Structural changes in renal arterioles in Type I diabetic patients

Aims/hypothesis. We aimed to obtain data on arteriolar structure in a follow-up study of microalbuminuric diabetic patients. Methods. Kidney biopsies were obtained at baseline and after 8 years in 18 Type I (insulin-dependent) diabetic patients. Albumin excretion rate, blood pressure and HbA(1C) were measured regularly, and the glomerular filtration rate (GFR) was measured at the time of the kidney biopsy. The biopsy was embedded into plastic blocks and serially sectioned with 1 mum sections. In levels 25 mum apart, afferent and efferent arteriolar profiles were identified and digitised in the electron microscope. The extra-cellular matrix as volume fraction of the media was measured, and estimates of thickness of matrix, media, endothelium and lumen were obtained. Baseline and follow-up biopsies were studied concomitantly. Results. A large increase was seen in matrix volume fraction in afferent (p = 0.0001) and in efferent arterioles (p = 0.0004). Estimated thickness of media and matrix increased, whereas endothelial cell thickness decreased, over the 8 years. There was a correlation between the parameters of diabetic glomerulopathy and arteriolar parameters in the biopsies done at 8 years, basement membrane thickness compared with afferent matrix volume fraction: r = 0.74, p = 0.0005. Also aggravation of glomerulopathy and arteriolar structure over 8 years showed positive correlation. Arteriolar parameters correlated with the albumin excretion rate (AER) and inversely with GFR. Conclusion/interpretation. The arteriolar accumulation of matrix parallels that taking place in glomeruli and shows association with functional parameters over 8 years in Type I diabetic patients with microalbuminuria. These changes are considered an important part of the structural lesions in the diabetic kidney underlying the development of diabetic nephropathy.