gastrointestinal tract

A gut feeling for mental health

February 4, 2019

Science Daily/VIB (the Flanders Institute for Biotechnology)

The first population-level study on the link between gut bacteria and mental health identifies specific gut bacteria linked to depression and provides evidence that a wide range of gut bacteria can produce neuroactive compounds.

 

In their manuscript entitled 'The neuroactive potential of the human gut microbiota in quality of life and depression' Jeroen Raes and his team studied the relation between gut bacteria and quality of life and depression. The authors combined faecal microbiome data with general practitioner diagnoses of depression from 1,054 individuals enrolled in the Flemish Gut Flora Project. They identified specific groups of microorganisms that positively or negatively correlated with mental health. The authors found that two bacterial genera, Coprococcus and Dialister, were consistently depleted in individuals with depression, regardless of antidepressant treatment. The results were validated in an independent cohort of 1,063 individuals from the Dutch LifeLinesDEEP cohort and in a cohort of clinically depressed patients at the University Hospitals Leuven, Belgium.

 

Prof Jeroen Raes (VIB-KU Leuven): 'The relationship between gut microbial metabolism and mental health is a controversial topic in microbiome research. The notion that microbial metabolites can interact with our brain -- and thus behaviour 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.'

 

Previously, Prof Raes and his team 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 their current study, they surprisingly found a similar community type to be linked to depression and reduced quality of life.

 

Prof Jeroen Raes (VIB-KU Leuven): '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 wellbeing share a set of common features.'

 

The authors also created a computational technique allowing the identification of gut bacteria that could potentially interact with the human nervous system. They studied genomes of more than 500 bacteria isolated from the human gastrointestinal tract in their ability to produce a set of neuroactive compounds, assembling the first catalogue of neuroactivity of gut species. Some bacteria were found to carry a broad range of these functions.

 

Mireia Valles-Colomer (VIB-KU Leuven): '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. 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. 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.'

 

These findings resulted from bioinformatics analyses and will need to be confirmed experimentally, however, they will help direct and accelerate future human microbiome-brain research.

 

Jeroen Raes and his team are now preparing another sampling round of the Flemish Gut Flora Project that is going to start next spring, five years after the first sampling effort.

https://www.sciencedaily.com/releases/2019/02/190204114617.htm

How bacteria in the gut influence neurodegenerative disorders

Understanding the role of the microbiome may lead to better treatments for Parkinson's, Alzheimer's

November 16, 2017

Science Daily/Society for Neuroscience

Humans have roughly as many bacterial cells in their bodies as human cells, and most of those bacteria live in the gut. New research released today reveals links between the gut microbiome -- the population of microorganisms living in the gastrointestinal tract -- and brain diseases such as Parkinson's and Alzheimer's, including potential new ways to track and treat these diseases.

 

Almost 100 trillion microbes -- some beneficial and some harmful -- live in the human gastrointestinal tract at any time, helping to regulate immune function and inflammation, two factors hypothesized to play a role in neurodegenerative diseases like Parkinson's and Alzheimer's. As brain-focused cures for such diseases remain elusive, scientists are looking to the microbiome for new insight and novel strategies.

 

Today's new findings show that:

  • ·      Metabolites derived from the microbiome block protein misfolding in test tubes and prevent neurodegeneration in a fly model of a disease related to Parkinson's, hinting that gut-derived metabolites may hold therapeutic promise (Lap Ho, abstract 573.23, see attached summary).
  • ·      A rat model of Parkinson's disease displays increased levels of an inflammatory protein in the colon, identifying a possible new biomarker for the disease (Doris J. M. Doudet, abstract 133.13, see attached summary).
  • ·      Nonhuman primates that received stomach injections of a protein associated with Parkinson's disease show signs of the disease in their brains, revealing that pathology can spread from the gut to the brain (Erwan Bezard, abstract 131.02, see attached summary).
  • ·      A gene associated with risk for Alzheimer's disease influences the gut microbiome of mice, potentiating a novel treatment strategy (Ishita Parikh, abstract 476.02, see attached summary).
  • ·      Probiotic treatment corrects memory problems in an Alzheimer's mouse model, suggesting that altering the microbiome may help delay the disease (Harpreet Kaur, abstract 126.23, see attached summary).

 

"The results presented today add to the growing body of evidence showing the influence of the gut on the brain and the crucial relationship between the two," said press conference moderator Tracy Bale, PhD, of the University of Maryland School of Medicine and Center for Brain Development and Maternal Mental Health. "Targeting the gut introduces a different and promising angle to tackle brain disorders across the lifespan."

https://www.sciencedaily.com/releases/2017/11/171116105027.htm

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