Adiponectin is sufficient, but not required, for exercise‐induced increases in the expression of skeletal muscle mitochondrial enzymes
Bibliographic record
Abstract
Key points Adiponectin is a regulator of skeletal muscle mitochondrial biogenesis. Previous research using the ob/ob mouse (leptin deficient, low adiponectin) has suggested that the presence of adipokines, including adiponectin, is necessary for exercise‐induced increases in mitochondrial content. In the current study, we examined the importance of adiponectin as a regulator of skeletal muscle mitochondrial content in response to exercise by comparing wildtype and adiponectin deficient mice. Adiponectin deficient mice showed no differences in resting , RER, or time to exhaustion during exercise when compared to wildtype mice. There were no differences in various protein markers of mitochondrial content. A single bout of treadmill running increased the mRNA expression of mitochondrial proteins similarly in wildtype and adiponectin deficient mice. Chronic exercise (8 weeks) also increased the protein content of mitochondrial markers similarly in wildtype and adiponectin deficient mice. We conclude that Ad is not required for exercise‐induced increases in muscle mitochondrial proteins. Abstract Adiponectin (Ad) has been proposed to be a regulator of mitochondrial biogenesis in skeletal muscle, and necessary for exercise‐induced increases in mitochondrial content. We first confirmed that Ad could acutely increase the expression of mitochondrial proteins during a 10 h incubation in isolated soleus and extensor digitorum longus (EDL) muscles. Next, we further examined the role of Ad as a regulator of mitochondrial content using Ad knockout (AdKO) mice. The AdKO animals showed no differences in resting , respiratory exchange ratio, or in time to exhaustion during exercise when compared to wild‐type (WT) mice. There was a reduction in resting palmitate oxidation in isolated soleus from AdKO animals (−23%, P < 0.05) but not EDL, and 5‐aminoimidazole‐4‐carboxamide (AICAR)‐stimulated palmitate oxidation was similar in both genotypes regardless of muscle. There were no differences in protein markers of mitochondrial content (COX4, CORE1, CS, PDHE1α) in red and white gastrocnemius between WT and AdKO animals. A single bout of treadmill running increased the phosphorylation of AMP‐activated protein kinase (AMPK) and the mRNA expression of mitochondrial proteins in red and white gastrocnemius in both WT and AdKO animals, with no differences between genotypes. Finally, 8 weeks of chronic exercise training increased the protein content of mitochondrial markers similarly (∼25–35%) in red gastrocnemius from both WT and AdKO mice. Collectively, our results demonstrate that the absence of Ad is not accompanied by reductions in mitochondrial protein content, or a reduction in aerobic exercise capacity. We conclude that Ad is not required for the maintenance of mitochondrial content, or for exercise‐induced increases in skeletal muscle mitochondrial proteins.
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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 | 0.001 |
| 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".