Abstract: Objective To study the effect of estrogen on hepatic steatosis and to investigate hepatic protective effect of estrogen and its possible mechanism.Methods Six weeks old female Sprague-Dawley(SD) rats were randomly divided into a sham operation,an ovariectomization (OVX),and an ovariectomization plus estradiol (E2) group.One week after the OVX operation,the rats in E2 group were treated intragastrically with estradiol (1 mg/kg),while those in other groups were given distilled water for 12 weeks.At the end of the experiment,insulin tolerance test was conducted.The hepatic levels of tumor necrosis factor-alpha (TNF-a),interleukin-6 (IL-6),and monocyte chemotactic protein 1 (MCP-1) were determined with enzyme-linked immunosorbent assay and hepatic steatosis and inflammation were observed with hematoxylin and eosin staining.Results The end weight,liver weight,visceral fat weight,and serum levels of alanine aminotransferase and aspartate aminotransferase were significantly higher in OVX group than in the sham operation group,but significantly lower in E2 group than in OVX group (all P < 0.05).For the rats of OVX,the structure of hepatic lobule was not clear;the cords of liver cells were disordered with a wide range of lipid droplets;and lobular and periportal inflammatory cell infiltration were observed.Compared to those of the OVX group,the degree of liver steatosis and inflammation were significantly decreased in E2 group (both P < 0.01).The hepatic contents of TNF-α,IL-6 and MCP-1 in OVX group were significantly higher than those in the sham operation group (all P < 0.05).Conclusion Estrogen replacement therapy can improve the degree of liver steatosis in ovariectomized rats and reduce the expression of hepatic inflammatory factors.