Date:
June 1, 2017
Source:
The Mount Sinai Hospital / Mount Sinai School of Medicine
Summary:
A new study uses a unique source -- baby teeth -- to reveal
that both the timing and amount of exposure can affect diagnosis.
FULL STORY
This is a cross-section of tooth
showing laser removal of the dentine layer, in tan, for analysis of metal
content.
Credit: J. Gregory, Copyright Mount
Sinai Health System, 2017
Using evidence found in baby teeth,
researchers from The Senator Frank R. Lautenberg Environmental Health Sciences
Laboratory and The Seaver Autism Center for Research and Treatment at Mount
Sinai found that differences in the uptake of multiple toxic and essential
elements over the second and third trimesters and early postnatal periods are
associated with the risk of developing autism spectrum disorders (ASD),
according to a study published June 1 in the journal Nature Communications.
The critical developmental windows
for the observed discrepancies varied for each element, suggesting that
systemic dysregulation of environmental pollutants and dietary elements may
serve an important role in ASD. In addition to identifying specific
environmental factors that influence risk, the study also pinpointed
developmental time periods when elemental dysregulation poses the biggest risk
for autism later in life.
According to the U.S. Centers for
Disease Control and Prevention, ASD occurs in 1 of every 68 children in the
United States. The exact causes are unknown, but previous research indicates
that both environmental and genetic causes are likely involved. While the
genetic component has been intensively studied, specific environmental factors
and the stages of life when such exposures may have the biggest impact on the
risk of developing autism are poorly understood. Previous research indicates
that fetal and early childhood exposure to toxic metals and deficiencies of
nutritional elements are linked with several adverse developmental outcomes,
including intellectual disability and language, attentional, and behavioral
problems.
"We found significant divergences
in metal uptake between ASD-affected children and their healthy siblings, but
only during discrete developmental periods," said Manish Arora, PhD, BDS,
MPH, Director of Exposure Biology at the Senator Frank Lautenberg Environmental
Health Sciences Laboratory at Mount Sinai and Vice Chair and Associate
Professor in the Department of Environmental Medicine and Public Health at the
Icahn School of Medicine at Mount Sinai. "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."
To determine the effects that the
timing, amount, and subsequent absorption of toxins and nutrients have on ASD,
Mount Sinai researchers used validated tooth-matrix biomarkers to analyze baby
teeth collected from pairs of identical and non-identical twins, of which at
least one had a diagnosis of ASD. They also analyzed teeth from pairs of
normally developing twins that 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 micro chemical composition from each
unique layer, which provides a chronological record of exposure. The team at
the Lautenberg Laboratory 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.
"Our data shows a potential
pathway for interplay between genes and the environment," says Abraham
Reichenberg, PhD, Professor of Psychiatry and Environmental Medicine and Public
Health at the Icahn School of Medicine at Mount Sinai. "Our findings
underscore the importance of a collaborative effort between geneticists and
environmental researchers for future investigations into the relationship between
metal exposure and ASD to help us uncover the root causes of autism, and
support the development of effective interventions and therapies."
Additional studies are needed to
determine whether the discrepancies in the amount of certain metals and
nutrients are due to differences in how much a fetus or child is exposed to
them or because of a genetic difference in how a child takes in, processes, and
breaks down these metals and nutrients.
Story Source:
Materials provided by The Mount Sinai Hospital
/ Mount Sinai School of Medicine.
Note: Content may be edited for style and length.
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