A new study involving people with irritable bowel syndrome (IBS) appears to reveal a two-way link between the gut microbiota and the brain regions involved in sensory processing.
The findings suggest that distressing brain signals may influence the composition of intestinal microbes, and in return, the chemicals in the gut can impact the structure of the human brain.
Specifically, the researchers found that in patients with IBS, having a history of early life trauma was associated with structural and functional brain changes as well as an alteration in gut microbial composition.
The findings suggest that brain signals sent to the gut and its microbes in people with a history of childhood trauma may lead to lifelong alterations in the gut microbiome. These changes in the gut microbiota may then feed back into sensory brain regions, altering the sensitivity to gut stimuli, a hallmark of people with IBS.
Prior research conducted in mice has demonstrated the impact of gut microbiota on brain function and behavior, as well as the influence of the brain on the composition of microbes in the gut. However, until now, only one study performed in human subjects has confirmed the translatability of such findings to the human brain.
Studies have also reported evidence for alterations in the composition of gut microbiota in IBS patients, but there has been little consistency among studies regarding the specific microbial alterations and the relationship of such alterations with the first symptoms of IBS, recurring abdominal pain and altered bowel habits.
For the study, researchers from the University of California, Los Angeles analyzed behavioral and clinical data, stool samples and structural brain images from 29 adults diagnosed with IBS and 23 healthy control subjects.
The scientists used DNA sequencing and various mathematical approaches to quantify composition, abundance, and diversity of the gut microbiota. They also estimated the microbial gene content and gene products of the stool samples. Then they cross-referenced these gut microbial measures with structural features of the brain.
Based on the composition of the microbes in the gut, the samples from those diagnosed with IBS clustered into two subgroups: One group was indistinguishable from the healthy control subjects, while the other differed. Those in the group with an altered gut microbiota were more likely to have a history of early life trauma and longer duration of IBS symptoms. The two groups also displayed differences in brain structure.
The findings suggest that brain signals sent to the gut and its microbes in people with a history of childhood trauma may lead to lifelong alterations in the gut microbiome. These gut bacteria changes may then feed back into sensory brain regions, altering the sensitivity to gut stimuli.
In the future, analysis of a person’s gut microbiota may become routine for people with IBS in clinical practice, and therapies such as certain diets and probiotics may become personalized based on an individual’s gut microbial profile.
Furthermore, subgroups of people with IBS distinguished by brain and microbial signatures may show different responsiveness to brain-directed therapies such as mindfulness-based stress reduction, cognitive-behavioral therapy and targeted drugs.
The study was published online in the peer-reviewed journal Microbiome.