title: Contribution to glucose tolerance of insulin-independent vs. insulin-dependent mechanisms in mice.
abstract: To study the contributions of insulin-dependent vs. insulin-independent mechanisms to intravenous glucose tolerance (K(G)), 475 experiments in mice were performed. An intravenous glucose bolus was given either alone or with exogenous insulin or with substances modulating insulin secretion and sensitivity. Seven samples were taken over 50 min. Insulin [suprabasal area under the curve (DeltaAUC(ins))] ranged from 0 to 100 mU. ml(-1). 50 min. After validation against the euglycemic hyperinsulinemic clamp, the minimal model of net glucose disappearance was exploited to analyze glucose and insulin concentrations to measure the action of glucose per se independent of dynamic insulin (S(G)) and the combined effect of insulin sensitivity (S(I)) and secretion. Sensitivity analysis showed that insulin [through disposition index (DI)] contributed to glucose tolerance by 29 +/- 4% in normal conditions. In conditions of elevated hyperinsulinemia, contribution by insulin increased on average to 69%. K(G) correlated with DI but was saturated for DeltaAUC(ins) above 15 mU. ml(-1). 50 min. Insulin sensitivity related to DeltaAUC(ins) in a hyperbolic manner, whereas S(G) did not correlate with the insulin peak in the physiological range. Thus glucose tolerance in vivo is largely mediated by mechanisms unrelated to dynamic insulin and saturates with high insulin.
authors.affiliation: Institute of Systems Science and Biomedical Engineering, Italian National Research Council, 35127 Padua, Italy. Giovanni.Pacini@ladseb.pd.cnr.it
authors.forename: G
authors.initials: G
authors.lastname: Pacini
authors.forename: K
authors.initials: K
authors.lastname: Thomaseth
authors.forename: B
authors.initials: B
authors.lastname: Ahrén
mesh_terms: D000818:Animals; D019540:Area Under Curve; D001786:Blood Glucose / Q000187:drug effects / Q000378:metabolism*; D003981:Diazoxide / Q000494:pharmacology; D004041:Dietary Fats / Q000494:pharmacology*; D005260:Female; D005934:Glucagon / Q000494:pharmacology; D052216:Glucagon-Like Peptide 1; D005947:Glucose / Q000008:administration & dosage; D015309:Glucose Clamp Technique; D005951:Glucose Tolerance Test; D007275:Injections, Intravenous; D007328:Insulin / Q000097:blood / Q000378:metabolism* / Q000494:pharmacology*; D000078790:Insulin Secretion; D007700:Kinetics; D051379:Mice; D008815:Mice, Inbred Strains; D008954:Models, Biological; D009479:Neuropeptides / Q000494:pharmacology; D010446:Peptide Fragments / Q000494:pharmacology; D051219:Pituitary Adenylate Cyclase-Activating Polypeptide; D011498:Protein Precursors / Q000494:pharmacology; D012044:Regression Analysis
chemical_list: C495402:Adcyap1 protein, mouse; D001786:Blood Glucose; D004041:Dietary Fats; D007328:Insulin; D009479:Neuropeptides; D010446:Peptide Fragments; D051219:Pituitary Adenylate Cyclase-Activating Polypeptide; D011498:Protein Precursors; D052216:Glucagon-Like Peptide 1; D005934:Glucagon; D005947:Glucose; D003981:Diazoxide