Diabetic nephropathy: from micro- to macroalbuminuria

Abstract

This brief review will focus on the major factors leading to incipient diabetic nephropathy (i.e. microalbuminuria) progressing to overt nephropathy (i.e. macroalbuminuria) and particularly on the role of glycaemic control and hypertension. Both experimental and cohort studies support the role of hyperglycaemia in the development of diabetic nephropathy. Some recent long-term interventional studies in microalbuminuric patients show conflicting results regarding the role played by good metabolic control in reducing the incidence of overt nephropathy. However, strict metabolic control, which is fundamental in normoalbuminuric patients, is of little use even in microalbuminuric patients. In general, levels of glycosylated haemoglobin less than two standard deviations above the upper normal range, commonly <7.5-8%, seem to protect patients from developing nephropathy. The results of many cross-sectional studies have shown that the progression of renal damage regularly is accompanied by arterial hypertension both in insulin-dependent diabetes mellitus (IDDM) and non-insulin-dependent diabetes mellitus (NIDDM). Many long-term interventional studies have been performed in order to understand the effect of antihypertensive treatment on the incidence of proteinuria in both normotensive and hypertensive patients with IDDM or NIDDM. These data show a marked effect of antihypertensive therapy in preventing the onset of overt nephropathy, and suggest the superiority of angiotensin-converting enzyme (ACE) inhibitors. We believe that optimal blood pressure values are approximately 120/70-75 mmHg in younger patients and 125-130/80-85 mmHg in older patients. In conclusion, antihypertensive treatment, ACE inhibitors per se and possibly strict metabolic control reduce the development of nephropathy, thus playing a striking role in the secondary prevention of renal failure.