University of Kentucky UKnowledge University of Kentucky Doctoral Dissertations Graduate School 2009 IDENTIFICATION AND CHARACTERIZATION OF THE GLUCAGON- LIKE PEPTIDE-2 HORMONAL SYSTEM IN RUMINANTS Christina C. Taylor Edwards University of Kentucky, [email protected] Right click to open a feedback form in a new tab to let us know how this document benefits ou.y Recommended Citation Edwards, Christina C. Taylor, "IDENTIFICATION AND CHARACTERIZATION OF THE GLUCAGON-LIKE PEPTIDE-2 HORMONAL SYSTEM IN RUMINANTS" (2009). University of Kentucky Doctoral Dissertations. 734. https://uknowledge.uky.edu/gradschool_diss/734 This Dissertation is brought to you for free and open access by the Graduate School at UKnowledge. It has been accepted for inclusion in University of Kentucky Doctoral Dissertations by an authorized administrator of UKnowledge. For more information, please contact [email protected]. ABSTRACT OF DISSERTATION Christina C. Taylor Edwards The Graduate School University of Kentucky 2009 IDENTIFICATION AND CHARACTERIZATION OF THE GLUCAGON-LIKE PEPTIDE-2 HORMONAL SYSTEM IN RUMINANTS _____________________________________ ABSTRACT OF DISSERTATION _____________________________________ A dissertation submitted in partial fulfillment of the requirements for the degree of Doctor of Philosophy in the College of Agriculture at the University of Kentucky By Christina C. Taylor Edwards Lexington, Kentucky Director: Dr. David Harmon, Professor of Animal Science Lexington, Kentucky 2009 Copyright © Christina C. Taylor Edwards 2009 ABSTRACT OF DISSERTATION IDENTIFICATION AND CHARACTERIZATION OF THE GLUCAGON-LIKE PEPTIDE-2 HORMONAL SYSTEM IN RUMINANTS The hormone glucagon-like peptide-2 (GLP-2) is important in the regulation of intestinal growth and blood flow in nonruminant animals. However, no research reports the existence of GLP-2 in ruminants. Therefore, this dissertation examined the existence of GLP-2 and its receptor, their response to physiological stimuli, and its ability to induce gastrointestinal growth and intestinal blood flow in ruminants. Experiments 1 and 2 established the gastrointestinal distribution of mRNA for proglucagon (the GLP-2 precursor) and the GLP-2 receptor. Furthermore, these experiments determined the effects of changing dietary energy intake on plasma GLP-2 concentrations and proglucagon and GLP-2 receptor mRNA expression. Experiment 3 examined the effect of exogenous bovine GLP-2 on splanchnic blood flow, splanchnic nutrient flux, and gastrointestinal growth. This research shows that ruminants possess a functional GLP-2 signaling system that responds to nutrient ingestion. Based on observed receptor distribution and growth changes with GLP-2 treatment, GLP-2 targets the small intestine and does not affect forestomach or large intestinal growth. Increases in ileal proglucagon mRNA expression and plasma GLP-2 with increasing energy intake demonstrate that GLP-2 responds to physiologic changes in nutrient intake and can be relevant to feeding practices. Furthermore, observed increases in small intestinal growth and blood flow with GLP-2 suggest that it could substantially affect the capacity of the gastrointestinal tract for nutrient absorption. Modification of GLP-2 through diet could allow for improvements in nutrient utilization and animal productivity. This research also has important implications for use of GLP-2 for human disease therapy as the observed down- regulation in the blood flow response to 10-d GLP-2 administration has never been reported in any species prior to this dissertation. This research systematically characterized and evaluated the potential role of GLP-2 in the control of gastrointestinal growth and splanchnic blood flow in ruminants. While it extends the knowledge of hormonal control of the gastrointestinal tract in ruminants, it also adds crucial information to the larger body of work investigating the actions of GLP- 2. This dissertation research has contributed to the groundwork necessary to enable the use of GLP-2 in improving the health and productivity of a diverse group of mammalian species. KEYWORDS: Glucagon-like peptide-2, ruminant, gastrointestinal growth, splanchnic blood flow, mRNA expression Christina C. Taylor Edwards _____________________________________ Student’s Signature April 29, 2009 _____________________________________ Date IDENTIFICATION AND CHARACTERIZATION OF THE GLUCAGON-LIKE PEPTIDE-2 HORMONAL SYSTEM IN RUMINANTS By Christina C. Taylor Edwards David L. Harmon _____________________________________ Director of Dissertation David L. Harmon _____________________________________ Director of Graduate Studies April 29, 2009 _____________________________________ Date RULES FOR THE USE OF DISSERTATIONS Unpublished dissertations submitted for the Doctor’s degree and deposited in the University of Kentucky library are as a rule open for inspection, but are to be used only with due regard to the rights of the authors. Bibliographical references may be noted, but quotations or summaries of parts may be published only with the permission of the author, and with the usual scholarly acknowledgements. Extensive copying or publication of the dissertation in whole or in part also requires consent of the Dean of the Graduate School of the University of Kentucky. A library that borrows this dissertation for use by its patrons is expected to secure the signature of each user. Name Date ______________________________________________________________________ ______________________________________________________________________ ______________________________________________________________________ ______________________________________________________________________ ______________________________________________________________________ ______________________________________________________________________ ______________________________________________________________________ ______________________________________________________________________ ______________________________________________________________________ ______________________________________________________________________ DISSERTATION Christina C. Taylor Edwards The Graduate School University of Kentucky 2009 IDENTIFICATION AND CHARACTERIZATION OF THE GLUCAGON-LIKE PEPTIDE-2 HORMONAL SYSTEM IN RUMINANTS _____________________________________ DISSERTATION _____________________________________ A dissertation submitted in partial fulfillment of the requirements for the degree of Doctor of Philosophy in the College of Agriculture at the University of Kentucky By Christina C. Taylor Edwards Lexington, Kentucky Director: Dr. David Harmon, Professor of Animal Science Lexington, Kentucky 2009 Copyright © Christina C. Taylor Edwards 2009 This dissertation is dedicated to those that encouraged and motivated me through the years. My parents, who taught me the love of learning. My sister, who can always make me laugh. My friends, especially Julie, Melissa, Sally, and Sandi, who encouraged me to continue but also helped me forget my frustrations. And above all, my husband Dave, who not only endured it all but helped with every single aspect of the research and writing of this dissertation. I am deeply grateful for your love and support. ACKNOWLEDGEMENTS The research presented in this dissertation could not have been accomplished without the significant contributions of many. I am grateful to the animals in these experiments, and hope that their contribution will improve the lives of other animals in the world. I also express gratitude for those that helped me with caring for these animals, including Chris Johnson, Pete Carew, Lauren Clark, and Josh Piel. Kirk Vanzant, manager of the Beef Unit has my appreciation. I sincerely thank Joey Clark, Dairy Unit manager, for his extensive help for this research. Jim May, manager of the Meat Lab, was extremely helpful in the collection of tissues. Dave Higginbotham, Feed Mill manager, was absolutely indispensible in this research and has my thanks. A great number of people helped with the sample collection and analysis for these experiments. I am grateful for the help of Dr. Kelly Brown, Anne Koontz, Anne Ballou, Edwena Miles, Fran Korthaus, Beth Kitts, Kyle Earing, Alex Silvia, and Mesa Doig. Additional people helped with multiple aspects of this research. Dr. Dave Edwards and Melissa Hudson both helped with much of the sample collection but were also critical for bouncing ideas back and forth during the analysis stages. Dr. Jimmy Klotz contributed greatly to the surgical preparation of the animals and sample collection. Dr. Shengfa Liao helped with sample collection but was instrumental in teaching the real- time RT-PCR techniques used in these experiments. Dr. Samer El-Kadi helped in many aspects, including surgical preparation, sample collection, and statistical analyses. I cannot express my gratitude enough for your help. The laboratory technicians in the Ruminant Nutrition Lab have contributed greatly to this research. Julie (Cannon) Riddell, who has helped with this dissertation research since her very first day of work, has been indispensible for help with tissue collections, surgeries, and assays. Likewise, I am also grateful to Dani True for help with tissue collections, surgeries, and assays. Dr. Winston Lin and Cyndi Roberts have also helped with plasma analysis, for which I am grateful. I am grateful to the personnel, including Louis Dionissopoulous and Kwangwon Son, of the Dr. Jamie Matthews lab for assistance with the use of the laboratory and training iii