Feeding and Gastrointestinal Motility : Regulation by Ghrelin Gene Products(Symposium : Frontiers Research and Practice in Psychosomatic Medicine)

Abstract

Gastrointestinal (GI) hormones are well known to be important regulators not only in GI functions but also in feeding behavior. Ghrelin, a motilin-related family of regulatory peptide from the stomach, is the recent addition of this list, which has a charactelistic n-octanoylated serine at position 3. In addition to its ability to stimulate growth hormone (GH) secretion, ghrelin increases appetite and gastric motility/emptying and induces a positive energy balance leading to body weight gain. Ghrelin is a complementary, yet antagonistic, signal to leptin reflecting acute and chronic changes in energy balance, the effects of which are mediated by hypothalamic neuropeptide Y (NPY) and agouti-related peptide (AgRP). Ghrelin induces the fasted pattern of gastroduodenal motility (phase III or hunger contractions) , and the ghrelin-NPY axis is involved in the physiological occurrence of the interdigestive phase III contractions in rodents. On the other hand, desacyl form of ghrelin that accounts for approximately 90% of total circulating ghrelin, decreases food intake and gastric emptying, and disrupts the fasted pattern of gastric motility. Obestatin, a recently identified ghrelin gene product, may also act inhibitory in appetite and GI motility regulation although much more controversial than ghrelin. The findings suggest that ghrelin gene products may differently regulate appetite and gastrointestinal motility through different endocrine/neural pathways along the gut-brain axis.