Assessing And Improving Pancreatic Islet Viability And Function
Craig S Nunemaker
Medicineuniversity Of Virginia Charlottesville
Grant 1K01DK081621-01 from National Institute Of Diabetes And Digestive And Kidney Diseases, IRG: DDK
Abstract: The long-term goal of my lab is to identify and elucidate the mechanisms and causes of diabetes and metabolic disorders by investigating dysfunctions in islet physiology. Diabetes mellitus is a metabolic disease that results from either a complete or relative deficiency of the hormone insulin and currently affects 20.8 million people in the U.S. and is increasing in incidence. The cost of caring for this disease is enormous, exceeding 135 billion dollars annually. Increasing evidence suggests that inflammation and immune responses lead to the destruction of insulin-producing beta-cells in pancreatic islets not only in type 1 diabetes (T1DM), but that these factors also contribute to beta-cell loss in type 2 diabetes (T2DM) and other metabolic disorders. Although glucose-stimulated insulin secretion (GSIS) is the standard measure of islet function, preliminary data suggest a more sensitive indicator of islet dysfunction is intracellular calcium ([Ca2+]i), which is closely linked with insulin secretion. Preliminary data show that pro-inflammatory cytokines induce dysfunction in islet [Ca2+]i handling at much lower cytokine concentrations than required to negatively impact insulin secretion. The working model of this proposal is that deficiencies in endogenous [Ca2+]i oscillations and glucose-stimulated changes in [Ca2+]i are indicators of early stages of damage to islet function and viability. Benefits of genetic or pharmacologic interventions to prevent or reverse diabetes will be predicted by [Ca2+]i measurements. The aims of this proposal are to develop more sensitive and accurate methods of assessing islet health (aim1), determine mechanisms of inflammatory cytokine-induced islet dysfunction (aim2), and test novel anti-inflammatory treatments to improve islet health using both novel and standard methods (aim3). The specific aims of this proposal are designed, in part, to evaluate human islets for transplantation, however, the proposed studies will have far greater impact. Accurate, sensitive, and systematic evaluations of islet dysfunction will be used to identify early indicators of dysfunction at the islet level and to elucidate their mechanism in diseases such as T1DM and T2DM, as well as to assess potential therapies for diabetes at the islet level. In addition, the source(s) of dysfunctional calcium handling will also be investigated as a possible mechanism(s) of islet damage; chiefly ER-stress, glycolytic disruption, and ion channels will be examined using a combination of physiological, molecular, and genetic approaches
Project start date: 2008-09-01
Project end date: 2011-08-31
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Grants awarded to Craig S Nunemaker
Assessing And Improving Pancreatic Islet Viability And Function
Craig S Nunemaker
Medicineuniversity Of Virginia Charlottesville
Grant 1K01DK081621-01 from National Institute Of Diabetes And Digestive And Kidney Diseases, IRG: DDK
Abstract: The long-term goal of my lab is to identify and elucidate the mechanisms and causes of diabetes and metabolic disorders by investigating dysfunctions in islet physiology. Diabetes mellitus is a metabolic disease that results from either a complete or relative deficiency of the hormone insulin and currently affects 20.8 million people in the U.S. and is increasing in incidence. The cost of caring for this disease is enormous, exceeding 135 billion dollars annually. Increasing evidence suggests that inflammation and immune responses lead to the destruction of insulin-producing beta-cells in pancreatic islets not only in type 1 diabetes (T1DM), but that these factors also contribute to beta-cell loss in type 2 diabetes (T2DM) and other metabolic disorders. Although glucose-stimulated insulin secretion (GSIS) is the standard measure of islet function, preliminary data suggest a more sensitive indicator of islet dysfunction is intracellular calcium ([Ca2+]i), which is closely linked with insulin secretion. Preliminary data show that pro-inflammatory cytokines induce dysfunction in islet [Ca2+]i handling at much lower cytokine concentrations than required to negatively impact insulin secretion. The working model of this proposal is that deficiencies in endogenous [Ca2+]i oscillations and glucose-stimulated changes in [Ca2+]i are indicators of early stages of damage to islet function and viability. Benefits of genetic or pharmacologic interventions to prevent or reverse diabetes will be predicted by [Ca2+]i measurements. The aims of this proposal are to develop more sensitive and accurate methods of assessing islet health (aim1), determine mechanisms of inflammatory cytokine-induced islet dysfunction (aim2), and test novel anti-inflammatory treatments to improve islet health using both novel and standard methods (aim3). The specific aims of this proposal are designed, in part, to evaluate human islets for transplantation, however, the proposed studies will have far greater impact. Accurate, sensitive, and systematic evaluations of islet dysfunction will be used to identify early indicators of dysfunction at the islet level and to elucidate their mechanism in diseases such as T1DM and T2DM, as well as to assess potential therapies for diabetes at the islet level. In addition, the source(s) of dysfunctional calcium handling will also be investigated as a possible mechanism(s) of islet damage; chiefly ER-stress, glycolytic disruption, and ion channels will be examined using a combination of physiological, molecular, and genetic approaches
Project start date: 2008-09-01
Project end date: 2011-08-31
Linking Metabolic And Electrical Rhythms In Beta-cells
Craig S Nunemaker
Virginia Commonwealth University Po Box 980568 Richmond, Va 232980568
Grant 5F32DK065462-03 from National Institute Of Diabetes And Digestive And Kidney Diseases, IRG: ZRG1
Abstract: Diabetes mellitus is a metabolic disorder marked by impaired insulin secretion and increased insulin resistance. Loss of pulsatile insulin secretion may be an early stage in this disorder. Our long-range hypothesis is that abnormal electrical oscillations, which might in turn reflect ion channel abnormalities and/or abnormal metabolic oscillations in the beta-cell, contributes to the abnormal secretion of diabetics. Dysfunctional activity of adenosine ATP-sensitive potassium channels (KATP channels) has been linked to insulin secretion abnormalities, however, a direct link between metabolic oscillations and rhythmic KATP channel activity has not been well established. KATP channel are hypothesized to reflect oscillatory changes in glucose metabolism and modulate spike-firing patterns in islets. To investigate the role of KATP channels in the generation and/or modulation of rhythms in metabolic and electrical activity, the mitochondrial membrane dye rhodamine 123 will be used as a measure of metabolic activity combined with electrophysiological techniques to simultaneously measure 9atterns of KATP channel or electrical activity. The role of calcium in metabolic and electrical processes will also be examined. These data will be used to construct and test a new mathematical model of islet electrical activity, based on slow metabolic rhythms acting through KATP channels.
Keywords: diabetes mellitus, electrophysiology, insulin, pancreatic islet, pancreatic islet function, potassium channel, protein structure function, calcium flux, glucose metabolism, mitochondria, benzopyran, laboratory mouse, postdoctoral investigator
Project start date: 2003-08-16
Project end date: 2005-12-31
5F32DK065462-03 (2005): $48296
5F32DK065462-02 (2004): $42976
Related Publications
Evidence of diminished glucose stimulation and endoplasmic reticulum function in non-oscillatory pancreatic islets. Endocrinology. 2008 Sep 25. [Epub ahead of print] PMID: 18818288 
12-Lipoxygenase-knockout mice are resistant to inflammatory effects of obesity induced by western diet. Am J Physiol Endocrinol Metab. 2008 Nov; 295( 5): E1065-75. Epub 2008 Sep 9. PMID: 18780776 Resolving the conundrum of islet transplantation by linking metabolic dysregulation, inflammation, and immune regulation. Endocr Rev. 2008 Aug; 29( 5): 603-30. Epub 2008 Jul 29. Review. PMID: 18664617 Nonobese diabetic (NOD) mice congenic for a targeted deletion of 12/15-lipoxygenase are protected from autoimmune diabetes. Diabetes. 2008 Jan; 57( 1): 199-208. Epub 2007 Oct 16. PMID: 17940120 Glucose-induced release of nitric oxide from mouse pancreatic islets as detected with nitric oxide-selective glass microelectrodes. Am J Physiol Endocrinol Metab. 2007 Mar; 292( 3): E907-12. Epub 2006 Nov 22. PMID: 17122087 
Glucose modulates [Ca2+]i oscillations in pancreatic islets via ionic and glycolytic mechanisms. Biophys J. 2006 Sep 15; 91( 6): 2082-96. Epub 2006 Jun 30. PMID: 16815907 Combined treatment with lisofylline and exendin-4 reverses autoimmune diabetes. Biochem Biophys Res Commun. 2006 Jun 9; 344( 3): 1017-22. Epub 2006 Apr 5. PMID: 16643856 Individual mice can be distinguished by the period of their islet calcium oscillations: is there an intrinsic islet period that is imprinted in vivo? Diabetes. 2005 Dec; 54( 12): 3517-22. PMID: 16306370 Insulin secretion in the conscious mouse is biphasic and pulsatile. Am J Physiol Endocrinol Metab. 2006 Mar; 290( 3): E523-9. Epub 2005 Oct 25. PMID: 16249252 Comparison of metabolic oscillations from mouse pancreatic beta cells and islets. Endocrine. 2004 Oct; 25( 1): 61-7. PMID: 15545708 Insulin feedback alters mitochondrial activity through an ATP-sensitive K+ channel-dependent pathway in mouse islets and beta-cells. Diabetes. 2004 Jul; 53( 7): 1765-72. PMID: 15220200 Steroid regulation of GnRH neurons. Ann N Y Acad Sci. 2003 Dec; 1007: 143-52. Review. PMID: 14993048 Dose-dependent switch in response of gonadotropin-releasing hormone (GnRH) neurons to GnRH mediated through the type I GnRH receptor. Endocrinology. 2004 Feb; 145( 2): 728-35. Epub 2003 Oct 23. PMID: 14576189 Calcium current subtypes in GnRH neurons. Biol Reprod. 2003 Dec; 69( 6): 1914-22. Epub 2003 Aug 6. PMID: 12904316 Mechanisms underlying episodic gonadotropin-releasing hormone secretion. Front Neuroendocrinol. 2003 Apr; 24( 2): 79-93. Review. PMID: 12762999 A targeted extracellular approach for recording long-term firing patterns of excitable cells: a practical guide. Biol Proced Online. 2003; 5: 53-62. Epub 2003 Feb 17. PMID: 12734556 Gonadotropin-releasing hormone neurons generate interacting rhythms in multiple time domains. Endocrinology. 2003 Mar; 144( 3): 823-31. PMID: 12586758 Estradiol-sensitive afferents modulate long-term episodic firing patterns of GnRH neurons. Endocrinology. 2002 Jun; 143( 6): 2284-92. PMID: 12021193