Background: Renin, secreted into the blood by the juxtaglomerular cells of the kidneys, is derived from a larger precursor, prorenin. Plasma prorenin activity is increased in patients with insulin-dependent (Type I) diabetes mellitus who have microvascular complications of their disease. We undertook this study to determine prospectively whether rising prorenin activity can predict the development of complications in young patients with Type I diabetes.
Methods and results: Plasma prorenin was measured in 135 children and adolescents with Type I diabetes. The mean (+/- SE) plasma prorenin activity among the 32 patients over the age of 10 years who had had uncomplicated diabetes for 0.1 to 5 years was 8.43 +/- 0.58 ng of angiotensin I per liter.second, as compared with 7.06 +/- 0.32 in 37 control subjects of the same age (P less than 0.05). In the 9 patients older than 10 who had retinopathy or overt albuminuria, the mean plasma prorenin activity was 13.09 +/- 1.43 ng of angiotensin I per liter.second (P less than 0.0001). In 34 patients 10 years old or older with uncomplicated diabetes, 3 to 13 measurements of plasma prorenin activity were taken during a follow-up period of 6 to 39 months. Urinary albumin was determined at each visit, and the patients had regular retinal examinations. Only 1 of the 20 patients who had consistently normal plasma prorenin values had overt albuminuria (ratio of urinary albumin to creatinine, greater than 0.017) or retinopathy, whereas one or both of these complications appeared in 8 of the 14 who had at least one high prorenin value. The plasma prorenin value was significantly higher in these eight patients at least 18 months before a complication was found.
Conclusions: Increased plasma prorenin activity identifies a group of young patients with diabetes who are at high risk for retinopathy or nephropathy.