The Amount of Dietary Methionine Required to Maximize Synthesis of Transmethylated Products Is Higher than That Needed for Protein Synthesis in Neonatal Piglets
Bibliographic record
Abstract
Methionine is required for synthesizing protein and other critical metabolites, acting as a precursor for >50 transmethylation reactions to produce metabolites such as creatine, phosphatidylcholine (PC), and methylated DNA. In neonatal piglets, because only one-third of dietary methionine is incorporated into protein compared to two-thirds for methylated products, both protein and non-protein demands need to be considered when determining the methionine requirement. Our major objective was to quantify how much dietary methionine is required to maximize protein synthesis and key transmethylated products (creatine, PC, methylated DNA). Twenty surgically altered Yucatan miniature piglets (8 ± 2 d) were fed complete diets for 5 d and then randomized to 20 test diets with methionine intakes ranging from 20%-220% of requirement (0.32 – 3.55 g methionine/100 g total AAs). Stable isotopes of phenylalanine and tyrosine were administered to determine whole-body protein synthesis. [ 3 H-methyl]-methionine was infused to measure methyl incorporation into transmethylated products, and 3 H-phenylalanine flooding dose was given to measure tissue-specific protein synthesis. Break-point analysis indicated a whole-body requirement of 1.73 ± 0.27 g methionine/100 g total AAs. [ 3 H-methyl] incorporation into PC increased linearly with dietary methionine, while hepatic creatine synthesis maximized at 1.84 ± 0.22 g methionine/100 g total AAs. DNA methylation rate was maximized at 1.52 ± 0.38 g methionine/100 g total AAs. Plasma concentrations of homocysteine were positively correlated with dietary methionine levels. These data suggest that DNA methylation is prioritized over hepatic creatine synthesis, while PC synthesis continuously increases with methionine intake with no discernible maximum rate. When methionine intake was limited, liver protein synthesis was prioritized, followed by kidney and muscle protein synthesis. These data suggest that protein synthesis should not be used to determine whole-body requirements since more methionine is required to meet non-protein demands for methionine.
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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) | 0.000 | 0.000 |
| Meta-epidemiology (broad) | 0.000 | 0.000 |
| Bibliometrics | 0.000 | 0.000 |
| Science and technology studies | 0.000 | 0.001 |
| Scholarly communication | 0.000 | 0.000 |
| 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".