The Effect Of Insulin Postreceptor Signal Pathway In Pathogenesis Of Gestational Diabetes Mellitus

Part 1 The relationship between GLUT-4 expression andtranslocation and insulin resistance in gestational diabetes mellitusObjective To investigate the GLUT-4 expression and translocation in gestational diabetesmellitus, analysis the relationship between GLUT-4 and insulin resistance in gestationaldiabetes mellitusMethods (1) Fasting insulin(FINS) and Fasting plasma glucose(FPG) was measured byoxidase assay and immunoradioassay .insulin resistance index was calculated usinghomeostasis model assessment (HOMA-IR) .intact skeletal muscle strips and biopsiesspecimen were obtained, Skeletal muscle plasma membranes and the intracellularmembranes were separated by sucrose gradient ultracentrifugation; (2) the GLUT-4translocation were measured by Western blot assay;(3)The distribution of GLUT-4 measuredby immunohistochemistry assay.Results (1) The levels of FPG, FINS, and insulin resistance index in GDM group weresignificantly higher than those in normal pregnancy group. (2) No significant differentwas observed in total GLUT-4 amount in skeletal muscle between control group and GDMgroup. (3) the amount of GLUT-4 in plasma membranes from GDM group wassignificant decreased in skeletal muscle cell from GDM compared to control group(P＜0.05).The translocation of GLUT-4 positively correlated with the FINS,FBG,HOMA-IR andlevels (r=-0.42, -0.46, -0.51, P＜0.05).Conclusions The GLUT-4 translocation from intracellular membranes to plasmamembranes was significant decreased in skeletal muscle cell from GDM, The decreasedGLUT-4 translocation correlated with GDM IR. Part2 The expression and phosphorylation of PI3K,PKB andGSK-3 in the skeletal muscle from pregnant women with gestationaldiabetes mellitusObjective To investigate the expression and phosphorylation of insulin signalingtransduction molecules in the skeletal muscle of patients with gestational diabetes mellitus,and explore molecular mechanisms of insulin resistance in gestational diabetes mellitusMethods The skeletal muscle samples from patients with GDM (GDM group ,n=26) ,normal pregnant women (control group, n=26) ; (1) The expression of PI3K,PKB,GSK-3 measured by immunohistochemistry assay; (2) The activity of PI3K was measuredby ELLISA method; (3) The phosphorylation of PKB and GSK-βwere determined bywestern blot assay.Results (1) The expression amount of PKB and GSK-3 protein in skeletal muscle cell wasnot found different among the control group and GDM group.(P＞0.05); (2) The amount ofPI3-Kp85 was significant higher than in control group (P＜0.05); (3) the phosphorylation ofPI3-K,PKB and GSK-3 activity of PI3-K decease in GDM group as compared with thecontrol group(P＜0.05).Conclusion The present results indicated that the decease of phosphorylation of PI3K,PKBand GSK-3βin the skeletal muscle of gestational diabetes mellitus may be one of themolecule mechanisms postreceptor signal transduction obstacle and insulin resistance ofGDM. Part 3 Sodium vandate improve IRS-1 tyrosine phosphorylationon insulin postreceptor signal transduction and GLUT-4translocation in skeletal muscle from pregnant women withgestational diabetes mellitusObjective To investigate the effect IRS-1 tyrosine phosphorylation on insulin postreceptorsignal transduction in skeletal muscle from women with gestational diabetes mellitusMethods The skeletal muscle samples from patients with GDM and normal pregnantwomen were incubated in medium containing sodium vandate; (1) The tyrosinephosphorylation of IRS-1 was measured by immunoprecipitation; (2) The activity of PI3-Kwas measured by ELLISA method; (3) the GLUT-4 translocations were measured byWestern blot.Results (1) Sodium vandate increased the tyrosine phosphorylation of the IRS-1; (2) andPI3-kinase activity and the translocation of GLUT-4 in skeletal muscle from pregnant; (3)but the value was still less than control subjectsConclusion Sodium vandate increase IRS-1 tyrosine phosphorylation and improve insulinsignal transduction Mediated GLUT-4 translocation in skeletal muscle from women withgestational diabetes mellitus. It was indicated as potential approach for insulin resistance.