If you're interested in the role of follistatin in (rather in relation to) aging, you're lucky because I accidentally uploaded a paid paper couple of days ago which has some information about that.
https://www.dropbox....en2016.pdf?dl=0
Granted not everyone develops diabetes as they age but quite a few people have pre-diabetic symptoms and this has some implications about how much you can actually get out of exercise if you're in that group. It doesn't give a clear answer if getting extra follistatin would help - in fact like in most cases when it comes to these proteins and their quantities in there is no clear answer.
Be very clear that this paper is not about your glucose levels ("prediabetes") but is rather about your *insulin* levels relative to glucagon. The distinction is worth making because not all prediabetes is the same. Sometimes prediabetes is about insulin resistance (so insulin levels go and stay high), but other times it may not reflect that.
I found an incredible rodent paper that demonstrates that during periods of starvation, when the body starts autophagy, that glucose levels *rise* while insulin continues to trend down:
https://www.ncbi.nlm...les/PMC3149698/
The study is fascinating because the control group is rats that are genetically disabled to do autophagy. When they look at starvation in both groups, sometime around hours 19 to 23 for the group that can do autophagy:
1) Free amino acids surge
2) Glucose levels go sharply up
3) Insulin levels continue to trend down, even in face of higher glucose
4) Glucagon continues to slightly trend up
What appears to be happening here is autophagy releases amino acids from inside of the cells. Autophagy is eating defective proteins, mitochondria, viruses, and bacteria, and these are producing large amounts of free amino acids. The FAA are then feeding gluconeogenesis to produce glucose.
This raises the question in adult humans with "prediabetes" is the cause of the high glucose level a) insulin resistance or b) autophagy? In my own case, I intermittent fast, and I have noticed that my glucose levels never come below 100 mg/dL during my fast. So even though I have no food to stimulate glucose higher or raise insulin, my glucose stays high. After I eat my first meal, glucose trends down, probably as a response to insulin going high after the meal. I am fairly sure that if we measured my metabolites during the fast, you would see stable rising glucagon and falling (and probably very low) insulin.
I am starting to wonder if much of adult prediabetes may in fact reflect a lot of collected garbage in our cells and the body being overwhelmed by trying to clean this out by autophagy in the overnight fast.