Effect Of Annexin1on The Function Of Islet Beta Cells Proliferation And Autophagy With Aging And Its Mechanism

To study the change of islet beta cells function and the difference of islet beta cellsproliferation, apoptosis, autophagy and Annexin protein expression with aging, webulit aging models successfully with three groups of Wistar rats. And futhermore,we inhibitted or enhanced the expression of Annexin1protein successfully inMIN6cells, and discussed the effect of Annexin1on the function of islet betacells proliferation and autophagy and its mechanism.Part1. The change of insulin secretion in islet beta cells with aging in rats4month-old,14month-old and24month-old normal male Wstar rats representedyoung group, adult group and old group respectively. We observed the seniumindex in islets and insulin secretion in beta cells. Result:①senium index: theexpression of p16in islets increased with aging (P<0.05).②function of beta cells:OGTT showed that delayed peak time, higher2h glucose and increased AUCgwere observed in adult and old rats compared with young rats. FINS increasedprogressively with aging(P<0.01); after glucose-stimulated, there were delayedpeak time, lower ΔI10/ΔG10and higher AUCi in old rats(P<0.05). GSIR index hadbeen shown to deteriorate progressively with aging (P<0.05). In this part, we builtsuccessfully aging islets model and found that insulin secretion decreased withaging.Part2. Change of proliferation, apoptosis and autophagy in islet beta cellswith agingThe objects of this part were same as the first part. We observed the change ofproliferation, apoptosis and autophagy in islet beta cells. Results:①proliferationand apoptosis in islet beta cells: the expression of TUNEL increasedage-dependently, while insulin and PCNA decreased age-dependently.②autophagy in islets: protein expression of LC3II, Atg7and the ratio of LC3II/I significant decreased with advancing age, while protein expression of p62andpolyUB increased (P<0.05). expression of Beclin-1/Atg6protein got higher inadult rats than in young rats, but got lower in old rats. In this part we certified thatproliferation of beta cells decreased, apoptosis increased and autophagic fucntiongot worse with aging in rats.Part3. Regulation mechanism of Annexin1on proliferation and autophagyin beta cellsWe found protein expression of Annexin1decreased with aging in rats islets. Byinhibitting or heightening Annexin1protein in MIN6cells, we observed cellproliferation with CCK-8, and found expression of cell cycle-related protein andsignal pathway of PI3K-Akt-mTOR, also watched protein expression ofapoptosis-related and autophagy-related. Result:①Protein expression of Annexin1decreased with aging in islets.②Annexin1promoted proliferation of MIN6cells. Expression of Annexin1protein related positively with expression of cyclinD1,cyclin E,CDK2and signal pathway of PI3K-Akt-mTOR.③Expression ofAnnexin1protein didn't have relation with caspase-3,caspase-8,caspase-9.④In MIN6cells, expression of LC3II and the ratio of LC3II/I related positively withAnnexin1protein, while expression of p62realted negatively with Annexin1.Our study showed that Annexin1protein was age-dependent. And Annexin1protein promoted cell proliferation by activating cyclin D1,cyclin E,CDK2andsignal pathway of PI3K-Akt-mTOR. Annexin1protein related positively with isletautophagic function, but might not relate with apoptosis of beta cells.In conclusion, insulin secretion decreased in rats islets with aging, which relatedwith less beta cells mass and poor function of islet beta cells. Weaken proliferationand increasing apoptosis in beta cells induced less cell mass. Subdued autophagicfunction might lead to depressed function of beta cells. Annexin1involved inregulating of proliferation and autophagy in beta cells, and have dependence onaging, which could explain the reason of decreased insulin secretion with aging.