| Objective: Progesterone and estrogen levels in the blood are closely related to the occurrence of insulin resistance in type 2 diabetes mellitus(T2DM).At present,the interaction and mechanisms of progesterone and estrogen in the development of insulin resistance in T2 DM are still unclear.The study was to establish a model of insulin resistance in T2 DM mice by intraperitoneal injection of streptozotocin combined with high-fat diet to investigate the effects and relationship of progesterone and estrogen combination in the development of insulin resistance in T2 DM mice,and to provide a theoretical basis for the diagnosis and treatment of insulin resistance in T2 DM.Methods: Mice were ovariectomized and fed with high fat diet for four weeks and then injected intraperitoneally with different doses of streptozotocin to establish a model of insulin resistance in T2 DM.Fasting plasma glucose levels were measured.Four weeks after administration of streptozotocin,glucose tolerance and insulin tolerance tests were performed,and the glucose consumption of isolated myocardium,gastrocnemius and liver in different groups was detected by perfusion experiment to determine the best modeling of insulin resistance in T2 DM.After the optimal insulin resistance model of T2 DM was defined,the mice were purchased and ovariectomized,then fed with high fat diet four weeks,and randomly divided into control group,model group and drug delivery group.Mice in the drug delivery group were injected streptozotocin intraperitoneally while progesterone or 17?-estradiol were administered subcutaneously.Fasting plasma glucose levels were measured each week,glucose tolerance test,insulin tolerance test and perfusion experiment of isolated myocardium,gastrocnemius and liver were performed after treatment with sex hormones for four weeks.The levels of blood insulin,C peptide(C-P),hepatocyte growth factor(HGF)were analyzed by Elisa experiment.Some tissues were fixed or frozen.Hematoxylin-Eosin Staining was used to detect the morphology of islet and number of islet cells,real-time reverse transcription-polymerase chain reaction(RT-qPCR)and immunofluorescence technique were used to detect the expression of insulin receptor,insulin receptor substrate-1(IRS-1)and insulin receptor substrate-2(IRS-2)in liver and skeletal muscle in mice.Results: The best modeling method for constructing T2 DM insulin resistance model in mice was fed with high fat diet for four weeks,and injected intraperitoneally STZ 30 mg/kg body weight,3 day in a row,and STZ 80 mg/kg body weight at the fourth day.The water consumption of T2 DM insulin resistance model mice was increased significantly,the urine glucose showed positive,the body weight of mice was decreased,the blood glucose was increased obviously,the glucose tolerance was impaired,the insulin secretion and insulin resistance index were decreased significantly,the insulin sensitivity of the peripheral tissues was significantly reduced,and the HGF level was increased significantly,and the model mice showed obvious insulin resistance,the islet beta cells were damaged,and their function was decreased significantly,the islet morphology changed,the number of islet cells was increased significantly,and there was hyperplasia.The basal glucose consumption of isolated myocardium,gastrocnemius and liver in model mice and the glucose consumption induced by exogenous insulin were decreased significantly when perfused at physiological glucose level or high glucose level.The expression of liver insulin receptor,IRS-1 and IRS-2 in model mice were obviously down-regulated,and the expression of skeletal muscle insulin receptor and IRS-1 were down-regulated as well.Progesterone 8 mg/kg body weight could reduce the blood glucose of model mice,increase the sensitivity of peripheral tissues to insulin,improve glucose tolerance,relieve insulin resistance,delay the occurrence of T2 DM in mice,and also increase the expression of mouse liver IRS-2 and skeletal IRS-1 significantly,but three doses of progesterone(0.1,2 or 8 mg/ kg body weight)caused the islet to shrink significantly,the islet cell function was obviously impaired,the progesterone 0.1 mg/kg body weight could reduce the expressions of IRS-1 and up-regulate the expressions of IRS-2 in the liver of T2 DM mice,and had no significant effect on the expression of insulin receptor in the liver.17?-estradiol 0.1 mg/kg body weight could reduce the blood glucose and insulin resistance index of model mice,enhance the sensitivity of peripheral tissues to insulin,improve glucose tolerance and insulin resistance,weaken the hyperplasia of islet cells in model mice and protect islet cells,and also could up-regulate the expressions of insulin receptor,IRS-1 and IRS-2 in mice liver,obviously delay the occurrence of insulin resistance in T2 DM mice induced by high fat feed combined with STZ.Subcutaneous injection of progesterone 8 mg/kg body weight could co-operate with the effect of 17?-estradiol by reducing blood glucose,improving glucose tolerance and delaying insulin resistance and increasing the expression of liver insulin receptor.Conversely,0.1 mg/kg body weight progesterone antagonized the effect of 17?-estradiol and aggravated glucose tolerance injury and insulin resistance by reducing the expression of insulin receptor in liver and skeletal and the expression of IRS-2 in skeletal of mice.Conclusion:1.The T2 DM mice induced by high fat diet combined with STZ can show severe insulin resistance.2.Progesterone shows a dual effect on the occurrence of diabetes mellitus.On the one hand,it can promote the occurrence of diabetes by shrinking islet,reducing the number of islet cells,on the other hand,it can delay the occurrence of T2 DM insulin resistance by increasing the sensitivity of peripheral tissue to insulin,improving glucose tolerance and relieving insulin resistance.3.17?-estradiol can improve insulin resistance and delay the occurrence of T2 DM by protecting islet cells,increasing the expressions of liver insulin receptor,IRS-1 and IRS-2.4.Progesterone 8 mg/kg body weight can enhance the preventive effect of 17?-estradiol from the occurrence of insulin resistance in T2 DM,while progesterone 0.1 mg/kg body weight can decrease the preventive effect of 17?-estradiol from T2 DM. |
PDF Full Text Request