Continuous Subcutaneous Insulin Infusion in Adults: Glycemic Advantage is Predicted by Venous Plasma C-Peptide Concentrations

Continuous subcutaneous insulin infusion (CSII) has been compared with conventional insulin injection treatment (CIT) supplemented by self-monitoring of capillary blood glucose (SMBG) in 18 nonobese adults with insulin-dependent diabetes mellitus (IDDM). Mean daily insulin dosage and rates of hypoglycemia were similar during CSII (duration of treatment 36 ± 2 wk mean ± SE) and CIT (31 ± 1.6 wk). On the basis of fasting C-peptide concentrations and postintravenous glucagon increments of < 0.1 pmol/ml, subjects were classified C-peptide negative (CP NEG) (N = 11), or C-peptide positive (CP POS) (N = 7). Relative to CIT, CP NEG subjects on CSII had significant decreases in premeal/bedtime and postmeal plasma glucose concentrations and glycosylated hemoglobin (percent of total). CP POS patients during each of CSII and CIT showed glycemic responses equivalent to those of CP NEG patients on CSII. In neither group could results be explained on the basis of improved beta cell function. Thus, therapeutic advantage of CSII was not apparent in IDDM adults retaining significant C-peptide activity.