title: Expression of mRNA for proglucagon and glucagon-like peptide-2 (GLP-2) receptor in the ruminant gastrointestinal tract and the influence of energy intake.
abstract: Glucagon-like peptide-2 (GLP-2) is a potent trophic gut hormone, yet its function in ruminants is relatively unknown. Experiment 1 was conducted as a pilot study to establish the presence of GLP-2 in ruminants and to ascertain whether it was responsive to increased nutrition, as in non-ruminants. Concentrations of intact GLP-2 in the blood and gut epithelial mRNA expression of proglucagon (GCG) and the GLP-2 receptor (GLP2R) were measured in 4 ruminally, duodenally, and ileally cannulated steers. Steers were fed to meet 0.75 x NE(M) for 21 d, and then increased to 1.75 x NE(M) requirement for another 29 d. Blood samples and ruminal, duodenal, and ileal epithelium biopsies were collected at low intake (Days -6 and -3), acute high intake (Days 1 and 3), and chronic high intake (Days 7 and 29) periods. Experiment 2 investigated the mRNA expression pattern of GCG and GLP2R in epithelial tissue obtained from the forestomachs (rumen, omasum, and abomasum) and intestines (duodenum, jejunum, ileum, and colon) of 18 forage-fed Angus steers (260 kg BW). In Experiments 1 and 2, real-time polymerase chain reaction showed that expression of GCG and GLP2R mRNA was detectable in forestomach tissues, but expression was greater (P < 0.001) in small intestinal and colon tissue. High energy intake tended (P = 0.07) to increase plasma GLP-2 during the acute period and was paralleled by a 78% increase (P = 0.07) in ileal GCG mRNA expression. After this initial adaptation, duodenal GCG mRNA expression increased (P = 0.08) during the chronic high intake period. Duodenal GLP2R mRNA expression was not affected by energy intake, but ileal GLP2R expression was increased after 29 d of high energy intake compared to both the low and acute high intake periods (P = 0.001 and P = 0.01, respectively). These data demonstrate that cattle express GCG and GLP2R mRNA primarily in small intestinal and colon tissues. Increased nutrient intake increases ileal GCG mRNA and plasma GLP-2, suggesting that GLP-2 may play a role in the trophic response of the ruminant gastrointestinal tract to increased feed intake.
authors.affiliation: Department of Animal and Food Sciences, University of Kentucky, Lexington, KY, USA.
authors.forename: C C
authors.initials: CC
authors.lastname: Taylor-Edwards
authors.forename: D G
authors.initials: DG
authors.lastname: Burrin
authors.forename: J C
authors.initials: JC
authors.lastname: Matthews
authors.forename: K R
authors.initials: KR
authors.lastname: McLeod
authors.forename: J J
authors.initials: JJ
authors.lastname: Holst
authors.forename: D L
authors.initials: DL
authors.lastname: Harmon
mesh_terms: D000818:Animals; D002417:Cattle / Q000502:physiology*; D003106:Colon / Q000737:chemistry; D002149:Energy Intake / Q000502:physiology*; D041981:Gastrointestinal Tract / Q000378:metabolism*; D015870:Gene Expression; D053767:Glucagon-Like Peptide 2 / Q000097:blood; D000067758:Glucagon-Like Peptide-2 Receptor; D007421:Intestine, Small / Q000737:chemistry; D008297:Male; D016133:Polymerase Chain Reaction; D052336:Proglucagon / Q000235:genetics*; D012333:RNA, Messenger / Q000032:analysis; D018027:Receptors, Glucagon / Q000235:genetics*; D012417:Rumen / Q000737:chemistry; D013279:Stomach, Ruminant / Q000737:chemistry
chemical_list: D053767:Glucagon-Like Peptide 2; D000067758:Glucagon-Like Peptide-2 Receptor; D012333:RNA, Messenger; D018027:Receptors, Glucagon; D052336:Proglucagon