💪 IGF-1 Splice Variant • Muscle Regeneration

MGF (Mechano Growth Factor)

Locally acting splice variant of IGF-1 (human IGF-1Ec) upregulated by mechanical stress and tissue injury to prime regeneration by activating muscle satellite cells.

Length 24 aa (E-domain) MW ~2,847 Da Family IGF-1 Variant

⚡ Executive Summary

MGF (Mechano Growth Factor) is an IGF-1 splice variant (IGF-1Ec) that rises locally after mechanical stress to “prime” tissue regeneration by expanding progenitor cells, especially muscle satellite cells. In humans, MGF increases within hours after resistance exercise — an effect blunted with aging. It differs mechanistically and temporally from systemic IGF-1. Evidence remains preclinical and mixed. WADA prohibited (S2).

🚫

WADA Prohibited: MGF and IGF-1 (and analogs) are on the WADA Prohibited List (S2). Athletes subject to anti-doping rules should not use MGF in any form.

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01 Overview 02 Properties 03 Mechanism 04 Evidence 05 Handling 06 Comparison 📋

Overview

💪 What is MGF?

MGF is an alternative splice variant of the IGF-1 gene that encodes a distinct C-terminal E-domain (Ec in humans, Eb in rodents).

Mechanical overload and injury shift IGF-1 splicing toward this variant in the affected tissue, creating a local, rapid response to stress.

🎯 Key Actions

• 🔄 Progenitor expansion — activates satellite cells
• ⚡ Rapid response — rises within 2–3 hours
• 📍 Local action — autocrine/paracrine signaling

⏱️ Prime-Then-Build Model

MGF acts as an early, local “primer” for regeneration. It expands the progenitor cell pool (more cells to repair) while delaying differentiation. This “prime-then-build” sequence aligns with observed kinetics: early MGF → later IGF-1Ea for differentiation and tissue rebuilding.

0–3h

MGF Surge

Rapid local response

3–24h

Proliferation

Satellite cell expansion

24h+

IGF-1Ea Rise

Differentiation begins

⚠️

Research only: MGF is a research peptide with no approved human therapeutic indications. Evidence is preclinical and mixed — some studies report null effects of synthetic MGF on muscle cells.

🔬

Entity Properties

Aliases	Mechano Growth Factor (MGF), IGF-1Ec (human), IGF-1Eb (rodent)
E-Domain Sequence	YQPPSTNKNTKSQRRKGSTFEEHK
Length	24 amino acids (E-domain peptide)
Molecular Weight	~2,847 Da
CAS Number	Not assigned for 24-aa research peptide
Family	Alternative splice variant of IGF-1; GH/IGF axis
Diluent(s)	Sterile saline or buffered saline
In Vitro Conc.	10–100 nM (typical range for E-peptide studies)
In Vivo Dose	~4.5 mg/kg/day continuous infusion (mouse MI models)
Storage	Lyophilized: cold & dry, protected from light. Solutions: minimize bench time, aliquot
Half-Life	~20 min in media (E-peptide is labile)

📝

Naming note: You may see “IGF-1Eb/Ec,” “MGF-E,” or “MGF-24aa-E.” We use MGF (IGF-1Ec) for human and MGF E-domain peptide for the 24-amino-acid synthetic research fragment.

⚙️

Mechanism of Action

🧠 How does MGF work?

MGF acts as an early, local signal that cooperates with (not replaces) IGF-1. It amplifies pro-proliferative cascades early so differentiation and tissue rebuilding can proceed later.

The MGF E-domain peptide increases proliferation and delays differentiation of human muscle progenitors in vitro — conceptually supplying more building blocks for later regeneration.

🔄 Progenitor Expansion

Activates satellite cells and other progenitors; delays differentiation to expand the repair cell pool

📡 MAPK/ERK Signaling

E-peptide activity often modulates IGF-1R toward MAPK/ERK (not AKT) in myoblasts

📍 Local Action

Produced and acts locally (autocrine/paracrine) after load/injury — distinct from systemic IGF-1

💡

Receptor debate: MGF’s receptor story is mixed. Some studies show E-peptide actions require or modulate IGF-1R; others describe IGF-1R-independent effects in neural models. Full-length IGF-1Ec can activate IGF-1R at higher concentrations.

📊

Research Evidence

🔬 Key Preclinical Findings

💪

Skeletal Muscle (Human)

MGF mRNA rises ~2.5h post-exercise in young adults; blunted response in older adults — a factor in age-related recovery

🧫

Cell Studies

MGF E-peptide increases proliferation and fusion potential of human muscle progenitors in vitro

❤️

Cardiac (Mouse MI)

Stabilized MGF E-peptide preserved cardiac function and delayed decompensation after myocardial infarction

🧠

Neuroprotection

MGF C-terminal peptide showed strong neuroprotection in ischemia models without classical IGF-1 behavior

🔁

Regeneration Timing

IGF-1 isoforms change over time: MGF/Ec early phases → IGF-1Ea later as fibers mature

⚠️

Mixed Results

Some studies found no effect of synthetic MGF on myoblast proliferation — model/peptide sensitivity matters

⚠️

Evidence grade: Most results are preclinical (cells/rodents/large animals). Human therapeutic evidence is absent, and synthetic peptides used can differ (sequence length, modifications), affecting outcomes. Balance enthusiasm with skepticism.

🧪

Research Handling

📘

Research use only. Design around MGF’s short-lived, local biology: choose models, dosing windows, and endpoints that capture early proliferative effects and later differentiation separately.

📊 Dosing Reference

• 🧫 In vitro: 10–100 nM E-peptide range
• 🐭 In vivo: ~4.5 mg/kg/day continuous infusion
• ⏱️ Timing: Sample early (hours) for proliferation

⚗️ Stability Considerations

• ⏳ Half-life: ~20 min in media (E-peptide is labile)
• ❄️ Storage: Lyophilized cold/dry; fresh aliquots
• 🔬 Modifications: D-Arg substitutions may stabilize

📋 Research Checklist

• ✓ Verify sequence (YQPPSTNKNTKSQRRKGSTFEEHK) and purity (HPLC/MS)
• ✓ Choose form: full-length pro-IGF-1Ec vs 24-aa E-domain peptide
• ✓ Include vehicle and IGF-1 comparator controls
• ✓ Time sampling to capture early proliferation AND later differentiation
• ✓ Plan readouts: Ki-67, satellite cell counts, MAPK/ERK, Myogenin, MyHC

⚖️

Comparison

MGF is a local, short-window primer; IGF-1 is a systemic builder; PEG-MGF seeks longer exposure via chemistry, but direct clinical data are lacking.

MGF

IGF-1Ec / E-domain 🔄 Local Primer

Early, local response to load/injury. Expands progenitor pools. Short-lived (~20 min half-life). Receptor behavior mixed.

IGF-1

Mature 70-aa hormone 📈 Systemic Builder

Endocrine/paracrine growth factor. Drives differentiation and anabolic signaling broadly. Well-characterized IGF-1R binding.

PEG-MGF

Pegylated analog ⏳ Extended Exposure

Designed to prolong MGF exposure via PEGylation. Preclinical rationale. No standardized human PK/efficacy data.

💡

Key distinction: MGF “primes” regeneration with a short, local signal that likely cooperates with IGF-1 — amplifying pro-proliferative cascades early so differentiation can proceed later.

❓

FAQ

What is MGF? An IGF-1 splice variant (IGF-1Ec) that rises locally after mechanical stress to prime tissue repair by expanding progenitor cells, especially muscle satellite cells. Distinct from circulating IGF-1. Is MGF the same as IGF-1? No. MGF is a locally acting splice variant with a unique E-domain. IGF-1 is systemic and drives differentiation/growth, whereas MGF surges early, locally, and emphasizes progenitor expansion. Does MGF act through IGF-1R? Mixed evidence. Several studies show E-peptide actions require or modulate IGF-1R; others describe IGF-1R-independent effects. Full-length IGF-1Ec can ligate IGF-1R at higher concentrations. Is MGF banned in sports? Yes. MGF and IGF-1 (and analogs) are on the WADA Prohibited List (S2). Athletes subject to anti-doping rules should not use MGF in any form. How stable is MGF? E-peptides degrade quickly — full-length EB half-life ~20 min in vitro. Many studies use stabilized analogs or delivery systems. Store lyophilized peptide cold/dry and limit time in solution. What is PEG-MGF? A pegylated MGF analog designed to extend exposure by slowing clearance. Concept supported by PEG literature, but no standardized human PK/efficacy data for PEG-MGF exists. ✅

Bottom line: MGF appears to “prime” regeneration (especially in muscle) with a short, local signal that cooperates with IGF-1 — amplifying pro-proliferative cascades early so differentiation and tissue rebuilding can proceed later. Evidence is preclinical and mixed; translating this into therapy will require standardized peptides, delivery methods, and human trials.