Glutamic Acid Decarboxylase Antibody Titer Research Articles

Gut microbiome and metabolic activity in type 1 diabetes: An analysis based on the presence of GADA.

ObjectiveType 1 diabetes (T1D) progression is affected by circulating glutamic acid decarboxylase antibody (GADA) that persist for many years. This study aimed at investigating whether and how the gut microbiome and its correlated metabolites change in T1D with the presence of GADA.MethodsWe used a radiobinding assay to measure GADA titers and identify the 49 T1D patients with GADA+ and 52 T1D patients with GADA-. The fresh feces and serum were analyzed using 16S rRNA gene sequencing and GC/MS. Then gut microbiome and serum metabolites were compared between the GADA+ patients and the GADA- patients. The association between gut microbial community and metabolites was assessed using the Spearman’s rank correlation.ResultsThe gut microbiome in diversity, composition, and function differed between these two groups. The abundance of genus Alistipes, Ruminococcus significantly increased in patients with GADA+ compared to that observed in the samples of GADA-. There were 54 significantly altered serum metabolites associated with tryptophan metabolism, phenylalanine, and tyrosine biosynthesis in individuals with GADA+ compared with those of GADA-For the serum metabolites, compared with those of GADA-, there were 54 significantly different metabolites with tryptophan metabolism, phenylalanine, and tyrosine and tryptophan biosynthesis decreased in individuals with GADA+. The abundance of Alistipes was positively correlated with altered metabolites involved in tryptophan metabolism.ConclusionWe demonstrate that T1D patients with GADA+ are characterised by aberrant profiles of gut microbiota and serum metabolites. The abundance of Alistipes disturbances may participate in the development of T1D patients with GADA by modulating the host’s tryptophan metabolism. These findings extend our insights into the association between the gut microbiota and tryptophan metabolism and GADA and might be targeted for preventing the development of T1D.

1260-P: Gut Microbiome and Metabolic Activity in Type 1 Diabetes—An Analysis Based on the Presence of GADA

Background: Type 1 diabetes (T1D) progression is affected by the level of circulating glutamic acid decarboxylase antibody (GADA) , a main manifestation of islet autoimmunity. The gut microbiome and serum metabolites may contribute to islet autoimmunity in patients with T1D. Methods: We used radiobinding assay to measure GADA titers and identify the GADA+ ones (n=49) in 1T1D patients. The gut microbiome was assessed by 16S rRNA gene sequencing, and the serum metabolites were analysed with GC/MS. Results: T1D patients with and without GADA exhibited compositional and functional changes in the gut microbiome. Profiles in patients with GADA were distinct, with a significant increase in the abundances of Alistipes, Ruminococcus, Prevotella, Dialister, and marked depletion of Bacteroides, Bifidobacterium, Roseburia. For the untargeted serum metabolites, compared with those of GADA-, there were 54 significantly different metabolites with tryptophan metabolism: phenylalanine, and tyrosine and tryptophan biosynthesis decreased in patients with GADA. In addition, patients with GADA had elevated concentrations of Indole-3-acetic-acid, a marker of intestinal inflammation and epithelial damage. Co-occurrence network analysis revealed that gut microbiome disturbances affected tryptophan metabolism, suggesting that disturbed gut microbiome may mediate T1D immunotypes. Tryptophan metabolism may mediate inflammation in the pathogenesis and pathophysiology of T1D. Conclusion: These findings suggest that metabolites produced by the patients with GADA gut microbiota could cause damage to intestinal and systemic homeostasis and could be targeted for preventing the development of T1D. Disclosure T.Yue: None. X.Zheng: None. Z.Liu: None. Y.Ding: None. J.W.Wei: None. W.Xu: None. J.Weng: None. S.Luo: None. Funding the National Key r&D Program (2017YFC1309600) the Anhui Provincial Natural science foundation (006212943003)

Rs3806265 and rs4612666 of the NLRP3 Gene Are Associated With the Titer of Glutamic Acid Decarboxylase Antibody in Type 1 Diabetes.

Background and AimsThe NLRP3 gene is reportedly associated with several autoimmune diseases. However, in the Chinese Han population, whether NLRP3 polymorphisms are associated with type 1 diabetes (T1D) is unclear. Therefore, this study examined the associations of rs3806265 and rs4612666 of the NLRP3 gene with T1D susceptibility and the clinical characteristics of Chinese Han T1D patients.MethodsIn total, 510 classic T1D patients and 531 healthy controls from the Chinese Han population were recruited for a case-control study. rs3806265 and rs4612666 of the NLRP3 gene were genotyped by MassARRAY. Logistic regression analysis and the chi-square test were used to compare the distributions of the alleles and genotypes of rs3806265 and rs4612666. The relationships between rs3806265 and rs4612666 and the clinical characteristics of T1D patients were analyzed by Kruskal-Wallis one-way ANOVA. Student’s t test was used to analyze normally distributed data. Bonferroni correction was used for multiple comparisons.Results1) rs3806265 was associated with glutamic acid decarboxylase antibody (GADA) titers (P = 0.02), and patients with the CC genotype had higher GADA titers than patients with the TT genotype. 2) rs4612666 was also associated with GADA titers (P=0.041). Compared with patients with the CC genotype, patients with the TT genotype had higher GADA titers. 3) rs3806265 and rs4612666 of the NLRP3 gene were not significantly associated with T1D susceptibility under different genetic models.Conclusionrs3806265 and rs4612666 of the NLRP3 gene were significantly associated with GADA titers in Chinese Han T1D patients.

Case Report: Multisystem Autoimmune and Overlapping GAD65-Antibody-Associated Neurological Disorders With Beneficial Effect of Epilepsy Surgery and Rituximab Treatment

Glutamic acid decarboxylase (GAD) antibodies are associated with disabling conditions such as stiff person syndrome, temporal lobe epilepsy (TLE), limbic encephalitis, cerebellar ataxia (CA), and ocular movement disorders, which are usually chronic and difficult to treat. GAD-related TLE has poor response to anti-seizure medications and immune therapies, and epilepsy surgery is rarely successful. We report on a 47-year-old female with history of migraine, autoimmune thyroid disease, ankylosing spondylitis, and drug-resistant TLE. A video electroencephalography recorded frequent seizures with temporo-insular semiology, correlating to left temporal epileptiform activity and left mesiotemporal hyperintensity on magnetic resonance imaging. GAD autoimmunity was confirmed by very high GAD antibody titers in serum and cerebrospinal fluid. Steroids, immunoglobulins, and cyclophosphamide had no effect, and selective left amygdalectomy was performed based on very restricted hypermetabolism on positron-emission tomography. After transient seizure freedom, significant epilepsy improvement was observed in spite of memory decline. Transient worsening was noted 1 year later during diabetes mellitus manifestation and 5 years later during presentation of progressive CA, which stabilized on rituximab treatment. We believe this case illustrates the diversity and the frequent overlap of GAD-associated disorders, the need of early and aggressive immunotherapy in severe patients, as well as the possible benefit from epilepsy surgery in some GAD-TLE.

GAD antibody-spectrum disorders: progress in clinical phenotypes, immunopathogenesis and therapeutic interventions.

Antibodies against glutamic acid decarboxylase (GAD), originally linked to stiff person syndrome (SPS), now denote the “GAD antibody-spectrum disorders” (GAD-SD) that also include autoimmune epilepsy, limbic encephalitis, cerebellar ataxia and nystagmus with overlapping symptomatology highlighting autoimmune neuronal excitability disorders. The reasons for the clinical heterogeneity among GAD-antibody associated syndromes remain still unsettled, implicating variable susceptibility of GABAergic neurons to anti-GAD or other still unidentified autoantibodies. Although anti-GAD antibody titers do not correlate with clinical severity, very high serum titers, often associated with intrathecal synthesis of anti-GAD-specific IgG, point to in-situ effects of GAD or related autoantibodies within the central nervous system. It remains, however, uncertain what drives these antibodies, why they persist and whether they are disease markers or have pathogenic potential. The review, focused on these concerns, describes the widened clinical manifestations and overlapping features of all GAD-SD; addresses the importance of GAD antibody titers and potential significance of GAD epitopes; summarizes the biologic basis of autoimmune hyperexcitability; highlights the electrophysiological basis of reciprocal inhibition in muscle stiffness; and provides practical guidelines on symptomatic therapies with gamma-aminobutyric acid-enhancing drugs or various immunotherapies.

Opsoclonus Myoclonus Ataxia Syndrome With Anti–Glutamic Acid Decarboxylase Antibody Positive: Response to Plasma Exchange

Abstract Objectives Opsoclonus myoclonus syndrome (OMS) is a very rare neurological disorder of probably autoimmune origin. Glutamic acid decarboxylase antibody (GAD-Ab) is one of many antibodies that have been associated with OMS. Common treatments include intravenous immunoglobulin (IVIG) and corticosteroids. To our knowledge, this is the fourth case of GAD-Ab-positive OMS reported and the first one responsive to plasma exchange (PLEX). Clinical Presentation The patient is a 77-year-old male who presented with new-onset tremors and gait disorder. He had been diagnosed with OMS and positive GAD-Ab 2 years ago. At the time of diagnosis, his condition was not responsive to IVIG or corticosteroids and seemed to improve following PLEX. He made a near full recovery and was prescribed a low dose of mycophenolate. The patient reported worsening in tremor and gait over the last several days. This was the first time he had signs of clinical relapse since diagnosis. His labs were notable for hyponatremia, elevated glucose, and acute kidney injury. Brain CT showed intracranial atherosclerosis and age-indeterminate generalized cortical atrophy, perhaps due to chronic microangiopathic white matter changes. GAD-Abs assessed on this admission were zero (normal is less than 5), whereas they were 143 before treatment 2 years ago, although no GAD-Ab titer was measured after PLEX. The patient received five sessions of PLEX with overall improvement. Conclusion We reported a rare case of OMS with positive GAD-Ab who responded to PLEX. GAD-Ab may be a predictive marker of patient symptoms and is recommended to be measured in patients with OMS before and after treatment.

Pathophysiological characteristics in patients with latent autoimmune diabetes in adults using clamp tests: evidence of a continuous disease spectrum of diabetes.

This study aimed to assess islet insulin secretion and insulin resistance in Chinese patients with latent autoimmune diabetes in adults (LADA). Twelve patients with LADA, 10 with type 1 diabetes mellitus (T1DM), 10 with type 2 diabetes mellitus (T2DM), and 10 nondiabetic healthy controls (HCs) were included. Patients with LADA were subtyped according to the glutamic acid decarboxylase antibody (GADA) titer (LADA1, GADA titer ≥ 180 U/mL; LADA2, GADA titer 18-180 U/mL). Insulin secretion and sensitivity were assessed using hyperglycemic and hyperinsulinemic-euglycemic clamp tests, respectively. The first-phase insulin secretion gradually increased in patients with T1DM, LADA1, LADA2, and T2DM to HCs (29.32 ± 6.00mU/L vs. 68.71 ± 4.50mU/L vs. 87.60 ± 11.60mU/L vs. 138.27 ± 13.18mU/L vs. 248.49 ± 21.97mU/L; P < 0.05). The second-phase insulin secretion (2ph) and maximum insulin secretion (MIS) were significantly lower in patients with LADA2 and T2DM than in HCs, but higher in those with LADA1 and T1DM. No significant differences in 2ph and MIS were observed between patients with LADA1 and T1DM, and between those with LADA2 and T2DM. The levels of insulin sensitivity index (ISI) during hyperinsulinemic-euglycemic clamps were lower in patients with LADA and T2DM than in those with T1DM. Patients with T1DM displayed lower ISI compared with HCs. Chinese patients with LADA and T1DM had impaired insulin sensitivity and β-cell function. Furthermore, the hypothesis that diabetes is a continuous spectrum from T1DM, LADA1, LADA2 to T2DM was confirmed in this study.

SUN-123 An Unusual Case of How Statin-Induced Diabetes Revealed Underlying Latent Autoimmune Diabetes of Adulthood

Introduction: Over the last two decades, multiple landmark trials have established the significant reduction in cardiovascular events with the use of statins for primary prevention. The JUPITER trial in 2008 first drew attention to statin-induced new-onset diabetes (NOD). We present an unusual case of a patient initially diagnosed with statin-induced diabetes that later was established as latent autoimmune diabetes of adulthood (LADA). Case: A 34-year-old Serbian woman with a past history only significant for hypothyroidism due to subtotal thyroidectomy for Graves’ disease was found to have an LDL of 260 mg/dL. Her family history was unremarkable. She occasionally drank alcohol and smoked half of a pack of cigarettes per day. Her BMI was 20. She was started on Atorvastatin 40 mg daily which decreased her LDL to 129 mg/dL. However, a year later, she was diagnosed with diabetes mellitus (DM) based on a hemoglobin A1c (HbA1C) of 7.5% and a glucose of 363 mg/dL after a 2-hour glucose tolerance test. Atorvastatin was thought to be the culprit and was therefore discontinued. She was monitored regularly with HbA1c testing without initiation of any medications and her HbA1C decreased to 5.9% within six months. Two years later, she became pregnant and was able to maintain a HbA1c less than 6.2% throughout her pregnancy with only dietary changes. Over a 6-year period, she had been able to maintain her blood sugar readings at goal and HbA1C between 5.6% and 6.2%. However, at age 40, her HbA1c suddenly increased to 7.3%, fasting blood sugar (FBS) readings increased to 180-220 mg/dL, and she had an unintentional 6-pound weight loss over a 12-month period. She was assessed for LADA and found to have glutamic acid decarboxylase antibody titer greater than 250 IU/mL (normal 0 - 5.0 IU/mL) and a low fasting C-peptide of 0.8 ng/mL (normal 0.8-3.5 ng/mL) with a FBS of 161 mg/dL. Based on those results, she was diagnosed with LADA and initiated on insulin therapy. Within 3 months her HbA1c decreased to 5.9%. Discussion: The association between statins and NOD has been well-established. The proposed mechanisms include both impaired insulin secretion and diminished insulin sensitivity. Patients at risk have a predisposition to diabetes including two or more of the following: metabolic syndrome, impaired fasting glucose, BMI of 30 or greater, and HbA1c 6.0% or greater. In a patient with a normal BMI and no apparent risk factors for statin-induced diabetes, LADA should be considered as another potential underlying risk factor for statin-induced NOD. Establishing the correct nature of DM has long term implications regarding the prognosis, treatment and complications associated with the disease.

Metabolic Characteristics of Recently Diagnosed Adult-Onset Autoimmune Diabetes Mellitus.

Among patients diagnosed with type 2 diabetes, autoimmune diabetes often remains undetected. Metabolic features of these patients are insufficiently characterized at present. This study compared age- and sex-matched adult (aged 41 to 62 years) humans with recent-onset diabetes: patients positive for antibodies against glutamic acid decarboxylase (GAD) and/or cytoplasmic islet-cell antigen with an insulin-free period of >6 months [antibody positive/insulin negative (ab+/ins-); previously termed latent autoimmune diabetes of adults], type 1 diabetes [antibody positive/insulin positive (ab+/ins+)], and type 2 diabetes [antibody negative/insulin negative (ab-/ins-)], as well as glucose-tolerant humans (controls) of the German Diabetes Study (n = 41/group). β-Cell function was assessed from glucagon tests and intravenous glucose tolerance tests (IVGTTs), and insulin sensitivity was determined from hyperinsulinemic-euglycemic clamps. Of the ab+/ins- patients, 33 (81%) were initially diagnosed as having type 2 diabetes. In ab+/ins-, body mass index (BMI) was higher than in ab+/ins+ (27.8 ± 5.3 kg/m2 vs 25.0 ± 3.5 kg/m2, P < 0.05), lower than in ab-/ins- (31.9 ± 5.8 kg/m2, P < 0.05), and similar to controls (29.4 ± 6.6 kg/m2). In ab+/ins-, GAD antibody titers correlated negatively with BMI (r = -0.40, P < 0.05) and with C-peptide secretion in glucagon stimulation tests (r = -0.33, P < 0.05). β-Cell function from IVGTT was 228% higher in ab+/ins- than in ab+/ins+ but 35% lower than in ab-/ins- and 61% lower than in controls (all P < 0.05). Insulin sensitivity in ab+/ins- was comparable to ab+/ins+ and controls but 41% higher than in ab-/ins- (P < 0.05) after adjustment for BMI and fasting blood glucose or hemoglobin A1c. Even shortly after diagnosis, ab+/ins- patients feature partly preserved β-cell function and chronic hyperglycemia, which possibly contributes to the observed impairment of whole-body insulin sensitivity.

Cerebrospinal Fluid Level of Glutamic Acid Decarboxylase (GAD) Antibody in Patients with Encephalitis

Background: Assaying the Glutamic Acid Decarboxylas( GAD) antibody in patients with encephalitis in cerebrospinal fluid and blood serum and its role in autoimmune encephalitis in children. Objective: This study Aimed at screening for GAD antibody in CSF of children presenting with acute encephalitis with non bacterial cause mostly autoimmune.Participants and methods: study is a pilot prospective study, conducted in the Pediatric department, Children’s Hospital, Ain Shams University.Fifty patients diagnosed with encephalitis exhibited at least one sign of parenchymatous brain dysfunction such as altered consciousness personality or behavior change, seizure, paresis, or ataxia. Encephalitis was defined as the presence of encephalopathy plus at least two of four findings: (1) fever (body temperature>38C); (2) abnormal cerebrospinal fluid examination (pleocytosis>5 white blood cells/mL and/or increased protein content>40 mg/dL) with negative cerebrospinal fluid culture; (3) abnormal electroencephalography findings compatible with encephalitis such as diffuse or focal slow activity, or periodic lateralized epileptiform discharges; and (4)abnormal results of neuroimaging, including computed tomography and magnetic resonance imaging (10), ,with age ranged from 6-144 Months; followed up In the period from September 2014 till March 2016.Basic clinical evaluation and laboratory investigations were done, GAD antibody level was measured in CSF and blood serum. Results: GAD receptor antibody titer was done in CSF which range from (36 -368 ng/l) with median of 64.83 (57.93-74.48), while in serum it range from (42.76-900) ng/l) with median 89.5(58.62-154.5).It was found that 6/50 (12%) patients had high GAD receptor antibody titer were high in CSF. The other 44/50 (88%) patients had low GAD antibody titer. In serum samples of twinty patients we had 8/20 (40%) patients had high GAD antibody titer and the rest were low GAD antibody titer 12/20 (60%).Significant occurrence of DCL, hospitalization plus mechanical ventilation and long term sequel were detected in patients with high GAD antibody titer. EEG findings; Two patients showed generalized epileptogenic activity, one patient had diffuse cortical dysfunction and two patient had multifocal epileptiform discharge and the rest of patients had normal finding. Eighty six precent had normal MRI findings,While 7 patients (14%) had non specific findings;3 patients had transient cortical meningeal enhancment,2 patients had high intensity in medial temporal lobe,one had abnormal signal intensity in medial temporal lobe and one patient had global brain atrophy. Conclusion: GAD Abs are directed against an intracellular antigen. The proposed pathogenic mechanisms of neurological disease in patients with antibodies directed against intracellular proteins is not clear. The present study emphasizes the importance of studying the CSF of patients with encephalitis suspected to be mediated by GAD autoimmunity.Both serum and CSF level must be assessed simultaneously as CSF level may change rapidly with fluctuation of disease. There are great efforts to be done to define the role of these GAD antibodies and to determine how they affect central nervous system function. These studies must be carried out so that appropriate treatments can be provided for the growing number of patients with possible antibody-mediated conditions.

Evaluation of Glutamic Acid Decarboxylase Antibody Levels in Patients with Juvenile Myoclonic Epilepsy and Mesial Temporal Lobe Epilepsy with Hippocampal Sclerosis.

Several clinical studies have been conducted to investigate the role of autoantibodies and immunological mechanisms in the etiology of treatment-resistant epilepsy in recent years. Some immunological treatments have been suggested as a result of these studies. In this study, we aimed to investigate the role of autoimmunity in partial and idiopathic generalized epilepsy and determine the relationship between drug resistance and autoimmune antibodies. Twenty-eight patients (24 treatment-responsive and 4 treatment-resistant) with juvenile myoclonic epilepsy (JME), 26 patients with mesial temporal lobe epilepsy with hippocampal sclerosis (MTLEHS) resistant to antiepileptic drug treatment, and 26 age-matched healthy control subjects were included in a two-year cross sectional study. Glutamic acid decarboxylase antibody (GADA) levels were measured with a radioimmunoassay method in the serum of the included subjects. High GADA titers were detected in 2 patients with JME (7.1%), 1 patient with MTLEHS (3.8%), and 1 healthy subject (3.8%). There was no statistically significant difference among the groups regarding the serum GADA level. Although a limited number of drug-resistant patients with JME our study did not show relationships among anti-GADAs, both epileptic syndromes and drug resistance. Because we did not determine any significant relationship between GADA levels and JME or MTLEHS, we do not recommend analysis of serum GADA levels in routine examinations where there is no evidence to suggest risk factors for autoimmunity.

High GADA titer increases the risk of insulin requirement in LADA patients: a 7-year follow-up (NIRAD study 7).

The aim of this study was to determine whether glutamic acid decarboxylase antibody (GADA) titer and other clinical parameters could define the risk of progression to insulin therapy in latent autoimmune diabetes in adults (LADA) patients during a 7-year follow-up. This study involved 220 LADA and 430 type 2 diabetes subjects followed up for 7 years from the time of GADA screening to evaluate their progression toward insulin therapy. Kaplan-Meier curves and multivariate logistic regression analysis were performed to identify the markers capable of influencing this progression. During the follow-up, the drop out was 4% in both groups. A total of 119 (56.1%) out of 212 LADA patients required insulin during the 7 years of follow-up. The Kaplan-Meier plots showed that 74/104 (71.1%) of high GADA titer required insulin compared with 45/108 (41.6%) of low GADA titer and with 86/412 (20.9%) of type 2 diabetes (P<0.0001 for both). A BMI of ≤25 kg/m2 and IA-2IC and zinc transporter 8 (ZnT8) positivity were also shown as the markers of faster progression (P<0.0001 for both). The proportion of LADA patients requiring insulin was significantly higher in the group of subjects treated also with sulfonylurea in the first year from diagnosis compared with those treated with diet and/or insulin sensitizers (P<0.001). The multivariate analysis confirmed that the presence of high GADA titer was a significant predictor of insulin requirement (P<0.0001, OR=6.95). High GADA titer, BMI ≤ 25, ZnT8 and IA-2IC positivity and sulfonylurea treatment, in the first year from diagnosis, significantly increase the progression toward insulin requirement in LADA patients.

Changes of follicular helper T cells in peripheral blood of patients with newly-diagnosed type 1 diabetes mellitus

Objective To observe the changes in follicular helper T cells (Tfh) in peripheral blood mononuclear cell (PBMC) of newly-diagnosed patients with type 1 diabetes mellitus (T1DM),to analyze its relationship with B lymphocyte and autoantibodies,and to explore the role played by Tfh cells in the pathogenesis of T1DM.Methods Eighteen patients with newly-diagnosed T1DM and 15 healthy control subjects were enrolled.The percentages of Tfh cells and B cells in PBMC with respective CD4+CXCRS+ICOS+and CD19+markers were assessed by flowcytometry.The mRNA expressions of interluekin 21 (IL-21) and Bcl-6 were detected in two groups by realtime PCR,and the association between Tfh and glutamic acid decarboxylase antibody (GADA) was analyzed.Results (1) The proportions of Tfh [(0.09 ± 0.01 vs 0.20 ± 0.01) ％,P＜0.01] and B lymphocyte [(1.68 ± 0.16 vs 3.4 ±0.25)％,P＜0.01] in PBMC from T1DM group were significantly higher than those in control group.(2) In comparison with control group,mRNA levels of Bcl-6 and IL-21 in PBMC of T1DM group were decreased by 30％ (P＜0.01) and 35％ (P＜0.05).(3) A positive correlation between the amount of Tfh cell and the titer of GADA was found (r =0.792,P ＜ 0.01).Conclusion The close relationship of Tfh cells with clinical and biochemical characteristics in newly-diagnosed patients with T1DM demonstrates an important role which may be played by Tfh cells in the pathogenesis of T1DM. Key words: Diabetes mellitus, type 1 ; Peripheral blood mononuclear cell; Follicular helper T cells

The age of onset of diabetes and glutamic acid decarboxylase titer measured long after diagnosis are associated with the clinical stage of slow-onset type 1 diabetes

AimsDiabetes mellitus is divided into 3 clinical stages: not insulin requiring, insulin requiring for control, and insulin requiring for survival. We investigated the clinical characteristics of patients with slow-onset type 1 diabetes (T1D) to examine which clinical factors influence the clinical stage. MethodsOne hundred fifty patients with slow-onset T1D were divided into 3 groups based on disease stage, and clinical features were compared among these groups. The patients were also divided into 4 groups based on the age of onset and the glutamic acid decarboxylase antibody (GAD-Ab) titer, which was measured long after diagnosis (mean, 9.2 years). The frequencies of the 3 stages were compared among these 4 groups. ResultsThe age of onset and the log (GAD-Ab) titer differed significantly among the 3 stages. The number of patients not requiring insulin was significantly higher and the number of those requiring insulin for survival was significantly lower in the group in which the age of onset was ≥50 and the log (GAD-Ab) titer <0.6, while the opposite pattern was observed in the group in which the age of onset was <50 and the log(GAD-Ab) titer ≥0.6. ConclusionsOur results suggest that the combination of the age of onset and GAD-Ab titer measured long after diagnosis might predict the clinical stage of slow-onset T1D.

GADA Titer-Related Risk for Organ-Specific Autoimmunity in LADA Subjects Subdivided according to Gender (NIRAD Study 6)

Latent autoimmune diabetes in adults (LADA) includes a heterogeneous population wherein, based on glutamic acid decarboxylase antibody (GADA) titer, different subgroups of subjects can be identified. The aim of the present study was to evaluate GADA titer-related risk for β-cell and other organ-specific autoimmunity in LADA subjects. Adult-onset autoimmune diabetes subjects (n=236) and type 2 diabetes (T2DM) subjects (n=450) were characterized for protein tyrosine phosphatase (IA-2IC and IA-2(256-760)), zinc transporter 8 (ZnT8), thyroid peroxidase, (TPO), steroid 21-hydroxylase (21-OH), tissue transglutaminase (tTG), and antiparietal cell (APC) antibodies. High GADA titer compared to low GADA titer showed a significantly higher prevalence of IA-2IC, IA-2(256-760), ZnT8, TPO, and APC antibodies (P≤0.04 for all comparison). 21-OH antibodies were detected in 3.4% of high GADA titer. A significant decreasing trend was observed from high GADA to low GADA and to T2DM subjects for IA-2(256-760), ZnT8, TPO, tTG, and APC antibodies (P for trend≤0.001). TPO was the only antibody showing a different prevalence between gender; low GADA titer and T2DM female patients had a higher frequency of TPO antibody compared to males (P=0.0004 and P=0.0006, respectively), where the presence of high GADA titer conferred an odds ratio of 8.6 for TPO compared to low GADA titer. After subdividing high and low GADA titer subjects according to the number of antibodies, we observed that 73.3% of high GADA titer subjects were positive for at least one or more antibodies, compared to 38.3% of low GADA titer (P<0.0001). In LADA subjects, high GADA titer was associated with a profile of more severe autoimmunity and, in male gender, specifically predisposed to thyroid autoimmunity. A regular screening for other antibodies is recommended in LADA patients according to GADA titer and gender.

Extralimbic autoimmune encephalitis associated with glutamic acid decarboxylase antibodies: An underdiagnosed entity?

Nonparaneoplastic glutamic acid decarboxylase antibody (GADAb)-related autoimmune encephalitis is a syndrome characterized by refractory seizures, progressive cognitive deficits, and psychiatric manifestations. The limbic subtype is well described, has characteristic affective and memory disturbances, and typical mesial temporal MRI abnormalities. We found only one single case report of the extralimbic subtype. We report clinical, radiological, and pathological findings of two additional cases with contrast-enhancing lesions. One of our cases presented as vasculitis, and the other imitated a tumor. Pathological evidence of both vasculitis and encephalitis has never been previously reported in any inflammatory condition affecting the brain. Our cases confirm prior reports that immune therapy can better control seizures associated with GADAb autoimmune encephalitis, and support the rationale for assaying for GADAb titers in patients with etiologically unclear extralimbic lesions and refractory epilepsy, independent of seizure types.

Value of zinc transporter 8 autoantibody in the diagnostic classification of acute-onset diabetics

to explore the application significance of zinc transporter 8 autoantibody (ZnT8A) in the diagnostic classification of acute-onset diabetics. according to the status of glutamic acid decarboxylase antibody (GADA) and tyrosine phosphatase antibody (IA2-A), 453 acute-onset diabetics were divided into A+ subgroup (any antibody positive) and A- subgroup (both antibodies negative). A total of 555 type 2 diabetics and 405 healthy controls were recruited. The distribution and correlated factors of ZnT8A were analyzed in the acute-onset diabetic group and two subgroups (A+ and A-). The clinical characteristics were compared between the patients with ZnT8A positive alone and patients without any antibody. All these islet antibodies were measured by radioligand assay. the prevalence of ZnT8A in acute-onset diabetics was 24.3% and it was significantly higher than that in type 2 diabetics (1.8%) and healthy controls (1.0%) (both P < 0.01). The frequency of ZnT8A in A+ subgroup was much higher than A- subgroup (29.7% vs 15.8%, P < 0.01). The positive rates of ZnT8A were much higher in all the subgroups with age at onset of < 30 yr than those with ≥ 30 yr (0 - 9, 34.9%; 10 - 19, 26.7%; 20 - 29, 26.3% vs ≥ 30 yr, 18.3%; all P < 0.05); furthermore, the rates were also higher in BMI < 21.0 kg/m(2) and 21.0 - 25.0 kg/m(2) subgroups than in BMI > 25.0 kg/m(2) subgroup (25.5% and 25.9% vs 8.7%, both P < 0.05). The ZnT8A level was only positively correlated with IA2-A titer (r = 0.165, P = 0.01), but not related to such factors as GADA titer, age at onset, duration, body mass index, HbA1c and CP levels (all P > 0.05). As compared with Ab- patients, the patients with ZnT8A positive alone had much higher insulin injection dosage [(35.5 ± 9.3) U/d vs (29.8 ± 14.7) U/d, P < 0.05], and much lower systolic blood pressures [(107 ± 15) mm Hg vs (113 ± 16) mm Hg, P < 0.05] and diastolic blood pressures [(69 ± 12) mm Hg vs (73 ± 12) mm Hg, P < 0.05]. ZnT8A testing may be applied in the diagnostic classification of acute-onset diabetics, especially in those without an evidence of GADA and IA2-A since it helps to identify a clinical phenotype which is more similar to the classic type 1 diabetes.

Relationship between serum glutamic acid decarboxylase antibody titer and the first-phase insulin release in newly-diagnosed type 2 diabetic patients

To investigate the relationship between serum glutamic acid decarboxylase antibody (GAD-Ab)titer and the first-phase insulin release (1PH)in newly-diagnosed type 2 diabetic patients. 1053 newly-diagnosed type 2 diabetic patients were divided into 3 groups, including 71 individuals with GAD-Ab≥1 U/ml (positive group), 171 individuals with GAD-Ab ranging from 0 to 1 U/ml (negative-1 group), and 811 individuals with GAD-Ab=0 (negative-2 group). IPH was evaluated by arginine stimulation test. In the patients of negative-2, negative-1, and positive groups, the respective values of 1 PH were subsequently decreased significantly (P< 0. 01) , and the detection rates of the decreased insulin secretion were 74. 85%, 87. 13%, and 100%, respectively. Stepwise regression analysis indicated that disease duration, GAD-Ab titer, HbA_1C, and body mass index were the major independent contributing factors. The titer of GAD-Ab has an important impact on 1PH defect in type 2 diabetic patient. Detection of GAD-Ab not only provides an evidence for clinical type, but would also be helpful in determining the islet β-cell function. Key words: Diabetes mellitus; Glutamic acid decarboxylase antibody; Arginine stimulation test

Six-year follow-up of pancreatic β cell function in adults with latent autoimmune diabetes

To investigate the characteristics of the progression of islet beta cell function in Chinese latent autoimmune diabetes in adult (LADA) patients with glutamic acid decarboxylase antibody (GAD-Ab) positivity, and to explore the prognostic factors for beta cell function. Forty-five LADA patients with GAD-Ab positivity screened from phenotypic type 2 diabetic (T2DM) patients and 45 T2DM patients without GAD-Ab matched as controls were followed-up every 6 mo. Sixteen patients in LADA1 and T2DM1 groups respectively have been followed-up for 6 years, while 29 patients in LADA2 and T2DM2 groups respectively for only 1.5 years. GAD-Ab was determined by radioligand assay, and C-peptides (CP) by radioimmune assay. The percentage of patients whose fasting CP (FCP) decreased more than 50% compared with the baseline reached to 25.0% at 1.5(th) year in LADA1 group, and FCP level decreased (395.8+/-71.5 vs 572.8+/-72.3 pmol/L, P<0.05) at 2.5(th) year and continuously went down to the end of follow-up. No significant changes of the above parameters were found in T2DM1 group. The average decreased percentages of FCP per year in LADA and T2DM patients were 15.8% (4.0-91.0%) and 5.2% (-3.5 to 35.5%, P=0.000) respectively. The index of GAD-Ab was negatively correlated with the FCP in LADA patients (r(s)=-0.483, P=0.000). The decreased percentage of FCP per year in LADA patients were correlated with GAD-Ab index, body mass index (BMI) and age at onset (r(s)=0.408, -0.301 and -0.523 respectively, P<0.05). Moreover, GAD-Ab was the only risk factor for predicting beta cell failure in LADA patients (B=1.455, EXP (B)=4.283, P=0.023). The decreasing rate of islet beta cell function in LADA, being highly heterogeneous, is three times that of T2DM patients. The titer of GAD-Ab is an important predictor for the progression of islet beta cell function, and age at onset and BMI could also act as the predictors.

Human fibroblasts ubiquitously express glutamic acid decarboxylase 65 (GAD 65): possible effects of connective tissue inflammation on GAD antibody titer.

Type 1 diabetes is caused by a destruction of pancreatic beta cells due to autoimmunity. Autoantibody against glutamic acid decarboxylase (GAD) 65 expressed in pancreatic beta cells is widely used as a predictive marker for pancreatic destruction. In this study, we hypothesized that if certain cells in periodontal tissues could express GAD, then it may influence GAD antibody titer. We used: 1) reverse transcription-polymerase chain reaction (PCR) analysis to detect GAD 65 mRNA in various cells; 2) nucleotide sequencing analysis to confirm that amplified PCR product is the gene encoding GAD; and 3) Western blotting to determine the expression of GAD 65 protein in human gingival fibroblasts. Immunohistochemical staining of GAD 65 protein in normal and inflamed gingiva was performed to examine the potential influence of periodontal inflammation on GAD 65 expression. GAD antibody titer in sera of periodontal patients as well as healthy subjects was measured to determine if periodontal patients could develop autoantibody against GAD 65. Cultured human gingival, periodontal, and dermal fibroblasts and mesangial cells expressed GAD mRNA. Nucleotide sequencing analyses confirmed the amplified PCR product as GAD 65. Western immunoblotting analyses and immunohistochemical staining revealed that the GAD 65 protein was expressed in vitro and in vivo. The expression of GAD 65 in inflamed tissue was higher than that in normal tissues. Two of 62 periodontal patients without diabetes showed an increased antibody titer against GAD 65, while none of the systemically healthy subjects showed an increased antibody titer against this antigen. We concluded that periodontal inflammation may result in higher levels of GAD and influence GAD antibody titer, and, hence, affect diabetic diagnosis based upon GAD antibody production.