Ten-year follow-up study of islet-cell antibodies and childhood diabetes mellitus

Autoantigens as Partners in Initiation and Propagation of Autoimmune Rheumatic Diseases

Systemic autoimmune diseases are characterized by specific targeting of a limited group of ubiquitously expressed autoantigens by the immune system. This review examines the mechanisms underlying their selection as immune targets. Initiation of autoimmune responses likely reflects the presentation of antigens with a distinct structure not previously encountered by the immune system, in a proimmune context (injury, malignancy, or infection). Causes of modified structure include somatic mutation and posttranslational modifications (including citrullination and proteolysis). Many autoantigens are components of multimolecular complexes, and some of the other components may provide adjuvant activity. Propagation of autoimmune responses appears to reflect a bidirectional interaction between the immune response and the target tissues in a mutually reinforcing cycle: Immune effector pathways generate additional autoantigen, which feeds further immune response. We propose that this resonance may be a critical principle underlying disease propagation, with specific autoantigens functioning as the hubs around which amplification occurs.

Prediction of type 1 diabetes in Sardinian schoolchildren using islet cell autoantibodies: 10-year follow-up of the Sardinian schoolchildren type 1 diabetes prediction study

AIMS

Stable genetic background makes individuals from the Mediterranean island of Sardinia ideal to define the predictive power of islet-related autoantibodies (IRAs): glutamic acid decarboxylase antibodies (GADA), tyrosine phosphatase-like antibodies (IA-2A), islet cell antibodies (ICA) to identify T1DM progressors. The aims of the present study were: (1) determination of IRAs reference limits in healthy non-diabetic Sardinian schoolchildren (SSc). (2) Predictive power evaluation of IRAs as single or combined determination to identify islet to identify T1DM progressors.

METHODS

Between 1986 and 1994, 8448 SSc were tested for IRAs. All were followed up for 10 years. The predictive power of single or combination of IRAs was determined as hazard ratio (HR), sensitivity, specificity, area under the ROC curve, negative and positive predictive value (NPV, PPV).

RESULTS

All 43 progressors to T1DM, but three showed at least one autoantibody positivity. HR for any single-autoantibody positivity was 55.3 times greater when compared to SSc negative for all IRAs. Any single autoantibody performed at least 64.9 % sensitivity with PPV always lower than 16 %. The best performing combination was ICA, plus IA-2A (showing 52.6 % sensitivity, 99.8 % specificity, 0.76 area under the ROC curve, 51.3 % PPV and 99.8 % NPV.

CONCLUSIONS

Determination of IRAs reference limits in healthy SSc by standard statistical methods is crucial to establish the power of IRAs as progression markers to T1DM. Our data offer a solid rationale for future testing of ICA and IA-2A as routine laboratory markers to identify individuals at high risk of T1DM in the general population.

Is It Time to Screen the General Population for Type 1 Diabetes?

Type 1 diabetes (T1D) is a chronic autoimmune disease characterized by destruction of insulin-producing β cells in the pancreas. The incidence of T1D is increasing dramatically, and the prevalence has doubled in the last 2 decades, further increasing the morbidity and mortality associated with the disease. T1D is now predictable with the measurement of antibodies directed against β cell proteins. Islet autoantibodies (IAs) are detectable from the peripheral blood months to years before clinical diagnosis. With the presence of two or more antibodies, the risk for developing T1D is nearly 100 % given enough time. Targeted screening for T1D risk has been carried out in first-degree relatives and those with a significant genetic risk. However, more than 85 % of individuals who are diagnosed with T1D do not have a family history. In light of the predictability of T1D and recent advances in IA measurement, general population screening is on the horizon. We provide an overview of the history of general population screening and discuss the rationale for and arguments against screening the general population for T1D risk.

Occurrence of type 1 diabetes in graves' disease patients who are positive for antiglutamic Acid decarboxylase antibodies: an 8-year followup study

Glutamic acid decarboxylase antibodies (GADAs) are one of the markers of islet cell autoimmunity and are sometimes present before the onset of type 1 diabetes (T1D). GADA can be present in Graves' patients without diabetes; however, the outcome of GADA-positive Graves' patients is not fully understood, and the predictive value of GADA for the development of T1D in Graves' patients remains to be clarified. We investigated the prevalence of GADA in 158 patients with Graves' disease and detected GADA in 10 patients. They were followed up to discover whether or not T1D developed. In the course of eight years, 2 patients with high titers of GADA developed T1D, both had long-standing antithyroid drug-resistant Graves' disease. Thus, Graves' disease with high GADA titer seems to be at high risk for T1D.

Prediction of type 1 diabetes in the general population

OBJECTIVE

To evaluate the utility of GAD antibodies (GADAs) and islet antigen-2 antibodies (IA-2As) in prediction of type 1 diabetes over 27 years in the general population and to assess the 6-year rates of seroconversion.

RESEARCH DESIGN AND METHODS

A total of 3,475 nondiabetic subjects aged 3-18 years were sampled in 1980, and 2,375 subjects (68.3%) were resampled in 1986. All subjects were observed for development of diabetes to the end of 2007. GADAs and IA-2As were analyzed in all samples obtained in 1980 and 1986.

RESULTS

A total of 34 individuals (1.0%; 9 developed diabetes) initially had GADAs and 22 (0.6%; 9 developed diabetes) IA-2As. Seven subjects (0.2%) tested positive for both autoantibodies. The positive seroconversion rate over 6 years was 0.4% for GADAs and 0.2% for IA-2As, while the inverse seroconversion rates were 33 and 57%, respectively. Eighteen subjects (0.5%) developed type 1 diabetes after a median pre-diabetic period of 8.6 years (range 0.9-20.3). Initial positivity for GADAs and/or IA-2As had a sensitivity of 61% (95% CI 36-83) for type 1 diabetes. Combined positivity for GADAs and IA-2As had both a specificity and a positive predictive value of 100% (95% CI 59-100).

CONCLUSIONS

One-time screening for GADAs and IA-2As in the general childhood population in Finland would identify approximately 60% of those individuals who will develop type 1 diabetes over the next 27 years, and those subjects who have both autoantibodies carry an extremely high risk for diabetes. Both positive and inverse seroconversions do occur over time reflecting a dynamic process of beta-cell autoimmunity.

Pre-type 1 diabetes dysmetabolism: maximal sensitivity achieved with both oral and intravenous glucose tolerance testing

OBJECTIVE

To determine the relationship of intravenous (IVGTT) and oral (OGTT) glucose tolerance tests abnormalities to diabetes development in a high-risk pre-diabetic cohort and to identify an optimal testing strategy for detecting preclinical diabetes.

STUDY DESIGN

Diabetes Prevention Trial-Type 1 Diabetes (DPT-1) randomized subjects to oral (n = 372) and parenteral (n = 339) insulin prevention trials. Subjects were followed with IVGTTs and OGTTs. Factors associated with progression to diabetes were evaluated.

RESULTS

Survival analysis revealed that higher quartiles of 2-hour glucose and lower quartiles of first phase insulin response (FPIR) at baseline were associated with decreased diabetes-free survival. Cox proportional hazards modeling showed that baseline body mass index (BMI), FPIR, and 2-hour glucose levels were significantly associated with an increased hazard for diabetes. On testing performed within 6 months of diabetes diagnosis, 3% (1/32) had normal FPIR and normal 2-hour glucose on OGTT. The sensitivities for impaired glucose tolerance (IGT) and low FPIR performed within 6 months of diabetes diagnosis were equivalent (76% vs 73%).

CONCLUSIONS

Most (97%) subjects had abnormal IVGTTs and/or OGTTs before the development of diabetes. The highest sensitivity is achieved using both tests.

Patterns of metabolic progression to type 1 diabetes in the Diabetes Prevention Trial-Type 1

OBJECTIVE

There is little information regarding the pattern of metabolic deterioration before the onset of type 1 diabetes. The goal of this study was to utilize data from the Diabetes Prevention Trial-Type 1 (DPT-1) to obtain a picture of the metabolic progression to type 1 diabetes over a period of approximately 2.5 years before its diagnosis.

RESEARCH DESIGN AND METHODS

Fifty-four DPT-1 participants (22 in the parenteral trial and 32 in the oral trial) were studied. All had oral glucose tolerance tests (OGTTs) at 6-month intervals from approximately 30 to 6 months before diagnosis. The vast majority also had OGTTs at diagnosis. Changes in OGTT glucose and C-peptide indexes from 30 to 6 months before diagnosis were examined by calculating slopes of the indexes for each individual over that time period. Changes from 6 months before diagnosis to diagnosis were examined by paired comparisons of the OGTT metabolic indexes between the time points.

RESULTS

Glucose levels increased gradually from 30 to 6 months before diagnosis in both the parenteral and oral groups (P < 0.001 for all indexes). Area under the curve (AUC) C-peptide (P < 0.05) and AUC C-peptide-to-AUC glucose ratio (P < 0.001) values decreased in the oral group; peak C-peptide-to-2-h glucose ratio values decreased in both groups (P < 0.001). In participants who also had OGTTs at diagnosis, AUC C-peptide (parenteral group, P < 0.05) and peak C-peptide (oral group, P < 0.05) values decreased from the last 6 months before diagnosis; stimulated C-peptide-to-glucose ratio values decreased in both groups (P < 0.001). Conversely, fasting C-peptide levels increased in both groups (oral group, P < 0.01). Fasting C-peptide-to-fasting glucose ratio values remained constant throughout the 30-month follow-up.

CONCLUSIONS

These data indicate that over a period of at least 2 years, glucose tolerance gradually deteriorates as stimulated C-peptide levels slowly decline in a substantial number of individuals who develop type 1 diabetes. However, fasting C-peptide levels are maintained, even at diagnosis.

Successful prospective prediction of type 1 diabetes in schoolchildren through multiple defined autoantibodies: an 8-year follow-up of the Washington State Diabetes Prediction Study

OBJECTIVE

Almost 90% of type 1 diabetes appears in individuals without a close family history. We sought to evaluate the best current predictive strategy, multiple defined autoantibodies, in a long-term prospective study in the general population.

RESEARCH DESIGN AND METHODS

Autoantibodies to pancreatic islets (islet cell antibodies [ICAs]) and defined autoantibodies (d-aab) to human GAD, IA2/ICA512, and insulin were tested in 4,505 Washington schoolchildren. Eight years later, 3,000 (67%) subjects were recontacted, including 97% of subjects with any test >99th percentile.

RESULTS

Six subjects developed diabetes (median interval 2.8 years), all from among the 12 individuals with multiple d-aab, representing 50% positive predictive value (95% CI 25-75%) and 100% sensitivity (58-100%). Among the others, diabetes occurred in 0 of 6 with one d-aab plus ICA, 0 of 26 with ICA only, 0 of 7 with one d-aab equaling the 99th percentile and another d-aab equaling the 97.5th percentile, 0 of 86 with one d-aab, and 0 of 2,863 with no d-aab or ICA. Adjusted for verification bias, multiple d-aab were 99.9% specific (99.86-99.93%). At this age, new d-aab seldom appeared. Once present, d-aab usually persisted regardless of disease progression, although less so for insulin autoantibodies. Insulin secretion by sequential glucose tolerance testing remained normal in four multiple d-aab subjects not developing diabetes. Of children developing diabetes, five of six (83%) would be included if HLA-DQ genotyping preceded antibody testing, but HLA-DQ did not explain outcomes among high-risk subjects, even when considered along with other genetic markers.

CONCLUSIONS

Multiple d-aab were established by age 14 years and prospectively identified all schoolchildren who developed type 1 diabetes within 8 years.

Low prevalence of GAD and IA2 antibodies in schoolchildren from a village in the southwestern section of the Netherlands

Glutamic acid decarboxylase (GAD) and insulinoma antigen 2 (IA2) antibodies are increasingly used as a tool to predict type I diabetes in children and as a differential diagnostic tool to distinguish type I and type II diabetes in adults. However, the background frequency of these antibodies in the general population has not been extensively studied and may differ between countries. The current study aims to establish the frequency of GAD and IA2 antibodies in an unselected population of schoolchildren and confirm the previously reported low prevalence of islet cell antibodies (ICA) in the general Dutch population. The study population consisted of 1403 unselected schoolchildren. All children were tested for GAD antibodies, and 1085 children were analyzed for IA2 antibodies by radiobinding assay. Development of diabetes was recorded during a 7-year follow-up. Five children (0.4%) were positive for GAD antibodies, one child (0.1%) was positive for IA2 antibodies. Two children developed diabetes during follow-up, one was positive for GAD antibodies only, the second was positive for both GAD and IA2 antibodies. The frequency of GAD and IA2 antibodies in the southwestern part of The Netherlands is low. This observation is in concordance with earlier studies on ICA in Dutch schoolchildren. For future diabetes prediction and intervention trials it is important to establish the background frequencies and predictive power of antibody screening in different populations.

Antibodies to SOX13 (ICA12) are associated with type 1 diabetes

SOX13 is an islet cell autoantigen (ICA12), identified by antibody screening of an islet cDNA library, using sera from patients with Type 1 diabetes. We ascertained the frequency of antibody reactivity to SOX13 and compared it with other Type 1 diabetes autoantibody reactivities. Antibodies were measured by radioimmunoprecipitation (RIP) using (35) S labelled SOX13 expressed in rabbit reticulocyte lysate. Sera from 109 subjects with Type 1 diabetes, 29 with Type 2 diabetes, 144 with other autoimmune diseases and from 201 controls were tested for anti-SOX13, and results were compared with the frequency of antibodies to glutamic acid decarboxylase (anti-GAD), islet cell antigen 512 (anti-ICA512) and islet cell cytoplasm (ICA). Anti-SOX13 were detected in 20 (18.3%) of 109 subjects with Type 1 diabetes, and more frequently in adults than in children (29% vs 10%). Anti-SOX13 usually occurred with anti-GAD but rarely with anti-ICA512. Seven sera positive for anti-SOX13 did not react with either GAD, ICA512 or islet cell cytoplasm indicating that anti-SOX13 represented a distinct population of antibodies. Reactivity to SOX13 represents a further autoantibody response in adults with Type 1 diabetes and may provide a useful disease marker in subjects in whom other autoantibody tests are negative.

HLA-DQ polymorphism and degree of heteroplasmy of the A3243G mitochondrial DNA mutation in maternally inherited diabetes and deafness

AIM

Maternally inherited diabetes and deafness (MIDD) associates with a mutation at position 3243 in mitochondrial DNA. Phenotypic expression of MIDD includes Type 1-like and Type 2-like diabetes. This study examined whether HLA-DQ phenotype and the degree of heteroplasmy in leucocyte and oral mucosa DNA influence clinical expression of the 3242 mutation.

METHODS

In a group of 20 unrelated probands with MIDD, eight with Type 1- like diabetes, 12 with Type 2-like diabetes, HLA-DQ type and degree of heteroplasmy for the 3243 mutation were determined. HLA-DQA1/DQB1 phenotypes were categorized as predisposing, neutral or protective for autoimmune-mediated Type 1 diabetes.

RESULTS

No differences were observed between Type 1 and Type 2-like MIDD groups with respect to the cumulative frequency of protective and predisposing HLA-DQ types. Predisposing HLA-DQ types are more prevalent in MIDD patients than in the control population (P < 0.05). Degrees of heteroplasmy for the 3243 mutation showed large variations in patients, ranging from 1 to 52% in leucocyte DNA. A strong correlation was seen between heteroplasmy in leucocyte DNA and DNA from oral mucosa cells (r = 0.89, P < 0.001). No correlation was observed between the degree of heteroplasmy and diabetic phenotype, even when group size was extended with diabetic relatives of patients with MIDD. The age of diagnosis of diabetes was not correlated with heteroplasmy, but the degree of heteroplasmy tended to decrease with age.

CONCLUSIONS

The phenotype of diabetes in MIDD appears to be independent of HLA-DQ phenotype and degree of heteroplasmy in leucocyte and oral mucosa DNA indicating that other, as yet unknown, factors modulate clinical expression of the 3243 mutation.

Clinical evaluation of a radioimmunoprecipitation assay for IA-2 antibody and comparison of GAD antibody in type 1 diabetes mellitus

We evaluated a insulinoma-associated protein (IA-2) antibody assay kit using 125I-labelled recombinant IA-2. IA-2 antibodies were present in patients with early-onset type 1 diabetes mellitus (DM) at frequencies of 74%, 67%, 57%, and 50% for respective periods <1 year, 1 < or =years<2, 2< or =years<3, and 3< or =years<4 after onset. IA-2 antibody frequency was low throughout the DM course as compared with glutamic acid decarboxylase (GAD) antibody frequency. No one had IA-2 antibody, but 29% still had positive GAD antibody titers after 11 years. Of the patients with 0<years<7 duration, 42% had IA-2 Ab+/GAD Ab+, 9% IA-2 Ab+/GAD Ab-, and 24% IA-2 Ab-/GAD Ab+. Prevalence of IA-2 and GAD antibody in 1243 patients with type 2 DM were 1.5% and 3.1%, respectively, and 1.1% had both. This new IA-2 antibody kit is easy to use and provides a specific, sensitive method for making routine assays. Furthermore, the combined analysis of GAD antibody provides high detection of type 1 DM.

Glutamic acid decarboxylase and islet cell antibodies in healthy Estonian children

The prevalence of antibodies to the 65 kDa isoform of glutamic acid decarboxylase (GADA) was compared with that of islet cell antibodies (ICA) in 614 non-diabetic Estonian children (314 males) aged 3-18 years representing the general population. GADA were analyzed with a radioligand assay, and ICA with a standard immunofluorescence method with a detection limit of 2.5 Juvenile Diabetes Foundation (JDF) units. Fourteen subjects (2.3%, 95% confidence interval [CI] 1.1-3.5%) tested positive for GADA (median level 10.8 relative units [RU], range 7.7-154.2 RU), while 10 (1.6%, CI 0.6-2.6%) had ICA (median levels 34 JDF units, range 3-97 JDF units). Five subjects (0.8%, CI 0.1-1.5%; p = 0.03 vs GADA and 0.15 vs ICA) were double positive. The individual with the second highest GADA level (129.3 RU) and the highest ICA level (97 JDF units) presented with type 1 diabetes 4 months later. A follow-up sample was obtained approximately 3-4 years after the first sampling in 14 subjects initially positive for ICA and/or GADA. Four of the nine initially ICA-positive children remained positive, but their levels decreased from a median of 42 to 18 JDF units (p = 0.06). Only two of the nine retested subjects initially positive for GADA remained positive in the second sample. These observations suggest that the prevalence of GADA in non-diabetic children is of the same magnitude as that of ICA. Combined positivity for both GADA and ICA is less prevalent than single antibody specificities, indicating that double autoantibody positivity may have a higher predictive value for future type 1 diabetes in the general population than either antibody separately. The evanescent character of diabetes-associated autoantibodies in a proportion of the unaffected children implies that more subjects may experience self-restricted beta-cell damage than the number progressing to actual disease.

Permanent neonatal diabetes mellitus: clinical presentation and epidemiology in Oman

AIM

To estimate the accurate incidence and prevalence of permanent neonatal diabetes mellitus, and to determine the clinical profile of this condition in the Sultanate of Oman.

METHODS

All children diagnosed as having permanent neonatal diabetes mellitus between 1991 and 1995 in Oman were included in the study.

RESULTS

The mean incidence was 2.2 per 100 000 live births/year and the prevalence among under 5s during 1995 was 2.0/100 000. Intrauterine growth retardation was noted in all (mean birthweight 1.86 kg), and diabetic ketoacidosis (mean plasma glucose 34.4 (SD 8.7) mmol/l, mean pH 7.17 (SD 0.09) in 80%. Hypertriglyceridaemia (mean serum triglyceride 19.06 (6.13) mmol/) was constant. No infant had clinical or immunological evidence of congenital viral infections. None had C-peptide excretion or circulating islet cell antibody during diagnosis or follow up. The other important features were parental consanguinity in all, HLA DR3/DR4 association in 80%, development of autoimmune hypothyroidism in one and observation of autoimmune disorders (insulin dependent diabetes mellitus and Hashimoto's thyroiditis) in family members.

CONCLUSIONS

These findings strongly suggest an immune mediated aetiology for diabetes mellitus. The reported incidence of permanent insulin dependent neonatal diabetes mellitus in Oman is the highest in the world.

Antibody screening in a population of children

The first large-scale (secondary) intervention trials have been initiated in first-degree family members of patients with insulin-dependent diabetes mellitus (IDDM). Within a few years, data from these studies may suggest that intervention is possible, thereby opening similar approaches in the general population. However, before large-scale intervention studies can be initiated, several problems need to be solved. One of these problems is the lack of knowledge on the natural course of beta-cell autoimmunity. This review analyses this and other issues related to population-based prediction for IDDM. At present, no long-term follow-up studies are available in large-sized populations, but data show that prediction in the general population is both technically feasible and likely to have sufficient power to be useful in prevention trials. More data need to be generated, not only to determine which markers are most likely to give good prediction but also to obtain knowledge on the natural course, psychosocial impact and cost-effectiveness of screening.

Identification and characterization of glima 38, a glycosylated islet cell membrane antigen, which together with GAD65 and IA2 marks the early phases of autoimmune response in type 1 diabetes

Immunoprecipitating IgG autoantibodies to glutamic acid decarboxylase, GAD65, and/or a tyrosine phosphatase, IA2, are present in the majority of individuals experiencing pancreatic beta cell destruction and development of type 1 diabetes. Here we identify a third islet cell autoantigen, a novel 38-kD protein, which is specifically immunoprecipitated with sera from a subset of prediabetic individuals and newly diagnosed type 1 diabetic patients. The 38-kD autoantigen, named glima 38, is an amphiphilic membrane glycoprotein, specifically expressed in islet and neuronal cell lines, and thus shares the neuroendocrine expression patterns of GAD65 and IA2. Removal of N-linked carbohydrates results in a protein of 22,000 Mr. Glima 38 autoantibodies were detected in 16/86 (19%) of newly diagnosed patients, including three very young children, who had a rapid onset of disease, and in 6/44 (14%) of prediabetic individuals up to several years before clinical onset. The cumulative incidence of GAD65 and glima 38 antibodies in these two groups was 83 and 80%, respectively, and the cumulative incidence of GAD65, glima 38, and IA2 antibodies in the same groups was 91 and 84%, respectively. GAD65, IA2, and glima 38 represent three distinct targets of immunoprecipitating IgG autoantibodies associated with beta cell destruction and type 1 diabetes.

Increased incidence of non-insulin-dependent diabetes mellitus among adolescents

OBJECTIVE

To determine whether a rise in the diagnosis of non-insulin- dependent diabetes mellitus (NIDDM) has accompanied the rise in obesity in the pediatric population, as it has among adults.

STUDY DESIGN

Medical records of 1027 consecutive patients from birth to age 19 years with a diagnosis of diabetes from 1982 to 1995 at a regional, university-affiliated pediatric diabetes referral center were reviewed and classified according to criteria of the National Diabetes Data Group.

RESULTS

The number of patients with a diagnosis of NIDDM rose from approximately 4% of new diagnoses of diabetes in patients from birth to age 19 years before 1992, to 16% in 1994. Among patients 10 to 19 years of age, NIDDM accounted for 33% of diagnoses of diabetes in 1994. The incidence of adolescent NIDDM in Greater Cincinnati increased tenfold, from 0.7/100,000 per year in 1982 to 7.2/100,000 per year in 1994. The mean (+/- SD) age and body mass index at presentation were 13.8 +/- 1.9 years and 37.7 +/- 9.6 kg/m2, respectively. The overall female/male ratio was 1.7:1, and female patients were seen 1 year earlier than male patients (p < 0.01). Male subjects had a higher body mass index than female subjects (p < 0.05). A first-degree relative with NIDDM was identified for 65% of patients. At presentation, 21% of the patients had had a diagnosis of at least one other condition associated with obesity.

CONCLUSION

There is an increasing incidence of NIDDM among adolescents in Greater Cincinnati, accompanying the national rise in adolescent obesity. Obesity and strong family histories of NIDDM are important risk factors. Because NIDDM leads to long-term morbidity, the prevention of obesity as well as early identification of overt disease, is critical.

Islet cell antibodies (ICA), insulin autoantibodies (IAA), islet cell surface antibodies (ICSA) and C-peptide in 1031 school children in a population with a high background incidence of IDDM

Islet cell antibodies (ICA), insulin autoantibodies (IAA) and islet cell surface antibodies (ICSA) together with C-peptide were determined in 1031 healthy schoolchildren to evaluate the frequency of autoimmune reactions towards endocrine pancreas and its relation to insulin secretion in non-diabetic children. The prevalence of ICA (levels > 6 JDF units) was 1.4% (14/1012) while 44 children (4.3%) were ICSA-positive and 40 (4%) had IAA. Girls had higher titres of ICSA than boys. Young children (7-8 years) more often had IAA than 12-13-year-old children who, however, had ICA three times more often than the young children. There were no clear associations between the different antibodies. Of the children, 2.4% had very low post-prandial serum C-peptide values (< or = 0.25 nmol/l). Serum C-peptide was higher in girls than in boys (P < 0.001) and in older children than in younger (P < 0.001). Girls with low levels of ICA had high C-peptide values, while girls with high ICA titers had low C-peptide values, the latter perhaps indicating partial beta cell loss. IAA and ICSA were not related to C-peptide values but both positive ICSA and high C-peptide values were most common in the autumn (P < 0.02 and P < 0.0001, respectively). One of the ICA-positive children developed diabetes in 1991, 4 years after the blood sample was taken. Since after 5 years only one of the children has developed IDDM, it can be concluded autoimmune reactions towards endocrine pancreas and insulin may occur in many children without the development of manifest diabetes. Those with high ICA titers may have lost so many beta cells that their insulin secretion is affected, which in some cases might lead to diabetes many years later.

Islet cell cytoplasmic antibody reactivity in midgestational human fetal pancreas

The reactivity of islet cell cytoplasmic antibodies (ICA)-positive and ICA-negative sera of recent onset type 1 diabetic patients was studied in human fetal pancreata of 12-18 weeks' gestation and compared with the reactivity of these sera in adult human control pancreata. The aims of the study were: (1) to observe the presence of ICA staining in human fetal islet cells; (2) to compare endpoint titres (in Juvenile Diabetes Foundation units) of ICA-positive patient sera in fetal pancreata and adult human control pancreata. Ten ICA-positive sera and eight ICA-negative sera from newly diagnosed diabetic patients and four sera from healthy controls were tested on three human adult and eight human fetal pancreata. As in the adult control pancreata. ICA-positive sera reacted to insulin-, glucagon-, and somatostatin-positive cells of fetal pancreata of all gestational ages. This was observed both in single cells and in cells in islet-like cell clusters. Dilution of a reference serum gave similar results in both adult and fetal pancreata. In contrast, the ICA-positive patient sera yielded a striking heterogeneity in fetal as well as in adult pancreata. However, end-point titres between adult and fetal pancreata did not differ significantly (P > 0.05). In conclusion, ICA-positive sera from recent onset diabetic patients show that the expression of molecules to which ICA react is present in all islet cells and starts before week 12 of gestation.

No association between anti-bovine serum albumin antibodies and islet cell reactive antibodies in newly diagnosed type 1 diabetic patients

Serological findings have suggested that antibodies (Ab) to bovine serum albumin (BSA-Ab) are associated with type 1 diabetes mellitus. The aim of our study was to evaluate a competitive fluid-phase radioimmunoassay for detecting BSA-Ab using different incubation times and to study a possible association of these BSA-antibodies with autoantibodies (AAb) frequently detected in type 1 diabetic patients. For the overnight incubation time, there was an enormous overlap in the [125I]BSA binding by serum samples between 52 newly diagnosed type 1 diabetic patients (mean [125I]BSA binding 23.6 +/- 17.4%) and 54 healthy blood donors (mean [125I]BSA binding 10.2 +/- 15.7%). By an incubation time of only 3 min the BSA-antibody prevalence was found to be 15.4% (8/52) for type 1 diabetic patients and 3.7% (2/54) for control subjects. However, there was no association between BSA-Ab and type 1 diabetes-associated antibodies as cytoplasmic islet cell antibodies (ICA), or glutamate decarboxylase autoantibodies. Our results confirm that (i) BSA-Ab occur more frequently in newly diagnosed type 1 diabetic patients compared with a healthy control group and (ii) that the BSA-Ab detected by the fluid-phase radioimmunoassay with an incubation time of 3 min are more disease-associated than the [125I]BSA binding after an overnight incubation. The competitive BSA-Ab fluid-phase radioimmunoassay described is a simple and rapid method to detect antibodies specifically reactive with BSA. It is suggested that the humoral immune reactivity to BSA in type 1 diabetic patients probably reflects an unspecific defect of the immune system and gives no additionally diagnostic value about the type 1 diabetes.

Cellular immunity to a determinant common to glutamate decarboxylase and coxsackie virus in insulin-dependent diabetes

Insulin-dependent diabetes (IDD) results from the autoimmune destruction of the insulin-producing pancreatic beta cells. Autoreactive T-lymphocytes are thought to play a pivotal role in the pathogenesis of IDD; however, the target antigens of these cells, as well as the inductive events in the disease, are unclear. PBMC in persons with or at increased risk for IDD show elevated reactivity to the beta cell enzyme glutamate decarboxylase (GAD). To identify the T-lymphocyte-reactive determinants of GAD, an overlapping set of synthetic peptides was used to stimulate the PBMC from these individuals, PBMC responsiveness to GAD peptides was not restricted to those with IDD, and a number of peptides elicited responses in PBMC. However, the major determinant of GAD recognized by persons at increased risk for IDD was amino acids 247-279, a region which has significant sequence similarity to the P2-C protein of Coxsackie B virus (47% of 15 increased risk [islet cell autoantibody-positive relatives]; 25% of 16 newly diagnosed IDD patients; and 0% of 13 healthy control subjects). Responses to tetanus and insulin antigens were not different between the study groups. In addition, PBMC from individuals responding to GAD peptides within 247-279 also responded to a Coxsackie viral peptide (i.e., P2-C amino acids 32-47), an observation supporting potential molecular mimicry in this immune response. Although the role of environmental agents in the pathogenesis of the disease remains unclear, these cellular immunological findings support the epidemiological evidence suggesting an inductive role for enteroviruses like Coxsackie B in the autoimmunity underlying IDD.

Value of antibodies to GAD65 combined with islet cell cytoplasmic antibodies for predicting IDDM in a childhood population

The value of a test for islet cell cytoplasmic antibodies together with a test for GAD65 antibodies to predict the subsequent development of diabetes over a period of 11.5 years was assessed in an open childhood population comprising 2,805 individuals. A single serum sample was obtained from each individual between 1975 and 1977 and screened for islet cell cytoplasmic antibodies for which eight individuals were positive (0.29%). During the average follow-up period of 11.5 years, four of eight islet cell antibody positive and three islet cell antibody negative individuals developed clinical diabetes. Sera from all individuals, who were islet cell antibody positive and/or developed diabetes (total of 11) and from 100 randomly selected control subjects were analysed for GAD65 antibodies. Six of eight islet cell antibody positive individuals were GAD65 antibody positive including all four who subsequently developed IDDM. Furthermore, one of the three islet cell antibody negative individuals who developed IDDM was GAD65 antibody positive both in 1976 and in 1989. Thus, a positive test for GAD65 antibodies alone correctly predicted diabetes in five of seven children, who developed the disease. Only one of the children, who developed diabetes was positive for insulin autoantibodies and this individual was also positive for islet cell cytoplasmic antibodies and GAD65 antibodies. One of the 100 control subjects was positive for GAD65 antibodies (1%). The results suggest that a single GAD65 antibody test may have a higher sensitivity for predicting IDDM than a test for islet cell cytoplasmic antibodies, but that a combined positive test for both antibodies increases the specificity for predicting IDDM over a period of 11.5 years.

Combined analysis of islet cell antibodies which cross-react with mouse pancreas, antibodies to the M(r) 64,000 islet protein, and antibodies to glutamate decarboxylase in subjects at risk for IDDM

With regard to progression to diabetes, ICA cross-reactive with mouse pancreas, antibodies to the M(r) 64,000 islet antigen (64K), antibodies immunotrapping brain GAD activity, and IAA were analysed in 53 ICA-positive first-degree relatives of IDDM patients and 18 ICA-positive schoolchildren without a family history of diabetes. Sera from 29 (55%) relatives did not bind to mouse pancreas, whereas 24 (45%) displayed cross-species reaction. ICA titres on human and mouse pancreas were weakly correlated in the overall population (p < 0.05) but more strongly (p < 0.01) in only those subjects who displayed antibodies on tissues from both species. GAD and 64K antibodies were detected in 31% and 35% of relatives. In schoolchildren, the frequencies of cross-species reactive ICA (22%), GAD antibodies (6%), 64K antibodies (22%), and IAA (6%), were lower (p < 0.05) than in relatives. A strong correlation (p < 0.0001) was observed between GAD and 64K antibodies. GAD or 64K antibodies were strongly correlated with ICA on human pancreas (p < 0.0001) but poorly with ICA on mouse pancreas (p = 0.05). After pre-incubation of sera with brain homogenate, ICA titres were unaffected on mouse pancreas but reduced on human pancreas. ICA-positive subjects who displayed neither cross-species reactive ICA nor GAD or 64K antibodies were more frequent (p < 0.05) among schoolchildren than relatives, whereas subjects who displayed all antibody specificities were more numerous (p < 0.04) in relatives. All relatives with ICA binding only to human pancreas, as well as all schoolchildren, permanently displayed an AIRG higher than the first control percentile and remained non-diabetic.(ABSTRACT TRUNCATED AT 250 WORDS)

The natural history of pre-type 1 (insulin-dependent) diabetes mellitus in patients with autoimmune endocrine diseases

An 11-year prospective study was carried out in 180 non-diabetic patients with organ-specific autoimmune diseases to evaluate islet cell antibodies in predicting Type 1 (insulin-dependent) diabetes mellitus. Islet cell antibodies were characterised according to titres, persistence, complement-fixing ability, and pattern. During follow-up, 14 of 46 patients with islet cell antibodies persistently greater than 5 Juvenile Diabetes Foundation Units (JDF-U) (30.4%), none of 23 with islet cell antibodies between 2.5 and 5 JDF-U or fluctuating, and 3 of 109 without islet cell antibodies (2.7%), developed diabetes. The cumulative risk of developing diabetes was 70%, 0%, and 4%, respectively. All the patients who developed diabetes were females. Eight progressed to insulin-dependence acutely, four showed a transient period of non-insulin-dependence, while two were still insulin-free. No difference was found in titres of islet cell antibodies for the risk of diabetes. Complement-fixing islet cell antibodies enhanced the cumulative risk for the disease in patients with conventional islet cell antibodies at low-middle (> or = 2.5-40 JDF-U), but not at high (> or = 80 JDF-U) titres. Forty-two patients with islet cell antibodies were investigated for the whole or the selective pattern. In the presence of the whole pattern the cumulative risk for diabetes rose to 100%, while with the selective pattern it declined to 34%. The whole pattern was found in 83% of patients who developed Type 1 diabetes acutely. In patients with organ-specific autoimmune diseases, the whole islet cell antibody pattern greatly enhances the prediction for diabetes.

Insulin autoantibodies and high titre islet cell antibodies are preferentially associated with the HLA DQA1*0301-DQB1*0302 haplotype at clinical type 1 (insulin-dependent) diabetes mellitus before age 10 years, but not at onset between age 10 and 40 years. The Belgian Diabetes Registry

Demographic and biological data were collected from all Caucasian Type 1 diabetic patients (n = 279) who were recruited at clinical onset by the Belgian Diabetes Registry over 34 months. The male/female ratio was significantly higher for onset between age 20 and 40 years (2.4) than before age 20 years (1.0); no age-or sex-differences were noticed in serum fructosamine concentration. Total and high concentrations of insulin autoantibodies and islet cell antibodies were preferentially associated with the HLA DQA1*0301-DQB1*0302 susceptibility haplotype. The occurrence of both types of antibodies was also correlated, irrespective of haplotype. At onset before age 10 years, the high risk genotype DQA1*0301-DQB1*0302/DQA1*0501-DQB1*0201 was more prevalent than all other DQA1-DQB1 genotypes taken together, leading to a higher prevalence of the DQA1*0301-DQB1*0302 haplotype in this age group (75%) than in the 10-39 years age group (54%). Under age 10 years, the presence of DQA1*0301-DQB1*0302 was strongly associated with insulin autoantibodies (90%) and islet cell autoantibodies (92% with 85% of high titre), whereas patients without this haplotype were less frequently positive for insulin autoantibodies (31%) or islet cell autoantibodies (38% high titre). In the group with onset at age 10-39 years, the DQA1*0301-DQB1*0302 haplotype presented a lower association with insulin autoantibodies (approximately 40%) and islet cell autoantibodies (50 to 65% high titre), prevalences which no longer differed from those in subjects lacking this haplotype.(ABSTRACT TRUNCATED AT 250 WORDS)

Quantification of human cytoplasmic islet-cell antibodies which cross-react with mouse pancreas: a follow-up study in type 1 (insulin-dependent) diabetic patients and in first-degree relatives

We studied the heterogeneity of cytoplasmic islet-cell antibodies for cross-reaction with mouse pancreas in 31 recent-onset Type 1 (insulin-dependent) diabetic patients and 31 first-degree relatives with islet-cell autoantibodies detected on human pancreas. Only six Type 1 diabetic patients displayed islet-cell antibodies binding to human pancreas but not to mouse pancreas. Among 15 first-degree relatives displaying such antibodies which did not react with mouse pancreas, including one identical twin and one subject with polyglandular autoimmunity, none developed diabetes or even lost acute insulin response to intravenous glucose after 5 years of follow-up. By contrast, 14 of 20 (70%) of the Type 1 diabetic patients with islet-cell antibodies detected on human pancreas, and five first-degree relatives who progressed to a loss of acute insulin response to glucose and then to either Type 1 diabetes or glucose intolerance, also displayed antibodies reactive with mouse islets. Surprisingly, islet-cell antibodies were detectable on mouse pancreas but not on human pancreas in four Type 1 diabetic patients and in one relative who progressed to diabetes. In the five relatives who progressed to metabolic abnormalities, islet-cell antibody titres on mouse pancreas, quantified by the fluorescence intensity per islet at each serum dilution, progressively increased concomitantly with the loss of acute insulin response to glucose, whereas islet-cell antibody titres on human pancreas remained stable. The usefulness of such quantification was also validated by the fact that antibody titres on mouse pancreas were decreased after 3 months (p < 0.01) in recent-onset Type 1 diabetic patients, while titres on human pancreas were not.(ABSTRACT TRUNCATED AT 250 WORDS)

Different rates of conversion to IDDM in siblings of type 1 diabetic children: the Montreal family study

This study was undertaken to analyze the risk of developing insulin-dependent diabetes (IDDM) in siblings of type 1 diabetic children. Islet-cell antibodies (ICA) were tested in 568 subjects, siblings of type 1 diabetic children. The subjects were followed prospectively for the conversion to clinical diagnosis of IDDM. As a result siblings who were islet cell antibody (ICA)+ positive at the time of diagnosis of the diabetic sibling (index case) had a significantly higher risk of developing IDDM than those who were ICA-. However, of the 19 siblings who developed IDDM, only 10 were ICA+ at the time of the first test but, 17 became ICA+ before diagnosis of IDDM. The interval between a positive test and the clinical diagnosis of IDDM varied between subjects (6-44 months, mean = 18.4 +/- 4.2 S.E. months) but it was less than 1 year in one subject. In addition to the higher risk of developing IDDM when ICA was positive, male sex and younger age of the subjects as well as young age of the index case and multiplex pedigrees were significant predictors of conversion to IDDM. The Cox's regression tree constructed using RECPAM identified three groups of varying rates of conversion to IDDM: (1) a group with the slowest progression characterized by ICA- and age of index case > 5 years or female sex (relative hazard = 1); (2) an intermediate progression group consisting of subjects who are ICA- and have both < 5 years of age and male sex (relative hazard = 8.78); (3) a group with the fastest progression consisting of subjects who are ICA+ (relative hazard = 31.45). From these results our data suggest that in addition to ICA, clinical markers such as age, sex and multiple pedigrees are also significant predictors of the rate of conversion to IDDM. Furthermore, screening for ICA in family intervention studies will have to be done frequently, perhaps yearly, and will have to be continued into adult life, particularly in ICA- subjects in order to identify the 85-90% of subjects who become ICA+ at the clinical diagnosis of IDDM.

Prospective evaluation of beta-cell function in insulin autoantibody-positive relatives of insulin-dependent diabetic patients

During the preclinical period of insulin-dependent diabetes mellitus (IDDM), progression to clinical IDDM is characterized by declining beta-cell function. Although the presence of insulin autoantibodies (IAA) improves the ability of islet cell antibodies (ICA) to predict subsequent clinical IDDM, few studies have examined the risk of developing IDDM in subjects positive for IAA but negative for both ICA and antibodies to glutamic acid decarboxylase (64kA). To investigate this question, detailed beta-cell function tests (acute insulin response to glucose [AIRgluc] and slope of glucose potentiation) were performed on eight IAA-positive first-degree relatives of insulin-dependent diabetics. All eight subjects were negative for ICA, and seven were tested for 64kA and were negative. Five subjects were studied prospectively for 22.4 +/- 9.4 months, while three subjects had only initial studies. Initial beta-cell function tests were normal in each subject. AIRgluc was 122.2% +/- 19.0% of the expected normal response, while slope was 168.6% +/- 20.6% of expected normal response. beta-cell function remained normal and remarkably stable in the five subjects followed prospectively. AIRgluc did not significantly change from an initial value of 147.9% +/- 23.1% of expected to 153.2% +/- 22.4% (NS). The slope of glucose potentiation varied little from 165.5% +/- 39.4% initially to 159.5% +/- 27.3% (NS) at the most recent determination. We conclude that among nondiabetic first-degree relatives of IDDM subjects, the presence of IAA in the absence of ICA and 64kA is not usually associated with and therefore does not reliably predict beta-cell dysfunction or progressive deterioration in beta-cell function.

Detection of autoantibodies against islet amyloid polypeptide in human serum. Lack of association with type 1 (insulin-dependent) diabetes mellitus, or with conditions favouring amyloid deposition in islets. The Belgian Diabetes Registry

A radiobinding assay for the detection of autoantibodies against islet amyloid polypeptide was developed, analytically validated, and--in parallel with a similar assay for the detection of autoantibodies against insulin--applied to sera from recent-onset Type 1 (insulin-dependent) diabetic patients and from age- and sex-matched control subjects. There was no difference in islet amyloid polypeptide autoantibody titres between patient groups and matched control subjects, nor within subject groups according to age. At onset of Type 1 diabetes, elevated islet amyloid polypeptide-autoantibody levels (> 97th percentile of control subjects) were only detected in 1 of 30 patients aged 0-19 years and in 2 of 35 patients aged 20-39 years. By contrast, insulin autoantibodies were frequently demonstrated, in particular at onset of diabetes under age 20 (0-19 years: 18 of 30 patients; 20-39 years: 10 of 35 patients; p < 0.01 vs matched control subjects). Islet amyloid polypeptide autoantibodies were not detectable in 3 insulinoma patients nor in 37 patients (aged 33-70 years) with Type 2 diabetes (vs 1 of 40 in matched control subjects). In positive serum, adsorption onto protein A-Sepharose removed islet amyloid polypeptide binding activity, hereby confirming its antibody nature. In conclusion, Type 1 diabetes is associated with an age-dependent autoantibody reaction against insulin but not against islet amyloid polypeptide. Conditions associated with amyloid deposition in islets (Type 2 diabetes, insulinoma and ageing) do not favour the formation of autoantibodies against islet amyloid polypeptide.

Relative contribution of HLA-DQA and -DQB alleles to predisposition to insulin-dependent diabetes mellitus

The presence of DQA and DQB alleles conferring protection or susceptibility was assessed in a panel of 39 insulin-dependent diabetes mellitus patients and 39 healthy control subjects from the central highland of Ethiopia. The results were grouped into three entities: a combination of alleles conferring susceptibility, a group conferring protection, and a group without any apparent HLA-DQ or -DR predisposition to insulin-dependent (type 1) diabetes mellitus (IDDM). Statistical analysis revealed that the relative risk of the first group is 64.1. If a similar approach is applied to the data on a study in caucasoid IDDM patients and controls of Kahlil and colleagues, the pattern is fully consistent with the data presented here, with an extraordinarily high relative risk (RR 258.2). It will be of interest to study whether this subdivision is reflected or supported by clinical or etiologic differences of the disease. The predictive value of susceptibility phenotypes appears to be more accurate by the proposed subdivision. Furthermore, in combination with islet-cell antibody analysis, assessment of genotype will permit more accurate identification of prediabetic individuals to be entered in clinical trials.

Islet cell antibodies in normal French schoolchildren

Islet-cell antibodies have been reported to be of predictive value for the future development of Type 1 (insulin-dependent) diabetes in first degree relatives of diabetic patients with the risk increasing in these subjects with the islet-cell antibodies titre. However, very little is known about islet-cell antibodies in background populations. Sera (n = 8363) from schoolchildren (6-17 years) in the French background population were screened for the presence of islet-cell antibodies by the indirect immunofluorescence technique. Islet-cell antibodies greater than 4.5 Juvenile Diabetes Foundation units were found in 150 sera (prevalence rate 1.8%; 95% confidence interval 1.5-2.1%). Only 17 sera demonstrated islet-cell antibody titre greater than or equal to 24 JDF units. No particular feature was found to be significantly different between islet-cell antibody-positive and islet-cell antibody-negative children (age, family history of diabetes, fasting plasma glucose, insulin autoantibodies). A second blood sample was obtained from 80 of 150 islet-cell antibody positive children after a mean interval of 8 months. Only 11 sera became less than 4.5 JDF units with islet-cell antibody titres being stable in the remaining sera, including the high-titre positive sera (greater than or equal to 24 JDF units). HLA-DQB typing was performed by restriction mapping techniques in 80 islet-cell antibody-positive, in 93 islet-cell antibody-negative and in 213 Type 1 diabetic children. The distribution of the susceptibility alleles (DQB1-Asp57-negative) was not significantly different between islet-cell antibody-positive and islet-cell antibody-negative children.(ABSTRACT TRUNCATED AT 250 WORDS)

Antibodies to the M(r) 64,000 (64K) protein in islet cell antibody positive non-diabetic individuals indicate high risk for impaired beta-cell function

A prospective study of a normal childhood population identified 44 islet cell antibody positive individuals. These subjects were typed for HLA DR and DQ alleles and investigated for the presence of antibodies to the M(r) 64,000 (64K) islet cell antigen, complement-fixing islet cell antibodies and radiobinding insulin autoantibodies to determine their potency in detecting subjects with impaired Beta-cell function. At initial testing 64K antibodies were found in six of 44 islet cell antibody positive subjects (13.6%). The same sera were also positive for complement-fixing islet cell antibodies and five of them had insulin autoantibodies. During the follow-up at 18 months, islet cell antibodies remained detectable in 50% of the subjects studied. In all six cases who were originally positive, 64K antibodies were persistently detectable, whereas complement-fixing islet cell antibodies became negative in two of six and insulin autoantibodies in one of five individuals. HLA DR4 (p less than 0.005) and absence of asparic acid (Asp) at position 57 of the HLA DQ beta chain (p less than 0.05) were significantly increased in subjects with 64K antibodies compared with control subjects. Of 40 individuals tested in the intravenous glucose tolerance test, three had a first phase insulin response below the first percentile of normal control subjects. Two children developed Type 1 (insulin-dependent) diabetes mellitus after 18 and 26 months, respectively. Each of these subjects was non-Asp homozygous and had persistent islet cell and 64K antibodies.(ABSTRACT TRUNCATED AT 250 WORDS)

Genetic, immunological, and metabolic determinants of risk for type 1 diabetes mellitus in families

Prospective studies of the relatives of people with Type 1 diabetes can provide insights into risk factors for processes leading to the ultimate destruction of the pancreatic islet B-cells. Relatives ascertained through the Children's Hospital of Pittsburgh diabetes registry were followed and rates of conversion to diabetes were determined. We studied the role of genetic and immunological markers, and used the oral glucose tolerance test (OGTT) to study metabolic disturbances among first-degree relatives. A group of siblings was serotyped for the HLA-A and -B antigens, and the degree of HLA haplotype sharing with the diabetic sibling was established. Later, islet cell antibody (ICA) assays were performed, and subjects were followed to determine the predictive value of ICA testing for the subsequent development of diabetes. The rate of conversion to diabetes among the siblings was 14 times greater than the rate observed in the general population from which they come. This is comparable to rates observed by other centres following relatives of people with Type 1 diabetes. Impaired glucose tolerance (by National Diabetes Data Group (USA) criteria) carried a three-fold greater risk for subsequent Type 1 diabetes than did a normal OGTT. Those relatives with detectable ICA were about 50 times more likely to convert to diabetes than were those without ICA. In a group of siblings in whom HLA haplotype sharing was determined, the prevalence of detectable ICA was greater among those who were HLA-identical to the diabetic sibling (9.9%) than among those who were haplo-identical (5.3%) or completely dissimilar (2.4%) at the HLA-A and -B regions.(ABSTRACT TRUNCATED AT 250 WORDS)

Novel considerations on the antibody/autoantigen system in type I (insulin-dependent) diabetes mellitus

Insulin dependent diabetes (IDDM) has an autoimmune pathogenesis. Included is the presence of antibodies to pancreatic islet cells. The first identified were islet cell antibodies (ICA), detected by indirect immunofluorescence, and which react with all cells within islets. Importantly, the autoantibodies are found several years prior to disease and although a pathogenic role for the autoantibodies is unclear, they have become useful markers of prediabetes. A number of studies of twins discordant for IDDM and of first degree relatives of IDDM patients have established that there is an increased risk for disease in individuals who have ICA, especially when ICA levels are high. This high predictive value of ICA decreases in the general population where the incidence of IDDM is lower than in first degree relatives, and both ICA and the disease risk associated with ICA, appear to be influenced by a genetic susceptibility. This has been sustained in a study of patients with endocrine autoimmunity and ICA (Polyendocrine Study) where the predictive value of very high levels of ICA is less than 50% in patients without a first degree relative with IDDM. Hence, there remain a substantial number of patients with ICA who do not develop disease. From these patients, it was demonstrated that ICA include at least two distinct specificities, one of which is beta cell specific and is not associated with a high risk for IDDM.(ABSTRACT TRUNCATED AT 250 WORDS)

The changing face of the epidemiology of insulin-dependent diabetes mellitus (IDDM): research designs and models of disease causation

Epidemiology can be broadly defined as the study of the cause and distribution of diseases in human populations. This review is concerned with the role of epidemiology in elucidating the cause of insulin-dependent diabetes mellitus (IDDM). Methodological aspects of epidemiologic studies are discussed including study designs and their limitations. Markers of genetic susceptibility to IDDM are examined in terms of their potential value for selecting high risk individuals for prospective follow-up studies of IDDM etiology. Models of disease causation pertinent to IDDM are presented with a primary focus on the recently developed epigenesis theory. Finally, a framework is provided that integrates approaches of infectious disease, chronic disease and genetic epidemiology, to link epidemiologic data with information from other disciplines, such as genetics, microbiology or immunology.

The interface between epidemiology and molecular biology in the search for the causes of insulin-dependent diabetes mellitus

Epidemiological techniques have been utilized to accumulate new knowledge about insulin-dependent diabetes mellitus (IDDM), leading to important insights into the disease process and the alteration of these mechanisms when viewed from a geographic or population base. More recently, highly powerful and sophisticated techniques of molecular biology have been added to the research arsenal, extending the knowledge on the genetic basis for IDDM and the probable environmental factors involved. The development and growth of the new discipline of epidemiological genetics promises exciting new developments for the future of our field as well as that of other major medical problems having a genetic base, but significantly influenced by environmental factors. This review stresses the importance of carefully validated diabetes registries in the study of the epidemiology of IDDM. The Children's Hospital of Pittsburgh and the University of Pittsburgh Medical Center have spear-headed the development of such registries, worldwide. The first international meeting on IDDM epidemiology in 1983 gave as a result, i.e., the finding that there were truly remarkable differences in the risk of developing IDDM depending upon the geographic location of the individual. Later collaborative work via the Diabetes Epidemiology Research International (DERI) group has confirmed the previous finding and added the description of secular trends and epidemics of IDDM. It is remarkable that the incidence rate of IDDM in children below 15 years vary from 1/100,000/yr in the Orient to 35/100,000/yr in Finland. The epidemiological approach in the study of IDDM has also stimulated research into the various facets of the etiology of the disease, genetic factors, autoimmune mechanisms and environmental factors.(ABSTRACT TRUNCATED AT 250 WORDS)

T-cell reactivity to 38 kD insulin-secretory-granule protein in patients with recent-onset type 1 diabetes

Type 1 diabetes seems to be an autoimmune disease in which T cells have a substantial role. A possible target antigen was suggested by the proliferation of CD4 T cells from a newly diagnosed patient in response to a 38 kD polypeptide of the insulin-secretory-granule membrane. To see whether this reactivity is widespread at disease onset, we have generated T-cell lines in vitro from peripheral blood mononuclear cells of nineteen children of caucasoid origin with newly diagnosed type 1 diabetes and sixteen healthy controls matched for age and HLA antigens. The procedure involved two cycles of incubation with a rat beta-cell tumour subcellular fraction enriched in secretory granules and plasma membrane components, followed by a proliferation assay. Fourteen (74% [95% confidence interval 49-91%]) of the patients' cell lines showed a positive proliferative response on subsequent exposure to the islet-cell antigen preparation compared with only two (13% [2-38%]) of the controls (p = 3 x 10(-4); difference 61% [44-87%]). Two subjects who had high titres of islet-cell autoantibodies (ICA) without clinical diabetes produced responsive T-cell lines. Reactivity towards the 38 kD fraction of insulin-secretory-granule membranes was found only in patients (eight of ten responders tested; 95% CI 44-98%) and one ICA-positive non-diabetic subject. Detection of an ongoing autoimmune T-cell response might be useful diagnostically and could lead to prevention of diabetes through specific immunotherapy.

Autoantibodies and genetic factors associated with the development of type 1 (insulin-dependent) diabetes mellitus in first degree relatives of diabetic patients

Factors associated with diabetes onset were analysed for their predictive value in 708 first-degree relatives of Type 1 (insulin-dependent) diabetic patients including 374 parents and 308 siblings of Type 1 diabetic patients. Relatives were prospectively followed for 2,304 subject years with blood samples for specific autoantibody evaluation. Islet cell cytoplasmic autoantibody titres were quantified in Juvenile Diabetes Foundation units with a threshold of positivity of 5 units. Insulin autoantibodies were determined using Tyr-A14 iodinated human insulin. HLA typing was performed in 92% of the relatives. During the time of study, 17 of 646 (2.6%) relatives showed islet cell antibodies. During follow-up, eight relatives developed diabetes, including six with high islet cell antibody titre. Taking titres above 20 units increased the positive predictive value from 35% to 75% whereas the presence of insulin autoantibodies did not increase the positive predictive value for the disease. Analysis of metabolic profiles months before the onset of diabetes by either oral or intravenous glucose loads, indicated a considerable level of heterogeneity with relatives with a high islet cell antibody titre who rapidly developed insulin-dependent diabetes, whereas other remained insulin-independent during the same observation period despite comparable titres. This study clearly indicates that initial islet cell antibody titre is not sufficient to predict individual outcome. Follow-up samples are clearly needed to monitor progression of the disease. Few relatives with persistent immunologic positivity progress to clinical Type 1 diabetes, suggesting that non-progressive and sub-clinical Beta-cell dysfunction is common.(ABSTRACT TRUNCATED AT 250 WORDS)

Can insulin-dependent diabetes mellitus be cured or prevented? A status report on immunomodulatory strategies and pancreas transplantation

The past decade has brought advances in our undestanding of the etiology of beta cell destruction leading to insulin-dependent diabetes mellitus. Most patients have an autoimmune process that begins months or years prior to overt disease. There are now reliable techniques to monitor the inflammatory process, with increasingly accurate methods for predicting disease in susceptible individuals. This information should lead to new techniques that will cure or possibly prevent diabetes.

Assessment of precision, concordance, specificity, and sensitivity of islet cell antibody measurement in 41 assays

Forty-one assays were analysed at the 3rd International Workshop on the standardisation of islet cell antibodies. Analysis of precision demonstrated assays consistently detecting blind duplicates within one doubling dilution and capable of discriminating one doubling dilution differences in islet cell antibody concentration. Some assays, however, reported duplicates discrepantly by more than seven doubling dilutions, and consequently could not distinguish even large quantities of islet cell antibodies. Precision was best in assays from laboratories which had participated in all three Standardisation Workshops and was not dependent upon methodology. The use of the Juvenile, Diabetes Foundation reference islet cell antibody standard and standard curves reduced the scatter of results, and was best amongst assays with better precision. Twenty-seven assays reported all ten blood donor sera as negative. However, 14 assays did not, and specificity (negativity in health) was less than 50% in three assays. Low specificity was strongly associated with poor precision. The detection limit of assays ranged from less than 5 to 50 JDF units and was partially dependent upon methodology. Assays incorporating extended incubation had the lowest detection limits without a decrease in the specificity of the ten blood donor sera. Precise quantification is fundamental for the standardisation and comparability of islet cell antibodies. Precise quantitative assays have been identified and reference standards and common units established.