title: Insulin and C-peptide secretion and kinetics in humans: direct and model-based measurements during OGTT.
abstract: To directly evaluate prehepatic secretion of pancreatic hormones during a 3-h oral glucose tolerance test (OGTT), we measured insulin and C-peptide in six healthy control, six obese, and six type 2 diabetic subjects in the femoral artery and hepatic vein by means of the hepatic catheterization technique. Hypersecretion in obesity was confirmed (309 +/- 66 nmol in obese vs. 117 +/- 22 in control and 79 +/- 13 in diabetic subjects, P </= 0.01), whereas early phase secretion was impaired in diabetes. We also measured hepatic insulin extraction (higher in diabetic than in control subjects, P = 0.03) and insulin clearance. The measured data were also used to validate a previously proposed mathematical model, developed to quantify prehepatic secretion, hepatic insulin extraction, and insulin clearance during OGTT, when C-peptide and insulin concentrations are systemically measured. We found good correspondence between experimental data and model estimates for prehepatic insulin secretion (P > 0.3, r(2) = 0.93), whereas estimation of hepatic insulin extraction and insulin clearance needs further investigation for improvement.
authors.affiliation: Institute of Systems Science and Biomedical Engineering, Italian National Research Council, 35127 Padua, Italy.
authors.forename: A
authors.initials: A
authors.lastname: Tura
authors.forename: B
authors.initials: B
authors.lastname: Ludvik
authors.forename: J J
authors.initials: JJ
authors.lastname: Nolan
authors.forename: G
authors.initials: G
authors.lastname: Pacini
authors.forename: K
authors.initials: K
authors.lastname: Thomaseth
mesh_terms: D000328:Adult; D001786:Blood Glucose / Q000032:analysis; D002096:C-Peptide / Q000097:blood / Q000378:metabolism*; D003924:Diabetes Mellitus, Type 2 / Q000503:physiopathology; D005260:Female; D005951:Glucose Tolerance Test; D006499:Hepatic Artery; D006503:Hepatic Veins; D006801:Humans; D007328:Insulin / Q000097:blood / Q000378:metabolism*; D000078790:Insulin Secretion; D007700:Kinetics; D008297:Male; D008875:Middle Aged; D008954:Models, Biological; D009765:Obesity / Q000503:physiopathology; D012680:Sensitivity and Specificity
chemical_list: D001786:Blood Glucose; D002096:C-Peptide; D007328:Insulin