Inhibition of DNA methyltransferase 1 increases nuclear receptor subfamily 4 group A member 1 expression and decreases blood glucose in type 2 diabetes

// Yng-Tay Chen 1 , Jiunn-Wang Liao 2 , Ya-Ching Tsai 1 and Fuu-Jen Tsai 1,3,4,5,6 1 Human Genetic Center, Department of Medical Research, China Medical University Hospital, China Medical University, Taichung, Taiwan 2 Graduate Institute of Veterinary Pathobiology, Research Center for Animal Medicine, Animal Disease Diagnostic Center, National Chung Hsing University, Taichung, Taiwan 3 Graduate Institute of China Medical Science, China Medical University, Taichung, Taiwan 4 Department of Medical Genetics, China Medical University Hospital, Taichung, Taiwan 5 School of Chinese Medicine, China Medical University, Taichung, Taiwan 6 Department of Health and Nutrition Biotechnology, Asia University, Taichung, Taiwan Correspondence to: Fuu-Jen Tsai, email: // Keywords : type 2 diabetes, DNA methylation, NR4A1, DNMT1, epigenetics, Gerotarget Received : March 01, 2016 Accepted : May 29, 2016 Published : June 14, 2016 Abstract Our previous genome-wide association studies showed that DNA methyltransferase 1 (DNMT1) is associated with increased susceptibility to type 2 diabetes (T2D) in Han Chinese individuals. Here, we aimed to further evaluate the role of DNMT1 in T2D. We performed a genome-wide DNA methylation array and found that the nuclear receptor subfamily 4 group A member 1 ( NR4A1 ) promoter was hypermethylated in patients with T2D and in a mouse model of T2D. Moreover, DNA hypermethylation of the NR4A1 promoter reduced NR4A1 mRNA expression. Transient transfection of human NR4A1 into RIN-m5F and 293T cells caused DNMT1 inhibition and induced insulin receptor activation. NR4A1knockdown by shRNA resulted in overexpression of DNMT1 and inhibition of insulin receptor, suggesting that the NR4A1 gene is involved in the epigenetics pathway. Furthermore, T2D model mice treated with the DNMT1 inhibitor aurintricarboxylic acid (ATA) showed reduced activation of DNMT1 in pancreatic β cells; this effect reversed the changes in NR4A1 expression and decreased blood glucose in T2D model mice. Thus, our results showed for the first time that DNMT1 caused NR4A1 DNA hypermethylation and blocked insulin signaling in patients with T2D. Importantly, ATA therapy may be useful for decreasing blood glucose levels by reversing NR4A1-dependent insulin signaling. These findings improve our understanding of the crucial roles of these regulatory elements in human T2D.