The Influence Mechanism Of Oxidative Stress On Rat Islet Cell Injury With Steroid Diabetes Mellitus

Objectives To establish steroid diabetes mellitus rat model by the means of high fat diet and injecting intraperitoneal dexamethasone to rat at the first. Then we observe insulin secertion, islet cells apoptosis, oxidative stress degree and Fox O1, PDX-1, Maf A protein expression degree of the rats and discuss the occurrence mechanism of steroid diabetes mellitus.Methods 40 male SD rats of 8 weeks are divided into two groups randomly:rats in ND group are fed with normal diet,and HFD group MD45% high fat diet.Rats in HFD group are divided into HFDO subgroup and HFD+DEX subgroup randomly after 12 weeks, rats in ND group are divided into NDO subgroup and ND+DEX subgroup randomly after 12 weeks. Then rats in HFD+DEX subgroup and ND+DEX subgroup are injected deamethasone to intraperitoneal with the dose of 5 mg/(kg.d),the other two groups are injected isodose normal saline.Groups of rats fodder feed unchanged. We evaluate whether steroid diabetes mellitus rat model is establishesd succesfully or not by the standard of fasting blood glucose is over 16.7mmol/L. We execute all rats after 16 weeks,and separate the pancreas.Drawing blood from taill vein and centrifuging it for use.Monitoring body weight, fasting blood glucose, fasting insulin, plasm triglycerides,total cholesterol and OGTT at regular intervals.To observe the pancreas structure by HE staining,to detecte islet cells apoptosis by TUNEL,to observe proinsulin, Bcl-2, Bax,Fox O1, Maf A, PDX-1 protein expression of pancreas islet by IHC method,to determine the content of plasm insulin and C peptide by Elisa kit,and plasm SOD, GSH, ROS and MDA by determination of the corresponding kit.Results 1 Conpared with ND group at 12 th week,the rats in HDF group gain more weight(t=91.286, P<0.01),and their plasm triglycerides and total cholesterol(t=17.280,P<0.01; t=21.925, P<0.01), fasting insulin(t=8.621, P<0.01), AUC(t=2.629, P<0.05)and HOMA-IR(t=6.271,P<0.01)is higher, but fasting blood glucose does not change obviously(t=-1.297, P>0.05).2 Conpared with NDO subgroup at 16 th week, the rats in ND+DEX subgroup body weight decreased(t=-93.736, P<0.01),and fasting blood glucose(t=152.438, P<0.01),plasm triglycerides and total cholesterol(t=10.115, P<0.01; t=2.172, P<0.05)and AUC(t=39.620, P<0.01)is increased. The rats in ND+DEX subgroup plasm insulin and C peptide is less(t=-40.306, P<0.01; t=-113.627, P<0.01).The rats in ND+DEX subgroup plasm SOD activity and GSH content is less(t=-17.825, P<0.01; t=-44.935, P<0.01), but ROS and MDA more(t=133.179, P<0.01; t=28.748, P<0.01). The rats in ND+DEX subgroup islet cells apoptosis index is higher(t=18.671, P<0.01) and Bcl-2/Bax lower(t=-8.218, P<0.01) at the same time. PI protein expression is less(t=-23.277, P<0.01) of the rats in ND+DEX subgroup pancreas islet cells as well as Maf A and PDX-1(t=-15.011,P<0.01; t=-12.250, P<0.01). Fox O1 protein expression in cell nuclear is more(t=18.562,P<0.01).Conpared with HFDO subgroup at 16 th week, the rats in HFD+DEX subgroup body weight decreased(t=-258.992, P<0.01),and fasting blood glucose(t=156.406, P<0.01),plasm triglycerides and total cholesterol(t=2.593, P<0.05; t=2.844, P<0.05)and AUC(t=190.725, P<0.01)is increased. The rats in ND+DEX subgroup plasm insulin and C peptide is less(t=-48.990, P<0.01; t=-159.606, P<0.01).The rats in HFD+DEX subgroup plasm SOD activity and GSH content is lower(t=-19.773, P<0.01; t=-37.030,P<0.01), but ROS and MDA more(t=106.208, P<0.01; t=33.912, P<0.01). The rats in HFD+DEX subgroup islet cells apoptosis index is higher(t=15.391, P<0.01)and Bcl-2/Bax lower(t=-15.777, P<0.01) at the same time. PI protein expression is less(t=-27.159,P<0.01) of the rats in ND+DEX subgroup pancreas islet cells as well as Maf A and PDX-1(t=-14.713, P<0.01; t=-10.750, P<0.01). Fox O1 protein expression in cell nuclear is more(t=14.710, P<0.01).Conclusions The reason for SDM rats' decreased insulin secretion may had relationship with oxidative stress degree being aggravated, and leading to Fox O1 protein express more in nuclear. Further inhibition the protein expression of PDX-1 and Maf A in islet cells, and Bcl-2/Bax is lower at the same time. This series of changes make islet cells apoptosis increased and dysfuncion finally.