Residual B-cell function in insulin dependent (Type 1) and non insulin-dependent (Type 2) diabetics (relationship between 24-hour C-peptide excretion and the clinical features of diabetes)

Abstract

Residual B-cell function was studied by measuring 24-hour C-peptide excretion in the urine of 73 Type 1 and 63 Type 2 (28 orally-controlled and 35 insulin-treated) diabetics. Urine C-peptide excretion correlated highly significantly with serum C-peptide concentrations in both the control (r = 0.74, P less than 0.01) and the three diabetic groups (r = 0.89, r = 0.74 and r = 0.89 respectively, P less than 0.001 for all). C-peptide in urine was measurable in 31 of 73 Type 1 diabetics (42%). The earlier the onset and the longer the duration of diabetes, the lower was the proportion of patients with detectable B-cell rest secretion. Preserved residual B-cell function was inversely correlated with the degree of metabolic lability. A significant inverse correlation was also found in this group between 24-hour C-peptide excretion and daily insulin demand (r = 0.78, P less than 0.001). Twenty-nine of the 35 insulin-treated Type 2 diabetics had secondary failure to sulfonylureas and were treated with insulin at the time of the study. Although their daily C-peptide excretion (6.11 +/- 3.71 nmol/24 h) was significantly lower than either the control value (11.30 +/- 0.94 nmol/1, P less than 0.001) or that of orally controlled patients (9.28 +/- 6.16 nmol/l, P less than 0.05) all patients had urine C-peptide concentration in the measurable range. The development of secondary failure to sulfonylureas does not therefore imply complete exhaustion of pancreatic B-cells.(ABSTRACT TRUNCATED AT 250 WORDS)