title: Green tea catechins decrease apolipoprotein B-100 secretion from HepG2 cells.
abstract: To understand the hypocholesterolemic activity of green tea, our in vitro studies screened the relative efficacy of two structurally distinct green tea catechins, epicatechin (EC) and epigallocatechin gallate (EGCG), on apolipoprotein B-100 (apoB) and lipid production using a well established human hepatoma cell-line, HepG2, as the model system. This study showed that HepG2 cells pretreated with EC and EGCG for 8 h exerted a dose-dependent inhibitory effect on apoB secretion. Total protein and albumin synthesis and secretion were unaffected indicating the effects on apoB secretion to be specific. Under lipid-rich conditions, apoB secretion was markedly reduced by EGCG and to a lesser extent by EC at 50 microM. Mechanistic study showed that tea catechins inhibited apoB secretion via a proteasome-independent pathway as indicated by a lack of response to N-acetyl-leucyl-leucyl-norleucinal (ALLN), a proteasome inhibitor. The effect on apoB secretion was also found to be independent of lipid biosynthesis. In summary, the data suggest that EGCG in contrast to EC is a potent inhibitor of apoB secretion. The results indicate that the gallate moiety in the catechin molecule may result in a beneficial effect on lipid metabolism in terms of apoB secretion.
authors.affiliation: Division of Medical Technology, University of Hawaii, Honolulu 96822, USA.
authors.forename: Winnie L
authors.initials: WL
authors.lastname: Yee
authors.forename: Qi
authors.initials: Q
authors.lastname: Wang
authors.forename: Trecito
authors.initials: T
authors.lastname: Agdinaoay
authors.forename: Kaohimanu
authors.initials: K
authors.lastname: Dang
authors.forename: Healani
authors.initials: H
authors.lastname: Chang
authors.forename: Andrew
authors.initials: A
authors.lastname: Grandinetti
authors.forename: Adrian A
authors.initials: AA
authors.lastname: Franke
authors.forename: Andre
authors.initials: A
authors.lastname: Theriault
mesh_terms: D000924:Anticholesteremic Agents / Q000494:pharmacology; D053299:Apolipoprotein B-100; D001055:Apolipoproteins B / Q000378:metabolism*; D002392:Catechin / Q000031:analogs & derivatives* / Q000494:pharmacology*; D015243:Cholesterol, VLDL / Q000378:metabolism; D003546:Cysteine Endopeptidases / Q000378:metabolism; D006801:Humans; D006888:Hydroxycholesterols / Q000378:metabolism; D008055:Lipids / Q000096:biosynthesis; D009097:Multienzyme Complexes / Q000378:metabolism; D046988:Proteasome Endopeptidase Complex; D013662:Tea; D014407:Tumor Cells, Cultured
chemical_list: D000924:Anticholesteremic Agents; D053299:Apolipoprotein B-100; D001055:Apolipoproteins B; D015243:Cholesterol, VLDL; D006888:Hydroxycholesterols; D008055:Lipids; D009097:Multienzyme Complexes; D013662:Tea; C007997:25-hydroxycholesterol; D002392:Catechin; C045651:epigallocatechin gallate; D003546:Cysteine Endopeptidases; D046988:Proteasome Endopeptidase Complex