Potential Protective Effect of Anti-zinc Transporter 8 Autoantibodies on Gestational Diabetes Mellitus in Iraqi Population

Abstract

Background: The human zinc transporter 8 (ZNT8), also known as the solute carrier family 30A, member 8 (SLC30A8), is a β-cell specific integral membrane protein, mainly restricted to the membrane of insulin secretory granules. ZnT8 plays a crucial role in both insulin synthesis and secretion as well as the viability of β-cells. The recently identified autoantibodies targeting the β-cell surface epitopes of ZnT8 have been proposed as a new risk factor for gestational diabetes mellitus (GDM). Due to the lack of prior research studies on the role of β-cell surface autoantibodies against ZnT8 in the immunologic etiology of GDM in Iraqi population, this study has been designed to explore the association between the rs13266634 C>T polymorphism in the SLC30A8 gene and the serum levels of ZnT8 as well as Zinc Transporter-8 Autoantibody (ZnT8A) in women diagnosed with GDM. Methods: A total of 50 participants with GDM and 50 controls from the Baghdad Teaching Hospital/Pregnancy Care unit at the Medical City, Baghdad, Iraq, were recruited in this case–control study. Serum levels of ZnT8 and ZnT8A were assayed with enzyme-linked immunosorbent assay, and Taqman real time polymerase chain reaction (RT-PCR) was used for rs13266634 single nucleotide polymorphism (SNP) genotyping. Results: ZnT8A levels were significantly lower in women with GDM than non-GDM women (P ≤ 0.01). A ZnT8A level lower than 20.0 pg/mL was significantly associated with a threefold higher risk for GDM with P ≤ 0.001. ZnT8 levels were significantly higher in the GDM subjects (P ≤ 0.05). The T allele at the rs13266634 C>T SNP significantly conferred a higher risk of GDM (P = 0.002). In view of that, the TT genotype, compared to the CC genotype, showed a significant association with increased GDM risk (P ≤ 0.01). Serum ZnT8A concentrations were significantly low among GDM women who had CT genotype (P = 0.003). Conclusion: The T variant at the SLC30A8 rs13266634 C>T polymorphism appears to play a key role in determining the β-cell autoimmunity by inducing an autoantibody response due to its hyperactivity of zinc transportation.