Bugs, breathing and blood pressure: microbiota–gut–brain axis signalling in cardiorespiratory control in health and disease

There is clear evidence of physiological effects of the gut microbiota on whole‐body function in health and disease. Microbiota–gut–brain axis signalling is recognised as a key player in behavioural disorders such as depression and anxiety. Recent evidence suggests that the gut microbiota affects neurocontrol networks responsible for homeostatic functions that are essential for life. We consider the evidence suggesting the potential for the gut microbiota to shape cardiorespiratory homeostasis. In various animal models of disease, there is an association between cardiorespiratory morbidity and perturbed gut microbiota, with strong evidence in support of a role of the gut microbiota in the control of blood pressure. Interventions that target the gut microbiota or manipulate the gut–brain axis, such as short‐chain fatty acid supplementation, prevent hypertension in models of obstructive sleep apnoea. Emerging evidence points to a role for the microbiota–gut–brain axis in the control of breathing and ventilatory responsiveness, relevant to cardiorespiratory disease. There is also evidence for an association between the gut microbiota and disease severity in people with asthma and cystic fibrosis. There are many gaps in the knowledge base and an urgent need to better understand the mechanisms by which gut health and dysbiosis contribute to cardiorespiratory control. Nevertheless, there is a growing consensus that manipulation of the gut microbiota could prove an efficacious adjunctive strategy in the treatment of common cardiorespiratory diseases, which are the leading causes of morbidity and mortality. A schematic representation of the proposed pathways by which the gut microbiota influences cardiorespiratory control in health and disease. Red text highlights potential sources of altered microbiota–gut–brain communication due to a perturbed gut microbiota that may result in adverse cardiorespiratory control, i.e. altered afferent vagal activity, sympathetic nervous system hyperactivity, modulated short‐chain fatty acid (SCFA) signalling and increased inflammation. HPA, hypothalamic–pituitary–adrenal axis; NA, noradrenaline; SNS, sympathetic nervous system. Images were obtained from Smart Servier Medical Art, to create a new composite figure, and are used under the terms of the Creative Commons Attribution 3.0 Licence (creative.commons.org).