The Effect Of Aging On Insulin Resistance Of Wistar Rats And Its Possible Mechanism

Objective:This study was designed to observe the effect of aging on body weight,blood glucose,blood insulin,blood fat and insulin sensitivity in healthy Wistar rats and insulin resistant Wistar rats,as well as on the morphous and function of the islet cells.The possible molecular mechanisms were also investigated through gene chips and real-time PCR.Methods:Different ages of healthy Wistar rats were fed with normal diet or high-glucose-high-fat diet.Blood glucose,blood insulin,blood fat and some index of oxidative stress such as TSOD,CuZnSOD,GSH,MDA were detected after 60 days.Insulin sensitivity was assessed by the euglycaemic-hyperinsulinaemic clamp technique and beta-cell function was assessed by oral glucose tolerance test and insulin release test.The islets were isolated from rats pancreata by a collagenase perfusion method and purified by Ficoll sedimentation.The cells acquired were stimulated by 2.8mmol/L glucose, 16.7mmol/L glucose and 200umol/l palmitic acid to observe the status of insulin releasing.Islets were stained with KI67 and insulin,TUNEL and insulin to observe the proliferation and apoptosis.The differentially expressed genes in islets were studied by complementary DNA microarrays,which was validated by real-time PCR and Western blot.Results:The result of the euglycaemic-hyperinsulinaemic clamp showed that the GIR of 4 month-old healthy rats was 26.02±5.66(mg·kg^-1·min^-1),14 month-old healthy rats was 19.16±2.58(mg·kg^-1·min^-1),24 month-old healthy rats was 10.73±1.43(mg·kg^-1·min^-1).Compared with healthy rats,the GIR of 4 month-old IR rats was 7.27±1.31(mg·kg^-1·min^-1),14 month-old IR rats was 4.22±2.63(mg·kg^-1·min^-1),24 month-old IR rats was 1.10±0.59(mg·kg^-1·min^-1). There was no difference in the rats blood glucose level,but blood insulin increased apparently along with aging(P≤0.05),which was higher in IR group than healthy group(P≤0.05).OGTT and IRT showed that AUCg and AUCi decreased with aging,especially in IR group(P≤0.05).TG,LDL-CH,CH all increased with aging(P≤0.05),in contrast,HDL-CH decreased with aging(P≤0.05).The protective factors of oxidative stress,for example,TSOD,CuZnSOD and GSH significantly decreased with aging(P≤0.05),but metabolites MDA had the opposite trend(P≤0.05).IR group has the same trend with aging when compared to healthy rats.KI67 and TUNEL staining indicated that along with aging the proliferation of islet cells decreased and apoptosis increased,which happened similarly in IR groups.Genes chips showed that IR groups and normal groups had 50 up-regulated genes and 10 down-regulated genes in common and predominantly the expression of cell signal transduction gene,related cell cycle regulatory factors,cell construction and movement genes,body and defense factors,energy and glycolipids metabolism genes.VCP gene was found to be the most relevant gene with aging and insulin resistance.Conclusion:The insulin resistant rat model was successfully set up and the data indicated that insulin sensitivity decreased with aging,older rats were insulin resistant compared to the younger rats,and when insulin resistance existed, aging would deteriorate it.Along with aging,blood fat disorder would occur, homeostasis of oxidative stress would be lost,proliferation of rats islets decreased and apoptosis increased,the ratio ofαandβcells increased.Therefore,insulin releasing is decresed when islets confronted with high glucose and high fat stiumulus,especially in insulin resistance.Data of gene chips and real-time PCR provided a possible explanation for aging and insulin resistance.VCP gene was the prompt of aging and insulin resistance might be related to insulin uesicae transport. ##本文无英文摘要内容...