Macro-microangiopathy and endothelial dysfunction in NIDDM patients with and without diabetic nephropathy

The Steno hypothesis suggests that albuminuria reflects widespread vascular damage (proliferative retinopathy and severe macroangiopathy) due to a generalized vascular (endothelial) dysfunction. We assessed this concept in NIDDM (non-insulin-dependent diabetic) patients with (13 female/ 39 male, age 60 +/- 7 years, group 1) and without (12 female /41 male, age 61 +/- 7 years, group 2) diabetic nephropathy compared to matched non-diabetic subjects (7 female/15 male, age 58 +/- 8 years, group 3). A 12-lead ECG was recorded and coded blindly using the Minnesota Rating Scale; the World Health Organization cardiovascular questionnaire was used to assess past and present evidence of myocardial infarction, angina pectoris, stroke, and peripheral vascular disease (digital systolic blood pressure determination). The degree of diabetic retinopathy was scored from fundus photography. The following variables were measured: transcapillary escape rate of albumin (initial disappearance of intravenously injected 125I-labelled human serum albumin), plasma concentrations of prorenin (radioimmunoassay) and serum concentrations of von Willebrand factor (enzyme-linked immunoadsorbent assay). Prevalence of ischaemic heart disease (ECG reading) (49/20/5)% and peripheral vascular disease as indicated by reduced systolic blood pressure on big toe (69/30/ 14)% was significantly higher in group 1 vs group 2 (p < 0.01) and in group 2 vs group 3 (p < 0.01), respectively. The prevalence and severity of retinopathy was higher in group 1 vs 2 (p < 0.01). Transcapillary escape rate of albumin (%/h) was elevated in group 1 and 2 as compared to control subjects: 7.9 (4.3-13.7); 7.4 (3.7-16.4) vs 6.0 (3.4-8.7), (p < 0.005), respectively. Plasma prorenin activity (IU/ml) was raised in group 1 and group 2 as compared to group 3: 272 (59-2405); 192 (18-813), and 85 (28-246), p < 0.001, respectively. Serum von Willebrand factor (IU/ ml) was elevated in group 1 as compared to group 2 and 3: 2.07 (0.83-4.34); 1.60 (0.30-2.99) and 1.50 (1.00-2.38), p < 0.001, respectively. Our study demonstrated that NIDDM patients with and without albuminuria had increased transcapillary escape of albumin and raised prorenin activity, whereas only those with albuminuria had increased von Willebrand factor. Patients with NIDDM may have abnormal endothelial function in the absence of albuminuria.