title: Hypocholesterolemic activity of onion is mediated by enhancing excretion of fecal sterols in hamsters.
abstract: Onion has been shown to favorably modify the lipoprotein profile. However, research on its underlying mechanism is lacking. The present study investigated the interaction of dietary onion powder with the protein expression of key receptors and enzymes involved in cholesterol metabolism. Thirty-six male hamsters were randomly divided into three groups and fed a high-cholesterol control diet or the two experimental diets supplemented with 1% onion powder (OP-1) or 5% onion powder (OP-5), for a period of 8 weeks. It was found that onion dose-dependently decreased plasma total cholesterol (TC) level. The change in plasma lipoprotein profile was accompanied by a greater excretion of both fecal neutral and acidic sterols. Western blot analysis revealed that onion up-regulated sterol regulatory element binding protein 2 (SREBP-2), liver X receptor alpha (LXRα) and cholesterol-7α-hydroxylase (CYP7A1) with no effect on 3-hydroxy-3-methylglutaryl-CoA reductase (HMGR) and LDL receptor (LDL-R). It was concluded that the hypocholesterolemic activity of onion powder was mediated by enhancement of fecal sterol excretion and up-regulation of LXRα and CYP7A1.
authors.affiliation: Department of Biology, The Chinese University of Hong Kong, Shatin, N.T., Hong Kong, China.
authors.forename: Lei
authors.initials: L
authors.lastname: Guan
authors.forename: Hau Yin
authors.initials: HY
authors.lastname: Chung
authors.forename: Yalun
authors.initials: Y
authors.lastname: Su
authors.forename: Rui
authors.initials: R
authors.lastname: Jiao
authors.forename: Cheng
authors.initials: C
authors.lastname: Peng
authors.forename: Zhen Yu
authors.initials: ZY
authors.lastname: Chen
mesh_terms: D000818:Animals; D000924:Anticholesteremic Agents / Q000494:pharmacology*; D002784:Cholesterol / Q000032:analysis / Q000097:blood; D002790:Cholesterol 7-alpha-Hydroxylase / Q000235:genetics; D006224:Cricetinae; D004032:Diet; D005243:Feces / Q000737:chemistry*; D008074:Lipoproteins / Q000097:blood; D008099:Liver / Q000737:chemistry / Q000201:enzymology; D000071518:Liver X Receptors; D008297:Male; D008647:Mesocricetus; D019697:Onions / Q000737:chemistry*; D057093:Orphan Nuclear Receptors / Q000235:genetics; D051782:Sterol Regulatory Element Binding Protein 2 / Q000235:genetics; D013261:Sterols / Q000032:analysis*; D015854:Up-Regulation / Q000187:drug effects
chemical_list: D000924:Anticholesteremic Agents; D008074:Lipoproteins; D000071518:Liver X Receptors; D057093:Orphan Nuclear Receptors; D051782:Sterol Regulatory Element Binding Protein 2; D013261:Sterols; D002784:Cholesterol; D002790:Cholesterol 7-alpha-Hydroxylase