The metabolic role of vagal afferent innervation

The regulation of energy and glucose balance contributes to whole-body metabolic homeostasis, and such metabolic regulation is disrupted in obesity and diabetes. Metabolic homeostasis is orchestrated partly in response to nutrient and vagal-dependent gut-initiated functions. Specifically, the sensory and motor fibres of the vagus nerve transmit intestinal signals to the central nervous system and exert biological and physiological responses. In the past decade, the understanding of the regulation of vagal afferent signals and of the associated metabolic effect on whole-body energy and glucose balance has progressed. This Review highlights the contributions made to the understanding of the vagal afferent system and examines the integrative role of the vagal afferent in gastrointestinal regulation of appetite and glucose homeostasis. Investigating the integrative and metabolic role of vagal afferent signalling represents a potential strategy to discover novel therapeutic targets to restore energy and glucose balance in diabetes and obesity. Metabolic homeostasis is orchestrated partly in response to nutrient-dependent vagal afferent signals transmitted from the gut to the central nervous system. This Review highlights our understanding of the vagal afferent system and its role in regulation of appetite and glucose homeostasis. Key points Vagal afferent nerve terminals innervate layers of the gastrointestinal wall to sense nutrient-related hormonal and/or mechanical signals and trigger neuronal transmission to the central nervous system to affect metabolic homeostasis. Nutrient-dependent hormonal and mechanical stimulation in the stomach and the intestine regulate feeding through the vagal afferent network. Nutrient-dependent hormonal stimulation in the intestine regulates glucose homeostasis through the vagal afferent network. Manipulating gut nutrient-dependent and vagal-dependent afferent firing represents a potential novel therapeutic strategy for obesity and diabetes.