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Originally published December 15 2013

MicroRNA responses to bacterial infection determined by gut microbiota

by Jonathan Benson, staff writer

(NaturalNews) New research out of France helps further clarify the role of intestinal microbiota in protecting the body against disease. Researchers from the Institut Pasteur in Paris found that the many billions of microorganisms that naturally line the intestinal tract help mitigate the proliferation of foodborne pathogens like Listeria monocytogenes, which apparently do not easily take hold when intestinal microbiota are in healthy balance.

Pascale Cossart and her colleagues, publishing their work in the open-access American Society for Microbiology journal mBio, observed that intestinal microRNA (miRNA) express themselves differently when intestinal microbiota are not in healthy balance or are lacking entirely. Mice bred to be free of germs, they found -- these mice had no intestinal flora at all -- exhibited an entirely different miRNA response compared to conventional mice with healthy flora.

Specifically, the expression of five intestinal miRNA molecules was observed to decrease in conventional mice exposed to Listeria compared to germ-free mice, which experienced no decrease whatsoever. This difference, researchers say, provides solid evidence that gut microbiota play an important role in the way the body responds to infection.

"We were surprised by the robustness of the intestinal miRNA signature in germ-free mice and conventional mice," stated Cossart. "Our results show that even very small variations in miRNA expression can have important outcomes."

Gut microbiota tell the body how to respond to pathogenic invaders

Earlier research by Cossart has determined that, upon infection with Listeria, both the bacterium and the host to which it is exposed reprogram the way they manufacture proteins. They do this, according to these previously published findings, by interacting with miRNA and other non-coding RNA molecules.

But this latest research looked specifically at whether or not, and how, gut microbiota react during this process. Both germ-free and conventional mice were exposed to the same bacterium, in this case Listeria, and researchers looked for variations in how the mice's bodies responded to exposure, which turned out to be strikingly disparate.

"24 hours after infection, germ-free mice harbored 10,000 times more L. monocytogenes bacteria in their small intestines and about 1,000 times more Listeria in their mesenteric lymph nodes than did the conventional mice," reads a press release about the study's findings.

"We found that even though the intestinal miRNA signature is globally stable, Listeria infection can affect the host miRNA response in a microbiota-dependent manner," added Cossart, noting that the conventional mice were far better protected against Listeria infection compared to the germ-free mice.

Probiotic foods, beverages crucially important for maintaining healthy gut microbiota

Though the findings still need to be replicated in human subjects, they admittedly have strong implications for human health. The importance of maintaining healthy gut flora, which can be achieved by ingesting plenty of probiotic-rich foods and beverages, is once again validated by the fact that, without this important bacteria, the body is unable to stave off harmful infections.

Imbalanced or lacking gut bacteria has also been linked to a host of other chronic illnesses, including gastrointestinal disorders, depression, heart disease and even cancer.

"Imbalances in gut bacteria... have been linked with diabetes, obesity, autism, eczema, psoriasis, asthma and inflammatory bowel conditions such [as] ulcerative colitis and Crohn's disease," writes Lucy Elkins for the U.K.'s Daily Mail.

To learn more about the importance of probiotics, be sure to check out this special report by Life Extension Magazine:

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