Disruption of cholesterol homeostasis by plant sterols.
The ABC transporters ABCG5 and ABCG8 limit absorption and promote excretion of dietary plant sterols. It is not known why plant sterols are so assiduously excluded from the body. Here we show that accumulation of plant sterols in mice lacking ABCG5 and ABCG8 (G5G8-/- mice) profoundly perturbs cholesterol homeostasis in the adrenal gland. The adrenal glands of the G5G8-/- mice were grossly abnormal in appearance (brown, not white) due to a 91% reduction in cholesterol content. Despite the very low cholesterol levels, there was no compensatory increase in cholesterol synthesis or in lipoprotein receptor expression. Moreover, levels of ABCA1, which mediates sterol efflux, were increased 10-fold in the G5G8-/- adrenals. Adrenal cholesterol levels returned to near-normal levels in mice treated with ezetimibe, which blocks phytosterol absorption. To determine which plant sterol(s) caused the metabolic changes, we examined the effects of individual plant sterols on cholesterol metabolism in cultured adrenal cells. Addition of stigmasterol, but not sitosterol, inhibited SREBP-2 processing and reduced cholesterol synthesis. Stigmasterol also activated the liver X receptor in a cell-based reporter assay. These data indicate that selected dietary plant sterols disrupt cholesterol homeostasis by affecting two critical regulatory pathways of lipid metabolism.
Yang
Chendong
C
Department of Molecular Genetics, McDermott Center for Human Growth and Development, University of Texas Southwestern Medical Center, Dallas 75390-9046, USA.
Yu
Liqing
L
Li
Weiping
W
Xu
Fang
F
Cohen
Jonathan C
JC
Hobbs
Helen H
HH
D000070996:ATP Binding Cassette Transporter, Subfamily G; D000071018:ATP Binding Cassette Transporter, Subfamily G, Member 5; D018528:ATP-Binding Cassette Transporters / Q000235:genetics / Q000502:physiology*; D000305:Adrenal Cortex Hormones / Q000378:metabolism; D000311:Adrenal Glands / Q000737:chemistry; D000818:Animals; D002784:Cholesterol / Q000031:analogs & derivatives* / Q000032:analysis / Q000378:metabolism*; D006706:Homeostasis / Q000187:drug effects / Q000502:physiology*; D008074:Lipoproteins / Q000172:deficiency* / Q000235:genetics; D051379:Mice; D018345:Mice, Knockout; D010840:Phytosterols / Q000032:analysis / Q000494:pharmacology*; D012855:Sitosterols / Q000032:analysis
C462600:ABCG5 protein, mouse; D000070996:ATP Binding Cassette Transporter, Subfamily G; D000071018:ATP Binding Cassette Transporter, Subfamily G, Member 5; D018528:ATP-Binding Cassette Transporters; C420604:Abcg3 protein, mouse; D000305:Adrenal Cortex Hormones; D008074:Lipoproteins; D010840:Phytosterols; D012855:Sitosterols; C021273:campesterol; C025473:gamma-sitosterol; D002784:Cholesterol