Share on PinterestScientists have found that gut bacteria may explain the link between Parkinson’s and IBD. Design by MNT; Photography by LumiNola/Getty Images & seb_ra/Getty Images
- People with inflammatory bowel disease (IBD) have an increased risk of developing Parkinson’s disease, a neurodegenerative condition.
- Disruption of the gut microbiome is a feature of both conditions, but experts do not know if this gut dysbiosis underlies the link between the two diseases.
- A new study comparing the microbiomes of people with IBD and Parkinson’s disease has found that people with either condition have depletions in similar types of beneficial bacteria.
- The findings suggest that therapies targeting the microbiome to reduce inflammation might reduce Parkinson’s risk in people with IBD.
Inflammatory bowel disease (IBD) affects around 5 million people around the world. It results in a number of gastrointestinal and other symptoms, which may be alleviated by medications and dietary changes.
Several studies have suggested that IBD may increase a person’s risk of developing Parkinson’s disease, a neurodegenerative disorder. One meta-analysis of studies found that the risk of Parkinson’s was 41% higher in people with IΒD than in those without the condition.
Gut inflammation is common in both IBD and Parkinson’s disease. And experts believe that one of the factors in this gut inflammation is dysbiosis, or disruption of the gut microbiome — the huge population of microorganisms that live in the gastrointestinal (GI) tract.
A new study analyzing the gut microbiomes of people with IBD and Parkinson’s has found that they share several differences from the microbiomes of healthy people. Most noticeably, people with IBD or Parkinson’s had greatly depleted numbers of bacteria that produce short-chain fatty acids — molecules that modulate the activity of the immune system.
The research, by scientists from the University of Florida, is published in npj Parkinson’s disease.
“This is an interesting study as it is the first time a direct comparison has been made between the gut microbiome of people with IBD and people with Parkinson’s. It adds to the emerging picture from previous studies.”
— Katherine Fletcher, research communications Lead, Parkinson’s UK, who was not involved in the study,
The gut microbiome’s role in IBD and Parkinson’s
Michael S. Okun, MD, medical advisor at the Parkinson’s Foundation and director at the Norman Fixel Institute for Neurological Diseases at UF Health, one of the study authors, told Medical News Today:
“This study identified potential unique features of the human Parkinson’s and inflammatory bowel disease microbiome and also used the gut ‘metagenomes’ to shed light on what may be going on in the GI tract.”
To identify whether the microbiome might help explain epidemiological links between the two diseases, they recruited 54 people with Parkinson’s disease, 26 with IBD, and 16 healthy control individuals. All were ages between 40 and 80 years, although those with Parkinson’s were, on average, older.
All study participants provided stool samples for analysis. The researchers identified the bacteria present in these stool samples using metagenomics. For comparison, the researchers also analyzed large open-access metagenomic datasets from 490 Parkinson’s disease and 234 control samples.
Fewer short-chain fatty acid-producing bacteria in Parkinson’s, IBD
In people with both Parkinson’s disease and IBD, several prominent short-chain fatty acid-producing species were depleted. They also had reduced SCFA synthesis pathways.
“Depletions in short-chain fatty acid (SCFA)-producing bacteria was one of the most interesting findings. Additionally, the most striking similarity between inflammatory bowel disease and Parkinson’s across every dataset was a shared depletion in similar organisms. One thing that will require a closer look is the depletions in pathways involved in the synthesis of acetate and butyrate [2 SCFAs] in both Parkinson’s and inflammatory bowel disease. These findings should raise more dialogue about commonalities in inflammatory pathways.”
— Michael S. Okun, MD
Many of the depleted bacteria are producers of butyrate, a SCFA that is thought to provide protection against neurodegeneration. In previous work, some of the same researchers have shown that people with higher levels of butyrate in their stool have a later age of onset of Parkinson’s, suggesting that it may help protect against the disease.
Fletcher highlighted discovering the depletion of these bacteria may be important:
“SCFA-producing bacteria release factors that are anti-inflammatory, and gut inflammation is seen in both IBD and PD and is associated with an increased risk of PD. One of the factors that SCFA-bacteria produce is butyrate which prevents epigenetic modification of the genes and this has been associated with neuroprotection in animal models of PD.”
Gut dysbiosis may be a cause or consequence
Because this was an observational study, it cannot determine whether the alterations in the microbiomes of people with Parkinson’s disease and IBD are causing the disease, or are a result of the conditions.
The researchers suggest that inflammation may result in a dysbiotic microbiome, which favours pathogenic microbes that are able to tolerate more extreme conditions. However, it is possible that the pathogenic bacteria cause the inflammation.
Possible treatment options for Parkinson’s and IBD
Previous research has found that anti-TNF therapies, which are commonly used to combat inflammation in IBD, may reduce the risk of developing Parkinson’s disease. However, while their study supported the role of inflammation as a risk factor, Okun urged caution:
“The data from this study should not become a rationale for clinicians to reflexively treat already diagnosed or at-risk folks with anti-TNF therapies. These drugs have risks, and although there may be future clinical trials, we are not there yet.”
However, Fletcher highlighted research into the effects of the drugs in people with a similar condition:
“This hypothesis is already being tested clinically. People with a sleep disorder called REM sleep behavior disorder (RBD), who have a very high risk of developing PD within 10 years and also an altered gut microbiome similar to PD, are being tested with anti-TNF therapy to see whether it slows down or prevents their conversion from RBD to PD.”
While Okun advised against the widespread use of pre- and probiotics as their effects may highly depend on a person’s gut microbiome, Fletcher told us that a healthy diet could be helpful. She emphasized that the Mediterranean diet, which modifies gut bacteria in a beneficial way, is associated with a reduced risk of Parkinson’s disease.
“This work highlights the importance of being able to pinpoint changes in the gut that might lead to Parkinson’s and finding ways to intervene. The results also show the importance of research into diet and supplements for Parkinson’s.”
— Katherine Fletcher
