Elevated Mitochondrial Oxidative Stress Blunts Skeletal Muscle Adaptations to Endurance Exercise
Bibliographic record
Abstract
Reactive oxygen species (ROS) are implicated in the regulation of numerous cellular processes including tissue repair, cell cycle dynamics and mitochondrial biogenesis. ROS have been shown to increase during muscle contractions, however details concerning their cellular origin and the specific species produced have not been not fully clarified. A coincident rise in ATP demand during contractions make ETC-derived superoxide a likely source of exercise-induced ROS, however the chronic consequences of this form of cellular stress have not been evaluated. PURPOSE: To determine the mitochondrial effects of endurance exercise training in mice possessing normal and impaired abilities to metabolize the mitochondrial superoxide radical. METHODS: Six-month-old mice containing normal (MnSOD+/+) or decreased (MnSOD+/-) levels of MnSOD underwent four months of progressive endurance exercise (MnSOD+/+EX, N=10; MnSOD+/- EX, N=8) or remained sedentary (MnSOD+/+SED, N=10; MnSOD+/- SED, N=8). At 10 months of age, mice were tested for maximum aerobic capacity and sacrificed 1 week later. Markers of mitochondrial content and function were assessed within the tibialis anterior muscle. RESULTS: Maximal exercise performance (total distance run) was greater in MnSOD+/+EX vs. MnSOD+/+SED (439±39 vs. 306±24 meters, P0.05). Maximum oxygen consumption and cytochrome c oxidase (COX) protein content was higher in EX vs. SED within each genotype (VO2max, MnSOD+/+ and MnSOD+/- greater by 12 and 13%, respectively, P<0.05; COX protein, MnSOD+/+ and MnSOD+/- higher by 46 and 39%, respectively, P<0.05). CONCLUSIONS: Greater levels of mitochondrial superoxide result in an attenuation of maximal aerobic energy provision following exercise training, likely due to oxidative damage to mitochondrial enzymes. This work was supported by a grant from the Canadian Institutes of Health Research.
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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) | 0.001 | 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".