URINARY PROTEOMIC SIGNATURE OF THE RETINAL MICROVASCULATURE

Abstract

Objective: The retinal vasculature provides a window into the body's microcirculation. Variations in retinal vessel diameters have been associated with adverse cardiovascular outcomes, such as stroke and coronary heart disease. As the pathogenesis of retinal microvascular diameter changes remain poorly understood, this study aimed to provide novel insights by characterizing the urinary proteomic signature of the retinal microvasculature. Design and method: The central retinal arteriolar equivalent (CRAE), central retinal venular equivalent (CRVE), and arteriole-to venule-ratio (AVR) were measured from digitized retinal photographs of 562 randomly recruited Flemish participants (mean age, 48.9 years; 50.9% women). The urinary proteome was analyzed using capillary electrophoresis coupled with mass spectrometry. Multivariable linear regression analysis identified significant urinary peptides with adjustment for age, sex, body mass index, smoking, hypertension, plasma glucose, total and HDL cholesterol, eGFR, and history of cardiovascular disease. Reactome pathway enrichment analysis was performed to interpret the proteomic signature. Results: Table 1 shows participant characteristics. Of the 359 peptides analyzed, 19 were significantly associated with CRAE after adjusting for potential confounders and multiple testing (Table 2). In the proteomic profile, 14 peptides (74%) were fragments of collagen I, III, and XI proteins, while the remaining peptides were fragments of the fibrinogen alpha chain (11%), xylosyltransferase 1 (5%), S100 calcium-binding protein A9 (5%), and hemoglobin subunit alpha (5%) proteins. Pathway analysis showed that these proteins were predominantly involved in endothelial cell proliferation and migration, collagen formation and degradation, and cell-extracellular matrix interactions (Figure 1). No peptides were significantly associated with CRVE and AVR following adjustment. Conclusions: This study revealed a novel urinary proteomic signature as a potential biomarker of retinal arteriolar narrowing. The signature suggests fibrosis and neovascularization may be involved in retinal microvascular diameter changes. Further investigation may help elucidate the pathophysiologic mechanisms underlying the relationship between microvascular and macrovascular disease.