Objective: 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.
Research design and methods: 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] > or = 140 mmHg or diastolic blood pressure [dBP] > or = mmHg or both); group 5: 16 normotensive subjects with microalbuminuria (albumin excretion rate [AER]: 20-200 micrograms/min); and group 6: 18 microalbuminuric-hypertensive subjects.
Results: 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).
Conclusions: 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.