Project Summary/Abstract Inorganic arsenic (iAs) is the top chemical on the ATSDR priority list of hazardous substances. Its role in carcinogenesis has been studied extensively, whereas its role in metabolic disorders has not. Recent human epidemiology studies have identified correlation between type 2 diabetes (T2D) and arsenic exposure. We found that the effect of iAs on metabolism shows sexual dimorphism in mice, with male mice more susceptible to glucose intolerance and female mice more susceptible to changes in hepatic lipid accumulation. We hypothesize that the metabolic and transcriptomic effect of iAs is modulated by estrogen through estrogen receptor (ER) and its co-repressor complex containing histone deacetylase 3 (HDAC3), which accounts for gender-specific effects of iAs in diabetes. We will determine whether loss of estrogen receptor (ER) increases susceptibility to iAs-induced diabetes; whether gain-of-function of ER through genetic manipulation of HDAC3 protects against iAs-induced diabetes; how ER modulates iAs-induced transcriptomic changes, and whether such modulation can be mimicked by HDAC inhibitors (HDIs). Our study addresses the knowledge gap in gender-specific susceptibility to diseases or environmental toxins, and has obvious translational value in prevention and treatment against environmental hazards in both genders, given the availability of selective estrogen receptor modulators (SERMs) and epigenome-modifying HDIs.