Factors influencing the magnitude, duration, and rate of fall of B-cell function in Type 1 (insulin-dependent) diabetic children followed for two years from their clinical diagnosis

The pattern of fall in B-cell function measured as plasma and 24 h urinary C-peptide excretion, as well as levels of islet cell antibodies, insulin antibodies and metabolic parameters, were followed for two years in 39 children aged 1–17 years prospectively from clinical onset of Type 1 (insulin-dependent) diabetes. At onset 32/36 patients had measurable plasma C-peptide (median 0.13 nmol/l). Maximum values of fasting and postprandial plasma C-peptide were reached at a median duration of three months. Thereafter both plasma and urinary C-peptide declined linearly. The median value of the rate of fall in postprandial plasma C-peptide was 0.019 nmol·1−1·month−1. Age at onset was positively correlated to the maximum value of postprandial plasma C-peptide in each patient (rs=0.57, p=0.0001) and throughout the observation time positively correlated to fasting and postprandial C-peptide and to the 24 h urinary C-peptide excretion (rsrange 0.35–0.70, p=0.03–0.0001). The rate of fall of postprandial C-peptide was unrelated to age at onset and was strikingly parallel in different age groups. Islet cell antibodies were present in 87% of the patients at onset and decreased to 38% at 24 months. Islet cell antibody litres were not correlated to age at onset or to plasma or urinary C-peptide at any single observation. However, islet cell antibody negative patients had significantly higher (p<0.05) postprandial plasma C-peptide values at 1, 9, and 12 months of duration, compared to islet cell antibody positive patients. Insulin antibodies and metabolic state at onset did not influence the C-peptide values. It is concluded that age at onset is the most important variable in predicting the duration and magnitude of endogenous insulin secretion during the first two years of Type 1 diabetes in children.