Abstract
Purpose::
Although we previously reported that retinal blood flow (RBF) decreases in patients with type 2 diabetes in the early stage of diabetic retinopathy, the exact mechanism of the impaired retinal circulation in these patients remains unclear. Prorenin, which had been believed to be an inactive precursor of renin, plays a key role in local activation of the renin-angiotensin system in diabetes. This study investigated the relation between the serum level of prorenin and the retinal circulation in patients with diabetes.
Methods::
Two hundred and seven patients with type 2 diabetes and no diabetic retinopathy (men, 104; women, 103) were enrolled in this study. Using a retinal laser Doppler velocimeter (Canon, CLBF model 100), we measured the vessel diameter and the blood velocity in the retinal arterioles and calculated the RBF simultaneously. Immediately after calculating the RBF, the serum levels of prorenin were measured using an antibody-activating direct kinetic assay in all patients. We assessed the relationship between the serum prorenin level and the retinal circulatory parameters.
Results::
There were no significant correlations between the serum prorenin levels and the vessel diameter (r=0.004, P=0.35) or the blood velocity (r=-0.12, P=0.065). However, there was a significant correlation between the serum prorenin level and the RBF in all patients with diabetes (r=-0.43, P<0.001).
Conclusions::
This study showed that the increased serum prorenin levels may be associated with decreased RBF in patients with type 2 diabetes with no retinopathy. These results suggest that increased prorenin might impair the retinal circulation in patients with the early stages of diabetic retinopathy.
Keywords: diabetic retinopathy