FGF23-Klotho axis in patients with rheumatoid arthritis.

Objectives: We aimed to compare serum Klotho and fibroblast growth factor-23 (FGF-23) levels between rheumatoid arthritis (RA) patients and healthy controls. Possible association between FGF-23 and soluble Klotho with different characteristic of the disease as well as their potential role as surrogate markers of cardiovascular disease (CVD) were studied.

Methods: Sixty-three patients with RA recruited at Vega-Baja Hospital, Orihuela (Spain) from November 2016 to May 2018 and sixty-five age- and sex-matched healthy controls were included in this study. Serum Klotho and FGF-23 were analysed using ELISA.

Results: Patients had higher serum levels of Klotho than healthy controls (p˂0.0001). They were positively associated with the presence of anticitrullinated peptide antibody and rheumatic factor (p<0.05). Klotho serum levels were higher in RA patients treated with biologic agents than in those undergoing conventional therapy (p=0.008). However, no association with carotid intima media thickness was found. Although no significant differences in serum FGF-23 levels between patients and controls were found (p=0.43), FGF-23 levels were positively associated with low-density lipoprotein (LDL-c) level (p<0.05) and smoking (p=0.008) in patients with RA.

Conclusions: The increased serum Klotho levels in RA patients, especially in those undergoing biologic therapy, may indicate a potential implication in the pathogenesis of the disease. Although levels of FGF-23 were related to LDL-c levels, the FGF-23-Klotho axis does not seem to be related to subclinical arteriosclerosis in RA.