Study On The Therapeutic Effects And Mechanism Of Swietenia Macrophylla King For Treating Nonalcoholic Fatty Liver Disease

Nonalcoholic fatty liver disease(NAFLD),a common liver disease,is often associated with dyslipidemia,type 2 diabetes,obesity and hypertension,etc.The fructus of Swietenia macrophylla King(Meliaceae)reported to has extensive pharmacological activities such as hypoglycemic,hypolipidemic,anti-inflammatory,analgesic,antioxidant and hypotensive effects,were used to treat diabetes,hyperlipidemia and hypertension and other diseases.However,the therapeutic effects and mechanisms of Swietenia macrophylla King fructus on NAFLD have not been studied extensively.The aim of this work was to assess the hypolipidemic,hypoglycemic and anti-inflammatory activities of Swietenia macrophylla King fructus extract(SFE)in NAFLD mice models in vivo and cellular models in vitro,as well as to elucidate its underlying molecular mechanism.In vivo,C57BL/6 mice were fed with a high-fat diet for 12 weeks to establish NAFLD model,and were treated with different doses of SFE(350,700 mg/kg/d)orally for the last 4weeks while obeticholic acid(OCA,40 mg/kg/d)was used as a positive control.The results showed as follows: The body weight of NAFLD mice was effectively reduced by SFE.The hyperglycemia and hyperlipidemia as well as the insulin resistance were improved by SFE in NAFLD mice.The lipid accumulation and pathological damage in liver tissues of NAFLD mice were improved by SFE,through reducing the TG content and AST level.The oxidative stress in NAFLD mice was alleviated by SFE,through reducing the accumulation of MDA to some extent and enhancing the activity of SOD.The hepatic inflammatory reaction in NAFLD mice was improved by SFE,through decreasing the expression levels of IL-6 and TNF-a.Mechanistically,SFE promoted the expression of FXR and down-regulated the expression of SREBP-1c and SCD1.These results suggest that SFE inhibited lipid synthesis by activating FXR expression and down-regulating the expression levels of SREBP-1c and SCD1.In vitro,the non-toxic experimental concentrations(1,10,20,40 μg/m L)of SFE were determined by CCK-8 method.A lipid accumulation model was established by inducing Hep G2 cells with 0.5 m M oleic acid(OA)and 0.25 m M palmitic acid(PA),and an inflammation model was established by inducing RAW 264.7 cells with 100 ng/m L lipopolysaccharide(LPS).The results showed that compared with SFE alone,the TG content in Hep G2 cells was significantly reduced by SFE-containing plasma.The activity of SREBP-1c promoter and PEPCK promoter were dose-dependently inhibited by SFE,which are the key protein of lipid synthesis pathway and the key enzyme of gluconeogenesis respectively.The anti-inflammatory activity assay revealed that the release of NO and the expression of pro-inflammatory cytokines IL-1β and IL-6 were significantly reduced by SFE in RAW 264.7 cells.The screening results of the active components of SFE in cellular screening models targeted on SREBP-1c and PEPCK showed that among 31 chemical components isolated from SFE,four chemical components including 7-deacetoxy-7α-hydroxygedunin(11),Swietemahonin E(23),Spicatin(25)and Aspergilfuranone B(29)had powerful inhibition of SREBP-1c and PEPCK promoter activity.Combined with the Hep G2 and NCTC 1469 cell viability results,Swietemahonin E and Spicatin were selected as active components for subsequent studies.The results showed as follows: The SREBP-1c and PEPCK promoter activity were dose-dependently inhibited by Swietemahonin E,and Spicatin dose-dependently inhibited SREBP-1c promoter activity and inhibited PEPCK promoter activity to some extent.The results of TG assay and oil red O staining showed that the lipid accumulation in hepatocytes was reduced by Swietemahonin E and Spicatin.The release of NO as well as the expression of IL-1β and IL-6 from RAW 264.7 cells was significantly reduced by Swietemahonin E and Spicatin.Mechanistically,Swietemahonin E and Spicatin down-regulated the m RNA expression of SREBP-1c,ACC1 and FASN induced by lipid synthesis agonist TO901317 and activated the m RNA expression of FXR and PPARα.In this study,the expression of FXR was knocked down on mouse primary hepatocytes,Spicatin administration significantly promoted the m RNA expression of FXR and significantly down-regulated the m RNA expression of SREBP-1c.In summary,SFE could reduce lipid accumulation through controlling FXR-SREBP-1c signaling pathway,meantime alleviated insulin resistance,decreased blood lipid,reduced inflammation and oxidative stress.Our findings provide the scientific basis to support the merit of SFE as a good potential to treat NAFLD.