Mice show symptoms matching those of humans with Parkinson's disease when exposed to the gut bacteria of Parkinson's patients, and got better when treated with antibiotics. If the discovery is found to apply to humans, it will open up new and potentially easier paths to treating the world's second most common neurodegenerative disease.
The last few years have seen an astonishingly rapid growth in the number of conditions suspected of being related to bacteria inhabiting the gut. Asthma, multiple sclerosis, and depression are just three of many recent examples.
The possibility that Parkinson's disease should be added to the list was raised by the observation that gastrointestinal symptoms not only often accompany the disease, but appear before more recognized signs. Three studies published last year all showed differences between the bacteria in the guts of people with Parkinson's disease and others of the same age.
Professor Sarkis Mazmanian of the California Institute of Technology noted that little had been done to test if the intestinal symptoms triggered Parkinson's or were just an early warning sign. He turned to a previously developed line of genetically modified mice with a condition considered similar enough to Parkinson's to be used as a research model.
Mazmanian raised some of these mice in sterile cages to ensure they were kept free from harmful bacteria, while others were kept in more normal conditions. Those exposed to fewer germs performed much better at a range of tasks, such as climbing poles and removing adhesive from their noses, in some cases almost matching mice without the Parkinson's-like genetics. Moreover, autopsies revealed fewer of the misfolded proteins associated with Parkinson's disease in the mice kept in clean cages.
Even where mice had been raised with exposure to bacteria, antibiotics reduced their symptoms, Mazmanian revealed in Cell.