The Gut Microbiome and Parkinson's Disease
by Rebecca Hölzel
Abnormal Gut Microbiome
The conditions that contribute to the development of Parkinson's Disease are likely very complex. A growing body of research has indicated, however, that the gut microbiome may play a key role in disease development and progression. Parkinson's Disease is commonly associate with abnormal gut microbiomes, including increased and decreased counts of bacteria normally found in healthy individuals. [1]
Studying the relationship between Parkinson's Disease and gut microbiota can be difficult because the gut microbiome is easily influenced by medications and diet. Therefore, studies that attempt to control for these factors are particularly valuable for elucidating the connection between Parkinson's and the gut. One study attempted to do so by recruiting newly diagnosed and unmedicated Parkinson's disease patients in addition to medicated patients with long-term disease progression. Controls were established using patient family members and patients visiting the diagnosing hospital for unrelated reasons. Using antibiotics or having other gut-related diseases constituted grounds for expulsion from the study. [2]
Fecal samples were collected from all patients and used to extract bacterial DNA. The 16S rRNA gene was amplified and sequenced using Illumina sequencing. The results were taxonomically arranged as measures of bacterial diversity and relative abundance of bacterial genera.[2]
Microbes and L-Dopa
Levodopa (L-dopa) is widely used in the treatment of Parkinson's Disease. Despite its efficacy, up to 56% of administered L-dopa fails to reach the brain because it is metabolized in other pathways. Gut bacteria are suspected to play a large role in loss of L-dopa function; as such, identifying any microbes responsible for metabolizing L-dopa is crucial.
Enterococcus faecalis was previously found to possess a tyrosine decarboxylase (TyrDC) capable of decarboxylating L-dopa and producing dopamine. The role of TyrDC in metabolizing L-dopa was confirmed by experiments that found knockout of the TyrDC gene drastically reduced Enterococcus faecalis dopamine production.
References
- ↑ Sampson, Timothy. (2020). "The Impact of Indigenous Microbes on Parkinson's Disease." Neurobiology of Disease, vol. 135. https://doi.org/10.1016/j.nbd.2019.03.014
- ↑ 2.0 2.1 Barichella, M., Severgnini, M., Cilia, R., Cassani, E., Bolliri, C., Caronni, S., Ferri, V., Cancello, R., Ceccarani, C., Faierman, S., Pinelli, G., De Bellis, G., Zecca, L., Cereda, E., Consolandi, C. and Pezzoli, G. (2019). "Unraveling Gut Microbiota in Parkinson's Disease and Atypical Parkinsonism. Movement Disorders, vol. 34, 396-405. https://doi.org/10.1002/mds.27581
Authored for BIOL 238 Microbiology, taught by Joan Slonczewski, 2022, Kenyon College
