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Siddiqui K, Nawaz SS, Alfadda AA, Mujammami M. Islet Autoantibodies to Pancreatic Insulin-Producing Beta Cells in Adolescent and Adults with Type 1 Diabetes Mellitus: A Cross-Sectional Study. Diagnostics (Basel) 2023; 13:diagnostics13101736. [PMID: 37238221 DOI: 10.3390/diagnostics13101736] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/09/2023] [Revised: 04/10/2023] [Accepted: 04/19/2023] [Indexed: 05/28/2023] Open
Abstract
(1) Background: Type 1 diabetes mellitus (T1D) is a chronic autoimmune disease caused by the destruction of pancreatic insulin-producing beta cells. T1D is one of the most common endocrine and metabolic disorders occurring in children. Autoantibodies against pancreatic insulin-producing beta cells are important immunological and serological markers of T1D. Zinc transporter 8 autoantibody (ZnT8) is a recently identified autoantibody in T1D; however, no data on ZnT8 autoantibody in the Saudi Arabian population have been reported. Thus, we aimed to investigate the prevalence of islet autoantibodies (IA-2 and ZnT8) in adolescents and adults with T1D according to age and disease duration. (2) Methods: In total, 270 patients were enrolled in this cross-sectional study. After meeting the study's inclusion and exclusion criteria, 108 patients with T1D (50 men and 58 women) were assessed for T1D autoantibody levels. Serum ZnT8 and IA-2 autoantibodies were measured using commercial enzyme-linked immunosorbent assay kits. (3) Results: IA-2 and ZnT8 autoantibodies were present in 67.6% and 54.6% of patients with T1D, respectively. Autoantibody positivity was found in 79.6% of the patients with T1D. Both the IA-2 and ZnT8 autoantibodies were frequently observed in adolescents. The prevalence of IA-2 and ZnT8 autoantibodies in patients with a disease duration < 1 year was 100% and 62.5%, respectively, which declined with an increase in disease duration (p < 0.020). Logistic regression analysis revealed a significant relationship between age and autoantibodies (p < 0.004). (4) Conclusions: The prevalence of IA-2 and ZnT8 autoantibodies in the Saudi Arabian T1D population appears to be higher in adolescents. The current study also showed that the prevalence of autoantibodies decreased with disease duration and age. IA-2 and ZnT8 autoantibodies are important immunological and serological markers for T1D diagnosis in the Saudi Arabian population.
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Affiliation(s)
- Khalid Siddiqui
- Strategic Center for Diabetes Research, College of Medicine, King Saud University, Riyadh 11461, Saudi Arabia
| | - Shaik Sarfaraz Nawaz
- Strategic Center for Diabetes Research, College of Medicine, King Saud University, Riyadh 11461, Saudi Arabia
| | - Assim A Alfadda
- Strategic Center for Diabetes Research, College of Medicine, King Saud University, Riyadh 11461, Saudi Arabia
- Department of Medicine, College of Medicine & King Saud University Medical City, King Saud University, Riyadh 11461, Saudi Arabia
- Obesity Research Center, College of Medicine, King Saud University, Riyadh 11461, Saudi Arabia
| | - Muhammad Mujammami
- Strategic Center for Diabetes Research, College of Medicine, King Saud University, Riyadh 11461, Saudi Arabia
- Department of Medicine, College of Medicine & King Saud University Medical City, King Saud University, Riyadh 11461, Saudi Arabia
- University Diabetes Center, King Saud University Medical City, King Saud University, Riyadh 11461, Saudi Arabia
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Abstract
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).
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Affiliation(s)
| | - Saeeda Baig
- Biochemistry, Ziauddin University, Karachi, PAK
| | - Asher Fawwad
- Medicine, Baqai Institute of Diabetology and Endocrinology, Baqai Medical University, Karachi, PAK
| | - Zil E Rubab
- Biochemistry, Ziauddin University, Karachi, PAK
| | | | - Nazish Waris
- Research, Baqai Institute of Diabetology and Endocrinology, Karachi, PAK
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Trisorus C, Aroonparkmongkol S, Kongmanas HB, Sahakitrungruang T. Prevalence of islet autoantibodies in Thai juvenile-onset type 1 diabetes. Pediatr Int 2018; 60:1002-1007. [PMID: 30151912 DOI: 10.1111/ped.13687] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 09/22/2017] [Revised: 05/29/2018] [Accepted: 08/17/2018] [Indexed: 12/16/2022]
Abstract
BACKGROUND 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). METHODS In this cross-sectional study, patients with T1DM diagnosed before age 15 years, and disease duration <10 years were enrolled. Serum ZnT8A, GADA, and IA2A were measured using commercial enzyme-linked immunosorbent assay kits. RESULTS The subjects consisted of 81 youths (30 boys, 51 girls) aged 12.3 ± 4.5 years with T1DM. The median diabetes duration was 3 years (range, 0-10 years). 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. CONCLUSION 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.
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Affiliation(s)
- Chayanis Trisorus
- Division of Pediatric Endocrinology, Department of Pediatrics, Faculty of Medicine, Chulalongkorn University, Bangkok, Thailand.,King Chulalongkorn Memorial Hospital, Thai Red Cross Society, Bangkok, Thailand
| | - Suphab Aroonparkmongkol
- Division of Pediatric Endocrinology, Department of Pediatrics, Faculty of Medicine, Chulalongkorn University, Bangkok, Thailand.,King Chulalongkorn Memorial Hospital, Thai Red Cross Society, Bangkok, Thailand
| | - Hataichanok Bansiddhi Kongmanas
- Division of Pediatric Endocrinology, Department of Pediatrics, Faculty of Medicine, Chulalongkorn University, Bangkok, Thailand.,King Chulalongkorn Memorial Hospital, Thai Red Cross Society, Bangkok, Thailand
| | - Taninee Sahakitrungruang
- Division of Pediatric Endocrinology, Department of Pediatrics, Faculty of Medicine, Chulalongkorn University, Bangkok, Thailand.,King Chulalongkorn Memorial Hospital, Thai Red Cross Society, Bangkok, Thailand
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Cheng L, Zhang D, Chen B. Tumor necrosis factor α-induced protein-3 protects zinc transporter 8 against proinflammatory cytokine-induced downregulation. Exp Ther Med 2016; 12:1509-1514. [PMID: 27588072 DOI: 10.3892/etm.2016.3457] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/27/2015] [Accepted: 04/15/2016] [Indexed: 12/12/2022] Open
Abstract
Zinc transporter 8 (ZnT8) is exclusively expressed in the pancreatic islet and is essential for insulin crystallization, hexamerization and secretion. Tumor necrosis factor α-induced protein-3 (TNFAIP3) is a zinc finger protein that serves a major role in the negative feedback regulation of NF-κB signaling in response to multiple stimuli, and is a central regulator of immunopathology. Although the role of TNFAIP3 in diabetes has been extensively studied, its effect on ZnT8 has not been fully elucidated. The present study aimed to verify whether proinflammatory cytokines, tumor necrosis factor α (TNF-α) and interleukin-1β (IL-1β), are able to affect ZnT8 expression in islet cells. In addition, the study aimed to determine the effect of TNFAIP3 overexpression on cytokine-altered ZnT8 activity, considering its effect on NF-κB signaling. Cell-based studies using NIT-1 cells overexpressing TNFAIP3 were used to assess the effect of cytokines on ZnT8 and NF-κB activation, as well as the effect of TNFAIP3 on ZnT8 expression. Western blot analysis and immunofluorescence staining were employed to determine the protein expression and NF-κB activation, respectively. The results indicated that cytokine stimulation led to TNFAIP3 upregulation, ZnT8 downregulation and NF-κB activation. Furthermore, TNFAIP3 overexpression protected ZnT8 from cytokine-induced downregulation. In conclusion, the current results suggest that inflammation or TNFAIP3 dysfunction may be involved in the pathogenesis of diabetes via ZnT8 expression, besides from islet cell apoptosis. In addition, restricting inflammation and enhancing TNFAIP3 expression may exert a positive effect in diabetes prevention, treatment and pancreatic cell transplantation.
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Affiliation(s)
- Liqing Cheng
- Department of Endocrinology and Metabolism, Southwest Hospital, Third Military Medical University, Chongqing 400038, P.R. China
| | - Dongmei Zhang
- Department of Dermatology, Southwest Hospital, Third Military Medical University, Chongqing 400038, P.R. China
| | - Bing Chen
- Department of Endocrinology and Metabolism, Southwest Hospital, Third Military Medical University, Chongqing 400038, P.R. China
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Abstract
Autoantibodies are currently the most robust biomarkers of type 1 diabetes and are frequently used to establish entry criteria for the participation of genetically at-risk individuals in secondary prevention/intervention clinical trials. Since their original description almost 40 years ago, considerable efforts have been devoted toward identifying the precise molecular targets that are recognized. Such information can have significant benefit for developing improved metrics for identifying/stratifying of at-risk subjects, developing potential therapeutic targets, and advancing understanding of the pathophysiology of the disease. Currently, four major molecular targets ([pro]insulin, GAD65, IA-2, and ZnT8) have been confirmed, with approximately 94% of all subjects with a clinical diagnosis of type 1 diabetes expressing autoantibodies to at least one of these molecules at clinical onset. In this review, we summarize some of the salient properties of these targets that might contribute to their autoantigenicity and methods that have been used in attempts to identify new components of the humoral autoresponse.
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Affiliation(s)
- Janet M Wenzlau
- Barbara Davis Center for Childhood Diabetes, University of Colorado Denver, 1775 Aurora Ct, Aurora, CO, 80045, USA,
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Huang G, Xiang Y, Pan L, Li X, Luo S, Zhou Z. Zinc transporter 8 autoantibody (ZnT8A) could help differentiate latent autoimmune diabetes in adults (LADA) from phenotypic type 2 diabetes mellitus. Diabetes Metab Res Rev 2013; 29:363-8. [PMID: 23390067 DOI: 10.1002/dmrr.2396] [Citation(s) in RCA: 39] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 11/25/2011] [Revised: 01/13/2013] [Accepted: 01/27/2013] [Indexed: 01/10/2023]
Abstract
BACKGROUND The ZnT8A is an independent marker for diagnosis of type 1 diabetes mellitus. We investigated the distribution and clinical features of ZnT8A positive latent autoimmune diabetes in adult (LADA) patients to explore the potential diagnostic application. METHODS A total of 3062 phenotypic T2DM patients were randomly selected from a national multicenter study - the LADA China Study. Radioligand binding assays were applied to detect the presence of ZnT8A, GADA and IA-2A. HbA1c , fasting C-peptide and serum lipid levels were followed up with ZnT8A positive patients. RESULTS The positive prevalence of ZnT8A, GADA and IA-2A in phenotypic T2DM patients was 1.99% (61/3062), 6.43% (197/3062) and 1.96% (60/3062), respectively. The ZnT8A positivity was lower than that of GADA(x² = 74.8, p < 0.001) but was comparable with that of IA-2A (p > 0.05). The positivity of ZnT8A in IA-2A positive patients was higher than that in GADA positive patients (38.3% vs. 10.7%, x² = 24.8, p < 0.001). On the basis of GADA and IA-2A positivity, the ZnT8A assay enhanced the diagnostic prevalence of LADA from 7.58 to 8.62%. The LADA patients who were positive for ZnT8A had higher systolic blood pressure when compared with GADA positive cases (p = 0.049) and higher total cholesterol levels when compared with antibody-negative T2DM patients (p = 0.035). CONCLUSION The detection of ZnT8A at the basis of GADA and IA-2A can improve diagnostic sensitivity of Chinese LADA.
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Affiliation(s)
- Gan Huang
- Diabetes Center, Second Xiangya Hospital, and Institute of Metabolism and Endocrinology, Key Laboratory of Diabetes Immunology, Ministry of Education, Central South University, Hunan Key Laboratory of Medical Epigenomics, Changsha, Hunan, China
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Howson JMM, Krause S, Stevens H, Smyth DJ, Wenzlau JM, Bonifacio E, Hutton J, Ziegler AG, Todd JA, Achenbach P. Genetic association of zinc transporter 8 (ZnT8) autoantibodies in type 1 diabetes cases. Diabetologia 2012; 55:1978-84. [PMID: 22526605 PMCID: PMC3369141 DOI: 10.1007/s00125-012-2540-2] [Citation(s) in RCA: 34] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 12/23/2011] [Accepted: 02/23/2012] [Indexed: 12/16/2022]
Abstract
AIMS/HYPOTHESIS Autoantibodies to zinc transporter 8 (ZnT8A) are associated with risk of type 1 diabetes. Apart from the SLC30A8 gene itself, little is known about the genetic basis of ZnT8A. We hypothesise that other loci in addition to SLC30A8 are associated with ZnT8A. METHODS The levels of ZnT8A were measured in 2,239 British type 1 diabetic individuals diagnosed before age 17 years, with a median duration of diabetes of 4 years. Cases were tested at over 775,000 loci genome wide (including 53 type 1 diabetes associated regions) for association with positivity for ZnT8A. ZnT8A were also measured in an independent dataset of 855 family members with type 1 diabetes. RESULTS Only FCRL3 on chromosome 1q23.1 and the HLA class I region were associated with positivity for ZnT8A. rs7522061T>C was the most associated single nucleotide polymorphism (SNP) in the FCRL3 region (p = 1.13 × 10(-16)). The association was confirmed in the family dataset (p ≤ 9.20 × 10(-4)). rs9258750A>G was the most associated variant in the HLA region (p = 2.06 × 10(-9) and p = 0.0014 in family cases). The presence of ZnT8A was not associated with HLA-DRB1, HLA-DQB1, HLA-A, HLA-B or HLA-C (p > 0.05). Unexpectedly, the two loci associated with the presence of ZnT8A did not alter risk of having type 1 diabetes, and the 53 type 1 diabetes risk loci did not influence positivity for ZnT8A, despite them being disease specific. CONCLUSIONS/INTERPRETATION ZnT8A are not primary pathogenic factors in type 1 diabetes. Nevertheless, ZnT8A testing in combination with other autoantibodies facilitates disease prediction, despite the biomarker not being under the same genetic control as the disease.
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Affiliation(s)
- J. M. M. Howson
- Juvenile Diabetes Research Foundation/Wellcome Trust Diabetes and Inflammation Laboratory, Cambridge Institute for Medical Research, Department of Medical Genetics, University of Cambridge, Addenbrooke’s Hospital, Hills Road, Cambridge, CB2 0XY UK
| | - S. Krause
- Forschergruppe Diabetes, Munich University of Technology, Munich, Germany
| | - H. Stevens
- Juvenile Diabetes Research Foundation/Wellcome Trust Diabetes and Inflammation Laboratory, Cambridge Institute for Medical Research, Department of Medical Genetics, University of Cambridge, Addenbrooke’s Hospital, Hills Road, Cambridge, CB2 0XY UK
| | - D. J. Smyth
- Juvenile Diabetes Research Foundation/Wellcome Trust Diabetes and Inflammation Laboratory, Cambridge Institute for Medical Research, Department of Medical Genetics, University of Cambridge, Addenbrooke’s Hospital, Hills Road, Cambridge, CB2 0XY UK
| | - J. M. Wenzlau
- Barbara Davis Diabetes Centre, University of Colorado, Denver, CO USA
| | - E. Bonifacio
- Centre for Regenerative Therapies, Dresden University of Technology, Dresden, Germany
| | - J. Hutton
- Barbara Davis Diabetes Centre, University of Colorado, Denver, CO USA
| | - A. G. Ziegler
- Forschergruppe Diabetes, Munich University of Technology, Munich, Germany
- Institute of Diabetes Research, Helmholtz Centre Munich, Neuherberg, Germany
| | - J. A. Todd
- Juvenile Diabetes Research Foundation/Wellcome Trust Diabetes and Inflammation Laboratory, Cambridge Institute for Medical Research, Department of Medical Genetics, University of Cambridge, Addenbrooke’s Hospital, Hills Road, Cambridge, CB2 0XY UK
| | - P. Achenbach
- Forschergruppe Diabetes, Munich University of Technology, Munich, Germany
- Institute of Diabetes Research, Helmholtz Centre Munich, Neuherberg, Germany
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Hardy AB, Wijesekara N, Genkin I, Prentice KJ, Bhattacharjee A, Kong D, Chimienti F, Wheeler MB. Effects of high-fat diet feeding on Znt8-null mice: differences between β-cell and global knockout of Znt8. Am J Physiol Endocrinol Metab 2012; 302:E1084-96. [PMID: 22338079 PMCID: PMC3774340 DOI: 10.1152/ajpendo.00448.2011] [Citation(s) in RCA: 51] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 02/02/2023]
Abstract
Genomewide association studies have linked a polymorphism in the zinc transporter 8 (Znt8) gene to higher risk of developing type 2 diabetes. Znt8 is highly expressed in pancreatic β-cells where it is involved in the regulation of zinc transport into granules. However, Znt8 is also expressed in other tissues including α-cells, where its function is as yet unknown. Previous work demonstrated that mice lacking Znt8 globally were more susceptible to diet-induced obesity (Lemaire et al., Proc Natl Acad Sci USA 106: 14872-14877, 2009; Nicolson et al., Diabetes 58: 2070-2083, 2009). Therefore, the main goal of this study was to examine the physiological impact of β-cell-specific Znt8 deficiency in mice during high-fat high-calorie (HFHC) diet feeding. For these studies, we used β-cell-specific Znt8 knockout (Ins2Cre:Znt8loxP/loxP) and whole body Znt8 knockout (Cre-:Znt8(-/-)) mice placed on a HFHC diet for 16 wk. Ins2Cre:Znt8loxP/loxP mice on HFHC diet had similar body weights throughout the study but displayed impaired insulin biosynthesis and secretion and were glucose intolerant compared with littermate control Ins2Cre mice. In contrast, Cre-:Znt8(-/-) mice became remarkably obese, hyperglycemic, hyperinsulinemic, insulin resistant, and glucose intolerant compared with littermate control Cre- mice. These data show that β-cell Znt8 alone does not considerably aggravate weight gain and glucose intolerance during metabolic stress imposed by an HFHC diet. However, global loss of Znt8 is involved in exacerbating diet-induced obesity and resulting insulin resistance, and this may be due to the loss of Znt8 activity in a tissue other than the β-cell. Thus, our data suggest that Znt8 contributes to the risk of developing type 2 diabetes through β-cell- and non-β-cell-specific effects.
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Affiliation(s)
| | | | | | | | | | - D. Kong
- 3Beth Israel Deaconess Medical Center, Harvard Medical School, Boston, Massachusetts; and
| | | | - M. B. Wheeler
- 1Department of Physiology and
- 2Department of Medicine, University of Toronto, Toronto, Ontario, Canada;
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Vermeulen I, Weets I, Costa O, Asanghanwa M, Verhaeghen K, Decochez K, Ruige J, Casteels K, Wenzlau J, Hutton JC, Pipeleers DG, Gorus FK. An important minority of prediabetic first-degree relatives of type 1 diabetic patients derives from seroconversion to persistent autoantibody positivity after 10 years of age. Diabetologia 2012; 55:413-20. [PMID: 22095238 PMCID: PMC3810367 DOI: 10.1007/s00125-011-2376-1] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 07/08/2011] [Accepted: 10/14/2011] [Indexed: 10/15/2022]
Abstract
AIMS/HYPOTHESIS The appearance of autoantibodies (Abs) before diabetes onset has mainly been studied in young children. However, most patients develop type 1 diabetes after the age of 15 years. In first-degree relatives aged under 40 years, we investigated the frequency of seroconversion to (persistent) Ab positivity, progression to diabetes and baseline characteristics of seroconverters according to age. METHODS Abs against insulin (IAA), glutamate decarboxylase (GADA), insulinoma-associated protein 2 (IA-2A) and zinc transporter 8 (ZnT8A) were measured during follow-up of 7,170 first-degree relatives. RESULTS We identified 379 (5.3%) relatives with positivity for IAA, GADA, IA-2A and/or ZnT8A (Ab(+)) at first sampling and 224 (3.1%) at a later time point. Most seroconversions occurred after the age of 10 years (63%). During follow-up, Abs persisted more often in relatives initially Ab(+) (76%) than in seroconverters (53%; p < 0.001). In both groups diabetes developed at a similar pace and almost exclusively with Ab persistence (136 of 139 prediabetic individuals). For both groups, progression was more rapid if Abs appeared before the age of 10 years. Baseline characteristics at seroconversion did not vary significantly according to age. CONCLUSIONS/INTERPRETATION Seroconversion to (persistent) Ab(+) occurs regardless of age. Although the progression rate to diabetes is higher under age 10 years, later seroconverters (up to age 40 years) have similar characteristics when compared with age-matched initially Ab(+) relatives and generate an important minority of prediabetic relatives, warranting their identification and, eventually, enrolment in prevention trials.
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Affiliation(s)
- I Vermeulen
- Diabetes Research Center, Brussels Free University, VUB, Laarbeeklaan 103, 1090 Brussels, Belgium
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10
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Abstract
BACKGROUND Identification of the major humoral epitopes in zinc transporter 8 (ZnT8) will expand the range of biomarkers for human type 1 diabetes and may provide clues to the mechanisms governing disease progression. Our initial studies suggested that most ZnT8-reactive sera recognize conformational epitopes in the final 100aa region of the molecule. Subsequently we identified residue 325 as a major determinant in two epitopes linked to a genetic polymorphism with high minor allele frequency (rs13266634). The goal of the current study was to extend this analysis to identify non-polymorphic epitopes in ZnT8. METHODS Although the carboxy-terminal domains of human and mouse ZnT8 are ∼80% identical, the mouse probe is not precipitated by the majority of human type 1 diabetes sera. Thus to identify key residues we systematically 'humanized' the mouse probe at each position that differs and evaluated the probes in radio-immunoassays. RESULTS As previously reported, only the alteration of Q>R325 by itself showed any restoration of binding to human sera. However, when clusters of structurally adjacent variant residues were also changed an additional region of antigenicity was revealed that depended on residues R332, E333, K336, and K340. Using a panel of 112 sera from recent onset subjects tested with the hC325Q and m-R325R332E333K336K340 probes, 39.3% of the subjects were ZnT8(Q)A+ , of which 38.6% (17/44) also recognized the mouse probe. CONCLUSIONS We conclude that the mR-REKK probe identifies a third major epitope in ZnT8 that may add to the diagnostic utility of measuring autoantibodies to this molecule.
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Affiliation(s)
| | | | | | - Howard W. Davidson
- Corresponding author: Howard W. Davidson, PhD, Barbara Davis Center for Childhood Diabetes, Mailstop B140, 1775 Aurora Court, Aurora, CO, 80045, Tel: 303-724-6852, Fax: 303-724-6816,
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