MGF

MGF (Mechano Growth Factor) is a splice variant of insulin-like growth factor 1 (IGF-1) generated in mechanically stressed muscle tissue (exercise, loading, injury). The full-length MGF transcript (IGF-1Ec) is produced by alternative splicing of the IGF-1 gene; its C-terminal E-domain encodes a unique 24-amino acid peptide that is proteolytically cleaved to act independently of the IGF-1 receptor. The sequence listed above is the MGF E-domain C-terminal peptide — the form sold by research peptide vendors.

MGF differs from mature IGF-1 in two key respects: it is locally produced in mechanically stressed tissue (not systemically circulated like liver-derived IGF-1), and the E-domain peptide activates satellite cells (muscle stem cells) through a receptor distinct from IGF-1R. This local, mechanosensitive satellite cell activation mechanism is proposed as a critical step in muscle repair and hypertrophy that declines with aging.

MGF is WADA-monitored (detected in anti-doping testing) and has no approved therapeutic indication.

The MGF E-domain peptide (the C-terminal 24 amino acids, Tyr-Gln-Pro-Pro-...) activates a receptor distinct from IGF-1R on satellite cells (muscle stem cells). This receptor engagement drives satellite cell proliferation — the expansion of the muscle progenitor pool necessary for muscle fiber repair after injury and adaptation to resistance exercise.

The full-length MGF transcript also contains the mature IGF-1 domain (which eventually acts through IGF-1R), but the E-domain peptide's activity is additive to and mechanistically distinct from canonical IGF-1 signaling. In ALS models, MGF E-domain provides superior motoneuron rescue compared to mature IGF-1, confirming that E-domain pharmacology extends beyond muscle to neuronal targets.

The plasma half-life of unmodified MGF E-domain peptide is approximately 5–10 minutes due to rapid proteolytic degradation — the primary limitation of the unmodified peptide as a therapeutic agent. PEG-MGF was developed to address this limitation.