The Gut-Organ Axis within the Human Body: Gut Dysbiosis and the Role of Prebiotics

Abstract

The human gut microbiota (GM) is a complex microbial ecosystem that colonises the gastrointestinal tract (GIT) and is comprised of bacteria, viruses, fungi, and protozoa. The GM has a symbiotic relationship with its host that is fundamental for body homeostasis. The GM is not limited to the scope of the GIT, but there are bidirectional interactions between the GM and other organs, highlighting the concept of the "gut-organ axis". Any deviation from the normal composition of the GM, termed "microbial dysbiosis", is implicated in the pathogenesis of various diseases. Only a few studies have demonstrated a relationship between GM modifications and disease phenotypes, and it is still unknown whether an altered GM contributes to a disease or simply reflects its status. Restoration of the GM with probiotics and prebiotics has been postulated, but evidence for the effects of prebiotics is limited. Prebiotics are substrates that are "selectively utilized by host microorganisms, conferring a health benefit". This study highlights the bidirectional relationship between the gut and vital human organs and demonstrates the relationship between GM dysbiosis and the emergence of certain representative diseases. Finally, this article focuses on the potential of prebiotics as a target therapy to manipulate the GM and presents the gaps in the literature and research.

Keywords: gut microbiota dysbiosis; gut–organ axis; prebiotics.

Figure 1

Schematic diagram depicting the influence of GM dysbiosis on the gut–organ axis. GM dysbiosis leads to the degradation of mucin, disrupts the gut’s protective barrier, increases its permeability, and enables pathogenic microorganisms, along with their by-products and endotoxins, to infiltrate. This invasion results in the activation of immune cells and triggers systemic inflammation through the peripheral circulation. The impact of GM dysbiosis extends beyond the gastrointestinal tract. Recent research indicates two-way interactions between the GM and various organs, emphasizing the idea of a “gut–organ axis”. This communication is facilitated through a range of signalling pathways and direct interactions between the host and the GM. Arrows indicate a bidirectional relationship between the gut and each organ. Parts of the figure were drawn using pictures from Servier Medical Art. Servier Medical Art by Servier is licensed under a Creative Commons Attribution 3.0 Unported License (https://creativecommons.org/licenses/by/3.0/ accessed on 25 August 2023).