Etiopathogenesis of Insulin Autoimmunity

Department of Clinical Sciences, Skåne University Hospital (SUS), Lund University, CRC Ing 72 Building 91:10, 205 02 Malmö, Sweden.
Anatomy research international 02/2012; 2012:457546. DOI: 10.1155/2012/457546
Source: PubMed


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.

13 Reads
  • Source
    [Show abstract] [Hide abstract]
    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.
    Journal of Biological Chemistry 08/2013; 288(40). DOI:10.1074/jbc.M113.478222 · 4.57 Impact Factor
  • [Show abstract] [Hide abstract]
    ABSTRACT: Oxidative stress and inflammatory reactions are known to hold an important role in the etiopathogeny and persistence of acute or chronic clinical entities. Isoprostanes--a group of prostaglandin-like compounds, active products of arachidonic acid--have proved to be representative biomarkers of lipid peroxidation. The aim of this study was to determine the activity of serum 8-iso-prostaglandin F2alpha, (8iPGF2alpha), as an in vivo oxidative stress marker, in paediatric patients with diabetes mellitus type 1 (DM1) and in a control group. The main goals of this study were the following: establishing a possible correlation between the activity of 8iPGF2alpha and the presence of an autoimmune disease associated with DM1 and identifying a possible correlation between 8iPGF2alpha, the value of glycosylated hemoglobin (HbA1c) and the pancreatic autoimmune markers GAD65, IA2, IA in the group of patients with DM1 and other associated autoimmune diseases. Fifty-one children and adolescents (31 males) aged 11.65 +/- 4.1 years with DM1 were enrolled in the study. Twenty-seven healthy children, age- and gender-matched, were enrolled as controls. Patients and controls underwent the 8iPGFzalpha assessment through an ELISA serum method. The mean 8iPGF2alpha value was 2090.6 +/- 3536.5 in the DM1 patient group and 509.9 +/- 493.5 in controls (p = 0.03). The mean 8iPGF2alpha value was 2178.19 +/- 4017.05 in patients with DM1 who did not suffer from other associated autoimmune diseases (n = 38) vs. 1834.95 +/- 1504.73 in patients with DM1 and other associated autoimmune diseases (n = 13) (p = 0.76). The correlation between the 8iPGF2alpha and the HbA1c values was determined by obtaining a correlation coefficient r = 0.38 and p = 0.0057. No correlation was observed between GAD65 and 8iPGF2alpha (r = 0.3; p = 0.29), IA2 and 8iPGF2alpha (r = -0.02; p = 0.92), IAA and 8iPGF2alpha (r = 0.4; p = 0.12). Oxidative stress reactions are more intense in patients with diabetes mellitus type 1 than in healthy patients. Similar results were obtained in patients associating other autoimmune diseases. 8iPGF2alpha can be an ideal marker for determining oxidative reactions in vivo.
    Clinical laboratory 02/2014; 60(2):253-9. DOI:10.7754/Clin.Lab.2013.121141 · 1.13 Impact Factor
  • Source
    [Show abstract] [Hide abstract]
    ABSTRACT: Variant specific zinc transporter 8 autoantibodies (ZnT8A) against either arginine (R) or tryptophan (W) at amino acid (aa) position 325 of the zinc transporter 8 (ZnT8) has been identified in T1D patients. Reciprocal cross-over tests revealed differences in half-maximal binding to indicate variable affinity of patient ZnT8 autoantibodies. Insufficient recombinant ZnT8 variant proteins have precluded detailed analyses of ZnT8 autoantibody affinity. The aims in the present study were to 1) generate recombinant ZnT8R- and ZnT8W-aa275-369 proteins 2) test the ZnT8R- and ZnT8W-aa275-369 proteins in reciprocal competitive radiobinding assays (RBA) against ZnT8R- and ZnT8W-aa268-369 labeled with 35S-methionine, and 3) determine the specificity and affinity of sera specific for either ZnT8 Arginine (R) or ZnT8 Tryptophan (W) autoantibodies in newly diagnosed type 1 diabetes (T1D) patients. The results demonstrate first that it was possible to produce recombinant human MBP-ZnT8aa275-369 protein purified to homogeneity for RBA reciprocal competition experiments. Second, high titer ZnT8WA sera diluted to half maximal binding showed significant specificity for respective variants of either ZnT8R or ZnT8W. Third, ZnT8WA positive sera showed high affinity for ZnT8W compared to ZnT8RA for ZnT8R. These data demonstrate that T1D patients may have single amino acid specific autoantibodies directed against either ZnT8R or ZnT8W and that the autoantibody affinity to the respective variant may be different. Further studies are needed to assess the mechanisms by which variant specific ZnT8A of variable affinity develop and their possible role in the pathogenic process leading to the clinical onset of T1D.
    Clinical & Experimental Immunology 09/2014; 179(2). DOI:10.1111/cei.12448 · 3.04 Impact Factor

Similar Publications