Large-scale analysis of association between polymorphisms in the transforming growth factor beta 1 gene (TGFB1) and osteoporosis: the GENOMOS study

Generic Platform for the Multiplexed Targeted Electrochemical Detection of Osteoporosis-Associated Single Nucleotide Polymorphisms Using Recombinase Polymerase Solid-Phase Primer Elongation and Ferrocene-Modified Nucleoside Triphosphates

Osteoporosis is a multifactorial disease influenced by genetic and environmental factors, which contributes to an increased risk of bone fracture, but early diagnosis of this disease cannot be achieved using current techniques. We describe a generic platform for the targeted electrochemical genotyping of SNPs identified by genome-wide association studies to be associated with a genetic predisposition to osteoporosis. The platform exploits isothermal solid-phase primer elongation with ferrocene-labeled nucleoside triphosphates. Thiolated reverse primers designed for each SNP were immobilized on individual gold electrodes of an array. These primers are designed to hybridize to the SNP site at their 3'OH terminal, and primer elongation occurs only where there is 100% complementarity, facilitating the identification and heterozygosity of each SNP under interrogation. The platform was applied to real blood samples, which were thermally lysed and directly used without the need for DNA extraction or purification. The results were validated using Taqman SNP genotyping assays and Sanger sequencing. The assay is complete in just 15 min with a total cost of 0.3€ per electrode. The platform is completely generic and has immense potential for deployment at the point of need in an automated device for targeted SNP genotyping with the only required end-user intervention being sample addition.

Arterial calcification, atherosclerosis and osteoporosis: only clinical associations or a genetic platform?

The review is devoted to the comorbidity of two multifactorial diseases  — atherosclerosis and osteoporosis. Numerous epidemiological, experimental and clinical studies have confirmed the relationship between these diseases based on common risk factors and pathogenetic mechanisms. At the same time, to assess the associations between osteoporosis and atherosclerosis-related cardiovascular diseases, the following surrogate markers are used: vascular calcification, vascular stiffness, bone mineral density. It is known that atherosclerosis and osteoporosis depend on the human genotype, and they are caused by the interaction between the environment and genes. The modifiable risk factors for these diseases are largely similar, and the common features of atherosclerosis and osteoporosis pathogenesis make it possible to formulate the concept of a unified genetic basis of their development. Advances in molecular technology have made it possible to conduct a genome-wide association study (GWAS) and successfully identify genetic markers associated with both atherosclerosis and osteoporosis. The review aim was to describe the genes associated with developing atherosclerosis, arterial calcification and osteoporosis, as well as to provide information on the current understanding of the general genetic basis for plaque formation, vascular calcium deposition, and a decrease in bone mass. The analysis of publications from the PubMed, Medline, Web of Science and Cochrane Library databases since 2000 have been carried out. The article describes the genetic markers associated with atherosclerosis and osteoporosis, as well as considers the achievements in studying genetics of osteoporosis and atherosclerosis-related cardiovascular diseases. In addition, modern approaches and directions for further research of these diseases was established. The review can be useful for medical practitioners to clarify various genetic associations and mechanisms that lead to this comorbidity.

Association of TGF-β1 and IL-10 Gene Polymorphisms with Osteoporosis in a Study of Taiwanese Osteoporotic Patients

Osteoporosis is a rising health threat in the increasingly aging world population. It is a common skeletal disease strongly linked to genetic predisposition. We aim to identify the effects of the anti-inflammatory TGF-β1- and IL-10-specific single-nucleotide polymorphism (SNP) combination on the risk for osteoporosis. We investigated and analyzed the relationships between three TGF-β1 SNPs (-509C/T, +869 T/C and +29T/C), one IL-10 SNP (+1927A/C) and the level of bone mineral density (BMD), as well as the risk of osteoporosis in Taiwanese osteoporotic patients. A total of 217 subjects were recruited, including 88 osteoporotic patients and 129 healthy controls, for SNPs, BMD and clinical characteristics statistical analyses. Females with TGF-β1 SNP (-509 C/C) and IL-10 SNP (+1927 C/C) genotypes showed a great benefit for femoral neck T-scores. However, the combination of TGF-β1 SNP (-509 T/T) and IL-10 SNP (+1927 A/A) genotypes in all subjects showed a significant decrease in total hip BMD T-scores. The TGF-β1 SNP (-509 C/T) genotype in all subjects and TGF-β1 SNP (-509 T/T) and IL-10 SNP (+1927 A/C) genotypes in males showed positive effects on body height. The combination of the many SNPs in the anti-inflammatory TGF-β1 and IL-10 genes may be cooperatively involved in the development of osteoporosis. Our data suggested that the specific SNP combination of TGF-β1 (-509) and IL-10 (+1927) may act as a predictive factor for postmenopausal osteoporosis in Taiwanese women.

Genomic Medicine: Lessons Learned From Monogenic and Complex Bone Disorders

Current genetic studies of monogenic and complex bone diseases have broadened our understanding of disease pathophysiology, highlighting the need for medical interventions and treatments tailored to the characteristics of patients. As genomic research progresses, novel insights into the molecular mechanisms are starting to provide support to clinical decision-making; now offering ample opportunities for disease screening, diagnosis, prognosis and treatment. Drug targets holding mechanisms with genetic support are more likely to be successful. Therefore, implementing genetic information to the drug development process and a molecular redefinition of skeletal disease can help overcoming current shortcomings in pharmaceutical research, including failed attempts and appalling costs. This review summarizes the achievements of genetic studies in the bone field and their application to clinical care, illustrating the imminent advent of the genomic medicine era.

High-throughput and efficient multilocus genome-wide association study on longitudinal outcomes

MOTIVATION

With the emerging of high-dimensional genomic data, genetic analysis such as genome-wide association studies (GWAS) have played an important role in identifying disease-related genetic variants and novel treatments. Complex longitudinal phenotypes are commonly collected in medical studies. However, since limited analytical approaches are available for longitudinal traits, these data are often underutilized. In this article, we develop a high-throughput machine learning approach for multilocus GWAS using longitudinal traits by coupling Empirical Bayesian Estimates from mixed-effects modeling with a novel ℓ0-norm algorithm.

RESULTS

Extensive simulations demonstrated that the proposed approach not only provided accurate selection of single nucleotide polymorphisms (SNPs) with comparable or higher power but also robust control of false positives. More importantly, this novel approach is highly scalable and could be approximately >1000 times faster than recently published approaches, making genome-wide multilocus analysis of longitudinal traits possible. In addition, our proposed approach can simultaneously analyze millions of SNPs if the computer memory allows, thereby potentially allowing a true multilocus analysis for high-dimensional genomic data. With application to the data from Alzheimer's Disease Neuroimaging Initiative, we confirmed that our approach can identify well-known SNPs associated with AD and were much faster than recently published approaches (≥6000 times).

AVAILABILITY AND IMPLEMENTATION

The source code and the testing datasets are available at https://github.com/Myuan2019/EBE_APML0.

SUPPLEMENTARY INFORMATION

Supplementary data are available at Bioinformatics online.

Sp1 Binding Site Polymorphism at COL1A1 Gene and Its Relation to Bone Mineral Density for Osteoporosis Risk Factor Among the Sikkimese Men and Women of Northeast India

Single nucleotide polymorphism in the first intron of Collagen type I alpha 1 (COL1A1) gene which is the binding site of specificity protein 1 (Sp1) transcription factor associated with low bone mineral density and osteoporosis. To evaluate such genetic factors among the Sikkimese population, a total of 150 cases (75 men and 75 women) with primary osteopenia and osteoporosis and 150 healthy controls (75 men and 75 women) of age range between 35 and 65 years were enrolled in this study. The COL1A1 genotypes [SS, Ss and ss] were assessed by restriction enzyme [MscI] digestion of DNA after amplification by polymerase chain reaction. There, only 2.7% women and 1.3% men cases had restriction site with heterozygous genotype (Ss) and no homozygous genotype (ss) were detected. There was no statistically significant association between low bone mass and genotypes on analysis (χ² = 1.014, P = 0.314; RR = 1.510) that, the Sp1 binding site polymorphism at the COLIA1 gene is very rare and has no contribution in the development low bone mineral density.

Polymorphisms in the TGFB1 and IL2RA genes are associated with clinical forms of leprosy in Brazilian population

BACKGROUND Leprosy is a chronic infectious disease caused by Mycobacterium leprae, and compromises the skin and peripheral nerves. This disease has been classified as multibacillary (MB) or paucibacillary (PB) depending on the host immune response. Genetic epidemiology studies in leprosy have shown the influence of human genetic components on the disease outcomes. OBJECTIVES We conducted an association study for IL2RA and TGFB1 genes with clinical forms of leprosy based on two case-control samples. These genes encode important molecules for the immunosuppressive activity of Treg cells and present differential expressions according to the clinical forms of leprosy. Furthermore, IL2RA is a positional candidate gene because it is located near the 10p13 chromosome region, presenting a linkage peak for PB leprosy. METHODS A total of 885 leprosy cases were included in the study; 406 cases from Rondonópolis County (start population), a hyperendemic region for leprosy in Brazil, and 479 cases from São Paulo state (replication population), which has lower epidemiological indexes for the disease. We tested 11 polymorphisms in the IL2RA gene and the missense variant rs1800470 in the TGFB1 gene. FINDINGS The AA genotype of rs2386841 in IL2RA was associated with the PB form in the start population. The AA genotype of rs1800470 in TGFB1 was associated with the MB form in the start population, and this association was confirmed for the replication population. MAIN CONCLUSIONS We demonstrated, for the first time, an association data with the PB form for a gene located on chromosome 10. In addition, we reported the association of TGFB1 gene with the MB form. Our results place these genes as candidates for validation and replication studies in leprosy polarisation.

Association of interleukin-6 (rs1800796) but not transforming growth factor beta 1 (rs1800469) with serum calcium levels in osteoporotic patients

BACKGROUND

Osteoporosis is a multifactorial disease with a strong genetic influence. Recent studies have demonstrated that cytokines, such as TGF-β1 and interleukin 6 (IL-6) play complex roles in the normal bone metabolism and pathophysiology of osteoporosis. Here, we investigated the roles of 2 polymorphisms mapping to the promoters of TGF-β1and IL-6 genes on the genetic susceptibility to osteoporosis as well as calcium and vitamin D levels.

METHODS

A cohort of 297 elderly participants in northern Iran comprising 181 osteoporotic patients (mean age ± SD, 68.36 ± 7.21 years) and 116 unrelated healthy controls (mean age ± SD, 64 ± 5.44 years) was studied for TGF-β1(C-509T) and IL-6 (G-634C) polymorphisms using PCR-RFLP method.

RESULTS

A significant relationship was observed between calcium level and IL-6 genotypes in osteoporotic males (P = 0.011) and females (P = 0.020). No significant differences were observed between osteoporotic and control groups with respect to allele frequency or genotype distribution based on the 2 selected polymorphisms under different genetic models. The results remained the same after comparing the BMD values of either the femur neck or lumbar spine with the genotypes of the elderly men and women when analyzed separately.

CONCLUSION

IL-6 genotype influences serum calcium levels in osteoporotic patients. The lack of association between the common genetic variations of TGF-β1 and IL-6 genes, and BMD highlights the complex genetic background of osteoporosis in the north of Iran.

The c.29T>C polymorphism of the transforming growth factor beta-1 (TGFB1) gene, bone mineral density and the occurrence of low-energy fractures in patients with inflammatory bowel disease

Gastrointestinal tract conditions are frequently associated with low bone mineral density and increased risk of fractures due to osteoporosis, the latter concerning particularly inflammatory bowel disease (IBD) patients. One of the candidate genes involved in osteoporosis is the transforming growth factor beta-1 (TGFB1) whose polymorphisms may be responsible for the development of this disease. The aim of this study was to analyse the frequency of TGFB1 polymorphic variants and determine the association between the c.29T>C TGFB1 polymorphism, and bone mineral density and fractures in IBD patients. The study subjects included 198 IBD patients [100 suffering from Crohn's disease (CD) and 98 from ulcerative colitis (UC)] and 41 healthy volunteers as a control group. Densitometric bone measurements were obtained using dual energy X-ray absorptiometry. The TGFB1 genotyping was conducted using restriction fragments length polymorphism. We conducted an analysis of genotype distribution's concordance with Hardy-Weinberg equilibrium. We found statistically significant differences in lumbar spine (L2-L4) and femoral neck BMD and T-scores between CD, UC and control subgroups. The distribution of TGFB1 polymorphic variants among CD and UC patients was concordant with Hardy-Weinberg equilibrium. There were no statistically significant differences in densitometric parameters (lumbar spine and femoral neck BMD, T-score, and Z-score) between carriers of different TGFB1 polymorphisms among IBD (CD and UC) patients nor among controls. We have found no statistically significant differences in the prevalence of low-energy fractures between groups of different TGFB1 polymorphic variant carriers. The allele dose effect, recessive effect and dominant effect analysis did not show an association between low-energy fractures and the TGFB1 polymorphisms among CD and UC patients. We have not observed an association between the c.29T>C TGFB1 polymorphic variant and the bone mineral density within the cancellous and cortical bones (L2-L4 and femoral neck, respectively), or the occurrence of fractures among the IBD patients and their family members.

Postmenopausal osteoporosis

Osteoporosis is a metabolic bone disorder that is characterized by low bone mass and micro-architectural deterioration of bone tissue. Fractures of the proximal femur, the vertebrae and the distal radius are the most frequent osteoporotic fractures, although most fractures in the elderly are probably at least partly related to bone fragility. The incidence of fractures varies greatly by country, but on average up to 50% of women >50 years of age are at risk of fractures. Fractures severely affect the quality of life of an individual and are becoming a major public health problem owing to the ageing population. Postmenopausal osteoporosis, resulting from oestrogen deficiency, is the most common type of osteoporosis. Oestrogen deficiency results in an increase in bone turnover owing to effects on all types of bone cells. The imbalance in bone formation and resorption has effects on trabecular bone (loss of connectivity) and cortical bone (cortical thinning and porosity). Osteoporosis is diagnosed using bone density measurements of the lumbar spine and proximal femur. Preventive strategies to improve bone health include diet, exercise and abstaining from smoking. Fractures may be prevented by reducing falls in high-risk populations. Several drugs are licensed to reduce fracture risk by slowing down bone resorption (such as bisphosphonates and denosumab) or by stimulating bone formation (such as teriparatide). Improved understanding of the cellular basis for osteoporosis has resulted in new drugs targeted to key pathways, which are under development.

Low bone mineral density in patients with type 1 diabetes: association with reduced expression of IGF1, IGF1R and TGF B 1 in peripheral blood mononuclear cells

BACKGROUND

The negative effects of type 1 diabetes (T1D) on growth factors of bone metabolism lead to a reduction in bone mineral density. This study aimed to evaluate the association between bone mineral density and insulin-like growth factor 1 (IGF1), insulin-like growth factor 1 receptor (IGF1R) and transforming growth factor beta 1 (TGFB1) expressions in children and adolescents with T1D. Moreover, the influences of age at diagnosis, time since diagnosis, glycaemic control and albuminuria on bone mineral density were investigated.

METHODS

Eighty-six T1D children/adolescents (T1D group) and ninety normoglycaemic controls (normoglycaemic group) were included. T1D patients were analysed as a whole and also in subsets of patients with good glycaemic control (glycated hemoglobin concentration ≤7.5%) and with poor glycaemic control (glycated hemoglobin concentration >7.5%). Bone mineral density was assessed by dual energy x-ray absorptiometry. Glycaemic control, renal function and bone markers were also assessed. IGF1, IGF1R and TGFB1 expressions were determined in peripheral blood mononuclear cells by real-time polymerase chain reaction.

RESULTS

Patients with T1D showed low bone mineral density and poor glycaemic control. Serum total calcium and urinary albumin-to-creatinine ratio were higher in patients with poor glycaemic control compared to those with good glycemic control (p = 0.003 and p = 0.035, respectively). There was a reduction of IGF1, IGF1R and TGFB1 expressions in the T1D patients and in the subset with poor glycaemic control compared to normoglycaemic controls (p < 0.05).

CONCLUSIONS

The decreased IGF1, IGF1R and TGFB1 expressions in the T1D patients, who presented with T1D at an early age, had been diagnosed with T1D for a longer time, had poor glycaemic control and albuminuria may contribute to low bone mineral density. Copyright © 2016 John Wiley & Sons, Ltd.

Osteoporosis: the current status of mesenchymal stem cell-based therapy

Osteoporosis, or bone loss, is a progressive, systemic skeletal disease that affects millions of people worldwide. Osteoporosis is generally age related, and it is underdiagnosed because it remains asymptomatic for several years until the development of fractures that confine daily life activities, particularly in elderly people. Most patients with osteoporotic fractures become bedridden and are in a life-threatening state. The consequences of fracture can be devastating, leading to substantial morbidity and mortality of the patients. The normal physiologic process of bone remodeling involves a balance between bone resorption and bone formation during early adulthood. In osteoporosis, this process becomes imbalanced, resulting in gradual losses of bone mass and density due to enhanced bone resorption and/or inadequate bone formation. Several growth factors underlying age-related osteoporosis and their signaling pathways have been identified, such as osteoprotegerin (OPG)/receptor activator of nuclear factor B (RANK)/RANK ligand (RANKL), bone morphogenetic protein (BMP), wingless-type MMTV integration site family (Wnt) proteins and signaling through parathyroid hormone receptors. In addition, the pathogenesis of osteoporosis has been connected to genetics. The current treatment of osteoporosis predominantly consists of antiresorptive and anabolic agents; however, the serious adverse effects of using these drugs are of concern. Cell-based replacement therapy via the use of mesenchymal stem cells (MSCs) may become one of the strategies for osteoporosis treatment in the future.

Osteoporosis and Bone Mass Disorders: From Gene Pathways to Treatments

Genomic technologies have evolved rapidly contributing to the understanding of diseases. Genome-wide association studies (GWAS) and whole-exome sequencing have aided the identification of the genetic determinants of monogenic and complex conditions including osteoporosis and bone mass disorders. Overlap exists between the genes implicated in monogenic and complex forms of bone mass disorders, largely explained by the clustering of genes encoding factors in signaling pathways crucial for mesenchymal cell differentiation, skeletal development, and bone remodeling and metabolism. Numerous of the remaining discovered genes merit functional follow-up studies to elucidate their role in bone biology. The insight provided by genetic studies is serving the identification of biomarkers predictive of disease, redefining disease, response to treatment, and discovery of novel drug targets for skeletal disorders.

The genetics of bone mass and susceptibility to bone diseases

Osteoporosis is characterized by low bone mass and an increased risk of fracture. Genetic factors, environmental factors and gene-environment interactions all contribute to a person's lifetime risk of developing an osteoporotic fracture. This Review summarizes key advances in understanding of the genetics of bone traits and their role in osteoporosis. Candidate-gene approaches dominated this field 20 years ago, but clinical and preclinical genetic studies published in the past 5 years generally utilize more-sophisticated and better-powered genome-wide association studies (GWAS). High-throughput DNA sequencing, large genomic databases and improved methods of data analysis have greatly accelerated the gene-discovery process. Linkage analyses of single-gene traits that segregate in families with extreme phenotypes have led to the elucidation of critical pathways controlling bone mass. For example, components of the Wnt-β-catenin signalling pathway have been validated (in both GWAS and functional studies) as contributing to various bone phenotypes. These notable advances in gene discovery suggest that the next decade will witness cataloguing of the hundreds of genes that influence bone mass and osteoporosis, which in turn will provide a roadmap for the development of new drugs that target diseases of low bone mass, including osteoporosis.

Polymorphisms Associated With Low Bone Mass and High Risk of Atraumatic Fracture

Osteoporosis is a serious disease characterized by high morbidity and mortality due to atraumatic fractures. In the pathogenesis of osteoporosis, except environment and internal factors, such as hormonal imbalance and genetic background, are also in play. In this study candidate genes for osteoporosis were classified according to metabolic or hormonal pathways, which regulate bone mineral density and bone quality (estrogen, RANKL/RANK/OPG axis, mevalonate, the canonical circuit and genes regulating the vitamin D system). COL1A1 and/or COL1A2 genes, which encode formation of the procollagen 1 molecule, were also studied. Mutations in these genes are well-known causes of the inborn disease ‘osteogenesis imperfecta’. In addition to this, polymorphisms in COL1A1 and/or COL1A2 have been found to be associated with parameters of bone quality in adult subjects. The authors discuss the perspectives for the practical utilization of pharmacogenetics (identification of single candidate genes using PCR) and pharmacogenomics (using genome wide association studies (GWAS) to choose optimal treatment for osteoporosis). Potential predictors of antiresorptive therapy efficacy include the following well established genes: ER, FDPS, Cyp19A1, VDR, Col1A1, and Col1A2, as well as the gene for the canonical (Wnt) pathway. Unfortunately, the positive outcomes seen in most association studies have not been confirmed by other researchers. The controversial results could be explained by the use of different methodological approaches in individual studies (different sample size, homogeneity of investigated groups, ethnic differences, or linkage disequilibrium between genes). The key pitfall of association studies is the low variability (7-10 %) of bone phenotypes associated with the investigated genes. Nevertheless, the identification of new genes and the verification of their association with bone density and/or quality (using both PCR and GWAS), remain a great challenge in the optimal prevention and treatment of osteoporosis.

Comprehensive transcriptome analysis of mesenchymal stem cells in elderly patients with osteoporosis

OBJECTIVE

To explore the role of aging in the pathogenesis of osteoporosis, several differentially expressed genes (DEGs) and altered biological pathways were identified in mesenchymal stem cells (MSCs) in elderly patients with osteoporosis.

METHODS

Raw data were downloaded from Gene Expression Omnibus database. A total of 14 human MSC samples were available, including five samples from elderly patients suffering from osteoporosis, five controls from young non-osteoporotic donors and five controls from old non-osteoporotic donors. The DEGs were identified using LIMMA package among the three groups. Gene ontology and KEGG pathway analysis were carried out using DAVID. A protein-protein interaction (PPI) network of DEGs was constructed with STRING and then visualized with Cytoscape.

RESULTS

A total of 3179 DEGs were screened, including 1071 up- and 2108 down-regulated genes. Compared with young and old controls, 271 and 781 genes were up-regulated in osteoporosis, respectively, and 17 genes were shared. Function and pathway enrichment showed that the up-regulated genes in osteoporosis were involved in extracellular matrix (ECM)-receptor interaction, focal adhesion and mammalian target of rapamycin signaling pathway. Moreover, a range of genes linked to cell adhesion, ECM-receptor interaction and cell cycle were revealed in the PPI network, such as transforming growth factor beta 1, insulin-like growth factor 2 and integrin beta 2.

CONCLUSION

A number of DEGs and altered pathways were screened in osteoporosis. Our study provided insights into the role of aging in the pathogenesis of osteoporosis and some DEGs might be potential biomarkers for osteoporosis.

Effect of MTHFR, TGFβ1, and TNFB polymorphisms on osteoporosis in rheumatoid arthritis patients

Diseases of the immune and the skeletal systems should be studied together for the deep interaction between them. Many studies consider osteoporosis (OP) as a risk factor for the prediction of disease progression in rheumatoid arthritis (RA). The aim of this research is to study the effect of four single nucleotide polymorphisms (SNPs) on RA patients with and without OP. The examined SNPs (MTHFR (C677T, and A1298C), TGFβ1 (T869C), and TNFB (A252G)) were tested by genotyping 17 RA patients with OP and 72 RA patients without OP. Associations were tested using four models (multiplicative, dominant, recessive, and co-dominant). The studied SNPs were not significantly associated with the risk of OP in RA. MTHFR, TGFβ1, and TNFB polymorphisms don't appear to be clinically useful genetic markers for predicting RA severity in Egyptian women population.

Correlation between TGF-β1 gene 29 T > C single nucleotide polymorphism and clinicopathological characteristics of osteosarcoma

Transforming growth factor (TGF)-β1 is the most abundant growth factor in human bone. Several polymorphisms have been described in the TGF-β1 gene. To explore the correlation between TGF-β1 gene single nucleotide polymorphism and the clinicopathological characteristics of osteosarcoma. TaqMAN PCR technique was used to detect the TGF-β1 gene polymorphism of 124 patients with osteosarcoma from last follow-up and 136 healthy controls. The difference of gender, age, and allele frequency between patient group and control group with χ (2) text were tested. The relationship between single nucleotide polymorphism and the risk of osteosarcoma with logistic regression and different survival rates of different genotypic patients with osteosarcoma through Kaplan-Meier were analyzed. There is no remarkable difference of the three genotypes in TGF-β1 gene 509C > T locus between the patient group and control group (P = 0.26). However, there are significant distributive differences in 29 T > C genotype (P = 0.04), which shows that patients carrying TT genotype have more risk to get osteosarcoma than patients carrying CC genotype (odds ratio (OR) = 2.10, 95 % confidence interval (CI) = 1.08-4.05). The percentage of T allele frequency of patient group, as 60.1 %, is larger than the control group, as 48.9 %. By comparing with patients carrying CC genotype, patients carrying TT genotype have two times risk of metastasis (OR = 2.30, 95 % CI = 1.05-5.06), and most of them are in the period of Enneking IIB (OR = 2.54, 95 % CI = 1.18-5.51). The survival analysis indicates that there is no any significant decrease when there is recurrence in patients carrying TT genotype. The morbidity and metastasis of osteosarcoma are relevant to TGF-β1 gene 29 T > C single nucleotide polymorphism.

Transforming growth factor Beta family: insight into the role of growth factors in regulation of fracture healing biology and potential clinical applications

The transforming growth factor beta (TGF-β) family forms a group of three isoforms, TGF-β1, TGF-β2, and TGF-β3, with their structure formed by interrelated dimeric polypeptide chains. Pleiotropic and redundant functions of the TGF-β family concern control of numerous aspects and effects of cell functions, including proliferation, differentiation, and migration, in all tissues of the human body. Amongst many cytokines and growth factors, the TGF-β family is considered a group playing one of numerous key roles in control of physiological phenomena concerning maintenance of metabolic homeostasis in the bone tissue. By breaking the continuity of bone tissue, a spread-over-time and complex bone healing process is initiated, considered a recapitulation of embryonic intracartilaginous ossification. This process is a cascade of local and systemic phenomena spread over time, involving whole cell lineages and various cytokines and growth factors. Numerous in vivo and in vitro studies in various models analysing cytokines and growth factors' involvement have shown that TGF-β has a leading role in the fracture healing process. This paper sums up current knowledge on the basis of available literature concerning the role of the TGF-β family in the fracture healing process.

Unveiling the mysteries of the genetics of osteoporosis

INTRODUCTION

Osteoporosis is a common disease characterised by low bone mineral density and an increased risk of fragility fractures.

METHODS

We conducted a literature review of relevant studies relating to the genetics of osteoporosis.

RESULTS

Family studies have revealed that bone density and fractures have a strong heritable component but environmental factors also play an important role. This makes identification of the causative genetic variants challenging. Linkage analysis has been successful in identifying the genes responsible for rare inherited diseases associated with abnormalities of bone mass but has been of limited value in osteoporosis. In contrast, genome-wide association studies in large cohort studies have identified 56 loci with robust evidence of association with bone density and 14 loci that predispose to fractures. Although the effect size of the implicated variants is small, many of the loci contain genes known to be involved in regulating bone cell activity through the RANK and Wnt signalling pathways, whereas others contain novel genes not previously implicated in bone metabolism. In a few instances, whole genome and exome sequencing have been successfully used to identify rare variants of large effect size that influence susceptibility to osteoporosis.

CONCLUSION

A future challenge will be to conduct fine mapping and functional analysis of the loci implicated in osteoporosis in order to identify the causal genetic variants and examine the mechanisms by which they influence bone cell function and bone mass. Ultimately this may lead to the identification of biomarkers for susceptibility to osteoporosis and fractures or new therapeutic targets.

Transforming growth factor beta1 (TGFβ1) polymorphisms and breast cancer risk

Transforming growth factor β1 (TGFβ1) is suggested to be involved in the pathogenesis of and in complications with breast cancer (BC). Polymorphisms in TGFβ1 gene (TGFβ1) have been suggested by many investigators to have a role in susceptibility to BC; however, many discordant data have been reported. Considering the role of ethnic variations, we performed an association study between TGFβ1 polymorphisms and BC among Iranian women. We sequenced DNA samples of 110 BC and 110 normal control women for the exons and their adjacent intronic regions of TGFβ1 using PCR. The allele, genotype, and haplotype frequencies were calculated using PowerMarker V3.25 and R 3.0.2 softwares. Ten single nucleotide polymorphisms (SNPs) were detected. Statistical analysis on the frequency of seven most frequent SNPs, including the three coding SNPs (cSNPs) revealed no significant difference between BC and control women. Moreover, among 11 constructed haplotypes, "GTGCCGC" was significantly different between two study groups. In conclusion, we found no association between the studied SNPs of TGFβ1 and BC among Iranian women, but a possible association between "GTGCCGC" haplotype and BC was seen. However, further studies are suggested to clarify this association.

Significant associations between the A163G and G1181C polymorphisms of the osteoprotegerin gene and risk of osteoporosis, especially in postmenopausal women: a meta-analysis

OBJECTIVE

Whereas some studies have reported that the osteoprotegerin (OPG) gene is associated with osteoporosis risk in some studies, their results have proved inconclusive. We performed a meta-analysis of studies on the associations between OPG A163G and G1181C polymorphisms and the risk of osteoporosis.

METHODS

A literature search in PubMed, Embase, Web of Science, Cochrane Library, and China Biological Medicine (CBM) databases was conducted to identify all eligible case-control studies published before August 15th, 2013. Pooled odds ratios with their corresponding 95% confidence intervals were used to evaluate the strength of the association under either a fixed- or random-effect model according to the heterogeneity test.

RESULTS

Ten case-control studies were included with a total of 1673 osteoporosis cases and 1554 healthy controls in this meta-analysis. For the OPG A163G polymorphism, the combined results showed that the G allele of the A163G polymorphism may be associated with an increased risk of osteoporosis. Stratified analyses showed that the magnitude of the effect was similar among the Caucasian and postmenopausal women subgroups. Unlike the A163G polymorphism, the meta-analysis results revealed that the C allele of the G1181C polymorphism may be associated with a decreased risk of osteoporosis, especially in the Asian and postmenopausal women subgroups. No publication bias was detected for either polymorphism.

CONCLUSION

Our findings showed that the G allele of the OPG A163G polymorphism may increase osteoporosis risk, whereas the C allele of the G1181C polymorphism may protect individuals from osteoporosis. Both of these effects were observed in postmenopausal women.

Genetic analysis of the relationship between bone mineral density and low-density lipoprotein receptor-related protein 5 gene polymorphisms

Background

A number of studies have examined the association between the polymorphisms of the low-density lipoprotein receptor-related protein 5 gene (LRP5), but previous results have been inconclusive. Thus we performed a meta-analysis of studies on the association between the LRP5 polymorphisms and bone mineral density (BMD) to assess their pooled effects.

Methods

Published literature from PubMed, EMBASE and ISI web of science were searched for eligible publications. Weighted mean difference (WMD) and 95% confidence interval (CI) was calculated using fixed- or random-effects model.

Results

A total of 19 studies with 25773 subjects were considered in this meta-analysis. Of them, 17 examined the association between the A1330V polymorphism and BMD, 8 were focused on the V667M polymorphism, and 2 analyzed the Q89R polymorphism. Individuals with the A1330V AA genotype showed significantly higher BMD than those with the AV/VV genotypes [at lumbar spine (LS): WMD = 0.02g/cm², 95% CI = 0.01-0.03, P < 10^-4; at femur neck (FN): WMD = 0.01g/cm², 95% CI = 0.00-0.02, P = 0.01] or VV genotype (at LS: WMD = 0.02g/cm², 95% CI = 0.01-0.04, P = 0.01). Significant associations were also detected in the analysis for V667M (VV vs. VM/MM: WMD at LS = 0.02g/cm², 95% CI = 0.02-0.03, P < 10^-5; WMD at FN = 0.01g/cm², 95% CI = 0.01-0.02, P = 0.0002). As for Q89R, subjects with the QQ genotype tended to have higher BMD than those with the QR/RR genotypes at FN (WMD = 0.03g/cm², 95% CI = 0.01-0.05, P = 0.005).

Conclusion

This meta-analysis demonstrated that the LRP5 polymorphisms may be modestly associated with BMD of LS and FN.

The future of pharmacogenetics for osteoporosis

The possibility to predict the outcome of medical treatments, both in terms of efficacy and development of adverse effects, is the main goal of modern personalized medicine. The principal aim of pharmacogenetics is to design specific predictive genetic tests, to be performed prior to any drug treatment, and to tailor the therapy for each patient based on the results of these tests. Few pharmacogenetic tests are today validated and commonly applied in clinical practice, and none in the area of osteoporosis and bone disorders. Surely, the complex regulation of bone metabolism and the involvement of numerous different molecular pathways makes it difficult to individuate responsible genes and polymorphisms involved in the modulation of anti-osteoporotic drug response and, subsequently, in designing specific predictive analyses.

Novel sequence variations in the CER1 gene are strongly associated with low bone mineral density and risk of osteoporotic fracture in postmenopausal women

Osteoporosis is a common skeletal disease characterized by a combination of low bone mass and increased fragility. In this case-control study, we investigated the possible association of two novel candidate genes, CER1 and TOB1, with bone mineral density (BMD) and fragility risk in 300 postmenopausal women of Hellenic origin. The entire CER1 and TOB1 gene sequences were amplified and resequenced to assess whether there is a correlation between these genes and BMD. We identified 26 variants in both genes. Statistical analysis did not reveal any correlation between TOB1 and osteoporosis. However, CER1 genetic analysis indicated that five polymorphisms, c.194C>G, c.507+506G>T, c.508-182A>G, c.531A>G, and c.*121T>C, were correlated, with a mean T score ≤-2.2. In particular, the greater number of vertebral fractures was found in patients with osteoporosis carrying the G allele of c.531A>G SNP (p = 0.015). When multiple logistic regression analysis was performed, only the c.507+506G>T polymorphism was independently associated with hip fractures or the presence of any fracture (OR = 6.95, p = 0.016, and OR = 5.33, p < 0.001, respectively). These results suggest that CER1 gene variations play a significant role in determining BMD and vertebral or hip fractures, which might be helpful in clinical practice to identify patients with increased fracture risk.

Identification of candidate gene regions in the rat by co-localization of QTLs for bone density, size, structure and strength

Susceptibility to osteoporotic fracture is influenced by genetic factors that can be dissected by whole-genome linkage analysis in experimental animal crosses. The aim of this study was to characterize quantitative trait loci (QTLs) for biomechanical and two-dimensional dual-energy X-ray absorptiometry (DXA) phenotypes in reciprocal F2 crosses between diabetic GK and normo-glycemic F344 rat strains and to identify possible co-localization with previously reported QTLs for bone size and structure. The biomechanical measurements of rat tibia included ultimate force, stiffness and work to failure while DXA was used to characterize tibial area, bone mineral content (BMC) and areal bone mineral density (aBMD). F2 progeny (108 males, 98 females) were genotyped with 192 genome-wide markers followed by sex- and reciprocal cross-separated whole-genome QTL analyses. Significant QTLs were identified on chromosome 8 (tibial area; logarithm of odds (LOD) = 4.7 and BMC; LOD = 4.1) in males and on chromosome 1 (stiffness; LOD = 5.5) in females. No QTLs showed significant sex-specific interactions. In contrast, significant cross-specific interactions were identified on chromosome 2 (aBMD; LOD = 4.7) and chromosome 6 (BMC; LOD = 4.8) for males carrying F344mtDNA, and on chromosome 15 (ultimate force; LOD = 3.9) for males carrying GKmtDNA, confirming the effect of reciprocal cross on osteoporosis-related phenotypes. By combining identified QTLs for biomechanical-, size- and qualitative phenotypes (pQCT and 3D CT) from the same population, overlapping regions were detected on chromosomes 1, 3, 4, 6, 8 and 10. These are strong candidate regions in the search for genetic risk factors for osteoporosis.

Associations of APOE gene polymorphisms with bone mineral density and fracture risk: a meta-analysis

To determine the association of the Apolipoprotein E (APOE) E4 gene polymorphism with bone mineral density (BMD) and fractures we conducted a meta-analysis of 17 reports. Despite lower trochanteric and lumbar BMD in APOE4 carriers, there is insufficient evidence to support a consistent association of APOE with bone health.

INTRODUCTION

APOE has been studied for its potential role in osteoporosis risk. It is hypothesized that genetic variation at APOE locus, known as E2, E3, and E4, may modulate BMD through its effects on lipoproteins and vitamin K transport. The purpose of this study was to determine the association of the APOE-E4 gene polymorphism with bone-related phenotypes.

METHODS

We conducted a meta-analysis that combined newly analyzed individual data from two community-based cohorts, the Framingham Offspring Study (N = 1,495) and the vitamin K clinical trial (N = 377), with 15 other eligible published reports. Bone phenotypes included BMD measurements of the hip (total hip and trochanteric and femoral neck sites) and lumbar spine (from the L2 to L4 vertebrae) and prevalence or incidence of vertebral, hip, and other fractures.

RESULTS

In sex-pooled analyses, APOE4 carriers had a 0.018 g/cm(2) lower weighted mean trochanteric BMD than non carriers (p = 0.0002) with no evidence for between-study heterogeneity. A significant association was also detected with lumbar spine BMD (p = 0.006); however, inter-study heterogeneity was observed. Associations with lumbar spine and trochanteric BMD were observed predominantly in women and became less significant in meta-regression (p = 0.055 and 0.01, respectively). There were no consistent associations of APOE4 genotype with BMD at other skeletal sites or with fracture risk.

CONCLUSIONS

Based on these findings, there is insufficient evidence to support a strong and consistent association of the APOE genotype with BMD and fracture incidence.

Polymorphisms in the 5' flank of COL1A1 gene and osteoporosis: meta-analysis of published studies

A meta-analysis of studies was conducted involving 24,511 participants with 7,864 fractures in which polymorphisms in the 5' flank of COL1A1 (rs1107946, rs2412298, and rs1800012) were related to osteoporosis phenotypes. Polymorphisms of all three sites were associated with BMD, and rs1800012 was associated with fracture but effect sizes were modest.

INTRODUCTION AND HYPOTHESIS

Polymorphisms in the 5' flank of COL1A1 gene have been implicated as genetic markers for susceptibility to osteoporosis, but previous studies have yielded conflicting results.

METHODS

We conducted a meta-analysis of 32 studies including 24,511 participants and 7,864 fractures in which alleles at the -1997G/T (rs1107946), -1663in/delT (rs2412298), and Sp1 binding site polymorphisms (rs1800012) of COL1A1 had been related to bone mineral density (BMD) or fracture.

RESULTS

For the Sp1 polymorphism, BMD values in TT homozygotes were 0.13 units [95% CI, 0.03 to 0.24] lower at the spine (p = 0.01) and 0.16 units [0.10 to 0.23] lower at the hip (p = 1 x 10⁻⁶) than GG homozygotes. Clinical fractures were 1.31-fold [1.04-1.65] increased in TT homozygotes (p = 0.02) and vertebral fractures were 1.34-fold [1.01-1.77] increased (p = 0.04). We also observed associations between spine BMD and allelic variants at the -1997G/T (p = 0.05) and the -1663indelT (p = 0.009) sites. We found no association between alleles at the -1997G/T or -1663indelT sites and fracture but power was limited.

CONCLUSIONS

The COL1A1 Sp1 polymorphism is associated with a modest reduction in BMD and an increased risk of fracture, although we cannot fully exclude the possibility that the results may have been influenced by publication bias. Further studies are required to fully evaluate the contribution of the -1997G/T and -1663in/delT sites to these phenotypes and to determine if they interact with the Sp1 polymorphism to regulate susceptibility to osteoporosis.

Genetic loci for bone architecture determined by three-dimensional CT in crosses with the diabetic GK rat

The F344 rat carries alleles contributing to bone fragility while the GK rat spontaneously develops type-2 diabetes. These characteristics make F344×GK crosses well suited for the identification of genes related to bone size and allow for future investigation on the association with type-2 diabetes. The aim of this study was to identify quantitative trait loci (QTLs) for bone size phenotypes measured by a new application of three-dimensional computed tomography (3DCT) and to investigate the effects of sex- and reciprocal cross. Tibia from male and female GK and F344 rats, representing the parental, F1 and F2 generations, were examined with 3DCT and analyzed for: total and cortical volumetric BMD, straight and curved length, peri- and endosteal area at mid-shaft. F2 progeny (108 male and 98 female) were genotyped with 192 genome-wide microsatellite markers (average distance 10 cM). Sex- and reciprocal cross-separated QTL analyses were performed for the identification of QTLs linked to 3DCT phenotypes and true interactions were confirmed by likelihood ratio analysis in all F2 animals. Several genome-wide significant QTLs were found in the sex- and reciprocal cross-separated progeny on chromosomes (chr) 1, 3, 4, 9, 10, 14, and 17. Overlapping QTLs for both males and females in the (GK×F344)F2 progeny were located on chr 1 (39-67 cM). This region confirms previously reported pQCT QTLs and overlaps loci for fasting glucose. Sex separated linkage analysis confirmed a male specific QTL on chr 9 (67-82 cM) for endosteal area at the fibula site. Analyses separating the F2 population both by sex and reciprocal cross identified cross specific QTLs on chr 14 (males) and chr 3 and 4 (females). Two loci, chr 4 and 6, are unique to 3DCT and separate from pQCT generated loci. The 3DCT method was highly reproducible and provided high precision measurements of bone size in the rat enabling identification of new sex- and cross-specific loci. The QTLs on chr 1 indicate potential genetic association between bone-related phenotypes and traits affecting type-2 diabetes. The results illustrate the complexity of the genetic architecture of bone size phenotypes and demonstrate the importance of complementary methods for bone analysis.

High-density polymorphisms analysis of 23 candidate genes for association with bone mineral density

Osteoporosis is a bone disease characterized by low bone mineral density (BMD), a highly heritable and polygenic trait. Women are more prone than men to develop osteoporosis due to a lower peak bone mass and accelerated bone loss at menopause. Peak bone mass has been convincingly shown to be due to genetic factors with heritability up to 80%. Menopausal bone loss has been shown to have around 38% to 49% heritability depending on the site studied. To have more statistical power to detect small genetic effects we focused on premenopausal women. We studied 23 candidate genes, some involved in calcium and vitamin-D regulation and others because estrogens strongly induced their gene expression in mice where it was correlated with humerus trabecular bone density. High-density polymorphisms were selected to cover the entire gene variability and 231 polymorphisms were genotyped in a first sample of 709 premenopausal women. Positive associations were retested in a second, independent, sample of 673 premenopausal women. Ten polymorphisms remained associated with BMD in the combined samples and one was further associated in a large sample of postmenopausal women (1401 women). This associated polymorphism was located in the gene CSF3R (granulocyte colony stimulating factor receptor) that had never been associated with BMD before. The results reported in this study suggest a role for CSF3R in the determination of bone density in women.

Cigarette smoking decreases TGF-b1 serum concentrations after long bone fracture

TGF-b1 serum concentrations are considered to be one of the most promising markers of fracture healing. Previously, we demonstrated significant differences in the post-traumatic time courses of patients with timely and delayed fracture healing. The aim of this study was to evaluate possible differences in the serum concentrations of TGF-b1 in cigarette-smoking vs. non-smoking patients with timely and delayed fracture healing in order to understand pathophysiological pathways through which smoking impairs fracture healing.Serum samples were collected from 248 patients undergoing surgical treatment for long bone fractures within 1 year of surgery. Samples from 14 patients with atrophic-type delayed fracture healing were compared with 14 matched patients with normal bone healing. Each group included seven smokers and seven non-smokers. Post-operative serum concentrations were analysed at 1, 2, 4, 8, and 12 weeks as well as 1 year after surgery. The patients were monitored both clinically and radiologically for the entire duration of the study.All patients increased TGF-b1 serum concentrations after surgery. In patients with normal fracture healing, significantly higher TGF-b1 levels were observed in non-smokers (70 ng/ml) than in smokers(50 ng/ml) at the 4th week after surgery (p = 0.007). Also at the 4th week, in patients with delayed healing, significantly lower TGF-b1 levels were observed in smokers than in non-smokers (38 ng/ml vs.47 ng/ml, p = 0.021). However, no significant differences between non-smokers with delayed healing and smokers with normal healing (p = 0.151) were observed at the 4th week after surgery. TGF-b1 serum concentrations reached a plateau in all groups from the 6th to the 12th week after surgery, with a slight decrease observed in the final measurement taken 1 year after surgery.This study demonstrates that, after fracture, TGF-b1 serum concentrations are reduced by smoking,and this reduction is statistically significant during the 4th week after surgery. Our findings may help reveal the mechanism by which smoking impairs fracture healing. Furthermore, these results may help to establish a serological marker that predicts impaired fracture healing soon after the injury. Surgeons will not only be able to monitor the bone healing, but they will also be able to monitor the success of additional treatments such as ultrasound and bone morphologic proteins (BMPs).

Genetics of osteoporosis

Osteoporosis is a common disease with a strong genetic component characterized by reduced bone mass, defects in the microarchitecture of bone tissue, and an increased risk of fragility fractures. Twin and family studies have shown high heritability of bone mineral density (BMD) and other determinants of fracture risk such as ultrasound properties of bone, skeletal geometry, and bone turnover. Osteoporotic fractures also have a heritable component, but this reduces with age as environmental factors such as risk of falling come into play. Susceptibility to osteoporosis is governed by many different genetic variants and their interaction with environmental factors such as diet and exercise. Notable successes in identification of genes that regulate BMD have come from the study of rare Mendelian bone diseases characterized by major abnormalities of bone mass where variants of large effect size are operative. Genome-wide association studies have also identified common genetic variants of small effect size that contribute to regulation of BMD and fracture risk in the general population. In many cases, the loci and genes identified by these studies had not previously been suspected to play a role in bone metabolism. Although there has been extensive progress in identifying the genes and loci that contribute to the regulation of BMD and fracture over the past 15 yr, most of the genetic variants that regulate these phenotypes remain to be discovered.

Molecular genetic studies of gene identification for osteoporosis: the 2009 update

Osteoporosis is a complex human disease that results in increased susceptibility to fragility fractures. It can be phenotypically characterized using several traits, including bone mineral density, bone size, bone strength, and bone turnover markers. The identification of gene variants that contribute to osteoporosis phenotypes, or responses to therapy, can eventually help individualize the prognosis, treatment, and prevention of fractures and their adverse outcomes. Our previously published reviews have comprehensively summarized the progress of molecular genetic studies of gene identification for osteoporosis and have covered the data available to the end of September 2007. This review represents our continuing efforts to summarize the important and representative findings published between October 2007 and November 2009. The topics covered include genetic association and linkage studies in humans, transgenic and knockout mouse models, as well as gene-expression microarray and proteomics studies. Major results are tabulated for comparison and ease of reference. Comments are made on the notable findings and representative studies for their potential influence and implications on our present understanding of the genetics of osteoporosis.

Cooperative effect of serum 25-hydroxyvitamin D concentration and a polymorphism of transforming growth factor-beta1 gene on the prevalence of vertebral fractures in postmenopausal osteoporosis

A T869-->C polymorphism of the transforming growth factor-beta1 (TGF-beta1) gene is reported to be associated with genetic susceptibility to both osteoporosis and vertebral fractures. A low serum 25-hydroxyvitamin D [25(OH)D] level is known to be associated with a higher risk for hip fracture. This study aimed to assess a possible cooperative effect of the gene polymorphism and vitamin D status on vertebral fracture risk. The prevalence of vertebral fracture in 168 postmenopausal female patients with osteoporosis was analyzed, and its association with the TGF-beta1 gene polymorphism and serum 25(OH)D concentration was assessed cross-sectionally. The fracture prevalence increased according to the rank order of the TGF-beta1 genotypes CC < CT < TT, as expected. A significant difference was found not only between the CC and TT genotypes (P = 0.005) but also between the CC and CT genotypes (P < 0.05) when the patients with serum 25(OH)D of more than the median value [22 ng/ml (55 nmol/l)] were analyzed. On the other hand, when those with serum 25(OH)D of less than the median value were analyzed, the protective effect of the C allele against the fracture was blunted; statistical significance in the difference of the fracture prevalence was lost between the CC genotype and the other genotypes. These data suggest that vitamin D fulfillment is prerequisite for the TGF-beta1 genotype in exerting its full effect on the fracture prevalence.

Genetics of osteoporosis

Osteoporosis is a common disease with a strong genetic component characterized by reduced bone mass and an increased risk of fragility fractures. Twin and family studies have shown that the heritability of bone mineral density and other determinants of fracture risk, such as ultrasound properties of bone, skeletal geometry, and bone turnover, is high, although heritability of fracture is modest. Many different genetic variants contribute to the regulation of these phenotypes. Most are common variants of small effect size, but there is evidence that rare variants of large effect size also contribute in some individuals. Many of the genes that regulate susceptibility to osteoporosis have been identified through studies of rare bone diseases, but genome-wide association studies have also been successful in identifying genes that predispose to osteoporosis. Although there has been extensive progress in this area over the past 10 years, most of the genetic variants that regulate susceptibility to osteoporosis remain to be discovered.

Mapping genes for osteoporosis--old dogs and new tricks

In stark contrast to its horticultural origins, modern genetics is an extremely technology-driven field. Almost all the major advances in the field over the past 20 years have followed technological developments that have permitted change in study designs. The development of PCR in the 1980s led to RFLP mapping of monogenic diseases. The development of fluorescent-tagged genotyping methods led to linkage mapping approaches for common diseases that dominated the 1990s. The development of microarray SNP genotyping has led to the genome-wide association study era of the new millennium. And now the development of next-generation sequencing technologies is about to open up a new era of gene-mapping, enabling many potential new study designs. This review aims to present the strengths and weaknesses of the current approaches, and present some new ideas about gene-mapping approaches that are likely to advance our knowledge of the genes involved in heritable bone traits such as bone mineral density (BMD) and fracture.

Genetic determinants of osteoporosis: common bases to cardiovascular diseases?

Osteoporosis is the most common and serious age-related skeletal disorder, characterized by a low bone mass and bone microarchitectural deterioration, with a consequent increase in bone fragility and susceptibility to spontaneous fractures, and it represents a major worldwide health care problem with important implications for health care costs, morbidity and mortality. Today is well accepted that osteoporosis is a multifactorial disorder caused by the interaction between environment and genes that singularly exert modest effects on bone mass and other aspects of bone strength and fracture risk. The individuation of genetic factors responsible for osteoporosis predisposition and development is fundamental for the disease prevention and for the setting of novel therapies, before fracture occurrence. In the last decades the interest of the Scientific Community has been concentrated in the understanding the genetic bases of this disease but with controversial and/or inconclusive results. This review tries to summarize data on the most representative osteoporosis candidate genes. Moreover, since recently osteoporosis and cardiovascular diseases have shown to share common physiopathological mechanisms, this review also provides information on the current understanding of osteoporosis and cardiovascular diseases common genetic bases.

Genetics of osteoporosis: accelerating pace in gene identification and validation

Osteoporosis is characterized by low bone mineral density and structural deterioration of bone tissue, leading to an increased risk of fractures. It is the most common metabolic bone disorder worldwide, affecting one in three women and one in eight men over the age of 50. In the past 15 years, a large number of genes have been reported as being associated with osteoporosis. However, only in the past 4 years we have witnessed an accelerated pace in identifying and validating osteoporosis susceptibility loci. This increase in pace is mostly due to large-scale association studies, meta-analyses, and genome-wide association studies of both single nucleotide polymorphisms and copy number variations. A comprehensive review of these developments revealed that, to date, at least 15 genes (VDR, ESR1, ESR2, LRP5, LRP4, SOST, GRP177, OPG, RANK, RANKL, COLIA1, SPP1, ITGA1, SP7, and SOX6) can be reasonably assigned as confirmed osteoporosis susceptibility genes, whereas, another >30 genes are promising candidate genes. Notably, confirmed and promising genes are clustered in three biological pathways, the estrogen endocrine pathway, the Wnt/beta-catenin signaling pathway, and the RANKL/RANK/OPG pathway. New biological pathways will certainly emerge when more osteoporosis genes are identified and validated. These genetic findings may provide new routes toward improved therapeutic and preventive interventions of this complex disease.

HSD11B1 polymorphisms predicted bone mineral density and fracture risk in postmenopausal women without a clinically apparent hypercortisolemia

INTRODUCTION

Endogenous glucocorticoid (GC) may participate in bone physiology, even in subjects with no glucocorticoid excess. 11beta-hydroxysteroid dehydrogenase type 1 (HSD11B1) is a primary regulator catalyzing the reduction of inactive cortisone to active cortisol. To elucidate genetic relevance of HSD11B1 variants to vertebral fracture and osteoporosis, we investigated the potential involvement of six HSD11B1 SNPs in postmenopausal women.

METHODS

All exons, their boundaries and the promoter region (approximately 1.5 kb) were directly sequenced in 24 individuals. Six polymorphisms were selected and genotyped in all study participants (n=1329). BMD was measured using dual-energy X-ray absorptiometry.

RESULTS

HSD11B1 +16374C>T and +27447G>C were associated with reduced vertebral fracture risk (p=0.016 and 0.032, respectively). Two of these (LD block2) in intron 5 (rs1000283 and rs932335) were significantly associated with bone mineral density (BMD) at the femoral neck (p=0.00005 and 0.0002, respectively). Specifically, HSD11B1 +16374C>T and +27447G>C polymorphisms were associated with higher BMD values of the femoral neck in multiple comparison (p=0.0002 and 0.0004, respectively) and Bonferroni corrected significance level (97% power). Consistent with these results, HSD11B1-ht21 and -ht22 comprising both SNPs also showed the evidence of association with BMD values of the femoral neck (p(domiant)=0.0002 and p(recessive)=0.00005, respectively).

CONCLUSION

Our results provide preliminary evidence supporting an association of HSD11B1 with osteoporosis in postmenopausal women. Also, these findings demonstrate that +16374C>T polymorphism may be useful genetic markers for bone metabolism.

Association of Collagen Type I α1 (COLIA1) Sp1 Polymorphism with Osteoporotic Fracture in Caucasian Post-menopausal Women: a Meta-analysis

This study was designed to summarize quantitatively the evidence for a relationship between collagen type I α1 (COLIA1) Sp1 polymorphism and osteoporotic fracture risk in Caucasian post-menopausal women. This meta-analysis included 16 studies, which analysed 2294 patients with fractures and 10285 controls. The combined results showed that there was a significant difference in genotype distribution (SS odds ratio [OR] 0.72; Ss OR 1.18; ss OR 1.97) between patients with fractures and controls. When stratifying by the fracture site, it was found that: (i) patients with vertebral fractures had a significantly higher frequency of the Ss genotype and a lower frequency of the SS genotype than controls; and (ii) patients with non-vertebral fractures had a significantly higher frequency of the ss genotype and a lower frequency of the SS genotype than controls. This meta-analysis suggests that the COLIA1 Sp1 polymorphism may be associated with osteoporotic fracture in Caucasian post-menopausal women.

Twenty bone-mineral-density loci identified by large-scale meta-analysis of genome-wide association studies

Bone mineral density (BMD) is a heritable complex trait used in the clinical diagnosis of osteoporosis and the assessment of fracture risk. We performed meta-analysis of five genome-wide association studies of femoral neck and lumbar spine BMD in 19,195 subjects of Northern European descent. We identified 20 BMD loci that reached genome-wide significance (GWS; P < 5 x 10(-8)), of which 13 map to regions not previously associated with this trait: 1p31.3 (GPR177), 2p21 (SPTBN1), 3p22 (CTNNB1), 4q21.1 (MEPE), 5q14 (MEF2C), 7p14 (STARD3NL), 7q21.3 (FLJ42280), 11p11.2 (LRP4, ARHGAP1, F2), 11p14.1 (DCDC5), 11p15 (SOX6), 16q24 (FOXL1), 17q21 (HDAC5) and 17q12 (CRHR1). The meta-analysis also confirmed at GWS level seven known BMD loci on 1p36 (ZBTB40), 6q25 (ESR1), 8q24 (TNFRSF11B), 11q13.4 (LRP5), 12q13 (SP7), 13q14 (TNFSF11) and 18q21 (TNFRSF11A). The many SNPs associated with BMD map to genes in signaling pathways with relevance to bone metabolism and highlight the complex genetic architecture that underlies osteoporosis and variation in BMD.

Collaborative meta-analysis: associations of 150 candidate genes with osteoporosis and osteoporotic fracture

BACKGROUND

Osteoporosis is a highly heritable trait. Many candidate genes have been proposed as being involved in regulating bone mineral density (BMD). Few of these findings have been replicated in independent studies.

OBJECTIVE

To assess the relationship between BMD and fracture and all common single-nucleotide polymorphisms (SNPs) in previously proposed osteoporosis candidate genes.

DESIGN

Large-scale meta-analysis of genome-wide association data.

SETTING

5 international, multicenter, population-based studies.

PARTICIPANTS

Data on BMD were obtained from 19 195 participants (14 277 women) from 5 populations of European origin. Data on fracture were obtained from a prospective cohort (n = 5974) from the Netherlands.

MEASUREMENTS

Systematic literature review using the Human Genome Epidemiology Navigator identified autosomal genes previously evaluated for association with osteoporosis. We explored the common SNPs arising from the haplotype map of the human genome (HapMap) across all these genes. BMD at the femoral neck and lumbar spine was measured by dual-energy x-ray absorptiometry. Fractures were defined as clinically apparent, site-specific, validated nonvertebral and vertebral low-energy fractures.

RESULTS

150 candidate genes were identified and 36 016 SNPs in these loci were assessed. SNPs from 9 gene loci (ESR1, LRP4, ITGA1, LRP5, SOST, SPP1, TNFRSF11A, TNFRSF11B, and TNFSF11) were associated with BMD at either site. For most genes, no SNP was statistically significant. For statistically significant SNPs (n = 241), effect sizes ranged from 0.04 to 0.18 SD per allele. SNPs from the LRP5, SOST, SPP1, and TNFRSF11A loci were significantly associated with fracture risk; odds ratios ranged from 1.13 to 1.43 per allele. These effects on fracture were partially independent of BMD at SPP1 and SOST.

LIMITATION

Only common polymorphisms in linkage disequilibrium with SNPs in HapMap could be assessed, and previously reported associations for SNPs in some candidate genes could not be excluded.

CONCLUSION

In this large-scale collaborative genome-wide meta-analysis, 9 of 150 candidate genes were associated with regulation of BMD, 4 of which also significantly affected risk for fracture. However, most candidate genes had no consistent association with BMD.

The bone mass density in postmenopausal women using hormonal replacement therapy in relation to polymorphism in vitamin D receptor and estrogen receptor genes

The aims of the study were as follows: (1) To identify the differences in spinal body mass density (BMD) in relation to polymorphism in vitamin D receptor (VDR) and estrogen receptor-alpha (ERalpha) genes in untreated women with postmenopausal osteoporosis. (2) To assess the efficacy of treatment in women with postmenopausal osteoporosis in relation to polymorphism in VDR and ERalpha genes. (3) To find the estradiol concentration necessary to protect bone tissue in patients with a given polymorphism in VDR and ERalpha genes.

METHODS

The study included 44 postmenopausal women with primary osteoporosis who used cyclic hormonal replacement therapy (HRT) for a year. The polymorphism of ERalpha and VDR genes were evaluated. We also determined the age, body mass index and spinal BMD before and after 12 months of administration the HRT.

RESULTS

We found a significant spinal BMD increase, what is connected with ERalpha genotype and both VDR and ERalpha genes. There is no such a correlation observed in polymorphism of VDR gene.

CONCLUSIONS

(1) There is no relationship between VDR and ERalpha genes polymorphism and the stage of osteoporosis related to the spinal BMD value before treatment. (2) The XX, PP or Bb markers or only X, P, B alleles are connected with a significant decrease of treatment efficacy. (3) Estradiol serum concentration before and during HRT is not dependent on the polymorphism of VDR and ERalpha genes.

Common variants in the region around Osterix are associated with bone mineral density and growth in childhood

Peak bone mass achieved in adolescence is a determinant of bone mass in later life. In order to identify genetic variants affecting bone mineral density (BMD), we performed a genome-wide association study of BMD and related traits in 1518 children from the Avon Longitudinal Study of Parents and Children (ALSPAC). We compared results with a scan of 134 adults with high or low hip BMD. We identified associations with BMD in an area of chromosome 12 containing the Osterix (SP7) locus, a transcription factor responsible for regulating osteoblast differentiation (ALSPAC: P = 5.8 x 10(-4); Australia: P = 3.7 x 10(-4)). This region has previously shown evidence of association with adult hip and lumbar spine BMD in an Icelandic population, as well as nominal association in a UK population. A meta-analysis of these existing studies revealed strong association between SNPs in the Osterix region and adult lumbar spine BMD (P = 9.9 x 10(-11)). In light of these findings, we genotyped a further 3692 individuals from ALSPAC who had whole body BMD and confirmed the association in children as well (P = 5.4 x 10(-5)). Moreover, all SNPs were related to height in ALSPAC children, but not weight or body mass index, and when height was included as a covariate in the regression equation, the association with total body BMD was attenuated. We conclude that genetic variants in the region of Osterix are associated with BMD in children and adults probably through primary effects on growth.

[The implementation of personalized treatment for osteoporosis]

AIM

To establish personalized treatment of osteoporosis.

METHODS

A T869-->C polymorphism in exon 1 of the transforming growth factor-beta1 gene, which results in a Leu-->Pro substitution at amino acid 10, is reported to be associated with the rate of bone loss as well as the response to active vitamin D treatment. Therefore, we determined this single nucleotide polymorphism (SNP) to estimate the need of active vitamin D treatment. We also determined serum level of 25 hydroxy-vitamin D to evaluate a degree of vitamin D fulfillment. Based on these data, we categorized postmenopausal patients into four groups; C homozygote with vitamin D deficiency patients to whom 1 microg/day active vitamin D was administered, C homozygote without vitamin D deficiency patients or those who bore at least one T-allele with vitamin D deficiency to whom 0.5 microg/day active vitamin D was administered, and patients who bore at least one T-allele without vitamin D deficiency to whom no drug was given. The patients were checked up every 6 months with regard to changes in bone mineral density and occurrence of fresh fractures.

RESULTS

The SNP was associated with prevalent vertebral fractures; the frequency of the T allele was significantly greater in patients with vertebral fractures. Furthermore, the serum level of 25 hydroxy-vitamin D was significantly lower in patients with vertebral fractures, which were observed in 17 out of 34 patients who bore at least one T-allele as well as vitamin D deficiency, while only 2 of 15 homozygous C-allele carriers without vitamin D deficiency suffered from fractures.

CONCLUSION

These findings suggest that the SNP in combination with the serum level of 25 hydroxy-vitamin D can predict fracture risk in postmenopausal osteoporosis.

Haplotypes of promoter and intron 1 polymorphisms in the COLIA1 gene are associated with increased risk of osteoporosis

Osteoporosis is a common age-related disease with a strong genetic influence. COLIA1 is one of the most extensively studied candidate genes and has consistently been associated with BMD and fracture. We examined the effects of the polymorphisms -1997G>T, -1663indelT, and +1245G>T and their haplotypes on vertebral fractures and bone mineral density (BMD) in a case-control study comprising 462 osteoporotic patients and 336 controls. The -1663indelT polymorphism was associated with a decreased lumbar spine (ls) BMD, 0.75 +/- 0.14 g/cm(2), in individuals with the del/del genotype versus 0.83 +/- 0.18 and 0.85 +/- 0.18 g/cm(2) in individuals with the ins/del and ins/ins genotypes, respectively (p = 0.02). The T-allele of the +1245G>T polymorphism, which was in strong linkage disequilibrium (LD) with -1663indelT, was also associated with a decreased lsBMD (p = 0.02). -1997G>T was not significantly associated with lsBMD. The three most common haplotypes accounted for 98.5% of the alleles. Individuals with one or two copies of haplotype 1 (-1997G/-1663ins/+1245G) had a significantly higher lsBMD, 0.84 +/- 0.18 and 0.85 +/- 0.15 g/cm(2), respectively, versus 0.78 +/- 0.15 g/cm(2) in noncarriers (p = 0.01). Individuals with two copies of haplotype 2 (-1997G/-1663del/+1245T) had a significantly lower lsBMD, 0.76 +/- 0.14 g/cm(2), versus 0.85 +/- 0.18 and 0.82 +/- 0.18 g/cm(2), respectively, in individuals with zero or one copy (p = 0.03). The odds ratio for vertebral fracture in individuals carrying the variant T-allele of the -1997G>T polymorphism was 1.49 (CI, 1.03-2.16; p = 0.03). Logistic regression revealed that this effect was partly independent of BMD. In conclusion, the -1663del and +1245T alleles influence BMD negatively, whereas the -1997T-allele has a minor effect on BMD but increases the risk of vertebral fractures. These findings are in agreement with functional studies showing that these polymorphisms influence gene expression.

Relationship between age-related serum concentrations of TGF-beta1 and TGF-beta2 and those of osteoprotegerin and leptin in native Chinese women

BACKGROUND

Transforming growth factor-beta 1 (TGF-beta1), TGF-beta2, osteoprotegerin (OPG), and leptin are important cytokines in the regulation of bone remodeling. We investigated the relationship of TGF-beta1 and TGF-beta2 concentrations with those of OPG and leptin in Chinese females.

METHODS

The serum concentrations of TGF-beta1, TGF-beta2, OPG, and leptin were measured by ELISA in 459 healthy Chinese females aged 25-80 y.

RESULTS

The mean values (+/-SD) of the serum concentrations of TGF-beta1, TGF-beta2, OPG, and leptin in Chinese females were 29.7+/-1.69 microg/l, 13.7+/-3.86 microg/l, 3.81+/-1.96 pmol/l, and 10.5+/-2.01 microg/l, respectively. Further, the serum TGF-beta1 concentrations of postmenopausal women were significantly lower than those of perimenopausal and premenopausal women (24.3+/-1.59 vs 33.4+/-1.69 and 37.6+/-1.64, respectively), while the TGF-beta2 concentrations of postmenopausal women were significantly higher than those of perimenopausal and premenopausal women (14.6+/-3.91 vs 13.5+/-3.93 and 11.7+/-2.68, respectively). The serum TGF-beta1 concentration was found to be significantly negatively correlated with age (r=-0.335, P=0.000) and the TGF-beta2 concentration, to be significantly positively correlated with age (r=0.230, P=0.000). The TGF-beta1 concentration was found to be significantly negatively correlated with both TGF-beta2 (r=-0.261, P=0.000) and OPG (r=-0.313, P=0.000) concentrations; a significantly positive correlation was found between the TGF-beta1 and leptin concentrations (r=0.164, P=0.000) and between TGF-beta2 and OPG concentrations (r=0.432, P=0.000).

CONCLUSION

These results provide age-related reference values of TGF-beta1 and TGF-beta2 in Chinese adult women, and reveal the relationships between these cytokines.