Effects And Mechanism Of Early Exercise And Administration Of Dipeptidyi Pcptidase-4Inhibitor On Structure And Function Of Islets In Kkay Mice

Objective：To study the changes of islet beta-cell morphology and function afterlifestyle intervention and administration of dpp-4inhibitor (MK0626) in high fat dietinduced kkay mice. This study included3parts:1. Introduction on the generalcharacteristic of hight fat diet induced kkay mice and evaluation on the changes ofgeneral indicators after interventions;2. The effect of intervention on morphologyprotection, proliferation and apoptosis in beta cell;3.The effect of intervention onexpression of transcription factor PDX-1and MafA.Method:1.(1)Establish the model of prediabetes-hyperinsulinism by administratinghigh fat diet in kkay mice:5weeks old male kkay mice, divided into high fat dietgroup and normal diet group, and C57BL/6mice served as control group.we collectthe data:①General features including weight, daily food intake, FBG, RBG, FINS,etal.;②OGTT and IPITT.then determine the proper time to start intervention.(2)5weeks old male HFD induced kkay mice were randomly divided into4groups: kkaynormal diet group(KN group), kkay high fat diet group(KH group), kkay exercisegroup(KE group), kkay DPP-4I group(KD group)and C57BL/6J served as normalcontrol group(CN group). The data we collected were the same as above. OGTT andIPITT were performed at the time of7w and15w respectively.2. Morphology,proliferation and apoptosis in islet beta-cells: analyzing the morphology and size inislet, distribution and ratio of beta cells to islet cells; detecting proliferation andapoptosis of beta cell by ki67and TUNEL stainning.3.Evaluate the expression ofPDX-1and MafA by immunohistochemisty and western blot.Result:1.(1)Compared with kkay normal diet group and C57normal control group,weight, FINS, OGTT2h INS and AUCg in high fat diet kkay mice have markedlyincreased (P<0.05), FBG were in relatively normal range, RBG were still under the diagnostic criteria of diabetes(lower than16.7mmol/L), indicating5week-old kkaymice will be proper models for the study after2weeks of high fat diet.(2)At15weeks old, weight in KE group and KD group were significantly lower than that inKN group and KH group(P<0.05), the same results appeared in theirs daily foodintake. FBG in CN, KN, KE and KD group were significantly lower than KHgroup(P<0.01); compared with CN group, intervention groups showed no significantdifferences in RBG, but markedly lower than KN group and KH group. FINS levelsamong CN group, KN group, KH group, KE group and KD group showed significantdifferences(P<0.01):0.586±0.27ng/ml,0.973±0.27ng/ml,0.732±0.16ng/ml,1.147±0.18ng/ml and1.271±0.13ng/ml respectively. AUCg in OGTT and IPITTrespectively showed the gluose tolerance and the insulin sensitivity of the mice inintervention group were better than those in KN and KH group(P<0.01).2.Islet area: After8weeks of intervention,islet area of kkay mice in KE and KD grouphave a dramatic reduction,compared with KN and KH group. Mass of Isletsdistributed in middle and lower trisection area increased obviously in bothintervention groups. There were significant differences between the interventiongroups and CN group in the propotion of insulin positive cells. Proliferation analysis:Propotion of ki67positive beta cells in KE group(1.94%±0.52%) and KDgroup(2.29%±0.3%) were higher than other groups(P<0.01). there were no significantdifferences in the propotion of TUNEL positive cells among these groups.3. Expression of MafA: compared with KN group and KH group, expression of MafAincreased markedly in KE group(62.79±2.76%VS14.69±2.43%,P<0.01;62.79±2.76%VS8.16±1.02%,P<0.01) and also in KD group(60.56±2.96%VS14.69±2.43%, P<0.01;60.56±2.96%VS8.16±1.02%, P<0.01) byimmunohistochemistry analysis. Western blot showed MafA expression in KE groupwas1.53and2.84folds respectively compared with KN group and KH group, and inKD group was1.79and3.35folds respectively. Unexpectly, There were no significantdifference in the expression of PDX-1among these groups by immunohistochemistry,but western blot showed only expression of PDX-1in KH group decreased obviouslycompared with CN group. Conclusion:1. It is a proper kkay mice model of prediabetes-hyperinsulinism byearly administrating high fat diet;2. Early intervention of life style and administrationof DPP-4I(mk0626) could decrease weight, BG and improve glucose tolerance andinsulin sensitivity markedly;3. Beta cell content and plasma insulin level could bemaintained afer intervention of life style and administration of DPP-4I(MK0626),thereby delayed the onset of diabetes.4. There was no obvious changes in theexpression of PDX-1at early stage of diabetes in kkay mice. MafA may play a crucialrole in the development of diabetes in this model, of which expresssion wereincreased after early intervention.