T Nation

Muscle Growth & Stem Cells?


#1
I recently found this passage in a book review online. I don't have the knowledge to determine if the comment has any merit. Can anyone comment?

"Our muscles grow in response to injury - it is the destruction of the outer member of muscle cells. We are literally "killing" muscle cells and injuring our bodies (on purpose mind you). The damaged muscle cell will receive help from a stem cell, called a satellite cell, which will adopt itself into the muscle cell and make it grow in size. This is why muscle grows with intense exercise/intentional injury.

Since muscles grow from stem cells, this raises the question as to the role of supplementation and nutrition in skeletal muscle growth. In his book, the author mentions the enzyme myostatin, which is a natural inhibitor of stem cell production. The people with this mutation are able to lift weights and injure muscle cells, but their body naturally produces so many stem cells that their muscles rapidly increase in size soon thereafter. Professional bodybuilders are known to have these mutations.

There is an evolutionary advantage to not having this mutation and that is that individuals with large muscles require a higher metabolism, and this can be a detriment to living in an environment with limited food resources.

There is no evidence that amino acids, proteins, and other supplements increase the natural amount of stem cells (called satellite cells) in skeletal muscle - This means they may have no effect in muscle regeneration. The reader should keep in mind that mice and cows with the myostatin mutations grow huge from simply grazing or running on mouse wheels - they do not chug protein shakes and waste money on supplements like so many aspiring but misinformed bodybuilders do.


#2

I can't comment on the book as I don't know which one it is, however to put your mind at ease, here's a quick muscle growth 101. With usual resistance training the eccentric portion of the movement causes microtrauma to the fibre (as long as sufficient resistence is used to create the necessary tension. The body will respond to this by remodelling the fibre to become thicker and therefore more resistent to damage in the future.

This requires protein, and if it is not supplied by the diet, the body will canabolise other tissue to provide it. So protein in the diet (whether from whole food or supplementation) is needed to prevent a catabolic state from occuring, and promoting an anabolic state (a least from a protein metabolism standpoint). This remodelling is called hypertrophy and is the primary way muscle growth occurs.

However there are at least two other ways muscles can grow. One way is for the muscle fibre to split and form a double (once it reaches a certain size limit), which allows each seperate fibre to hypertrophy once more. The other way, as you mentioned in your post, is to recruit satellite cells. These are both termed hyperplasia, the former will happen with regular weight training, the latter requires a more traumatic stimulus.

This could be via unintentional injury or intentional damage using very high tension levels such as those created using heavy eccentric stresses, especially in the form of negatives. Using methods such as negatives activate satellite cells into growth of new muscle fibres. This supply of satellite cells is limited however, although researchers have not come to a definate conclusion on how much, estimates are approximately 10%.

As far as metabolism is concerned hyperplasia like hypertrophy requires protein in order to occur. So the bottom line is in order to support muscle growth, higher levels of protein are required and supplements are a convenient and efficient way to achieve this especially in the peri-workout timeframe.


#3

Thank you for the explanation. Does the writer of the above post have a point though? Is the harnessing of myostatin, whether possible or not, the end all of muscle growth? A search regarding comments on Biotest's former myostatin supplement shows many said it was the "only thing that actually made me grow." Interesting.


#4

Yes myostatin is an important component of muscle growth, however it seems that although the sulfo-polysaccharide that was the key ingredient in the product did bind to myostatin in serum, it did not significantly affect muscle mass. In other studies, a recombinant human antibody is used to knock out the gene, and this does affect subsequent muscle growth.

The recent studies are demonstrating that certain substances can affect the expression of the gene. Some of these substances can inhibit the gene, these include Growth hormone and Androgens. Others including glucocorticoids and substances found in tobacco smoke increase the expression of the gene.

So if you are using methods to maximise and support the output of testosterone and growth hormone you get the benefit of the primary actions and the secondary effects they afford. As you quite rightly said it is interesting and it is worth keeping an eye on in the near future.


#5

Thanks very much. Would be great if myostatin could be inhibited in a legal product. Who knows? Maybe someday.