Parkinson’s might be caused by common bug found in the gut, researchers say

Parkinson’s might be caused by a little-known aquatic bacteria, researchers have said. 

A buildup of proteins that kill of brain cells has been identified as a marker of Parkinson’s, which affects 145,000 people in the UK and 500,000 in the US.

Scientists have been probing the cause for decades. Now, researchers in Finland say this process may be caused in part by bacteria Desulfovibrio (DSV).

Lab experiments suggest that the bacteria, commonly found in the gut, causes proteins clump together, resulting in the injury or death of cells.

‘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 only appear when about 80 per cent of the nerve cells have been lost

Researchers at the University of Helsinki believed DSV — which is found in water, soil and the digestive tracts of humans and animals — could play a role in Parkinson’s.

So they took faecal samples from ten Parkinson’s patients and their healthy spouses, so the researchers could isolate the bacteria. 

Lab tests showed that all Parkinson’s patients had the bacteria in their faeces, along with eight of their partners.

DSV strains were then fed to organisms called nematode worms – which are known for making copies of protein alpha-synuclein. The researchers also fed some worms the bacteria E-coli as a control.

Previous research has suggested this protein is an indication that the degenerative disease is developing.

The results show that worms fed DSV strains from Parkinson’s patients bore ‘significantly more’ protein aggregates than those fed the same bacteria from healthy individuals or ones that were fed E-coli.

And in follow-ups, researchers also found worms fed the bacteria extracted from Parkinson’s patients died in ‘significantly higher quantities’, according to the results published in the journal Frontiers in Cellular and Infection Microbiology.

‘These results suggest that bacteria contribute to PD (Parkinson’s disease) development by inducing alpha-syn aggregation,’ the authors wrote. 

Study author Professor Per Saris, microbiologist at the university, believes DSV causes proteins to clump together in the intestinal cells, which then ‘travel towards the brain’ through the vagus nerve — the longest cranial nerve in the body, which travels from the stomach to the brain.

He said: ‘Our findings are significant, as the cause of Parkinson’s disease has gone unknown despite attempts to identify it throughout the last two centuries. 

‘The findings indicate that specific strains of DSV bacteria are likely to cause Parkinson’s disease. 

‘The disease is primarily caused by environmental factors, that is, environmental exposure to the DSV bacterial strains that cause Parkinson’s disease.

‘Only a small share, or roughly 10 per cent, of Parkinson’s disease is caused by individual genes.’

However, the authors wrote that if it was as simple as DSV causing Parkinson’s the case would have been solved long ago. 

They say that Parkinson’s patients instead have a higher abundance of the bacteria — as DSV was also found in 80 per cent of the healthy individuals. 

But Professor Saris said: ‘Our findings make it possible to screen for the carriers of these harmful DSV bacteria. 

‘Consequently, they can be targeted by measures to remove these strains from the gut, potentially alleviating and slowing the symptoms of patients with Parkinson’s disease.’

While the average age of diagnosis in the UK is around 65, scientists believe that Parkinson’s begins to develop, with nerve cells starting to die off, up to 20 years before symptoms show. 

Symptoms can include uncontrollable tremors, slow movements and muscle stiffness, but experts say they often only appear when about 80 per cent of the nerve cells have been lost.

These nerve cells produce dopamine, a chemical messenger that helps to control body movement. 

If these become damaged or die, levels of dopamine are reduced 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 which measures dopamine levels. 

Men are 50 per cent more likely to develop the condition than women — which it has been suggested could be because the female hormone oestrogen has a protective effect.