Gut Bacteria Changes Could Aid Earlier Diagnosis of Parkinson’s Disease

New research has shown that significant changes in gut microbiota happen in the early stages of Parkinson’s disease and can begin before the onset of symptoms. Scientists from China and Germany studied the bacteria in the guts of individuals with early Parkinson’s disease, REM sleep behavior disorder (RBD), their close relatives, and healthy people. The study found similar bacterial changes in the guts of people with RBD and those with Parkinson’s disease, with some beneficial bacteria being depleted and some harmful bacteria becoming more abundant. People who were closely related to those with RBD displayed the same changes. The study identified 12 potential biomarkers that could help distinguish people with RBD from healthy individuals.

Parkinson’s Disease Diagnosis Challenges

Early diagnosis is a significant challenge in the fight against Parkinson’s disease. Up to 20 years before a patient develops Parkinson’s disease, they can have subtle problems with their senses, muscles, and minds. One predictor is sleep disorders, particularly RBD. Parkinson’s disease or a related disorder, such as multiple system atrophy or dementia with Lewy bodies, eventually manifests in the vast majority of RBD patients. A recent study found some of the characteristics of RBD in close family members of RBD patients, along with digestive issues, suggesting that these individuals may be harboring gut bacteria changes. So scientists considered whether these relatives could be key to investigating the extremely early stages of Parkinson’s disease.

The research analyzed stool samples from 441 people in Hong Kong, including people with RBD or a family history of the disease, people who had Parkinson’s disease with motor symptoms for less than five years, and healthy people for comparison. The composition of gut bacteria in the early Parkinson’s disease group was significantly different from the control group. The RBD group’s bacterial composition was similar to the early Parkinson’s disease group but different from the control and RBD relatives’ groups.

Researchers identified a decrease in bacteria that produce short-chain fatty acids (SCFA), which maintain the gut barrier and have anti-inflammatory properties. Their depletion may lead to higher intestinal permeability and subsequent aggregation of alpha-synuclein in the gut. Another observation was a progressive increase in Collinsella bacteria across groups from control to relatives of RBD, to RBD patients to Parkinson’s disease. This pro-inflammatory bacteria can contribute to making the gut more permeable and is also associated with Alzheimer’s and other neurological disorders.

The study has limitations, including a small sample size and a cross-sectional study, which does not prove cause and effect. The groups with RBD or Parkinson’s disease and the control groups had more men and were, on average, older than the group of relatives of RBD patients. However, the results are significant as this research could lead to earlier diagnosis and targeted treatments for Parkinson’s disease.