The pulsatility of glucose-dependent insulin secretion is disrupted in Type 2 diabetics (T2DM) and their first-degree relatives, and in animal models of the disease. Although dysfunctional electrical and calcium oscillations in beta cells likely contribute to insulin secretory deficits, the nature of this oscillatory dysfunction is not known;nor have the mechanisms underlying normal beta cell oscillations been fully elucidated. Research conducted during the previous period supports the hypothesis that oscillations in secretion result from complex interactions between electrical (EO) and metabolic oscillators (MO) intrinsic to islet beta cells (the 'Dual Oscillator Model';DOM). Pilot data obtained using a new experimental paradigm show that metabolic oscillations can dominate the electrical oscillator, have a distinctive time course unlike the predictions of other models, and can be decoupled from calcium. Building on this progress, we propose to: examine the properties of the EO and MO, elucidate how EO and MO interact to produce oscillations, and test the validity of the dual oscillator framework (Aim 1);investigate additional ionic mechanisms contributing to the DOM, including novel ion currents (Aim 2);determine whether islet metabolic oscillations are glycolytic or mitochondrial in origin, and design novel FRET probes and mass spectrometry approaches to measure intracellular fuel metabolites in living islets (Aim 3);and determine whether the dual oscillator accounts for the oscillatory properties of normal human islets or a mouse lacking KCNQ1, a putative beta cell potassium channel linked to T2DM;
Aim 4). Completion of these aims will represent the most comprehensive effort to date to understand the underlying oscillatory mechanisms of pancreatic islets, and will increase our insight into islet function in both health and disease.
Patients with Type 2 diabetes secrete less insulin from their pancreatic islets and the pattern of this secretion is abnormal. Normal secretory patterns are required for proper insulin responses, but is poorly understood, we will systematically study the underlying mechanisms of these patterns at the cellular and subcellular levels using mouse and human islets. A better understanding of these processes may provide new ways to restore normal insulin secretion and reverse diabetes in these patients.
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