Vagal stimulation exaggerates the inhibitory ghrelin response to oral fat in humans.

Ghrelin, the growth hormone secretagogue receptor ligand, is a key regulator of adiposity and food intake. However, the regulation of ghrelin in response to dietary fat intake remains largely unclear. Furthermore, cephalic elevation of ghrelin may influence fat absorption and postprandial lipaemia. Therefore, the aim of this study was to examine the effect of fat ingestion and vagal stimulation on the regulation of plasma ghrelin. Vagal stimulation was achieved by modified sham feeding (MSF). Eight healthy subjects (four male/four female) consumed a 50 g fat load on two separate occasions. On one occasion, the fat load was preceded by the MSF of a meal for 1 h. Blood, appetite and breath were analysed for 5 h postprandially.A 25% (S.E.M. 3.4) suppression in ghrelin concentration was observed after fat ingestion (P<0.001), without an increase in glucose or insulin. MSF in addition to oral fat enhanced ghrelin suppression further, as well as elevating plasma triacylglycerol (P<0.001) and reducing appetite (P<0.001). The fasting ghrelin concentration was inversely correlated with gastric half-emptying time (P=0.036). We conclude that ghrelin release may be influenced directly by both vagal stimulation and oral fat ingestion.