title: Fuel metabolism in Canada geese: effects of glucagon on glucose kinetics.
abstract: During prolonged fasting, birds must rely on glucose mobilization to maintain normoglycemia. Glucagon is known to modulate avian energy metabolism during prolonged fasting, but the metabolic effects of this hormone on long-distance migrant birds have never been investigated. Our goal was to determine whether glucagon regulates the mobilization of the main lipid and carbohydrate fuels in migrant birds. Using the Canada goose (Branta canadensis) as a model species, we looked for evidence of fuel mobilization via changes in metabolite concentrations. No changes could be found for any lipid fraction, but glucagon elicited a strong increase in glucose concentration. Therefore, we aimed to quantify the effects of this hormone on glucose kinetics using continuous infusion of 6-[(3)H]-d-glucose. Glucagon was found to cause a 50% increase in glucose mobilization (from 22.2 ± 2.4 μmol·kg(-1)·min(-1) to 33.5 ± 3.3 μmol·kg(-1)·min(-1)) and, together with an unchanged rate of carbohydrate oxidation, led to a 90% increase in plasma glucose concentration. This hormone also led to a twofold increase in plasma lactate concentration. No changes in plasma lipid concentration or composition were observed. This study is the first to demonstrate how glucagon modulates glucose kinetics in a long-distance migrant bird and to quantify its rates of glucose mobilization.
authors.affiliation: Department of Biology, University of Ottawa, Ottawa, Ontario, Canada EricVaillancourt@uOttawa.ca.
authors.forename: Eric
authors.initials: E
authors.lastname: Vaillancourt
authors.affiliation: Department of Biology, University of Ottawa, Ottawa, Ontario, Canada.
authors.forename: Jean-Michel
authors.initials: JM
authors.lastname: Weber
mesh_terms: D000222:Adaptation, Physiological; D000818:Animals; D001786:Blood Glucose / Q000378:metabolism*; D004734:Energy Metabolism; D005777:Geese / Q000097:blood*; D005934:Glucagon / Q000097:blood*; D007700:Kinetics; D019344:Lactic Acid / Q000097:blood; D008055:Lipids / Q000097:blood; D010084:Oxidation-Reduction
chemical_list: D001786:Blood Glucose; D008055:Lipids; D019344:Lactic Acid; D005934:Glucagon
keywords: Branta canadensis; hepatic glucose production; in vivo tracer infusion; indirect calorimetry; metabolic substrates