Project 2: Arsenic- Obesity- Diabetes Interactions

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ABSTRACT: PROJECT 2 Inorganic arsenic (iAs) is a ubiquitous, naturally-occurring environmental toxicant that affects over 200 million people worldwide. Chronic exposure to iAs is associated with numerous human diseases, including type 2 diabetes (T2D). Results of epidemiological studies suggest that efficiency of iAs metabolism, which depends in part on polymorphisms in iAs-methyltransferase (AS3MT) and on other genetic factors, affects the risk of T2D risk in iAs-exposed populations. Obesity, the number 1 risk factor for T2D, has also been shown to modify iAs metabolism and a recent study found that obese individuals are at higher risk of developing T2D when exposed to iAs. In addition, our preliminary studies show that obesity exacerbates T2D phenotype in iAs-exposed mice in a sex-dependent manner, and that the responses to the diabetogenic effects iAs exposure differ between genetically diverse mouse strains. Project 2 addresses a fundamental gap in understanding the interaction between iAs exposure, iAs metabolism, genetics, obesity and sex in the context of type T2D etiology. Our goal is to determine the relative contributions of these five critical factors to T2D risk, using genetically diverse male and female mice with different capacities to metabolize iAs. We hypothesize that there is an interaction between iAs exposure, iAs metabolism and obesity that increases the risk of T2D, and that the outcome depends on genetic background and sex. We plan to use a unique mouse population, the Collaborative Cross, to test our hypothesis. Four key findings underlie our hypothesis: (1) Polymorphisms in AS3MT are linked to both the differences in the capacity to metabolize (methylate) iAs and to T2D risk in populations exposed to iAs; (2) methylated metabolites of iAs are more potent than iAs as inhibitors of beta cell function and insulin signaling in laboratory models; (3) obesity affects iAs metabolism and increases T2D risk in humans, and exacerbates diabetic phenotype in mice exposed to iAs; finally (4) genetics, which is known to influence metabolic health in obese individuals, has also been shown to affect susceptibility to the diabetogenic effects of iAs exposure in both mice and humans. This project is led by a strong team (Drs. Pardo-Manuel de Villena, Styblo, Fry and Zou) with complimentary expertise in genetics, molecular biology, iAs toxicology and metabolism, iAs-induced T2D and statistics. We use the unique Collaborative Cross population, state of the art techniques and carefully controlled experimental design to characterize the interaction between iAs exposure, iAs metabolism and obesity that increases the risk of T2D, and will establish the influence of genetic background and sex. The project is aligned with the theme of the UNC-SRP “Identifying novel methods to reduce iAs exposure and elucidating mechanisms underlying iAs-induced metabolic dysfunction with a vision for disease prevention.” New mechanistic understanding of the role of obesity, genetics, sex and dose in disease, along with the vision of translating these findings to human populations, will enable novel tangible solutions to mitigate the effects of iAs-induced T2D.