C-peptide response to a glucose load in young blacks and Indians with insulin-dependent diabetes mellitus.

Residual beta cell function based on C-peptide assays was estimated in 39 patients (27 Blacks, 12 Indians) with insulin-dependent diabetes mellitus and 18 controls (9 Blacks, 9 Indians) using glucose as a stimulus. The diabetic patients showed significantly lower maximal C-peptide values (mean 0,53 +/- 0,08 nmol/l) and delayed peak levels (mean 137 minutes after ingestion of glucose) compared with the controls (mean 2,15 +/- 0,31 nmol/l and 54 minutes respectively). Just over 20% of the patients had no residual beta cell function, this conclusion being made on the basis of undetectable basal C-peptide levels which failed to rise after glucose stimulation. A significant correlation was seen between glycosylated haemoglobin levels and maximal C-peptide levels (r = 0,45, P less than 0,01). C-peptide levels tended to be lower in Black than in Indian patients, but the difference was not significant.