Hormonal
Insulin promotes protein anabolism by inducing the transcription factor ATF4, which activates genes for amino acid uptake and synthesis, while glucocorticoids inhibit this pathway by repressing ATF4.
This research highlights that muscle building (anabolism) is actively regulated by hormones. Insulin promotes muscle growth by turning on specific genetic programs (ATF4) for amino acid handling, while stress hormones (glucocorticoids) shut these programs down. For practical application, this suggests that chronic stress or high cortisol levels can directly inhibit the molecular machinery required for muscle protein synthesis, independent of protein intake.
These studies identify ATF4 as an anabolic transcription factor that is repressed by glucocorticoids and induced by insulin.
Why this rating
The study uses multiple cell lines (L cells, MEF, myotubes), multiple methods (microarray, qPCR, immunoblot, RNAi), and demonstrates causality via knockdown and inhibition.
Source
Role of the Transcription Factor ATF4 in the Anabolic Actions of Insulin and the Anti-anabolic Actions of Glucocorticoids
Christopher M. Adams · Journal of Biological Chemistry · 2007
DOI 10.1074/jbc.m610510200
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