Microalbuminuria, endothelial dysfunction and cardiovascular risk

Microalbuminuria was originally considered to be an important new risk factor for diabetic nephropathy. More recently, it has been convincingly shown that microalbuminuria is also an independent risk factor for cardiovascular morbidity and mortality in Type 1 and Type 2 diabetic patients. Even in the non-diabetic background population, microalbuminuria is a risk factor for cardiovascular mortality. What is the link between increased loss of albumin in urine and cardiovascular disease and mortality? As microalbuminuria is apparently associated with increased universal vascular sieving of albumin in terms of the transcapillary escape rate of albumin (TER-alb), microalbuminuria may reflect this universal sieving. The pathophysiology of increased TER-alb is unknown, but could be caused by haemodynamics or damage to the functional properties of the vascular wall. A number of studies have provided evidence of endothelial dysfunction in patients with microalbuminuria, which may be the common link accounting for the associations mentioned above. In this context, a number of markers of endothelial cell dysfunction have been found to be increased in patients with microalbuminuria. In addition, a number of functional in vivo tests of endothelial dysfunction have been performed in Type 1 and Type 2 diabetic patients as well as in normal controls. Overall, these studies indicate the existence of a functional vascular dysfunction in Type 1 diabetic patients and normal controls with microalbuminuria, which may be related to dysfunction of endothelial cells.