Down Syndrome is the most common genetic cause of intellectual disability and occurs when there is an extra 21st chromosome, trisomy 21. Down Syndrome patients often experience premature aging and are therefore at early risk for age-related conditions like Alzheimer’s disease. Scientists from Italy published a study in November in PLOS One that compared the gut microbiome of Down Syndrome patients with that of healthy individuals.
The scientists hypothesized that the gut microbiome of Down Syndrome (DS) patients was contributing to the aging of the patients and would present similarly to the microbiome of an aged individual. They compared the gut microbiome of 17 patients with DS with previously published data for 16 age-matched individuals as well as 5 elderly individuals and 3 individuals who were 100 years old. Interestingly, they found that the microbiomes of patients with DS were very similar to the microbiomes of healthy individuals. In this case, their hypothesis did not end up as they predicted.
It is important to note that this study only included 17 test subjects who were all under the age of 35. Future studies will need to be conducted with larger patient cohorts as well as older patients to truly get a good understanding of the gut microbiome profiles of the entire population of patients and better understand this hypothesis.
There was, however, an unexpected finding that I found to be quite interesting. While the general makeup of the DS patients' microbiomes were similar to those of healthy individuals, there were subpopulations of bacteria that were more or less abundant in DS patients. Individuals with DS had elevated levels of Parasporobacterium and Sutterella and reduced levels of Veilonellaceae. This increase of Sutterella and decrease of Veilonellaceae has previously been described in autistic children with stomach problems. Specifically in this study, Sutterella abundance was positively correlated with Aberrant Behavior Checklist (ABC) scores for the DS individuals. The ABC test is a 58 item report checklist used to assess maladaptive behavior in people with developmental disabilities.
This positive correlation tells us that this bacterium in the gut may play a role in maladaptive behavior in patients with various conditions. Although the original hypothesis was not confirmed, this very interesting result will need to be further explored to better understand the role of the gut microbiome in individuals with autism spectrum disorder and Down Syndrome.