An osteoprotegerin gene polymorphism is associated with an increased risk of hip fracture in Japanese patients with rheumatoid arthritis: results from the IORRA Observational Cohort Study

OPG/RANK/RANKL Single-Nucleotide Polymorphisms in Rheumatoid Arthritis: Associations with Disease Susceptibility, Bone Mineral Density, and Clinical Manifestations in a Chinese Han Population

Objective

The osteoprotegerin (OPG)/receptor activator of nuclear factor-κB (RANK)/receptor activator of nuclear factor-κB ligand (RANKL) system plays a pivotal role in the balance between osteoblasts and osteoclasts and is closely related to the pathogenesis of rheumatoid arthritis (RA). The present study aimed to clarify the associations of OPG/RANK/RANKL gene single-nucleotide polymorphisms (SNPs) with disease susceptibility, bone mineral density (BMD), and clinical manifestations in RA patients.

Methods

A case-control study including 319 RA patients and 330 healthy controls was conducted. All subjects were genotyped for rs4355801 and rs1023968 in OPG, rs10805033 in RANK, and rs9533155 and rs875625 in RANKL. BMD and clinical manifestations were recorded.

Results

An association was found between OPG rs4355801 and risk of RA. In recessive models, the GG genotype of rs4355801 was associated with an increased risk of RA compared with the AA/AG genotypes (OR=1.679, 95% CI: 1.062-2.655, p=0.025). A correlation between RANKL rs9533155 and BMD was found in RA patients. Patients with the GG genotype (n=108) in RANKL rs9533155 had the more decreased BMD values at lumbar level 2 (t=3.424, p=0.009), lumbar level 3 (t=3.171, p=0.019), lumbar level 4 (t=4.187, p=0.001), and total lumbar levels 2-4 (t=2.989, p=0.021) compared with CC+GC genotypes. No associations were found between the OPG, RANK, and RANKL SNPs and clinical manifestations of RA (all p>0.05). Logistic regression analysis indicated that older age (OR=1.057, 95% CI: 1.017-1.099, p=0.005), higher HAQ (OR=2.786, 95% CI: 1.329-5.841, p=0.007), and GG genotype of rs9533155 (OR=3.242, 95% CI: 1.254-8.376, p=0.015) were risk factors of lumbar osteoporosis onset in RA patients.

Conclusion

In summary, OPG rs4355801 is associated with susceptibility to RA and RANKL rs9533155 GG genotype potentially contributes to decreased BMD in RA. Studies with larger sample sizes are needed to confirm the present findings.

Clinical Observations of Osteoporosis in Japanese Patients with Rheumatoid Arthritis

Osteoporosis is the one of the major adverse outcomes in patients with rheumatoid arthritis (RA). Recently, we and others have been reported many clinical observations related to osteoporosis in Japanese RA patients. In this article, I reviewed these findings. Japanese patients with RA have a two-fold risk of fractures compared with those without RA. Among the fractures in Japanese RA patients, three quarters of the fractures were non-vertebral fractures. The incidence of non-vertebral fractures did not change, despite an improvement in RA disease activity. Older age, female gender, history of fractures, history of total knee replacements, disease activity scores in 28 joints (DAS28), health assessment questionnaire disability index (HAQ-DI), low bone mineral density, glucocorticoid dose, and vitamin D deficiency were significantly associated with fractures. Older age, high body mass index (BMI), HAQ-DI, and polypharmacy were significantly associated with falls. BMI (both overweight and underweight), DAS28, and HAQ-DI were significantly associated with frailty. Half and three quarters of Japanese men and women with RA had vitamin D deficiency, respectively. The incidence of osteonecrosis of the jaw may be higher in Japanese RA patients than those without RA. Undertreatment of osteoporosis appears to exist in Japanese patients with RA.

Selected RANKL/RANK/OPG system genetic variants in diabetic foot patients

Purpose

Diabetic foot is a complication of long-lasting diabetes mellitus affecting up to 15% of patients, both in type 1 and type 2 diabetes. Osteoprotegerin is involved in osteogenesis and calcification. The aim of the study was to assess the role of selected osteoprotegerin gene variants in diabetes patients with diabetic foot.

Methods

The study involved 300 patients with diabetes and diabetic foot and 968 healthy controls. The study group was formed by 243 patients with diabetic foot of neuropathic origin, 102 with diabetic foot of neuroischemic origin and 77 with Charcot neuroarthropathy.

Results

Compared to controls, rs1872426 and rs1485286 showed correlation with diabetic foot in diabetes subjects. Significant associations between rs2073618, rs1872426, rs7464496 and rs1485286 in men were reported. The aforementioned correlations were also present in type 2 diabetes patient subgroup. Variant rs1485286 was associated to diabetic foot of neuropathic origin. Sex-specificity for females was present for rs6993813 in patients with diabetic foot of neuropathic origin and type 1 diabetes. Variants rs1872426, rs2073617 and rs1485286 were correlated with CN. We found that age, body weight, body mass index, waist circumference, hip circumference and waist-hip ratio were among the basic risk factors of diabetic foot.

Conclusions

The following variants TNFRSF11B (rs2073618, rs2073617, rs1872426, rs1032128, rs7464496, rs11573829 and rs1485286), COLEC10 (rs6993813, rs3134069) and TNFSF11 (rs9533156) present differences in allele frequencies in diabetic foot patients and show correlation with gender, diabetes type and diabetic foot etiology.

Identification of novel genetic loci for osteoporosis and/or rheumatoid arthritis using cFDR approach

There are co-morbidity between osteoporosis (OP) and rheumatoid arthritis (RA). Some genetic risk factors have been identified for these two phenotypes respectively in previous research; however, they accounted for only a small portion of the underlying total genetic variances. Here, we sought to identify additional common genetic loci associated with OP and/or RA. The conditional false discovery rate (cFDR) approach allows detection of additional genetic factors (those respective ones as well as common pleiotropic ones) for the two associated phenotypes. We collected and analyzed summary statistics provided by large, multi-center GWAS studies of FNK (femoral neck) BMD (a major risk factor for osteoporosis) (n = 53,236) and RA (n = 80,799). The conditional quantile-quantile (Q-Q) plots can assess the enrichment of SNPs related to FNK BMD and RA, respectively. Furthermore, we identified shared loci between FNK BMD and RA using conjunction cFDR (ccFDR). We found strong enrichment of p-values in FNK BMD when conditional Q-Q was done on RA and vice versa. We identified 30 novel OP-RA associated pleiotropic loci that have not been reported in previous OP or RA GWAS, 18 of which located in the MHC (major histocompatibility complex) region previously reported to play an important role in immune system and bone health. We identified some specific novel polygenic factors for OP and RA respectively, and identified 30 novel OP-RA associated pleiotropic loci. These discovery findings may offer novel pathobiological insights, and suggest new targets and pathways for drug development in OP and RA patients.

Time-averaged disease activity fits better joint destruction in rheumatoid arthritis

Disease activity of rheumatoid arthritis (RA), evaluated as Disease Activity Score (DAS), is associated with joint destruction. Since joint destruction reflects the history of disease activities, we hypothesized that time-averaged disease activity would better correlate with joint destruction than one-time disease activity. We recruited RA patients in IORRA (n = 557) and KURAMA (n = 204) cohorts, and calculated time-averaged DAS28 to model a modified Sharp/van der Heijde score (SHS). We evaluated the fitting of the model using time-averaged DAS28 among 1000 models in which we randomly picked up one-time DAS28. We also used clinical disease activity index (CDAI) or data in the BeSt study (European population). After conditioning on autoantibody and disease duration, time-averaged DAS28 showed significant improvement of model fitting compared with one-time DAS28 in both cohorts (p = 0.001 and 0.034, respectively). Time-averaged CDAI also showed a better fit. Integration of multiple DAS fit SHS better in the BeSt study. A good fit of time-averaged DAS could be observed using five to six time points of DAS. In conclusion, time-averaged disease activity fits the joint destruction model better than one-time disease activity. Usage of time-averaged disease activity as a covariate would increase the power of studies to identify novel correlates of joint destruction.

Estrogen receptor α (ESR1) IVS1-397T>C polymorphism lowers risk of fracture

BACKGROUND

Genetic factors are reported to affect fracture incidence. Many groups have explored the correlation of fracture risk with ESR1 IVS1-397T>C. The observed associations, however, are largely inconsistent. This meta-analysis of data from early-released studies was performed in an effort to determine the role of IVS1-397T>C in fracture.

METHODS

Relevant studies were searched through Pubmed, Embase, ScienceDirect, and Wiley Online Library databases. 16 studies meeting all selection criteria were finally identified. We calculated ORs with 95% CIs to assess risk of fracture. Subgroup analyses were performed by subtype, ethnicity and gender.

RESULTS

Data on 2916 cases and 19170 controls were analyzed in the meta-analysis. Overall, we found moderately decreased risk in association with IVS1-397 CC genotype (OR = 0.82, 95% CI = 0.73-0.92; OR = 0.84, 95% CI = 0.76-0.94). The decrease persisted in both hip fracture (OR = 0.82, 95% CI = 0.71-0.94; OR = 0.83, 95% CI = 0.73-0.94) and vertebral fracture (OR = 0.67, 95% CI = 0.50-0.91; OR = 0.78, 95% CI = 0.64-0.97; OR = 0.82, 95% CI = 0.68-0.98) when data were stratified by subtype. We also found a significant trend of decreasing risk in relation to the CC genotype in Caucasian, male and female. All fixed-effects meta-analysis results were homogeneous.

CONCLUSION

The meta-analysis demonstrates that risk of fracture seems likely to be decreased due to IVS1-397 CC or CT genotype.