Anabolic resistance: the effects of aging, sexual dimorphism, and immobilization on human muscle protein turnoverThis paper is one of a selection of papers published in this Special Issue, entitled 14th International Biochemistry of Exercise Conference – Muscles as Molecular and Metabolic Machines, and has undergone the Journal’s usual peer review process.
Bibliographic record
Abstract
In healthy active older persons, there is no derangement of muscle protein metabolism. However, there is a major deficit in the ability of older muscles to regulate their maintenance during feeding and exercise. The dose-response relationship between myofibrillar protein synthesis and the availability of essential amino acids (EAA) is shifted down and to the right, and giving extra amino acids is unable to overcome this. There is no sex difference in basal or fed muscle protein metabolism in the young, but postmenopausal women have a greater anabolic resistance than older men. Anabolic resistance is also shown by the decreased phosphorylation in the PKB-mTOR-eIF4BP1 pathway in response to increased EAA. The muscle synthetic system is refractory to EAA provision, irrespective of the availability of insulin, insulin-like growth factor 1, and growth hormone. However, insulin is a major regulator of muscle protein breakdown, and there is a blunting of the ability of older muscle to decrease proteolysis in response to low concentrations of insulin, such as those observed after a light breakfast. Providing more EAA seems not to be useful, and modern N-balance data confirm that the dietary protein requirements of older persons are not increased. The sigmoidal dose-response relationship between muscle protein synthesis and resistance exercise intensity is shifted downward and to the right in older men. Decreased physical activity itself, even in young subjects, can produce anabolic resistance of muscle protein synthesis, which cannot be overcome by increasing amino acid availability. Exercise may retune the amino acid and (or) insulin sensitivity of muscle in older people.
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 | 0.001 | 0.001 |
| 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".