To study why in type II diabetes, microalbuminuria, a marker of generalized vascular dysfunction, and hypertension have been linked with both renal and cardiovascular organ damage.
To investigate the effect of moderately elevated blood pressure on vascular damage, the transcapillary escape rate of albumin (TERalb) was measured by intravenous injection of purified 125I-human serum albumin in 9 healthy control subjects (group 1), 9 nondiabetic hypertensive subjects (group 2), and 73 nonobese type II diabetic patients stratified as follows: group 3: 17 normoalbuminuric-normotensive subjects; group 4: 22 normoalbuminuric-hypertensive subjects (systolic blood pressure [sBP] ≥ 140 mmHg or diastolic blood pressure [dBP] ≥ mmHg or both); group 5: 16 normotensive subjects with microalbuminuria (albumin excretion rate [AER]: 20–200 μg/min); and group 6: 18 microalbuminuric-hypertensive subjects.
Groups 3–6 had similar age, sex, duration of diabetes (group 3: 7.8 ± 5.5; group 4: 9.7 ± 8.7; group 5: 12.1 ± 8.1; and group 6: 10.7 ± 8.3 years), BMI, HbA1c (7.8 ± 1.1, 7.5 ± 1.5, 8.7 ± 1.5, and 7.7 ± 1.1%, respectively), blood glucose, and lipid profile. Systolic and diastolic blood pressure did not differ in the three hypertensive group (group 2: 154 ± 3/99 ± 6; group 4: 149 ± 13/95 ± 6; group 6: 154 ± 15/91 ± 9 mmHg) and were significantly lower (P < 0.001) in group 3 (126 ± 12/76 ± 7), group 5 (128 ± 11/77 ± 5), and healthy control subjects (group 1: 133 ± 7/81 ± 4). TERalb was similar in control subjects (5.77 ± 1.06%/h) and in normoalbuminuric-normotensive subjects (5.81 ± 1.51%/h) but significantly higher (P < 0.0001) in microalbuminuric subjects with or without hypertension (9.11 ± 1.65 and 8.60 ± 1.50%/h, respectively) as well as in normoalbuminuric diabetic patients with hypertension (8.10 ± 2.27%/h) and in essential hypertensive subjects (8.12 ± 1.68%/h).
By stepwise regression, TERalb was related (step 1) to log-AER (r = 0.30) or to the presence of microalbuminuria (r = 0.36) and (step 2) to dBP (multiple r = 0.40) or to the presence of hypertension (multiple r = 0.51) in the whole diabetic cohort (groups 3–6). TERalb was related to dBP (r = 0.47) or to the presence of hypertension (r = 0.56) only in normoalbuminuric diabetic patients (groups 3 and 4) and to log-AER (r = 0.56) or the presence of microalbuminuria (r = 0.68) only in normotensive patients (groups 3 and 5). In type II diabetic patients, TERalb was elevated in subjects with increased albuminuria, irrespective of blood pressure levels, but also was independently related to the presence of mild-to-moderate systemic hypertension.
