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Retroconversion of docosahexaenoic acid (22:6) to eicosapentaenoic acid (20:5) is undetectable in serum of young women
Author(s) -
Brenna J. Thomas,
Zhang Ying,
Vandal Milène,
Cunnane Stephen C.
Publication year - 2008
Publication title -
the faseb journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.709
H-Index - 277
eISSN - 1530-6860
pISSN - 0892-6638
DOI - 10.1096/fasebj.22.1_supplement.297.1
Subject(s) - eicosapentaenoic acid , docosahexaenoic acid , polyunsaturated fatty acid , chemistry , medicine , endocrinology , fatty acid , biochemistry
Background . The polyunsaturated fatty acid (PUFA) 22:6 is widely accepted to be synthesized from 20:5 via these steps: 20:5 → 22:5 → 24:5 → 24:6 → 22:6. Many papers report apparent retroconversion of 22:6 to 20:5, presumed to be by reverse of this pathway, but this hypothesis has not been directly tested in human adults. Methods . Four young adult women were given a single oral dose of [U‐ 13 C]‐22:6, and serum was collected several times on day 1 and weekly until 28 days post‐dose. FAME were prepared and analyzed by high precision GC‐combustion isotope ratio mass spectrometry, and data are expressed as nmol 13 C‐FA per ml serum. Results . On average, 22:6* peaked at 24 h and dropped smoothly until day 28, when it remained well above baseline. In contrast, no other n‐3 PUFA showed an increase in labeling of more than a few percent above baseline, and there were no trends attributable to retroconversion. 16:0* peaked at 11% of the 22:6* peak on day 1, dropped to baseline, then gradually increased to a plateau at 4 days, while 18:0* peaked on day 2 at about 7% of the 22:6* peak. These changes were driven primarily by one subject. Conclusions . Increases in serum 20:5 often ascribed to increasing dietary 22:6 may not be due to retroconversion but to other mechanisms such as sparing of 20:5 oxidation. Alternatively, retroconversion may be driven by much higher levels of dietary 22:6. Funding: Canadian Institutes of Health Research.