While the exact cause of autism is unknown, its development in children has been linked to various genetic and environmental factors—including zinc deficiency.
It is still not clear whether this deficiency contributes to autism, but scientists have defined a possible mechanism for how this could work, according to a paper published in Frontiers in Molecular Neuroscience.
For their study, the researchers demonstrated how zinc shapes the connections, or synapses, between brain cells (neurons) that form during early development via a complex molecular machinery controlled by autism-linked genes.
"Autism is associated with specific variants of genes involved in the formation, maturation and stabilization of synapses during early development," Sally Kim, lead author of the study from Stanford University School of Medicine, said in a statement.
"Our findings link zinc levels in neurons—via interactions with the proteins encoded by these genes—to the development of autism," Kim said.
The team found that when a brain signal was transferred via a synapse, zinc entered the target neuron where it could bind two of these proteins, known as SHANK2 and SHANK3. Those proteins cause changes in the composition and function of adjacent signal receptors, called AMPARs, on the neuron's surface at the synapse.
The finding that zinc shapes the properties of developing synapses via SHANK proteins suggests that a lack of the mineral during early development could potentially contribute to autism by impairing the function of synapses, which enable brain cells to communicate with one another.
"Understanding the interaction between zinc and SHANK proteins could therefore lead to diagnostic, treatment and prevention strategies for autism," suggested John Huguenard, co-senior author of the study, of Stanford University School of Medicine.
It's important to note, however, that at present it isn't possible to make any concrete conclusions or begin recommending that children take zinc supplements.
"Currently there are no controlled studies of autism risk with zinc supplementation in pregnant women or babies, so the jury is still out," Craig Garner, co-author of the study from the German Centre for Neurodegenerative Diseases, said. "But experimental work in autism models also published in this Frontiers Research Topic holds promise."
Taking too much zinc can reduce the amount of copper the body absorbs, which can result in anemia and weakening of bones. Furthermore, zinc deficiency does not necessarily imply a dietary deficiency, and could be caused by problems with absorption in the gut, for example.
"Nevertheless, our findings offer a novel mechanism for understanding how zinc deficiency—or disrupted handling of zinc in neurons—might contribute to autism," Garner said.
Autism is a lifelong developmental disability that affects how people perceive the world and interact with others. The autism spectrum contains a range of similar disorders, such as Asperger's syndrome.