2‐ 15N Glutamine tracer overestimate rates of Arginine and Citrulline synthesis in healthy adult men
Bibliographic record
Abstract
Recent studies have documented transfer of labeled nitrogen from 2–15N glutamine (Gln) to citrulline (Cit) and arginine (Arg) in fasting human adults. Conversely, in neonates we have shown no synthesis of Arg from glutamate. Therefore, we performed a multitracer study with 2‐ 15 N and 1‐ 13 C Gln given enterally to 5 healthy men fed a standardized milkshake diet. There was no difference in plasma enrichments between the two Gln tracers. 1‐ 13 C isomers of Cit and Arg were synthesized from 1‐ 13 C Gln. Three isomers each of Cit and Arg were synthesized from the 2‐ 15 N Gln tracer; 2‐ 15 N, 5‐ 15 N and 2,5 15 N 2 . The enrichments of these isomers of Cit and Arg expressed as atom percent excess are shown in the . Enrichment of Arg and Cit isomers synthesized from 1‐ 13 C and 2‐ 15 N Gln 1–13C 2–15N 5–15N 2,5–15N Cit (%) 1.4 1 2.6 1,2 4.0 2 0.8 Arg (%) 0.14 1 0.4 1 0.8 0.1 Significantly greater enrichment was found of both 5‐ 15 N Arg and Cit compared to 2‐ 15 N isomers 2 , indicating the amino N from Gln is mostly transferred to Arg and Cit by transamination. Similarly, the enrichment of the 1‐ 13 C isomers was significantly less than the 2‐ 15 N isomers 1 suggesting rapid formation of α‐ketoglutarate and recycling of the nitrogen label. Our results show Gln is acting primarily as a nitrogen donor for Arg synthesis and studies using 15 N label overestimate Arg synthesis rates. Grant Funding Source: CIHR
Fetched live from OpenAlex and de-inverted. Abstracts are not stored in this database: the inverted indexes are 8.6 GB of the frame’s 9.3 GB of text, and the host has 13 GB free.
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 | 0.001 | 0.001 |
| Meta-epidemiology (narrow) | 0.001 | 0.001 |
| Meta-epidemiology (broad) | 0.001 | 0.000 |
| Bibliometrics | 0.001 | 0.000 |
| Science and technology studies | 0.000 | 0.000 |
| Scholarly communication | 0.001 | 0.000 |
| Open science | 0.000 | 0.000 |
| Research integrity | 0.001 | 0.000 |
| Insufficient payload (model declined to judge) | 0.002 | 0.001 |
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".