MGF
MGF (mechano growth factor, also known as IGF-1Ec) is an alternatively-spliced isoform of the IGF-1 gene that is transiently upregulated in skeletal muscle after mechanical loading or exercise-induced damage, studied mainly through endogenous mRNA expression research and in-vitro cell assays rather than trials of injected synthetic peptide.
This page is a research-orientation summary, not a dosing guide. For anything beyond general background, read the primary literature or talk to a qualified clinician — specifics like amount, frequency, or administration aren't something we publish here.
What it does & how it works
MGF arises from alternative splicing of the IGF-1 gene, producing a transcript with a distinct C-terminal 'E domain' (Ec in humans, Eb in rodents) absent from the systemic, liver-derived IGF-1Ea isoform. Some in-vitro work suggests the MGF/E-domain peptide can act at least partly independently of the IGF-1 receptor, with proposed roles in activating satellite (muscle stem) cells to proliferate before they differentiate and fuse into muscle fibers. Its expression is induced locally and transiently by mechanical stretch or exercise-induced microtrauma, distinguishing its proposed role from the more systemic, endocrine action of IGF-1Ea.
Typical results seen in research
Human resistance-exercise studies show a significant rise in muscle MGF mRNA in young adults within hours after high-resistance training, an increase that was blunted in older adults in at least one comparative study — this demonstrates an endogenous expression response to loading, not the effect of injecting synthetic MGF peptide. Separate in-vitro work using a synthetic 24-amino-acid MGF C-terminal (E) peptide applied to cultured human muscle progenitor cells showed it stimulated their proliferation and altered subsequent fusion potential. No controlled human or animal trials have tested injected synthetic MGF peptide for muscle hypertrophy, recovery, or strength outcomes.
How it’s commonly used
In research settings, synthetic MGF (E-domain) peptide has been administered via injection, generally intramuscular or subcutaneous near the muscle of interest, reflecting its proposed local, tissue-specific mode of action; it is not taken orally, as it would be degraded by digestive proteolysis.
- The Journal of Physiology · 2003 Expression of IGF-I splice variants in young and old human skeletal muscle after high resistance exercise
- Physiology (Bethesda) · 2005 Mechanical signals, IGF-I gene splicing, and muscle adaptation
- The Journal of Physiology · 1999 Expression of insulin growth factor-1 splice variants and structural genes in rabbit skeletal muscle induced by stretch and stimulation
- Mechanisms of Ageing and Development · 2011 Mechano Growth Factor E peptide (MGF-E), derived from an isoform of IGF-1, activates human muscle progenitor cells and induces an increase in their fusion potential at different ages
Curated from published literature for research orientation. Not an exhaustive review, and not a substitute for reading primary sources.