Effect Of Angiotensin (1-7) On High Glucose-induced MIN6 Cells Dedifferentiation Through PI3K/Akt/FoxO1 Signaling Pathway And Its Mechanism

Background and Objective:β cells dysfunction were caused by premature apoptosis of β cells in the past view.However,recent studies have found that dedifferentiation is one of the important mechanisms that cause β cells dysfunction,and the changes caused by β cells dedifferentiation are reversible.Multiple clinical evidence-based studies in recent years have found that renin-angiotensin system(RAS)blockers can reduce can reduce new-onset diabetes incidence of diabetes high risk population.The applicant’s previous researches also found that angiotensin Ⅱ(Ang Ⅱ),an important active member of RAS,damages the function of pancreatic β cells by inducing β cells apoptosis,local islet inflammation and oxidative stress,leading to β cells dysfunction and glucose metabolism disorders.Angiotensin-(1-7)(Ang-(1-7)),which is a physiological antagonist of AngⅡ,can reduce the islet β cells apoptosis rate,improve local islet inflammation,oxidative stress and insulin resistance in diabetic mice.However,the effect and mechanism of Ang-(1-7)on high glucose-induced islet β-cell dedifferentiation are not clear.The aim of this study was to investigate whether Ang-(1-7)could prevent dedifferentiation of β cells in a high-glucose state in vitro and its possible mechanisms,and to provide a new target for the prevention and treatment of diabetes.Methods:Mouse insulinoma cell line(MIN6)were subcultured in RPMI-1640 medium [10 % fetal bovine serum(FBS),1 % penicillin-streptomycin mixture] at 37 ℃ and 5 % CO2 environment.The cells were randomly divided into the following groups according to the experimental aim:(i)Control group,(ii)high-glucose(HG,25 mmol/L)alone group,(iii)HG + Ang-(1-7)group,(iiii)HG + Ang-(1-7)+ specific Mas R antagonist A779 group,(iiiii)HG Ang-(1-7)+ phosphatidylinositol-3-kinase(PI3K)inhibitor LY492002 group.Cytomorphology changes of MIN6 cells in each group was detected by Inverted phase contrast microscope,Phenotypic changes in β cells were investigated by immunofluorescence,quantitative real-time PCR,The expression levels of protein kinase B(Akt),phosphorylated Akt(p-Akt),forkhead box O1(Fox O1),phosphorylated FoxO1(p-FoxO1)in β cells were measured by western blot.Results:Pancreatic β cells dedifferentiation occurred in response to high-glucose stress and was accompanied by Pdx1,Maf A reduction and Oct4,Nanog increase,however,whic were alleviated by exogenous Ang-(1-7),treatment of MIN6 cells with A779 or LY294002 partially abolished the effects of Ang-(1-7).Moreover,high glucose decreased Akt,FoxO1 phosphorylation in MIN6 cells,but pretreatment with Ang-(1-7)partly rescued these defects.A779 and LY294002 exerted a suppressive effect on Ang-(1-7)mediated Akt and FoxO1 phosphorylation.Conclusion:Ang-(1-7)prevent pathtological dedifferentiation of pancreatic β cells in high glucose-induced MIN6 cells may through activation of PI3K-Akt-FoxO1 signaling pathway.