The phosphatidylethanolamine N-methyltransferase pathway is quantitatively not essential for biliary phosphatidylcholine secretion
Bibliographic record
Abstract
The phosphatidylethanolamine N-methyltransferase (PEMT) pathway of phosphatidylcholine (PC) biosynthesis is not essential for the highly specific acyl chain composition of biliary PC. We evaluated whether the PEMT pathway is quantitatively important for biliary PC secretion in mice under various experimental conditions. Biliary bile salt and PC secretion were determined in mice in which the gene encoding PEMT was inactivated (Pemt(-/-)) and in wild-type mice under basal conditions, during acute metabolic stress (intravenous infusion of the bile salt tauroursodeoxycholate), and during chronic metabolic stress (feeding a taurocholate-containing diet for 1 week). The activity of CTP:phosphocholine cytidylyltransferase, the rate-limiting enzyme of PC biosynthesis via the CDP-choline pathway, and the abundance of multi-drug-resistant protein 2 (Mdr2; encoded by the Abcb4 gene), the canalicular membrane flippase essential for biliary PC secretion, were determined. Under basal conditions, Pemt(-/-) and wild-type mice exhibited similar biliary secretion rates of bile salt and PC ( approximately 145 and approximately 28 nmol/min/100 g body weight, respectively). During acute or chronic bile salt administration, the biliary PC secretion rates increased similarly in Pemt(-/-) and control mice. Mdr2 mRNA and protein abundance did not differ between Pemt(-/-) and wild-type mice. The cytidylyltransferase activity in hepatic lysates was increased by 20% in Pemt(-/-) mice fed the basal (bile salt-free) diet (P < 0.05). We conclude that the biosynthesis of PC via the PEMT pathway is not quantitatively essential for biliary PC secretion under acute or chronic bile salt administration.
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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 | 0.000 |
| Meta-epidemiology (narrow) | 0.001 | 0.000 |
| Meta-epidemiology (broad) | 0.000 | 0.000 |
| Bibliometrics | 0.000 | 0.000 |
| Science and technology studies | 0.000 | 0.001 |
| Scholarly communication | 0.001 | 0.001 |
| Open science | 0.000 | 0.000 |
| Research integrity | 0.000 | 0.001 |
| 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".