Bone mineral density of the lumbar spine is associated with TNF gene polymorphisms in early postmenopausal Japanese women

Ovariectomy Activates Chronic Low-Grade Inflammation Mediated by Memory T Cells, Which Promotes Osteoporosis in Mice

The loss of estrogen (E₂ ) initiates a rapid phase of bone loss leading to osteoporosis in one-half of postmenopausal women, but the mechanism is not fully understood. Here, we show for the first time how loss of E₂ activates low-grade inflammation to promote the acute phase of bone catabolic activity in ovariectomized (OVX) mice. E₂ regulates the abundance of dendritic cells (DCs) that express IL-7 and IL-15 by inducing the Fas ligand (FasL) and apoptosis of the DC. In the absence of E₂ , DCs become long-lived, leading to increased IL-7 and IL-15. We find that IL-7 and IL-15 together, but not alone, induced antigen-independent production of IL-17A and TNFα in a subset of memory T cells (T_MEM ). OVX of mice with T-cell-specific ablation of IL15RA showed no IL-17A and TNFα expression, and no increase in bone resorption or bone loss, confirming the role of IL-15 in activating the T_MEM and the need for inflammation. Our results provide a new mechanism by which E₂ regulates the immune system, and how menopause leads to osteoporosis. The low-grade inflammation is likely to cause or contribute to other comorbidities observed postmenopause. © 2020 American Society for Bone and Mineral Research.

Important gene-gene interaction of TNF-α and VDR on osteoporosis in community-dwelling elders

Gene effects on osteoporosis have been studied separately and may have been masked by gene–gene and gene–environment interactions. We evaluated gene–gene and gene–physical activity interactions of the variants of tumor necrosis factor-α (TNF-α) and vitamin D receptor (VDR) genes on osteoporosis. A total of 472 elders were included. Seven variants (TNF-α: rs1799964, rs1800629, rs3093662; VDR: rs7975232, rs1544410, rs2239185, rs3782905) were genotyped. Bone mineral densities of the lumbar spine, femoral neck, and total hip were measured by dual-energy X-ray absorptiometry. Predictive models’ ability to discriminate osteoporosis status was evaluated by areas under the receiver operating characteristics (AUROC) curve. After multivariable adjustment, significant interactions of TNF-α rs1800629 and VDR rs3782905 were observed on overall and lumbar spine osteoporosis. In elderly women, we found that those carrying the CG/CC genotype of VDR rs3782905 were significantly associated with increased odds of overall osteoporosis compared with those carrying the GG genotype of VDR rs3782905 among those carrying TNF-α rs1800629 GG genotype. The adjusted odds ratios (ORs) for VDR rs3782905 CG/CC genotype in elderly women carrying TNF-α rs1800629 AG/AA and GG genotypes were 0.1 (0.01, 0.98) and 3.54 (1.51, 8.30), respectively. We observed significant differences in AUROCs between the model with traditional covariates plus variants and their interaction term and the model with traditional covariates only (AUROCs: 0.77 and 0.81; p = 0.028). Although the sample size of this study may have been relatively small, our results suggest that the interaction of the CG/CC genotype of VDR rs3782905 with TNF-α rs1800629 GG genotype was associated with increased odds of overall and lumbar spine osteoporosis in elderly women.

The associations of TNF-α gene polymorphisms with bone mineral density and risk of osteoporosis: A meta-analysis

OBJECTIVE

Fracture is a common consequence of osteoporosis and is associated with high morbidity and mortality. Recently, increasing evidence has suggested that polymorphisms in tumor necrosis factor-α (TNF-α) gene were associated with osteoporosis risk and bone mineral density (BMD), but results remain conflicting. We herein performed a meta-analysis based on evidence currently available from the literature to make a more precise estimation of these relationships.

METHODS

The PubMed, EMBASE, Cochrane Library, CNKI (China National Knowledge Infrastructure) and Wan Fang databases were searched for eligible studies. Articles meeting the inclusion criteria were comprehensively reviewed and all available data were accumulated. The pooled odds ratios (ORs) or mean differences (MDs) and corresponding 95% confidence intervals (CIs) were applied to assess the strength of the relationships.

RESULTS

A total of 15 studies involving 5273 subjects were included in our meta-analysis. The GG genotype of TNF-α G308A was associated with an increased risk of osteoporosis under a mutant model (GG vs GA+AA: OR = 0.63, 95% CI: 0.51-0.77, P < 0.0001, I²  = 31%). Additionally, we also observed a significant association between G308A polymorphism and BMD of lumbar spine (AA vs GG: P = 0.01, I²  = 53%). However, TNF-α T1031C, C857T and C863A polymorphisms had no obvious impacts on osteoporosis risk.

CONCLUSIONS

The present meta-analysis demonstrated that TNF-α G308A polymorphism may act as a potential candidate biomarker for screening, diagnosis, and treatment of osteoporosis, which will help improve individualized therapy of osteoporosis patients in clinics.

Associations of TNF-α and IL-6 polymorphisms with osteoporosis through joint effects and interactions with LEPR gene in Taiwan: Taichung Community Health Study for Elders (TCHS-E)

Osteoporosis (OST) is a complex multifactorial disease considered to result from interactions of multiple gene and environmental factors. Tumor necrosis factor (TNF)-α and interleukin (IL)-6 are pleiotropic cytokines essential for bone remodeling; and hormone leptin has immunomodulatory effects that stimulate the synthesis of IL-6 and TNF-α. Leptin is involved in the modulation of bone growth and turnover; and its actions are bound by leptin receptor (LEPR). Prior studies evaluated the effects of TNF-α, IL-6, and LEPR gene polymorphisms separately on bone mineral densities (BMD) or OST. In this study, we assessed the roles of TNF-α and IL-6 gene polymorphisms in OST through joint effects and interactions with LEPR gene. We also evaluated possible joint effects and interactions between these polymorphisms and physical activity. Ten tag-SNPs (rs1799964, rs1800629, rs3093662 in TNF-α; rs1880243, rs1800796, rs1554606 in IL-6; and rs1751492, rs8179183, rs1805096, rs1892534 in LEPR) were used to genotype 103 OST cases and 369 controls. BMD of lumbar spine (LS), femoral neck (FN), and total hip (TH) were measured by dual-energy X-ray absorptiometry. Our data showed that TNF-α and IL-6 polymorphisms were associated with overall and site-specific OST in both sexes, and that these associations were dependent on rs1805096 and rs1892534 genotypes of LEPR. In men, LEPR A-G-G-G haplotype was associated with FN OST (OR 4.65, 95 % CI 1.61-13.40, p = 0.004). Genotype AA/AG of LEPR rs1751492 was associated with overall and FN OST in women without physical activity, but not in women with physical activity (p < 0.05 for interaction between physical activity and LEPR rs1751492). In men, we detected significant interactions of IL-6 rs1800796 with LEPR rs1805096 and rs1892534 for FN and TH OST (all p < 0.05). Our data indicate that LEPR gene may play joint and interactive roles with TNF-α and IL-6 genes and physical inactivity in development of OST. Haplotype analyses revealed that the correlations tended to be prominent in men with FN OST.

TNF-α and IL10 gene polymorphisms in women with postmenopausal osteoporosis

OBJECTIVE

Postmenopausal osteoporosis is a common disorder characterized by decreased bone mineral density (BMD). Proinflammatory cytokines are among the significant factors involved in bone turnover. They are the stimulants of bone resorption, acting directly on osteoclasts and osteoclast precursors. In this study, we examined the TNF-α (-308G>A) (rs1800629) and IL10 (-1082G>A) (rs1800896), (-592C>A) (rs1800872) polymorphisms in postmenopausal women with BMD T-scores less than and greater than or equal to -2.5 SD.

STUDY DESIGN

This study included 224 postmenopausal women with BMD T-scores lower than -2.5 SD (mean: -3.02±0.53) and 238 postmenopausal women with BMD T-scores -2.5 SD and greater (mean: -1.33±0.51).

RESULTS

There was a decrease in the frequency of IL10 1082 G allele carriers (GG and GA genotypes) in women with T-scores below -2.5 SD (GG+GA vs AA: OR=0.65, 95% CI=0.44-0.97, p=0.037). With regard to the TNF-α -308 G>A polymorphism, in the women with T-scores below -2.5 SD, the increased frequency of GG homozygotes and G allele carriers was detected (AA+GA vs GG: OR=0.54, 95% CI=0.35-0.82, p=0.004).

CONCLUSIONS

The results of our study suggest an association between TNF-α -308G>A and IL10 -1082G>A polymorphisms and postmenopausal osteoporosis.

Changes of serum cytokines-related Th1/Th2/Th17 concentration in patients with postmenopausal osteoporosis

BACKGROUND

Postmenopausal osteoporosis is now hypothetically considered to be an autoimmune and inflammatory process in which many pro-inflammatory and T cell-derived cytokines play important roles in the loss of bone mass. For instance, interleukin-2 (IL-2), interferon-γ (IFN-γ), and tumor necrosis factor-α (TNF-α) secreted by Th1 and IL-6, IL-4, and IL-10 secreted by Th2 have been shown to be involved in the pathogenesis of osteoporosis. Interleukin-17 (IL-17) is a characteristic cytokine secreted by Th17 cells of the CD4 + subgroup. Although IL-17 has been shown to enhance bone resorption in ovariectomized mouse model, bone cells and genetic research, human-related studies of IL-17 are few.

METHODS

According to WHO classification of osteoporosis by the T scores of BMD, the subjects were divided into the postmenopausal osteoporosis group (T scores≤-2.5), the postmenopausal osteopenia group (-2.5 < T scores<-1), and the postmenopausal normal BMD group (T scores≥-1); 30 subjects in each group. Cytometric bead array (CBA) technique was employed for serum determination of the primary indexes including IL-17A, IL-2, IFN-γ, TNF-α, IL-6, IL-4, and IL-10 concentrations in the 90 volunteers. In the meantime, serum calcium, phosphorus, magnesium, and alkaline phosphatase concentrations were also determined in the patients. One-way analysis of variance (one-way ANOVA) was employed in data analysis to determine whether the testing results of various parameters had significant differences. The bivariate correlation was tested with the Pearson correlation coefficient. When p < 0.05, the difference was considered to have statistical significance.

RESULTS

Serum IL-17A concentration was significantly higher in the postmenopausal osteoporosis group than in the postmenopausal osteopenia group and the postmenopausal normal BMD group, but the difference between the postmenopausal osteopenia group and the postmenopausal normal BMD group had no statistical significance. IL-17A was negatively correlated with BMD. To our knowledge, we discovered for the first time that serum concentrations of IFN-γ and IL-4 were significantly lower in the postmenopausal osteoporosis group than in the postmenopausal normal BMD group; IFN-γ and IL-4 were positively correlated with BMD. In addition, we also determined that BMI was negatively correlated with BMD; IL-17A was positively correlated with serum calcium. However, no significant differences in IL-6, TNF-α, IL-2, and IL-10 were observed among the three groups; these three factors were not correlated with BMD.

CONCLUSIONS

Our experiments have confirmed the roles of IL-17 in the pathogenesis of postmenopausal osteoporosis and in the promotion of bone resorption. Targeted therapy of IL-17, IFN-γ, and IL-4 may be beneficial in the treatment of patients with postmenopausal osteoporosis. Our experiments have also confirmed the roles of IFN-γ and IL-4 in the pathogenesis of postmenopausal osteoporosis and in the inhibition of bone resorption.

HDL cholesterol and bone mineral density: is there a genetic link?

Overwhelming evidence has linked cardiovascular disease and osteoporosis, but the shared root cause of these two diseases of the elderly remains unknown. Low levels of high density lipoprotein cholesterol (HDL) and bone mineral density (BMD) are risk factors for cardiovascular disease and osteoporosis respectively. A number of correlation studies have attempted to determine if there is a relationship between serum HDL and BMD but these studies are confounded by a number of variables including age, diet, genetic background, gender and hormonal status. Collectively, these data suggest that there is a relationship between these two phenotypes, but that the nature of this relationship is context specific. Studies in mice plainly demonstrate that genetic loci for BMD and HDL co-map and transgenic mouse models have been used to show that a single gene can affect both serum HDL and BMD. Work completed to date has demonstrated that HDL can interact directly with both osteoblasts and osteoclasts, but no direct evidence links bone back to the regulation of HDL levels. Understanding the genetic relationship between BMD and HDL has huge implications for understanding the clinical relationship between CVD and osteoporosis and for the development of safe treatment options for both diseases.

Association between polymorphisms in tumor necrosis factor (TNF) and TNF receptor genes and circulating TNF, soluble TNF receptor levels, and bone mineral density in postmenopausal Korean women

OBJECTIVE

The aim of the present study was to investigate the relationship of polymorphisms in the tumor necrosis factor (TNF)-alpha, TNF-beta, and TNF receptor (TNFR) genes to circulating TNF, soluble TNFR (sTNFR) levels, and bone mineral density (BMD) in women.

METHODS

The TNF-alpha G(-308)A, C(-857)T, C(-863)A, T(-1031)C, TNF-beta A252G, TNFRI A36G, TNFRII T676G, A1663G, A1668G, and C1690T polymorphisms were analyzed in 377 postmenopausal Korean women. The levels of serum TNF-alpha, TNF-beta, sTNFRI, sTNFRII, and bone turnover markers were measured. BMD was examined by dual energy x-ray absorptiometry.

RESULTS

After adjustment for age, body mass index, and years since menopause, no significant differences in BMD of the lumbar spine and femoral neck and serum levels of bone turnover markers were detected, according to single polymorphisms in TNF and TNFR genes and combined polymorphisms. However, the frequencies of the TT genotype of TNF-alpha T(-1031)C polymorphism, the non-AA genotype of TNF-beta A252G polymorphism, and the GG genotype of TNFRII A1663G polymorphism were significantly higher in osteoporotic women than in women with normal BMD, respectively (P < 0.05). The TNFRII T676G polymorphism affected the serum sTNFRI and sTNFRII levels. The serum sTNFRII levels in the CC genotype of TNFRII C1690T polymorphism were the highest, with a G or C allele dose effect, and the TNFRII G676C/C1690T haplotype genotype also affected serum sTNFRII levels.

CONCLUSIONS

TNF-alpha T(-1031)C, TNF-beta A252G, and TNFRII A1663G polymorphisms may be genetic factors for osteoporosis in Korean postmenopausal women, and the TNFRII T676G and C1690T polymorphisms and their combined polymorphism affected serum sTNFRII levels. The TNFRII T676G polymorphism also affected the serum sTNFRI levels.

Quantitative trait loci, genes, and polymorphisms that regulate bone mineral density in mouse

This is an in silico analysis of data available from genome-wide scans. Through analysis of QTL, genes and polymorphisms that regulate BMD, we identified 82 BMD QTL, 191 BMD-associated (BMDA) genes, and 83 genes containing known BMD-associated polymorphisms (BMDAP). The catalogue of all BMDA/BMDAP genes and relevant literatures are provided. In total, there are substantially more BMDA/BMDAP genes in regions of the genome where QTL have been identified than in non-QTL regions. Among 191 BMDA genes and 83 BMDAP genes, 133 and 58 are localized in QTL regions, respectively. The difference was still noticeable for the chromosome distribution of these genes between QTL and non-QTL regions. These results have allowed us to generate an integrative profile of QTL, genes, polymorphisms that determine BMD. These data could facilitate more rapid and comprehensive identification of causal genes underlying the determination of BMD in mouse and provide new insights into how BMD is regulated in humans.

SNP ID-info: SNP ID searching and visualization platform

Many association studies provide the relationship between single nucleotide polymorphisms (SNPs), diseases and cancers, without giving a SNP ID, however. Here, we developed the SNP ID-info freeware to provide the SNP IDs within inputting genetic and physical information of genomes. The program provides an "SNP-ePCR" function to generate the full-sequence using primers and template inputs. In "SNPosition," sequence from SNP-ePCR or direct input is fed to match the SNP IDs from SNP fasta-sequence. In "SNP search" and "SNP fasta" function, information of SNPs within the cytogenetic band, contig position, and keyword input are acceptable. Finally, the SNP ID neighboring environment for inputs is completely visualized in the order of contig position and marked with SNP and flanking hits. The SNP identification problems inherent in NCBI SNP BLAST are also avoided. In conclusion, the SNP ID-info provides a visualized SNP ID environment for multiple inputs and assists systematic SNP association studies. The server and user manual are available at http://bio.kuas.edu.tw/snpid-info.

The bare bones of race

In this paper I examine claims of racial difference in bone density and find that the use and definitions of race in medicine lack a theoretical foundation. My central argument is that the social produces the biological in a system of constant feedback between body and social experience. By providing a different angle of vision on claimed racial differences I hope to move the conversation away from an ultimately futile discussion of nature versus nurture, where time is held constant and place seen as irrelevant, and begin to build a new paradigm for examining the contributions of geographic ancestry, individual lifecycle experience, race, and gender to varied patterns of health and disease.

Assessment of laboratory measurements and -308 TNFalpha gene promoter polymorphisms in normal bone mineral density

The aim of this study was to identify and evaluate laboratory parameters associated with normal bone mineral density (BMD) and to test if -308 tumour necrosis factor (TNF) alpha gene promoter polymorphisms could influence BMD. We performed a comparative cross-sectional study of four main groups: young healthy individuals (20-30 years); subjects aged 50 years or over with normal BMD; osteoporotic subjects aged 50 years or over; osteoporotic women with active rheumatoid arthritis. Variables assessed included anthropometric features, diet intake, lifestyle, calcium-phosphorus balance, markers of bone turnover, sexual hormones, hormones related with body mass and growth, cytokines involved in inflammation and bone turnover, and -308 TNF alpha gene promoter polymorphisms. One hundred fifty-nine subjects were evaluated. Across the four groups, zinc serum levels were higher in men as compared to women. In addition, zinc serum levels were also higher in individuals with normal BMD as compared to osteoporotic subjects. Serum calcium levels were higher in normal BMD group. On the other hand, follicle-stimulating hormone (FSH) and luteinizing hormone (LH) levels were significantly higher in normal bone mass postmenopausal women and men as compared to age-matched osteoporotic groups. Finally, leptin was significantly lower in men, after correcting these results for body mass index values. The remaining variables assessed had a similar distribution among the different studied groups. In our population, low serum levels of leptin and high serum levels of zinc, calcium, FSH, and LH were associated with a higher BMD.

Vertebral body integrity: a review of various anatomical factors involved in the lumbar region

The body of the vertebra can be affected in the majority of the conditions involving the lumbar spine. Multiple references, both books and periodicals, have been reviewed, and the anatomical factors responsible for the vertebral body integrity in the lumbar spine have been included under the following important areas, namely, morphology, development, genetics, microscopic examination using histology, structural architecture, blood supply, neuromuscular control, and biomechanics.

INTRODUCTION

The anatomy provides a three-dimensional frame work to support the interaction between the physiological and pathological alterations. The body of the vertebra can be affected in a majority of acute or chronic conditions involving the lumbar spine. The etiology of these conditions is multifactorial, which has been dealt with in previous studies sporadically. This study aims to review and incorporate the important anatomical factors which can influence the integrity of vertebral bodies in the lumbar region and manifest as low back pain.

METHODS

Multiple references, both books and periodicals, have been reviewed for the literature. Electronic databases, including Medline and PubMed, were used to collect the latest information. They were finally arranged in an anatomical framework for the article. An attempt has been made to cover these relevant issues in an integrated way in the article and have been structured into introduction, morphology, development, genetics, microscopic examination using histology, structural architecture, blood supply, neuromuscular control, biomechanics, and conclusion. The aforementioned anatomical aspects, some of which have received less attention in the literature, may be helpful to clinicians for restoring the mobility, stability, and load bearing capacity of the lumbar spine as well as planning better management strategies, especially for the chronic low back pain.

RESULTS

In our article all the anatomical factors affecting the integrity of vertebral body, including the morphology, development, genetics, growth and ossification, blood supply, specifically in the lumbar region, have been described, which were not covered earlier. The limitations of this review is its wide dimensions; hence, there are fair scopes of missing many relevant facts, as all of them cannot be compiled in a single article. We have attempted to confine our views to different anatomical domains only, this is our second limitation. Additional studies are required to incorporate and discuss the uncovered relevant scientific details.

CONCLUSIONS

The integrity of the body of the lumbar vertebra is multifactorial (Fig. 8). The vast spectrum of the anatomical domain influencing it has been summarized. The evolution of erect posture is a landmark in the morphology of human beings and the lumbar lordosis, which has also contributed to the gross design of the vertebral body, is one of the most important adaptations for axial loading and bipedal movements. The role of metamerism in the evolution of vertebrate morphology is repeated in the development of spine. The body of the vertebra is intersegmental in origin, which results in dual vascular and nerve supply, both from superior and inferior aspects of the body of the lumbar vertebrae. The vertebral body ossifies from three primary centers, one for centrum, which will form the major portion of body, and the other two for neural arches. The cartilaginous growth plate is mainly responsible for the longitudinal vertebral growth. Regional differentiation of the vertebral column, and the definite pattern of the structure of the different vertebra, is regulated by a large number of genetic factors, including the Hox genes. The vertebral body design therefore provides the requirements for optimal load transfer by maximal strength with minimal weight. Bone mineral density (BMD), bone quality, microarchitecture, and material properties are the important factors that contribute to bone strength. BMD is highly heritable; bone mineral distribution and architecture are also shown to be under strong genetic influence. All the aforementioned factors finally integrate to ensure mainly the mobility, stability, and load bearing capacity of the lumbar spine.

Tumor necrosis factor-alpha haplotype is strongly associated with bone mineral density in patients with Crohn's disease

BACKGROUND AND AIM

There is limited consensus on the major variables that determine bone integrity and bone loss in patients with Crohn's disease. Twin and family studies in the general population indicate that up to 85% of variance in bone mineral density is inherited. The aim was to determine the prevalence of bone loss and both molecular and clinical risk factors for bone loss in a large Crohn's disease population.

METHODS

This was a cross-sectional study of 304 patients with Crohn's disease attending the Inflammatory Bowel Disease unit at Royal Brisbane and Women's Hospital, Queensland. The results of bone density testing were ascertained directly and by a mailed questionnaire. Bone mineral density data were combined with clinical information and correlated with single nucleotide polymorphisms within the tumor necrosis factor-alpha (TNF-alpha), interleukin-10, and NOD2/CARD15 genes.

RESULTS

Of 304 Crohn's disease patients, 101 had undergone previous bone density testing. Forty-five patients (45%) had been diagnosed with osteopenia and 18 (18%) were osteoporotic. After multivariate analysis, both the TNF-alpha GT haplotype and the -857 CC genotype showed strong associations with bone mineral density overall (P = 0.003 and P = 0.002, respectively). Body mass index (P = 0.01) and previous bowel resection in female patients (P = 0.03) were predictive of a higher spine bone density, while body mass index (P = 0.003) and the effect of years since first bowel resection (P = 0.02) remained independent predictors of proximal femur bone mineral density. There were no other significant associations observed.

CONCLUSIONS

This study has identified a novel protective association between a TNF-alpha haplotype and bone mineral density in Crohn's disease. It confirms the important influence of body mass index and intestinal resection on bone loss in this population.

Polymorphisms in pro- and anti-inflammatory cytokine genes and susceptibility to atherosclerosis: a pathological study of 1503 consecutive autopsy cases

Atherosclerosis is a chronic inflammatory disease in the intima of the arterial wall, where cytokines play a crucial role in the pathogenesis of this disease. However, the question of whether or not genetic variations in the cytokine genes could influence the development of atherosclerosis has been poorly investigated. We investigated the relationship of nine common single-nucleotide polymorphisms (SNPs) in tumor necrosis factor-alpha (TNF-alpha), interleukin (IL)-1beta, IL-10, IL-4 and transforming growth factor (TGF)-beta1 with the atherosclerotic severity in 10 different arteries based on 1503 consecutive autopsies of elderly Japanese subjects registered in the Japanese SNPs for geriatric research (JG-SNP) study. The -1031C allele of TNF-alpha was a significant protective factor for atherogenesis in the carotid, femoral and intracranial arteries [odds ratio (OR): 0.72, 0.73 and 0.70, respectively]. The -511T of IL-1beta and the +29T of TGF-beta1 were significant risk factors for atherogenesis in the subclavian and intracranial arteries (OR: 1.35 and 1.48, respectively). In contrast, conventional risk factors for atherogenesis, such as hypertension and diabetes mellitus, conferred independent risks for almost all arteries. Functional SNPs in TNF-alpha, IL-1beta and TGF-beta1 genes play a role in atherogenesis, although their influences are less pronounced than those of conventional risk factors and appear to be limited to specific arteries in the Japanese elderly.

Molecular genetic studies of gene identification for osteoporosis: a 2004 update

This review summarizes comprehensively the most important and representative molecular genetics studies of gene identification for osteoporosis published up to the end of December 2004. It is intended to constitute a sequential update of our previously published review covering the available data up to the end of 2002. Evidence from candidate gene association studies and genome-wide linkage studies in humans, as well as quantitative trait locus mapping animal models are reviewed separately. Studies of transgenic and knockout mice models relevant to osteoporosis are summarized. An important extension of this update is incorporation of functional genomic studies (including DNA microarrays and proteomics) on osteogenesis and osteoporosis, in light of the rapid advances and the promising prospects of the field. Comments are made on the most notable findings and representative studies for their potential influence and implications on our present understanding of genetics of osteoporosis. The format adopted by this review should be ideal for accommodating future new advances and studies.

Gene polymorphisms involved in the regulation of bone quality

Osteoporotic fractures in subjects at advanced age constitute a tremendous and growing problem. Established lifestyle risk factors can explain only a modest proportion of the liability to osteoporotic fractures. Bone mineral density (BMD) is considered the best established risk factor for osteoporotic fractures. The importance of genetic factors in the quality of bone is substantial, but no consensus exists yet on the genes that are involved. However, concomitant diseases, balance disorders and lifestyle habits are more important for fractures in elderly subjects. The abundance of common sequence variations, so-called polymorphisms, in the human genome and their high frequency in the population have made them targets to explain variation in the risk. Some genes have been identified that appear to be involved in the regulation of bone mass and in the pathogenesis of osteoporosis. Among these are those coding for the two estrogen receptors (ERalpha and ERbeta), the androgen receptor (AR) and the vitamin D receptor (VDR). In addition, enzymes involved in the biogenesis of estrone and estradiol have attracted attention as well as polymorphisms in the regulatory region of the type I collagen gene, COLIA1, affecting the binding site for the transcription factor Specificity protein 1 (Sp1). Although evidence suggests that the quality of bone is determined to a large extent by genetic factors, research so far has not been able to unequivocally identify genes involved in this matter. Over the last years a large number of studies have pointed to the variability in many genes and their relation with BMD, bone-related symptoms or specific therapies. The findings emphasize the complexity of the genetics of bone mass and bone loss.

ALDH2 polymorphisms and bone mineral density in an elderly Japanese population

INTRODUCTION

Osteoporosis is a multifactorial genetic disease which greatly increases the risk of bone fracture in elderly persons.

METHODS

Four hundred and three recipients of a community health screening program were examined for the presence/absence of osteoporosis and 11 kinds of gene polymorphisms as a means of determining the relation between these gene polymorphisms and osteoporosis. The gene polymorphisms screened were: alcohol sensitivity-associated polymorphisms of alcohol dehydrogenase (ADH2) Arg47His, aldehyde dehydrogenase (ALDH2) Glu487Lys, smoking sensitivity-associated polymorphisms of glutathione S transferase (GST) M1, (GST)T1, NAD(P)H quinone oxidoreductase 1 (NQO1) C609T, inflammation-associated polymorphisms of interleukin-1beta (IL-1B)T-31C, tumor necrosis factor alpha (TNF-alpha) T-1031C, endothelial constitutive nitric oxide synthase (ecNOS) Glu298Asp, longevity-associated polymorphism of mitochondrial DNA (mtDNA) 5178 A/C, allergy-associated polymorphism of interleukin-4 (IL-4), and immunity-associated polymorphism of CD14.

RESULTS

A significant association was found between the ALDH2Glu478Lys gene polymorphisms and osteoporosis. In the osteoporosis group of patients, a significant difference was noted between the Lys/Lys group and the group comprising Glu/Lys and Glu/Glu groups (namely, the genotypes including Glu alleles). In the Lys/Lys group, after age, sex, BMI, smoking history and alcohol consumption history had been adjusted for, the morbidity rate was significantly elevated [odds ratio (OR): 3.33; 95% confidence interval (95% CI): 1.28-8.71; p=0.014], and the effect was even more evident in the sub-group of women with osteoporosis (OR: 4.31; 95% CI: 1.24-14.92; p=0.021).

CONCLUSIONS

The present results suggest that active prophylactic interventions such as dietary, exercise, and pharmacological therapies should be offered to non-carriers of the Glu allele (Lys/Lys).

Haplotyping of TNFalpha gene promoter using melting temperature analysis: detection of a novel -856(G/A) mutation

Tumor necrosis factor alpha (TNFalpha) is a potent cytokine with a wide range of pro-inflammatory activities and plays a critical role in the pathogenesis of a number of infectious, inflammatory, autoimmune, and metabolic diseases. We determined four single-nucleotide polymorphisms (SNPs), -1031(C/T), -863(C/A), -857(C/T), and -308(G/A) in the TNFalpha promoter region using melting temperature analysis, among 1451 geriatric autopsy samples. Two adjacent SNPs, -863(C/A) and -857(C/T), were directly assayed by a single probe reaction, which correctly determined three of four expected haplotypes. Sequence confirmation related that the most rare haplotype (8/2902 chromosomes, frequency: 0.26%) contains a novel mutation of -856(G/A), instead of the predicted haplotype. These results indicate that melting temperature analysis provides a robust method to determine the polymorphisms in the TNFalpha promoter.

Bone loss in Crohn's disease: exercise as a potential countermeasure

Crohn's disease (CD) is associated with a number of secondary conditions including osteoporosis, which increases the risk of bone fracture. The cause of metabolic bone disease in this population is believed to be multifactorial and may include the disease itself and associated inflammation, high-dose corticosteroid use, weight loss and malabsorption, a lack of exercise and physical activity, and an underlying genetic predisposition to bone loss. Reduced bone mineral density has been reported in between 5% to 80% of CD sufferers, although it is generally believed that approximately 40% of patients suffer from osteopenia and 15% from osteoporosis. Recent studies suggest a small but significantly increased risk of fracture compared with healthy controls and, perhaps, sufferers of other gastrointestinal disorders such as ulcerative colitis. The role of physical activity and exercise in the prevention and treatment of CD-related bone loss has received little attention, despite the benefits of specific exercises being well documented in healthy populations. This article reviews the prevalence of and risk factors for low bone mass in CD patients and examines various treatments for osteoporosis in these patients, with a particular focus on physical activity.

Toll-like receptor 9 regulates tumor necrosis factor-alpha expression by different mechanisms. Implications for osteoclastogenesis

CpG oligodeoxynucleotides (CpG-ODNs), mimicking bacterial DNA, stimulate osteoclastogenesis via Toll-like receptor 9 (TLR9) in receptor activator of NF-kappa B ligand (RANKL)-primed osteoclast precursors. This activity is mediated via tumor necrosis factor (TNF)-alpha induction by CpG-ODN. To further reveal the role of the cytokine in TLR9-mediated osteoclastogenesis, we compared the ability of CpG-ODN to induce osteoclastogenesis in two murine strains, BALB/c and C57BL/6, expressing different TNF-alpha alleles. The induction of osteoclastogenesis and TNF-alpha release by CpG-ODN was by far more noticeable in BALB/c-derived than in C57BL/6-derived osteoclast precursors. Unexpectedly, as revealed by Northern analysis, CpG-ODN induction of TNF-alpha mRNA increase was more efficient in C57BL/6-derived cells. The cytokine transcript abundance was increased due to both increased message stability and rate of transcription. The difference between the two cell types was the result of a higher transcription rate in CpG-ODN-induced C57BL/6-derived cells caused by a single nucleotide polymorphism in kappa B2a site within the TNF-alpha promoter sequence. CpG-ODN enhanced the rate of the cytokine translation in BALB/c-derived cells. Thus, CpG-ODN modulated both transcription and translation of TNF-alpha. The induction of transcription was more evident in C57BL/6-derived cells, while the induction of translation took place only in BALB/c-derived osteoclast precursors. Altogether the cytokine was induced to a larger extent in BALB/c-derived osteoclast precursors, consistent with the increased CpG-ODN osteoclastogenic effect in these cells.