Introduction
Chronic inflammation which is observed in inflammatory bowel diseases (IBD), Overweight/ obesity, cardiovascular and neurodegenerative diseases, type I diabetes (T1D), depression /anxiety have recently become a real challenge. One of the factors potentially linking these diseases is the increased permeability of the intestinal barrier. The intestinal barrier consists of the mucus layer, intestinal microbiota, intestinal epithelial cells (IECs) and lamina propria. The intestinal barrier is characterized by selective permeability, which means that ions, water, and low-molecular substances can freely pass through it, while it is impermeable to toxins, pathogens, macromolecules, and food allergens. When these substances leave the intestine, the immune system is over-activated, resulting in the induction of inflammation, which, if it persists for a long time, leads to serious health consequences. Therefore, maintaining the integrity of the intestinal barrier is one of the most important aspects of ensuring health. The paracellular space between enterocytes is sealed by tight junctions (TJs), adherence junctions (AJs) and desmosomes. The role of the microbiota in preserving the intestinal barrier largely depends on the fact that commensal microbes adhere to the intestinal mucosa and constitute an additional protective layer. Modulation of microbiota composition by biotics appears to be an interesting concept to enhance the gut barrier, to treat or even prevent the onset or aggravation of chronic diseases.
Summary and Future Perspectives
Increasing intestinal permeability causes chronic inflammation, which is one of the etiological factors of inflammatory diseases, which presently constitute a global challenge. The so-called “leaky gut” is associated with diseases such as IBS, CD, celiac disease, chronic liver disease, diabetes, food allergies and sensitivities, polycystic ovary syndrome, depression and anxiety. The knowledge of the activity of various biotics is becoming extented. An increasing number of scientific reports indicate that the microbiota and general homeostasis in the intestinal environment are factors that guarantee health.
The modern lifestyle and model of nutrition lead rather to dysbiosis, which is one of the reasons for intestinal permeability. The multiplicity and diversity of diseases associated with the increase in intestinal permeability indicate the need for strategies to restore gut balance and explain the mechanisms underlying the maintenance of the intestinal barrier function. In this context, the use of biotics seems to be promising. In both in vitro and in vivo experimental models, probiotics, prebiotics, synbiotics and postbiotics were shown to enhance the intestinal barrier. Most studies indicate the regulation of gene expression of TJ proteins as a potential mechanism of biotics action on the gut barrier. The positive effect of biotics was repeatedly reported by in vitro and in vivo models. However, it was rarely confirmed in human trials. Another problem underlined in this review is that many clinical trials were conducted with the subjects without ongoing leaky gut; thus, improvement cannot be expected. Therefore, there is a need for well-designed clinical trials clearly demonstrating the role of biotics in restoring the integrity of the intestinal barrier. The available clinical trials on biotics have little focus on gut barrier function but rather on systemic effects.
Therefore, further clinical trials are needed to show the relationship between biotics and gut barrier function in human subjects. Moreover, there is a need to explore whether alternative biotics, such as postbiotics, can affect the gut barrier. It is also necessary to understand the mechanisms that are regulated by various biotics for restoring intestinal integrity, which will allow for the development of therapies eliminating the causes of diseases associated with the leaky gut rather than just symptomatic treatment.
prepared by: Nazila Kassaian
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