Incorporation oftrans-8- andcis-8-octadecenoic acid isomers in human plasma and lipoprotein lipids |
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Authors: | E A Emken R O Adlof W K Rohwedder R M Gulley |
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Affiliation: | (1) Northern Regional Research Center, ARS/USDA, 1815 N. University St., 61604 Peoria, IL;(2) St. Francis Medical Center, Peoria, Illinois |
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Abstract: | Mixtures of deuterium-labeledtrans-8-,cis-8- andcis-9-octadecenoic acids (8t–18∶1, 8c–18∶1, 9c–18∶1) were fed as triglycerides (TG) to two adult male subjects. Blood samples
were collected sequentially over a 48-hour period. Plasma and lipoprotein lipids were separated by thin layer chromatography
and analyzed by gas chromatography-mass spectroscopy. Results indicate (i) absorption of the 8t- and 8c–18∶1 isomers were
similar to 9c–18∶1; (ii) the 8t–18∶1 isomer was cleared approximately 30% faster than 9c–18∶1 from plasma TG; (iii) cholesterol
ester samples contained 8.4 times less 8t–18∶1 than 9c–18∶1; (iv) incorporation at the 1-acyl phosphatidylcholine (PC) position
was higher for 8t–18∶1 and 8c–18∶1 (2.2 and 1.7 times) than for 9c–18∶1; and (v) discrimination at the 2-acyl PC position
was 4.6-fold against 8t–18∶1 and 1.3-fold against 8c–18∶1 compared with 9c–18∶1. Discrimination against uptake of the Δ-8
isomers in both neutral and phospholipid classes suggests that both 8t- and 8c–18∶1 may be preferentially oxidized relative
to 9c–18∶1. Except for triglycerides, data for each of the lipid classes from total plasma and individual lipoprotein samples
were similar. These data indicate that differences for incorporation and turnover of the 8t- and 8c–18∶1 isomers relative
to 9c–18∶1 are not substantially influenced by the lipoprotein classes. The maximum isotopic enrichment detected in the chylomicron
triglycerides fractions was 60%, which indicates that a substantial amount of endogenous triglycerides was mobilized during
absorption of the deuterated fats. |
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