Tyrosine requirements in children with classical PKU determined by indicator amino acid oxidation
Bibliographic record
Abstract
Tyrosine (Tyr) is an essential amino acid in phenylketonuria (PKU) because of the limited hydroxylation of phenylalanine (Phe) to Tyr. The recommended intakes for Tyr in PKU are at least five times the recommended phenylalanine intakes. This suggests that Phe and Tyr contribute approximately 20 and 80%, respectively, of the aromatic amino acid (AAA) requirement (REQ). In animals and normal humans, dietary Tyr was shown to spare 40-50% of the Phe requirement, proportions that reflect dietary and tissue protein composition. We tested the hypothesis that the Tyr REQ in PKU would account for 45% of the total AAA REQ by indicator amino acid oxidation (IAAO). Tyr REQ was determined in five children with PKU by examining the effect of varying dietary Tyr intake on lysine oxidation and the appearance of (13)CO(2) in breath (F(13)CO(2)) under dietary conditions of adequate energy, protein (1.5 g x kg(-1) x day(-1)), and phenylalanine (25 mg x kg(-1) x day(-1)). Lysine oxidation and F(13)CO(2) were determined using a primed 4-h oral equal-dose infusion of L-[1-(13)C]lysine. Lysine oxidation and F(13)CO(2) decreased linearly as Tyr intake increased, to a break point that was interpreted as the mean dietary Tyr requirement (16.3 and 19.2 mg x kg(-1) x day(-1), respectively). At Tyr intakes of >16.3 and 19.2 mg x kg(-1) x day(-1), lysine oxidation and F(13)CO(2), respectively, were low and constant. This represents 40.4 and 44.4%, respectively, of the total AAA intake. The current recommendations for Tyr intake in PKU patients appear to be overestimated by a factor of approximately 5. This study is the first application of the IAAO technique in a pediatric population and in humans with an inborn error of metabolism.
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How this classification was reachedexpand
Full frame distilled prediction
Teacher imitationNot calibrated prevalence, not ground truth. Human validation pending. Learned from the 10,348 direct Codex labels and 10,348 direct Gemma labels. Candidate is the union of thresholded teacher heads; consensus is their intersection. These outputs are machine_predicted_unvalidated and are not human labels or direct frontier model labels.
Codex and Gemma teacher scores by category
| Category | Codex | Gemma |
|---|---|---|
| Metaresearch | 0.000 | 0.000 |
| Meta-epidemiology (narrow) | 0.000 | 0.000 |
| Meta-epidemiology (broad) | 0.001 | 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 | 0.000 |
| Insufficient payload (model declined to judge) | 0.000 | 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 teacher head, 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".