For clues to Parkinson’s brain symptoms, a gut check is in order.

Intestinal microbes send signals that set off the disease’s characteristic brain inflammation and motor problems in mice, researchers report December 1 in Cell. Doctors might someday be able to treat Parkinson’s by fixing this bacterial imbalance.

“It’s quite an exciting piece of work,” says John Cryan, a neuroscientist at University College Cork in Ireland who wasn’t involved in the study. “The relationship between the brain and gut for Parkinson’s has been bubbling up for many years.” The new research, he says, “brings the microbiome really into the forefront for the first time.”

Parkinson’s affects more than 10 million people worldwide, and roughly 70 percent of those patients also have gastrointestinal issues like constipation.  Sometimes the GI symptoms show up years before the muscle weakness and other neurological problems. Several recent studies in humans have suggested a link between gut microbes and Parkinson’s. But it wasn’t clear whether intestinal microbes were actually causing the disease, says study coauthor Sarkis Mazmanian, a microbiologist at Caltech. “What our study adds is a functional, mechanistic role for the microbiome.”

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