Establishment Of Type 2 Diabetes Rat Model And The Expression Of INS And PDX-1 Protein In Pancreatic Tissue

With the aging of the population and the social environment changes,the incidence of Type 2 diabetes mellitus(T2DM)has been increasing year by year,but its etiology has not been fully elucidated.It is currently considered that the main reasons are insulin resistance(IR),injury of islet B cell function and insulin secretion deficiency.Furthermore,in recent years,the incidence of T2DM in pets has been increasing year by year,leading to its increased complication,which affect the quality of pets and master's life,bringing economic losses and trauma.However,the studies of T2DM in the veterinary field is still insufficient.Therefore,a reliable and stable T2DM disease model plays key roles in the clinical research of pathogenesis and new intervention measures.In the present study,we established T2DM rat models,and further determined the protein expression of INS and PDX-1,which helps to further illuminate the pathogenesis of T2DM and provides theoretical supporting of T2DM in medical science and veterinary clinical.1 Establishment and evaluation of Type 2 diabetes rat modelIn this experiment,male Wistar rats were selected to establish T2DM by feeding high-fructose high-fat diet for 4 weeks,and were injected 2%STZ at 30 mg/kg to without fasting.One week later,fasting plasma glucose(FPG)and fasting insulin(FINS)were measured by radioimmunoassay,and ISI was calculated using the formula 1/(FPG*FINS).At the same time,i.p.glucose tolerance test(IPGTT)was conducted,and the area under the IPGTT curve was calculated as SIPGTT.The FPG,FINS,ISI and SIPGTT were used to evaluate the T2DM rat model.When the experiment finished,the success rate and mortality rat were calculated.Results showed that after modeling for 4 w,FPG,FINS and SIPGTT of experimental group increased significantly when compared with control group(P<0.01),while the ISI reduced significantly(P<0.01),these results indicate that when after modeling for 4 w,the rats of experimental group had great IR.As the results of 5 w,FPG,FINS and SIPGTT of experimental group were higher than that of control group(P<0.01),and the FPG of experimental group ? 7.0 mmol/L;ISI of experimental group was lower than control group(P<0.01).At the end of the experiment,there were 11 rats died and 2 rats were not successfully established in the experimental group,so the mortality rate was 18.3%(11/60)and the success rate was 78.3%(47/60).The result showed us that the high-fructose high-fat diet was able to cause IR and low-dose STZ can make destoryed the islet B cells by elevating GLU,which is similar to the pathological features of T2DM in clinical.The effect of modeling is better than which using single high-fat diet,The success rate is high and the death is the mortality rate is low.To sum up,IR can be successfully induced by feeding the high-fructose high-fat diet.After IR,adding small dose of STZ was able to destroy the B cells of the islets,which led to the increase of blood glucose,and better simulated the natural pathogenesis of T2DM.2 Expression of INS and PDX-1 protein in pancreatic tissue of T2DM rat modelIn order to further explore the pathogenesis of T2DM,the expression of INS,which was the important protein that can reduce blood glucose was studied,and the expression of PDX-1,the major regulator of INS gene was also studied.20 model rats were selected randomly to perform immunohistochemistry for the expression of INS in pancreas tissues,and Western Blot method was used to measure the expression of PDX-1 protein at 0 w,1 w,3 w,5 w,FPG(5 rats were killed at every time point).FINS,ISI and SIPGTT were measured and ISI was calculated.The immunohistochemical results showed that the INS positive cells were decreased significantly in the pancreas of experimental group,and the WB results also showed that the PDX-1 were decreased significantly in the pancreas of experimental group,indicating that the decrease of INS protein expression has a relationship with the decrease of PDX-1 protein expression.FPG,FINS and SIPGTT of experimental group increased significantly when compared with control group,while ISI decreased significantly(P<0.01).These results indicated that the model is stable.In summary,the T2DM rat model were stable during the experimental period,and the decrease in INS protein expression might be caused by decreased expression of PDX-1 protein.