Fundamental studies on the pathogenesis of diabetic complications using transgenic mice expressing human aldose reductase

我们建立了大量表达人醛糖还原酶的转基因小鼠，以探讨增强的多元醇途径在糖尿病并发症发病机制中的作用。在我们之前的研究中，这些转基因小鼠通过半乳糖喂养16周表现出显著的多元醇积累，与运动神经传导速度的显著延迟和周围神经的神经纤维萎缩相关，从而证明多元醇通路在糖尿病神经病变的病因学中的意义。在本研究中，我们通过腹腔注射链脲佐菌素使转基因小鼠患糖尿病8周，并检查外周神经和肾脏病变的生化、电生理和结构异常。与非转基因同窝对照小鼠的变化进行比较。转基因和同窝对照小鼠均显示出相当水平的体重减轻和高血糖症。相比之下，运动神经传导更少， ...更多信息 与非糖尿病转基因和同窝对照小鼠相比，糖尿病转基因小鼠和糖尿病同窝小鼠的ST严重减慢。生化测量结果显示，糖尿病转基因小鼠中山梨糖醇和果糖明显积累，但这种糖水平仅在糖尿病同窝小鼠中适度升高。两个糖尿病组的肌醇水平没有改变。形态学分析表明，与糖尿病同窝仔和非糖尿病组相比，糖尿病转基因小鼠中有显著的有髓纤维萎缩。这些发现证实，与糖尿病同窝小鼠相比，即使在相似的高血糖水平下，人醛糖还原酶转基因小鼠也发生了严重的神经病变变化，表明醛糖还原酶表达是神经病变及其严重程度的关键决定因素。另一方面，肾小球肥大和系膜扩张是人类和动物糖尿病肾病早期肾脏病变的特征性变化。肾脏形态计量学分析表明，糖尿病转基因小鼠和同窝对照小鼠的肾小球大小和系膜区与离子糖尿病组相比，显着扩大，而糖尿病转基因小鼠的值是最大的。这些发现再次表明，增强的多元醇途径影响糖尿病肾小球病变的发展，并且醛糖还原酶的表达介导了多元醇途径的这种增强的活性。初步试验中，醛糖还原酶抑制剂显着抑制糖尿病转基因小鼠的神经病变和肾小球的变化，但没有在糖尿病同窝仔梅斯。因此，由醛糖还原酶调节的多元醇途径是糖尿病并发症发生发展的重要决定因素，有效抑制该途径对糖尿病并发症的预防和治疗具有重要意义。少

We have established transgenic mice, which express large amount of human aldose reductase, to explore the role of an enhanced polyol-pathway in the pathogenesis of diabetic complications. In our preceding studies, these transgenic mice exhibited significant accumulation of polyols by galactose feeding for 16 weeks associated with significant delay of motor nerve conduction velocity and nerve fiber atrophy of the peripheral nerve, thus demonstrating the implication of polyol pathway in the etiology of diabetic neuropathy. In the current study, we made transgenic mice diabetic for 8 weeks by intraperitoneal injection of streptozotocin and examined biochemical, electrophysiological and structural abnormalities in the peripheral nerve as well as renal lesions. Comparison was made with the changes in non-transgenic littermate control mice. Both transgenic and littermate control mice showed comparable levels of reduced body weight and hyperglycemia. By contrast, motor nerve conduction was mo … More st severely slowed in diabetic trasgenic mice followed by diabetic littermate mice compared to non-diabetic transgenic and littermate control mice. Biochemical measurements disclosed marked accumulation of sorbitol and fructose in diabetic transgenic mice, but such sugar levels were only modestly elevated in diabetic littermate mice. Myo-inositol levels were not altered in both diabetic groups. Morphometric analysis demonstrated significant myelinated fiber atrophy in diabetic transgenic mice compared with diabetic littermate and non-diabetic groups. These findings confirmed that transgenic mice for human aldose reductase developed severe neuropathic changes compared with diabetic littermate mice even under similar levels of hyperglycemia, suggesting that the aldose reductase expression is a critical determinant for the development of neuropathy and its severity. On the other hand, glomerular hypertrophy and mesangial expansion are characteristic changes of early renal lesions in human and animal diabetic nephropathy. Morphometric analysis on the kidney demonstrated significant enlargement of glomerular size and mesangial area in diabetic transgenic and littermate control mice as compared with ion-diabetic groups, while the values of diabetic transgenic mice were the greatest. These findings again indicate that an enhanced polyol pathway influences the development of diabetic glomerulopathy and an expression of aldose reductase mediates such an enhaneced activity of polyol pathway. Preliminary trials with aldose reductase inhibitors significantly inhibited neuropathic and glomerular changes in diabetic transgenic mice but not in diabetic littermate mace. It was thus concluded that the polyol pathway regulated by aldose reductase is an important determinant of the progression of diabetic complications and its effective inhibition may be valuable for the prevention and treatment of diabetic complications. Less