Renal iron expression and urinary transferrin excretion in lupus nephritis: A case-control study

BackgroundLupus nephritis (LN) is a key manifestation of systemic lupus erythematosus (SLE).Aim of the workTo assess urinary transferrin level, renal iron accumulation and transferrin receptor (TfR) gene expression in SLE.Patients and methodsA case-control study was conducted on 80 SLE patients (40 with LN and 40 without LN), and 90 age and sex matched healthy control. Iron markers (Serum iron, ferritin, TfR gene, and urinary transferrin) were assessed in all participants. Iron accumulation and TfR gene expression were evaluated in renal biopsy for LN cases. Disease activity was assessed by Systemic Lupus Erythematosus Disease Activity Index-2K(SLEDAI2k).ResultsOf 80 patients, 85% were female. Mean SLEDAI was 15.0525 ± 1.1592, the disease duration was of mean 47.6 ± 26.56 months, and mean age was 31.32 ± 8.85. Serum and urinary iron biomarkers were significantly higher in SLE patients compared to controls except for iron which was lower in lupus patients with similar significant difference between patients subgroups. TfR gene expression in renal tissue didn't significantly differ across LN classes. Tubular iron deposition was observed histopathologicaly. Urinary transferrin showed significant correlation with activity score and proteinuria (r = 0.94, r = 0.43 and p < .0001, p = .03) while serum TfR significantly correlated with disease activity and ESR (r = 0.61, r = 0.4 and p < .0001, p = .03, respectively). TfR gene expression on renal tissue did not correlate with urinary transferrin, disease activity or other laboratory parameters.ConclusionsElevated urinary transferrin and serum TfR correlated with disease activity in lupus population and may serve as a potential non-invasive biomarker for lupus nephritis.