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

Associations of osteoprotegerin (OPG) TNFRSF11B gene polymorphisms with risk of fractures in older adult populations: meta-analysis of genetic and genome-wide association studies

The meta-analysis of osteoprotegerin (OPG) (TNFRSF11B) polymorphisms from genetic association studies and genome-wide association studies was performed in order to test the hypothesis of association between OPG polymorphisms and fracture. The findings showed a significant 13% to 37% protective effect of OPG on fractures in postmenopausal women (PSM) (rs2073618), overall, ≥ 60y and Western subjects (rs3134069 and rs3134070).

PURPOSE

Fractures in older people usually result from compromised bone integrity. The multifactorial aetiology of fractures includes both genetic and environmental factors. Inconsistency of reported associations of osteoprotegerin (OPG) (TNFRSF11B) polymorphisms with fracture in the older adult population warranted a meta-analysis to determine more precise estimates.

METHODS

We searched for all available literature on OPG (TNFRSF11B) and fracture. Four polymorphisms were examined, one exonic (rs2073618) and three intronic (rs3134069, rs3134070 and rs3102735). The first two intron polymorphisms were combined (OPGI: osteoprotegerin intron) on account of complete linkage disequilibrium. Risks were estimated with odds ratios (ORs) and 95% confidence intervals (CIs) using the allele-genotype model that included variant (var), wild-type (wt) and heterozygote (het). Multiple comparisons were Bonferroni-corrected. We used meta-regression to examine sources of heterogeneity. Zero heterogeneity (homogeneity: I² = 0%) and high significance (P^a < 0.00001) were the criteria for strength of evidence. Significant outcomes were subjected to sensitivity analysis and publication bias assessment.

RESULTS

From 13 articles (11 genetic association and two genome-wide), this meta-analysis generated five significant pooled ORs, all indicating reduced risks (ORs 0.44-0.87). Of the five, four highly significant comparisons (P^a ≤ 0.00001-0.002) survived the Bonferroni correction, one in rs2073618 het model of the postmenopausal women (OR 0.87, 95% CI 0.81-0.92, I² = 0%) and the other three in OPGI wt model of the overall analysis, ≥ 60 y and Western subjects (ORs 0.63-0.71, 95% CI 0.47-0.86, I² = 97-99%). These findings were consistent, had high significance and high statistical power and were robust and without evidence of publication bias. Four covariates (year of publication, study quality, fracture type/site and sample size) were the sources of heterogeneity in the OPGI overall outcomes (P^a = 0.0001-0.03).

CONCLUSION

Evidence showed that the OPG (TNFRSF11B) polymorphisms reduced the risk for fracture in older adults, particularly protective among postmenopausal women, ≥ 60 y and Western subjects.

Polymorphisms of FDPS, LRP5, SOST and VKORC1 genes and their relation with osteoporosis in postmenopausal Romanian women

OBJECTIVES

This study aimed to assess the relationship between bone mineral density and genotypes of four polymorphisms in previously detected osteoporosis-candidate genes (FDPS rs2297480, LRP5 rs3736228, SOST rs1234612, VKORC1 rs9934438) in postmenopausal Romanian women with primary osteoporosis.

METHODS

An analytical, prospective, transversal, observational, case-control study on 364 postmenopausal Romanian women was carried out between June 2016 and August 2017 in Cluj Napoca, Romania. Clinical data and blood samples were collected from all study participants. Four polymorphisms were genotyped using TaqMan SNP Genotyping assays, run on a QuantStudio 3 real-time PCR machine.

RESULTS

Women with TT genotype in FDPS rs2297480 had significantly lower bone mineral density values in the lumbar spine and total hip, and the presence of the T allele was significantly associated with the osteoporosis. Women carrying the CC genotype in LRP5 rs3736228 tend to have lower bone mineral density values in the femoral neck and total hip. No significant association was found for the genotypes of SOST rs1234612 or VKORC1 rs9934438.

CONCLUSIONS

Our study showed a strong association between bone mineral density and polymorphisms in the FDPS gene, and a borderline association with LRP5 and SOST polymorphisms in postmenopausal Romanian women with osteoporosis. No association was found for VKORC1.

New Molecules Modulating Bone Metabolism – New Perspectives in the Treatment of Osteoporosis

In this review the authors outline traditional antiresorptive pharmaceuticals, such as bisphosphonates, monoclonal antibodies against RANKL, SERMs, as well as a drug with an anabolic effect on the skeleton, parathormone. However, there is also a focus on non-traditional strategies used in therapy for osteolytic diseases. The newest antiosteoporotic pharmaceuticals increase osteoblast differentiation via BMP signaling (harmine), or stimulate osteogenic differentiation of mesenchymal stem cells through Wnt/β-catenin (icarrin, isoflavonoid caviunin, or sulfasalazine). A certain promise in the treatment of osteoporosis is shown by molecules targeting non-coding microRNAs (which are critical for osteoclastogenesis) or those stimulating osteoblast activity via epigenetic mechanisms. Vitamin D metabolites have specific antiosteoporotic potencies, modulating the skeleton not only via mineralization, but markedly also through the direct effects on the bone microstructure.