The gastrointestinal microbiome – what do we know now and what will we learn next?

Abstract

As a result of technological advances in recent years, particularly the advent of a number of molecular tools in the research setting, a growing body of evidence has started to elucidate the importance of the gastrointestinal microbiome in a variety of interactions with the host. It is now thought to have a number of significant effects on a host's health, including aiding digestion, providing nutritional benefits to the host, immune regulation and defence against enteropathogens. It also has extra-intestinal roles including brain development, which in turn influence appetite and behaviour. Every individual harbours a unique microbiome that is also dynamic. Genetic and environmental factors including stress, diet and antibiotics can all have a significant impact on microbiome make-up, both during development and throughout life. The gastrointestinal microbiome has also been directly implicated in the pathogeneses of both gastrointestinal and systemic disease, particularly enteropathies and diseases such as obesity. There is also a growing interest in its role in communicating with and potentially influencing brain function, referred to as the ‘microbiota–gut–brain axis’. Manipulation of the microbiome has been associated with changes in behaviour, such as the onset of anxious behaviours in dogs, mice and humans. This has also been linked to neurodegenerative diseases such as Alzheimer's in humans. This article explores our current understanding of the gastrointestinal microbiome and its role in both health and disease, as well as the role that dysbiosis may play in disease states. It briefly considers ways in which we may be able to manipulate it therapeutically in companion animals. It also looks at some of the unanswered questions that remain, and considers the potential next steps for researchers.