Liver fatty acid binding protein: A potential urinary and tissue biomarker for lupus nephritis

Aim of the workTo assess urinary liver fatty acid binding protein (uL-FABP) levels and tissue expression (tL-FABP) in renal biopsies of active and inactive lupus nephritis (LN) patients and examine their relationship with disease characteristics.Patients and methodsuL-FABP levels and tL-FABP expression were assessed in 75 systemic lupus erythematosus (SLE) patients; 25 active LN, 25 inactive LN and 25 SLE without LN as well as 10 matched healthy control.ResultsMean age was 33.9 ± 6.7 years, disease duration 4.6 ± 2.4 years and were 66 females and 9 males. Patients with active LN had higher uL-FABP higher than patients with inactive LN and without LN. uL-FABP in patients with active and inactive LN significantly correlated with renal SLEDAI (r = 0.96, r = 0.92 respectively and p < 0.0001) and 24-h urinary protein (r = 0.97, r = 0.68 respectively and p < 0.0001) but negatively correlated with the estimated Glomerular Filtration Rate (r = −0.97, r = −0.84 respectively and p < 0.0001). uL-FABP significantly correlated with grade of renal biopsy in active and inactive LN (F = 155.6 and 40.7 respectively, p < 0.0001). L-FABP was highly expressed in renal tissue of LN patients; the tubules seemed to be the main location for tL-FABP staining. The uL-FABP levels significantly correlated with the chronicity index score of renal pathology (F = 17.6, p < 0.0001) and the expression of tL-FABP in active and inactive LN (F = 21.4 and 42.2 respectively, p < 0.0001).ConclusionUrinary and tissue L-FABP levels were associated with active renal disease. Urinary levels of L-FABP might be a potential non invasive marker for the presence of renal involvement in patients with SLE alternative to renal biopsy.