Therapeutic Effect Of Osthole On Fat Milk-induced Fatty Liver And Its Mechanisms In Mice

Aim: To examine the therapeutic effect of osthole on fat milk-induced fatty liver in mice and investigate the potential mechanisms. Methods: A mouse model with hyperlipidemic fatty liver was established by feeding fat milk for 4 weeks. The experimental mice were then treated with osthole 10-40 mg/kg for 6 weeks. After oral administration, the mice in model and medicine-treated groups were continuously given fat milk for 2 weeks again. Whereafter, the lipid levels in serum and hepatic tissue, hepatic weight coefficient and histological evaluation were measured. The gene expression of SREBP-1c, SREBP-2, FAS, LDLR and CYP7A in mouse hepatic tissues was examined by RT-PCR. BRL cells were cultured in RPMI 1640 and divided into six groups as follows: RPMI 1640, RPMI 1640 with 25, 50, 100, 200μg/mL osthole and 200μg/mL lipanthyl, respectively. After incubation with drugs for 24 hours, the gene expression of PPARα, SREBP-1c, SREBP-2, FAS, LDLR and CYP7A was measured with RT-PCR. In order to determine whether the mechanisms of osthole treatment were associated with the pathway of PPARα, BRL cells were divided into 4 groups as follows: RPMI 1640, PRMI 1640 with 200μg/mL osthole, RPMI 1640 with 1μmol/L MK886 (a PPARαinhibitor), RPMI 1640 with 1μmol/L MK886 plus 200μg/mL osthole (BRL cells were preincubated with MK886 1μmol/L for 2 hours). After osthole was added to cells and incubated for 24 hours, changes of these gene expression including SREBP1c/2, FAS, LDLR and CYP7A were examined. Results: After treatment with osthole 10-40 mg/kg for 6 weeks, the levels of serum total cholesterol (TC), triglyceride (TG), free fatty acid (FFA) were decreased, especially in the 40 mg/kg group (P<0.01), the coefficient of hepatic weight, and the contents of TC, TG and FFA in hepatic tissue were also significantly decreased (P<0.01). Importantly, the histological evaluation of liver specimens demonstrated that osthole dramatically decreased lipid accumulation. Osthole could significantly increase the mRNA expression of CYP7A (P<0.01), decrease the mRNA expression of SREBP-1c, SREBP-2, FAS and LDLR in hepatic tissues in fat milk-induced fatty liver mice (P<0.05 or P<0.01). In vitro, Osthole at 25-200μg/mL also increased the mRNA expression of PPARαand CYP7A (P<0.05 or P<0.01), decrease the mRNA expression of SREBP-1c, SREBP-2, FAS and LDLR in cultured-BRL cells (P<0.05 or P<0.01). And after pretreatment with PPARαinhibitor MK886 for 2h, the regulation of 200μg/mL osthole on mRNA expression of SREBP-1c, SREBP-2, FAS and LDLR and CYP7A was decreased or cancelled. Conclusion: Osthole had therapeutic effect on fat milk-induced fatty liver in mice, the mechanisms might be associated with its regulation of the SREBP-1c/2 mRNA expression and their target genes FAS, LDLR and CYP7A via increasing PPARαmRNA expression.