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In vivo compartmental metabolism of 13 C docosahexaenoic acid, studied by gas chromatography‐combustion isotope ratio mass spectrometry
Author(s) -
Croset Martine,
Brossard Nicole,
Pachiaudi Christiane,
Normand Sylvie,
Lecerf Jean,
Chirouze Véronique,
Riou Jean Paul,
Tayot Jean Louis,
Lagarde Michel
Publication year - 1996
Publication title -
lipids
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.601
H-Index - 120
eISSN - 1558-9307
pISSN - 0024-4201
DOI - 10.1007/bf02637061
Subject(s) - chemistry , mass spectrometry , isotope , isotope ratio mass spectrometry , chromatography , docosahexaenoic acid , gas chromatography , gas chromatography–mass spectrometry , combustion , lipidology , radiochemistry , clinical chemistry , fatty acid , polyunsaturated fatty acid , biochemistry , organic chemistry , physics , quantum mechanics
The exchange of docosahexaenoic acid (22:6n‐3) within lipid pools in rat and human has been followed as a function of time after the ingestion of triglycerides (TG) containing 22:6n‐3 labeled with 13 C( 13 C 22:6n‐3). The 13 C abundance in the fatty acid was measured by gas‐chromatography‐combustion isotope ratio mass spectrometry which allowed the detection of 0.001 atom 13 C percent 12 C. The 13 C 22:6n‐3 appearance was rapid in the TG of very low density lipoprotein plus chylomicron fraction, in which the maximal labeling was observed at 3 and 2 h after ingestion in rat and human, respectively. Concomitant with the TG utilization of this fraction by lipoprotein lipase from tissues, unesterified 13 C 22:6n‐3 appeared in the plasma albumin. 13 C 22:6n‐3 bound to albumin was mostly present in unesterified form before 12 h post‐ingestion while after that period, lysophosphatidylcholine (lysoPC) bound to albumin carried higher 13 C 22:6n‐3 concentrations. These lyso‐PC were mostly from hepatic origin and might represent a potential source of 22:6n‐3 redistribution to tissues. The 13 C 22:6n‐3 uptake into rat brain PC and phosphatidylethanolamine was still increasing when the concentration of plasma unesterified 13 C 22:6n‐3 had already dropped to a minimal plateau value and during the period of maximal plasma circulation of 13 C 22:6n‐3‐lysoPC bound to albumin. In contrast, the uptake of 13 C 22:6n‐3 into blood platelet PC occurred during the phase of important circulation of 13 C‐22:6n‐3 bound to albumin, suggesting the in vivo efficiency of the Lands pathway for this fatty acid. It is concluded that 13 C 22:6n‐3 esterified in TG is rapidly absorbed and redistributed within plasma lipoproteins and that its redistribution within the two lipid species bound to albumin might influence its uptake by platelets and rat brain.