U.S. children with autism
Fatty diet triggers nerve cell birth
Extra neurons in brain linked to more pounds in mouse study
By Laura Sanders
Cheeseburgers pack on the pounds, but
in mice a high-fat diet also packs on new
nerve cells in the brain. More brain cells
may seem like a good thing, but these
newly sprouted cells appear to trigger
weight gain, a new study finds.
If the same thing happens in humans,
these nerve cells may be a target for anti-obesity treatments.
“This kind of work will definitely
inform how we think about the under-
lying factors that relate to obesity,” says
endocrinologist Jeffrey Flier of Har-
vard Medical School in Boston. There’s
increasing interest, he says, in how
long-term changes in brain circuitry —
like new nerve cell production — affect
eating and hunger. “That is going to be a
very interesting frontier.”
With some key exceptions, most
regions in the adult brain don’t make
new nerve cells. But in a small sliver of
brain tissue called the median eminence,
new nerve cells are born throughout life,
neuroscientist Seth Blackshaw of Johns
A special cell called a tanycyte (green)
was caught giving birth to a new nerve
cell (white arrow) in a brain region
called the median eminence.
Hopkins University School of Medicine
and colleagues report online March 25 in
Nature Neuroscience. The median eminence is part of the brain’s metabolism
hub known as the hypothalamus.
One signal to step up production in the
median eminence, the team found, is a
diet high in fat.
In the study, mice that ate the rodent
version of a steady stream of Big Macs
gained weight. This unhealthy diet also
kicked nerve cell production into high
gear. Adult mice eating a fatty diet for
U.S. autism rate
continues to rise
Prevalence estimate hits
new high at 1 in 88 children
By Bruce Bower
New federal data indicate that 1 in 88
U.S. children had autism or other autism
spectrum disorders in 2008, up from 1
in 110 kids in 2006 and 1 in 150 in 2002.
Although that’s a worrisome trend,
the reasons for autism’s rising prevalence — measured in nonrepresentative
national samples of 8-year-olds — remain
unclear. The Centers for Disease Control
and Prevention in Atlanta released the
latest autism figures on March 30.
CDC researchers used health and educational records to identify children with
autism spectrum disorders among more
than 38,000 kids in parts of 14 states.
“Such a big increase ... in such a short
time seems a little odd, and there’s a lot
of noise in these data,” says psychiatrist
Fred Volkmar of the Yale Child Study
Center in New Haven, Conn.
Some of the clatter stems from divergent diagnostic and record-keeping practices, Volkmar says. Some children with
learning problems may get labeled with
autism spectrum disorders to receive
special education services, he notes.
U.S. children with autism
several weeks pumped out about four
times as many new nerve cells in the
median eminence as mice that ate regular chow.
To see whether these newborn nerve
cells were up to no good, Blackshaw and
his team shut down production with a
carefully targeted laser. Even while continuing to gorge on a high-fat diet, these
mice started moving around more and
didn’t gain as much weight as mice on
a high-fat diet that could still make the
new nerve cells. Take away the steady
stream of new nerve cells, and the
pounds didn’t pile on as fast.
The newborn cells’ parents turn out to
be a kind of brain cell that resides in the
median eminence. Both mice and people
have these cells, called tanycytes. “There’s
been a lot of speculation about what
their function may be,” says Blackshaw.
The scientists don’t yet know how
these newborn nerve cells can influence
metabolism. Other studies, including
those by Flier, have found that a high-fat
diet actually reduces nerve cell turnover
in other parts of the hypothalamus.
Blackshaw warns that it’s too soon to
know if a similar thing is going on in people. “This is the very first step in trying
to understand this process,” he says.
markedly state to state, the CDC reports.
Prevalence ranged from 21. 2 cases for
every 1,000 children in Utah to 4. 8 cases
for every 1,000 kids in Alabama.
Overall, 1 in 54 boys, versus 1 in 252
girls, had autism spectrum disorders.
The magnitude of that sex difference
also varied substantially across states.
CDC’s autism data show rate hikes
among black and Hispanic children,
reflecting corrections for underdiagnosis
in minority populations, says anthropologist R. Richard Grinker of George Washington University in Washington, D. C.
Grinker says the new figures underestimate autism’s prevalence, because
they rely on school and medical records
rather than in-person screening.
DANIEL LEE/BLACKSHAW LAB