lead chelation study

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Chelation Therapy Reduces Lead-Exposure Problems But Could Create

Lasting Effects For Children Treated For Autism, CU Researchers Find

12/13/2006

http://news.biocompare.com/newsstory.asp?id=163528

Source: Cornell University News Service

Lead chelation therapy -- a chemical treatment to remove lead from the

body -- can significantly reduce learning and behavioral problems that

result from lead exposure, a Cornell study of young rats finds.

However, in a further finding that has implications for the treatment of

autistic children, the researchers say that when rats with no lead in

their systems were treated with the lead-removing chemical, they showed

declines in their learning and behavior that were similar to the rats

that were exposed to lead.

Chelating drugs, which bind to lead and other metals in the blood, are

increasingly being used for the treatment of autism in children.

" Although these drugs are widely used to treat lead-exposed children,

there is remarkably little research on whether or not they improve

cognitive outcomes, the major area of concern in relation to childhood

lead poisoning, " said Barbara Strupp, Cornell associate professor of

nutritional sciences and of psychology and the senior author of the

study, which was published in a recent issue of Environmental Health

Perspectives.

Studies on the safety or effectiveness of the drugs for treating autism

are similarly lacking, Strupp said.

Strupp added that to her knowledge this is the first report that shows

that chelation therapy can reduce behavioral and learning problems due

to lead exposure as well as the first to show that this type of

treatment can have lasting adverse effects when administered in the

absence of elevated levels of heavy metals.

The study used succimer (brand name, Chemet), the most widely prescribed

drug for the treatment of lead poisoning. Doctors prefer succimer to

other such drugs because it can be given orally on an outpatient basis,

and it leaches less zinc, iron and other essential minerals out of the

body. Although the Centers for Disease Control recommends chelation

therapy only for children whose blood lead levels exceed 45 micrograms

per deciliter, such drugs as succimer are commonly administered at much

lower levels of exposure, due to concerns about lasting complications

with even slightly elevated blood lead levels.

It is important to remove lead from the body as quickly as possible to

prevent or lessen lasting damage to the developing brain. High-lead

exposure from peeling lead-based paint can lead to coma, convulsions and

even death. At lower levels, lead exposure causes attention deficits,

delinquency and difficulty regulating emotions and can lower IQ scores

at a rate of about one IQ point per microgram/deciliter of exposure.

The study used rats -- whose mental and behavioral responses to lead

exposure are similar to humans' -- and exposed them to moderate- and

high-lead levels (administered via mothers' milk). A third group -- the

control -- was not exposed. Exposures were followed by a treatment with

succimer or placebo. Immediately thereafter, the researchers conducted

automated tests over six months on the rats' attention, memory and

abilities to learn and regulate emotions.

The rats with moderate-lead exposure benefited greatly from the

succimer: Their test results were indistinguishable from the control

test results. Rats exposed to higher lead levels showed benefits in the

emotional domain: After succimer treatment, they behaved similarly to

the control group. However, the treatment only slightly improved their

learning deficit.

In the group that had no lead exposure but were given succimer, " we

found lasting cognition and emotion-regulation that were as pervasive

and large as rats with high lead exposure, " said Strupp. She added that

one possibility is that succimer, in the absence of lead, may disrupt

the balance of such essential minerals as zinc and iron. " These findings

raise concerns about the use of chelating agents in treating autistic

children, " she said.

The study was funded by the National Institutes of Health.

Among other colleagues, Diane Stangle, a psychology graduate student,

and Stephane Beaudin, a research associate in nutritional sciences,

contributed to this work.