Regulation of Erythropoietin Expression in Response to Exercise in Mouse and Human Skeletal Muscle
Bibliographic record
Abstract
Erythropoietin (EPO) is the master regulator of erythropoiesis and also plays a role in cytoprotection, cell proliferation and heart contractility. In human skeletal muscle, EPO mRNA expression increases in response to acute exercise, however, whether glycolytic or oxidative muscle fibers differentially produce EPO is unknown. Thus, the purpose of this study was to examine EPO mRNA expression in oxidative and glycolytic muscles following acute exercise in mice. Further, we also examined whether training status had an effect on EPO expression. Experiment 1 involved young healthy men (age, 21.4 ± 2.8 years; VO 2 peak, 47.1 ± 11.8 mL min −1 kg −1 ) from a previously published study (Edgett et al. 2016) who performed a single bout of exercise at ~55% of peak aerobic work rate for 1 hour. Muscle biopsies were obtained from the vastus lateralis at rest and 3 hours post‐exercise. Experiment 2 involved 8 week‐old male C57/B6 mice that were either exercise‐trained by treadmill running (1 hour/day, 4 days/week) or remained sedentary (untrained) for 5 weeks. Following the intervention, all mice performed an exhaustive exercise bout that began at a speed of 12 m/min with a 20‐degree grade; speed was subsequently increased by 1 m/min at 2, 5, 10, 20, 30 and 40 min, or until mice reached exhaustion. Soleus (oxidative muscle) and extensor digitorum longus (EDL, glycolytic muscle) were harvested at 1, 2 and 4 hours post‐exercise. All samples were analyzed by real‐time qPCR for changes in EPO mRNA expression. In agreement with a previous report, EPO mRNA expression increased 14 ± 5% in human skeletal muscle 3 hours post‐exercise. In experiment 2, EPO expression increased 4.1 ± 2.8 and 7.4 ± 1.7 fold at 1 hour post‐exercise in the soleus muscle of untrained and trained mice, respectively, before returning towards baseline. In EDL, post‐exercise EPO expression increased 4.1 ± 1.0 fold by 2 hours and plateaued thereafter in only untrained mice; this response was blunted in trained mice. Here we show that EPO expression increased post‐exercise in both glycolytic and oxidative murine skeletal muscles; training had a fiber‐type‐specific differential effect in these muscles. Future studies should determine the physiological significance of skeletal muscle‐derived EPO. Support or Funding Information This study was supported by funding from the Natural Sciences and Engineering Research Council of Canada (NSERC) to B.A.E., K.R.B., B.J.G. and J.A.S.
Fetched live from OpenAlex and de-inverted. Abstracts are not stored in this database: the inverted indexes are 8.6 GB of the frame’s 9.3 GB of text, and the host has 13 GB free.
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 | 0.000 | 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) | 0.002 | 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".