AMPK activation increases uncoupling protein-3 expression and mitochondrial enzyme activities in rat muscle without fibre type transitions
Bibliographic record
Abstract
The present study examined the effect of chronic activation of 5′-AMP-activated protein kinase (AMPK) on the metabolic profile, including uncoupling protein-3 (UCP-3) and myosin heavy chain (MHC)-based fibre phenotype of rodent fast-twitch tibialis anterior muscle. Sprague-Dawley rats were given daily injections of 5-aminoimidazole-4-carboxamide-1-β-D-ribofuranoside (AICAR), a known activator of AMPK, or vehicle (control) for 28 days. After AICAR treatment, UCP-3 expression at the mRNA level was elevated 1.6 ± 0.1-fold (P < 0.006) and corresponded to a 3.3 ± 0.2-fold increase in UCP-3 protein content (P < 0.0001). In addition, the activities of the mitochondrial reference enzymes citrate synthase (EC 4.1.3.7) and 3-hydroxyacyl-CoA-dehydrogenase (EC 1.1.1.35), which are known to increase in proportion to mitochondrial volume density, were elevated 1.6-fold (P < 0.006), while the activity of lactate dehydrogenase (EC 1.1.1.27) was reduced to 80 % of control (P < 0.02). No differences were detected after AICAR treatment in the activities of the glycolytic reference enzymes glyceraldehydephosphate dehydrogenase (EC 1.2.1.12) or phosphofructokinase (EC 2.7.1.11), nor were MHC-based fibre-type transitions observed, using immunohistochemical or electrophoretic analytical methods. These changes could not be attributed to variations in inter-organ signalling by metabolic substrates or insulin. We conclude that an AMPK-dependent pathway of signal transduction does mimic some of the metabolic changes associated with chronic exercise training, but does not affect expression of the MHC-based structural phenotype. Thus, the metabolic and MHC-based fibre types do not appear to be regulated in a co-ordinated way, but may be independently modified by different signalling pathways.
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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 | 0.000 |
| Meta-epidemiology (broad) | 0.000 | 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 | 0.000 | 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".