Study On The Mechanism Of Several Plant Polyphenols Inhibiting Hepatocyte Lipid And Promoting Cholesterol Effusion

In this study six kinds of vegetable polyphenols and tea polyphenols, punicalagin, ellagic acid, gallic acid, phlorizin, EGCG, and purified pomegranate peel polyphenols (PPPs), were selected as tested polyphenols. An in vitro steatosis hepatic cell model was established to evaluate the lipid-lowering and hepatoprotective effects of these tested polyphenols as well as the molecule mechanisms of the cholesterol efflux of pomegranate polyphenols. The results we had found are as follows:1. The content of punicalagin was the highest in the polyphenols of PPPs, followed by catechin, ellagic acid, gallic acid, epicatechin, chlorogenic acid, rutin, and caffeic acid2. Both the accumulation degree of lipid profile and the TG and TC level satisfied for the present experiment after incubating with model culture solution(contained50%fetal calf serum) for48hrs. Model was successfully established at this condition.3. The six kinds of tested plant polyphenols all possessed the lipid-lowering effects in HL7702cells. The prevention group possessed stronger lipid-lowering and hepatoprotective effects than the treatment group. Furthermore, it was found that PPPs were the most effective polyphenol among all the tested samples, which had similar lipid-lowering and hepatoprotective effects in comparison with lovastatin. EGCG also showed similar lipid-lowering and hepatoprotective effects as compared to PPPs. The lipid-lowering and hepatoprotective effects of PPPs were better than its main monomer components (punicalagin, EA, and GA). Among the monomer components, punicalagin was the most effective monomer at the lipid-lowering and hepatoprotective aspects. Above all, the good lipid-lowering and hepatoprotective effects of PPPs might be attributed to the combined effects of several monomer components of polyphenols obtained from pomegranate peels.4. Punicalagin and PPPs increased the cholesterol efflux by up-regulating the expression of LXRa and ABCA1in HL7702hepatic cells. The expression of LXRa and ABCA1presented a dose-dependent manner along with the increasing concentration of punicalagin and PPPs. The up-regulating effects of the PPPs were as evident as the lovastatin(positive drug). The mechanism of increasing of the cholesterol efflux by PPPs and punicalagin might be the up-regulation of LXRa expression, in return, up-regulate the ABCA1expression, and then promote the transformation of cholesterol to bile acid.These in vitro findings might provide certain reference for the prevention and treatment of hyperlipidemia and atherosclerosis by dietary polyphenols.