Insulin antibodies in diabetic children before treatment: A marker for islet B-cell destruction?

Insulin antibodies were measured in the sera of 28 newly diagnosed diabetic children (age 8.0 ± 4.0 (±SD) years) prior to insulin therapy and after 3, 6, 9, and 12 months. The levels at diagnosis and after 12 months were compared to endogenous insulin production at onset and after 12 to 14 months. Endogenous insulin production was evaluated through the measurement of 24-h urinary C-peptide excretion, fasting plasma C-peptide levels and plasma C-peptide levels after glucagon stimulation. Insulin antibodies were detected in 29% of the patients (8 out of 28). In all but one patient antibodies binding porcine and human insulin were detected. No relationship was found between the presence of antibodies binding human or porcine insulin at diagnosis and age. After 1 year 27 out of 28 patients presented insulin antibodies. No relationship was found between the presence of insulin antibodies before therapy and 1 year after therapy. Insulin antibodies prior to diagnosis showed no relationship with the urinary C-peptide excretion at diagnosis (with antibodies 67 ± 27%, without antibodies 76 ± 11%). However, after 1 year significantly lower urinary C-peptide excretions were found in patients with insulin antibodies prior to therapy (with antibodies, 17 ± 7%, without antibodies, 31 ± 5%, p < 0.02). Peak plasma C-peptide levels after 1 year were possibly lower in patients with insulin antibodies before treatment (with antibodies 0.17 ± 0.06 nmol/l, without antibodies 0.26 ± 0.04 nmol/l, p < 0.1). Fasting C-peptide levels did not differ significantly between the two groups after 1 year of therapy (with antibodies 0.11 ± 0.03 nmol/l, without antibodies 0.14 ± 0.02 nmol/l). Thus, insulin auto-antibodies may be a marker for islet B-cell destruction in Type 1 diabetes.