A gut bacteria may cause Parkinson’s Disease

Summary: the microbiome and Parkinson's Disease

A virulent strain of hidrogen sulfide-generating bacteria known as Desulfovibrio (DSV), may be the cause of Parkinson's disease, by producing proteic aggregates that reach the brain from the gut using the vagal nerve.

The bacteria-gut link to Parkinson's disease

What is Parkinson's disease

Parkinson's disease (PD) the second-most common neurodegenerative disease after Alzheimer's disease. It is chronic neurodegenerative disorder that provokes many physical symptoms related to motricity such as rigidity, tremors, slowness of movements and and postural instability; as well as non-motor effects (mood and behaviour disorders, apathy, depression, hallucinations, cognitive dysfunction, and pain among others).

Nearly 90,000 people in the U.S. are diagnosed with PD each year. More than 10 million people worldwide are living with PD.

The disease can be diagnosed but there are currently no therapies that can halt the progression of PD.

PD patients lose specialized neurons that produce dopamine, a neurotransmitter known as the "feel good" hormone. PD is also characterized by the presence of abnormal agglomerations of &alpha-synuclein, a protein, known as Lewy bodies (LBs) in the neurons in many parts of the central, enteric, and peripheral autonomic nervous systems.

In this study (1) the authors found that the a bacteria found in the digestive system, known as Desulfovibrio (DSV), induces alpha-synuclein aggregation.

They took ten Parkinson's disease patients and ten healthy individuals, who were the spouses of the patients, and obtained samples of different Desulfovibrio strains from their feces. They then fed them to healthy Caenorhabditis elegans worms. The study found that:

• All tested DSV bacteria produced alpha-syn aggregation in the head region of the C. elegans worms.
• The DSV bacteria coming from the PD patients feces produced roughly 16 times more volume of α-synuclein than the DSV bacteria obtained from their healthy spouses, and also a larger quantity of aggregations.
• PD patients' DSV bacteria killed of the worms quicker.

The authors conclude that "DSV strains from PD patients appear to have greater virulence that enables them to have stronger toxicity and cause more alpha-syn aggregation," and suspect it has to do with the DSV bacteria's ability to produce hydrogen sulfide H₂S. This chemical has harmful effects on human cells that eventually provoke the formation of α-synuclein aggregations.

They propose that thse gut DSV bacteria then breach the gut barrier, colonize cells and spread via the vagal nerve to the central nervous system in the brain.

The positive side is that it opens the door to possible therapeutic alternatives such as eliminating or controlling the concentration of DSV bacteria to minimize their ability to infect and produce α-synuclein aggregates.

References and Further Reading

(1) Vy A. Huynh, Timo M., Takala Kari E., Murros Bidhi Diwedi, Per E. J. Saris (2023). Desulfovibrio bacteria enhance alpha-synuclein aggregation in a Caenorhabditis elegans model of Parkinson’s disease . Front. Cell. Infect. Microbiol., 01 May 2023, Sec. Molecular Bacterial Pathogenesis Vol 13-2023. https://doi.org/10.3389/fcimb.2023.1181315.