Cambridge, Massachusetts – A study published November 24th in the journal Cell Metabolism reveals that E-coli bacteria from the gut sends signals to the brain to tell when its host is full or needs more food. Until now, it had been thought that our stomach was responsible for letting us know when we were hungry and when to stop eating, but investigators found that the microbes in our gut are the ones who influence our food ingestion.

For the study, researchers injected rats and mice with small doses of the bacterial proteins that are produced after feeding. They discovered that these bacterial proteins reduced food intake not only in those rats and mice that had been previously fed, but also in those who had not eaten. In the paper, they revealed that “full” bacterial proteins, ClpB, helped release peptide YY, which is a hormone associated with satiety, whereas “hungry” bacterial proteins did not stimulate that process.

The study revealed that E-coli bacteria from the gut sends signals to the brain to tell when its host is full or needs more food. Credit:

“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,” declared lead author Sergueï Fetissov of Rouen University and INSERM’s Nutrition, Gut & Brain Laboratory, in France.

It was also found that E-coli bacteria from the gut, known as E. coli K12, expand in numbers when exposed to nutrients, producing about a billion other bacteria. But 20 minutes after a meal, E-coli bacteria stop growing to start producing different types of proteins than they did before their feeding, which inhibits appetite. That is the same amount of time a human requires to start feeling full or tired after consuming nutrients. It remains unknown how other E-coli proteins and species of bacteria affect hunger and satiation.

Researchers explain that the reason gut microbes have such a behavior might be that, since they are not able to gather food by themselves, they need a way to communicate to their host when more nutrients are needed. This helps them survive and regulate their populations. Otherwise, microbes would disappear if their host environment became irregular.

Fetissov pointed out the importance of having a stable gut bacteria population in order to maintain the right appetite levels. Previous studies have shown that an altered gut bacteria can lead to an overproduction of Firmicutes, a bacteria type that breaks down fiber and absorbs dietary fat. As a consequence, gut microbes retain weight even when the host does not eat extra food.

High fat and sugar diets might also disrupt gut bacteria and, therefore, reduce the brain’s ability to detect when to stop eating. Moreover, it has been discovered in mice studies that high levels of fat interfere with gut microbe changes and that alteration can cause weight gain and depression.

Source: Medical News Today