Study on the Mechanism of Estrogen Participating in Liver Tissue Lipid Metabolism through Autophagy
Objective To explore the role of estrogen induced autophagy in regulating liver lipid metabolism.Methods C57BL/6 female mice were divided into menopausal group(22 months old)and control group(12 weeks old).The levels of estradiol(E2),the main active ingredient of estrogen of two groups of mice were compared;Lipid deposition in mouse liver was observed;RT-PCR was used to detect autophagy levels and lipid metabolism levels in mouse liver;Western-blot analysis was used to detect the expression levels of autophagy related proteins and lipid metabolism related proteins in mice,and the expression of metabolism related pathways phosphatidylinositol 3-kinase(PI3K)/protein kinase B(AKT)/mammol/Lalian target of rapamycin(mTOR)and AMP-activated protein kinase(AMPK)/mTOR proteins was also detected.HepG2 cells were divided into three groups:Control group,free fatty acids(FFA)group,and FFA+E2 group.The model was verified by observing lipid deposition in liver cells.After treatment with 100 nmol/L E2,cells were stained with oil red O to observe the deposition of adipose lipids in liver cells.RT-PCR was used to detect the mRNA expression of target genes such as autophagy and lipid metabolism.Results The levels of E2 in postmenopausal mice were significantly lower than those in young mice,and liver oil red O staining showed significant deposition of red lipid droplets.The expres-sion of autophagy related genes(LC3B,ATG5,ATG7)and autophagy related LC3B protein in the liver of postmenopausal mice decreased,while there was no significant change in liver adipogenic genes(FAS,SCD1).The expression of lipid metabolism related genes(CPT1A,PPARα)decreased,and the differ-ence was statistically significant(P＜0.05).The expression of autophagy related protein pathways PI3K,AKT,and mTOR in postmenopausal mice was upregulated,while the expression of AMPK was downregulated(P＜0.05).Oil red O staining showed that compared with the control group,red spotted lipid droplets appeared in the FFA group cells.After treatment with 100 nmol/L estrogen,the number of scattered red lipid droplets in the cells decreased.RT-PCR results showed that compared with the control group,the expression of autophagy genes and protein LC3B,genes ATG5,and ATG7 decreased,the expression of adipogenic genes FAS and SCD1 increased,and the expression of CPT1A and PPARα decreased in the FFA group(P＜0.05);Comparing with the FFA group,it was found that autophagy genes LC3B and protein,genes ATG5,ATG7,and lipid metabolism genes CPT1A and PPARα were upregulated to varying degrees in the FFA+E2 group,while the expression of lipid genes FAS and SCD1 was decreased(P＜0.05).Conclusion Autophagy plays a role in estrogen induced improvement of lipid metabolism in liver tissue.
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