| Theme |
The Gastrointestinal Tract and Appetite Control : Essential Clinical Knowledge |
| Title |
Regulation of Appetite by Acyl—ghrelin |
| Author |
Koji Ataka |
Department of Psychosomatic Internal Medicine, Kagoshima University Graduate School of Medical & Dental Sciences, |
| Author |
Akihiro Asakawa |
Department of Psychosomatic Internal Medicine, Kagoshima University Graduate School of Medical & Dental Sciences, |
| Author |
Akio Inui |
Department of Psychosomatic Internal Medicine, Kagoshima University Graduate School of Medical & Dental Sciences, |
| [ Summary ] |
Ghrelin is a 28‒amino acids peptide, mainly produced in the stomach, which enables the hunger signals to be sent from the gut to the brain (brain‒gut axis). Ghrelin acquires its orexigenic activity through serine‒octanoylation (C8 : 0), enabled by ghrelin O‒acyltransferase (GOAT). The acyl‒ghrelin is secreted from the stomach when the state of hunger is reached, and binds the ghrelin receptor (growth hormone secretagogue receptor 1a ; GHSR1a) localized in the brain, leading to an increase in food intake. Acyl‒ghrelin contributes to both homeostatic and hedonic eating disorders. In diet‒induced obesity, the acyl‒ghrelin level is lower than in control subjects with normal body mass index (BMI), and the amount of ghrelin receptors in the brain decreases, resulting in the dysfunction of acyl‒ghrelin signals. In patients with anorexia nervosa, the acyl‒ghrelin level is higher than in healthy controls. In this chapter, we will review the functions and action mechanisms of ghrelin involved in appetite regulation, and the impairment processes of the ghrelin system causing obesity and anorexia nervosa. |