title: Increased plasma ghrelin suppresses insulin release in wethers fed with a high-protein diet.
abstract: Ghrelin is a multifunctional peptide that promotes an increase of food intake and stimulates GH secretion. Ghrelin secretion is regulated by nutritional status and nutrients. Although a high-protein (HP) diet increases plasma ghrelin secretion in mammals, the mechanisms and the roles of the elevated ghrelin concentrations due to a HP diet have not been fully established. To clarify the roles of elevated acylated ghrelin upon intake of a HP diet, we investigated the regulation of ghrelin concentrations in plasma and tissues in wethers fed with either the HP diet or the control (CNT) diet for 14 days, and examined the action of the elevated plasma ghrelin by using a ghrelin-receptor antagonist. The HP diet gradually increased the plasma acylated-ghrelin concentrations, but the CNT diet did not. Although the GH concentrations did not vary significantly across the groups, an injection of ghrelin-receptor antagonist enhanced insulin levels in circulation in the HP diet group. In the fundus region of the stomach, the ghrelin levels did not differ between the HP and CNT diet groups, whereas ghrelin O-acyltransferase mRNA levels were higher in the group fed with HP diet than those of the CNT diet group were. These results indicate that the HP diet elevated the plasma ghrelin levels by increasing its synthesis; this elevation strongly suppresses the appearance of insulin in the circulation of wethers, but it is not involved in GH secretion. Overall, our findings indicate a role of endogenous ghrelin action in secretion of insulin, which acts as a regulator after the consumption of a HP diet.
authors.affiliation: Laboratory of Animal PhysiologyLaboratory of Functional MorphologyGraduate School of Agricultural Science, Tohoku University, 1-1 Tsutsumidori-Amemiyamachi, Aoba-ku, Sendai 981-8555, Japan takahac@vmas.kitasato-u.ac.jp.
authors.forename: T
authors.initials: T
authors.lastname: Takahashi
authors.affiliation: Laboratory of Animal PhysiologyLaboratory of Functional MorphologyGraduate School of Agricultural Science, Tohoku University, 1-1 Tsutsumidori-Amemiyamachi, Aoba-ku, Sendai 981-8555, Japan.
authors.forename: K
authors.initials: K
authors.lastname: Sato
authors.affiliation: Laboratory of Animal PhysiologyLaboratory of Functional MorphologyGraduate School of Agricultural Science, Tohoku University, 1-1 Tsutsumidori-Amemiyamachi, Aoba-ku, Sendai 981-8555, Japan.
authors.forename: S
authors.initials: S
authors.lastname: Kato
authors.affiliation: Laboratory of Animal PhysiologyLaboratory of Functional MorphologyGraduate School of Agricultural Science, Tohoku University, 1-1 Tsutsumidori-Amemiyamachi, Aoba-ku, Sendai 981-8555, Japan.
authors.forename: T
authors.initials: T
authors.lastname: Yonezawa
authors.affiliation: Laboratory of Animal PhysiologyLaboratory of Functional MorphologyGraduate School of Agricultural Science, Tohoku University, 1-1 Tsutsumidori-Amemiyamachi, Aoba-ku, Sendai 981-8555, Japan.
authors.forename: Y
authors.initials: Y
authors.lastname: Kobayashi
authors.affiliation: Laboratory of Animal PhysiologyLaboratory of Functional MorphologyGraduate School of Agricultural Science, Tohoku University, 1-1 Tsutsumidori-Amemiyamachi, Aoba-ku, Sendai 981-8555, Japan.
authors.forename: Y
authors.initials: Y
authors.lastname: Ohtani
authors.affiliation: Laboratory of Animal PhysiologyLaboratory of Functional MorphologyGraduate School of Agricultural Science, Tohoku University, 1-1 Tsutsumidori-Amemiyamachi, Aoba-ku, Sendai 981-8555, Japan.
authors.forename: S
authors.initials: S
authors.lastname: Ohwada
authors.affiliation: Laboratory of Animal PhysiologyLaboratory of Functional MorphologyGraduate School of Agricultural Science, Tohoku University, 1-1 Tsutsumidori-Amemiyamachi, Aoba-ku, Sendai 981-8555, Japan.
authors.forename: H
authors.initials: H
authors.lastname: Aso
authors.affiliation: Laboratory of Animal PhysiologyLaboratory of Functional MorphologyGraduate School of Agricultural Science, Tohoku University, 1-1 Tsutsumidori-Amemiyamachi, Aoba-ku, Sendai 981-8555, Japan.
authors.forename: T
authors.initials: T
authors.lastname: Yamaguchi
authors.affiliation: Laboratory of Animal PhysiologyLaboratory of Functional MorphologyGraduate School of Agricultural Science, Tohoku University, 1-1 Tsutsumidori-Amemiyamachi, Aoba-ku, Sendai 981-8555, Japan.
authors.forename: S G
authors.initials: SG
authors.lastname: Roh
authors.affiliation: Laboratory of Animal PhysiologyLaboratory of Functional MorphologyGraduate School of Agricultural Science, Tohoku University, 1-1 Tsutsumidori-Amemiyamachi, Aoba-ku, Sendai 981-8555, Japan.
authors.forename: K
authors.initials: K
authors.lastname: Katoh
mesh_terms: D000217:Acyltransferases / Q000235:genetics / Q000378:metabolism; D000818:Animals; D001786:Blood Glucose / Q000378:metabolism; D004032:Diet; D004044:Dietary Proteins / Q000008:administration & dosage*; D005748:Gastric Fundus / Q000187:drug effects / Q000378:metabolism; D015870:Gene Expression / Q000187:drug effects; D054439:Ghrelin / Q000097:blood* / Q000378:metabolism; D006041:Goats; D013006:Growth Hormone / Q000097:blood; D007150:Immunohistochemistry; D007328:Insulin / Q000097:blood* / Q000378:metabolism; D000078790:Insulin Secretion; D008297:Male; D009842:Oligopeptides / Q000494:pharmacology; D009919:Orchiectomy; D054440:Receptors, Ghrelin / Q000037:antagonists & inhibitors / Q000235:genetics / Q000378:metabolism; D020133:Reverse Transcriptase Polymerase Chain Reaction
chemical_list: D001786:Blood Glucose; D004044:Dietary Proteins; D054439:Ghrelin; D007328:Insulin; D009842:Oligopeptides; D054440:Receptors, Ghrelin; C041048:growth hormone releasing hexapeptide; D013006:Growth Hormone; D000217:Acyltransferases
keywords: antagonist; ghrelin; growth hormone; insulin; protein diet