Studies have shown that the intestinal flora plays an important role in the construction of the intestinal barrier, mainly including the following aspects.
(1) Forming a biofilm barrier
The normal intestinal physiological flora can adhere to the intestinal mucosa to form a biofilm barrier. The intestinal biofilm barrier can form a steric hindrance, preventing harmful bacteria from contacting the intestinal mucosa. At the same time, some probiotics can also produce antibacterial substances such as bacteriocin and hydrogen peroxide. In addition, some intestinal bacteria can also metabolize to produce short-chain fatty acids, reduce the pH of the intestinal tract, and inhibit the growth and reproduction of harmful bacteria. Therefore, the intestinal flora is involved in the construction of the first intestinal barrier.
(2) Promote the formation of the mucus barrier
The mucus barrier of the intestine is mainly composed of mucin and immunoglobulin A secreted by intestinal goblet cells and epithelial cells. Mucins bind to gut bacteria, preventing harmful bacteria from binding to the intestinal epithelium. Immunoglobulin A has antibody activity against certain viruses, bacteria and general antigens. It is an important barrier of the intestinal mucosa and the first line of defense to prevent pathogens from invading the body. Studies have found that normal intestinal flora can stimulate intestinal epithelial cells to secrete mucin and immunoglobulin A, and promote the formation of the mucus barrier.
(3) Affect the formation of intestinal epithelial cell layer
Intestinal epithelial cells differentiate from pluripotent stem cells in crypts. Studies have found that the normal flora in the gut can affect the differentiation of intestinal epithelial cells. For example, Clostridium butyricum and its metabolites can promote intestinal epithelial cell proliferation. At the same time, there are tight junctions between intestinal epithelial cells, which can effectively prevent the invasion of intestinal harmful substances. The gut microbiota can influence the expression of tight junction proteins, thereby affecting the integrity of the intestinal barrier.
(4) Affects intestinal immune barrier function
The intestinal immune barrier is composed of intestinal lymphoid tissue and intestinal secretory immunoglobulins. The immune barrier can stimulate the secretion of intestinal mucus and accelerate the flow of the mucus layer, thereby preventing bacterial adhesion and colonization. Studies have found that the presence of normal intestinal flora is the key to the development of the intestinal lymphatic system. After the intestinal flora is killed with antibiotics, the intestinal lymph cannot develop normally and become weak and the immunity is weakened! Probiotics such as Clostridium butyricum can activate the immune system. The expression of cells and immunoglobulins plays an important role in improving the immune barrier function of the intestinal mucosa.