Side-by-side · Research reference

Follistatin-344vsLL-37

Side-by-side comparison across mechanism, dosage, evidence, side effects, administration, and stack synergies. Citations on every claim where available.

AHuman-MechanisticHUMAN-REVIEWED4/58 cited

BHuman-MechanisticHUMAN-REVIEWED15/35 cited

Follistatin-344

Myostatin/Activin Antagonist · Research Use

15–25%FST/MSTN ratio ↑

344 AACirculating isoform

ResearchPhase status

Research · No approved protocol

LL-37

Cathelicidin · Human AMP

Broad-spectrumAntimicrobial activity

Membrane disruptionPrimary mechanismLu 2026 He 2026

Innate immunityHost defense rolePinheiro 2026 Zhang 2026

Endogenous · Secreted at inflammation sites

01Mechanism of Action

Parameter

Follistatin-344

LL-37

Primary target

Myostatin (MSTN/GDF-8) and Activin A

Bacterial membranes · Phosphatidylserine-exposed cellsHe 2026 Lu 2026

Pathway

FST-344 binds MSTN/Activin → prevents ActRIIB receptor engagement → disinhibits muscle anabolism

hCAP-18 precursor → Proteinase-3 cleavage → LL-37 release → Membrane insertion/disruption

Downstream effect

Elevated follistatin/myostatin ratio, increased muscle protein synthesis, attenuated muscle atrophy signalingJeong 2026

Membrane permeabilization, cytokine induction, autophagy, phagosome-lysosome fusion, chemotaxisAhmad 2026 Zhang 2026

Feedback intact?

Yes — indirect antagonist, preserves endogenous regulation

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Origin

Endogenous glycoprotein, 344-AA isoform lacking heparin-binding domain (vs FST-315)

Endogenous human cathelicidin (37-AA fragment, residues 134–170 of hCAP-18)

Antibody development

Not documented in available trials (endogenous protein)

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02Dosage Protocols

Parameter

Follistatin-344

LL-37

Clinical protocol

None — no approved dosing regimen

Follistatin-344 measured as endogenous biomarker, not administered exogenously in cited trials.

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Research context

Endogenous modulation via exercise + nutrition

Resistance training + EAA intake elevated FST/MSTN ratio by 15–25% in 12-week RCT (older women).

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Evidence basis

Human observational / biomarker studies

In vitro, animal models, human observational

Half-life

Not established

Circulating isoform; lacks tissue-binding domain of FST-315.

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Endogenous expression

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Constitutive in neutrophils, epithelial tissues

Upregulated during infection and inflammation.Pinheiro 2026

Exogenous (experimental)

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Dose varies by study; antimalarial ~10–50 μM in vitro

No FDA-approved exogenous formulation.

Plasma levels (malaria)

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Elevated in infected patients and miceHe 2026

Exogenous administration reduced parasitemia in murine models.He 2026

03Metabolic / Fat Loss Evidence

Parameter

Follistatin-344

LL-37

Primary target

Muscle mass preservation, not direct lipolysis

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Indirect fat effect

Increased lean mass → elevated resting metabolic rate

Not primary mechanism. Muscle-sparing during deficit.

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Clinical evidence

Lorcaserin trial (6 mo) showed no MAFI axis changes during fat lossRamirez-Cisneros 2026

Suggests follistatin not primary driver of fat loss in weight-reduction interventions.

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GLP-1RA studies

Liraglutide (35 days) — no significant MAFI axis modulation despite fat/lean changes

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04Side Effects & Safety

Parameter

Follistatin-344

LL-37

Clinical safety data

None — no human exogenous administration trials in literature

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Theoretical risks

Excessive myostatin inhibition → muscle overgrowth, impaired glucose tolerance

Based on myostatin-null animal models and clinical myostatin inhibitor trials.

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Endogenous elevation (exercise)

No adverse effects reported in 12-week resistance + EAA trials

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Cancer risk (theoretical)

Myostatin inhibition may promote tumor growth in malignancy (preclinical data)

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Regulatory status

Not approved for human use — research peptide only

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Cytotoxicity (high dose)

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Membrane disruption in host cells at supraphysiological concentrations

Pro-inflammatory signaling

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Can exacerbate inflammation in certain contexts (context-dependent)Pinheiro 2026

Biofilm formation risk

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LL-37-DNA complexes may stabilize dental plaque biofilmsTanabe 2026

Theoretical cancer risk

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Immunomodulatory roles in tumor microenvironment under investigation

Absolute Contraindications

Follistatin-344

·Active malignancy
·No approved protocol — research use only

LL-37

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Relative Contraindications

Follistatin-344

·Insulin resistance / Type 2 diabetes (monitor glucose)
·Pregnancy / lactation (unknown safety profile)

LL-37

·Active autoimmune disease (theoretical immune dysregulation)

05Administration Protocol

Parameter

Follistatin-344

LL-37

1. Regulatory status

Follistatin-344 is not approved for human administration. All cited studies measure endogenous serum follistatin as a biomarker, not as an exogenous therapeutic agent.

LL-37 is constitutively expressed in neutrophils and epithelial cells, cleaved from hCAP-18 by proteinase-3 at sites of infection or inflammation.

2. Endogenous modulation

Resistance exercise combined with essential amino acid (EAA) supplementation elevated the follistatin/myostatin ratio by 15–25% in 12-week randomized trials. Protein intake (1.2–1.5 g/kg/day) synergizes with training to upregulate endogenous follistatin.

Synthetic LL-37 and derivatives (e.g., SAMP-12aa) tested in vitro and animal models. Administered via topical, intraperitoneal, or intravenous routes in research settings.

3. Measurement context

Serum follistatin and follistatin/myostatin ratio are used diagnostically in sarcopenia screening and as biomarkers of muscle anabolic balance in clinical trials.

LL-37 is resistant to pepsin degradation at gastric pH. Synthetic short peptides designed to retain this stability while reducing toxicity.Lu 2026

4. Research consideration

Gene therapy and recombinant follistatin delivery are under preclinical investigation for muscular dystrophy and sarcopenia. No human safety or efficacy data for exogenous FST-344 administration.

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06Stack Synergy

Follistatin-344

+ BPC-157

Multi-pathway

View BPC-157 →

Follistatin-344 (myostatin antagonist) and BPC-157 (tissue repair peptide) address complementary pathways in muscle recovery. FST-344 promotes muscle protein synthesis by disinhibiting myostatin signaling, while BPC-157 accelerates healing of tendons, ligaments, and microtears via angiogenesis and collagen synthesis. Combined, they may support both hypertrophy and structural repair during high-volume training or injury recovery.

Follistatin-344: No approved protocol — endogenous modulation via resistance exercise + EAA
BPC-157: 250–500 mcg SQ · twice daily · near injury site or systemic
Duration: 4–8 weeks
Primary benefit: Muscle hypertrophy + accelerated soft tissue repair

+ TB-500

Moderate

View TB-500 →

TB-500 (thymosin beta-4 fragment) promotes cell migration, angiogenesis, and anti-inflammatory signaling in muscle and connective tissue. Follistatin-344's anabolic signaling may synergize with TB-500's regenerative effects during muscle damage or overtraining, particularly in older adults where both myostatin inhibition and tissue repair are rate-limiting.

Follistatin-344: Endogenous upregulation (resistance training + protein)
TB-500: 2–5 mg SQ · twice weekly · loading phase 4 weeks, then maintenance
Frequency: Twice weekly TB-500, daily training stimulus for FST
Primary benefit: Enhanced recovery, reduced inflammation, muscle growth support

LL-37

— no documented stacks