Gut bacteria may send different biological signals in Parkinson’s disease

A new study from the University of Oulu suggests that gut bacteria may send different biological signals in Parkinson’s disease. The findings add to growing evidence that changes in the gut could be linked to Parkinson’s disease and may eventually help researchers identify new underlying mechanisms for the condition.

Rather than looking only at which bacteria are present in the gut, the researchers focused on the biological messages they send. Gut bacteria release extracellular vesicles, tiny particles that carry proteins and other molecules and can travel between cells, likely extending the microbial signaling beyond the gut.

The study, published in iScience, found that people with Parkinson’s disease had more of these vesicles in their stool samples than healthy individuals. The vesicles were also larger on average and carried a different mix of bacterial proteins, suggesting that microbial communication may be altered in the disease.

Microbiome research has traditionally focused on which bacteria are present and how their relative abundance changes. Our findings suggest that we should also ask what these bacteria are sending out into the body.”

Anatoliy Samoylenko, Senior Research Fellow at the University of Oulu and author of the study

The researchers analyzed faecal samples from 20 people with Parkinson’s disease and 19 healthy controls. They isolated extracellular vesicles produced by the gut microbiota and characterized them using nanoparticle tracking analysis, electron microscopy, 16S rRNA sequencing and mass spectrometry-based proteomics.

The analyses revealed differences between the Parkinson’s disease and control groups at several levels. Both the gut microbiota itself and the vesicles it produced showed distinct bacterial compositions. The vesicles from people with Parkinson’s disease also carried a different set of proteins.

A possible missing link in the gut–brain connection

Scientists have become increasingly interested in the connection between the gut and the brain. Growing evidence suggests that the gut microbiota may play a role in Parkinson's disease, although the underlying mechanisms remain unclear.

Extracellular vesicles can carry biologically active molecules, including proteins, lipids and nucleic acids, and may enable communication between microbes and their host. The new findings suggest that Parkinson’s-related changes in the gut microbiota may affect not only which bacteria are present, but also the molecular signals they send.

“Extracellular vesicles could provide a previously underappreciated link between the gut microbiota and the host,” says Samoylenko. “The next question is whether the altered vesicles have functional effects on intestinal, immune or nervous system cells.”

The researchers emphasize that this is an early step towards understanding how the gut microbiota may be involved in Parkinson’s disease. Larger and long-term studies are needed to determine whether these changes contribute to disease development or progression.

The findings also suggest that microbial extracellular vesicles could eventually serve as biomarkers for Parkinson’s disease. Profiles based on vesicle abundance, size, microbial origin and molecular cargo could complement conventional microbiome analyses and help identify disease-related changes.

In the longer term, understanding the biological effects of microbial vesicles may identify new underlying mechanisms and reveal new therapeutic targets in Parkinson’s disease. If certain vesicles or the molecules they carry contribute to inflammation or neurodegeneration, they could become targets for future interventions.