Epinephrine Responsiveness is Reduced in Livers from Trained Mice
Bibliographic record
Abstract
Catecholamines increase liver glucose production at least in part through increases in glycogenolysis and gluconeogenesis. To date, the effects of prior exercise training on the liver’s response to epinephrine, in vivo, have not been fully elucidated. To examine the role of epinephrine signaling on indices of liver glucose production in trained mice, male C57BL/6 mice were subject to either 12 days of voluntary wheel running (TR) or remained sedentary (SED). Epinephrine (0.5 mg/kg body weight), or vehicle were injected intraperitoneally following 12 days of training and tissues harvested 15 minutes post‐injection. The rise in blood glucose following epinephrine injection was significantly blunted in trained compared to sedentary mice and this was paralleled by a blunted reduction in liver glycogen in trained mice. There was a main effect of epinephrine to increase the phosphorylation of protein kinase‐A substrates (pPKAs), which was driven by increases in the sedentary, but not trained, mice. Similarly, epinephrine‐induced increases in the mRNA expression of α‐ and β‐adrenergic receptor 1 and 2 and glucose‐6‐phosphatase were greater in SED compared to TR mice. Exercise and epinephrine decreased serum insulin levels and increased glucagon levels, however, there were no differences within epinephrine treated groups. Changes in phosphorylated AKT, AMPK, and phosphodiesterase 4B protein content, negative regulators of PKA signaling, do not explain the protective effects of exercise training against epinephrine induced increases in blood glucose and liver glycogen breakdown. Taken together our data suggest that prior exercise training reduces the liver’s response to epinephrine. This could be beneficial in the context of training‐induced sparing of glycogen during exercise. Support or Funding Information This work was funded, in part, through a National Sciences and Engineering Research Council of Canada (NSERC) grant to D.C.W., who is a Tier II Canada Research Chair in Lipids, Metabolism, and Health. H.A.D was supported by an Ontario Graduate Scholarship. G.L.M. was supported by an Ontario Graduate Scholarship and subsequently an NSERC Canada Graduate Scholarship. L.K.T. was supported by a Dairy Farmers of Ontario Doctoral Research Assistantship and an NSERC Postgraduate Scholarship.
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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) | 0.000 | 0.001 |
| Bibliometrics | 0.001 | 0.000 |
| Science and technology studies | 0.000 | 0.001 |
| Scholarly communication | 0.001 | 0.000 |
| Open science | 0.000 | 0.000 |
| Research integrity | 0.001 | 0.002 |
| Insufficient payload (model declined to judge) | 0.007 | 0.001 |
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".