Can intestinal bacteria cause autism in mice

Processed foods: is there a link to the rise in autism?


Substances that are commonly found in processed foods cause molecular changes in neural stem cells. This is what researchers at the University of Central Florida (UCF) have observed. They suspect there is a link to the rise in autism and processed food consumption during pregnancy.

With the increasing number of children diagnosed with autism, the more urgent the need to find the causes of the disorder becomes day by day. UCF researchers now appear to have discovered a link between the diet of pregnant women and autism. If pregnant women consume a high proportion of processed foods, it could potentially affect the developing brain of the unborn child, the researchers said.

Prof. Drs. Saleh Naser, Dr. Latifa Abdelli and a research associate at UCF, Aseela Samsam, have demonstrated the molecular changes that occur when brain stem cells are frequently and excessively exposed to a certain acid that is commonly found in processed foods. In a study published on June 19 in Scientific Reports, the UCF scientists found out how high levels of propionic acid (PPA) are used to increase the shelf life of packaged foods and to inhibit the formation of mold in commercial processed cheese and bread is used, the development of neurons in the fetal brain is impaired.

Professor Naser, who specializes in gastroenterological research at the Burnett School of Biomedical Sciences, began the study after reports showed that autistic children commonly suffer from stomach problems such as irritable bowel syndrome. He wondered about a possible connection between the gut and the brain and began to investigate how the microbiome - or gut bacteria - differs between people with autism and people without it.

"Studies have shown that the PPA levels in stool samples from children with autism are higher and that the intestinal flora is different in autistic children," explained Prof. Naser. "I wanted to find out why."
In the laboratory, the scientists found that exposure of neural stem cells to excessive amounts of PPA damages brain cells in a number of ways. First, the acid disrupts the natural balance between brain cells by reducing the number of neurons and causing glial cell overproduction. While glial cells help neurons develop and function, too many glial cells disrupt connectivity between neurons. They also cause inflammation, which has been found in the brains of autistic children.
Excessive amounts of the acid also decrease and damage the pathways neurons use to communicate with the rest of the body. The combination of reduced neurons and damaged signaling pathways affects the brain's ability to communicate and leads to behaviors that are common in children with autism, including repetitive behavior, mobility problems, and the inability to interact with others.
Previous studies have suggested links between autism and environmental and genetic factors, but according to Professor Nasers and Abdelli, their study is the first to discover the molecular link between elevated PPA levels, glial cell production, impaired neural circuitry, and autism. The 18-month study was self-funded by the UCF.

PPA occurs naturally in the gut, and a mother's gut flora changes during pregnancy and can lead to acidity increases. But the authors state that eating packaged foods that contain the acid can further increase the amount of PPA in the woman's intestines, so that it then passes to the fetus.
More research needs to be done before clinical conclusions can be drawn. Next, the team will try to validate its results in mice by examining whether a diet high in PPA causes autism in mice that are genetically predisposed to the disease. The scientists hope their results will fuel studies aimed at preventing the disorder.
"This research is only the first step towards a better understanding of autism spectrum disorder," concluded the UCF scientists. "But we are confident that we are on the right track to finally uncover the genesis of autism."

Source: EurekAlert! University of Central Florida, Scientific Report