Parkinson’s, a disease of the central nervous system, affects approximately one million people in the United States. While the disease known for impairing motor skills, it can also have digestive symptoms such as constipation years before diagnosis. Because of this phenomenon, scientists have begun to investigate the role of gut microbiome composition in this awful disease. One such study conducted by a team at Caltech used transgenic mice to get to the answer. All of the mice overexpressed the protein human a-synuclein, which can form the insoluble fibrils that lead to Parkinson’s. However, the researchers raised some of the mice germ-free, or gave them antibiotics, so no intestinal microbes formed. In these mice, Parkinson’s-like symptoms and brain pathology decreased. In addition, the researchers found that the mice that did have gut microbiota had brain inflammation that the germ-free mice didn’t. Only when the researchers fed the germ-free mice short-chain fatty acids (to stimulate gut microbiota) did they show signs of inflammation and other Parkinson’s symptoms. This suggests that gut microbiota that produce short-chain fatty acids could be what triggers this disease.

The researchers then tried to investigate more about which gut bacteria could cause Parkinson’s. Since different communities of gut bacteria live in people with Parkinson’s disease than in healthy people, they wanted to find out if these different communities are merely a byproduct or a cause of the disease. To do so, they transplanted human gut-derived microbes from Parkinson’s patients into some mice, and microbes from healthy people into others. The transgenic mice with microbiota from the Parkinson’s patients ended up with typical Parkinson’s symptoms like motor dysfunction. However, wild-type mice (mice that didn’t overexpress human a-synuclein) weren’t affected. This finding shows that people who are genetically predisposed to Parkinson’s can be afflicted with symptoms if introduced to microbes that are associated with the disease.

This is such groundbreaking work because it establishes a causality between the gut microbiome and Parkinson’s. It also raises questions about the negative affects of short-chain fatty acids on the mice in this study, since they’ve been known to be beneficial in humans. The researchers wish to continue their work by investigating the types of microbes in people with Parkinson’s to get to the fundamental cause of the disease and possible cures.

Do you think that short-chain fatty acids are actually harming humans in unseen ways? Is investigating human gut microbiomes is the right path to find the cure to Parkinson’s? Let me know in the comments!

Three-dimensional Human Intestinal Cells

Human Intestinal Cells Cultured with Gut Bacteria

Credit: Scitechnol Publisher, URL:


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