Rapid Upregulation of GLUT 4 and MCT 4 Expression During 16 Hours of Heavy Intermittent Exercise
Bibliographic record
Abstract
PURPOSE: To investigate the repetition-dependent effects of heavy exercise on the expression of glucose and lactate transporters in working skeletal muscle. METHODS: Glucose (GLUT 1, GLUT 4) and lactate (MCT 1, MCT 4) transporter expression were assessed in vastus lateralis using Western blot analyses in response to a 16 hour protocol of intermittent exercise involving 6 min of cycle exercise performed at ∼90% peak aerobic power (VO2peak) once per hour. Participants were 12 untrained volunteers (VO2peak=44.3±0.66 ml.kg-1.min-1, mean±SE) with average age of 21.8±0.86 yr and body mass of 70.2±3.6 kg. Tissue samples were obtained at rest prior to exercise at repetition one (R1), 2 (R2), 9 (R9) and 16 (R16). RESULTS: When compared to R1 (100±15%), GLUT 4 was observed to increase (P<0.05) at R2 (128±24%) and to remain elevated (P<0.05) at R9 (152±27%) and R16 (131±25%). For MCT 4, higher (P<0.05) contents were observed at R9 (124±22%) and R16 (128±19%) compared to R1 (100±13%) and R2 (118±20%). No relative changes (%) were observed in GLUT 1 (117±25, 104±13 and 103±12) or MCT 1 (120±17, 105±12, 109±15) at R2, R9 and R10, respectively. The cycle exercise resulted in up to a 24 fold increase in muscle lactate. CONCLUSIONS: These results demonstrate that if appropriately stimulated rapid increases can be induced in both GLUT 4 and MCT 4 in contracting muscle. The stimulating effect probably relates to the demands for large effluxes of lactate and large influxes of glucose given the glycolytic demands of the task. Supported by Natural Sciences and Engineering Council of Canada
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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 | 0.000 | 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 | 0.000 |
| 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".