Serum angiotensin converting enzyme in diabetic retinopathy.

Serum levels of angiotensin converting enzyme (SACE) were measured in 118 diabetic patients divided into the following four groups: 44 insulin-treated diabetic patients with severe retinopathy, 38 non insulin-treated diabetic patients with severe retinopathy, 18 diabetic patients, including both insulin-treated and non insulin-treated subjects with background retinopathy, 18 diabetic patients, insulin-treated and non insulin-treated without signs of retinopathy. Nineteen retinopathic patients non diabetic were also studied in order to verify whether SACE levels are altered when retinopathy is present independently from diabetes. The control group was composed of 44 normal subjects. When the data from the above six groups of subjects were submitted to statistical tests (one-way ANOVA, T-test of Bonferroni and test of Student-Newman-Keuls), the study yielded the following results: i) a remarkable difference between the SACE levels in healthy subjects and those in the three groups of diabetic retinopathic patients considered; ii) a non statistically significant difference of SACE levels between normal subjects and diabetic patients without retinopathy; iii) a non statistically significant comparison of SACE levels of normal subjects versus non diabetic retinopathic patients. Therefore, we concluded that while primitive diseases of the retina are not associated with an increase of SACE levels, yet when diabetes and retinopathy coexist, the SACE levels increase remarkably (in rather an independent way from the type of diabetes, the age of subjects, the stage of retinal disease and the daily average insulin dose), suggesting that most of the enzyme's increase originates from the endothelium of peripheral vasa, widely involved in most of the retinopathic diabetic patients.