Diabetic nephropathy and antihypertensive treatment: what are the lessons from clinical trials?

Diabetic nephropathy is the most serious problem among current issues in nephrology, as 40% of the cases of end-stage renal disease are due to this entity. The close relationship between type 2 diabetes and hypertension makes the problem even more severe. The knowledge of the intrarenal effects of angiotensin II and the greater effect of angiotensin converting enzyme inhibitors (ACEI) on reducing albuminuria suggested in the past a trend toward preferable use of these drugs in diabetic nephropathy. The first relevant clinical trials yielded rather poor conclusions because of lack of blind randomization and short duration. Subsequent double-blind studies with adequate numbers of patients and sufficient duration underlined the importance of blood pressure (BP) control as well as the rather poor response of diabetic nephropathy to any treatment. In most of these studies, the changes in albuminuria or microalbuminuria were a substitute end point for the renal function. Three clinical trials using angiotensin II receptor blockers (ARB), planned specifically to monitor the progression of renal damage, have been recently published. They showed better renal protection by ARB, as compared with placebo or calcium channel blockers (CCB), beyond or independently of the BP reduction. Nevertheless, these recent trials, like the previous ones with similar results, invariably demonstrate slightly better control of BP in the groups of the active drug. Another issue is that the vast majority of the patients need so many nonstudy drugs to keep their pressure under control, that the isolation of advantageous effects of certain drugs seems unrealistic.