Gut–organ axis: a microbial outreach and networking

Human gut microbiota (GM) includes a complex and dynamic population of microorganisms that are crucial for well‐being and survival of the organism. It has been reported as diverse and relatively stable with shared core microbiota, including Bacteroidetes and Firmicutes as the major dominants. They are the key regulators of body homeostasis, involving both intestinal and extra‐intestinal effects by influencing many physiological functions such as metabolism, maintenance of barrier homeostasis, inflammation and hematopoiesis. Any alteration in GM community structures not only trigger gut disorders but also influence other organs and cause associated diseases. In recent past, the GM has been defined as a ‘vital organ’ with its involvement with other organs; thus, establishing a link or a bi‐ or multidirectional communication axis between the organs via neural, endocrine, immune, humoral and metabolic pathways. Alterations in GM have been linked to several diseases known to humans; although the exact interaction mechanism between the gut and the organs is yet to be defined. In this review, the bidirectional relationship between the gut and the vital human organs was envisaged and discussed under several headings. Furthermore, several disease symptoms were also revisited to redefine the communication network between the gut microbes and the associated organs. Significance and Impact of the Study: Gut microbiota (GM) and its metabolites play a crucial role in maintaining the health of various vital organs. Literature review and evidences suggest that any alteration in GM composition and diversity not only triggers gut disorders but also influences other organs and cause‐associated diseases. In this review, we have attempted to provide the readers a broad overview of the complex role of GM and its vital connection with other human organs. Our effort will foster the development of personalized treatment that can be adopted and evolved by targeting the microbiome in a deliberately controlled manner.