Effects of high glucose and insulin on expression of glucose transporter 4, Cbl-associated protein and cytoskeleton protein F-actin in rat glomerular mesangial cells in vitro / 中华肾脏病杂志

ABSTRACT

Objective To investigate the effects of high glucose and insulin on the expression of glucose transporter 4 (GLUT4), Cbl-associated protein (CAP) and cytoskeleton protein F-actin of glomerular mesangial cells (GMCs), in order to explore the function of GLUT4, Cbl-associated protein and F-actin in the pathogenesis and development of diabetic nephropathy (DN). Methods Cultured 1097 rat glomerular mesangial cells were divided into 8 groups control, 10-9 mol/L insulin, 10-8 mol/L insulin, 10-6 mol/L insulin, high glucose (30 mmol/L), mannitol (25 mmol/L mannitol+5 mmol/L glucose), high glucose plus 10-6 mol/L insulin, high glucose plus 10-9 mol/L insulin. Expression of CAP mRNA and GLUT4 was measured by RT-PCR and immunohistochemistry method. F-actin was stained by rhodamine-pholloidin and the fluorescent intensity was calculated by image analysis system. Results The expression of GLUT4 mRNA and protein, CAP mRNA was found in normal giomerular mesangial cells (control), and there was no significant difference in 10-9 mol/L insulin group. The expression of GLUT4 mRNA (P<0.05) and protein (P<0.01), CAP mRNA (P<0.01) level was decreased in high glucose group compared with that of control group, but there was no significant difference in mannitol group. The expression of GLUT4 and CAP mRNA up-regulated with the increase of concentration of insulin. The expressions of GLUT4 mRNA in 10-8 mol/L insulin and 10-6 mol/L insulin groups were 2.06-fold and 2.66-fold of 10-9 mol/L insulin group, of GLUT4 protein were 1.93-fold and 2.83-fold of control, and of CAP mRNA were 1.91-fold and 2.15-fold of control, respectively. The expressions of GLUT4 mRNA, GLUT4 protein, CAP mRNA in high glucose plus insulin group were 2.15-fold, 2.08-fold, 2.14-fold of high glucose group respectively. High glucose decreased the fluorescent intensity of F-actin to 44.5% (P<0.01). 10-8 mol/L insulin and 10-6 mol/L insulin groups increased to 1.224-fold (P<0.05), 1.296-fold (P<0.01) in a concentration-dependent manner. The spearman correlation coefficient between GLUT4 and F-actin was 0.929 (P=0.001), between GLUT4 mRNA and CAP mRNA was 0.905 (P=0.002). Conclusions (1) A certain expression of GLUT4 mRNA and protein, CAP mRNA from GMC is found in normal glomerular mesangial cells. (2) High glucose can inhibit the expression of GLUT4 and CAP mRNA significantly, and facilitate the depolymerization of F-aetin. (3) Insulin can reverse down-regnlation of GLUT4 and CAP mRNA caused by high glucose. (4) GLUT4, CAP and F-actin are important factors in the development of DN.