Evaluation of the pancreas reserve in siblings of type I diabetic children

Introduction: The purpose of this study was to determine the pancreas reser ve in siblings of diabetic patients by screening islet cell antibodies (ICA ), insulin auto antibodies (IAA), reduced C-peptide levels, first-phase ins ulin release and the derangement of cellular immunity (reduction of natural killer cells, abnormality of the T cell subpopulations). Methods and Results: Twelve siblings (aged 9.3 +/- 2.8 years) of diabetic c hildren were evaluated and results were compared with the control group (12 .1 +/- 3.5 years). For siblings of the diabetic children, fasting, postpran dial and glucagon response C-peptide mean values were 2.2 +/- 1.2, 7.2 +/- 7.1 and 5.3 +/- 3.6 ng/mL, respectively, while in the control group they we re 1.5 +/- 0.8, 3.6 +/- 2.0 and 5.1 +/- 2.9 ng/mL, respectively. There were no differences between the two groups. In 33%, postprandial C-peptide, and in 11% of the siblings, glucagon response C-peptide values were exaggerate d. In siblings the first phase insulin release (FPIR) during an intravenous glucose tolerance test was 128.5 +/- 96.6 (above the 50th percentile) and stimulated insulin release (SIR) was 103.8 +/- 92.5 (above 25th percentile) . Sibling values were significantly lower than the control group (FPIR 152. 4+/-42.5, P=0.01; SIR 13479+/-38.2, P=0.01). Values for FPIR (in two childr en) and SIR (three cases) were below the 5th percentile. In one, FPIR and S IR levels were both below the Ist percentile. Islet cell antibodies and IAA were also present in this subject. Treatment with nicotinamide was started in the cases with FPIR and SIR below the 5th percentile. We did not observ e overt diabetic symptoms during the follow-up period of more than 3 years. Conclusion: We recommend that borderline insulin secretion be tested annual ly in siblings who show insufficient FPIR.