More Evidence That Parkinson's Starts In The Gut And Not In The Brain According To Scientists

Scientists have discovered more new evidence that Parkinson's could possibly start in the gut before it spreads to the brain, as they observed lower rates of the disease in patients who had undergone a procedure called a truncal vagotomy.

This operation removes parts of the vagus nerve - which connects the digestive tract with the brain - and during a five-year study, patients who had this connection entirely removed had 40% less chances to develop Parkinson's disease than those who hadn't.

According to a team led by Bojing Liu from the Karolinska Institute in Sweden, this is an important difference, and it backs up earlier work connecting the development of the brain disease to something occurring inside our bellies.

If we can understand more about the way this connection operates, we may be better able to prevent it.

"These results provide preliminary evidence that Parkinson's disease may start in the gut," says Liu.

"Other evidence for this hypothesis is that people with Parkinson's disease often have gastrointestinal problems such as constipation, that can start decades before they develop the disease."

The vagus nerve helps in controlling different unconscious processes such as heart rate and digestion, and removing parts of it in a vagotomy is often done to remove an ulcer if the stomach produces a dangerous level of acid.

For this study, the researchers took a look at 40 years of data from Swedish national registers, in order to compare 9,430 people who had a vagotomy against 377,200 people who hadn't.

The likelihood of people in these 2 groups to develop Parkinson's was statistically similar firstly - until the researchers examined the kind of vagotomy that had been carried out on the first group.

19 people in total (only 0.78% of the sample) developed Parkinson's more than 5 years after a truncal (complete) vagotomy, compared to 60 people (1.08%) who had a selective vagotomy.

Compare that to the 3,932 (1.15%) of people who had no surgery and developed Parkinson's after being monitored for at least 5 years, and it seems clear that the vagus nerve is playing a role here.

So what's going on? One scenario the scientists put forward is that gut proteins begin to fold in the wrong way, and that genetic 'mistake' gets carried up to the brain in a way, with that mistake being spread from cell to cell.

Parkinson's develops as neurons in the brain are destroyed, leading to tremors, stiffness, and difficulties with movement - but scientists aren't certain how it's caused in the first place. The new study offers them a helpful tip about where to search.

The recent research isn't alone in its conclusions. Last year, experiments on mice showed that there's a connection between certain mixes of gut bacteria and increased possibilities of developing Parkinson's.

Moreover, earlier this year a study in the US named differences between the gut bacteria of those with Parkinson's in comparison with those who didn't have the disease.

All of this is useful for scientists who are trying to prevent Parkinson's because if we know where it begins, we can block off the source.

However, we shouldn't get ahead of ourselves; the researchers behind the new evidence point out that Parkinson's is complicated disease, and they weren't able to include controls for all possible factors, including caffeine intake and smoking.

Also, it's worth noting that Parkinson's disease is classed as a syndrome: a collection of different but linked symptoms that might have multiple causes.

"Much more research is needed to test this theory and to help us understand the role this may play in the development of Parkinson's," says Lui.

The research has been published in Neurology.

Reference: Science Alert