Myostatin inhibitors may make injuries more likely

Published on January 23, 2008 at 12:58 AM · 4 Comments

Block the action of a protein that normally regulates muscle mass, and watch your muscles grow.

That may sound like a good idea to people with muscle-wasting diseases such as muscular dystrophy, and to older people, whose muscles naturally get smaller and weaker with age. Drugs that restrict the protein myostatin, which normally prevents muscles from being overly bulky, are currently under study, but not on the market, for some medical conditions.

Such drugs, called myostatin inhibitors, also are stirring interest among body builders and athletes. There are already signs of a nascent black market for what might become another illegal performance-enhancing drug in organized sports.

Now, a new University of Michigan study in mice suggests that while myostatin inhibitors may indeed bulk up muscles, they may also bring a troubling side effect – small, brittle tendons that could make muscle injuries more likely.

“Those interested in myostatin inhibitors need to be aware of the fact that by doing these things to muscles, they may be having negative effects on tendons,” says John A. Faulkner, Ph.D., the study's senior author and professor in the Department of Molecular and Integrative Physiology at the U-M Medical School. He is also a research professor at the U-M Institute of Gerontology and professor of biomedical engineering at the U-M College of Engineering. The study results appear in the Jan. 8 print issue of the Proceedings of the National Academy of Sciences.

When you lift weights at the gym, muscle tissue gets damaged. That sets off the release of myostatin, starting a process that clears away damaged proteins and sets the stage for muscle rebuilding, says the study's first author, Christopher L. Mendias, Ph.D. The study suggests we need normal myostatin action for other reasons, too.

“It also appears to make tendons bigger and more flexible,” says Mendias, a U-M post-doctoral research fellow in the Regenerative Sciences Training Program in the Department of Surgery at the U-M Medical School.

It is known that blocking myostatin's activity increases muscle mass and strength, but also makes muscle fibers more vulnerable to injury. The U-M team broke new ground by asking if myostatin also affected the make-up and performance of tendons, the fibrous, tough tissues that connect muscle to bone.

Tendons are stiffer than muscles to begin with, and get stiffer with age. If tendons are brittle and short, as they were in myostatin-lacking mice in the study, they can't adequately do their important job of buffering against muscle injuries.

“The tendon acts like a spring,” Faulkner says, to reduce some of the force on the muscle in a lengthening contraction. Contraction-induced injury is the most common way we injure our muscles. This type of injury already occurs frequently in people with muscular dystrophy – so short, brittle tendons could aggravate the problem if myostatin inhibitors turn out to cause the effect in people.

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  1. Thomas Haggerty Thomas Haggerty United States says:

    Has anyone else seen the myostatin inhibitor stuff that’s gone up at It looks like a company called Peak Wellness is ready to roll out a new product. It’s called MYO-T12. I don’t know what to think about this. The science seems to be there, as far as serum myostatin reductions. They’re talking 46%! I’m going to be very interested in seeing if this stuff is for real.

  2. Steven H Steven H United States says:

    Yeah I've seen that myo-t12 on prosource but it says it's on back order. A couple months ago they had this other stuff called Flostaxan and it did the same thing, but then it just disappeared, I was going to order some but it was gone??? I'm not a professional athlete but i do love to work out so I think it would be perfect for the regular gym rat that just wants to get crazy big!!!

  3. Cornell Cornell United States says:

    It is a long story but Flostaxan was developed with a partner.  The man with brains let that company go down the tubes and released myo-t12 in what looks like a pretty cut throat move not to share any profits for the real deal.

  4. bob bob United States says:

    The stuff currently on the market is not scientifically proven to work...

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