Stress can make people sick , and bacteria in the intestine could, according to a study 1 with mice. Research suggests that a stressed brain switches off determined glands directly in the intestine, which is on the Dearbacteria and the breeding immune system of the body has an impact.

The study is a technical masterpiece, according to the neurobiologist John Cryan from University College Cork in Ireland, who examined the study. Most of the work for the connection between the intestine and the brain focused on How bacteria influence the brain , so Cryan welcomes research on how psychological states 'top-down' can take control over bacteria. "It's a really cool part of the puzzle," said Cryan. Research was published on August 8 in Cell

intestinal brain exchange

researchers have long known that the intestine and the brain 'communicate'. Under stress, the brain stimulates the distribution of hormones, the intestinal states like Inflammatory bowel diseases can trigger. Certain bacteria in the intestine can release chemical signals that influence the brain and behavior.

The neural communication paths are less understood. In order to find out more, the neurobiologist Ivan de Araujo from the Max Planck Institute for Biological Cybernetics in Tübingen, Germany, and his colleagues called small organs called Brunner-Drands, which can be found in the walls of the small intestine. Little is known about these glands, except that they produce mucus and contain numerous neurons.

de Araujo's team found that the removal of the Brunner glands of mice made the animals more susceptible to infections. It also increased markers for inflammation, an electricity of immune protection fabrics and cells that can damage tissue . The team observed a similar effect in humans: people who were removed from the part of the intestine that contains Brunner glands had higher values ​​of white blood cells-a marker for inflammation-as people who were removed from other areas.

bacteria in the household

A more precise analysis showed that the removal of the Brunner glands of mice Bacteria of the genus lactobacillus eliminated that live in the small intestine. In a healthy gastrointestinal tract, lactobacilli stimulate the production of proteins that act like mortar between the cells of the intestine and hold most of the intestinal contents inside, while certain nutrients enter the bloodstream. But if lactobacilli have disappeared, the intestine 'leaky' and "things that should not get into the bloodstream will do so," says de Araujo. The immune system attacks this foreign molecules, which causes the inflammation and illness in mice without Brunner glands.

Then the researchers examined the neurons of the glands. They found that the neurons are connected to fibers in the vagus nerve, a communication path between the intestine and brain. These fibers lead directly to the brain amygdalacre, which is involved in emotions and stress reactions.

mice with intact brunner glands under chronic stress had the same effect as the removal of the glands: the lactobacillus values ​​fell and the inflammation increased. This indicated that the stress switched off the Brunner glands.

communication channels

Assya Rolls, Neuroimmunologist at Technion-Israel Institute of Technology in Haifa, is impressed by the direct connection between the brain, Brunner glands, bacteria and immune system. "The specificity of the connection is amazing," she says. However, she warns that the paths in mice are not necessarily identical to those in humans.

"This paper is pretty inspiring," says Christoph Thaiss, microbiologist and neurobiologist at the University of Pennsylvania in Philadelphia. Understanding the specific paths that combine the brain and intestine could help researchers examine questions, such as why some people are more stress -resistant than others.

de Araujo says that the study could have an impact on the treatment of stress -related disorders such as inflammatory bowel diseases. His group now examines whether chronic stress affects this path in infants that receive their lactobacillus on breast milk. "We are enthusiastic about the idea that these glands are important for normal development and immune function in early life," says de Araujo.