Parkinson’s might be caused by common bug found in the gut, researchers say
Parkinson’s may be caused by a little-known aquatic bacteria, researchers have said.
A buildup of proteins that kill brain cells has been identified as a marker of Parkinson’s disease, which affects 145,000 people in the UK and 500,000 in the US.
Scientists have been investigating the cause for decades. Now researchers in Finland say this process may be partially caused by the bacteria Desulfovibrio (DSV).
Lab experiments suggest that the bacteria, commonly found in the gut, cause proteins to clump together, resulting in cell injury or death.
“The findings indicate that specific strains of DSV bacteria are likely to cause Parkinson’s disease,” the scientists said.
Symptoms can include uncontrollable tremors, slow movements and muscle stiffness, but experts say they often don’t appear until about 80 percent of the nerve cells are lost.
Researchers at the University of Helsinki believed that DSV – which is found in water, soil and the digestive tract of humans and animals – could play a role in Parkinson’s.
So they took stool samples from ten Parkinson’s patients and their healthy spouses so the researchers could isolate the bacteria.
Laboratory tests showed that all Parkinson’s patients had the bacteria in their stools, along with eight of their partners.
DSV strains were then fed to organisms called nematode worms, which are known for making copies of the protein alpha-synuclein. The researchers also fed some worms the E-coli bacteria as a control.
Previous research has suggested that this protein is an indication that the degenerative disease is developing.
Show the results that worms fed DSV strains from Parkinson’s patients contained ‘significantly more’ protein aggregates than worms fed the same bacteria from healthy individuals or worms fed E-coli.
And in follow-ups, researchers also found that worms fed on the bacteria extracted from Parkinson’s patients died in “significantly greater amounts,” according to results published in the journal Frontiers in cellular and infection microbiology.
“These results suggest that bacteria contribute to the development of PD (Parkinson’s disease) by inducing alpha-syn aggregation,” the authors wrote.
Study author Professor Per Saris, a microbiologist at the university, believes that DSV causes proteins to clump together in the intestinal cells, which then “travel to the brain’ via the vagus nerve – the longest cranial nerve in the body, running from the stomach to the brain.
He said: ‘Our findings are significant as the cause of Parkinson’s disease is unknown despite efforts to identify it over the last two centuries.
‘The findings indicate that specific strains of the DSV bacteria are likely to cause Parkinson’s disease.
‘The disease is mainly caused by environmental factors, that is, exposure of the environment to the DSV bacterial strains that cause Parkinson’s disease.
“Only a small portion, about 10 percent, of Parkinson’s disease is caused by individual genes.”
However, the authors wrote that if it were as simple as DSV causing Parkinson’s disease, the case would have been resolved long ago.
They say that Parkinson’s patients instead have a higher amount of bacteria – as DSV was also found in 80 percent of healthy individuals.
But Professor Saris said: ‘Our findings make it possible to screen for the carriers of these harmful DSV bacteria.
“Consequently, they could be targeted by measures to remove these stresses from the gut, potentially alleviating and delaying the symptoms of Parkinson’s disease patients.”
Although the average age of diagnosis in the UK is around 65, scientists believe that Parkinson’s disease begins to progress, with nerve cells beginning to die, up to 20 years before symptoms become apparent.
Symptoms can include uncontrollable tremors, slow movements and muscle stiffness, but experts say they often don’t appear until about 80 percent of the nerve cells are lost.
These nerve cells produce dopamine, a chemical messenger that helps control body movements.
If these become damaged or die, dopamine levels decrease and movements become slow and abnormal.
Doctors diagnose the disease by studying a patient’s symptoms and movement, often followed by a DaT scan — a type of brain scan that measures dopamine levels.
Men are 50 percent more likely to develop the condition than women – which may be suggested because the female hormone estrogen has a protective effect.