Gut microbes could be the one responsible for telling people that dinner is done. Researchers of a new study have found chemical clues suggesting that when certain bacteria in the stomach already had enough to eat, they inform the brain it is time to push away the plate.

In animal experiments, researchers found evidence suggesting that certain microbes in the body have a way of letting the brain know they have had enough nutrients. The signals they send also appear to have the ability to turn on and off the hunger of their host.

For the new study published in Cell Metabolism, Serguei Fetissov, from Rouen University in France, and colleagues looked at the proteins produced by the E.coli bacteria, which are prevalent in the human gut, and noticed that about 20 minutes after feeding and multiplying in number, the bacteria switch from producing a set of proteins to another.

When Fetissov and colleagues injected small doses of the post-meal proteins into rodents, they noticed that they reduced their food intake regardless if they were previously fed or kept hungry. Further analysis likewise revealed that one protein stimulated the release of a hormone that play a role in satiety.

 "Our study shows that bacterial proteins from E. coli can be involved in the same molecular pathways that are used by the body to signal satiety, and now we need to know how an altered gut microbiome can affect this physiology," Fetissov said.

Once they are provided with nutrients, the bacteria were found to produce more or less a billion more of their kind. Interestingly, they stop growing after producing about one billion and then start producing new proteins that inhibit the effect of appetite.

The researchers said that E.coli could be hijacking a molecular pathway to produce signals that make animals feel full. By doing so, the bacteria also find a way to self-regulate their populations.

The findings of the study show the microbes have a crucial role in the physiology of appetite and may even help people who suffer from eating disorders.

"These data show that bacterial proteins produced after nutrient-induced E. coli growth may signal meal termination," the researchers wrote.

"Continuous exposure to E. coli proteins may influence long-term meal pattern."

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