Intervention effects of the triterpenoids from Cyclocarya paliurus on free fatty acids-induced steatosis in HepG2 cells

To investigate the therapeutic effects of triterpenoids from Cyclocarya paliurus on non-alcoholic fatty liver disease(NAFLD), the model of NAFLD in HepG2 cells was induced by free fatty acids(FFAs). Cytotoxicity of the triterpenoids from C. paliurus was determined by MTT method, and the effects of triterpenoids without cytotoxicity on intracellular triglyceride(TG)and superoxide dismutase(SOD)were detected by the kits. Data indicated that compound 4 ［2α, 3α, 23-trihydroxy-12, 20(30)-dien-28-ursolic acid, TUA］ had hypolipidemic and antioxidant activities. After being treated with TUA and FFAs for 24 h, the intracellular lipid content was observed using Oil Red O staining, and intracellular TG, malondialdehyde(MDA), SOD and reactive oxygen species(ROS)levels were determined by the assay kits. The protein expression of nuclear factor erythroid 2-related factor 2(Nrf2), heme oxygenase-1(HO-1)and NAD(P)H quinone oxidoreductase 1(NQO-1)were measured by Western blot. The results showed that TUA significantly increased SOD activity, and decreased intracellular TG, ROS and MDA levels in FFAs-induced HepG2 cells. Moreover, TUA dramatically improved Nrf2, NQO-1, and HO-1 expression. However, the dramatic increase in TG, ROS, MDA levels and the reduction in SOD, NQO-1 and HO-1 expression following Nrf2 inhibitor brusatol treatment were observed. In conclusion, these results suggest that TUA has the therapeutic effect on NAFLD which may be associated with Nrf2 activation.