Blood glucose and lipid control as risk factors in the progression of renal damage in type 2 diabetes.

One of the central functions of the kidney is to excrete low molecular weight, water soluble, plasma, waste products into the urine, whereas macromolecules, the size of albumin and larger, are retained. The flow of the glomerular filtrate is thought to follow an extracellular route, passing through the endothelial fenestrae, then across the glomerular basement membrane and finally through the slit diaphragm between the foot processes of podocytes. Recently it has been hypothesized that microalbuminuria leading to proteinuria and to end stage renal disease (ESRD) is mainly due to an altered glomerular fitration barrier at podocyte level. The "conditio sine qua non" for the development of diabetic ESRD is hyperglycemia. However, arterial hypertension and abnormalities of blood lipid concentrations and structure are also an important antecedent of such complication in diabetes mellitus. Interestingly it has been suggested that hyperglycemia, arterial hypertension and dyslipidemia cause disorderes of albumin excretion rate by damaging podocyte and slit diaphragm protein scaffold with over production of and extracellular release of oxygen radical species at glomerular level. The present review will briefly discuss recent reports which describe the relationship between blood glucose and lipid abnormalities and the occurrence and progression of renal damage in diabetes mellitus. More particularly we will give evidence that the risk of a rapid decline of glomerular function abruptly increases when glycated hemoglobin is steadily higher than 7.5% and postprandial blood glucose is above 200 mg/dL. Eventually we will analyze recent reports showing that treatment with statins, the inhibitors of hydroxymethylglutaryl-coenzyme A reductase, ameliorate the course of renal function in type 2 diabetic patients. It is not yet fully understood whether this effect is due to the lowering of the circulating levels of low density lipoproteins (LDL) or to an improved endothelial function or to lower patterns of LDL oxidation.