Analysis of Gut Microorganisms in Parkinson’s Disease

Understanding Parkinson’s Disease

A recent analysis has focused on the gut microorganisms present in patients with Parkinson’s disease (PD) to determine if specific gut microbe patterns are linked to the condition. PD is a prevalent, progressive disorder that primarily affects the brain’s motor control functions. Initial symptoms may manifest as limb weakness, stiffness, or mild tremors. As the disease advances, patients may experience balance and walking difficulties, diminished facial expressions, issues with swallowing, and cognitive challenges such as depression, anxiety, or dementia.

Potential Role of Gut Microorganisms

While the exact causes of PD remain unclear, they may involve a mix of genetic and environmental influences. Recent research has highlighted the significance of gut microorganisms, collectively known as the microbiome, in relation to human health and disease. PD patients often experience gastrointestinal issues, such as constipation, early in their diagnosis. Some researchers have proposed that specific gut microorganisms might trigger PD by migrating through the gut lining and reaching the brain via the nervous system. However, earlier studies indicating changes in the gut microbiome among PD patients have produced inconsistent results.

Largest Gut Microbiome Analysis to Date

Researchers at the University of Alabama conducted the most extensive gut microbiome analysis to date, comparing PD patients with healthy individuals to identify any distinctive microbial patterns. Their findings were recently published in the journal npj Parkinson’s Disease. The team reanalyzed data from a 2017 study that included 197 PD cases and 130 healthy controls, alongside a new dataset comprising 323 PD cases and 184 controls. They utilized DNA sequencing, computer analysis, and network analysis tools to examine gut microorganisms present in stool samples from both groups.

Findings on Opportunistic Pathogens

The study identified 15 types of gut microorganisms linked to PD, as well as three polymicrobial clusters with shared functional characteristics. Notably, opportunistic pathogens were found to be more prevalent in PD patients, while short-chain fatty acid-producing microbes were less abundant, and carbohydrate-metabolizing probiotic microbes were more prevalent. While the latter two findings had been previously documented, the identification of an increased presence of opportunistic pathogens represents a novel discovery. Although typically harmless, these pathogens can lead to infections if the immune system is weakened or if they invade sterile areas of the body, such as the brain.

Implications for Future Research

The researchers caution that the identification of overabundant opportunistic pathogens in the gut microbiomes of PD patients does not imply causation. However, the findings open avenues for further investigation into the potential role these microorganisms may have in PD. Professor Haydeh Payami, the study’s lead author, stated, “The exciting question is whether these are pathogens capable of triggering PD, or are they irrelevant to PD but able to penetrate the gut and grow because the gut lining is compromised in PD.”

Professor Payami believes that the study’s large sample size and comprehensive analysis enabled the discovery of opportunistic pathogens not previously noted in earlier research. She emphasized the need for larger, more powerful studies and longitudinal research to track changes from early to advanced disease stages, as well as the application of next-generation metagenome sequencing.

References

1. Wallen AD, Appah M, Dean MN, et al. Characterizing dysbiosis of gut microbiome in PD: evidence for overabundance of opportunistic pathogens. (Nature partner journal) npj Parkinsons Dis. 6, 11 (2020). https://doi.org/10.1038/s41531-020-0112-6
2. University of Alabama at Birmingham, Press release, 18 June 2020. “The Parkinson’s disease gut has an overabundance of opportunistic pathogens.” https://www.eurekalert.org/pub_releases/2020-06/uoaa-tpd061820.php

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