Stable Isotope Tracer and Gas-Chromatography Combustion Isotope Ratio Mass Spectrometry to Study the in Vivo Compartmental Metabolism of Docosahexaenoic Acid

✍ Scribed by N. Brossard; C. Pachiaudi; M. Croset; S. Normand; J. Lecerf; V. Chirouze; J.P. Riou; J.L. Tayot; M. Lagarde

• Publisher: Elsevier Science
• Year: 1994
• Tongue: English
• Weight: 666 KB
• Volume: 220
• Category: Article
• ISSN: 0003-2697
• DOI: 10.1006/abio.1994.1318

✦ Synopsis

A gas-chromatography combustion isotope ratio mass spectrometry (GCC-IRMS) method using carbon 13 (\left({ }^{13} \mathrm{C}\right))-stable isotope to trace (\mathrm{n-3}) polyunsaturated fatty acids (PUFA) turnover in vivo is presented. Natural ({ }^{13} \mathrm{C}) abundance of commercial n-3 PUFA was measured from 100 to (300 \mathrm{ng}) of fatty acids and was -27.58 , -27.83 , and -28.16 for (22: 6 n-3,22: 5 n-3), and (20: 5 n-3), expressed as (\delta^{13} \mathrm{C} %) versus Pee Dee Belemnite (PDB), respectively. Precision of (\delta^{13} \mathrm{C} %) values was comparable for the three PUFA and gave relative standard deviations of (0.95-0.97 %). Isotope enrichment of 0.0010 at. (%) could be detected. Triglycerides enriched in (\left[{ }^{13} \mathrm{C}\right]) 22:6n-3 ([ (\left.{ }^{13} \mathrm{C}\right]) 22:6-TG) were synthesized by growing a microalgae on (\left[1-{ }^{13} \mathrm{C}\right]) glucose. (\left[{ }^{13} \mathrm{C}\right] 22: 6 \mathrm{n}-3) represented (36 \mathrm{wt} %) of total triglyceride fatty acids and had an isotope enrichment of 2.0420 at.%, which was the double of natural abundance. The isotope enrichment of 22:6n-3 in lipids from rat lipoproteins and red cells could be followed as a function of time after ingestion of (3 \mathrm{mg}\left[{ }^{13} \mathrm{C}\right]) 22:6-TG and showed specific patterns according to the lipid compartments. The retroconversion of (\left[{ }^{13} \mathrm{C}\right] 22: 6 \mathrm{n}-3) was also detected in HDL phosphatidylcholine by the appearance of (\left[{ }^{13} \mathrm{C}\right] 22: 5 n-3) and (\left[{ }^{13} \mathrm{C}\right]) 20:5n-3. On the other hand, 22:6n-3 natural ({ }^{13} \mathrm{C}) abundance in human lipid classes of lipoproteins and blood cells has been measured using (10 \mathrm{ml}) plasma, even for the more limiting lipid compartments in terms of