Osteoprotegerin as biomarker for persistence of rheumatoid arthritis

Osteoprotegerin and MTHFR gene variations in rheumatoid arthritis: association with disease susceptibility and markers of subclinical atherosclerosis

We aimed to explore whether the rs2073618 variant (G1181C) of the osteoprotegerin (OPG) gene and the methylenetetrahydrofolate reductase (MTHFR) rs1801131 (A1298AC) and rs1801133 (C677T) gene polymorphisms contribute to rheumatoid arthritis (RA) susceptibility and RA related subclinical atherosclerosis. Overall 283 RA patients and 595 healthy controls (HC) were genotyped for common variants of the OPG and MTHFR genes using PCR based assays. Clinical and laboratory parameters were recorded following thorough chart review. Surrogate markers of subclinical atherosclerosis (Carotid/Femoral intima media thickness/plaque formation) along with traditional risk factors for atherosclerosis were assessed in all RA patients and 280HC. Increased prevalence of the CC genotype of the rs2073618 variant was detected in RA patients vs HC (42.4% vs. 33%, p-value: 0.04). RA patients with high serum titers of rheumatoid factor (RF) or anti-cyclic citrullinated peptide (CCP) antibodies displayed increased prevalence of the CC genotype of the rs2073618 variant of the OPG gene compared to HC (48.6% and 47.5 vs 33.3%, p-values: 0.0029and 0.0077 respectively). Of interest, this genotype turned to be associated with higher carotid IMT scores (0.872 ± 0.264 vs 0.816 ± 0.284, p-value: 0.01) and marginally with higher rates of carotid plaque formation (66% vs 54.1%, p = 0.06). The MTHFR 1298CC genotype was more prevalent only in the anti-CCP positive group compared to HC, with no associations detected with markers of subclinical atherosclerosis, following adjustment for traditional cardiovascular (CVD) risk factors. Reduced rates of carotid/femoral plaque formation were detected among RA patients harboring the MTHFR TT genotype (52.4 vs 72.7, p-value: 0.009, respectively). This association remained significant following adjustment for classical CVD risk factors (OR [95% CI 0.364 [0.173-0.765], p-value: 0.008). Genetic variations of the osteoprotegerin and MTHFR genes seem to increase susceptibility for seropositive RA and potentially contribute to subclinical atherosclerosis linked to RA. Larger studies are needed to confirm these findings.

Effect of Osteoprotegerin and Dickkopf-Related Protein 1 on Radiological Progression in Tightly Controlled Rheumatoid Arthritis

Objective

To analyze the association between circulating osteoprotegerin (OPG) and Dickkopf-related protein 1 (DKK-1) and radiological progression in patients with tightly controlled rheumatoid arthritis (RA).

Methods

Serum levels of OPG and DKK-1 were measured in 97 RA patients who were treated according to a treat-to-target strategy (T2T) aimed at remission (DAS28<2.6). Radiologic joint damage progression was assessed by changes in the total Sharp-van der Heijde score (SHS) on serial radiographs of the hands and feet. The independent association between these biomarker levels and the structural damage endpoint was examined using regression analysis

Results

The mean age of the 97 RA patients (68 women) at the time of the study was 54 ± 14 years, and the median disease duration was 1.6 ± 1.5 years. Most patients were seropositive for either RF or ACPA, and the large majority (76%) were in remission or had low disease activity.

After a median follow-up time of 3.3 ± 1.5 years (range, 1–7.5 yrs.), the mean total SHS annual progression was 0.88 ± 2.20 units. Fifty-two percent of the patients had no progression (defined as a total SHS of zero). The mean serum OPG level did not change significantly over the study period (from 3.9 ± 1.8 to 4.07 ± 2.23 pmol/L), whereas the mean serum DKK-1 level decreased, although not significantly (from 29.9 ± 10.9 to 23.6 ± 18.8 pmol/L).

In the multivariate analysis, the predictive factors increasing the likelihood of total SHS progression were age (OR per year = 1.10; p = 0.003) and a high mean C-reactive protein level over the study period (OR = 1.29; p = 0.005). Circulating OPG showed a protective effect reducing the likelihood of joint space narrowing by 60% (95% CI: 0.38–0.94) and the total SHS progression by 48% (95% CI: 0.28–0.83). The DKK-1 levels were not associated with radiological progression.

Conclusion

In patients with tightly controlled RA, serum OPG was inversely associated with progression of joint destruction. This biomarker may be useful in combination with other risk factors to improve prediction in patients in clinical remission or low disease activity state.