LRP5 Polymorphisms and response to risedronate treatment in osteoporotic men

Bone fragility and osteoporosis in children and young adults

Osteoporosis is a metabolic bone disorder which increases fragility fracture risk. Elderly individuals, especially postmenopausal women, are particularly susceptible to osteoporosis. Although rare, osteoporosis in children and young adults is becoming increasingly evident, highlighting the need for timely diagnosis, management and follow-up. Early-onset osteoporosis is defined as the presence of a low BMD (Z-score of ≤ -2.0 in individuals aged < 20 years; T-score of ≤ -2.5 in those aged between 20 to 50 years) accompanied by a clinically significant fracture history, or the presence of low-energy vertebral compression fractures even in the absence of osteoporosis. Affected children and young adults should undergo a thorough diagnostic workup, including collection of clinical history, radiography, biochemical investigation and possibly bone biopsy. Once secondary factors and comorbidities are excluded, genetic testing should be considered to determine the possibility of an underlying monogenic cause. Defects in genes related to type I collagen biosynthesis are the commonest contributors of primary osteoporosis, followed by loss-of-function variants in genes encoding key regulatory proteins of canonical WNT signalling (specifically LRP5 and WNT1), the actin-binding plastin-3 protein (encoded by PLS3) resulting in X-linked osteoporosis, and the more recent sphingomyelin synthase 2 (encoded by SGMS2) which is critical for signal transduction affecting sphingomyelin metabolism. Despite these discoveries, genetic causes and underlying mechanisms in early-onset osteoporosis remain largely unknown, and if no causal gene is identified, early-onset osteoporosis is deemed idiopathic. This calls for further research to unravel the molecular mechanisms driving early-onset osteoporosis that consequently will aid in patient management and individualised targeted therapy.

Early-Onset Osteoporosis

Osteoporosis is a skeletal disorder with enhanced bone fragility, usually affecting the elderly. It is very rare in children and young adults and the definition is not only based on a low BMD (a Z-score < - 2.0 in growing children and a Z-score ≤ - 2.0 or a T-score ≤ - 2.5 in young adults) but also on the occurrence of fragility fractures and/or the existence of underlying chronic diseases or secondary factors such as use of glucocorticoids. In the absence of a known chronic disease, fragility fractures and low BMD should prompt extensive screening for secondary causes, which can be found in up to 90% of cases. When fragility fractures occur in childhood or young adulthood without an evident secondary cause, investigations should explore the possibility of an underlying monogenetic bone disease, where bone fragility is caused by a single variant in a gene that has a major role in the skeleton. Several monogenic forms relate to type I collagen, but other forms also exist. Loss-of-function variants in LRP5 and WNT1 may lead to early-onset osteoporosis. The X-chromosomal osteoporosis caused by PLS3 gene mutations affects especially males. Another recently discovered form relates to disturbed sphingolipid metabolism due to SGMS2 mutations, underscoring the complexity of molecular pathology in monogenic early-onset osteoporosis. Management of young patients consists of treatment of secondary factors, optimizing lifestyle factors including calcium and vitamin D and physical exercise. Treatment with bone-active medication should be discussed on a personalized basis, considering the severity of osteoporosis and underlying disease versus the absence of evidence on anti-fracture efficacy and potential harmful effects in pregnancy.

Genetic polymorphisms and their influence on therapeutic response to alendronate-a pilot study

Introduction: Osteoporosis has a strong genetic contribution, and several genes have been shown to influence bone mineral density. Variants in the human genome are considered important causes of differences in drug responses observed in clinical practice. In terms of bone mineral density, about 26–53% of patients do not respond to amino-bisphosphonate therapies, of which alendronate is the most widely used. Material and method: The current study is prospective, observational, analytical, longitudinal and cohort type. It included 25 postmenopausal women treated with alendronate for 1 year. Bone mineral density at lumbar spine and proximal femur was measured and bone turnover markers (C-terminal telopeptide of type I collagen and procollagen 1N-terminal propeptide) were evaluated at 0 and 12 months of treatment. Six single nucleotide polymorphisms in osteoporosis-candidate genes were genotyped (FDPS rs2297480, LRP5 rs3736228, SOST rs1234612, VKORC1 rs9934438, GGPS1 rs10925503 and RANKL rs2277439). Treatment response was evaluated by percentage changes in bone mineral density and bone turnover markers. Results: The heterozygous CT of FDPS rs2297480 showed lower increases in BMD values in the lumbar spine region and the homozygous CC of the GGPS1 rs10925503 showed lower increases in terms of BMD at the total hip region. No association was found for LRP5 rs3736228, SOST rs1234612, VKORC1 rs9934438 and RANKL rs2277439. Conclusions: Romanian postmenopausal women with osteoporosis carrying the CT genotype of FDPS rs2297480 or the CC genotype of GGPS1 rs10925503 could have an unsatisfactory response to alendronate treatment. Key words: osteoporosis; genetic polymorphism; alendronate; bone mineral density; bone turnover markers,

Bone metabolism genes variation and response to bisphosphonate treatment in women with postmenopausal osteoporosis

Introduction

Long-term treatment is used in patients with osteoporosis, and bisphosphonates (BPs) are the most commonly prescribed medications. However, in some patients this therapy is not effective, cause different side effects and complications. Unfortunately, at least one year is needed to identify and confirm an ineffectiveness of BPs therapy on bone mineral density (BMD). Among other factors, a response to BPs therapy may also be explained by genetic factors. The aim of this study was to analyze the influence of SOST, PTH, FGF2, FDPS, GGPS1, and LRP5 gene variants on the response to treatment with aminobisphosphonates.

Materials and methods

Women with postmenopausal osteoporosis were included to this study if they used aminobisphosphonates for at least 12 months. Exclusion criteria were: persistence on BPs therapy less than 80%, bone metabolic diseases, diseases deemed to affect bone metabolism, malignant tumours, using of any medications influencing BMD. The study protocol was approved by the local ethics committee. The BMD at the lumbar spine and femoral neck were measured using dual x-ray absorptiometry (GE Lunar) before and at least 12 months after treatment with BPs. According to BMD change, patients were divided in two groups–responders and non-responders to BPs terapy. Polymorphic variants in SOST, PTH, FGF2, FDPS, GGPS1, and LRP5 genes were determined using PCR analysis with TaqMan probes (Thermo Scientific).

Results

In total, 201 women with BPs therapy were included in the study. No statistically significant differences were observed in age, age at menopause, weight, height, BMI and baseline BMD levels between responders (122 subjects) and non-responders (79 subjects).

As single markers, the SOST rs1234612 T/T (OR = 2.3; P = 0.02), PTH rs7125774 T/T (OR = 2.8, P = 0.0009), FDPS rs2297480 G/G (OR = 29.3, P = 2.2×10⁻⁷), and GGPS1 rs10925503 C/C+C/T (OR = 2.9; P = 0.003) gene variants were over-represented in non-responders group. No significant association between FGF2 rs6854081 and LRP5 rs3736228 gene variants and response to BPs treatment was observed. The carriers of T-T-G-C allelic combination (constructed from rs1234612, rs7125774, rs2297480, and rs10925503) were predisposed to negative response to BPs treatment (OR = 4.9, 95% CI 1.7–14.6, P = 0.005). The C-C-T-C combination was significantly over-represented in responders (OR = 0.1, 95% CI 0.1–0.5, P = 0.006).

Conclusions

Our findings highlight the importance of identified single gene variants and their allelic combinations for pharmacogenetics of BPs therapy of osteoporosis. Complex screening of these genetic markers could be used as a new strategy for personalized antiresorptive therapy.

Polymorphisms in key bone modulator cytokines genes influence bisphosphonates therapy in postmenopausal women

Osteoporosis is a multifactorial and debilitating disease resulting from decreased bone mineral density (BMD) and loss of tissue microarchitecture. Ineffective therapies may lead to bone fractures and subsequent death. Single nucleotide polymorphisms (SNPs) in key immune regulator genes have been associated with therapeutic response to bisphosphonates, which are the first therapeutic line of choice for osteoporosis. However, cytokine pathways and their relation with therapeutic adhesion remain to be fully elucidated. Aimed at better understanding these processes, we investigated the response to bisphosphonate therapy in postmenopausal women and four SNPs in key proinflammatory cytokines genes: IL23R +2284 (C>A) (rs10889677), IL17A +672 (G>A) (rs7747909), IL12B +1188 (T>G) (rs3212227) and INF-γ -1616 (G>A) (rs2069705). A total of 69 patients treated with bisphosphonate were followed for a period of 1 up to 4 years, genotyped and compared according to their changes in bone mineral density (BMD) and level of biochemical markers during their treatment. The INF-γ -1616 G/G associated with increased BMD values in femoral neck (GG/AA, p = 0.016) and decreased BMD values in total hip (GG/GA, p = 0.019; GG/AA, p = 0.011). In relation to biochemical markers, INF-γ -1616 SNP associated with increased alkaline phosphatase (GG/AA; p < 0.0001) and parathyroid hormone levels (AA/GA; p = 0.017). Vitamin D values changes were related to IL17A +672 (GG/GA, p = 0.034) and to IL12B +1188 (TT/TG, p = 0.046) SNPs. Besides, significant differences in changes of calcium levels correlated with IL23R +2284 (CC/CA, p = 0.016) genotypes. Altogether, we suggest that these polymorphisms may play an important role for therapeutic decisions in osteoporosis treatment.

Low density lipoprotein receptor-related protein 5 gene polymorphisms and osteoporosis in Thai menopausal women

Background

Osteoporosis, characterized by low bone mineral density (BMD) and high bone fracture risk, is prevalent in Thai menopausal women. Genetic factors are known to play a key role in BMD. Low density lipoprotein receptor-related protein 5 (LRP5), a co-receptor in the Wnt/beta-catenin pathway, is involved in many aspects of bone biology. As coding single nucleotide polymorphisms (cSNPs) of LRP5, including A1330V (rs3736228), and Asian-related Q89R (rs41494349) and N740N (rs2306862), are associated with lowered BMD, this study aimed to determine the relationship between these LRP5 polymorphisms and BMD in 277 Thai menopausal women.

Results

Only rs3736228 deviated from the Hardy–Weinberg equilibrium of allele frequency (p = 0.022). The median, range and p value for the BMD related to each SNP parameter were compared (Mann–Whitney U test). Significant differences were observed between wild-type and risk alleles for both rs3736228 (total radial, p = 0.011; and radial 33, p = 0.001) and rs2306862 (radial 33: p = 0.015) SNPs, with no significant difference for rs41494349 SNP. Linkage disequilibrium was strong for both rs3736228 and rs2306862 SNPs. Haplotype analysis identified high CC frequency in both normal and osteopenia/osteoporosis groups, with a significant odds ratio for carrying the TT haplotype; however, this was non-significant after adjusting for age. Multivariate binary logistic regression analysis performed for rs3736228 showed that individuals with a body mass index <25 kg/m² had an increased risk of osteoporosis for each decade, but the polymorphism had no effect.

Conclusions

This study did not identify LRP5 polymorphisms as a risk factor for osteoporosis in Thai menopausal women. Further studies with larger sample sizes are needed to further clarify the role of LRP5 as a genetic determinant of osteoporosis.

Electronic supplementary material

The online version of this article (doi:10.1186/s12952-016-0059-7) contains supplementary material, which is available to authorized users.

Association Between Geranylgeranyl Pyrophosphate Synthase Gene Polymorphisms and Bone Phenotypes and Response to Alendronate Treatment in Chinese Osteoporotic Women

Objective To investigate the relationship between geranylgeranyl pyrophosphate synthase (GGPPS) gene polymorphisms and bone response to alendronate in Chinese osteoporotic women.Methods A total of 639 postmenopausal women with osteoporosis or osteopenia were included and randomly received treatment of low dose (70 mg per two weeks) or standard dose (70 mg weekly) of alendronate for one year. The six tag single nucleotide polymorphisms of GGPPS gene were identified. Bone mineral density (BMD), serum cross-linked C-telopeptide of type I collagen (β-CTX), and total alkaline phosphatase (ALP) were measured before and after treatment. GGPPS gene polymorphisms and the changes of BMD and bone turnover markers after treatment were analyzed.Results rs10925503 polymorphism of GGPPS gene was correlated to serum β-CTX levels at baseline, and patients with TT genotype had significantly higher serum β-CTX level than those with TC or CC genotype (all P<0.05). No correlation was found between polymorphisms of GGPPS gene and serum total ALP levels, as well as BMD at baseline. After 12 months of treatment, lumbar spine and hip BMD increased and serum bone turnover markers decreased significantly (P<0.01), and without obvious differences between the low dose and standard dose groups (all P>0.05). However, GGPPS gene polymorphisms were uncorrelated to percentage changes of BMD, serum total ALP, and β-CTX levels (all P>0.05).Conclusion GGPPS gene polymorphisms are correlated to osteoclasts activity, but all tag single nucleotide polymorphisms of GGPPS gene have no influence on the skeletal response to alendronate treatment.

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.

LRP5 polymorphisms and response to alendronate treatment in Chinese postmenopausal women with osteoporosis

AIM

To investigate the association between LRP5 gene polymorphisms and response to alendronate in Chinese osteoporotic women.

MATERIALS & METHODS

Six hundred and thirty nine Chinese postmenopausal women with osteopenia or osteoporosis were included and received alendronate treatment. The A1330V polymorphism of LRP5 was investigated. Bone mineral density (BMD) and bone turnover markers (ALP and β-isomerized carboxy-telopeptide of type I collagen [β-CTX]) were measured before and after treatment. The correlation of LRP5 polymorphisms with changes in BMD and bone turnover biomarkers were analyzed after treatment.

RESULTS

After 12 months of treatment, participants with CC and CT genotypes had a larger increase in lumbar spine BMD and a larger decrease in serum β-CTX and ALP levels than those with TT genotype (all p < 0.001). No significant genotype-treatment interaction was found in hip BMD.

CONCLUSION

The A1330V polymorphism of LRP5 is possibly correlated with response to alendronate treatment in Chinese women with osteoporosis, and the TT genotype could possibly predict a weak response to alendronate.

Common polymorphism in the LRP5 gene may increase the risk of bone fracture and osteoporosis

The low-density lipoprotein receptor-related protein 5 gene (LRP5) was identified to be linked to the variation in bone mineral density and types of bone diseases. The present study was aimed at examining the association of LRP5 rs3736228 C>T gene with bone fracture and osteoporosis by meta-analysis. A systematic electronic search of literature was conducted to identify all published studies in English or Chinese on the association of the LRP5 gene with bone fracture and osteoporosis risks. All analyses were calculated using the Version 12.0 STATA software. Odds ratios (ORs) and their corresponding 95% confidence interval (95% CI) were calculated. An updated meta-analysis was currently performed, including seven independent case-control studies. Results identified that carriers of rs3736228 C>T variant in the LRP5 gene were associated with an increased risk of developing osteoporosis and fractures under 4 genetic models but not under the dominant model (OR = 1.19, 95% CI = 0.97~1.46, and P = 0.103). Ethnicity-subgroup analysis implied that LRP5 rs3736228 C>T mutation was more likely to develop osteoporosis and fractures among Asians and Caucasians in majority of subgroups. These results suggest that there is a modest effect of the LRP5 rs3736228 C>T on the increased susceptibility of bone fracture and osteoporosis.

Pharmacogenetics of osteoporosis

The challenge of personalized medicine is to move away from the traditional 'one-size-fits-all' pharmacology to genotype-based individualized therapies. As an individual's response to drugs is under the control of genes, personal genetic profiles could help clinicians to predict individual drug response and prescribe the right drug and dose, thereby optimising efficacy and avoiding risk of adverse effects. Currently, the concrete application of pharmacogenetics into clinical practice is limited to a few drugs, and the genetic prediction of drug response is far from clear for many of thve principal complex disorders. This is even more evident in the field of osteoporosis and metabolic bone disorders, for which few pharmacogenetic studies have been conducted, and no conclusive results are available. In this chapter, we review recent research on pharmacogenetics of osteoporosis, evaluate criticisms, and offer possible suggestions for improvements in this field and for possible future applications into clinical practice.

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.

Pharmacogenomics of osteoporotic fractures

Osteoporosis is a prevalent disease that typically reduces bone strength and predisposes to fractures. It is a multifactorial disorder resulting from the interaction of genetic and acquired factors. Candidate gene studies and, more recently, genome-wide studies have identified a number of polymorphisms significantly associated with bone mass and fractures. Anti-resorptive drugs, which inhibit the differentiation and activity of osteoclasts, are frequently used to treat patients with osteoporosis.Several candidate gene studies have explored the association of genetic factors with drug response, including some common polymorphisms of the gene encoding FDPS (Farnesyl diphosphate synthase), an enzyme that is the main target of aminobisphosphonates. Although scarce data are available, interesting opportunities are open for a better understanding of the pharmacogenetics of osteoporosis and osteoporotic fractures. They include the reanalysis of data already available from epidemiological studies and clinical trials, as well as obtaining pharmacogenetic data in new studies. However, based upon the experience with previous genome-wide association studies, large collaborative efforts would be likely needed to obtain meaningful results.

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.

Pharmacogenetics of osteoporosis: towards novel theranostics for personalized medicine?

Osteoporosis is a complex multifactorial bone disorder with a strong genetic basis. It is the most common, severe, progressive skeletal illness that has been increasing, particularly in developed countries. Osteoporosis will no doubt constitute a serious clinical burden in healthcare management in the coming decades. The genetics of osteoporosis should be analyzed from both the disease susceptibility and the pharmacogenetic treatment perspectives. The former has been widely studied and discussed, while the latter still requires much more information and research. This article provides a synthesis of the literature on the genetics of osteoporosis and an update on progress made in pharmacogenetics of osteoporosis in recent years, specifically regarding the new molecular targets for antiresorptive drugs. In-depth translation of osteoporosis pharmacogenetics approaches to clinical practice demands a new vision grounded on the concept of "theranostics," that is, the integration of diagnostics for both disease susceptibility testing, as well as for prediction of health intervention outcomes. In essence, theranostics signals a broadening in the scope of inquiry in diagnostics medicine. The upcoming wave of theranostics medicine also suggests more distributed forms of science and knowledge production, both by experts and end-users of scientific products. Both the diagnosis and personalized treatment of osteoporosis could conceivably benefit from the emerging postgenomics field of theranostics.

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.

Pharmacogenomics of osteoporosis: a pathway approach

Osteoporosis is frequent in postmenopausal women and old men. As with other prevalent disorders, it is the consequence of complex interactions between genetic and acquired factors. Candidate gene and genome-wide association studies have pointed to several genes as determinants of the risk of osteoporosis. Some of them were previously unsuspected and may help to find new therapeutic targets. Several drugs already available are very effective in increasing bone mass and decreasing fracture risk. However, not all patients respond properly and some of them suffer fragility fractures despite therapy. Investigators have tried to identify the genetic features influencing the response to antiosteoporotic therapy. In this article we will review recent data providing insight into new genes involved in osteoporosis and the pharmacogenetic data currently available.

Pharmacogenetics of osteoporosis: what is the evidence?

The early genetic prediction of personal drug therapy outcome, both in terms of identification of poor responders or nonresponders, as well as of subjects at risk of developing adverse reactions, and its translation into the clinical practice are the main challenges of personalized medicine. The application of pharmacogenetic predictive tests will be very useful mostly in cases of chronic disorders, as in metabolic bone diseases, that require long-term treatments and for whom exist effective differently acting drugs to be alternatively chosen. Pharmacogenetic tests, prior to drug administration, would hypothetically grant the optimization of drug therapy, based on patient's genotype, to ensure maximum efficacy with minimal adverse effects. This review aims to offer an overview on the principal findings in the field of pharmacogenetics of osteoporosis, and it will discuss future perspectives and possible clinical applications of pharmacogenetic tests for antiresorptive drugs.

Pharmacogenetics of osteoporosis-related bone fractures: moving towards the harmonization and validation of polymorphism diagnostic tools

Osteoporosis is one of the most common skeletal chronic conditions in developed countries, hip fracture being one of its major healthcare outcomes. There is considerable variation in the implementation of current pharmacological treatment and prevention, despite consistent recommendations and guidelines. Many studies have reported conflicting findings of genetic associations with bone density and turnover that might predict fracture risk. Moreover, it is not clear whether genetic differences exist in relation to the morbidity and efficiency of the pharmacotherapy treatments. Clinical response, including beneficial and adverse events associated with osteoporosis treatments, is highly variable among individuals. In this context, the present article intends to summarize putative candidate genes and genome-wide association studies that have been related with BMD and fracture risk, and to draw the attention to the need for pharmacogenetic methodology that could be applicable in clinical translational research after an adequate validation process. This article mainly compiles analysis of important polymorphisms in osteoporosis documented previously, and it describes the simple molecular biology tools for routine genotype acquisition. Validation of methods for the easy, fast and accessible identification of SNPs is necessary for evolving pharmacogenetic diagnostic tools in order to contribute to the discovery of clinically relevant genetic variation with an impact on osteoporosis and its personalized treatment.

Common allelic variants of the farnesyl diphosphate synthase gene influence the response of osteoporotic women to bisphosphonates

Farnesyl diphosphate synthase (FDPS) is necessary for osteoclast survival and activity and is considered as a major molecular target of aminobisphosphonates. Our objective was to analyze the influence of FDPS polymorphisms on bone mineral density (BMD) and the response to antiresortive drugs. Three single-nucleotide polymorphisms of FDPS were analyzed in 1186 postmenopausal women. There was only a marginally significant association of baseline hip BMD with rs11264359 alleles (P=0.043). However, among 191 women receiving antiresortive therapy, there was a very significant association between rs2297480 or rs11264359 alleles and the BMD changes after aminobisphosphonate therapy for an average period of 2.5 years (P=0.001). The genotype explained 7.2% of the variance in the BMD response. On the other hand, there was no association between the BMD changes after raloxifene therapy and any of the polymorphisms studied. These results suggest that common polymorphisms of the FDPS gene influence the response to aminobisphosphonates.

Pharmacogenetics of osteoporosis

Osteoporosis is the most common and serious skeletal disorder of the elderly; it is characterized by reduced bone mass and deterioration of bone microarchitecture, with an increased risk of low-trauma fractures. Genetic factors are important predisposing elements influencing individual bone strength variability and susceptibility to osteoporosis and related complications. The genetics of osteoporosis encompasses two main areas: disease susceptibility and pharmacogenetics of drug response. The former has been widely studied while the latter is still largely untouched. Pharmacogenetics is the study of relationships between genetic variations and inter-individual differences in drug response in terms of efficacy and adverse effects, representing an opportunity to identify new biomarkers for drug development and drug response. However, pharmacogenetic approaches to osteoporosis are still in their infancy, needing to be developed further and combined with functional studies. This article provides an overview on the current basic research applications in the pharmacogenetics of osteoporosis and their implications for clinical practice.

Pharmacogenetics of osteoporosis

Osteoporosis is a complex bone disorder with a strong genetic basis. The genetics of osteoporosis encompasses two main areas: genetics of disease susceptibility and pharmacogenetics of drug response. The former has been widely studied in the past few decades, while the latter is still largely untouched. This review will provide an overview of the pharmacogenetics of osteoporosis, focusing on the major recent advances in the past two years.