Guts & Brains: stomach bugs linked to goings-on in the head

New studies show that an ulcer-causing bacterium may trigger Parkinson's and that digestive problems may hardwire the brain for depression.

Two new rodent studies reveal that stomach microbes and irritation can also affect the brain.

1. Helicobacter pylori (pictured) – a bacterium that causes ulcers and stomach cancer – may also trigger Parkinson’s disease, a neurological disorder with 60,000 new cases a year in the US.

H. pylori lives in the stomachs of half the people in the world and also helps protect against allergies, asthma, and acid reflux.

Some studies have suggested that Parkinson’s patients are more likely than others to have had ulcers at some point in their lives and are more likely to be infected with H. pylori. But it’s been circumstantial thus far.

Parkinson’s disease kills dopamine-producing cells in the brain, and patients often have trouble controlling their movements.

Now new evidence shows that middle-aged mice infected with the bacterium developed abnormal movement patterns over several months of infection, according to study researcher Traci Testerman of Louisiana State University.

Young mice infected with the bacterium didn’t show any signs of movement problems.

Helicobacter-infected mice make less dopamine in parts of their brain that control movement, possibly indicating that dopamine-making cells are dying just as they do in patients with Parkinson’s.

The research was reported yesterday at a meeting of the American Society for Microbiology. Via Science News.

2. Digestive problems early on may set the brain up for depression.

Scientists have assumed that the hormones released during mood alterations lead to gut problems. But now researchers are finding that it’s the other way around.

A team led by Pankaj Pasricha of Stanford gave young rats a mild stomach irritant, and then tested them for symptoms of depression at 10 weeks old.

These rats showed more signs of depression and higher levels of stress hormones in the brain than healthy control rats.

Blocking signals from nerves in the gut made no difference to their depression, suggesting that ongoing gut pain wasn't the trigger. Blocking receptors to stress hormones in the brain, on the other hand, did alleviate the effects.

The study was published in PLoS One earlier this month. Via New Scientist.

Images: H. pylori (top), Sprague Dawley rat (bottom) via Wikimedia

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