Increased Transcapillary Escape Rate of Albumin in Microalbuminuric Type II Diabetic Patients

Abstract

OBJECTIVE To evaluate microvascular permeability by the transcapillary escape rate of albumin (TERalb) in type II diabetic patients with normo- and microalbuminuria. RESEARCH DESIGN AND METHODS The TERalb has been measured following intravenous injection of 125I-labeled human serum albumin in 32 normotensive type II diabetic patients and 9 healthy control subjects matched for sex and age. Type II diabetic subjects were grouped in normoalbuminuric, albumin excretion rate (AER) <20 μg/min (n = 18), and microalbuminuric, AER 20-200 μg/min (n = 14) categories. RESULTS In type II diabetic patients, no differences were noted between normo- and microalbuminuric groups for known diabetes duration (8.3 ± 5.9 vs. 11.7 ± 8.0 years), blood pressure (BP) (129/76 ± 16/8 vs. 131/76 ± 14/5 mmHg), current metabolic control (HbA1c: 8.0 ± 1.4 vs. 8.5 ± 1.6%), and serum lipids. However, previous 2-year mean HbA1c levels were significantly higher in microalbuminuric patients (8.7 ± 1.45 vs. 7.6 ± 1.29%; P < 0.05). The TERalb was similar in control subjects and normoalbuminuric patients (5.16 ± 1.09 vs. 5.71 ± 1.66 %/h) and significantly higher in the microalbuminuric group (8.98 ± 1.35 %/h; P < 0.0001). The increased leak of albumin was not explained by differences in diabetes duration, BP, or metabolic control at the time of investigation and was independently related to the presence of microalbuminuria (r = 0.63, percent explained variance ∼40) and mean “historical” HbA1c (multiple r = 0.705; total explained variance ∼50%). CONCLUSIONS Type II diabetic patients with microalbuminuria show an increased TERalb, i.e., a widespread microvascular damage that may be important in the pathogenesis of long-term complications. Our findings may contribute to the explanation of why albuminuria seems to be an independent cardiovascular risk factor in type II diabetes.