The recent discovery of transporters in the intestinal mucosa and the canalicular
membrane has given new insights into the regulation of intestinal absorption as well
as the biliary output of cholesterol and plant sterols. The 2 adenosine triphosphate
(ATP)-binding cassette (ABC) half-transporters ABCG5 and ABCG8 are expressed in the
mucosa cells and the canalicular membrane, and they resecrete sterols, especially
absorbed plant sterols, back into the intestinal lumen and from the liver into bile.
Defects of either of these cotransporters lead to the rare inherited disease of phytosterolemia,
which is clinically defined by hyperabsorption and diminished biliary excretion of
plant sterols. Furthermore, it has been recently demonstrated that the Niemann-Pick
C1-Like 1 (NPC1L1) transporter is most likely responsible for the transport of cholesterol
and plant sterols from the brush border membrane into the intestinal mucosa. Ezetimibe
interferes with NPC1L1, reducing the intestinal uptake of cholesterol and plant sterols.
These new findings contribute to our understanding of cholesterol and plant sterol
concentrations in serum, and the effect of dietary and drug intervention to reduce
serum concentrations of sterols.
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Published online: May 11, 2005
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© 2005 Elsevier Inc. Published by Elsevier Inc. All rights reserved.
