The glucoregulatory response to intravenous glucose infusion in normal man: Roles of insulin and glucose

Luigi Saccà, Dino Vitale, Marco Cicala, Bruno Trimarco, Biagio Ungaro

Research output: Contribution to journalArticle

Abstract

In order to differentiate the roles of hyperinsulinemia and hyperglycemia per se in the homeostatic response to i.v. glucose administration, two groups of normal subjects were given either glucose alone (3.5 mg kg-1 min-1) or glucose (3 mg kg-1 min-1) in conjunction with somatostatin (500 μg hr-1), insulin (0.15 mU kg-1 min-1) and glucagon (1 ng kg-1 min-1). Glucose kinetics were measured by the primed-constant infusion of 3-3H-glucose. During the infusion of glucose alone, plasma glucose stabilized at levels 45-50 mg/dl above the fasting values. Endogenous glucose output was markedly suppressed by 85%-90% while glucose uptake rose to values very close to the infusion rate of exogenous glucose. Glucose clearance remained unchanged. Plasma insulin rose three-fourfold while plasma glucagon fell by 25%-30%. When glucose was infused with somatostatin, insulin, and glucagon, plasma insulin was maintained at levels 50% above baseline while glucagon remained at preinfusion levels. Under these conditions, the infusion of exogenous glucose resulted in a progressive increase of plasma glucose which did not stabilize until the end of the study period (190 mg/dl at 120 min). Endogenous glucose production was consistently suppressed (52%) but significantly less than observed with the infusion of glucose alone (p <0.01). Glucose uptake increased to the same extent as with glucose alone, despite the more pronounced hyperglycemia. Thus, glucose clearance fell significantly below baseline (25%-30%; p <0.01). These data demonstrate that hyperglycemia per se (fixed, near basal levels of insulin and glucagon) certainly contributes to the glucoregulatory response to i.v. glucose administration by both inhibiting endogenous glucose output and increasing tissue glucose uptake. However, the extra-insulin evoked by hyperglycemia is necessary for the glucoregulatory system to respond to the glucose load with maximal effectiveness.

Original languageEnglish
Pages (from-to)457-461
Number of pages5
JournalMetabolism
Volume30
Issue number5
DOIs
Publication statusPublished - 1981

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ASJC Scopus subject areas

  • Endocrinology
  • Endocrinology, Diabetes and Metabolism

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