How Gut Microbes and Brain Disorders Could Be Linked

Findings May Lead to Microbiome Drugs for Neurodegenerative and Neuropsychiatric Disorders

Fifteen years ago, neuroscientist Jane Foster discovered that bacteria in the gut may have influence over brain function and behavior. She came to this conclusion by conducting studies using two groups of mice. One group had healthy gut microbes and the other group lacked a microbiome altogether. Foster found something curious, the mice with missing gut bacteria appeared less anxious than the healthy group of mice. With this experiment, the researcher came to the realization that gut function and behavior are linked. Fast forward to today, when the gut-brain connection is a readily acceptable theory. The link has now even been tied to many neurodegenerative and neuropsychiatric disorders including Alzheimer’s disease, Parkinson’s disease and autism. Currently, millions of research dollars are being spent by the National Institute of Health to further explore this connection.

While focusing on gut bacteria and its relationship to autism, husband and wife research team, Gloria Choi and Jun Huh, started investigating the connection using mice studies. Their research zeroed in on  T-helper 17 cells which defend against bacteria and fungi by generating molecules known as cytokines. When an infection was mimicked in pregnant mice, Choi and Huh discovered the T-helper 17 cells became hyperactive producing a cytokine called IL-17. This molecule was able to travel into the brains of the mother’s developing pups and then bound to their brain receptors. Later these offspring showed increased neural activity resulting in autism-like behaviors. This discovery may have real world implications. Choi and Huh are now concerned that the coronavirus pandemic could lead to an increased risk of autism during the next several years. They are currently collecting stool samples from pregnant women who are infected with COVID-19 and analyzing their gut bacteria as well as their levels of IL-17 in their blood. 

A neurobiologist named Mauro Costa-Mattioli is studying microbes in a different way. He is searching for microbes that cause brain dysfunction to figure out how they cause damage. A breakthrough in his research came when Costa-Mattioli discovered that mice who had autism-like behaviors were exposed to a bacterium called Lactobacillus reuteri, their behaviors disappeared. Costa-Mattioli’s discovery that certain bacteria may be able to alleviate autism symptoms caught the attention of biopharmaceutical companies who are now interested in developing drugs that have the ability to modify a person’s microbiome. Two companies are currently interested in correcting the microbiome through pharmaceuticals. Axial Therapeutics has raised $25 million and Finch Therapeutics has raised $90 million towards becoming the first companies to develop microbiome drug treatments for autism. 

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