Every nine minutes, someone in the United States is diagnosed with Parkinson’s disease (PD) [1]. Despite tremendous progress in the field, the exact mechanisms behind its pathological initiation and progression is still unclear– how do alpha-synuclein proteins begin building up within dopamine-producing neurons in the brain? New research suggests that researchers may have been previously looking in the wrong place.
Enter the gut-brain axis (GBA). The GBA is a highly integrated network of nerves connecting the central and enteric nervous system. Recent research proposes a potential relationship between our gut bacteria and the neurons influencing neurodevelopment and neuroregeneration– the GBA serves as the link between these two systems [2].
Three chief hypotheses could explain this fascinating pathway [1]. First, intestinal microbiota are known to not only break down complex food components that the body can't process, but also develop and regulate the immune system [3]. Motile immune cells in the gut are designed to migrate where needed in the body– including moving towards the brain. Second, researchers predict that the vagus nerve, a key connector of the brain to various organs and digestive tract, could be the conduit for the microbiome connection to the brain. Finally, the microbiome-gut-brain connection could be complemented by chemical communication through metabolites, or small molecules made by the microbiome to break down food, drugs, and other substances [1].
Many researchers have noted that symptoms in the gut are often the first ones to manifest in PD patients. Dysregulation of the brain-gut-microbiota axis in PD may be associated with gastrointestinal symptoms that precede motor symptoms, supporting the hypothesis that gut could be the source of pathological PD progression [4]. Also, researchers have found alpha-synuclein aggregation in the guts of many PD patients– this led them to sequence the microbiomes of individuals with PD over the years, discovering that beneficial bacteria like Prevotella, Faecalibacterium, and Roseburia are reduced in those with the disease compared to people without it [3].
This connection hints that gut bacteria could help detect neurodegenerative and neurodevelopmental diseases early on. It also suggests that changing the gut microbiome might offer a new way to treat diseases that have been difficult to manage.
So what’s the answer to potentially preventing PD? While researchers are still determining exactly how the gut and brain are linked in Parkinson's disease, the gut-brain axis is proving to be a critical piece of the puzzle. One of the most exciting aspects of this research is the role diet plays in shaping the gut microbiome. By increasing fiber-rich foods, such as fruits, vegetables, and whole grains, we can support beneficial bacteria that may protect against disease [5]. As scientists continue to explore how gut bacteria influence brain health, dietary interventions could become a key part of preventing or slowing the progression of Parkinson’s. Though research is still in the early stages of delineating this complex relationship, it offers a promising new direction for treatment and prevention strategies that could one day change the lives of millions.
Graphic by Haynes Lewis
Reviewed by Laila Khan-Farooqi
References
[1] Backman, I. (n.d.). Does Parkinson’s Disease Begin in the Gut? Retrieved October 10, 2024, from https://medicine.yale.edu/news-article/does-parkinsons-disease-begin-in-the-gut/
[2] Ambrosini, Y. M., Borcherding, D., Kanthasamy, A., Kim, H. J., Willette, A. A., Jergens, A., Allenspach, K., & Mochel, J. P. (2019). The Gut-Brain Axis in Neurodegenerative Diseases and Relevance of the Canine Model: A Review. Frontiers in Aging Neuroscience, 11, 130. https://doi.org/10.3389/fnagi.2019.00130
[3] Klann, E. M., Dissanayake, U., Gurrala, A., Farrer, M., Shukla, A. W., Ramirez-Zamora, A., Mai, V., & Vedam-Mai, V. (2022). The Gut–Brain Axis and Its Relation to Parkinson’s Disease: A Review. Frontiers in Aging Neuroscience, 13. https://doi.org/10.3389/fnagi.2021.782082
[4] Mulak, A., & Bonaz, B. (2015). Brain-gut-microbiota axis in Parkinson’s disease. World Journal of Gastroenterology : WJG, 21(37), 10609–10620. https://doi.org/10.3748/wjg.v21.i37.10609
[5] Bicknell, B., Liebert, A., Borody, T., Herkes, G., McLachlan, C., & Kiat, H. (2023). Neurodegenerative and Neurodevelopmental Diseases and the Gut-Brain Axis: The Potential of Therapeutic Targeting of the Microbiome. International Journal of Molecular Sciences, 24(11), 9577. https://doi.org/10.3390/ijms24119577
Comments