The Mind-Gut Wiring How Emotional Signals From Your Brain Influences Your Behavior, Relationship With Food, and Your Well-being

By Jim Colajuta

For generations, we have been taught that bacteria are pathogens that cause illness. The shocking truth is that your gut contains more bacterial cells than the rest of your body. Even more incredible, research reveals that these so-called "gut germs" keep us healthy rather than causing illness. At any given time, numerous strains of bacteria live in the human gut, and the gut, like a rainforest or a barrier reef, is a complex habitat. The gut microbiome refers to this bacterial ecosystem in the intestine.

Excess and deficiency of nutrients significantly impact gut microbial communities in rodents and humans, acting directly on the microbiota or indirectly via host physiology. Furthermore, the effects of diet on the microbiome in determining health or disease can vary significantly depending on the individual's age and environment.

• Language: English
• Publisher: vincenzo nappi
• Release date: Nov 1, 2022
• ISBN: 9798215108116

Book preview

The mind-gut connection

the mind-gut connection

Chapter 1

Introduction

THE POPULAR ADAGE follow your gut instinct has a neurological basis, namely the gut-brain axis. The interplay of the brain and the stomach in health and sickness has been proposed for ages. The observations aided in understanding the connection between the two organs, which are topographically separated. Patients suffering from gastrointestinal disorders (e.g., irritable bowel syndrome (IBS) and inflammatory bowel disease (IBD)) frequently suffer from mental illnesses such as anxiety and depression. A complicated bidirectional communication system is in operation (the gut-brain axis). The anatomy and physiology of these two organs differ tremendously. The stomach, small (duodenum, jejunum, ileum), and big (cecum, colon, rectum) intestines comprise the human gut.

The small and large gut walls are made up of functionally distinct layers. The serosa and musculature comprise the outer layer (with taenia coli in the colon). The submucosa and muscularis mucosae are located in the intermediate layer. The laminar propria and columnar epithelium make up the inner layer. The luminal surface is lined by this basic intestinal epithelium. The surface of the small intestine is formed into villi (finger-like projections) and crypts.

In contrast, villi are lacking in the large intestine, which contributes to the colon's smaller surface area than the small intestine. Intestinal stem cells sit near the bottom of the epithelial crypts and give rise to new epithelial (progenitor) cells. As a result, the lining of the intestine is constantly regenerated. In the small and large intestines, enterocytes and colonocytes are the primary intestinal epithelial cell types. Their primary role is nutrient and water absorption. Paneth cells, which live towards the base of the crypts and release lysozymes and anti-microbial peptides, have been proven to be critical for intestinal stem cells because they are engaged in the provision of the microenvironmental niche in the base of the crypts. Goblet cells secrete mucus and are more prevalent in the large intestine than in the small intestine. Although enteroendocrine cells account for less than 1% of all intestinal epithelial cells, they play a significant role in the endocrine system because they release gastrointestinal hormones. The microfold or M cells must be mentioned in terms of immunity. They are linked to lymphoid tissue in the intestines and lymphoid tissue in the mucosa. M cells are in charge of absorbing and transporting antigens found in luminal material to lymphoid organs. Tight junctions connect the apical ends of epithelial cells and control paracellular transport via a semipermeable epithelium. A coordinated interplay between the intestinal layers must carry out the intestine's physiologic functions. The digestive system performs various tasks, including but not limited to digesting, secretion, absorption, mixing, peristalsis, and defense.

The brain and the spinal cord constitute the central nervous system. The brain tissue comprises three compartments: neural cells (e.g., neurons, glial cells), the circulatory system, and the interstitial system. The latter two include the brain microenvironment, which provides a living environment for neural cells and has been shown to play an active role in brain function. Axons, dendrites, and synapses connect neurons, allowing them to process and send information over long distances. Despite their major significance in the brain, neurons are outnumbered by glial cells. Glial cells in the brain (astrocytes, oligodendrocytes, and microglia) perform various activities, including pathogen protection and neuronal metabolism support. To achieve that goal, they are constantly communicating with neurons. Because the brain is so important to our health, homeostasis must be adequately maintained. As a result, the flow of chemicals and ions between the blood and brain is strictly controlled by a single barrier, the blood-brain barrier (BBB). The transport of big molecules via an intact BBB is strongly constrained, which is both a blessing and a curse for therapeutic activity. A properly functioning BBB is essential throughout life because abnormalities in the BBB make the brain vulnerable to harm and have been linked to various neurological disorders.

Intrinsic (enteric nervous system) and extrinsic sympathetic, parasympathetic (pelvic nerves and vagus nerves), and sensory (spinal and vagal pathways) neurons innervate the gut. As a result, the central nervous system regulates gastrointestinal function while signaling neural impulses from the gut to the brain. The autonomic nerve system (ANS) and the hypothalamic-pituitary-adrenal (HPA) axis are two pathways that connect the brain to the gut. The ANS and HPA axis has been implicated in emotional affects on the gut, such as changes in gut motility and inflammation when under stress. In the gastrointestinal tract, sympathetic innervation primarily inhibits and slows intestinal transit and secretion, as well as modulates mucosal immunity. Despite their modest size, enteroendocrine cells are key mediators in the gut-brain axis because their output is involved in digestive activities and brain communication. Histamine and serotonin production from enterochromaffin cells is influenced by parasympathetic innervation, among other things. As a result, many bidirectional communication networks between the gut and the brain allow for flexible communication and interaction in the gut-brain axis. Signals from the gut can be triggered by various stimuli, including but not limited to hunger/satiety stimuli, mechanical and chemical stimuli, and inflammation. The ghrelin-dopamine (hunger and food reward) and cytokine-sickness (inflammation) responses are two examples of gut-brain transmission. Disturbances in gut-brain communication can be seen in symptoms or diseases like nausea and vomiting triggered by drugs or toxins, as well as anxiety, depression, and pain in chronic gastrointestinal disorders.

The microbiota-gut-brain axis

TRILLIONS OF MICROORGANISMS inhabit the human body. These bacteria dwell in unique bodily environments such as the skin, vagina, and gut. The microbial composition of various ecosystems changes greatly according to the diverse niches. The digestive system is the most populated organ, with 101 to 1012 microorganisms (growing from the stomach to the colon). Microbiota comprises archaea, bacteria, eukaryotes (e.g., fungi), and viruses. Due to established cultivation and sequencing methods, research has mainly focused on the role of the bacteria in this system. the microbiota is involved in many diseases. The spectrum of these diseases includes mental illnesses (depression, anxiety), neurodevelopmental disorders (autism), inflammatory conditions (allergies), and gastrointestinal disorders (IBD,