Muscle fiber type comparison of PDH kinase activity and isoform expression in fed and fasted rats
Bibliographic record
Abstract
Fiber type specificity for expression of all three rat skeletal muscle pyruvate dehydrogenase kinase (PDK) isoforms (PDK1, 2, and 4) was determined in fed and 24-h fasted rats. PDK activity and isoform protein and mRNA contents were determined in white gastrocnemius (WG; fast-twitch glycolytic), red gastrocnemius (RG; fast-twitch oxidative), and soleus (Sol; slow-twitch oxidative) muscles. PDK activity was lower in WG compared with oxidative muscles (RG, Sol) in both fed and fasted rats. PDK activities from fed muscles were 0.12 +/- 0.04, 0.30 +/- 0.01, and 0.36 +/- 0.08 min(-1) in WG, Sol, and RG, respectively, and increased in fasted muscles (0.36 +/- 0.09, 0.68 +/- 0.18, and 0.80 +/- 0.14 min(-1)). This correlated with increased PDK4 protein and to a lesser extent with PDK4 mRNA. PDK2 protein was not different between fiber types in fed or fasted rats, but PDK2 mRNA content was twofold greater in RG from fasted rats compared with fed rats. PDK1 was unaltered by fasting in all muscle types at both the protein and mRNA level, but in both fed and fasted rats had much greater protein and mRNA content in the oxidative vs. glycolytic muscles. In conclusion, PDK activity and PDK1 and 4 protein and mRNA were lower in glycolytic vs. oxidative muscles from fed and fasted rats. Fasting for 24 h induced a two- to threefold increase in PDK activity that was mainly due to increases in PDK4 protein and mRNA. PDK1 and 2 protein and mRNA were generally unaltered by fasting in all fiber types, except for increased PDK2 mRNA in the fast oxidative fibers. Because the PDK isoforms vary greatly in their kinetic properties, their relative proportions in the three fiber types at any given time during fasting could significantly alter the acute regulation of the pyruvate dehydrogenase complex.
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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 | 0.001 | 0.000 |
| Science and technology studies | 0.000 | 0.000 |
| Scholarly communication | 0.000 | 0.000 |
| Open science | 0.000 | 0.000 |
| Research integrity | 0.000 | 0.000 |
| Insufficient payload (model declined to judge) | 0.002 | 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".