Mutual Links between the Endocannabinoidome and the Gut Microbiome, with Special Reference to Companion Animals: A Nutritional Viewpoint †

SIMPLE SUMMARY: Dysbiosis, which is an imbalance of gut microbial composition and function, can be caused by several external as well as internal factors, contributing to the onset of human and animal disorders, not limited to the gastrointestinal tract. Accordingly, the mechanisms leading to disease development involve a crucial interaction between the gut microbiota, their metabolic products, and the host. The expanded endocannabinoid system, also known as the “endocannabinoidome”, includes endocannabinoids (e.g., anandamide) and endocannabinoid-like mediators (e.g., palmitoylethanolamide), their receptors and metabolic enzymes. Dysregulation of this newly recognized endogenous system is also involved in several diseases. It is becoming increasingly apparent that a link between the endocannabinoidome and the gut microbiome exists. Here, we review some of the latest discoveries related to the functional link between these two complex systems and the disorders emerging from the malfunctioning of such a mutual interaction: for example, idiopathic inflammation, chronic enteropathies, metabolic disease and certain neuroinflammatory disorders. It is expected that in the near future new nutritional tools will emerge based on the expanding knowledge in this cutting-edge field. ABSTRACT: There is growing evidence that perturbation of the gut microbiome, known as “dysbiosis”, is associated with the pathogenesis of human and veterinary diseases that are not restricted to the gastrointestinal tract. In this regard, recent studies have demonstrated that dysbiosis is linked to the pathogenesis of central neuroinflammatory disorders, supporting the existence of the so-called microbiome-gut-brain axis. The endocannabinoid system is a recently recognized lipid signaling system and termed endocannabinoidome monitoring a variety of body responses. Accumulating evidence demonstrates that a profound link exists between the gut microbiome and the endocannabinoidome, with mutual interactions controlling intestinal homeostasis, energy metabolism and neuroinflammatory responses during physiological conditions. In the present review, we summarize the latest data on the microbiome-endocannabinoidome mutual link in health and disease, focalizing the attention on gut dysbiosis and/or altered endocannabinoidome tone that may distort the bidirectional crosstalk between these two complex systems, thus leading to gastrointestinal and metabolic diseases (e.g., idiopathic inflammation, chronic enteropathies and obesity) as well as neuroinflammatory disorders (e.g., neuropathic pain and depression). We also briefly discuss the novel possible dietary interventions based not only on probiotics and/or prebiotics, but also, and most importantly, on endocannabinoid-like modulators (e.g., palmitoylethanolamide) for intestinal health and beyond.