Vervoort G, Lutterman J A, Smits P, Berden J H, Wetzels J F
Department of Internal Medicine, University Hospital Nijmegen, The Netherlands.
J Hypertens. 1999 Dec;17(12 Pt 2):1911-6. doi: 10.1097/00004872-199917121-00021.
An increase in urinary albumin excretion (UAE) in type 1 diabetic patients might reflect changes in vascular permeability and/or local haemodynamic factors. Indeed, transcapillary escape of albumin (TERalb), a measure of systemic capillary efflux, is increased in diabetic patients, even in those with a modest increase of albuminuria. In normo-albuminuric type 1 diabetic patients, systemic capillary and glomerular flow is increased. We hypothesized that these haemodynamic changes contribute to an elevated TERalb, even in the phase preceding micro-albuminuria.
We measured TERalb in 39 normo-albuminuric type 1 diabetic patients and 46 healthy controls. TERalb was calculated from the disappearance curve of 125I-albumin. Renal and systemic haemodynamics were measured by standard techniques. Forearm blood flow (FBF) was measured by plethysmography. Endothelial function was assessed by intra-arterial infusion of acetylcholine. The structural integrity of the vessel wall was determined by the post-occlusive reactive hyperaemia test.
TERalb was increased in diabetic patients (5.53+/-0.40 versus 4.39+/-0.21 %/h, P = 0.01). Patients were divided into tertiles with respect to their TERalb. There were no differences in UAE, blood pressure, metabolic parameters, endothelial function or maximal vasodilatation after occlusion between the groups. However, filtration fraction and FBF were significantly increased in the group of diabetic patients with the highest levels of TERalb. Overall, in diabetic patients, FBF was significantly correlated with TERalb.
TERalb is increased in normo-albuminuric type 1 diabetic patients. In these patients with an increased capillary permeability, there is no evidence of endothelial dysfunction or vessel wall damage. However, both FBF and filtration fraction are increased. Therefore, the increased vascular permeability in the early phase of type 1 diabetes is associated with general haemodynamic alterations. Notably, such an increase in vascular permeability is not necessarily reflected by abnormal UAE. This could be due to either a lack of change in glomerular permeability or due to the fact that the threshold for tubular reabsorption of albumin has not been exceeded.
1型糖尿病患者尿白蛋白排泄量（UAE）增加可能反映血管通透性和/或局部血流动力学因素的变化。实际上，白蛋白经毛细血管的逸出率（TERalb），即一种衡量全身毛细血管外流的指标，在糖尿病患者中升高，即使是那些白蛋白尿仅有适度增加的患者。在正常白蛋白尿的1型糖尿病患者中，全身毛细血管和肾小球血流量增加。我们推测，即使在微量白蛋白尿前期，这些血流动力学变化也会导致TERalb升高。
我们测量了39例正常白蛋白尿的1型糖尿病患者和46例健康对照者的TERalb。TERalb由125I - 白蛋白的消失曲线计算得出。通过标准技术测量肾脏和全身血流动力学。用体积描记法测量前臂血流量（FBF）。通过动脉内注射乙酰胆碱评估内皮功能。通过闭塞后反应性充血试验确定血管壁的结构完整性。
糖尿病患者的TERalb升高（5.53±0.40对4.39±0.21%/小时，P = 0.01）。根据TERalb将患者分为三分位数组。各组之间在UAE、血压、代谢参数、内皮功能或闭塞后最大血管扩张方面无差异。然而，TERalb水平最高的糖尿病患者组的滤过分数和FBF显著增加。总体而言，在糖尿病患者中，FBF与TERalb显著相关。
正常白蛋白尿的1型糖尿病患者的TERalb升高。在这些毛细血管通透性增加的患者中，没有内皮功能障碍或血管壁损伤的证据。然而，FBF和滤过分数均增加。因此，1型糖尿病早期血管通透性增加与总体血流动力学改变有关。值得注意的是，这种血管通透性增加不一定由异常的UAE反映出来。这可能是由于肾小球通透性没有变化，或者是由于尚未超过白蛋白肾小管重吸收的阈值。
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