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Autoantibodies to glutamic acid decarboxylase and phenotypic features associated with early insulin treatment in individuals with adult-onset diabetes mellitus.

We investigated the association of serum antibodies to glutamic acid decarboxylase (GADab) with early start of insulin treatment (< or = 1 year from diagnosis, or < or = 2 years from diagnosis) using data from a representative sample of 374 adult-onset insulin-treated individuals from the Tasmanian Diabetes Register. Furthermore, we examined whether this association was stronger than the phenotypic characteristics (age at diagnosis, sex, family history of diabetes, level of obesity, duration of diabetes) often used for diabetes classification. In this cohort, 35.9% of males and 38.5% of females were GADab positive. Within the first year from diagnosis, 78.4% of GADab positive people compared to 44.0% of GADab negative people (p < 0.001) had started insulin treatment. Univariate associations with insulin treatment < or = 1 year from diagnosis included GADab positivity, no family history of diabetes, lower BMI for men, and GADab positivity and lower BMI for women. In multivariate models, significant associations with insulin treatment < or = 1 year from diagnosis included a family history of diabetes (OR = 0.47, 95% CI = 0.23-0.95) and GADab positivity (OR = 2.19, 95% CI = 1.01-4.73) for men, but only GADab positivity (OR = 7.53, 95% CI = 3.09-18.30) for women. Age at diagnosis was not associated with insulin treatment < or = 1 year or < or = 2 years from diagnosis for either sex. These findings indicate that a positive GADab test result is strongly associated with start of insulin treatment within 1 or 2 years from diagnosis, more so than characteristics such as level of obesity and age at diagnosis.

Adult↗

Autoantibodies to glutamic acid decarboxylase and insulin in islet cell antibody positive presymptomatic type 1 diabetes mellitus: frequency and segregation by age and gender.

The frequency of antibodies to glutamic acid decarboxylase (GAD) and insulin (IAA) in presymptomatic Type 1 diabetes mellitus with a positive test for antibodies to islet cell antigen (ICA) was examined. Thirty-two persons positive for ICA (> 10 JDF units) were tested 2 to 48 months before their ascertained onset of Type 1 diabetes. ICA was quantitated by immunofluorescence as JDF units, anti-GAD by radioimmunoprecipitation and anti-insulin by radioimmunoassay. There was a positive test for anti-GAD in 25 (78%), and for IAA in 23 (72%), of the 32 prediabetic ICA-positive subjects. Stratification according to age at the onset of diabetes showed differing frequencies of anti-GAD and IAA in the prediabetic stage. Thus the positivity rate for anti-GAD for 18 subjects older than 10 years at onset of diabetes was 83%, and for 14 aged 10 or younger at onset was 71%; conversely, the rate for IAA for 18 subjects older than 10 at onset was 56% and for 14 aged 10 or less at time of onset was 93% (p = 0.01). The frequency of anti-GAD was higher in females (88%) than males (71%) whereas the frequency of IAA was higher in males (82%) than in females (60%). Since autoantibodies to GAD and insulin occur in presymptomatic Type 1 diabetes with differences in frequencies by age and gender, the stimuli to autoimmunity may operate differently at different ages, and may also be gender-related.

Adolescent↗

The ethnic distribution of antibodies to glutamic acid decarboxylase: presence and levels of insulin-dependent diabetes mellitus in Europid and Asian subjects.

Our objective was to ascertain the frequency of antibodies to glutamic acid decarboxylase (GAD) in Europids and four Asian ethnic groups with insulin-dependent diabetes mellitus (IDDM) to gain insight into why the prevalence and incidence of IDDM varies so widely among ethnic and/or geographically diverse population groups. The subjects in this study were Europid (n = 49), Japanese (n = 16), Thai (n = 7), Korean (n = 21), and Chinese (n = 13) persons with IDDM with a duration ranging from 5 to 14 years. There were similar numbers of healthy controls matched for each ethnic group. A validated radioimmunoprecipitation assay used GAD from pig brain radiolabeled with 125I using chloramine T. Islet cell cytoplasmic antibodies measured by indirect immunofluorescence were expressed as Juvenile Diabetes Foundation units. The prevalence of antibodies to GAD, compared with Europids (63%), was much lower in all Asian populations with IDDM: Japanese (31%), Thai (29%), Korean (5%), and Chinese (27%). The mean level of antibodies to GAD, however, among diabetics from each population who gave a positive reaction, was similar. For all groups, the prevalence of antibodies to GAD was much higher than that of islet cell cytoplasmic antibodies. Almost all IDDM subjects positive for islet cell antibodies had antibodies to GAD, but the converse did not hold. A radioimmunoprecipitation assay for antibodies to GAD applied to serum from subjects with IDDM in various ethnic groups showed that Europids with IDDM had a much higher prevalence of such antibodies than did Asians. This held for all ethnic groups, and particularly Koreans. Thus, among different populations, there may be etiologic heterogeneity of IDDM.(ABSTRACT TRUNCATED AT 250 WORDS)

Asian People↗

Diagnostic significance of antibodies to glutamic acid decarboxylase in Japanese diabetic patients with secondary oral hypoglycemic agents failure.

Some non-insulin-dependent diabetes mellitus (NIDDM) patients are positive for antibodies to glutamic acid decarboxylase (anti-GAD), and they tend to develop insulin deficiency. The aim of this study was to evaluate the prevalence of anti-GAD in NIDDM with secondary failure of sulfonylurea agents (NIDDM-SF) and to investigate the diagnostic significance of seropositivity for anti-GAD in NIDDM-SF patients by evaluating human leukocyte antigen (HLA)-DRB1 alleles concurrently. The prevalence of anti-GAD in NIDDM-SF, NIDDM, and new-onset (within 1 year after onset) insulin-dependent diabetes mellitus (IDDM) was 9.3% (39/420), 3.1% (12/392), and 65.0% (13/20), respectively. Pancreatic beta cell function deteriorated in NIDDM-SF patients positive for anti-GAD. HLA-DRB1 allele typing revealed that NIDDM-SF patients positive for anti-GAD were significantly associated with DRB1*0901 (RR = 2.81, P < 0.01), which is one of the susceptible alleles to IDDM. Shorter interval before development of secondary failure and insulin deficiency were significantly associated with the presence of DRB1*0901 (P < 0.05) in NIDDM-SF patients positive for anti-GAD. In conclusion, nearly 10% of NIDDM-SF patients are positive for anti-GAD, suggesting that an autoimmune mechanism might play an important role in the pathogenesis of NIDDM-SF patients. In addition, a combination of serological marker (anti-GAD) and genetic marker (HLA-DRB1) is useful for predicting clinical course of NIDDM patients with secondary failure of sulfonylurea agents.

Adolescent↗

Antibodies to glutamic acid decarboxylase and peripheral nerve function in type 1 diabetes.

Autoimmune mechanisms have been implicated in the pathophysiology of diabetic neuropathy. We studied the association between glutamic acid decarboxylase (GAD65) and islet cell (IA-2) autoantibodies as well as autoantibodies to the autonomic nervous system and peripheral nerve function in recent onset type 1 diabetes. Thirty-seven patients (27 females and 10 males) enrolled 2-22 months after diagnosis. Humoral factors, glycemic control, and peripheral nerve function were measured annually for 3 yr. Patients with high GAD65Ab had worse glycemic control and higher insulin requirements. Patients with high GAD65Ab had slower motor nerve conduction velocities in the median, ulnar, and peroneal nerves (P < 0.025 for each nerve). The mean motor nerve conduction velocity Z scores at the time of the third evaluation was 0.341 +/- 0.25 for the low GAD65Ab patients and -0.600 +/- 0.25 for the high GAD65Ab patients (P < 0.01). Similar differences between the low and high GAD65Ab groups were observed for F wave latencies, thermal threshold detection, and cardiovascular autonomic function. The composite peripheral nerve function Z scores in the low GAD65Ab patients were 0.62 +/- 11, 0.71 +/- 0.19, and 0.21 +/- 0.14 at the first, second, and third evaluations, significantly different from those in the high GAD65Ab patients in whom they were -0.35 +/- 0.15, -0.46 +/- 0.18, and -0.42 +/- 0.16 (P < 0.001). In summary, GAD65Ab in patients with recent onset type 1 diabetes are associated with worse glycemic control and slightly worse peripheral nerve function. Although the latter remained within normal limits and none of the patients had clinical neuropathy, the GAD65Ab-related differences in composite peripheral nerve function were highly significant (P < 0.001) and could not be attributed to GAD65Ab-related differences in glycemic control.

Adolescent↗

Distribution of messenger RNAs encoding the enzymes glutaminase, aspartate aminotransferase and glutamic acid decarboxylase in rat brain.

In situ hybridization histochemistry (ISHH) using synthetic oligonucleotide probes has been used to identify cells containing the mRNAs coding for glutaminase (GluT), aspartate aminotransferase (AspT) and glutamic acid decarboxylase (GAD). The distribution of GAD mRNA confirms previous descriptions and matches the distribution of GAD detected using specific antibodies. AspT mRNA is widely distributed in the brain, but is present at high levels in GABAergic neuronal populations, some that may be glutamatergic, and in a subset of neurons which do not contain significant levels of either GAD or GluT mRNA. Particularly prominent are the neurons of the magnocellular division of the red nucleus, the large cells in the deep cerebellar nuclei and the vestibular nuclei and neurons of the lateral superior olivary nucleus. GluT mRNA does not appear to be present at high levels in all GAD-containing neurons, but is seen prominently in many neuronal populations that may use glutamate as a neurotransmitter, such as neocortical and hippocampal pyramidal cells, the granule cells of the cerebellum and neurons of the dentate gyrus of the hippocampus. The heaviest labelling of GluT mRNA is seen in the lateral reticular nucleus of the medulla. ISHH using probes directed against the mRNAs encoding these enzymes may be an important technique for identifying glutamate and aspartate using neuronal populations and for examining their regulation in a variety of experimental and pathological circumstances.

Animals↗

Increased therapeutic efficacy of cis-platinum complexes of poly-L-glutamic acid against a murine carcinoma.

Cis-diamminedichloroplatinum(II) (cis-DDP) and cis diamminediaquoplatinum(II) nitrate (cis-aq) were complexed to poly-L-glutamic acid (PG) of Mr 13,000 or 58,000. Soluble complexes were formed by mixing the platinum(II) compounds with the PG preparations in water at a molar ratio of one platinum(II) to 5 glutamyl residues of the PG. Compared to free cis-DDP, the complexes were about 2 to 6 times less cytotoxic to F9 embryonal carcinoma cells in vitro. In vivo studies with this tumor indicated that when administered i.p. one day after the tumor cells, the complexes were somewhat less active than cis-DDP. However, in comparison to the free drug which, due to its toxicity, was effective only within a very narrow dose range, the complexes were much less toxic, manifesting a wide therapeutic range in which no mortality occurred either from the tumor or as a result of the toxic effects of the drug. Cis-DDP and cis-aq complexes of PG Mr-58,000 were somewhat more toxic than the complexes of PG Mr, 13,000. The in vivo anti-tumor activity of most complexes was superior to that of free cis-DDP when tested in mice carrying high tumor loads. Due to their wide therapeutic range, the complexes could be given at high drug doses resulting in increased life span of the tumor-bearing mice. Moreover, 3 repeated injections of these high doses did not cause death from toxicity and resulted in partial or total eradication of advanced tumors.

Animals↗

[Effects of poly-L-lysine, poly-L-glycine and poly-L-glutamic acid on ANS fluorescence and electrokinetic potential of splenic lymphocytes in the mouse].

The in vivo effect of either poly-L-Lysine, poly-L-Glutamic acid or poly-L-Glycine on mouse spleen cell populations was investigated. The membrane fluorescence changes of activated splenic lymphocytes were studied. Experiments were performed with the hydrophobic fluorescent probe: 1-anilino-8-naphthalene sulphonate (ANS). Kinetic studies further indicated that the course of fluorescence changes may vary considerably depending upon homopolymers. These fluorescence intensity changes would be in direct or inverse relation to the electrokinetic surface potential changes of activated lymphocytes, as assessed by the electrophoretic mobility analysis. It could be concluded that the relation (direct or inverse) between ANS fluorescence and electrokinetic potential depends upon the net electrical charge of the homopolymer used. In further experiments, the determination of the net electrical charge of some tumour antigens could be considered without hard purifications.

Action Potentials↗

Immunodominant epitopes of glutamic acid decarboxylase 65 and 67 in insulin-dependent diabetes mellitus.

To find the dominant epitopes of a major autoantigen in insulin-dependent diabetes mellitus (IDDM), glutamic acid decarboxylase (GAD), we studied the reactivity of peripheral blood T lymphocytes with peptides covering both major isoforms. A significant response to GAD 65 or GAD 67 peptides was detected in 13 of 15 IDDM patients and in 9 of 10 normal controls. Controls most frequently recognised the central region of GAD 65 (residues 161-243). IDDM patients preferentially recognised residues 473-555 (p < 0.03). T-cell responses to GAD 67 peptides were similar in IDDM patients and controls. T lymphocytes from IDDM patients recognise a distinct dominant epitope of GAD, which may be an important target for the disease process.

Adolescent↗

Derivatives of glutamic acid and trehalose which can be transformed into long-living free radicals by the loss of an electron are identified in some bacteria.

A derivative of glutamic acid (ammonigenin) and a trisaccharide named lysodektose which are converted into long-living free radicals by the loss of one electron were isolated from Brevibacterium ammoniagenes and Micrococcus lysodeikticus. Structural formulae suggested for both substances based on ESR-, NMR- and mass spectra, isotopic substitution experiments and other data are: lactone of N-hydroxy-N-(2-carbamoylethyl)-glutamyl-4-amino-2-hydroxybutyric amide and 6-O-[2-deoxy-2-(N-methyl)-hydroxylamino-beta-D-glucopyranosyl]- alpha, alpha-trehalose. Radical forms appear on reversible oxidation of hydroxylamino groups to nitroxyl groups. Participation in the protection of bacterial cells and regulation of their metabolism is suggested for these compounds.

Bacteria↗

Differential detection of rat islet and brain glutamic acid decarboxylase (GAD) isoforms with sequence-specific peptide antibodies.

We studied the distribution of the M(r) 65,000 and M(r) 67,000 isoforms of glutamic acid decarboxylase, GAD65 and GAD67, in rat islets and brain by immunocytochemistry. Synthetic peptides representing selected GAD65 or GAD67 sequences were used to produce sequence-specific antibodies, allowing differential immunocytochemical detection of the two isoforms. GAD-specific reactivity of each peptide antiserum was confirmed by ELISA, immunoblotting, and immunoprecipitation. Immunostaining specificity was verified by displacement with either immunizing or irrelevant peptide. Dual immunostaining with GAD isoform-specific antibodies and polyclonal antibodies to glucagon showed that GAD65 was primarily detected in rat pancreatic islet beta-cells, whereas alpha-cells had weak GAD65 staining. In contrast, GAD67 was detected primarily in alpha-cells. In rat brain, GAD65 and GAD67 were present in neuron cell bodies and processes. These data demonstrate that antibodies raised against the N-terminus of GAD allow differential immunocytochemical identification of GAD67 and GAD65. Differential expression of GAD isoforms within islet alpha- and beta-cells supports the role of GAD65 in autoimmune diabetes and stiff-man syndrome.

Animals↗

Immunological properties of conjugates of ragweed pollen antigen E with methoxypolyethylene glycol or a copolymer of D-glutamic acid and D-lysine.

The major allergen of ragweed pollen, antigen E, was modified by coupling its amino acid groups with either methanol, methoxypolyethylene glycol (MPEG) of 5,000 daltons, or a synthetic copolymer of D-glutamic acid and D-lysine (DGL) of 34,000 daltons, all appropriately activated. The conjugates were characterized chemically and immunologically. Compared to the native antigen, the methoxy conjugate showed little reduction in allergenic activity, but the other two conjugates showed strong reductions, as measured by heterologous passive cutaneous anaphylaxis in rats sensitized with murine anti-antigen E reaginic sera. The MPEG conjugate was apparently nonimmunogenic in mice known to be high responders to the native antigen. MPEG and DGL conjugates retained the immunosuppressive property of the native antigen as subcutaneous treatment of antigen E sensitized mice with these two conjugates led to significant long-lasting depression of their antigen E-specific IgE and IgG antibody levels. These immunological changes are believed to result from reduction of antigenic valency and specificity upon coupling the bulky molecules to the protein antigens.

Animals↗

High prevalence of antibodies to glutamic acid decarboxylase in comparison to islet cell antibodies in patients with long-standing insulin-dependent diabetes mellitus.

To elucidate the clinical significance of antibodies to glutamic acid decarboxylase (GAD Ab) compared to islet cell antibodies (ICA) in recent-onset and long-standing insulin-dependent diabetes mellitus (IDDM). We examined GAD Ab and ICA in 29 recent-onset and 85 long-standing patients with IDDM. GAD Ab was detected by a radioimmunoassay kit using purified pig brain GAD as an antigen. The prevalence of GAD Ab in the recent-onset diabetic patients was 55.2%, slightly lower than that of ICA (65.5%). In contrast, the prevalence of GAD Ab in long-standing diabetic patients was 42.4%, which was significantly higher than that of ICA (23.5%) (p < 0.01). GAD Ab were consistently detected in approximately 40% of patients with long-standing disease, while ICA decreased according to duration of disease. The GAD Ab titer in ICA-positive patients (mean +/- SD, 1588.2 +/- 6755.1; range, 6-38574) was significantly higher than that in ICA-negative patients (mean +/- SD, 13.4 +/- 17.9; and range, 5-72 units) (p < 0.001). These findings suggest that GAD Ab are more useful than ICA to know participation of immune disorders in long-standing patients with IDDM.

Adult↗

Inhibition of glutamate carboxypeptidase II by phosphonamidothionate derivatives of glutamic acid.

A limited series of N-thiophosphonyl-glutamates were found to be inhibitors of the prostate-specific membrane antigen (PSMA) form of glutamate carboxypeptidase II. Comparative inhibitory profiles of an analogous O-thiophosphonyl-2-hydroxyglutarate revealed that the amido-linkage of the N-thiophosphonyl-glutamate provides a significant enhancement of inhibitory potency presumably due to significant hydrogen-bonding interactions with acceptor groups in the active-site of PSMA resulting in tighter binding. An analogous N-phosphonyl-glutamate exhibited significantly greater inhibitory potency than the parent N-thiophosphonyl-glutamate indicating that the sulfur ligand of the N-thiophosphonyl-glutamates is responsible for less favorable active-site interactions than oxygen, potentially due to steric crowding from the longer P-S bond or as a result of active-site metal substitution of Co(II) for Zn(II) arising from assay conditions.

Antigens, Surface↗