title: Both subcutaneously and intravenously administered glucagon-like peptide I are rapidly degraded from the NH2-terminus in type II diabetic patients and in healthy subjects.
abstract: To fate of exogenous glucagon-like peptide I (GLP-I)(7-36) amide was studied in nondiabetic and type II diabetic subjects using a combination of high-pressure liquid chromatography (HPLC), specific radioimmunoassays (RIAs), and a sensitive enzyme-linked immunosorbent assay (ELISA), whereby intact biologically active GLP-I and its metabolites could be determined. After GLP-I administration, the intact peptide could be measured using an NH2-terminally directed RIA or ELISA, while the difference in concentration between these assays and a COOH-terminal-specific RIA allowed determination of NH2-terminally truncated metabolites. Subcutaneous GLP-I was rapidly degraded in a time-dependent manner, forming a metabolite, which co-eluted on HPLC with GLP-I(9-36) amide and had the same immunoreactive profile. Thirty minutes after subcutaneous GLP-I administration to diabetic patients (n = 8), the metabolite accounted for 88.5 +/- 1.9% of the increase in plasma immunoreactivity determined by the COOH-terminal RIA, which was higher than the levels measured in healthy subjects (78.4 +/- 3.2%; n = 8; P < 0.05). Intravenously infused GLP-I was also extensively degraded, but no significant differences were seen between the two groups. Intact GLP-I accounted for only 19.9 +/- 3.4% of the increase in immunoreactivity measured with the COOH-terminal RIA in normal subjects (n = 8), and 25.0 +/- 4.8% of the increase in diabetic subjects (n = 8), the remainder being the NH2-terminally truncated metabolite.
authors.affiliation: Department of Medical Physiology, Panum Institute, University of Copenhagen, Denmark.
authors.forename: C F
authors.initials: CF
authors.lastname: Deacon
authors.forename: M A
authors.initials: MA
authors.lastname: Nauck
authors.forename: M
authors.initials: M
authors.lastname: Toft-Nielsen
authors.forename: L
authors.initials: L
authors.lastname: Pridal
authors.forename: B
authors.initials: B
authors.lastname: Willms
authors.forename: J J
authors.initials: JJ
authors.lastname: Holst
mesh_terms: D000328:Adult; D002851:Chromatography, High Pressure Liquid; D003924:Diabetes Mellitus, Type 2 / Q000097:blood / Q000378:metabolism*; D004797:Enzyme-Linked Immunosorbent Assay; D005260:Female; D005934:Glucagon; D052216:Glucagon-Like Peptide 1; D004763:Glucagon-Like Peptides; D006801:Humans; D007262:Infusions, Intravenous; D007279:Injections, Subcutaneous; D008297:Male; D008875:Middle Aged; D010446:Peptide Fragments / Q000008:administration & dosage / Q000378:metabolism* / Q000493:pharmacokinetics; D011863:Radioimmunoassay; D012016:Reference Values; D012680:Sensitivity and Specificity; D013997:Time Factors
chemical_list: D010446:Peptide Fragments; C055453:glucagon-like peptide 1 (7-36)amide; D004763:Glucagon-Like Peptides; D052216:Glucagon-Like Peptide 1; D005934:Glucagon