HETEROGENEOUS NATURE OF MICROALBUMINURIA IN NIDDM - STUDIES OF ENDOTHELIAL FUNCTION AND RENAL STRUCTURE

Microalbuminuria (MA) is associated with microangiopathy (renal and re tinal lesions) in insulin-dependent diabetic (IDDM) patients. In contr ast MA does not reflect microvascular damage in a substantial number o f non-insulin-dependent diabetic (NIDDM) patients. MA predicts cardiov ascular disease in NIDDM patients with increased von Willebrand factor (vWF) plasma levels which are hypothesized to reflect endothelial dys function. However, it is not known whether MA is consequent to general ised endothelial dysfunction or to renal injury. Thus, this study eval uated vWF plasma levels in relation to renal and retinal structural ab normalities in NIDDM patients with MA. Kidney biopsies, fundoscopy and measures of vWF plasma levels were performed in 32 NIDDM patients wit h MA. These patients were allocated to two renal structural categories : A) Without renal structural abnormalities (C I, n = 10): normal or n ear-normal renal structure, and B) With renal structural abnormalities (n = 22), further divided into: C II (n = 12) with typical diabetic n ephropathology, predominantly glomerulopathy, and C III (n = 10) with atypical patterns of renal injury (more advanced tubulo-interstitial a nd arteriolar than glomerular changes). vWF plasma levels were signifi cantly higher in category B (C II: 195 +/- 49 % and C III: 161 +/- 46 %) than in category A (C I: 119 +/- 42 %), (chi-square, p < 0.05). Dia betic retinopathy was also related to vWF plasma levels (ANOVA, p < 0. 05). These data suggest that there are two types of MA in NIDDM: one a ssociated with increased vWF levels, established renal injury and freq uently retinopathy, and the other characterized by normal vWF levels, normal renal structure and absent or mild diabetic retinopathy, We pro pose that vWF plasma levels in NIDDM patients with MA may help to iden tify patients with important renal structural changes, increased retin opathy risk and, perhaps, generalised endothelial dysfunction. Whether vWF plasma levels predict end-stage renal disease and cardiovascular events deserves longitudinal studies.