HOME HELP FEEDBACK SUBSCRIPTIONS ARCHIVE SEARCH TABLE OF CONTENTS		QUICK SEARCH:   [advanced] Author: Keyword(s): Year:  Vol:  Page:

This Article Full Text Full Text (PDF) Alert me when this article is cited Alert me if a correction is posted Citation Map Services Email this article to a friend Similar articles in this journal Similar articles in PubMed Alert me to new issues of the journal Download to citation manager Request Permissions Citing Articles Citing Articles via HighWire Citing Articles via Google Scholar Google Scholar Articles by Moschetta, A. Articles by van Erpecum, K. J. Search for Related Content PubMed PubMed Citation Articles by Moschetta, A. Articles by van Erpecum, K. J. Social Bookmarking                      What's this?

Journal of Lipid Research, Vol. 43, 1046-1053, July 2002
Copyright © 2002 by Lipid Research, Inc.

Research Articles

Incorporation of cholesterol in sphingomyelin- phosphatidylcholine vesicles has profound effects on detergent-induced phase transitions

Antonio Moschetta^*,, Peter M. Frederik, Piero Portincasa, Gerard P. vanBerge-Henegouwen^* and Karel J. van Erpecum^1,*

^* Gastrointestinal Research Unit, Departments of Gastroenterology and Surgery, University Medical Center, Utrecht
Section of Internal Medicine, Department of Internal and Public Medicine, University Hospital, Bari, Italy
Department of Electron Microscopy, Maastricht University, The Netherlands

¹ To whom correspondence should be addressed. e-mail: k.j.vanerpecum{at}azu.nl

ABSTRACT

Vesicle micelle transitions are important phenomena during bile formation and intestinal lipid processing. The hepatocyte canalicular membrane outer leaflet contains appreciable amounts of phosphatidylcholine (PC) and sphingomyelin (SM), and both phospholipids are found in the human diet. Dietary SM enrichment inhibits intestinal cholesterol absorption. We therefore studied detergent-induced vesicle micelle transitions in SM-PC vesicles. Phase transitions were evaluated by spectrophotometry and cryotransmission electron microscopy (cryo-TEM) after addition of taurocholate (3–7 mM) to SM-PC vesicles (4 mM phospholipid, SM/PC 40%/60%, without or with 1.6 mM cholesterol). After addition of excess (5–7 mM) taurocholate, SM-PC vesicles were more sensitive to micellization than PC vesicles. As shown by sequential cryo-TEM, addition of equimolar (4 mM) taurocholate to SM-PC vesicles induced formation of open vesicles, then (at the absorbance peak) fusion of bilayer fragments into large open structures (around 200 nm diameter) coexisting with some multilamellar or fused vesicles and thread-like micelles and, finally, transformation into an uniform picture with long thread-like micelles. Incorporation of cholesterol in the SM/PC bilayer changed initial vesicular shape from spherical into ellipsoid and profoundly increased detergent resistance. Disk-like micelles and multilamellar vesicles, and then extremely large vesicular structures, were observed by sequential cryo-TEM under these circumstances, with persistently increased absorbance values by spectrophotometry.

These findings may be relevant for bile formation and intestinal lipid processing. Inhibition of intestinal cholesterol absorption by dietary SM enrichment may relate to high resistance against bile salt-induced micellization of intestinal lipids in presence of the sphingolipid.

Abbreviations: cryo-TEM, cryo-transmission electron microscopy; PC, phosphatidylcholine; SM, sphingomyelin

Supplementary key words micelles • spectrophotometry • taurocholate

CiteULike    Complore    Connotea    Del.icio.us    Digg    Reddit    Technorati    What's this?

This article has been cited by other articles:

				A. Nilsson and R.-D. Duan Absorption and lipoprotein transport of sphingomyelin J. Lipid Res., January 1, 2006; 47(1): 154 - 171. [Abstract] [Full Text] [PDF]