The Study Of Mechanism Of Angiotensin â…¡ On Insulin Action In L6 Rat Myoblasts

Objective To study the effect of AngⅡon conductions involved in insulin signal pathway including IRS1、P^tyr-IRS1、GLUT4（total protein and membrane protein）、PI3K、PKB in L6 rat skeletal myoblast,thus explore the possible mechanism of AngⅡon glucose utilization. Methods L6 rat myoblast cells cultured and myotubes differentiated were divided into four groups according to different treatment by AngⅡor JAK2-PKA signaling pathway inhibitor H89: control normal group （CN group）, insulin group （Ins group）, insulin + angiotensinⅡgroup （Ins+AngⅡgroup） and insulin+angiotensinⅡ+H89 group （Ins+AngⅡ+H89 group）.IRS1、GLUT4、PI3K、PKB mRNA were detected by RT-PCR,IRS1,P^tyr-IRS1 and GLUT4 （total and membrane protein） were detected by immunofluorescence and Western blot. Results GLUT4 mRNA by RT-PCR among four groups were not different significantly （P>0.05）;there were no difference about mRNA expression of IRS1 among latter three groups （P>0.05）,but the three groups had higher IRS1 expression than that of CN group（P<0.05）;there were no difference about mRNA expression of PI3K among latter three groups （P>0.05）,but the three groups had higher PI3K expression than that of CN group（P<0.05）;PKB mRNA by RT-PCR among four groups were not different significantly （P>0.05）. Immunofluorescence and Western blot results show IRS1, P^tyr-IRS1 and GLUT4（ membrane protein ）expression in latter three groups were significantly higher than those of CN group （P<0.05）;while there were no difference of IRS1 expression among latter three groups （P>0.05）;the expression of P^tyr-IRS1 and GLUT4 membrane protein in Ins+ AngⅡ+H89 group were much higher than those of Ins+ AngⅡgroup,and much lower than Ins group（P<0.05）;Western blot show GLUT4（total protein） expression among four groups were no difference（P>0.05）.Conclusion AngⅡinhibits IRS1 tyrosine phosphorylation and GLUT4 transfer from cytoplasm to plasma membrane in skeletal muscle cells,JAK2-PKA signaling pathway might be the mechanism of AngⅡon effective glucose utilization ,therefore insulin resistance induced;but impaired insulin pathway downstream of PI3K may be non-dependent transport of GLUT4 obstacles.