Researchers at a meeting of the American Society for Microbiology last week reported that Helicobacter pylori, a bacterium that lives in the stomachs of about half the people in the world, may help trigger Parkinson’s disease.
Parkinson’s disease is a neurological disorder that kills dopamine-producing cells in parts of the brain that control movement. About 60,000 new cases of the disease are diagnosed each year in the United States.
H. pylori causes chronic low-level inflammation of the stomach lining and is strongly linked to the development of duodenal and gastric ulcers, and stomach cancer.
Previous studies suggested that people with Parkinson’s disease are more likely than healthy people to have had ulcers at some point in their lives and are more likely to be infected with H. pylori.
Middle-aged mice infected with H.pylori develop abnormal movement patterns over several months of infection. Helicobacter-infected mice make less dopamine in parts of the brain that control movement, possibly indicating that dopamine-making cells are dying just as they do in Parkinson’s disease patients.
Young mice, on the other hand, don’t show any signs of movement problems after infection with the bacterium.
The bacteria didn’t have to be alive to cause the problem. Feeding mice killed H. pylori produced the same effect, suggesting that some biochemical component of the bacterium is responsible.
A candidate for the disease-causing molecule is modified cholesterol. H. pylori can’t make its own cholesterol, so it steals cholesterol from its host and then sticks a sugar molecule on it. The structure of the modified cholesterol resembles a toxin from a tropical cycad; people in Guam who have eaten the plant’s seeds have developed a disease called ALS-parkinsonism dementia complex.
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