Fellowship/Muniappan: Engineering of Liver to Produce Insulin for Diabetes Therapy

The establishment of surrogate islet beta cells is important for the treatment of diabetes. Hepatocytes have a similar glucose sensing system as beta cells of the pancreas that secrete insulin and have the potential to serve as surrogate beta-cells. Our preliminary data indicate that infection of Hepa 1-6 liver cells with an adenovirus expressing the human insulin cDNA results in expression and secretion of insulin in a glucoseindependent manner. Furthermore, L-arginine at low levels of glucose significantly stimulates the release of insulin from these cells, compared to high concentrations of glucose. Based on these preliminary investigations, we conclude that liver cells can be engineered to produce and secrete insulin in a regulated manner. In this application we propose to test whether our findings with the liver cell line also apply to animal models by carrying out the following experiments: 1) Express human insulin in liver of streptozotocin(STZ) mice and determine whether we can prevent hyperglycemia. Furthermore, characterize the molecular mechanisms of insulin secretion in response to secretagogues such as L-arginine. 2) Test whether the beta-cell specific transcription factors PDX-1, NeuroD and MafA enable insulin production and secretion in liver cells. 3) Generate metabolically inactive insulin analogs to prevent autoimmune attack in Nonobese diabetic (NOD) mice expressing human insulin. The data obtained from this proposal will help to develop strategies to engineer liver cells to produce and secrete insulin in a regulated manner as in pancreatic beta cells, which will contribute to the development of new therapeutic concepts for treating diabetes mellitus.