title: Meal-induced enhancement in insulin sensitivity is not triggered by hyperinsulinemia in rats.
abstract: Several reports confirmed the phenomenon of postprandial increase in whole-body insulin sensitivity. Although the initial step of this process is unknown, the pivotal role of postprandial hyperinsulinemia has strongly been suggested. The aim of the present study was to determine whether hyperinsulinemia per se induces insulin sensitization in healthy male Wistar rats. Rapid insulin sensitivity test (RIST) were performed in fasted, anesthetized rats before and during stable hyperinsulinemia achieved by hyperinsulinemic euglycemic glucose clamping (HEGC) with insulin infused either through the jugular vein (systemic HEGC) or into the portal circulation (portal HEGC) at a rate of 3 mU/(kg min). Insulin sensitivity expressed by the rapid insulin sensitivity (RIST) index (in milligrams per kilogram) was characterized by the total amount of glucose needed to maintain prestudy blood glucose level succeeding an intravenous bolus infusion of 50 mU/kg insulin over 5 minutes. In fasted animals, the RIST index was 37.4 +/- 3.1 mg/kg. When hyperinsulinemia mimicking the postprandial state was achieved by systemic HEGC, the RIST index (39.7 +/- 10.6 mg/kg) showed no significant changes as compared with the pre-HEGC values. Hyperinsulinemia achieved by portal insulin infusion also failed to modify the RIST index (35.7 +/- 4.3 mg/kg). The results demonstrate that acute hyperinsulinemia, no matter how induced, does not yield any sensitization to the hypoglycemic effect of insulin.
authors.affiliation: Department of Pharmacology and Pharmacotherapy, University of Debrecen, H-4032 Debrecen, Nagyerdei krt 98, Hungary. barna.peitl@king.pharmacol.dote.hu
authors.forename: Barna
authors.initials: B
authors.lastname: Peitl
authors.forename: Róbert
authors.initials: R
authors.lastname: Döbrönte
authors.forename: József
authors.initials: J
authors.lastname: Németh
authors.forename: Csaba
authors.initials: C
authors.lastname: Pankucsi
authors.forename: Réka
authors.initials: R
authors.lastname: Sári
authors.forename: Angelika
authors.initials: A
authors.lastname: Varga
authors.forename: Zoltán
authors.initials: Z
authors.lastname: Szilvássy
mesh_terms: D000818:Animals; D001786:Blood Glucose / Q000187:drug effects / Q000378:metabolism*; D004435:Eating; D005215:Fasting; D015309:Glucose Clamp Technique; D006946:Hyperinsulinism / Q000097:blood*; D007262:Infusions, Intravenous; D007328:Insulin / Q000008:administration & dosage / Q000494:pharmacology*; D007601:Jugular Veins; D008297:Male; D051381:Rats; D017208:Rats, Wistar
chemical_list: D001786:Blood Glucose; D007328:Insulin