Zinc Transporter 8 Antibody Research Articles

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

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. 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. 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. 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.

281-OR: Type 2 Diabetes Diagnosed between 16-30 Years in South Asian and White Individuals Is Phenotypically Similar

Aim: The incidence of type 2 diabetes is increasing rapidly in young adults. Older south Asian people (SA) develop type 2 diabetes at leaner BMI compared to white and are less likely to be obese. We hypothesised that obesity may be a bigger driver of young-onset type 2 diabetes in SA people and studied the BMI difference in white and SA people with young adult-onset type 2 diabetes. Methods: Data from two UK cross-sectional cohorts were examined to identify adults diagnosed with any type of diabetes <30 years. We defined type 2 diabetes as a fasting C-peptide level >600pmol/L and negativity to GAD-antibodies (YDX study) and GAD, IA-2 and ZnT8 antibodies (MY DIABETES study). We studied phenotypic differences between SA and white ethnicity. Results: Sixty white and 71 SA people with type 2 diabetes diagnosed <30 years were identified, of which 92% (n= 55) white and 83% (n=59) SA were diagnosed 16-30 years. Median age-at-diagnosis (25 vs. 24 years, p=0.6) and duration (8.8 vs. 9.5 years, p=0.8) were similar between white and SA ethnicity. BMI, though lower in SAs than white (29 vs. 32 kg/m2, p=0.0007), was consistent with ethnic-specific obesity. HbA1c (68 vs. 60 mmol/mol, p=0.1), HDL (1.0 vs. 1.1mmol/L) and triglycerides (2.2 mmol/L vs. 1.7) were similar in white vs. SA. Fasting C-peptide was no different between ethnicities 847 pmol/L white vs. 1018 SA, p=0.1. Percentage insulin-treated was similar between both groups: white 54%, SA 66% p=0.2. Conclusion: Type 2 diabetes diagnosed between 16-30 years is associated significantly with the presence of obesity in both ethnicities. The similarity observed in glycaemia, lipid profiles and fasting C-peptide along with similar durations, suggest the degree of insulin resistance to be equal across ethnic groups. This young-onset south Asian phenotype may contrast older-onset cases where SA people are observed to be significantly leaner and more insulin resistant than white counterparts. Disclosure S. Misra: None. I.F. Godsland: None. N. Bhardwaj: None. N. Oliver: Advisory Panel; Self; Medtronic, Roche Diabetes Care, UNEEG. Research Support; Self; Dexcom, Inc., Roche Diabetes Care. K.R. Owen: None. D.G. Johnston: None. Funding Diabetes Research & Wellness Foundation; European Foundation for the Study of Diabetes

1482-P: Effect of Age on Diabetes-Specific Autoantibodies in a Large Laboratory-Based Cohort

Type 1 diabetes mellitus (T1DM) can occur at any age, the presence of diabetes related autoantibodies predicts increased risk of disease and supports an autoimmune etiology for T1DM. Since 2017, Mayo Clinic Laboratories has been offering a comprehensive type 1 diabetes autoantibody evaluation (DM1Eval) which includes testing for 4 autoantibodies targeting glutamic acid decarboxylase autoantibodies (GAD), protein tyrosine phosphatase-like islet antigen 2 (IA-2), insulin (IAA), and zinc transporter 8 protein (ZnT8). The aim of this study was to determine the frequency of individual antibodies and antibody clusters (2, 3 or 4) stratified into 4 ages groups (children 0-17, young adult 18-35, middle aged 36-55 and older >55 years). Over a 30 month period (June 2017-Nov 2019) the DM1Eval was performed on 6,446 samples. At least 1 autoantibody was found in 3596 (56%) of all samples: 68% of children, 49% of young adults, 40% of middle aged and 41% of older adults. In patients with at least 1 antibody positive, GAD 65 antibodies were the most common in all age groups followed by ZnT8 in those <36 years or IAA antibody in those 36 and older older (Figure). The frequencies of IA2 and ZnT8 antibodies dropped significantly with increasing age strata. Autoantibody clusters of 3 or 4 antibodies were more frequently encountered in younger patients (41% of pediatric and 27% of young adult patients in contrast to just 12% in middle and older age groups). Disclosure A.R. Dahl: None. S. Pittock: None. A. McKeon: None. J. Foster: None. J. Mills: None.

Older age of childhood type 1 diabetes onset is associated with islet autoantibody positivity >30 years later: the Pittsburgh Epidemiology of Diabetes Complications Study.

To examine the association between islet autoantibody positivity and clinical characteristics, residual β-cell function (C-peptide) and prevalence of complications in a childhood-onset (age <17 years), long-duration (≥32 years) type 1 diabetes cohort. Islet autoantibodies (glutamic acid decarboxylase, insulinoma-associated protein 2 and zinc transporter-8 antibodies) were measured in the serum of participants who attended the 2011-2013 Pittsburgh Epidemiology of Diabetes Complications study follow-up examination (n=177, mean age 51 years, diabetes duration 43 years). Prevalences of islet autoantibodies were: glutamic acid decarboxylase, 32%; insulinoma-associated protein 2, 22%; and zinc transporter-8, 4%. Positivity for each islet autoantibody was associated with older age at diabetes onset (glutamic acid decarboxylase antibodies, P=0.03; insulinoma-associated protein 2 antibodies, P=0.001; zinc transporter-8 antibodies, P<0.0001). Older age at onset was also associated with an increasing number of autoantibodies (P = 0.001). Glutamic acid decarboxylase antibody positivity was also associated with lower HbA1c (P = 0.02), insulinoma-associated protein 2 antibody positivity was associated with lower prevalence of severe hypoglycaemic episodes (P=0.02) and both distal and autonomic neuropathy (P=0.04 for both), and zinc transporter-8 antibody positivity was associated with higher total and LDL cholesterol (P=0.01). No association between autoantibody positivity and C-peptide was observed. The strong association between islet autoantibody positivity and older age at type 1 diabetes onset supports the hypothesis of a less aggressive, and thus more persistent, immune process in those with older age at onset. This observation suggests that there may be long-term persistence of heterogeneity in the underlying autoimmune process.

Japanese Adult-Onset Type 1 Diabetic Sisters with Different Disease States: A Case Report

We encountered type 1 diabetic sisters with different islet-associated antibodies and pancreatic β-cell injury rates. The younger sister had different disease susceptibility human leukocyte antigen (HLA) haplotypes (DRB1*0901-DQB1*0303/DRB1*0802-DQB1*0302) on both chromosomes, while the older sister showed a disease susceptibility HLA haplotype (DRB1*0901-DQB1*0303/-) on one chromosome. Furthermore, the younger sister was positive for anti-glutamic acid decarboxylase antibody (GADA), anti-insulinoma-associated protein-2 antibody (IA-2A), and zinc transporter 8 antibody (ZnT8A), and showed depleted endogenous insulin secretory ability at the time of diagnosis. On the other hand, the older sister was positive only for GADA and ZnT8A, and the ability to secrete endogenous insulin was relatively retained at onset. From our cases and existing reports, we verified that: 1) having a HLA haplotype for disease susceptibility on both chromosomes; 2) having HLA-DQ8 and HLA-A24, -DQA1*03 and -DR9; 3) having more islet autoantibodies including IA-2A and ZnT8A may be involved in accelerating the progression of type 1 diabetes by enhancing the damage to pancreatic β-cells.

Organ-specific autoantibodies in Chinese patients newly diagnosed with type 1 diabetes mellitus.

This study aims to investigate the prevalence of islet autoantibodies and other organ-specific autoantibodies in type 1 diabetes mellitus (T1DM) patients and characterize their clinical features. Glutamic acid decarboxylase antibody (GADA), insulinoma antigen 2 antibody (IA-2A), zinc transporter 8 antibody (ZnT8A) and tetraspanin7 antibody (TSPAN7A) were assayed by radioligand or luciferase immunoprecipitation system assays in 205 newly diagnosed acute-onset T1DM patients and 170 healthy controls. Other organ-specific autoantibodies, including thyroid peroxidase antibody (TPOA), thyroglobulin antibody (TGA), tissue transglutaminase antibody (tTGA) and 21-hydroxylase antibody (21-OHA), were also measured. The prevalence of GADA, IA-2A, ZnT8A, TSPAN7A, TPOA, TGA and 21-OHA was higher in T1DM patients than in healthy controls. The combinational assay of various islet autoantibodies could increase the frequency of autoantibody positivity in T1DM to 85.4%. GADA+ IA-2A+ T1DM patients preferentially had TPOA and TGA, while IA-2A+ patients often had tTGA. Patients positive for two or more islet autoantibodies often had TPOA and TGA. BMI of multiple islet autoantibody-positive patients was lower than that of patients with single or no islet autoantibodies, and there were no significant differences in C-peptide and glycated hemoglobin between patients positive for islet autoantibodies combined with other organ-specific antibodies and noncombined patients. Younger female patients who were islet autoantibody positive were more likely to have TPOA and TGA. The frequency of Graves' disease was much higher in T1DM patients than in healthy controls. T1DM usually occurs together with other organ-specific autoantibodies. Measuring of other organ-specific autoantibodies will be beneficial for T1DM patients.

A Unique Case of Atezolizumab-Induced Autoimmune Diabetes

Immunotherapy is a novel treatment that can cause autoimmune diabetes in rare cases. More cases occur following use of the inhibitor to the protein programmed cell death-1 rather than the inhibitor to programmed cell death-ligand 1. We report a unique case of autoimmune diabetes following atezolizumab use. A 55-year-old, Aboriginal Australian female with no prior history of diabetes was commenced on atezolizumab for recurrent squamous cell lung carcinoma. Two months following its commencement, there was the onset of fatigue, polyuria, polydipsia, and new hyperglycemia. Subsequently she was found to have a borderline-low C peptide level of 0.6 nmol/L (reference range is 0.5 to 1.0 nmol/L), and positive zinc transporter-8 antibodies. Following the diagnosis of autoimmune diabetes, 5 units of glargine insulin was commenced which maintained euglycemia and resolved her symptoms of hyperglycemia. There are few case reports of atezolizumab-induced autoimmune diabetes. We present the first case associated with zinc transporter-8 antibodies, and a unique case of autoimmune diabetes in a patient of Aboriginal Australian background.

MON-154 Abnormal Glucose Homeostasis in Spinal Muscular Atrophy (SMA) Leading to a Transient Episode of Diabetic Ketoacidosis (DKA)

SMA is a rare autosomal recessive neuromuscular disorder affecting 4-10/100,000 live births. Fasting hyperglycemia, hyperglucagonemia, and glucose resistance attributed to a decrease in pancreatic β cells and an increase in α cells have been reported in mice and humans with SMA(1). Rare cases of DKA and T1DM have been reported in humans. We report a case of DKA in the setting of SMA with restoration of euglycemia off insulin following the resolution of DKA. A 22-year-old man with genetically-confirmed SMA type 2 and no history of diabetes presented with nausea, vomiting, polyuria, and polydipsia. Weight is 38kg and BMI 16.2. Family history is negative for diabetes. On admission, labs were consistent with DKA: venous BG of 289 mg/dL, anion gap of 23 (n=4-12), lactate of 1.1 mmol/L (n=0.6-1.9 mmol/L), WBC of 35.7 (n=4.3-10.0 thous/microL), bicarbonate of 7 mEq/L (n=23-27 mEq/L), beta-hydroxybutyrate of 8.99 mmol/L (n<0.30 mmol/L), and pH of 7.09 (n=7.35-7.40). Viral serology was positive for adenovirus. DKA was treated with IV insulin followed by subcutaneous insulin glargine 5 units in 24 hours. Over the next 48 hours, patient maintained his BG between 90-172 mg/dL on glargine 4 units QHS. Two days after his discharge from the hospital, he self-discontinued all insulin. At his follow-up appointments 13 and 46 days later, he remained euglycemic off insulin (glucose meter download showed a mean BG of 97 mg/dL with SD 17 mg/dL; A1c 5.6% with Hb of 13.2). Autoimmune markers drawn within 24 hours of admission were negative: GAD 65 antibody 0.01 nmol/L (n < 0.02 nmol/L) and IA-2 and ZnT8 antibodies were undetectable. C-peptide was 3.9 ng/mL and 3.3 ng/mL with concurrent venous BG 114 mg/dL and 142 mg/dL, respectively. It is extremely unusual that this patient with SMA, low BMI, and no family history of diabetes presented with DKA followed by complete resolution of hyperglycemia off insulin. The etiology of this patient’s DKA is unclear, as he does not exhibit signs of insulin resistance or autoimmune markers of T1DM. We hypothesize that our patient has hyperglucagonemia and normal insulin production from an increased pancreatic α cells:β cells ratio but functionally-preserved β cells to maintain euglycemia at baseline. However, decreased number of β cells fail to compensate for increased insulin needs during periods of stress, leading to DKA. This poses unique clinical challenges in managing this patient's BG in between periods of stress to prevent future episodes of DKA. We propose daily use of CGM, A1c check every 3 months, and adding insulin at the earliest sign of stress and/or hyperglycemia. On a broader spectrum, we recommend periodic monitoring of venous BG in patients with SMA and considering additional testing with A1c and OGTT when abnormal venous BG is found on lab. 1. Bowerman, M, et al. Glucose metabolism and pancreatic defects in spinal muscular atrophy. Ann Neurol. 2012; 72(2): 256-268.

Prevalence of islet autoantibodies in Thai juvenile-onset type 1 diabetes.

Type 1 diabetes mellitus (T1DM) is caused by autoimmune destruction of islet β-cells of the pancreas. There are overlapping phenotypes in a significant proportion of youth with type 1 and 2 diabetes. Thus, positive pancreatic autoantibodies are helpful to diagnose T1DM. Zinc transporter 8 antibody (ZnT8A) is a recently identified autoantibody in T1DM and no data on ZnT8A in the Thai population have been reported. The aim of this study was therefore to estimate the prevalence of ZnT8A in Thai juvenile-onset T1DM and to evaluate its diagnostic value relative to glutamic acid decarboxylase and insulinoma-2 antigen antibodies (GADA and IA2A). In this cross-sectional study, patients with T1DM diagnosed before age 15years, and disease duration <10years were enrolled. Serum ZnT8A, GADA, and IA2A were measured using commercial enzyme-linked immunosorbent assay kits. The subjects consisted of 81 youths (30 boys, 51 girls) aged 12.3 ± 4.5years with T1DM. The median diabetes duration was 3years (range, 0-10years). The prevalence of ZnT8A, GADA, and IA2A was 54.3%, 75.3%, and 45.7%, respectively. ZnT8A were detected in 16% of T1DM patients negative for both GADA and IA2A. A combination of ZnT8A, GADA and IA2A could detect 80.2% of patients with T1DM. Combined use of ZnT8A and GADA identified 100% of antibody-positive patients. The prevalence of ZnT8A in Thai juvenile-onset T1DM appears to be higher than in previous studies from Asia. ZnT8A could replace IA2A as an autoimmunity marker in Thai pediatric T1DM patients, with better diagnostic performance.

Overweight Individuals with Type 1 Diabetes Are Less Likely to Present with Diabetic Ketoacidosis—Data from the After Diabetes Diagnosis Research Support System (ADDRESS-2) Cohort

Introduction: Insulin resistance has been proposed to accelerate progression to type 1 diabetes (T1D) in antibody positive relatives of affected individuals. We hypothesised that overweight individuals with confirmed T1D would be less likely to present with diabetic ketoacidosis (DKA), signifying an earlier onset of T1D, due to concomitant insulin resistance. Methods: The ADDRESS-2 study recruits incident clinician-assigned T1D cases within 6-months of diagnosis and systematically assesses pancreatic autoimmunity by GAD-65, IA-2 and ZnT8 antibodies. People with at least two positive antibodies were selected to confirm diagnosis of T1D and categorised for adiposity according to BMI (adults) or Z-scores (children). Odds ratios (OR) for presentation with DKA were compared, adjusted for potential confounders and sub-analysed by whether adult or child at recruitment. Results: 31% (969/ 3132) were positive for two or more pancreatic antibodies. Of these 44% (424/969) presented with DKA. The proportions with DKA varied significantly by adiposity: 59% underweight (16/27), 47% normal (280/601), 39% overweight (103/263), 30% obese (19/63) and 40% severely obese (6/15) (p=0.02). When adjusted for age, being overweight or obese was associated with lower risk of DKA in adults (OR 0.58, p=0.006; 0.44, p=0.03, respectively) not children (OR 0.9, p=0.81; 0.51, p=0.12, respectively). Higher adiposity category was associated with higher daily insulin-requirements independent of age, with obesity associated with a 4 unit/day increase (p=0.03) and severe obesity, 11 units/day increase (p=0.008). Conclusion: Adults with T1D are less likely to present with DKA if overweight or obese. Despite smaller proportions of DKA, insulin requirements are higher. These data suggest that, in adults, T1D presentation is unmasked by the insulin resistance of obesity prior to absolute insulin deficiency and ketoacidosis. Disclosure S. Misra: None. A. Kaur: None. I.F. Godsland: None. H.C. Walkey: None. D.G. Johnston: None. N. Oliver: Advisory Panel; Self; Dexcom, Inc., Roche Diabetes Care Health and Digital Solutions, Medtronic. Research Support; Self; Dexcom, Inc., Roche Diabetes Care Health and Digital Solutions. Other Relationship; Self; Novo Nordisk A/S, Takeda Development Centre Europe Ltd..

Prevalence of ZnT8 Antibody in Turkish Children and Adolescents with New Onset Type 1 Diabetes

Objective:Zinc transporter 8 protein (ZnT8A) is a transmembrane protein which functions to transfer zinc to insulin vesicles. Antibodies formed against ZnT8A (ZnT8A) are regarded as an independent autoimmunity demonstrator in type 1 diabetes (T1D). The aim of this study was to investigate the prevalence of ZnT8A in Turkish children with new onset T1D.Method:Eighty four patients between 1-18 years of age diagnosed with T1D between February 2015-March 2016 and the control group consisting of 50 healthy children without any autoimmune diseases were included in the study. Serum samples for ZnT8A testing were taken from the patient group within a week of diagnosis. A ZnT8A enzyme-linked immunosorbent assay was used in the analyses.Results:ZnT8A positivity was detected in 58% of the patients with new onset T1D and 8% of the control group. ZnT8A were demonstrated in 5 of 11 patients with negative results for classical diabetes antibodies [insulinoma antigen-2 antibody (IA-2A), glutamic acid decarboxylase (GAD) or insulin autoantibodies]. No association was found between ZnT8A positivity and age, gender, presence or degree of ketoacidosis at presentation, hemoglobin A1c, insulin or C-peptide concentration, or the presence of either thyroid or celiac antibodies.Conclusion:ZnT8A prevalence in children with T1D in Turkey was compatible with the literature. The ratio of patients who are clinically considered to have T1D but have negative routine diabetes auto-antibodies were observed to decrease nearly by 50% when ZnT8 antibodies were added to the panel. ZnT8 measurement should be more widespread for clarifying the etiology in T1D.

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

BackgroundThe 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 methodsIn 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. ResultsOur 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) ConclusionOur 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.

Anti-Zinc Transporter Protein 8 Antibody Testing Is Not Informative in Routine Prediabetes Screening in Young Patients with Autoimmune Thyroiditis and Celiac Disease

Background/Aims: Patients with type 1 diabetes mellitus (T1DM), autoimmune thyroiditis (ATD), and celiac disease (CD) are at increased risk for developing other autoimmune diseases. We evaluated zinc transporter 8 (ZnT8) prevalence in patients with ATD and/or CD in order to define the usefulness of ZnT8 autoantibodies for prediabetes screening. Methods: Eighty-one young patients with ATD and/or CD were included in the study; 32 subjects with clinical onset of T1DM were enrolled as a control group. GAD65, IA-2, and ZnT8 antibodies were measured. An intravenous glucose tolerance test, C-peptide, glycosylated hemoglobin levels, and genomic analysis of HLA-DQA1* and -DQB1* were also considered in patients positive for autoantibodies. Results: The ZnT8 prevalence was higher in T1DM patients than in patients with other autoimmune diseases (p < 0.001); positive ZnT8 detection was found in 2 ATD (p = 0.004) and 3 ATD + CD (p = 0.04) patients. Positive ZnT8 was associated with GAD65 (p = 0.01) but not with IA-2 positivity. No correlation between ZnT8 detection and the number of T1DM-susceptible HLA-DQ heterodimers was found. Pathological C-peptide levels and insulin response were found in subjects with islet autoimmunity and genetic susceptibility. Conclusion: ZnT8 autoantibodies detection in ATD and/or CD patients is low, and routine ZnT8 screening is not justified. ZnT8 evaluation may be recommended in subjects with autoimmune diseases as a marker for predicting compromised insulin secretion.

Positive autoantibodies to ZnT8 indicate elevated risk for additional autoimmune conditions in patients with Addison's disease.

Autoimmune Addison’s disease (AAD) associates with exceptional susceptibility to develop other autoimmune conditions, including type 1 diabetes (T1D), marked by positive serum autoantibodies to insulin (IAA), glutamic acid decarboxylase (GADA) and insulinoma-associated protein 2 (IA-2A). Zinc transporter 8 (ZnT8) is a new T1D autoantigen, encoded by the SLC30A8 gene. Its polymorphic variant rs13266634C/T seems associated with the occurrence of serum ZnT8 antibodies (ZnT8A). This study was designed to determine the prevalence of serum ZnT8A and their clinical implication in 140 AAD patients. Other beta cell and thyroid-specific autoantibodies were also investigated, and ZnT8A results were confronted with the rs13266634 genotype. ZnT8A were detectable in 8.5 %, GADA in 20.7 %, IA-2A in 5.7 %, IAA in 1.6 % and various anti-thyroid antibodies in 7.1–67.8 % individuals. Type 1 diabetes was found in 10 % AAD patients. ZnT8A were positive in 57.1 % of T1D patients and 3.4 % non-diabetic AAD. Analysis of ZnT8A enabled to identify autoimmunity in two (14.3 %) T1D individuals previously classified as autoantibody-negative. ZnT8A-positive patients revealed significantly higher number of autoimmune conditions (p < 0.001), increased prevalence of T1D (p < 0.001) and other beta cell-specific autoantibodies. Carriers of the rs13266634 T-allele displayed increased frequency (p = 0.006) and higher titres of ZnT8A (p = 0.002). Our study demonstrates high incidence of ZnT8A in AAD patients. ZnT8A are associated with coexisting T1D and predictive of T1D in non-diabetic subjects. Moreover, positive ZnT8A in AAD indicate elevated risk for additional autoimmune conditions. Autoantibodies to beta cell antigens, comprising ZnT8, could be included in routine screening panels in AAD.

Prokaryotic Expression of Bioactive Zinc Transporter 8 Antigens and Detection of Diabetes Specific Autoantibodies in a Single Dot Immunogold Filtration Assay.

Type 1 diabetes mellitus is an autoimmune disease, and islet autoantibodies secreted by auto-reactive plasma cells are diagnostic indicators of the immune processes. Autoantibodies to zinc transporter 8 (ZnT8) have been identified as a novel reliable biomarker for the prediction, diagnosis, monitoring, and prognosis of autoimmune diabetes, complementing the panel of existing diagnostic autoantibodies. Although the enzyme-linked immunosorbent assay (ELISA) and radioimmunoassay are the most frequently used testing methods, they do not allow simultaneous detection of multiple autoantibodies. Another obstacle is the cost of ZnT8 production for antibody assays. This study aimed to develop a cost-effective expression system for the production of two ZnT8 C-terminal fragments containing main ZnT8 antigen epitopes and establish an improved reliable and rapid assay for the detection of anti-ZnT8 antibodies with a potential to simultaneously measure multiple autoantibodies. The coding codons of the human ZnT8 were optimized for prokaryotic expression and the mutation was achieved using site-directed mutagenesis. A total of 42 newly diagnosed type 1 diabetes patients (16 males and 26 females) and 100 healthy controls (57 males and 43 females) were enrolled for sera. The dot immunogold filtration assay (DIGFA) was evaluated by comparing with ELISA as the "gold standard". Two ZnT8 antigens (arginine and tryptophan ZnT8 at position 325) were successfully produced. We established a rapid DIGFA method for the simultaneous detection of anti-ZnT8 antibodies, with the sensitivity, specificity, accuracy, Youden index, and positive and negative likelihood ratio being 64.3%, 96.4%, 85.7%, 0.607, 18.0, and 0.370, respectively, and the results did not significantly differ from those for ELISA (p = 0.22). These results demonstrate that the pColdII expression system is suitable for the production of bioactive ZnT8 antigens and that DIGFA can be a rapid, reliable, and highly specific method for the detection of ZnT8 antibodies, which can be potentially applied to identify a panel of diabetes-specific autoantibodies simultaneously.

The prevalence of ZnT8 antibodies in patients with gestational diabetes

The prevalence of ZnT8 antibodies in patients with gestational diabetes

ZnT8 antibodies in patients with cystic fibrosis: An expression of secondary beta-cell damage?

Cystic Fibrosis-Related Diabetes (CFRD) is caused by a severe insulin deficiency with associated different degrees of insulin resistance. Data concerning the potential impact of autoimmunity are conflicting. Ninety subjects with cystic fibrosis (CF) were tested for glucose tolerance and autoantibodies against insulin (IAA), glutamic acid decarboxylase (GADA), protein tyrosine phosphatase (IA2) and zinc transporter 8 (Znt8A). Eighty-three subjects showed a normal glucose tolerance (92.2%), 6 subjects (6.6%) impaired glucose tolerance and 1 subject (1.1%) newly diagnosed CFRD. Four subjects were found positive for both IAA and GADA (4.4%), one subject (1.1%) for both IA2 and GADA, and one subject (1.1%) for isolated GADA. Three subjects (3.3%) showed isolated ZnT8A positivity. ZnT8A positivity in CF patients is uncommon and not associated with other autoantibodies. ZnT8A may not represent a specific indicator of a primary autoimmune beta-cell destruction, but possibly the expression of a secondary damage of the pancreatic islets with autoantigen release.

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.

Zinc transporter-8 autoantibodies improve prediction of type 1 diabetes in relatives positive for the standard biochemical autoantibodies.

OBJECTIVEWe assessed diabetes risk associated with zinc transporter-8 antibodies (ZnT8A), islet cell antibodies (ICA), and HLA type and age in relatives of people with type 1 diabetes with the standard biochemical autoantibodies (BAA) to insulin (IAA), GAD65 (GAD65A), and/or insulinoma-associated protein 2 antigen (IA-2A).RESEARCH DESIGN AND METHODSFor this analysis, 2,256 relatives positive for at least one BAA, of whom 142 developed diabetes, were tested for ZnT8A, ICA, and HLA genotype followed by biannual oral glucose tolerance tests. ZnT8A were also tested in 911 randomly chosen antibody-negative relatives.RESULTSZnT8A were associated with the other BAA (548 of 2,256 [24.3%] BAA+ vs. 8 of 911 [0.8%] BAA−, P < 0.001) and BAA number (177 of 1,683 [10.5%] single-, 221 of 384 [57.6%] double-, and 150 of 189 [79.4%] triple-BAA positivity, P < 0.001). The 4-year diabetes risk was higher in single BAA+ relatives with ZnT8A than ZnT8A− relatives (31 vs. 7%, P < 0.001). In multivariable analysis, age ≤20 years (hazard ratio 2.13, P = 0.03), IA-2A (2.15, P = 0.005), IAA (1.73, P = 0.01), ICA (2.37, P = 0.002), and ZnT8A (1.87, P = 0.03) independently predicted diabetes, whereas HLA type (high and moderate vs. low risk) and GAD65A did not (P = 0.81 and 0.86, respectively).CONCLUSIONSIn relatives with one standard BAA, ZnT8A identified a subset at higher diabetes risk. ZnT8A predicted diabetes independently of ICA, the standard BAA, age, and HLA type. ZnT8A should be included in type 1 diabetes prediction and prevention studies.

Discordant association of islet autoantibodies with high‐risk HLA genes in Chinese type 1 diabetes

To reveal the aetiology of diabetes, the relationships between the islet autoantibodies, human leukocyte antigen (HLA)-A and DRB1 genotypes in the Chinese patients with type l diabetes (T1D) were investigated in our study. In the cross-sectional and case-control study, peripheral blood samples were collected from 600 T1D patients and 102 healthy controls. The genetic polymorphisms of HLA-A and DRB1 are examined with polymerase chain reaction-sequence oligonucleotide probe method. The zinc transporter 8 antibody (ZnT8A), glutamic acid decarboxylase antibody (GADA) and protein-tyrosine-phosphatase-2 autoantibody (IA2A) were detected by radioligand assay. The A*2402, DRB1*0301, DRB1*0405 and DRB1*0901 alleles, and A*1101-DRB1*0901, A*2402-DRB1*0405 and A*2402-DRB1*0901 haplotypes were associated with T1D (all p<0.05). The positive rates of ZnT8A in patients carried DRB1*0901, IA2A in patients carried DRB1*0405 and A*1101-DRB1*0901 and GADA in patients carried DRB1*0901 and A*2402-DRB1*0901 were significantly higher than those not carried (p<0.05). HLA-DRB1*0901 was the independent risk factor of positive antibody in T1D patients. In addition, higher body mass index is also related with the loss of islet function besides high-risk HLA gene and islet autoantibody (p<0.05). The discordant association of autoantibodies with high-risk HLA gene may indicate the different immunology mechanisms of those autoantibodies. And metabolic burden resulting from overweight may accelerate apoptosis of beta cells.