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H. Yokota, T. Nagaoka, A. Takahashi, E. Sato, A. Yoshida; Reduced Compliance of the Retinal Arteriolar Circulation With Increased Serum Prorenin in Patients With Type 2 Diabetes. Invest. Ophthalmol. Vis. Sci. 2008;49(13):2741. doi: https://doi.org/.
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The pulsatility ratio (PR), pulsatility index (PI) and resistivity index (RI) indicate the degree of vascular resistance and compliance. Using these parameters, we investigated if there is an association between retinal hemodynamic abnormalities and serum prorenin levels in diabetes. Prorenin is a key enzyme in the receptor associated prorenin system (RAPS), which is thought to be a crucial mechanism in local activation of renin-angiotensin system in diabetes.
Normal subjects (25 men, 19 women) and patients with diabetes (74 men, 73 women) with simple retinopathy or without diabetic retinopathy were enrolled. Using retinal laser Doppler velocimetry (Canon, CLBF model 100), we measured the peak systolic velocity (PSV) and end diastolic velocity (EDV) and calculated PR [=PSV/EDV], PI [=(PSV-EDV)/mean velocity], and RI [=(PSV-EDV)/PSV]. Immediately after measurement, blood was collected from all participants. The serum levels of prorenin (SPR) were measured using the antibody-activating direct kinetic assay.
In normal subjects, there was no correlation among the parameters. However, in diabetes, for PR (all Xs in formulas are log (SPR)), Y=0.89+1.4X (Y=PR) (correlation coefficient: r=0.32, p<0.01), for PI, Y=0.71+0.20X (Y=PI)(r=0.29, p<0.01), and for RI, Y=0.54+0.084X (Y=RI)(r=0.29, p<0.01).
Increased levels of prorenin are statistically correlated with PR, PI, and RI in the retinas in patients with diabetes and not in normal subjects. Measuring prorenin might be a good marker for retinal microvascular abnormalities in diabetes. We believe that RAPS might play a key role in the pathogenesis of diabetic retinopathy.
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