For years, scientists have wondered: Could the gut be whispering secrets about Parkinson’s disease long before symptoms appear?

In our latest study, we dove deep into that question—analyzing over 1,000 gut microbiome samples from individuals with and without Parkinson’s disease across five countries. This was no ordinary analysis—it was a harmonized meta-analysis designed to overcome the inconsistencies that plagued earlier studies.

What we found was striking:

The gut in Parkinson’s patients is more diverse—but not in a good way.
We discovered an overabundance of bacteria that consume GABA, a neurotransmitter essential for calming the brain. One standout species, Evtepia gabavorous, may deplete GABA availability—potentially increasing neuronal excitability and worsening symptoms. This novel player could only be identified through the meta-analysis, which aligns with the recently identified role of Evtepia gabavorous to consume GABA, and the recent link between other GABA-modulating bacteria and PD prognosis. 

 We also uncovered a rise in pro-inflammatory microbes like Klebsiella variicola and Streptococcus anginosus. These bacteria are not innocent bystanders—they produce compounds that could trigger neuroinflammation, mitochondrial stress, and even α-synuclein buildup—the protein closely tied to Parkinson’s progression.

 On a functional level, we saw clear shifts in microbial metabolic pathways—suggesting the gut microbiome isn't just altered in Parkinson’s, but actively involved.

This study offers the clearest microbial fingerprint of Parkinson’s to date—and with it, a potential path to earlier diagnosis and future therapeutic targets.

https://doi.org/10.1038/s41531-025-00950-z