<Shin Chan-young's brain science that brings thoughts>

When your stomach is comfortable, your mind is also comfortable... ‘Gut function-brain’ interaction hypotheses presented one after another

2020-06-24

Intestinal microbes, influence on brain development, presentation of the possibility of treating brain diseases

Thousands of related research results have been published, and the proof is yet to be... attention to simplification

When we are freed from excessive stress and our mind is not troubled and peaceful, we often say that we feel comfortable. The meaning of being comfortable literally means that digestion is good and the function and condition of the intestines are good, and at the same time it refers to a state in which you can stretch your legs out and sleep well without worry or anxiety. Mental health and intestinal health have long been intertwined. You seem to know from experience that it exists. When I was young, my mother always tried to take care of the savory taste of chewing pills even though I didn't have a mother.

The hypothesis that the gut and the brain are connected in a direct or indirect way and can influence each other is the Gut-Brain axis hypothesis. In other words, the brain influences the function of the intestines, and in turn, the function of the intestines can affect the function of the brain. The enteric nervous system originally has an automatic function of digesting food and facilitating excretion by autonomously activating the stomach and intestines when food comes in. Although it does not play a very direct and powerful role in the function of the intestine, the possibility that the function of the intestine affects various nervous system functions and diseases has recently been raised.

At this time, the intestinal microbes play a key role, and more than 100 trillion microorganisms live in the intestines, including yeast, bacteria, fungi, viruses, and protozoa, which are approximately 10 times the number of all cells in our body. Research results are continuously being published that they not only help digest food and maintain intestinal health, but also have an important effect on the dynamics of the drugs we take, and even affect brain development and emotional state. Fluctuations in the gut microbiome caused by excessive antibiotic treatment cause emotional disorders such as anxiety disorders and depression, and degenerative brain diseases such as Alzheimer's. It has also been reported that it may cause Injecting the gut microbiota of people with emotional or developmental disabilities into germ-free mice causes the mice to show abnormal behavior, and research results have reported that the symptoms can be treated by injecting the gut microbiota of normal people into laboratory mice exhibiting behavioral abnormalities. Research in this field is of great interest to both the general public and scholars. Even recent studies suggest that it can be developed as a treatment for brain diseases by claiming that even when only one or two types of intestinal microbes are injected, there is a symptomatic treatment effect. For example, it has been reported that when a specific lactic acid bacterium called Lactobacillus (L.) reuteri was injected into autistic mice, symptoms improved and synaptic plasticity in the brain region called the ventral tegmental area was restored. It has been suggested that these effects are due to the normalization of vagus nerve activity and oxytocin signaling in the brain, which has attracted extraordinary attention.

More than 3,000 research papers in this field have already been published, raising expectations that intestinal microbes are the ultimate solution to various brain diseases, but excessive simplification and exaggeration should be avoided. As a result of a comprehensive analysis of various research papers on the relationship between brain health and gut microbes, the team led by Professor Richard Hansen in the UK and the team led by Professor Jens Walter at the University of Alberta, Canada, etc. It is also pointed out that it is in a state where there is no clear separation and proof of whether it is a phenomenon that occurs concurrently with a disease or just a disease, and that more rigorous and faithful research designs are needed to avoid erroneous research results. Even in this field, it seems that there is an attitude of trying to talk only one side of the story if someone says it is good.

These days I feel anxious, depressed, impatient, and sometimes angry. After having a pork belly lunch with close colleagues at a knight’s restaurant that I often went to, I felt like my digestion went well and my mind felt at ease when I received yogurt from the nice-looking owner as dessert. Even such a small margin is not an easy reality. I hope that a world that is comfortable and comfortable in the heart will come soon.

Professor Shin Chan-young, Konkuk University School of Medicine