Mechanisms Of Apigenin Reducing Lipid Accumulation Induced By Palmitic Acid In HepG2 Cells

In recent years,fatty liver has attracted much attention as a disease.Fatty liver is a common pathological change of liver caused by excessive accumulation of fat in hepatocytes,which can lead to disorders of lipid metabolism in liver and other related diseases.Autophagy is a conservative process in which lysosomes break down intracellular components to provide energy and regenerate organelles by circulating nutrients.It has been found that intracellular lipid droplets(LDs)are also considered as substrates for autophagy.Autophagy mobilizes lipids from LDs to maintain lipid balance,thus avoiding intracellular lipid overload.The loss of autophagy is related to lipid metabolism disorders such as fatty liver and obesity.Apigenin,also known as apigenin,is a natural flavonoid compound,in which celery has the highest content.Recent studies have found that apigenin has lipid-lowering activity,but the specific mechanism is not clear.Therefore,this paper studied the effects of apigenin on lipid accumulation and autophagy,and determined the specific mechanism.The main contents and results of this paper are as follows:(1)To investigate the effect of apigenin on lipid accumulation in HepG2 cells induced by palmitic acid.MTT assay was used to screen the non-toxic dose of apigenin and palmitic acid in HepG2 cells.And the results showed that the non-toxic dose of apigenin in HepG2 cells was from 0 to 160 μM and the non-toxic dose of palmitic acid in HepG2 cells was from 0 to 250 μM.Cell lipid accumulation was observed by oil red O staining.The contents of TC and TG in HepG2 cells were measured by intracellular total cholesterol(TC)and triglyceride(TG)kits.The results showed that the content of TC and TG in HepG2 cells induced by palmitic acid decreased significantly after the treatment of apigenin,and the content of TC and TG decreased accordingly.Western Blot was used to detect the effect of apigenin on the expression of AMP-activated protein kinase(AMPK)pathway protein in HepG2 cells.It was found that apigenin activates the phosphorylation of AMPK in HepG2 cells inhibited by palmitic acid,and significantly reduces the levels of sterol regulatory element binding protein 1c(SREBP1c),sterol regulatory element binding protein 2(SREBP2)and 3-hydroxy-3-methylglutaryl CoAreductase(HMGCR)and fatty acid synthase(FAS).(2)To investigate the effect of apigenin on autophagy inhibited by palmitic acid.Cell immunofluorescence staining was used to detect the effect of apigenin on the expression of LC3 in cells.Cell MDC staining was used to detect the effect of apigenin on the formation of autophagosomes in cells.It was found that the fluorescence in the palmitic acid group decreased significantly,while that in the co-treatment of apigenin and palmitic acid increased significantly.Western Blot was used to detect the effect of apigenin on the expression of rapamycin target protein(mTOR)pathway protein.It was found that apigenin could inhibit the activation of mTOR induced by palmitic acid and significantly reduce the expression of P62 protein induced by palmitic acid.The expression of microtubule-associated protein 1 light chain 3(LC3)protein showed the opposite trend.(3)To investigate the correlation between apigenin on palmitic acid-induced lipid accumulation and autophagy in HepG2 cells.TC and TG kit,oil red O staining,MDC staining,immunofluorescence staining,AMPK,LC3 and P62 protein analysis showed the following results.Compound C,an inhibitor of AMPK,proved that apigenin could activate AMPK signaling pathway in HepG2 cells,and Compound C could eliminate apigenin-induced autophagy.CQ,the autophagy inhibitor,proved that CQ could eliminate apigenin-induced autophagy in HepG2 cells,and CQ significantly eliminated the down-regulation of apigenin-induced lipid accumulation,resulting in increased lipid accumulation in HepG2 cells induced by palmitic acid.In conclusion,apigenin can inhibit the excessive accumulation of lipids in HepG2 cells induced by palmitic acid and play a role through AMPK pathway.Apigenin may promote autophagy of HepG2 cells by inhibiting the activation of mTOR,thus reducing the accumulation of lipids induced by palmitic acid.