Investigators will consider diabetic nephropathy as persistent proteinuria associated to diabetic retinopathy and decreased endogen glomerular filtration rate (in subjects without a diagnosis of other kidney or urinary tract diseases). In Type 1 diabetics, diabetic nephropathy will be diagnosed if the history of diabetes is longer than 10 years prior to the onset of proteinuria; in diabetic type 2, proteinuria associated to a decreased glomerular filtration rate at diagnosis time, investigators will deem diabetic nephropathy.