The most common form of Type II diabetes, which is epidemic in the United States, initiates from target cell resistance to insulin combined with inadequate pancreatic islet ?-cell insulin secretion. Lipid signaling plays key roles in the pathway that controls insulin secretion. My sponsor's lab and I have generated preliminary evidence that the lipid signaling enzyme phosphatidylinositol 4-phosphate 5-Kinase a (PI4P5Ka), which generates phosphatidylinositol 4,5 bisphosphate (PIP2), restricts regulated insulin secretion;hence inhibiting this signaling enzyme may present a potential therapeutic opportunity. PIP2 functions in multiple cell biological processes. The initial goal of this NRSA application is to delineate the mechanisms through which PI4P5Ko>generation of PIP2 inhibits insulin secretion, including examining calcium signaling and actin cytoskeletal reorganization in pancreatic islet cells in response to glucose challenge, since there is precedent for PIP2 involvement in these events, and they are key to the secretory process. In the second goal, I will develop an animal model to test whether acutely decreasing PI4P5Ka in pancreatic islet ? -cells using RNAi constitutes a potential approach that could benefit Type II diabetic patients.
Aim 1 : To establish the mechanism via which PI4P5Ka inhibition leads to increased insulin release. I will explore whether the facilitation of insulin release via PI4P5Ka inhibition is dependent on dynamic changes in the actin cytoskeletal mesh, or whether there is involvement at the level of calcium or potassium signaling. These experiments will be addressed by employing actin stabilizing and destabilizing reagents, calcium channel activators, and K+ channel blockers.
Aim 2 : To determine if acute elimination of PI4P5Ka ameliorates Type II diabetes. Using a novel method, transgenic mice that can undergo conditional silencing of PI4P5Ka in their pancreatic islets will be generated and crossed with hypoinsulinemic Type ll-predisposed mice. Glucose tolerance tests and insulin measurements will be performed before and after transient or long-term Pl4P5Ka silencing. The results will model the expectations for pharmacological inhibition of PI4P5Ka in type ll-diabetic patients using siRNA approaches.
This research aims to provide an alternative therapeutic approach to the management of Type II diabetes.
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