Kang M J, Ingram A, Ly H, Thai K, Scholey J W
Department of Medicine, University of Toronto, Toronto, Ontario, Canada.
Kidney Int. 2000 Oct;58(4):1677-85. doi: 10.1046/j.1523-1755.2000.00328.x.
Several studies have suggested that transforming growth factor-beta1 (TGF-beta1) is an important determinant of diabetic glomerular injury. TGF-beta1 forms a heteromeric complex with two cellular receptor subtypes, designated TGF-beta RII and TGF-beta RI, but the effects of diabetes mellitus on glomerular TGF-beta receptor expression have not been completely elucidated. We first compared the effect of experimental type I diabetes mellitus and uninephrectomy on glomerular TGF-beta receptor expression in spontaneously hypertensive rats (SHRs), and then sought to determine whether changes in TGF-beta receptor expression were strain specific by studying normotensive Wistar-Kyoto (WKY) rats.
Five groups of male SHRs were studied. The first group received streptozotocin (60 mg/kg IV) and was studied after one week. The second group received streptozotocin and was studied after two weeks. The third group received streptozotocin (60 mg/kg IV) but received insulin to maintain euglycemia. The fourth group of age-matched SHRs served as the control group, while a fifth group of SHRs underwent uninephrectomy. Four groups of male WKY rats were also studied. The first group of WKY rats served as the age-matched control group. The second group of WKY rats received streptozotocin, while a third group of WKY rats underwent uninephrectomy. The fourth group underwent uninephrectomy and received streptozotocin. At each time point, glomeruli were isolated for protein extraction, and the protein was subjected to Western blot analysis of TGF-beta RII and TGF-beta RI expression.
Basal expression of both TGF-beta receptors per microgram of glomerular protein was similar in normotensive WKY rats and hypertensive SHRs. Hyperglycemia (blood glucose level, 17.8 +/- 2.9 mmol/L) led to an early twofold increase in TGF-beta RII protein expression and a fourfold increase in TGF-beta RI protein expression in the glomeruli of hypertensive diabetic SHRs compared with euglycemic SHRs (blood glucose level, 5.8 +/- 0.8 mmol/L), which was sustained after two weeks. Insulin treatment (blood glucose level, 5. 2 +/- 0.9 mmol/L) normalized both TGF-beta RII and TGF-beta RI expression in the glomeruli of SHRs that received streptozotocin. Glomerular capillary hypertension in the uninephrectomized SHRs led to a twofold increase in glomerular TGF-beta RII protein expression, but did not reproduce the effect of diabetes mellitus on TGF-beta RI expression. In contrast to the findings in SHRs, neither hyperglycemia (blood glucose level, 15.5 +/- 2.1 mmol/L), uninephrectomy, nor hyperglycemia (blood glucose level, 16.8 +/- 3.0 mmol/L) and uninephrectomy altered TGF-beta receptor expression in the glomeruli of normotensive WKY rats.
These studies support the hypothesis that hemodynamic factors and metabolic factors influence glomerular TGF-beta receptor in vivo in the SHRs.
多项研究表明，转化生长因子β1（TGF-β1）是糖尿病肾小球损伤的重要决定因素。TGF-β1与两种细胞受体亚型形成异源复合物，分别称为TGF-β RII和TGF-β RI，但糖尿病对肾小球TGF-β受体表达的影响尚未完全阐明。我们首先比较了实验性I型糖尿病和单侧肾切除对自发性高血压大鼠（SHR）肾小球TGF-β受体表达的影响，然后通过研究正常血压的Wistar-Kyoto（WKY）大鼠来确定TGF-β受体表达的变化是否具有品系特异性。
对五组雄性SHR进行研究。第一组接受链脲佐菌素（60mg/kg静脉注射），一周后进行研究。第二组接受链脲佐菌素，两周后进行研究。第三组接受链脲佐菌素（60mg/kg静脉注射），但接受胰岛素以维持血糖正常。第四组年龄匹配的SHR作为对照组，而第五组SHR进行单侧肾切除。还对四组雄性WKY大鼠进行了研究。第一组WKY大鼠作为年龄匹配的对照组。第二组WKY大鼠接受链脲佐菌素，而第三组WKY大鼠进行单侧肾切除。第四组进行单侧肾切除并接受链脲佐菌素。在每个时间点，分离肾小球进行蛋白质提取，并对蛋白质进行TGF-β RII和TGF-β RI表达的蛋白质印迹分析。
每微克肾小球蛋白中两种TGF-β受体的基础表达在正常血压的WKY大鼠和高血压的SHR中相似。与血糖正常的SHR（血糖水平，5.8±0.8mmol/L）相比，高血糖（血糖水平，17.8±2.9mmol/L）导致高血压糖尿病SHR肾小球中TGF-β RII蛋白表达早期增加两倍，TGF-β RI蛋白表达增加四倍，两周后仍持续。胰岛素治疗（血糖水平，5.2±0.9mmol/L）使接受链脲佐菌素的SHR肾小球中TGF-β RII和TGF-β RI表达均恢复正常。单侧肾切除的SHR中的肾小球毛细血管高血压导致肾小球TGF-β RII蛋白表达增加两倍，但未重现糖尿病对TGF-β RI表达的影响。与SHR的结果相反，高血糖（血糖水平，15.5±2.1mmol/L）、单侧肾切除，以及高血糖（血糖水平，16.8±3.0mmol/L）和单侧肾切除均未改变正常血压WKY大鼠肾小球中的TGF-β受体表达。
这些研究支持以下假设，即血流动力学因素和代谢因素在体内影响SHR肾小球中的TGF-β受体。
