Urinary liver-type fatty acid-binding protein in pediatric nephrotic syndrome and tubular dysfunction

BackgroundUrinary liver-type fatty acid-binding protein (uL-FABP) has recently been identified as a biomarker for kidney injury. uL-FABP excretion in pediatric relapsing nephrotic syndrome and tubular dysfunction, however, has not been reported previously. MethodsWe measured uL-FABP level in children with steroid-sensitive nephrotic syndrome (SSNS), in those with tubular dysfunction, and in control subjects. ResultsuL-FABP was markedly increased in relapsing SSNS (median, 30.3g/gCr; range, 12.6-171.0g/gCr; n= 13), and also in the tubular dysfunction group (median, 164.8g/gCr; range, 41.6-834.5g/gCr; n = 7), compared with the control subjects (median, 3.0g/gCr; range, 1.1-13.9g/gCr; n = 21). uL-FABP level was significantly correlated with urinary protein excretion in the SSNS group, and in the total group. Additionally, in the SSNS group, elevated uL-FABP in the relapsing stage returned to a level similar to that in the control group on remission of NS. In the tubular dysfunction group, uL-FABP was significantly correlated with urinary 2-microglobulin. ConclusionUrinary protein amount, and the ability of the proximal tubules to reabsorb low-molecular-weight proteins, should also be considered when evaluating the clinical significance of uL-FABP as a biomarker for kidney injury in children.