Dataset for: Diabetic rats present higher urinary loss of proteins and lower renal expression of megalin, cubilin, ClC-5 and CFTR

Diabetic nephropathy (DN) occurs in around 40% of those with diabetes. Proteinuria is the main characteristic of DN and develops as a result of increased permeability of the glomerulus capillary wall and/or decreased proximal tubule endocytosis. The goal of this work was to evaluate renal function and the expression of megalin, cubilin, CFTR (cystic fibrosis transmembrane conductance regulator) and ClC-5 in the proximal tubule and renal cortex of rats with type 1 diabetes. Male Wistar rats were randomly assigned to control (CTRL) and diabetic (DM) groups for 4 weeks. Renal function was assessed in 24-h urine by calculating clearance and fractional excretion of solutes. The RNA and protein content of ClC-5, CFTR, megalin and cubilin was determined in the renal proximal tubule and cortex using real-time polymerase chain reaction and western blotting techniques, respectively. The results showed higher creatinine clearance and higher urinary excretion of proteins, albumin and transferrin in the DM group than in the CTRL group. Furthermore, the renal cortex and proximal tubule of diabetic animals showed downregulation of megalin, cubilin, ClC-5 and CFTR, critical components of the endocytic apparatus. These data suggest dysfunction in proximal tubule low-molecular-weight endocytosis and protein glomerulus filtration in the kidney of diabetic rats.

糖尿病肾病（Diabetic nephropathy, DN）在约40%的糖尿病患者中发病。蛋白尿（Proteinuria）是糖尿病肾病的核心临床特征，其发生源于肾小球毛细血管壁（glomerulus capillary wall）通透性升高和/或近端小管内吞作用（proximal tubule endocytosis）减弱。本研究旨在评估1型糖尿病（type 1 diabetes）大鼠的肾功能，以及megalin、cubilin、CFTR（囊性纤维化跨膜传导调节因子，cystic fibrosis transmembrane conductance regulator）与ClC-5在其近端小管及肾皮质中的表达水平。

将雄性Wistar大鼠随机分为对照组（CTRL）与糖尿病组（DM），造模周期为4周。通过收集24小时尿液，计算溶质清除率与分数排泄率以评估肾功能。分别采用实时聚合酶链反应（real-time polymerase chain reaction）与蛋白质印迹法（western blotting）检测肾近端小管与肾皮质中ClC-5、CFTR、megalin及cubilin的RNA与蛋白表达水平。

结果显示，相较于对照组，糖尿病组大鼠的肌酐清除率（creatinine clearance）更高，尿液中蛋白质、白蛋白（albumin）与转铁蛋白（transferrin）的排泄量亦显著升高。进一步分析发现，糖尿病大鼠的肾皮质与近端小管内，作为内吞装置关键组分的megalin、cubilin、ClC-5及CFTR均出现表达下调（downregulation）。

上述数据表明，糖尿病大鼠肾脏的近端小管低分子量物质内吞功能与肾小球蛋白滤过功能均出现异常。