Bowels and brains

The first records of fecal transplantation date back to 4th century China for gastrointestinal complaints. Fifteen centuries later, in the 1950s, bacteriologist Stanley Falkow, concerned about the side effects of antibiotics in surgical patients, converted half of his patients’ stools into pill form to be taken daily during their postsurgical recovery. Anecdotally, the treatment group had better outcomes than the nontreatment group, but the results were never published. Dr Falkow was dismissed from his post for engaging in what was then thought to be a repellant research project. 

Moving ahead to current day, one promising autism research path involves administering microbes that live in our intestines to autistic children. Autism was first recognized as a medical disorder in 1942 by Dr Leo Kanner at Johns Hopkins Hospital. According to the Centers for Disease Control and Prevention, about one in 59 children in the US is currently diagnosed with autism. That figure is up from one in 150 children in the year 2000. The possible causes of autism are not understood. No medical treatments have been approved, although among other approaches, behavioral therapy, speech therapy, nutritional therapy, and psychiatric medications have been of some value. 

One recent promising research approach involves the bowel microbiome. The microbiome is the collection of microbes in our intestines that is involved in digestion, some aspects of the management of the immune system, and prevention of overgrowth of harmful bacteria. According to researchers at Arizona State University many children with autism have gastrointestinal problems. The Arizona research team found that the microbiomes of 18 children with autism were of lower diversity of gut microbes than those of typically developing children and were lacking certain other strains of bacteria as well. At the end of the 2-year study improvements in the children’s gut symptoms remained and an evaluator found significant improvement in their language, social interaction, and behavior. 

There seems to be some signaling connection between the microbes living in the intestines and brain functions. In a recent study a special type of fecal transplant—a technique known as microbiota transfer therapy (MTT)—originally pioneered by Australian gastroenterologist Dr Thomas Borody showed an improvement in intestinal health and autism symptoms that lasted long after the treatment was carried out. This extraordinary but small and somewhat uncontrolled project is described in detail in the Science and Technology section of the Economist magazine.

Several laboratory studies have now been done with rodents harboring gut bacteria from autistic human donors. The mice have been found to exhibit a rodent’s version of autism: repetitive behaviors, restricted movements, and reduced social and vocal communication with other mice. The US Food and Drug Administration is reviewing the MTT procedure and adults with autism are being recruited for a large scale fecal transplantation trial.

These developments are raising important questions. How is the bowel environment related to the brain? Why the increased incidence of autism spectrum disorders in recent years? How relevant are the findings to the causes of adult dementia?
—George Szasz, CM, MD

Suggested reading
Brooks M. Medscape. Processed foods during pregnancy may be linked to autism. 26 June 2019. 

Kang D-W, Adams JB, Coleman DM, et al. Long-term benefit of microbiota transfer therapy on autism symptoms and gut microbiota. Scientific Reports 2019:9;5821.

The Economist. Autism-spectrum disorder. More evidence that autism is linked to gut bacteria. 30 May 2019.

This posting has not been peer reviewed by the BCMJ Editorial Board.

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