New Belgian research reveals a link between specific types of gut bacteria and depression. The findings, published in the journal Nature Microbiology, also provide evidence showing that a wide range of gut bacteria can produce neuroactive compounds.
Researchers called it the first population-level study on the link between gut bacteria and mental health, aggregating data from hundreds of people rather than studying animals or clinical trial subjects.
For the study, researchers from the Flanders Institute for Biotechnology (VIB-KU Leuven) in Belgium compared fecal microbiome data with general practitioner diagnoses of depression from 1,054 individuals enrolled in the Flemish Gut Flora Project.
Through this analysis, they were able to pinpoint specific groups of microorganisms that positively or negatively correlated with mental health. They discovered that two bacterial genera, Coprococcus and Dialister, were consistently depleted in people with depression, regardless of antidepressant treatment.
The findings were confirmed in an independent group of 1,063 individuals from the Dutch LifeLinesDEEP study, as well as by looking a group of clinically depressed patients at the University Hospitals Leuven, Belgium.
“The relationship between gut microbial metabolism and mental health is a controversial topic in microbiome research,” said study leader Professor Jeroen Raes from VIB-KU Leuven.
“The notion that microbial metabolites can interact with our brain — and thus behavior and feelings — is intriguing, but gut microbiome-brain communication has mostly been explored in animal models, with human research lagging behind. In our population-level study we identified several groups of bacteria that co-varied with human depression and quality of life across populations.”
In previous research, the team had identified a microbial community constellation or enterotype, characterized by low microbial count and biodiversity, that was observed to be more prevalent among Crohn’s disease patients. In the new study, they surprisingly discovered a similar community type to be linked to depression and reduced quality of life.
“This finding adds more evidence pointing to the potentially dysbiotic nature of the Bacteroides2 enterotype we identified earlier. Apparently, microbial communities that can be linked to intestinal inflammation and reduced well-being share a set of common features,” said Raes.
The research team also developed a computational technique allowing the identification of gut bacteria that could potentially interact with the human nervous system.
They studied the genomes of more than 500 bacteria isolated from the human gastrointestinal tract and their ability to produce a set of neuroactive compounds, essentially creating the first catalog of neuroactivity of gut species. Some bacteria were found to carry a broad range of these functions.
“Many neuroactive compounds are produced in the human gut. We wanted to see which gut microbes could participate in producing, degrading, or modifying these molecules,” said researcher and first author Mireia Valles-Colomer, a doctoral student in Raes’ lab.
“Our toolbox not only allows to identify the different bacteria that could play a role in mental health conditions, but also the mechanisms potentially involved in this interaction with the host,” she said.
“For example, we found that the ability of microorganisms to produce DOPAC, a metabolite of the human neurotransmitter dopamine, was associated with better mental quality of life.”
The findings resulted from bioinformatics analyses and will need to be confirmed experimentally. However, the results will help direct and accelerate future human microbiome-brain research.
The hope is that by understanding how human’s stomach bacteria impact mood, future treatments can target or include changes in diet or adding supplements to help improve a person’s mood, or even clinical depression.