Figure 1: Central and Peripheral Energy Regulation:

Important enteric sensory modalities detect nutrients and distention. This results in hormone secretion, including ghrelin, CCK, GLP-1, and PYY, and afferent autonomic signaling. Enteric-derived hormones act on autonomic nerve endings embedded in the lumen wall and result in signaling to the nucleus of the solitary tract in the brainstem via afferent vagal and splanchnic nerves. These hormones, along with leptin and adiponectin which are largely derived from adipose tissues in response to alterations in nutrient stores, may also enter the circulatory system and activate AGRP and POMC receptors at the arcuate nucleus. Both of these signaling modalities can result in anorexigenic and orexigenic signals to the periventricular nucleus and other brain regions, which subsequently communicate with other central nervous system domains that moderate feeding behaviors and physical activity. Gastric emptying, gastric accommodation, and other enteric secretory and motor functions are modified by the above hormones, intra-enteric neuronal signaling, and efferent autonomic signaling via efferent vagus nerve pathways, which reciprocally influence distention and nutrient signaling.