環境毒素、成藥恐引發胎兒自閉症

Autism can be triggered by abnormal levels of lipid molecules in the brain that affect the interaction between two key neural pathways in early brain development in the womb, researchers at York University have learned.

The scientists discovered that environmental causes such as exposure to chemicals in some cosmetics and common over-the-counter medications can affect the levels of these lipids.

Autism is a primary disorder of brain development with symptoms ranging from mild to severe and including repetitive behavior, deficits in social interaction, and impaired language. It is four times more prevalent in boys than in girls and the incidence continues to rise.

The U.S. Center for Disease Control and Prevention estimates that 1 in 68 children now has autism, based on data from 2010.

“We have found that the abnormal level of a lipid molecule called Prostaglandin E2 in the brain can affect the function of Wnt proteins. It is important because this can change the course of early embryonic development,” explained Professor Dorota Crawford in the Faculty of Health and a member of the York Autism Alliance Research Group.

Prostaglandin E2 (PGE2) is a bioactive fatty acid, a natural lipid-derived molecule involved in healthy, normal functioning of the human body. The York University researchers write, “Abnormal PGE2 signalling has been associated with pathologies of the nervous system.”

“Extracellular stimuli such as immunological and infectious agents, environmental toxins such as mercury and lead, and exposure to drugs including misoprostol and valproic acid can trigger the local production of PGE2 via specific biosynthetic pathways, resulting in altered cell signal transmission that modulates biological functions such as sleep, fever, inflammation, and pain,” the authors state.

In addition, the study published Monday in the journal “Cell Communication and Signaling,” states, “Increasing evidence for the contribution of environmental factors in the etiology of neurodevelopmental disorders like ASD [autism spectrum disorder] has prompted urgency to reveal their potential exogenous causes and underlying mechanisms.”

“Environmental factors like exposure to drugs, toxins or infectious agents cause disruptions in PGE2 signalling by increasing the levels of oxidative stress, consequent lipid peroxidation, and the immunological response; these factors and consequences that disturb normal PGE2 signalling have all been linked to ASD,” the study states.

According to Crawford, genes do not undergo significant changes in evolution, so even though genetic factors are the main cause, environmental factors such as insufficient dietary supplementations of fatty acids, exposures to infections, various chemicals or drugs can change gene expression and contribute to autism.

“The statistics are alarming. It’s 30 percent higher than the previous estimate of 1 in 88 children, up from only two years earlier. Perhaps we can no longer attribute this rise in autism incidence to better diagnostic tools or awareness of autism,” said Crawford.