title: Effects of antecedent hypoglycemia, hyperinsulinemia, and excess corticosterone on hypoglycemic counterregulation.
abstract: This study aimed to differentiate the effects of repeated antecedent hypoglycemia, antecedent marked hyperinsulinemia, and antecedent increases in corticosterone on counterregulation to subsequent hypoglycemia in normal rats. Specifically, we examined whether exposure to hyperinsulinemia or elevated corticosterone per se could impair subsequent counterregulation. Four groups of male Sprague-Dawley rats were used: 1) normal controls (N) had 4 days of sham antecedent treatment; 2) an antecedent hypoglycemia group (AH) had 7 episodes of hyperinsulinemic hypoglycemia over 4 days; 3) an antecedent hyperinsulinemia group (AE) had 7 episodes of hyperinsulinemic euglycemia; and 4) an antecedent corticosterone group (AC) had 7 episodes of intravenous corticosterone to simulate the hypoglycemic corticosterone levels in AH rats. On day 5, hyperinsulinemic euglycemic-hypoglycemic clamps were performed. Epinephrine responses to hypoglycemia were impaired (P < 0.05 vs. N) after antecedent hypoglycemia and hyperinsulinemia. This correlated with diminished (P < 0.05 vs. N) absolute glucose production responses in AH rats and diminished incremental glucose production responses in AE rats. Paradoxically, norepinephrine responses were increased (P < 0.05 vs. N) after antecedent hypoglycemia. Glucagon and corticosterone responses were unaffected by antecedent hypoglycemia and hyperinsulinemia. In AC rats, incremental but not absolute glucose production responses were decreased (P < 0.05 vs. N). However, neuroendocrine counterregulation was unaltered. We conclude that both antecedent hypoglycemia and hyperinsulinemia impair epinephrine and glucose production responses to subsequent hypoglycemia, suggesting that severe recurrent hyperinsulinemia may contribute to the development of hypoglycemia-associated autonomic failure.
authors.affiliation: Department of Physiology, Faculty of Medicine, University of Toronto, 1 King's College Circle, Toronto, Ontario, Canada M5S 1A8.
authors.forename: K
authors.initials: K
authors.lastname: Shum
authors.forename: K
authors.initials: K
authors.lastname: Inouye
authors.forename: O
authors.initials: O
authors.lastname: Chan
authors.forename: J
authors.initials: J
authors.lastname: Mathoo
authors.forename: D
authors.initials: D
authors.lastname: Bilinski
authors.forename: S G
authors.initials: SG
authors.lastname: Matthews
authors.forename: M
authors.initials: M
authors.lastname: Vranic
mesh_terms: D000818:Animals; D001786:Blood Glucose / Q000378:metabolism; D001835:Body Weight; D003345:Corticosterone / Q000008:administration & dosage / Q000097:blood / Q000494:pharmacology*; D005934:Glucagon / Q000097:blood; D005947:Glucose / Q000096:biosynthesis; D015309:Glucose Clamp Technique; D006706:Homeostasis; D006946:Hyperinsulinism / Q000503:physiopathology*; D007003:Hypoglycemia / Q000139:chemically induced / Q000503:physiopathology*; D007328:Insulin; D007700:Kinetics; D008297:Male; D009638:Norepinephrine / Q000097:blood; D051381:Rats; D017207:Rats, Sprague-Dawley
chemical_list: D001786:Blood Glucose; D007328:Insulin; D005934:Glucagon; D005947:Glucose; D003345:Corticosterone; D009638:Norepinephrine