Chicken Ghrelin: Purification, cDNA Cloning, and Biological Activity

Abstract

In this study, we report the purification, cDNA cloning, and characterization of the novel growth hormone-releasing peptide, ghrelin, in the chicken (Gallus gallus). Chicken ghrelin is composed of 26 amino acids (GSSFLSPTYKNIQQQKDTRKPTARLH) and possesses 54% sequence identity with human ghrelin. The serine residue at position 3 (Ser(3)) is conserved between the chicken and mammalian species, as its acylation by either n-octanoic or n-decanoic acid. Chicken ghrelin mRNA is predominantly expressed in the stomach, where it is present in the proventriculus but absent in the gizzard. Using RT-PCR analysis, low levels of expression were also detectable in brain, lung, and intestine. Administration of chicken ghrelin increases plasma GH levels in both rats and chicks, with a potency similar to that of rat or human ghrelin. In addition, chicken ghrelin also increases plasma corticosterone levels in growing chicks at a lower dose than in mammals. The present results indicate that the stimulatory effect of ghrelin on GH secretion is evolutionarily conserved, whereas its effect on adrenal function seems to be unique in the chicken.

Changes in ghrelin mRNA level, plasma growth hormone concentration and performance in different dietary energy and protein levels in broiler chicken

“…Results of the present study are in agreement with Geelissen et al (2003), who reported that chicken ghrelin in proventriculus tissue and glandular portion of the avian stomach. Ghrelin mRNA expression is mainly observed in the proventriculus (Kaiya et al, 2002), ghrelin-immunopositive cells and ghrelin mRNA expressing cells are observed in the mucosal layer of the proventriculus (Wada et al, 2003), who indicating that the primary site of ghrelin production is the proventriculus. Richards et al, (2006) showed that proventriculus had the highest ghrelin gene expression in broiler chicken.…”

Distribution and Morphology of Ghrelin-Immunopositive Cells in the Liver of the African Ostrich

“…In non-mammalian vertebrates, the ghrelin peptide has been purified from stomach extracts, which has revealed that ghrelin immunoreactivity and mRNA expression are primarily detected in the stomach or intestine (Kaiya et al, 2002). However, the expression of ghrelin mRNA was also identified in various organs of non-mammalian vertebrates other than the stomach, and there appears to be a speciesspecific difference in ghrelin expression (Kaiya et al, 2008).…”

Ghrelin Gene Expression in Broiler Proventriculus Tissue are Changed by Feed Restriction, Different Dietary Energy and Protein Levels

“…Chicken ghrelin was isolated from the proventriculus as endogenous ligand for the growth hormone secretagogue receptor (Kojima et al, 1999), which contains 26 amino acids with the third serine residue from the N-terminus of the mature peptide being acylated with n-octonoic or n-decanoic acid (Kaiya et al, 2002). Ghrelin-producing cells have also been detected in the arcuate nuclei of the rat hypothalamus, which is a feeding control center (Kojima et al, 1999;Cowley et al, 2003).…”