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Primary dentition study links exposure to toxins in early life to autism

June 09, 2017

NEW YORK, USA: Evidence found in primary dentition has suggested that exposure to specific toxins and nutrients is associated with the risk of developing autism spectrum disorder (ASD). The study suggests that primary teeth from children with autism contain more toxic lead and less of the essential nutrients zinc and manganese, compared with teeth from children without autism. The researchers determined the second and third trimesters and early postnatal periods to be critical developmental windows.

While the genetic component of ASD has been intensively studied, specific environmental factors and the stages of life when such exposures may have the greatest impact on adverse developmental outcomes, including intellectual disability and language, attentional and behavioral problems, are poorly understood. In addition to identifying specific environmental factors, the present study pinpointed developmental periods when elemental dysregulation poses the greatest risk for developing autism later in life.

The researchers, at the Icahn School of Medicine at Mount Sinai, New York, studied twins to control for genetic influences. The data were drawn from the Roots of Autism and ADHD Twin Study in Sweden, in which 154 twin pairs had participated as of September 2016, including 11.3 percent of all ASD-discordant twins in Sweden in the specified age range.

To determine the effects that the timing, amount and subsequent absorption of toxins and nutrients have on ASD risk, Mount Sinai researchers used validated tooth matrix biomarkers to analyze primary teeth collected from pairs of identical and nonidentical twins, of whom at least one had a diagnosis of ASD. They also analyzed teeth from pairs of normally developing twins who served as the study control group. During fetal and childhood development, a new tooth layer is formed every week or so, leaving an imprint of the microchemical composition from each unique layer and thus providing a chronological record of exposure. The team at the Senator Frank R. Lautenberg Environmental Health Sciences Laboratory at Mount Sinai used lasers to reconstruct these past exposures along incremental markings, similar to using growth rings on a tree to determine the tree’s growth history.

“We found significant divergences in metal uptake between ASD-affected children and their healthy siblings, but only during discrete developmental periods,” explained Dr. Manish Arora, Director of Exposure Biology at the Lautenberg Laboratory. “Specifically, the siblings with ASD had higher uptake of the neurotoxin lead, and reduced uptake of the essential elements manganese and zinc, during late pregnancy and the first few months after birth, as evidenced through analysis of their baby teeth. Furthermore, metal levels at three months after birth were shown to be predictive of the severity of ASD eight to ten years later in life.”

Figures released by the Centers for Disease Control and Prevention state that ASD occurs in 1 in every 68 children in the U.S.

The study, titled “Fetal and postnatal metal dysregulation in autism,” was published online on June 1 in the Nature Communications journal and was conducted in collaboration with researchers from Karolinska Institutet, Stockholm, and the University of Gothenburg, Sweden.

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