Biomarkers in ocular surface lavage in diabetic retinopathy

Diabetes mellitus (DM) patients have different micro and macrovascular affections. Diabetic Retinopathy (DR) is a consequence of a lack of glucose control and glucotoxicity. Oxidative stress (OxS) is related to the progress of vascular and tissular dysfunction. The present study evaluated the enzymatic activity of myeloperoxidase (MPO), Arginase, Glutathione S-Transferase (GST), and the metabolite Methylglyoxal (MGO) as precursors of Advanced Glycation End-products (AGEs) in the ocular surface lavage (OSL) and serum of DM patients at different DR stages and in patients without DM as a control group. We also determined the relationship of OxS biomarkers with DR stage and with local and systemic responses. Demographic and clinical data included in the statistical analysis were age, DM diagnostic age, intraocular pressure (IOP), and systemic glucose. All biomarkers were analyzed by colorimetric assays and measurements were obtained using spectrophotometry. MPO, MGO, and arginase in OSL samples showed a statistically significant increase in diabetic patients with respect to healthy patients. However, serum MPO, GST, and arginase were significantly lower in all diabetic patients compared to healthy patients. MPO, MGO, and arginase levels in OSL showed a positive correlation with systemic glucose, and MPO and MGO were positively correlated with age and diagnostic age of DM. Serum biomarkers showed an inverse correlation to that observed in the OSL evaluation. MPO, MGO, and arginase OSL levels showed a statistically significant correlation with MPO, MGO, and arginase serum levels. IOP showed a discrete correlation with serum MGO (Rho 0.2822, p= 0.086), and a statistically significant increase in IOP was observed in the 4th quartile of serum MGO level. The present pilot study demonstrates the differential contribution of OxS biomarkers in OSL concerning a systemic evaluation, and their correlation in the different stages of DR, which is mainly explained by glucotoxicity since there was an increase in MGO concentrations.