Gene/Protein Disease Symptom Drug Enzyme Compound
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Query: UMLS:C0011854 (type 1 diabetes)
 20,749 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

GAD is a major islet cell autoantigen in human type 1 diabetes mellitus. Autoantibodies are preferentially directed against the 65-kD isoform of the enzyme which is the only form expressed in human islets of Langerhans. The NOD mouse is a spontaneous model of type 1 diabetes, frequently employed in studies dealing with the immunopathogenesis of the disease. In the present study the reactivity of sera from 34 prediabetic and 15 diabetic NOD mice was tested against GAD protein present in islets of Langerhans and cerebellum, and against recombinant, semi-purified GAD-65 and GAD-67. A rabbit antiserum (K2) raised against GAD-67 could readily recognize the recombinant GAD-67 and the isoform present in rat and mouse islets and mouse brain. A MoAb (GAD-6) specific for the GAD-65 isoform reacted against the recombinant GAD-65 and the isoform present in rat islets and mouse brain, whereas no reactivity was observed when using mouse islets. However, when testing the NOD mice sera by immunohistochemistry, immunoprecipitation and Western blot, no reactivity against any of the isoforms of GAD could be detected. Using reverse transcription polymerase chain reaction (PCR), GAD-67 mRNA could be detected in mouse and rat islets and in mouse brain. GAD-65 mRNA could also be detected in rat islets and mouse brain, but apparently a much lower copy number is present in mouse islets. These findings stress important differences in the immune response occurring in the animal model NOD mouse compared with human type 1 diabetes, and emphasize that human and animal type 1 diabetes possibly represent the final outcome of several different etiological factors.
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PMID:Absence of autoantibodies against glutamate decarboxylase (GAD) in the non-obese diabetic (NOD) mouse and low expression of the enzyme in mouse islets. 814 57

To clarify whether GAD-ab are associated with diabetic autonomic neuropathy and/or complement fixing antibodies against sympathetic ganglia, adrenal medulla, and vagus nerve, we examined 133 diabetic patients (95 with IDDM). GAD-ab were determined by a radioligand binding assay using in vitro expression of recombinant GAD-65 whereas sympathetic ganglia antibodies, adrenal medulla antibodies, vagus nerve, and ICA were evaluated by indirect immunofluorescence assays. Autonomic nerve function was evaluated by objective tests (heart rate reactions to deep breathing and to tilt). In the total material of 133 patients, GAD-ab were detected in 36 patients, all of whom had IDDM. The frequency of GAD-ab was similar (38%) in IDDM patients with and without signs of autonomic neuropathy (21 of 55 vs 15 of 40). In addition, there were no significant associations between GAD-ab and autonomic nerve antibodies; GAD-ab were detected in 9 of 21 (43%) of patients with and in 27 of 112 (24%) of patients without sympathetic ganglia antibodies, in 5 of 15 (33%) of patients with and 31 of 118 (26%) without adrenal medulla antibodies, and in 5 of 15 (33%) with and 31 of 118 (26%) of patients without vagus nerve antibodies. The frequency of ICA, however, was significantly increased in patients with sympathetic ganglia antibodies compared with those without sympathetic ganglia antibodies (10 of 21 [48%] vs 21 of 112 [19%]; p < 0.01). In conclusion, GAD-ab were neither associated with disturbed autonomic nerve function nor with antibodies against autonomic nerve structures.
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PMID:Glutamic acid decarboxylase antibodies, autonomic nerve antibodies and autonomic neuropathy in diabetic patients. 817 44

The effects of plasmapheresis on islet autoantibody levels, C-peptide (beta-cell function), and hemoglobin-A1c (HbA1c, metabolic control) were tested in a prospective blinded study of 18 newly diagnosed insulin-dependent diabetes mellitus (IDDM) patients randomly assigned to receive plasmapheresis (P), carried out as double filtration, or sham (S) treatment at diagnosis and 3 months thereafter. At diagnosis, 6 of 8 patients (75%) in group P and 9 of 10 patients (90%) in group S had islet cell antibodies (ICA), whereas 4 of 8 (50%) and 7 of 10 (70%) patients, respectively, had glutamic acid decarboxylase antibodies (GAD65-Ab), with no significant differences between the groups in ICA and GAD65-Ab levels. After 6 months, P patients showed significantly lower ICA levels than S patients (11 +/- 6 and 128 +/- 47 Juvenile Diabetes Foundation International Units, respectively; P < 0.02) due to an increase in ICA levels in 8 of 9 (88%) of the S patients not seen in P patients (P < 0.002). Concurrently, HbA1c stabilized in P, but not in S, patients and was significantly lower by 24 months (6.58 +/- 0.54% vs. 9.76 +/- 1.21%; P < 0.05). Moreover, fasting C-peptide increased significantly (214 +/- 11 pmol/L; P < 0.05) over the first 6 months in P. After the initial 6 months, ICA levels tended to decrease in all patients and were not detected after 60 months. GAD65-Ab levels were not influenced by plasmapheresis and, also in contrast to ICA, increased significantly (P < 0.05) in the whole study population after 60 months. In fact, 4 initially negative patients became GAD65-Ab positive after diagnosis (in 2 patients > 24 months after diagnosis). We conclude that plasmapheresis of newly diagnosed IDDM patients does not change subsequent GAD65-Ab levels, but ICA are significantly decreased with associated improved C-peptide and HbA1c levels.
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PMID:Islet cell antibodies, but not glutamic acid decarboxylase antibodies, are decreased by plasmapheresis in patients with newly diagnosed insulin-dependent diabetes mellitus. 817 73

Knowing the autoantigen target(s) in an organ-specific autoimmune disease is essential to understanding its pathogenesis. Insulin-dependent diabetes mellitus (IDDM) is an autoimmune disease characterized by lymphocytic infiltration of the islets of Langerhans (insulitis) and destruction of insulin-secreting pancreatic beta-cells. Several beta-cell proteins have been identified as autoantigens, but their importance in the diabetogenic process is not known. The non-obese diabetic (NOD) mouse is a murine model for spontaneous IDDM. Here we determine the temporal sequence of T-cell and antibody responses in NOD mice to a panel of five murine beta-cell antigens and find that antibody and T-cell responses specific for the two isoforms of glutamic acid decarboxylase (GAD) are first detected in 4-week-old NOD mice. This GAD-specific reactivity coincides with the earliest detectable response to an islet extract, and with the onset of insulitis. Furthermore, NOD mice receiving intrathymic injections of GAD65 exhibit markedly reduced T-cell proliferative responses to GAD and to the rest of the panel, in addition to remaining free of diabetes. These results indicate that the spontaneous response to beta-cell antigens arises very early in life and that the anti-GAD immune response has a critical role in the disease process during this period.
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PMID:Immune response to glutamic acid decarboxylase correlates with insulitis in non-obese diabetic mice. 823 29

Patients with insulin-dependent diabetes (IDDM) possess antibodies to islet proteins of M(r)-64,000. Potential autoantigens of this M(r) include glutamate decarboxylase (GAD) and 65 kD heat shock protein. We have detected two distinct antibody specificities in IDDM that bind 50,000 M(r) or 37,000/40,000 M(r) proteolytic fragments of 64,000 M(r) proteins. In this study, we investigated relationships of these proteolytic fragments to GAD and heat shock proteins. Polyclonal antibodies to GAD bound 50,000 M(r) fragments of islet antigen. Recombinant GAD65, but not GAD67, blocked binding to this antigen, suggesting that 50,000 M(r) fragments are derived from islet GAD65. In contrast, GAD antibodies did not recognize 37,000/40,000 M(r) fragments, and neither GAD isoforms blocked autoantibody binding to precursors of these fragments. The 37,000/40,000 M(r) fragments, but not the 50,000 M(r) fragments, were detected after trypsin treatment of immunoprecipitates from insulinoma cells that lacked expression of major GAD isoforms. Antibodies in IDDM did not bind native or trypsinized islet heat shock proteins. Thus, IDDM patients possess antibodies to GAD, but also distinct antibodies to a 64,000 M(r) protein that is not related to known GAD isoforms or heat shock proteins.
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PMID:Detection of pancreatic islet 64,000 M(r) autoantigens in insulin-dependent diabetes distinct from glutamate decarboxylase. 832 89

Cytoplasmic islet cell antibodies are well-established predictive markers of IDDM. Although target molecules of ICA have been suggested to be gangliosides, human monoclonal ICA of the immunoglobulin G class (MICA 1-6) produced from a patient with newly diagnosed IDDM recognized glutamate decarboxylase as a target antigen. Here we analyzed the possible heterogeneity of target antigens of ICA by subtracting the GAD-specific ICA staining from total ICA staining of sera. This was achieved 1) by preabsorption of ICA+ sera with recombinant GAD65 and/or GAD67 expressed in a baculovirus system and 2) by ICA analysis of sera on mouse pancreas, as GAD antibodies do not stain mouse islets in the immunofluorescence test. We show that 24 of 25 sera from newly diagnosed patients with IDDM recognize islet antigens besides GAD. In contrast, GAD was the only islet antigen recognized by ICA from 7 sera from patients with stiff man syndrome. Two of these sera, however, recognized antigens besides GAD in Purkinje cells. In patients with IDDM, non-GAD ICA were diverse. One group, found in 64% of the sera, stained human and mouse islets, whereas the other group of non-GAD ICA was human specific. Therefore, mouse islets distinguish two groups of non-GAD ICA and lack additional target epitopes of ICA besides GAD. Longitudinal analysis of 6 sera from nondiabetic ICA+ individuals revealed that mouse-reactive ICA may appear closer to clinical onset of IDDM in some individuals. Mouse-reactive ICAs, however, remained absent in 36% of the patients at diagnosis of IDDM.
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PMID:Cytoplasmic islet cell antibodies recognize distinct islet antigens in IDDM but not in stiff man syndrome. 840 7

At and before onset, most insulin-dependent diabetics (IDDM) have islet GAD65 autoantibodies (GAD65Ab). Since IDDM also occurs in older patients where non-insulin-dependent diabetes is common, we studied GAD65Ab at onset to classify diabetes type. Our quantitative immunoprecipitation assay uses recombinant human islet GAD65 stably expressed in hamster fibroblasts. Electrophoretic mobility was identical to native islet GAD65. Like native antigen, recombinant GAD65 migrated as two bands during electrophoresis, but converted to one under stronger reduction. Immunoprecipitation was linear with respect to antibody or antigen concentration. In 120 population-based diabetic patients of all ages grouped by treatment at onset and after 18 mo, GAD65Ab were present in 70% on insulin (n = 37), 10% on oral agent (n = 62, P < 0.0001), 69% changing from oral agent to insulin (n = 16, P < 0.001), and 1 of 33 controls. 65% with GAD65Ab, versus 8% without, changed from oral agent to insulin (P < 0.01). The GAD65Ab quantitative index was remarkably stable, and only 2 of 32 patients changed antibody status during follow-up. Concordance between GAD65Ab and islet cell antibodies was 93%. Quantitative correlation was approximate but significant. This highly sensitive, quantitative, high capacity assay for GAD65Ab reveals treatment requirements better than clinical criteria, perhaps guiding immunomodulatory therapy.
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PMID:Quantitative assay using recombinant human islet glutamic acid decarboxylase (GAD65) shows that 64K autoantibody positivity at onset predicts diabetes type. 842 32

Glutamic acid decarboxylase autoantibodies may aid in rapid screening strategies predicting IDDM before clinical onset. Rat islets contain GAD65 and GAD67 autoantibody targets, but human islets express only GAD65, now confirmed by direct immunoprecipitation from radiolabeled rat and human islets. Because human IDDM involves beta-cell-specific autoimmunity, we tested 190 new IDDM patients and 51 healthy control subjects for antibodies to recombinant human islet GAD65, rat islet GAD67, or human insulinoma/cerebellum GAD67, each expressed separately in hamster fibroblasts. By using immunoprecipitation, sodium dodecyl sulfate-polyacrylamide gel electrophoresis, and densitometric fluorogram scanning, 132 of 190 (70%) of new IDDM patients had GAD65 autoantibodies, whereas only 17 of 190 (9%) had antibodies to rat GAD67 (P < 0.001). Of healthy control subjects, 2 of 51 (3.9%) and 1 of 51 (1.9%) had antibodies to GAD65 and GAD67, respectively. All 17 GAD67 antibody-positive patients also had GAD65 antibodies; 14 of 17 with greater GAD65 than GAD67 index. Control studies showed comparable reactivity between recombinant rat and human GAD67 and between different subcellular preparations of recombinant GAD67 of either species. In conclusion, only GAD65 is expressed in human islets, the autoantibody response is primarily to this isoform, and GAD67 antibodies add little to IDDM detection.
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PMID:Autoantibodies in IDDM primarily recognize the 65,000-M(r) rather than the 67,000-M(r) isoform of glutamic acid decarboxylase. 845 15

Plasmids containing cDNA for the rat 67- and 65-kD isoforms of glutamate decarboxylase (GAD-67 and GAD-65) were expressed in COS-cells, and lysates of [35S]methionine-labeled cells were used for immunoprecipitations. Sera from 38 patients with type 1 (insulin-dependent) diabetes mellitus, which precipitated a 64-kD antigen from rat islets, reacted with recombinant GAD-65 in relation to their anti-64-kD titers. The eight strongest sera also precipitated recombinant GAD-67, suggesting that certain epitopes are common to both isoforms. Subsequently, [35S]methionine-labeled GAD-65 was purified from COS cell lysates and employed in a binding assay with 50 sera of patients with recent onset of type 1 diabetes mellitus. 38 sera (76%) precipitated labeled GAD-65 with titers that correlated with islet cell antibodies (ICA), determined in a standard immunofluorescence assay. 2 sera were GAD positive but ICA negative, 4 were positive only for ICA, and 6 were negative for both GAD and ICA, as were the sera of 20 controls. The data illustrate that antibodies against GAD-65 are present in a majority of patients with type 1 diabetes mellitus and that autoantibodies against other islet cell antigens also exist. The radioligand-binding assay, which is convenient and sensitive for detecting GAD antibodies, will facilitate the screening of individuals with autoimmune islet cell disease.
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PMID:Demonstration of GAD-65 as the main immunogenic isoform of glutamate decarboxylase in type 1 diabetes and determination of autoantibodies using a radioligand produced by eukaryotic expression. 848 75

Glutamic acid decarboxylase (GAD) catalyzes formation of gamma-aminobutyric acid from glutamic acid and is a major autoantigen in insulin-dependent diabetes mellitus. Its two isoforms, GAD65 and GAD67, are encoded by two separate genes. We prepared human islet cDNA library and screened it with cDNA probes of rat brain GAD67. We cloned the cDNA for GAD67, the large isoform of glutamic acid decarboxylase, and determined its nucleotide sequence. Sequencing of the resulting clone identified a 1,785 residue open-reading frame encoded a 594 amino acid polypeptide that showed a 99.4% similarity with GAD67 from human brain. The bacterially expressed human islet GAD67 protein was enzymatically active and immunoreactive. The isolation of cDNA for this additional islet GAD isoforms will be important in studying the etiology and pathogenesis of IDDM.
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PMID:Cloning and expression of large isoform of glutamic acid decarboxylase from human pancreatic islet. 850 3


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