Treatment advances in many chronic conditions in the next three to five years will likely involve the microbiome and genetic therapies – whether new treatments will involve pre-pro-biotic or fecal transplants new approaches may mean many elusive areas in prevention and treatment will have novel therapies. Consider that bacteria outnumber our cells by a factor of ten to one! It is hard to consider this is not affecting our health and wellbeing. A recent set of papers shed light on a communication superhighway between our brains and our gut that may lead us to new approaches to address depression and other aspects of mental health soon.
In the current issue of Nature Microbiology, a study by MireiaValles-Colmer from the Leuven-Unversity in Belgium and colleagues examines the potential implications gut microbial metabolism may have on mental health. First some level setting, a lot of what we already know about the gut microbiota is derived from animal models. What we have learned from early research is the nervous and endocrine systems are in close two-way communication with the gut. The field of study is expanding to look at casual pathways in Parkinson’s, Alzheimer’s and depression.
Rodent models are being developed to explore the role of microbiota in altering behaviors. The challenge is this space is new, and it is likely many complex variables that are as yet unknown means we have a limited view of how microbiota impact the complex human phenotype. This nascent research and early models are providing us a taxonomy and analytic pathways to explore further- this paper presents one great example of this. While the link between the gut and the brain is in the early stages, this study adds more to our understanding of the connections between them.
The Belgian Flemish Gut Flora Project (FGFP) followed a cohort of 1,054 people measuring the self-reported quality of life (QOL), and general practitioner reported levels of depression to assess any relationship between gut bacteria and mood. The average age of the sample was fifty years old, and the sample had an average Body Mass Index on the bordering on overweight. As a first step, the authors built upon prior studies examining depression metadata and quality of life, they validated the Dutch LifeLines study (DEEP) sample which also had over a thousand participants with microbiome samples in addition to QOL and depression data.
The findings are fascinating, while not speculating on causality the authors were able to show a difference in those with depression, namely depleted levels of Coprococcus and Dialister, while higher QOL was evident in participants who had healthy levels of Coprococcus, and Faecalibacterium, even after controlling for confounding variables. Inflammation has a role in the etiology of disease, and Coprococcus and Dialister are known for their anti-inflammatory properties.
It is not yet known if low levels of these bacteria mean you are more prone to depression, or if depression tends to deplete these bacteria in the microbiome. This depletion holds even for the participants who were taking antidepressants. This study, building on others in humans is so exciting and provides more research paths to explore. At a population level, we see that there are indeed links between the microbiome and mental health and future research will tell us more about the directions of these links. I eagerly await more studies on this topic!
Thanks for reading – Trina
(Opinions are my own)
The Neuroactive potential of the human gut microbiota in quality of life and depression