Insulin Administration May Trigger Type 1 Diabetes in Japanese Type 2 Diabetes Patients With Type 1 Diabetes High-Risk HLA Class II and the Insulin Gene VNTR Genotype

Context: Insulin administration causes various types of immune responses to insulin. We previously reported three cases of type 1 diabetes mellitus (T1DM) triggered by insulin administration in Japanese type 2 diabetes mellitus patients. Objective: The objective of this study was to collect information and characterize insulin-triggered T1DM immunologically and genetically. Methods: Data for six patients (four men and two women) with insulin-triggered T1DM aged 59.5 ± 12.8 years were collected. Serum or urinary C-peptides, islet-related autoantibodies, insulin antibody, human leukocyte antigen, or the insulin gene variable number of tandem repeat genotype were analyzed. Th1- or Th2-associated responses were evaluated using an Enzyme-Linked ImmunoSpot assay. Results: None of the subjects had received insulin therapy or had an autoantibody to the 65-kDa isoform of glutamic acid decarboxylase before insulin administration. After insulin administration blood glucose control deteriorated acutely without any apparent cause, whereas C-peptide levels rapidly decreased to insulin-deficient levels. The mean duration of insulin administration to the development of T1DM was 7.7 ± 6.1 months. Islet-related autoantibodies became positive, whereas insulin allergy or a high titer of insulin antibody was observed in several cases. All had T1DM high-risk human leukocyte antigen class II (IDDM1) and the insulin gene variable number of tandem repeats genotype (IDDM2). GAD-reactive and insulin peptide-reactive Th1 cells, but not Th2 cells, were identified in two of four cases. Conclusions: The findings suggest that insulin administration may have triggered TIDM in patients with type 2 diabetes mellitus. IDDM1 and IDDM 2 as well as autoreactive T cells may contribute to the development of T1DM. Developing insulin-triggered T1DM if a patient's blood glucose control acutely deteriorates after insulin administration should be carefully considered.