Association of the methylenetetrahydrofolate reductase C677T polymorphism and fracture risk in Chinese postmenopausal women

Fracture risk prediction in old Chinese people-a narrative review

With aging, the burden of osteoporotic fracture (OF) increases substantially, while China is expected to carry the greatest part in the future. The risk of fracture varies greatly across racial groups and geographic regions, and systematically organized evidence on the potential predictors for fracture risk is needed for Chinese. This review briefly introduces the epidemiology of OF and expands on the predictors and predictive tools for the risk of OF, as well as the challenges for their potential translation in the old Chinese population. There are regional differences of fracture incidence among China. The fracture incidences in Hong Kong and Taiwan have decreased in recent years, while it is still increasing in mainland China. Although the application of dual-energy X-ray absorptiometry (DXA) is limited among old Chinese in the mainland, bone mineral density (BMD) by DXA has a predictive value similar to that worldwide. Other non-DXA modalities, especially heel QUS, are helpful in assessing bone health. The fracture risk assessment tool (FRAX) has a good discrimination ability for OFs, especially the FRAX with BMD. And some clinical factors have added value to FRAX, which has been verified in old Chinese. In addition, although the application of the osteoporosis self-assessment tool for Asians (OSTA) in Chinese needs further validation, it may help identify high-risk populations in areas with limited resources. Moreover, the translation use of the muscle quality and genetic or serum biomarkers in fracture prediction needs further works. More applicable and targeted fracture risk predictors and tools are still needed for the old Chinese population.

Genetic variants modify the associations of concentrations of methylmalonic acid, vitamin B-12, vitamin B-6, and folate with bone mineral density

BACKGROUND

Elevated plasma homocysteine has been found to be associated with an increased risk of osteoporosis, especially hip and vertebral fractures. The plasma concentration of homocysteine is dependent on the activities of several B vitamin-dependent enzymes, such as methylenetetrahydrofolate reductase (MTHFR), methionine synthase (MTR), methionine synthase reductase (MTRR), and cystathionine β-synthase (CBS).

OBJECTIVES

We investigated whether genetic variants in some of the genes involved in 1 carbon metabolism modify the association of B vitamin-related measures with bone mineral density (BMD) and strength.

METHODS

We measured several B vitamins and biomarkers in participants of the Framingham Offspring Study, and performed analyses of methylmalonic acid (MMA) continuously and <210 nmol/L; pyridoxal-5'-phosphate; vitamin B-12 continuously and ≥258 pmol/L; and folate. The outcomes of interest included areal and volumetric BMD, measured by DXA and quantitative computed tomography (QCT), respectively. We evaluated associations between the bone measures and interactions of single nucleotide polymorphism with a B vitamin or biomarker in Framingham participants (n = 4310 for DXA and n = 3127 for QCT). For analysis of DXA, we validated the association results in the B-PROOF cohort (n = 1072). Bonferroni-corrected locus-wide significant thresholds were defined to account for multiple testing.

RESULTS

The interactions between rs2274976 and vitamin B-12 and rs34671784 and MMA <210 nmol/L were associated with lumbar spine BMD, and the interaction between rs6586281 and vitamin B-12 ≥258 pmol/L was associated with femoral neck BMD. For QCT-derived traits, 62 interactions between genetic variants and B vitamins and biomarkers were identified.

CONCLUSIONS

Some genetic variants in the 1-carbon methylation pathway modify the association of B vitamin and biomarker concentrations with bone density and strength.  These interactions require further replication and functional validation for a mechanistic understanding of the role of the 1-carbon metabolism pathway on BMD and risks of fracture.

Perturbations of Lipids and Oxidized Phospholipids in Lipoproteins of Patients with Postmenopausal Osteoporosis Evaluated by Asymmetrical Flow Field-Flow Fractionation and Nanoflow UHPLC-ESI-MS/MS

Osteoporosis, a degenerative bone disease characterized by reduced bone mass and high risk of fragility, is associated with the alteration of circulating lipids, especially oxidized phospholipids (Ox-PLs). This study evaluated the lipidomic changes in lipoproteins of patients with postmenopausal osteoporosis (PMOp) vs. postmenopausal healthy controls. High-density lipoproteins (HDL) and low-density lipoproteins (LDL) from plasma samples were size-sorted by asymmetrical flow field-flow fractionation (AF4). Lipids from each lipoprotein were analyzed by nanoflow ultrahigh performance liquid chromatography-electrospray ionization-tandem mass spectrometry (nUHPLC-ESI-MS/MS). A significant difference was observed in a subset of lipids, most of which were increased in patients with PMOp, when compared to control. Phosphatidylethanolamine plasmalogen, which plays an antioxidative role, was increased in both lipoproteins (P-16:0/20:4, P-18:0/20:4, and P-18:1/20:4) lysophosphatidic acid 16:0, and six phosphatidylcholines were largely increased in HDL, but triacylglycerols (50:4 and 54:6) and overall ceramide levels were significantly increased only in LDL of patients with PMOp. Further investigation of 33 Ox-PLs showed significant lipid oxidation in PLs with highly unsaturated acyl chains, which were decreased in LDL of patients with PMOp. The present study demonstrated that AF4 with nUHPLC-ESI-MS/MS can be utilized to systematically profile Ox-PLs in the LDL of patients with PMOp.

Causes, Consequences and Public Health Implications of Low B-Vitamin Status in Ageing

The potential protective roles of folate and the metabolically related B-vitamins (vitamins B12, B6 and riboflavin) in diseases of ageing are of increasing research interest. The most common cause of folate and riboflavin deficiencies in older people is low dietary intake, whereas low B12 status is primarily associated with food-bound malabsorption, while sub-optimal vitamin B6 status is attributed to increased requirements in ageing. Observational evidence links low status of folate and the related B-vitamins (and/or elevated concentrations of homocysteine) with a higher risk of degenerative diseases including cardiovascular disease (CVD), cognitive dysfunction and osteoporosis. Deficient or low status of these B-vitamins alone or in combination with genetic polymorphisms, including the common MTHFR 677 C → T polymorphism, could contribute to greater disease risk in ageing by causing perturbations in one carbon metabolism. Moreover, interventions with the relevant B-vitamins to optimise status may have beneficial effects in preventing degenerative diseases. The precise mechanisms are unknown but many have been proposed involving the role of folate and the related B-vitamins as co-factors for one-carbon transfer reactions, which are fundamental for DNA and RNA biosynthesis and the maintenance of methylation reactions. This review will examine the evidence linking folate and related B-vitamins with health and disease in ageing, associated mechanisms and public health implications.

Association between the methylenetetrahydrofolate reductase c.677C>T polymorphism and bone mineral density: an updated meta-analysis

Many studies have reported an association between the methylenetetrahydrofolate reductase (MTHFR) c.677C>T polymorphism and reduced bone mineral density (BMD), but results have been inconsistent. We, therefore, performed a meta-analysis to further explore this association. Twenty-one studies, comprising 33,045 subjects, analyzed the association of MTHFR c.677C>T with femoral neck BMD. Significant association with reduced BMD was observed in Caucasians (recessive model: WMD = -0.004 g/cm(2), 95 % CI -0.008 to -0.006), post-menopausal women (recessive model: WMD = -0.005 g/cm(2), 95 % CI -0.007 to -0.003), men (dominant model: WMD = -0.004 g/cm(2), 95 % CI -0.005 to -0.004; recessive model: WMD = -0.004 g/cm(2), 95 % CI -0.005 to -0.004; TT vs. CC: WMD = -0.006 g/cm(2), 95 % CI -0.006 to -0.006; CT vs. CC: WMD = -0.003 g/cm(2), 95 % CI -0.003 to -0.003), and cohort studies (recessive model: WMD = -0.003 g/cm(2), 95 % CI -0.006 to -0.001). Twenty-two studies, which included 32,271 subjects, analyzed the MTHFR c.677C>T association with lumbar spine BMD. Significant association with reduced BMD was observed in Caucasians, women, post-menopausal women, men, and cohort studies. Seven studies, comprising 6806 subjects, analyzed the MTHFR c.677C>T association with total hip BMD, but no significant association was observed in any population. Nine studies involving 5591 subjects analyzed the association with total body BMD. Significant association with reduced BMD was observed in overall and women subgroup analyses. In summary, this meta-analysis indicates that the MTHFR c.677C>T polymorphism is associated with reduced BMD in lumbar spine and femoral neck in Caucasians, post-menopausal women, and men, and with total body BMD in women. In addition, our results suggest that new studies examining the association between MTHFR c.677C>T polymorphism and BMD of lumbar spine and femoral neck in Asians is warranted, because I (2) > 75.0 % was observed.

B vitamins, homocysteine and bone health

Nutrition is one of the most important modifiable factors involved in the development and maintenance of good bone health. Calcium and Vitamin D have confirmed and established roles in the maintenance of proper bone health. However, other nutritional factors could also be implicated. This review will explore the emerging evidence of the supporting role of certain B Vitamins as modifiable factors associated with bone health. Individuals with high levels of homocysteine (hcy) exhibit reduced bone mineral density (BMD), alteration in microarchitecture and increased bone fragility. The pathophysiology caused by high serum homocysteine is not completely clear regarding fractures, but it may involve factors, such as bone mineral density, bone turnover, bone blood flow and collagen cross-linking. It is uncertain whether supplementation with B Vitamins, such as folate, Vitamin B1, and Vitamin B6, could decrease hip fracture incidence, but the results of further clinical trials should be awaited before a conclusion is drawn.

Association of blood lead levels with methylenetetrahydrofolate reductase polymorphisms among Chinese pregnant women in Wuhan city

BACKGROUND

Pregnancy is an important stimulus of bone lead release. Elevated blood lead levels (BLLs) may cause adverse pregnancy outcomes for mothers and harmful lead effects on fetuses. However, the reports about maternal BLL changes during pregnancy are conflicting to some extent. This article is to explore the variations in BLLs among pregnant women. The relationships of BLLs with methylenetetrahydrofolate reductase (MTHFR) gene C677T, A1298C, and G1793A polymorphisms, which are associated with bone resorption, were also studied. A total of 973 women, including 234, 249, and 248 women in their first, second, and third trimesters, respectively, and 242 non-pregnant women, were recruited at the Wuhan Women and Children Medical Health Center.

METHODS

BLLs were determined using a graphite furnace atomic absorption spectrometer. Single-nucleotide polymorphisms of MTHFR were identified with the TaqMan probe method.

RESULTS

The geometric mean (geometric standard deviation) of BLLs was 16.2 (1.78) μg/L for all participants. All the studied MTHFR alleles were in Hardy-Weinberg equilibrium. Multiple-linear regression analysis revealed the following results. Among the pregnant women, those that carried MTHFR 677CC (i.e. wild-genotype homozygote) and 1298CC (i.e. mutant-genotype homozygote) exhibited higher BLLs than those that carried 677CT/TT (standardized β = 0.074, P = 0.042) and 1298AC/AA (standardized β = 0.077, P = 0.035) when other covariates (e.g., age, no. of children, education and income, etc.) were adjusted. The BLLs of pregnant women consistently decreased during the pregnancy and these levels positively correlated with BMI (standard β = 0.086-0.096, P<0.05).

CONCLUSIONS

The 1298CC mutant-type homozygote in the MTHFR gene is a risk factor for high BLLs among low-level environmental lead-exposed Chinese pregnant women, whose BLLs consistently decreased during gestation.

Homocysteine, an additional factor, is linked to osteoporosis in postmenopausal women with type 2 diabetes

We explored the relationship between plasma total homocysteine concentration and osteoporosis in postmenopausal patients with type 2 diabetes. Postmenopausal patients with type 2 diabetes (n = 258) were enrolled in a cross-sectional hospital-based study. Osteoporosis was documented by dual energy X-ray absorptiometry. Plasma total homocysteine concentration was measured using fluorescence polarization immunoassay. Risk factors for osteoporosis and determinants of homocysteine were obtained from blood samples and interviewer questionnaire. We found that plasma total homocysteine levels were higher in subjects with osteoporosis and diabetes than without [(9.5 ± 2.0) vs. (10.4 ± 2.4) μmol/l, p = 0.001]. The association of homocysteine with osteoporosis was independent of possible risk factors for osteoporosis in diabetes (e.g., duration of diabetes, HbA1c, body mass index, serum 25-hydroxyvitamin D, thiazolidinediones, and retinopathy) and determinants of homocysteine concentration (age, serum folate and vitamin B12, renal status, and biguanide use) [OR 1.40 (1.02-1.90), p = 0.036]. In addition, bone mineral density was closely correlated with homocysteine as a continuous variable after adjusting for age [r = -0.64 (-0.69 to -0.58), p = 0.002]. Furthermore, per increase of 5.0 μmol/l, plasma homocysteine was related to osteoporosis, after controlling for per unit increase of other factors [OR 1.42 (1.07-1.96), p = 0.027]. The optimal cut-off point for the plasma homocysteine level distinguishing diabetic patients with osteoporosis from without was 10.18 μmol/l. The results suggest that plasma total homocysteine concentration is independently associated with the occurrence of osteoporosis in postmenopausal patients with type 2 diabetes. Future prospective studies are warranted to clarify the relationship.

Association between vitamin D receptor gene polymorphisms (Fok1 and Bsm1) and osteoporosis: a systematic review

Osteoporosis is a health concern characterized by reduced bone mineral density (BMD) and increased risk of fragility fractures. Many studies have investigated the association between genetic variants and osteoporosis. Polymorphism and allelic variations in the vitamin D receptor gene (VDR) have been found to be associated with bone mineral density. However, many studies have not been able to find this association. Literature review was conducted in several databases, including MEDLINE/Pubmed, Scopus, EMBASE, Ebsco, Science Citation Index Expanded, Ovid, Google Scholar, Iran Medex, Magiran and Scientific Information Database (SID) for papers published between 2000 and 2013 describing the association between Fok1 and Bsm1 polymorphisms of the VDR gene and osteoporosis risk. The majority of the revealed papers were conducted on postmenopausal women. Also, more than 50% studies reported significant relation between Fok1, Bsm1 and osteoporosis. Larger and more rigorous analytical studies with consideration of gene-gene and gene-environment interactions are needed to further dissect the mechanisms by which VDR polymorphisms influence osteoporosis.

Pregnancy-associated osteoporosis with a heterozygous deactivating LDL receptor-related protein 5 (LRP5) mutation and a homozygous methylenetetrahydrofolate reductase (MTHFR) polymorphism

Pregnancy-associated osteoporosis (PAO) is a rare, idiopathic disorder that usually presents with vertebral compression fractures (VCFs) within 6 months of a first pregnancy and delivery. Spontaneous improvement is typical. There is no known genetic basis for PAO. A 26-year-old primagravida with a neonatal history of unilateral blindness attributable to hyperplastic primary vitreous sustained postpartum VCFs consistent with PAO. Her low bone mineral density (BMD) seemed to respond to vitamin D and calcium therapy, with no fractures after her next successful pregnancy. Investigation of subsequent fetal losses revealed homozygosity for the methylenetetrahydrofolate reductase (MTHFR) C677T polymorphism associated both with fetal loss and with osteoporosis (OP). Because her neonatal unilateral blindness and OP were suggestive of loss-of-function mutation(s) in the gene that encodes LDL receptor-related protein 5 (LRP5), LRP5 exon and splice site sequencing was also performed. This revealed a unique heterozygous 12-bp deletion in exon 21 (c.4454_4465del, p.1485_1488del SSSS) in the patient, her mother and sons, but not her father or brother. Her mother had a normal BMD, no history of fractures, PAO, ophthalmopathy, or fetal loss. Her two sons had no ophthalmopathy and no skeletal issues. Her osteoporotic father (with a family history of blindness) and brother had low BMDs first documented at ages ∼40 and 32 years, respectively. Serum biochemical and bone turnover studies were unremarkable in all subjects. We postulate that our patient's heterozygous LRP5 mutation together with her homozygous MTHFR polymorphism likely predisposed her to low peak BMD. However, OP did not cosegregate in her family with the LRP5 mutation, the homozygous MTHFR polymorphism, or even the combination of the two, implicating additional genetic or nongenetic factors in her PAO. Nevertheless, exploration for potential genetic contributions to PAO may explain part of the pathogenesis of this enigmatic disorder and identify some at-risk women.

Fracture is additionally attributed to hyperhomocysteinemia in men and premenopausal women with type 2 diabetes

AIMS/INTRODUCTION

Data on hyperhomocysteinemia in relation to fractures in diabetes are limited. We aimed to explore the relationship between plasma total homocysteine concentrations and fractures in men and premenopausal women with type 2 diabetes.

MATERIALS AND METHODS

Diabetic and control participants (n = 292) were enrolled in a cross-sectional hospital-based study. Bone mineral density and fractures were documented by dual energy X-ray absorptiometry and X-ray film, respectively. Plasma total homocysteine concentrations were measured using fluorescence polarization immunoassay. Risk factors for low bone mineral density or fractures and determinants of homocysteine were obtained from blood samples and the interviewer questionnaire.

RESULTS

Plasma total homocysteine levels were higher in diabetic participants with fractures than without (8.6 [2.1] μmol/L vs 10.3 [3.0] μmol/L, P = 0.000). Diabetic participants with fractures had similar bone mineral densities as control participants. The association of homocysteine with the fracture was independent of possible risk factors for fractures (e.g., age, duration of diabetes, glycated hemoglobin, body mass index, thiazolidenediones and retinopathy) and determinants of homocysteine concentration (e.g., age, sex, serum folate and vitamin B12, renal status and biguanide use; odds ratio 1.41, 95% confidence interval 1.05-2.03, P = 0.020). Furthermore, per increase of 5.0 μmol/L plasma homocysteine was related to the fracture, after controlling for per unit increase of other factors (odds ratio 1.42, 95% confidence interval 1.12-1.78, P = 0.013).

CONCLUSIONS

Plasma total homocysteine concentration is independently associated with occurrence of fractures in men and premenopausal women with type 2 diabetes. Future prospective studies are warranted to clarify the relationship.

B-vitamins and bone in health and disease: the current evidence

Osteoporosis, a metabolic skeletal disease characterised by decreased bone mass and increased fracture risk, is a growing public health problem. Among the various risk factors for osteoporosis, calcium and vitamin D have well-established protective roles, but it is likely that other nutritional factors are also implicated. This review will explore the emerging evidence supporting a role for certain B-vitamins, homocysteine and the 677 C → T polymorphism in the gene encoding the folate-metabolising enzyme methylenetetrahydrofolate reductase, in bone health and disease. The evidence, however, is not entirely consistent and as yet no clear mechanism has been defined to explain the potential link between B-vitamins and bone health. Coeliac disease, a common condition of malabsorption, induced by gluten ingestion in genetically susceptible individuals, is associated with an increased risk both of osteoporosis and inadequate B-vitamin status. Given the growing body of evidence linking low bone mineral density and/or increased fracture risk with low B-vitamin status and elevated homocysteine, optimal B-vitamin status may play an important protective role against osteoporosis in coeliac disease; to date, no trial has addressed this possible link.

Association between seven common OPG genetic polymorphisms and osteoporosis risk: a meta-analysis

Functional polymorphisms of the osteoprotegerin (OPG) gene are known to be involved in bone mineral density and the development of osteoporosis; however, some conflicting results have been reported. The aim of this meta-analysis is to provide a relatively comprehensive assessment of the relationship between seven common OPG genetic polymorphisms (T149C, A163G, G209A, T245G, T950C, G1181C, and C1217T) and osteoporosis risk. A literature search for eligible studies published before August 1st, 2013 was conducted in PubMed, Embase, Web of Science, Cochrane Library, and CNKI (China National Knowledge Infrastructure) databases. Pooled odds ratios and their corresponding 95% confidence intervals were used to evaluate the strength of the association under fixed- or random-effect models according to a heterogeneity test. All analyses were performed using the STATA software, version 12.0. Fourteen case-control studies with a total of 2383 osteoporosis cases and 2280 healthy controls were included in this meta-analysis. Among the seven polymorphisms, A163G and G1181C revealed significant associations with osteoporosis risk. For A163G (rs3102735), the combined results showed that the G allele of the A163G polymorphism may be associated with an increased risk of osteoporosis. Stratified analyses showed that the magnitude of the effect was similar in Caucasian and postmenopausal woman subgroups. For G1181C (rs2073618), however, we found that individuals with the C allele of the G1181C polymorphism had a decreased risk of osteoporosis, especially in Asian and postmenopausal woman subgroups. In summary, this meta-analysis indicated that the G allele of the OPG A163G polymorphism might increase osteoporosis risk in Caucasians, whereas individuals with the C allele of the G1181C polymorphism had a decreased risk of osteoporosis, especially in Asians. Both of these effects were observed in postmenopausal women. These polymorphisms could probably be used with other genetic markers together to identify individuals at a high risk of osteoporosis.

Association of homocysteine, vitamin B12, and folate with bone mineral density in postmenopausal women: a meta-analysis

BACKGROUND

The relationship of homocysteine (Hcy), folate, and vitamin B12 with bone mineral density (BMD) has been investigated in postmenopausal women. However, the relationship is still controversial.

PURPOSE

To evaluate the association of Hcy, folate, vitamin B12 and BMD in postmenopausal women with a meta-analysis.

METHODS

We searched for all published articles indexed in Medline (1950-2012), Embase (1974-2012), and China National Knowledge Infrastructure (1994-2012). Any case-control or cohort study relating to Hcy, vitamin B12, folate, and BMD was included, and the data were extracted independently by two reviewers. Criteria for inclusion were the assessment of Hcy, vitamin B12, folate, and BMD in postmenopausal women as outcomes. We performed this meta-analysis with Review Manager 5.1 software. Odds ratios and 95 % confidence intervals (CI) were used to evaluate the results.

RESULTS

Six eligible studies were selected for meta-analysis. Our analysis suggested that vitamin B12 and Hcy levels were significantly higher in postmenopausal osteoporosis (PMOP) group than that in controls (P = 0.007, <0.05; 95 % CI 3.06-19.38 and P = 0.0003, <0.05; 95 % CI 0.75-2.52, respectively). Folate level was lower in PMOP group than that in controls, but this difference was not statistically significant (P = 0.09, 95 % CI -3.33 to 0.25).

CONCLUSIONS

Hcy and vitamin B12, but not folate, were related to BMD in PMOP. Extra vitamin B12 may not play a protective role for osteoporosis in postmenopausal women. Future studies are needed to confirm them, especially the relationship between increased vitamin B12 and BMD.

Association between methylenetetrahydrofolate reductase C677T polymorphism and bone mineral density: the Dong-gu Study and the Namwon Study

The purpose of this study was to examine the association between the methylenetetrahydrofolate reductase (MTHFR) C677T polymorphism and bone mineral density (BMD). Two large cohort studies were performed: the Dong-gu Study (3,621 men and 5,409 women) and the Namwon Study (3,703 men and 5,672 women). We assessed lumbar spine and femoral neck BMD by dual-energy X-ray absorptiometry. Genotypes were determined by real-time polymerase chain reaction. Multiple linear regression analysis was performed to evaluate the association between MTHFR C677T and BMD, adjusting for age, weight and height. The MTHFR C677T genotype frequencies for CC, CT, and TT genotypes were 34.5, 48.7, and 16.8%, respectively, in the Dong-gu Study and 33.6, 49.2, and 17.2%, respectively, in the Namwon Study. There are no significant differences between the MTHFR C677T genotype and the BMD at the lumbar spine and femoral neck in men or women in both cohorts.

Association of the MTHFR C677T polymorphism and bone mineral density in postmenopausal women: a meta-analysis

Osteoporosis is a condition characterized by low bone mineral density (BMD) and micro-architectural changes in the bone tissue. The risk of osteoporosis is partly determined by genetic factors. The role of C677T polymorphism of methylenetetrahydrofolate reductase (MTHFR) gene has been investigated in postmenopausal osteoporosis. However, the relationship between MTHFR polymorphism and BMD is still controversial. We carried out a meta-analysis of 5,833 subjects to evaluate the association of MTHFR and BMD in postmenopausal women. Databases of MEDLINE, Web of Science, Scopus and CNKI were retrieved for all publications relating to MTHFR polymorphism and BMD in postmenopausal women. Five eligible studies were selected for meta-analysis. All these articles studied the association of MTHFR polymorphism and BMD of the femoral neck and lumbar spine in postmenopausal women. Our analysis suggested that postmenopausal women with the TT genotype had lower femoral neck BMD than the women with the CC/CT genotype, and the weighted mean difference (WMD) was -0.01 g/cm(2) [95% confidence interval (CI): (-0.01, -0.01), P < 0.01]. However, BMD of the lumbar spine of postmenopausal women with the TT genotype was not significantly different from that of women with the CC/CT genotype. In the random effects model, the WMD between the TT and TC/CC genotype was -0.01 g/cm(2) [95% CI: (-0.04, 0.01), P = 0.32]. The C677T polymorphism of the MTHFR gene is associated with BMD of the femoral neck in postmenopausal women. Women with the TT genotype of the MTHFR gene have lower BMD, suggesting that the TT genotype may be a risk factor for postmenopausal osteoporosis.

Susceptibility genes for osteoporotic fracture in postmenopausal Chinese women

To identify the susceptibility genes for osteoporotic fracture in postmenopausal Chinese women, a two-stage case-control association study using joint analysis was conducted in 1046 patients with nontraumatic vertebra, hip, or distal radius fractures and 2303 healthy controls. First, 113 single-nucleotide polymorphisms (SNPs) in 16 potential osteoporosis candidate genes reported in recent genomewide association studies, meta-analyses studies, large-scale association studies, and functional studies were genotyped in a small-sample-size subgroup consisting of 541 patients with osteoporotic fractures and 554 healthy controls. Variants and haplotypes in SPTBN1, TNFRSF11B, CNR2, LRP4, and ESR1 that have been identified as being associated with osteoporotic fractures were further reanalyzed in the entire case-control group. We identified one SNP in TNFRSF11B (rs3102734), three SNPs in ESR1 (rs9397448, rs2234693, and rs1643821), two SNPs in LRP4 (rs17790156 and rs898604), and four SNPs in SPTBN1 (rs2971886, rs2941583, rs2941584, and rs12475342) were associated with all of the broadly defined osteoporotic fractures. The most significant polymorphism was rs3102734, with increased risk of osteoporotic fractures (odds ratio, 1.35; 95% confidence interval [CI], 1.17-1.55, Bonferroni p = 2.6 × 10(-4) ). Furthermore, rs3102734, rs2941584, rs12475342, rs9397448, rs2234693, and rs898604 exhibited significant allelic, genotypic, and/or haplotypic associations with vertebral fractures. SNPs rs12475342, rs9397448, and rs2234693 showed significant genotypic associations with hip fractures, whereas rs3102734, rs2073617, rs1643821, rs12475342, and rs2971886 exhibited significant genotypic and/or haplotypic associations with distal radius fractures. Accordingly, we suggest that in addition to the clinical risk factors, the variants in TNFRSF11B, SPTBN1, ESR1, and LRP4 are susceptibility genetic loci for osteoporotic fracture in postmenopausal Chinese women.

Association of MTHFR C667T polymorphism with bone mineral density and fracture risk: an updated meta-analysis

This meta-analysis investigated the association of C677T polymorphism in MTHFR gene with bone mineral density (BMD) and fracture risk. The results suggested that C677T polymorphism was marginally associated with fracture risk. In addition, this polymorphism was modestly associated with BMD of lumbar spine, femoral neck, total hip, and total body, respectively.

INTRODUCTION

The methylenetetrahydrofolate reductase (MTHFR) gene has been implicated in the regulation of BMD and, thus, may serve as a potential risk factor for the development of fracture. However, results have been inconsistent. In this study, a meta-analysis was performed to clarify the association of C677T polymorphism in MTHFR gene with BMD and fracture risk.

METHODS

Published literature from PubMed and EMBASE were searched for eligible publications. Pooled odds ratio (OR) or weighted mean difference (WMD) and 95% confidence interval (CI) were calculated using a fixed- or random-effects model.

RESULTS

Twenty studies (3,525 cases and 17,909 controls) were included in this meta-analysis. The TT genotype of C677T polymorphism was marginally associated with an increased risk of fracture under recessive model (TT vs. TC + CC: OR = 1.23, 95% CI 1.04-1.47). Using this model, similar results were found among East Asians (OR = 1.40, 95% CI 1.07-1.83), female subpopulation (1.27, 95% CI 1.04-1.55), cohort studies (OR = 1.24, 95% CI 1.08-1.44), and subjects younger than aged 60 years (OR = 1.51, 95% CI 1.10-2.07). In addition, under homogeneous co-dominant model, there was a modest association of C677T polymorphism with BMD of lumbar spine (WMD = -0.017 g/cm(2); 95%CI, -0.030-(-0.005) g/cm(2)), femoral neck (WMD = -0.010 g/cm(2); 95% CI -0.017-(-0.003) g/cm(2)), total hip (WMD = -0.013 g/cm(2), 95% CI -0.022-(-0.004) g/cm(2)), and total body (WMD = -0.020 g/cm(2); 95% CI -0.027-(-0.013) g/cm(2)), respectively.

CONCLUSIONS

This meta-analysis suggested that C677T polymorphism was marginally associated with fracture risk. In addition, this polymorphism was modestly associated with BMD of lumbar spine, femoral neck, total hip, and total body, respectively.

Vitaminas B12, B6, B9 e homocisteína e sua relação com a massa óssea em idosos

O número de idosos nos últimos anos tem apresentado incremento em todo o mundo, o que acaba gerando inúmeras preocupações com a saúde dessa população, já que nessa fase da vida as alterações fisiológicas os tornam mais propensos a doenças, principalmente as crônicas não-transmissíveis. A osteoporose, uma doença osteometabólica frequente nos idosos, torna-se alvo de importantes estudos, uma vez que suas consequências afetam tanto a saúde física quanto a psicossocial. Contudo, são diversos os fatores que predispõem à osteoporose, entre os quais a deficiência de vitamina B12, vitamina B9 (folato) e vitamina B6 (piridoxina). A carência dessas vitaminas eleva os níveis de homocisteína, que age interferindo nas ligações cruzadas do colágeno, resultando em diminuição da resistência óssea e, consequentemente, na osteoporose e fraturas ósseas tanto em homens quanto em mulheres. Nesse contexto, este artigo tem como objetivo realizar uma revisão de literatura nas bases de dados LILACS e PubMed, sobre a relação dos níveis séricos de vitamina B12, folato, vitamina B6 e homocisteína com a diminuição da massa óssea em idosos.

Analysis of three functional polymorphisms in relation to osteoporosis phenotypes: replication in a Spanish cohort

Osteoporosis is a complex disease involving many putative genetic factors. Association analysis of functional SNPs in candidate genes is an important tool for their identification. However, this approach is affected by limited power, population stratification, and other drawbacks that lead to discordant results. Replication in independent cohorts is essential. We performed association analyses of three functional polymorphisms previously associated with bone phenotypes--namely, Ala222Val in MTHFR, Ile1062Val in LRP6, and -13910C>T in LCT--in a cohort of 944 postmenopausal Spanish women, all of them with lumbar spine (LS) bone mineral density (BMD) data and most with femoral neck (FN) BMD and fracture data. We found significant differences between genotypes only for the MTHFR polymorphism and vertebral factures, with an OR of 2.27 (95% CI 1.17-4.38) for the TT vs. CC/CT genotypes, P = 0.018. We present genotype and allele frequency data for LCT -13910C>T for a Spanish population, where the T allele (conferring lactase persistence) has a frequency of 38.6%. Genotype frequencies were consistent with observed clines in Europe and with the prevalence of lactase nonpersistence. The LCT -13910C>T polymorphism was significantly associated with height and weight, such that T allele carriers were 0.88 cm taller (95% CI 0.08-1.59 cm, P = 0.032, adjusted by age) than CC individuals and TT homozygotes were 1.91 kg heavier than CC/CT individuals (95% CI 0.11-3.71 kg, P = 0.038, adjusted by age). In conclusion, no significant association was observed between the studied polymorphisms and LS BMD or FN BMD in postmenopausal Spanish women, and only MTHFR Ala222Val was associated with vertebral fractures.

Vitamin B12 in health and disease

Vitamin B(12) is essential for DNA synthesis and for cellular energy production.This review aims to outline the metabolism of vitamin B(12), and to evaluate the causes and consequences of sub-clinical vitamin B(12) deficiency. Vitamin B(12) deficiency is common, mainly due to limited dietary intake of animal foods or malabsorption of the vitamin. Vegetarians are at risk of vitamin B(12) deficiency as are other groups with low intakes of animal foods or those with restrictive dietary patterns. Malabsorption of vitamin B(12) is most commonly seen in the elderly, secondary to gastric achlorhydria. The symptoms of sub-clinical deficiency are subtle and often not recognized. The long-term consequences of sub-clinical deficiency are not fully known but may include adverse effects on pregnancy outcomes, vascular, cognitive, bone and eye health.

Association analyses suggest multiple interaction effects of the methylenetetrahydrofolate reductase polymorphisms on timing of menarche and natural menopause in white women

OBJECTIVE

This study aimed to investigate whether polymorphisms of the methylenetetrahydrofolate reductase (MTHFR) gene are associated with age at menarche and age at natural menopause in white women.

METHODS

In a cross-sectional study, a total of 305 randomly selected unrelated white women were genotyped for six single nucleotide polymorphisms (SNPs) of the MTHFR gene (including one common replacement, rs1801133). This sample was comprehensively analyzed for the association of the SNPs with age at menarche. Then a subsample of 210 women who experienced natural menopause was analyzed for the association of the MTHFR gene with age at natural menopause.

RESULTS

Duration of breast-feeding was a significant predictor of earlier natural menopause (P < 0.05). No individual SNPs were associated with either age at menarche or age at natural menopause. However, three significant (P < 0.05) SNP-SNP interaction effects (rs2066470/rs1476413, rs2066470/rs4846049, and rs17037390/rs4846049) on the onset of menarche were determined. Three haplotypes were significantly associated with age at menopause (P < 0.05). Four SNPs (rs2066470, rs17037390, rs1801133, and rs4846048) indicated significant interaction effects with various lifestyle factors on age at natural menopause.

CONCLUSIONS

The results of our study suggest that the MTHFR gene may influence the onset of menarche and natural menopause. This effect is probably due to the multiple SNP-SNP and SNP-environment interactions. More independent studies are needed to further clarify the possible contribution of this gene to the timing of menarche and menopause.

Bone tissue and hyperhomocysteinemia

Bone tissue quality is determined not only by multiple architectural variables, but also by the mechanical properties of collagen type 1. Homocysteinuria is a genetic disease whose manifestations include severe hyperhomocysteinemia and decreased bone strength. The effects of smaller homocysteine elevations on bone tissue are difficult to demonstrate in clinical studies. Studies in animals and in humans suggest that homocysteine may weaken collagen crosslinks and, if present in large amounts, interfere with bone remodeling. Whether routine homocysteine assays should be performed to detect bone frailty remains unclear. In clinical practice, the focus should be on identifying patients with potential causes of homocysteine elevation (e.g., medications), who should then be given vitamin D and folic acid supplementation if needed. This approach may improve not only bone health, but also vascular and general health.

Genetic epidemiology in aging research

Over the last two decades, aging research has expanded to include not only age-related disease models, and conversely, longevity and disease-free models, but also focuses on biological mechanisms related to the aging process. By viewing aging on multiple research frontiers, we are rapidly expanding knowledge as a whole and mapping connections between biological processes and particular age-related diseases that emerge. This is perhaps most true in the field of genetics, where variation across individuals has improved our understanding of aging mechanisms, etiology of age-related disease, and prediction of therapeutic responses. A close partnership between gerontologists, epidemiologists, and geneticists is needed to take full advantage of emerging genome information and technology and bring about a new age for biological aging research. Here we review current genetic findings for aging across both disease-specific and aging process domains. We then highlight the limitations of most work to date in terms of study design, genomic information, and trait modeling and focus on emerging technology and future directions that can partner genetic epidemiology and aging research fields to best take advantage of the rapid discoveries in each.

Associations between methotrexate treatment and methylenetetrahydrofolate reductase gene polymorphisms with incident fractures in Japanese female rheumatoid arthritis patients

Several case reports have described associations between pathological nonvertebral fractures and low-dose methotrexate (MTX) in rheumatoid arthritis (RA) patients. Furthermore, a significant association between the C677T polymorphism in the methylenetetrahydrofolate reductase (MTHFR) gene and incident fractures has been reported in postmenopausal women. We attempted to determine whether MTX use and MTHFR polymorphisms are associated with incident fracture risk in Japanese female RA patients. DNA samples, laboratory data, and clinical data were obtained from 731 female RA patients more than 50 years old as part of the Institute of Rheumatology Rheumatoid Arthritis (IORRA) observational cohort study. Genotyping of the MTHFR polymorphisms C677T and A1298C was performed using TaqMan SNP Genotyping Assays. MTX use, MTHFR polymorphisms, and other potential risk factors predictive of fracture were analyzed by Cox proportional hazards regression models, including time-dependent covariates. During 78 months from October 2000 to March 2007, 25 and 90 patients developed vertebral and nonvertebral fractures, respectively. Patients with nonvertebral fractures were more likely to take MTX (P = 0.011; odds ratio, 1.77; 95% confidence interval, 1.13-2.76) compared to patients without fractures. Although the C677T and A1298C polymorphisms were not significantly associated with incident fracture risk, MTX use, age, disease duration, and Japanese health assessment questionnaire score were significantly (P < 0.05) and independently associated with nonvertebral fracture incidence. Our results suggest that MTX use is associated with a nonvertebral fracture risk, whereas MTHFR polymorphism status does not appear to be a clinically useful marker for predicting fracture risk in Japanese female RA patients.

Methylenetetrahydrofolate reductase (MTHFR) C677T polymorphism is associated with spinal BMD in 9-year-old children

The C677T MTHFR polymorphism has been associated with lumbar spine and hip BMD. In older adults, the genetic effect has been reported in women only. However, in younger adults, this influence may only be present in men. This study is the first to investigate associations between the C677T MTHFR polymorphism and bone phenotypes in children. Regression analyses were used to study the relationship between MTHFR genotype and bone phenotypes derived from total body DXA scans in children 9.9 yr of age from the Avon Longitudinal Study of Parents and Children (ALSPAC). A total of 5816 children had both genetic and DXA data for the total body less head region (TBLH) and 3196 for the spine. A strong association was observed between the C677T MTHFR genotype and spine BMD (p < 0.001; 0.10 SD decrease per T allele). There was some evidence that this genetic effect was stronger in boys compared with girls (p = 0.04 for sex interaction). In contrast, there was no association between the C677T MTHFR genotype and TBLH BMD. The association between MTHFR genotype and spine BMD was attenuated particularly in girls by high maternal dietary intakes of vitamin B(6) and folate during pregnancy but not by child dietary intakes at 7 yr. To the extent that these findings reflect known influences of C677T MTHFR genotype on plasma homocysteine levels, our results suggest that the latter is an important regulator of spinal BMD in childhood.

Interactive effects of COMT Val108/158Met and MTHFR C677T on executive function in schizophrenia

Schizophrenia is characterized by heritable deficits in executive function. Two common, functional polymorphisms, catechol-O-methyltransferase (COMT) Val108/158Met and methylenetetrahydrofolate reductase (MTHFR) C677T, have separately been associated with executive function performance in schizophrenia. Given the closely related biochemistry of MTHFR and COMT, it is plausible that the T and Val alleles act synergistically to impair executive function. This investigation of 185 outpatients with schizophrenia examined the interactive effects of these two polymorphisms on Wisconsin Card Sorting Task (WCST) performance. Two WCST measures consistently associated with schizophrenia, perseverative errors and inability to generate categories, were contrasted among compound COMT-MTHFR genotype groups. Individuals homozygous for the COMT Val allele who also carried at least one copy of the MTHFR T allele exhibited a significantly higher percentage of perseverative errors than patients in the other genotype groups. While the T allele also exerted a negative effect on category generation, COMT genotype did not contribute to category performance. It is plausible that cumulative effects of the MTHFR T and COMT Val alleles on intracellular methylation profiles and prefrontal dopamine transmission underlie their interactive effect on perseverative errors.

Genetic variation in candidate osteoporosis genes, bone mineral density, and fracture risk: the study of osteoporotic fractures

Candidate osteoporosis gene variants were examined for associations with fracture risk and bone mineral density (BMD). A total of 9,704 white women were recruited at four U.S. clinical centers and enrolled into the Study of Osteoporotic Fractures, a longitudinal cohort study. Genotyping of 31 polymorphisms from 18 candidate osteoporosis genes was performed in 6,752 women. Incident radiographic fractures were identified at the third and eighth examinations compared with the baseline examination. BMD was measured at the total hip by dual-energy X-ray absorptiometry. Analyses were adjusted for age, clinic site, and self-reported ethnicity. During a mean follow-up of 14.5 years, a total of 849 hip, 658 vertebral, and 2,496 nonhip/nonvertebral fractures occurred in 6,752 women. Women carrying the ALOX15_G48924T T/T genotype had a higher rate of hip fracture (hazard ratio [HR] = 1.33;95% confidence interval [95% CI] = 1.00-1.77) compared with the G/G genotype. Compared with those carrying the PRL_T228C T/T genotype, women with either the C/C (HR = 0.80; 95% CI = 0.67-0.95) or C/T (HR = 0.81; 95% CI = 0.68-0.97) genotype had a lower rate of nonvertebral/nonhip fractures. Women carrying the BMP2_A125611G G/G genotype had a higher rate of vertebral fracture (odds ratio [OR] = 1.51; 95% CI = 1.03-2.23) compared with the A/A genotype. Women with the ESR1_C1335G G/G genotype had a higher rate of vertebral fracture (OR = 1.64; 95% CI = 1.07-2.50) compared with the C/C genotype. Compared with those with the MMP2_C595T C/C genotype, women with the C/T (OR = 0.79; 95% CI = 0.65-0.96) or T/T (OR = 0.44; 95% CI = 0.27-0.72) genotype had a lower rate of vertebral fracture. In conclusion, polymorphisms in several candidate genes were associated with hip, vertebral, and nonhip/nonvertebral fractures but not with total hip BMD in this large population based cohort study.

The role of hyperhomocysteinemia as well as folate, vitamin B(6) and B(12) deficiencies in osteoporosis: a systematic review

Hyperhomocysteinemia (HHCY) has been suggested as a new risk factor for osteoporosis. Recent epidemiological, clinical and experimental studies provide a growing body of data, which is reviewed in this article. Epidemiological and (randomized) clinical trials suggest that HHCY increases fracture risk, but has minor effects on bone mineral density. Measurement of biochemical bone turnover markers indicates a shift of bone metabolism towards bone resorption. Animal studies confirm these observations showing a reduced bone quality and stimulation of bone resorption in hyperhomocysteinemic animals. Homocysteine (HCY) has been found to accumulate in bone by collagen binding. Cell culture studies demonstrate that high HCY levels stimulate osteoclasts but not osteoblasts, indicating again a shift of bone metabolism towards bone resorption. Regarding B-vitamins, only a few in vivo studies with equivocal results have been published. However, two large cell culture studies confirm the results obtained with exogenous HCY administration. In addition, HHCY seems to have adverse affects on extracellular bone matrix by disturbing collagen crosslinking. In conclusion, existing data suggest that HHCY (and possibly B-vitamin deficiencies) adversely affects bone quality by a stimulation of bone resorption and disturbance of collagen crosslinking.

Molecular genetic studies of gene identification for osteoporosis

This review comprehensively summarizes the most important and representative molecular genetics studies of gene identification for osteoporosis published up to the end of September 2007. It is intended to constitute a sequential update of our previously published reviews covering the available data up to the end of 2004. Evidence from candidate gene-association studies, genome-wide linkage and association studies, as well as functional genomic studies (including gene-expression microarray and proteomics) on osteogenesis and osteoporosis, are reviewed separately. Studies of transgenic and knockout mice models relevant to osteoporosis are summarized. The major results of all studies are tabulated for comparison and ease of reference. 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.

The synergistic effect of bone mineral density and methylenetetrahydrofolate reductase (MTHFR) polymorphism (C677T) on fractures

A functional polymorphism in methylenetetrahydrofolate reductase (MTHFR) has been identified at codon 677 (C677T). The T-allele variant (valine type) has lower enzyme activity than the wild type (C-allele or alanine type), resulting in a slightly elevated homocysteine level, which has been recently recognized as a risk factor for fracture. However, whether subjects bearing the T allele have higher susceptibility to fractures is still controversial. We have investigated the effects of MTHFR polymorphism on fracture susceptibility in Japanese postmenopausal women. A total of 502 postmenopausal ambulatory Japanese women were followed up for 5.1 +/- 3.4 (mean +/- SD) years, and a total of 155 patients with incident fractures (121 patients with vertebral fractures and 34 cases with fractures at other sites) were recorded. When compared with the patients without any fractures, the patients with incident fractures were older, had more prevalent fractures, had higher urinary levels of bone turnover markers as well as plasma homocysteine level, but were shorter in body height and had lower bone mineral density. The prevalence of the TT genotype of MTHFR was significantly higher in the patients with incident fractures compared to the other genotypes. The subjects with the TT genotype had a higher incidence rate of fracture and higher plasma level of homocysteine than the subjects bearing the non-TT genotype. This relationship was observed in both osteoporotic and nonosteoporotic groups. The hazard ratio for TT genotype without osteoporosis, non-TT genotype with osteoporosis, and TT genotype with osteoporosis was 1.49 (0.91-2.45), 3.64 (2.50-5.29), and 7.21 (4.34-11.97), respectively, compared to the non-TT genotype without osteoporosis. A higher hazard ratio for the TT genotype with osteoporosis was still apparent after adjustment for age, body size, and number of prevalent vertebral fractures. These results indicate that the TT genotype of MTHFR may be a risk factor for future fracture in addition to the traditional risk factors.

Relationship of circulating total homocysteine and C-reactive protein to trabecular bone in postmenopausal women

Homocysteine (Hcy) and C-reactive protein (CRP) are novel risk factors for osteoporosis. The purpose of this analysis was to determine the relationship of Hcy and CRP to volumetric trabecular bone, but also to assess their relationship to areal composite bone in healthy postmenopausal women (N=184). We used peripheral quantitative computed tomography to assess volumetric bone at the distal tibia and dual-energy X-ray absorptiometry to assess areal composite bone at the proximal femur and lumbar spine. Multiple regression revealed that 22% of the variability in trabecular bone mineral content (F=9.59, p<or=0.0001) was accounted for by weight (12.4%; p<or=0.0001), hemoglobin (5.5%; p=0.0006), uric acid (4.2%; p=0.003), and blood glucose (1.5%; p=0.07). Multiple regression revealed that 5.4% of the variability in trabecular bone mineral density (F=3.36; p=0.020) was accounted for by hemoglobin (4.2%; p=0.006) and Hcy (1.5%; not significant, p=0.10). Total Hcy and CRP were not significantly related to trabecular bone, perhaps because these were nonosteoporotic women. However, our results suggested a weak but negative relationship between Hcy and trabecular bone. Further investigation is needed to examine the relationship of Hcy as an endogenous bioactive molecule to trabecular bone loss in early postmenopausal women and the response of trabecular bone to dietary intervention.