Pilot & Feasibility Program Application Abstract
Innovations in phenotyping islet function in mouse metabolic disorders
Craig Nunemaker (Charlottesville, VA)
A key element in many metabolic disorders is dysfunction in pancreatic islets of Langerhans, which secrete peptides to regulate metabolism. With the rising rates of obesity in the U.S. increases in diabetes, cardiovascular disease, metabolic syndrome, and other obesity-related disorders are expected to dramatically increase. Investigating these metabolic disorders at the level of the islet is crucial to a full understanding of metabolic disorders. The most common method for assessing basic islet function is to measure glucose stimulated insulin secretion in static conditions—a method that requires a large number of islets, lacks information on the dynamics of insulin responses, and has a high material cost for insulin assays. I propose to develop a series of tests that chiefly uses fluorescent imaging techniques to compare the health and function of islets in vitro from different mouse models. What makes this proposal unique is that many islets can be assessed simultaneously and individually, so that a small number of islets from a small number of mice would be sufficient to thoroughly characterize islet function for the model. By prelabeling one set of islets, islets from both wild type and experimental mice can be compared simultaneously under identical conditions with a high degree of temporal precision. This technique will provide valuable and novel information about dynamic changes in islet metabolic rates and secretory responses for mouse models by making direct comparisons of the latency, amplitude, and trajectory of an islet’s response to glucose or other stimuli, allowing very subtle deficiencies or enhancements in islet function to be discerned. This method also has many advantages over existing techniques because variable conditions such as background fluorescence, chamber perifusion dynamics, etc. are eliminated by directly comparing islets from two or more treatment groups in simultaneous recordings. Using these fluorescent assessment techniques and a systematic experimental approach, I will describe and characterize islet dysfunction in mouse models of diabetes and metabolic disorders by measuring and comparing (a) islet metabolism, (b) intracellular calcium, (c) patterns of insulin secretion, and (d) rates of cell death. These simple but powerful tests will be designed to identify potential mechanisms of islet dysfunction from glucose transport to exocytosis in order to target future research directions for investigators.
Back to Top