GAD65Ab Levels Research Articles

Glutamic acid decarboxylase antibody-associated neurological syndromes: Clinical and antibody characteristics and therapy response

BackgroundAntibodies against glutamic acid decarboxylase (GAD-abs) at high serum levels are associated with diverse autoimmune neurological syndromes (AINS), including cerebellar ataxia, epilepsy, limbic encephalitis and stiff-person syndrome. The impact of low serum GAD-ab levels in patients with suspected AINS remains controversial. Specific intrathecal GAD-ab synthesis may serve as a marker for GAD-ab-associated nervous system autoimmunity. We present characteristics of a multicentric patient cohort with suspected AINS associated with GAD antibodies (SAINS-GAD+) and explore the relevance of serum GAD-ab levels and intrathecal GAD-ab synthesis. MethodsAll patients with SAINS-GAD+ included in the registry of the German Network for Research on Autoimmune Encephalitis (GENERATE) from 2011 to 2019 were analyzed. High serum GAD-ab levels were defined as RIA>2000 U/mL, ELISA>1000 U/mL, or as a positive staining pattern on cell-based assays. ResultsOne-hundred-one patients were analyzed. In descending order they presented with epilepsy/limbic encephalitis (39%), cerebellar ataxia (28%), stiff person syndrome (22%), and overlap syndrome (12%). Immunotherapy was administered in 89% of cases with improvements in 46%. 35% of SAINS-GAD+ patients had low GAD-ab serum levels. Notably, unmatched oligoclonal bands in CSF but not in serum were more frequent in patients with low GAD-ab serum levels. GAD-ab-levels (high/low) and intrathecal GAD-ab synthesis (present or not) did not impact clinical characteristics and outcome. ConclusionsOverall, immunotherapy in SAINS-GAD+ was moderately effective. Serum GAD-ab levels and the absence or presence of intrathecal GAD-ab synthesis did not predict clinical characteristics or outcomes in SAINS-GAD+. The detection of unmatched oligoclonal bands might outweigh low GAD-ab serum levels.

Serum Branch Chain Amino Acids (BCAAs) Are Elevated Due to Decreased Catabolism in Patients With Ketosis-Prone Diabetes at the Time of Presentation With DKA

Patients with “A-β+” Ketosis-Prone Diabetes (KPD) develop diabetic ketoacidosis (DKA) despite lacking islet autoantibodies and a phenotype of T1D, have good beta cell function and can come off insulin therapy 4–8 weeks after the DKA episode. When near-normoglycemic and stable on metformin, they have accelerated BCAA catabolism which promotes ketogenesis (Patel SG et al, Diabetes 2013). Here we measured BCAAs, their metabolites and acylcarnitine esters (C5,C3) in blood samples obtained from adults with DKA (N=74) compared to those with non-ketotic hyperglycemic crisis (N=21) at the time of acute presentation to the emergency center, and to healthy controls (N=17). Of the DKA patients, 53 were classified as likely A-β+ KPD based on absence of GAD65Ab and C-peptide levels or clinical features, and the 21 patients with non-ketotic hyperglycemia were classified as T2D. Serum concentrations of leucine, isoleucine and valine and their respective branch chain keto acids (BCKA) were higher (p<0.05) in KPD patients compared to T2D and control. The ratio of each BCKA to its precursor BCAA was calculated as an index of its rate of transamination. Serum KIC/Leu, KMV/Ile and KIV/Val were significantly lower (p<0.05) in KPD compared to T2D. The ratio of each acylcarnitine to its precursor BCKA was calculated as an index of its rate of entry and metabolism within mitochondria. Serum C5/KIC, C5/KMV and C5/KIC+KMV were lower (p<0.05) in KPD patients compared to T2D patients. Serum C3/KIV, C3/KMV and C3/KIV+KMV were significantly lower (p<0.05) in KPD patients compared to controls. Since KIC can be converted to acetoacetate and then reduced to β-hydroxybutyrate (BHOB), and KIC and KMV can be metabolized to acetyl CoA, the ratios of KIC+KMV/C2 and KIC/BHOB were calculated as indicators of their relative conversion to acetyl CoA and acetoacetate respectively. KIC+KMV/C2 was significantly lower (p<0.001) in KPD than T2D and control and KIC/BOHB was lower (p<0.001) in KPD than T2D. Acetyl carnitine was markedly elevated in the KPD group, indicating accelerated production of acetyl CoA from free fatty acids. During acute DKA, KPD patients have higher serum BCAAs because their catabolism is decreased, due to slower rate of transamination in the cytosol by BCAA transaminase 1 (BCAT1) and slower rate of entry into mitochondria and metabolism to acetyl CoA and acetoacetate by BCAT2, BCKA dehydrogenase and other catabolic enzymes. This is diametrically opposite to their profile in the stable, near-normoglycemic state, when BCAA catabolism is accelerated. We propose that during acute DKA, accelerated flux of fatty acids to acetyl CoA diminishes carnitine and NAD+ availability for mitochondrial transport and metabolism of BCAA catabolites in KPD patients, whereas in the near-normoglycemic state they have heightened dependence on BCAA catabolism for energy production through acetyl CoA and ketogenesis.

Relationship between serum GAD-Ab and the genetic polymorphisms of GAD2 and type 2 diabetes mellitus.

In this study, we investigated the relationship between serum glutamic acid decarboxylase (GAD) autoantibody (Ab) levels and single nucleotide polymorphisms (SNPs) of the glutamic acid de-carboxylase 2 (GAD2) 5'-untranslated region and the susceptibility to type 2 diabetes in the Han population. The distributions of patients with SNPs in the GAD2 5'-untranslated region (rs2236418, rs185649317, and rs8190590) and type 2 diabetes and that of the healthy group were genotyped and analyzed using Sequenom MassArray SNP genotyp-ing. GAD-Ab levels were also detected. The frequency distributions of the AA, AG, and GG genotypes in the polymorphic site rs2236418 in the diabetes GAD-Ab-positive group were 45.9, 42.8, and 11.4%, respectively, whereas those in the control group were 36.6, 43.7, and 19.8%, respectively. The difference between the 2 groups was statis-tically significant (P < 0.05). Unlike the GG genotype, the AA and AA + AG genotypes increased the risk of GAD-Ab (odds ratios (95% confidence intervals) = 2.623 (1.351-4.937) and 2.152 (1.375-4.202), respectively). The associations of the 3 SNPs of the GAD2 gene 5'-un-translated region polymorphisms with susceptibility to type 2 diabe-tes in the Chongqing Han population were significant. The SNP of rs2236418 in the Chongqing Han population of diabetic patients with serum GAD-Ab levels was significantly correlated with the SNPs rs185649317 and rs8190590.

From anti-GAD to ataxia with ocular motor apraxia type 2: through the looking glass

Dear Sirs,Elevated levels of anti-glutamic acid decarboxylase anti-bodies (GAD-Ab) are found in serum and cerebrospinalfluid in various autoimmune diseases such as diabetesmellitus and stiff-man syndrome. GAD-Abs also have beenreported in 14 patients presenting with cerebellar ataxiaand ocular motor disturbances [1, 2]. We report newinsights about one patient of the first published series ([1],patient 1) who came to our examination at age 57. Sinceshe was adopted, her neonatal and familial history was notknown. Since age 16, she showed progressive cerebellarataxia associated with axonal sensory-motor neuropathy,leading to use of a wheelchair at age 43. In 1995, when thepatient was 38 years old, further investigations revealedelevated levels of plasmatic GAD-Ab [1, 2]; her levelsremained significantly elevated and pathological in a sec-ond laboratory examination at 282 U/mL at age43, 115 U/mLat age 57 (positive rate[1 U/mL), and 3,911 cpm (positiverate[200 cpm) in a third laboratory at age 58. Each of thelaboratories used radioimmunoassay for measurement, asin the initial report of 1995. Indeed, her condition hadworsened and elevated plasmatic GAD-Ab levels persistedover time despite treatment by IV Immunoglobulin [3],plasmapheresis, cyclophosphamide then azathioprine,which had been started at age 38. At age 57, she hadmarked cerebellar ataxia (scale for the assessment andrating of ataxia (SARA) score at 23.5/40) with disablingdysarthria, dysmetria, hypotonia and severe distal amyot-rophy. Oculographic recording confirmed ocular motorapraxia. Electroneuromyography found severe axonalsensory motor neuropathy; brain MRI showed markedcerebellar atrophy. Her alpha-fetoprotein (AFP) serumlevel was elevated at 52.5 lg/L (normal\7 lg/L). Becauseof the combination of progressive cerebellar atrophyoccurring at around 15 years old with axonal sensory motorpolyneuropathy, ocular motor apraxia and elevated AFPserum level [4], we suspected the diagnosis of ataxia with

Prevalence and immunological spectrum of temporal lobe epilepsy with glutamic acid decarboxylase antibodies

High levels of glutamic acid decarboxylase (GAD)-ab were initially described in patients with stiff person syndrome, and have since also been observed in patients with other neurological diseases. Temporal lobe epilepsy (TLE) seems to be specially associated. Our purpose is to describe the prevalence of GAD-ab in patients with TLE, and to characterize the clinical-immunological profile of TLE patients with high levels of GAD-ab. An immunological profile including GAD-ab and antinuclear, anti-DNA, anti-cardiolipin, anti-transglutaminase and antithyroid antibodies was determined in a consecutive series of patients with TLE. As adulthood onset is the least common onset in TLE + hipocampal sclerosis and febrile seizures, we selected patients whose onset was after 30 years of age, to expand the spectrum of aetiologies. Patients were divided into two groups: known aetiology, 19 patients (45%) and unknown aetiology, 23 (55%). The clinical-immunological study included TLE patients with high GAD-ab levels (>1000 IU). Amongst 42 patients, serum GAD-ab levels were positive in 5 (152-11, 963 IU/ml), all from the unknown aetiology group. Thus, GAD-ab levels were positive in 21.7% and high in 8.7% of the unknown aetiology group. The immunological profile study included nine patients (seven pharmacoresistant), of whom six were women (66%) with mean age 41 years. Three patients reported acute debut, four (44%) insulin-dependent diabetes mellitus, five (55%) other concomitant autoimmune diseases, four (44%) memory impairment and four moderate-to-severe mood disturbance. Intrathecal synthesis of GAD-ab was observed in seven patients (77%). Temporal lobe epilepsy with GAD-ab is not a rare condition. In the subgroup of patients with high titres, this epilepsy is often pharmacoresistant and associated with memory impairment, depression and other autoimmune diseases.

PO.01 IDDM associated with cerebellar ataxia; drug resistant complex partial seizures and intrathecal synthesis of anti GAD-Ab

High levels of antibodies to glutamic acid decarboxylase (anti GAD-Ab) are an uncommon association in neurological conditions. We describe a patient who initially presented with cerebellar ataxia. Four years later...

抗GAD抗体陽性C型慢性肝炎に対するインターフェロン療法の検討

Development of type 1 diabetes mellitus (T1DM) has been reported in patients receiving interferon (IFN) therapy for hepatitis C virus (HCV) infection. We studied two patients with chronic HCV infection who had an anti-glutamic acid decarboxylase antibody (GAD-ab) before IFN therapy. Their blood sugar and GAD-ab levels were monitored during IFN therapy. Case 1 was a 61-year-old man with 16.9 U/mL of GAD-ab. The GAD-ab level decreased during IFN therapy, but remained positive. Case 2 was a 65-year-old woman with 2.0 U/mL of GAD-ab. Her GAD-ab level increased during IFN therapy, but decreased after withdrawal of IFN. Insulin secretion in both patients was kept within physiologically normal range during IFN therapy, and the treatment was completed without developing T1DM in both cases.

Glutamate Cysteine Ligase Catalytic Subunit Promoter Polymorphisms and Associations with Type 1 Diabetes Age-at-onset and GAD65 Autoantibody Levels

The purpose of this study was to test the hypothesis that glutamate cysteine ligase catalytic subunit (GCLC) promoter polymorphisms are susceptibility factors for type 1 diabetes (T1D), T1D age-at-onset and T1D autoantibodies. T1D patients and control subjects from the Swedish Childhood Diabetes Registry and the Swedish Diabetes Incidence Study registry were genotyped for two GCLC promoter polymorphisms; the GCLC -129 C to T single nucleotide polymorphism (GCLC -129 SNP) and the GCLC GAG trinucleotide repeat polymorphism (GCLC TNR). Glutamate decarboxylase antibody (GAD65Ab) positive T1D patients with the GCLC -129 SNP C/T genotype have increased GAD65Ab levels (p-value, <0.05) compared to the GCLC -129 SNP C/C genotype. T1D patients with an age-at-onset of 14-35 years who possess the GCLC -129 SNP T/T genotype have a higher GAD65Ab index than T1D patients with the GCLC -129 SNP C/C genotype (p-value <0.05). In addition, T1D patients with an age-at-onset of 14-35 years possess the GCLC TNR 7/8 genotype at a lower frequency than the control subjects (OR, 0.33, 95% CI, 0.13-0.82). The GCLC -129 SNP and GCLC TNR appear to be in linkage disequilibrium (p-value<0.0001). These results suggest that GCLC promoter polymorphisms may influence GAD65Ab levels and may influence the age at which T1D is diagnosed.

Association Between Insulin Resistance and GAD65-autoantibody Levels—A Pilot Study in an Adult Non-diabetic Population

The aim of this pilot study was to investigate any association between insulin resistance (IR) and serum levels of autoantibodies against the glutamic acid decarboxylase (GAD65Ab) among adult non-diabetic subjects.Based on calculations of IR using the IR homeostasis model in a Swedish adult non-diabetic population (n=756) participating in the WHO MONICA-study, an insulin sensitive group (n=54, M/F:27/27) and an insulin resistant group (n=46 M/F:24/22) were identified. Serum from the subjects were analysed for the presence of GAD65Ab. There was no significant difference in GAD65Ab levels between the groups. However, there was a correlation between IR and serum GAD65Ab within the insulin sensitive group (Spearman ρ 0.4, p<0.01).Our observation could indicate that IR could serve as an initiator or a progression factor in the autoimmune process in subjects predisposed to autoimmunity. This finding will be further investigated in a larger study including subjects with a continuum of IR.

High GAD65 autoantibody levels in nondiabetic adults are associated with HLA but not with CTLA-4 or INS VNTR.

To explore the relationship between genetic background and antibody levels in a nondiabetic population. We evaluated if high levels of autoantibodies against the 65 kDa isoform of glutamic acid decarboxylase (GAD65Ab), were associated with high-risk genes, i.e. HLA, CTLA-4 and INS VNTR genes. Seventy-five (M/F 39/36) subjects exceeding the 95th percentile of GAD65 autoantibody index and 75 age and sex matched subjects below the 95th percentile, randomly selected amongst participants in the Västerbotten Intervention Programme. The GAD65 Ab were measured in a radioligand-binding assay. HLA class II typing was performed by an oligoblot hybridization method. CTLA-4 repeat length was analysed and divided into short forms and long forms. Class I and class III alleles of INS VNTR were detected. Differences in distribution were tested by Pearson chi-square with Yates correction. Odds ratios (OR) were used to compare groups calculated with Cochran's and Mantel-Haenszel statistics. The DQB1*0201-DQA1*0501-DRB1*03 haplotype was increased in subjects with high GAD65Ab levels (P = 0.04). This increase seemed to be explained by a difference in haplotype frequencies amongst men (P = 0.01). Calculating OR showed a significant association between the DQB1*0201-DQA1*0501-DRB1*03 haplotype and elevated levels of GAD65Ab in all subjects (OR 2.2, 95% CI 1.02-4.9) as well as in men (OR 4.6, 95% CI 1.3-15.9). There was no association between high levels of GAD65Ab and either INS VNTR or CTLA-4 polymorphisms. Our study suggests that adult males with the DQB1*0201-DQA1*0501-DRB1*03 haplotype tend to develop high GAD65Ab titres. As none of these subjects have developed diabetes these data suggest that HLA may be important in GAD65Ab formation but that additional factors are required for the progression to overt type 1 diabetes.

Stable GAD65 Autoantibody Epitope Patterns in Type 1 Diabetes Children Five Years after Onset

Autoantibodies to GAD65 (GAD65Ab) are prominent in type 1 diabetes. These autoantibodies may be present both years before and after the clinical diagnosis of type 1 diabetes and are widely used as a marker for the disease. Recently it has been demonstrated that progression to type 1 diabetes is accompanied by GAD65Ab epitope maturation. Here we examine whether autoantibody maturation processes also progress after the clinical diagnosis of type 1 diabetes. Antibody reactivity to GAD65, GAD67 and GAD65/67 fusion proteins was measured by radioimmunoassays in 62 children with type 1 diabetes. Samples were taken at diagnosis and five years later. While the overall GAD65Ab level declined over time, the epitope pattern was remarkably stable with no significant changes in binding pattern. Loss of GAD65Ab-positivity was associated with significantly lower GAD65Ab indices at diagnosis compared to patients' sera that remained GAD65Ab-positive. The decrease in GAD65Ab levels did not correlate to residual C-peptide levels. Our data suggest that processes controlling GAD65Ab levels and epitope binding patterns remain stable during the first five years of type 1 diabetes.

Treatment outcome for IDDM patients in relation to glutamic acid decarboxylase autoantibodies and serum IgG to periodontal pathogens.

Patients with insulin-dependent diabetes mellitus (IDDM) have elevated risk for periodontitis (PD) relative to subjects without diabetes. Whether refractory PD in IDDM patients is related to autoimmunity as indicated by serum glutamic acid decarboxylase autoantibody GAD Ab levels or to host bacterial immunity as reflected by serum antibody titers to periodontal pathogens is unknown. To determine if non-surgical periodontal treatment outcome differs between GAD Ab-seropositive and -seronegative IDDM patients by assessing the following parameters: (1) pretreatment serum levels of GAD Ab, (2) pretreatment serum IgG titers to key periodontal pathogens, and (3) changes in periodontal pocket probing depth (PDC) after treatment. Before and two months after periodontal treatment of 11 GAD Ab-seronegative and 7 -seropositive subjects, PDC was assessed and serum GAD Ab and IgG to Porphyromonas gingivalis (Pg), Bacteroides forsythus (BJ), and Actinobacillus actinomycetemcomitans (Aa) were studied using established radioligand precipitation and enzyme-linked immunosorbent assays, respectively. The PDC decrease was significantly better for GAD Ab-seronegative subjects than for seropositive subjects (median 1.4 mm+/-0.5 s.d. versus 0.5 mm+/-0.3 s.d., p<0.03, Mann-Whitney). GAD Ab levels and PDC were positively correlated (r=+0.71, p<0.05) for sero-positive subjects but were neutral (r=-0.07) for seronegative subjects. Serum IgG to Pg and GAD Ab levels were positively associated (r2=0.42) in seropositive subjects. Logistic regression analysis confirmed that GAD Ab status was the primary discriminator for PDC (p<0.04). Detection of elevated GAD Ab levels in combination with elevated IgG titers to Pg before treatment is indicative of IDDM patients with refractory PD.

Newly diagnosed latent autoimmune diabetes in adults (LADA) is associated with low level glutamate decarboxylase (GAD65) and IA-2 autoantibodies. Diabetes Incidence Study in Sweden (DISS).

A quantitative assay with microSepharose was used to determine GAD65Ab and IA-2Ab levels in 771 population-based patients diagnosed with diabetes mellitus at 15 to 34 years of age, and in 828 matched controls. Among the patients, 587 (76%) were classified with type I, 108 (14%) with type II, and 76 (10%) with unclassifiable diabetes. The levels above normal demonstrated a prevalence of GAD65Ab in 66% of type I diabetes, 50% of type II diabetes and 54% of unclassifiable patients and for IA-2Ab in 40%, 17% and 21%, respectively. Among the autoantibody-positive sera, the LADA patients had a lower GAD65Ab index (median 0.19, p < 0.0001) and IA-2Ab index (median 0.28, p < 0.0001) than the type I patients (median 0.37 and 0.66). Patients with unclassifiable diabetes had a GAD65Ab (median 0.43) or IA-2Ab (median 0.63) index which was not different from the type I diabetes patients. Our data demonstrate that young adult new-onset LADA patients have low level GAD65Ab and IA-2Ab. The low-level autoantibodies may signify a less aggressive beta-cell autoimmunity, which may explain why these patients are often classified with type II or non-insulin-dependent diabetes.

Clinical characteristics, and time course of pancreatic beta-cell function and glutamic acid decarboxylase antibodies in Thai patients with adult-onset Type 1 diabetes: distinction between patients of rapid- and slow-onset.

In order to study the clinical characteristics, time course of beta cell function and glutamic acid decarboxylase antibodies (GAD65Ab) in Thai patients with adult-onset Type 1 diabetes and to examine the distinctive features between patients with rapid-and slow-onset, 61 Thai patients with Type 1 diabetes who had age of disease onset at or after 20 years were studied. All patients were treated with insulin at the time of study and had fasting C-peptide levels +/-0.33 nmol/l. Twenty-six (42.6%) were in rapid-onset and 35 (57.4%) were in slow-onset groups. Fourty-four of 61 (70.5%) were male. About three-fourths had body mass index (BMI) < 19 kg/m2 at the time of insulin therapy. Only 7 of 61 (11.5%) patients had ketoacidosis at first presentation. Five patients had associated autoimmune thyroid disease and 10 (16.7%) patients had family history of diabetes in first-degree relatives. GAD65Ab was positive in 31 patients (50.8%); 10 (38.5%) were in rapid-onset and 21 (60.0%) were in slow-onset groups. GAD65Ab particularly of high levels were persistently elevated during 3-4 years follow-up period. The persistence of GAD65Ab were not associated with changes in fasting C-peptide levels. At the time of insulin dependency, there were no distinctive clinical features between rapid- and slow-onset patients except higher fasting C-peptide (0.08+/-0.08 vs. 0.14+/-0.10 nmol/l; p = 0.023) and GAD65Ab levels (19.6+/-17.4 vs. 46.1+/-49.7 U/ml; p = 0.036) in slow-onset patients. Fasting C-peptide levels of patients in the latter group were also demonstrated to be higher after 3-4 years of follow-up. In conclusion, most Thai patients with adult-onset Type 1 diabetes in this study were male and had significant degree of weight loss and lean BMI prior to insulin therapy. The presence of GAD65Ab did not predict clinical features or rate of beta cell loss. Patients in rapid-onset group had lower fasting C-peptide and GAD65Ab levels than those of slow-onset group which confirms the slower process of beta cell failure in the latter.

Glutamate decarboxylase antibody levels predict rate of β-cell decline in adult-onset diabetes

Glutamate decarboxylase autoantibodies (GAD65Ab) and β-cell function were evaluated at and 3 years after diabetes onset in consecutive subjects over 15 years of age. At onset, 21 32 (66%) insulin-treated patients (mean age 43, range 16–79 years) had GAD65Ab; all GAD65Ab persisted 3 years later. At onset, 20 82 (24%) non-insulin-treated patients (mean age 56, range 20–79 years) had GAD65Ab. Of those with persistent GAD65Ab, 8 non-insulin-treated and 11 insulin-treated patients consented to follow-up glucose and glucagon stimulation tests. For non-insulin-treated patients, quantitative GAD65Ab index at onset correlated inversely with 1+3 min C-peptide response to glucose ( r = −0.68, P < 0.05) and to glucagon ( r = −0.79, P < 0.05) 3 years later. Those with high (> 0.50) initial GAD65Ab index had lower C-peptide (fasting, 1+3 min after glucose and after glucagon) 3 years later, versus those with low (<0.50) initial GAD65Ab index ( P < 0.05). In conclusion, not only did GAD65Ab presence predict future insulin dependence, but higher GAD65Ab levels may mark more rapid decline in β-cell function in apparent non-insulin-dependent diabetes.

Radioimmunoassay Detects the Frequent Occurrence of Autoantibodies to the Mr 65,000 Isoform of Glutamic Acid Decarboxylase in Japanese Insulin-Dependent Diabetes

Glutamic acid decarboxylase antibodies (GAD65Ab) are common in new onset Caucasian insulin-dependent diabetic (IDDM) patients but it is unclear if this marker is also prevalent in patients of other ethnic backgrounds. We determined antibodies against human recombinant GAD in Japanese diabetic patients using a radioimmunoassay with competition between in vitro translated 35S-GAD65 and non-labelled recombinant human GAD65 (rhGAD65). GAD67 antibodies (GAD67Ab) were similarly analyzed but without antigen competition. In 73 Japanese diabetic patients, GAD65Ab were found in 11/16 (69%) of patients with short-duration (less than 5 yrs) IDDM, 6/23 (26%) with long-duration (5 or more yrs) IDDM and 10/20 (50%) with slowly progressive diabetes. High GAD65Ab levels were associated with concomitant autoimmune diseases (p = 0.021). GAD67Ab were found in 4/16 (25%) of patients with short-duration IDDM, 3/23 (13%) with long-duration IDDM and 2/20 (10%) with slowly progressive diabetes. In 14 non-insulin dependent diabetic (NIDDM) patients, GAD65Ab and GAD67Ab were not found (0/14) and 1/50 (2%) healthy controls were positive in either assay. Among the GAD67Ab-positive samples, 8/9 (88%) were also high level GAD65Ab positive, 7/9 (77%) were displaced by an excess of rhGAD65 and the antibody levels correlated (r2 = 0.573; p = 0.003). Our data are consistent with a strong association of GAD65Ab also in Japanese IDDM, and suggest that, when present, GAD67Ab are frequently directed to epitope(s) common to GAD65 and GAD67.