Effect Of Visfatin On GLUT4and PI3K In Skeletal Muscle Of Diabetic Rats

Objective: Visfatin is a novel adipocytokine whose plasma concentration increasesin obesity and Type2diabetes mellitus（T2DM） disorders. It has a insulin-mimeticglucoselowering effect, at present its mechanism is well understood. It maybe a usefultarget for the development of hypoglycemic agents. The rats were fed with normal dietor plus high-fat diet were induced to become T2DM model by intraperitoneal injectionof streptozotocin（STZ）. The purpose of the study is to investigate the effect of visfatinon PI3K and GLUT4expression and the relationship between visfatin and PI3Ksignalling pathway in skeletal muscle of T2DM rats model by intraperitoneal injectionof visfatin.Methods:1、Groups and modelsWistar rats were randomly divided into four groups: normal diet feeding group（N）,high-fat diet feeding group（H）, normal diet feeding plus STZ-induced diabetic group（N+S）and high-fat diet feeding plus STZ-induced diabetic group（H+S）. Diabetic ratswere induced by intraperitoneal injection of45mg kg^-1STZ to establish the models ofT2DM. Plasma glucose levels was measured by cutting rat tail vien after72hours.When plasma glucose levels was higher than16.7mmol L-1, the diabetic models ofSTZ-induced rats was thought to be founded succeccfully.Visfantin wereintraperitoneally injected in partial rats（group V+N+S and group V+H+S）from groupN+S and group H+S after8weeks of establishment of models.2、Administration methods and materialsGroup V+N+S and group V+H+S rats were given intraperitoneal injection ofvisfatin（4μg Kg-1） at the end of the experiment. FPG of rats tail vien blood weredetermined by automatic blood glucose meter. Abdominal aortic blood of each groups were transferred to anticoagulant tube and plasma were separated by centrifuge. At thesame time, skeletal muscles were obtained and frozen at-70℃refrigerator.3、Index detection（1）Fasting plasma glucose（FPG）, fasting insulin（FINS）: FPG levels of abdominalaortic blood were measured by GOD. FINS levels of abdominal aortic blood weremeasured by ELISA. ISI=ln（1/FPG×FINS）.（2）PI3K and GLUT4protein expression: They were assessed by western blotting.（3）GLUT4mRNA expression: They were measured with real time RT-PCR.4、Statistical analysesAll statistical analyses were performed using SPSS version17.0for Windowssoftware. All of the data are expressed as mean±SEM. Paired data of continuousvariables were compared using paird design data student′s-test. Comparisons amonggroups were made by ANOVA. In order to improve the normality of the skewedvariables, natural log transformation of thoese variables were made and used insubsequent analyses. P values less than0.05were considered statistically significant.Results:1、Comparison of FPG, FINS and ISI of rats in different groupsFPG levels of diabetes rats′tail vien blood were decreased（P<0.05） afterintraperitoneal injection of visfatin in group V+N+S and group V+H+S. Compared withgroup N, FPG levels of diabetes rats′abdominal aortic blood had no significantlychanged（P>0.05） in group H, and were increased（P<0.05） in the other groups.Compared with group H, FPG levels were increased （P<0.05） in group H+S and groupV+H+S. FPG levels were decreased（P<0.05） in group V+N+S compared with groupN+S, and in group V+H+S compared with group H+S. Compared with group N, FINSlevels had no significantly changed（P>0.05） in each groups. Compared with group N,ISI had no significantly changed（P>0.05） in group H, and were decreased（P<0.05） inthe other groups. Compared with group H, ISI were decreased in group H+S and groupV+H+S（P<0.05）. ISI were increased（P<0.05） in group V+N+S compared with groupN+S, and in group V+H+S compared with group H+S respectively.2、The protein expression of GLUT4and PI3K in skeletal muscle of rats in eachgroupsCompared with group N, GLUT4and PI3K protein expression had no significantlychanged（P>0.05） in group H,and were decreased in the other groups（P<0.05）.Compared with group H, GLUT4and PI3K protein expression were decreased in group H+S and group V+H+S（P<0.05）. GLUT4and PI3K protein expression were increased（P<0.05） in group V+N+S compared with group N+S,and in group V+H+S comparedwith group H+S respectively.3、GLUT4mRNA expression in skeletal muscle of rats in each groupsCompared with group N, GLUT4mRNA expression had no significantly changed（P>0.05） in group H,and were decreased（P<0.05） in the other groups. Compared withgroup H, GLUT4mRNA expression were decreased（P<0.05） in group H+S and groupV+H+S. GLUT4mRNA expression were increased（P<0.05） in group V+N+Scompared with group N+S, and in group V+H+S compared with group H+Srespectively.Conclusion:Visfatin can promote PI3K protein expression，furtherly increase GLUT4mRNAand protein expression, and then lower glucose levels by PI3K signalling pathway inskeletal muscle of diabetic rats.