Follow-up of kidney biopsies in normoalbuminuric patients with type 1 diabetes.

To study the development of diabetic glomerulopathy, we performed two kidney biopsies after 10.5 and 17 years of type 1 diabetes in 19 normoalbuminuric, normotensive adolescents (10 males). The biopsies were examined with light and electron microscopy. The glomerular filtration rate and effective renal plasma flow, determined with inulin and para-aminohippuric acid clearances, respectively, and ambulatory blood pressure were studied. Between the biopsies, significant increases occurred in glomerular volume, foot process width, mesangial matrix, and mesangial volume fraction/glomerulus. The metabolic control affected the basement membrane thickness, mesangial matrix, and mesangial volume fraction/glomerulus. The mesangial matrix and mesangial volume fraction/glomerulus were higher in female patients on the first biopsy, but on the second biopsy, the levels in males increased to those in females. The night-time systolic and mean arterial blood pressures from the first biopsy seemed to predict the mesangial matrix and mesangial volume fraction/glomerulus, foot process width, and slit pore length on the second biopsy. Despite normoalbuminuria and normal blood pressure, patients with type 1 diabetes have morphological changes of diabetic glomerulopathy that progress. The night-time blood pressure can be used to predict morphological changes of diabetic nephropathy in adolescents who are normoalbuminuric and normotensive.