Abstract: The invention provides an assay for identifying agents that can prevent and treat diabetes. Specifically, the assay is a novel tool for identifying agents that can up regulate cholecystokinin (CCK) expression in pancreatic islets of mammals. The increased expression of CCK triggers an increase in pancreatic ?-cell mass and plasma insulin levels, which have been found to protect against the onset of diabetes. Also, disclosed are representative therapeutic agents identified through the assay of the invention. The methods of the invention are efficient and readily amenable to high-throughput drug screening protocols.