BODY & BrAiN
Muscles make natural antidepressant
Exercise blocks brain toxin linked to stress, mouse study shows
BY LAURA SANDERS
A powerful body can protect the brain,
a new study suggests. Toned muscles
filter a toxin to keep depression at bay,
researchers report in the Sept. 25 Cell.
By discovering a previously unknown
link between muscles and the brain in
mice, the results provide compelling
evidence for the healing power of exercise, says psychiatrist Andrew Miller
of Emory University in Atlanta. “This
paper really emphasizes ‘strong body,
strong mind.’ ” The finding also hints
at new ways to treat brain disorders,
Researchers have known that in
response to a good workout, muscles
produce a compound called PGC- 1 alpha
1, which is a general do-gooder around
the body. The compound prompts the
body to make more blood vessels and
mitochondria, for instance. The new
study shows that PGC- 1 alpha 1’s protec-
tive effects extend to the brain.
In the study, mice were exposed to five
weeks of unpredictable stressors, such
as food deprivation, strobe lights and
loud noises. At the end of their ordeal,
mice showed signs of stress-induced
depression, such as not drinking as much
sweet water and giving up in a tank of
water instead of struggling to swim. The
brains of these mice also showed signs
of depression: Key genes changed their
behavior in response to the stress.
But mice genetically tweaked to
produce more PGC- 1 alpha 1 in their
skeletal muscles seemed immune to
chronic stress and showed fewer depres-
sive signs, says study coauthor Maria
Lindskog of the Karolinska Institutet
in Stockholm. “Nothing happened,”
When produced in response to exer-
cise, PGC- 1 alpha 1 kicks off a chain of
chemical events in muscles that culmi-
nates in neutralizing a stress-induced
toxin called kynurenine. An injection
of kynurenine, which travels easily
bet ween the body and brain, caused mice
to show signs of depression, even when
the animals weren’t exposed to stress-
ors. That result “suggests kynurenine
may be a much more malignant mol-
ecule than we had previously appreci-
ated,” Miller says.
But PGC- 1 alpha 1 in the muscle leads
to conversion of kynurenine into a form
that can’t pass into the brain. The results
show how muscle can have a profound
effect on other organs, Lindskog says.
“It’s like a detoxifying organ, almost.”
Mice that ran on an exercise wheel,
covering more than four kilometers a
night for eight weeks, also experienced
benefits, the team found. And there are
hints that people could achieve the same
Hominids in Eurasia 330,000 years ago crafted stone tools using flake-making technology
they may have invented themselves.
HUMANS & SOciEt Y
Hominids’ stone flakes may
not owe origin to Africans
BY MEGHAN ROSEN
More than 300,000 years ago, Stone Age
people in Eurasia may have invented
new toolmaking technology on their
own instead of borrowing it from African
migrants, as some researchers suspected.
A mix of stone artifacts sandwiched
between lava flows in Armenia suggest
that an early toolmaking method arose
independently in multiple spots around
the world, researchers report in the
Sept. 26 Science.
“This tells us that archaic humans
were a lot more innovative than we give
them credit for,” says archaeologist Mark
White of Durham University in England.
For almost 20 years, he says, scientists
have argued about whether a way to make
stone flakes, called Levallois technology,
was invented in Africa and then spread
to Eurasia.“It’s one of those hypotheses
that gets stuck like glue to the scientific
consciousness,” White says.
The new find may loosen up the glue.
The Armenian site holds evidence of both
old tools — stone hand axes — and ne wer
stone flakes, as well as signs of a transition from one toolmaking technology to
the other. What’s more, the stone flakes
from the Armenian site don’t really look
like those found in Africa, says Harvard
archaeologist Christian Tryon.
So the Eurasian hominids may have
developed their own Levallois flake making, rather than having African immigrants bring the technology in, says study
coauthor Daniel Adler, an archaeologist
at the University of Connecticut in Storrs.
Adler’s team didn’t uncover any bones
at the site, so the researchers can’t say
who these hominids were.
But scientists do know that about
1.75 million years ago, African homi-
nids invented a way to make stone tools
with two faces, such as hand axes, by
hammering chips off big lumps of rock.
Archaeologists think hominids brought
this toolmaking method to Eurasia some
600,000 to 900,000 years ago.
Hundreds of thousands of years
later, Levallois flake-making technol-
ogy emerged in Africa, some scientists
believe. By whittling stones into dome-
shaped chunks, toolmakers could strike
off sharp flakes, possibly useful for cut-
ting and slicing. That innovation may
have let hunter-gatherers carry stone
flakes instead of heavy hand axes.
Some researchers see such innovation