Endocrine Abstracts

Background: Diabetic retinopathy (DR) is one of the most common complications resulting from uncontrolled diabetes mellitus (DM). DR is the leading cause of blindness and low vision. DR is usually diagnosed at an advanced stage, so despite the individual treatment, it is only possible to slow down the progression of DR. Therefore, new potential biomarkers are needed for an earlier DR prognosis to prevent the development of DR. According to the latest studies, ubiquitin-proteasome system (UPS) dysfunction is associated with an increased risk of developing DR. UPS is the main protein quality control system which is responsible for recognition and degradation of damaged proteins. DNA methylation has been linked to a variety of pathological conditions such as tumorigenesis. However, the role of epigenetic modifications of UPS and UPS related genes in the pathogenesis of DR is poorly understood. The aim of this study was to analyze UPS (PSMA6) an UPS related (KEAP1) genes methylation levels in samples of DR patients and to identify their association with patients’ clinical data.

Materials and methods: 120 blood samples, taken from patients with the diagnosis of DM and DR, were analyzed. DNA was extracted by salting out method from peripheral blood tissue leukocytes. PSMA6 and KEAP1 genes methylation level was determined by RT–PCR analysis with SYTO 9 fluorescent dye using OneStep qMethyl™ kit. Associations of PSMA6 and KEAP1 genes methylation level and the patients’ gender, age, duration of DM and the stage of DR were analyzed.

Results: PSMA6 gene methylation levels were higher in the group of patients with non-proliferative DR (NPDR) compared to patients with proliferative DR (PDR) (P<0.01). Increased KEAP1 gene methylation level was observed in the group of patients with DM compared to patients with NPDR and PDR (P<0.001). Increased levels of KEAP1 gene methylation were observed in patients with shorter duration of DM (P0.001). In different groups of DR severity, the methylation level of the KEAP1 gene was the lowest in the group of patients with more advanced stage of DR – PDR, and the highest in the group of patients without DR (P0.001).

Conclusions: KEAP1 gene could be used as a prognostic biomarker for determining the severity of DR or as a risk factor for the development of DR.