title: Enteral nutrients potentiate the intestinotrophic action of glucagon-like peptide-2 in association with increased insulin-like growth factor-I responses in rats.
abstract: Glucagon-like peptide-2 (GLP-2) is a nutrient-dependent, intestinotrophic hormone derived from posttranslational processing of proglucagon in the distal bowel. GLP-2 is thought to act through indirect mediators, such as IGF-I. We investigated whether intestinal expression of GLP-2 and IGF-I system components are increased with the mucosal growth induced by enteral nutrient (EN) and/or a low dose of GLP-2 in parenterally fed rats. Rats were randomized to four treatment groups using a 2 x 2 design and maintained with parenteral nutrition (PN) for 7 days: PN alone, EN, GLP-2, and EN+GLP-2; n = 7-9. The two main treatment effects are +/-GLP-2 (100 microg.kg body wt(-1).day(-1)) and +/-EN (43% of energy needs, days 4-6). Combination treatment with EN+GLP-2 induced synergistic intestinal growth in ileum, resulting in greater mucosal cellularity, sucrase segmental activity, and gain of body weight (ENxGLP-2, P < 0.04). In addition, EN+GLP-2 induced a significant 28% increase in plasma concentration of bioactive GLP-2, a significant 102% increase in ileal proglucagon mRNA with no change in ileal dipeptidyl peptidase-IV (DPP-IV) specific activity, and significantly reduced plasma DPP-IV activity compared with GLP-2. This indicates that EN potentiates the intestinotrophic action of GLP-2. Proliferation of enterocytes due to GLP-2 infusion was associated with greater expression of ileal proglucagon, GLP-2 receptor, IGF-I, IGF binding protein-3 mRNAs, and greater IGF-I peptide concentration in ileum (P < 0.032). Ileal IGF-I mRNA was positively correlated with expression of proglucagon, GLP-2R, and IGFBP-5 mRNAs (R2 = 0.43-0.56, P < 0.0001). Our findings support the hypothesis that IGF-I is one of the downstream mediators of GLP-2 action in a physiological model of intestinal growth.
authors.affiliation: Department of Nutritional Sciences, University of Wisconsin-Madison, 1415 Linden Drive, Madison, WI 53706, USA.
authors.forename: Xiaowen
authors.initials: X
authors.lastname: Liu
authors.forename: Sangita G
authors.initials: SG
authors.lastname: Murali
authors.forename: Jens J
authors.initials: JJ
authors.lastname: Holst
authors.forename: Denise M
authors.initials: DM
authors.lastname: Ney
mesh_terms: D000818:Animals; D001835:Body Weight; D049109:Cell Proliferation; D018819:Dipeptidyl Peptidase 4 / Q000378:metabolism; D004750:Enteral Nutrition; D020895:Enterocytes / Q000378:metabolism*; D053767:Glucagon-Like Peptide 2 / Q000008:administration & dosage / Q000378:metabolism*; D000067758:Glucagon-Like Peptide-2 Receptor; D006801:Humans; D007082:Ileum / Q000254:growth & development / Q000378:metabolism; D007262:Infusions, Intravenous; D018972:Insulin-Like Growth Factor Binding Protein 3 / Q000378:metabolism; D018975:Insulin-Like Growth Factor Binding Protein 5 / Q000378:metabolism; D007334:Insulin-Like Growth Factor I / Q000235:genetics / Q000378:metabolism*; D007413:Intestinal Mucosa / Q000378:metabolism*; D007422:Intestines / Q000201:enzymology / Q000254:growth & development; D007583:Jejunum / Q000254:growth & development / Q000378:metabolism; D008297:Male; D009584:Nitrogen / Q000378:metabolism; D010288:Parenteral Nutrition; D052336:Proglucagon / Q000378:metabolism; D012333:RNA, Messenger / Q000378:metabolism; D051381:Rats; D017207:Rats, Sprague-Dawley; D018027:Receptors, Glucagon / Q000378:metabolism; D011994:Recombinant Proteins / Q000378:metabolism; D015398:Signal Transduction; D013393:Sucrase / Q000378:metabolism; D013997:Time Factors; D015854:Up-Regulation
chemical_list: D053767:Glucagon-Like Peptide 2; D000067758:Glucagon-Like Peptide-2 Receptor; D018972:Insulin-Like Growth Factor Binding Protein 3; D018975:Insulin-Like Growth Factor Binding Protein 5; D012333:RNA, Messenger; D018027:Receptors, Glucagon; D011994:Recombinant Proteins; D052336:Proglucagon; D007334:Insulin-Like Growth Factor I; D013393:Sucrase; D018819:Dipeptidyl Peptidase 4; D009584:Nitrogen