Study Links Free Radicals to the Spectrum of Autism
A Metabolic Flaw May Account Partly For The Range In Severity Shown In Children With The Developmental Disorder, Scientists Report.
By Robert Lee Hotz for the LA Times.
Many autistic children share a chronic flaw in the body’s natural defenses against oxygen free radicals – corrosive molecules in the body that can severely damage developing brain cells, scientists said Saturday in San Diego.
The molecular havoc caused by free radicals – natural byproducts of
metabolism – is believed to be a major factor in the cell damage that
underlies aging.
Researchers at the University of Arkansas for Medical Sciences in
Little Rock found that a single breakdown in the body’s metabolism might
underlie many of the puzzling symptoms of autism, a complex developmental
disability with a spectrum of behaviors.
“This is a very promising thing to look at because it gets at the
actual metabolic processes in the brain,” said UCLA neurologist George
Bartzokis, who did not participate in the research. “The brain is especially
vulnerable to damage from free radicals.”
Those with autism typically have difficulty communicating and interacting with other people. It strikes some in infancy. Other children may develop normally for several years before falling into a private world where normal social interaction and behavior becomes impossible.
The new findings also may help shed light on the condition’s range in
severity because maturing neurons and synapses are especially vulnerable to
this biomolecular bombardment. Autism could therefore cause different
symptoms and degrees of severity in children depending on when the disorder is triggered.
Normally, the body shields itself from such damage with a chemical
produced by every cell called glutathione, which neutralizes oxygen free
radicals. It binds to them, altering their electron balance and sees them
safely expelled from the body.
By analyzing blood samples from 95 autistic children and 75 healthy
ones, researchers led by biochemist S. Jill James at the University of
Arkansas determined that levels of this protective antioxidant were
abnormally low in many autistic children.
They presented their work at the Experimental Biology 2005 conference
in San Diego.
The finding is suggestive, several experts said, because glutathione
also is crucial for neutralizing toxic heavy metals such as mercury, which
is found in food, the air and, at one time, a vaccine preservative called
thimerosal.
“When glutathione is less available, then it is easier for things to
get out of balance and the free radicals can cause more damage,” James said.
“One interpretation of this finding is that children with autism would be
less able to detoxify and eliminate these heavy metals.”
The researchers cautioned that they do not know whether this metabolic
flaw precedes the disorder or is one of its symptoms. Indeed, no one knows
what causes autism, which has increased in prevalence 10-fold during the
last 15 years. So far, there is no medical test that can identify it
reliably.
Most experts agree that autism most probably involves the interaction
of many genes that together predispose a child to the condition, combined
with some outside factor that triggers the disorder. No one has identified
any genes for autism, nor is there any consensus on what environmental
factor is involved.
“We have added now the fact that there may also be a metabolic
component that reflects both the underlying genetics and the environment,”
James said.
