Effect of angiotensin converting enzyme inhibitor or beta blocker on glomerular structural changes in young microalbuminuric patients with Type I (insulin-dependent) diabetes mellitus

Aims/hypothesis. To investigate the influence of angiotensin converting enzyme inhibitors and beta blockers on the progression of early diabetic glomerulopathy. Methods. Thirteen patients with Type I (insulin-dependent) diabetes mellitus (mean age 18.8 years) with microalbuminuria 31 (19-160) mu g/min were randomised to treatment with enalapril (group 1, n = 7) or metoprolol (group 2, n = 6). Renal biopsies were taken before and after 38 (36-48) months of treatment. Albumin excretion rate, blood pressure and HbA(1c) were measured every third month. A reference group without antihypertensive treatment (group 3, n = 9), with similar age, diabetes duration and degree of microalbuminuria as group 1 and 2, had baseline and follow-up renal biopsies taken previously with an interval of 26-34 months, analysed at the same laboratory. Glomerular structures were measured by stereological methods. Results. Measurements of basement membrane thickness, mesangial and matrix volume fractions were similar among groups at baseline. Structural variables were only increased in group 3 at follow-up. Delta values in basement membrane thickness and diabetic glomerulopathy index per 24 months were lower in group 1 and 2 than in group 3 (p < 0.05). Microalbuminuria returned to normal in group 1 and 2 only. Decreased albumin excretion rate tended to inversely correlate with increased basement membrane thickness (p = 0.08) and diabetic glomerulopathy index (p = 0.05). Mean HbA(1c) was similar between groups. Mean diastolic blood pressure was lower in group 1 and 2 than in group 3 (p < 0.01). Mean HbA(1c) and mean diastolic blood pressure correlated to changes in basement membrane thickness, mesangial volume fraction and diabetic glomerulopathy index (p < 0.05), Conclusion/interpretation. Contrary to findings in the group without antihypertensive treatment, no progression of glomerulopathy was seen in those treated with enalapril or metoprolol.