Parkinson's disease linked to gut bacteria: study

Gut bacteria may play a critical role in the development of Parkinson's disease, according to a new study that may eventually lead to new treatment strategies for the common neurodegenerative disease.

The study, published this week in the U.S. journal Cell, showed that changes in the composition of gut bacterial populations, or possibly gut bacteria themselves, are actively contributing to and may even cause the deterioration of motor skills that is the hallmark of this disease.

"We have discovered for the first time a biological link between the gut microbiome and Parkinson's disease," senior study author Sarkis Mazmanian of the California Institute of Technology, said in a statement.

"More generally, this research reveals that a neurodegenerative disease may have its origins in the gut, and not only in the brain as had been previously thought."

Mazmanian hailed their discovery as "a paradigm shift" that "opens entirely new possibilities for treating patients."

Parkinson's disease is caused by the accumulation of abnormally shaped Alpha-synuclein proteins (Alpha Syn) in neurons, leading to particularly toxic effects in dopamine-releasing cells located in brain regions that control movement.

As a result, patients experience debilitating symptoms such as tremors, muscle stiffness, slowness of movement, and impaired gait.

First-line therapies currently focus on increasing dopamine levels in the brain, but these treatments can cause serious side effects and often lose effectiveness over time.

Up to 10 million people worldwide suffer from the condition, making it the second most common neurodegenerative disease after Alzheimer's.

In the new study, the researchers utilized mice that overproduce Alpha Syn. One group of mice had a complex consortium of gut bacteria, while the others, called germ-free mice, were bred in a completely sterile environment and thus lacked gut bacteria.

The researchers had both groups of mice perform several tasks to measure their motor skills, such as running on treadmills, crossing a beam, and descending from a pole and found the germ-free mice performed significantly better than the mice with a complete microbiome.

However, germ-free showed worse motor symptoms when they either were treated with microbial metabolites called short-chain fatty acids or received fecal transplants of gut microbes from patients with Parkinson's disease.

Taken together, the results suggested that gut microbes exacerbate motor symptoms by creating an environment that could favor the accumulation of Alpha Syn, the researchers said.

The findings have important implications for the treatment of Parkinson's disease.

"For many neurological conditions, the conventional treatment approach is to get a drug into the brain. However, if Parkinson's disease is indeed not solely caused by changes in the brain but instead by changes in the microbiome, then you may just have to get drugs into the gut to help patients, which is much easier to do," Mazmanian said.

"This new concept may lead to safer therapies with fewer side effects compared to current treatments." Enditem