FGF-21 levels identify RA patients at risk of functional decline

Levels of fibroblast growth factor (FGF)-21, an adipokine linked to metabolic stress, correlate with obesity and inflammatory cytokines, as well as with worsening physical functioning in patients with rheumatoid arthritis (RA), suggests a study.

RA patients aged 18–70 years completed whole-body dual-energy x-ray absorptiometry and peripheral quantitative computed tomography at baseline and follow-up to quantify lean mass, fat mass, and muscle density.

Muscle strength at the hand and knee was assessed using dynamometry, and physical functioning was measured with the Health Assessment Questionnaire (HAQ) and the Short Physical Performance Battery (SPPB). FGF-21 and inflammatory cytokines were measured at baseline.

The investigators performed linear and logistic regression analyses to assess associations between FGF-21 levels and both body composition and physical functioning over time.

Of the 113 RA patients enrolled, 84 (74 percent) returned for follow-up at a median of 2.68 years. FGF-21 levels at baseline correlated with age, smoking, methotrexate use, adiposity, and inflammatory cytokines (ie, tumour necrosis factor receptor type 1, YKL-40, vascular endothelial growth factor [VEGF], and resistin). The highest FGF-21 quartile correlated with worse SPPB and HAQ.

In addition, higher baseline FGF-21 levels were associated with worsening in muscle density and area z-scores (β, –0.06, 95 percent CI, –0.12 to 0.008; p=0.08; β, –0.05, 95 percent CI, –0.10 to 0.006; p=0.08, respectively) and a greater probability of a clinically meaningful worsening of HAQ (OR, 2.37, 95 percent CI, 1.21–4.64; p=0.01).

Finally, as association was found between the fourth FGF-21 quartile and worsening of SPPB (β, –0.57, 95 percent CI, –1.04 to –0.09; p=0.02).

“These data support the hypothesis that FGF-21 can identify patients at risk of functional decline,” the investigators said.