Parasitic worms that hide in the intestines of some people may be revolting, but they seem to prevent disease Crohn and other types of inflammatory bowel disease (IBD). A new study may explain how revealing that to allow beneficial microbes in the gut to supplant the bacteria that promote inflammation. The findings could lead to new ways to treat diseases of the gut by mimicking the effects of parasites.
"It is a beautifully made paper," says immunologist Joel Weinstock of Tufts University in Boston, who was not connected to the work. "It has not been shown previously that one of the mechanisms [of IBD] is through changes in the intestinal flora."
In people with IBD, inflammation in the results of digestive symptoms such as diarrhea and bleeding and can sometimes lead to bowel obstructions or other serious complications. Because parasitic worms, or helminths, can be harmful, they seem to be unlikely allies against these diseases. "They are called parasites for a reason," says immunologist Ken Cadwell of the New York University School of Medicine in New York City, co-author of the new study. However, the EIA is rare in parts of the world where helminths are prevalent, and it is surging in most developed countries, where few people now carry intestinal intruders. This difference suggests, the researchers say they are protective.
to determine how to could be our frenemies, Cadwell and his colleagues tested mice with the same genetic defect found in many people with Crohn's disease. mucus secreting cells in the bowel dysfunction in animals, reducing the amount of mucus that protects the intestinal mucosa of harmful bacteria. the researchers also detected a change in the microbiome rodents, the natural microbial community in their guts. The abundance of a microbe, an inflammation-inducing bacteria in the Bacteroides rises in mice with the genetic defect.
The researchers found that feeding rodents a type of intestinal worms restored their mucus-producing cells to normal. At the same time, the levels of both indicators of inflammation decreased in the intestines of animals. In addition, the range of bacteria in the intestines of displaced rodents, the team announced today online Science . Bacteroides numbers have plunged, while the prevalence of species in a different microbial group, Clostridiales increased. A second species of worm also trigger similar changes in the intestines of mice, the team confirmed
To check whether helminths cause the same effects in people, the scientists compared two populations in Malaysia :. Urban population living in Kuala Lumpur, which harbor some intestinal parasites, and members of indigenous groups, the Orang Asli who live in a rural area where worms are common. One type of Bacteroides proinflammatory microbes, predominated in the people of Kuala Lumpur. It was rarer among Orang Asli, where a member of Clostridiales group was plentiful. Orang Asli treat with drugs to kill their intestinal worms reversed this trend, favoring Bacteroides species on Clostridiales species, the team documented.
Cadwell and his colleagues also asked whether Clostridiales and Bacteroides microbes disagreed with others. They analyzed two sets of data on the frequencies of different gut microbes, which include results for American healthy residents and children in North America who have IBD. They saw the same relationship when Clostridiales species are in place Bacteroides varieties are down, and vice versa.
The findings of the study suggest that parasitic worms deliver their benefits indirectly through their impact on the microbial mix in the intestines. Worms are "having an anti-inflammatory effect by kicking something that is inflammatory," said Cadwell. Clostridiales group members can get a boost when worms are around, he said, because the intestines produce more mucus, bacteria feed on.
"This is a good proof of concept," says Gabriel Nunez immunologist at the University of Michigan, Ann Arbor, who was not connected to the research. It supports "the principle that some of these diseases may be related to changes in the microbiome. "But he warned that researchers still need direct evidence that Bacteroides species are responsible for Crohn's disease.
turn the results into a treatment for IBD could be difficult. Two recent clinical trials helminth treatment for Crohn's disease, in which participants drank a solution containing worm eggs, stopped early because the results been disappointing. These studies may not be the last word, however. Cadwell said the worm therapy might work in more or less 30% of Crohn's patients who have the same genetic defect as mice. and Weinstock noted that if researchers can determine how parasites trigger the change in the composition of microbe, "we may be able to bypass and develop a small molecule drug to achieve the effect of a safe manner."
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