As part of a new series, the FNR speaks to five experts about research trends in their domain. Biomedical scientists are fascinated with microbiome research: Mahesh Desai of LIH explains how important bacterial communities living in and on the human body are for our health.
Researchers have long known that the human gut is home to populations of bacteria that help us digest our food. But in recent years, it has become increasingly clear that the microbes living in our body, known collectively as the microbiome, have a decisive influence on our health. Evidence is mounting that the metabolic products of these tiny helpers can even affect the processes going on in our brain.
This suggests that the bacteria also influence the course and possibly even the onset of so-called neurodegenerative diseases.
“Researchers discovered recently that there is indeed a correlation between the composition of the gut microbiome and diseases such as Parkinson’s, Alzheimer’s and autism,” says Dr. Mahesh Desai, Head of the Ecoimmunology and Microbiome research group at the Department of Infection and Immunity of the Luxembourg Institute of Health (LIH) in Esch-sur-Alzette.
“This observation will radically change our understanding of these neurodegenerative diseases in future.”
Rallying the body’s natural bacteria to halt diseases
In the past, medical professionals presumed the primary causes behind the onset of neuropathological disorders were to be found in the very neurons themselves, or in the DNA that governs the growth of these cells.
“The latest research findings show, however, that the composition of the gut microbiome is different in those suffering from neurodegenerative diseases,” Desai explains.
“We still don’t know exactly which processes in the brain the bacteria influence, why they do so, and why certain microbes disappear from the gut. But I expect we will constantly improve our understanding of these correlations over the years to come, and thus open up entirely new possibilities for scientists to use the body’s natural bacteria to stop the pathogenic processes in the brain.”
Conceivably, we could employ microbiome-targeted therapeutics that correct the composition of the gut microbiome and thereby relieve symptoms. This could be to give the patient prebiotics, for example, which are dietary polysaccharides that certain beneficial bacteria feed on and generate metabolic products that improve health.
“We need a complete bacterial orchestra.”
Diet, in turn, must also have a decisive effect on the collective population of bacteria in the human gut.
Desai’s research studies have shown, for example, that mice host higher numbers of mucus-foraging microbes in their gut if they are fed a uniform, low-fibre diet over several weeks. At the same time, Desai and his team observed that these bacterial species started to attack the mucus lining that protects the inside of the intestine.
This so-called mucus barrier prevents pathogens and other intruders from getting into the tissue of the intestine. By altering the body’s bacterial population, the wrong diet could possibly lead to further structures in the human body being attacked and certain diseases occurring.
These could be not only the neurodegenerative diseases mentioned earlier, but also metabolic disorders such as diabetes or cardiovascular diseases, Desai is convinced. The researcher likens the interplay between bacteria to an orchestra working as an ensemble to control the functions of the human body and its organs:
“Only if the orchestra is complete and no instrument plays too loudly or too quietly do you have a perfect concert with no off-notes.”
About Mahesh Desai
Dr Mahesh Desai is Head of the Ecoimmunology and Microbiome research group at the Department of Infection and Immunity of the Luxembourg Institute of Health (LIH).
In 2017, he won an FNR Award in the category ‘Outstanding Scientific Publication’ for the publication ‘A dietary fiber-deprived gut microbiota degrades the colonic mucus barrier and enhances pathogen susceptibility‘ published in the prestigous journal ‘Cell‘.
INFO BOX: In search of the right microbiome
In search of the right microbiome
In recent years researchers have found evidence that, in the gut of people suffering from neurodegenerative diseases such as Alzheimer’s and Parkinson’s disease (PD), certain species of bacteria occur in greater numbers while others are lacking.
In 2016, an international research team reported in the scientific journal “Cell” that mice are protected against Parkinson’s disease if they grow up germ-free, that is if they have no bacteria living in their body.
At the same time, the researchers showed that mice develop typical symptoms of PD if they are colonised by gut bacteria taken from a Parkinson’s patient.
Whether the course of neurological diseases can be influenced by targetedly correcting the composition of the microbiome in those affected is currently a subject of intense investigation in research teams the world over.
 (Timothy et al., 2016, Cell, 167:1469−1480)