Retroconversion of docosahexaenoic acid (22:6) to eicosapentaenoic acid (20:5) is undetectable in serum of young women
Bibliographic record
Abstract
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.
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How this classification was reachedexpand
Full frame machine prediction
Teacher imitationNot calibrated prevalence, not ground truth. Human validation pending. The Gemma side is a direct model label for every work in the frame, read from the title-only record. The Codex side is a classifier learned from the 10,348 direct Codex labels and calibrated to design-weighted sample rates; fields without enough sample support carry no Codex call. Candidate is the union of the two sides; consensus is their intersection. These outputs are machine_predicted_unvalidated and are not human labels.
Distilled classifier scores by category (both heads)
| Category | Codex | Gemma |
|---|---|---|
| Metaresearch | 0.000 | 0.001 |
| Meta-epidemiology (narrow) | 0.000 | 0.000 |
| Meta-epidemiology (broad) | 0.000 | 0.000 |
| Bibliometrics | 0.000 | 0.000 |
| Science and technology studies | 0.000 | 0.000 |
| Scholarly communication | 0.000 | 0.000 |
| Open science | 0.000 | 0.000 |
| Research integrity | 0.000 | 0.000 |
| Insufficient payload (model declined to judge) | 0.001 | 0.000 |
Machine scores (provisional)
The two teacher heads of the student model, read on this work. A score orders the frame for review; it never asserts a category, and the validation status ships verbatim with every row.
Baseline scores from an immature model (maturity gate not passed, 7 training rounds). Scores rank; they never assert a category.
score_only:v0-immature-baseline · verbatim from the scoring run: score_only means the number may rank works, and no category label ships from itClassification
machine, unvalidatedMachine predicted; a candidate call from one source (direct Gemma or distilled Codex), not a consensus.
How this classification was reached, model by model and score by score, is at the end of the page under "How this classification was reached".