Hyperglycaemia suppresses the secretion of ghrelin, a novel growth-hormone-releasing peptide: responses to the intravenous and oral administration of glucose

Ghrelin is a novel growth hormone (GH)-releasing peptide, isolated from the stomach, which may also cause a positive energy balance by stimulating food intake and reducing fat utilization. However, whether glucose influences the release of ghrelin remains unknown. Accordingly, we examined circulating levels of ghrelin and GH in response to the intravenous or oral administration of 50 g of glucose in eight healthy humans. After the administration of intravenous glucose (50 g), the plasma ghrelin level decreased significantly from 127+/-9 to 98+/-9 fmol/ml (P<0.01), associated with an increase in plasma glucose from 85+/-3 to 357+/-19 mg/dl (P<0.01). Ingestion of 50 g of glucose decreased the plasma ghrelin level significantly from 134+/-12 to 97+/-15 fmol/ml (P<0.01), associated with an increase in plasma glucose from 93+/-3 to 166+/-10 mg/dl (P<0.01). The decrease in the plasma ghrelin level lasted for more than 30 min after recovery of the plasma glucose level. In conclusion, ghrelin secretion may be suppressed, at least in part, by an increased plasma glucose level in healthy humans.