title: Glucagon-like peptide 1 undergoes differential tissue-specific metabolism in the anesthetized pig.
abstract: Glucagon-like peptide 1 (GLP-1) metabolism was studied in halothane-anesthetized pigs (n = 7) using processing-independent (PI) and COOH-terminal (C) radioimmunoassays (RIA) and an enzyme-linked immunosorbent assay (ELISA) specific for biologically active GLP-1. Renal extraction of endogenous GLP-1 was detected by PI-RIA (33.1 +/- 13.3%) and C-RIA (16.0 +/- 6.3%) and by all assays during GLP-1 infusion (ELISA, 69.4 +/- 6.3%; PI-RIA, 32.6 +/- 7.3%; C-RIA, 43.7 +/- 3.4%), indicating substantial fragmentation. Hepatic and pulmonary degradation were undetectable under basal conditions, but exogenous GLP-1 elimination by the liver (43.6 +/- 8.9%) and lungs (10.1 +/- 3.2%) was measured by ELISA, suggesting primarily NH2-terminal degradation. Endogenous GLP-1 extraction by the hindleg was only detected by C-RIA (16.0 +/- 6.3%). During GLP-1 infusion, greater hindleg extraction was measured by ELISA (38.5 +/- 6.8%) and C-RIA (33.0 +/- 6.4%) than by PI-RIA (11.4 +/- 3.2%), indicating limited degradation at each terminus or more substantial COOH-terminal degradation. A shorter (P < 0.01) plasma half-life was revealed by ELISA (1.5 +/- 0.4 min) than by PI-RIA (4.5 +/- 0.6 min) or C-RIA (4.1 +/- 0.5 min). Metabolic clearance rates measured by PI-RIA (20.0 +/- 3.8 ml.min-1.kg-1) and C-RIA (15.5 +/- 1.6 ml.min-1.kg-1) were shorter (P < 0.01) than that measured by ELISA (106.8 +/- 14.7 ml.min-1.kg-1). Tissue-specific differential metabolism of GLP-1 occurs, and NH2-terminal degradation, rendering GLP-1 inactive, is particularly important in its clearance.
authors.affiliation: Department of Medical Physiology, Panum Institute, Copenhagen, Denmark.
authors.forename: C F
authors.initials: CF
authors.lastname: Deacon
authors.forename: L
authors.initials: L
authors.lastname: Pridal
authors.forename: L
authors.initials: L
authors.lastname: Klarskov
authors.forename: M
authors.initials: M
authors.lastname: Olesen
authors.forename: J J
authors.initials: JJ
authors.lastname: Holst
mesh_terms: D000818:Animals; D052216:Glucagon-Like Peptide 1; D009928:Organ Specificity; D010455:Peptides / Q000378:metabolism*; D011863:Radioimmunoassay; D013552:Swine
chemical_list: D010455:Peptides; D052216:Glucagon-Like Peptide 1