One of the constraints of the research lies in the notable presence of a robust placebo effect, possibly stemming from the perceived invasiveness of the placebo intervention by the participants.
There exists evidence indicating that the more invasive a placebo intervention, the more pronounced the placebo response.
Additionally, it is plausible that a portion of the observed effect within the placebo cohort may not solely be attributed to the placebo effect, as suggested by Santens.
“The placebo effect was quite large. This may be due to the nature of the treatment with large expectations, on the one hand. On the other hand, there is preliminary evidence that [fecal transplant] with one’s own stool might also have a limited positive effect, at least on gut function. Therefore, we will try placebo treatment with colored inactive solutions in the next steps.”
Small advancements have been noted in previous trials investigating fecal transplants among patients with Parkinson’s disease.
Herbert DuPont, MD, a clinical professor of medicine specializing in infectious diseases at Baylor College of Medicine in Houston, TX, served as the primary author of a paper published in Frontiers In Neurology in 2023, demonstrating the potential impact of fecal transplants on Parkinson’s symptoms.
Although not directly involved in the current study, DuPont, in his remarks to MNT regarding its outcomes, elucidated that disruptions in the microbiome of Parkinson’s patients have been well-documented over the years. He highlighted various pathways through which the gut could influence Parkinson’s disease, including direct neural connections via the central nervous system, the vagus nerve, the enteric nervous system, and spinal nerves to the brain.
“The other way is through the immune system. Eighty percent of immune cells of the body are in the gastrointestinal tract, and our immune response is dependent on a healthy microbiome,“ DuPont added.
"And lastly, hormone synthesis plays a role," he conveyed to us. "Compounds, bioactive substances, and metabolites generated by the microbiota traverse the bloodstream or the vagus nerve, influencing the brain. These three pathways are all of significant importance."
Braak’s hypothesis of Parkinson’s disease
Pertinent to the context of this investigation is Braak’s theory concerning Parkinson’s disease, which posits that the onset of Parkinson’s occurs when a pathogen infiltrates the body via the nasal passage, reaches the gastrointestinal tract, and triggers the aggregation of alpha-synuclein in both the nasal cavity and the digestive system.
Certain researchers speculate that this accumulation subsequently disseminates to the nervous system and the brain, potentially instigating the development of Parkinson’s disease.
DuPont explained:
“We believe that neural connections are very important in the movement of alpha-synuclein, the small protein that is involved in producing cell death in the brain. And this is the so-called Braak’s hypothesis. And I think this is correct, but I think the biochemicals are very important. And I think the immune system is very important.”
Single dose of fecal matter could improve symptoms
"I believed it was crucial to demonstrate that a solitary infusion of fecal transplant could yield long-lasting benefits," DuPont expressed, reflecting on the study results.
"In my view, for a chronic condition characterized by genetic abnormalities and enduring physiological alterations, multiple administrations of fecal matter might be necessary to elicit an impact, and that's been the approach in our investigations. However, this study indicates that even a single dose can produce an effect," he supplemented.
Multiple dosing may necessitate providing the transplant via capsules, for example, which would involve processing the fecal matter in a way that might destroy many of the cells, microorganisms, enzymes and biochemicals that could be beneficial.
In prior investigations led by DuPont, examinations involved transplants utilizing fresh, frozen, and freeze-dried fecal matter. "This study has inspired me to consider the possibility of administering, perhaps, frozen or fresh samples in forthcoming endeavors," DuPont revealed.
"I believe the research on Parkinson's could serve as a precursor to exploring similar interventions for other neurodegenerative ailments. Conditions such as multiple sclerosis and Alzheimer's could potentially yield comparable success stories," he speculated.
Santens disclosed that the team behind the recent study was pursuing additional inquiries into the microbial compositions of participants in correlation with the study's recent findings. "We aim to secure funding for a larger, multicenter trial, incorporating insights from this preliminary study […] Additionally, we are examining patient profiles to potentially identify subsets that may be optimal candidates for this therapy," he shared.
