Sunday, September 23, 2012

Tackling obesity by manipulating gut flora

Antibiotics could one day be the standard treatment for regulating weight, suggests a new study in Nature Immunology that examines the interactions between diet, the bacteria in our gut, and our immune systems.

The 500 different types of bacteria present in our gut provide the enzymes necessary for the uptake of nutrients, synthesize certain vitamins and boost absorption of energy from food. Last century, farmers learned that by tweaking the microbial mix in their livestock with low-dose oral antibiotics, they could accelerate weight gain.

In the new study, researchers at the University of Chicago found they were able to manipulate some of the mechanisms that regulate weight gain. They focused on the relationship between the immune system, gut bacteria, digestion and obesity. Their findings show how weight gain requires not just caloric overload but also a delicate, adjustable - and transmissible - interplay between intestinal microbes and the immune response.

"Diet-induced obesity depends not just on calories ingested but also on the host's microbiome," said the study's senior author Yang-Xin Fu, professor of pathology at the University of Chicago Medical Center. "For most people, host digestion is not completely efficient, but changes in the gut flora can raise or lower digestive efficiency."

In one experiment, the researchers compared normal mice with mice that have a genetic defect that renders them unable to produce lymphotoxin, a molecule that helps to regulate interactions between the immune system and bacteria in the bowel. On a standard diet, both groups of mice maintained a steady weight. But after nine weeks on a high-fat diet, the normal mice increased their weight by one-third, most of it fat. Mice lacking lymphotoxin ate just as much, but did not gain weight....

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