Zinc Deficiency during Pregnancy Linked to Autism in Babies

The emergence of autism in children has not only been linked to genes encoding synaptic proteins—among others—but also environmental insults such as zinc deficiency. Although it is unclear whether zinc deficiency contributes to autism, scientists have now defined in detail a possible mechanistic link.

Foods and spices containing zinc. Image credit: US Dep. of Agriculture

"Autism is associated with specific variants of genes involved in the formation, maturation and stabilization of synapses during early development," says study senior author Dr. Sally Kim of Stanford University School of Medicine.

"Our findings link zinc levels in neurons—via interactions with the proteins encoded by these genes—to the development of autism."

They found that when a signal is transferred via a synapse, zinc enters the target neuron where it can bind two such proteins: Shank2 and Shank3. These proteins in turn cause changes in the composition and function ('maturation') of adjacent signal receptors, called 'AMPARs', on the neuron's surface at the synapse.

"In developing rat neurons, we found that Shank 2 and 3 accumulate at synapses in parallel with a switch to mature AMPARs. Adding extra zinc accelerated the switch—but not when we reduced the accumulation of Shank 2 or 3," explains Dr. Huong Ha - the study's lead author, a former Stanford graduate student.

In other words, zinc shapes the properties of developing synapses via Shank proteins.

This suggests that a lack of zinc during early development might contribute to autism through impaired synaptic maturation and neuronal circuit formation.

Understanding the interaction between zinc and Shank proteins could therefore lead to diagnostic, treatment and prevention strategies for autism.

Currently, there are no controlled studies of autism risk with zinc supplementation in pregnant women or babies. No conclusions or recommendations for zinc supplements can be made at this time.

Taking too much zinc reduces the amount of copper the body can absorb, which can lead to anemia and weakening of the bones. Furthermore, zinc deficiency does not necessarily imply a dietary deficiency—and could result instead from problems with absorption in the gut, for example. (Tasnim News Agency)

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