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Follistatin 344
A naturally occurring glycoprotein that inhibits myostatin and activin, studied for its potential to promote muscle growth beyond normal genetic limits.
Overview
Follistatin 344 is the 344-amino acid isoform of follistatin, a naturally occurring glycoprotein that binds to and neutralizes members of the TGF-beta superfamily, most notably myostatin and activin. Myostatin acts as a negative regulator of muscle mass, and by neutralizing it, follistatin removes the brake on muscle growth.
The myostatin-follistatin axis was dramatically demonstrated by Belgian Blue cattle, which carry natural myostatin mutations resulting in extreme muscular development. Rare human myostatin deficiency cases show similar effects. These examples fueled interest in pharmacological myostatin inhibition for therapeutic and performance purposes.
Gene therapy approaches using follistatin have shown remarkable results in animal models of muscular dystrophy. Clinical trials using AAV delivery of follistatin have been conducted in Becker muscular dystrophy and inclusion body myositis patients with promising preliminary results.
Synthetic follistatin 344 as an injectable peptide is distinct from gene therapy. When administered as a recombinant protein, it has a relatively short half-life, limiting sustained myostatin inhibition. Manipulating fundamental growth regulatory pathways carries risks including effects on reproductive function, as activin plays roles in fertility.