Ghrelin, an endogenous ligand of the GH secretagogue-receptor, has recently been shown to stimulate GH secretion and to have orexigenic and adipogenic effects in rodents, but little is known about its regulation and biological function in humans. Gastric motor function is under control of the central nervous system; however, the afferent and efferent loops of this feedback control mechanism remain to be elucidated. In the study presented here we investigated the effect of nutrient intake on circulating human ghrelin levels, and a possible association between ghrelin levels and gastric emptying. Ten healthy volunteers received a standard meal after an overnight fast. Food intake significantly decreased plasma ghrelin levels from 248.5 +/- 15.0 to 179.5 +/- 17.9 fmol/ml (120 min after meal, p=0.047). Gastric emptying half-time (non-invasive 13C-octanoic acid breath test) was correlated with fasting plasma ghrelin levels (r=0.74, p=0.0013). Ghrelin appears to be one possible candidate to provide feedback signaling between nutrient intake, gastric motor function and the central nervous system.

Objective: Ghrelin is a new gastric hormone that has been identi®ed as an endogenous ligand for the growth hormone (GH) secretagogue receptor subtype 1a (GHS-R1a). Ghrelin administration however not only stimulates GH secretion but also induces adiposity in rodents by increasing food intake and decreasing fat utilization. We hypothesized that impaired ghrelin secretion in anorexia nervosa may be involved in the pathogenesis of this eating disorder. To examine this hypothesis and to further investigate the role for ghrelin in regulating energy homeostasis, we analyzed circulating ghrelin levels in patients with anorexia nervosa and examined possible correlations with clinical parameters before and after weight gain. Methods: Plasma ghrelin levels were measured in overnight fasting plasma samples from 36 female patients with anorexia nervosa (age: 25X0^1X2 years, BMI: 15X2^0X2 kgam 2 ) before and after weight gain following psychotherapeutic treatment intervention in a psychosomatic institution. Plasma ghrelin levels were also measured in fasting plasma samples from 24 age-matched female controls (31^1X4 years, BMI: 22X9^0X45 kgam 2 ). For quanti®cation of ghrelin levels a commercially available radioimmunoassay (Phoenix Pharmaceuticals, USA) was used. Results: Fasting plasma ghrelin levels in anorectic patients were signi®cantly higher (1057^95 pg/ml) than in normal age-matched female controls 514^63 pgaml n 24, P 0X02X Therapeutic intervention in a psychosomatic institution caused an BMI increase of 14% P , 0X001 leading to a signi®cant decrease in circulating ghrelin levels of 25%, P 0X001X A signi®cant negative correlation between Dghrelin and DBMI was observed (correlation coef®cient: 20.47, P 0X005Y n 36X Conclusion: We show for the ®rst time that fasting plasma levels of the novel appetite-modulating hormone ghrelin are elevated in anorexia nervosa and return to normal levels after partial weight recovery. These observations suggest the possible existence of ghrelin resistance in cachectic states such as caused by eating disorders. Future studies are necessary to investigate putative mechanisms of ghrelin resistance such as a possible impairment of intracellular ghrelin receptor signaling in pathophysiological states presenting with cachexia.

Acute hyperglycaemia appears to be more important than the neuropathy of the enteric nervous system in the pathophysiology of diabetic gastroparesis. The rate of gastric emptying is obviously not dependent on the phase of a meal, but rather on the composition and the caloric content.

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