Effects of short-term energy deficit on muscle protein breakdown and intramuscular proteolysis in normal-weight young adults
Bibliographic record
Abstract
The effects of short-term energy deficit (ED) on direct measures of muscle proteolysis and the intracellular mechanisms by which muscle proteins are degraded at rest and following aerobic exercise are not well described. This study evaluated the effects of a short-term diet-induced ED, on muscle fractional breakdown rate (FBR), intramuscular 26S proteasome activity, caspase-3 activation, and PSMA2 and MAFbx expression at rest, in the postabsorptive state, and following a single bout of moderate aerobic exercise (45 min at 65% peak oxygen uptake). Six men and 4 women participated in two 10-day diet interventions: weight maintenance (WM) followed by ED (80% estimated energy requirements). Dietary protein (1.5 g·kg(-1)·day(-1)) intake was constant for WM and ED. Mixed muscle FBR, proteasome activity, and intracellular proteolytic factor expression were measured using stable isotope methodology, fluorescent enzyme activity assays, and Western blotting, respectively. Overall, FBR and caspase-3 activation increased 60% and 11%, respectively, in response to ED (P < 0.05), but were not influenced by exercise. During ED, 26S proteasome α-subunit PSMA2 expression was 25% higher (P < 0.05) after exercise compared with rest. Exercise did not influence PSMA2 expression during WM, and MAFbx expression and 26S proteasome activity were not affected by ED or exercise. These data illustrate the effects of short-term, moderate ED on muscle protein degradation. In the context of skeletal muscle integrity during weight loss interventions, this work demonstrates a need for further investigations aimed at mitigating muscle loss associated with energy deficit imposed for intentional reduction of total body weight.
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How this classification was reachedexpand
Full frame distilled prediction
Teacher imitationNot calibrated prevalence, not ground truth. Human validation pending. Learned from the 10,348 direct Codex labels and 10,348 direct Gemma labels. Candidate is the union of thresholded teacher heads; consensus is their intersection. These outputs are machine_predicted_unvalidated and are not human labels or direct frontier model labels.
Codex and Gemma teacher scores by category
| 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) | 0.000 | 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 teacher head, 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".