Myostatin and Bodybuilding

Myostatin, also known as GDF-8, is a protein present in skeletal muscle during the embryonic period and in adulthood. It regulates skeletal muscle growth through an interaction with the Activin IIB receptor via the junction of myostatin with a polypeptide.

The primary function of myostatin is to restrict muscle growth, keeping satellite cells quiescent. When the muscle undergoes an injury, satellite cells migrate to replace the damaged cells. Without Myostatin, the brake that acts on satellite cells could be eliminated, allowing muscle cells to proliferate.

“In recent decades, it was observed that some cattle breeds had a mutation in the Myostatin gene, resulting in a non-functional protein. This demonstrated that Myostatin inhibited skeletal muscle growth, and the main characteristic of these animals carrying this mutation was an exacerbated growth of muscles, a phenomenon called “double muscling.” Recently, the case of an extremely muscular German child was found who had a double dose of a mutation that inactivates Myostatin; this child presented a phenotype similar to “double muscling.”

Genetic manipulation performed with transgenic mice revealed that when Myostatin deficiency occurs, there is a drastic and generalized increase in skeletal muscle mass, mainly due to a higher number of fat-free muscle fibers, leading to a volume increase of approximately 2 to 3 times more than wild mice.

Recent results show that our body also contains the Myostatin inhibitor known as follistatin. Although follistatin appears to be a potent inhibitor of Myostatin activity, it also functions as an actinina inhibitor. Actinins are involved in multiple functions in various organs; by blocking them, follistatin would affect multiple tissues, such as smooth and cardiac muscle, and not only skeletal muscle.

Regarding the use of Myostatin in sports, the disclosure of this protein has brought various reactions from different segments in the health area. Amateur and professional athletes noted the possibility of using its blockers to extrapolate exercise performance and training responsiveness, reaching the maximum of human capacity.

The effect of strength training on Myostatin expression was tested by muscle biopsy of the vastus lateralis muscle, which were taken at rest one hour before, one hour after, and 48 hours after five sessions of 10 repetitions on the leg press, both before and after 21 weeks of supervised strength training, in two situations: untrained individuals (pre-training) and trained individuals (post-training).

At the beginning of training (untrained individuals), the 3 biopsies examined showed no change in Myostatin mRNA content; however, after 21 weeks of training (trained individuals), there was a decrease in Myostatin mRNA content after one hour, and this decrease was even greater after 48 hours of the end of the training session, indicating that training had an effect and suggesting that lower Myostatin expression leads to greater muscle growth.

With the advancement of therapeutic knowledge, Myostatin appears to be a potential candidate for gene therapy, assisting in effective treatment for various pathological conditions, such as HIV, sarcopenia, cancer (cachexia), muscular dystrophy, among others.”

Matsakas, A. and P. Diel (2005). "The growth factor myostatin, a key regulator in skeletal muscle growth and homeostasis." Int J Sports Med 26(2): 83-9.

Reardon, K. A., J. Davis, et al. (2001). "Myostatin, insulin-like growth factor-1, and leukemia inhibitory factor mRNAs are upregulated in chronic human disuse muscle atrophy." Muscle Nerve 24(7): 893-9.

Hulmi, J. J., J. P. Ahtiainen, et al. (2007). "Postexercise myostatin and activin IIb mRNA levels: effects of strength training." Med Sci Sports Exerc 39(2): 289-97.

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