PEG-MGF

PEG-MGF is a PEGylated synthetic peptide based on the E-peptide of mechano growth factor, a splice variant of insulin-like growth factor 1. The PEGylated form itself has little published characterization and no human evidence.

Last reviewed 2026-10-25 by the PeptideWiki editorial team. Editorial policy.

Overview

Mechano growth factor (MGF) is the name given to a splice variant of the insulin-like growth factor 1 (IGF-1) gene that is expressed in skeletal muscle in response to mechanical loading or damage. In humans this variant is known as IGF-1Ec, and its rodent counterpart as IGF-1Eb. The variants share the mature IGF-1 sequence but differ in the C-terminal E-peptide, a region normally cleaved from the precursor. Research interest has centered on the distinct E-peptide of MGF, which some studies suggested has activity of its own.

PEG-MGF refers to a synthetic peptide based on the MGF E-peptide to which a polyethylene glycol (PEG) chain has been attached, intended to slow clearance. There is very little peer-reviewed literature characterizing PEG-MGF specifically: its exact sequence, PEG size and attachment site are not standardized across sources. Most published MGF research uses native or modified E-peptides in cells and animals, and there are no human trials.

Structure

The MGF E-peptide is the C-terminal extension unique to the IGF-1Ec (human) or IGF-1Eb (rodent) precursor, produced by alternative splicing that includes an insert from exon 5. Synthetic MGF peptides used in research typically correspond to a C-terminal portion of this E-domain of around 24 residues, sometimes with D-amino acid or other substitutions to slow degradation. PEG-MGF adds a polyethylene glycol chain, but the polymer length, attachment chemistry and position are not consistently defined in the literature. Because PEG is polydisperse, the product is a distribution of masses rather than a single defined molecule.

Mechanism

Native IGF-1 acts through the IGF-1 receptor to promote growth and anabolic signaling. The MGF E-peptide was proposed by some investigators to have separate activity, including stimulating proliferation of muscle precursor (satellite) cells and protecting cells from injury, possibly independent of the IGF-1 receptor. A specific receptor for the E-peptide has not been identified.

Findings on E-peptide activity are not consistent across laboratories, and some studies found little effect of synthetic MGF peptides on muscle cells. The mechanism of PEG-MGF has not been specifically studied in detail; any activity is assumed to derive from the attached E-peptide, with PEGylation intended to extend persistence. These assumptions have not been validated in published characterization studies.

Research

Discovery of MGF in loaded muscle

MGF was described in the 1990s by researchers studying gene expression in skeletal muscle subjected to stretch and exercise. They identified an IGF-1 splice variant whose expression increased rapidly after mechanical loading or damage and named it mechano growth factor. Subsequent work in rodents and humans examined its expression after exercise, injury and aging, often using messenger RNA measurements. These studies describe a gene expression response rather than effects of administered peptide.

Synthetic E-peptide studies

Cell-culture studies tested synthetic MGF E-peptides on myoblasts, cardiomyocytes, neurons and other cell types, with some reporting increased proliferation or survival. Animal studies examined injected E-peptides in models of muscle injury, cardiac ischemia and neural damage. Results have been mixed, and independent studies have questioned whether synthetic E-peptides reproduce the reported effects. Most of this work does not involve PEGylated forms.

PEGylated forms

Published peer-reviewed data on PEG-MGF specifically are sparse. A small number of animal studies have used PEGylated MGF peptides, but formulations differ and characterization is limited. Without standardized structure and pharmacokinetic data, results with one PEG-MGF preparation cannot be assumed to apply to another. PEG-MGF should be regarded as a poorly characterized research material. Researchers should be cautious about attributing results to a defined molecule.

Evidence quality

The MGF field combines a well-documented splice variant with uncertain and contested evidence about the activity of its isolated E-peptide. For PEG-MGF there is almost no characterization, no human data and no safety assessment. Claims about this material extend far beyond what has been published, and it should be treated as preclinical and poorly defined. Any use should be framed as exploratory laboratory research, with careful characterization of the material itself.

Regulatory status

PEG-MGF is not approved by the FDA for any use, and it is not a recognized substance for US pharmacy compounding. There are no human clinical trials of PEG-MGF. WADA prohibits mechano growth factors, including MGF and PEGylated forms, at all times under class S2.

Status changes often. See the regulatory tracker for dated updates.

Quality and identity testing

PEG-MGF is difficult to characterize, and a certificate of analysis should state the exact peptide sequence, PEG molecular weight, attachment site and chemistry. Because PEG is polydisperse, mass spectrometry shows a distribution of masses rather than a single peak; MALDI-TOF is typically used, and the expected mass on this page applies only to the peptide portion. Free (un-PEGylated) peptide, multiply PEGylated species and free PEG should be quantified, often by size-exclusion or reverse-phase HPLC. Identity of the peptide portion should be confirmed, for example by analysis after cleavage or by peptide mapping. Net peptide content is particularly important because PEG contributes much of the mass.

For a walkthrough of each section of a certificate, see how to read a COA.

Storage and stability

Store lyophilized PEG-MGF sealed at -20 °C or colder, protected from light and moisture, and allow vials to reach room temperature before opening. PEG chains can undergo oxidative degradation, and PEGylated material can be hygroscopic, so tight sealing is important. Prepare solutions in sterile water or buffer for lab use, keep them refrigerated for short-term work, aliquot for longer storage, and avoid repeated freeze-thaw cycles. Supplier-specific stability data are rarely available, which adds to uncertainty.

Download the PEG-MGF data sheet (PDF): sequence, masses, expected MS ions and handling on one printable page.

Latest research

Frequently asked questions

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References

1. Yang S, Alnaqeeb M, Simpson H, Goldspink G Cloning and characterization of an IGF-1 isoform expressed in skeletal muscle subjected to stretch. J Muscle Res Cell Motil. 1996. Find on PubMed
2. PubMed: all indexed literature on PEG-MGF
3. ClinicalTrials.gov: registered studies mentioning PEG-MGF