A functional link has been found between gut bacteria and Parkinson's disease. The scientists suggest that changes in the organic composition of bacteria populations or in the gut bacteria themselves contribute to the deterioration of motor skills, which is a symptom of Parkinson's.
The research was conducted by researcher Sarkis Mazmanian of the California Institute of Technology and his team, and was published on Dec. 1 in the journal Cell.
Gut Bacteria - Essential To The Nervous System
No less than 1 million people are affected by Parkinson's disease in the United States alone, while there are up to 10 million cases worldwide, making it the second most common neurodegenerative disease.
Among the most common symptoms of Parkinson's disease are tremors; experiencing difficulty while walking is the first sign of the disease. Additionally, three-quarters of the people who suffer from Parkinson's disease also have gastrointestinal problems, mainly constipation.
The gut hosts a various number of bacteria, called microbiome, which have an essential role in the development and functionality of both the immune and nervous systems. Some of these bacteria are helpful or benign, and some can become intrusive to the proper functioning of our bodies.
According to the study, as much as 70 percent of the neurons we have in the peripheral nervous system are in the intestines, which makes the gut's nervous system related to the central nervous system.
"Gut bacteria provide immense physiological benefit, and we do not yet have the data to know which particular species are problematic or beneficial in Parkinson's disease," noted Mazmanian.
Parkinson's Disease - Influenced By Gut Bacteria
As part of the lab tests, the researchers used mice having symptoms of Parkinson's, and divided them into two categories: one group was bred in a sterile, microbe-free environment, while the other was raised in non-sterile cages.
The researchers then introduced gut microbiota from human Parkinson's disease patients into the mice. A series of measures were taken in order for the scientists to analyze how the two groups of mice performed in terms of Parkinson's disease symptoms. The animals were tested through a number of tasks that targeted a series of body functions, from motor skills to running or descending from a pole.
The researchers observed that the physical impairments related to the disease such as motor deficits were heightened, compared to when the mice received gut microbiota transplants from healthy donors. Additionally, the scientists discovered that the animals who were bred in the lab in environmentally sterile conditions performed significantly better than their counterparts.
"These findings reveal that gut bacteria regulate movement disorders in mice and suggest that alterations in the human microbiome represent a risk factor for [Parkinson's disease]," the researchers wrote.