A new study, published in the journal Cell, suggests Parkinson’s disease may be caused by bacteria living in the gut.
Scientists say the findings could eventually lead to new ways of treating the brain disorder, such as drugs to kill gut bugs or probiotics.
In Parkinson’s disease the brain is progressively damaged, leading to patients experiencing a tremor and difficulty moving.
Californian researchers used mice genetically programmed to develop Parkinson’s disease as they produced very high levels of the protein alpha-synuclein, which is associated with damage in the brains of Parkinson’s patients.
Experts found that only those animals with bacteria in their stomachs developed symptoms. Sterile mice remained healthy.
Parkinson’s disease is the second most common neurodegenerative disorder and the most common movement disorder
Further tests showed transplanting bacteria from Parkinson’s patients to mice led to more symptoms than bacteria taken from healthy people.
Dr. Timothy Sampson, one of the researchers at the California Institute of Technology, said: “This was the <<eureka>> moment, the mice were genetically identical, the only difference was the presence or absence of gut microbiota.
“Now we were quite confident that gut bacteria regulate, and are even required for, the symptoms of Parkinson’s disease.”
Researchers believe the bacteria are releasing chemicals that over-activate parts of the brain, leading to damage.
The bacteria can break down fiber into short-chain fatty acids. It is thought an imbalance in these chemicals triggers the immune cells in the brain to cause damage.
Dr. Sarkis Mazmanian said: “We have discovered for the first time a biological link between the gut microbiome and Parkinson’s disease.
“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.
“The discovery that changes in the microbiome may be involved in Parkinson’s disease is a paradigm shift and opens entirely new possibilities for treating patients.”
Parkinson’s disease is currently incurable.
The findings need to be confirmed in humans, but the researchers hope that drugs that work in the digestive system or even probiotics may become new therapies for the disease.
The trillions of bacteria that live in the gut are hugely important to health, so wiping them out completely is not an option.
Researchers have found that a certain type of bacteria that live in the gut have been used to reverse obesity and Type-2 diabetes in animal studies.
Research, published in Proceedings of the National Academy of Sciences, showed that a broth containing a single species of bacteria could dramatically alter the health of obese mice.
It is thought to change the gut lining and the way food is absorbed.
Similar tests now need to take place in people to see if the same bacteria can be used to shed the pounds.
The human body is teeming with bacteria – the tiny organisms outnumber human cells in the body 10 to one.
And there is growing evidence that this collection of bacteria or “microbiome” affects health.
Studies have shown differences between the types and numbers of bacteria in the guts of lean and obese people.
Researchers have found that a certain type of bacteria that live in the gut have been used to reverse obesity and Type-2 diabetes in animal studies
Meanwhile gastric bypass operations have been shown to change the balance of bacteria in the gut.
Researchers at the Catholic University of Louvain, in Belgium, worked with a single species of bacteria Akkermansia muciniphila. It normally makes up 3-5% of gut bacteria, but its levels fall in obesity.
Mice on a high fat diet – which led them to put on two to three times more fat than normal, lean, mice – were fed the bacteria.
The mice remained bigger than their lean cousins, but had lost around half of their extra weight despite no other changes to their diet.
They also had lower levels of insulin resistance, a key symptom of Type-2 diabetes.
Prof. Patrice Cani, from the Catholic University of Louvain, said: “Of course it is an improvement, we did not completely reverse the obesity, but it is a very strong decrease in the fat mass.
“It is the first demonstration that there is a direct link between one specific species and improving metabolism.”
Adding the bacteria increased the thickness of the gut’s mucus barrier, which stops some material passing from the gut to the blood. It also changed the chemical signals coming from the digestive system – which led to changes in the way fat was processed elsewhere in the body.
Similar results were achieved by adding a type of fiber to diets which led to an increase in the levels of Akkermansia muciniphila.
Prof. Patrice Cani said it was “surprising” that just one species, out of the thousands in the gut, could have such an effect.
He said this was a “first step” towards “eventually using these bacteria as prevention or treatment of obesity and Type-2 diabetes” and that some form of bacteria-based therapy would be used “in the near future”.