Gut feeling: bacteria may inspire bowel treatment

WASHINGTON Wed May 28, 2008 2:06pm EDT

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WASHINGTON (Reuters) - A substance produced by one of the many types of bacteria that inhabit the human gut may inspire a new kind of drug for inflammatory bowel disease, scientists said on Wednesday.

The researchers found that a complex sugar molecule made naturally by a species of intestinal bacteria called Bacteroides fragilis prevented the development of an animal version of inflammatory bowel disease in laboratory mice.

They expressed hope this sugar molecule could be developed as a natural treatment for inflammatory bowel disease.

"We are colonized in our intestine normally with many bacteria -- 100 trillion or so," Dennis Kasper, a professor of medicine, microbiology and molecular genetics at Harvard Medical School in Boston who helped lead the research published in the journal Nature, said in a telephone interview.

"In this mixture of bacteria, there are some bacteria that may induce disease, and there are some bacteria that may prevent disease," Kasper added.

Considering the huge number of bacteria in the gut -- there are roughly a thousand species -- the potential for discovering substances made by some of these microorganisms that have the potential to treat human diseases is promising, Kasper said.

Inflammatory bowel disease refers to a group of disorders in which the intestines become inflamed, probably due to an immune reaction of the body against its own intestinal tissue.

Ulcerative colitis and Crohn's disease are two major types of the disease. Symptoms include severe diarrhea and abdominal pain. There is no known cure for either condition.

Mice genetically engineered to be prone to inflammatory bowel disease were infected with bacteria called Helicobacter hepaticus, which causes an inflammatory bowel condition akin in those mice to Crohn's disease and ulcerative colitis.

When the scientists exposed the mice to the "good" bacterium, Bacteroides fragilis, they were protected from an inflammatory bowel condition due to the action of a sugar molecule, called polysaccharide A, made by the bacterium.

Mice that were given oral doses of just the sugar molecule also were protected.

The sugar molecule worked by stimulating the mouse immune system to make a substance called interleukin-10, which changes the body's response to the disease-causing bacteria, dampening inflammation, the researchers said.

"Growing up, we've all thought of bacteria as being bad and always causing disease -- which may be justified because many bacteria do cause disease," Sarkis Mazmanian, a California Institute of Technology biology professor who also worked on the study, said in a telephone interview.

"But by and large, most organisms in our environment are either benign or actually beneficial. So the ripple effect of this work is that hopefully people's conception will change, and they will realize that there are good, beneficial bacteria out there and within us," Mazmanian added.

(Editing by Maggie Fox)

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