Microbiota and gut neuropeptides: a dual action of antimicrobial activity and neuroimmune response

The gut microbiota is comprised of a vast variety of microbes that colonize the gastrointestinal tract and exert crucial roles for the host health. These microorganisms, partially via their breakdown of dietary components, are able to modulate immune response, mood, and behavior, establishing a chemical dialogue in the microbiota–gut–brain interphase. Changes in the gut microbiota composition and functionality are associated with multiple diseases, in which altered levels of gut-associated neuropeptides are also detected. Gut neuropeptides are strong neuroimmune modulators; they mediate the communication between the gut microbiota and the host (including gut–brain axis) and have also recently been found to exert antimicrobial properties. This highlights the importance of understanding the interplay between gut neuropeptides and microbiota and their implications on host health. Here, we will discuss how gut neuropeptides help to maintain a balanced microbiota and we will point at the missing gaps that need to be further investigated in order to elucidate whether these molecules are related to neuropsychiatric disorders, which are often associated with gut dysbiosis and altered gut neuropeptide levels.