Researchers identified gene mutations present in two families with the unusual autism and found the mutations caused lower levels of certain amino acids in their blood. In an experiment described Thursday in the journal Science, mice bred with same gene mutations that were given a supplement of branched chain amino acids, or BCAAs, had fewer seizures and improved autism symptoms.
The next step is to see if the BCAA supplement does the same for patients with the uncommon autism, researchers said. While the autism found in the two families is extremely rare and may not affect other people, the discovery might help identify other forms of autism, said Gaia Novarino, an author of the study and scientist at the University of California, San Diego.
"This can be an example that there possibly are rare forms of autism that are treatable," Novarino said in a telephone interview. "We don't know how many there are out there. So that's what we want to look at and find."
About 1 in 88 children in the United States are diagnosed with an autism-related condition. The disorder hurts brain development and is linked to poor social interaction and communication skills, repeated body movements, and unusual attachments to objects. Twenty five percent of autistic children also have epilepsy, according to the study by researchers from Yale University and the University of California, San Diego.
Because the disorder affects individuals in a wide spectrum of ways, researchers have begun comparing autism to cancer and investigating potential genetic and environmental causes. As with cancer, it is difficult to pinpoint how or why autism strikes some people.
The study focused on a gene, Branched Chain Ketoacid Dehydrogenase Kinase, that was found in a family of Turkish descent and in a second one of Egyptian ancestry, through sequencing their exomes, or the region of the genome that creates proteins. The defect causes lower levels of BCAAs in the blood than typically found, according to the study.
BCAAs are essential nutrients that the body can't make. It is acquired through proteins in foods such as meat and dairy. The BCAAs leucine, isoleucine, and valine spur the building of protein in muscles, according to WebMD, a provider of health information to consumers and doctors. Supplements containing these amino acids are promoted for helping reduce muscle breakdown during exercise and increase mental concentration. They've also been used to treat patients with amyotrophic lateral sclerosis, or Lou Gehrig's Disease.
To further test their theory, the researchers took skin samples from the patients and converted them into neural stem cells. These cells acted normally in the presence of an environment rich in the depleted amino acids.
The particular genetic variant is related to another disorder called Maple Syrup Urine Disease, where the opposite occurs — those affected have a toxic buildup of branched chain amino acids. Patients with this disorder have urine that smells like maple syrup and can develop mental retardation, according to the National Institutes of Health.
Novarino cautioned that the findings shouldn't be applied to people without this very specific and rare form of the disorder.
"Not all autism patients will have to take amino acid supplementations, because it probably won't work," she said.
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