Effect of 5-year enalapril therapy on progression of microalbuminuria and glomerular structural changes in type 1 diabetic subjects

A 5-year randomized, double blind, placebo-controlled study was carried out to determine the effect of the angiotensin-converting enzyme (ACE) inhibitor enalapril (E) on the progress of renal function and histology in subjects with type 1 diabetes and microalbuminuria. Seventy three type 1 diabetic patients with BP <140/90 and with persistent albuminuria (AER 20-200 microg/min) and normal renal function were randomly assigned to receive E (n=37) or placebo (n=36). A percutaneous renal biopsy was successfully performed in 69 patients and repeated in 59 patients after 5 years. The mean glomerular volume (MGV), mesangial volume (Vv mes) and glomerular basement membrane thickness (GBMT) were measured histomorphometrically. Before treatment, both groups had similar clinical characteristics, blood pressure, HbA(1c), albumin excretion rate (AER), glomerular filtration rate (GFR), serum creatinine and renal structural damage. Blood pressure was well controlled in both groups. In the patients treated with E, albuminuria decreased significantly (P<0.05) and only 8.1% (3/37) of subjects progressed to clinical albuminuria (AER >300 mg/24 h) compared with 30.5% (11/36) in the placebo group. The E treatment resulted in absolute risk reduction of 22.4 percentage points for the development of clinical albuminuria over a 5-year period (P<0.01). After 5 years of treatment, GBM thickness showed a consistent, though statistically insignificant, increase in the placebo group, whereas it remained stable in the E group. A significant increase in MGV and Vv mes was also observed in the placebo group on completion of the study. The present study indicates that long term therapy with E may decrease or delay the progression of structural glomerular damage in microalbuminuric diabetic subjects without marked hypertension (BP <140/90).