Autism linked to gut bacteria in new study

Autism spectrum disorder (ASD) is defined by a broad array of behaviors, including difficulty with communication, restricted interests and repetitive behaviors. Spectrum refers to the fact that people with autism show a wide variety of symptoms with the intensity of those symptoms differing from person to person.

A new study from researchers at Caltech illustrates that the behaviors associated with ASD can be linked to the gut microbiome in mice. The study does not establish cause, but it does provide interesting evidence that there could be relatively unexplored contributors to the symptoms of autism.

What is the gut microbiome and how does it influence health?

In a press release summarizing the research, Caltech explained the gut microbiome this way:

The communities of microorganisms that inhabit the human gut are called the microbiota, and their collective genomes are known as the microbiome. These organisms live in a symbiotic state with humans. In exchange for a warm and nutrient-rich environment, bacteria help us digest food, affect metabolism, and educate our immune system.

The microbiome has come under increasing scrutiny for its role in a number of health discussions. We went over the broad implications in a prior post about NASA cataloguing the microbiome of the International Space Station to better understand how to manage health for long-range space travel:

I believe so strongly in the importance of the microbiome that I dedicated my entire 2019 Biotech 201 series to the secrets of the human microbiome. You can watch those talks for yourself if you want more information (or anytime you’re craving a dose of science).

Evidence continues to grow that the microbiome plays an enormous role in human health, perhaps bigger than we’ve imagined. Just this year, researchers published a paper in Science Advances exploring the potential impact of the gut microbiome on schizophrenia symptoms. We even detailed a hypothesis that gum disease might be linked to Alzheimer’s in an earlier Shareable Science.

Learning to appreciate the effect the microbiome has on the rest of the body opens up all new doors to understanding the complexities of human health.

Linking autism and the microbiome

Even with context of why the microbiome makes sense as a subject of research for understanding behavioral symptoms, we still have work to do in order to understand how researchers linked autism spectrum behaviors with the microbiome.

The researchers used lab mice that are grown in the absence of microorganisms for the tests. Some mice received gut microorganisms from children with autism, while others received gut microorganisms from people without autism.

Here’s what Caltech says happened next:

The mice with microbiota from individuals with ASD exhibited autism-like behaviors, whereas the mice harboring microbiota from typically-developing individuals did not show these symptoms. Specifically, they spent less time socially interacting with other mice, vocalized less, and exhibited repetitive behaviors. These symptoms are analogous to behavioral characteristics of people with ASD.

The researchers are quick to point out that they did not find causative proof. However, they found a bevy of interesting information about potential interactions between the microbiome and autism-linked behaviors.

For example, researchers found a decrease of certain products of metabolism in the mice that received the microbiota from children with autism. Notably, scientists marked a decrease in 5-aminovaleric acid (5AV) and taurine, which are linked to neural receptors that handle inhibition. The team then found that another kind of mouse, one that naturally exhibits autism-like behaviors, could be treated with 5AV and taurine to reduce behavioral symptoms.

A more complete approach to autism

When you study something like ASD, you don’t expect to find a single cause. The disorder, after all, is a spectrum. It manifests in so many different ways that you would expect to find a variety of different factors at work (some genetic, others environmental) to create the disorder in each individual.

However, researchers relish any chance to narrow the focus as to what could impact the behaviors linked to autism. These clues could help better understand the total picture of what ASD means. Scientists could also find ways to treat specific symptoms.

For example, we already have tools to adjust the microbiomes of individuals. In fact, one two-year study from Arizona State University found autism symptoms could be significantly reduced using a technique called microbiota transfer therapy (MTT). Although this is a very preliminary finding, further research may open the door for treatments that modify gut bacterial communities to alleviate behavioral symptoms. Along similar lines, specific dietary changes might also become relevant for managing symptoms.

Expanding understanding

It’s important to know where we are and where we definitely are not. We definitely are not at a point where we can claim to know what causes autism spectrum disorder. Dietary supplements and adjusting the gut microbiome are intriguing possibilities, but both are early-stage hypotheses requiring significantly more rigorous testing. However, we are in a place to understand a little bit more of the complexities of this disorder and catch a glimpse of the larger landscape.

Each step forward narrows the focus of study while broadening the range of possibilities.

To schedule a media interview with Dr. Neil Lamb or to invite him to speak at an event or conference, please contact Margetta Thomas by email at mthomas@hudsonalpha.org or by phone: Office (256) 327-0425 | Cell (256) 937-8210