UMLS:C0011849 - FACTA Search

Gene/Protein Disease Symptom Drug Enzyme Compound
Pivot Concepts: Target Concepts:

Query: UMLS:C0011849 (diabetes)
277,896 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Glutamate decarboxylase (GAD65) is a major autoantigen in insulin-dependent diabetes (IDDM) and the neurological disorder Stiff-Man-Syndrome (SMS). We derived a human monoclonal autoantibody (MICA 2) from peripheral blood of a patient newly diagnosed with IDDM, which reacted with GAD65 in Western blots. This indicated that a linear epitope is recognized by MICA 2. Using an epitope cDNA library we mapped the MICA 2 epitope to a contiguous stretch of 26 amino acids (506-531) in the C-terminus of GAD65. Neither blocking experiments with synthetic peptides nor analysis of overlapping decapeptides expressed as fusion proteins allowed us to further narrow down the epitope to the typical size of linear epitopes of 6-8 amino acids. We suggest that a miniconformational epitope provided by amino acids 506-531 is recognized by MICA 2, which withstands SDS gel electrophoresis without destruction or partially refolds during the Western blot procedure. A sequence homology with human heat shock protein 60 (HSP60) maps to this region of GAD65 but no cross-reactivity of MICA 2 with HSP60 occurred. Our data demonstrate that reactivity of an antibody in Western blots does not necessarily define a classic linear epitope of 6-8 amino acids and describe a new autoreactive epitope in GAD65 different from those reported for sera from patients with SMS.
...
PMID:Mapping of an autoreactive epitope within glutamate decarboxylase using a diabetes-associated human monoclonal autoantibody and an epitope cDNA library. 874 89

Two homozygous lines of transgenic NOD/Lt mice expressing MHC class II I-E molecules at quantitatively different levels were utilized to study mechanisms of I-E-mediated diabetes prevention. In line 12, I-E expression on APC at levels comparable with that in BALB/cByJ controls conferred only partial diabetes resistance. In line 5, greater than normal I-E levels on APC correlated with nearly complete resistance. Levels of endogenously encoded I-Ag7 correlated inversely with transgene-induced I-E expression. T cell transfer experiments into NOD/severe combined immunodeficient mice demonstrated the presence of pathogenic T cells in I-E+ donors, and that continuous expression of I-E on hemopoietically derived APC was required to block their pathogenic function. T cells from transgenic and nontransgenic NOD/Lt mice primed in vivo against the beta cell autoantigen 65-kDa isoform of glutamic acid decarboxylase (GAD65) and two peptides derived from this protein proliferated when restimulated in vitro. However, reverse-transcription PCR and ELISA measurements of cytokine mRNA and protein levels showed that the GAD65-reactive T cells from both line 5 and line 12 mice produced higher levels of IL-4 and lower levels of IFN-gamma than similar T cells from standard NOD/Lt mice. Thus, the inverse relationship between I-E and I-Ag7 expression was associated with qualitative differences in T cell responses to putative beta cell autoantigens. Collectively, these data indicate quantitative increases in I-E expression on APC may block insulin-dependent diabetes mellitus by altering the balance of cytokines produced by beta cell autoreactive T cells.
...
PMID:Quantitative thresholds of MHC class II I-E expressed on hemopoietically derived antigen-presenting cells in transgenic NOD/Lt mice determine level of diabetes resistance and indicate mechanism of protection. 875 36

IDDM (type I diabetes) is generally believed to result from T-cell-mediated autoimmune destruction of the insulin-producing beta-cells in the pancreatic islets of Langerhans. In the last few years, considerable progress has been made with regard to the identification and characterization of candidate autoantigens recognized by autoantibodies; several of these candidate autoantigens are recognized by T-cells, including insulin, GAD65 and GAD67, heat-shock protein 65 (hsp65), and islet-cell antigen 69 (ICA69). In addition to these, a number of unidentified beta-cell antigens, including insulin-secretory granule membrane proteins and a 38-kDa protein, have been shown to stimulate T-cells of IDDM patients. However, T-cell autoreactivity to islet antigens is not specific for IDDM, and the T-cell target antigens are not specific for beta-cells. Moreover, the autoantigens involved in the initiation of the insulitis must be defined, and the mechanism of the T-cell-dependent beta-cell destruction remains to be unraveled. This review focuses on T-cell autoreactivity in IDDM in humans and the implications of the present knowledge for immunointervention and monitoring of immunotherapeutic trials.
Diabetes 1996 Sep
PMID:T-cell responses to autoantigens in IDDM. The search for the Holy Grail. 877 14

Autoantibodies to glutamic acid decarboxylase (GAD) are useful diagnostic and predictive markers for Type 1 (insulin-dependent) diabetes mellitus. In the present study we describe a development of simple, reproducible, and quantitative radioimmunoassays for detecting GAD65 and GAD67 antibodies, and compare sensitivity and specificity of these assays with native GADAb radioimmunoassay. We used in vitro transcribed and translated recombinant human islet GAD65 and GAD67 as antigens, and anti-human IgG was used to separate free from antibody-bound ligand. By using these assays, GAD65Ab and GAD67Ab were detected in 65% and 25% of recent-onset Japanese patients with Type 1 diabetes, respectively, but none of 71 healthy control subjects tested were postive for GAD65Ab and GAD67Ab. Moreover, none of 48 patients with other autoimmune disease had GAD65Ab or GAD67Ab. There was a 100% correlation between the sensitivity and specificity of GAD65Ab assay and native GADAb assay. GAD65Ab and GAD67Ab were concordant in 28% of Type 1 diabetic sera and the levels of GAD65Ab in doubly positive patients were significantly higher than those in only GAD65Ab positive patients (P < 0.01). GAD65Ab are specific markers for Type 1 diabetes, and the radioimmunoassay using in vitro translated GAD and anti-human IgG, which is sensitive, convenient and low cost for detecting GAD antibodies, will facilitate large population screening of Type 1 diabetes.
Diabetes Res Clin Pract 1996 Apr
PMID:Detection of recombinant GAD65 and GAD67 antibodies using a simple radioimmunoassay. 880 83

The non-obese diabetic (NOD) mouse develops diabetes as a result of spontaneous T cell mediated destruction of the insulin-producing beta-cells. Tolerization to glutamic acid decarboxylase (GAD65) has been reported to inhibit spontaneous T cell proliferative responses to GAD65 and GAD65 peptides and prevent insulitis and diabetes in NOD mice. To evaluate the role of T cells responsive to GAD65 in induction of diabetes in NOD mice we generated T cell clones from spleen cells of three prediabetic NOD mice using the reported immunodominant human GAD65 peptides nos. 17, 34 and 35, which are spontaneously recognized by NOD spleen cells. The ten T cell clones established from two female and one male NOD mice recognized either the GAD65 peptide no. 35 which has an identical amino acid sequence in mice and humans or recognized the human GAD65 peptide no. 17 which is different in two amino acids from murine GAD65 peptide no. 17. None of the clones exhibited responses to islet cells, and GAD65 peptide no. 17 responsive clones did not cross react with the murine GAD65 peptide no. 17. All clones were CD4 positive and expressed the alpha/beta T cell receptor, but differed in their V beta usage. Analysis of in vitro production of IFN gamma, IL-2 and IL-4 demonstrated a TH1 and TH0 like functional subset of the individual clones. In vivo, neither the autoreactive T cell clones specific for GAD65 peptide no. 35 nor the xenoreactive clones specific for GAD65 peptide no. 17 were able to accelerate diabetes in young NOD mice or transfer diabetes into NODscid mice.
...
PMID:Peripheral T cell clones from NOD mice specific for GAD65 peptides: lack of islet responsiveness or diabetogenicity. 881 71

Insulin-dependent diabetes mellitus (IDDM) in the non-obese diabetic (NOD) mouse results from a T lymphocyte mediated destruction of the insulin-producing beta cells of the pancreas and serves as a model for human type I diabetes. The NOD mouse develops insulitis at 4 weeks of age and diabetes later in life. It has previously been shown that a T helper 1 (Th1) response to the islet antigen, glutamic acid decarboxylase (GAD65, henceforth GAD) spontaneously develops in NOD mice concurrent with the onset of lymphocytic infiltration into the islets (insulitis). The proliferative T cell response in the spleen is initially confined to the carboxy-terminal region of GAD65 (peptides 509-528 and 524-543) followed by a progression to nearby determinants and a variety of upstream determinants. We have produced a set of overlapping synthetic peptides spanning the 509-543 region of GAD and surveyed the responses raised by immunization with peptide GAD(524-543), which is the more immunogenic of the two peptides. NOD mice immunized with GAD(524-543) demonstrate splenic proliferative responses to 524-538 and 527-541 but not to 521-535 or 530-543. Four T cell hybridomas were produced from spleen cells of GAD(524-543)-immunized NOD female mice. Each hybridoma displayed a unique cytokine profile when stimulated with peptides 524-538 and 527-541, assaying IL-2, IFN-gamma, and IL-5 production by peptide-stimulated hybridomas. To identify MHC and TCR contact residues critical for the stimulation of the hybridomas, a truncated peptide (GAD 526-538) and a panel of analogue peptides were synthesized containing single-amino acid substitutions. Hybridoma 35.13.2 was non-responsive to the truncated peptide and all of its variants. However, the four residues 530 (A), 531 (P), 536 (R), and 537 (M) were found to be critical for the activation of the three remaining hybridomas, suggesting that these positions in the GAD-524-543 determinant were MHC binding residues or conserved TCR contact sites.
...
PMID:T cells with multiple fine specificities are used by non-obese diabetic (NOD) mice in the response to GAD(524-543). 881 72

The processes that lead to the production of islet cell autoantibodies in insulin-dependent (type 1) diabetes mellitus (IDDM) are largely unknown. Humoral autoimmunity may be the result of an antigen-independent polyclonal B cell activation, or a consequence of an antigen driven B cell activation and selection for the antigen. We have analysed the gene elements encoding the immunoglobulin variable regions of seven human monoclonal islet cell antibodies (MICA) 1-7 directed to the major islet autoantigen glutamate decarboxylase (GAD65). These autoantibodies were derived from two patients with newly diagnosed IDDM. The variable gene regions of the MICA revealed different sequences, and no relation between V gene usage and shared epitope recognition of the MICA was evident. An elevated usage of VH 1, VH 4 and Vlambda 2 gene segments was observed. The underrepresentation of VH 3 family members in the MICA discriminated them from most autoantibodies. The high relative avidities for GAD65 of MICA 1, 3, 4 and 6 and their high, nonrandom ratio of replacement versus silent mutations in the antigen binding regions indicated that the humoral response to GAD65 is driven by the antigen. MICA 2, 5 and 7 showed as well an excess of replacement mutations in the antigen binding regions, but revealed lower relative avidities for their antigen. Since these clones accumulated many somatic mutations in their variable gene regions, they may be characteristic for later stages of the autoimmune disease. The results suggest that, in humans, an antigen driven B cell activation and affinity maturation process may contribute to the production of GAD65-autoantibodies found in patients with IDDM.
...
PMID:Evidence for somatic mutation and affinity maturation of diabetes associated human autoantibodies to glutamate decarboxylase. 881 73

To study the heterogeneity of islet cell antibodies (ICA), recombinant rat and human GAD65 expressed as bacterial fusion proteins were used to inhibit ICA reactivity in sera from recent onset type 1 diabetic children and ICA-positive first degree relatives of diabetic patients. Rat GAD65 was expressed as a fusion protein in the expression vector RSET and inhibited ICA (GAD+ICA) in 26% of 23 recent onset patients, 29% of 14 ICA positive first degree relatives (FDR) who progressed to diabetes (prediabetics) and 50% of 20 FDR who did not progress to diabetes 18 months to 5 years (31 +/- 14 months) after collection of the sample. GAD+ICA were inversely associated with the presence of insulin autoantibodies (IAA) (P = 0.006). GAD antibodies (GAD-Ab) were also detected by immunoprecipitation of in vitro transcribed and translated [35S] methionine-labelled human GAD65. GAD-Ab were present in 83% of recent onset patients, 86% of prediabetics and 95% of the relatives who did not progress to diabetes. The level of GAD-Ab was higher in the presence of GAD+ICA (1.39 +/- 0.57 vs 0.79 +/- 0.6 index units; P = 0.001). ICA levels were higher in GAD-Ab negative than in GAD-Ab positive sera (377 +/- 256 vs 195 +/- 231 JDFU; P = 0.03). Our results confirm that a recombinant GAD65 fusion protein can be used to detect ICA heterogeneity. However, neither inhibition of ICA with recombinant GAD, nor direct detection of GAD-Ab improved the prediction of progression to clinical diabetes in ICA positive FDR.
...
PMID:Reactivity of islet cell antibodies (ICA) to recombinant glutamic acid decarboxylase (GAD). 882 14

An insulin granule membrane protein, phogrin (phosphatase homologue of granules from rat insulinoma), with homology to islet cell antigen (ICA) 512/IA-2 has recently been cloned from an insulinoma cDNA expression library with antigranule membrane sera. We have developed a radioimmunoassay for detecting antiphogrin autoantibodies using in vitro transcribed and translated phogrin and have established the sensitivity and specificity of this assay. Thirty-two of 57 (56%) new-onset patients with type I diabetes and 26 of 44 (59%) first-degree relatives followed to diabetes had anti-phogrin antibody levels exceeding the 99th percentile of 108 normal control subjects. Levels of antiphogrin autoantibodies correlated with ICA512/IA-2 autoantibodies (r = 0.82, P < 0.0001), but minimally with insulin autoantibodies (r = 0.20, P = 0.05) and not with GAD65 autoantibodies (r = 0.16, P = 0.12). Ninety-eight percent (57 of 58) of patients positive for anti-phogrin autoantibodies were also positive for autoantibodies against ICA512/IA-2. Nine percent (9 of 101) of new-onset patients and relatives followed to diabetes were ICA512/IA-2 autoantibody-positive but anti-phogrin autoantibody-negative. Preincubation of sera with recombinant ICA512/IA-2 protein completely for the majority and partially for a minority inhibited binding to in vitro translated phogrin. In three relatives in which ICA512/IA-2 autoantibodies converted to positivity with sequential follow-up, anti-phogrin autoantibodies developed at the same time. These results suggest that anti-phogrin and ICA512/IA-2 autoantibodies are related subsets of anti-islet autoantibodies.
Diabetes 1996 Oct
PMID:Autoantibodies to protein tyrosine phosphatase-like proteins in type I diabetes. Overlapping specificities to phogrin and ICA512/IA-2. 882 69

We studied the prevalence of mitochondrial gene mutations in subjects with insulin-dependent diabetes mellitus (IDDM) in a Chinese population living in Taiwan. Eighty-four subjects with insulin-dependent diabetes mellitus and 105 unrelated normal controls were recruited in the present study. Both an A-to-G mutation at position 3243 and a mutation at position 8,344 of the mitochondrial DNA were screened by polymerase chain reaction-restriction fragment length polymorphism methods and confirmed by direct DNA sequence analysis. The insulin secretory response was assessed by the C-peptide response to glucagon administration. Among 84 IDDM patients, two (2.4%) subjects were found to carry the 3,243 nucleotide pair (np) mutation. There was no np 8,344 mutation in this series. Of the two subjects carrying a mitochondrial gene mutation, case 1 manifested initially as gestational diabetes mellitus. Manifestation of case 2 was consistent with MELAS, a syndrome of mitochondrial encephalomyopathy, lactic acidosis, and stroke-like episodes. The pancreatic beta cell reserve was reduced, as the glucagon-stimulated C-peptide response was very low in these two cases. HLA genotyping studies revealed that case 2 carried DRB1*0301-DQA1*0501-DQB*0201/ DRB1*0405-DQA1*0301-DQB1*0302, which was the most susceptible genotype to IDDM in our population. Anti-GAD65 antibody was also positive in this patient. In addition to the nuclear genes, a defective mitochondrial gene might contribute to some of the clinical cases with IDDM.
...
PMID:Mitochondrial gene mutations in patients with insulin-dependent diabetes mellitus in Taiwan. 883 Mar 30

<< Previous 1 2 3 4 5 6 7 8 9 10 Next >>