Preventive And Therapeutic Effects Of Drocurcumin On Oleic Acid Induced Nonalcoholic Fatty Liver Disease In Vitro And Its Mechanism

Nonalcoholic fatty liver disease(NAFLD)is one of the most common metabolic syndrome due to the absorption of fatty acids,synthesis of fatty acids,transportation of fatty acids and oxidative loose imbalance,the liver disease damaged by excessive triglycerides in the liver.There are different theories on the pathogenesis of NAFLD,and the theory of "two strikes" is generally accepted.The first hit include diet that contain high level of lipid,sedentary and other bad habits,lack of exercise,obesity and so on,resulting in lipid accumulation in the liver.The second attack is lipid peroxidation leads to inflammatory reaction,which further cause liver damage and eventually leads to NAFLD.Over the past few decades,including the reagents that reduce lipid accumulation,insulin sensitizer,antioxidants,and reagents that reduce the release of inflammatory factors have been used for clinical treatment of NAFLD.But these drugs have potential side effects,for example,insulin sensitizer pioglitazone have side effects,such as,weight gain,edema,heart failure and decrease of bone density.In addition,it is reported that pioglitazone increase the risk of bladder cancer if used for more than two years;The use of antioxidants vitamin E will significantly increase the risk of prostate cancer in healthy men.Therefore,there is no symptomatic drug to treat NAFLD at present.Therefore,it is of practical significance to carry out research on drugs related to prevention and treatment of NAFLD.Curcumin is a polyphenol compound extracted from turmeric,which was reported that it can prevent from the diabetes and cure the obesity desease,studies have shown that curcumin can decrease the lipid content in the liver,thereby improving the symptoms of NAFLD.Dihydrocumin(DHC)is a metabolite of Curcumin,its effect on NAFLD is unknown,this paper will establish an in vitro model of non-alcoholic liver disease on HepG2 cells and L02 cells,aimed to explore the prevention and treatment function and mechanism of DHC on NAFLD in vitro.This paper mainly studies from following four aspects:1.The regulation of DHC on lipid metabolism disorder in liver in NAFLD cell modelsThe accumulation of lipid in the liver is obvious in non-alcoholic liver diseases.The uptake of fatty acids,fatty acid metabolism,fatty acid oxidation,and fatty acid metabolism lose balance and lead to excessive lipid,in which the cholesterol binding element protein 1C(SREBP-1C)is the key factor in the lipid metabolism process.The content of body the peroxidase proliferation receptor a(PPARa)can reduce triglyceride in the liver,and the increase of PPARa can reduce the accumulation of lipid and reduce the liver damage.One of the members of the Patatin like phospholipase family(PNPLA3)plays an important role in the metabolism of glycolipid.2.The regulation of DHC on insulin resistance in NAFLD model cellsExcessive accumulation of lipid in the liver can lead to insulin resistance.Insulin resistance can lead to the degeneration of liver fat,produce a large number of inflammatory cytokines,cause lipid toxicity,produce oxidative stress,and cause inflammatory reaction.PI3K pathway regulates cell metabolism,affects cell growth,changes cell survival rate,and AKT is the downstream gene of PI3K.PI3K/AKT pathway can regulate the insulin sensitivity of the liver.By increasing insulin sensitivity to promote the ability of liver cells to absorb glucose and inhibit the development of NAFLD.3.The regulation of DHC on oxidative stress damage in NAFLD model cellsExcessive accumulation of free fatty acids may lead to the production of reactive oxygen species(ROS).Oxidative stress has been shown to play an important role in the pathogenesis of NAFLD,which can cause certain damage at the cell level,such as lipid peroxidation in cell membrane,and cell death.The up regulation of Nrf2 can enhance the antioxidant capacity of hepatocytes.CYP2E1 and CYP4A are key enzymes in lipid peroxidation.The over expression of their proteins will cause oxidative damage.4.The regulation of DHC on inflammatory response of NAFLD model cells.Nitrification stress exists in the pathogenesis of NAFLD,and NO is the key indicator of nitrification stress.The content of nitrification is increased in NAFLD,which is closely related to the inflammation and oxidative damage of liver cells.Result:1.The effect of DHC on the prevention of NAFLD in vitro:(1)DHC reduced the amount of SREBP-1C and PNPLA3 mRNA and protein expression in cells by increasing PPARa in HepG2 cells,and reduced the content of TG in cells to improve lipid metabolism disorder.(2)DHC improved insulin resistance by increasing the protein expression of phosphatidylinositol kinase(PI3K)and phosphorylated protein kinase B(pAKT)in HepG2 cells to increase the glucose uptake in HepG2 cells.(3)DHC can improve oxidative stress and inflammatory response by increasing the protein expression of nuclear transcription factor 2(Nrf2)and decreasing the content of nitric oxide(NO).2.The effect of DHC on the treatment of NAFLD in vitro:(1)In liver lipid metabolism,DHC reduced the mRNA and protein expression of SREBP-1C and PNPLA3 in HepG2 cells and L02 cells,increased the mRNA and protein expression of PPARa,and decreased the content of TG.(2)In insulin resistance,DHC improved the uptake of 2-NBDG(a deoxyglucose analogs fluorescein)in HepG2 and L02 cells,and improves the protein expression of PI3K and pAKT in cells.(3)In oxidative stress and inflammatory response,DHC decreased the content of ROS and NO in L02 cells,while the expression of cytochrome 4A(CYP4A)protein decreased and the protein expression of Nrf2 increasedin cells;DHC increased the expression of Nrf2 and reduced the CYP4A protein in HepG2 cells.The content of NO decreased in HepG2 cells,but the ROS content increased in cells.