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

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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±6.7years, disease duration 4.6±2.4years 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.