The Columbus Dispatch, Ohio
April 10--Doctors and scientists know that stress can lead to illness. They just don't know why.
But they are starting to understand where it all might begin.
Ohio State University researchers say they have found that stress-related illnesses likely start in an unlikely place -- among the hordes of good and bad bacteria that live in our guts.
There are as many as 500 species of bacteria living inside our large intestines. With a combined population that approaches 100 trillion, these microbes help transfer nutrients and vitamins to the body while others help break down wastes and kill harmful food-borne bacteria.
Michael Bailey, an OSU immunologist and animal physiologist, found that stress in mice activates the immune system to fight off illness, even when there is no threat.
Other researchers say Bailey's work might be the first to demonstrate a link between gut bacteria and the immune system. And they say it could help lead the way to new treatments for stress-related diseases in people, including heart disease, inflammatory bowel disease and diarrhea.
"It identifies a potential signal, or source of a signal, that's responsible for the inflammatory stress response," said Monika Fleshner, an integrative physiologist at the University of Colorado and president-elect of the Psychoneuroimmunology Research Society.
Fleshner said stress causes the human immune system to overproduce a class of proteins called cytokines, which are linked to inflammation or swelling in body tissues. These proteins typically emerge when the body is fighting off a disease.
"A lot of symptoms of diseases are caused by the inflammatory response," Bailey said. "When we feel sick, those are cytokines signaling to the brain that you should feel sick."
It's unclear what health risks high concentrations of cytokines pose to people who aren't sick but are stressed out. Bailey said some research suggests that cytokines are a factor in heart disease and chronic inflammatory bowel disease.
Bailey's research found that stressed-out mice (aggressive mice are placed in their cages) had high concentrations of inflammatory cytokine in their blood. In some cases, levels of this type of cytokine were 100 times more concentrated in stressed mice than in non-stressed mice.
Stress also altered the normal balance of gut bacteria. Colonies of clostridium, a class of 100 species of bacteria, grew 28 percent in mice while another class, bacteroides, shrank nearly in half.
Bailey established the link between the bacteria and the inflammatory cytokine when he treated the mice with antibiotics.
The stressed-out mice treated with antibiotics had low concentrations of bacteria and low levels of the inflammatory cytokine. That meant that the changes in bacteria levels and not some other stress-related factor were influencing cytokine production.
The research, published late last year in the journal Brain, Behavior and Immunity, show that what happens in the gut has a direct link to health, said Mark Lyte, a microbial endocrinologist at Texas Tech University's Health Sciences Center.
Lyte helped design Bailey's experiment and is a co-author of the study.
Bailey said more work needs to be done to further define how changes in gut bacteria activate the body's immune response.
"Is it a single bacteria or a group that affect this response?" he said. "The other thing is trying to understand which immune cells in the body are producing these cytokines."
Fleshner said she also will work to find answers to these questions.
"If we could understand a little more about potentially using bacteria to quiet those inflammatory processes, we could have a whole new (treatment) strategy," she said.
To see more of The Columbus Dispatch, or to subscribe to the newspaper, go to http://www.columbusdispatch.com.
Copyright (c) 2011, The Columbus Dispatch, Ohio
Distributed by McClatchy-Tribune Information Services.
For more information about the content services offered by McClatchy-Tribune Information Services (MCT), visit www.mctinfoservices.com.