Effects of 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD) on the differentiation of embryonic stem cells towards pancreatic lineage and pancreatic beta cell function

Animal and epidemiological studies demonstrated association of persistent exposure of TCDD, an endocrine disrupting chemical, to susceptibility of type 2 diabetes (T2D). High doses of TCDD were commonly employed in experimental animals to illustrate its diabetogenic effects. Data linking the epigenetic effects of low doses of TCDD on embryonic cells to T2D susceptibility risks is very limited. To address whether low dose exposure to TCDD would affect pancreatic development, hESCs pretreated with TCDD at concentrations similar to human exposure were differentiated towards pancreatic lineage cells, and their global DNA methylation patterns were determined. Our results showed that TCDD-treated hESCs had impaired pancreatic lineage differentiation potentials and altered global DNA methylation patterns. Four of the hypermethylated genes (PRKAG1, CAPN10, HNF-1B and MAFA) were validated by DNA bisulfite sequencing. PRKAG1, a regulator in the AMPK signaling pathway critical for insulin secretion, was selected for further functional study in the rat insulinoma cell line, INS-1E cells. TCDD treatment induced PRKAG1 hypermethylation in hESCs, and the hypermethylation was maintained after pancreatic progenitor cells differentiation. Transient Prkag1 knockdown in the INS-1E cells elevated glucose stimulated insulin secretions (GSIS), possibly through mTOR signaling pathway. The current study suggested that early embryonic exposure to TCDD might alter pancreatogenesis, increasing the risk of T2D.