Figure 5.

EPA suppresses SELENOP gene expression by inhibiting SREBP-1c binding to Selenop promoter DNA. A, deficiency of the putative SREBP-1-binding site canceled EPA-induced suppression of SELENOP promoter activity. H4IIEC3 cells were co-transfected with each reporter vector and control reporter vector at 48 h and then treated with the indicated concentrations of EPA for 24 h. Signals were normalized to the control reporter vector. Data represent mean ± S.D. (error bars) (n = 4). ***, p < 0.001 versus vehicle-treated cells. B, chromatin immunoprecipitation assay of H4IIEC3 cells treated with EPA. H4IIEC3 hepatocytes were grown in 15-cm dishes and transfected with 30.4 μg of pcDNA3.1(+) mCherry-mature SREBP-1c plasmid vectors per dish together with 91.2 μl of FuGENE6. Forty-eight hours later, cells were treated with 0.25 mm EPA for 24 h. Chromatin samples precipitated with anti-RFP, or anti-normal IgG were amplified using primers for the −200 to −100 bp region of the rat Selenop promoter. C, scheme of selenoprotein P suppression by EPA in the liver. SREBP-1c positively regulates SELENOP promoter activity. EPA suppresses SREBP-1c activity, resulting in suppression of selenoprotein P expression. Thus, the hypoglycemic effects of EPA may be mediated at least in part by selenoprotein P suppression in the liver.