A new study from the Baylor College of Medicine involving mice has found that the lack of a single species of bacteria in the gut is linked with autism-like social behaviors in mice.
What's more, restoring that bacteria reversed those behaviors.
Many animals, including humans, have microbes that live in the gut to assist with digestion. In recent years, scientists have found that this population of microbes (termed the microbiota) has also been found to play a role in obesity, allergies, and even behavior. While it has been known that gut bacteria can be heavily influenced by diet for better or for worse, this new study has shown that a mother's diet can influence the microbiome of the offspring.
In the study, a group of 60 female mice were fed a high-fat diet, while a control group ate a healthy diet. Each group of mice got pregnant, gave birth, and fed the offspring until they were old enough to wean. The offspring from the high-fat diet group had much higher instances of autism-like social behaviors than those whose mothers ate the normal diet. After the two groups of young mice began interacting, however, the symptoms of the ASD-like mice began disappearing.
So what happened?
When the gut microbes of the mice were examined, one specific species of bacteria was nine times more abundant in the typical mice than those with ASD-like symptoms. After the two populations were combined, the ASD-like mice were exposed to the feces of the typical mice, which contained that bacterial species. Because mice eat the droppings of one another, the bacteria was introduced into the guts of the ASD-like mice.
Mice who were bred to not have any gut microbes at all also had the same social deficiencies as the mice born to mothers with high-fat diets and they, too, had those symptoms reversed after being introduced to the typical mouse population.
The bacteria, Lactobacillus reuteri, is also involved with the production of oxytocin. Oxytocin is often nicknamed "the cuddling hormone" because of its function associating social behavior with happy feelings. Once the bacteria was boosted to normal levels, activity in the reward center of the brain also increased.
After the results of this study were published in Cell, many have wondered how this could translate into humans, particularly those with severe social limitations.
"Whether it would be effective in humans, we don't know yet, but it is an extremely exciting way of affecting the brain from the gut," senior author Mauro Costa-Mattioli said.
Even if this does someday translate into a potential therapy for individuals with autism, it brings up further questions of how it would be received because the idea of eliminating symptoms of autism is contentious. Some within the ASD community are constantly searching for new treatment options, while others feel that trying to "cure" neurodiversity is offensive.
Regardless of how the ethical policies of ASD treatment eventually play out, this study gives an exciting avenue of research that could answer many more questions.
As rates of Autism Spectrum Disorder (ASD) continue to rise, the hunt for possible risk factors and treatments does as well. ASD is characterized by many different developmental and behavioral traits, with many affecting the individual's social life. This can include a lack of interaction, communication, empathy, and more.
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