β-Cell Function and the Development of Diabetes-Related Complications in the Diabetes Control and Complications Trial

In patients with type 1 diabetes, measurement of connecting peptide (C-peptide), cosecreted with insulin from the islets of Langerhans, permits estimation of remaining beta-cell secretion of insulin. In this retrospective analysis to distinguish the incremental benefits of residual beta-cell activity in type 1 diabetes, stimulated (90 min following ingestion of a mixed meal) C-peptide levels at entry in the Diabetes Control and Complications Trial (DCCT) were related to measures of diabetic retinopathy and nephropathy and to incidents of severe hypoglycemia. Based on the analytical sensitivity of the assay (0.03 nmol/l) and study entry criteria, the DCCT subjects were divided into four groups of stimulated…