THE HULK GENE
BEFORE
spending prolonged periods in orbit
can return to Earth without any loss
of strength. All this may be possible
and sooner than you might think.
This past October, researchers in
China announced that they had
engineered brother and sister
beagles (named Hercules and
Tiangou) with disruptions in both
copies of their myostatin genes.
Consequently, the siblings look like
canine versions of the Incredible
Hulk and the She-Hulk. Another
dog breed, the whippet, has seen
a gene mutation among its ranks
without human intervention.
“Bully whippets” have one or both
copies of their myostatin genes
mutated, causing the normally
wispy dogs to be loaded with rip-
pling muscles.
Presently, Pfizer is conducting a Phase 2 study of an
intravenous myostatin blocker on 6- to 10-year-old boys
with Duchenne and Becker muscular dystrophy to see
if it will help restore muscle mass and strength lost to
the diseases. As of this writing, however, no results of
human testing have been reported.
“There is every expectation that we will see the same
efects in humans that we do in mice, given that myo-
statin plays a role in regulating muscle mass in humans,
but we just don’t know,” says Lee. “There’s no data
AFTER
GUNTER
SCHLIERKAMP,
reimagined
at right as a
375-pound
bodybuilding
monster. The real
Gunter is at left.
when stem cells are constantly being called into action
is anyone’s guess. Do stem cells replenish indefinitely,
or is there a finite supply? Another potential risk is the
long-term efect on involuntary muscles, like the heart.
The hearts of bully whippets and Piedmontese cattle
aren’t especially large, but could long-term use of a
myostatin inhibitor lead to heart-muscle growth?
Regardless of risks, unknowns, or medical caveats,
it’s a sure bet that athletes will be hurdling over one
another to be among the first in their sports to take
Unforeseen long-
ON A SLIDING SCALE OF
MORALITY, HOW DOES
GENE-MUTATION THERAPY
COMPARE WITH STEROID
USE, FIXING A GAME, OR
CORKING A BAT?
134
MUSCLE & FITNESS
FEBRUARY 2016
for personal glory?
On a sliding scale of morality, how does gene-
mutation therapy compare with steroid use, fixing a
game, or corking a bat? Certainly, it would become
illegal to administer such therapy without the consent
of a physician, so how does one justify breaking the law
in the name of athletic performance?
With any new technology comes debate over how it
should be used, regulated, and harnessed. The current
state of genetic testing in the area of muscle growth
necessitates that the time for such discussion is now.
addressing that as of yet. That will be answered to some
extent by the clinical trial being run by Wyeth Pharma-
ceuticals. Of course, it’s not yet known what the long-
term efects of living a life without myostatin will be.”
One potential long-term downside to quieting the
myostatin gene function has to do with the source of
new muscle growth—satellite stem cells. It appears that
myostatin exists to regulate growth, which it does by
ensuring that muscle cells do not overdraw from the store
of satellite stem cells kept in reserve. What happens