Identical and Nonidentical Twins: Risk and Factors Involved in Development of Islet Autoimmunity and Type 1 Diabetes

OBJECTIVE

There are variable reports of risk of concordance for progression to islet autoantibodies and type 1 diabetes in identical twins after one twin is diagnosed. We examined development of positive autoantibodies and type 1 diabetes and the effects of genetic factors and common environment on autoantibody positivity in identical twins, nonidentical twins, and full siblings.

RESEARCH DESIGN AND METHODS

Subjects from the TrialNet Pathway to Prevention Study (N = 48,026) were screened from 2004 to 2015 for islet autoantibodies (GAD antibody [GADA], insulinoma-associated antigen 2 [IA-2A], and autoantibodies against insulin [IAA]). Of these subjects, 17,226 (157 identical twins, 283 nonidentical twins, and 16,786 full siblings) were followed for autoantibody positivity or type 1 diabetes for a median of 2.1 years.

RESULTS

At screening, identical twins were more likely to have positive GADA, IA-2A, and IAA than nonidentical twins or full siblings (all P < 0.0001). Younger age, male sex, and genetic factors were significant factors for expression of IA-2A, IAA, one or more positive autoantibodies, and two or more positive autoantibodies (all P ≤ 0.03). Initially autoantibody-positive identical twins had a 69% risk of diabetes by 3 years compared with 1.5% for initially autoantibody-negative identical twins. In nonidentical twins, type 1 diabetes risk by 3 years was 72% for initially multiple autoantibody-positive, 13% for single autoantibody-positive, and 0% for initially autoantibody-negative nonidentical twins. Full siblings had a 3-year type 1 diabetes risk of 47% for multiple autoantibody-positive, 12% for single autoantibody-positive, and 0.5% for initially autoantibody-negative subjects.

CONCLUSIONS

Risk of type 1 diabetes at 3 years is high for initially multiple and single autoantibody-positive identical twins and multiple autoantibody-positive nonidentical twins. Genetic predisposition, age, and male sex are significant risk factors for development of positive autoantibodies in twins.

Low-Dose Anti-Thymocyte Globulin (ATG) Preserves β-Cell Function and Improves HbA1c in New-Onset Type 1 Diabetes

OBJECTIVE

A pilot study suggested that combination therapy with low-dose anti-thymocyte globulin (ATG) and pegylated granulocyte colony-stimulating factor (GCSF) preserves C-peptide in established type 1 diabetes (T1D) (duration 4 months to 2 years). We hypothesized that 1) low-dose ATG/GCSF or 2) low-dose ATG alone would slow the decline of β-cell function in patients with new-onset T1D (duration <100 days).

RESEARCH DESIGN AND METHODS

A three-arm, randomized, double-masked, placebo-controlled trial was performed by the Type 1 Diabetes TrialNet Study Group in 89 subjects: 29 subjects randomized to ATG (2.5 mg/kg intravenously) followed by pegylated GCSF (6 mg subcutaneously every 2 weeks for 6 doses), 29 to ATG alone (2.5 mg/kg), and 31 to placebo. The primary end point was mean area under the curve (AUC) C-peptide during a 2-h mixed-meal tolerance test 1 year after initiation of therapy. Significance was defined as one-sided P value < 0.025.

RESULTS

The 1-year mean AUC C-peptide was significantly higher in subjects treated with ATG (0.646 nmol/L) versus placebo (0.406 nmol/L) (P = 0.0003) but not in those treated with ATG/GCSF (0.528 nmol/L) versus placebo (P = 0.031). HbA_1c was significantly reduced at 1 year in subjects treated with ATG and ATG/GCSF, P = 0.002 and 0.011, respectively.

CONCLUSIONS

Low-dose ATG slowed decline of C-peptide and reduced HbA_1c in new-onset T1D. Addition of GCSF did not enhance C-peptide preservation afforded by low-dose ATG. Future studies should be considered to determine whether low-dose ATG alone or in combination with other agents may prevent or delay the onset of the disease.

Neuropeptide Y autoantibodies in patients with long-term type 1 and type 2 diabetes and neuropathy

AIMS

The neurotransmitter Neuropeptide Y (NPY) was previously reported as a minor autoantigen in newly diagnosed type 1 diabetes (T1D) patients. The single nucleotide polymorphism at rs16139 (T1128C, L7P) in the NPY gene was associated with an increased risk for the development of type 2 diabetes (T2D). We aimed to develop a radiobinding assay for NPY-L (Leucine) and NPY-P (Proline) autoantibodies (A) to study the levels and the association with other islet autoantibodies and neuropathy.

METHODS

Autoantibodies against NPY-L, NPY-P, ZnT8, GAD65 and IA-2 were studied in T1D (n=48) and T2D (n=26) patients with duration up to 42 and 31years. A subgroup of T1D (n=32) patients re-examined, 5-8years after first visit, was tested for peripheral (Z-score) and autonomic neuropathy (E/I ratio).

RESULTS

NPY-LA and NPY-PA were detected in 23% and 19% in T1D (p<0.001), and 12% and 23% in T2D patients (p<0.001) compared to 2.5% controls (n=398). The levels of NPYA declined during follow-up in the T1D patients (p<0.001). The neuropathy was not related to the NPYA or the other islet autoantibodies.

CONCLUSIONS

Regardless of the absence of an association between NPYA and neuropathy, NPY may contribute to the pathogenesis of T1D and T2D as a minor autoantigen.

Thyroid autoimmunity in relation to islet autoantibodies and HLA-DQ genotype in newly diagnosed type 1 diabetes in children and adolescents

AIMS/HYPOTHESIS

The aim of this work was to investigate, in children newly diagnosed with type 1 diabetes: (1) the prevalence of autoantibodies against thyroid peroxidase (TPOAb) and thyroglobulin (TGAb); and (2) the association between TPOAb, TGAb or both, with either islet autoantibodies or HLA-DQ genes.

METHODS

Blood samples from 2,433 children newly diagnosed with type 1 diabetes were analysed for TPOAb and TGAb in addition to autoantibodies against arginine zinc transporter 8 (ZnT8RA), tryptophan zinc transporter 8 (ZnT8WA), glutamine zinc transporter 8 (ZnT8QA), glutamic acid decarboxylase (GADA), insulin (IAA), insulinoma-associated protein-2 (IA-2A), HLA-DQA-B1 genotypes, thyroid-stimulating hormone (TSH) and free thyroxine (T4).

RESULTS

At type 1 diabetes diagnosis, 12% of the children had thyroid autoantibodies (60% were girls; p < 0.0001). GADA was positively associated with TPOAb (p < 0.001) and with TGAb (p < 0.001). In addition, ZnT8A was associated with both TPOAb (p = 0.039) and TGAb (p = 0.015). DQB1*05:01 in any genotype was negatively associated with TPOAb (OR 0.55, 95% CI 0.37, 0.83, p value corrected for multiple comparisons (p c) = 0.012) and possibly with TGAb (OR 0.55, 95% CI 0.35, 0.87, p c = 0.07). Thyroid autoimmunity in children newly diagnosed with type 1 diabetes was rarely (0.45%) associated with onset of clinical thyroid disease based on TSH and free T4.

CONCLUSIONS/INTERPRETATION

GADA and ZnT8A increased the risk for thyroid autoimmunity at the time of clinical diagnosis of type 1 diabetes, while HLA-DQB1*05:01 reduced the risk. However, the associations between thyroid autoimmunity and HLA-DQ genotype were weak and did not fully explain the co-occurrence of islet and thyroid autoimmunity.

Antigenicity and epitope specificity of ZnT8 autoantibodies in type 1 diabetes

The single nucleotide polymorphism (SNP) rs13266634 encodes either an Arginine (R) or a Tryptophan (W) (R325W) at the amino acid position 325 in the Zinc Transporter 8 (ZnT8) protein. Autoantibodies (Ab) that recognize ZnT8R, ZnT8W or both at the polymorphic site are common in newly diagnosed type 1 diabetes (T1D) patients. The epitope specificity and affinity of ZnT8Ab are poorly understood, but may be of importance for the prediction and clinical classification of T1D. Therefore, the aims were to 1) determine the immunogenicity of short (318-331) ZnT8 peptides in mice and 2) test the affinity of short and long (268-369) ZnT8 proteins in T1D patients positive for either ZnT8RAb or ZnT8wAb. Sera from BALB/cByJ mice immunized with short R, W or Q (Glutamine) ZnT8 peptides were tested for ZnT8-peptide antibodies in ELISA and radiobinding assay (RBA). Using reciprocal permutation experiment, short synthetic ZnT8R and ZnT8W (318-331) and long in vitro transcription translation ZnT8R and ZnT8W (268-369) proteins were tested in competitive RBA with R- and W-monospecific T1D sera samples. All mouse sera developed non-epitope-specific peptide antibodies in ELISA and only 6/12 mice had ZnT8-RWQ antibodies in RBA. Both long ZnT8R and ZnT8W (268-369), but not any short, proteins displaced labelled ZnT8 (268-369) proteins in binding to T1D ZnT8Ab-specific sera. The reciprocal cross-over tests showed that half-maximal displacement varied 2- to 11-fold indicating variable affinity of patient ZnT8Ab, signifying crucial autoantibody epitope spreading. The present approach should make it possible to dissect the importance of the R325W ZnT8 autoantigen epitope in the T1D pathogenesis.

Triple specificity of ZnT8 autoantibodies in relation to HLA and other islet autoantibodies in childhood and adolescent type 1 diabetes

OBJECTIVE

To establish the diagnostic sensitivity of and the relationships between autoantibodies to all three Zinc transporter 8 (Zinc transporter 8 autoantibody to either one, two, or all three amino acid variants at position 325, ZnT8A) variants to human leukocyte antigen (HLA)-DQ and to autoantibodies to glutamic acid decarboxylase (GADA), insulinoma-associated protein 2 (IA-2A), and insulin (IAA).

METHODS

We analyzed 3165 patients with type 1 diabetes (T1D) in the Better Diabetes Diagnosis study for HLA-DQ genotypes and all six autoantibodies (ZnT8RA, arginine 325 Zinc transporter 8 autoantibody; ZnT8WA, tryptophan 325 Zinc transporter 8 autoantibody; ZnT8QA, glutamine 325 Zinc transporter 8 autoantibody; GADA, IA-2A, and IAA).

RESULTS

ZnT8A was found in 65% of the patients and as many as 108 of 3165 (3.4%) had 1-3 ZnT8A alone. None had ZnT8QA alone. Together with GADA (56%), IA-2A (73%), and IAA (33%), 93% of the T1D patients were autoantibody positive. All three ZnT8A were less frequent in children below 2 yr of age (p < 0.0001). All three ZnT8A were associated with DQA1-B1*X-0604 (DQ6.4) and DQA1-B1*03-0302 (DQ8). ZnT8WA and ZnT8QA were negatively associated with DQA1-B1*05-02 (DQ2).

CONCLUSIONS

Analysis of ZnT8A increased the diagnostic sensitivity of islet autoantibodies for T1D as only 7% remained islet autoantibody negative. The association between DQ6.4 and all three ZnT8A may be related to ZnT8 antigen presentation by the DQ6.4 heterodimer.

The environment and the origins of islet autoimmunity and Type 1 diabetes

Type 1 diabetes involves the specific destruction of the pancreatic islet β-cells, eventually resulting in a complete dependency of exogenous insulin. The clinical onset of diabetes is preceded by the appearance of autoantibodies against β-cell antigens. The human leukocyte antigen (HLA) region is the single most important genetic determinant of Type 1 diabetes susceptibility, yet variability in the HLA region has been estimated to explain only approximately 60% of the genetic influence of the disease. Over 50 identified non-HLA genetic polymorphisms support the notion that genetics alone cannot explain Type 1 diabetes. Several lines of evidence indicate that environmental triggers may be integral in inducing the onset of islet autoimmunity in genetically susceptible individuals. The association between environmental factors and the clinical onset is complicated by observation that the rate of progression to clinical onset may be affected by environmental determinants. Hence, the environment may be aetiological as well as pathogenic. Putative inductive mechanisms include viral, microbial, diet-related, anthropometric and psychosocial factors. Ongoing observational cohort studies such as The Environmental Determinants of Diabetes in the Young (TEDDY) study aim to ascertain environmental determinants that may trigger islet autoimmunity and either speed up or slow down the progression to clinical onset in subjects with persistent islet autoimmunity.

DETECTION OF LACTOBACILLI IN MONTHLY MAIL-IN STOOL SAMPLES FROM 3-18 MONTHS OLD INFANTS AT GENETIC RISK FOR TYPE 1 DIABETES

The feasibility to detect lactobacilli in mail-in infant stools collected monthly from 3-18 months old children was investigated. The aim was to determine total lactobacilli and Lactobacillus plantarum (L. plantarum) content (ng/g feces) in 50 infants each from Colorado (648 samples), Finland (624 samples) and Sweden (685 samples) who participated in the TEDDY (The Environmental Determinants of Diabetes in the Young) study. Total lactobacilli content varied markedly between 5 and 16,800 ng/g feces in the three clinical sites within and between individuals especially in infants. L.plantarum also varied markedly intra- and inter-individually from <0.5 - 736 ng/g feces. A higher variability of total lactobacilli was found before 10 months of age than after in the three different clinical sites. Sweden had the lowest total lactobacilli content compared to Colorado and Finland while the L.plantarum content was higher in Sweden. Mail-in stool samples from infants should prove useful in analyzing probiotics in childhood.

C-peptide in the classification of diabetes in children and adolescents

AIM

To report C-peptide results in newly diagnosed patients and the relation to clinical diagnosis of diabetes.

METHODS

A nation-wide cohort, the Better Diabetes Diagnosis study was used to determine serum C-peptide at diagnosis in 2734 children and adolescents. Clinical data were collected at diagnosis and follow-up. C-peptide was determined in a validated and controlled time-resolved fluoroimmunoassay.

RESULTS

The clinical classification of diabetes, before any information on human leukocyte antigen, islet autoantibodies, or C-peptide was received, was type 1 diabetes (T1D) in 93%, type 2 diabetes (T2D) in 1.9%, maturity onset diabetes of the young (MODY) in 0.8%, secondary diabetes (0.6%), while 3.3% could not be classified. In a random, non-fasting serum sample at diagnosis, 56% of the patients had a C-peptide value >0.2 nmol/L. Children classified as T2D had the highest mean C-peptide (1.83 + 1.23 nmol/L) followed by MODY (1.04 ± 0.71 nmol/L) and T1D (0.28 ± 0.25 nmol/L). Only 1/1037 children who had C-peptide <0.2 nmol/L at diagnosis was classified with a type of diabetes other than T1D. Predictive value of C-peptide >1.0 nmol/L for the classification of either T2D or MODY was 0.46 [confidence interval 0.37-0.58].

CONCLUSIONS

More than half of children with newly diagnosed diabetes have clinically important residual beta-cell function. As the clinical diagnosis is not always straightforward, a random C-peptide taken at diagnosis may help to classify diabetes. There is an obvious use for C-peptide determinations to evaluate beta-cell function in children with diabetes.

Low risk HLA-DQ and increased body mass index in newly diagnosed type 1 diabetes children in the Better Diabetes Diagnosis study in Sweden

Objective

Type 1 diabetes and obesity has increased in childhood. We therefore tested the hypothesis that type 1 diabetes HLA-DQ risk genotypes may be associated with an increased body mass index (BMI).

Design

The type 1 diabetes high risk HLA-DQ A1*05:01-B1*02:01/A1*03:01-B1*03:02 genotype along with lower risk DQ genotypes were determined at the time of clinical onset by PCR and hybridization with allele-specific probes. Body mass index was determined after diabetes was stabilized.

Subjects

A total of 2403 incident type 1 diabetes children below 18 years of age were ascertained in the Swedish national Better Diabetes Diagnosis (BDD) studybetween May 2005 to September 2009. All children classified with type 1 diabetes including positivity for at least one islet autoantibody were investigated.

Results

Overall, type 1 diabetes HLA-DQ risk was negatively associated with BMI (p<0.0008). The proportion of the highest risk A1*05:01-B1*02:01/A1*03:01-B1*03:02 genotype decreased with increasing BMI (p<0.0004). However, lower risk type 1 diabetes DQ genotypes were associated with an increased proportion of patients who were overweight or obese (p<0.0001). Indeed, the proportion of patients with the low risk A1*05:01-B1*02:01/A1*05:01-B1*02:01 genotype increased with increasing body mass index (p<0.003). The magnitude of association on the multiplicative scale between the A1*05:01-B1*02:01/A1*05:01-B1*02:01 genotype and increased body mass index was significant (p<0.006). The odds ratio in patients with this genotype of being obese was 1.80 (95% CI 1.21–2.61; p<0.006). The increased proportion of overweight type 1 diabetes children with the A1*05:01-B1*02:01 haplotype was most pronounced in children diagnosed between 5 and 9 years of age.

Conclusions

Susceptibility for childhood type 1 diabetes was unexpectedly found to be associated with the A1*05:01-B1*02:01/A1*05:01-B1*02:01 genotype and an increased BMI. These results support the hypothesis that overweight may contribute to the risk of type 1 diabetes in children positive for HLA-DQ A1*05:01-B1*02:01.

The three ZNT8 autoantibody variants together improve the diagnostic sensitivity of childhood and adolescent type 1 diabetes

AIMS

We tested whether autoantibodies to all three ZnT8RWQ variants, GAD65, insulinoma-associated protein 2 (IA-2), insulin and autoantibodies to islet cell cytoplasm (ICA) in combination with human leukocyte antigen (HLA) would improve the diagnostic sensitivity of childhood type 1 diabetes by detecting the children who otherwise would have been autoantibody-negative.

METHODS

A total of 686 patients diagnosed in 1996-2005 in Skåne were analyzed for all the seven autoantibodies [arginin 325 zinc transporter 8 autoantibody (ZnT8RA), tryptophan 325 zinc transporter 8 autoantibody (ZnT8WA), glutamine 325 Zinc transporter 8 autoantibody (ZnT8QA), autoantibodies to glutamic acid decarboxylase (GADA), Autoantibodies to islet-antigen-2 (IA-2A), insulin autoantibodies (IAA) and ICA] in addition to HLA-DQ genotypes.

RESULTS

Zinc transporter 8 autoantibody to either one or all three amino acid variants at position 325 (ZnT8RWQA) was found in 65% (449/686) of the patients. The frequency was independent of age at diagnosis. The ZnT8RWQA reduced the frequency of autoantibody-negative patients from 7.5 to 5.4%-a reduction by 28%. Only 2 of 108 (2%) patients who are below 5 years of age had no autoantibody at diagnosis. Diagnosis without any islet autoantibody increased with increasing age at onset. DQA1-B1(*)X-0604 was associated with both ZnT8RA (p = 0.002) and ZnT8WA (p = 0.01) but not with ZnT8QA (p = 0.07). Kappa agreement analysis showed moderate (>0.40) to fair (>0.20) agreement between pairs of autoantibodies for all combinations of GADA, IA-2A, ZnT8RWQA and ICA but only slight ( < 0.19) agreement for any combination with IAA.

CONCLUSIONS

This study revealed that (1) the ZnT8RWQA was common, independent of age; (2) multiple autoantibodies were common among the young; (3) DQA1-B1(*)X-0604 increased the risk for ZnT8RA and ZnT8WA; (4) agreement between autoantibody pairs was common for all combinations except IAA. These results suggest that ZnT8RWQA is a necessary complement to the classification and prediction of childhood type 1 diabetes as well as to randomize the subjects in the prevention and intervention of clinical trials.

Changes in GAD65Ab-specific antiidiotypic antibody levels correlate with changes in C-peptide levels and progression to islet cell autoimmunity

CONTEXT

The previously reported absence of 65-kDa glutamate decarboxylase antibody (GAD65Ab)-specific antiidiotypic antibodies (anti-Id) in type 1 diabetes (T1D) patients at clinical onset could be due to an inability to mount an antibody response to GAD65Ab or a longitudinal decline in anti-Id levels.

OBJECTIVE AND DESIGN

We investigated anti-Id levels in longitudinal samples obtained from T1D patients (n = 41) (clinical diagnosis - 12 months), and latent autoimmune diabetes in adults (LADA) patients (n = 32) who received alum-formulated human recombinant GAD65 (baseline - 12 months). We also determined anti-Id levels in a small cohort of Type 2 diabetes patients during their development of autoimmune T cell responses.

RESULTS

At clinical onset T1D patients presented no or low anti-Id levels. However, 22/41 T1D patients showed ≥50% increase in GAD65Ab-specific anti-Id levels during follow-up; peaking at 3 (n = 1), 6 (n = 10), 9 (n = 10), or 12 (n = 1) months. Increasing anti-Id levels marked patients who experienced a temporary increase in C-peptide levels. Anti-Id levels correlated significantly with glycated hemoglobin and C-peptide levels at 6 and 9 months (P values ranged from <0.001 to <0.05). In LADA patients receiving placebo, anti-Id levels declined in seven of nine patients, whereas four of five patients receiving 20 μg alum-formulated human recombinant GAD65 showed increasing anti-Id levels. Changes in anti-Id and C-peptide levels closely correlated (P < 0.0001). The significant decline in anti-Id levels (P = 0.03) in T2D patients developing T cell autoimmune responses supports our hypothesis that declining anti-Id levels are associated with developing islet autoimmunity.

CONCLUSIONS

The close association between GAD65Ab-specific anti-Id levels and β-cell function may provide a novel marker for the progression of autoimmune diabetes.

Altered natural killer (NK) cell frequency and phenotype in latent autoimmune diabetes in adults (LADA) prior to insulin deficiency

Approximately 10% of the patients diagnosed with type 2 diabetes (T2D) have detectable serum levels of glutamic acid decarboxylase 65 autoantibodies (GADA). These patients usually progress to insulin dependency within a few years, and are classified as being latent autoimmune diabetes in adults (LADA). A decrease in the frequency of peripheral blood natural killer (NK) cells has been reported recently in recent-onset T1D and in high-risk individuals prior to the clinical onset. As NK cells in LADA patients have been investigated scarcely, the aim of this study was to use multicolour flow cytometry to define possible deficiencies or abnormalities in the frequency or activation state of NK cells in LADA patients prior to insulin dependency. All patients were GADA-positive and metabolically compensated, but none were insulin-dependent at the time blood samples were taken. LADA patients exhibited a significant decrease in NK cell frequency in peripheral blood compared to healthy individuals (P=0.0018), as reported previously for recent-onset T1D patients. Interestingly, NKG2D expression was increased significantly (P<0.0001), whereas killer cell immunoglobulin-like receptor (KIR)3DL1 expression was decreased (P<0.0001) within the NK cell population. These observations highlight a defect in both frequency and activation status of NK cells in LADA patients and suggest that this immunological alteration may contribute to the development of autoimmune diabetes by affecting peripheral tolerance. Indeed, recent evidence has demonstrated a regulatory function for NK cells in autoimmunity. Moreover, the decrease in NK cell number concords with observations obtained in recent-onset T1D, implying that similar immunological dysfunctions may contribute to the progression of both LADA and T1D.

The type 1 diabetes protective HLA DQB1*0602 allele is less frequent in gestational diabetes mellitus

AIMS/HYPOTHESIS

We tested whether gestational diabetes mellitus (GDM) is associated with HLA-DQ genotypes.

METHODS

A total of 764 mothers with non-autoimmune (GAD65, insulinoma-associated protein 2 [IA-2] and insulin autoantibody-negative) GDM were ascertained between September 2000 and August 2004 in the population-based Diabetes Prediction in Skåne (DiPiS) study. HLA-DQB1 genotypes were determined in these mothers and in 1191 randomly selected non-diabetic control mothers also negative for islet autoantibodies. The data were analysed in relation to maternal age, country of birth, number of pregnancies/siblings and pregnancy weight gain.

RESULTS

The frequency of type 1 diabetes high-risk HLA-DQ alleles (DQB1*0201, DQB1*0302) did not differ between GDM mothers and controls. In contrast, the low-risk DQB1*0602 allele was less prevalent (OR 0.64, 95% CI = 0.51-0.80, p = 0.0006) in GDM than in control mothers. The difference in DQB1*0602 frequency between GDM mothers and controls remained after multiple logistic regression analysis correcting for maternal age, country of birth, number of pregnancies/siblings and weight gain during pregnancy (OR 0.67, 95% CI 0.51-0.88, p = 0.009).

CONCLUSIONS/INTERPRETATION

The negative association between mothers who have non-autoimmune GDM and HLA-DQ*0602 suggest that this allele may protect not only from type 1 diabetes but also from GDM.

GAD65 vaccination: 5 years of follow-up in a randomised dose-escalating study in adult-onset autoimmune diabetes

AIMS/HYPOTHESIS

The aim of this study was to ascertain whether treatment of GAD65 autoantibody (GADA)-positive diabetic patients with alum-formulated recombinant GAD65 (GAD-alum) is safe and does not compromise beta cell function.

METHODS

This Phase 2, placebo-controlled, dose-escalation clinical trial, which was randomized through a central office, was performed in 47 GADA-positive type 2 diabetic patients, who received subcutaneous injections of GAD-alum (4 [n = 9], 20 [n = 8], 100 [n = 9] or 500 [n = 8] microg) or placebo (n = 13) at weeks 1 and 4 of the trial. Participants and caregivers were blinded to group assignments. The primary outcome was safety as assessed by neurological tests, medications and beta cell function evaluated over 5 years, representing the end of the trial.

RESULTS

No severe study-related adverse events occurred during the 5 year follow-up. None of the dose groups was associated with an increased risk of starting insulin treatment compared with the placebo group. The use of oral hypoglycaemic agents did not differ between the dose groups. After 5 years, fasting C-peptide levels declined in the placebo group (-0.24; 95% CI -0.41 to -0.07 log(10) nmol/l; p = 0.01) and the 500 microg dose group (-0.37; 95% CI -0.57 to -0.17 log(10) nmol/l; p = 0.003), but not in the 4 microg (-0.10; 95% CI -0.28 to 0.07 log(10) nmol/l; p = 0.20), 20 microg (0.04; 95% CI -0.12 to 0.19 log(10) nmol/l; p = 0.58) and 100 microg (0.00; 95% CI -0.20 to -0.20 log(10) nmol/l; p = 0.98) dose groups.

CONCLUSIONS/INTERPRETATION

The primary outcome of safety was achieved, since no severe study-related adverse events occurred.

TRIAL REGISTRATION

Because the study was initiated before 1 July 2005, the protocol was not registered in a registry.

B-cell function and islet cell and other organ-specific autoantibodies in relatives to insulin-dependent diabetic patients

The pancreatic B-cell function (glucose tolerance, C-peptide release) and organ-specific autoantibodies, including islet cell cytoplasmic and cell surface (mouse), were studied in 45 first-degree relatives of patients with insulin-dependent diabetes mellitus diagnosed before the age of 30 years. Compared to 107 healthy persons without any family history of either insulin-dependent or non-insulin-dependent diabetes mellitus, the prevalence of autoantibodies was increased among the relatives. The prevalence of islet cell antibodies did not differ between relatives and controls and none of the individuals had complement-fixing islet cell antibodies. There was no difference in glucose tolerance or C-peptide release between relatives and controls, whether they had autoantibodies or not. At a three-year follow-up, none of the individuals had developed insulin-dependent diabetes.

Genetic dissection reveals diabetes loci proximal to the gimap5 lymphopenia gene

Congenic DRF.(f/f) rats are protected from type 1 diabetes (T1D) by 34 Mb of F344 DNA introgressed proximal to the gimap5 lymphopenia gene. To dissect the genetic factor(s) that confer protection from T1D in the DRF.(f/f) rat line, DRF.(f/f) rats were crossed to inbred BBDR or DR.(lyp/lyp) rats to generate congenic sublines that were genotyped and monitored for T1D, and positional candidate genes were sequenced. All (100%) DR.(lyp/lyp) rats developed T1D by 83 days of age. Reduction of the DRF.(f/f) F344 DNA fragment by 26 Mb (42.52-68.51 Mb) retained complete T1D protection. Further dissection revealed that a 2 Mb interval of F344 DNA (67.41-70.17 Mb) (region 1) resulted in 47% protection and significantly delayed onset (P < 0.001 compared with DR.(lyp/lyp)). Retaining <1 Mb of F344 DNA at the distal end (76.49-76.83 Mb) (region 2) resulted in 28% protection and also delayed onset (P < 0.001 compared with DR.(lyp/lyp)). Comparative analysis of diabetes frequency in the DRF.(f/f) congenic sublines further refined the RNO4 region 1 interval to approximately 670 kb and region 2 to the 340 kb proximal to gimap5. All congenic DRF.(f/f) sublines were prone to low-grade pancreatic mononuclear cell infiltration around ducts and vessels, but <20% of islets in nondiabetic rats showed islet infiltration. Coding sequence analysis revealed TCR Vbeta 8E, 12, and 13 as candidate genes in region 1 and znf467 and atp6v0e2 as candidate genes in region 2. Our results show that spontaneous T1D is controlled by at least two genetic loci 7 Mb apart on rat chromosome 4.

Temporal trends of HLA genotype frequencies of type 1 diabetes patients in Sweden from 1986 to 2005 suggest altered risk

The aim of this study was to compare the frequency of human leukocyte antigen (HLA) genotypes in 1-18-year-old patients with type 1 diabetes newly diagnosed in 1986-1987 (n = 430), 1996-2000 (n = 342) and in 2003-2005 (n = 171). We tested the hypothesis that the HLA DQ genotype distribution changes over time. Swedish type 1 diabetes patients and controls were typed for HLA using polymerase chain reaction amplification and allele specific probes for DQ A1* and B1* alleles. The most common type 1 diabetes HLA DQA1*-B1*genotype 0501-0201/0301-0302 was 36% (153/430) in 1986-1987 and 37% (127/342) in 1996-2000, but decreased to 19% (33/171) in 2003-2005 (P \ 0.0001). The 0501-0201/0501-0201 genotype increased from 1% in 1986-1987 to 7% in 1996-2000 (P = 0.0047) and to 5% in 2003-2005 (P > 0.05). This study in 1-18-year-old Swedish type 1 diabetes patients supports the notion that there is a temporal change in HLA risk.

The non-inherited maternal HLA haplotype affects the risk for type 1 diabetes

The aim was to test the hypothesis that the human leucocyte antigen (HLA) haplotype that is not inherited from the mother, that is, the non-inherited maternal antigen (NIMA) affects the risk for type 1 diabetes (T1D). A total of 563 children with T1D and 286 non-diabetic control children from Sweden were genotyped for DRB1, DQA1 and DQB1 alleles. The frequency of positively (DR4-DQA1*0301-B1*0302 and DR3-DQA1*0501-B1*0201), negatively (DR15-DQ A1*0102-B1*0602) or neutrally (all other) T1D associated HLA haplotypes were compared between NIMA and non-inherited paternal antigen (NIPA). All comparisons were carried out between HLA-matched patients and controls. The frequency of positively associated NIMA was higher among both DR4/X-positive healthy individuals compared wit DR4/X-positive patients (P < 0.00003) and DR3/X-positive healthy individuals compared with DR3/X-positive patients (P < 0.009). No such difference was observed for NIPA. High-risk NIMA was increased compared to NIPA among healthy DR3/X- and DR4/X-positive children (P < 0.05). There was no difference in frequency of positively associated haplotypes between patient NIMA and NIPA. The NIMA but not the NIPA affects the risk for T1D, suggesting that not only the inherited but also non-inherited maternal HLA haplotypes, perhaps through microchimerism or other mechanisms, may influence the risk for the disease.

Children developing type 1 diabetes before 6 years of age have increased linear growth independent of HLA genotypes

AIMS/HYPOTHESIS

High birthweight and increased childhood growth are risk factors for type 1 diabetes. Relative birthweight is associated with HLA genotypes that confer a high risk of diabetes. Our aims were to test whether young children prior to clinical onset of type 1 diabetes have increased: (1) birthweight or birth length standard deviation scores (SDS); (2) height development SDS; or (3) BMI SDS during first 18 months of life and whether these parameters are related to HLA genotypes or mid-parental height (MPH).

METHODS

Birthweight, birth length, weight and height were obtained from 58 type 1 diabetes children and 155 controls matched for HLA or not in the Diabetes Prediction in Skåne study.

RESULTS

Birth length SDS corrected for MPH was increased in children developing diabetes compared with all (p < 0.048) and with non-HLA- (p < 0.050) but not with HLA-matched controls. Children developing diabetes had increased height gain at 0 to 18 months of age (p < 0.005). Diabetic children were significantly taller from 6 to 18 months of age when correcting for MPH compared with non-HLA-matched as well as HLA-matched controls, but BMI was not increased.

CONCLUSIONS/INTERPRETATION

Birth length SDS was associated with diabetes risk HLA. When corrected for MPH, children developing diabetes were taller at birth than non-HLA- but not taller than HLA-matched controls. Diabetic children had increased MPH-corrected height up to 18 months of age compared with both HLA- and non-HLA-matched controls. High-risk HLA affects prenatal growth, but other factors may explain the increased postnatal linear growth in children developing diabetes.

Carboxypeptidase B-like and trypsin-like activities in isolated rat pancreatic islets

Trypsin-like and carboxypeptidase B-like proteinases are believed to play important roles in the conversion of proinsulin into insulin as well as in the intracellular processing of a variety of other precursor forms. To facilitate the study of these enzymes we have developed sensitive methods for their detection in tissue preparations and incubation media. Studies with rat islet homogenates indicate the presence of both trypsin-like and carboxypeptidase B-like activities with slightly acidic pH optima. The trypsin-like activity was activated by thiols and inhibited by several thiol reagents but the carboxypeptidase was inhibited only by chelating agents. These properties suggest that these enzymes are related to the tissue cathepsins. Additional experimental approaches to the problems of positively identifying and localizing converting enzymes at the subcellular level are briefly discussed.

Biosynthesis of insulin and glucagon: a view of the current state of the art

It is now well established that insulin biosynthesis proceeds through a precursor molecule, proinsulin. This single polypeptide chain form has been identified as a ribosomal product in the microsomal fraction from islet tissues. The newly synthesized peptide chain, after folding and thiol oxidation, is transferred to the Golgi apparatus where it begins to undergo proteolytic processing to insulin and packaging into secretory granules. The secretion from the cells of significant amounts of newly synthesized material by exocytosis begins only one hour or more after biosynthesis and this process is regulated by several factors, including glucose. Foci of current attention discussed in this paper include (1) the possible existence of larger precursor forms than proinsulin, especially short-lived biosynthetic transients with extended NH2-termini analogous to the recently described immunoglobulin L chain and proparathyroid hormone precursors; (2) the large-scale production of insulin by chemical or genetic engineering approaches; (3) isolation of beta-cell plasma membranes; (4) regulatory mechanisms for the biosynthesis and secretion of insulin, the possible role of mRNA modification in this process, and effects of somatostatin on insulin biosynthesis and secretion; (5) studies on the secretion, metabolism and clinical usefulness of the proinsulin C-peptide; (6) finally, the biosynthesis of glucagon and other peptide hormones and the general significance of precursor forms.

Increased lipid oxidation heralds diabetes onset in DR.lyp/lyp rats

AIM

The BB rat model of type 1 diabetes exhibits altered body weight gain and body temperature regulation prior to hyperglycemia onset, implying the existence of as yet unidentified biomarkers of autoimmune processes that destroy pancreatic beta cells. To investigate this hypothesis, we compared the metabolic profile of diabetes-resistant DR.lyp/+ rats and their diabetes-prone, congenic DR.lyp/lyp littermates in the days leading up to diabetes onset.

METHODS

Except for the Gimap5 mutation on chromosome 4, congenic DR.lyp/lyp rats are genetically identical to DR.lyp/+ littermates. They invariably develop hyperglycemia at 46-81 days of age, whereas DR.lyp/+ rats do not develop diabetes. In addition to daily food intake and body weight, indirect calorimetry was performed continuously on male DR.lyp/lyp and DR.lyp/+ rats (n=6/group) for 6-18 days to measure locomotor activity, VO (2), VCO (2) and RQ.

RESULTS

DR.lyp/lyp rats exhibited a progressive decrease of RQ compared to DR.lyp/+ rats 0.005+/-0.001 units/day (p<0.005). Limiting the analysis to the six days prior to diabetes onset revealed a larger decrease of 0.007+/-0.002 units/day (p<0.001) in DR.lyp/lyp animals, whereas RQ of the DR.lyp/+ rats remained unchanged. This metabolic change occurred prior to hyperglycemia onset and was not associated with changes of any other parameter.

CONCLUSIONS

Diabetes onset in DR.lyp/lyp rats is heralded by a progressive shift towards lipid oxidation relative to carbohydrate metabolism.

No evidence of association of the PDCD1 gene with Type 1 diabetes

AIMS

To test the association between the immunoreceptor PD-1 (PDCD1) gene and Type 1 diabetes mellitus (T1DM). This gene has been reported to be associated with other autoimmune diseases such as systemic lupus erythematosus (SLE) as well as T1DM.

METHODS

Genotyping of single nucleotide polymorphisms (SNPs) in the PDCD1 gene was performed using polymerase chain reaction-restriction fragment length polymorphism (PCR-RFLP), pyrosequencing and TaqMan in two separate cohorts of Swedish patients and control subjects: a family study consisting of 184 multiplex and eight simplex families and a case-control study consisting of 586 patients and 836 control subjects. Three SNPs were genotyped: PD-1 7146, PD-1 7785 and PD-1 8738.

RESULTS

We did not detect any association or linkage between SNPs in PDCD1 and T1DM. We further performed a meta-analysis for association of PD-1 7146, PD-1 7785 and PD-1 8738 to T1DM. We detected heterogeneity in association with weak evidence for overall association.

CONCLUSIONS

We conclude that PDCD1 is unlikely to be a major susceptibility gene for T1DM.

Epitope analysis of GAD65 binding in both cord blood and at the time of clinical diagnosis of childhood type 1 diabetes

The GAD65 epitope immunoglobulin binding pattern in cord blood of children (n=37), who later developed type 1 diabetes at 3.2-14.9 years of age, was analyzed. First, the binding at diagnosis was compared with that in the cord blood serum. The next comparison was between the cord blood serum and the mothers' serum taken at delivery. Basal GAD65 binding levels were determined in Protein A Sepharose-based radiobinding assays with (35)S-labeled human and rat GAD65, rat GAD67 and GAD65/67 fusion proteins representing N-terminal (N), middle (M) and C-terminal (C) epitopes. In the first comparison, 28/37 children had GAD65 binding above 2.44 relative units (RU) (upper three quartiles), representing a marked increase from birth in the binding to human GAD65 (p<0.0001), rat GAD65 (p<0.0001), N- (p=0.04), M- (p<0.0001), C- (p=0.001), and M + C-epitopes (p<0.0001), but not to rat GAD67. At birth, 9/37 had GAD65 binding above 1.56 RU (upper quartile) demonstrating that their binding of human (35)S-GAD65 was higher in cord blood than in the mother (p=0.008). Higher cord blood binding was also observed for the N- (p=0.02) terminal epitope but not for rat GAD65, rat GAD67, and the remaining epitopes. These data suggest that differences in the epitope GAD65 binding between mother and child at birth are limited. In contrast, the epitope pattern at diagnosis differed from that at birth, supporting the view that disease-associated epitopes develop between birth and diagnosis.

Islet cell autoantibody levels after the diagnosis of young adult diabetic patients

AIMS

The aim was to determine the course of islet cell antibodies [glutamate decarboxylase (GADA), tyrosine phosphatase-like islet antigen 2 (IA-2A) and islet cell (ICA)] after the diagnosis of the diabetic patient.

METHODS

The Diabetes Incidence Study in Sweden (DISS) attempted to prospectively enrol all newly diagnosed diabetic patients aged 15-34 years during 1992 and 1993. C-peptide and autoantibody levels were determined from venous blood samples at diagnosis and again at yearly intervals for 6 years.

RESULTS

After the first year, the odds of remaining GADA positive decreased by 9% per year [odds ratio (OR) = 0.91, 95% confidence interval (CI) = 0.85-0.96] while the mean GADA index remained unchanged ( = 0.8, P = 0.37). There was no change in the percentage of subjects testing IA-2A positive after the first year ( = 0.1, P = 0.75). However, the mean index decreased 0.04 per year (95% CI: 0.03-0.05)-a 7.9% decline (95% CI: 5.4-10.4%). The odds of a subject testing positive for ICA decreased by 24% per year (OR = 0.76, 95% CI = 0.70-0.82). The mean ICA levels decreased 0.75 per year (95% CI: 0.66-0.84)-a 16.4% decline (95% CI: 14.1-18.6%). The rate of change in titres for all three autoantibodies was independent of gender, human leucocyte antigen genotype and C-peptide status.

CONCLUSIONS

GADA levels remained high while ICA levels declined. In contrast to a previous study, we found that the proportion of IA-2A subjects remaining positive did not decrease after the first year, while the average index decreased slightly.

Relative predispositional effects of HLA class II DRB1-DQB1 haplotypes and genotypes on type 1 diabetes: a meta-analysis

The direct involvement of the human leukocyte antigen class II DR-DQ genes in type 1 diabetes (T1D) is well established, and these genes display a complex hierarchy of risk effects at the genotype and haplotype levels. We investigated, using data from 38 studies, whether the DR-DQ haplotypes and genotypes show the same relative predispositional effects across populations and ethnic groups. Significant differences in risk within a population were considered, as well as comparisons across populations using the patient/control (P/C) ratio. Within a population, the ratio of the P/C ratios for two different genotypes or haplotypes is a function only of the absolute penetrance values, allowing ranking of risk effects. Categories of consistent predisposing, intermediate ('neutral'), and protective haplotypes were identified and found to correlate with disease prevalence and the marked ethnic differences in DRB1-DQB1 frequencies. Specific effects were identified, for example for predisposing haplotypes, there was a statistically significant and consistent hierarchy for DR4 DQB1*0302s: DRB1*0405 =*0401 =*0402 > *0404 > *0403, with DRB1*0301 DQB1*0200 (DR3) being significantly less predisposing than DRB1*0402 and more than DRB1*0404. The predisposing DRB1*0401 DQB1*0302 haplotype was relatively increased compared with the protective haplotype DRB1*0401 DQB1*0301 in heterozygotes with DR3 compared with heterozygotes with DRB1*0101 DQB1*0501 (DR1). Our results show that meta-analyses and use of the P/C ratio and rankings thereof can be valuable in determining T1D risk factors at the haplotype and amino acid residue levels.

IA-2 autoantibodies in incident type I diabetes patients are associated with a polyadenylation signal polymorphism in GIMAP5

In a large case-control study of Swedish incident type I diabetes patients and controls, 0-34 years of age, we tested the hypothesis that the GIMAP5 gene, a key genetic factor for lymphopenia in spontaneous BioBreeding rat diabetes, is associated with type I diabetes; with islet autoantibodies in incident type I diabetes patients or with age at clinical onset in incident type I diabetes patients. Initial scans of allelic association were followed by more detailed logistic regression modeling that adjusted for known type I diabetes risk factors and potential confounding variables. The single nucleotide polymorphism (SNP) rs6598, located in a polyadenylation signal of GIMAP5, was associated with the presence of significant levels of IA-2 autoantibodies in the type I diabetes patients. Patients with the minor allele A of rs6598 had an increased prevalence of IA-2 autoantibody levels compared to patients without the minor allele (OR=2.2; Bonferroni-corrected P=0.003), after adjusting for age at clinical onset (P=8.0 x 10(-13)) and the numbers of HLA-DQ A1*0501-B1*0201 haplotypes (P=2.4 x 10(-5)) and DQ A1*0301-B1*0302 haplotypes (P=0.002). GIMAP5 polymorphism was not associated with type I diabetes or with GAD65 or insulin autoantibodies, ICA, or age at clinical onset in patients. These data suggest that the GIMAP5 gene is associated with islet autoimmunity in type I diabetes and add to recent findings implicating the same SNP in another autoimmune disease.

Relationship between increased relative birthweight and infections during pregnancy in children with a high-risk diabetes HLA genotype

AIMS/HYPOTHESIS

Children with high-risk type 1 diabetes HLA genotype have increased risk of high relative birthweight (HrBW), while cord blood islet autoantibodies decrease the risk. As gestational infections may affect offspring type 1 diabetes risk, the aims were to test whether: (1) children of mothers reporting gestational infections have increased HrBW; (2) gestational infections explain islet autoantibody reduction of HrBW; and (3) gestational infections affect the association between HLA and HrBW.

SUBJECTS AND METHODS

HLA genotypes and autoantibodies to glutamic acid decarboxylase, insulinoma-associated protein 2 and insulin were determined in cord blood of children born to non-diabetic mothers in the Diabetes Prediction in Skåne (DiPiS) study. Mothers reported gestational infections when the child was 2 months old.

RESULTS

Fever or gastroenteritis during pregnancy was reported by 2,848/19,756 mothers (14%); 339 in more than one trimester. Children whose mothers reported infections had increased risk of HrBW (p = 0.0003), particularly in the absence of cord blood islet autoantibodies (interaction between HrBW, islet autoantibodies and infections, p = 0.0005). The effect on HrBW by high-risk HLA-DQ2/8 was aggravated by infections in more than one trimester (odds ratio [OR] = 5.24; p = 0.003) (interaction; p = 0.022). When infections were reported, cord blood islet autoantibodies decreased HrBW (OR = 0.34; p = 0.0002).

CONCLUSIONS/INTERPRETATION

This study revealed that: (1) gestational fever, gastroenteritis, or both, increased the risk of HrBW; (2) cord blood islet autoantibodies decreased the risk of HrBW only in combination with infections; and (3) infections aggravated the association between HLA-DQ2/8 and HrBW. These data suggest an interaction between HLA, gestational infections, islet autoantibodies and fetal growth.

Glutamate Cysteine Ligase Catalytic Subunit Promoter Polymorphisms and Associations with Type 1 Diabetes Age-at-onset and GAD65 Autoantibody Levels

The purpose of this study was to test the hypothesis that glutamate cysteine ligase catalytic subunit (GCLC) promoter polymorphisms are susceptibility factors for type 1 diabetes (T1D), T1D age-at-onset and T1D autoantibodies. T1D patients and control subjects from the Swedish Childhood Diabetes Registry and the Swedish Diabetes Incidence Study registry were genotyped for two GCLC promoter polymorphisms; the GCLC -129 C to T single nucleotide polymorphism (GCLC -129 SNP) and the GCLC GAG trinucleotide repeat polymorphism (GCLC TNR). Glutamate decarboxylase antibody (GAD65Ab) positive T1D patients with the GCLC -129 SNP C/T genotype have increased GAD65Ab levels (p-value, <0.05) compared to the GCLC -129 SNP C/C genotype. T1D patients with an age-at-onset of 14-35 years who possess the GCLC -129 SNP T/T genotype have a higher GAD65Ab index than T1D patients with the GCLC -129 SNP C/C genotype (p-value <0.05). In addition, T1D patients with an age-at-onset of 14-35 years possess the GCLC TNR 7/8 genotype at a lower frequency than the control subjects (OR, 0.33, 95% CI, 0.13-0.82). The GCLC -129 SNP and GCLC TNR appear to be in linkage disequilibrium (p-value<0.0001). These results suggest that GCLC promoter polymorphisms may influence GAD65Ab levels and may influence the age at which T1D is diagnosed.

GAD65 autoantibody epitopes in adult patients with latent autoimmune diabetes following GAD65 vaccination

AIMS

Subcutaneous injection of recombinant human GAD65 (rhGAD65) in patients with latent autoimmune diabetes in adults (LADA) correlates with an increase in C-peptide levels. In this study we analysed the effect of rhGAD65 administration on the GAD65-specific autoimmune response.

METHODS

Longitudinal serum samples obtained from LADA patients (n = 47) who received 4, 20, 100 or 500 microg alum-formulated rhGAD65 or placebo by subcutaneous injection twice (4 weeks apart) were analysed for their epitope recognition using GAD65-specific recombinant Fab and GAD65/67 fusion proteins.

RESULTS

Overall, minor changes in the epitope pattern were observed using either approach. Only in the 500-microg dosage group was an increase in GAD65Ab level associated with a significant increase in the binding to a conformational epitope located at the middle part of GAD65.

CONCLUSIONS

Our data suggest that the apparent beneficial effects of 20 microg alum-formulated recombinant human GAD65 is not explained by changes in the GAD65Ab epitope pattern.

A variant in the transcription factor 7-like 2 (TCF7L2) gene is associated with an increased risk of gestational diabetes mellitus

AIMS/HYPOTHESIS

Genetic and epidemiological studies suggest an association between gestational diabetes mellitus and type 2 diabetes. Both are polygenic multifactorial disorders characterised by beta cell dysfunction and insulin resistance. Our aim was to investigate whether common genetic variants that have previously been associated with type 2 diabetes or related phenotypes would also confer risk for gestational diabetes mellitus.

MATERIALS AND METHODS

In 1,881 unrelated pregnant Scandinavian women (649 women with gestational diabetes mellitus, 1,232 non-diabetic control subjects) we genotyped the transcription factor 7-like 2 (TCF7L2 rs7903146), adiponectin (ADIPOQ +276G > T), peroxisome-proliferator activated receptor, gamma 2 (PPARG Pro12Ala), PPARG-coactivator, 1 alpha (PPARGC1A Gly482Ser), forkhead box C2 (FOXC2 -512C > T) and beta3-adrenergic receptor (ADRB3 Trp64Arg) polymorphisms using TaqMan allelic discrimination assay or RFLP.

RESULTS

The CC, CT and TT genotype frequencies of the TCF7L2 rs7903146 variant differed significantly between women with gestational diabetes mellitus and control women (46.3, 43.6 and 10.1% vs 58.5, 35.3 and 6.2%, p = 3.7 x 10(-6), corrected p value [Pc] for multiple testing Pc = 2.2 x 10(-5)). The T-allele was associated with an increased risk of gestational diabetes mellitus (odds ratio 1.49 [95% CI 1.28-1.75], p = 4.9 x 10(-7) [Pc = 2.8 x 10(-6)]). Compared with wild-type CC-genotype carriers, heterozygous (CT-genotype) and homozygous (TT-genotype) carriers had a 1.6-fold (95% CI 1.26-1.93, p = 3.7 x 10(-5) [Pc = 0.0002]) and a 2.1-fold (95% CI 1.41-2.99, p = 0.0001 [Pc = 0.0008]) increased risk of gestational diabetes mellitus, respectively. The other polymorphisms studied were not significantly associated with gestational diabetes mellitus (ADIPOQ +276G > T: 1.17 [1.01-1.36], p = 0.039 [Pc = 0.23]; PPARG Pro12Ala: 1.06 [0.87-1.29], p = 0.53; PPARGC1A Gly482Ser: 0.96 [0.83-1.10], p = 0.54; FOXC2 -512C > T: 1.01 [0.87-1.16], p = 0.94; and ADRB3 Trp64Arg: 1.22 [0.95-1.56], p = 0.12).

CONCLUSIONS/INTERPRETATION

The TCF7L2 rs7903146 variant is associated with an increased risk of gestational diabetes mellitus in Scandinavian women.

Evidence for immunological priming and increased frequency of CD4+ CD25+ cord blood T cells in children born to mothers with type 1 diabetes

Maternal transmission of islet autoantibodies to children born to mothers with type 1 diabetes (T1D) has been shown to protect from autoantibodies and diabetes development later in life. However, the factors conferring disease protection are poorly understood. The aim of this study was to evaluate comparatively proinflammatory cytokines, autoantibodies and lymphocyte subsets in cord blood (CB) of children born to mothers with either T1D (n = 13), gestational diabetes (GDM) (n = 32) or healthy mothers (n = 81) in relation to transplacental passage of autoantibodies. The results are consistent with early priming of the fetal immune system only in children born to mothers with T1D. Levels of interleukin (IL)-1beta (P = 0.022), tumour necrosis factor (TNF)-alpha (P = 0.002) and IL-8 (P = 0.0012), as well as the frequency of CD4(+) CD25(+) T cells (P < 0.01) were significantly increased, and the increased levels correlated positively with anti-GAD65 autoantibody (GADA) levels. Moreover, CD4(+) CD25(+) T cells of children born to T1D mothers exhibited a more pronounced memory phenotype with increased CCR4 expression and down-regulation of CD62L. These data suggest that early activation of the fetal immune system as a consequence of maternal autoimmunity and transplacental passage of GADA may influence the generation and expansion of fetal regulatory T cells. This might induce an early antigen-specific immunological tolerance that could protect against T1D later in life.

Prenatal viral exposure followed by adult stress produces glucose intolerance in a mouse model

AIMS/HYPOTHESIS

It has been suggested that the uterine environment may influence metabolic disease occurring later in adult life, and that adult stress may promote disease outcome. Using a mouse model, we tested whether in utero exposure to Ljungan virus (LV) followed by adult exposure to stress produces diabetes. The influence of the timing of viral exposure over the course of pregnancy was also tested.

MATERIALS AND METHODS

Pregnant CD-1 mice were exposed i.p. to LV on pregnancy days 4, 8, 12 or 17. Adult male mice from these pregnancies were stressed by being kept in shared cages. Stress only, LV exposure in utero only, and no-stress/no virus exposure groups were also followed. Outcome variables included bodyweight, epididymal fat weight, baseline glucose, glucose tolerance tests (60 and 120 min) and serum insulin.

RESULTS

We demonstrated that male mice developed a type 2-like diabetes, including obesity, as adults if infected during pregnancy with LV. Diabetes at the age of 11 weeks was more severe in mice whose mothers were infected earlier than in those whose mothers were infected later in pregnancy. Only animals infected in utero and kept under stress developed diabetes; infection or stress alone did not cause disease.

CONCLUSIONS/INTERPRETATION

This work demonstrates that a type 2 diabetes-like disease can be virus-induced in a mouse model. Early in utero viral insults can set the stage for disease occurring during adult life, but the final manifestation of diabetes is dependent on the combination of early viral exposure and stress in adult life.

Common variants in MODY genes increase the risk of gestational diabetes mellitus

AIMS/HYPOTHESIS

Impaired beta cell function is the hallmark of gestational diabetes mellitus (GDM) and MODY. In addition, women with MODY gene mutations often present with GDM, but it is not known whether common variants in MODY genes contribute to GDM.

SUBJECTS AND METHODS

We genotyped five common variants in the glucokinase (GCK, commonly known as MODY2), hepatocyte nuclear factor 1-alpha (HNF1A, commonly known as MODY3) and 4-alpha (HNF4A commonly known as MODY1) genes in 1,880 Scandinavian women (648 women with GDM and 1,232 pregnant non-diabetic control women).

RESULTS

The A allele of the GCK -30G-->A polymorphism was more common in GDM women than in control subjects (odds ratio [OR] 1.28 [95% CI 1.06-1.53], p=0.008, corrected p value, p=0.035). Under a recessive model [AA vs GA+GG], the OR increased further to 2.12 (95% CI 1.21-3.72, p=0.009). The frequency of the L allele of the HNF1A I27L polymorphism was slightly higher in GDM than in controls (1.16 [95% CI 1.001-1.34], p=0.048, corrected p value, p=0.17). However, the OR increased under a dominant model (LL+IL vs II; 1.31 [95% CI 1.08-1.60], p=0.007). The rs2144908, rs2425637 and rs1885088 variants, which are located downstream of the primary beta cell promoter (P2) of HNF4A, were not associated with GDM.

CONCLUSIONS/INTERPRETATION

The -30G-->A polymorphism of the beta-cell-specific promoter of GCK and the I27L polymorphism of HNF1A seem to increase the risk of GDM in Scandinavian women.

Reduction of tissue transglutaminase autoantibody levels by gluten-free diet is associated with changes in subsets of peripheral blood lymphocytes in children with newly diagnosed coeliac disease

Tissue transglutaminase (tTG) autoantibodies decline after gluten-free diet in patients with coeliac disease. We tested the hypothesis that gluten-free diet-induced change in tTG autoantibody levels affects subsets of peripheral blood lymphocytes. Peripheral blood was obtained from 20 children with biopsy-proven active coeliac disease. Gluten-free diet was initiated and the children examined again after three and six months. tTG autoantibodies were measured in radioligand binding assays and lymphocyte subsets by flow cytometry. IgA-tTG levels at diagnosis, 2204 U/ml (median, range 113-24990), were reduced over six months to 76 U/ml (median, range 1-1261) (P < 0.001). At six months, 12/20 (60%) children had reduced their IgA-tTG levels to < 100 U/ml and these children showed a decrease in B cells (mean change -3.8%, P = 0.014), CD4+ T cells (mean -4.32%, P = 0.011) and CD4+ T cells expressing CD25high (mean change -0.62%, P = 0.036). In contrast, the CD4+CD25(high)CCR4+ T cell population increased during the same period (mean change 11.5%, P = 0.0036). The decline in IgA-tTG levels correlated to the decrease in B cells (r = 0.56, P = 0.01), CD4+ T cells (r = 0.66, P = 0.004) as well as CD4+CD25high T cells (r = 0.59, P = 0.01). A negative correlation was found between the decline in IgA-tTG and CD4+CD25high T cells expressing CD45RO (r = -0.49, P = 0.03) and CCR4 (r = -0.54, P = 0.01). This is the first observational study on the effect of gluten-free diet on concurrent changes of tTG autoantibodies and specific peripheral blood lymphocyte subsets. Our data suggest that flow cytometry may be a useful complement to tTG autoantibodies when studying the effects of gluten-free diet in children with coeliac disease.

Targeting type 1 diabetes before and at the clinical onset of disease

Autoimmune type 1 diabetes is strongly associated with a number of immune abnormalities that manifest themselves before and at the time of clinical diagnosis. The clinical onset is associated with a major loss of the pancreatic islet beta cells. Insulin treatment is the only treatment option since numerous trials with agents that suppress or modulate immune function have failed to preserve beta cell function long term. Recent studies suggest that it is possible to predict clinical onset of diabetes by combining genetic with autoantibody testing. In this review we will summarize current and future drug targets for subjects at risk for type 1 diabetes as well as for subjects with recent onset disease. We will also discuss the possible importance of initiating as well as contributing factors such as reactive oxygen species and modified autoantigens. It is speculated that drug targets of factors important to disease pathogenesis may provide safe and effective adductive treatment to preserve beta cell function in autoantibody positive subjects who are at maximum risk for disease.

D6S265*15 marks a DRB1*15, DQB1*0602 haplotype associated with attenuated protection from type 1 diabetes mellitus

AIMS/HYPOTHESIS

The HLA class II DQB1*0602 allele confers strong dominant protection against type 1 diabetes but protection is not absolute. The aim of this study was to identify markers within the HLA region that differentiate DQB1*0602 haplotypes and show different associations with disease risk.

METHODS

We defined alleles at eight microsatellite markers spanning the HLA region in a case-control cohort from Sweden.

RESULTS

We found that allele 15 at marker D6S265 (109 kb centromeric of HLA-A) was over-represented among patients carrying DRB1*15, DQB1*0602. A detailed haplotype analysis showed that DRB1*15, DQB1*0602 haplotypes carrying D6S265*15 have a ten-fold higher odds ratio (OR) than those carrying other alleles and thus confer reduced protection [OR D6S265*15=0.186 (95% CI 0.074, 0.472) vs OR D6S265*15-=0.017 (95% CI 0.005, 0.062), p<0.001].

CONCLUSIONS/INTERPRETATION

Our data support the existence of a locus that modifies the protective effect associated with DQB1*0602. Typing for allele D6S265*15 can identify a less protective DQB1*0602 haplotype, thereby allowing a more accurate prediction of type 1 diabetes risk.

Association of the E23K polymorphism in the KCNJ11 gene with gestational diabetes mellitus

AIMS/HYPOTHESIS

Gestational diabetes mellitus (GDM) and type 2 diabetes share a common pathophysiological background, including beta cell dysfunction and insulin resistance. In addition, women with GDM are at increased risk of developing type 2 diabetes later in life. Our aim was to investigate whether, like type 2 diabetes, GDM has a genetic predisposition by studying five common polymorphisms in four candidate genes that have previously been associated with type 2 diabetes.

MATERIALS AND METHODS

We studied 1,777 unrelated Scandinavian women (588 with GDM and 1,189 pregnant non-diabetic controls) for polymorphisms in the genes encoding potassium inwardly rectifying channel subfamily J, member 11 (KCNJ11 E23K), insulin receptor substrate 1 (IRS1 G972R), uncoupling protein 2 (UCP2 -866G-->A) and calpain 10 (CAPN10 SNP43 and SNP44).

RESULTS

The EE, EK and KK genotype frequencies of the KCNJ11 E23K polymorphism differed significantly between GDM and control women (31.5, 52.7 and 15.8% vs 37.3, 48.8 and 13.9%, respectively; p=0.050). In addition, the frequency of the K allele was increased in women with GDM (odds ratio [OR]=1.17, 95% CI 1.02-1.35; p=0.027), and this effect was greater under a dominant model (KK/EK vs EE) (OR=1.3, 95% CI 1.05-1.60; p=0.016). Analysis of the IRS1 G972R polymorphism showed that RR homozygosity was found exclusively in women with GDM (91.0, 8.3 and 0.7% vs 90.7, 9.3 and 0.0% for GG, GR and RR genotypes, respectively; p=0.014). The genotype and allele frequencies of the other polymorphisms studied were not statistically different between the GDM and control women.

CONCLUSIONS/INTERPRETATION

The E23K polymorphism of KCNJ11 seems to predispose to GDM in Scandinavian women.

Increased risk of diabetes among relatives of female insulin-treated patients diagnosed at 15-34 years of age

AIMS

This study aimed to determine the risk of developing diabetes among relatives of patients diagnosed between 15 and 34 years of age who were treated with insulin. Our second aim was to determine whether there was a difference in risk of diabetes between relatives of male and female patients.

METHODS

A questionnaire was sent to patients in the Diabetes Incidence Study in Sweden registry diagnosed between 1983 and 1993 to determine the presence of first-degree relatives with diabetes.

RESULTS

In 3087 index patients treated with insulin, 17.8% (95% confidence interval 16.5, 19.2) had a first-degree relative (excluding offspring) treated with insulin, the frequency being higher in female (19.8%) than in male (16.5%, P = 0.018) patients. A total of 10.7% had a parent treated with insulin. The prevalence of insulin-treated diabetes was higher among parents of female (12.5%) than of male (9.5%), insulin-treated index patients (P = 0.0068). A similar difference was observed using life table analysis (P = 0.0025), which also showed that the risk by 63 years of age was 7.6% for parents of female and 4.9% for parents of male insulin-treated index patients. In insulin-treated index patients, 8.4% had a sibling with insulin-treated diabetes.

CONCLUSIONS

We conclude that the risk for relatives of women with insulin-treated diabetes was higher than for relatives of insulin-treated male patients. We suggest that greater genetic susceptibility is required for females compared with males in the 15-34 age group in order to develop diabetes and hence females might carry more diabetes genes since more of their relatives also develop diabetes.

Diabetes-associated HLA genotypes affect birthweight in the general population

AIMS/HYPOTHESIS

The aim of our study was to test the hypothesis that HLA genotypes conferring risk of diabetes, cord blood autoantibodies, or both are associated with increased birthweight.

METHODS

HLA genotypes were determined in dried blood spots of cord blood from a total of 16,709 children born to healthy mothers in the Diabetes Prediction in Skåne (DiPiS) study, a population-based observational clinical investigation of newborn children. Children born to mothers with diabetes or gestational diabetes were excluded. Autoantibodies to glutamic acid decarboxylase (GAD65Ab) and insulinoma-associated protein 2 were determined in standard radioligand binding assays. Birthweight was adjusted for gestational age and divided into quartiles. The upper quartile was defined as high relative birthweight (HrBW) and the lower quartile as low relative birthweight (LrBW).

RESULTS

Genotypes conferring risk of type 1 diabetes were strongly associated with relative birthweight (rBW) (p=0.01). The high-risk HLA-DQ2/8, DQ8/0604 and DQ8/X genotypes were associated with HrBW (odds ratio [OR] [95% CI]=1.20 [1.08-1.33], p=0.0006). The HLA-DQB1*0603 allele, which is negatively associated with type 1 diabetes, was also associated with HrBW (p=0.025), confirming a previous report on DQB1*0603-linked HLA-DR13. GAD65Ab were negatively associated with HrBW (OR [95% CI]=0.72 [0.56-0.93], p=0.01). Regression analysis showed that the HLA-associated increase in rBW was independent of confounding factors.

CONCLUSIONS/INTERPRETATION

HLA genotypes may be associated with intrauterine growth independent of type 1 diabetes risk. The epidemiological observation that high birthweight is a risk factor for type 1 diabetes could possibly result from a moderating effect on intrauterine growth of HLA genotypes conferring a high risk of diabetes.

Epitope analysis of insulin autoantibodies using recombinant Fab

Autoantibodies to insulin are often the first autoantibodies detected in young children with type 1 diabetes and can be present before the onset of clinical diabetes. These autoantibodies and their epitopes are, however, not well characterized. We explored the use of monoclonal antibodies and their recombinant Fab as reagents for epitope analysis. In this study we cloned and characterized the recombinant Fab of the insulin-specific monoclonal antibody CG7C7. We found the epitope of this antibody to be located predominantly at the A-chain loop of the insulin molecule. The recombinant Fab was then used to compete for insulin binding against insulin autoantibodies present in sera from patients with type 1 or type 1.5 diabetes. In competition experiments with sera positive for autoantibodies to insulin the recombinant Fab significantly reduced the binding to [125I]-insulin by sera of type 1 (n = 35) and type 1.5 diabetes [latent autoimmune diabetes in adults (LADA)] (n = 14) patients (P < 0.0001). We conclude that competition between insulin-specific monoclonal antibodies or their recombinant Fab and insulin autoantibodies should prove useful in the epitope analysis of autoantibodies to insulin.

Conformation-dependent GAD65 autoantibodies in diabetes

AIMS/HYPOTHESIS

Conformation-dependent autoantibodies directed against GAD65 are markers of Type 1 diabetes. In this study we aimed to determine whether the substitution of GAD65 with GAD67 amino acids would affect the binding of conformation-dependent GAD65 autoantibodies.

METHODS

We used PCR-based site-directed mutagenesis to generate a series of mutated GAD65 cDNA constructs in which specific GAD65 coding sequences for regions of the protein critical for autoantibody binding were replaced with GAD67 coding sequences.

RESULTS

The introduction of a point mutation at position 517, substituting glutamic acid with proline, markedly reduced the binding of disease-associated GAD65 antibodies. The binding of GAD65 antibodies to the E517P mutant was reduced in the sera of all newly diagnosed Type 1 diabetes patients ( n=85) by a mean of 72% ( p<0.0001) compared with binding to wild-type GAD65. Patients with latent autoimmune diabetes in adults ( n=24) showed a similar reduction in binding (79% reduction, p<0.0001). First-degree relatives who subsequently progressed to Type 1 diabetes ( n=12) showed a reduction in binding of 80% compared with a reduction of only 65% among relatives who had not progressed to disease ( n=38; p=0.025). In healthy GAD65Ab-positive individuals who did not progress to diabetes during a 9-year follow-up period ( n=51), binding to GAD65-E517P was reduced by only 28% compared with binding to wild-type GAD65.

CONCLUSIONS/INTERPRETATION

Differences in autoantibody binding to wild-type GAD65 versus GAD65-E517P may provide predictive information about Type 1 diabetes risk beyond that provided by the presence or absence of GAD65 autoantibodies. Lack of binding to mutant GAD65-E517P defines GAD65-positive individuals who are at higher risk of developing diabetes.

Genotypic and phenotypic differences between Arabian and Scandinavian women with gestational diabetes mellitus

AIMS/HYPOTHESIS

Gestational diabetes mellitus is a heterogeneous disorder characterised by impaired insulin secretion and action. Our aim was to study whether autoimmunity, variations in genes affecting insulin secretion and action, or both, contribute to the development of gestational diabetes and whether the pathogenesis of the disease differs between women with a Scandinavian or Arabian background.

METHODS

We studied a total of 500 unrelated women with gestational diabetes (400 Scandinavian and 100 Arabian) and 550 unrelated pregnant non-diabetic control women (428 Scandinavian and 122 Arabian) matched for ethnicity.

RESULTS

Arabian women with gestational diabetes were 50% more insulin resistant for the same BMI compared with Scandinavian women with the disease (homeostasis model assessment [HOMA-IR]; 3.2+/-0.3 vs 2.2+/-0.2, p=0.02). Both Scandinavian (4.2% vs 0.9%, p=0.008) and Arabian (4.6% vs 0.0%, p=0.03) women with gestational diabetes had a higher frequency of GAD antibodies (GAD65Ab) than the matched controls. The frequency of HLA-DQB1 risk genotypes was slightly higher in Scandinavian women with gestational diabetes than in the Scandinavian controls (46.3% vs 38.8%, p=0.03) but no significant difference was found between the Arabian women with gestational diabetes and the Arabian controls (47% vs 51.6%, p=0.47). There were no significant differences in the frequency of the insulin gene variable number of tandem repeat ( INS VNTR) alleles and genotypes or the peroxisome proliferator-activated receptor-gamma 2 ( PPAR gamma 2-Pro12Ala) polymorphism between the women with gestational diabetes and the control women either in Arabian or in Scandinavian women.

CONCLUSIONS/INTERPRETATION

Gestational diabetes mellitus was associated with the presence of GAD65Ab in both study groups. Scandinavian women with gestational diabetes may share some genetic features with Type 1 diabetes. In addition, Arabian women with gestational diabetes are more insulin resistant than Scandinavian women with gestational diabetes and with the same BMI.

Standardization of antibody preparations for use in immunogenicity studies: a case study using the World Health Organization International Collaborative Study for Islet Cell Antibodies

The immunogenicity of biological therapeutic products is currently a high profile regulatory and biotechnology industry issue. The immune responses raised against biotechnology products range from the benign, to affecting product efficacy, to those that have serious deleterious clinical impact. The most widely used marker of immunogenicity is the detection and measurement of antibody responses induced in vivo to a product. This relies on assays that are sensitive and robust. In order to assess the parameters of an assay during its design, development and validation, it is extremely useful to have a reference standard to compare assay results. However, immune responses lead to polyclonal antibody preparations that can vary by affinity and avidity. This makes it extremely difficult to select a preparation that will behave similarly in different test systems and against different antibody samples. The case example of the WHO standardization of islet cell antibodies illustrates the difficulties in the process and the mechanisms required to produce a suitable antibody standard.