Two-step islet autoantibody screening for risk assessment of type 1 diabetes in relatives

Prediction and prevention of Type 1 diabetes mellitus

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

Serum transforming growth factor β1 during diabetes development in non-obese diabetic mice and humans

Recent data show that regulatory cells with transforming growth factor (TGF)-β1-dependent activity are able to restore self-tolerance in overtly diabetic non-obese diabetic (NOD) mice. Thus, TGF-β1 seems to have a relevant role in protection from autoimmune diabetes. Our aim was to investigate the possible significance of serum TGF-β1 measurement in the natural history of diabetes in NOD mice, as well as in children positive for at least one islet-related antibody. Serum TGF-β1 (both total and active) was measured by enzyme-linked immunosorbent assay at monthly intervals in 26 NOD mice during the spontaneous development of diabetes and, on a yearly basis, in nine siblings of patients with type 1 diabetes (T1D) with a follow-up of 4 years. Diabetes appeared between the 12th week of age and the end of the study period (36 weeks) in 17 mice. TGF-β1 serum level variations occurred in the prediabetic period in both NOD mice and humans and diabetes diagnosis followed a continuing reduction of active TGF-β1 (aTGF-β1) serum levels. In mice, aTGF-β1 serum levels measured at 4 weeks of age correlated positively with severity of insulitis, and negatively with percentage of insulin-positive cells. Our findings suggest that in NOD mice serum TGF-β1 levels during the natural history of the diabetes reflect the course of islet inflammation. The measurement of aTGF-β1 in islet-related antibody-positive subjects may provide insights into the natural history of prediabetic phase of T1D.

Sustained IL-1alpha, IL-4, and IL-6 elevations following correction of hyperglycemia in children with type 1 diabetes mellitus

OBJECTIVE

An imbalance of pro-/anti-inflammatory cytokines may accelerate diabetic vascular complications and interfere with proper wound healing. Currently, limited available literature suggests that plasma concentrations of certain pro- and anti-inflammatory cytokines may be altered during hyperglycemia/diabetes mellitus. It is still unclear, however, whether these concepts also apply to children with diabetes, and whether alterations in circulating cytokine levels are a permanent feature of diabetes or an acute effect of fluctuating glucose concentrations.

METHODS

Twenty-two children with type 1 diabetes mellitus (T1DM) were studied. In 13 children, postprandial morning plasma glucose was >11.1 mmol/L at least once (hyperglycemic group, or HyG group); in 9 subjects, plasma glucose never exceeded 10.6 mmol/L (non-hyperglycemic group, or non-HyG group). After admission, intensive euglycemia (5.0-6.1 mmol/L) was achieved in all participants via intravenous insulin and dextrose for at least 90 min. Blood samples were drawn every 30 min to determine plasma levels of 14 cytokines and chemokines.

RESULTS

Interleukin IL-1alpha, IL-4, and IL-6 were elevated in HyG group compared with non-HyG not only when plasma glucose was elevated but also during the first 2 h following return to euglycemia. The levels of the other 11 cytokines were not significantly different.

CONCLUSIONS

Specific cytokines (IL-1alpha, IL-4, and IL-6) are acutely elevated during hyperglycemia in children with T1DM, and these elevations persist for hours after hyperglycemia has been corrected. Therefore, aside from glycemic control, additional therapeutic measures against elevated proinflammatory signals may be necessary for preventing vascular complications in children with hyperglycemic diabetes.

[Susceptibility markers in Tunisian first-degree relatives of patients with type 1 diabetes]

To identify the profile of anti-pancreas autoantibodies and elucidate the HLA DRB1, DQB1 polymorphism in Tunisian first-degree relatives of patients with type 1 diabetes, we recruited 96 relatives from 21 families with at least one diabetic child. Islet cell antibodies (ICA) were detected by immunofluorescence on monkey pancreas; glutamate decarboxylase (GADA), IA2 (IA2-A) and insulin (IAA) antibodies were measured by RIA. HLA class II DRB1 and DQB1 alleles were typed by PCR-SSP. ICA, GADA, IA2-A and IAA were found in respectively 11.5, 4.2, 5.2 and 8.3% of relatives. Twenty-two out of 96 had at least one antibody and 20 out of these 22 had a susceptibility allele (DRB1*03, DRB1*04, DQB1*02 or DQB1*0302) with or without protective allele (DRB1*11, DRB1*13, DRB1*15 or DQB1*06). All of the 5 relatives having 2 autoantibodies or more carried the DRB1*04-DQB1*0302 susceptible haplotype. In conclusion, this observational study confirms in a Tunisian population known epidemiological data and demonstrates the usefulness of follow-up to determine the predictive value of studied markers.

Progression to type 1 diabetes in islet cell antibody-positive relatives in the European Nicotinamide Diabetes Intervention Trial: the role of additional immune, genetic and metabolic markers of risk

AIMS/HYPOTHESIS

To examine the role of additional immune, genetic and metabolic risk markers in determining risk of diabetes in islet cell antibody (ICA)-positive individuals with a family history of type 1 diabetes recruited into the European Nicotinamide Diabetes Intervention Trial.

METHODS

Five hundred and forty-nine first-degree relatives with confirmed ICA levels > or =20 Juvenile Diabetes Foundation units (mean age 15.9 years; interquartile range 10.4-33.7 years) were recruited from 20 countries. OGTTs and IVGTTs were performed at baseline, antibodies to glutamate decarboxylase (GADA), protein tyrosine phosphatase (IA-2A) and insulin (IAA) were determined by RIA, and HLA class II genotyping was performed by PCR of sequence-specific oligonucleotides.

RESULTS

One hundred and fifty-nine participants developed diabetes within 5 years. Univariate analysis showed that the cumulative risk of development of diabetes within 5 years varied according to age, relationship to the proband, positivity for IAA, IA-2A and GADA, number and combination of islet antibodies, HLA class II genotype, baseline glucose tolerance, and first-phase insulin secretion, but not gender or incidence of childhood type 1 diabetes in the background population. Children aged < or =10 years had a 59% risk of diabetes within 5 years, compared with 11% in those > or =25 years (p<0.0001). Using multivariate analysis, independent determinants were age, first-phase insulin response, baseline glucose tolerance and number of additional antibody markers, but not antibody type or genotype. Individuals <25 years with two or more additional antibodies at baseline had a 62% risk of diabetes within 5 years and these combined criteria identified 81% of the cases in the whole cohort.

CONCLUSIONS/INTERPRETATION

We suggest that screening and recruitment for future intervention trials should be limited to family members aged <25 years, and should be based on islet autoantibodies alone.

Developments in the prediction of type 1 diabetes mellitus, with special reference to insulin autoantibodies

The prodromal phase of type 1 diabetes is characterised by the appearance of multiple islet-cell related autoantibodies (Aab). The major target antigens are islet-cell antigen, glutamic acid decarboxylase (GAD), protein-tyrosine phosphatase-2 (IA-2) and insulin. Insulin autoantibodies (IAA), in contrast to the other autoimmune markers, are the only beta-cell specific antibodies. There is general consensus that the presence of multiple Aab (> or = 3) is associated with a high risk of developing diabetes, where the presence of a single islet-cell-related Aab has usually a low predictive value. The most commonly used assay format for the detection of Aab to GAD, IA-2 and insulin is the fluid-phase radiobinding assay. The RBA does not identify or measure Aab, but merely detects its presence. However, on the basis of molecular studies, disease-specific constructs of GAD and IA-2 have been employed leading to somewhat improved sensitivity and specificity of the RBA. Serological studies have shown epitope restriction of IAA that can differentiate diabetes-related from unrelated IAA, but current assays do not distinguish between disease-predictive and non-predictive IAA or between IAA and insulin antibodies (IA). More recently, phage display technology has been successful in identifying disease-specific anti-idiotopes of insulin. In addition, phage display has facilitated the in vitro production of antibodies with high affinity. Identification of disease-specific anti-idiotopes of insulin should enable the production of a high affinity reagent against the same anti-idiotope. Such a development would form the basis of a disease-specific radioimmunoassay able to identify and measure particular idiotypes, rather than merely detect and titrate IAA.

Prediabetes in children: natural history, diagnosis, and preventive strategies

The clinical manifestation of type 1 diabetes mellitus is preceded by an asymptomatic prodromal period called prediabetes or preclinical diabetes. It may last from a few months to several years, during which the autoimmune destruction of the insulin-producing beta-cells in the pancreas progresses. The genes on the human leukocyte antigen (HLA) and insulin gene region are major genetic determinants for genetic disease susceptibility, while dietary compounds and viral infections are the most likely environmental factors contributing to the etiopathogenesis. T cells are thought to be the effector cells for the beta-cell destruction, and glutamic acid decarboxylase, insulinoma-associated protein 2 and insulin represent the three major autoantigens. Autoantibodies are early detectable markers of an ongoing disease process and are used to diagnose prediabetes. Among first-degree relatives of patients with type 1 diabetes, the risk for clinical disease can be graded from <5% in those with one or no antibodies to >90% in individuals who carry the HLA-DQB1*02/0302 risk genotype and are positive for multiple autoantibodies. beta-Cell function may also be tested in autoantibody-positive individuals and low first-phase insulin response is highly predictive for rapid progression to the clinical disease. However, dynamic course and individual variation of the disease process complicates the disease prediction, and it is not known whether all individuals with signs of prediabetes will inevitably progress to clinical type 1 diabetes. Until clinically applicable prevention for the condition exists, the screening for the risk markers of type 1 diabetes should actively be undertaken only in the context of research projects. Several major national and international multicenter studies are ongoing to test the potential of various agents (e.g. insulin and nicotinamide) or early elimination of dietary compounds (e.g. cow's milk proteins) to delay or prevent the onset of clinical type 1 diabetes.

Type 1 diabetes islet autoantibody markers

The diagnosis of type 1 diabetes versus other forms of diabetes such as type 2 diabetes is paramount to guiding proper therapy. Several islet autoantibodies have been identified that serve to diagnose immune-mediated, type 1a diabetes in clinically ambiguous cases. These autoantibodies also serve to predict type 1 diabetes in nondiabetic individuals. The most useful islet autoantibodies include islet cell cytoplasmic autoantibodies, insulin autoantibodies, glutamic acid decarboxylase autoantibodies, and insulinoma-associated-2 autoantibodies. Once type 1 diabetes can be safely and reliably prevented, large-scale islet autoantibody screening programs of the general pediatric population may be warranted. It is controversial whether islet autoantibodies influence the course of type 1 diabetes following diagnosis.

Risk of type 1 diabetes development in children with incidental hyperglycemia: A multicenter Italian study

OBJECTIVE

The aim of our study was to determine whether children with incidental hyperglycemia are at an increased risk of developing type 1 diabetes.

RESEARCH DESIGN AND METHODS

A total of 748 subjects, 1-18 years of age (9.04 +/- 3.62, mean +/- SD), without family history of type 1 diabetes, without obesity, and not receiving drugs were studied and found to have incidental elevated glycemia defined as fasting plasma glucose >5.6 mmol/l confirmed on two occasions. Subjects were tested for immunological, metabolic, and immunogenetic markers.

RESULTS

Islet cell antibodies >5 Juvenile Diabetes Foundation units were found in 10% of subjects, elevated insulin autoantibody levels in 4.6%, GAD antibody in 4.9%, and anti-tyrosine phosphatase-like protein autoantibodies in 3.9%. First-phase insulin response (FPIR) was <1st centile in 25.6% of subjects. The HLA-DR3/DR3 and HLA-DR4/other alleles were more frequent in hyperglycemic children than in normal control subjects (P = 0.012 and P = 0.005, respectively), and the HLA-DR other/other allele was less frequent than in normal control subjects (P = 0.000027). After a median follow-up of 42 months (range 1 month to 7 years), 16 (2.1%) subjects (11 males and 5 females), 4.1-13.9 years of age, became insulin dependent. All had one or more islet autoantibodies, and the majority had impaired insulin response and genetic susceptibility to type 1 diabetes. Diabetes symptoms were recorded in 11 patients and ketonuria only in 4 patients. The cumulative risk of type 1 diabetes was similar in males and females, and it was also similar in subjects under or over 10 years, whereas the cumulative risk of type 1 diabetes was increased in subjects with one or more autoantibodies and in those with FPIR <1st centile.

CONCLUSIONS

Children with incidental hyperglycemia have a higher-than-normal frequency of immunological, metabolic, or genetic markers for type 1 diabetes and have an increased risk of developing type 1 diabetes.

Islet autoantibodies in the prediction of diabetes in school children

In 1987 serum was collected from 1031 non-diabetic schoolchildren in the Southeast area of Sweden with the aim of evaluating islet autoantibody status (ICA, GADA and IA2-ab) in the prediction of diabetes in schoolchildren. The clinical development of Type 1 diabetes in the children was assessed in 1994 and 1997. The combination of ICA, GADA and IA2-ab were found in four subjects whereas six had two and 35 children one of these antibodies. After 10 years, six of the 1031 children had developed clinical diabetes and five of these six children were positive for islet antibodies. Two were positive for all three antibodies, two were positive for ICA and GADA, and one was positive for GADA. Among the individual autoantibodies, ICA showed the highest positive predictive value (29%) whereas the predictive value for the combination of two autoantibodies was highest for GADA and ICA (40%). Thus, GADA and ICA measurements may be a rational approach to detect schoolchildren at risk for developing diabetes.

Disease-associated autoantibodies as predictive markers of type 1 diabetes mellitus in siblings of affected children

The long latent preclinical period of type 1 diabetes mellitus (DM) makes it possible to identify individuals at increased risk for clinical DM before the beta-cell destructive process has reached the point of no return. A series of reports on the predictive value of DM-associated autoantibodies are available in first-degree relatives of patients with type 1 DM, but only a few of these studies target exclusively siblings and young siblings of affected children. When planning screening of siblings for DM risk, their age needs to be considered, as predictive characteristics of autoantibodies seem to vary in different age groups. Autoimmunity may be initiated early in life and therefore early screening for signs of beta-cell autoimmunity is crucial to avoid missing young children en route to overt DM and to be able to start intervention, when clinically applicable preventive modalities become available, before the disease process has advanced too far. Young age, positivity for at least two autoantibodies, high levels of autoantibodies and low first phase insulin response are highly predictive for progression to clinical disease in initially unaffected siblings of children with type 1 DM.

Update on the genetics of the idiopathic inflammatory myopathies

A number of lines of investigation suggest that, as is likely the case for other autoimmune diseases, the idiopathic inflammatory myopathies (IIM) develop as a result of specific environmental exposures in genetically susceptible individuals. Current data imply that multiple genes are involved in the etiology of these complex disorders. Targeted gene studies and whole genome approaches have begun to identify several genetic risk factors for autoimmune diseases, but the rarity and heterogeneity of the IIM have limited our knowledge of their associated genes. Current findings suggest that human leukocyte antigen (HLA) genes on chromosome 6, particularly HLA DRB1*0301 and the linked allele DQA1*0501, have the strongest associations with all clinical forms of IIM in white patients. Different HLA alleles, however, may confer risk or protection for myositis in distinct ethnic, serologic, and environmental exposure groups. Non-HLA genetic risk factors, which have been documented for other autoimmune diseases, are now being identified for the IIM. These include polymorphic genes encoding immunoglobulin heavy chains (defined by serologic markers known as Gm allotypes), cytokines and their receptors, and certain proteins that accumulate in the myocyte vacuoles of inclusion body myositis patients. Selected allelic polymorphisms of interleukin-1 receptor antagonist variable number tandem repeats and genes for tumor necrosis factor alpha and interleukin-1 alpha also have recently been associated with IIM. The pathogenic bases for the differences among the many clinically, pathologically and immunologically defined syndromes known as the IIM will be elucidated through a better understanding of the multiple genes that define risks for their development, as well as through investigations of gene-gene and gene-environment interactions.

Distribution of autoantibodies to glutamic acid decarboxylase across the spectrum of diabetes mellitus seen in South Africa

AIMS

This study investigated the association between glutamic acid decarboxylase antibodies (GAD-AB) and Type 1, Type 2, pancreatic and lipoatrophic diabetes mellitus (DM) in South African patients.

METHODS

Four groups were selected: group A, 100 Black Type 1 DM patients (age at onset < 35 years, body mass index (BMI) < 27 kg/m2 and insulin dependent within 1 year of presentation); group B, 80 Black Type 2 DM patients (age at onset > 35 years, BMI > 27 kg/m2 and controlled on oral hypoglycaemic agents for at least 1 year after presentation); group C, 10 patients of varying ethnicity with DM or impaired glucose tolerance secondary to chronic pancreatitis; group D, five patients of varying ethnicity with DM associated with total lipodystrophy. Fifty healthy Black control subjects were also studied (group E). Serum GAD-AB and random C-peptide levels were measured by radioimmunoassay.

RESULTS

Mean C-peptide concentration was significantly lower in Type 1 DM patients than Type 2 DM patients (P < 0.00001). Forty-four patients with Type 1 DM were GAD-AB-positive compared to two patients with Type 2 DM. Two control subjects were also GAD-AB-positive. No patient in the other groups had a titre > 1 U/ml. Type 1 DM patients who were GAD-AB-positive did not differ from those who were GAD-AB-negative for age at onset, duration of DM or C-peptide concentrations.

CONCLUSIONS

Auto-immune beta-cell destruction has an important role in the pathogenesis of Type 1 DM amongst African patients. However, Type 2 African DM patients and other diabetes subtypes are largely GAD-AB-negative.

Contribution of reduced insulin sensitivity and secretion to the pathogenesis of hepatogenous diabetes: effect of liver transplantation

Diabetes mellitus frequently complicates cirrhosis but the pathogenic mechanisms are unknown. To assess the contribution of reduced insulin action and secretion, 24 cirrhotic-diabetic patients waiting for liver transplant because of an unresectable hepatocarcinoma underwent an oral glucose tolerance test (OGTT) to assess the beta-cell function and an insulin clamp combined with [3-(3)H]glucose infusion to measure whole body glucose metabolism before and 2 years after the transplant. Seven cirrhotic nondiabetic patients, 11 patients with chronic uveitis on similar immunosuppressive therapy, and 7 healthy subjects served as control groups. Cirrhotic patients showed a profound insulin resistance, and diabetics in addition also showed increased endogenous glucose production (P <.05) and insulin deficiency during the OGTT (P <.05). Liver transplantation normalized endogenous glucose production and insulin sensitivity but failed to cure diabetes in 8 of the 24 patients because a markedly low insulin response during the OGTT. Age, body mass index, family history of diabetes, immunosuppressive drugs, and pathogenesis of cirrhosis did not predict in whom liver transplant was going to cure diabetes. On the contrary, a reduced secretory response characterized the patients in whom the transplant would not be curative. In summary, insulin resistance was a primary event complicating cirrhosis but additional beta-cell secretory defects were crucial for development of diabetes. Liver transplantation, lessening insulin resistance, cured hepatogenous diabetes in 67% of cirrhotic-diabetic patients; nevertheless 33% were still diabetics because the persistence of a reduced beta-cell function, which makes these patients eventually eligible for combined islet transplantation.

Autoantibodies to IA-2 in insulin-dependent diabetes mellitus. Measurements with a new immunoprecipitation assay

An immunoprecipitation assay for autoantibodies (Abs) to the human islet cell antigen IA-2 has been developed using 125I-labelled recombinant IA-2 expressed in E. coli. With this assay IA-2 Abs were detected in 103/217 (47%) of IDDM patients of different ages and with different disease duration. IA-2 Ab prevalence was higher in younger patients (at the age of 15 years or below) with the recent onset IDDM (64/113; 57%) compared to patients above the age of 15 years (11/25; 44%). One of 40 (2.5%) Graves' disease patients and five of 204 (2.5%) of NIDDM patients were also positive. IA-2 Abs were not detected in sera from patients with Hashimoto's thyroiditis (n=32), myasthenia gravis (n=20) or systemic lupus erythematosus (n=10). IA-2 Ab measurements based on 125I-labelled IA-2 showed a good correlation with the results of an immunoprecipitation assay based on 35S-labelled IA-2 produced in the in vitro transcription/translation system (r=0.78; n=113; p<0.001). Out of 217 IDDM sera which were tested for IA-2 Abs, 140 (65%) were positive for Abs to glutamic acid decarboxylase (GAD) and 166 (76%) were positive for Abs to IA-2 and/or Abs to GAD. In addition, Abs to IA-2, to GAD and to insulin were analysed in sera from recent onset IDDM patients who had not been treated with insulin (n=117). In all, 76/117 (65%) of these sera were positive for GAD Abs, 66/117 (56%) for IA-2 Abs, 45/117 (38%) for insulin Abs. However, 98/117 (84%) were positive for at least one of the three Abs confirming earlier observations on the complementarity of Ab testing in IDDM. Overall, the IA-2 Ab assay based on 125I-labelled recombinant IA-2 showed good sensitivity, precision and specificity which, combined with an easy and convenient protocol, makes it attractive for routine use.

Maturity-onset diabetes of the young (MODY): a new challenge for pediatric diabetologists

The differential diagnosis of hyperglycemia in childhood and adolescence has to take into consideration early-onset non-insulin-dependent diabetes, defined as maturity onset diabetes of the young (MODY). To date, mutations in genes of five proteins have been shown to cause MODY: glucokinase (MODY2), hepatic nuclear factor-1 alpha (HNF-1 alpha) (MODY3), hepatic nuclear factor-4 alpha (HNF-4 alpha) (MODY1), insulin promoter factor 1 (IPF-1) (MODY4) and hepatic nuclear factor-1 beta (HNF-1 beta) (MODY5), but other MODY genes still await elucidation. Clinical and metabolic heterogeneity of these subtypes of type 2 diabetes need to be defined, as deficiency of each factor has its own phenotype. Pediatric diabetologists should be aware of the increasing importance of MODY as a possible cause of hyperglycemia in children and adolescents. This will allow for the early diagnosis of these metabolic conditions and for the appropriate follow-up and treatment.