Effects of oral creatine and resistance training on serum myostatin and GASP-1
- 05-31-2010, 06:35 PM
- 05-31-2010, 09:07 PM
- 06-01-2010, 07:48 PM
Myostatin (also known as growth differentiation factor 8) is a secreted TGF beta protein family member that inhibits muscle differentiation and growth. Myostatin is produced primarily in skeletal muscle cells, circulates in the blood and acts on muscle tissue, by binding a cell-bound receptor called the activin type II receptor. In humans, myostatin is encoded by the MSTN gene.
Animals lacking myostatin or animals treated with substances such as follistatin that block the binding of myostatin to its receptor have significantly larger muscles.
Myostatin is a member of the TGF beta superfamily of proteins.
Human myostatin consists of two identical subunits, each consisting of 109 amino acid residues. Its total molecular weight is 25.0 kDa. The protein is made in an inactive form. For it to be activated, a protease cleaves the NH3-terminal, or "pro-domain" portion of the molecule, resulting in the now-active COOH-terminal dimer.
Myostatin binds to the activin type II receptor, resulting in a recruitment of a coreceptor called Alk-3 or Alk-4. This coreceptor then initiates a cell signaling cascade in the muscle, which includes the activation of transcription factors in the SMAD family - SMAD2 and SMAD3. These factors then induce myostatin-specific gene regulation. When applied to myoblasts, myostatin inhibits their differentiation into mature muscle fibers.
Recently, myostatin has also been shown to inhibit Akt, a kinase which is sufficient to cause muscle hypertrophy, in part through the activation of protein synthesis.
Therefore myostatin acts in two ways, by inhibiting muscle differentiation, and by inhibiting Akt-induced protein synthesis.
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