How your mental state affects your gut health

The circuit between the brain and the gut influences the gut microbiome and modulates the immune system.

A study has uncovered an important brain-gut connection linking psychological state and changes in the gut microbiome, with significant implications for immune function and stress-related health. This study revealed how stress-sensitive brain circuits influence the composition of gut bacteria through the Brunner's glands in the small intestine. This sheds light on the complex mechanisms by which mental states influence physical health and suggests new possibilities for therapeutic intervention in conditions such as inflammatory bowel disease.

The brain and gut are constantly communicating, and this two-way communication between the brain and gut is critical to many aspects of health. For example, it is well established that psychological stress reduces the number of beneficial bacteria in the gut, thereby impairing immunity. However, the exact mechanism remains unclear so far.

A new study conducted by researchers at the Icahn School of Medicine at Mount Sinai in New York and the Max Planck Institute for Biological Cybernetics in Tübingen, Germany has identified a circuit that connects the brain to certain intestinal glands. These organs, called Brunner's glands, are located in the upper part of the small intestine and secrete the protein mucin, the main component of mucus that lines the intestinal wall and serves as a substrate for the growth of beneficial intestinal bacteria. As the research team found, removing Brunner's glands from mice reduced the number of bacteria. lactic acid bacteriaa genus of bacteria that is abundant in the small intestines of many animals, including humans. Result: Decrease lactic acid bacteriamice were more likely to die from intestinal infections and showed various signs of systemic inflammation.

Direct connection from the amygdala to the gut

The researchers also showed that the brain uses the vagus nerve as a communication pathway to control the activity of the Brunner gland. This nerve is a major part of the parasympathetic nervous system, which controls many organ systems throughout the body and plays an important role in rest and relaxation.

The researchers demonstrated that it connects the Brunner's gland with the amygdala, an area of ​​the brain responsible for emotional responses. Specifically, fear and anxiety reduce activity in the amygdala, which sends fewer signals to the vagus nerve. When this happens, the Brunner's glands release less mucus, which affects your immune system. In fact, exposing mice to chronic stress had the same effect on the composition and health of their microbiome as surgically removing their glands. “The Brunner gland is more important than previously thought,” said lead author Hao Zhang of the Icahn School of Medicine. “As a unique system controlled by the vagus nerve, they directly connect the brain to the gut microbiome.”

Potential treatments for inflammatory bowel disease

This result may explain why psychosocial stress increases the likelihood of infection. At the same time, it also provides new ways to counter this phenomenon. Stimulating the amygdala or vagus nerve in stressed mice was enough to normalize mucus secretion and completely reverse the effects of stress on the gut microbiome and immunity. Feeding mice probiotics also appears to be sufficient to reduce the negative effects of stress.

This study has broad implications for understanding the relationship between psychological states, gut health, and immunity. By providing a specific mechanism by which the brain controls the gut microbiome, it provides an explanation for the well-documented association between mental health disorders such as anxiety and depression and gastrointestinal and immune conditions. Masu. Researchers are now very interested in clinical applications of their findings. “We believe that the gland may be an important mediator of inflammatory bowel disease,” said lead author Ivan de Araujo of the Max Planck Institute for Biocybernetics. “Studying them further may provide new insights into disease mechanisms and potential treatments.”