Follistatin 344

Follistatin 344 is a recombinant form of the naturally occurring single-chain glycoprotein Follistatin, which consists of 344 amino acids in its longest isoform. Follistatin is produced in nearly all tissues and is primarily known for its role as a potent inhibitor of activin, myostatin, and other members of the TGF-beta superfamily. By neutralizing myostatin, the primary negative regulator of muscle growth, Follistatin can promote significant muscle development.

The mechanism of action centers on Follistatin's ability to bind activin and myostatin with high affinity, preventing them from interacting with their receptors. Myostatin normally acts as a brake on muscle growth, and its inhibition by Follistatin removes this constraint, allowing enhanced muscle protein synthesis and satellite cell activation. Follistatin 344 is the unprocessed form that gets cleaved into shorter variants (FS-315 and FS-288) in different tissues, each with slightly different binding properties.

Animal research has demonstrated dramatic increases in muscle mass following Follistatin administration or gene transfer, with myostatin knockout animals showing double-muscled phenotypes. Gene therapy studies using Follistatin have shown promise for muscular dystrophy treatment, with clinical trials demonstrating safety and improved muscle function in Becker muscular dystrophy patients. Research continues into its applications for sarcopenia, muscle wasting conditions, and as a potential countermeasure for muscle atrophy in spaceflight.