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Amino acid before pregnancy may lower autism risk


Getting more of the amino acid carnitine, which can be found in red meat and whole milk, before and during pregnancy could be a way to protect children from a type of autism. Carnitine is also available as a supplement.

Carnitine, which the body can manufacture itself or extract from dietary sources, is required for transport of fatty acids into mitochondria, the compartment within the cell that converts fats into energy.

Earlier studies have shown inherited mutations in a gene required for the body to synthesize carnitine are associated with the risk for development of autism-spectrum disorders, but the basis for that association has been unclear—until now.

Findings from a new study show genetic defects in the body’s ability to manufacture carnitine might be associated with an increased risk of autism because carnitine deficiency interferes with the normal processes by which neural stem cells promote and organize embryonic and fetal brain development.

Zhigang Xie, an assistant research scientist at the Texas A&M Health Science Center College of Medicine and lead author of the study, has refined a new technology allowing him to mark, follow and analyze individual neural stem cells in their native environment in an actual developing brain.

“It’s very difficult to study neural stem cells in their complex natural environment,” Xie said. “But now we have a technology that makes such studies possible.”

In the study, Xie and his colleagues found neural stem cells that can’t produce carnitine don’t behave properly and are inappropriately depleted from the developing brain, but when genetically at-risk neural stem cells are supplied with carnitine from an outside source, they function properly.

“Inborn errors in carnitine production cause significant issues in a cell type one would believe has to contribute to autism risk,” said Vytas A. Bankaitis, Texas A&M chemistry professor and collaborator on the study.

Since the autism risk gene is located on the X chromosome and males have only one X chromosome (females have two), they are at greater risk.

Because the gene mutation is a recognized autism risk gene and its location on the chromosome is known, researchers suggest one possible first step for prevention is to test women for the mutation before pregnancy. If a woman is a carrier for the mutated autism risk gene, she can supplement her diet with carnitine before and during pregnancy to ensure a sufficient supply of the nutrient is available to the developing fetus, thus helping offset the genetic defect.

“In retrospect, this preventative approach seems obvious,” Bankaitis said. “But metabolic deficiencies are complicated scenarios to interpret, and we believe these complexities obscured what will hopefully prove to be a rather simple path toward prevention.”

One note: This particular prevention strategy will not apply to all cases of autism.

“Even if this strategy works, it will not be a panacea for reducing all autism risk,” Bankaitis said. “While it could work in cases involving carnitine-deficiency, other pathways are also in play because as many as 1,000 genes might ultimately be found to relate to autism risk.”

But any progress in preventing autism is welcome, especially in the black community where children with autism are one to two years older than white children before they’re diagnosed. Early intervention is key to addressing the disorder.

“We have indications, at least for some types of autism risk, that a dietary carnitine prevention method might be effective,” Xie said. “For some individuals, this simple nutritional supplement might really help reduce the risk of developing autism spectrum disorder. Any progress on the prevention front would be welcome given the number of people affected.”

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