title: A green tea catechin extract upregulates the hepatic low-density lipoprotein receptor in rats.
abstract: Green tea extracts have hypocholesterolaemic properties in epidemiological and animal intervention studies. Upregulation of the low-density lipoprotein (LDL) receptor may be one mechanism to explain this as it is the main way cholesterol is removed from the circulation. This study aimed to determine if a green tea extract could upregulate the hepatic LDL receptor in vivo in the rat. A green tea extract (GTE) enriched in its anti-oxidant constituents, the catechins, was fed to rats (n = 6) at concentrations of either 0, 0.5, 1.0 or 2.0% (w/w) mixed in with their normal chow along with 0.25% (w/w) cholesterol for 12 days. Administration of the GTE had no effect on plasma total or LDL cholesterol concentrations but high-density lipoprotein significantly increased (41%; p < 0.05). Interestingly, there was a significant increase in LDL receptor binding activity (2.7-fold) and LDL receptor protein (3.4-fold) in the 2% (w/w) treatment group compared to controls. There were also significant reductions in liver total and unesterified cholesterol (40%). Administration of the GTE significantly reduced cholesterol absorption (24%) but did not affect cholesterol synthesis. These results show that, despite no effect on plasma cholesterol, the GTE upregulated the LDL receptor in vivo. This appears to be via a reduction in liver cholesterol concentration and suggests that the green tea extract was able to increase the efflux of cholesterol from liver cells.
authors.affiliation: Heart Research Institute, University of Sydney, 114 Pyrmont Bridge Road, Camperdown, NSW 2050, Australia. bursillc@hri.org.au
authors.forename: Christina A
authors.initials: CA
authors.lastname: Bursill
authors.forename: Paul D
authors.initials: PD
authors.lastname: Roach
mesh_terms: D000284:Administration, Oral; D000818:Animals; D000924:Anticholesteremic Agents / Q000494:pharmacology; D002392:Catechin / Q000302:isolation & purification / Q000494:pharmacology*; D002791:Cholesterol, Dietary / Q000008:administration & dosage; D008076:Cholesterol, HDL / Q000097:blood / Q000378:metabolism; D008078:Cholesterol, LDL / Q000097:blood / Q000378:metabolism; D004305:Dose-Response Relationship, Drug; D007408:Intestinal Absorption / Q000187:drug effects; D008099:Liver / Q000187:drug effects / Q000378:metabolism*; D008297:Male; D010936:Plant Extracts / Q000494:pharmacology*; D051381:Rats; D017207:Rats, Sprague-Dawley; D011973:Receptors, LDL / Q000187:drug effects* / Q000378:metabolism*; D013662:Tea / Q000737:chemistry; D015854:Up-Regulation
chemical_list: D000924:Anticholesteremic Agents; D002791:Cholesterol, Dietary; D008076:Cholesterol, HDL; D008078:Cholesterol, LDL; D010936:Plant Extracts; D011973:Receptors, LDL; D013662:Tea; D002392:Catechin