Glucose-6-phosphate isomerase is associated with disease activity and declines in response to infliximab treatment in rheumatoid arthritis.

Background Rheumatoid arthritis (RA), a systemic autoimmune disease characterized by synovial inflammation, can cause cartilage and bone damage as well as disability. The aim of this study was to explore whether serum glucose-6-phosphate isomerase (GPI) is correlated with disease activity and the value of GPI in the evaluation of infliximab treatment in patients with RA. Methods Sixty-two patients with RA who had an inadequate response to methotrexate (MTX) were enrolled in Peking University People's Hospital from July 1, 2016 to July 31, 2018. Infliximab (3 mg/kg, intravenous at weeks 0, 2, and 6 and then every 8 weeks) was administered to patients with stable background MTX therapy. Serum samples were obtained at baseline and week 18. Serum GPI levels were determined using enzyme-linked immunosorbent assay. The associations between serum GPI levels and clinical features were analyzed. Results Serum GPI was positively correlated with Disease Activity Score in 28 joints (DAS28), swollen joint count, tender joint count and C-reactive protein level (P < 0.001, P < 0.001, P < 0.001, and P = 0.033, respectively). The change of DAS28 in GPI-positive patients was greater than that in GPI-negative patients (P < 0.001). Compared with those for patients receiving MTX monotherapy at baseline, the GPI levels were significantly declined when MTX was combined with infliximab (P < 0.001). Conclusion Serum GPI is related to disease activity and clinical response to infliximab treatment.