The effect of metabolic control on development and progression of diabetic nephropathy

The progressively growing number of patients with end-stage renal failure (ESRF) associated with diabetes mellitus and requiring renal replacement therapy (RRT) stimulated both nephrologists and diabetologists to investigate the mechanisms linking hyperglycaemia to diabetic renal failure and to set up measures to prevent the onset and slow the progression of diabetic nephropathy. Over the last few decades, a large number of studies have investigated both the incidence of diabetic nephropathy and the relationship between metabolic control and the development of diabetic nephropathy. Chronologically, the first type of diabetes and diabetic nephropathy to be studied was type I, and it is only in recent years that metabolic control has been proven to be a contributor to the development of nephropathy in such patients. Recently, the DCCT demonstrated that metabolic control in the prealbuminuric phase was effective in reducing the incidence of microalbuminuria, even if it was unable to reduce the incidence of overt proteinuria in patients with type I diabetes and established proteinuria. On the other hand, in type II diabetes, the number of studies demonstrating a favourable effect of metabolic control on onset and progression of diabetic nephropathy is only slightly greater than those that failed to show a favourable effect. This feature may suggest that in type II patients, genetic and ethnic differences, nutritional aspects, lifestyle and other confounding factors may play a relevant role in the course of the disease. However, the trials performed and the retrospective analyses generally agree that glycated haemoglobin two standard deviations greater than the mean is related to a worsening in progression of diabetic nephropathy and to an enhanced risk of other complications. In general, a glycated haemoglobin < or =8% seems advisable. Moreover, in both type I and type II, greater emphasis should be placed on the major risk factors such as hypertension, smoking habits and hyperlipidaemia.