Research
Hormonal
FoxO transcription factors promote muscle atrophy by upregulating ubiquitin ligases (atrogin-1/MAFbx and MuRF1) and autophagy genes.
FoxO factors are responsible for breaking down muscle protein. They are inhibited by the IGF1-Akt pathway (activated by training). When Akt is low (e.g., during inactivity or starvation), FoxO is active, leading to muscle loss. To prevent this, maintain resistance training and adequate protein intake.
GoodRefutesHIGH confidence
FoxO factors are required for the transcriptional regulation of the ubiquitin ligases atrogin-1, also called muscle atrophy F-box (MAFbx) and muscle ring finger 1 (MuRF1), leading to the ubiquitylation of myosin and other muscle proteins... and their degradation via the proteasome.
Why this rating
Supported by transfection experiments and knockout models in mice.
Source
Regulation of skeletal muscle growth by the IGF1-Akt/PKB pathway: insights from genetic models
Stefano Schiaffino et al. · Skeletal Muscle · 2011
DOI 10.1186/2044-5040-1-4
narrative_reviewCited 804×
Read the paper DOI resolved against Crossref · corpus check 2026-06-10
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- Activation of the IGF1-Akt/PKB pathway in skeletal muscle drives hypertrophy by simultaneously stimulating protein synthesis via mTOR and inhibiting protein degradation via FoxO transcription factors.Strong
- Blocking myostatin signaling prevents muscle wasting and induces hypertrophy in adult skeletal muscle.Good
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