Caltech study finds link between Parkinson's disease and gut bacteria

Posted December 05, 2016

They say it's plausible because those suffering from Parkinson's also have digestive issues, typically constipation, and that can start a decade before the tremors begin.

The team of researchers from the California Institute of Technology was led by Sarkis Mazmanian, made a decision to act based on previous studies which revealed that the gut bacteria of people suffering from Parkinson looked different than that of healthy individuals.

He said the gut is home to "a diverse community of beneficial and sometimes harmful bacteria" - the microbiome - that is vital for immune and nervous system function.

According to New Scientist, it's possible that the origins of Parkinson's come from within the gut. Parkinson's disease affects around 10 million people worldwide, being the second most common neurodegenerative disease.

Parkinson's disease is a neurodegenerative disorder where brain cells accumulate excessive amounts of a protein called alpha-synuclein.

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

To address the need for safer and more effective treatments, Mazmanian and first author Timothy Sampson of the California Institute of Technology turned to gut microbes as an intriguing possibility.

"Because GI problems often precede the motor symptoms by many years, and because most PD cases are caused by environmental factors, we hypothesised that bacteria in the gut may contribute to PD", he said. In addition, bidirectional communication between the gut and the brain has been implicated in neurological disorders such as anxiety, depression and autism spectrum disorders (ASD). A total of a million people in the US and up to 10 million worldwide have this condition, the second most common neurodegenerative disease after Alzheimer's disease. The researchers then took samples of gut microbes from human Parkinson's patients and transplanted the bacteria into the guts of the mice.

The researchers raised the mice in either normal conditions or in a germ-free environment. In fact, these mice showed nearly normal performance on tasks such as traversing a beam, removing an adhesive from their nose, and climbing down a pole. Treating germ-free mice with short-chain fatty acids could mimic the effects of the microbiome on PD symptoms.

Caltech researchers have shown in mouse models that gut bacteria can encourage the progression of some Parkinson's disease hallmarks. However, what if we told you that the gut bacteria actually helps the development of Parkinson's disease?

Researchers used mice genetically programmed to develop Parkinson's as they produced very high levels of the protein alpha-synuclein, which is associated with damage in the brains of Parkinson's patients. People with Parkinson's harbor distinct gut bacteria that influence the disease's severity. However, antibiotics or fecal microbe transplants are far from being viable therapies at this time.

Beck notes that there has been mixed evidence on the use of antibiotics to treat Parkinson's.

“What we extrapolate from that is that there is a microbial profile that is different in Parkinsons, ” said Mazmanian.

As a result, the rodents displayed motor symptoms and alpha-synuclein aggregation that are characteristic of the disease.

Dr Patrick Lewis, from the University of Reading, said: "This study really does reinforce the idea that examining what goes on in the stomach of people with Parkinson's could provide really important insights into what happens in disease, and potentially a new area of biology to target in trying to slow down or halt the changes in the brain". The work was funded by the Larry L. Hillblom Foundation, the Knut and Alice Wallenberg Foundation, the Swedish Research Council, Mr. and Mrs. Larry Field, the Heritage Medical Research Institute, and the National Institutes of Health.