Although 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 unclear whether this deficiency contributes to autism, but scientists have defined a possible mechanism for how this might work, according to a paper published in Limits in molecular neuroscience.
For their research, the researchers have shown how zinc forms the connections, or synapses, between brain cells (neurons) formed during early development through a complex molecular machine 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 Stanford University School of Medicine study, said in a statement.
"Our findings link zinc levels in neurons – through interactions with the proteins encoded by these genes – to the development of autism," Kim said.
The team discovered that when a brain signal was transmitted 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 surface of the neuron at the synapse.
The finding that zinc forms the properties of the development of synapses via SHANK proteins suggests that a lack of the mineral during early development may contribute to autism by disrupting the function of synapses, allowing brain cells to communicate with each other.
"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, at Stanford University School of Medicine.
However, it is important to note that it is currently not possible to draw concrete conclusions or to start by recommending that children take zinc supplements.
"Currently there are no controlled studies on autism risk with zinc supplementation in pregnant women or babies, so the jury is still out," Craig Garner, co-author of the study of the German center for neurodegenerative diseases, said. "But experimental work in autism models that is also published in this Frontiers Research topic is promising."
Taking too much zinc can reduce the amount of copper that the body absorbs, which can lead to anemia and weakening of the bones. In addition, zinc deficiency does not necessarily imply a nutritional deficiency and can for example be caused by problems with absorption in the intestine.
"Nonetheless, our findings provide a new mechanism to understand how zinc deficiency – or a disrupted treatment of zinc in neurons – could contribute to autism," said Garner.
Autism is a lifelong developmental disorder 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.