title: Hyperinsulinemia decreases second-phase but not first-phase arginine-induced insulin release in humans.
abstract: The aim of this study was to investigate the effect of hyperinsulinemia on the first and second phase of arginine-induced insulin release in humans. Seven healthy subjects underwent three studies (lasting 360 min): a control study using saline infusion and two euglycemic clamps using a low-dose (0.33 mU.kg-1.min-1) and a high-dose (1.20 mU.kg-1.min-1) insulin infusion. After a 3-h equilibration period, arginine (25 g) was infused for 30 min, and insulin and C-peptide responses to arginine were followed for 180 min. At the end of the equilibration period, before arginine administration, steady-state insulin levels were (means +/- SE) 60.0 +/- 2.4, 165.6 +/- 1.8, and 455.4 +/- 7.8 pmol/l during saline, low-dose, and high-dose insulin infusions, respectively. The time course of insulin release during the arginine test was calculated from C-peptide concentrations by using C-peptide kinetic modeling and deconvolution. In particular, first-phase and second-phase insulin response was obtained by integrating the time course of the insulin release during either the first 5 min or the following 40 min of the arginine test, respectively. Whereas first-phase insulin release was independent of any effect induced by either insulin infusion, second-phase insulin release was reduced in a similar degree by both insulin infusion doses. First phase was 75.5 +/- 10.1, 73.7 +/- 12.8, and 73.4 +/- 10.3 pmol/kg, whereas second phase was 266.1 +/- 46.0, 143.1 +/- 33.5, and 133.0 +/- 30.2 pmol/kg for saline, low-dose, and high-dose insulin infusions, respectively.(ABSTRACT TRUNCATED AT 250 WORDS)
authors.affiliation: Istituto Scientifico San Raffaele, Cattedra di Clinica Medica, Università di Milano, Italy.
authors.forename: P M
authors.initials: PM
authors.lastname: Piatti
authors.forename: A E
authors.initials: AE
authors.lastname: Pontiroli
authors.forename: A
authors.initials: A
authors.lastname: Caumo
authors.forename: G
authors.initials: G
authors.lastname: Santambrogio
authors.forename: L D
authors.initials: LD
authors.lastname: Monti
authors.forename: S
authors.initials: S
authors.lastname: Costa
authors.forename: F
authors.initials: F
authors.lastname: Garbetta
authors.forename: L
authors.initials: L
authors.lastname: Baruffaldi
authors.forename: C
authors.initials: C
authors.lastname: Cobelli
authors.forename: G
authors.initials: G
authors.lastname: Pozza
mesh_terms: D000328:Adult; D001120:Arginine / Q000494:pharmacology*; D001786:Blood Glucose / Q000378:metabolism*; D002096:C-Peptide / Q000097:blood; D005934:Glucagon / Q000097:blood; D015309:Glucose Clamp Technique; D006801:Humans; D006946:Hyperinsulinism / Q000097:blood / Q000503:physiopathology*; D007262:Infusions, Intravenous; D007328:Insulin / Q000097:blood / Q000378:metabolism* / Q000494:pharmacology; D000078790:Insulin Secretion; D007700:Kinetics; D008297:Male; D012016:Reference Values; D013004:Somatostatin / Q000097:blood; D013997:Time Factors
chemical_list: D001786:Blood Glucose; D002096:C-Peptide; D007328:Insulin; D013004:Somatostatin; D005934:Glucagon; D001120:Arginine