Diabetes Antibody Standardization Program: first assay proficiency evaluation

Prediction of future insulin-deficiency in glutamic acid decarboxylase autoantibody enzyme-linked immunosorbent assay-positive patients with slowly-progressive type 1 diabetes

AIMS/INTRODUCTION

This study aimed to identify risk factors that contribute to the progression of slowly-progressive type 1 diabetes by evaluating the positive predictive value (PPV) of factors associated with the progression to an insulin-dependent state.

MATERIALS AND METHODS

We selected 60 slowly-progressive type 1 diabetes patients who tested positive for glutamic acid decarboxylase autoantibodies (GADA) at diagnosis from the Japanese Type 1 Diabetes Database Study. GADA levels in these patients were concurrently measured using both radioimmunoassay (RIA) and enzyme-linked immunosorbent assay (ELISA) techniques.

RESULTS

Compared with the non-progressor group (fasting C-peptide [F-CPR] levels maintained ≥0.6 ng/mL), the progressor group showed a younger age at diagnosis, lower body mass index (BMI), lower F-CPR levels and a higher prevalence of insulinoma-associated antigen-2 autoantibodies (IA-2A). The PPV of RIA-GADA increased from 56.3 to 70.0% in the high titer group (≥10 U/mL), and further increased to 76.9, 84.2, 81.0 and 75.0% when combined with specific thresholds for age at diagnosis <47 years, BMI <22.6 kg/m2, F-CPR <1.41 ng/mL and IA-2A positivity, respectively. In contrast, the PPV of ELISA-GADA (71.8%) remained the same at 73.1% in the high titer group (≥180 U/mL), but increased to 81.8, 82.4 and 79.0% when evaluated in conjunction with age at diagnosis, BMI and F-CPR level, respectively.

CONCLUSIONS

Our findings show that, unlike RIA-GADA, ELISA-GADA shows no association between GADA titers and the risk of progression to an insulin-dependent state. The PPV improves when age at diagnosis, BMI and F-CPR levels are considered in combination.

Investigation of Monogenic Diabetes Genes in Thai Children with Autoantibody Negative Diabetes Requiring Insulin

Purpose

The objective of this study was to clarify the phenotypic characteristics of monogenic diabetes abnormalities in Thai children with autoantibody-negative insulin.

Patients and Methods

Two hundred and thirty-one Thai type 1 diabetes (T1D) patients out of 300 participants with recent-onset diabetes were analyzed for GAD65 and IA2 pancreatic autoantibodies. A total of 30 individuals with T1D patients with negative autoantibody were screened for 32 monogenic diabetes genes by whole-exome sequencing (WES).

Results

All participants were ten men and twenty women. The median age to onset of diabetes was 8 years and 3 months. A total of 20 people with monogenic diabetes carried genes related to monogenic diabetes. The PAX4 (rs2233580) in ten patients with monogenic diabetes was found. Seven variants of WFS1 (Val412Ala, Glu737Lys, Gly576Ser, Cys673Tyr, Arg456His, Lys424Glu, and Gly736fs) were investigated in patients in this study. Furthermore, the pathogenic variant, rs115099192 (Pro407Gln) in the GATA4 gene was found. Most patients who carried PAX4 (c.575G>A, rs2233580) did not have a history of DKA. The pathogenic variant GATA4 variant (c.1220C>A, rs115099192) was found in a patient with a history of DKA.

Conclusion

This study demonstrated significant genetic overlap between autoantibody-negative diabetes and monogenic diabetes using WES. All candidate variants were considered disease risk with clinically significant variants. WES screening was the first implemented to diagnose monogenic diabetes in Thai children, and fourteen novel variants were identified in this study and need to be investigated in the future.

New advances in type 1 diabetes

Type 1 diabetes is an autoimmune condition resulting in insulin deficiency and eventual loss of pancreatic β cell function requiring lifelong insulin therapy. Since the discovery of insulin more than 100 years ago, vast advances in treatments have improved care for many people with type 1 diabetes. Ongoing research on the genetics and immunology of type 1 diabetes and on interventions to modify disease course and preserve β cell function have expanded our broad understanding of this condition. Biomarkers of type 1 diabetes are detectable months to years before development of overt disease, and three stages of diabetes are now recognized. The advent of continuous glucose monitoring and the newer automated insulin delivery systems have changed the landscape of type 1 diabetes management and are associated with improved glycated hemoglobin and decreased hypoglycemia. Adjunctive therapies such as sodium glucose cotransporter-1 inhibitors and glucagon-like peptide 1 receptor agonists may find use in management in the future. Despite these rapid advances in the field, people living in under-resourced parts of the world struggle to obtain necessities such as insulin, syringes, and blood glucose monitoring essential for managing this condition. This review covers recent developments in diagnosis and treatment and future directions in the broad field of type 1 diabetes.

Impact of GAD65 and IA2 autoantibodies on islet allograft survival

Introduction

Islet transplantation (ITx) shows promise in treating T1D, but the role of islet autoantibodies on graft survival has not been clearly elucidated. We aimed to analyze the effect of GAD65 and IA2 autoantibody status on graft survival and attainment of insulin independence in subjects with T1D who underwent ITx.

Method

We conducted a retrospective cohort study on 47 ITx recipients from 2000 to 2018. Islet infusion was performed via intrahepatic portal (n=44) or onto the omentum via laparoscopic approach (n=3). Immunosuppression involved anti-IL2 receptor antibody, anti-TNF, and dual combinations of sirolimus, tacrolimus, or mycophenolate mofetil (Edmonton-like) in 38 subjects (80.9%). T-cell depletion induction with Edmonton-like maintenance was used in 9 subjects (19%). GAD65 and IA2 autoantibodies were assessed pre-transplant and post-transplant (monthly) until graft failure, and categorized as persistently negative, persistently positive, or seroconverters. Graft survival was analyzed using U-Mann-Whitney test, and Quade's nonparametric ANCOVA adjusted for confounders. Kaplan-Meier and Log-Rank tests were employed to analyze attainment of insulin independence. P value <0.05 indicated statistical significance.

Results

ITx recipients with persistent autoantibody negativity (n = 21) showed longer graft function (98 [61 - 182] months) than those with persistent autoantibody positivity (n = 18; 38 [13 - 163] months), even after adjusting for immunosuppressive induction protocol (P = 0.027). Seroconverters (n=8) had a median graft survival time of 73 (7.7 - 167) months, which did not significantly differ from the other 2 groups. Subjects with persistently single antibody positivity to GAD65 (n = 8) had shorter graft survival compared to negative islet autoantibody (GAD65/IA2) subjects (n = 21; P = 0.016). Time of graft survival did not differ in subjects with single antibody positivity to IA2. The proportion of insulin independence attainment was similar irrespective of autoantibody status.

Conclusion

The persistence of islet autoantibodies, as markers of islet autoimmunity, may represent an underappreciated contributing factor to the failure of transplanted β cells. Whether induction with T-cell depletion may lead to improved graft survival, independent of islet autoantibody status, could not be evaluated in our cohort. Larger prospective studies are needed to further address the role of islet autoantibody status on islet graft survival.

Refining the Definition of Stage 1 Type 1 Diabetes: An Ontology-Driven Analysis of the Heterogeneity of Multiple Islet Autoimmunity

OBJECTIVE

To estimate the risk of progression to stage 3 type 1 diabetes based on varying definitions of multiple islet autoantibody positivity (mIA).

RESEARCH DESIGN AND METHODS

Type 1 Diabetes Intelligence (T1DI) is a combined prospective data set of children from Finland, Germany, Sweden, and the U.S. who have an increased genetic risk for type 1 diabetes. Analysis included 16,709 infants-toddlers enrolled by age 2.5 years and comparison between groups using Kaplan-Meier survival analysis.

RESULTS

Of 865 (5%) children with mIA, 537 (62%) progressed to type 1 diabetes. The 15-year cumulative incidence of diabetes varied from the most stringent definition (mIA/Persistent/2: two or more islet autoantibodies positive at the same visit with two or more antibodies persistent at next visit; 88% [95% CI 85-92%]) to the least stringent (mIA/Any: positivity for two islet autoantibodies without co-occurring positivity or persistence; 18% [5-40%]). Progression in mIA/Persistent/2 was significantly higher than all other groups (P < 0.0001). Intermediate stringency definitions showed intermediate risk and were significantly different than mIA/Any (P < 0.05); however, differences waned over the 2-year follow-up among those who did not subsequently reach higher stringency. Among mIA/Persistent/2 individuals with three autoantibodies, loss of one autoantibody by the 2-year follow-up was associated with accelerated progression. Age was significantly associated with time from seroconversion to mIA/Persistent/2 status and mIA to stage 3 type 1 diabetes.

CONCLUSIONS

The 15-year risk of progression to type 1 diabetes risk varies markedly from 18 to 88% based on the stringency of mIA definition. While initial categorization identifies highest-risk individuals, short-term follow-up over 2 years may help stratify evolving risk, especially for those with less stringent definitions of mIA.

Guidelines and Recommendations for Laboratory Analysis in the Diagnosis and Management of Diabetes Mellitus

BACKGROUND

Numerous laboratory tests are used in the diagnosis and management of diabetes mellitus. The quality of the scientific evidence supporting the use of these assays varies substantially.

APPROACH

An expert committee compiled evidence-based recommendations for laboratory analysis in screening, diagnosis, or monitoring of diabetes. The overall quality of the evidence and the strength of the recommendations were evaluated. The draft consensus recommendations were evaluated by invited reviewers and presented for public comment. Suggestions were incorporated as deemed appropriate by the authors (see Acknowledgments). The guidelines were reviewed by the Evidence Based Laboratory Medicine Committee and the Board of Directors of the American Association for Clinical Chemistry and by the Professional Practice Committee of the American Diabetes Association.

CONTENT

Diabetes can be diagnosed by demonstrating increased concentrations of glucose in venous plasma or increased hemoglobin A1c (HbA1c) in the blood. Glycemic control is monitored by the people with diabetes measuring their own blood glucose with meters and/or with continuous interstitial glucose monitoring (CGM) devices and also by laboratory analysis of HbA1c. The potential roles of noninvasive glucose monitoring, genetic testing, and measurement of ketones, autoantibodies, urine albumin, insulin, proinsulin, and C-peptide are addressed.

SUMMARY

The guidelines provide specific recommendations based on published data or derived from expert consensus. Several analytes are found to have minimal clinical value at the present time, and measurement of them is not recommended.

Guidelines and Recommendations for Laboratory Analysis in the Diagnosis and Management of Diabetes Mellitus

BACKGROUND

Numerous laboratory tests are used in the diagnosis and management of diabetes mellitus. The quality of the scientific evidence supporting the use of these assays varies substantially.

APPROACH

An expert committee compiled evidence-based recommendations for laboratory analysis in screening, diagnosis, or monitoring of diabetes. The overall quality of the evidence and the strength of the recommendations were evaluated. The draft consensus recommendations were evaluated by invited reviewers and presented for public comment. Suggestions were incorporated as deemed appropriate by the authors (see Acknowledgments). The guidelines were reviewed by the Evidence Based Laboratory Medicine Committee and the Board of Directors of the American Association of Clinical Chemistry and by the Professional Practice Committee of the American Diabetes Association.

CONTENT

Diabetes can be diagnosed by demonstrating increased concentrations of glucose in venous plasma or increased hemoglobin A1c (Hb A1c) in the blood. Glycemic control is monitored by the people with diabetes measuring their own blood glucose with meters and/or with continuous interstitial glucose monitoring (CGM) devices and also by laboratory analysis of Hb A1c. The potential roles of noninvasive glucose monitoring, genetic testing, and measurement of ketones, autoantibodies, urine albumin, insulin, proinsulin, and C-peptide are addressed.

SUMMARY

The guidelines provide specific recommendations based on published data or derived from expert consensus. Several analytes are found to have minimal clinical value at the present time, and measurement of them is not recommended.

Islet Autoantibody Standardization Program: interlaboratory comparison of insulin autoantibody assay performance in 2018 and 2020 workshops

AIMS/HYPOTHESIS

The Islet Autoantibody Standardization Program (IASP) aims to improve the performance of immunoassays measuring autoantibodies in type 1 diabetes and the concordance of results across laboratories. IASP organises international workshops distributing anonymised serum samples to participating laboratories and centralises the collection and analysis of results. In this report, we describe the results of assays measuring IAA submitted to the IASP 2018 and 2020 workshops.

METHODS

The IASP distributed uniquely coded sera from individuals with new-onset type 1 diabetes, multiple islet autoantibody-positive individuals, and diabetes-free blood donors in both 2018 and 2020. Serial dilutions of the anti-insulin mouse monoclonal antibody HUI-018 were also included. Sensitivity, specificity, area under the receiver operating characteristic curve (ROC-AUC), partial ROC-AUC at 95% specificity (pAUC95) and concordance of qualitative/quantitative results were compared across assays.

RESULTS

Results from 45 IAA assays of seven different formats and from 37 IAA assays of six different formats were submitted to the IASP in 2018 and 2020, respectively. The median ROC-AUC was 0.736 (IQR 0.617-0.803) and 0.790 (IQR 0.730-0.836), while the median pAUC95 was 0.016 (IQR 0.004-0.021) and 0.023 (IQR 0.014-0.026) in the 2018 and 2020 workshops, respectively. Assays largely differed in AUC (IASP 2018 range 0.232-0.874; IASP 2020 range 0.379-0.924) and pAUC95 (IASP 2018 and IASP 2020 range 0-0.032).

CONCLUSIONS/INTERPRETATION

Assay formats submitted to this study showed heterogeneous performance. Despite the high variability across laboratories, the in-house radiobinding assay (RBA) remains the gold standard for IAA measurement. However, novel non-radioactive IAA immunoassays showed a good performance and, if further improved, might be considered valid alternatives to RBAs.

Bivalent GAD autoantibody ELISA improves clinical utility and risk prediction for adult autoimmune diabetes

AIM/INTRODUCTION

To investigate the differences in the clinical significance and glutamic acid decarboxylase autoantibody (GADA) affinity between RIA (RIA-GADA) and ELISA (ELISA-GADA) in patients with type 1 diabetes.

METHODS

A total of 415 patients with type 1 diabetes were enrolled, including 199 acute-onset type 1 diabetes, 168 slowly progressive type 1 diabetes (SPIDDM), and 48 fulminant type 1 diabetes. GADA affinity was measured by a competitive binding experiment using unlabeled recombinant human GAD65 protein, and the diagnostic performance of both assays and the relationship between GADA affinity and the decline of fasting C-peptide (F-CPR) were examined.

RESULTS

While the ELISA-GADA displayed a higher sensitivity than the RIA method in diagnosing type 1 diabetes in acute-onset patients, about 40% of SPIDDM patients with low-titer RIA-GADA were determined as negative by the ELISA method. Patients with type 1 diabetes with RIA-GADA alone had an older age of onset, less diabetic ketoacidosis, a higher BMI, and a higher F-CPR compared with patients positive for both RIA-GADA and ELISA-GADA. Additionally, 36% of RIA-GADA-positive patients had low-affinity GADA (<10¹⁰  L/mol), which was significantly higher than in the ELISA-GADA-positive patients (4%, P < 0.0001). Furthermore, over a 3 year monitoring period, F-CPR levels decreased in ELISA-GADA-positive SPIDDM, whereas it was maintained in patients with RIA-GADA alone, regardless of GADA affinity.

CONCLUSIONS

These results suggest that bivalent ELISA for GADA is superior to the RIA method in diagnosing type 1 diabetes. Moreover, the diagnostic superiority of the ELISA-GADA made possible the concurrent identification of SPIDDM patients at high-risk of early progression, and allowed for more accurate clinical diagnosis and management.

The measurement of autoantibodies to insulin informs diagnosis of diabetes in a childhood population negative for other autoantibodies

AIMS

Some childhood type 1 diabetes cases are islet autoantibody negative at diagnosis. Potential explanations include misdiagnosis of genetic forms of diabetes or insufficient islet autoantibody testing. Many NHS laboratories offer combinations of three autoantibody markers. We sought to determine the benefit of testing for additional islet autoantibodies, including insulin (IAA) and tetraspanin 7 (TSPAN7A).

METHODS

Radiobinding assays (RBAs) were used to test for four islet autoantibodies in children with newly diagnosed type 1 diabetes (n = 486; 54.1% male; median age 10.4 years [range 0.7-18.0]; median duration 1 day [range -183 to 14]). Islet autoantibody negative children were tested for TSPAN7A using a luminescence-based test. Where available, islet cell antibody (ICA) and human leucocyte antigen (HLA) data were considered.

RESULTS

Using three autoantibody markers, 21/486 (4.3%) children were autoantibody negative. Testing for IAA classified a further 9/21 (42.9%) children as autoantibody positive. Of the remaining 12 (2.5%) autoantibody negative children, all were TPAN7A negative, seven were ICA negative and one was positive for the protective variant DQB1*0602. One was subsequently diagnosed with Maturity Onset of Diabetes in the Young, but follow-up was not available in all cases.

CONCLUSIONS

Using highly sensitive assays, testing for three autoantibodies fails to detect islet autoimmunity in approximately 1/20 children diagnosed with type 1 diabetes. Testing for IAA in children <5 years and GADA in those >10 years was the most effective strategy for detecting islet autoimmunity. The ability to test for all islet autoantibodies should inform clinical decisions and make screening for monogenic diabetes more cost-effective.

The frequency of CD4+ and CD8+ circulating T stem cell memory in type 1 diabetes

Introduction

Methods

Results

Conclusion

Comparing the clinical significance and antigen specificity of insulinoma-associated antigen-2 autoantibodies between radioimmunoassay and enzyme-linked immunosorbent assay in Japanese patients with type 1 diabetes

AIMS/INTRODUCTION

This study aimed to investigate the clinical significance and antigen specificity of autoantibodies to insulinoma-associated antigen-2 (IA-2A) by radioimmunoassay (RIA; IA-2A-RIA) and enzyme-linked immunosorbent assay (ELISA; IA-2A-ELISA) in Japanese patients with type 1 diabetes.

MATERIALS AND METHODS

A total of 338 type 1 diabetic patients were enrolled, including 38 fulminant type 1 diabetes, 168 acute-onset type 1 diabetes and 137 slowly-progressive type 1 diabetes (SPIDDM). The concordance, correlation of autoantibody titer, and the relationship between IA-2A and progression to the insulin-deficient state were examined. Also, competitive assay was used to examine the antigen specificity.

RESULTS

The prevalence of IA-2A-ELISA was 4-5% lower than that of IA-2A-RIA in both the acute-onset type 1 diabetes and SPIDDM, but the diagnostic sensitivities of both subtypes, when measured in combination with glutamic acid decarboxylase autoantibody, were comparable. The diagnosis of type 1 diabetes using either the RIA or ELISA methods showed substantial agreement with the exponential correlation of autoantibody titers detected by RIA and ELISA. Among the SPIDDM patients, the fasting C-peptide for IA-2A-positive cases by ELISA, but not the RIA method, was significantly lower than in the negative cases (P < 0.05). Furthermore, IA-2A-ELISA proved superior to the RIA method in predicting the progression to insulin deficiency in SPIDDM. Competitive analysis showed that even sera with discrepant results by RIA and ELISA have IA-2-specific autoantibodies.

CONCLUSION

These results suggest that IA-2A-ELISA is a reliable marker not only for the diagnosis of type 1 diabetes, but also for the prediction of future insulin dependency; that is, detection of IA-2A-ELISA helps identify a subtype of SPIDDM patients who would likely progress onto insulin-deficient state.

Evaluating the Immunopathogenesis of Diabetes After Acute Pancreatitis in the Diabetes RElated to Acute Pancreatitis and Its Mechanisms Study: From the Type 1 Diabetes in Acute Pancreatitis Consortium

ABSTRACT

The association between acute pancreatitis (AP) and diabetes mellitus (DM) has long been established, with the initial descriptions of AP patients presenting with DM after a bout of AP published in the 1940s and 50s. However, the potential mechanisms involved, particularly those components related to the immune system, have not been well defined. The Diabetes RElated to Acute pancreatitis and its Mechanisms (DREAM) study is a multicenter clinical study designed to understand the frequency and phenotype of DM developing after AP. This article describes one objective of the DREAM study: to determine the immunologic mechanisms of DM after AP, including the contribution of β-cell autoimmunity. This component of the study will assess the presence of islet autoimmunity, as well as the magnitude and kinetics of the innate and adaptive immune response at enrollment and during longitudinal follow-up after 1 or more episodes of AP. Finally, DREAM will evaluate the relationship between immune features, DM development, and pancreatitis etiology and severity.

Cross-Talk between Obesity and Diabetes: Introducing Polyphenols as an Effective Phytomedicine to Combat the Dual Sword Diabesity

: Obesity-associated diabetes mellitus, a chronic metabolic affliction accounting for 90% of all diabetic patients, has been affecting humanity extremely badly and escalating the risk of developing other serious disorders. It is observed that 0.4 billion people globally have diabetes, whose major cause is obesity. Currently, innumerable synthetic drugs like alogliptin and rosiglitazone are being used to get through diabetes, but they have certain complications, restrictions with severe side effects, and toxicity issues. Recently, the frequency of plant-derived phytochemicals as advantageous substitutes against diabesity is increasing progressively due to their unparalleled benefit of producing less side effects and toxicity. Of these phytochemicals, dietary polyphenols have been accepted as potent agents against the dual sword "diabesity". These polyphenols target certain genes and molecular pathways through dual mechanisms such as adiponectin upregulation, cannabinoid receptor antagonism, free fatty acid oxidation, ghrelin antagonism, glucocorticoid inhibition, sodium-glucose cotransporter inhibition, oxidative stress and inflammation inhibition etc. which sequentially help to combat both diabetes and obesity. In this review, we have summarized the most beneficial natural polyphenols along with their complex molecular pathways during diabesity.

Genetic Variants Associated with Neuropeptide Y Autoantibody Levels in Newly Diagnosed Individuals with Type 1 Diabetes

(1) Autoantibodies to the leucine variant of neuropeptide Y (NPY-LA) have been found in individuals with type 1 diabetes (T1D). We investigated the association between the levels of NPY-LA and single nucleotide polymorphisms (SNP) to better understand the genetic regulatory mechanisms of autoimmunity in T1D and the functional impacts of increased NPY-LA levels. (2) NPY-LA measurements from serum and SNP genotyping were done on 560 newly diagnosed individuals with T1D. SNP imputation with the 1000 Genomes reference panel was followed by an association analysis between the SNPs and measured NPY-LA levels. Additionally, functional enrichment and pathway analyses were done. (3) Three loci (DGKH, DCAF5, and LINC02261) were associated with NPY-LA levels (p-value < 1.5 × 10−6), which indicates an association with neurologic and vascular disorders. SNPs associated with variations in expression levels were found in six genes (including DCAF5). The pathway analysis showed that NPY-LA was associated with changes in gene transcription, protein modification, immunological functions, and the MAPK pathway. (4) Conclusively, we found NPY-LA to be significantly associated with three loci (DGKH, DCAF5, and LINC02261), and based on our findings we hypothesize that the presence of NPY-LA is associated with the regulation of the immune system and possibly neurologic and vascular disorders.

Cellular Chitchatting: Exploring the Role of Exosomes as Cardiovascular Risk Factors

Exosomes are small bi-lipid membranous vesicles (30–150 nm) containing different biological material such as proteins, lipids and nucleic acid. These small vesicles, inducing a cell to cell signaling pathway, are able to mediate multidirectional crosstalk to maintain homeostasis or modulate disease processes. With their various contents, exosomes sort and transfer specific information from their origin to a recipient cell, from a tissue or organ in the close proximity or at distance, generating an intra-inter tissue or organ communication. In the last decade exosomes have been identified in multiple organs and fluids under different pathological conditions. In particular, while the content and the abundance of exosome is now a diagnostic marker for cardiovascular diseases, their role in context-specific physiological and pathophysiological conditions in the cardiovascular system remains largely unknown. We summarize here the current knowledge on the role of exosomes as mediators of cardiovascular diseases in several pathophysiological conditions such as atherosclerosis and diabetes. In addition, we describe evidence of intercellular connection among multiple cell type (cardiac, vasculature, immune cells) as well as the challenge of their in vivo analysis.

Auto-Antikörper-Diagnostik in der Diabetologie – Aktueller Stand der Analytik und klinische Anwendung in Deutschland

Die Messung von spezifischen Autoantikörpern gegen beta-Zellproteine (beta-AAK) hat in den letzten Jahren das diagnostische Repertoire in der Diabetologie erweitert. Das Vorliegen von beta-AAK kann als erstes Stadium in der Entwicklung eines Typ-1-Diabetes mellitus (DM) gewertet werden, ohne dass Symptome bzw. metabolische Veränderungen vorliegen. Da sich diese oft Jahre vor der klinischen Manifestation in Personen mit hohem Erkrankungsrisiko nachweisen lassen, stellen sie wichtige prädiktive und frühdiagnostische Marker dar. Weiterhin kann die Bestimmung von beta-AAK zur Unterscheidung von Patienten mit einem Typ-1-DM auf der einen und Typ-2-DM und Maturity-Onset Diabetes of the Young (MODY) auf der anderen Seite indiziert sein. Auch für die Differenzialdiagnostik von Patienten mit Insulinmangel aufgrund einer autoimmunen Betazelldestruktion und von Patienten mit klinisch sehr ähnlichem „severe-insulin-deficient“-Diabetes, die aber beide eine unterschiedliche Prognose haben, ist die Antikörperdiagnostik zielführend. Die Abschätzung des Risikos für die Entwicklung eines Typ-1-DM bei Patienten, die an autoimmunen Endokrinopathien leiden, stellt einen weiteren Einsatzbereich für beta-AAK dar.

Analytisch sind die beta-AAK mit recht unterschiedlichen Methoden messbar; häufig aber weichen die erhaltenen Messergebnisse bei verschiedenen Testmethoden beträchtlich voneinander ab. Es müssen daher eigene Cut-off Werte vom beauftragten Labor definiert werden, um die erhaltenen Ergebnisse klinisch interpretieren zu können. Zur besseren Vergleichbarkeit der Messergebnisse gibt es derzeit international abgestimmte Harmonisierungsbestrebungen. Für teilnehmende Laboratorien angebotene Ringversuche für die Bestimmungen der Autoantikörper gegen Insulin (IAA), Insulinoma-Antigen 2 (IA-2), Zink Transporter-8 (ZnT8) und Glutamatdecarboxylase (GAD65) können die analytische Qualität ebenfalls verbessern.

Characteristic phenotype of Chinese patients with adult-onset diabetes who are autoantibody positive by 3-Screen ICA™ ELISA

AIMS

To assess the prevalence of diabetes-associated autoantibodies in Chinese patients recently diagnosed with adult-onset diabetes and to evaluate the potential role of the autoantibody markers for characterization of disease phenotype in the patient population.

METHODS

The study included 1273 recent-onset adult patients with phenotypic type 2 diabetes mellitus (T2DM). Serum samples were tested using the 3-Screen ICA™ ELISA (3-Screen) designed for combined measurement of GADAb and/or IA-2Ab and/or ZnT8Ab. 3-Screen positive samples were then tested for individual diabetes-associated and other organ-specific autoantibodies. Clinical characteristics of patients positive and negative in 3-Screen were analysed.

RESULTS

Forty-four (3.5%) of the T2DM patients were positive in 3-Screen, and 38 (86%) of these were also positive for at least one of GADAb, IA-2Ab and ZnT8Ab in assays for the individual autoantibodies. 3-Screen positive patients had lower BMI, higher HbA1c, lower fasting insulin levels and lower fasting C-peptide levels compared to 3-Screen negative patients. Analysis using a homeostatic model assessment (HOMA2) indicated that HOMA2-β-cell function was significantly lower for the forty-four 3-Screen positive patients compared to 3-Screen negative patients. Twenty (45%) 3-Screen positive patients were also positive for at least one thyroid autoantibody.

CONCLUSIONS

The 3-Screen ELISA has been used successfully for the first time in China to detect diabetes autoantibodies in patients with phenotypic T2DM. 3-Screen positive patients presented with poorer β cell function.

Mistaken Identity: The Role of Autoantibodies in Endocrine Disease

BACKGROUND

Autoimmune endocrine diseases can be thought of as a case of mistaken identity. The immune system mistakenly attacks one's own cells, as if they were foreign, which typically results in endocrine gland hypofunction and inadequate hormone production. Type 1 diabetes mellitus and autoimmune thyroid disorders (Hashimoto and Graves diseases) are the most common autoimmune endocrine disorders, while conditions such as Addison disease are encountered less frequently. Autoantibody production can precede clinical presentation, and their measurement may aid verification of an autoimmune process and guide appropriate treatment modalities.

CONTENT

In this review, we discuss type 1 diabetes mellitus, autoimmune thyroid disorders, and Addison disease, emphasizing their associated autoantibodies and methods for clinical detection. We will also discuss efforts to standardize measurement of autoantibodies.

CONCLUSIONS

Autoimmune endocrine disease progression may take months to years and detection of associated autoantibodies may precede clinical onset of disease. Although detection of autoantibodies is not necessary for diagnosis, they may be useful to verify an autoimmune process.

Islet Autoantibody Type-Specific Titer Thresholds Improve Stratification of Risk of Progression to Type 1 Diabetes in Children

OBJECTIVE

To use islet autoantibody titers to improve the estimation of future type 1 diabetes risk in children.

RESEARCH DESIGN AND METHODS

Prospective cohort studies in Finland, Germany, Sweden, and the U.S. followed 24,662 children at increased genetic or familial risk to develop islet autoimmunity and diabetes. For 1,604 children with confirmed positivity, titers of autoantibodies against insulin (IAA), GAD antibodies (GADA), and insulinoma-associated antigen 2 (IA-2A) were harmonized for diabetes risk analyses.

RESULTS

Survival analysis from time of confirmed positivity revealed markedly different 5-year diabetes risks associated with IAA (n = 909), GADA (n = 1,076), and IA-2A (n = 714), when stratified by quartiles of titer, ranging from 19% (GADA 1st quartile) to 60% (IA-2A 4th quartile). The minimum titer associated with a maximum difference in 5-year risk differed for each autoantibody, corresponding to the 58.6th, 52.4th, and 10.2nd percentile of children specifically positive for each of IAA, GADA, and IA-2A, respectively. Using these autoantibody type-specific titer thresholds in the 1,481 children with all autoantibodies tested, the 5-year risk conferred by single (n = 954) and multiple (n = 527) autoantibodies could be stratified from 6 to 75% (P < 0.0001). The thresholds effectively identified children with a ≥50% 5-year risk when considering age-specific autoantibody screening (57-65% positive predictive value and 56-74% sensitivity for ages 1-5 years). Multivariable analysis confirmed the significance of associations between the three autoantibody titers and diabetes risk, informing a childhood risk surveillance strategy.

CONCLUSIONS

This study defined islet autoantibody type-specific titer thresholds that significantly improved type 1 diabetes risk stratification in children.

Long-term Persistence of Allosensitization After Islet Allograft Failure

BACKGROUND

Allosensitization has been reported after discontinuation of immunosuppression following graft failure in islet transplantation (ITx) recipients, though duration of its persistence is unknown.

METHODS

We evaluated 35 patients with type 1 diabetes who received ITx, including 17 who developed graft failure (ITx alone, n = 13; ITx plus bone marrow-derived hematopoietic stem cells, n = 4) and 18 with persistent graft function. Panel-reactive antibody (PRA) was measured yearly for the duration of graft function within 1 y after graft failure at enrollment and yearly thereafter.

RESULTS

In ITx alone graft failure patients, 61% (8/13) were PRA-positive at 6 y postgraft failure, and 46% (6/13) developed donor-specific anti-HLA antibodies (DSA to 2 ± 1 donors) during follow-up. The degree of sensitization was variable (cPRA ranging between 22% and 100% after graft failure). Allosensitization persisted for 7-15 y. Three subjects (3/13) were not allosensitized. In ITx plus bone marrow-derived hematopoietic stem cell recipients, cPRA-positivity (88%-98%) and DSA positivity persisted for 15 y in 75% (3/4) of subjects.

CONCLUSIONS

Allosensitization was minimal while subjects remained on immunosuppression, but after discontinuation of immunosuppressive therapy, the majority of subjects (77%) became allosensitized with persistence of PRA positivity for up to 15 y. Persistence of allosensitization in this patient population is of clinical importance as it may result in longer transplant waiting list times for identification of a suitable donor in the case of requiring a subsequent transplant.

Advances in Type 1 Diabetes Prediction Using Islet Autoantibodies: Beyond a Simple Count

Islet autoantibodies are key markers for the diagnosis of type 1 diabetes. Since their discovery, they have also been recognized for their potential to identify at-risk individuals prior to symptoms. To date, risk prediction using autoantibodies has been based on autoantibody number; it has been robustly shown that nearly all multiple-autoantibody-positive individuals will progress to clinical disease. However, longitudinal studies have demonstrated that the rate of progression among multiple-autoantibody-positive individuals is highly heterogenous. Accurate prediction of the most rapidly progressing individuals is crucial for efficient and informative clinical trials and for identification of candidates most likely to benefit from disease modification. This is increasingly relevant with the recent success in delaying clinical disease in presymptomatic subjects using immunotherapy, and as the field moves toward population-based screening. There have been many studies investigating islet autoantibody characteristics for their predictive potential, beyond a simple categorical count. Predictive features that have emerged include molecular specifics, such as epitope targets and affinity; longitudinal patterns, such as changes in titer and autoantibody reversion; and sequence-dependent risk profiles specific to the autoantibody and the subject's age. These insights are the outworking of decades of prospective cohort studies and international assay standardization efforts and will contribute to the granularity needed for more sensitive and specific preclinical staging. The aim of this review is to identify the dynamic and nuanced manifestations of autoantibodies in type 1 diabetes, and to highlight how these autoantibody features have the potential to improve study design of trials aiming to predict and prevent disease.

Islet Autoimmunity and HLA Markers of Presymptomatic and Clinical Type 1 Diabetes: Joint Analyses of Prospective Cohort Studies in Finland, Germany, Sweden, and the U.S

OBJECTIVE

To combine prospective cohort studies, by including HLA harmonization, and estimate risk of islet autoimmunity and progression to clinical diabetes.

RESEARCH DESIGN AND METHODS

For prospective cohorts in Finland, Germany, Sweden, and the U.S., 24,662 children at increased genetic risk for development of islet autoantibodies and type 1 diabetes have been followed. Following harmonization, the outcomes were analyzed in 16,709 infants-toddlers enrolled by age 2.5 years.

RESULTS

In the infant-toddler cohort, 1,413 (8.5%) developed at least one autoantibody confirmed at two or more consecutive visits (seroconversion), 865 (5%) developed multiple autoantibodies, and 655 (4%) progressed to diabetes. The 15-year cumulative incidence of diabetes varied in children with one, two, or three autoantibodies at seroconversion: 45% (95% CI 40-52), 85% (78-90), and 92% (85-97), respectively. Among those with a single autoantibody, status 2 years after seroconversion predicted diabetes risk: 12% (10-25) if reverting to autoantibody negative, 30% (20-40) if retaining a single autoantibody, and 82% (80-95) if developing multiple autoantibodies. HLA-DR-DQ affected the risk of confirmed seroconversion and progression to diabetes in children with stable single-autoantibody status. Their 15-year diabetes incidence for higher- versus lower-risk genotypes was 40% (28-50) vs. 12% (5-38). The rate of progression to diabetes was inversely related to age at development of multiple autoantibodies, ranging from 20% per year to 6% per year in children developing multipositivity in ≤2 years or >7.4 years, respectively.

CONCLUSIONS

The number of islet autoantibodies at seroconversion reliably predicts 15-year type 1 diabetes risk. In children retaining a single autoantibody, HLA-DR-DQ genotypes can further refine risk of progression.

The Role of Heat Shock Proteins in Type 1 Diabetes

Type 1 diabetes (T1D) is a T-cell mediated autoimmune disease characterized by recognition of pancreatic β-cell proteins as self-antigens, called autoantigens (AAgs), followed by loss of pancreatic β-cells. (Pre-)proinsulin ([P]PI), glutamic acid decarboxylase (GAD), tyrosine phosphatase IA-2, and the zinc transporter ZnT8 are key molecules in T1D pathogenesis and are recognized by autoantibodies detected in routine clinical laboratory assays. However, generation of new autoantigens (neoantigens) from β-cells has also been reported, against which the autoreactive T cells show activity. Heat shock proteins (HSPs) were originally described as “cellular stress responders” for their role as chaperones that regulate the conformation and function of a large number of cellular proteins to protect the body from stress. HSPs participate in key cellular functions under both physiological and stressful conditions, including suppression of protein aggregation, assisting folding and stability of nascent and damaged proteins, translocation of proteins into cellular compartments and targeting irreversibly damaged proteins for degradation. Low HSP expression impacts many pathological conditions associated with diabetes and could play a role in diabetic complications. HSPs have beneficial effects in preventing insulin resistance and hyperglycemia in type 2 diabetes (T2D). HSPs are, however, additionally involved in antigen presentation, presenting immunogenic peptides to class I and class II major histocompatibility molecules; thus, an opportunity exists for HSPs to be employed as modulators of immunologic responses in T1D and other autoimmune disorders. In this review, we discuss the multifaceted roles of HSPs in the pathogenesis of T1D and in autoantigen-specific immune protection against T1D development.

Gluten-free diet impact on dynamics of pancreatic islet-specific autoimmunity detected at celiac disease diagnosis

OBJECTIVE

Almost 6% of celiac disease (CD) patients at diagnosis are positive for at least one of the main pancreatic islet autoantibodies that characterize type 1 diabetes (T1D). Few information, dated back to almost two decades ago, exist as to whether a gluten-free diet (GFD) could reduce the islet-specific autoimmunity detected in patients at CD diagnosis. Aim of the study was to evaluate the impact of GFD on 31 patients who presented islet-specific autoimmunity at CD diagnosis.

METHODS

CD patient sera collected at diagnosis and throughout the GFD were analyzed for the main humoral autoantibodies so far identified in T1D, directed against one or more among insulin, glutamic-acid decarboxylase, tyrosine-phosphatase 2, and zinc cation-efflux transporter autoantigens.

RESULTS

GFD (median duration 39 months) was associated to a decrease or disappearance of the islet-specific autoantibodies in 71% of CD patients. Almost 80% of the patients who became autoantibody-negative during the GFD were positive for only one of the islet-specific autoimmune markers at CD diagnosis, with none of them developing diabetes. Conversely, 80% of the CD patients positive at diagnosis for ≥2 islet-specific autoantibodies were still positive after more than two years of GFD, with 25% of them developing T1D.

CONCLUSIONS

Various factors appear to influence, individually or in combination, the effects of the GFD on pancreatic islet-specific autoimmune response detected at CD diagnosis. These factors include the number of diabetes autoantibodies found at CD diagnosis, the adherence to the GFD, its duration and an asymptomatic clinical presentation of CD.

Increased diagnosis of autoimmune childhood-onset Japanese type 1 diabetes using a new glutamic acid decarboxylase antibody enzyme-linked immunosorbent assay kit, compared with a previously used glutamic acid decarboxylase antibody radioimmunoassay kit

AIMS/INTRODUCTION

We compared the results of testing for glutamic acid decarboxylase antibodies (GADAb) using a radioimmunoassay (RIA) and an enzyme-linked immunosorbent assay (ELISA) in individuals with childhood-onset type 1 diabetes mellitus.

MATERIALS AND METHODS

Serum specimens were collected from 1,024 Japanese children (426 boys and 598 girls) in 2013. The median age at diagnosis was 7 years (0-18 years). The blood specimens were obtained at a median age of 13 years (2-22 years).

RESULTS

Among the 628 children whose serum specimens were collected within 5 years after diagnosis, the rate of GADAb positivity was 47.9% using RIA and 69.4% using ELISA. The participants were divided into four groups according to their RIA and ELISA results for GADAb as follows: group I (RIA+/ELISA+), group II (RIA+/ELISA-), group III (RIA-/ELISA+) and group IV (RIA-/ELISA-). The clinical and genetic characteristics of group I and group III were quite similar in terms of age at diagnosis, male/female ratio, relatively high positive rates for both autoantibody to protein tyrosine phosphatase IA-2 and autoantibody to the cation efflux transporter zinc transporter 8, and human leukocyte antigen genotype. Group II contained just five patients, and was characterized by a younger age at diagnosis, low positive rates for both autoantibody to protein tyrosine phosphatase IA-2 and autoantibody to the cation efflux transporter zinc transporter 8, and a unique human leukocyte antigen genotype. If the positive rates of either autoantibody to protein tyrosine phosphatase IA-2 or autoantibody to the cation efflux transporter zinc transporter 8 or both were added to the GADAb results using RIA, the percentage of autoimmune type 1 diabetes increased from 47.9% to 78.5%.

CONCLUSIONS

The diagnosis of autoimmune childhood-onset Japanese type 1 diabetes increased when GADAb results were obtained using a new ELISA method, compared with a previously utilized RIA method.

Serum C-peptide and osteocalcin levels in children with recently diagnosed diabetes

BACKGROUND

We explored the association of C-peptide (marker of secreted insulin), proinsulin and proinsulin ⁄C-peptide ratio (PI/C) (markers of beta-cell endoplasmic reticulum [ER] stress) with undercarboxylated (uOC) and carboxylated osteocalcin (cOC) and their ratio (uOC/cOC) in children with recently diagnosed type 1 (T1D) or type 2 diabetes (T2D), and the correlation of these variables with partial remission (PR) in children with T1D.

METHODS

Demographic and clinical data of children with new-onset diabetes (n = 68; median age = 12.2 years; 33.8% non-Hispanic White, 45.6% Hispanic/Latino, 16.2% African American and 4.4% other) were collected at diagnosis and during the first (V1), second (V2) and third clinical visits at 9.0, 32.0 and 175.7 weeks, respectively. Serum proinsulin, C-peptide, uOC and cOC values were measured 7.0 weeks after diagnosis. PR was defined as insulin dose-adjusted HbA1c (IDAA1c) ≤9.

RESULTS

In children with new-onset T1D with DKA (33.3%) or T2D (29.4%), Spearman's correlation coefficient revealed a positive association between the C-peptide levels and both uOC and uOC/cOC ratio. In T1D (n = 48), both higher serum C-peptide levels and low PI:C ratio were associated with higher BMI percentile (β = 0.02, P = .001; β = -0.01, P = .02, respectively) and older age at diagnosis (β = 0.13, P = .001; β = -0.12, P = .001, respectively). Furthermore, in children with T1D, C-peptide levels at V1 correlated with IDAA1c ≤ 9 at V1 (P = .04).

CONCLUSION

C-peptide levels are associated with a higher uOC and uOC/cOC ratio in paediatric diabetes. In new-onset T1D children, older age and higher BMI were associated with lower beta-cell stress and higher preserved function, which was predictive of PR on follow-up.

Reduced display of conformational epitopes in the N-terminal truncated GAD65 isoform: relevance for people with stiff person syndrome or DQ8/8-positive Type 1 diabetes mellitus

AIMS

To investigate whether the N-terminal truncated glutamic acid decarboxylase 65 (GAD65) isoform is as well recognized by people with stiff person syndrome as it is by people with Type 1 diabetes, and whether conformational GAD65 antibody epitopes are displayed properly by the isoform.

METHODS

GAD65 antibody-positive healthy individuals (n=13), people with stiff-person syndrome (n=15) and children with new-onset Type 1 diabetes (n=654) were analysed to determine binding to full-length GAD65 and the N-terminal truncated GAD65 isoform in each of these settings. GAD65 autoantibody epitope specificity was correlated with binding ratios of full-length GAD65/N-terminal truncated GAD65.

RESULTS

The N-terminal truncated GAD65 isoform was significantly less recognized in GAD65Ab-positive people with stiff-person syndrome (P=0.002) and in healthy individuals (P=0.0001) than in people with Type 1 diabetes. Moreover, at least two specific conformational GAD65Ab epitopes were not, or were only partially, presented by the N-terminal truncated GAD65 isoform compared to full-length GAD65. Finally, an N-terminal conformational GAD65Ab epitope was significantly less recognized in DQ8/8 positive individuals with Type 1 diabetes (P=0.02).

CONCLUSIONS

In people with stiff person syndrome preferred binding to the full-length GAD65 isoform over the N-terminal truncated molecule was observed. This binding characteristic is probably attributable to reduced presentation of two conformational epitopes by the N-terminal truncated molecule. These findings support the notion of disease-specific GAD65Ab epitope specificities and emphasize the need to evaluate the applicability of novel assays for different medical conditions.

Systematic Assessment of Immune Marker Variation in Type 1 Diabetes: A Prospective Longitudinal Study

Immune analytes have been widely tested in efforts to understand the heterogeneity of disease progression, risk, and therapeutic responses in type 1 diabetes (T1D). The future clinical utility of such analytes as biomarkers depends on their technical and biological variability, as well as their correlation with clinical outcomes. To assess the variability of a panel of 91 immune analytes, we conducted a prospective study of adults with T1D (<3 years from diagnosis), at 9–10 visits over 1 year. Autoantibodies and frequencies of T-cell, natural killer cell, and myeloid subsets were evaluated; autoreactive T-cell frequencies and function were also measured. We calculated an intraclass correlation coefficient (ICC) for each marker, which is a relative measure of between- and within-subject variability. Of the 91 analytes tested, we identified 35 with high between- and low within-subject variability, indicating their potential ability to be used to stratify subjects. We also provide extensive data regarding technical variability for 64 of the 91 analytes. To pilot the concept that ICC can be used to identify analytes that reflect biological outcomes, the association between each immune analyte and C-peptide was also evaluated using partial least squares modeling. CD8 effector memory T-cell (CD8 EM) frequency exhibited a high ICC and a positive correlation with C-peptide, which was also seen in an independent dataset of recent-onset T1D subjects. More work is needed to better understand the mechanisms underlying this relationship. Here we find that there are a limited number of technically reproducible immune analytes that also have a high ICC. We propose the use of ICC to define within- and between-subject variability and measurement of technical variability for future biomarker identification studies. Employing such a method is critical for selection of analytes to be tested in the context of future clinical trials aiming to understand heterogeneity in disease progression and response to therapy.

Islet Autoantibody Standardization Program 2018 Workshop: Interlaboratory Comparison of Glutamic Acid Decarboxylase Autoantibody Assay Performance

BACKGROUND

The Islet Autoantibody Standardization Program (IASP) aims to improve the performance of immunoassays measuring type 1 diabetes (T1D)-associated autoantibodies and the concordance of results among laboratories. IASP organizes international interlaboratory assay comparison studies in which blinded serum samples are distributed to participating laboratories, followed by centralized collection and analysis of results, providing participants with an unbiased comparative assessment. In this report, we describe the results of glutamic acid decarboxylase autoantibody (GADA) assays presented in the IASP 2018 workshop.

METHODS

In May 2018, IASP distributed to participants uniquely coded sera from 43 new-onset T1D patients, 7 multiple autoantibody-positive nondiabetic individuals, and 90 blood donors. Results were analyzed for the following metrics: sensitivity, specificity, accuracy, area under the ROC curve (ROC-AUC), partial ROC-AUC at 95% specificity (pAUC95), and concordance of qualitative and quantitative results.

RESULTS

Thirty-seven laboratories submitted results from a total of 48 different GADA assays adopting 9 different formats. The median ROC-AUC and pAUC95 of all assays were 0.87 [interquartile range (IQR), 0.83-0.89] and 0.036 (IQR, 0.032-0.039), respectively. Large differences in pAUC95 (range, 0.001-0.0411) were observed across assays. Of formats widely adopted, bridge ELISAs showed the best median pAUC95 (0.039; range, 0.036-0.041).

CONCLUSIONS

Several novel assay formats submitted to this study showed heterogeneous performance. In 2018, the majority of the best performing GADA immunoassays consisted of novel or established nonradioactive tests that proved on a par or superior to the radiobinding assay, the previous gold standard assay format for GADA measurement.

Discrepancy of glutamic acid decarboxylase 65 autoantibody results between RSR radioimmunoassay and enzyme-linked immunosorbent assay in patients with type 1 diabetes is related to autoantibody affinity

AIM/INTRODUCTION

Autoantibodies to the 65 kDa isoform of glutamic acid decarboxylase (GADA) are a valuable diagnostic and predictive marker for type 1 diabetes. Recently, it has been reported that a significant proportion of sera in the commercial RSR radioimmunoassay (RIA) that have tested positive for GADA have then turned negative in RSR enzyme-linked immunosorbent assay (ELISA) tests in patients with type 1 diabetes. The present study aimed to investigate whether the GADA result discrepancies between RSR-RIA and RSR-ELISA are related to autoantibody affinity.

METHODS

GADA affinity was measured by a competitive binding experiment using unlabeled recombinant human GAD65 in 12 discordant samples (5 RIA[+]/ELISA[-] and 7 RIA[-]/ELISA[+] sera). Furthermore, the effect of the initial incubation time on the GADA positivity was also examined using the ELISA test.

RESULTS

GADA affinities were >1010  L/mol in two of five RIA(+)/ELISA(-) and all of seven RIA(-)/ELISA(+) sera. After an initial incubation time longer than the recommended 1 h, the GADA titer in three of five RIA(+)/ELISA(-) sera and all RIA(-)/ELISA(+) sera increased 1.6- to 100-fold. However, the titer in 12 GADA-negative sera from healthy controls remained unchanged after the longer incubation. The increment ratio of GADA titer was positively correlated with GADA affinity (r = 0.991, P < 0.001).

CONCLUSIONS

The RSR-RIA test identifies both high- and low-affinity GADA, whereas the RSR-ELISA test identifies only high-affinity GADA. A longer initial incubation time in the RSR-ELISA test increases the sensitivity of GADA with the same specificity in patients with type 1 diabetes.

Immunological biomarkers for the development and progression of type 1 diabetes

Immune biomarkers of type 1 diabetes are many and diverse. Some of these, such as the autoantibodies, are well established but not discriminative enough to deal with the heterogeneity inherent to type 1 diabetes progression. As an alternative, high hopes are placed on T cell assays, which give insight into the cells that actually target the beta cell or play a crucial role in maintaining tolerance. These assays are approaching a level of robustness that may allow for solid conclusions on both disease progression and therapeutic efficacy of immune interventions. In addition, 'omics' approaches to biomarker discovery are rapidly progressing. The potential emergence of novel biomarkers creates a need for the introduction of bioinformatics and 'big data' analysis systems for the integration of the multitude of biomarker data that will be available, to translate these data into clinical tools. It is worth noting that it is unlikely that the same markers will apply to all individuals. Instead, individualised signatures of biomarkers, combining autoantibodies, T cell profiles and other biomarkers, will need to be used to classify at-risk patients into various categories, thus enabling personalised prediction, prevention and treatment approaches. To achieve this goal, the standardisation of assays for biomarker discovery, the integration of analyses and data from biomarker studies and, most importantly, the careful clinical characterisation of individuals providing samples for these studies are critical. Longitudinal sample-collection initiatives, like INNODIA, should lead to novel biomarker discovery, not only providing a better understanding of type 1 diabetes onset and progression, but also yielding biomarkers of therapeutic efficacy of interventions to prevent or arrest type 1 diabetes.

The first 142 amino acids of glutamate decarboxylase do not contribute to epitopes recognized by autoantibodies associated with Type 1 diabetes

AIMS

Glutamate decarboxylase (GAD) antibodies are the most widely used predictive marker for Type 1 diabetes, but many individuals currently found to be GAD antibody-positive are unlikely to develop diabetes. We have shown previously that radioimmunoassays using N-terminally truncated ³⁵ S-GAD₆₅ (96-585) offer better disease specificity with similar sensitivity to full-length ³⁵ S-GAD₆₅ (1-585). To determine whether assay performance could be improved further, we evaluated a more radically truncated ³⁵ S-GAD₆₅ (143-585) radiolabel.

METHODS

Samples from people with recent-onset Type 1 diabetes (n = 157) and their first-degree relatives (n = 745) from the Bart's-Oxford family study of childhood diabetes were measured for GAD antibodies using ³⁵ S-labelled GAD₆₅ (143-585). These were screened previously using a local radioimmunoassay with ³⁵ S-GAD₆₅ (1-585). A subset was also tested by enzyme-linked immunosorbent assay (ELISA), which performs well in international workshops, but requires 10 times more serum. Results were compared with GAD antibody measurements using ³⁵ S-GAD₆₅ (1-585) and ³⁵ S-GAD₆₅ (96-585).

RESULTS

Sensitivity of GAD antibody measurement was maintained using ³⁵ S-GAD₆₅ (143-585) compared with ³⁵ S-GAD₆₅ (1-585) and ³⁵ S-GAD₆₅ (96-585). Specificity for Type 1 diabetes was improved compared with ³⁵ S-GAD₆₅ (1-585), but was similar to ³⁵ S-GAD₆₅ (96-585). Relatives found to be GAD antibody-positive using these truncated labels were at increased risk of diabetes progression within 15 years, compared with those positive for GAD(1-585) antibody only, and at similar risk to those found GAD antibody-positive by ELISA.

CONCLUSIONS

The first 142 amino acids of GAD₆₅ do not contribute to epitopes recognized by Type 1 diabetes-associated GAD antibodies. Low-volume radioimmunoassays using N-terminally truncated ³⁵ S-GAD₆₅ are more specific than those using full-length GAD₆₅ and offer practical alternatives to the GAD antibody ELISA for identifying children at increased risk of Type 1 diabetes.

Serum undercarboxylated osteocalcin correlates with hemoglobin A1c in children with recently diagnosed pediatric diabetes

BACKGROUND

Osteocalcin (OC), a hormone secreted by osteoblasts, improves beta-cell function in vitro and in vivo. We aimed to understand the relationship between OC and hemoglobin A1c (HbA1c) in pediatric diabetes.

METHODS

Children (n = 70; mean [SD] age = 11.8 years [3.1]; 34.3% non-Hispanic white, 46.3% Hispanic, 14.9% African-American, 4.5% other) newly diagnosed with diabetes (69.1% type 1 diabetes [T1D], 30.9% type 2 diabetes [T2D]) were studied. We collected clinical data at diagnosis and first clinical visit (V1) 9 weeks later (interquartile range [IQR] = 7.9-12.0). Serum undercarboxylated OC (uOC) and carboxylated OC (cOC) were measured 7.0 weeks (IQR 4.3-8.9) after diagnosis.

RESULTS

Mean [SD] uOC was 20.3 (19.6) ng/mL, cOC 29.7 [13.7] ng/mL and u/cOC 0.68 [0.81]. uOC, cOC, or u/cOC were not different by gender, race/ethnicity, age, diabetes type, BMI percentile, or random C-peptide, glucose or HbA1c at diagnosis. However, among 61 children with V1 within 4 months of diagnosis, uOC was higher in those with V1 HbA1c < 7.5% (HbA1c < 58 mmol/mol) (uOC=33.1 [22.0]) compared with children with HbA1c ≥ 7.5% (uOC=17.4 [2.3], P = .0004). The difference was larger among patients with T2D (34.6 and 4.7 ng/mL, respectively, P = .0001) than T1D (32.2 and 19.3, P = .0169), and in males (36.1 and 17.4, P = .018) than females (27.6 and 17.3, P = .072). Analysis for u/cOC were similar while there were no differences in cOC. uOC was inversely correlated with HbA1c at V1 (Spearman's rho = -0.29, P = .02).

CONCLUSION

Our findings suggest that serum uOC is inversely related to HbA1c shortly after diagnosis of pediatric diabetes. This potentially modifiable factor of glucose metabolism warrants further studies.

Optimizing Multiplexed Detections of Diabetes Antibodies via Quantitative Microfluidic Droplet Array

Sensitive, single volume detections of multiple diabetes antibodies can provide immunoprofiling and early screening of at-risk patients. To advance the state-of-the-art suspension assays for diabetes antibodies, porous hydrogel droplets are leveraged in microfluidic serpentine arrays to enhance reagent transport. This spatially multiplexed assay is applied to the detection of antibodies against insulin, glutamic acid decarboxylase, and insulinoma-associated protein 2. Optimization of assay protocol results in a shortened assay time of 2 h, with better than 20 pg mL Supporting Information detection limits across all three antibodies. Specificity and cross-reactivity tests show negligible background, nonspecific antibody-antigen, and nonspecific antibody-antibody bindings. Multiplexed detections are able to measure within 15% of target concentrations from low to high ranges. The technique enables quantifications of as little as 8000 molecules in each 500 µm droplet in a single volume, multiplexed assay format, a breakthrough necessary for the adoption of diabetes panels for clinical screening and monitoring in the future.

T1D Autoantibodies: room for improvement?

PURPOSE OF REVIEW

Type 1 diabetes (T1D) is now predictable by measuring major islet autoantibodies (IAbs) against insulin and other pancreatic β cells proteins including GAD65 (GADA), islet antigen 2 (IA-2A), and zinc transporter 8 (ZnT8A). The assay technology for IAbs has made great progress; however, several important aspects still need to be addressed and improved.

RECENT FINDINGS

Currently a radio-binding assay has been well established as the 'gold' standard assay for all four IAbs. New generation of nonradioactive IAb assay with electrochemiluminescence technology has been shown to further improve sensitivity and disease specificity. Recently, multiplexed assays have opened the possibility of more efficient screening in large populations. Identification of potential new autoantibodies to neo-antigens or neo-epitopes posttranslational modification is a new important field to be explored.

SUMMARY

Individuals having a single positive autoantibody are at low risk for progression to T1D, whereas individuals expressing two or more positive autoantibodies, especially on multiple tests over time, have nearly 100% risk of developing clinical T1D when followed for over two decades. More efficient and cost effective IAb assays will hopefully lead to point-of-care screening in the general population.

Next-Generation Autoantibody Testing by Combination of Screening and Confirmation-the CytoBead® Technology

Occurrence of autoantibodies (autoAbs) is a hallmark of autoimmune diseases, and the analysis thereof is an essential part in the diagnosis of organ-specific autoimmune and systemic autoimmune rheumatic diseases (SARD), especially connective tissue diseases (CTDs). Due to the appearance of autoAb profiles in SARD patients and the complexity of the corresponding serological diagnosis, different diagnostic strategies have been suggested for appropriate autoAb testing. Thus, evolving assay techniques and the continuous discovery of novel autoantigens have greatly influenced the development of these strategies. Antinuclear antibody (ANA) analysis by indirect immunofluorescence (IIF) on tissue and later cellular substrates was one of the first tests introduced into clinical routine and is still an indispensable tool for CTD serology. Thus, screening for ANA by IIF is recommended to be followed by confirmatory testing of positive findings employing different assay techniques. Given the continuous growth in the demand for autoAb testing, IIF has been challenged as the standard method for ANA and other autoAb analyses due to lacking automation, standardization, modern data management, and human bias in IIF pattern interpretation. To address these limitations of autoAb testing, the CytoBead® technique has been introduced recently which enables automated interpretation of cell-based IIF and quantitative autoAb multiplexing by addressable microbead immunoassays in one reaction environment. Thus, autoAb screening and confirmatory testing can be combined for the first time. The present review discusses the history of autoAb assay techniques in this context and gives an overview and outlook of the recent progress in emerging technologies.

DPD epitope-specific glutamic acid decarboxylase (GAD)65 autoantibodies in children with Type 1 diabetes

AIM

To study whether DPD epitope-specific glutamate decarboxylase autoantibodies are found more frequently in children with milder forms of Type 1 diabetes.

METHODS

We prospectively evaluated 75 children with new-onset autoimmune Type 1 diabetes, in whom we collected demographic, anthropometric and clinical data and measured islet autoantibodies. Glutamate decarboxylase 65 autoantibody-positive samples were analysed for epitope specificities using recombinant Fab against the DPD-defined epitope of glutamate decarboxylase 65.

RESULTS

After adjustment for age, positive DPD epitope recognition was significantly associated with higher C-peptide levels at onset (P = 0.02, r² =0.21, n = 35), and high DPD recognition in the highest quartile tended to be associated with HbA_1c ≤ 53 mmol/mol (7%) at the last follow-up [mean (sd) follow-up 1.3 (0.4) years; P = 0.07; for the model, P = 0.044, n = 30)]. Age- and sex-adjusted BMI percentile was significantly correlated with recognition of the DPD-defined epitope (P < 0.03, r² =0.14, n = 34), but this correlation was driven by the older age group (age ≥ 10 years; P = 0.016, r² =0.27, n = 21) and was not significant in younger children (P = 0.93, n = 13). There were no independent associations with sex, race/ethnicity, diabetic ketoacidosis, HbA_1c , HLA DR3-DQ2/DR4-DQ8 or autoantibody number.

CONCLUSIONS

Our findings suggest that recognition of the DPD-defined glutamate decarboxylase 65 autoantibody epitope at Type 1 diabetes onset is directly associated with β-cell function, BMI and age, which supports the hypothesis that immunological factors contribute to the clinical heterogeneity of Type 1 diabetes. Larger studies relating epitope-specific glutamate decarboxylase 65 autoantibody to clinical phenotype in children with Type 1 diabetes are warranted.

Increased inflammation is associated with islet autoimmunity and type 1 diabetes in the Diabetes Autoimmunity Study in the Young (DAISY)

Background

Type 1 diabetes (TID) is characterized by a loss of pancreatic islet beta cell function resulting in loss of insulin production. Genetic and environmental factors may trigger immune responses targeting beta cells thus generating islet antibodies (IA). Immune response pathways involve a cascade of events, initiated by cytokines and chemokines, producing inflammation which can result in tissue damage.

Methods

A nested case-control study was performed to identify temporal changes in cytokine levels in 75 DAISY subjects: 25 diagnosed T1D, 25 persistent IA, and 25 controls. Serum samples were selected at four time points: (T1) earliest, (T2) just prior to IA, (T3) just after IA, and (T4) prior to T1D diagnosis or most recent. Cytokines (IFN-α2a, IL-6, IL-17, IL-1β, IP-10, MCP-1, IFN-γ, IL-1α, and IL-1ra) were measured using the Meso Scale Discovery system Human Custom Cytokine 9-Plex assay.

Results

Multivariate mixed models adjusting for HLA risk, first-degree relative status, age, and gender, showed MCP-1 and IFN-үto be significantly higher at T3 in T1D compared to IA subjects. At T4, IP-10 was significantly higher in IA subjects than controls.

Conclusions

This repeated measures nested case-control study identified increased inflammatory markers in IA children who developed T1D compared to IA children who had not progressed to clinical disease. It also showed increased inflammation in both T1D and IA children when compared to controls. Results suggest inflammation may be related to both the development of IA and progression to T1D.

Incidence of childhood-onset type 1 diabetes in Biscay, Spain, 1990-2013

OBJECTIVE

To identify the incidence rate (IR) and epidemiologic trends of childhood type 1 diabetes mellitus (T1DM) in children aged 0 to 14-yr-old from 1990 to 2013, in the north of Spain (Biscay).

SUBJECTS AND METHODS

A prospective-retrospective study was performed. Capture-recapture method was used: primary cases were ascertained from hospital register and a secondary independent data source was obtained from diabetes associations and public health plan database. Age and sex-standardized incidence rates were calculated using direct method, assuming an equal distribution in each age/sex group. In order to identify and analyse trends the period studied was divided into two (1990-2001 and 2002-2013) 11-year periods. The 95% confidence interval (CI) was estimated assuming the Poisson distribution.

RESULTS

A total of 399 new cases were identified throughout the study. Mean age at diagnosis was 8.9 ± 3.7 yr. Completeness of ascertainment was 99.1%. Mean annual age-standardized IR was 10.7 (95% CI: 9.6-11.7). The mean incidence for the 0-4, 5-9 and 10-14 age groups was 5.1, 14.6 and 13.2 per 100,000 children/yr, respectively. The incidence rate trend in the whole group was not statistically significant. In the 10-14 age group we found a yearly average increase (2.5% [CI 95% 0.4-4.6]; P < 0.05) and analysing by sex, this statistically significant incidence trend was observed only in boys. We did not find a seasonal onset pattern.

CONCLUSIONS

The IR did not increase in this population during the period studied unlike the results in other Spanish regions and European Countries.