Endothelin-1 as a biomarker of diabetic retinopathy and a factor in its progression

Background. In modern conditions, the development of simple screening programs using available indicators that can be used as biomarkers is highly relevant. Potentially, endothelin-1 (ET-1), which is involved in the mechanisms of early vascular disorders in diabetic retinopathy (DR), can be considered as such. Aim of the study was to determine the content of ET-1 at different stages of DR and the possibility of its use as a diagnostic and prognostic factor of DR progression. Materials and methods. 136 patients with type 2 diabetes mellitus were examined and divided into groups: 1st — non-proliferative (NPDR, 60 eyes), 2nd — preproliferative DR (PPDR; 42 eyes) and 3rd — proliferative DR (PDR; 34 eyes). Patients were examined and treated for 2 years. ET-1 in blood serum was determined by enzyme-linked immunosorbent assay. The results were analyzed in the EZR v. 1.54 package (Austria). Results. In patients with type 2 diabetes and DR, a significant increase in the content of blood ET-1 was found compared to the control group without diabetes. In NPDR, it exceeded the control level by 2.2 times, in PPDR and PDR — by 3.8–4.1 times (p < 0.001). The content of ET-1 in PPDR and PDR did not differ (p > 0.05) but was higher than in NPDR (by 1.7–1.9 times; p < 0.05). Thus, in the development of DR, ET-1 had two peaks — the first one in the NPDR development (the threshold level is above 1.015 pg/ml) and the second one — in the further NPDR progression (more than 2.0 pg/ml; the accuracy of the prediction is 92.5 %). ET-1 content had direct relationships with systolic (r = 0.512) and diastolic pressure (r = 0.432), fasting glycemia (r = 0.187), central retinal thickness (r = 0.491) and volume (r = 0.478), levels of glycated hemoglobin (r = 0.566), total cholesterol (r = 0.352) and its fractions. The risk of DR progression after 2 years of observation increased with increasing ET-1 content (p < 0.001; odds ratio 5.18; 95% confidence interval 2.69–9.98). Conclusions. The obtained results confirmed and specified the possibility of using ET-1 level in the blood as a highly informative biomarker of NPDR and the prognosis of its progression.