Bacteria living in the gut may contribute to movement problems seen in disorders such as Parkinson's disease.
Timothy Sampson and Sarkis Mazmanian at the California Institute of Technology in Pasadena and their team generated mice that lacked their own bacteria and had been genetically engineered so that their brains overproduce α-synuclein — a protein that forms clumps in the brains of people with Parkinson's. They found that these germ-free mice moved more freely and accumulated less α-synuclein in their brains than animals with gut microbes. When the team transplanted microbes from the faeces of people with Parkinson's disease into the guts of the mice, the animals showed more movement dysfunction than those that received bacteria from healthy humans.
The authors think that molecules made by gut microbes could activate certain immune cells and boost inflammation in general, which then enhances the clumping of α-synuclein in the brain.