Diabetic nephropathy: An update on renal structure

The renal lesions underlying renal dysfunction differ in type 1 and type 2 diabetes, although the clinical manifestations of diabetic nephropathy, proteinuria, decreased glomerular filtration rate and increasing blood pressure are similar. Indeed, in type 1 diabetes, although also tubular, interstitial and arteriolar lesions are present, the most important structural changes involve the glomerulus, while several type 2 diabetic patients, despite the presence of microalbuminuria or proteinuria, have normal glomerular structure with or without tubulo-interstitial and arteriolar abnormalities. The clinical manifestations of diabetic nephropathy are strongly related with the structural changes, especially with the degree of mesangial expansion in both type 1 and type 2 diabetes. In the last years it has been demonstrated that also changes in the structure and number of podocytes may be involved in the progression of diabetic nephropathy. Previous studies using light and electron microscopic morphometric analysis described the renal structural changes and the renal structural–functional relationships, documenting the contribution of kidney biopsy studies in understanding the pathogenesis of diabetic nephropathy and in identifying the patients with higher risk to progress to end stage renal disease. Finally this review will summarize studies in pancreas transplant recipients demonstrating that the lesions of diabetic nephropathy in humans are reversible, if normoglycemia is achieved and maintained for a long period of time.