Appearance of islet cell autoantibodies after clinical diagnosis of diabetes mellitus

Islet cell antibodies (ICA) and glutamic acid decarboxylase antibodies (GAD65Ab) are often present at diagnosis of insulin dependent diabetes mellitus (type I diabetes) and are supposed to decline in level and frequency during the first years of disease. We have analysed ICA and GAD65Ab at onset and after one year in 395 population based randomly selected 15-34 year old patients newly diagnosed with diabetes mellitus, to study how these autoantibodies persist, disappear and appear and their relation to C-peptide levels. Of the 395 samples 212 (54%) were positive for ICA, 250 (63%) were positive for GAD65Ab and 170 (43%) were positive for both. At follow up after one year, 27/183 (15%) of the ICA negative patients and 25/145 (17%) of the GAD65Ab negative patients had converted to positivity. Among the 103 patients negative for both ICA and GAD65Ab, 16 turned positive for one or both antibodies after one year. Patients converting to positivity for one or the other antibody after one year, had lower C-peptide levels after one year than patients who initially were and remained negative, supporting the hypothesis that these patients have a genuine type I diabetes. In conclusion, newly diagnosed patients may be negative for autoantibodies at diagnosis but develop these antibodies later on during the disease.

Auto- and alloimmune reactivity to human islet allografts transplanted into type 1 diabetic patients

Allogeneic islet transplantation can restore an insulin-independent state in C-peptide-negative type 1 diabetic patients. We recently reported three cases of surviving islet allografts that were implanted in type 1 diabetic patients under maintenance immune suppression for a previous kidney graft. The present study compares islet graft-specific cellular auto- and alloreactivity in peripheral blood from those three recipients and from four patients with failing islet allografts measured over a period of 6 months after portal islet implantation. The three cases that remained C-peptide-positive for >1 year exhibited no signs of alloreactivity, and their autoreactivity to islet autoantigens was only marginally increased. In contrast, rapid failure (<3 weeks) in three other cases was accompanied by increases in precursor frequencies of graft-specific alloreactive T-cells; in one of them, the alloreactivity was preceded by a sharply increased autoreactivity to several islet autoantigens. One recipient had a delayed loss of islet graft function (33 weeks); he did not exhibit signs of graft-specific alloimmunity, but developed a delayed increase in autoreactivity. The parallel between metabolic outcome of human beta-cell allografts and cellular auto- and alloreactivity in peripheral blood suggests a causal relationship. The present study therefore demonstrates that T-cell reactivities in peripheral blood can be used to monitor immune mechanisms, which influence survival of beta-cell allografts in diabetic patients.

Islet cell and glutamic acid decarboxylase antibodies present at diagnosis of diabetes predict the need for insulin treatment. A cohort study in young adults whose disease was initially labeled as type 2 or unclassifiable diabetes

OBJECTIVE

To clarify the predictive value of islet cell antibody (ICA) and GAD65 antibody (GADA) present at diagnosis with respect to the need for insulin treatment 6 years after diagnosis in young adults initially considered to have type 2 or unclassifiable diabetes.

RESEARCH DESIGN AND METHODS

The patient material was representative of the entire Swedish population, consisting of patients who were 15-34 years old at diagnosis of diabetes in 1987-1988 but were not considered to have type 1 diabetes at onset. At follow-up, 6 years after the diagnosis, it was noted whether the patient was treated with insulin. The presence of ICA was determined by an immunofluorescence assay, and GADAs were measured by a radioligand assay.

RESULTS

Six years after diagnosis, 70 of 97 patients were treated with insulin, and 27 of 97 patients were treated with oral drugs or diet alone. At diagnosis, ICAs and GADAs were present in 41 (59%) of 70 patients and 41 (60%) of 68 patients, respectively, of those now treated with insulin, compared with only 1 (4%) of 26 patients and 2 (7%) of 27 patients who were still not treated with insulin. For either ICA or GADA, the corresponding frequencies were 50 (74%) of 68 for patients who were later treated with insulin and 3 (12%) of 26 for those who were still not treated with insulin, respectively. The sensitivity for later insulin treatment was highest (74%) for the presence of ICA or GADA, and the specificity was highest (100%) for ICA and GADA. The positive predictive value was 100% for the combination of ICA and GADA, 98% for ICA alone, and approximately 95% for GADA alone.

CONCLUSIONS

Determination of the presence of ICA and GADA at diagnosis of diabetes improves the classification of diabetes and predicts the future need of insulin in young adults.

Islet autoantibodies in cord blood from children who developed type I (insulin-dependent) diabetes mellitus before 15 years of age

Islet autoantibodies are early markers for Type I (insulin-dependent) diabetes mellitus. The aim of this study was to establish whether islet autoantibodies were present at birth in children who developed Type I diabetes before 15 years of age. Cord blood sera from 81 children who developed Type I diabetes between 10 months and 14.9 years of age were tested for glutamic acid decarboxylase autoantibodies (GAD65Ab), islet cell antigen 512 autoantibodies (ICA512Ab), insulin autoantibodies (IAA) all by quantitative radioligand binding assays and islet cell autoantibodies (ICA) by indirect immunofluorescence. Cord blood sera from 320 randomly selected matched children were controls. The children who developed Type I diabetes had an increased frequency of cord blood islet autoantibodies compared with control subjects: Glutamic acid decarboxylase autoantibodies were detected in 6% (5/81) patients and 2% (5/320) control subjects (p = 0.03); islet cell antigen 512 autoantibodies in 5% (4/73) patients and 1% (4/288) control subjects (p = 0.06); insulin autoantibodies (IAA) in 0% (0/79) patients and 0.3% (1/320) control subjects (p = 0.36); and islet cell autoantibodies in 10% (8/81) patients compared with 0.6% (2/320) control subjects (p = 0.0001). Taken together, 17% (14/81) patients had one or more islet autoantibody compared with 4% (12/320) control subjects (p = 0.0001). Whereas none of the control children had more than one antibody, 4% (3/81) children who later developed Type I diabetes were double positive (p = 0.002). Although glutamic acid decarboxylase autoantibodies' concentrations in cord-blood correlated to those in the mothers' blood at the time of delivery, no corresponding correlation was found for the other two types of autoantibodies. The increased frequency of cord blood islet autoantibodies suggests that the Type I diabetes process could already be initiated in utero.

Species-specific autoantibodies in type 1 diabetes

GAD65 autoantibodies (GAD65Ab) are important markers for type 1 (insulin-dependent) diabetes mellitus. Although most patients have GAD65Ab at the time of clinical diagnosis, there are also GAD65Ab-positive individuals in the population at low risk of developing type 1 diabetes. The aim of this study was to test the hypothesis that the GAD65Ab reactivity to GAD65 cloned from human, mouse, and rat in newly diagnosed type 1 diabetic patients differ from antibody-positive healthy individuals. Sera from 254 new-onset 0- to 34-yr-old type 1 diabetic patients and 270 controls were assayed for their reactivity to human, mouse, and rat GAD65. Among the type 1 diabetic patients there was a significant better binding of human GAD65 compared to either mouse (P = 0.03) or rat GAD65 (P = 0.0005). The preference for human GAD65 increased with increasing age at onset (P = 0.0002). This differentiation was not observed in 88 GAD65Ab-positive control subjects. Our data indicate that recognition of epitopes by GAD65Ab in type 1 diabetes is different from that in nontype 1 diabetes, GAD65Ab-positive individuals.

Radioimmunoassay for glutamic acid decarboxylase-65

BACKGROUND

Glutamic acid decarboxylase-65 (GAD65), the enzyme that catalyzes the formation of gamma-aminobutyric acid (GABA), is the major autoantigen in both type 1 (insulin-dependent) diabetes and stiff-man syndrome (SMS). The observation that GAD65 autoantibodies may be present for years before the clinical onset of diabetes raises the question of when GAD65 is available to initiate an immune response to allow the formation of autoantibodies. In order to address this question it will be necessary to measure GAD65 in tissue, cells, and plasma.

METHODS

A radioimmunoassay (RIA) was developed for GAD65 based on the use of a polyclonal rabbit antiserum directed to the N-terminus of GAD65.

RESULTS

Using the GAD65 RIA, we have determined the GAD65 content in a human GAD65 gene transfected cell line and in beta-cell preparations from different species. The assay detects an increase of immunoreactive GAD65 after glucose-stimulation and GAD65 that is discharged from rat beta cells after their exposure to the diabetogenic agent streptozotocin. It also measures good recovery of GAD65 added to human plasma samples.

CONCLUSIONS

The GAD65 RIA makes it possible to determine both cellular and extracellular levels of GAD65; this might be useful in investigating the mechanisms leading to the formation of GAD65 autoantibodies in type 1 diabetes and SMS patients.

Recombinant human platelet-activating factor acetylhydrolase reduces the frequency of diabetes in the diabetes-prone BB rat

Platelet-activating factor (PAF) has been implicated in the development of type 1 diabetes. Our previous studies have suggested that PAF inhibitors reduce insulitis and the frequency of diabetes in BB rats. In this study, serum PAF levels were reduced to address the hypothesis that PAF is important for the development of insulitis. From the age of 35 days on, DP-BB rats were treated with human recombinant PAF acetylhydrolase (rPAF-AH), which efficiently inactivates PAF. Our data indicate that intraperitoneal injections of rPAF-AH reduce the incidence of diabetes in the DP-BB rat. Daily intraperitoneal injections of 6.0 mg/kg body wt rPAF-AH reduced the frequency of diabetes in saline-injected rats from 90% (27/30) to 57% (17/30) (P = 0.004). As found by morphometric analysis on pancreatic islets, DP-BB rats protected from diabetes had less severe degrees of insulitis in a dose-dependent manner. DP-BB rats protected by rPAF-AH also had a higher percentage of insulin-positive cells in pancreas sections compared with those from diabetic animals. We therefore speculated that the beta-cells were protected from insulitis by rPAF-AH.

The development of a World Health Organisation international standard for islet cell antibodies: the aims and design of an international collaborative study

Islet cell antibodies (ICA) are a specific marker for Type 1 (insulin-dependent) diabetes mellitus. ICA are found in the serum of over 80% of newly diagnosed patients and the levels of ICA are directly of prognostic value. Standardisation of ICA and the uniform reporting of ICA levels in international units is critical to preclinical/clinical research and the development of assays for ICA as diagnostics, in particular for the differential diagnosis of late onset Type 1 and Type 2 diabetes. Proficiency studies carried out by the Immunology of Diabetes Workshops on Standardization have clearly shown that a single reference material, serum sample 673, obtained by Dr J. Ludvigsson, has significantly reduced inter- and intra-assay variability in the reporting of ICA levels. Nevertheless, this material is a frozen serum of limited shelf-life and is difficult to distribute on a worldwide and routine basis. Therefore, the Immunology of Diabetes Workshop Standardization Committee and the Juvenile Diabetes Foundation International requested that the National Institute for Biological Standards and Control (NIBSC) organise an international collaborative study to compare the activities of lyophilised, stable ICA preparations. In addition, the purpose was to investigate if sample 673 could also serve as a standard for GAD65 and IA-2 antibodies. Twenty participants in eight countries have been recruited to the study.

Severe insulin resistance in a patient with type 1 diabetes and stiff-man syndrome treated with insulin lispro

We describe a patient with type 1 diabetes with recurrent diabetic ketoacidosis and severe insulin resistance. Extensive evaluation of the etiology of the insulin resistance did not reveal an etiology, and well over 1000 U of daily insulin did not prevent the ketoacidosis. Her blood glucose and insulin requirements were improved with glucocorticoids and octreotide, but the effects of both of these agents were short-lived. She was given a trial of insulin lispro with immediate and dramatic effects, lowering her HbA1c from 14.6 to 5.1% in 7 months with a decrease in insulin requirements of 1600-100 U per day. Besides her diabetes, she had a history of pain and stiffness affecting numerous muscle groups, and hospitalization was required for pain control. The diagnosis of stiff-man syndrome (SMS) was confirmed with high titers of glutamic acid decarboxylase 65 antibodies in both serum and cerebral spinal fluid. In summary, we describe the first patient with type 1 diabetes, SMS, and severe insulin resistance. Although the etiology of the insulin resistance is unknown, due to the efficacious response to insulin lispro, hydrocortisone, and perhaps octreotide, we propose an immune-mediated etiology. Although rare, this syndrome needs to be considered as an etiology of insulin resistance.

Etiological diagnosis of primary adrenal insufficiency using an original flowchart of immune and biochemical markers

Approximately 70-80% of cases of primary adrenal insufficiency are classified as idiopathic. An effective protocol for the etiological diagnosis of primary adrenal insufficiency is needed to ensure correct patient management. With the aim of developing an algorithm for the etiological diagnosis of primary adrenal insufficiency, we studied 56 Italian patients with nonsurgical primary adrenal insufficiency and 24 French patients with X-linked adrenoleukodystrophy (ALD) for serum levels of adrenal cortex, steroid-21-hydroxylase (21OHAb), islet cell (ICA), glutamate decarboxylase (GAD65Ab), IA2/ICA512 (ICA512Ab), thyroid peroxidase (TPOAb) autoantibodies, and plasmatic concentrations of very long chain fatty acids (VLCFA). High levels of 21OH and adrenal cortex antibodies were found in 35/42 (83%) and 17/42 (40%) Italian patients with idiopathic adrenal insufficiency, respectively. Levels of adrenal autoantibodies correlated inversely with disease duration (P < 0.0001). Elevated VLCFA were found in 4/42 (10%) idiopathic patients. A total of 34/35 (97%) idiopathic patients with a disease duration of less than 20 yr was positive for either 21OHSAb or elevated levels of VLCFA. None of 14 patients with posttuberculosis adrenal insufficiency had elevated levels of either adrenal antibodies or VLCFA. ICA, GAD65Ab, ICA512Ab, and TPOAb were found in 6/56 (11%), 8/56 (14%), 4/56 (7%), and 23/56 (41%) patients, respectively. None of 24 French ALD patients with adrenal insufficiency was positive for organ-specific autoantibodies. The measuring of 21OH antibodies and plasma VLCFA levels enabled a correct diagnosis of autoimmune (89%) and ALD (8%) in 97% of patients with idiopathic primary adrenal insufficiency of less than 20 yr of duration. The results of our study have important therapeutic and prognostic implications.

Pituitary autoantibodies in patients with hypopituitarism and their relatives

Autoantibodies to human pituitary cytosol proteins were determined by immunoblotting in sera from patients with hypopituitarism and their relatives. Reactivity to an M(r) 49,000 protein was significantly more frequent in patients (6/21 (28%) P < 0.05) as well as in relatives (10/35 (28%) P < 0.02) compared with controls (3/44 (6.8%)). Autoantibodies to this particular protein have previously been detected in sera from 70% of patients with biopsy-proven lymphocytic hypophysitis. Unlike patients with biopsy-proven lymphocytic hypophysitis, none of the patients in this study presented with a suspected pituitary adenoma or showed an enlarged sella turcica. Cisternal herniation was seen in 6/21 patients and this may very well represent the end stage of lymphocytic hypophysitis. Since organ specific autoantibodies are frequent in patients with autoimmune endocrine disease as well as in their unaffected relatives, autoantibodies to this M(r) 49,000 pituitary cytosolic protein may represent markers for an immunological process affecting the pituitary gland.

Glutamate decarboxylase antibodies in non-diabetic pregnancy precedes insulin-dependent diabetes in the mother but not necessarily in the offspring

We studied the risk for diabetes of glutamate decarboxylase (GAD65Ab) and islet cell (ICA) autoantibodies in non-diabetic pregnant mothers and their children. Pregnancy and cord blood sera were collected in 1970-87 from about 35,000 mothers who delivered a child in the city of Malmö, Sweden. A total of 42 mothers were identified in 1988 who, 1-18 years after their pregnancies, had developed either insulin-dependent (n = 22) or non-insulin dependent (n = 20) diabetes mellitus. First, in 123 pregnant mothers selected as controls, 0.8% had GAD65Ab and 0.8% ICA. Second, among the mothers with non-insulin dependent diabetes, 7/20 (35%) had GAD65Ab eight months to 13 years, 10 months before clinical diagnosis. Third, in mothers who later developed insulin-dependent diabetes, 12/22 (55%) had GAD65Ab and 10/22 (45%) had ICA in pregnancies preceding the clinical diagnosis by 13 months to 9 years, 4 months. In 1996, none of the children born to the 42 mothers have developed diabetes. GAD65Ab and ICA in non-diabetic pregnancies may predict insulin-dependent diabetes in the mother but not necessarily in the offspring.

A simple and rapid microSepharose assay for GAD65 and ICA512 autoantibodies in diabetes. Diabetes Incidence Study in Sweden (DISS)

GAD65Ab and ICA512Ab are strongly associated with insulin-dependent (Type 1) diabetes mellitus. A novel, simple radio-antigen binding assay with microSepharose conjugated with monoclonal antibodies specific for human immunoglobulin light chains was developed to provide diagnostic sensitivity and specificity of GAD65Ab and ICA512Ab for Type 1 diabetes. The Receiver Operating Characteristic (ROC) curve was used to determine the upper level of Normal in 583 new onset Type 1 diabetic patients and in 829 matched controls. The sensitivity of GAD65Ab and ICA512Ab was 66% (384/583) and 41% (211/520), respectively, and the diagnostic specificity was 96% for both autoantibodies. Levels, but not frequency, of GAD65Ab were higher among female Type 1 diabetes patients, whereas ICA512Ab levels did not differ between males and females. Positivity for GAD65Ab. ICA512Ab or both showed a sensitivity of 74% and a specificity of 92% for Type 1 diabetes. This simple, one-step centrifugation, high-capacity radio-antigen binding assay has a high precision and reproducibility to accurately detect both GAD65Ab and ICA512Ab. This assay should also prove useful in other autoantibody assays against conformation-sensitive autoantigens.

Inverse relationship between GAD65 antibody levels and severe retinopathy in younger type 1 diabetic patients

Several risk factors for severe non-proliferative and proliferative retinopathy in type 1 diabetes mellitus have been proposed without explaining the rapid progression of retinopathy in some patients. Since GAD65 autoantibodies (GAD65Abs) are detected against glutamic acid decarboxylase (GAD), which is mainly expressed in islets and nervous tissue in type 1 diabetic patients, the aim of the present investigation was to test the hypothesis whether GAD65Abs are associated with rapidly progressing severe retinopathy. Patients with severe non-proliferative or proliferative retinopathy (n = 27) were compared with another group, which in spite of long diabetes duration had no or only mild signs of retinopathy (n = 28). GAD65Abs were analysed in a radioimmunoassay using in vitro translated human GAD65, and the levels were expressed as an index in relation to positive and negative reference samples. Using a cut-off level representing the 99th percentile of normals, 6/27 (22%) with and 9/28 (32%) without severe retinopathy were considered GAD65Ab positive. Although there was no difference in the number of GAD65Ab positive patients, the GAD65Ab levels were lower in patients with (0.30; 0.11-0.64) than without (0.68; 0.34-1.12) severe retinopathy (P = 0.03). The patients were also subjected to HLA-DR and DQ typing by PCR and hybridization with oligospecific probes. DQ2/8 was more common in patients with (56%) than without (29%) severe retinopathy (P = 0.05), but DQ2/8 could not account for the lower GAD65Ab levels in patients with severe retinopathy. It is concluded that GAD65Ab levels are inversely correlated with severe retinopathy in young type 1 diabetic patients.

Association between autoantibody markers and subtypes of DR4 and DR4-DQ in Swedish children with insulin-dependent diabetes reveals closer association of tyrosine pyrophosphatase autoimmunity with DR4 than DQ8

HLA DQA1*0301-DQB1*0302 (DQ8) and DQA1*0501-DQB1*0201 (DQ2) are positively and DQA1*0102-DQB1*0602 (DQ6) negatively associated with IDDM. In DQA1*0301-DQB1*0302 (DQ8)-positive patients, susceptibility is also mediated by DRB1*0401. The aim of the study was to determine the association between HLA-DR4 and DQ and the presence of GAD65, ICA512, and insulin autoantibodies as well as ICA in 425 Swedish children with IDDM and 367 controls in the age group of 0-15 years. We found that ICA512 autoantibodies were associated primarily with DRB1*0401 and not with DQA1*0301-DQB1*0302 (DQ8). No such hierarchy could be demonstrated for insulin autoantibodies, which were associated with both DQA1*0301-DQB1*0302 (DQ8) and DRB1*0401. GAD65 autoantibodies, known to be closely associated with DQA1*0501-DQB1*0201 (DQ2)-DRB1*0301 haplotype, also showed no preferential association with DQA1*0301-DQB1*0302 (DQ8) versus DRB1*04. These results suggest that the immune response to different beta-cell autoantigens may be mediated via HLA class II molecules from different loci. Design of the antigen-specific immuno-intervention trials should take into account these HLA-DR and DQ subtype associations.

Immunology in diabetes: an update

Type 1 (insulin-dependent) diabetes mellitus is strongly associated with autoimmune phenomena connected to the loss of beta-cells in the pancreatic islets. Despite considerable progress in our understanding of genetic susceptibility factors and islet autoimmunity preceding the clinical onset of Type 1 diabetes there are considerable gaps in our knowledge. First, the etiology is unclear. It is speculated that multiple etiological factors may initiate a common pathogenic pathway which results in immune-mediated beta-cell destruction. In 1998 we will need to learn more about the possible importance of gestational infections, as well as isolation of viral DNA or RNA from the blood of new-onset patients or marker-positive individuals. The scan of the whole genome has provided a smorgasbord of genetic regions which confer diabetes risk either alone or in combination. HLA remains the major genetic risk factor, and while HLA peptide binding information is considerable, we understand less of autoantigen processing and presentation. Cloned autoantigens and their use in standardized autoantibody assays have improved our ability to identify individuals at risk for diabetes. The diagnostic sensitivity and specificity of autoantibody markers for Type 1 diabetes are high as are their predictive values. We need methods to combine autoantibodies with genetic risk factors. The identification of individuals in different stages of their pathogenesis, including patients with so-called slowly progressive Type 1 diabetes (SPIDDM, LADA etc.), allow approaches to novel therapeutic interventions. Insulin is currently the therapeutic agent of choice and although spontaneous insulin-dependent diabetes in the NOD mouse and the BB rat can be prevented by immune suppression or modulation, this has not yet been possible in humans. The 1998 research on the interaction between environmental factors and susceptibility genes to initiate beta-cell specific autoreactivity should allow the development of therapies for prevention, and perhaps a cure, of insulin-dependent (Type 1) diabetes.

Immune surveillance: paraneoplastic or environmental triggers of autoimmunity

Autoimmunity associated with tumor cell development seems an important mechanism by which to prevent progression to clinical cancer. In this brief review, tumor autoantigens associated with paraneoplastic syndrome, non-HLA-associated organ-specific autoimmune diseases, and the highly cell-specific autoimmune eradication of the islet beta cells in type 1 diabetes are compared and discussed. It is suggested that autoreactivity is important in preventing tumor formation; however, it may be at the expense of the development of autoimmune disease. Although the cytotoxic T lymphocytes (CTL) induction by HLA class I has been studied and used in clinical trials, little is understood about the initiation and HLA class II mediated induction of an immune response to neoplastic cells. This induction apparently takes place because paraneoplastic disorders are often due to an immune response to the tumor cell resulting in a cross-reactivity with a normally expressed autoantigen on a remote nontumor-associated target cell. The problem of immune surveillance to eradicate neoplasm or downregulate pathological autoimmunity are therefore closely related phenomena. An improved understanding of immune mediated tumor suppression should therefore greatly benefit immunotherapy of type 1 diabetes, and the two areas of research would benefit from an interdisciplinary endeavor.

Autoantibodies to the GM2-1 islet ganglioside and to GAD-65 at type 1 diabetes onset

The GM2-1 islet ganglioside has been sequenced, found to be a novel ganglioside structure with a sialic acid moiety in the terminal position and two residues of non-acetylated galactosamine and also shown to be a target of autoantibodies in a subset of ICA+ relatives of type 1 diabetic patients who subsequently progressed to the overt disease. In the present study we determined whether antibodies to GM2-1 or to other pancreatic gangliosides (a) are also expressed at disease onset and (b) are correlated with other diabetes-associated autoantibodies. Pancreatic gangliosides were extracted from human pancreas and purified by thin layer chromatography (TLC). Anti-ganglioside autoantibodies were determined using an indirect immunoperoxidase technique performed directly on TLC plates in the following groups of patients: (a) newly diagnosed type 1 diabetic subjects before insulin therapy (n = 45); all were tested for GAD65 autoantibodies in a fluid-phase RIA using 35S-methionine-labelled recombinant human GAD65. Of these patients, 24 were also tested for insulin autoantibodies (IAA) by a competitive fluid phase radioimmunoassay and 21 were tested for GAD67 reactivity. (b) Forty-two age- and sex-matched normal control subjects. Autoantibodies to GM2-1, but not to other pancreatic gangliosides (GM3, GD3, GD1a), were expressed in 31 of 45 new-onset type 1 diabetic subjects and in one of 42 normal controls (P < 0.01), while anti-GAD65, IAA and anti-GAD67 were found in 31 of 45, 12 of 24 and three of 21 patients respectively, but not in the control group of subjects. Interestingly, occurrence of GM2-1 autoantibodies was significantly correlated (P < 0.005) with positivity for GAD65 autoantibodies, but not for IAA or GAD67 autoantibodies. It is of note that both GAD and gangliosides are mainly expressed in islets and in neuronal tissues and, therefore, type 1 diabetes may be regarded as a neuroendocrine autoimmune disease.

Antibodies to GAD and glycemic control in recent-onset IDDM

OBJECTIVE

To analyze the effect of antibodies to glutamic acid decarboxylase (GAD65Ab) and islet cells (ICA512Ab) on glycemic control early in IDDM.

RESEARCH DESIGN AND METHODS

GAD65Ab and ICA512Ab were measured twice in 35 patients (10 male, 25 female; age 10-40 years) initially within 2 years of diagnosis and again 1 year later. The glycosylated hemoglobin was measured one to four times each year, and the average glycosylated hemoglobin for the preceding year was calculated each time the antibodies were measured.

RESULTS

The mean HbA1 at the time of the initial evaluation was 8.04 +/- 0.30 (reference range 4.7-7.3% for nondiabetic patients), the average GAD65Ab index was 0.735 +/- 0.306, and the mean ICA512Ab index was 1.94 +/- 0.65. The GAD65Ab index correlated with HbA1 (r = 0.41, P < 0.025), whereas the ICA512Ab index did not (r = 0.13). One year later, the mean GAD65Ab index was 0.94 +/- 0.34, the mean ICA512Ab index was 1.04 +/- 0.40, and the mean HbA1 was 9.03 +/- 0.30. The GAD65Ab index correlated with HbA1 (r = 0.61 P < 0.001), whereas the ICA512Ab index did not (r = -0.06). Stratification of patients into tertiles according to the average GAD65 index revealed, at the follow-up evaluation, that the better glycemic control in the lowest GAD65Ab tertile was accomplished with significantly less insulin (0.43 +/- 0.08 U/kg for the lowest tertile vs. 0.71 +/- 0.09 and 0.64 +/- 0.09 for the middle and highest tertiles, respectively; P < 0.05).

CONCLUSIONS

In summary, patients with IDDM and low GAD65Ab have better glycemic control even though they require less insulin. The ICA512Ab index, however, fails to correlate with glycemia.

Age governs gender-dependent islet cell autoreactivity and predicts the clinical course in childhood IDDM

Most IDDM patients temporarily restore some of their beta-cell function following the initiation of insulin therapy. The aim of this study was to analyse the influence of age, gender, metabolic state at diagnosis and presence of autoantibodies (GAD65 antibodies and ICA) on the duration of the clinical partial remission. In total, 149 consecutively diagnosed IDDM children, 0-16 y old (70F, 79M, mean age 9.5 y) were studied. Partial remission was arbitrarily defined as the period when the insulin dose was below 0.5 U/BW 24 h-1 and HbA1c below 7.5%, and occurred in 119/149 patients with a duration between 1 and 38 months. Cox's regression analysis showed that the factors significantly associated with the duration of remission were age, gender, interaction between age and gender, ICA and a high initial HbA1c, whereas GAD65Ab had no influence. Young boys had the shortest remission period, while adolescent boys had the longest, as compared to young and adolescent girls. The ICA-negative patients (n = 42) had a longer remission period (median 9.7 months) than the ICA-positive children (n = 107; 5.0 months; p = 0.0001), regardless of GAD65Ab status. We speculate that the relative insulin resistance, which is more pronounced in pubertal girls than in boys, may be associated with a more rapid increase of exogenous insulin requirement. These findings are important when evaluating the effect of islet cell autoreactivity on the clinical course of IDDM in children.

Associations of GAD65- and IA-2- autoantibodies with genetic risk markers in new-onset IDDM patients and their siblings. The Belgian Diabetes Registry

OBJECTIVE

To investigate the association of GAD (65-kDa) autoantibodies (GAD65-Abs) and IA-2 autoantibodies (IA-2-Abs) with human leukocyte antigen (HLA)-DQ and insulin gene (INS) risk markers in patients with recent-onset IDDM and their siblings.

RESEARCH DESIGN AND METHODS

Blood was sampled from 608 recent-onset IDDM patients and 480 siblings, aged 0-39 years and consecutively recruited by the Belgian Diabetes Registry, to determine GAD65- and IA-2-Ab (radiobinding assay), HLA-DQ- (allele-specific oligonucleotyping), and INS-genotypes (restriction fragment length polymorphism analysis; siblings, n = 439).

RESULTS

At the onset of IDDM, GAD65-Abs were preferentially associated with two populations at genetic risk but only in the 20- to 39-year age-group: 1) their prevalence was higher in carriers of DQA1*0301-DQB1*0302 (88 vs. 73% in non[DQA1*0301-DQB1*0302], P = 0.001), and 2) an association was found in patients lacking this haplotype but carrying DQA1*0501-DQB1*0201, together with INS I/I (87 vs. 54% vs. non[INS I/I], P = 0.003). Siblings of IDDM patients also presented the association of GAD65-Abs with DQA1*0301-DQB1*0302 (13 vs. 2% non[DQA1*0301-DQB1*0302], P < 0.001), while associations with the second genetic risk group could not yet be assessed. At the onset of IDDM, IA-2-Ab prevalence was higher in carriers of DQA1*0301-DQB1*0302 (69 vs. 39% non[DQA1*0301-DQB1*0302], P < 0.001) but not of DQA1*0501-DQB1*0201 or INS I/I. This association was present in both the 0- to 19- and the 20- to 39-year age-groups. It was also found in siblings of IDDM patients (4 vs. 0% non[DQA1*0301-DQB1*0302], P < 0.001).

CONCLUSIONS

Both GAD65- and IA-2-Abs exhibit higher prevalences in presence of HLA-DQ- and/or INS-genetic risk markers. Their respective associations differ with age at clinical onset, suggesting a possible usefulness in the identification of subgroups in this heterogeneous disease.