Association of the Low Density Lipoprotein Receptor-Related Protein 1 (LRP1) Expression With Diabetic Macular Oedema

Abstract

Purpose: : Diabetic macular oedema is the leading cause of visual loss in diabetic patients and is characterized by accumulation of extracellular fluid in the retina. Recently, we have demonstrated that LRP1 is highly expressed in retina under ischemic retinopathies and it is downregulated in macrophages treated with insulin, suggesting that LRP1 play a key role in diabetic pathogenesis. The objective of this work was to determine the surface expression of LRP1 in peripheral blood monocytes, in association with others biochemical parameters, in order to discriminate patients with clinically significant macular edema (CSMO) and Diabetes Mellitus (DM)without CSMO.

Methods: : Peripheral whole blood samples were obtained of patients with CSMO (n=9) and DM patients with different stages of retinopathy (n=21). Quantitative assays were performed for more than 22 different biochemical parameters measured by conventional clinical laboratory tests. LRP1 was determined in peripheral blood monocytes by flow cytometry using RD1-conjugated monoclonal antibody against human LRP1 alpha chain. At least 2,000 gated monocytes were acquired in each sample using the flow cytometer Cytoron Absolute (Ortho Diagnostic System, Raritan, NJ) operated with Immunocount II software. The data was analyzed by WinMDI 2.8 software. All biochemical parameters were analyzed using Lineal Discriminant Analysis (forward stepwise mode) and Kruskal Wallis (Statistica version7.0).

Results: : Discriminant analysis allows selecting 12 biochemical parameters out of 21 analyzed as the most important for discrimination. The parameters statistically selected included LRP1 together with CD4, CD3, TLCD4+CD8+, haematocrit, Red cell Distribution Width, lymphocytes, platelets, HDL cholesterol, LDL cholesterol, cholesterol and HbA1c. These 12 parameters allow differentiating CSMO from DM patients with 96,7% certainty. This means that only 1 out of 30 patients analyzed was misclassified. The mean value of monocytes LRP1 was statistically different between both groups of patients (p≤0.05).

Conclusions: : LRP1 was differentially expressed in peripheral blood monocytes of CSMO respect to DM patients. In addition, LRP1 together with other biochemical parameters allowed to statistically discriminating patients with CSMO from DM without CSMO.

Keywords: diabetes • edema • discrimination