Serum Fibulin-5, VEGF-C, and selenium-binding protein-1 levels across stages of diabetic retinopathy: An observational study on pathophysiological associations

INTRODUCTION: Diabetic retinopathy (DR) is a major microvascular complication of diabetes characterized by vascular in-stability and oxidative stress. This study aimed to evaluate the serum levels of Fibulin-5, Selenium-Binding Protein-1 (SBP-1), and Vascular Endothelial Growth Factor-C (VEGF-C) across different clinical stages of DR and to investigate their independent pathophysiological associations.
METHODS: This cross-sectional study included 179 participants categorized into four groups: healthy controls (n=45), di-abetes mellitus (DM) without retinopathy (n=45), non-proliferative DR (NPDR) (n=45), and proliferative DR (PDR) (n=44). Serum levels were measured using ELISA. The strength of clinical associations was evaluated via ROC analysis, and independent relationships were assessed using multivariable logistic regression models adjusting for age and HbA1c.
RESULTS: Serum Fibulin-5 and SBP-1 levels were significantly elevated in the NPDR group compared to all other groups (p<0.001 for both). In multivariable regression, both Fibulin-5 (OR: 3.13, p=0.0004) and SBP-1 (OR: 1.63, p=0.004) main-tained a strong, independent association with the NPDR stage, distinct from systemic glycemic control. VEGF-C levels did not show significant differences among the groups (p=0.310).
DISCUSSION AND CONCLUSION: The stage-specific dramatic elevations of Fibulin-5 and SBP-1 in NPDR suggest a systemic reflection of a compensatory mechanism against early retinal microvascular injury and oxidative stress, which appears to diminish in the advanced PDR stage. These findings provide novel observational insights into the systemic dynamics of extracellu-lar matrix remodeling and redox stress in DR pathogenesis.

Keywords: Diabetic retinopathy, Fibulin-5, ROC analysis, SBP-1, VEGF-C