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Papers In Press, published online ahead of print October 1, 2004
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Department of Medicine, University of Illinois at Chicago, Chicago, IL 60612
Corresponding Author: psubbaia{at}uic.edu
The percentage of saturated cholesteryl esters (CE) synthesized by human LCAT is several times higher than expected from the sn-2 acyl composition of plasma phosphatidylcholine (PC), whereas the synthesis of 20:4 CE and 22:6 CE is much lower than expected. To explain these discrepancies, we proposed that LCAT transfers some saturated fatty acids from the sn-1 position of PC species that contain 20:4 or 22:6 at sn-2. The present studies provide in vivo evidence for this hypothesis. We determined the composition and synthesis of CE species in plasma of volunteers before and after a 6 week dietary supplementation with docosahexaenoic acid (22:6, DHA). In addition to an increase in the DHA content of all plasma lipids, there was a significant (+12%, p<0.005) increase of 16:0 CE, although there was no increase in 16:0 at sn-2 of PC. The increase of DHA in CE was much lower than its increase in sn-2 of PC. Ex vivo synthesis of CE species in plasma showed a significant (+24%, p<0.005) increase in the synthesis of 16:0 CE after DHA supplementation, which correlated positively with the increase of 22:6, but not of 16:0, at sn-2 of PC. These results show that the positional specificity of human LCAT is altered when the concentration of 16:0-22:6 PC is increased by DHA supplementation.
Revised on September 19, 2004
Accepted on September 19, 2004
Evidence for altered positional specificity of LCAT in vivo: Increased synthesis of saturated cholesteryl esters after dietary supplementation with docosahexaenoic acid
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