Influence of exogenous insulin on C-peptide levels in subjects with type 2 diabetes.
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.
Albareda
M
M
Department of Endocrinology, Hospital Sant Pau, UAB, Sant Antonio Ma Claret, 167, 08025 Barcelona, Spain.
Rigla
M
M
Rodríguez-Espinosa
J
J
Caballero
A
A
Chico
A
A
Cabezas
R
R
Carreras
G
G
Pérez
A
A
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
D001786:Blood Glucose; D002096:C-Peptide; D007004:Hypoglycemic Agents; D007328:Insulin; D005934:Glucagon