Breath [<sup>13</sup>CO<sub>2</sub>] recovery from an oral glucose load during exercise: comparison between [U-<sup>13</sup>C] and [1,2-<sup>13</sup>C]glucose
Bibliographic record
Abstract
The purpose of the present experiment was to compare 13CO2 recovery at the mouth, and the corresponding exogenous glucose oxidation computed, during a 100-min exercise at 63 +/- 3% maximal O2 uptake with ingestion of glucose (1.75 g/kg) in six active male subjects, by use of [U-13C] and [1,2-13C]glucose. We hypothesized that 13C recovery and exogenous glucose oxidation could be lower with [1,2-13C] than [U-13C]glucose because both tracers provide [13C]acetate, with possible loss of 13C in the tricarboxylic acid (TCA) cycle, but decarboxylation of pyruvate from [U-13C]glucose also provides 13CO2, which is entirely recovered at the mouth during exercise. The recovery of 13C (25.8 +/- 2.3 and 27.4 +/- 1.2% over the exercise period) and the amounts of exogenous glucose oxidized computed were not significantly different with [1,2-13C] and [U-13C]glucose (28.9 +/- 2.6 and 30.7 +/- 1.3 g, between minutes 40 and 100), suggesting that no significant loss of 13C occurred in the TCA cycle. This stems from the fact that, during exercise, the rate of exogenous glucose oxidation is probably much larger than the flux of the metabolic pathways fueled from TCA cycle intermediates. It is thus unlikely that a significant portion of the 13C entering the TCA cycle could be diverted to these pathways. From a methodological standpoint, this result indicates that when a large amount of [13C]glucose is ingested and oxidized during exercise, 13CO2 production at the mouth accurately reflects the rate of glucose entry in the TCA cycle and that no correction factor is needed to compute the oxidative flux of exogenous glucose.
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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) | 0.001 | 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 | 0.001 | 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".