AB1373 Urinary protein profile comparison between sle patients with and without renal involvement

Background Lupus nephropathy (NL) is an important cause of morbidity and mortality in patients with Systemic Lupus Erythematosus (SLE). The objective of the renal biopsy is to determine the type of glomerulonephritis that the patient presents to direct treatment. Considering that it is a specialised technique and not risk free, a proteomics study is proposed to determine biomarkers that help us to differentiate patients diagnosed with SLE with and without renal involvement. Objectives To determine if there is a different pattern of proteins between patients diagnosed with SLE with and without renal involvement. Methods We selected 12 patients diagnosed with SLE with renal involvement and 14 patients diagnosed with SLE without renal involvement. There were no differences between groups according to race, gener and age. The patients were classified as high, low or negative level of proteinuria in the urine. A 24 hour urine sample was obtained for analysis. Results We have done a Principal Component Analysis (PCA) where we can see differences between samples from patients who have high level of proteinuria in 24 hours and patients who have not renal involvement. Patients with positive proteinuria but not high level are a little confuse figure 1. A total of 292 proteins (identified with at least two peptides with a FDR Consistent with the nature of the sample, the Gene Ontology (GO analysis) of the whole list of identified proteins revealed the presence of extracellular (277 proteins, p=2.25E-171) and secretion-related proteins (49 proteins, p=1.1E-09), among others. Proteins related to defensive processes were prominent among them. Interestingly, the subset of proteins whose abundance increases upon renal damage is comprised of typical highly-abundant serum proteins. These proteins render a large number of peptides, suggesting they are very abundant. This protein pattern may reflect the higher albuminuria characteristic of patients with affected renal function. On the other hand, a number of proteins became significantly less abundant upon renal damage. The presence of highly abundant serum proteins in the urine of patients with compromised renal function may explain this phenomenon, since this will provoke a dramatic reduction in the relative abundance of the proteins already present in their urine. Conclusions A different protein pattern is observed between the two groups of patients, so in a more detailed study we can indicate if some of these can serve as prognostic markers for this type of patients. Disclosure of Interest None declared