The whole blood DNA methylation patterns of extrinsic apoptotic signalling pathway-related genes in autoimmune thyroiditis among areas with different iodine levels

Autoimmune thyroiditis (AIT) has a complex aetiology and the susceptibility to it is determined by a combination of genetic and environmental factors, although these are not yet fully understood. The present research aimed to explore the DNA methylation patterns in whole blood of extrinsic apoptotic signalling pathway-related genes in AIT among areas with different iodine levels. We selected the iodine-fortification areas, iodine-adequate areas and water-based iodine-excess areas from Shandong Province of China as survey sites. Totally, 176 AIT cases and 176 controls were included. MethylTarget(TM) and QT-PCR technology were used to detect candidate genes' DNA methylation levels and mRNA expression levels, respectively. We found that death associated protein kinase 1 (DAPK1) DNA methylation levels in AIT cases (especially in female) were significantly higher than controls (t = 2.7715, P = 0.0059; t = 2.4638, P = 0.0143 in female). There were differences in DAPK1 (t = 2.5384, P = 0.0121), TNF superfamily member 8 (t = 2.1667, P = 0.0334) and TNF-alpha-induced protein 8 (TNFAIP8) (t = 2.5672, P = 0.0121) genes methylation between cases and controls with different water iodine levels. The mRNA expression of DAPK1 (t = 4.329, P < 0.001) and TNFAIP8 (t = 3.775, P < 0.001) in the cases was increased. We identified the differences in the DNA methylation status of the extrinsic apoptotic signalling pathway-related genes between AIT and controls and in different iodine levels areas. The results were verified at the mRNA level. The environmental iodine may affect DNA methylation to some extent.

Automated summary

The present study aimed to explore the DNA methylation patterns in AIT patients and different iodine levels areas. The findings showed that DNA methylation levels of the DAPK1 gene were higher in AIT cases, and there were differences in methylation between cases and controls in different iodine levels areas. The results suggest that environmental iodine may affect DNA methylation to some extent.