Myostatin is a protein produced naturally in skeletal muscle cells of adult mammals. This protein is circulated in the blood and lymph nodes and has been found to decrease the production rate of muscle stem cells, thus inhibiting muscle growth. The discovery of myostatin in 1997 led to further research involving the inhibition of this protein to treat muscular dystrophy.
Additional research has also explored the possibility of manipulating myostatin for the purposes of enhancing athletic performance, but the efficacy and side effects of this action are still not yet understood.
Excessive Muscle Growth
A 2007 study titled "A Mutation in the Myostatin Gene Increases Muscle Mass and Enhances Racing Performance in Heterozygote Dogs" explored the mutation of myostatin genes in racing dogs. This study by the National Human Genome Research Institute at the National Institutes of Health in Bethesda, Md. found that the dogs that possessed single copies of these genes, which had been mutated to produce lower levels of myostatin, had experienced increased muscle growth that enabled them to regularly outperform dogs that did not possess these genes. However, dogs that possessed two copies of these genes had a side effect that researchers described as "grossly overmuscled."
Consequences of Myostatin Deletion Still Unclear
One 2009 study by the Beth Israel Deaconess Medical Center and Harvard Medical School in Boston, Mass., titled "Effects of Myostatin Deletion in Aging Mice", studied the inhibition of myostatin for the treatment of age-related muscle loss in cardiac tissue. They found that while "the cardiac consequences of inhibiting myostatin remain unclear, myostatin deletion does not affect aging-related increases in cardiac mass and appears beneficial for bone density, insulin sensitivity, and heart function in senescent mice."
Muscular Dystrophy Treatment
A 2008 study "Myostatin Inhibition by a Follistatin-Derived Peptide Ameliorates the Pathophysiology of Muscular Dystrophy Model Mice", done by the Institute for Comprehensive Medical Science at Fujita Health University in Aichi, Japan, explored the possibility of inhibiting myostatin to treat muscular dystrophy, a disease that causes the weakening of skeletal muscles. The researchers found that this treatment had potential and did not observe any negative side effects, but they also acknowledged that more research was needed to verify these results and observe any possible long-term side effects.
Possible Side Effect of Muscular Dystrophy Treatment
In contrast to the Japanese study, researchers at the Burnham Institute in La Jolla, Calif., did find a possible side effect of using myostatin inhibition as a muscular dystrophy treatment. Their 2005 study titled "Elimination of Myostatin Does Not Combat Muscular Dystrophy in DY Mice but Increases Postnatal Lethality" found that while the muscular dystrophy mice did experience increased muscle regeneration as a result of myostatin inhibition, it came at the expense of the formation of necessary fats. In addition, the inflammation and degeneration of existing muscle were not alleviated, leading them to conclude that "any future therapy based on myostatin may have undesirable side effects."
Additional Research Needed
While myostatin reduction can lead to the side effect of excessive muscle growth, little evidence of negative side effects has been found in using myostatin inhibition for treatment of diseases. However, in all of the aforementioned studies and in the overwhelming majority of research currently being done regarding the effects of myostatin inhibition, researchers have concluded that more research is needed to verify their findings and to identify any possible side effects.