Leaky Gut Syndrome – Intestinal Mucosal Permeability
The gastrointestinal tract represents the body's largest interface with the external environment. In adults, approximately one tonne of nutrients is transported across this “barrier wall” each year. At the same time, the intestinal mucosa acts as an effective barrier against the absorption of incompletely digested food components, bacterial endotoxins, inorganic pollutants, and heavy metals. A wide range of noxious agents can lead to a loss of this barrier function, which increases the risk of uncontrolled antigen influx into the lamina propria and eventually into the systemic circulation. This uncontrolled antigen influx not only triggers local but also systemic immune responses, which, if persistent, can contribute to the development of serious illnesses.
The cellular junctions of enterocytes only become a functioning barrier due to the low permeability of their tight junctions. However, the sealing function of these tight junctions is not as absolute as the name might suggest; rather, they also carry out specific transport tasks. Depending on the balance between paracellular and transcellular permeability, the epithelium may be described as “tight” or “leaky.”
Leaky Gut Syndrome: Causes and Consequences
Disruptive factors such as stress, medication, alcohol, nicotine, microorganisms (e.g. enteropathogenic E. coli), bacterial toxins (particularly Clostridium perfringens toxin), and proinflammatory cytokines can significantly impair the integrity of epithelial cells and tight junctions: the intestinal epithelium becomes permeable to allergens, toxins, and pathogens. The uncontrolled passage of harmful substances (noxae) from the intestinal lumen culminates in a severe disruption of the intestinal barrier – known as Leaky Gut Syndrome. This triggers immune cascades that lead to sensitisation (e.g. to food components) and increased antibody production, while the release of inflammatory mediators causes damage to epithelial structures. If the inflammation persists, a vicious cycle develops.
The parameters alpha-1-antitrypsin and zonulin in stool, as well as LPS in serum, are used to assess the function and condition of the intestinal mucosa. These parameters can provide evidence of the processes described above.
Consequences include:
- Intestinal inflammation
- Inadequate nutrient absorption
- Absorption of high-molecular antigens, which results in antibody formation
- Formation of circulating immune complexes
- Autoimmune cross-reactions with the body’s own tissues
- Generation of autoreactive T cells
The entry of bacteria and bacterial products into the bloodstream leads to increased immune activity and systemic inflammatory responses. Clinically, this can result in chronic infections, cardiovascular disorders, allergies, and autoimmune diseases.
