Babies who don’t get enough zinc while in the womb may be more likely to develop autism, a new study claims.
Scientists still don’t have a definitive answer for what causes autism, but the vast majority of research shows it is down to a combination of ‘environmental factors’ and genetic defects.
In a new paper published today, US and German scientists say they have evidence that zinc levels may be one of the defining environmental factors that sew the seeds of the behavioral disorder.
More research is needed to confirm whether there could be a causal link, but the team says they have defined a possible mechanistic link.
US and German scientists say they have evidence that zinc levels may be one of the defining environmental factors that sew the seeds of autism spectrum disorder
They found zinc shapes the connections or ‘synapses’ between brain cells that form during early development, via a complex molecular machinery encoded by autism risk genes.
However they caution research is at its early stage and the findings does not mean pregnant women should start taking zinc supplements to prevent autism.
Senior author Dr Sally Kim of Stanford University School of Medicine in California said: ‘Autism is associated with specific variants of genes involved in the formation, maturation and stabilisation of synapses during early development.
‘Our findings link zinc levels in neurons – via interactions with the proteins encoded by these genes – to the development of autism.’
Co-senior author Professor Craig Garner of the German Centre for Neurodegenerative Diseases added: ‘Currently, there are no controlled studies of autism risk with zinc supplementation in pregnant women or babies, so the jury is still out.
‘We really can’t make any conclusions or recommendations for zinc supplementation at this point, but experimental work in autism models also published in this Frontiers Research Topic holds promise.
‘Nevertheless, our findings offer a novel mechanism for understanding how zinc deficiency – or disrupted handling of zinc in neurons – might contribute to autism.’
Zinc helps with making new cells and enzymes, processing carbohydrate, fat and protein in food and wound healing.
Foods rich in the mineral include meat, shellfish, dairy foods such as cheese, bread and cereals.
The NHS said most people get enough zinc from their diet and should not take more than 25mg of zinc supplements a day unless advised to by a doctor.
Too much reduces the amount of copper the body can absorb, which can lead to anaemia and weakening of the bones.
The study published in the journal Frontiers in Molecular Neuroscience found 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.
Experiments showed the mechanism of zinc-Shank-mediated AMPAR maturation in developing synapses.
Lead author Researcher Dr Huong Ha at Stanford explained: ‘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.
‘Furthermore, our study shows mechanistically how Shank2 and 3 work in concert with zinc to regulate AMPAR maturation, a key developmental step.’
Co-senior author Professor John Huguenard, also of Stanford added in other words, zinc shapes the properties of developing synapses via Shank proteins.
Prof Huguenard concluded: ‘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.’
- Note to readers: Speak to your doctor before altering your diet