Osthol attenuates hepatic steatosis via decreased triglyceride synthesis not by insulin resistance

AIM: To evaluate the effects of osthol on intrahepatic fat synthesis, beta-oxidation, inflammation, and insulin resistance by multifaceted analysis. METHODS: Sprague-Dawley rats (n = 30) were randomly divided into control, non-alcoholic fatty liver disease (NAFLD), and osthol groups. NAFLD and osthol groups were fed with a high-fat diet for 14 wk. After 8 wk of the high-fat diet, the osthol group also received osthol 20 mg/kg orally 5 times/wk. To assess the insulin resistance, oral glucose tolerance was performed at the end of 14 wk. Immunohistochemical (4-HNE, F4/80) and hematoxylin and eosin (HE) staining were performed on liver tissue extracts after animal sacrifice at 14 wk. SREBP1c, FAS, SCD-1, PPAR-alpha, CROT, MCP-1, IRS-1, and IRS-2 mRNA expressions were assessed with reverse transcription-polymerase chain reaction. RESULTS: HE staining revealed that, compared with the NAFLD group, the osthol group showed significantly decreased intrahepatic fat content (39.4% vs 21.0%; P = 0.021). SREBP1c expression in the NAFLD group increased compared to controls (P = 0.0001), while osthol treatment decreased SREBP1c expression compared with the NAFLD group (P = 0.0059). In the osthol group, intrahepatic FAS and SCD-1, which act downstream of SREBP1c, decreased significantly compared with the NAFLD group. Moreover, PPAR-alpha expression in the osthol group was also significantly higher than in the NAFLD group (P = 0.0147). CONCLUSION: Osthol treatment attenuated liver steatosis by decreasing de novo liver triglyceride synthesis and had nominal effects on insulin resistance and liver inflammation. (C) 2014 Baishideng Publishing Group Inc. All rights reserved.