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Cholesteryl ester absorption by small intestinal brush border membrane is protein-mediated
S Compassi1, M Werder, D Boffelli
1Laboratorium für Biochemie, Eidgenössische Technische Hochschule Zürich, ETH-Zentrum, Zürich, Switzerland.
Biochemistry
|December 19, 1995
Summary
A newly identified protein in intestinal brush border membrane vesicles (BBMV) facilitates direct absorption of long-chain cholesteryl esters, challenging prior beliefs about cholesterol ester hydrolysis necessity.
Area of Science:
- Biochemistry
- Cell Biology
- Gastroenterology
Background:
- Cholesterol absorption is crucial for human health.
- Traditionally, cholesterol esters are thought to require hydrolysis before absorption.
Purpose of the Study:
- To investigate the mechanism of long-chain cholesteryl ester absorption in the small intestine.
- To identify proteins involved in cholesterol ester uptake.
Main Methods:
- Preparation of brush border membrane vesicles (BBMV) from rabbit small intestine.
- Assays for cholesterol ester and free cholesterol absorption kinetics.
- Protein purification using gel filtration and anion-exchange chromatography.
- Antibody production and functional inhibition studies.
Main Results:
- A protein in BBMV catalyzes the direct absorption of long-chain cholesteryl esters and ethers.
- Cholesteryl oleate does not require hydrolysis for BBMV incorporation.
- Absorption kinetics for free and esterified cholesterol are similar.
- A water-soluble form of the protein facilitates cholesterol exchange between vesicles.
- Purified protein and its antibodies inhibit cholesterol ester uptake.
Conclusions:
- Contrary to prevailing beliefs, long-chain cholesteryl esters can be absorbed intact by the brush border membrane.
- A novel protein mediates direct uptake of cholesterol esters, independent of hydrolysis.
- This mechanism's contribution to overall absorption may be limited by ester solubility.