Background/Purpose:

Amyloid β (Aβ) accumulation in the brain is a risk factor for Alzheimer’s disease (AD). The incidence of AD increases with age. Rheumatoid arthritis (RA) patients have been reported to be at a lower risk of AD, and the non-steroidal anti-inflammatory drugs (NSAIDs) used to treat RA have also been shown to have an effect against AD. In this study, we measured the concentration of anti-Aβ autoantibodies (anti-AβAAB) in the serum of treatment-naive RA patients who had not previously undergone drug therapy.

Methods:

The study subjects were 174 patients with no treatment history, who presented for initial outpatient examination, complaining of joint pain between the years 2010 and 2014. They comprised of 106 patients (mean age 55.5 ± 17.2 years) diagnosed with RA based on the 2010 American College of Rheumatology/European League Against Rheumatism Classification Criteria for Rheumatoid Arthritis, and 68 (mean age: 59.1 ± 12.8 years) with unclassified arthritis (UA) who were not classifiable as having RA. Serum was collected at initial examination and stored frozen at –80ºC, with all samples measured at the same time. Anti-AβAAB was measured by an ELISA assay developed in our department. We investigated the association among anti-AβAAB titers, age, and laboratory test results (C-reactive protein, rheumatic factor, anti-CCP antibodies [CCP], IgG, IgA, and IgM). Similar measurements were also made in 50 healthy individuals (mean age: 54.6 ± 14.3 years) as control.

Results:

Anti-AβAAB titer values were 17.0 ± 2.3 units in the RA group, 11.2 ± 0.95 units in the UA group, and 8.3 ± 0.87 units in the control group, being significantly higher in the RA group than in the UA (p < 0.02) or control (p < 0.002) group. An investigation of the association between anti-AβAAB titer and laboratory test results identified a weak positive correlation with age in the control and UA groups (r = 0.240, r = 0.234), and a negative correlation with age in the RA group (r = –0.418). An investigation of the association between anti-AβAAB titer and CCP classified RA patients into the following three groups: in half (n = 57) both anti-AβAAB titer and CCP were low (anti-AβAAB < 20 units, CCP < 200 IU/ml), in one quarter (n = 25) anti-AβAAB titer was high and CCP was low, and in the other quarter (n = 24) anti-AβAAB titer was low and CCP was high.

Conclusion:

The anti-AβAAB titer was significantly higher in treatment-naive RA patients. In the RA group, the anti-AβAAB titer negatively correlated with age. RA patients with high anti-AβAAB titer tended to have low levels of CCP, and those with high CCP tended to have low levels of anti-AβAAB. Studies involving larger numbers of patients to investigate changes in anti-AβAAB titer during treatment are required, but our results suggest that CCP levels may be implicated in the relationship between RA and AD.

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ACR Meeting Abstracts - https://acrabstracts.org/abstract/measurement-of-anti-amyloid-%ce%b2-autoantibodies-in-patients-with-rheumatoid-arthritis/