Gut Bacteria May Cause Parkinson's Disease

A new study suggests that specific strains of common gut bacteria may cause Parkinson's disease.

The researchers at the University of Helsinki examined whether strains of Desulfovibrio — gut bacteria that reduce sulfate — found in patients can result in progress toward Parkinson's disease (PD).

The study published in the journal Frontiers included 20 participants — 10 patients with Parkinson's disease and 10 healthy individuals who were their spouses. The PCR analysis revealed that all fecal samples of PD patients and eight fecal samples of healthy individuals were positive for Desulfovibrio bacteria (DSV).

The research found higher levels of DSV in Parkinson's patients than in healthy controls. Moreover, the concentration of Desulfovibrio species correlated with the severity of the disease.

Using roundworm as a model, the researchers found that DSV strains in patients with Parkinson's disease cause aggregation of a neuronal protein called alpha-synuclein on a statistically significant level.

The protein alpha-synuclein is the pathological hallmark of Parkinson's disease. In patients with PD, the protein misfolds and aggregates into clumps called Lewy Bodies which are thought to be toxic. When the clumps are passed from one neuron to another, they may cause the spread of the disease through the brain.

Moreover, roundworms fed with DSV bacteria from PD patients saw a higher fatality compared to bacteria from healthy participants, "possibly due to the unbearable amount of accumulated alpha-syn aggregates and different bacterial toxicity."

"The findings indicate that specific strains of Desulfovibrio bacteria are likely to cause Parkinson's disease. The disease is primarily caused by environmental factors, that is, environmental exposure to the Desulfovibrio bacterial strains that cause Parkinson's disease. Only a small share, or roughly 10%, of Parkinson's disease is caused by individual genes," Professor Per Saris from the University of Helsinki says in a press release.

Desulfovibrio bacteria are found in the environment, such as soil, water, and sewage, as well as in the digestive tracts of animals and humans.

The researchers at Helsinki University say their findings make it possible to screen for the carriers of DVS species. Removing these strains from the gut could potentially alleviate and slow the symptoms of Parkinson's disease.

Parkinson's is the second most common neurodegenerative disease after Alzheimer's, affecting nearly one million people in the United States, with about 90,000 new cases diagnosed each year. According to the Parkinson's Foundation, the primary risk factor for developing the condition is age, and PD is more common in men than women. Early symptoms of PD include tremors, rigidity, and difficulty walking, whereas cognitive decline typically appears in later stages.

The research authors note that future studies are necessary to further evaluate the role of DSV properties in the development of Parkinson's disease.