Adding to the growing body of evidence suggesting a link between the gut microbiome and Parkinson’s disease, a new study reveals that the disease itself, as well as the medications used to treat it, appear to have distinct effects on the composition of the trillions of bacteria in the gut.
The findings are published in the journal Movement Disorders.
“Our study showed major disruption of the normal microbiome — the organisms in the gut — in individuals with Parkinson’s,” said Haydeh Payami, Ph.D., professor in the Department of Neurology from the University of Alabama at Birmingham (UAB) School of Medicine.
At this point, researchers aren’t sure which comes first. Does having Parkinson’s cause changes in the gut microbiome, or are these bacterial changes a predictor or early warning sign of Parkinson’s? What they do know is that the first signs of Parkinson’s often arise around the same time as gastrointestinal symptoms such as inflammation or constipation.
“The human gut hosts tens of trillions of microorganisms, including more than 1,000 species of bacteria,” she said. “The collective genomes of the microorganisms in the gut is more than 100 times larger than the number of genes in the human genome. We know that a well-balanced gut microbiota is critical for maintaining general health, and alterations in the composition of gut microbiota have been linked to a range of disorders.”
For the study, the researchers evaluated 197 patients with Parkinson’s and 130 controls. The findings confirm that Parkinson’s is accompanied by an imbalance in the gut microbiome. Some species of bacteria were present in larger numbers in Parkinson’s patients than in healthy individuals, while other species were diminished. Different medications used to treat Parkinson’s also appeared to affect the composition of the microbiome in different ways.
“It could be that, in some people, a drug alters the microbiome so that it causes additional health problems in the form of side effects,” Payami said. “Another consideration is that the natural variability in the microbiome could be a reason some people benefit from a given drug and others are unresponsive. The growing field of pharmacogenomics — tailoring drugs based on an individual’s genetic makeup — may need to take the microbiome into consideration.”
The researchers also detected an unexpected difference in gut imbalance between patients from different areas of the country, which may reflect the environmental, lifestyle, and diet differences between the three regions from which the participants came: the Northeast, Northwest, and South.
Another function of the microbiome is to help the body rid itself of xenobiotics — chemicals not naturally found in the body often arising from environmental pollutants. In fact, there was evidence that the composition of bacteria responsible for removing those chemicals was different in individuals with Parkinson’s. This may be relevant because exposure to pesticides and herbicides in agricultural settings is known to increase the risk of developing Parkinson’s.
Payami says the study of the microbiome is a relatively new field, and a better understanding of macrobiotics may provide unexpected answers for Parkinson’s disease and potentially other disorders.
“This opens up new horizons, a totally new frontier,” she said. “There are implications here for both research and treatment of Parkinson’s disease. Therapies that regulate the imbalance in the microbiome may prove to be helpful in treating or preventing the disease before it affects neurologic function.”
However, Payami warns against final conclusions until more data are available. She says that another study is underway at UAB with both Parkinson’s patients and healthy individuals in an effort to replicate and confirm the results.
“The present findings lend support to the notion that the composition of the gut microbiome may hold new information for assessing efficacy and toxicity of Parkinson’s medications,” said Payami. “Additional studies are needed to assess the effects of those drugs, with larger numbers of treated and untreated patients as well as individuals who do not have Parkinson’s.”