Effects Of High Glucose And Insulin On The Expression And The Time Course Of Translocation Of GLUT4 Of Glomerular Mesangial Cells

Objective: Diabetes mellitus (DM)is a disease which means a great hazard to people' s health. Diabetic nephropathy (DN) is one of the most hazardous chronic complications of DM. It is proved that insulin resistance is a key feature of type 2 diabetes mellitus, and the impaired mechanism of glucose transport is an important aspect of insulin resistance. Insulin stimulates glucose transport by promoting the translocation of glucose transporter 4(GLUT4) from an intracellular pool to the plasma membrane through two sigalling pathways, including PI3K and CAP/Cbl to regulate glucose homeostasis. The aim of the present study was to examine effects of high glucose and insulin on the expression of GLUT4 and the time course of translocation of GLUT4 translocation of glomerular mesangial cells (GMCs)in order to explore the role of GLUT4 in the genesis and development of DN and seek a new path for the prevention and cure of DN. Method: Cultured 1097 rat GMCs were divided into 8groups:①control,②10^-9mol/L insulin,③10^-8 mol/L insulin,④10^-6 mol/L insulin,⑤high glucose,⑥mannitol,⑦high glucose plus 10^-6 mol/L insulin,⑧high glucose plus 10^-9 mol/L insulin. GLUT4 mRNA expression was examined by reverse transcription-polymerase chain reaction(RT-PCR).Confocal microscopy was performed to detect the presence of GLUT4 in every group and the time course of GLUT4 translocation in Group②,③,④.Results:1. GLUT4 could be detected in normal GMC.2. Insulin enhanced the expression of GLUT4. High glucose decreased the expression of GLUT4 obviously.3. Insulin induced the translocation of GLUT4 of GMC.4. The time course of GLUT4 tranclocation was similar in 10^-8 mol/L insulin and 10^-6 mol/L insulin .Maximal translocation of GLUT4 was reached at 15 min after insulin incubation. The fluorescent intensity of GLUT4 located in the plasma membrane at all time points after 15 min was not significantly different (P＞0.05).Conclusion:1. Normal GMCs can express GLUT4; insulin can induce the translocation of GLUT4 of GMC.2. High glucose can inhibit the expression of GLUT4 on the GMCs.3. Insulin can partly reverse the effects caused by high glucose above.4. The time course of the translocation of GLUT4 induced by insulin of different concentrations was similar. 5. GLUT4plays a significant role in the genesis and development of DN.