Quercetin Attenuates Atherosclerosis via Modulating Apelin Signaling Pathway Based on Plasma Metabolomics

Objective:To interpret the pharmacology of quercetin in treatment of atherosclerosis(AS).Methods:Fourteen apolipoprotein E-deficient(ApoE^(-/-))mice were divided into 2 groups by a random number table:an AS model(ApoE^(-/-))group and a quercetin treatment group(7 in each).Seven age-matched C57 mice were used as controls(n=7).Quercetin[20 mg/(kg·d)]was administered to the quercetin group intragastrically for 8 weeks for pharmacodynamic evaluation.Besides morphological observation,the distribution of CD11b,F4/80,sirtuin 1(Sirt1)and P21 was assayed by immunohistochemistry and immunofluorescence to evaluate macrophage infiltration and tissue senescence.Ultra-performance liquid chromatography/tandem mass spectrometry(UPLC-MSC/MS)was performed to study the pharmacology of quercetin against AS.Then,simultaneous administration of an apelin receptor antagonist(ML221)with quercetin was conducted to verify the possible targets of quercetin.Key proteins in apelin signaling pathway,such as angiotensin domain type 1 receptor-associated proteins(APJ),AMP-activated protein kinase(AMPK),peroxisome proliferator-activated receptor-γcoactivator-1α(PGC-1α),tissue plasminogen activator(TPA),uncoupling protein 1(UCP1)and angiotensinⅡreceptor 1(AT1R),were assayed by Western blot.Results:Quercetin administration decreased lipid deposition in arterial lumen and improved the morphology of ApoE^(-/-)aortas in vivo.Quercetin decreased the densities of CD11b,F4/80 and P21 in the aorta and increased the level of serum apelin and the densities of APJ and Sirt1 in the aorta in ApoE^(-/-)mice(all P<0.05).Plasma metabolite profiling identified 118 differential metabolites and showed that quercetin affected mainly glycerophospholipids and fatty acyls.Bioinformatics analysis suggested that the apelin signaling pathway was one of the main pathways.Quercetin treatment increased the protein expressions of APJ,AMPK,PGC-1α,TPA and UCP1,while decreased the AT1R level(all P<0.05).After the apelin pathway was blocked by ML221,the effect of quercetin was abated significantly,confirming that quercetin attenuated AS by modulating the apelin signaling pathway(all P<0.05).Conclusion:Quercetin alleviated AS lesions by up-regulation the apelin signaling pathway.