How the gut bacteria protect against deadly symptoms during infection

How the gut bacteria protect against deadly symptoms during infection

In a paper published in Science, researchers reported finding a strain of microbiome Escherichia coli bacteria in mice capable of improving the animals’ tolerance to infections of the lungs and intestines by preventing wasting–a common and potentially deadly loss of muscle tissue that occurs in serious infections.

If a similarly protective strain is found in humans, it could offer a new avenue for countering muscle wasting, which afflicts patients suffering from sepsis and hospital-acquired infections, many of which are now antibiotic resistant.

The Salk team identified a population of laboratory mice that appeared resistant to muscle wasting. By comparing the makeup of the intestinal microbiome of these mice with mice that lacked resistance, the team identified a strain of E. coli that was present only in the wasting-resistant mice.
 
When normal mice were given an oral treatment of this beneficial E. coli strain, they gained the ability to maintain their muscle and fat mass during intestinal infections of the bacteria Salmonella Typhimurium and pneumonia caused by the bacteria Burkholderia thailandensis.
 
The team discovered that during an infection by the pathological bacteria, the E. coli left the gut and moved into the fat tissues to induce protective responses that nourish the muscles.
 
Normally, mice with lung and intestinal infections see a drop in a hormone known as insulin-like growth factor 1 (IGF-1), a molecule that signals the body to retain muscle mass. But the protective E. coli activated the IGF-1 pathway in the fat tissues, maintaining normal IGF-1 levels and maintaining the animal’s muscle in spite of the pathogenic infections.
 
The Salk team further found that the E. coli strain was activating the IGF-1 muscle maintenance pathway through an intermediary, a molecular complex in cells known as the inflammasome. Part of the body’s innate immune system, the inflammasome responds to an infection by triggering inflammation in the infected area to destroy the offending microbes. The E. coli used this same alarm system to tell the body to maintain IGF-1 levels and hence muscle mass.

Whether such a microbial ‘superhero’ could come to the rescue of humans with infections remains to be seen. 


http://www.salk.edu/news/pressrelease_details.php?press_id=2127

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