What is follistatin?
Follistatin, a single-chain glycosylated protein, has been studied for its potential benefits in various health conditions. It has been found to have several beneficial effects, particularly in the context of muscle health and metabolic diseases.
Follistatin, also known as FST, belongs to the tissue growth factor β family. It is known to antagonise (or work to reduce the effect of) many members of this family, including activin A, growth differentiation factor 11, and myostatin [1]. Follistatin was initially discovered in ovarian follicular fluid and identified as a suppressor of pituitary follicle-stimulating hormone (FSH) secretion.
Follistatin has two major isoforms, FST288 and FST315. The FST315 isoform is the predominant form, while the FST288 variant accounts for less than 5% of the encoded mRNA [2].
What are the possible benefits of taking follistatin?
Follistatin is expressed in various tissues and has been found to play a protective role under a variety of stresses [3]. It is also involved in the regulation of muscle mass, as it can inhibit myostatin activity, a protein that normally limits skeletal muscle mass [4].
In terms of therapeutic applications, follistatin has been explored as a systemic therapeutic agent in models of muscle injury. It has been found to increase body weight and lean muscle mass after weekly administration in normal mice. It also induced improvements in muscle repair after injury/atrophy by modulating the early inflammatory phase, allowing for increased macrophage density, and leading to an accelerated restoration of myofibers and muscle function [1].
In terms of metabolic health, follistatin has been associated with decreased abdominal fat content, improved glucose clearance, and improved plasma lipid profiles in mice. This suggests that follistatin could potentially be used to treat metabolic syndrome and restrict fat accumulation [5].
However, comprehensive studies have not been done in humans and more research is needed to fully understand the benefits of follistatin in humans. If you are considering supplementation please discuss with a licensed physician.
What are the possible risks of taking follistatin?
One of the main concerns is that follistatin is available on the black market, often labelled as "follistatin 344" or "follistatin 315". However, not all products sold under these labels actually contain follistatin. In a study, only nine out of 17 tested products contained follistatin, while some others contained growth-promoting peptides [5].
Moreover, follistatin is a potent inhibitor of the myostatin pathway, which can result in an increase in skeletal muscle mass. However, its ability to interact with the pituitary activin-inhibin axis and suppress the secretion of follicle-stimulating hormone (FSH) calls for caution in its unregulated use [6].
Look here to compare how follistatin compares to MK-677, another peptide involved in muscle building.
Conclusion
While Follistatin may have benefits for metabolic disease and muscle building, the evidence does not strongly support its use as all studies currently have been done on animals. More research is needed to fully understand the potential benefits and limitations of Follistatin in this context.
Crucially if you are thinking of taking these supplements, please consider the risks carefully and discuss with a licensed medical practitioner as they are often under-researched and the side effects ill understood. Additionally, some peptides are illegal to purchase in certain countries.