Role of estrogen receptors in pancreatic beta-cell survival and insulin secretion

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DESCRIPTION (provided by applicant): In diabetes, the death of insulin-producing ¿-cells in the pancreas by apoptosis leads to insulin dependence. Yet, the events that promote ¿-cell death are still not fully understood. It is essential to increase our basic knowledge of the processes regulating ¿-cell survival in order to develop novel and efficient therapies for diabetic patients. Evidence suggests that the female hormone, 17¿-estradiol (estradiol), protects insulin production and prevents diabetes. Although estradiol acts primarily via two distinct estrogen receptors (ERs), ERa and ER¿, the individual contributions of these ERs in protecting ¿-cell survival have not been established. Our long-term goal is to determine how to protect insulin production in diabetic patients by modulating estrogen signaling pathways in a gender non-specific manner. Our objective for this application is to elucidate the respective roles played by ERa, ER¿, and non-classical estrogen actions in ¿-cell survival and insulin production in vivo, through the use of genetic mouse models. Based on the preliminary data we have generated, our hypothesis is that ERa protects ¿-cell survival; whereas, ER¿ reduces ERa function and provokes ¿-cell apoptosis. In order to test this hypothesis, we will first use a ¿-cell ERa deficient mouse (¿ERaKO) to demonstrate that selective elimination of ERa in ¿-cells impairs insulin production and provokes diabetes. Next, we will study a ¿-cell ER¿ deficient mouse (¿ER¿KO) to demonstrate that conversely, selective elimination of ER¿ in ¿-cells improves insulin production and prevents diabetes. Finally, we will create a combined ¿-cell specific ERa/ER¿ knockout mouse (¿ERa¿KO). Using this last model we will demonstrate that in absence of the classical ERa and ER¿ in ¿-cells, estradiol protects insulin production and prevents diabetes via non-genomic actions involving a novel membrane ER. Through the proposed research - which is the first investigation of ERs in ¿-cell survival in vivo - we plan to demonstrate that classical and non-classical estrogen receptors are important to ¿-cell survival in vivo, and therefore represent viable targets for therapeutic intervention.