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Journal of Lipid Research, Vol. 43, 1026-1034, July 2002
Copyright © 2002 by Lipid Research, Inc.
Cardiovascular Research Institute and Department of Medicine, University of California, San Francisco, San Francisco, CA 94143-0130
2 To whom correspondence should be addressed. e-mail: havelr{at}itsa.ucsf.edu
Although editing of apolipoprotein (apo)B in the small intestine, yielding apoB-48, is thought to be nearly complete in adult humans, small amounts of intestinal apoB-100 may also be produced. We have evaluated the fraction of unedited apoB secreted from the intestine postprandially in subjects with primary combined hyperlipidemia, a disorder in which secretion of apoB-100 into the blood is increased. Three hours after these subjects and healthy controls were fed a fat-rich meal containing retinol, the distribution of retinyl esters (RE) between plasma triglyceride-rich lipoprotein (TRL) fractions containing apoB-100 and apoB-48 was measured under conditions minimizing transfer of RE between lipoprotein particles. The estimated maximal percentage of unedited intestinal apoB-100 (
3%) was not increased in subjects with primary combined hyperlipidemia, suggesting that reduced editing of intestinal mRNA does not contribute to the pathogenesis of this disorder. Postprandially, the triglyceride content of TRL containing apoB-48 more than doubled, leading to a 20% increase in mean diameter, yet the surface concentration of phospholipids and soluble apolipoproteins (apoE and total apoC) was unchanged. Furthermore, the surface concentrations of these components did not differ among TRL containing apoB-48 and two smaller fractions of apoB-100 TRL with distinct immunoreactivities.
These findings suggest that available surface area is a major determinant of the particle content of each of these surface components of TRL species of differing size and origin.
Abbreviations: apo, apolipoprotein; CE, cholesteryl ester(s); FC, free cholesterol; PL, phospholipid(s); RE, retinyl ester(s); TC, total cholesterol; TG, triglyceride(s); TRL, triglyceride rich lipoprotein(s)
Supplementary key words apolipoprotein B editing immunoaffinity chromatography retinol retinyl esters
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