Effects of age, duration and treatment of insulin-dependent diabetes mellitus on residual beta-cell function: observations during eligibility testing for the Diabetes Control and Complications Trial (DCCT). The DCCT Research Group.

To examine the effects of age and duration and treatment of insulin-dependent diabetes (IDDM) on residual beta-cell function, we measured the fasting and Sustacal-stimulated serum C-peptide levels in 610 conventionally treated IDDM patients (age, 13-39 yr; duration of diabetes, 1-15 yr) during eligibility screening for the Diabetes Control and Complications Trial (DCCT). Fasting and stimulated C-peptide values were closely correlated (r = 0.83; P less than 0.001), and both declined with increasing duration of disease. However, among patients who had been diabetic for more than 5 yr, 11% (33 of 296) of adults compared with 0 of 75 adolescents (P less than 0.001) retained substantial insulin secretory capacity. Patients with stimulated C-peptide levels greater than 0.2 pmol/mL had a significantly lower mean fasting plasma glucose level [177 +/- 6 (+/- SEM) vs. 222 +/- 6 mg/dL; P less than 0.001), a smaller rise in glucose after Sustacal administration (151 +/- 5 vs. 184 +/- 3 mg/dL; P less than 0.001), and lower hemoglobin A1C (8.4 +/- 0.2% vs. 9.3 +/- 0.1%; P less than 0.001) than the patients with a stimulated C-peptide level of 0.05 pmol/mL or less, even though the C-peptide secretors were receiving less insulin (0.52 +/- 0.02 vs. 0.78 +/- 0.02 U/kg X day; P less than 0.001). To determine the effects of treatment of beta-cell function, 33 patients with stimulated C-peptide values between 0.2 and 0.5 pmol/mL at entry in the DCCT were restudied 1 yr after randomization to standard treatment (n = 15) or an experimental (n = 18) treatment designed to achieve and maintain near-normal glucose levels. Although C-peptide levels declined in both groups, experimental treatment was associated with slightly less of a decline in stimulated C-peptide values compared to Standard treatment. The results of C-peptide measurements in this large and well defined population of IDDM patients demonstrate that residual beta-cell function continues for a longer period of time in adults compared to adolescents with IDDM. This endogenous insulin secretion contributes significantly to metabolic control and may be prolonged by intensive insulin treatment regimens.

RCT Entities:   Population Interventions Outcomes