Over twenty million people in the United States have diabetes mellitus, half of which are undiagnosed. In both human and economic terms, it is one of our nation’s most costly health conditions. Diabetes is the leading cause of kidney failure, blindness in adults, and amputations. It is a major risk factor for heart disease, stroke, and birth defects, shortens average life expectancy by up to 15 years, and costs the nation in excess of $100 billion annually in health- related expenditures. At present, there is no method to prevent or cure diabetes, and available treatment have only limited success in controlling its devastating consequences.