Researchers say they’ve uncovered a link between gut bacteria and the onset of Parkinson’s disease. The findings suggest a new way of treating one of the world’s most debilitating diseases.
Parkinson’s causes a variety of physical changes, especially in the digestive system. Patients often complain of constipation or bloating, trouble swallowing, and indigestion. These symptoms often begin years before patients lose motor control, the hallmark of the disease. 
For the study, researchers worked with mouse models of the brain disorder and discovered that changes in gut microbes may play a role in triggering Parkinson’s. The team, led by Sarkis Mazmanian of the California Institute of Technology, transplanted fecal samples from people with Parkinson’s into mice raised in a germ-free setting and found that the rodents’ symptoms worsened. The same did not happen when the mice were injected with fecal matter from people without Parkinson’s.
“What we extrapolate from that is that there is a microbial profile that is different in Parkinson’s. Perhaps those changes are contributing to disease; we’re a long way from proving that’s the case in humans, but at least in mouse models that’s what the data suggest.”
Mazmanian theorizes that breakdown products of the bacteria are toxic and circulate to the brain. There are also many nerve connections between the intestines and the brain, so it’s possible that influencing the nerves in the gut affects nerves in the brain. 
“Coupled with emerging research that has linked gut bacteria to disorders such as anxiety, depression, and autism, we propose the provocative hypothesis that certain neurologic conditions that have classically been studied as disorders of the brain may also have etiologies in the gut.”
There are about a dozen species of microbes that might be important to the disease, according to Mazmanian, and some of them are missing in people with Parkinson’s disease. This suggests the missing microbes may provide some protection against the neurodegenerative disorder. 
“There are particular classes of bacteria that are selectively missing or depleted in the Parkinson’s population and found in the healthy population.” 
The study doesn’t show that gut microbes cause Parkinson’s, but it suggests that a pivot from treating the brain to treating the gut might be more effective. The researchers hope the findings will lead to the development of “next generation” probiotics that are like commercially available probiotics on steroids. 
“One can imagine one day, maybe in our lifetimes, patients will be prescribed drugs, and in the pills will be the bacteria that protect them from disease or even maybe treat their disease symptoms.”
 NBC News