Molecular analysis of glucose transporter in glomerular mesangial cells

已知肾小球系膜区的异常在糖尿病肾病的发生发展过程中起着至关重要的作用，系膜细胞可能参与了这些异常的发生发展。为了阐明系膜细胞的作用，我们在体外研究了高糖环境下的系膜细胞，发现了各种代谢紊乱，这些代谢紊乱可能与体内所见的系膜异常有关。葡萄糖通过特定的葡萄糖转运体(GLUT)转运到细胞内后，似乎会引起系膜细胞的各种代谢异常。本研究通过Western印迹和Northern印迹分析对系膜细胞葡萄糖转运蛋白进行了研究。用抗GLUT1和GLUT4的单抗进行Western blotting，检测到GLUT 1，但没有检测到GLUT 4。利用GLUT 1、2、3、4和5的cDNA进行Northern印迹分析，只检测到GLUT 1mRNA，这与Western blotting的结果一致。此外，胰岛素样生长因子-1(IGF-1)能够促进系膜细胞对葡萄糖的摄取，刺激GLUT-1基因的表达。由于系膜细胞具有丰富的IGF-1受体，且糖尿病时肾组织中IGF-1水平升高，因此IGF-1可能调节系膜细胞的葡萄糖转运量，并在糖尿病时增加。综上所述，GLUT 1是系膜细胞的主要葡萄糖转运体，受IGF-1调控，并可能在糖尿病代谢紊乱的演变中发挥作用。

It has been known that the abnormalities of mesangial area in glomeruli play a crucial role in the progression of diabetic nephropathy, and the mesangial cells might participate in the evolution of these abnormalities. In order to clarify the role of mesangial cells, the cells were investigated under high concentration of glucose in vitro and various metabolic derangements have been detected, which might be related to the mesangial abnormalities seen in vivo. The glucose appears to cause various.metabolic abnormalities in mesangial cells after transported intracellularly via specific glucose transporter(GLUT). In this study, the glucose transporter in mesangial cells was characterized by western blot and northern blot analyses. The western blotting using monoclonal antibodies against GLUTs 1 and 4 showed the presence of GLUT 1 but failed to detect GLUT 4. The northern blot analysis using cDNAs for GLUT 1,2,3,4,and 5 revealed the presence of GLUT 1 mRNA only, which was compatible with the results of western blotting. Furthermore, insulin-like growth factor 1 (IGF-1), which was able to increase the glucose uptake in mesangial cells, was found to stimulate the gene expression of GLUT 1. Since the mesangial cells possesses an abundant amount of receptors for IGF-1 and the IGF-1 levels in renal tissue is increased in diabetic state, the amount of glucose transport in mesangial cells may be regulated by IGF-1 and be increased in diabetes mellitus. In summary, GLUT 1 is a main glucose transporter in mesangial cells, regulated by IGF-1, and may play a role in the evolution of metabolic derangements found in diabetes mellitus.