What is the intestinal mucosa and its role in health?

The article was professionally consulted with Specialist Doctor I Le Nguyen Hong Tram - Gastroenterologist - Department of Medical Examination & Internal Medicine - Vinmec Nha Trang International General Hospital.

The intestinal mucosa is considered an important barrier, where millions of bacteria and antigens come into contact with the immune system. Problems with this intestinal barrier can lead to a variety of digestive conditions, such as inflammatory bowel disease, celiac disease...

The human body has many mucosal epithelium, which form direct barriers between the external environment and the internal host. The digestive tract is one of the most obvious examples. This place plays an important role in the regulation of the immune system and for general health. The intestinal mucosa acts as a semi-permeable barrier, both absorbing nutrients and sensing immunity, while restricting the movement of antigens and harmful microorganisms. The interplay of structural components and molecular interactions in the intestinal mucosa help regulate this complex task, thereby maintaining intestinal integrity and immune homeostasis. The function of the intestinal barrier can be compromised by severe structural damage to the mucosa, or changes in the involved components.
Problems occurring in the intestinal lining have been linked to many diseases, including celiac disease, inflammatory bowel disease (IBD), colon carcinoma, chronic liver disease, type 1 diabetes, obesity . Intestinal mucosal dysfunction and antigenic failure to enter the intestinal epithelium can affect the immune systems of susceptible individuals, disrupting microbial balance, thereby initiating inflammatory mechanisms in the gut or more distant organ systems.

The intestinal mucosa is seen as a physical and immune defense barrier, including several factors that support function:
The outer mucus layer is in contact with the intestinal microbiota. Antibacterial proteins (AMP) and secretory immunoglobulin A (sIgA) molecules. Single cell layer with specialized epithelium. The inner lining, where adaptive immune cells reside (T cells, B cells, macrophages, and dendritic cells). The mucus layer is the first physical line of defense that foreign molecules encounter when reaching the intestinal lumen, helping to prevent bacteria from coming into direct contact with epithelial cells. The main building blocks of the mucus layer have a reticular, gel-like structure above the intestinal epithelium.
The small intestine has only one layer of mucus gel, while the colon has two layers:
An outer layer: Allows colonic bacteria to colonize for a long time. A dense inner layer free of bacteria. Immunomodulators (AMP and sIgA) are released in the mucus gel, assisting in the physical separation of the microbiota. The composition of the mucus layer can influence the microbiota in the gut, and the microbiome also determines the properties of the mucus gel.
Beneath the mucus layer, epithelial cells are considered to be the strongest determinants of the intestinal physical barrier. A group of pluripotent stem cells that give rise to five different cell types, including:
Absorbent enterocytes. Goblet cells. Endocrine cells. Paneth cells. Micro cells. Together these cells form a monopolar and continuous layer that separates the intestinal lumen from the lamina propria. Since cell membranes are impermeable, hydrophilic solutes in the absence of specific transporters are greatly limited. The intestinal mucosa is not considered a static structure, as they are highly dynamic and responsive to both internal and external stimuli (eg, cytokines, bacteria, dietary factors).

3.1. Diet Food is not only an important source of nutrients, but also plays a role in regulating various physiological functions in the gastrointestinal tract, including intestinal mucosal function. Flavonoids are an example of plant-based ingredients that have been shown to provide benefits for the epithelial barrier. Flavonoids are found in most vegetables, fruits, green and black tea, red wine, chocolate, and coffee. According to a study in mice, flavonoid-rich cranberry extract significantly increased the incidence of Akkermansia, a mucin-degrading bacteria that resides in the mucus layer of the intestines.
Recently, industrial food additives are widely used to improve the quality of foods, but are also associated with intestinal mucosal dysfunction and increased incidence of immunodeficiency diseases. Translate . For example carboxymethylcellulose and polysorbate-80 are the two most commonly used additives in the food industry. When consuming a lot of processed foods daily, they reduce the thickness of mucus, making bacteria more exposed to the epithelium,...
Diet high in fat and sugar (Western diet) also altered the microbiome composition in mice, reduced mucus layer thickness with fewer goblet cells, and increased levels of inflammatory markers.
Along with nutritional compounds, vitamins, minerals and trace elements from food are also associated with changes in the intestinal lining. More specifically, vitamin D, A and zinc deficiencies have been found to damage the epithelial barrier, increasing the risk of infection and inflammation.

3.2. Alcohol Studies have shown the effects of ethanol ingestion on the intestinal epithelial barrier. Specifically, ethanol and its metabolite acetaldehyde have been found to decrease intestinal mucosal function by directly damaging epithelial cells, disrupting osteocytes, and activating oxidative stress responses. The microbiome also mediates the action of alcohol because it is involved in the production of acetaldehyde. Chronic alcohol abuse can worsen digestive disorders.
3.3. Drugs Nonsteroidal anti-inflammatory drugs (NSAIDs) are known to damage the gastrointestinal tract, so doctors often prescribe them along with proton pump inhibitors (PPIs) to reduce the incidence of NSAID-induced gastroduodenal injury. cause. However, the combination of NSAIDs and PPIs did not prevent damage to the small and large intestine, possibly even exacerbating the effect of the drug on the intestinal mucosal barrier.
3.4. Smoking The impact of smoking on gut health is conflicting and has some unexplained problems, especially in ulcerative colitis. Overall, the potential risks of smoking to the intestinal lining certainly exist. Secondhand smoke can actually tighten the intestinal barrier, but this effect will be influenced by many factors, including genetics, disease-specific triggers, intestinal site, pattern of smoke exposure, as well as such as interactions with immune factors and microorganisms.
3.5. Stress Stress is a lifestyle factor that has been linked to the deterioration of the intestinal lining (through interactions between the gut and the brain). It is also a risk factor for the onset and reactivation of chronic digestive disorders. Most studies on the effects of stress on intestinal mucosal regulation have been performed in animals, with limited human data.
Recent studies have also focused on exercise-induced stress (a combination of physical and psychological stress). Specifically, athletes often experience abdominal pain due to the release of stress hormones during intense physical activity. However, the extent of the response may depend on the individual's stress level, genetics, and life experience.
In summary, the mucus layer and intestinal epithelial cells are key determinants of the intestinal mucosa and have a fundamental role in health. Western diets, heavy alcohol consumption, stress, and certain medications have detrimental effects on the role of the intestinal mucosa. Intestinal mucosal dysfunction may be associated with inflammatory bowel disease, celiac disease, and nonalcoholic fatty liver disease. The roles of the intestinal mucosa in many other extraintestinal disorders require further investigation.

References: Nature.com, Ncbi.nlm.nih.gov