Section 01
What it's used for
Early-stage muscle repair signal
Research shows MGF is essential for muscle regeneration after injury. It activates the muscle's stem-like repair cells (satellite cells) more strongly than mature IGF-1, suggesting a distinct role in the earliest repair phase.
▸Clinical wording
Research demonstrates MGF is essential for muscle regeneration following damage. It activates satellite cells more potently than mature IGF-1, suggesting a unique role in the early repair phase.
Heart repair after injury
MGF levels rise in heart tissue after blood-flow-related damage, suggesting a protective and regenerative role. In preclinical animal studies, it improved heart function after a simulated heart attack (myocardial infarction).
▸Clinical wording
MGF expression in cardiac tissue following ischemic damage suggests cardioprotective and regenerative roles. Preclinical studies show improved cardiac function post-myocardial infarction.
Tendon and bone repair signal
MGF is also produced in damaged tendons and bone tissue, suggesting it plays a role in repairing musculoskeletal injuries more broadly, not just muscle. This wider repair role remains an area of ongoing research.
▸Clinical wording
MGF is expressed in damaged tendons and bone, suggesting roles in musculoskeletal tissue repair beyond muscle.
Age-related muscle loss research
MGF production naturally declines with age, which may contribute to the reduced ability of older adults to regenerate muscle. Researchers are studying whether restoring MGF levels could address this age-related deficit.
▸Clinical wording
Age-related decline in MGF expression may contribute to impaired muscle regeneration in the elderly. MGF supplementation research addresses this deficit.
Section 02
Mechanism of Action
A damage-triggered rewrite of one gene
- One growth-factor gene can be read two ways, and a short insert produces a different tail end.
- In damaged rat muscle that version appeared quickly and then faded within days.
- The standard version rose later, in step with the fall of the first one.
- The early version appeared before the markers of muscle stem cell activation.
▸Clinical wording
Damage-triggered switch in IGF-1 gene splicing
The IGF-1 gene is alternatively spliced, and a 49 bp insert in humans (52 bp in rodents) shifts the reading frame to produce an isoform with a distinct C-terminal E domain, called IGF-1Ec in humans and IGF-1Eb or mechano growth factor in rodents. In rat tibialis anterior, damage from stretch combined with electrical stimulation or from bupivacaine injection raised the MGF transcript rapidly and then let it decline within days, while systemic IGF-1Ea rose later, in step with the fall in MGF. MGF expression preceded M-cadherin and MyoD, the markers of satellite cell activation, whereas IGF-1Ea peaked after them.
More muscle cells, later maturing
- In mouse muscle cell culture the fragment raised cell division while holding back final maturation.
- Blocking the usual growth-factor receptor did not stop it, so a different receptor was proposed.
- In human muscle cells it extended dividing lifespan in young donors but not in old ones.
▸Clinical wording
Satellite cell proliferation with delayed terminal differentiation
In C2C12 myoblast culture the isolated E domain increased proliferation while inhibiting terminal differentiation, the opposite balance to mature IGF-1; blocking the IGF-1 receptor with an antibody did not abolish the effect, which led the authors to propose a different receptor. In primary human myoblasts from donors of several ages, the synthetic 24-amino-acid E peptide extended proliferative lifespan and delayed replicative senescence in neonatal and young-adult cultures but not in old-adult ones, and it lowered the fraction of cells held back as reserve cells while raising fusion.
One signalling branch, not the other
- In muscle cell culture the peptide switched on one growth pathway but left a second one untouched.
- That response continued even when the usual growth-factor receptor was blocked.
- In human vessel-lining cells it raised growth, movement, tube formation and vessel-growth signals.
- Blocking the pathway with a chemical inhibitor removed the growth response entirely.
▸Clinical wording
ERK/MAPK signalling without Akt engagement
Synthetic MGF peptide has been reported to phosphorylate ERK but not Akt in myoblast culture, with the ERK response persisting when the IGF-1 receptor was blocked; full-length IGF-1, by contrast, engages ERK first and PI3K/Akt afterwards. In human EA.hy926 endothelial cells 10 ng/ml of the 24-amino-acid peptide raised proliferation, migration and tube formation and restored VEGF and angiopoietin-1 expression suppressed by serum starvation, and the MEK inhibitor PD98059 abolished the proliferation response and largely blocked migration.
Pulling stem cells toward a signal
- Human repair stem cells moved toward the fragment more strongly than toward the parent growth factor.
- Scrambling the sequence or changing one building block destroyed that pull, while cell numbers stayed flat.
- In rat marrow cells the same movement needed both a signalling enzyme and the growth-factor receptor.
- Mice engineered to overproduce it roughly doubled newly dividing cells in two brain regions.
▸Clinical wording
Chemotaxis of stem and progenitor cells
Human mesenchymal stem cells migrated toward an E-domain peptide analogue more strongly than toward IGF-1 over 20 h in culture; a scrambled sequence and a serine-to-alanine substitution near the carboxy end both lost the activity, while proliferation was unchanged. In rat bone marrow stromal cells the peptide likewise drove migration without proliferation, shifted expression away from osteogenic and toward adipogenic genes, and its migratory effect required both ERK1/2 and the IGF-1 receptor. Transgenic MGF overexpression roughly doubled BrdU-labelled cells in mouse dentate gyrus and subventricular zone.
Unclear target and failed repeats
- The full-length protein does activate the growth-factor receptor, but needs about nine times the concentration.
- The short synthetic fragment sold as this peptide activated that receptor at no concentration tested.
- No such natural short fragment has ever been isolated from tissue.
- Two pharmaceutical groups found no effect at all in three different muscle cell systems.
▸Clinical wording
Unresolved receptor identity and failed replications
Full-length MGF protein does activate the IGF-1 receptor: in kinase receptor activation assays it reached a maximum close to recombinant IGF-1 but needed roughly nine-fold higher concentrations, whereas the synthetic 24-amino-acid E peptides gave no receptor activation at any concentration tested. E peptides did not phosphorylate the receptor directly in myoblasts yet raised its cell-surface availability by about 40%, and their mitogenic and motogenic effects vanished under IGF-1R kinase or MEK blockade. No endogenous 24-amino-acid peptide has been isolated, and two pharmaceutical groups saw no effect of up to 500 ng/ml on C2C12 cells, primary human myoblasts or mouse muscle stem cells.
Section 03
Biological Pathways
- IGF-1 splice-variant inductionIn rat muscle, stretch or injury raises the C-terminal E-domain splice variant (MGF, IGF-1Ec) rapidly, preceding the satellite-cell activation markers MyoD and M-cadherin, ahead of a later systemic IGF-1Ea rise.
- ERK/MAPK proliferation without AktThe synthetic E-domain peptide phosphorylates ERK but not Akt; the ERK response persists under IGF-1 receptor blockade, driving proliferation while delaying differentiation and replicative senescence.
- Stem and progenitor cell chemotaxisMesenchymal and bone-marrow stromal cells migrate toward the E-domain peptide through ERK1/2 and the IGF-1 receptor, shifting marrow cells toward adipogenic over osteogenic genes without changing proliferation.
- Unresolved IGF-1 receptor engagementFull-length MGF activates the IGF-1 receptor at roughly nine-fold higher concentration than IGF-1, while the synthetic peptide shows no direct activation yet raises receptor surface availability by about 40%.
Section 04
Dosage Information
YQPPSTNKNTKSQRRKGSTFEEHK (24 amino acids, IGF-1Ec splice variant C-terminal peptide)| Route / system | Context | Range studied | Limitation |
|---|---|---|---|
| Intramuscular — rodent injury models | Mouse muscle-bruise study, the only live-animal dosing | 5 µg in 20 µl into each calf muscle right after the injury and again on days 1 and 2 — all of it inside one muscle of a 25 g mouse | MGF did not restore fibre regrowth there; only scarring fell. Micrograms placed inside one mouse muscle do not convert into a whole-body dose for a person. |
| Intramuscular — mouse gene transfer | A gene copy, not the peptide — source of the 25% figure | Not the peptide: the MGF gene injected once into a mouse muscle raised fibre thickness about 25% in two weeks | The muscle then made MGF itself for weeks. Injecting ready-made peptide copies neither that duration nor that place, so the 25% belongs to no microgram dose. |
| Subcutaneous or intramuscular | Circulating practice, no trial behind it | 200–400 µg 2–3 times weekly after training — roughly 2–6 µg/kg for a 70–90 kg adult | Rodent work injected the muscle itself; a dose under the skin is another experiment nobody ran. MGF breaks down fast in blood, and no half-life is published. |
| Human dosing — none at any route | No registered or published trial in people | No human dose exists. The only human material exposed to MGF is muscle cells in a dish; a 2014 repeat found nothing up to 500 ng/ml | The practice numbers were not scaled down from a human study — there is none. They were picked to resemble doses of other injectable peptides in the same shops. |
Results
Syringe Fill Level (100u syringe)
Set positive values for: Recommended dose per kg.
Research Use Only. This information is for educational and research purposes only. Not intended for medical advice or self-medication.
Section 05
Protocols
No protocols featuring this peptide yet. Browse All Protocols
Section 06
Stability & Storage
Lyophilised powder
MGF is supplied as a lyophilised powder and is kept at -20°C before use. It is usually reconstituted with bacteriostatic water.
After reconstitution
The reconstituted solution is kept at 2-8°C and used within 14 days. MGF degrades extremely quickly in serum, with a half-life of only minutes, which is one reason PEG-MGF was later developed for greater stability.
Section 07
Side Effects & Precautions
Limited human safety data. Injection site pain due to intramuscular administration. Theoretical hypoglycemia risk from IGF-1 receptor activation. Potential for uncontrolled cell proliferation. Most safety data is extrapolated from IGF-1 research.
Section 08
Regulatory Status
It remains a research peptide: no approved label, indication, dose or established human safety data exist for it.
FDA / United States
Not approved
Unlike its pegylated relative PEG-MGF, plain MGF has never been nominated for the 503A bulk-substances process; it is not on the 503A Bulks List either, so section 503A opens no lawful route to human use.
EU / EMA
Not approved
MGF has no EU marketing authorisation and does not appear among medicines evaluated by the CHMP.
WADA
Prohibited under S2
As an IGF-1 splice variant, MGF is named among the growth factors covered by category S2 (Peptide Hormones, Growth Factors and Related Substances) — banned at all times, in and out of competition, with no therapeutic-use exemption.
Clinical trials
No completed human trial exists
Published evidence is limited to animal and in-vitro models of muscle-satellite-cell activation; translation to human physiology, dosing or safety has not been demonstrated.
A «research use only» label does not turn MGF into an approved medicine and says nothing about its purity. Regulatory status differs between jurisdictions and changes over time — check the current documents of your own regulator before relying on any of this.
Section 09
Research Studies
- [1]Different roles of the IGF-I Ec peptide (MGF) and mature IGF-I in myoblast proliferation and differentiationYang SY, Goldspink G. · FEBS Letters · 2002
- [2]Expression and splicing of the insulin-like growth factor gene in rodent muscle is associated with muscle satellite (stem) cell activation following local tissue damageHill M, Goldspink G. · The Journal of Physiology · 2003
- [3]Muscle satellite (stem) cell activation during local tissue injury and repairHill M, Wernig A, Goldspink G. · Journal of Anatomy · 2003
- [4]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 agesKandalla PK, Goldspink G, Butler-Browne G, Mouly V. · Mechanisms of Ageing and Development · 2011
- [5]Minireview: Mechano-Growth Factor: A Putative Product of IGF-I Gene Expression Involved in Tissue Repair and RegenerationMatheny RW Jr, Nindl BC, Adamo ML. · Endocrinology · 2010
- [6]Insulin-Like Growth Factor-I E-Peptide Activity Is Dependent on the IGF-I ReceptorBrisson BK, Barton ER. · PLoS ONE · 2012
- [7]Potency of Full-Length MGF to Induce Maximal Activation of the IGF-I R Is Similar to Recombinant Human IGF-I at High Equimolar ConcentrationsJanssen JAMJL, Hofland LJ, Strasburger CJ, van den Dungen ESR, Thevis M. · PLoS ONE · 2016
- [8]Mechano-growth factor peptide, the COOH terminus of unprocessed insulin-like growth factor 1, has no apparent effect on myoblasts or primary muscle stem cellsFornaro M, Hinken AC, Needle S, et al. · American Journal of Physiology - Endocrinology and Metabolism · 2014
- [9]Migration and proliferation of human mesenchymal stem cells is stimulated by different regions of the mechano-growth factor prohormoneCollins JM, Goldspink PH, Russell B. · Journal of Molecular and Cellular Cardiology · 2010
- [10]Mechano growth factor E peptide regulates migration and differentiation of bone marrow mesenchymal stem cellsCui H, Yi Q, Feng J, Yang L, Tang L. · Journal of Molecular Endocrinology · 2014
- [11]New proangiogenic activity on vascular endothelial cells for C-terminal mechano growth factorDeng M, Wang Y, Zhang B, Liu P, Xiao H, Zhao J. · Acta Biochimica et Biophysica Sinica · 2012
- [12]Mechano growth factor, a splice variant of IGF-1, promotes neurogenesis in the aging mouse brainTang JJ, Podratz JL, Lange M, Scrable HJ, Jang MH, Windebank AJ. · Molecular Brain · 2017
- [13]Mechano-Growth Factor: an important cog or a loose screw in the repair machinery?Zablocka B, Goldspink PH, Goldspink G, Gorecki DC. · Frontiers in Endocrinology · 2012
Section 10
Frequently Asked Questions
The human evidence is limited to cell-culture studies, and it's inconsistent: some work found the isolated MGF peptide increased human myoblast proliferation and extended their lifespan, but a 2014 study specifically designed to test this found no apparent effect on myoblasts or primary muscle stem cells at concentrations up to 500 ng/mL. No injection trial in humans has ever been run.
Not from the peptide — from a mouse experiment where the MGF gene itself, not a peptide injection, was delivered into muscle tissue, and the muscle then produced MGF on its own for weeks. That raised muscle-fiber thickness by about 25% over two weeks. A microgram dose of premade peptide copies neither that sustained internal production nor that experiment's method, so the figure doesn't transfer to peptide injections.
No human dose exists in the research record at all — the only human exposure on file is muscle cells in a dish. The 200 to 400 µg, two to three times weekly figures that circulate were not scaled down from any human study; they were set to resemble dosing patterns of other injectable peptides sold by the same suppliers.
The sourced material covers this only briefly: native MGF breaks down in serum within minutes, and PEG-MGF was developed afterward specifically for greater stability. Beyond that stability rationale, no efficacy or safety data for either form in humans is included in this record.
Human safety data is essentially absent — what's cited is mostly extrapolated from IGF-1 research generally, not measured for MGF itself. Documented concerns include injection-site pain from intramuscular administration, a theoretical hypoglycemia risk from IGF-1 receptor activation, and a theoretical risk of uncontrolled cell proliferation given its growth-factor nature.
As a lyophilized powder it's kept at −20°C before use. Once reconstituted with bacteriostatic water, it's kept at 2–8°C and used within 14 days — though inside the body it degrades within minutes, since its half-life in serum is only that long.
It isn't FDA-approved and is classified as a research compound. WADA prohibits it under category S2 (growth factors) as a splice variant of IGF-1, banned both in and out of competition.