GDF-8 is a propeptide that is designed to inhibit naturally occurring myostatin. Myostatin is an important protein that works to prevent the growth and development of muscle cells . Animals such as the Belgian blue bull produce less myostatin than other breeds of cow and this is responsible for the breeds extremely lean, hyper-sculpted, ultra-muscular physique due to an increased number of muscle fibres . GDF-8 works by binding myostatin so that it cannot be activated, which prevents it from binding to its own receptors .These receptors normally function to switch off muscle growth when myostatin is bound, but because the binding is blocked by GDF-8 then muscle growth can continue unrestricted. It has been shown that the lack of myostatin gives rise to significant increases in muscle mass in both humans and animals. Also in bone, the lack of myostatin has been shown to increase bone mineral density. Animal studies using GDF-8 showed increases in muscle and bone repair in a model of tissue injury, suggesting that the peptide can be used to repair damaged muscle and bone . The peptide has also been investigated for its potential in treating the muscle wasting disorder Duchenne’s muscular dystrophy. The study showed that the peptide was a potential pharmacological strategy for treatment of diseases associated with muscle wasting and further studies are ongoing . Finally, a recent study in mice showed a remarkable level of muscle growth after blocking myostatin signalling by overexpressing the myostatin propeptide . The same study also proved that muscle growth was induced by the peptide and that the muscle was capable of generating normal levels of force.
GDF-8 needs to be completely reconstituted in BAC water and administered at a dose of 20 mcg/kg. This concentration has been shown to generate optimal muscle gains in animal studies. The peptide is stable once injected and has a half-life of around 5 days. It is recommended to administer GDF-8 via subcutaneous injection, but the peptide can also be dosed intramuscularly. Based on the extended half-life of the peptide it should be used every five days over a 25-day period.
- GDF-8 has not been tested on humans, neither has its safety been assessed in clinical trials. However, animal studies have treated mice with a large dose (50 mg/kg) of GDF-8 for up to 17 days, but did not report on any side effects.
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- Hamrick, M.W., et al., Recombinant myostatin (GDF-8) propeptide enhances the repair and regeneration of both muscle and bone in a model of deep penetrant musculoskeletal injury. J Trauma, 2010. 69(3): p. 579-83.
- Collins-Hooper, H., et al., Propeptide-Mediated Inhibition of Myostatin Increases Muscle Mass Through Inhibiting Proteolytic Pathways in Aged Mice. The Journals of Gerontology: Series A, 2014. 69(9): p. 1049-1059.