title: Influence of exogenous insulin on C-peptide levels in subjects with type 2 diabetes.
abstract: OBJECTIVE
  The aim of this study was to determine whether the influence of insulin therapy on fasting and stimulated C-peptide levels in type 2 diabetic subjects is due to plasma glucose reduction or a direct effect of exogenous insulin.
  
  
  METHODS
  Plasma glucose and serum C-peptide levels were determined before and after IV injection of 1mg glucagon on three separate days in 21 type 2 diabetic subjects. Day 1: without pharmacological treatment and fasting plasma glucose > 11.1 mmol/L; day 2: fasting plasma glucose 4.4-7.8 mmol/L, 1h after withdrawing intravenous regular insulin infusion; day 3: fasting plasma glucose 4.4-7.8 mmol/L with bed-time NPH insulin.
  
  
  RESULTS
  Fasting and glucagon stimulated C-peptide levels were higher on day 1 than days 2 and 3. Fasting, but not stimulated C-peptide levels, were lower on day 3 than day 2. These differences were not appeared when the percentage of C-peptide increment or the C-peptide/glucose ratio were compared in the three days.
  
  
  CONCLUSIONS
  Blood glucose reduction instead of exogenous insulin is responsible for the C-peptide decrease during insulin therapy in type 2 diabetic subjects.
authors.affiliation: Department of Endocrinology, Hospital Sant Pau, UAB, Sant Antonio Ma Claret, 167, 08025 Barcelona, Spain.
authors.forename: M
authors.initials: M
authors.lastname: Albareda
authors.forename: M
authors.initials: M
authors.lastname: Rigla
authors.forename: J
authors.initials: J
authors.lastname: Rodríguez-Espinosa
authors.forename: A
authors.initials: A
authors.lastname: Caballero
authors.forename: A
authors.initials: A
authors.lastname: Chico
authors.forename: R
authors.initials: R
authors.lastname: Cabezas
authors.forename: G
authors.initials: G
authors.lastname: Carreras
authors.forename: A
authors.initials: A
authors.lastname: Pérez
mesh_terms: D000368:Aged; D001786:Blood Glucose / Q000378:metabolism; D002096:C-Peptide / Q000097:blood*; D003924:Diabetes Mellitus, Type 2 / Q000097:blood* / Q000188:drug therapy*; D005215:Fasting / Q000097:blood; D005260:Female; D005934:Glucagon / Q000494:pharmacology; D006801:Humans; D007004:Hypoglycemic Agents / Q000627:therapeutic use*; D007328:Insulin / Q000627:therapeutic use*; D008297:Male; D008875:Middle Aged
chemical_list: D001786:Blood Glucose; D002096:C-Peptide; D007004:Hypoglycemic Agents; D007328:Insulin; D005934:Glucagon