[Trp3, Arg5]-ghrelin(1–5) stimulates growth hormone secretion and food intake via growth hormone secretagogue (GHS) receptor

Ghrelin, a 28 amino acid peptide identified as an endogenous ligand for growth hormone secretagogue (GHS) receptor, stimulates food intake and growth hormone (GH) secretion. We designed low molecular weight peptides with affinity for the GHS receptor based on the primary structure of ghrelin. We found that [Trp3, Arg5]-ghrelin(1–5) (GSWFR), a novel pentapeptide composed of all l-amino acids, had affinity for the GHS receptor (IC50 = 10 μM). GSWFR stimulated GH secretion after intravenous or oral administration. Centrally administered GSWFR increased food intake in non-fasted mice. The orexigenic action of GSWFR was inhibited by a GHS receptor antagonist, [d-Lys3]-GH-releasing peptide-6, suggesting that GSWFR stimulated food intake through the GHS receptor. The orexigenic action of GSWFR was also inhibited by a neuropeptide Y (NPY) Y1 receptor antagonist, BIBO3304. These results suggest that the GSWFR-induced feeding is mediated by the NPY Y1 receptor.