Peroxisome proliferator-activated receptor α (PPARα) is a ligand-dependent transcription factor that regulates the expression of genes involved in lipid metabolism and transport. Ligands/activators of PPARα, like fibrate-type drugs, may have hypolipidemic effects. To identify food that contains activators of PPARα, a transactivation assay employing a clone of CHO-K1 cells stably transfected with a (UAS)[sub4]-tk-alkaline phosphatase reporter and a chimeric receptor of Gal4-rPPARα LBD was used to screen ethyl acetate (EA) extracts of a large variety of food materials. It was found that the EA extract of bitter gourd (Momordica charantia), a common oriental vegetable, activated PPARα to an extent that was equivalent to or even higher than 10 µM Wy-14643, a known ligand of PPARα. This extract also activated PPARγ to a significant extent which was comparable to 0.5 µM BRL-49653. The activity toward PPARα was mainly in the soluble fraction of the organic solvent. The EA extract prepared from the whole fruit showed significantly higher activity than that from seeds or flesh alone. The bitter gourd EA extract was then incorporated into the medium for treatment of a peroxisome proliferator-responsive murine hepatoma cell line, H4IIEC3, for 72 h. Treated cells showed significantly higher activity of acyl CoA oxidase and higher expressions of mRNA of this enzyme and fatty acid-binding protein, indicating that the bitter gourd EA extract was able to act on a natural PPARα signaling pathway in this cell line. It is thus worth further investigating the PPAR-associated health benefits of bitter gourd. Copyright ? 2003 National Science Council, ROC and S. Karger AG, Basel.
