Medically reviewed by Onikepe Adegbola, MD, PhD
Scientists found that these neurons adapt to appetite and body temperature. These new findings were carried out at the Pasteur Institute and demonstrated that direct contact occurs between the gut microbiota and the brain.
(Microbiota: Microorganisms found at the specific site/location).
This extraordinary discovery and new findings could be used in research. “Decoding the Direct Dialogue between the Gut Microbiota and the Brain” will be published in the Science Journal. Data from these studies can help develop new treatments for metabolic disorders such as diabetes and obesity.
NOD2 and Muropeptides Mechanism
You can find Bacteria in large amounts in the animal’s gut. The by-products from gut microbiota circulate in the bloodstream. They regulate host physiological processes such as immunity, metabolism, and brain functions. Scientists from the Institute Pasteur investigated how bacteria in the gut directly control the activity of particular neurons in the brain.
To investigate the mechanism, a team of scientists specifically focused on the NOD2 (nucleotide oligomerization domain) receptor. NOD2 receptor is a part of immune cells. Since the receptor acts with the immune system, it recognizes the presence of muropeptides. Mostly, muropeptides are the building blocks of bacterial cell walls. They can serve as signaling molecules and also trigger adaptive responses.
NOD2 is a type of protein and particularly an intracellular pattern recognition receptor. This NOD2 protein complex regulates the activity of multiple genes. These proteins can regulate genes that control immune activities and other inflammatory responses.
Previous studies have found that NOD2 receptor variants are associated with digestive disorders, neurological disorders, and mood disorders.
Hypothalamic Neurons and NOD2 Receptor
The pre-existing data was not sufficient to demonstrate a direct relationship between neuronal activity in the brain and bacterial activity in the gut. To discover the direct relationship between gut microbiota and brain cells, a team of scientists at the Institute Pasteur were using brain imaging techniques in animal studies. These studies were conducted on a group of mice and experts were able to observe new findings.
The scientists observed that the NOD2 receptor is expressed by neurons in different regions of the brain, and in particular, in the hypothalamus, by using brain imaging techniques. The hypothalamus is responsible for many daily activities including eating, drinking, regulating body temperature, maintaining energy levels, and regulating stress levels.
Findings show that bacterial muropeptides from the gut suppress the hypothalamic neurons’ electrical activity. But if the NOD2 receptor is absent within the gut cells, these neurons are no longer suppressed by muropeptides, meaning the muropeptides can alter bodily functions such as loss of control over appetite or weight gain which can lead to serious disorders.
Hence in the absence of NOD2 receptors, the brain loses control of food intake and body temperature. Mice in the study gained weight and were more susceptible to type 2 diabetes, especially in older females.
Initially, the neurons and muropeptides relationship was thought to be associated with the immune system. But this extraordinary finding led to a discovery that shows bacterial fragments act directly on the hypothalamus, which is known to manage vital functions such as body temperature, reproduction, hunger, and thirst.
Researchers at the intersection between neurosciences, immunology, and microbiology may now pursue new interdisciplinary projects toward therapeutic solutions. These new findings will lead to new therapeutic research for neurodegenerative diseases such as diabetes and obesity.
Institut Pasteur. (2022, April 15). Decoding a direct dialog between the gut microbiota and the brain. ScienceDaily. Retrieved April 24, 2022 from www.sciencedaily.com/releases/2022/04/220415100551.htm