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- Kanatsuna, Norio, et al.
(author)
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Autoimmunity against INS-IGF2 expressed in human pancreatic islets.
- 2013
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In: Journal of Biological Chemistry. - 1083-351X. ; 288:40, s. 29013-29023
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Journal article (peer-reviewed)abstract
- Insulin is a major autoantigen in islet autoimmunity and progression to type 1 diabetes. It has been suggested that the insulin B-chain may be critical to insulin autoimmunity in type 1 diabetes. INS-IGF2 consists of the preproinsulin signal peptide, the insulin B-chain and eight amino acids of the C-peptide in addition to 138 amino acids from the IGF2 gene. We aimed to determine 1) expression of INS-IGF2 in human pancreatic islets and 2) autoantibodies in newly diagnosed type 1 diabetes children and controls. INS-IGF2, expressed primarily in beta cells, showed higher levels of expression in islets from normal compared to donors with either type 2 diabetes (p=0.006) or high HbA1c levels (p<0.001). INS-IGF2 autoantibody levels were increased in newly diagnosed type 1 diabetes patients (n=304) compared to healthy controls (n=355; p<0.001). Displacement with cold insulin and INS-IGF2 revealed that more patients than controls had doubly reactive insulin-INS-IGF2 autoantibodies. These data suggest that INS-IGF2, which contains the preproinsulin signal peptide, the B-chain and eight amino acids of the C-peptide may be an autoantigen in type 1 diabetes. INS-IGF2 and insulin may share autoantibody binding sites, thus complicating the notion that insulin is the primary autoantigen in type 1 diabetes.
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2. |
- Kanatsuna, Norio, et al.
(author)
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Doubly reactive INS-IGF2 autoantibodies in children with newly diagnosed autoimmune (type 1) diabetes.
- 2015
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In: Scandinavian Journal of Immunology. - : Wiley. - 1365-3083 .- 0300-9475. ; 82:4, s. 361-369
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Journal article (peer-reviewed)abstract
- The splice variant INS-IGF2 entails the preproinsulin signal peptide, the insulin B-chain, eight amino acids of the C-peptide and 138 unique amino acids from an ORF in the IGF2 gene. The aim was to determine whether levels of specific INS-IGF2 autoantibodies (INS-IGF2A) were related to age at diagnosis, islet autoantibodies, HLA-DQ, or both, in newly diagnosed type 1 diabetes patients and controls. Patients (n=676), 0-18 years of age, diagnosed with type 1 diabetes in 1996-2005 and controls (n=363) were analyzed for specific INS-IGF2A after displacement with both cold insulin and INS-IGF2 to correct for non-specific binding and identify double reactive sera. GADA, IA-2A, IAA, ICA, ZnT8RA, ZnT8WA, and ZnT8QA, and HLA-DQ genotypes were also determined. The median level of specific INS-IGF2A was higher in patients than controls (p<0.001). Irrespective of age at diagnosis, 19 % (126/676) of the patients had INS-IGF2A when the cut-off was the 95th percentile of the controls (p<0.001). The risk of INS-IGF2A was increased among HLA-DQ2/8 (OR=1.509; 95th CI 1.011, 2.252; p=0.045) but not in 2/2, 2/X, 8/8, 8/X or X/X (X is neither 2 nor 8) patients. The association with HLA-DQ2/8 suggests that this autoantigen may be presented on HLA-DQ trans, rather than cis heterodimers. Autoantibodies reactive with both insulin and INS-IGF2A at diagnosis support the notion that INS-IGF2 autoimmunity contributes to type 1 diabetes. This article is protected by copyright. All rights reserved.
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3. |
- Kanatsuna, Norio, et al.
(author)
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Etiopathogenesis of insulin autoimmunity.
- 2012
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In: Anatomy Research International. - : Hindawi Limited. - 2090-2751 .- 2090-2743. ; 2012
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Journal article (peer-reviewed)abstract
- Autoimmunity against pancreatic islet beta cells is strongly associated with proinsulin, insulin, or both. The insulin autoreactivity is particularly pronounced in children with young age at onset of type 1 diabetes. Possible mechanisms for (pro)insulin autoimmunity may involve beta-cell destruction resulting in proinsulin peptide presentation on HLA-DR-DQ Class II molecules in pancreatic draining lymphnodes. Recent data on proinsulin peptide binding to type 1 diabetes-associated HLA-DQ2 and -DQ8 is reviewed and illustrated by molecular modeling. The importance of the cellular immune reaction involving cytotoxic CD8-positive T cells to kill beta cells through Class I MHC is discussed along with speculations of the possible role of B lymphocytes in presenting the proinsulin autoantigen over and over again through insulin-carrying insulin autoantibodies. In contrast to autoantibodies against other islet autoantigens such as GAD65, IA-2, and ZnT8 transporters, it has not been possible yet to standardize the insulin autoantibody test. As islet autoantibodies predict type 1 diabetes, it is imperative to clarify the mechanisms of insulin autoimmunity.
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