Hypotheses:~Primary: Prophylactic administration of metabolically active insulin can prevent or delay clinical onset of diabetes in a high risk group of nondiabetic siblings as defined by positivity for autoantibodies against IA-2 (IA-2-A).~Secondary: 1) Untreated siblings with positivity for IA-2-A develop clinical diabetes significantly faster than untreated offspring with the same marker positivity. 2) Plasma proinsulin levels increase disproportionately before clinical onset of Type 1 diabetes both in siblings and offspring. 3) Prophylactic administration of metabolically active insulin reduces the plasma proinsulin/C-peptide ratio in non-diabetic antibody positive siblings and offspring. 4) Prophylactic administration of metabolically active insulin reduces the presence and/or levels of diabetes-associated autoantibodies directed against islet cell components.~Endpoints: Fasting glycemia; fasting and stimulated plasma C-peptide and proinsulin values; islet cell autoantibodies; incidence of hypoglycemia; body weight gain.
Prophylactic administration of metabolically active insulin can prevent or delay clinical onset of diabetes in a high risk group of nondiabetic siblings as defined by positivity for autoantibodies against IA-2 (IA-2-A).