Abstract
(Pro)renin receptor [(P)RR], a new component of the tissue renin-angiotensin system (RAS), plays a crucial role in inflammation and angiogenesis in the eye, thus contributing to the development of proliferative diabetic retinopathy (PDR). In this study, we investigated systemic factors related to plasma levels of soluble form of (P)RR [s(P)RR] in patients with PDR. Twenty type II diabetic patients with PDR and 20 age-matched, non-diabetic patients with idiopathic macular diseases were enrolled, and plasma levels of various molecules were measured by enzyme-linked immunosorbent assays. Human retinal microvascular endothelial cells were stimulated with several diabetes-related conditions to evaluate changes in gene expression using real-time quantitative PCR. Of various systemic parameters examined, the PDR patients had significantly higher blood sugar and serum creatinine levels than non-diabetic controls. Protein levels of s(P)RR, prorenin, tumor necrosis factor (TNF)-α, complement factor D (CFD), and leucine-rich α-2-glycoprotein 1 (LRG1) significantly increased in the plasma of PDR subjects as compared to non-diabetes, with positive correlations detected between s(P)RR and these inflammatory molecules but not prorenin. Estimated glomerular filtration rate and serum creatinine were also correlated with plasma s(P)RR, but not prorenin, levels. Among the inflammatory molecules correlated with s(P)RR in the plasma, TNF-α, but not CFD or LRG1, application to retinal endothelial cells upregulated the mRNA expression of (P)RR but not prorenin, while stimulation with high glucose enhanced both (P)RR and prorenin expression. These findings suggested close relationships between plasma s(P)RR and diabetes-induced factors including chronic inflammation, renal dysfunction, and hyperglycemia in patients with PDR.
Highlights
Diabetes mellitus (DM) affects over 415 million people worldwide [1], approximately onethird of whom will eventually develop diabetic retinopathy (DR), one of the most common complications in diabetes
A total of 40 subjects with type 2 diabetes complicated by proliferative diabetic retinopathy (PDR) (n = 20, the PDR group) and without diabetes suffering from idiopathic retinopathies (n = 20, the non-DM group) were included in the analysis
Among basal characteristics of participating patients, there were no significant differences between the non-DM and PDR groups except for random blood sugar (RBS) levels, serum creatinine levels and Logarithm of the minimum angle of resolution (Log MAR)
Summary
Diabetes mellitus (DM) affects over 415 million people worldwide [1], approximately onethird of whom will eventually develop diabetic retinopathy (DR), one of the most common complications in diabetes. DR, a form of microangiopathy in the retina, is one of the leading causes of severe vision loss and blindness when it progresses to the stage of proliferative DR. Involvement of plasma (P)RR in the pathogenesis of PDR
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