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Baby teeth revealed how a child metabolized essential and toxic elements and differed among children with attention deficit hyperactivity disorder (ADHD) or autism spectrum disorder versus those without such symptoms, a small twin study suggested.

Prenatal and newborn children form a new tooth layer daily which captures an imprint of chemicals circulating in the body and produces a chronological exposure record, like rings on a tree. This record, which shows cyclical processes involved in metabolizing nutrients and metals during fetal and early postnatal development, differed significantly in children who had ADHD, autism, or both disorders, reported Christine Austin, PhD, of the Icahn School of Medicine at Mount Sinai in New York City, and colleagues in .

These findings suggest metabolic regulation of nutrients and toxins may play a role in ADHD and autism, the authors noted.

"With more research, this could lead to an early detection tool, which could mean early treatment, which could potentially mean a better life outcome," Austin told 木瓜直播. "If there's a critical time when these metals get dysregulated, maybe we can counter that."

However, she also cautioned that it would be premature to use these markers for diagnostic purposes. The study did not include sensitivity/specificity analyses, for example.

The study is a continuation of earlier research by the same team, who previously showed that children with autism had disrupted zinc-copper metabolism patterns in utero or in their earliest months of life.

Most environmental epidemiological research focuses on metal concentrations at a single time point -- looking at blood levels of lead, for example -- Austin noted. "Our research looks at cycles of metal metabolism," she said. "It's a different thing than just looking at high exposure versus low exposure."

In the current study, Austin and co-authors used naturally shed baby teeth to reconstruct prenatal and early-life exposures to nutrients and toxic elements in 74 children from the Roots of Autism and ADHD Twin Study in Sweden (). The twins were discordant for ADHD, autism, and other neurodevelopmental diagnoses; 30 were complete twin pairs, 11 were children from twin pairs whose sibling did not donate a tooth, and one set of children were triplets.

The team used a laser ablation technique to sample each tooth at an average of 152 locations; tooth data ranged from the second trimester up until about the first year. They measured temporal profiles of lead, cobalt, zinc, vanadium, and other elements in 13 children with ADHD, eight with autism, 12 with both ADHD and autism, and 41 typically developing children, and characterized cyclic metabolic patterns of these metals.

The researchers identified cyclical properties specific to ADHD and also found distinct elemental signatures in children who had either ADHD or autism, as well as in children who had both disorders.

In children with ADHD, the regularity of elemental cycles consistently was reduced for cobalt (β −0.03, P=0.017), lead (β −0.03, P=0.016), and vanadium (β −0.03, P=0.01), compared with typically developing children. Similarly, the complexity of these elemental cycles was reduced (cobalt β −0.13, P=0.017; lead β −0.18, P=0.016; vanadium β −0.15, P=0.008) in children with ADHD.

"The discovery that autism spectrum disorder, attention-deficit/hyperactivity disorder, and the combined presentation of autism and ADHD each have a unique metabolic signature can inform future studies on what might cause the disorders," said co-author Paul Curtin, PhD, also of the Icahn School of Medicine at Mount Sinai, in a statement. "It could help us determine the pathways implicated in the different diseases, which, in turn, could inform the development of treatment and prevention strategies."

Austin cautioned that the study's sample size was small and results may be influenced by a number of factors; organic environmental chemicals may play a role in ADHD, the authors noted. Further work is needed in non-twin studies, they added.

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