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Follistatin vs Myostatin: What Is the Actual Relationship?
The phrase follistatin vs myostatin is slightly misleading, because the two are not competing drugs — they are a natural regulator and its natural antagonist locked in a physiological balance. Myostatin is produced largely by muscle tissue itself and circulate
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- The phrase follistatin vs myostatin is slightly misleading, because the two are not competing drugs — they are a natural regulator and its natural antagonist locked in a physiological balance. Myostatin is produced largely by muscle tissue itself and circulates in a latent, propeptide-bound form that can be activated proteolytically; once active, it tonically suppresses muscle growth.[4] Follistatin is one of the endogenous molecules that keeps that suppression in check. In healthy tissue, the ratio of active myostatin/activin to available follistatin helps set the “operating point” for muscle mass.
- An elegant demonstration of just how tightly linked they are came from transgenic mouse experiments in which follistatin was over-expressed specifically in skeletal muscle. Those mice developed dramatic increases in muscle mass comparable to what is seen in myostatin-knockout animals — strong evidence that follistatin’s muscle effect operates through the same axis that myostatin controls.[3] The reverse experiment is equally telling: systemic over-expression of myostatin in adult mice induced profound muscle and fat loss resembling cachexia, confirming that myostatin acts on adult tissue, not only during development.[4]
- So the relationship is antagonistic and quantitative. More follistatin activity generally means less effective myostatin/activin signaling, which generally means a shift toward muscle accretion in the models studied. But two cautions follow immediately. First, follistatin also neutralizes activins, so it is a broader intervention than a pure anti-myostatin agent — the two are not interchangeable. Second, the impressive results come overwhelmingly from experiments that chronically raise follistatin levels via genetic engineering or gene transfer, producing sustained local expression. That is a very different exposure profile from a bolus injection of recombinant protein, which the body clears rapidly. The strength of the myostatin–follistatin relationship in biology is not in dispute; whether an injectable peptide can exploit it usefully in humans very much is.