Differences in the humoral autoreactivity to zinc transporter 8 between childhood- and adult-onset type 1 diabetes in Japanese patients

Fulminant type 1 diabetes: Focusing on triggering factors

Fulminant type 1 diabetes (FT1D) is a novel type of type 1 diabetes that is caused by extremely rapid destruction of the pancreatic β cells. Early diagnosis or prediction of FT1D is critical for the prevention or timely treatment of diabetes ketoacidosis, which can be life-threatening. Understanding its triggers or promoting factors plays an important role in the prevention and treatment of FT1D. In this review, we summarised the various triggering factors of FT1D, including susceptibility genes, immunological factors (cellular and humoural immunity), immune checkpoint inhibitor therapies, drug reactions with eosinophilia and systemic symptoms or drug-induced hypersensitivity syndrome, pregnancy, viral infections, and vaccine inoculation. This review provides the basis for future research into the pathogenetic mechanisms that regulate FT1D development and progression to further improve the prognosis and clinical management of patients with FT1D.

Cellular zinc metabolism and zinc signaling: from biological functions to diseases and therapeutic targets

Zinc metabolism at the cellular level is critical for many biological processes in the body. A key observation is the disruption of cellular homeostasis, often coinciding with disease progression. As an essential factor in maintaining cellular equilibrium, cellular zinc has been increasingly spotlighted in the context of disease development. Extensive research suggests zinc's involvement in promoting malignancy and invasion in cancer cells, despite its low tissue concentration. This has led to a growing body of literature investigating zinc's cellular metabolism, particularly the functions of zinc transporters and storage mechanisms during cancer progression. Zinc transportation is under the control of two major transporter families: SLC30 (ZnT) for the excretion of zinc and SLC39 (ZIP) for the zinc intake. Additionally, the storage of this essential element is predominantly mediated by metallothioneins (MTs). This review consolidates knowledge on the critical functions of cellular zinc signaling and underscores potential molecular pathways linking zinc metabolism to disease progression, with a special focus on cancer. We also compile a summary of clinical trials involving zinc ions. Given the main localization of zinc transporters at the cell membrane, the potential for targeted therapies, including small molecules and monoclonal antibodies, offers promising avenues for future exploration.

Fulminant type 1 diabetes linked with fetal death in utero

Fulminant type 1 diabetes is a relatively new subtype of type 1 diabetes characterised by a sudden onset of severe diabetic ketoacidosis (DKA) in patients with no history of diabetes and can cause imminent death if untreated. We discuss a rare case of a Pacific Islander woman who was 36 weeks pregnant and presented to the emergency department with DKA and fetal death in utero having had a normal glucose tolerance test 4 weeks earlier. She was diagnosed with fulminant type 1 diabetes and was treated with an intravenous insulin-dextrose infusion. She delivered a stillborn female infant and was discharged on regular subcuticular insulin. This case is helpful in understanding a rare, lethal disease that is not well reported globally and especially in Australia, as it requires prompt recognition and treatment to prevent detrimental outcomes.

Improving diagnostic accuracy of 3 Screen ICA ELISA kit in the identification of Japanese type 1 diabetes

AIM/INTRODUCTION

This study aimed to investigate the clinical utility of 3 Screen ICA ELISA in identifying immune-mediated type 1 diabetes in Japanese subjects.

METHODS

We compared the positivity of 3 Screen ICA were compared with autoantibodies against GAD, IA-2, and ZnT8 in 638 patients with type 1 diabetes and 159 healthy control subjects.

RESULTS

With a cut-off value of 20.0 index, 67.4% of acute-onset type 1 diabetic patients, 71.8% of slowly progressive type 1 diabetic (SPIDDM) patients, and none of the fulminant type 1 diabetic patients showed 3 Screen ICA levels above this threshold. The prevalence of 3 Screen ICA was 14.2% higher in acute-onset type 1 diabetes and 1.6% higher in SPIDDM than in GADA. 3 Screen ICA-positive cases were found in 4.8% of cases of individual autoantibody-negative acute-onset type 1 diabetes and 3.8% of SPIDDM, indicating improved diagnostic sensitivity with the 3 Screen ICA. Among individual autoantibody-negative patients, the sum of each autoantibody level was significantly lower in fulminant type 1 diabetes than in acute onset type 1 diabetes and in SPIDDM (P < 0.0001). Additionally, 84.2% of patients negative for individual autoantibodies but positive for 3 Screen ICA had a sum of individual autoantibody levels of ≥4.7 U/mL. Furthermore, 3 Screen ICA levels were significantly higher in patients with type 1 diabetes with other autoimmune diseases than in those without (P < 0.0001).

CONCLUSION

Our findings suggest that the 3 Screen ICA ELISA may be a valuable screening tool for Japanese patients with type 1 diabetes, potentially increasing the diagnostic sensitivity and accuracy beyond the existing GADA, IA-2A, and ZnT8A tests.

Anti-Islet Autoantibodies in Type 1 Diabetes

Anti-islet autoantibodies serve as key markers in immune-mediated type 1 diabetes (T1D) and slowly progressive T1D (SPIDDM), also known as latent autoimmune diabetes in adults (LADA). Autoantibodies to insulin (IAA), glutamic acid decarboxylase (GADA), tyrosine phosphatase-like protein IA-2 (IA-2A), and zinc transporter 8 (ZnT8A) are currently employed in the diagnosis, pathological analysis, and prediction of T1D. GADA can also be detected in non-diabetic patients with autoimmune diseases other than T1D and may not necessarily reflect insulitis. Conversely, IA-2A and ZnT8A serve as surrogate markers of pancreatic β-cell destruction. A combinatorial analysis of these four anti-islet autoantibodies demonstrated that 93-96% of acute-onset T1D and SPIDDM cases were diagnosed as immune-mediated T1D, while the majority of fulminant T1D cases were autoantibody-negative. Evaluating the epitopes and immunoglobulin subclasses of anti-islet autoantibodies help distinguish between diabetes-associated and non-diabetes-associated autoantibodies and is valuable for predicting future insulin deficiency in SPIDDM (LADA) patients. Additionally, GADA in T1D patients with autoimmune thyroid disease reveals the polyclonal expansion of autoantibody epitopes and immunoglobulin subclasses. Recent advancements in anti-islet autoantibody assays include nonradioactive fluid-phase assays and the simultaneous determination of multiple biochemically defined autoantibodies. Developing a high-throughput assay for detecting epitope-specific or immunoglobulin isotype-specific autoantibodies will facilitate a more accurate diagnosis and prediction of autoimmune disorders. The aim of this review is to summarize what is known about the clinical significance of anti-islet autoantibodies in the pathogenesis and diagnosis of T1D.

Clinical and HLA genotype analysis of immune checkpoint inhibitor-associated diabetes mellitus: a single-center case series from China

Objective

To investigate the clinical characteristics and HLA genotypes of patients with immune checkpoint inhibitor-associated diabetes mellitus (ICI-DM) in China.

Methods

We enrolled 23 patients with ICI-DM and 51 patients with type 1 diabetes (T1D). Clinical characteristics of the patients were collected. HLA-DRB1, HLA-DQA1, and HLA-DQB1 genotyping was conducted via next-generation sequencing.

Results

The ICI-DM patients had a male predominance (70.6%), a mean body mass index (BMI) of 21.2 ± 3.5 kg/m², and a mean onset of ICI-DM in 5 (IQR, 3-9) cycles after ICI therapy. Most (78.3%) ICI-DM patients were treated with anti-PD-1, 78.3% presented with diabetic ketoacidosis, and all had low C-peptide levels and received multiple insulin injections. Compared to T1D patients, ICI-DM patients were significantly older (57.2 ± 12.4 vs 34.1 ± 15.7 years) and had higher blood glucose but lower HbA1c levels (P<0.05). Only two (8.7%) ICI-DM patients were positive for islet autoantibodies, which was lower than that in T1D patients (66.7%, P<0.001). A total of 59.1% (13/22) of ICI-DM patients were heterozygous for an HLA T1D risk haplotype, and DRB1*0901-DQA1*03-DQB1*0303 (DR9) and DRB1*0405-DQA1*03-DQB1*0401 were the major susceptible haplotypes. Compared to T1D, the susceptible DR3-DQA1*0501-DQB1*0201 (DR3) and DR9 haplotypes were less frequent (17.7% vs 2.3%; P=0.011 and 34.4% vs 15.9%; P=0.025), whereas the protective haplotypes (DRB1*1101-DQA1*05-DQB1*0301 and DRB1*1202-DQA1*0601-DQB1*0301) were more frequent in ICI-DM patients (2.1% vs 13.6%; P=0.006 and 4.2% vs 15.9%; P=0.017). None of the ICI-DM patients had T1D-associated high-risk genotypes DR3/DR3, DR3/DR9, and DR9/DR9. Among the 23 ICI-DM patients, 7 (30.4%) presented with ICI-associated fulminant type 1 diabetes (IFD), and 16 (69.6%) presented with ICI-associated type 1 diabetes (IT1D). Compared to IT1D patients, IFD patients exhibited marked hyperglycemia and low C-peptide and HbA1c levels (P<0.05). Up to 66.7% (4/6) of IFD patients were heterozygous for reported fulminant type 1 diabetes susceptibility HLA haplotypes (DRB1*0405-DQB1*0401 or DRB1*0901-DQB1*0303).

Conclusion

ICI-DM shares similar clinical features with T1D, such as acute onset, poor islet function and insulin dependence. However, the lack of islet autoantibodies, the low frequencies of T1D susceptibility and high frequencies of protective HLA haplotypes indicate that ICI-DM represents a new model distinct from classical T1D.

A child with mitochondrial DNA deletion presenting diabetes mellitus as an initial symptom

Children with mitochondrial disease may present with diabetes mellitus (DM) without autoimmune antibodies as an initial manifestation, however, it is difficult to make a precise diagnosis in early stages. We present a 2-year-old male patient with mitochondrial disease who showed insulin-dependent DM without autoimmune antibodies as an initial symptom. He later presented with progressive motor deterioration, hearing disability, ptosis, external ophthalmoplegia, and retinitis pigmentosa at 6 years and 6 months. T2- and diffusion-weighted imaging revealed high signal lesions in the subcortical white matter, anterior thalamus, globus pallidus, and brainstem. MR spectroscopy showed elevated lactate and low N-acetylaspartate in the affected white matter. Genetic analysis revealed a single large-scale mitochondrial DNA deletion at 7117-13994, leading to a diagnosis of mitochondrial DNA deletion syndrome associated with insulin-dependent DM. Although the frequency of DM in pediatric mitochondrial disease is low, mitochondrial disease, especially due to mitochondrial DNA deletion, should be considered as a differential diagnosis in those with insulin-dependent DM without autoimmune antibodies, and MRI and MR spectroscopy are recommended for an early diagnosis.

The relationship between GAD65 autoantibody and the risk of T1DM onset

Objectives

Type 1 diabetes mellitus (T1DM) is a well-known autoimmune disease, characterized by β-cell destruction in pancreas islet cells, which results insulin deficiency and subsequent hyperglycemic sequelae. While there is screening for type 2 DM that leads to better glycemic control and outcome, the majority of T1DM patients are diagnosed when much of the pancreatic cells and their function are disturbed. The aim of this article is to present an overview of the effective factors in the positivity of Glutamic acid decarboxylase antibody )GADA( and identifying the high-risk individuals for T1DM.

Methods

We searched English literature available at National Library of Medicine via PubMed, and Google Scholar through December 2020. Finally, 79 papers have been included in the study. Studies were summarized based on the number of positive autoantibodies and onset of T1DM over time and GADA correlation with different variables.

Conclusions

GADA is an easy marker to measure that can be detected many months prior to the clinical presentation and remains positive even after early childhood.

Residual endogenous insulin secretion in Japanese children with type 1A diabetes

We investigated serum C-peptide immunoreactivity (CPR) levels in registered data from a multi-center collaborative nationwide type 1 diabetes study. The CPR levels were obtained from 576 and 409 children during the early registration (2013/2014) and late observation (2016/2017) periods, respectively. The percentages of children with a CPR < 0.1 or < 0.3 ng/mL increased according to the duration since diagnosis. Among patients with 5 or more years since diagnosis, 69% had a CPR < 0.1 and 95% had a CPR < 0.3 in the early registration period. A significant negative correlation was observed between the HbA1c and the CPR levels, and the HbA1c levels were significantly higher among children with a CPR < 0.1 or < 0.3 than among those with a CPR ≥ 0.6 ng/mL. During the late observation period, the prevalence of a CPR < 0.1 ng/mL was 88% among long-standing patients and 77% among patients aged 18–20 yr. Regarding the characteristics of “Responders” with a sustained CPR ≥ 0.6 ng/mL at 5 or more years since diagnosis, six of the seven were adolescent females; five of the seven had an HLA DR4-DQ4 haplotype. When type 1A diabetes mellitus (T1AD) children transit to adult care centers, most of them may have some difficulty in glycemic control because of the depleted endogenous insulin.

Identification of a subgroup of black South Africans with type 1 diabetes who are older at diagnosis but have lower levels of glutamic acid decarboxylase and islet antigen 2 autoantibodies

AIMS

To compare the age at diagnosis and prevalence of islet autoantibody [glutamic acid decarboxylase (65 kDa) 65 and islet antigen 2] positivity in black and white participants with type 1 diabetes in South Africa, and to analyse the relationship between age at diagnosis and the presence of autoantibodies.

METHODS

Participants were recruited from diabetes outpatient departments and autoantibodies to glutamic acid decarboxylase (65 kDa) and islet antigen 2 were measured by enzyme-linked immunosorbent assay.

RESULTS

We recruited 472 (353 black and 119 white) participants with type 1 diabetes. Age at diagnosis of diabetes was later in black (19.7 ± 10.5) than in white participants (12.7 ± 10.8 years; P < 0.001) with a median (interquartile range) disease duration of 5.0 (2.0-10.0) and 8.5 (4.0-20.0) years (P < 0.001), respectively. An older age at diagnosis (≥ 21 years) was more frequent in black (152 of 340, 45%) than in white participants (24 of 116, 21%; P < 0.001). The prevalence of islet antigen 2 autoantibodies was 19% (66/352) in black and 41% in white participants (48/118; P < 0.001). There was no significant difference in glutamic acid decarboxylase (65 kDa) autoantibody positivity between black (212/353, 60%) and white participants (77/117, 66%; P = 0.269). In black, but not white, participants the prevalence of both glutamic acid decarboxylase (65 kDa) and islet antigen 2 autoantibody positivity was significantly lower in participants diagnosed at age ≥ 21 years (P < 0.001 for both comparisons).

CONCLUSIONS

The older age at diagnosis, lower prevalence of islet antigen 2 autoantibodies and a distinct subgroup of participants with type 1 diabetes with age at diagnosis of > 20 years in the black compared to white population suggest a difference in the immunological aetiology of type 1 diabetes in these two population groups.

Islet, thyroid and transglutaminase antibodies in adult Bulgarian patients with type 1 diabetes

AIM

The aim of the study was to assess the prevalence and relationship of islet antibodies and autoantibodies of the most common associated autoimmune diseases-autoimmune thyroid disease (AITD) and celiac disease, in adult Bulgarian patients with type 1 diabetes of short duration.

MATERIAL AND METHODS

160 type 1 diabetes patients, of mean age 36.3 ± 10.9 years, mean BMI 23.0 ± 4.2 kg/m² and mean disease duration 1.35 ± 1.69 years were enrolled. Pancreatic islet cell antibodies-glutamic acid decarboxylase antibodies (GAD 65-Ab), tyrosine phosphatase antibodies (IA 2-Ab), and zinc transporter 8 antibodies (ZnT8-Ab), thyroid antibodies-thyroperoxidase and thyroglobulin antibodies, and transglutaminase antibodies (TTG-IgA-Ab) were assessed by ELISA.

RESULTS

87.5% of the patients had one or more of the islet antibodies-78.1% had GAD 65-Ab, 53.1%-ZnT8-Ab, and 34.4%-IA 2-Ab. 5% presented as just ZnT8-Ab positive. GAD 65-Ab identified 90.6% of the antibody positive patients. The addition of IA 2-Ab as a second immunologic marker identified 94.4%, while the use of ZnT8-Ab in second place identified 98.8% of the cases. 24.4% presented with positive thyroid antibodies and 33.8% had AITD. No relation was found between any of the islet antibodies and AITD. None of the patients was TTG-IgA-Ab positive. No significant correlations were established between the antibodies with different organ specificity.

CONCLUSIONS

In adult Bulgarian type 1 diabetes patients ZnT8-Ab is an independent diagnostic marker rating second in prevalence and diagnostic significance after GAD 65-Ab. AITD affects about one third of this population and routine screening is required, while screening for celiac disease is not justified.

Possible involvement of autoimmunity in fulminant type 1 diabetes

Fulminant type 1 diabetes (FT1D) is characterized by a relatively low HbA1c level at the onset, despite the abrupt occurrence of marked hyperglycemia with ketosis or ketoacidosis. The initial symptoms/findings are flu-like, absence of islet-associated autoantibodies, and a drastic decrease in β-cells and α-cells, which strongly suggest the involvement of a viral infection. In fact, we successfully demonstrated that a FT1D-like phenotype can be reproduced in encephalomyocarditis virus-induced diabetes murine model. However, there is a discussion on the possible involvement of autoimmunity rather than viral infection as the underlying cause of FT1D. For example, HLA-DRB1*04:05, a susceptible antigen of type 1A diabetes, is reportedly associated with FT1D in Japan. Moreover, anti-glutamic acid decarboxylase antibody is reportedly detected in ~ 5% of the patients. Additionally, half of the patients with anti-programmed cell death-1 therapy-related type 1 diabetes fulfilled the criteria of the disease. These findings suggest that islet-associated autoimmunity can partially contribute to the development of FT1D. Furthermore, using nonobese diabetic mice with reduced regulatory T-cell (Treg) numbers, we found that a human FT1D-like phenotype can be induced by islet-associated autoimmunity through collaboration between innate immunity (macrophages and/or natural killer cells) and acquired immunity (predominantly cytotoxic CD8⁺ T cells) in genetically predisposed individuals of autoimmune type 1 diabetes with low Tregs or Treg dysfunction. To clarify greater details regarding the association of autoimmunity in the pathogenesis of FT1D, further studies using suitable animal models and accumulation of the relevant patients are required.

Zinc transporter 8 autoantibodies complement glutamic acid decarboxylase and insulinoma-associated antigen-2 autoantibodies in the identification and characterization of Japanese type 1 diabetes

AIMS/INTRODUCTION

This study aimed to investigate the significance of zinc transporter 8 autoantibody (ZnT8A) in identifying and characterizing autoimmune-mediated type 1 diabetes in Japanese individuals.

METHODS

ZnT8A were determined in 324 patients with type 1 diabetes, 191 phenotypic type 2 diabetes and 288 healthy control individuals using bridging-type enzyme-linked immunosorbent assay in addition to autoantibodies to glutamic acid decarboxylase and insulinoma-associated antigen-2.

RESULTS

We set a cut-off value of 10.0 U/mL, and 25% of the type 1 diabetic patients had ZnT8A levels exceeding this level. The prevalence of ZnT8A was significantly higher in patients with acute-onset type 1 diabetes than in those with slowly progressive and fulminant type 1 diabetes (P < 0.05). ZnT8A were more frequent in patients aged ≤10 years, but less frequent in patients with duration ≥5 years (P < 0.05). ZnT8A were detected in 5.2% of phenotypic type 2 diabetic patients, with 90% of these being ZnT8A-single-positive. Furthermore, the ZnT8A levels in the phenotypic type 2 diabetes cohort (143.8 ± 194.9 U/mL) were significantly higher than those in the type 1 diabetes cohort (22.9 ± 8.3 U/mL, P < 0.05). In the acute-onset and slowly progressive type 1 diabetic patients with duration ≤5 years, additional measurement of glutamic acid decarboxylase autoantibodies significantly increased the disease sensitivity in patients aged ≤10 years, but not in patients aged ≥11 years (11.7 vs 3.6%, P < 0.05). Multivariate analysis showed that ZnT8A positivity was independently associated with age at sampling and insulinoma-associated antigen-2 autoantibody positivity.

CONCLUSIONS

These results suggest that the bridging-type ZnT8A enzyme-linked immunosorbent assay might provide a valuable additional marker for Japanese patients with type 1 diabetes, which could, in turn, allow for an increase in the number of identifiable cases and differentiate clinical phenotypes.

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.

Association of Zinc Transporter-8 Autoantibody (ZnT8A) with Type 1 Diabetes Mellitus

BACKGROUND

Zinc transporter 8 autoantibody (ZnT8A), discovered through bioinformatics, is identified as another major biomarker for type 1 diabetes mellitus (T1DM), expanding the panel of diagnostic autoantibodies. The absence of standard autoantibodies in T1DM patients and the presence of ZnT8A in individuals before disease development has led the researchers to evaluate ZnT8A to gather information about the frequency and its association. Therefore, we aim to find out the concentration of ZnT8A and its association with T1DM.

METHODS

A case-control study with 25 type 1 diabetes mellitus patients and 25 first-degree relatives of cases as controls was conducted at Ziauddin University in collaboration with the Baqai Institute of Diabetology and Endocrinology (BIDE), Karachi. Demographic data were collected from patients on a standard questionnaire. Blood samples were collected, after approval from Ziauddin Ethics Review Committee, from subjects and serum was separated to estimate ZnT8A by using sandwich enzyme-linked immunosorbent assay (ELISA).

RESULTS

The mean age at diagnosis of T1DM patients was 13.40±5.05 years, and the duration of diabetes was 7.74±5.85 years. The frequency of ZnT8A was found higher in cases (19 (76%)) compared to controls (6 (24%)). ZnT8A concentrations were significantly higher in cases (13.82 ng/ml) compared to the controls (8.78 ng/ml; p= 0.024). The cut-off value of 9 ng/ml was selected for measuring sensitivity, specificity, and accuracy, which were determined as 76%, 76%, and 76%, respectively.

CONCLUSIONS

ZnT8A was found significantly associated with T1DM. Subjects with ZnT8A values ≥ 9 ng/ml are 10 times more at risk to develop T1DM (p = 0.000).

What has zinc transporter 8 autoimmunity taught us about type 1 diabetes?

Zinc transporter 8 (ZnT8), a protein highly specific to pancreatic insulin-producing beta cells, is vital for the biosynthesis and secretion of insulin. ZnT8 autoantibodies (ZnT8A) are among the most recently discovered and least-characterised islet autoantibodies. In combination with autoantibodies to several other islet antigens, including insulin, ZnT8A help predict risk of future type 1 diabetes. Often, ZnT8A appear later in the pathogenic process leading to type 1 diabetes, suggesting that the antigen is recognised as part of the spreading, rather than the initial, autoimmune response. The development of autoantibodies to different forms of ZnT8 depends on the genotype of an individual for a polymorphic ZnT8 residue. This genetic variant is associated with susceptibility to type 2 but not type 1 diabetes. Levels of ZnT8A often fall rapidly after diagnosis while other islet autoantibodies can persist for many years. In this review, we consider the contribution made by ZnT8 to our understanding of type 1 diabetes over the past decade and what remains to be investigated in future research.

Clinical characteristics of anti-glutamic acid decarboxylase antibody-positive fulminant type 1 diabetes

This research aimed to examine the relationship between anti-glutamic acid decarboxylase antibody (GADA) titers and clinical parameters at onset and to clarify the association between clinical severity and GADA titers in GADA-positive fulminant type 1 diabetes. This cross-sectional observational study included 20 cases with GADA-positive fulminant type 1 diabetes (4 cases from our hospital and 16 from cases reported in the literature). The association between GADA titers and clinical parameters [age, sex, body weight, body mass index, period from appearance of any prodromal symptoms to diagnosis, period from development of hyperglycemic symptoms to diagnosis, GADA titer, HbA1c level, blood pH and HCO₃^- level, serum levels of ketone bodies and pancreatic exocrine enzymes] were analyzed. Spearman's rank correlation coefficient (r_s) was used for the correlation analysis. The results showed that there was a significant inverse correlation between GADA titers and the "period from appearance of any prodromal symptoms to diagnosis" (r_s = -0.559, p < 0.05). Moreover, GADA titers were inversely correlated with blood pH and HCO₃^- level (r_s = -0.576, p < 0.05, r_s = -0.578, p < 0.05, respectively), and positively correlated with serum levels of total ketone bodies, acetoacetate, and 3-hydroxybutyrate (r_s = 0.661, p < 0.05; r_s = 0.700, p < 0.05; and r_s = 0.782, p < 0.01, respectively). These findings suggest that higher GADA titers may be linked to more severe clinical severity of GADA-positive fulminant type 1 diabetes at onset. This association may be attributed to possible pre-existence of autoimmunity-related β-cell damage before the onset of fulminant type 1 diabetes.

In silico identification and wet lab validation of novel cryptic B cell epitopes in ZnT8 zinc transporter autoantigen

Zinc transporter 8 (ZnT8) is a novel immunodominant autoantigen, associated with Type-1 diabetes. A non-synonymous polymorphism (R325W) in its gene is associated with Type-2 diabetes. In this study, we performed an in silico B cell epitope prediction followed by wetlab validation of ZnT8. Apart from the previously characterized polymorphic epitope (BE-5 TAASR*DS), two novel epitopes BE-2 (N-terminus) and BE-6 (C-terminus) were identified. Wet lab validation of these epitopes was carried out by measuring ZnT8 specific isotypes (IgG, IgM and IgA) in the sera of Normal Glucose Tolerant (NGT), Type-1 diabetic (T1DM) and Type-2 diabetic (T2DM) patients by indirect ELISA. Unexpectedly, compared to NGT, significantly decreased levels of IgG and IgA isotypes was seen in T1DM subjects without complications. IgM levels were reduced in T1DM subjects with retinopathy. Newly diagnosed T1DM subjects initiated on insulin therapy showed an increase in IgA and decrease in IgM titre. Like T1DM, significantly reduced level of IgG, IgM and IgA was seen in T2DM subjects. For the first time, we have identified novel cryptic B cell epitopes in ZnT8 autoantigen against which the naturally occurring autoantibody levels were found to be reduced in diabetes.

Could ZnT8 antibodies replace ICA, GAD, IA2 and insulin antibodies in the diagnosis of type 1 diabetes?

BACKGROUND

The zinc transporter 8 (ZnT8) is an islet β-cell secretory granule membrane protein coded by the SLC30A8 gene, identified as a novel autoantigen in human type 1 diabetes (T1D). As no data of ZnT8ab in Algerian patients have been reported, we aim to evaluate the prevalence of ZnT8ab in young Algerians with T1D and determine whether ZnT8ab could be a better diagnostic tool to replace the other conventional autoantibodies detected in patients with type 1 diabetes. For this purpose, we evaluated the prevalence of islets cells antibodies (ICA), glutamic acid decarboxylase (GAD), islet antigen type 2 (IA2), insulin (IA) autoantibodies (ab) and for the first time in Algeria, the zinc transporter 8 (ZnT8) in young Algerian patients with type 1 diabetes.

PATIENTS AND METHODS

In our cross-sectional study, 160 patients between 1 and 35 years old, diagnosed with type 1 diabetes were enrolled. ICAab was analyzed by indirect immunofluorescence (IIF), GADab, IA2ab, IAab and ZnT8ab were analyzed by ELISA, fasting blood glucose was performed by enzymatic method (glucose-oxidase) and HbA1c by turbid metric method.

RESULTS

Our cohort was composed with 74 males and 86 females (OR=1.16); the mean of age was 14.09 [1-35] years old and the median diabetes duration was 4.10 [1-18] years. Our cohort had a mean of HbA1c of 9.22 [5.40-15]%, the mean of birth weight was 3360.52 [2200-4800]g; the mean of BMI was 19.30 [16.04-22.46]kg/m². Out of 160 patients, 44 (27.5%) were under mother breastfeeding and 116/160 (72.5%) were under artificial feeding. One antibody, at least, was found in 94.38% and the ZnT8ab was significantly more positive in females (70.3%) than in males (10.7%) (***P=8.033×10^-15). The concentration of ZnT8ab was higher in females than in males (females=122.25UI/mL versus males=51.38UI/mL; *P=0.03); ICAab, GADab and ZnT8ab were more present in patients with consanguineous parents (***P=0.0002, *P=0.019 and *P=0.03; respectively) CONCLUSION: Our study on ZnT8ab in T1D is the first in the Maghreb region and we observed a prevalence of 46.25%. The positivity of ZnT8ab enabled us to classify in T1DA 50% of diabetics with obvious T1D phenotype and negative routine autoantibodies, thus ZnT8ab is a good tool for differential diagnosis of type 1 diabetes. According to our results, a simultaneous analysis for ZnT8 and IA2 autoantibodies can be a better and efficient diagnosis of type 1A diabetes from the beginning of the disease.

Association of Autoimmune Thyroid Disease with Anti-GAD Antibody ELISA Test Positivity and Risk for Insulin Deficiency in Slowly Progressive Type 1 Diabetes

The presence of antiglutamic acid decarboxylase antibody (GADA) is required for the diagnosis of slowly progressive type 1 diabetes (SPT1D). We examined the factors influencing GADA determination by radioimmunoassay (GADA-RIA) and by enzyme-linked immunosorbent assay (GADA-ELISA). Sixty patients with SPT1D and 154 patients with type 2 diabetes were examined by both GADA-RIA and GADA-ELISA and for the presence of autoimmune thyroid disease (AITD). We compared the clinical characteristics of these patients based on the positivity or negativity of GADA-RIA and GADA-ELISA, and the existence or nonexistence of AITD. Thirty of 60 (50.0%) GADA-RIA-positive patients were GADA-ELISA negative, whereas none of the 154 GADA-RIA-negative patients were GADA-ELISA positive. Concomitant AITD was significantly less in patients with GADA-RIA and without GADA-ELISA and was significantly more in patients with GADA-RIA and GADA-ELISA. In GADA-RIA-positive patients, there was no significant difference in the GADA-RIA titer among the GADA-ELISA-negative patients with and without AITD, and the GADA-ELISA-positive patients without AITD; whereas the frequency of insulin deficiency was significantly higher in the patients with AITD and/or GADA-ELISA than in those without AITD and GADA-ELISA. Examination of GADA-ELISA and AITD in GADA-RIA-positive patients might be useful in predicting insulin deficiency in these patients.

Screening of ZnT8 autoantibodies in the diagnosis of autoimmune diabetes in a large French cohort

AIM OF THE STUDY

Evaluate the added value of screening anti-ZnT8 antibodies (ZnT8A) in addition to the classical anti-GAD (GADA) and anti-IA-2 (IA-2A) antibodies for the diagnosis of type-1 diabetes (T1D) within a large cohort of both children and adults.

MATERIALS AND METHODS

Retrospective 2-year study including 516 patients (215 children, 301 adults) who had blood tests at diabetes onset and/or for diabetes classification. ZnT8A, GADA, and IA-2A were analyzed in all samples.

RESULTS

Among those individuals included, 142 (28%) were ZnT8A-positive. A total of 228/516 suffered from T1D, of whom 110 (48%) were ZnT8A-positive and 166 (73%) GADA and/or IA-2A positive. When adding ZnT8A to GADA/IA-2A, 184 (81%) patients were positive for ≥1 Ab. Regarding the 122 patients at T1D onset, 75 (61%) were positive for ZnT8A and the proportion of patients with T1D with ≥1 Ab reached 89%. The highest prevalence of ZnT8A was observed in children aged 6-10years. Fourteen of the 124 patients positive for ZnT8A with a known clinical diagnosis suffered from a disease other than T1D.

CONCLUSIONS

ZnT8A should be included in routine evaluation at diabetes onset and is a valuable biological marker to classify newly-diagnosed diabetics. The predictive value in our high-risk subjects has to be confirmed.

Clinical features of cases of seroconversion of anti-glutamic acid decarboxylase antibody during the clinical course of type 2 diabetes: a nationwide survey in Japan

The pathogenesis of type 1 diabetes is different from that of type 2 diabetes, and anti-glutamic acid decarboxylase antibody (GADA) helps to diagnose autoimmune type 1 diabetes. Some studies reported that GADA seroconversion occurs during the clinical course of type 2 diabetes, leading to development of "type 1 on type 2 diabetes". To clarify the clinical characteristics and triggers of GADA seroconversion, we performed a nationwide questionnaire survey for clinical cases identified by literature search, and obtained information on 38 cases (24 with insulin therapy and 14 without it). The diabetes duration up to determination of GADA seroconversion was significantly longer in the group with insulin therapy than that without it. This finding was particularly noted in insulin-treated non-obese patients with lower serum C-peptide levels. In these patients, insulin therapy could have masked sudden increases in plasma glucose and HbA1c levels, possibly leading to delayed determination of GADA seroconversion. In non-obese patients without insulin therapy, an abrupt rise in the plasma glucose and HbA1c levels was observed at immediately before the determination, a finding which may help to predict GADA seroconversion. From the results of the present survey, we could not determine apparent triggers of GADA seroconversion. Thus, physicians may need to consider the possibility of concurrent type 1 diabetes during the therapeutic course of type 2 diabetes; GADA measurement should be considered when non-obese type 2 diabetic patients not receiving insulin therapy experience unexpected abrupt hyperglycemia and when those receiving insulin therapy show low serum C-peptide levels.

Importance of Zinc Transporter 8 Autoantibody in the Diagnosis of Type 1 Diabetes in Latin Americans

There is a scarcity of data of zinc transporter-8 autoantibody (ZnT8A) on mixed populations such as Brazilian. Therefore, we evaluated the relevance of ZnT8A for type 1 diabetes (T1D) diagnosis and the role of ZnT8 coding gene (SLC30A8) in T1D predisposition. Patients with T1D (n = 629; diabetes duration = 11 (6-16) years) and 651 controls were genotyped for SLC30A8 rs16889462 and rs2466295 variants (BeadXpress platform). ZnT8 triple antibody was measured by ELISA; glutamic acid decarboxylase (GAD65A) and protein tyrosine phosphatase (IA-2A) autoantibodies by radioimmunoassay.

RESULTS

Znt8A was detected in 68.7% of recent-onset T1D patients and 48.9% of the entire patient cohort, similar to GAD65A (68.3% and 47.2%) and IA-2A (64.8% and 42.4%) positivities respectively. ZnT8A was the only antibody in 8.4% of patients. Znt8A and IA2A frequencies and titers were independent of gender and ethnicity, whereas GAD65A titers were greater in females. The diabetes duration-dependent decline in ZnT8A frequency was similar to GAD65A and IA-2A. The SLC30A8 rs2466293 AG + GG genotypes were associated with T1D risk in non-European descents (56.2% × 42.9%; p = 0.018), and the GG genotype with higher ZnT8A titers in recent-onset T1D: 834.5 IU/mL (711.3-2190.0) × 281 IU/mL (10.7-726.8); p = 0.027. Conclusion ZnT8A detection increases T1D diagnosis rate even in mixed populations. SLC30A8 rs2466293 was associated with T1D predisposition in non-European descents.

Clinical and Genetic Characteristics of Non-Insulin-Requiring Glutamic Acid Decarboxylase (GAD) Autoantibody-Positive Diabetes: A Nationwide Survey in Japan

Aims

Glutamic acid decarboxylase autoantibodies (GADAb) differentiate slowly progressive insulin-dependent (type 1) diabetes mellitus (SPIDDM) from phenotypic type 2 diabetes, but many GADAb-positive patients with diabetes do not progress to insulin-requiring diabetes. To characterize GADAb-positive patients with adult-onset diabetes who do not require insulin therapy for >5 years (NIR-SPIDDM), we conducted a nationwide cross-sectional survey in Japan.

Methods

We collected 82 GADAb-positive patients who did not require insulin therapy for >5 years (NIR-SPIDDM) and compared them with 63 patients with insulin-requiring SPIDDM (IR-SPIDDM). Clinical and biochemical characteristics, HLA-DRB1-DQB1 haplotypes, and predictive markers for progression to insulin therapy were investigated.

Results

Compared with the IR-SPIDDM group, the NIR-SPIDDM patients showed later diabetes onset, higher body mass index, longer duration before diagnosis, and less frequent hyperglycemic symptoms at onset. In addition, C-peptide, LDL-cholesterol, and TG were significantly higher in the NIR-SPIDDM compared to IR-SPIDDM patients. The NIR-SPIDDM group had lower frequency of susceptible HLA-DRB1*04:05-DQB1*04:01 and a higher frequency of resistant HLA-DRB1*15:01-DQB1*06:02 haplotype compared to IR-SPIDDM. A multivariable analysis showed that age at diabetes onset (OR = 0.82), duration before diagnosis of GADAb-positive diabetes (OR = 0.82), higher GADAb level (≥10.0 U/ml) (OR = 20.41), and fasting C-peptide at diagnosis (OR = 0.07) were independent predictive markers for progression to insulin-requiring diabetes. An ROC curve analysis showed that the optimal cut-off points for discriminating two groups was the GADAb level of 13.6 U/ml, age of diabetes onset of 47 years, duration before diagnosis of 5 years, and fasting C-peptide of 0.65 ng/ml.

Conclusions

Clinical, biochemical and genetic characteristics of patients with NIR-SPIDDM are different from those of IR-SPIDDM patients. Age of diabetes onset, duration before GADAb-positivity, GADAb level, and fasting C-peptide at diagnosis must be carefully considered in planning prevention trials for SPIDDM.

Current and Future Clinical Applications of Zinc Transporter-8 in Type 1 Diabetes Mellitus

Objective:

To evaluate the utility of zinc transporter-8 (ZnT8) in the improvement of type 1 diabetes mellitus (T1DM) diagnosis and prediction, and to explore whether ZnT8 is a potential therapeutic target in T1DM.

Data Sources:

A search was conducted within the medical database PubMed for relevant articles published from 2001 to 2015. The search terms are as follows: “ZnT8,” “type 1 diabetes,” “latent autoimmune diabetes in adults,” “type 2 diabetes,” “islet autoantibodies,” “zinc supplement,” “T cells,” “β cell,” “immune therapy.” We also searched the reference lists of selected articles.

Study Selection:

English-language original articles and critical reviews concerning ZnT8 and the clinical applications of islet autoantibodies in diabetes were reviewed.

Results:

The basic function of ZnT8 is maintaining intracellular zinc homeostasis, which modulates the process of insulin biosynthesis, storage, and secretion. Autoantibodies against ZnT8 (ZnT8A) and ZnT8-specific T cells are the reliable biomarkers for the identification, stratification, and characterization of T1DM. Additionally, the results from the animal models and clinical trials have shown that ZnT8 is a diabetogenic antigen, suggesting the possibility of ZnT8-specific immunotherapy as an alternative for T1DM therapy.

Conclusions:

ZnT8 is a novel islet autoantigen with a widely potential for clinical applications in T1DM. However, before the large-scale clinical applications, there are still many problems to be solved.

Different role of zinc transporter 8 between type 1 diabetes mellitus and type 2 diabetes mellitus

Diabetes can be simply classified into type 1 diabetes mellitus and type 2 diabetes mellitus. Zinc transporter 8 (ZnT8), a novel islet autoantigen, is specifically expressed in insulin‐containing secretory granules of β‐cells. Genetic studies show that the genotypes of SLC30A8 can determine either protective or diabetogenic response depending on environmental and lifestyle factors. The ZnT8 protein expression, as well as zinc content in β‐cells, was decreased in diabetic mice. Thus, ZnT8 might participate in insulin biosynthesis and release, and subsequently involved deteriorated β‐cell function through direct or indirect mechanisms in type 1 diabetes mellitus and type 2 diabetes mellitus. From a clinical feature standpoint, the prevalence of ZnT8A is gradiently increased in type 2 diabetes mellitus, latent autoimmune diabetes in adults and type 1 diabetes mellitus. The frequency and epitopes of ZnT8‐specific T cells and cytokine release by ZnT8‐specific T cells are also different in diabetic patients and healthy controls. Additionally, the response to ZnT8 administration is also different in type 1 diabetes mellitus and type 2 diabetes mellitus. In the present review, we summarize the literature about clinical aspects of ZnT8 in the pathogenesis of diabetes, and suggest that ZnT8 might play a different role between type 1 diabetes mellitus and type 2 diabetes mellitus.

Changes in Zinc Transporter 8 Autoantibodies Following Type 1 Diabetes Onset: The Type 1 Diabetes Genetics Consortium Autoantibody Workshop

Zinc transporter 8 autoantibodies (ZnT8A) were analyzed in sera from 1,504 subjects as part of the Type 1 Diabetes Genetics Consortium (T1DGC) Autoantibody Workshop. For these participants with type 1 diabetes (T1D), samples were collected within 3 years of T1D diagnosis. ZnT8A were detected in 862 subjects (57.3%), with the highest frequencies and median titers being associated with the shortest duration of disease. ZnT8A were present at similar frequencies in non-Hispanic whites, non-Hispanic blacks, and Hispanics, but significantly less prevalent in those of Asian ancestry. Sera containing ZnT8A selectively recognizing at least one of the SLC30A8 single nucleotide polymorphisms (encoding ZnT8A) were detected in all populations; however, Trp-specific sera were much less frequent in non-Hispanic blacks, consistent with the anticipated lower frequency of the SLC30A8 rs13266634 T allele in African American populations. ZnT8A positivity was associated with HLA-DQ8, but this was primarily due to the DRB1*0404-DQ8 haplotype. This was in contrast to autoantibodies to IA-2 that were strongly associated with DRB1*0401-DQ8. These effects appeared essentially independent of racial or ethnic background. The DRB1*0401-DQ8 and DRB1*0404-DQ8 haplotypes were associated with T1D subjects positive for GAD65, IA-2, and ZnT8A. In contrast to DRB1*0401-DQ8, there was no significant association of DRB1*0404-DQ8 with single or dual autoantibody positivity. The DRB1*0404-DQ8 haplotype was also associated with T1D subjects whose sera recognized both polymorphic variants of zinc transporter 8, an effect not seen for DRB1*0401-DQ8.

Development of a novel ultrasensitive enzyme immunoassay for human glutamic acid decarboxylase 65 antibody

Background

We developed a novel, ultrasensitive enzyme immunoassay (immune complex transfer enzyme immunoassay) for determination of glutamic acid decarboxylase autoantibody concentrations in serum samples from patients with type 2 diabetes.

Methods

We developed an immune complex transfer enzyme immunoassay for glutamic acid decarboxylase autoantibody and measured glutamic acid decarboxylase autoantibody from 22 patients with type 1 diabetes, 29 patients with type 2 diabetes, and 32 healthy controls.

Results

A conventional ELISA kit identified 10 patients with type 1 diabetes and one patient with type 2 diabetes as glutamic acid decarboxylase autoantibody positive, whereas 15 patients with type 1 diabetes and six patients with type 2 diabetes were identified as glutamic acid decarboxylase autoantibody positive using immune complex transfer enzyme immunoassay.

Conclusions

Immune complex transfer enzyme immunoassay is a highly sensitive and specific assay for glutamic acid decarboxylase autoantibody and might be clinically useful for diabetic onset prediction and early diagnosis.

Type 1 diabetes and autoimmunity

Type 1 diabetes (T1D) is an organ-specific autoimmune disease caused by the autoimmune response against pancreatic β cells. T1D is often complicated with other autoimmune diseases, and anti-islet autoantibodies precede the clinical onset of disease. The most common coexisting organ-specific autoimmune disease in patients with T1D is autoimmune thyroid disease, and its frequency is estimated at > 90% among patients with T1D and autoimmune diseases. The prevalence of anti-thyroid antibodies in children with T1D at disease onset is about 20% and is particularly common in girls. Furthermore, patients with anti-thyroid antibodies are 18 times more likely to develop thyroid disease than patients without anti-thyroid antibodies. Therefore, for early detection of autoimmune thyroid disease in children with T1D, measurement of anti-thyroid antibodies and TSH at T1D onset and in yearly intervals after the age of 12 yr is recommended. Anti-islet autoantibodies are predictive and diagnostic markers for T1D. The most frequently detected autoantibodies in Japanese patients are GAD autoantibodies (~80%) followed by IA-2 autoantibodies (~60%), insulin autoantibodies (~55%) and ZnT8 autoantibodies (~50%). In a combined analysis, 94% of Japanese patients with T1D can be defined as having type 1A diabetes. Furthermore, autoantibodies to ZnT8 and IA-2 are associated with childhood-onset and acute-onset patients. Thus, it is important to develop a diagnostic strategy for patients with type 1A diabetes in consideration of the age or mode of disease onset.

Zinc transporter-8 autoantibodies can replace IA-2 autoantibodies as a serological marker for juvenile onset type 1 diabetes in India

INTRODUCTION

Zinc transporter-8 (ZnT8) is an islet cell secretory granule membrane protein recently identified as an autoantigen in type 1 diabetes (T1D). The aim of this study was to estimate the prevalence of antibodies to ZnT8 (ZnT8A) in juvenile onset T1D and to determine the utility of ZnT8A as an independent marker of autoimmunity either alone in antibody-negative subjects or in conjunction with glutamic acid decarboxylase (GAD) and insulinoma-2 antigen antibodies (GADA and IA2A).

RESEARCH DESIGN

ZnT8A, GADA, and IA2A were measured in sera of consecutive T1D patients (n = 88, age range 2-18 years) within 4 years of diagnosis and 88 sex-matched controls.

RESULTS

The prevalences of GADA, ZnT8a, and IA2A were 64.7%, 31.8% and 19.3%, respectively. In newly diagnosed patients, the frequency of ZnT8A was 45%. ZnT8A were positive in 26% of patients negative for both GADA and IA2A. IA2A were positive only in two patients who were negative for other two antibodies. Combined use of ZnT8A and GADA could detect 97% of antibody positive patients. In receiver operating characteristic (ROC) analysis, the performances of GADA and ZnT8As were better than that of IA2A; and AUCs of GADA, ZnT8A, and IA2A for the prediction of T1D were 0.8, 0.65, and 0.59, respectively.

CONCLUSIONS

ZnT8A complements GADA and increases the diagnostic sensitivity for detection of autoimmunity in juvenile-onset T1D. Inclusion of ZnT8A increases the proportion of patients with antibody positivity to nearly 80%. ZnT8A can replace IA2A as a serological marker for autoimmunity in Indian T1D patients without loss of sensitivity and specificity.

Novel enzyme-linked immunosorbent assay for bivalent ZnT8 autoantibodies

Autoantibodies to zinc transporter 8 (ZnT8A) are a powerful diagnostic or predictive marker in type 1 diabetes. However, the widely used current ZnT8A radioligand binding assay (RBA) has proved to be difficult for many laboratories to implement. The aim of this study was the development and characterization of the performance of a novel fluid-phase ZnT8A enzyme-linked immunosorbent assay (ELISA) in relation to standard RBA in type 1 diabetes. Sera from 114 patients with type 1 diabetes and 140 blinded Islet Autoantibody Standardization Program (IASP2012) samples were studied. The sensitivity of ELISA-ZnT8A is equivalent to or slightly higher than that of conventional RBA with similar specificity. Furthermore, the median SD score using this ELISA was significantly higher than that obtained with RBA (P < 0.0001). Multiple logistic regression analysis revealed that ELISA-ZnT8A positivity was associated with younger age of onset (≤20 years; OR 15.91, P = 0.0002), acute-onset form of type 1 diabetes (OR 3.38, P = 0.019), and the presence of IA-2 autoantibodies (OR 3.75, P = 0.014). Furthermore, the levels of ELISA-ZnT8A were associated with the reactivity to ZnT8-325Arg, but not ZnT8-325Trp. We conclude that this nonradioactive bivalent ZnT8A assay has high performance and should facilitate large-scale autoantibody screening. Moreover, these results suggest that the humoral autoimmunity against ZnT8 is related to a high risk of faster development of type 1 diabetes and the ZnT8A levels are associated with the known aa325 variants.

The zinc transporter, Slc39a7 (Zip7) is implicated in glycaemic control in skeletal muscle cells

Dysfunctional zinc signaling is implicated in disease processes including cardiovascular disease, Alzheimer's disease and diabetes. Of the twenty-four mammalian zinc transporters, ZIP7 has been identified as an important mediator of the ‘zinc wave’ and in cellular signaling. Utilizing siRNA targeting Zip7 mRNA we have identified that Zip7 regulates glucose metabolism in skeletal muscle cells. An siRNA targeting Zip7 mRNA down regulated Zip7 mRNA 4.6-fold (p = 0.0006) when compared to a scramble control. This was concomitant with a reduction in the expression of genes involved in glucose metabolism including Agl, Dlst, Galm, Gbe1, Idh3g, Pck2, Pgam2, Pgm2, Phkb, Pygm, Tpi1, Gusb and Glut4. Glut4 protein expression was also reduced and insulin-stimulated glycogen synthesis was decreased. This was associated with a reduction in the mRNA expression of Insr, Irs1 and Irs2, and the phosphorylation of Akt. These studies provide a novel role for Zip7 in glucose metabolism in skeletal muscle and highlight the importance of this transporter in contributing to glycaemic control in this tissue.

Diagnostic criteria for acute-onset type 1 diabetes mellitus (2012): Report of the Committee of Japan Diabetes Society on the Research of Fulminant and Acute-onset Type 1 Diabetes Mellitus

Type 1 diabetes is a disease characterized by destruction of pancreatic β‐cells, which leads to absolute deficiency of insulin secretion. Depending on the manner of onset and progression, it is classified as fulminant, acute‐onset or slowly progressive type 1 diabetes. Here, we propose the diagnostic criteria for acute‐onset type 1 diabetes mellitus. Among the patients who develop ketosis or diabetic ketoacidosis within 3 months after the onset of hyperglycemic symptoms and require insulin treatment continuously after the diagnosis of diabetes, those with anti‐islet autoantibodies are diagnosed with ‘acute‐onset type 1 diabetes mellitus (autoimmune)’. In contrast, those whose endogenous insulin secretion is exhausted (fasting serum C‐peptide immunoreactivity <0.6 ng/mL) without verifiable anti‐islet autoantibodies are diagnosed simply with ‘acute‐onset type 1 diabetes mellitus’. Patients should be reevaluated after certain periods in case their statuses of anti‐islet autoantibodies and/or endogenous insulin secretory capacity are unknown.

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.

Zinc transporters, mechanisms of action and therapeutic utility: implications for type 2 diabetes mellitus

Zinc is an essential trace element that plays a vital role in maintaining many biological processes and cellular homeostasis. Dysfunctional zinc signaling is associated with a number of chronic disease states including cancer, cardiovascular disease, Alzheimer's disease, and diabetes. Cellular homeostasis requires mechanisms that tightly control the uptake, storage, and distribution of zinc. This is achieved through the coordinated actions of zinc transporters and metallothioneins. Evidence on the role of these proteins in type 2 diabetes mellitus (T2DM) is now emerging. Zinc plays a key role in the synthesis, secretion and action of insulin in both physiological and pathophysiological states. Moreover, recent studies highlight zinc's dynamic role as a "cellular second messenger" in the control of insulin signaling and glucose homeostasis. This suggests that zinc plays an unidentified role as a novel second messenger that augments insulin activity. This previously unexplored concept would raise a whole new area of research into the pathophysiology of insulin resistance and introduce a new class of drug target with utility for diabetes pharmacotherapy.

Prevalence of ZnT8 antibody in relation to phenotype and SLC30A8 polymorphism in adult autoimmune diabetes: results from the HUNT study, Norway

Zinc transporter 8 (ZnT8), a product of the SLC30A8 gene, is a target-antigen in autoimmune diabetes. Associations between ZnT8 antibody (ZnT8A), phenotype and the genetic variant rs13266634 in the SLC30A8 gene have primarily been studied in patients with young-onset diabetes. We explored such associations in adult-onset autoimmune diabetes identified from the all-population based Nord-Trøndelag health Study (HUNT) ZnT8A (assayed by a fusion probe of C-terminal Arg325 and Trp325), and antibodies against glutamic decarboxylase (GADA) and tyrosine phosphatase-like protein insulinoma antigen-2 (IA-2A) were analysed in 266 subjects classified as having adult-onset autoimmune diabetes ( ≥ 25 years of age at diagnosis). Of these, 161 subjects fulfilled the criteria of latent autoimmune diabetes in adults (LADA), whereas 105 subjects were termed "classical" type 1 diabetes. Ten out of 161 LADA (6.2%) and 23 out of 105 adult-onset "classical" type 1 diabetic patients (22%) were ZnT8A positive. Adult-onset diabetic subjects positive both for GADA and IA-2A (n = 17), had lower waist circumference (p = 0.024) and higher fasting glucose levels (p = 0.023) than those positive both for GADA and ZnT8A (n = 13). Genotyping results of rs13266634 (available in 178 adult-onset diabetic subjects), showed a tendency for association between ZnT8A positivity and the TT- and CC genotypes of SNP rs13266634 (p = 0.101) using the standard cut-off level of 0.06ai, and a significant association at a lower cut-off level of 0.01ai (p = 0.005). We conclude that ZnT8A positivity in a population of adult-onset autoimmune diabetes is a less strong marker of autoimmunity than IA-2A. Further, positivity could be influenced by polymorphism of the SLC30A8 gene.

Clinical and genetic characteristics of autoimmune polyglandular syndrome type 3 variant in the Japanese population

OBJECTIVE

Type 1 diabetes (T1D) is commonly associated with autoimmune thyroid disease (AITD), and the occurrence of both T1D and AITD in a patient is defined as autoimmune polyglandular syndrome type 3 variant (APS3v). We aimed to clarify the differences in the clinical and genetic characteristics of APS3v patients and T1D patients without AITD [T1D/AITD(-)] in the Japanese population.

DESIGN/PATIENTS

Our subjects were 54 APS3v patients and 143 T1D/AITD(-) patients who were consecutively diagnosed at Nagasaki University Hospital from 1983 to the present.

RESULTS

A remarkable female predominance, a slow and older age onset of T1D, and a higher prevalence of glutamic acid decarboxylase autoantibodies were observed in APS3v patients compared to T1D/AITD(-) patients. The older onset age of T1D in APS3v patients was associated with a higher proportion of slow-onset T1D. Among the two major susceptible human leukocyte antigen (HLA) class II haplotypes in Japanese T1D, DRB1*0405-DQB1*0401, but not DRB1*0901-DQB1*0303, was associated with APS3v patients. Furthermore, DRB1*0803-DQB1*0601 was not protective in patients with APS3v. The frequencies of the GG genotype in +49G>A and +6230G>A polymorphism in the CTLA4 gene were significantly higher in T1D/AITD(-) patients, but not in APS3v patients, compared to control subjects.

CONCLUSIONS

In conclusion, we found notable differences in the clinical and genetic characteristics of APS3v patients and T1D/AITD(-) patients in the Japanese population, and the differences in the clinical characteristics between the two groups may reflect distinct genetic backgrounds including the HLA DRB1-DQB1 haplotypes and CTLA4 gene polymorphisms.

Zinc transporter 8 autoantibodies in fulminant, acute-onset, and slow-onset patients with type 1 diabetes

BACKGROUND

The aim of this study was to determine the prevalence and role of autoantibodies to zinc transporter 8 (ZnT8A) in three forms (fulminant, acute-onset, and slow-onset) of Japanese patients with type 1 diabetes.

METHODS

One-hundred and ninety-six new-onset patients with type 1 diabetes were studied: 85 were fulminant, 81 acute-onset, and 30 slow-onset type 1 diabetes. ZnT8A were determined by radioimmunoassay using a hybrid ZnT8 carboxy-terminal construct (aa268-369) carrying 325Trp and 325Arg. Furthermore, ZnT8A epitopes were analysed using ZnT8 constructs incorporating the known aa325 variants (Trp, Arg, and Gln).

RESULTS

ZnT8A were detected in 58% patients with acute-onset and 20% with slow-onset type 1 diabetes (p<0.0005). In contrast, none of sera from fulminant type 1 diabetes were reactive to ZnT8 construct. Conversion of Arg or Trp to Gln at aa325 abolished reactivity in 59% of patients with an age of onset>10 years, which was significantly higher than that in patients≤10 years of age (33%, p<0.05).

CONCLUSIONS

These results suggest that ZnT8A are an additional useful marker for acute-onset type 1 diabetes, but not a diagnostic marker for fulminant type 1 diabetes, and ZnT8A epitope recognition is different according to the onset age.

Detection and characterization of ZnT8 autoantibodies could help to screen latent autoimmune diabetes in adult-onset patients with type 2 phenotype

Autoantibodies to zinc transporter 8 (ZnT8A) constitute an additional marker of autoimmune diabetes, complementing those already used in diagnosis support. ZnT8A could also be found in latent autoimmune diabetes of adults (LADA). The aim of this study was to evaluate the prevalence of ZnT8A in adult-onset diabetic patients in Argentinian population. A total of 271 patients diagnosed for diabetes at mean age 53.4 ± 10.9, body mass index ≤ 30, without insulin treatment for the first year of disease, and initially classified as type 2 diabetic patients were tested for ZnT8A using cDNA plasmids encoding the C-terminal domains (aa 268-369) carrying 325Arg, 325Trp, and a dimeric cDNA construct carrying both 325Arg and 325Trp (ZnT8 Arg-Trp325). We also analyzed proinsulin autoantibodies (PAA), glutamic acid decarboxylase autoantibodies (GADA), and protein tyrosine phosphatase IA-2 autoantibodies (IA-2A). A subset of 101 patients was followed during 6 years in order to analyze insulin requirement. Out of the 271 patients, 22.1% presented at least one humoral marker, 2.6% were PAA+, 12.5% were GADA+, 3.3% were IA-2A+, and 10.7% were ZnT8A+. Among the latter, 7.0% were ZnT8A-Arg325, 51.7% were ZnT8A-Trp325, and 62.1% were ZnT8A-Arg-Trp325. Furthermore, the prevalence of autoantibodies in the group of patients treated with insulin (n = 18) was 55.6%. These results demonstrated that a significant proportion of autoimmune adult-onset diabetic patients presented ZnT8A as the only humoral marker. Between them, the higher prevalence was for ZnT8A-Trp325. We suggest that screening for LADA patients, best performed with a minimal set of marker determination, must include at least the screening of GADA and ZnT8A-Arg-Trp325.