Increased risk for endocrine autoimmunity in Italian type 2 diabetic patients with GAD65 autoantibodies

OBJECTIVE: Glutamic acid decarboxylase (GAD)65 autoantibodies (GAD65Ab) in type 2 diabetic subjects with secondary failure to sulphonylurea treatment identify the so-called latent autoimmune diabetes of the adult (LADA). The aim of our study was to estimate the risk for endocrine autoimmunity in type 2 diabetic subjects with GAD65Ab. DESIGN AND PATIENTS: We analysed serum samples from 600 adult subjects with a clinical diagnosis of type 2 diabetes mellitus for the presence and levels of GAD65Ab and antibodies directed against the islet autoantigen IA-2/ICA512 (IA-2/ICA512Ab). All the patients had been treated initially with hypoglycaemic agents and/or diet for at least 1 year. GAD65Ab+ subjects were studied for the presence of thyroid peroxidase autoantibodies (TPOAb), 21 hydroxylase autoantibodies (21OHAb) and frequency of HLA class II haplotypes. RESULTS: GAD65Ab were found in 67/600 (11%) and IA-2/ICA512Ab in 12/600 (2%) subjects (P < 0.0001). The presence of GAD65Ab, but not that of IA-2/ICA512Ab, was significantly associated with insulin therapy, low BMI (P < 0.0001) and low basal C-peptide (P < 0.01). Islet-cell antibodies (ICA) were detected in 43/67 (64%) GAD65Ab+ and in 10/12 (83%) IA-2/ICA512Ab + subjects. TPOAb occurred more frequently in GAD65Ab+ (16/67, 24%) than in GAD65Ab-subjects (9/174, 5%) (P < 0.0001). 21OHAb were detected only in GAD65Ab+ subjects (3/67, 4.5%) (P = 0.03 vs. GAD65Ab-subjects). None of the 21OHAb+ subjects had metabolic or clinical signs of adrenal dysfunction. HLA-DRB1*03-DQA1*0501-DQB1*0201 (DR3-DQ2) was significantly more frequent in GAD65Ab+ subjects than in healthy controls (OR = 5.42, corrected P < 0.0026). The presence of TPOAb was significantly associated with DR3-DQ2 (P = 0.024). CONCLUSIONS: Our study demonstrates that the presence of GAD65Ab identifies a subgroup of type 2 diabetic patients with high risk for thyroid and adrenal autoimmunity, and that both GAD65Ab and TPOAb are associated with the presence of HLA-DR3-DQ2, in these patients.     

Coincidence of high antiislet and antithyroid autoantibody titles in first-degree relatives of patients with type 1 diabetes.

An association between thyroid and islet autoantibodies has been reported for patients with type 1 diabetes and their first-degree relatives. However no general agreement on this association has been reached since several studies reported controversial data. In the present study, sera from 429 healthy first-degree relatives of type 1 diabetic patients have been examined for the presence of thyroid and islet autoantibodies. Autoantibodies against glutamate decarboxylase (GAD65Ab) and tyrosine-phosphatase IA-2 (IA-2/ICA512Ab) have been detected by radioimmunoassay techniques with in vitro translated recombinant human 35S-autoantigens. The presence of autoantibodies against thyroid peroxidase (TPOAb) and thyroglobulin (TgAb) has been estimated by commercial radioimmunoassay kits. An increased frequency of TgAb was found in subjects who were positive for GAD65Ab (p=0.0257). However, no significant association between TPOAb and GAD65Ab or IA-2Ab or between TgAb and IA-2Ab could be established. These data indicate an increased rate of coincidence between TgAb and GAD65Ab in healthy first-degree relatives of type 1 diabetic patients. Accordingly a common genetic background leading to the appearance of both TgAb and GAD65Ab may be suggested.     

Epitope-restricted 65-kilodalton glutamic acid decarboxylase autoantibodies among new-onset Sardinian type 2 diabetes patients define phenotypes of autoimmune diabetes

The 65-kDa glutamic acid decarboxylase (GAD65) autoantibodies (GAD65Abs), commonly found in type 1 diabetes mellitus (T1DM) patients, are also found at lower frequencies in type 2 diabetes mellitus (T2DM) patients. GAD65Abs in T1DM patients are epitope specific, in contrast to those found in other GAD65Ab-positive individuals, including T2DM patients. Our aim was to assess whether epitope-specific GAD65Abs, or the additional presence of islet antigen 2 (IA-2) autoantibodies, better define T1DM phenotypes among T2DM patients. GAD65 and IA-2 autoantibodies were analyzed in 1436 Sardinian subjects classified with T2DM and in 384 nondiabetic patient controls. Autoantibody binding specificity to the N-terminal, middle (M), and C-terminal (C) portions of the GAD65 molecule was evaluated. Among the T2DM patients, 5.1% had GAD65 (P < 0.001) and 2.4% had IA-2 autoantibodies, compared with 1.3 and 1.6%, respectively, among the controls. GAD65Ab-positive T2DM patients with M+C (epitope-specific) reactivity were found to have the lowest body mass index (P < 0.001), followed by GAD65Ab/IA-2Ab-positive patients (P < 0.01), and non-M+C-reactive (non-epitope-specific) patients (P < 0.02). In GAD65Ab-positive T2DM patients, c-peptide levels were lower in M+C-reactive compared with non-M+C-reactive patients. Sardinian T2DM patients with M+C-predominant GAD65Ab reactivity have clinical features more similar to those of T1DM patients. Thus, GAD65Ab epitope analysis may help to define T1DM phenotypes among newly diagnosed GAD65Ab-positive patients classified with T2DM.     

Sexual dimorphism in transmission of expression of islet autoantibodies to offspring

Summary To help elucidate the mode of inheritance of insulin-dependent diabetes mellitus (IDDM), we measured GAD (glutamic acid decarboxylase) autoantibodies (GAD65Ab), insulin autoantibodies (IAA), and cytoplasmic islet cell autoantibodies (ICA) in 292 sequentially screened non-diabetic offspring of patients with IDDM. The prevalence of these islet autoantibodies was higher in offspring of diabetic fathers than in offspring of diabetic mothers. The prevalences of GAD65Ab, IAA, and ICA in the offspring of diabetic fathers were 11.5%, 10.8%, and 8.1% vs 2.1%, 1.4%, and 2.8%, respectively in the offspring of diabetic mothers (p<0.002, p<0.001, and p=0.06 NS). Amongst autoantibody-positive relatives the IAA and ICA levels were significantly higher in offspring of diabetic fathers than of diabetic mothers (p<0.002 and p<0.01, respectively). The frequencies of these autoantibodies were equal in male and female offspring. We conclude that IDDM mothers transmitted islet autoimmunity less frequently to their offspring than IDDM fathers. Given the markedly lower frequency of autoantibodies in offspring of mothers, larger sample sizes will be required to determine whether islet autoantibodies are influenced by age of IDDM onset of mothers, maternal age of pregnancy, and presence of diabetes in these mothers prior to conception.Abbreviations IDDM Insulin-dependent diabetes mellitus - GAD glutamic acid decarboxylase - GAD65Ab glutamic acid decarboxylase autoantibodies - IAA insulin autoantibodies - ICA cytoplasmic islet cell autoantibodies - JDF Juvenile Diabetes Foundation     

Glutamic acid decarboxylase and ICA512/IA-2 autoantibodies as disease markers and relationship to residual beta-cell function and glycemic control in young type 1 diabetic patients

Circulating autoantibodies (Ab) to islet autoantigens, glutamic acid decarboxylase (GAD(65)), and tyrosine phosphatase ICA512/IA-2 have been proposed as predictive markers of type 1 diabetes mellitus. To ascertain residual beta-cell function and the clinical relevance for monitoring autoimmunity after clinical manifestation of disease, we studied 63 children at diagnosis of type 1 diabetes (mean SD age 7.5 +/- 4 years) and 91 adolescent patients with type 1 diabetes (age 14.7 +/- 1.6 years) with a mean duration of disease of 7 +/- 3.5) years. Forty-two normal adolescent subjects (age 14.6 +/- 1.8 years) without a family history of diabetes were the control group. Anti-GAD(65) and ICA512/IA-2 Ab were assessed by a quantitative radioimmunoprecipitation assay. The relationship between humoral autoimmunity and clinical parameters was explored. GAD(65) and ICA512/IA-2 Ab were detected in 56% and 63% of newly diagnosed children and the prevalence was not different in relationship to clinical characteristics. Levels of GAD(65) Ab positively correlated with diagnosis age (P <.05). Both Ab were associated with islet cell antibodies (ICA) (P <.05), but one fifth of patients had at least 1 of the 2 Ab and absent ICA. At onset, only age showed a significant relationship to residual C-peptide secretion. Among the cohort of patients with diabetes of short-mid duration, GAD(65) and ICA512/IA-2 Ab were present in 44% and 45% of cases (P >.05 and P <.05 v newly diagnosed children, respectively) and more patients were identified by these Ab (68%) than by ICA alone (34%) (P <.05). In this cohort, levels of ICA512/IA-2 Ab negatively correlated with levels of glycosylated hemoglobin (HbA(1c)) (P <.005) and with daily insulin requirement (P <.05). Moreover, the presence of some residual C-peptide secretion was significantly associated with the presence of ICA512/IA-2 Ab (P <.05). Our findings confirm that positivity for either GAD(65) or ICA512/IA-2 Ab is a highly sensitive marker of type 1 diabetes in the pediatric age group, identifying a group of patients with absent ICA immunofluorescence. The persistence of Ab to islet tyrosine phosphatase possibly represents a marker of better glycemic control and less insulin requirement, indicating residual beta-cell function, thus conferring clinical and prognostic relevance to these Ab, as well as potential usefulness in intervention strategies.     

羧基肽酶-H抗体对成人隐匿性自身免疫糖尿病的诊断意义

目的 探讨羧基肽酶—H自身抗体(CPH—Ab)阳性的2型糖尿病(T2DM)患者的临床特征及该抗体对成人隐匿性自身免疫糖尿病(LADA)的诊断价值。方法 选择临床初诊为T2DM患者545例，1型糖尿病(T1DM)患者85例，健康对照123例进行CPH—Ab测定，同时检测T2DM患者谷氨酸脱羧酶抗体(GAD—Ab)。比较各组CPH—Ab的阳性率以及T2DM中依据CPH—Ab、GAD—Ab划分的3组患者的临床特点。采用放射免疫沉淀法检测CPH—Ab和GAD—Ab。结果 CPH—Ab阳性率在T2DM患者(5．5％，30／545)高于T1DM患者(0％，0／85)和正常对照(0．8％，1／123)(P＜0．05)，30例CPH—Ab阳性的T2DM患者只有1例同时GAD—Ab阳性。CPH—Ab在低体重(BMI＜21kg／m^2)者中的阳性率较高，且该抗体阳性的患者具有起病年龄跨度大、病程较长、低体重、易发生酮症等特点，其空腹C肽介于GAD—Ab阳性与两种抗体(GAD—Ab和CPH—Ab)均阴性的T2DM患者之间，反映代谢综合征的指标水平较低(包括较低的BMI、血压和甘油三酯)，而周围神经病变的比例较高。结论 CPH—Ab阳性糖尿病患者的临床特点介于经典的LADA(GAD—Ab阳性)与T2DM患者间。CPH抗体检测是LADA诊断的一项新指标。     

Clinical, biochemical, and immunological characteristics of newly diagnosed nonobese diabetic patients aged 18-45 years in China

BackgroundThe purpose was to characterize the clinical, biochemical, and immunological features of newly diagnosed adult-onset nonobese diabetic patients in China.MethodsNewly diagnosed diabetic patients aged 18–45 years with body mass index<23 kg/m² were included. Excluding one mitochondrial diabetes patient, there were 102 diabetic patients enrolled in this study. Clinical and biochemical data were collected and analyzed. Radioimmunoassay was used to detect islet autoantibodies.ResultsAmong the 102 study participants, 68.6% had type 1 diabetes (T1DM), 20.6% had type 2 diabetes (T2DM), and 10.8% had latent autoimmune diabetes in adults (LADA). About 92% of the T1DM patients presented hyperglycemic symptoms. The corresponding number in T2DM and LADA patients was 13% and 38%, respectively (P<.01). C-peptide in T2DM patients (1.4±0.7 ng/ml) was significantly higher than that in T1DM (0.4±0.3 ng/ml) and LADA (0.4±0.2 ng/ml) patients (P<.01). The prevalence of glutamic acid decarboxylase antibody (GADA) (64.3%) in T1DM patients was higher than that of insulin autoantibody (17.1%) (P<.05). GADA and islet cell antibody (ICA) combination was positive in 75.7% of T1DM patients.ConclusionT1DM patients accounted for majority of the study sample. In addition, the clinical symptoms of T1DM patients were more severe compared with T2DM patients. GADA is the most sensitive autoantibody marker for adult-onset T1DM and LADA. GADA and ICA are the best test combination for adult-onset autoimmune diabetes. Specific types of diabetes should be in mind when diabetes presents itself with special transmission mode or with other extrapancreatic manifestations.     

The broad clinical phenotype of Type 1 diabetes at presentation

Immune‐mediated (auto‐immune) Type 1 diabetes mellitus is not a homogenous entity, but nonetheless has distinctive characteristics. In children, it may present with classical insulin deficiency and ketoacidosis at disease onset, whereas autoimmune diabetes in adults may not always be insulin dependent. Indeed, as the adult‐onset form of autoimmune diabetes may resemble Type 2 diabetes, it is imperative to test for diabetes‐associated autoantibodies to establish the correct diagnosis. The therapeutic response can be predicted by measuring the levels of autoantibodies to various islet cell autoantigens, such as islet cell antibodies (ICA), glutamate decarboxylase 65 (GAD65), insulin, tyrosine phosphatase (IA‐2) and IA‐2β, and zinc transporter 8 (ZnT8) and evaluating β‐cell function. A high risk of progression to insulin dependency is associated with particular genetic constellations, such as human leukocyte antigen risk alleles, young age at onset, the presence of multiple autoantibodies, including high titres of anti‐GAD antibodies; such patients should be offered early insulin replacement therapy, as they respond poorly to diet and oral hypoglycaemic drug therapy. Hence, considering the broad spectrum of phenotypes seen in adult‐onset diabetes, treatment targets can only be reached by identification of immune‐mediated cases, as their management differs from those with classical Type 2 diabetes.     

Insulin autoantibody could help to screen latent autoimmune diabetes in adults in phenotypic type 2 diabetes mellitus in Chinese

Latent autoimmune diabetes in adults (LADA) is characterized by a relatively mild diabetes onset, autoantibody positivity, and eventual requirement for insulin therapy. Glutamic acid decarboxylase autoantibodies (GADA) or cytoplasmic islet cell autoantibodies (ICA) play a key role in distinguishing LADA from type 2 diabetes mellitus (T2DM) in clinical practice. The aim of our research was to determine whether insulin autoantibody (IAA) has some additional value in diagnosing LADA. We analyzed IAA, GADA, and IA-2A (antibodies to insulinoma-associated antigen-2) in 1,003 newly diagnosed phenotypic T2DM patients, 110 type 1 diabetes mellitus (T1DM) patients, and 317 normal controls to survey the prevalence of IAA in phenotypic T2DM patients and the overlapping positivity of IAA with other autoantibodies. Sera were drawn within 7?days from the start of insulin therapy. Results showed that 3.39% of the newly diagnosed phenotypic T2DM, 0.95% of normal control (χ²?=?5.3, P?<?0.05), and 21.82% of T1DM (χ²?=?68.2, P?<?0.001) were positive for IAA at diagnosis. The combination frequency of three antibodies was 10.47%, which was higher than any single antibody testing. Combination testing of IAA with GADA and IA-2A could improve LADA diagnose rate by 2.39% than that of GADA and IA-2A. IAA-positive subjects had diabetes family history more common compared to its matched group (67.6% vs. 14.7%, P?=?0.000). Postprandial C-peptide in IAA-positive group tended to be lower, but the difference was not statistically significant (P?=?0.084). We concluded that IAA can be used to screen LADA in phenotypic T2DM in the Chinese population.     

Autoantibody recognition of COOH-terminal epitopes of GAD65 marks the risk for insulin requirement in adult-onset diabetes mellitus

Some type 2 diabetic subjects develop secondary failure to sulphonylurea treatment and require insulin therapy. To test the diagnostic sensitivity and specificity of epitopes of GAD65 autoantibodies (GAD65Ab) for insulin requirement, in patients with latent autoimmune diabetes of the adult, we studied 569 adult subjects with a clinical diagnosis of type 2 diabetes mellitus. All the patients had been initially treated with hypoglycemic agents and/or diet for at least 1 yr. The presence of GAD65Ab (61/569, 10.7%) depended on insulin therapy (P<0.0001), low BMI (P<0.0001), and low basal C-peptide (P = 0.01). The majority of GAD65Ab-positive subjects (47/61, 77%) had antibodies directed to both middle (GAD65-MAb) and COOH-terminal (GAD65-CAb) epitopes. However, GAD65-CAb were more frequent in insulin-treated subjects (92% of GAD65Ab+ individuals) than in subjects treated with hypoglycemic agents and/or diet (18.2% of GAD65Ab+ individuals), while the exclusive presence of GAD65-MAb was more frequent in subjects treated with hypoglycemic agents and/or diet (81.8% vs. 8%) (P<0.0001). The presence of GAD65-CAb had a diagnostic specificity for insulin requirement as high as 99.4% (compared with 96.9% of GAD65Ab as measured in the traditional radiobinding assay) and identified a subgroup of patients with low BMI, low basal C-peptide values, and a need for insulin therapy. Subjects carrying only GAD65-MAb were phenotypically indistinguishable from GAD65Ab-negative patients. Patients positive for GAD65-M+CAb, but not those positive for GAD65-MAb only, showed an increased risk for thyroid autoimmunity, as revealed by the presence of thyroid peroxidase autoantibodies. Our study demonstrates that the use of epitope-specific antibody assays improves the diagnostic specificity of GAD65Ab, and that the presence of GAD65Ab binding to COOH-terminal epitopes is strongly associated with a need for insulin requirement.     

LADA患者外周血单个核细胞对胰岛素和谷氨酸脱羧酶的增殖反应

目的探讨成人隐匿性自身免疫糖尿病(LADA)患者外周血单个核细胞(PBMC)对胰岛素和谷氨酸脱羧酶(GAD)的增殖反应。方法密度梯度离心法分离21例LADA、25例2型糖尿病(DM)及20名正常对照PBMC,3HTdR掺入法检测其对胰岛素和GAD及其分别联合白细胞介素2(IL2)刺激的增殖反应,以刺激指数(SI)反映增殖反应强度。结果(1)PBMC对PHA、胰岛素或GAD刺激的增殖反应在LADA、2型DM和正常对照组间差异无统计学意义。(2)对于胰岛素或GAD联合IL2(胰岛素 IL2,GAD IL2)刺激,LADA组SI高于2型DM组(5.1vs0.8;;7.0vs0.8,均P<0.05);;胰岛素 IL2刺激较胰岛素或IL2单独刺激的倍增值,GAD IL2刺激较GAD或IL2单独刺激的倍增值LADA组高于2型DM组(4.0vs1.0;;3.4vs0.3;;6.3vs1.2;;4.6vs0.3,均P<0.05)。(3)LADA患者胰岛素刺激的SI胰岛素与GAD抗体指数呈负相关。结论LADA患者体内存在已致敏的T细胞,其活化效应在特异性抗原(GAD或胰岛素)和IL2共刺激时方可被发现。     

Diabetes-related antibodies in adult diabetic patients

Islet autoimmunity is made evident by the appearance of islet-cell antibodies directed against insulin (IAA), glutamic acid decarboxylase (GADA), protein tyrosine phosphatase IA-2 (IA-2Ab) and other autoantigens. IAA and IA-2Ab are predominantly detected in childhood type 1 diabetes mellitus (T1DM), while frequency of GADA is not affected by age. In adult-onset T1DM patients, GADA is the immune marker of higher diagnostic sensitivity. In adult diabetic patients not requiring insulin treatment for at least 6 months after diagnosis, GADA identifies the so-called latent autoimmune diabetes in adults (LADA). In over 80% of cases, LADA patients develop insulin dependency within a few years after the diagnosis and have an increased risk for the development of other organ-specific autoimmune diseases. High GADA titers identify a subgroup of LADA patients with low body mass index (BMI), low C-peptide levels and increased frequency of T1DM-related HLA class II haplotypes. GADA assay should be offered to every diabetic patient, and in cases of positivity screening for other autoimmune diseases should be carried out.     

Prediction and prevention of Type 1 diabetes mellitus

Type 1A diabetes mellitus (T1DM) is caused by autoimmune islet β-cell destruction with consequent severe insulin deficiency. We can now predict the development of T1DM by determining four biochemically characterized islet autoantibodies, namely those antibodies against insulin, glutamic acid decarboxylase 65, insulinoma antigen (IA)-2 (ICA512) and the zinc transporter ZnT8. We can also prevent T1DM in animal models, but the final goal is the prevention of T1DM in humans. Multiple clinical trials are underway investigating methods to prevent β-cell destruction.     

GAD autoantibodies and epitope reactivities persist after diagnosis in latent autoimmune diabetes in adults but do not predict disease progression: UKPDS 77

Aims/hypothesis Latent autoimmune diabetes in adults (LADA) is a slowly progressive form of autoimmune diabetes, with autoantibodies to islet proteins developing in older patients who have no immediate requirement for insulin therapy. Markers of its clinical course are uncharacterised. The aim of this study was to determine whether persistence of, or changes in, GAD65 autoantibodies (GADAs) in the LADA patients who participated in the United Kingdom Prospective Diabetes Study (UKPDS) were associated with disease progression or insulin requirement. Methods GADA levels and their relative epitope reactivities to N-terminal, middle and C-terminal regions of human GAD65 were determined in 242 UKPDS patients who were GADA-positive at diagnosis; samples taken after 0.5, 3 and 6 years of follow-up were tested using a radiobinding assay. Comparisons were made of GADA status with clinical details and disease progression assessed by the requirement for intensified glucose-lowering therapy. Results GADA levels fluctuated between 0.5 and 6 years but persisted in 225 of 242 patients. No association of GADA levels with disease progression or insulin requirement was observed. Antibody reactivity was directed to C-terminal and middle epitopes of GAD65 in >70% patients, and the N-terminal in <9%. There were no changes in epitope reactivity pattern over the 6 year follow-up period, nor any association between epitope reactivity and insulin requirement. Conclusions/interpretation GADAs persist for 6 years after diagnosis of LADA, but levels and reactivity to different GAD65 epitopes are not associated with disease progression. Electronic supplementary material The online version of this article (doi:) contains supplementary material, which is available to authorised users.     

两种胰岛细胞抗体染色亚型与糖尿病的关系

目的 调查胰岛细胞抗体（ICA）亚型与自身免疫性糖尿病（DM）临床表现多样性间的关系。方法 收集急性起病Ⅰ型DM（58例）、成人隐匿性自身免疫性DM（LADA,45例）、2型DM（325例）及正常对照组（59例）血清,ICA用间接免疫过氧化物酶法测定。根据ICA染色形态对全部ICA阳性血清进行亚型划分,再用患者血清和抗胰高血糖素抗体或抗胰岛素抗体进行免疫双重染色,鉴定不同ICA亚型着染的胰岛细胞类型。结果 ICA在1型DM、LADA、2型DM及正常对照者的阳笥率分别为67.24%1、51.11% 、9.54%、1.69%。在光镜下,ICA可区分为两种染色形态：使整个胰岛弥漫着色的称为弥漫型,仅使胰岛周边的部分细胞着色的称为边缘型。免疫双重染色证实,弥漫型ICA使胰岛α、β细胞着染,边缘型ICA仅使α细胞着染。2型DM中边缘型ICA的比例（18／31）显著高于1型DM（4／39）或LADA（3／23）（P＜0.001)。DM患者中,弥漫型ICA与边缘型ICA比较,前者发病年龄轻、空腹血糖高、残存胰岛功能差。结论 临床上诊断为2型DM的患者中有9％可能为LADA。自身免疫性DM的临床亚型与不同的ICA染色亚型有一定联系,弥漫型ICA患者病情重,进展较快,而边缘型ICA可能与缓慢进展的β细胞损伤有关。     

Epitope analysis of GAD65 autoantibodies in adult-onset type 1 diabetes and latent autoimmune diabetes in adults with thyroid autoimmunity

This study aimed at determining which GAD65 epitopes the spontaneous antibodies recognized and whether the epitope-specific GAD65Abs could be associated with the development of thyroid autoimmunity in Chinese adult-onset type 1 diabetes (T1DM) and latent autoimmune diabetes in adults (LADA). The levels of GAD65Abs and their reactivities to N-terminal (GAD65-N), middle (GAD65-M) and C-terminal (GAD65-C) regions of human GAD65 were measured by radioligand assay in 109 patients with adult-onset T1DM and 107 with LADA. TPOAb, TGAb and the genotypes of HLADQA1-DQB1 were determined. The percentage of LADA patients with GAD65-NAb was significantly higher than that of adult-onset T1DM patients (21.5% vs. 11.0%, P = 0.037), but LADA patients with GAD65-CAb less than T1DM patients (47.7% vs. 70.6%, P = 0.001). LADA patients with both GAD65-M and GAD65-CAb (GAD65-M + CAb) appeared to be at higher risk for the development of thyroid autoimmunity, lower serum C-peptide level and the requirement for insulin therapy (P < 0.05). More frequent T1DM patients with HLADQA1*03-DQB1*0303 developed GAD65-M + CAb (55.8% vs. 35.1%, P = 0.008). In comparison with those without thyroid autoimmunity, more frequent T1DM patients and LADA patients with thyroid autoimmunity displayed GAD65-M + CAbs (44.0% vs.16.9% and 53.1% vs. 17.3%, P = 0.002 and <0.001, respectively) with a diagnostic specificity of 83.1 or 82.7% for thyroid autoimmunity, respectively. LADA patients with GAD65-M + CAbs had clinical features similar to T1DM patients. Adult-onset T1DM and LADA patients with GAD65-M + CAbs are at an increased risk for the development of thyroid autoimmunity.     

Type 1A diabetes mellitus-associated autoimmunity.

Type 1A diabetes mellitus has become one of the most intensively studied autoimmune disorders, with characterized animal models and extensive prospective studies of the development of anti-islet autoimmunity. It is now possible to predict the development of type 1A diabetes mellitus, beginning with HLA-encoded genetic susceptibility, followed by the development of a series of anti-islet autoantibodies. Prediction primarily is based on the detection of multiple anti-islet autoantibodies reacting with cloned islet antigens. Multiple international workshops fostered the development of specific and sensitive radioassays for autoantibodies reacting with GAD65 (glutamic acid decarboxylase), ICA512 (also termed IA-2, a tyrosine phosphatase-like protein), and insulin. Similar high throughput radioassays have been applied using autoantigens for additional autoimmune disorders including celiac disease and Addison's disease. Relatives of patients with type 1A diabetes mellitus inherit susceptibility to express multiple autoantibodies, and a subset of autoantibody-positive individuals inherit susceptibility to progress to overt disease. This article reviews autoimmune disorders associated with type 1A diabetes mellitus.     

Prevalence of diabetes-associated autoantibodies among patients presenting with type 2 diabetes and related metabolic differences

BackgroundTo explores the prevalence of autoantibodies (zinc transporter 8 autoantibodies (ZnT8A), antibodies to insulin (IAAs), glutamic acid decarboxylase autoantibody (GAD65)), the relation of the type of positive autoantibody and the number of positive autoantibodies with the glycemic and lipid profile of the patients with LADA (Latent Autoimmune Diabetes in Adults) and compares it to the metabolic profile of patients presenting with type 2 diabetes (T2DM).Methods263 patients with T2DM were recruited for this cross-sectional study in Tehran, Iran. Data from patients included complete medical history, GAD65, ZnT8A, IAA and routine metabolic laboratory workup. Assay for autoantibodies were conducted using ELISA kits. The association between autoantibodies and glycemic and lipid profile of patients with diabetes was assessed using univariate and multivariate regression analysis.ResultsOur study revealed that among 263 patients with T2DM, 29 (11%) cases were positive for IAAs, 9 (3.4%) for ZnT8A, and 12 (4.6%) for GAD65. Six (2.3%) of the patients had triple positive antibodies. Patients with positive results were younger, had lower body mass index (BMI), c-peptide, triglyceride, low-density lipoprotein (LDL), and higher high-density lipoprotein (HDL), HbA1c and fasting blood glucose (FBG) levels. Triple antibody positivity was significantly associated with lower levels of C-Peptide, Triglycerides, FBG, and HbA1c compared to triple negative antibodies.ConclusionPatients with LADA positive for either of the autoantibodies (GAD65, ZnT8 and IAA) presented with worse glycemic control. Measurement of these autoantibodies can assist in discrimination of these patients and help with earlier control of glycemic profile.