In vivo compartmental metabolism of13C docosahexaenoic acid, studied by gas chromatography‐combustion isotope ratio mass spectrometry

• Published in: Lipids Vol. 31; no. 1Part1; pp. S109 - S115
• Main Authors: Croset, Martine, Brossard, Nicole, Pachiaudi, Christiane, Normand, Sylvie, Lecerf, Jean, Chirouze, Véronique, Riou, Jean Paul, Tayot, Jean Louis, Lagarde, Michel
• Format: Journal Article
• Language: English; Japanese
• Published: Berlin/Heidelberg Springer‐Verlag 01.01.1996
• ISSN: 0024-4201; 1558-9307
• DOI: 10.1007/BF02637061

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 with13C(13C 22:6n‐3). The13C abundance in the fatty acid was measured by gas‐chromatography‐combustion isotope ratio mass spectrometry which allowed the detection of 0.001 atom13C percent12C. The13C 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, unesterified13C 22:6n‐3 appeared in the plasma albumin.13C 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 higher13C 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. The13C 22:6n‐3 uptake into rat brain PC and phosphatidylethanolamine was still increasing when the concentration of plasma unesterified13C 22:6n‐3 had already dropped to a minimal plateau value and during the period of maximal plasma circulation of13C 22:6n‐3‐lysoPC bound to albumin. In contrast, the uptake of13C 22:6n‐3 into blood platelet PC occurred during the phase of important circulation of13C‐22:6n‐3 bound to albumin, suggesting thein vivo efficiency of the Lands pathway for this fatty acid. It is concluded that13C 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.