PEG-MGF

Overview

PEG-MGF is the pegylated form of Mechano Growth Factor (MGF), the distinct 24-amino-acid C-terminal E-peptide encoded by the IGF-1Ec splice variant (IGF-1Eb in rodents) that is transiently upregulated in muscle after mechanical loading or damage. MGF is related to but pharmacologically distinct from mature IGF-1 and IGF-1 LR3. Pegylation extends its half-life from minutes to several hours, and the compound is marketed as a research chemical for muscle repair protocols. It is not FDA-approved for any indication.

Mechanism of Action

The MGF E-peptide acts locally on muscle satellite (stem) cells, promoting their proliferation and delaying terminal differentiation, which expands the progenitor pool available for fusion into damaged myofibers. Receptor-blocking studies by Yang & Goldspink (2002) indicated that the E-peptide acts through a receptor distinct from the classical IGF-1R, although the exact receptor remains unconfirmed — this is one reason MGF is mechanistically separable from mature IGF-1 or IGF-1 LR3. Conjugation of polyethylene glycol to the peptide reduces renal clearance and proteolysis, extending plasma half-life from minutes (native MGF) to several hours.

Research Summary

Evidence is almost entirely preclinical: recombinant MGF and the MGF-24aa E-peptide promote satellite cell activation in rodent and porcine muscle and in human myoblast cultures (Yang & Goldspink 2002; Kandalla et al. 2011; Qin et al. 2012). Reviews (Matheny et al. 2010; Zabłocka et al. 2012) note that pegylated and stabilized MGF analogs extend in vivo activity but that the signaling receptor, pharmacokinetics in humans, and long-term safety remain poorly characterized. There are no published randomized controlled human trials of PEG-MGF. MGF and all IGF-1 analogs are explicitly prohibited at all times under the WADA Prohibited List (S2: Peptide Hormones, Growth Factors and Related Substances).

Dosing Information

Reported Side Effects

• Injection-site pain, erythema, or swelling
• Localized muscle soreness
• Theoretical mild hypoglycemia (minimal with localized dosing due to MGF's local rather than systemic IGF-1R activity)
• Unknown long-term effects — no human safety data

Research References

• Different roles of the IGF-I Ec peptide (MGF) and mature IGF-I in myoblast proliferation and differentiation (Yang & Goldspink, FEBS Lett 2002) (2002)
• Mechano Growth Factor E peptide (MGF-E) activates human muscle progenitor cells and increases their fusion potential at different ages (Kandalla et al., Mech Ageing Dev 2011) (2011)
• Minireview: Mechano-growth factor: a putative product of IGF-I gene expression involved in tissue repair and regeneration (Matheny et al., Endocrinology 2010) (2010)
• Mechano-Growth Factor: an important cog or a loose screw in the repair machinery? (Zabłocka et al., Front Endocrinol 2012) (2012)
• MGF promotes proliferation and inhibits differentiation of porcine satellite cells by down-regulation of key myogenic transcription factors (Qin et al., Mol Cell Biochem 2012) (2012)