Polly J. Bingley

The British Diabetic Association Cohort Study, II: cause‐specific mortality in patients with insulin‐treated diabetes mellitus

Aims To assess mortality in patients with diabetes incident under the age of 30u2003years.

Diabetes Antibody Standardization Program: evaluation of assays for autoantibodies to glutamic acid decarboxylase and islet antigen-2

Aims/hypothesisIslet autoantibodies are important in diabetes classification and risk assessment, and as endpoints in observational studies. The Diabetes Autoantibody Standardization Program (DASP) aims to improve and standardise measurement of autoantibodies associated with type 1 diabetes. We report results for glutamic acid decarboxylase autoantibodies (GADA) and islet antigen-2 autoantibodies (IA-2A) from three DASP workshops (2002–2005).MethodsUp to 60 laboratories in 18 countries participated in each workshop. Participants received coded serum aliquots from 50 patients with newly diagnosed type 1 diabetes (median age 18xa0years, range 9–35xa0years) and 100 blood donor controls. Results were analysed using receiver operator characteristic (ROC) curves with sensitivity adjusted to 95% specificity in workshop controls.ResultsGADA assays performed well in all three workshops (median area under the ROC curve [AUC] 0.94; interquartile range 0.91–0.95) and performance was similar to DASP 2000. Performance of IA-2A assays improved over the workshop programme. Median AUC was 0.81 (interquartile range 0.79–0.83) in DASP 2002, 0.82 (interquartile range 0.78–0.84) in 2003, and 0.85 (interquartile range 0.82–0.87) in 2005 (pu2009<u20090.0001). Performance of GADA ELISA improved between 2002 and 2005, and, in DASP 2005, achieved higher median AUC and adjusted sensitivity than RIA. IA-2A ELISA improved and, in DASP 2005, achieved AUCs equivalent to in-house RIA. Assays using IA-2ic or full length IA-2 clones were more sensitive than those using IA-2bdc, with higher AUC (pu2009=u20090.004).Conclusions/interpretationGADA and IA-2A assays perform well in discriminating health and disease. The workshop format highlights systematic differences related to assay method and allows full evaluation of novel methods. The programme of autoantibody workshops in type 1 diabetes provides a model for other autoimmune diseases.

The TrialNet Natural History Study of the Development of Type 1 Diabetes: objectives, design, and initial results

Objectives:u2002 TrialNet’s goal to test preventions for type 1 diabetes has created an opportunity to gain new insights into the natural history of pre‐type 1 diabetes. The TrialNet Natural History Study (NHS) will assess the predictive value of existing and novel risk markers for type 1 diabetes and will find subjects for prevention trials.

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

Aims/hypothesisLatent autoimmune diabetes in adults (LADA) is a slowly progressive form of autoimmune diabetes, with autoantibodies to islet proteins developing in older patients who have no immediate requirement for insulin therapy. Markers of its clinical course are uncharacterised. The aim of this study was to determine whether persistence of, or changes in, GAD65 autoantibodies (GADAs) in the LADA patients who participated in the United Kingdom Prospective Diabetes Study (UKPDS) were associated with disease progression or insulin requirement.MethodsGADA levels and their relative epitope reactivities to N-terminal, middle and C-terminal regions of human GAD65 were determined in 242 UKPDS patients who were GADA-positive at diagnosis; samples taken after 0.5, 3 and 6xa0years of follow-up were tested using a radiobinding assay. Comparisons were made of GADA status with clinical details and disease progression assessed by the requirement for intensified glucose-lowering therapy.ResultsGADA levels fluctuated between 0.5 and 6xa0years but persisted in 225 of 242 patients. No association of GADA levels with disease progression or insulin requirement was observed. Antibody reactivity was directed to C-terminal and middle epitopes of GAD65 in >70% patients, and the N-terminal in <9%. There were no changes in epitope reactivity pattern over the 6xa0year follow-up period, nor any association between epitope reactivity and insulin requirement.Conclusions/interpretationGADAs persist for 6xa0years after diagnosis of LADA, but levels and reactivity to different GAD65 epitopes are not associated with disease progression.

Autoantibodies to islet antigen-2 are associated with HLA-DRB1*07 and DRB1*09 haplotypes as well as DRB1*04 at onset of type 1 diabetes: the possible role of HLA-DQA in autoimmunity to IA-2

Aims/hypothesisTo further our understanding of antigen presentation by HLA class II molecules, we have examined the influence of HLA class II genotype on expression of autoantibodies to islet antigen-2 (IA-2A).MethodsHLA class II genotype and IA-2A were determined within 3xa0months of diagnosis in 618 patients with type 1 diabetes (median age 11xa0years [range 0.7–20.9]). Antibodies to the juxtamembrane region of IA-2 were measured by a radiobinding assay in 481 of 484 IA-2A-positive patients.ResultsIA-2A prevalence was highest in patients carrying at least one HLA-DRB1*04-DQA1*0301 (385 of 450; 86%), DRB1*07-DQA1*(0201 or 0301) (58 of 64; 91%) or DRB1*09-DQA1*0301 haplotype (18 of 19; 95%). Multiple regression showed that IA-2A were strongly associated with the number of these haplotypes carried; only 69 of 132 (52%) patients carrying none of these haplotypes had IA-2A, compared with 322 of 391 (82%) patients with one and 93 of 95 (98%) with two of these haplotypes (pu2009<u20090.001). IA-2 juxtamembrane antibodies were less frequent in IA-2A-positive patients with one (35%) or two (36%) DRB1*03-DQB1*02 or DRB1*07-DQB1*02 haplotypes than in those negative for these haplotypes (52%) (pu2009=u20090.002), but showed an independent positive association with IA-2A level (pu2009<u20090.001).Conclusions/interpretationHLA class II alleles strongly influence the prevalence of IA-2A. The high IA-2A prevalence in patients carrying DRB1*04, DRB1*07 and DRB1*09 alleles in linkage disequilibrium with DQA1*0301 or the closely related DQA1*0201 suggests the humoral response to IA-2 may be driven by HLA-DQA1 genes.

Mortality of South Asian patients with insulin-treated diabetes mellitus in the United Kingdom: A cohort study

Aimsu2003 To investigate mortality in South Asian patients with insulin‐treated diabetes and compare it with mortality in non South Asian patients and in the general population.

Diabetes mellitus among young adults in Sri Lanka—role of GAD antibodies in classification and treatment: The Sri Lanka Young Diabetes study

A bstractAims/hypothesisDiabetes mellitus is increasing among young adult South Asians. The aim of this study was to determine the prevalence and phenotypic characteristics of diabetes subtypes based on GAD65 autoantibody (GADA) status in those with young adult-onset diabetes in Sri Lanka.MethodsClinical, metabolic and GADA data were available for 992 consecutively recruited individuals with diabetes aged ≤45xa0years (age at diagnosis 16–40xa0years). Participants were classified according to the following definitions: type 1 diabetes, insulin-dependent <6xa0months from diagnosis; latent autoimmune diabetes in adults (LADA), GADA-positive, age ≥30xa0years and insulin-independent ≥6xa0months from diagnosis; type 2 diabetes, GADA-negative and insulin-independent ≥6xa0months from diagnosis.ResultsThe median (interquartile range) age at diagnosis and diabetes duration were 33.0 (29.0–36.1) and 4.0 (1.1–7.1) years, respectively; 42.1% were male. GADA positivity was seen in 5.4% of participants (nu2009=u200954) and GADA levels negatively correlated with age at diagnosis (pu2009<u20090.0001), BMI (pu2009<u20090.0001) and time to insulin requirement (pu2009=u20090.006). Type 1 diabetes, type 2 diabetes and LADA were present in 7.0%, 89.7% and 2.6%, respectively. The remaining 0.7% of the participants were GADA-positive, insulin independent ≥6xa0months from diagnosis and were diagnosed at age <30xa0years. The metabolic syndrome and homeostasis model assessment of beta cell function (HOMA %B) were lowest in GADA-positive type 1 diabetes and increased progressively in latent autoimmune diabetes, GADA-negative type 1 diabetes and type 2 diabetes. Among those requiring insulin, 69.2% had fasting C-peptide levels in the lowest quartile, whereas only 19.5% were GADA-positive (pu2009<u20090.0001).Conclusions/interpretationThe prevalence of GADA-positive autoimmune diabetes is low among individuals with young adult-onset diabetes in Sri Lanka. Young-onset diabetic phenotypes appear as a continuum from autoimmune type 1 diabetes to type 2 diabetes.

Reanalysis of twin studies suggests that diabetes is mainly genetic

EDITOR—Two twin studies of type 1 diabetes have reached opposite conclusions. In one, a population based cohort of Danish twins in which one or both cotwins had type 1 diabetes was studied for the presence of islet autoantibodies.1 High rates of autoantibody positivity were identified in twins with and without diabetes. Since positivity did not differ between the monozygotic and dizygotic twins it was suggested that a shared intrauterine or early postnatal environment might be more important than genetic factors. The second study found that the prevalence of islet autoantibodies was lower in initially unaffected dizygotic twins than monozygotic twins and did not differ from that found in unaffected non-twin siblings. The authors concluded that islet autoimmunity is determined predominantly …

Measurement of nicotinamide and N-methyl-2-pyridone-5-carboxamide in plasma by high performance liquid chromatography

We describe a simple and reproducible method for simultaneous determination of nicotinamide and its major human biological metabolite N-methyl-2-pyridone-5-carboxamide (2pyr). Previous assays for nicotinamide in plasma and in urine have been complicated by the use of tedious extraction procedures or HPLC conditions which, although often allowing simultaneous analysis of several metabolites, add to the difficulties of performing multiple analyses. The procedure we describe is simple, using a rapid column clean-up of samples prior to injection, which can then be done using an autosampler. Both nicotinamide and its major metabolite 2pyr can be assayed rapidly, with good reproducibility, and at the same time.

Beta cell function and ongoing autoimmunity in long-standing, childhood onset type 1 diabetes

Aims/hypothesisThis study aimed to determine the frequency of residual beta cell function in individuals with long-standing type 1 diabetes who were recruited at diagnosis, and relate this to baseline and current islet autoantibody profile.MethodsTwo hour post-meal urine C-peptide:creatinine ratio (UCPCR) and islet autoantibodies were measured in samples collected from 144 participants (median age at diagnosis: 11.7xa0years; 47% male), a median of 23xa0years (range 12–29xa0years) after diagnosis. UCPCR thresholds equivalent to mixed meal-stimulated serum C-peptide >0.001xa0nmol/l, ≥0.03xa0nmol/l and ≥0.2xa0nmol/l were used to define ‘detectable’, ‘minimal’ and ‘residual/preserved’) endogenous insulin secretion, respectively. Autoantibodies against GAD (GADA), islet antigen-2 (IA-2A), zinc transporter 8 (ZnT8A) and insulin (IAA) were measured by radioimmunoassay.ResultsEndogenous C-peptide secretion was detectable in 51 participants (35.4%), including residual secretion in seven individuals (4.9%) and minimal secretion in 14 individuals (9.7%). In the 132 samples collected more than 10xa0years after diagnosis, 86 participants (65.2%) had at least one islet autoantibody: 42 (31.8%) were positive for GADA, 69 (52.3%) for IA-2A and 14 of 104 tested were positive for ZnT8A (13.5%). The level of UCPCR was related to age at diagnosis (pu2009=u20090.002) and was independent of diabetes duration, and baseline or current islet autoantibody status.Conclusions/interpretationThere is evidence of ongoing autoimmunity in the majority of individuals with longstanding diabetes. Endogenous insulin secretion continues for many years after diagnosis in individuals diagnosed with autoimmune-mediated type 1 diabetes above age 5. These findings suggest that some beta cells are protected from continued autoimmune attack in longstanding type 1 diabetes.