The vagus nerve and the inflammatory reflex—linking immunity and metabolism

Vagus-nerve signalling regulates immune activation and metabolic homeostasis. Dysregulation of metabolism and immune function in obesity results in chronic inflammation associated with insulin resistance and type 2 diabetes mellitus. In this Review, exploiting the vagus-nerve-mediated inflammatory reflex in the treatment of obesity-related disorders is discussed. The vagus nerve has an important role in regulation of metabolic homeostasis, and efferent vagus nerve-mediated cholinergic signalling controls immune function and proinflammatory responses via the inflammatory reflex. Dysregulation of metabolism and immune function in obesity are associated with chronic inflammation, a critical step in the pathogenesis of insulin resistance and type 2 diabetes mellitus. Cholinergic mechanisms within the inflammatory reflex have, in the past 2 years, been implicated in attenuating obesity-related inflammation and metabolic complications. This knowledge has led to the exploration of novel therapeutic approaches in the treatment of obesity-related disorders.