The body is truly an interconnected machine with vast multitudes of dependencies. A living body requires that different systems act symbiotically to ensure that individual systems work correctly. With much of our ancient health knowledge referring to balanced bodily health it should come as no surprise that gut bacteria protect even the neuronal networks of the human body. Modern science is finally here to help us decipher, and fully understand, what humans have believed for millennia.
Many researchers around the world have been hypothesizing viral infections of the central nervous system (CNS) to be fundamentally connected to the onset of various chronic psychiatric and neurological disorders. Parkinson’s, Alzheimer’s, and multiple sclerosis have all been implicated as initiated by a CNS viral infection.
Meanwhile, there has also been an increasing body of studies that suggest the diverse population of bacteria living in our gut (the microbiome) can be fundamentally interlinked with our immune system. Antibiotics have been found to disrupt our gut microbiome significantly, causing the efficacy of vaccines to be impaired and the spreading of the flu infection to take place.
Now, new research from the University of Utah School of Medicine shows an association between neurodegenerative disease, viral infections, our immune system, and the gut microbiome. The study suggests that disruptions to the gut microbiome can allow harmful viruses to trigger neurological diseases (like multiple sclerosis) and inhibit the immune system. The study has been published in the journal eLife Sciences.
The investigation began by researchers wanting to analyze what role the gut microbiome could be playing in the onset of neurodegenerative disease. Lead author David Garrett Brown explained:
We wanted to investigate whether gut microbes could alter the immune response to a virus in the central nervous system and whether this affects the amount of damage the virus causes.
The Study (Phase 1)
- Mice infected with a specific strain of hepatitis virus known to result in acute encephalomyelitis were monitored. They chose an animal model with this disease because it closely resembles neurodegenerative symptoms similar to those seen in multiple sclerosis.
- The researchers split the mice up into two different groups. One group was raised with various microbiome disruptions, such as being administered doses of antibiotics known to eliminate many gut bacterial populations. The other group was raised with a healthy microbiome.
The Results
- The mice with disrupted microbiomes exhibited noticeably weaker immune responses to the hepatitis virus.
- Eventually, they suffered from worse signs of neurodegeneration – including paralysis.
- And, they had less active brain immune cells (called microglia) than the mice with a healthy microbiome.
The Study (Phase 2)
- The researchers concentrated on what mechanism the gut bacteria could be using to enhance the activity of microglia in the brain and CNS.
- TLR4 – an immune signaling protein – was found to be the key to the process.
- To confirm that microglia activity could be enhanced through TLR4 signaling from the microbiome, the team gave TLR4 to the mice with disrupted microbiomes.
The Results
- The mice raise with antibiotics showed increased neurological damage from the virus.
- Antibiotics disrupt gut bacteria that protect complex neuron systems.
June Round, co-senior author on the study, said:
We’ve shown that gut microbes protect infected mice from paralysis by turning on a specific pathway in central nervous system cells. This suggests that signals from microbes are essential to quickly clear viruses in the nervous system and prevent damage from multiple sclerosis-like diseases.
Our results emphasize the importance of maintaining a diverse community of bacteria in the gut, and that interventions to restore this community after taking antibiotics may be necessary.
As exciting as these findings are, there are still several unresolved questions. The researchers don’t yet know which particular gut bacteria species could be responsible for this specific TLR4 signaling. However, they do know for sure that antibiotics can disrupt our vital gut bacteria population resulting in health risks, and doctors should be looking for ways to fix these disruptions.
