People with certain diseases, such as inflammatory bowel disease, those who eat food they are intolerant to or who ingest or consume chemical products (such as tobacco) can have alterations in their intestinal barrier. The intestinal barrier protects the body from the entry of external agents while, at the same time, allowing the absorption of nutrients. Any loss of barrier function, or increased intestinal permeability, allows external agents to come into contact with immune cells in the intestine. The inflammatory response triggered can lead to tissue damage in the form of ulcers and, in some cases, scarring and intestinal fistula formation.
In recent years, the functioning and particular role of the intestinal barrier and the group of microorganisms (microbiota) that live in contact with it have been the focus of many studies. Although the exact mechanism is not known in its entirety, intestinal permeability is believed to be linked to various autoimmune and metabolic diseases. Therefore, therapeutic treatments focused on improving the intestinal barrier and its microbiota are a promising field of research; although this is still in its preliminary stages.
Some studies have found that leaky gut syndrome contributes to the development of autoimmune diseases such as type 1 diabetes, multiple sclerosis, rheumatoid arthritis and celiac disease. In addition, intestinal microbiota plays a fundamental role in the regulation of immunity, since imbalances or dysbiosis are observed in the microorganisms that make up the intestinal microbiota of patients with autoimmune diseases.
The gastrointestinal lining of each person is approximately 32 m² in surface area, equivalent to a studio flat. The main function of the intestine is to process and digest food, then distribute the absorbed nutrients throughout the body. This is performed with the collaboration of millions of microorganisms (intestinal microbiota) that live inside it.
Although this relationship between the body and the microbiota (mainly bacteria, viruses and fungi) is highly beneficial, there is a barrier throughout the entire intestine. This is vital, and acts as the first line of defence in safeguarding against the entry of external agents and these microorganisms. Maintaining this barrier is essential, as it separates these microorganisms from immune cells that would otherwise trigger an inflammatory response if both came into contact.
In fact, the intestine is the organ that has the highest concentration of immune cells, such as macrophages, B cells (that produce antibodies) and many others. When the immune system detects the presence of danger (for example, an infectious agent) it responds by launching an inflammatory response aimed at eliminating this danger. If this inflammatory response is maintained over time, it can trigger other diseases.
The microbiota and intestinal barrier communicate with each other via a complex network of interactions that are normally in balance and contribute to the health of the human body. Alterations in the barrier, due to certain foods, physical conditions, chemical substances or changes in the composition and function of the intestinal microbiota can alter this balance and lead to disease. However, the exact mechanisms linking dysbiosis, intestinal permeability and autoimmune diseases have still to be fully elucidated.
Information documented by:
Dr Azucena Salas, group leader of the Inflammatory Bowel Disease Unit at Clínic-IDIBAPS and a member of CIBEREHD.
