Follistatin 344: Complete Research Guide with Preclinical Data and Where to Buy

What Is Follistatin 344?

Follistatin 344 is the 344-amino acid isoform of follistatin (FST), a secreted glycoprotein that functions as a potent endogenous antagonist of transforming growth factor-β (TGF-β) superfamily ligands — most critically myostatin (GDF-8), activin A, and activin B. Through high-affinity binding and neutralization of these growth-inhibiting signaling molecules, follistatin 344 exerts powerful pro-myogenic effects in skeletal muscle tissue, making it one of the most studied proteins in muscle physiology and therapeutic muscle biology research.

The 344-isoform is particularly relevant for systemic muscle research because, unlike the shorter 288 isoform (which is heparin-bound and tends to remain local to the gonads), FST344 circulates freely and acts systemically on muscle, bone, and other tissues. The dramatic muscle hypertrophy observed in myostatin-knockout “double-muscled” cattle and in follistatin-overexpressing mice has established the myostatin/follistatin axis as one of the most important levers in muscle biology.

Mechanism of Action

• Myostatin (GDF-8) Neutralization: Binds myostatin with sub-nanomolar affinity (Kd ~0.3 nM), forming an inactive complex that prevents myostatin from signaling through its ActRII receptors — the primary mechanism of FST344’s pro-hypertrophic effect
• Activin A/B Antagonism: Inhibits activin signaling that suppresses muscle protein synthesis and promotes atrophy; also relevant for fertility and reproductive biology research
• BMP Regulation: Modulates bone morphogenetic protein (BMP) signaling, influencing bone metabolism and differentiation
• Satellite Cell Activation: By relieving myostatin suppression, FST344 promotes activation and proliferation of muscle satellite cells (muscle stem cells) — the cellular basis for hypertrophic adaptation
• mTOR Pathway Activation: Downstream Smad2/3 inhibition (normally activated by myostatin) leads to increased mTOR activity and protein synthesis rate

Key Research Data

Muscle Hypertrophy Models

• Lee & McPherron (PNAS, 2001): Systemic FST overexpression in mice produced 100–200% increase in muscle mass — approximately double the effect of myostatin knockout alone, due to FST’s additional activin A inhibition
• Guo et al. (Molecular Therapy, 2012): AAV-mediated FST344 delivery to aged mice restored muscle mass and strength to young adult levels within 8 weeks
• Short-term protein administration studies: Recombinant FST344 injection increased muscle wet weight by 15–25% in rodent models within 2–3 weeks

Muscular Dystrophy Research

• FST344 gene therapy significantly improved muscle strength, histology, and diaphragm function in mdx (Duchenne muscular dystrophy) mouse models
• Reduced necrosis and fibrosis in dystrophic muscle with FST344 overexpression
• Clinical translation efforts underway for Becker and Duchenne muscular dystrophy

Sarcopenia and Aging Research

• Myostatin levels increase with age while circulating follistatin declines — the inverse relationship contributes to sarcopenic muscle loss
• Exogenous FST344 administration in aged rodents reversed atrophy markers and improved grip strength
• Identified as a primary mechanism for exercise-induced muscle maintenance in the elderly

Follistatin 344 Dosage Reference for Research

95%+ HPLC

Follistatin 344 — 1mg

Purity: 95%+ HPLC

Format: Lyophilized Powder

Testing: Third-Party COA

$280

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Research Disclaimer: This product is sold strictly for in vitro research and laboratory use only. Not for human consumption. Not medical advice.