title: Quantification of the glycemic response to microdoses of subcutaneous glucagon at varying insulin levels.
abstract: OBJECTIVE
  Glucagon delivery in closed-loop control of type 1 diabetes is effective in minimizing hypoglycemia. However, high insulin concentration lowers the hyperglycemic effect of glucagon, and small doses of glucagon in this setting are ineffective. There are no studies clearly defining the relationship between insulin levels, subcutaneous glucagon, and blood glucose.
  
  
  METHODS
  Using a euglycemic clamp technique in 11 subjects with type 1 diabetes, we examined endogenous glucose production (EGP) of glucagon (25, 75, 125, and 175 μg) at three insulin infusion rates (0.016, 0.032, and 0.05 units/kg/h) in a randomized, crossover study. Infused 6,6-dideuterated glucose was measured every 10 min, and EGP was determined using a validated glucoregulatory model. Area under the curve (AUC) for glucose production was the primary outcome, estimated over 60 min.
  
  
  RESULTS
  At low insulin levels, EGP rose proportionately with glucagon dose, from 5 ± 68 to 112 ± 152 mg/kg (P = 0.038 linear trend), whereas at high levels, there was no increase in glucose output (19 ± 53 to 26 ± 38 mg/kg, P = NS). Peak glucagon serum levels and AUC correlated well with dose (r2 = 0.63, P < 0.001), as did insulin levels with insulin infusion rates (r2 = 0.59, P < 0.001).
  
  
  CONCLUSIONS
  EGP increases steeply with glucagon doses between 25 and 175 μg at lower insulin infusion rates. However, high insulin infusion rates prevent these doses of glucagon from significantly increasing glucose output and may reduce glucagon effectiveness in preventing hypoglycemia when used in the artificial pancreas.
authors.affiliation: Oregon Health & Science University, Portland, OR elyoussj@ohsu.edu.
authors.forename: Joseph
authors.initials: J
authors.lastname: El Youssef
authors.affiliation: Oregon Health & Science University, Portland, OR.
authors.forename: Jessica R
authors.initials: JR
authors.lastname: Castle
authors.affiliation: Oregon Health & Science University, Portland, OR.
authors.forename: Parkash A
authors.initials: PA
authors.lastname: Bakhtiani
authors.affiliation: Institut de Recherches Cliniques de Montréal, Montreal, Canada.
authors.forename: Ahmad
authors.initials: A
authors.lastname: Haidar
authors.affiliation: Legacy Health, Portland, OR.
authors.forename: Deborah L
authors.initials: DL
authors.lastname: Branigan
authors.affiliation: Legacy Health, Portland, OR.
authors.forename: Matthew
authors.initials: M
authors.lastname: Breen
authors.affiliation: Oregon Health & Science University, Portland, OR Legacy Health, Portland, OR.
authors.forename: W Kenneth
authors.initials: WK
authors.lastname: Ward
mesh_terms: D000328:Adult; D001786:Blood Glucose / Q000187:drug effects*; D018592:Cross-Over Studies; D003922:Diabetes Mellitus, Type 1 / Q000097:blood / Q000188:drug therapy*; D005260:Female; D005934:Glucagon / Q000008:administration & dosage* / Q000494:pharmacology; D005947:Glucose / Q000378:metabolism; D015309:Glucose Clamp Technique; D006801:Humans; D007003:Hypoglycemia / Q000517:prevention & control; D007328:Insulin / Q000008:administration & dosage / Q000627:therapeutic use*; D008297:Male; D008875:Middle Aged; D019397:Pancreas, Artificial
chemical_list: D001786:Blood Glucose; D007328:Insulin; D005934:Glucagon; D005947:Glucose