Pyruvate dehydrogenase (PDH) activity in response to skeletal muscle contraction at two stimulation frequencies in PDH kinase 4 knockout mice
Bibliographic record
Abstract
Pyruvate dehydrogenase (PDH) plays a key role in carbohydrate oxidation within skeletal muscle. PDH is deactivated by PDH kinase (PDK), with the predominant skeletal muscle isoforms being PDK2 and 4. Although PDK2 is most abundant under normal conditions, PDK4 expression accounts for the majority of PDH deactivation following starvation and high fat diets, but little is known about what role PDK4 plays during an acute bout of muscle contraction. This study examined the differential activation of PDH (PDHa) during electrically stimulated contraction of fast‐twitch muscle from PDK4 knockout mice (KO) and wild type (WT) littermates. Extensor digitorum longus muscles were removed from KO and WT after a 24h fast (n=5) and placed in an organ bath (25°C) with the distal tendon fixed to a stationary hook; proximal tendon attached to a force transducer. Muscles were incubated for 30 min (Rest) and then stimulated to contract at low (10 Hz) or higher intensity (40 Hz) for 3 min. Force produced by KO and WT muscle was the same throughout the stimulation period. PDHa activity increased compared to rest at both intensities (KO: Rest, 0.88±0.19; 10Hz, 1.70±0.14; 40Hz, 3.75±0.14; WT: Rest, 0.34±0.12; 10Hz, 0.83±0.14 (p=0.059); 40Hz, 1.82±0.14 mmol/min/kg ww; p<0.001). Between groups, PDHa activity in KO muscle was greater than WT at all intensities. Therefore, the absence of PDK4 resulted in much higher PDHa activity at rest and both contraction intensities, suggesting an important role of PDK4 in regulating contraction‐mediated carbohydrate oxidation. Supported by NSERC and NIH (RAH)
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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 | 0.001 |
| Meta-epidemiology (broad) | 0.001 | 0.001 |
| Bibliometrics | 0.001 | 0.000 |
| Science and technology studies | 0.000 | 0.001 |
| Scholarly communication | 0.000 | 0.000 |
| Open science | 0.000 | 0.000 |
| Research integrity | 0.001 | 0.002 |
| Insufficient payload (model declined to judge) | 0.003 | 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".