title: Glycemic thresholds for activation of counterregulatory hormone and symptom responses in islet transplant recipients.
abstract: BACKGROUND
  In patients with type 1 diabetes and reduced awareness of hypoglycemia, the glycemic thresholds for activation of counterregulatory hormone and symptom responses to hypoglycemia are impaired, in part due to recurrent episodes of hypoglycemia. Islet transplantation can ameliorate occurrences of hypoglycemia in these patients.
  
  
  OBJECTIVE
  The objective of the study was to determine whether the avoidance of hypoglycemia achieved through islet transplantation results in improved glycemic thresholds for counterregulatory responses.
  
  
  METHODS
  The study was conducted at a general clinical research center.
  
  
  METHODS
  Seven islet transplant recipients, six type 1 diabetic, and eight nondiabetic control subjects participated in the study.
  
  
  METHODS
  We performed a stepped hyperinsulinemic hypoglycemic clamp and, in 12 subjects, a paired hyperinsulinemic euglycemic clamp to calculate the glycemic thresholds for and magnitude of counterregulatory responses.
  
  
  RESULTS
  The glycemic thresholds for all counterregulatory hormone and symptom responses in the islet transplant group were comparable with normal and higher than in the type 1 diabetes group (P < 0.01 for glucagon; P < 0.05 for epinephrine). The magnitude of the glucagon and epinephrine responses in the islet transplant group, although greater than in the type 1 diabetes group (P < 0.05 for both), remained less than normal (P < 0.01 for glucagon; P < 0.05 for epinephrine). The magnitude of GH secretion in the islet transplant group was comparable with normal and greater than in the type 1 diabetes group (P < 0.05).
  
  
  CONCLUSIONS
  The glycemic thresholds for activation of counterregulatory hormone and symptom responses appear normal after islet transplantation; however, the magnitudes of the glucagon and epinephrine responses remain impaired.
authors.affiliation: University of Pennsylvania School of Medicine, Division of Endocrinology, Diabetes, and Metabolism, 778 Clinical Research Building, 415 Curie Boulevard, Philadelphia, Pennsylvania 19104-6149, USA. rickels@mail.med.upenn.edu
authors.forename: Michael R
authors.initials: MR
authors.lastname: Rickels
authors.forename: Mark H
authors.initials: MH
authors.lastname: Schutta
authors.forename: Rebecca
authors.initials: R
authors.lastname: Mueller
authors.forename: Shiv
authors.initials: S
authors.lastname: Kapoor
authors.forename: James F
authors.initials: JF
authors.lastname: Markmann
authors.forename: Ali
authors.initials: A
authors.lastname: Naji
authors.forename: Karen L
authors.initials: KL
authors.lastname: Teff
mesh_terms: D000328:Adult; D001786:Blood Glucose / Q000502:physiology*; D003922:Diabetes Mellitus, Type 1 / Q000097:blood / Q000628:therapy*; D004837:Epinephrine / Q000097:blood; D005260:Female; D005934:Glucagon / Q000097:blood*; D015309:Glucose Clamp Technique; D019382:Human Growth Hormone / Q000097:blood; D006801:Humans; D007003:Hypoglycemia / Q000097:blood; D007328:Insulin / Q000097:blood; D016381:Islets of Langerhans Transplantation; D008297:Male; D008875:Middle Aged; D014180:Transplantation
chemical_list: D001786:Blood Glucose; D007328:Insulin; D019382:Human Growth Hormone; D005934:Glucagon; D004837:Epinephrine