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So this is a story that is popping up all over the place today, and for good reason, it’s fascinating! In a recent article published in the journal Cell, titled “Gut Microbiota Regulate Motor Deficits and Neuroinflammation in a Model of Parkinson’s Disease.” In this article the researchers describe how they (in a MOUSE model system) found the motor dysfunction of mice with Parkinsons disease could be transferred to healthy mice by transplanting the intestinal bacteria from the Parkinsons mice into the intestines of the healthy mice. Lets break all of this down a little bit.

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# What is Parkinson’s Disease? Parkinson’s Disease is a neurodegenerative disorder effecting primarily the motor system (aka the part of your nervous system that controls the functioning of your skeletal muscles). The symptoms of this disease have a slow onset and begin with shaking, a hunched posture, a slowing of your movements and difficulties in walking.

Source : The Posture of Someone With Parkinson’s Disease

As the disease progresses, difficulties thinking and forming memories (dementia) occur. The cause of Parkinson’s disease is unknown, however doctors speculate that both “genetic and environmental factors” are involved (that’s doctor speak for we have no clue what the precise causative agent is). This video does a good job describing what the symptoms are, and how doctors look for them, it’s quite informative:

While we don’t understand the root cause, we do know why the symptoms occur. Parkinson’s disease symptoms occur because neurons in the area of the brain responsible for controlling movement become impaired. These neurons are responsible for producing a compound called dopamine and when they get messed up, they produce less dopamine. Dopamine is used by the brain to transport signals from one region of the brain to other regions, and when there is less available, the ways that the nerves activate or “fire” change. The changes to the firing patterns leads to the difficulties people have when moving around.

Is there a cure for Parkinson’s Disease?

No, however people who have Parkinson’s disease do not usually die any earlier then people without the disease. They just have a much lower quality of life for those years.

There is a Link Between Intestinal Bacteria and Neurological Development and Certain Disorders

Malfunctioning neurons are the main cause of a wide variety of diseases in humans. One such cause for neurological malfunction is amyloidosis which is the term given for clumping of proteins which in turn coat parts of the cell and mess with cellular activities. There are a variety of amyloid proteins, and malfunctioning of these proteins lead to a variety of neurological diseases you are likely familiar with including Alzheimers, Huntingtons and Parkinson's(DING DING DING!!!). (Citation)

In Parkinson’s disease the amyloid protein that aggregates is thought to be α-synuclien (αSyn) (Citation) , it clumps inside of neurons and those involved in dopamine responses are particularly succeptible. So the clumping of α-synuclien is one such way that the dopamine producing neurons lose their functionality. As we discussed above, this results in less dopamine, and less dopamine means Parkinson’s symptoms.

But how are gut bacteria involved? Well a lot of research has been published recently showing how the presence of certain bacteria are necessary for development of the nervious system (in mouse models). In one case reserachers found that mice treated with an antibiotic targeting speficic bacteria had changes to the neurons that develop and form in the hippocampus area of the brain (area responsible for memory and spacial awareness) (Citation).

Source

This shows a link between bacteria in the body (microbiome constituents) and function of the nervous system (which is quite surprising to me!).

So, Please Tell Me About This New Article @justtryme90!

Okay, glad you asked with such enthusiasm! In this article the authors were looking at the effect that gut bacteria had on α-synuclien. They did this by creating mice which produce the human α-synuclien protein (the one that when it blobs together leads to the impairment of brain neurons, and reduced dopamine production). These mice which express a bunch of the α-synuclien all show parkinson’s symptoms (movement difficulties etc.) What the researchers found was that if they treated the mice with antibiotics such that the gut microbiome was depleted, the amount of α-synuclien clumping was reduced, and with it the amount of difficulties of the mice to move around. Basically they observed that the gut microbiota is required to generate the negative changes to movement (Parkinson’s symptoms) in these mice.

They discuss a number of possibilities for why this might be. One interesting discussed reason was inflammation. It is known that clumping of α-synuclien is enhanced by an inflammatory environment in the body. Removal/reduction of the gut microbiota from these mice may have reduced the inflammatory state of the mice (the gut microbiome is known to increase inflammation through production of short-chain fatty acids (Citation). Short-chain fatty acids can cross the blood prain barrier and potentially impact nerve cells directly, but they also increase inflammation through increasing production of cytokines by brain cells called microglia. Cytokines are important signaling compounds that play a role in the inflammatory response of the body. So the authors logical pathway here was, gut bacteria produce more short-chain fatty acids, which in turn increase cytokine production and inflammation, and the increase inflammation results in clumping of α-synuclien, leading to Parkinson’s symptoms.

The other really interesting result from this paper was that gut bacteria from parkinson’s patients transplanted into a succeptible α-synuclien enhanced mouse resulted in those mice having more difficulties moving around, then were mice transplanted with gut bacteria from healthy non parkinson’s patients. This is also quite surprising, and taken together with the previously discussed result (removing bacteria reduces symptoms) seems to indicate that their truly is a role between bacteria present in the gut and parkinson’s disease!

TL;DR Breakdown Summary

Parkinson’s disease results in a drastically reduced quality of life by causing a variety of problems with moving ones body. In a mouse model researchers showed that the difficulties in moving around seen with Parkinson’s were reduced when the amount of gut bacteria were destroyed by antibiotics, and that the gut bacteria from parkinson’s sufferers could make movement more difficult for mice when transplanted. Illustrating a direct link between the gut microbiome and Parkinson’s disease symptoms.

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Sources:
https://en.wikipedia.org/wiki/Parkinson's_disease
http://www.mayoclinic.org/diseases-conditions/parkinsons-disease/basics/definition/con-20028488
https://www.ncbi.nlm.nih.gov/pubmed/25588378
https://nihseniorhealth.gov/parkinsonsdisease/whatcausesparkinsonsdisease/01.html
https://en.wikipedia.org/wiki/Hippocampus
http://ehp.niehs.nih.gov/1003013/
https://en.wikipedia.org/wiki/Microglia

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