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

Pilot study of the effect of surgical menopause on bone mineral density and quality in patients with gynecological malignancies

AIM

To investigate the effects of surgical menopause on bone mineral density and bone quality because bilateral salpingo-oophorectomy for the treatment of gynecological malignancies is common even in premenopausal patients. This study is prospective one of bone mineral density and quality measurements after surgery for perimenopausal gynecologic malignancies.

METHODS

In 50 women who underwent surgical menopause for a diagnosis of gynecological malignancies, bone mineral density (BMD), blood levels of tartrate-resistant acid phosphatase 5b (TRACP-5b) and bone-specific alkaline phosphatase (BAP) as bone metabolism markers, and urinary pentosidine level as bone quality marker were measured before surgery and at multiple points up to 24 months after surgery.

RESULTS

In a group of 22 patients who did not undergo hormone replacement therapy (HRT) (HRT- group), BMD of the lumbar spine and total hip continued to decrease significantly from 6 months postoperatively. Percentages of changes in BMD progressively increased over time after surgery. TRACP-5b and urinary pentosidine levels significantly increased 6 months postoperatively compared with preoperative levels. Comparisons between 10 patients who underwent HRT (HRT+ group) and the HRT- group revealed significant reductions in the percentage of change in lumbar spine BMD only and TRACP-5b and urinary pentosidine levels 12 months postoperatively in the former group.

CONCLUSIONS

In this pilot study, we showed that BMD and bone-related markers are altered in patients with surgical menopause. It also suggested that HRT may reduce these influences on bone metabolism.

Association of Methylenetetrahydrofolate Reductase (MTHFR) Polymorphism with Osteosarcoma in a Mexican Population

The methylenetetrahydrofolate reductase (MTHFR) gene 677C➔T polymorphism is capable of altering folate metabolism and can modify certain neoplasia risk. Reports have suggested that folate can have an influence on bone development and so it is of interest to know if the MTHFR 677C➔T polymorphism is associated with the malignant transformation process of this tissue. The polymorphism was determined in 55 patients with osteosarcoma and in 180 healthy individuals. Compared with C/T+C/C genotypes, a 3.7-fold reduction in osteosarcoma probability is possible with the T/T genotype (OR 0.27, CI 95% 0.07-0.82). Undoubtedly, further studies, utilizing large samples and carried out on different populations, are necessary to confirm these results.

Nitric oxide is associated with fracture risk in Japanese women

Although nitric oxide (NO) is a known factor that regulates the bone physiology, few and discordant results have been obtained in human studies evaluating the effect of nitrates on bone health. We investigated for the relationship between serum NOx level and incident osteoporotic fracture rate prospectively in a cohort consisting of Japanese women. A total of 871 subjects (67.5 ± 10.8 y/o) were analyzed. During the observation period (8.8 ± 7.2 yrs), incident osteoporotic fractures occurred in 267 participants (209 vertebral fractures, 57 long-bone fractures, and 1 both types). Hazard ratio, by the Cox proportional hazards model, of serum NOx for incident fracture was 0.64 (95% confidence interval 0.53-0.78, p < 0.001) after adjustment for baseline age (1.13, 1.06-1.21, p < 0.001), lumbar bone mineral density (L-BMD; 0.85, 0.78-0.92, p < 0.001), presence of prevalent fracture (3.27, 2.49-4.32, p < 0.001), and treatment of osteoporosis (0.70, 0.53-0.92, p = 0.010). The relationships between serum level of NOx and bone-related parameters were examined by multiple regression analysis; body mass index (p < 0.001) and L-BMD (p = 0.011) were significantly associated with serum NOx level. These results suggest that the low circulating NOx is one of the independent predictors for osteoporotic fracture occurrence in postmenopausal women.

Associations of Homocysteine Metabolism With the Risk of Spinal Osteoarthritis Progression in Postmenopausal Women

CONTEXT

Although homocysteine accumulation is a reported risk factor for several age-related disorders, little is known about its relationship with osteoarthritis (OA).

OBJECTIVE

We investigated for associations of homocysteine and C677T polymorphism in methylenetetrahydrofolate reductase (MTHFR), which is involved in homocysteine clearance, with the development and progression of spinal OA through a combined cross-sectional and longitudinal cohort study.

METHODS

A total of 1306 Japanese postmenopausal outpatients participating in the Nagano Cohort Study were followed for a mean 9.7-year period. Cross-sectional multiple logistic regression for spinal OA prevalence at registration by serum homocysteine level was performed with adjustment for confounders. In addition to Kaplan-Meier analysis, multivariate Cox regression was employed to examine the independent risk of MTHFR C677T variant for spinal OA progression.

RESULTS

Multivariate regression analysis revealed a significant association between homocysteine and spinal OA prevalence (odds ratio 1.38; 95% CI 1.14-1.68). Kaplan-Meier curves showed a gene dosage effect of the T allele in MTHFR C677T polymorphism on the accelerated progression of spinal OA severity (P = 0.003). A statistically significant independent risk of the T allele for spinal OA advancement was validated by Cox regression analysis. Respective adjusted hazard ratios for the CT/TT and TT genotypes were 1.68 (95% CI, 1.16-2.42) and 1.67 (95% CI, 1.23-2.28).

CONCLUSION

Circulating homocysteine and C677T variant in MTHFR are associated with the prevalence rate and ensuing progression, respectively, of spinal OA. These factors may represent potential interventional targets to prevent OA development and improve clinical outcomes.

Associations of LRP5 and MTHFR Gene Variants with Osteoarthritis Prevalence in Elderly Women: A Japanese Cohort Survey Randomly Sampled from a Basic Resident Registry

Objective

Osteoarthritis (OA) is a common and degenerative joint disorder in the elderly. A greater importance of understanding the relationship between genetic factors and OA prevalence has emerged with population aging. We therefore investigated the associations of several bone disease-related genetic variants with the prevalence of OA and osteoporosis in Japanese elderly women from the Obuse study cohort, which was randomly sampled from a basic town resident registry.

Methods and Results

In total, 206 female participants (mean ± standard deviation age: 69.7 ± 11.0 years) who completed OA, bone mineral density, and genotype assessments were included. The number of patients diagnosed as having knee/hip OA and osteoporosis was 59 (28.6%) and 30 (14.6%), respectively. Fisher’s exact testing revealed significant relationships between the minor T allele of LDL receptor related protein 5 (LRP5) rs3736228 and the prevalence of knee/hip OA and osteoporosis. The respective odds ratios (ORs) of the TT genotype for knee/hip OA and osteoporosis were 7.28 (95% confidence interval [CI] 2.22–28.08) and 5.24 (95% CI 0.95–26.98). An additional subgroup analysis for knee OA revealed that the frequency of the common C allele of methylenetetrahydrofolate reductase (MTHFR) rs1801133 had a statistically significant protective association with the prevalence of knee OA (OR 0.58, 95% CI 0.35–0.97).

Conclusion

In sum, the present study demonstrated significant associations of LRP5 rs3736228 and MTHFR rs1801133 with knee/hip OA and osteoporosis prevalences and knee OA prevalence, respectively, in Japanese elderly women. These results will help further the understanding of OA pathogenesis and related genetic risk factors.

[The role of glycation end products in the development and progression of diabetic neuroarthropathy]

Diabetic neuroarthropathy (DNOAP, Charcot's foot) is a serious complication of diabetes mellitus, the genesis of which is not fully understood. In most cases, this pathology is diagnosed late, which leads to the development of severe deformities of the foot, up to the loss of support ability of the limb. There is no single hypothesis for the formation of Charcot's foot, but there are factors predisposing to its development, as well as a few likely provoking events. Excessive formation and accumulation of end products of glycation may play an important role in the pathogenesis of this complication of diabetes. End products of glycation (AGE) are a variety of compounds formed as a result of a non-enzymatic reaction between carbohydrates and free amino groups of proteins, lipids and nucleic acids. There are various factors that lead to the accumulation of AGE in the human body. Allocate endogenous and exogenous factors. The former include certain diseases, such as diabetes mellitus, renal failure, which accelerate glycation processes. Exogenous factors leading to the formation of lipo-oxidation and glyco-oxidation products include tobacco smoke and prolonged heat treatment of food.This review provides information on the role of glycation end products in the development and progression of complications in patients with diabetes mellitus.

Advanced glycation end products in musculoskeletal system and disorders

The human population is ageing globally, and the number of old people is increasing yearly. Diabetes is common in the elderly, and the number of diabetic patients is also increasing. Elderly and diabetic patients often have musculoskeletal disorder, which are associated with advanced glycation end products (AGEs). AGEs are heterogeneous molecules derived from non-enzymatic products of the reaction of glucose or other sugar derivatives with proteins or lipids, and many different types of AGEs have been identified. AGEs are a biomarker for ageing and for evaluating disease conditions. Fluorescence, spectroscopy, mass spectrometry, chromatography, and immunological methods are commonly used to measure AGEs, but there is no standardized evaluation method because of the heterogeneity of AGEs. The formation of AGEs is irreversible, and they accumulate in tissue, eventually causing damage. AGE accumulation has been confirmed in neuromusculoskeletal tissues, including bones, cartilage, muscles, tendons, ligaments, and nerves, where they adversely affect biomechanical properties by causing charge changes and forming cross-linkages. AGEs also bind to receptors, such as the receptor for AGEs (RAGE), and induce inflammation by intracellular signal transduction. These mechanisms cause many varied aging and diabetes-related pathological conditions, such as osteoporosis, osteoarthritis, sarcopenia, tendinopathy, and neuropathy. Understanding of AGEs related pathomechanism may lead to develop novel methods for the prevention and therapy of such disorders which affect patients' quality of life. Herein, we critically review the current methodology used for detecting AGEs, and present potential mechanisms by which AGEs cause or exacerbate musculoskeletal disorders.

Non-invasive skin autofluorescence, blood and urine assays of the advanced glycation end product (AGE) pentosidine as an indirect indicator of AGE content in human bone

Background

Bone mineral density (BMD) measurements are widely used to assess fracture risk. However, the finding that some fracture patients had high BMD together with the low contribution of drugs to osteoporosis suggests that bone strength factors other than BMD contribute to bone quality. We evaluated the amount of advanced glycation end products (AGEs) by non-invasive assays of serum and urine as well as by skin autofluorescence to measure the levels of a representative AGE, pentosidine, to investigate whether pentosidine can serve as an indirect indicator of AGEs formation in bone collagen.

Methods

A total of 100 spinal surgery patients without fragility fracture (54 males and 46 females) treated at our hospital were enrolled. The amount of pentosidine in blood, urine, skin and bone (lumbar lamina) samples from these patients was measured. AGE accumulation was assessed by measuring skin autofluorescence. We examined the correlation between pentosidine content in tissues and body fluid, as well as skin AGEs with age, height, body weight, BMI, and estimated glomerular filtration rate (eGFR).

Results

A significant age-related increase in pentosidine levels in tissues was observed, while there was a significant negative correlation between tissue pentosidine and eGFR. The amount of skin pentosidine was significantly and positively correlated with pentosidine content of the bone in those under 50 years of age. Urine pentosidine also correlated positively with bone pentosidine and skin pentosidine, but only in females. The total amount of AGEs in skin did not correlate with bone pentosidine.

Conclusion

In this study, the strong correlation between the pentosidine content in each sample and eGFR may indicate that renal dysfunction with advancing age increases oxidative stress and induces AGEs formation in collagen-containing tissues. The correlation of skin pentosidine concentration and eGFR, with AGEs formation in bone collagen suggests that pentosidine would be a useful indirect index of decreased bone quality. Skin AGEs estimated by autofluorescence in clinical situations may not be suitable as an indirect assessment of bone quality. Because urine pentosidine correlated positively with bone pentosidine and skin pentosidine in females, urine pentosidine may be a candidate for an indirect assessment of bone quality.

The role of folate receptor and reduced folate carrier polymorphisms in osteoporosis development

Introduction: Osteoporosis is a chronic metabolic disease with multifactorial etiology. One of possible osteoporosis causes may be impairment of osteoclasts function which leads to increased bone resorption. This may be a result of many metabolic changes. It is believed that changes of folate-methionine metabolism in osteoporosis play an essential role in the etiology of this disease.

Objective: The aim of this study was to examine how polymorphisms of SLC19A1 and FOLR3 genes may play the key role in folate-methionine pathway and influence on the etiology of osteoporosis.

Results: The statistically overrepresentation of mutated GG genotype of FOLR3 (rs11235449) was observed in the control group compared to the osteopenia (34.9% in osteopenia vs. 37.8% in controls, p=0.025, OR=0.61). As to the SLC19A1 (rs3788200) polymorphism we have noted the statistically significant over-representation of wild-type GG genotype (35.8% vs. 26.2%, p=0.046, OR=1.57) and overrepresentation of wild-type G allele (56.9% vs. 50.2%, p=0.061, OR=1.31) in osteopenia group if compared to the controls.

Conclusions: In our study we shown the protective role of mutated GG genotype of FOLR3 (rs11235449) polymorphism to osteopenia progress and possible role of wild-type GG genotype and wild-type G allele of SLC19A1 (rs3788200) polymorphism in osteopenia development.

Multiple vitamin deficiencies additively increase the risk of incident fractures in Japanese postmenopausal women

The associations of multiple vitamin deficiencies on incident fractures were uncertain, the relationships between serum vitamin markers and incident bone fractures were investigated in Japanese postmenopausal women. The number of deficiencies was additively associated with incident fracture after adjustment for possible confounding factors including the treatment of osteoporosis.

INTRODUCTION

To evaluate the associations of multiple vitamin deficiencies on incident fractures, the relationships between serum vitamin markers and incident bone fractures were investigated in Japanese postmenopausal women.

METHODS

This analysis used a subset of the ongoing cohort maintained by a primary care institution. Inclusion criteria of the present study were postmenopausal women aged ≥ 50 years, without vitamin supplementation and secondary osteoporosis. Baseline serum concentrations of 25-hydroxyvitamin D (25(OH)D), undercarboxylated osteocalcin (ucOC), and homocysteine (Hcy) were measured to assess vitamin D, vitamin K, and vitamin B, respectively. Since 25(OH) D positively relates to vitamin D, ucOC and Hcy negatively relate to vitamin K and vitamin B nutrients, respectively, the subjects with lower (25(OH)D) or higher (ucOC or Hcy) values than each median value was defined as subjects with the corresponding vitamin deficiency. Subjects were divided into four groups according to the number of deficiency: no deficiency, single deficiency, double deficiencies, and triple deficiencies. Relationships between the vitamin deficiencies and incident fractures were evaluated by Cox regression analysis.

RESULTS

A total of 889 subjects were included in this analysis; their mean and SD age was 68.3 ± 9.5 years, and the follow-up period was 6.3 ± 5.1 years. The numbers of subjects in the four groups were 139 (15.6%), 304 (34.2%), 316 (35.5%), and 130 (14.6%) for the groups with no, single, double, and triple deficiencies, respectively. Incident fractures were observed in 264 subjects (29.7%) during the observation period. The number of deficiencies was significantly associated with incident fracture (hazard ratio 1.25, 95% confidence interval 1.04-1.50, P = 0.018) after adjustment for possible confounding factors including the treatment of osteoporosis.

CONCLUSION

Accumulation of vitamin deficiencies was related to incident fractures.

Homocysteine and age-associated disorders

There are numerous theories of aging, a process which still seems inevitable. Aging leads to cancer and multi-systemic disorders as well as chronic diseases. Decline in age- associated cellular functions leads to neurodegeneration and cognitive decline that affect the quality of life. Accumulation of damage, mutations, metabolic changes, failure in cellular energy production and clearance of altered proteins over the lifetime, and hyperhomocysteinemia, ultimately result in tissue degeneration. The decline in renal functions, nutritional deficiencies, deregulation of methionine cycle and deficiencies of homocysteine remethylation and transsulfuration cofactors cause elevation of homocysteine with advancing age. Abnormal accumulation of homocysteine is a risk factor of cardiovascular, neurodegenerative and chronic kidney disease. Moreover, approximately 50% of people, aged 65 years and older develop hypertension and are at a high risk of developing cardiovascular insufficiency and incurable neurodegenerative disorders. Increasing evidence suggests inverse relation between cognitive impairment, cerebrovascular and cardiovascular events and renal function. Oxidative stress, inactivation of nitric oxide synthase pathway and mitochondria dysfunction associated with impaired homocysteine metabolism lead to aging tissue degeneration. In this review, we examine impact of high homocysteine levels on changes observed with aging that contribute to development and progression of age associated diseases.

The Effects of Homocysteine on the Skeleton

PURPOSE OF REVIEW

Homocystinuria is a congenital metabolic disorder in which cystathionine β-synthase deficiency results in a prominent increase in homocysteine (serum levels > 100 μM), causing mental retardation, atherosclerotic cerebral infarction, and osteoporosis accompanied by fragility fractures. Encountering a case with excessive homocysteinemia such as that seen in hereditary homocystinuria is unlikely during usual medical examinations. However, in individuals who have vitamin B or folate deficiency, serum homocysteine concentrations are known to increase. These individuals may also have a polymorphism in methylenetetrahydrofolate reductase, MTHFR (C677T: TT type), which regulates homocysteine metabolism. These changes in homocysteine levels may elicit symptoms resembling those of homocystinuria (e.g., Alzheimer's disease, atherosclerosis, osteoporosis).

RECENT FINDINGS

High serum homocysteine has been shown to have detrimental effects on neural cells, vascular endothelial cells, osteoblasts, and osteoclasts. Homocysteine is also known to increase oxidative stress, disrupt cross-linking of collagen molecules, and increase levels of advanced glycation end products, which results in reduced bone strength through a mechanism that goes beyond low bone density and increased bone resorption. Therefore, high serum homocysteine may be regarded as a factor that can reduce both bone mass and impair bone quality. In this review, we outline the epidemiology and pathophysiology of osteoporosis associated with hyperhomocysteinemia.

Comprehensive analyses of how tubule occlusion and advanced glycation end-products diminish strength of aged dentin

In clinical dentistry, since fracture is a major cause of tooth loss, better understanding of mechanical properties of teeth structures is important. Dentin, the major hard tissue of teeth, has similar composition to bone. In this study, we investigated the mechanical properties of human dentin not only in terms of mineral density but also using structural and quality parameters as recently accepted in evaluating bone strength. Aged crown and root dentin (age ≥ 40) exhibited significantly lower flexural strength and toughness than young dentin (age < 40). Aged dentin, in which the dentinal tubules were occluded with calcified material, recorded the highest mineral density; but showed significantly lower flexural strength than young dentin. Dentin with strong alignment of the c-axis in hydroxyapatite exhibited high fracture strength, possibly because the aligned apatite along the collagen fibrils may reinforce the intertubular dentin. Aged dentin, showing a high advanced glycation end-products (AGEs) level in its collagen, recorded low flexural strength. We first comprehensively identified significant factors, which affected the inferior mechanical properties of aged dentin. The low mechanical strength of aged dentin is caused by the high mineral density resulting from occlusion of dentinal tubules and accumulation of AGEs in dentin collagen.

Effects of Collagen Crosslinking on Bone Material Properties in Health and Disease

Data have accumulated to show that various types of collagen crosslinking are implicated in the health of individuals, as well as in a number of disease states, such as osteoporosis, diabetes mellitus, chronic kidney disease, inflammatory bowel disease, or in conditions of mild hyperhomocysteinemia, or when glucocorticoid use is indicated. Collagen crosslinking is a posttranslational modification of collagen molecules and plays important roles in tissue differentiation and in the mechanical properties of collagenous tissue. The crosslinking of collagen in the body can form via two mechanisms: one is enzymatic crosslinking and the other is nonenzymatic crosslinking. Lysyl hydroxylases and lysyl oxidases regulate tissue-specific crosslinking patterns and quantities. Enzymatic crosslinks initially form via immature divalent crosslinking, and a portion of them convert into mature trivalent forms such as pyridinoline and pyrrole crosslinks. Nonenzymatic crosslinks form as a result of reactions which create advanced glycation end products (AGEs), such as pentosidine and glucosepane. These types of crosslinks differ in terms of their mechanisms of formation and function. Impaired enzymatic crosslinking and/or an increase of AGEs have been proposed as a major cause of bone fragility associated with aging and numerous disease states. This review focuses on the effects of collagen crosslinking on bone material properties in health and disease.

Recent genetic discoveries in osteoporosis, sarcopenia and obesity

Osteoporosis is a skeletal disorder characterized by low bone mineral density (BMD) and an increased susceptibility to fractures. Evidence from genetic studies indicates that BMD, a complex quantitative trait with a normal distribution, is genetically controlled. Genome-wide association studies (GWAS) as well as studies using candidate gene approaches have identified single-nucleotide polymorphisms (SNPs) that are associated with BMD, osteoporosis and osteoporotic fractures. These SNPs have been mapped close to or within genes including those encoding WNT/β-catenin signaling proteins. Understanding the genetics of osteoporosis will help to identify novel candidates for diagnostic and therapeutic targets. Genetic factors are also important for the development of sarcopenia, which is characterized by a loss of lean body mass, and obesity, which is characterized by high fat mass. Hence, in this review, we discuss the genetic factors, identified by genetic studies, which regulate the body components related to osteoporosis, sarcopenia, and obesity.

Diabetes, collagen, and bone quality

Diabetes increases risk of fracture, although type 2 diabetes is characterized by normal or high bone mineral density (BMD) compared with the patients without diabetes. The fracture risk of type 1 diabetes as well as type 2 diabetes increases beyond an explained by a decrease of BMD. Thus, diabetes may reduce bone strength without change in BMD. Whole bone strength is determined by bone density, structure, and quality, which encompass the micro-structural and tissue material properties. Recent literature showed that diabetes reduces bone material properties rather than BMD. Collagen intermolecular cross-linking plays an important role in the expression of bone strength. Collagen cross-links can be divided into beneficial enzymatic immature divalent and mature trivalent cross-links and disadvantageous nonenzymatic cross-links (Advanced glycation end products: AGEs) induced by glycation and oxidation. The formation pathway and biological function are quite different. Not only hyperglycemia, but also oxidative stress induces the reduction in enzymatic cross-links and the formation of AGEs. In this review, we describe the mechanism of low bone quality in diabetes and the usefulness of the measurement of plasma or urinary level of AGEs for estimation of fracture risk.

Low calcium intake is associated with high plasma homocysteine levels in postmenopausal women

Nutritional interventions targeting homocysteine remain controversial, and further nutritional research is warranted. We thus sought to explore the determinants of plasma homocysteine other than B-group vitamins. This cross-sectional study surveyed the nutritional status of 713 Japanese postmenopausal women using a semiquantitative food frequency questionnaire. Associations between total energy, protein, fat, carbohydrate, and vitamin A and K intakes and homocysteine were insignificant. Mean homocysteine in the second (536.1 ± 34.7 mg/day) and third (712.9 ± 115.6 mg/day) tertiles of calcium intake were lower than in the first tertile (379.6 ± 76.6 mg/day) by -0.57 nmol/mL (95 % confidence interval, -1.10 to-0.04, p = 0.04) and -1.18 nmol/mL (-1.76 to -0.60, p<0.01), respectively, after adjustment for lifestyle and clinical factors (trend p\0.01). Mean homocysteine in those with dietary calcium intake above the median (>536 mg/day) were lower regardless of the folic acid concentration; the differences were -1.59 nmol/mL (-2.33 to -0.85, p = 0.02) and -0.75 nmol/mL (-1.37 to-0.12, p<0.01) for the high (<7.8 ng/mL) and low folic acid groups, respectively. There was no significant association between calcium and folic acid (p = 0.08). In conclusion, further prospective research to confirm our findings is needed for the development of nutritional inventions targeting homocysteine.

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.

Polymorphism of SLC25A32, the folate transporter gene, is associated with plasma folate levels and bone fractures in Japanese postmenopausal women

AIM

Elevation of homocysteine is associated with an increased risk for bone fractures. We previously reported that the methylenetetrahydrofolate reductase (MTHFR) gene polymorphism is associated with homocysteine levels and fracture. The association between the fracture and folate levels or their related gene polymorphisms is not completely clear. We speculated that the SLC25A32 gene, the mitochondrial inner membrane folate transporter, also could be implicated in the regulation of folate metabolism and fracture.

METHODS

A total of 851 Japanese postmenopausal women participated in the association study between the single nucleotide polymorphism genotype and plasma homocysteine or folate. We also tested the association between the candidate single nucleotide polymorphism and 663 postmenopausal women.

RESULTS

The AA genotype of rs2241777 single nucleotide polymorphism at the 3'UTR region in the SLC25A32 gene was associated with lower plasma folate concentration compared with the other genotypes in 851 postmenopausal women. A total of 674 postmenopausal ambulatory Japanese women were followed up for 5.5 ± 0.1 years (mean ± SE). The AA genotype groups also showed an apparently higher rate and earlier onset of incident fractures than the other genotypes. A total of 407 participants had >70% young-adult mean bone mineral density at the start of the observation.

CONCLUSIONS

These results show that the SLC25A32 gene polymorphism could be a risk factor for lower folate concentration and future fracture.

Plasma level of homocysteine associated with severe vertebral fracture in postmenopausal women

The aim of this cross-sectional cohort study was to clarify risk factors for severe vertebral fractures in postmenopausal Japanese women. Subjects were ambulatory volunteers age over 50 years who were recruited from a population of outpatients at a primary care institute. At registration, age, body mass index (BMI), bone mineral density (BMD), and present illness were investigated. Biochemical parameters including urinary levels of type I collagen cross-linked N-telopeptides (NTXs), and pentosidine and plasma levels of homocysteine were measured. Values were compared with different fracture grades (grade 0-3). A total of 1,475 postmenopausal women (66.6 ± 9.0 years) were included in the present study. Distributions of vertebral fracture grades were grade 1, 137 cases (9.3 %); grade 2, 124 cases (8.4 %); and grade 3, 162 cases (11.0 %). Age, BMI, BMD, NTX, pentosidine, and homocysteine were significantly associated with vertebral fracture in unadjusted analysis. In addition, a higher prevalence of hypertension was observed in patients with severe fracture. When comparing vertebral fracture grade 0 versus grade 2-3 by multiple regression analysis, pentosidine and homocysteine levels were a significant risk for moderate/severe vertebral fracture (odds ratio [OR] = 1.17, 95 % confidence interval [CI] 1.00-1.38, p = 0.049; OR = 1.22, 95 % CI 1.03-1.46, p = 0.013). Homocysteine levels were also a significant risk when comparing vertebral fracture grade 0 versus grade 3 (OR = 1.27, 95 % CI 1.04-1.58, p = 0.021). Plasma level of homocysteine was an independent risk for severe vertebral fractures.

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.

Guidelines for the use of bone metabolic markers in the diagnosis and treatment of osteoporosis (2012 edition)

Recently the clinical application of bone metabolic markers has achieved significant progress and the measurements of these indices give us a better understanding of the pathogenesis of osteoporosis. Bone metabolic markers were adapted to select drug treatment for osteoporosis and to evaluate drug efficacy. Therefore, the proper application and assessment of bone metabolic markers in clinical practice is very important. To achieve these aims, the committee on the guidelines for the use of biochemical markers of bone turnover in osteoporosis authorized by the Japan Osteoporosis Society has summarized recent progress in bone markers and proposed the proper utilization of bone markers. Although the use of bone metabolic markers now has an important role in the daily management of osteoporosis, their use in Japan is still insufficient because of insurance coverage limitations. Since the Japan Osteoporosis Society first created the 2001 guidelines, new bone metabolic markers have been introduced into clinical practice. The availability of new osteoporosis treatments that promote bone formation has changed the clinical application of bone metabolic markers in current practice. Therefore, revisions to the current clinical practice are needed which led to the proposal to create these new 2012 guidelines.

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.

Association between the stress fracture and bone metabolism/quality markers in lacrosse players

Background

Overuse injury including stress fracture is a serious problem for athletes. Recently, the importance of bone metabolism and quality as factors preventing overuse injury has been increasingly recognized. Hence, we hypothesized that markers of bone metabolism and quality are related to overuse injuries.

Methods

The subjects, which were elite university lacrosse players (male, n = 35; age, 19.8 ± 1.1; female, n = 49; age, 20.0 ± 1.0), were divided into a stress fracture group and a control group. We measured the subjects’ physical characteristics (height, weight, body mass index, and body fat) and bone architecture was evaluated using quantitative ultrasound. Bone alkaline phosphatase, N-telopeptide cross-link of type I collagen, tartrate-resistant acid phosphatase 5b (TRAP-5b), homocysteine, and pentosidine were measured from blood samples obtained from all subjects.

Results

No significant difference was observed between groups with respect to height, weight, body mass index, and body fat, as well as quantitative ultrasound. Further, there were no significant differences in the levels of bone alkaline phosphatase, N-telopeptide cross-link of type I collagen, or TRAP-5b between stress fracture and control groups in all subjects and in male subjects. However, a significant increase in TRAP-5b level was observed in the stress fracture group compared with the control in the female subjects (409.9 ± 209.3 and 318.6 ± 81.6 mU/dL, respectively; P < 0.05). Homocysteine and pentosidine did not differ between groups.

Conclusion

These results suggest that osteoclast activity of female athletes with stress fractures may be enhanced by TRAP-5b.

The association between plasma homocysteine levels, methylation capacity and incident osteoporotic fractures

BACKGROUND

An elevated level of plasma homocysteine (Hcy) is a known risk factor for osteoporotic fractures. In addition, Hcy is related to DNA-methylation metabolism. To determine whether the association between Hcy and fractures is explained by an altered methylation capacity, we investigated the associations between levels of s-adenosylmethionine (SAM) and S-adenosylhomocysteine (SAH) and fracture risk.

METHODS

We studied 503 females aged 55 years and over from the Rotterdam Study (RS) in whom plasma Hcy, SAM and SAH levels were measured. Bone mineral density (BMD) at the hip was assessed using DXA. Incident fractures were recorded over a mean period of 7.0 years. Cox proportional hazards analysis and linear regression were used to assess relationships between plasma metabolite levels, incident osteoporotic fractures and BMD.

RESULTS

Over a total of 3502 person-years of follow-up, 103 subjects sustained at least one osteoporotic fracture. Whereas incidence of osteoporotic fractures was associated with quartiles of Hcy (p=0.047), it was not associated with quartiles of SAM, SAH or SAM/SAH-ratio (all p for trend>0.6). Stepwise linear regression showed that SAM/SAH-ratio, but not Hcy, was independently associated with hip BMD (β=0.073, p=0.025).

CONCLUSION

Since SAM, SAH and SAM/SAH-ratio were not associated with osteoporotic fractures, alterations in methylation capacity most likely do not appear to be an important factor in the association between Hcy and fractures.

Skin advanced glycation end-product accumulation is negatively associated with calcaneal osteo-sono assessment index among non-diabetic adult Japanese men

This study aims to determine the relationship between advanced glycation end-product (AGE) accumulation in skin tissue and bone strength, assessed by quantitative ultrasound, among healthy adult Japanese men. The results of the study suggest that men with higher AGE accumulation in skin tissue have a lower osteo-sono assessment index.

INTRODUCTION

AGE accumulate in bone collagen with age and diabetes and decrease the mechanical properties of bone. Although increased AGE levels are associated with fractures among diabetic patients and elderly women, it is unclear whether a relationship between increased AGE levels and bone strength is present in apparently healthy adult males. The aim of this study was to determine the relationship between AGE accumulation in tissue and the mechanical properties of bone among adult Japanese men, using quantitative ultrasound as a surrogate measure of the latter.

METHODS

Skin autofluorescence (AF), which is a noninvasive method for measuring tissue AGEs, and osteo-sono assessment index (OSI), which is determined by quantitative ultrasound, were measured in 193 adult Japanese men (median age 43 years; interquartile range 37.0-55.0 years).

RESULTS

Adjusted for age, BMI, calcium intake, physical activity, smoking status, and education level, log-transformed skin AF had a negative association with log-transformed OSI (β = -0.218, P < 0.01). Adjusted geometric means (95% CI) for OSI across the tertiles of skin AF were 2.81 (2.75-2.87) for the lowest tertile, 2.81 (2.74-2.87) for the middle tertile, and 2.66 (2.61-2.73) for the highest tertile; thus, OSI for the highest skin AF appeared to be 5.0% lower than that for the lowest and middle skin AF tertiles (P < 0.01).

CONCLUSION

Among apparently healthy adult Japanese men, those with higher skin AF had a lower OSI, indicating a relationship between AGE accumulation and bone strength. A long-term prospective study is required to clarify the causality.

Urinary pentosidine and plasma homocysteine levels at baseline predict future fractures in osteoporosis patients under bisphosphonate treatment

To clarify what kind of risk factors predict incident fractures in patients treated with bisphosphonates, the authors investigated the relationship between baseline characteristics and incident vertebral fracture in Japanese osteoporosis patients undergoing bisphosphonate treatment. This was a multi-center follow-up study conducted at three centers, in which a total of 251 Japanese patients with osteoporosis (mean age 70.5 years) from the three centers were followed for 3.2 ± 2.0 years. Baseline data, including pre-existing fractures, bone mineral density in the lumbar spine (LBMD), bone metabolic markers, urinary pentosidine, and plasma homocysteine, were evaluated. Changes in LBMD, bone turnover markers, and incident fractures after the treatment were followed. Sixty-one patients developed incident vertebral fractures; this group of patients was older and had lower LBMD, a higher prevalent vertebral fracture number, and higher homocysteine and pentosidine levels than patients who did not develop incident vertebral fractures. Changes in LBMD, urinary N-terminal telopeptides of type I collagen (NTX), and bone-derived alkaline phosphatase showed no significant association with the occurrence of vertebral fractures. Cox's proportional hazard model demonstrated that age, prevalent fracture, pentosidine, and homocysteine were independent predictors of the incident vertebral fracture rate under bisphosphonate treatment. Higher baseline levels of pentosidine and homocysteine in osteoporosis patients are potential risk factors for incident vertebral fractures when these patients are treated with bisphosphonates. Further clarification is needed to explain why such patients have higher fracture susceptibility.

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.

Raloxifene ameliorates detrimental enzymatic and nonenzymatic collagen cross-links and bone strength in rabbits with hyperhomocysteinemia

We demonstrate a reduction in enzymatic divalent immature and trivalent pyridinium cross-links and an increase in the nonenzymatic cross-link, pentosidine (Pen), in rabbits with methionine (Met)-induced hyperhomocysteinemia. Such detrimental cross-link formation in bone was ameliorated by raloxifene (RLX) treatment.

INTRODUCTION

Collagen cross-links are determinants of bone quality. Homocysteine (Hcys) interferes with collagen cross-linking. Because RLX is thought to ameliorate bone quality, we investigated whether RLX ameliorated hyperhomocysteinemia-induced cross-link abnormalities using a Met-rich diet rabbit model.

METHODS

We divided New Zealand white rabbits into six groups (n = 6 per group): baseline control, sham operation, sham + 1% Met diet, ovariectomy (OVX), 1% Met diet + OVX, OVX + RLX (10 mg/kg/day), and 1% Met diet + OVX + RLX. RLX was administered for 16 weeks. We measured the amount of enzymatic immature and mature pyridinium cross-links and the nonenzymatic cross-link, Pen, and correlated the cross-link content to bone strength.

RESULTS

Hcys levels were significantly higher in the Met diet groups than in the normal diet groups. Met-fed rabbits with or without OVX showed a significant reduction of enzymatic cross-links, whereas an increase in Pen was observed in Met-fed rabbits with OVX. The cross-link content of the RLX-treated Met-fed rabbits with OVX was restored to similar levels as the sham group, accompanied by an improvement of bone strength.

CONCLUSION

These results demonstrate that hyperhomocysteinemia reduced bone strength via a reduction of enzymatic cross-links and an increase of nonenzymatic cross-links. RLX may ameliorate hyperhomocysteinemia-induced detrimental cross-linking in rabbits with OVX and may improve bone strength via the amelioration of collagen cross-links.

Collagen cross-links as a determinant of bone quality: a possible explanation for bone fragility in aging, osteoporosis, and diabetes mellitus

Collagen cross-linking, a major post-translational modification of collagen, plays important roles in the biological and biomechanical features of bone. Collagen cross-links can be divided into lysyl hydroxylase and lysyloxidase-mediated enzymatic immature divalent cross-links,mature trivalent pyridinoline and pyrrole cross-links, and glycation- or oxidation-induced non-enzymatic cross-links(advanced glycation end products) such as glucosepane and pentosidine. These types of cross-links differ in the mechanism of formation and in function. Material properties of newly synthesized collagen matrix may differ in tissue maturity and senescence from older matrix in terms of crosslink formation. Additionally, newly synthesized matrix in osteoporotic patients or diabetic patients may not necessarily be as well-made as age-matched healthy subjects. Data have accumulated that collagen cross-link formation affects not only the mineralization process but also microdamage formation. Consequently, collagen cross-linking is thought to affect the mechanical properties of bone. Furthermore,recent basic and clinical investigations of collagen cross-links seem to face a new era. For instance, serum or urine pentosidine levels are now being used to estimate future fracture risk in osteoporosis and diabetes. In this review, we describe age-related changes in collagen cross-links in bone and abnormalities of cross-links in osteoporosis and diabetes that have been reported in the literature.

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.