Are zinc transporter type 8 antibodies a marker of autoimmune thyroiditis in non-obese adults with new-onset diabetes?
OBJECTIVE
The diagnosis of autoimmune diabetes in non-obese adults is based on the detection of glutamic acid decarboxylase autoantibodies (GADA), islet cell antibodies (ICA) and antibodies to tyrosine phosphatase (IA-2A). Zinc transporter 8 (ZnT8) has been identified as a new autoantigen in patients with type 1 diabetes mellitus. The coincidence of autoimmune thyroiditis (AITD) with diabetes is common; therefore, screening of TSH and thyroid peroxidase antibodies (ATPO) is recommended during the diagnosis of diabetes. In this study, we determined whether the occurrence of islet autoantibodies is associated with a positive titre of ATPO in newly diagnosed adult-onset autoimmune diabetic patients.


METHODS
THE STUDY INVOLVED 80 NON-OBESE ADULTS AGED 44 (INTERQUARTILE RANGE (IQR): 37-51) years with a BMI of 24.0 (IQR: 22.2-26.0) kg/m(2) and new-onset diabetes. The markers of autoimmune diabetes (GADA, ICA, IA-2A and ZnT8A), TSH and thyroid peroxidase antibodies (ATPO) were evaluated.


RESULTS
IN THE STUDY POPULATION, 70% (N=56) OF THE SUBJECTS WERE POSITIVE FOR AT LEAST ONE OF THE FOUR ASSESSED MARKERS OF AUTOIMMUNE DIABETES (83.9% GADA, 62.5% ICA, 42.8% IA-2A AND 33% ZNT8A) AND 37.5% OF THE SUBJECTS WERE POSITIVE FOR ATPO. THE ZNT8A-POSITIVE SUBJECTS HAD HIGHER ATPO TITRES THAN THE ZNT8A-NEGATIVE SUBJECTS (172.7 (IQR: 0.36-410.4) vs 92.4 (IQR: 0-23.7) IU/ml, P=0.001). Based on the assessed islet autoantibodies, the occurrence of positive ZnT8A and GADA was found to be related to a positive titre of ATPO using logistic regression (OR=5.48, 95% CI: 1.65-18.14, P=0.006 and OR=3.42, 95% CI: 1.09-10.71, P=0.03 respectively).


CONCLUSIONS
In non-obese adults with new-onset diabetes, the presence of GADA and especially ZnT8 autoantibodies increases the risk of AITD.
Departments of Internal Medicine and Diabetology.
Anita
A
Rogowicz-Frontczak
Dorota
D
Zozuliłska-Ziołkiewicz
Monika
M
Litwinowicz
Paweł
P
Niedźwiecki
Krystyna
K
Wyka
Bogna
B
Wierusz-Wysocka
D000328:Adult; D001323:Autoantibodies / Q000276:immunology*; D027682:Cation Transport Proteins / Q000276:immunology*; D003922:Diabetes Mellitus, Type 1 / Q000276:immunology*; D005260:Female; D005968:Glutamate Decarboxylase / Q000276:immunology*; D006801:Humans; D007453:Iodide Peroxidase / Q000276:immunology*; D007515:Islets of Langerhans / Q000276:immunology*; D008297:Male; D008875:Middle Aged; D012307:Risk Factors; D013967:Thyroiditis, Autoimmune / Q000097:blood / Q000175:diagnosis / Q000276:immunology*; D013972:Thyrotropin / Q000097:blood; D000075703:Zinc Transporter 8
D001323:Autoantibodies; D027682:Cation Transport Proteins; C492522:SLC30A8 protein, human; D000075703:Zinc Transporter 8; D013972:Thyrotropin; D007453:Iodide Peroxidase; D005968:Glutamate Decarboxylase