15
Aug
Pesticide-Induced Gut Microbiota Composition Alterations Linked to Parkinson’s Disease Prognosis
(Beyond Pesticides, August 15, 2024) Adding to research that has linked insecticide disruption of the gut microbial community to the progression of Parkinson’s Disease (PD) in the brain is a recently published study that further examines the gut-brain mechanism at work. A review by neuroscientist Nabanita Ghosh, PhD in Chemical Research in Toxicology—coauthored by Krishnendu Sinha, PhD, molecular toxicologist and applied pharmacologist, and molecular toxicologist Parames C. Sil, PhD—focuses on how pesticide-induced microbial community alterations specifically drive the initiation of PD and the precise mechanism. The study also explores microbiota changes at different stages of PD progression, offering recent findings.
The researchers derive their data from the examination of PD patients, evaluating the “interaction between pesticides and gut bacteria in PD patients, summarizing how pesticides cause imbalances in gut bacteria, the resulting changes, and their overall effects on the PD prognosis.”
The review “looks at how pesticides and gut bacteria separately influence PD development and progression, highlighting the harmful effects of pesticides and changes in gut bacteria.” The team concludes that pesticide exposure is connected to PD onset through “disturbances in gut function and alterations in intestinal microbiota.” However, the “exact role of microbial factors in this connection remains unclear.”
The study also points out a rise in the presence and decline of specific bacterial families and genera in PD patients compared to those without PD. Additionally, the review compiles a list of differential abundances of gut bacteria that are associated with nonmotor and motor symptoms in PD patients, as each stage of the disease may correlate with a particular microbial profile.
The team reports on recent research findings concerning variations in the gut microbial community among individuals with PD. Several studies show alterations in gut bacteria composition and “subsequent changes in products and metabolites in PD patients.” A recent systematic review reveals differences in 53 microbial families and 98 genera between people with PD and those without. Recent studies suggest gut bacteria could serve as markers for disease staging in PD and could be a possible indicator of chemical and pesticide exposure.
This review highlights several studies that report altered abundances of specific gut bacterial families and genera upon exposure to different pesticides.
It is proven that several classes of pesticides are damaging to gut homeostasis leading to gut dysbiosis (microbiome imbalance). Recent PD research has focused on the microbiome-gut-brain axis and vagus nerve, the nerve connecting the brain to the gut. However, the influence of pesticide exposure on gut microbiota has recently gained more attention. The gastrointestinal tract being the first exposure site, pesticides can cause alterations in the gut microbiota, possibly leading to the development of PD. Pesticides and microbial community changes disrupt the intestinal barrier, thereby causing inflammation and alpha-synuclein (a-syn) accumulation (a 140 amino acid protein in multiple brain regions). Research indicates that PD could start in the gut under these conditions.
It is critical to preserve the Gut-Brain Axis in the prevention and onset of neurodegenerative disease. The gut has an important relationship with the central nervous system (CNS) via the sympathetic and parasympathetic nervous system. This review explores the immediate effects of pesticide exposure on both the CNS and ENS (enteric nervous system regulating the gastrointestinal tract).
Environmental pathogens, such as pesticides, entering the gut can disrupt the nervous system leading to abnormal accumulation of a-syn proteins that can disperse to different brain regions via the vagus nerve. Additionally, the review reports on recent research suggesting that gut bacteria are essential in forming the blood-brain barrier (BBB) and influencing microglia (central nervous system cell) and astrocyte (nervous system tissue) functions, as studies display shifts in the microbial profile and also products and metabolites in PD patients.
Growing evidence suggests a strong link between the microbial profile and PD. An April 19 Daily News focuses on a recently proposed research paradigm that describes the entry of toxicants to the gut as one of the most common pathways for neurological harm in PD and Lewy Body Disease (LBD), another form of dementia.
The strong evidence linking PD to pesticides does not stop global pesticide usage from continuing and even expanding. Specifically, paraquat (PQ) has been linked to PD and has been prohibited in over 60 nations, but remains in use in the United States, Australia, India, and Africa. Paraquat is highly acutely toxic to human health, through ingestion, inhalation, or even dermal administration. This herbicide can cause severe damage and chronic issues that can lead to death through respiratory failure. While glyphosate and other types of pesticides have been closely linked to depression in farmers, PQ is one of the most fatal pesticides on the market and is frequently involved in suicides and accidental exposures resulting in death. In September of 2022 the U.S. Environmental Protection Agency (EPA) asked the federal court to reconsider approval of PQ due to its detrimental risks to human health and the environment. Supporting this notion, evidence suggests that the elimination of PQ will prevent PQ-induced death and suicides without reducing agricultural productivity. This information is critical as advocates push for both EPA and the federal court to restrict the usage of PQ.
The research team for the study states, “Usage of hazardous pesticides has to be minimized and must be altered with benign substitutes, and supplemented with protective equipment. Alternative medicinal or nutritional strategies need to be explored for individuals who cannot evade pesticide contact.”
Despite the close link between pesticide exposure and PD onset through gut dysbiosis, the specific role of microbial factors remains elusive. While several studies suggest a link between the clinical features of PD and changed microbial compositions in PD patients, further research is needed to propose mechanistic explanations and better our understanding of the interactions between the gut microbiota and the brain. Additionally, the associations of several bacterial families and genera with pesticide-induced and PD-related gut dysbiosis indicate a potential link that requires further study.
While the precise mechanisms of pesticides’ contribution to the onset and progression of PD remains unclear, the adverse effects to gut microbial community from PQ exposure justify forceful regulatory action to ban its use, according to health advocates. With the elimination of harmful pesticides and lifestyle adjustments, the nation can start to seriously address the epidemic of PD and neurodegeneration. Even though there is no existing cure for PD, the neuroprotective role of a healthy gut microbiome can be supported with probiotics that supply healthy microbes such as Lactobacillus, Blautia, Roseburia, Lachnospiraceae, Prevotellaceae, and Akkermansia.
All unattributed positions and opinions in this piece are those of Beyond Pesticides.
Sources:
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See Beyond Pesticides info:
- Research Links Parkinson’s and Lewy Body Disease with Chemical Effects on Brain and Gut. https://beyondpesticides.org/dailynewsblog/2024/04/research-links-parkinsons-and-lewy-body-disease-with-chemical-effects-on-brain-and-gut/
- Recent Studies Continue To Highlight Connection Between Depression and Suicide in Pesticide-Exposed Farmers. https://beyondpesticides.org/dailynewsblog/2024/07/recent-studies-continue-in-highlighting-connection-between-depression-and-suicide-in-pesticide-exposed-farmers/
- EPA Asks Federal Court to Allow Reconsideration of Its Decision to Permit Paraquat’s Continued Use. https://beyondpesticides.org/dailynewsblog/2022/10/epa-asks-federal-court-to-allow-reconsideration-of-its-decision-to-permit-paraquats-continued-use/
