BMI (kg/m2)a | 0.38 | <0.001 |
| DPD (nmol/mmol Cr)b | −0.08 | <0.05 |
| BAP (U/L)b | −0.14 | <0.001 |
BMI body mass index, DPD deoxypyridinoline, BAP bone alkaline phosphatase
aPearson correlation
bSpearman’s rank correlation
The characteristics of the subjects stratified according to LRP5 A1330V polymorphism are shown in Table 3. LRP5 A1330V polymorphism showed a distribution that followed Hardy–Weinberg equilibrium (P = 0.30). The allele frequency of LRP5 A1330V polymorphism (51% AA, 42% AV, and 7% VV) was similar to that reported previously in a Japanese population (46% AA, 45% AV, and 9% VV) [15]. ANOVA and post hoc Tukey test showed that mean BMD was significantly lower in subjects with VV genotype than in those with AA genotype. There were no significant differences in mean values of age, height, weight, and BMI and the median values of DPD and BAP among the three LRP5 A1330V genotypes. In addition, Kruskal–Wallis test indicated no intergroup differences in past history of exercise, current exercise, smoking status, and alcohol intake (Table 3). Table 4 shows the results obtained by multiple linear regression analysis that assessed various factors for an influence on BMD. As a result, age, BMI, LRP5 A1330V polymorphism, past history of exercise, current exercise, smoking status, and alcohol intake were selected among subjects with variance inflation factor <10, i.e., height and weight were excluded. The parameters showing an independent association with BMD were BMI (coefficient = 0.007, P = 0.000), past history of exercise (coefficient = 0.014, P = 0.005), LRP5 A1330V polymorphism (coefficient = −0.007, P = 0.018), and current exercise (coefficient = 0.014, P = 0.030). The variance inflation factors in this regression model were all <1.06, and the adjusted R2 value was 16% (Table 4).
Table 3.
Characteristics of subjects stratified according to low-density lipoprotein receptor related protein 5 (LRP5) A1330V polymorphism
| Valuable | AA (n = 424) | AV (n = 346) | VV (n = 59) | P |
|---|---|---|---|---|
| Age (years)a | 38.0 ± 6.9 | 37.6 ± 6.4 | 37.7 ± 7.3 | 0.76 |
| Height (cm)a | 169.8 ± 6.3 | 170.1 ± 5.7 | 169.8 ± 5.9 | 0.71 |
| Weight (kg)a | 68.0 ± 10.5 | 67.9 ± 9.8 | 65.0 ± 9.4 | 0.09 |
| BMI (kg/m2)a | 23.6 ± 3.2 | 23.5 ± 3.1 | 22.6 ± 3.1 | 0.07 |
| BMD (g/m2)a | 0.562 ± 0.062 | 0.555 ± 0.057 | 0.540 ± 0.048* | 0.02 |
| Bone metabolism markers | ||||
| DPD (nmol/mmol Cr)b | 3.6 (7.2) | 3.4 (10.0) | 3.4 (5.1) | 0.18 |
| BAP (U/L)b | 24.3 (80.7) | 24.4 (77.6) | 24.9 (35.3) | 0.64 |
| Lifestyle | ||||
| Past history of exercise (%) | ||||
| Yes | 80.6 | 79.5 | 79.7 | 0.93 |
| No | 19.4 | 20.5 | 20.3 | |
| Current exercise (%) | ||||
| ≤2 days/week | 89.8 | 89.8 | 91.4 | 0.93 |
| ≥3 days/week | 10.2 | 10.2 | 8.6 | |
| Smoking status (%) | ||||
| Yes | 57.9 | 56.7 | 67.8 | 0.28 |
| No | 42.1 | 43.3 | 32.2 | |
| Alcohol intake (%) | ||||
| Yes | 67.1 | 69.8 | 64.9 | 0.64 |
| No | 32.9 | 30.2 | 35.1 | |
Past history of exercise was determined from exercise habits until the age of 20 years
Data were analyzed by analysis of variance and post hoc Tukey test or Kruskal–Wallis test
Age, height, weight, BMI, and BMD were analyzed by analysis of variance and post hoc Tukey test
DPD, BAP, past history of exercise, current exercise, smoking status, and alcohol intake were analyzed by Kruskal–Wallis test
BMI body mass index, BMD bone mineral density, DPD deoxypyridinoline, BAP bone alkaline phosphatase
* P < 0.05 compared with AA genotype (post hoc Tukey test)
aValues are mean ± SD
bValues are median (interquartile range)
Table 4.
Multiple linear regression analysis on variables associated with bone mineral density among 829 men
| Coefficient | Standard error | t | P | |
|---|---|---|---|---|
| Age (years) | 0.000 | 0.000 | 1.0 | 0.337 |
| BMI (kg/m2) | 0.007 | 0.001 | 10.9 | 0.000 |
| LRP5 A1330V polymorphisma | −0.007 | 0.003 | −2.4 | 0.018 |
| Past history of exerciseb | 0.014 | 0.005 | 2.8 | 0.005 |
| Current exercisec | 0.014 | 0.006 | 2.2 | 0.030 |
| Smoking statusd | 0.006 | 0.004 | 1.5 | 0.143 |
| Alcohol intakee | 0.008 | 0.004 | 1.9 | 0.056 |
Multiple linear regression analysis, adjusted R2 = 0.16
Past history of exercise was determined from exercise habits until the age of 20 years
BMI body mass index, LRP5 low-density lipoprotein receptor related protein 5
aLRP5 A1330V polymorphism was rated as 0 (AA genotype), 1 (AVgenotype) or 2 (VV genotype)
bPast history of exercise was rated as 0 (no), or 1 (yes)
cCurrent exercise was rated as 0 (≤2 days/week) or 1 (≥3 days/week)
dSmoking status was rated as 0 (no) or 1 (yes)
eAlcohol intake was rated as 0 (no) or 1 (yes)
Discussion
In this study, we found that Japanese male workers with VV genotype had significantly lower BMD than those with AA genotype. In addition, we found that LRP5 A1330V polymorphism was an independent determinant of BMD of Japanese male workers after adjusting for age, BMI, and other lifestyle variables by multiple linear regression analysis. The significant association between LRP5 A1330V polymorphism and BMD detected in this study agrees with the results of previous studies performed in Japanese women [15], Caucasian men [12–14], and Caucasian women [16], which have indicated that allelic variation of LRP5 A1330V polymorphism contributes to regulation of BMD. However, none of the previous studies have evaluated Japanese male population. To our knowledge, this is the first report of an association between LRP5 A1330V polymorphism and BMD in Japanese men. LRP5 A1330V polymorphism is probably a useful genetic marker for predicting BMD in Japanese men.
LRP5 is a coreceptor in the canonical Wnt signaling pathway [19, 20], which is involved in differentiation of osteoblast precursors into mature osteoblasts, which in turn increases bone formation [21]. This Wnt signaling pathway also induces upregulation of osteoprotegerin (OPG) expression and downregulation of receptor activator of nuclear factor κB ligand (RANKL) expression in osteoblasts, resulting in inhibition of bone resorption [21]. A recent study demonstrated that the Wnt signaling pathway regulates BMD through LRP5 [20]. In addition, a previous study has provided extensive genetic and functional data indicating that the LRP5 gene and the Wnt signaling pathway have a substantial influence on bone formation and the risk of osteoporosis and that LRP5 signaling is essential for normal morphology, normal development, and bone health [22]. In vitro, a previous study investigated functional differences between LRP5 A1330 and V1330 in HEK293T cells with or without co-expression vectors for Wnt3a [23]. The results showed that Wnt3a-induced T-cell factor/lymphoid enhancer factor (Tcf-Lef) activity was significantly reduced in cells containing LRP5–V1330 compared with those containing the wild-type allele [LRP5–A1330 versus LRP5–V1330, 1.900 ± 0.064 versus 1.597 ± 0.101; mean ± standard error (SE)]. In the case of cells not treated with Wnt3a, Tcf-Lef activity of cells with LRP5–V1330 was not significantly changed compared with that of those with LRP5–A1330 (LRP5–A1330 versus LRP5–V1330, 1 ± 0.056 versus 0.975 ± 0.015; mean ± SE). In addition, the association between the LRP5 A1330V polymorphism and total-body BMD was replicated in 739 postmenopausal women (AA versus VV; P = 0.0026). Although the exact mechanism by which LRP5 A1330V polymorphism influences BMD is not fully understood, this polymorphism might have an effect on Wnt signaling [23]. Our result that LRP5 A1330V polymorphism is associated with BMD implies the need for further studies on the functions of LRP5 and the polymorphisms associated with bone metabolism.
In this study, exercise (past or current) was also a significant independent determinant of the BMD. Past history of exercise was assessed from exercise habits until the age of 20 years in this study. We categorized current exercise on the basis of frequency (≤2 days/week versus ≥3 days/week) because the American College of Sports Medicine has developed guidelines for exercise to improve bone health and their recommendation is exercise from 3 to 5 times per week [24]. There is some evidence that exercise has a beneficial effect on BMD [24, 25], and the most beneficial effect of exercise on BMD might be obtained during growth [24, 26]. We previously reported on the relation between lifestyle and BMD in some of the present subjects [19], and our results suggested that exercise influenced the BMD of male workers. After taking genetic factors into account, we found that exercise (past or current) had an independent influence on BMD, suggesting that exercise may be useful to protect against osteoporosis even in persons who have genetic susceptibility to a low BMD. A large-scale prospective study will be needed to define the relation between BMD and physical activity, as well as the influence of LRP5 A1330V polymorphism.
Alcohol intake was not an independent determinant of BMD after adjustment for age, BMI, LRP5 A1330V polymorphism, past history of exercise, current exercise, and smoking. The effect of alcohol on BMD remains unclear [6]. A dose-dependent effect of alcohol on bone metabolism has also been reported [27]. A recent meta-analysis revealed that persons consuming more than half to one drink per day had a lower risk of hip fracture than abstainers, and persons consuming more than two drinks per day had a higher risk [28]. However, the precise mechanism by which moderate intake of alcohol alters bone metabolism is still unknown. We did not assess the alcohol consumption of drinkers in the present study. The amount and frequency of alcohol consumption may be important factors determining the influence of alcohol on BMD.
Smoking was also not an independent determinant of BMD after adjustment for age, BMI, LRP5 A1330V polymorphism, past history of exercise, current exercise, and alcohol intake. Some previous studies have shown negative correlation between history of smoking and BMD in elderly men [29, 30]. However, we could not find a relationship between smoking and bone loss in our study. This discrepancy could have occurred because the duration of smoking in our younger subjects was shorter than that of the subjects in other studies. Clearly, further prospective studies will be required to define the relationship between bone loss and smoking.
In this study, BMD was negatively correlated with DPD and BAP, which are bone metabolism markers. Rogers et al. investigated the value of measurements of biochemical markers for the prediction of bone loss rates in 60 postmenopausal Caucasian women aged 49–62 years. Rogers found a significant negative correlation (Spearman rank correlation) between the measured biochemical markers and the rate of change in BMD (BAP: r = −0.43, P = 0.0009; DPD: r = −0.35, P = 0.0076) [31]. In addition, a previous study in Japanese women aged 45 years or older with elevated levels of serum osteocalcin (OC), bone-specific alkaline phosphatase (bone ALP), type I collagen crosslinked C-terminal telopeptide (CTX), or free and total (tDPD) forms of immunoreactive deoxypyridinoline showed that bone loss during the follow-up period in these women was significantly greater than that in women with lower levels of these markers [32]. However, these previous studies targeted women. Only one previous study [33] has examined the association between bone metabolism markers and BMD in Japanese men. Yoshikawa investigated age-related changes of BMD in 443 Japanese adult males (mean baseline age 54.3 ± 10.4 years; mean follow-up 4.8 years) in association with bone metabolic markers [33]. They found that the annual percentage change of BMD was 0.405 ± 1.56% at the lumbar spine and −0.249 ± 1.12% at the femoral neck, and that these changes were correlated with DPD (r = −0.323 and −0.439, respectively) [32]. Bone strength reflects the influence of two main factors: BMD and bone quality [34]. Bone quality depends on bone architecture, mineralization, turnover, and accumulation of microfractures, while biochemical markers of bone turnover are considered to reflect the extent of bone formation or bone resorption [35]. When high levels of DPD and BAP are detected, metastatic bone tumor, metabolic bone disease, or abnormal calcium metabolism can be suspected, but these parameters were not significantly associated with LRP5 A1330V polymorphism in the present study. Because the examined bone metabolism markers are useful indicators for changes in BMD in relatively short period, the absence of correlation between these markers and LRP5 polymorphism would indicate that the correlation between BMD and this polymorphism may be established at younger age. Further studies about the association between bone metabolism markers and BMD, as well as the influence of LRP5 A1330V polymorphism, are required.
In conclusion, LRP5 A1330V polymorphism and exercise may influence BMD in Japanese male workers. These findings suggest that investigation of LRP5 A1330V polymorphism may be useful for identifying individuals who are susceptible to osteoporosis, while exercise may be useful for protecting Japanese male workers from osteoporosis even if they have genetic susceptibility to low BMD.
Conflicts of interest
None.
References
- 1.Cooper C, Campion G, Melton LJ., 3rd Hip fractures in the elderly: a world-wide projection. Osteoporos Int. 1992;2:285–289. doi: 10.1007/BF01623184. [DOI] [PubMed] [Google Scholar]
- 2.Center JR, Nguyen TV, Schneider D, Sambrook PN, Eisman JA. Mortality after all major types of osteoporotic fracture in men and women: an observational study. Lancet. 1999;353:878–882. doi: 10.1016/S0140-6736(98)09075-8. [DOI] [PubMed] [Google Scholar]
- 3.Qaseem A, Snow V, Shekelle P, Hopkins R, Jr, Forciea MA, Owens DK. Clinical Efficacy Assessment Subcommittee of the American College of Physicians: screening for osteoporosis in men: a clinical practice guideline from the American College of Physicians. Ann Intern. 2008;1489:680–684. doi: 10.7326/0003-4819-148-9-200805060-00008. [DOI] [PubMed] [Google Scholar]
- 4.Byers RJ, Hoyland JA, Braidman IP. Osteoporosis in men: a cellular endocrine perspective of an increasingly common clinical problem. J Endocrinol. 2001;168:353–362. doi: 10.1677/joe.0.1680353. [DOI] [PubMed] [Google Scholar]
- 5.Lewiecki EM. Management of osteoporosis. Clin Mol Allergy. 2004;2:9. doi: 10.1186/1476-7961-2-9. [DOI] [PMC free article] [PubMed] [Google Scholar]
- 6.Krall EA, Dawson-Hughes B. Heritable and life-style determinants of bone mineral density. J Bone Miner Res. 1993;81:1–9. doi: 10.1002/jbmr.5650080102. [DOI] [PubMed] [Google Scholar]
- 7.Nguyen TV, Blangero J, Eisman JA. Genetic epidemiological approaches to the search for osteoporosis genes. J Bone Miner Res. 2000;15:392–401. doi: 10.1359/jbmr.2000.15.3.392. [DOI] [PubMed] [Google Scholar]
- 8.Richards JB, Rivadeneira F, Inouye M, Pastinen TM, Soranzo N, Wilson SG, et al. Bone mineral density, osteoporosis, and osteoporotic fractures: a genome-wide association study. Lancet. 2008;371:1505–1512. doi: 10.1016/S0140-6736(08)60599-1. [DOI] [PMC free article] [PubMed] [Google Scholar]
- 9.Meurs JB, Trikalinos TA, Ralston SH, Balcells S, Brandi ML, Brixen K, et al. GENOMOS Study. Large-scale analysis of association between LRP5 and LRP6 variants and osteoporosis. JAMA. 2008;299:1277–1290. doi: 10.1001/jama.299.11.1277. [DOI] [PMC free article] [PubMed] [Google Scholar]
- 10.Lee YH, Woo JH, Choi SJ, Ji JD, Song GG. Association between the A1330V polymorphism of the low-density lipoprotein receptor-related protein 5 gene and bone mineral density: a meta-analysis. Rheumatol Int. 2009;29:539–544. doi: 10.1007/s00296-008-0745-y. [DOI] [PubMed] [Google Scholar]
- 11.Tran BN, Nguyen ND, Eisman JA, Nguyen TV. Association between LRP5 polymorphism and bone mineral density: a Bayesian meta-analysis. BMC Med Genet. 2008;9:55. doi: 10.1186/1471-2350-9-55. [DOI] [PMC free article] [PubMed] [Google Scholar]
- 12.Saarinen A, Välimäki VV, Välimäki MJ, Löyttyniemi E, Auro K, Uusen P, et al. The A1330V polymorphism of the low-density lipoprotein receptor-related protein 5 gene (LRP5) associates with low peak bone mass in young healthy men. Bone. 2007;40:1006–1012. doi: 10.1016/j.bone.2006.11.010. [DOI] [PubMed] [Google Scholar]
- 13.Brixen K, Beckers S, Peeters A, Piters E, Balemans W, Nielsen TL, et al. 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. Calcif Tissue Int. 2007;81:421–429. doi: 10.1007/s00223-007-9088-z. [DOI] [PMC free article] [PubMed] [Google Scholar]
- 14.Meurs JB, Rivadeneira F, Jhamai M, Hugens W, Hofman A, Leeuwen JP, et al. Common genetic variation of the low-density lipoprotein receptor-related protein 5 and 6 genes determines fracture risk in elderly white men. J Bone Miner Res. 2006;21:141–150. doi: 10.1359/JBMR.050904. [DOI] [PubMed] [Google Scholar]
- 15.Ezura Y, Nakajima T, Urano T, Sudo Y, Kajita M, Yoshida H, et al. 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. Bone. 2007;40:997–1005. doi: 10.1016/j.bone.2005.06.025. [DOI] [PubMed] [Google Scholar]
- 16.Giroux S, Elfassihi L, Cardinal G, Laflamme N, Rousseau F. LRP5 coding polymorphisms influence the variation of peak bone mass in a normal population of French-Canadian women. Bone. 2007;40:1299–1307. doi: 10.1016/j.bone.2007.01.004. [DOI] [PubMed] [Google Scholar]
- 17.Funakoshi Y, Omori H, Katoh T. Association between bone mineral density and lifestyle factors or vitamin D receptor gene polymorphism in adult male workers: a cross-sectional study. Environ Health Prev Med. 2009;14:328–335. doi: 10.1007/s12199-009-0104-y. [DOI] [PMC free article] [PubMed] [Google Scholar]
- 18.Nishizawa Y, Nakamura T, Ohta H, Kushida K, Gorai I, Shiraki M, et al. Committee on the Guidelines for the Use of Biochemical Markers of Bone Turnover in Osteoporosis Japan Osteoporosis Society. Guidelines for the use of biochemical markers of bone turnover in osteoporosis (2004) J Bone Miner Metab. 2005;23:97–104. doi: 10.1007/s00774-004-0547-6. [DOI] [PubMed] [Google Scholar]
- 19.Mao J, Wang J, Liu B, Pan W, Farr GH, 3rd, Flynn C, et al. Low-density lipoprotein receptor-related protein-5 binds to Axin and regulates the canonical Wnt signaling pathway. Mol Cell. 2001;7:801–809. doi: 10.1016/S1097-2765(01)00224-6. [DOI] [PubMed] [Google Scholar]
- 20.Gong Y, Slee RB, Fukai N, Rawadi G, Roman-Roman S, Reginato AM, et al. Osteoporosis-Pseudoglioma Syndrome Collaborative Group. LDL receptor-related protein (LRP5) affects bone accrual and eye development. Cell. 2001;107:513–523. doi: 10.1016/S0092-8674(01)00571-2. [DOI] [PubMed] [Google Scholar]
- 21.Kobayashi Y, Maeda K, Takahashi N. Roles of Wnt signaling in bone formation and resorption. Jpn Dent Sci Rev. 2008;44:76–82. doi: 10.1016/j.jdsr.2007.11.002. [DOI] [Google Scholar]
- 22.Koay MA, Brown MA. Genetic disorders of the LRP5-Wnt signalling pathway affecting the skeleton. Trends Mol Med. 2005;11:129–137. doi: 10.1016/j.molmed.2005.01.004. [DOI] [PubMed] [Google Scholar]
- 23.Urano T, Shiraki M, Usui T, Sasaki N, Ouchi Y, Inoue S. A1330V variant of the low-density lipoprotein receptor-related protein 5 (LRP5) gene decreases Wnt signaling and affects the total body bone mineral density in Japanese women. Endocr J. 2009;56:625–631. doi: 10.1507/endocrj.K09E-133. [DOI] [PubMed] [Google Scholar]
- 24.Kohrt WM, Bloomfield SA, Little KD, Nelson ME, Yingling VR. American College of Sports Medicine. American College of Sports Medicine Position Stand: physical activity and bone health. Med Sci Sports Exerc. 2004;36:1985–1996. doi: 10.1249/01.MSS.0000142662.21767.58. [DOI] [PubMed] [Google Scholar]
- 25.Kelley GA, Kelley KS, Tran ZV. Exercise and bone mineral density in men: a meta-analysis. J Appl Physiol. 2000;88:1730–1736. doi: 10.1152/jappl.2000.88.5.1730. [DOI] [PubMed] [Google Scholar]
- 26.Karlsson MK. Physical activity, skeletal health and fractures in a long term perspective. J Musculoskelet Neuronal Interact. 2004;4:12–21. [PubMed] [Google Scholar]
- 27.Friday KE, Howard GA. Ethanol inhibits human bone cell proliferation and function in vitro. Metabolism. 1991;40:562–565. doi: 10.1016/0026-0495(91)90044-W. [DOI] [PubMed] [Google Scholar]
- 28.Berg KM, Kunins HV, Jackson JL, Nahvi S, Chaudhry A, Harris KA, et al. Association between alcohol consumption and both osteoporotic fracture and bone density. Am J Med. 2008;121:406–418. doi: 10.1016/j.amjmed.2007.12.012. [DOI] [PMC free article] [PubMed] [Google Scholar]
- 29.Tamaki J, Iki M, Fujita Y, Kouda K, Yura A, Kadowaki E, et al. Impact of smoking on bone mineral density and bone metabolism in elderly men: the Fujiwara-kyo Osteoporosis Risk in Men (FORMEN) study. Osteoporosis Int. 2010. [Epub ahead of print]. [DOI] [PubMed]
- 30.Hannan MT, Felson DT, Dawson-Hughes B, Tucker KL, Cupples LA, Wilson PW, et al. Risk factors for longitudinal bone loss in elderly men and women: the Framingham Osteoporosis Study. J Bone Miner Res. 2000;15:710–720. doi: 10.1359/jbmr.2000.15.4.710. [DOI] [PubMed] [Google Scholar]
- 31.Rogers A, Hannon RA, Eastell R. Biochimical markers as predictors of rates of bone loss after menopausa. J Bone Miner Res. 2000;15:1398–1404. doi: 10.1359/jbmr.2000.15.7.1398. [DOI] [PubMed] [Google Scholar]
- 32.Iki M, Morita A, Ikeda Y, Sato Y, Akiba T, Matsumoto T, et al. JPOS Study Group. Biochemical markers of bone turnover predict bone loss in perimenopausal women but not in postmenopausal women-the Japanese Population-based Osteoporosis (JPOS) Cohort Study. Osteoporos Int. 2006;17:1086–95. [DOI] [PubMed]
- 33.Yoshikawa T. Age-related changes in bone mineral density in Japanese adult males: association with bone metabolic markers. Kawasakii Med J. 2007;33:35–42. [Google Scholar]
- 34.NIH Consensus Development Panel on Osteoporosis Prevention, Diagnosis, and Therapy. Osteoporosis prevention, diagnosis, and therapy. JAMA. 2001;285:785–95. [DOI] [PubMed]
- 35.Chesnut CH, 3rd, Rosen CJ. Bone Quality Discussion Group. Reconsidering the effects of antiresortive therapies in reducing osteoporotic fracture. J Bone Miner Res. 2001;16:2163–2172. doi: 10.1359/jbmr.2001.16.12.2163. [DOI] [PubMed] [Google Scholar]