Gastric ghrelin in the regulation of appetite and metabolism

Abstract

Since its isolation 11 years ago, several groups have focused on elucidating the physiological actions of ghrelin. After its fi rst action was described, namely, the regulation of GH secretion, ghrelin has been found to play additional roles in the regulation of energy balance. In addition to the initial measures of circulating ghrelin levels, the possibility of studying direct secretion of ghrelin from the stomach eliminating interferences with other organs uncovered an autonomous gastric mechanism regulating its own ghrelin secretion in order to adapt the organism to the different energetic requirement in each stage of life. This mechanism is sensitive to age-related changes, different hormonal factors, variations in nutritional status, and composition of the diet. Thus, ghrelin secreted from the stomach can contribute to the maintenance of energy homeostasis at different levels: at central level in order to regulate food intake, on adipose tissue, liver and muscle in order to affect adiposity and glucose metabolism, and fi nally it can act in a paracrine fashion in the stomach to interact with other gastrointestinal hormones regulating gastric emptying, motility, and fi nally energy balance.