New Research On Appetite-Suppressing Bacteria Could Help Fight Obesity

03/24/2015 08:06am ET | Updated March 24, 2015
Escherichia coli bacteria, computer artwork. E. coli bacteria are a normal part of the intestinal flora in humans and other animals, where they aid digestion. However, some strains, for instance enterohaemorrhagic E. coli (EHEC), can produce a toxin (Shiga toxin) that leads to severe illness or even death. Normal strains can also produce infections in weakened or immunosuppressed people.

Scientists already know that different kinds of gut bacteria -- those microbes inside our GI tracts that don't share our DNA yet are oh-so-integral to our health -- play crucial roles in breaking down our food, producing some vitamins and keeping harmful microbes at bay. For people struggling with excess weight and obesity, there is even more exciting emerging research on how gut bacteria may play a role in helping maintain our weight.

And in that same vein, one researcher may have found a way to engineer a gut bacterium that helps suppress hunger pangs.

Sean Davies of Vanderbilt University presented some tantalizing research Mar. 22 at the National Meeting & Exposition of the American Chemical Society conference in Denver, Colorado. Davies explained that he was able to engineer bacteria that releases a lipid responsible for feelings of satiety, or fullness. The programmed bacteria, which he tested in obese mice, could one day point to a microbial, low-maintenance strategy for helping people lose weight or maintain a healthy weight, he explained by email in advance of the presentation.

Davies first fed his mice a high-fat diet for three months, causing them to become obese. Then he administered the engineered bacteria, which secreted chemicals called N-acyl-phosphatidylethanolamines (NAPEs) that are then converted into lipids that suppressed hunger in mice. After six weeks on the treatment, the mice who were given the NAPE-secreting bacteria stopped gaining weight, but the two control groups (mice who got no bacteria and mice who got bacteria that didn’t secrete NAPE) continued to pack on the ounces.

“This shows that our strategy is not necessarily limited to prevention of obesity, but might be useful even to treat obesity,” said Davies.

Another important detail about Davies’ experiment is that he also created a safeguard for certain genetically-engineered mice that lacked the enzymes to convert NAPE into the hunger-suppressing lipids. When he added that missing enzyme into the bacteria, the enzyme-deficient mice were able to continue converting their NAPEs into the hunger-suppressesors. Why is this significant? Because it’s suspected that some obese people might be converting enough NAPE in their intestines, which may be why they overeat in the first place.

“Our newer version of this engineered bacteria should in theory be able to help them,” said Davies.

This work builds on research Davies published in 2014, where he showed that NAPE-producing bacteria protected mice from gaining weight, despite a high-fat diet or a genetic propensity to obesity. These benefits persisted for four weeks after the special water was taken away from the mice.

“At this moment, there is not a way for people to use this [experiment], but that is certainly our long term goal,” concluded Davies. “Our next steps are to better understand the precise mechanisms by which our bacteria reduce food intake and inhibit obesity and to further engineer them so that they are ready for human trials, [but] that may take quite awhile.”

At least one reason it’s going to take a while is that Davies still hasn’t figured out how to prevent accidental transference of the engineered bacteria from person to person via fecal exposure -- something that could unintentionally cause weight loss in a person who doesn’t need to lose weight.

“…you could imagine that there might be some individuals, say the very young or old or those with specific diseases, who could be harmed by being exposed to an appetite-suppressing bacteria,” said Davies in a statement. "So, we are working on genetically modifying the bacteria to significantly reduce its ability to be transmitted."

In addition to Davies' work on the issue, a 2013 study showed that being exposed to gut bacteria from either an overweight or slim person made mice either gain or lose weight.

But beyond weight loss therapy, gut bacteria’s potential therapeutic applications are being explored in anxiety, autoimmune diseases, autism, diabetes and schizophrenia.

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