title: Effects of solid-phase extraction of plasma in measuring gut metabolic hormones in fasted and fed blood of lean and diet-induced obese rats.
abstract: Glucagon-like peptide-1 (GLP-1), peptide YY (3-36) [PYY(3-36)], amylin, ghrelin, insulin, and leptin are thought to act as hormonal signals from periphery to brain to control food intake. Here, we determined the effects of solid-phase extraction of plasma in measuring these hormones in blood of lean and diet-induced obese rats. Individual enzyme-linked immunoassays and a multiplex assay were used to measure active GLP-1, total PYY, active amylin, active ghrelin, insulin, leptin, and total GIP in response to (1) addition of known amounts of the peptides to lean and obese plasma, (2) a large meal in lean and obese rats, and (3) intravenous infusions of anorexigenic doses of GLP-1, PYY(3-36), amylin, and leptin in lean rats. Extraction of lean and obese plasma prior to assays produced consistent recoveries across assays for GLP-1, PYY, amylin, ghrelin, and insulin, reflecting losses inherent to the extraction procedure. Plasma extraction prior to assays generally revealed larger meal-induced changes in plasma GLP-1, PYY, amylin, ghrelin, and insulin in lean and obese rats. Plasma extraction and the multiplex assay were used to compare plasma levels of GLP-1, PYY, and amylin after a large meal with plasma levels produced by IV infusions of anorexigenic doses of GLP-1, PYY(3-36), and amylin. Infusions produced dose-dependent increases in plasma peptide levels, which were well above their postprandial levels. These results do not support the hypothesis that postprandial plasma levels of GLP-1, PYY(3-36), and amylin are sufficient to decrease food intake by an endocrine mechanism.
authors.affiliation: Department of Biomedical Sciences, Creighton University, Omaha, Nebraska VA Research Service, VA Nebraska Western Iowa Health Care System, Omaha, Nebraska rogerreidelberger@creighton.edu.
authors.forename: Roger
authors.initials: R
authors.lastname: Reidelberger
authors.affiliation: Department of Biomedical Sciences, Creighton University, Omaha, Nebraska VA Research Service, VA Nebraska Western Iowa Health Care System, Omaha, Nebraska.
authors.forename: Alvin
authors.initials: A
authors.lastname: Haver
authors.affiliation: Department of Biomedical Sciences, Creighton University, Omaha, Nebraska.
authors.forename: Krista
authors.initials: K
authors.lastname: Anders
authors.affiliation: Department of Biomedical Sciences, Creighton University, Omaha, Nebraska.
authors.forename: Bettye
authors.initials: B
authors.lastname: Apenteng
authors.affiliation: EMD Millipore Corp., Billerica, Massachusetts.
authors.forename: Craig
authors.initials: C
authors.lastname: Lanio
mesh_terms: D000818:Animals; D059305:Diet, High-Fat / Q000009:adverse effects*; D004435:Eating / Q000187:drug effects / Q000502:physiology*; D005215:Fasting / Q000097:blood*; D005768:Gastrointestinal Hormones / Q000008:administration & dosage / Q000097:blood*; D007262:Infusions, Intravenous; D008297:Male; D009765:Obesity / Q000097:blood* / Q000139:chemically induced; D051381:Rats; D052616:Solid Phase Extraction / Q000379:methods*; D013851:Thinness / Q000097:blood*
chemical_list: D005768:Gastrointestinal Hormones
keywords: Amylin; GLP‐1; PYY(3‐36); ghrelin; intravenous infusion