The role of fatty acid-binding proteins in evaluating kidney involvement in patients with ankylosing spondylitis

Kidney involvement is one of the extraarticular manifestations of ankylosing spondylitis (AS). Due to a number of disadvantages of traditional parameters for evaluating renal function, an active search is underway for new markers.

Objective: to evaluate urinary excretion of liver-type and heart-type fatty acid-binding proteins (L-FABP and H-FABP) in patients with AS.

Subjects and methods. Urine samples were examined in 50 patients (37 men and 13 women) at least 18 years of age with a reliable diagnosis of AS without secondary nephropathy (with the exception of AS-associated changes). The median age of the patients was 39 [34; 56] years; the duration of AS was 10 [7; 18] years. L-FABP and H-FABP levels were measured by enzyme-linked immunosorbent assay. The values obtained were given for urinary creatinine excretion. The results were compared with those of the gender- and age-matched control group.

Results and discussion. L-FABP excretion in patients with AS without chronic kidney disease (CKD) was significantly higher than that in the control group: 0.05 [0.01; 0.09] and 0.03 [0; 0.06] ng/mmol of creatinine, respectively (p=0.04). Only 6 patients were found to have H-FABP excretion and its level did not exceed 601.5 ng/mmol of creatinine. In healthy volunteers, the excretion of H-FABP was below the detection range. The level of FABPs did not depend on age, glomerular filtration rate (GFR), or disease activity. The level of H-FABP correlated with albuminuria (rs=0.49; p<0.05). L-FABP and H-FABP concentrations were weakly correlated with each other (rs=0.24; p<0.05).

Conclusion. Urinary excretion levels of L-FABP and H-FABP are higher in patients with AS than those in healthy individuals. The found correlations may indicate the excretion of these FABPs at different stages of kidney involvement and thus be of interest for assessing the level and stage of tubulopathy in patients with AS.

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