Estimation of B-cell function by the urinary excretion rate of C-peptide in diabetic patients: comparison with C-peptide response to glucagon and to a mixed meal.

This study examined the relationship between the C-peptide response to intravenous glucagon and mixed meal stimulation and the 24 h urinary excretion rate of C-peptide and its urinary excretion during the glucagon test in nine control subjects, eighteen Type 1 (insulin-dependent) and twenty-two Type 2 (non-insulin-dependent) diabetic patients. Compared to controls (61.0 +/- 7.1 micrograms), the 24-h urine excretion rate of C-peptide was 8.2 +/- 3.1 micrograms (p less than 0.001) in Type 1 and 89.8 +/- 12.9 micrograms (p = NS) in Type 2 diabetic patients. C-peptide urinary excretion rate during the glucagon test was 6.92 +/- 1.11 micrograms, 0.42 +/- 0.10 microgram (p less than 0.001) and 6.47 +/- 1.13 micrograms (p = NS) respectively. Fasting serum C-peptide values were 1.53 +/- 0.16 ng/ml in controls, 0.42 +/- 0.09 ng/ml in Type 1 (p less than 0.0001) and 2.08 +/- 0.22 ng/ml in Type 2 diabetics (p = NS); C-peptide areas under the curve after glucagon stimulation were, respectively, 241.6 +/- 20.3 ng/ml, 29.2 +/- 5.9 ng/ml (p less than 0.0001) and 170.9 +/- 17.9 ng/ml (p less than 0.03) and after the meal test they were 204.7 +/- 15.6, 68.7 +/- 19.8 ng/ml (p less than 0.0001) and 265.5 +/- 32.9 ng/ml (p = NS).(ABSTRACT TRUNCATED AT 250 WORDS)