Effects of C-peptide on insulin-induced hypoglycaemia and its counterregulatory responses in IDDM patients

Recent studies indicate that C-peptide, when given to patients with insulin-dependent (Type 1) diabetes mellitus (IDDM), exerts significant effects on microvascular and neuronal functions. Adjuvant therapy with C-peptide has been advocated in the treatment of IDDM patients. Since endogenous insulin secretion is believed to be of importance for the alpha-cell function, we addressed the issue whether C-peptide given acutely interferes with the responses to hypoglycaemia. Seven IDDM patients were randomly exposed to hypoglycaemia with and without exogenous C-peptide. Insulin and and C-peptide were given intravenously in equimolar amounts for 3 hours. The decrease of blood glucose was faster and more pronounced during C-peptide infusion, yielding a significantly lower AUC 0-180 min of blood glucose (38.5 +/- 1.6 vs 44.4 +/- 2.2 mmol l(-1)h(-1); p = 0.032). No difference between the two experiments was found concerning glucagon when the AUC, delta-values or levels at separate points of time were calculated. In conclusion, the main finding of this study was that exogenous C-peptide, given acutely, gave rise to a more rapid onset of hypoglycaemia yielding no detectable differences with respect to the response of glucagon and other counterregulatory hormones.