Type 1 diabetes is an autoimmune disease caused by T-lymphocyte generated ROS-mediated destruction of the insulin-producing beta cells. Mitochondrial and glycolytic enzyme dysfunction, pyridine cofactor and triosephosphate imbalance, and poly-ADP ribose polymerase (PARP) activation have each been implicated, suggesting that a metabolic mediator such as the NAD+/NADH ratio may be affected. We propose that zinc (Zn2+) potentiates some of these dysfunctions. Zn2+ is prevalent in the pancreas where it is released from beta-cell insulin secretory granules, both free and bound to insulin, and is taken back up into neighboring beta-cells. Zn2+ toxicity was recently implicated in islet-cell death that occurs secondarily to acute streptozotocin (STZ) exposure in vitro and in vivo. We show that niacinamide, pyruvate, NAD+, and sirtinol prevent Zn2+toxicity in neurons and beta-cells by counteracting the Zn2+-induced decrease in NAD+ levels in vitro (subset work in vivo). Niacinamide was shown to be an effective prophylactic for human, and animal type-1 diabetes if given before onset. Recently, we demonstrated that NOD animals have abnormally strong Zn2+ staining of islets as they age, and pyruvate attenuates beta-cell death, and diabetes in the NOD model. We propose that the autoimmune reaction stresses beta-cells which in turn release toxic concentrations of Zn2+. This causes death of adjoining beta-cells by NAD+depletion. Manipulations which raise [NAD+]i or lower [Zn2+]i will be protective. Niacinamide is an NAD+catabolism inhibitor and the precursor of NAD+, and the conversion of pyruvate to lactate acts to restore NAD+levels and metabolic enzymes, thereby reducing death. Sirtinol is a specific inhibitor of the sirtuin pathway which consists of NAD+dependent protein deacetylases.
In specific aim 1, we will 1) measure [Zn2+]i, and 65Zn2+accumulation in isolated islets induced by Zn2+, cytokine, and streptozotocin exposures;2) Determine the effects of these exposures on beta-cell metabolism, and the ability of pyruvate, niacinamide, and sirtinol to restore metabolism;3) Lentiviral or genetic manipulation of NAD+ synthesis and catabolism will be used to explore the specific pathways involved in Zn2+ mediated NAD+ loss and beta-cell death.
In specific aim 2, we will determine the ability of pyruvate, and niacinamide to reduce the metabolic derangements and diabetic incidence in the NOD model. Zinc transporter 5 (ZnT5) was suggested to load Zn2+ into secretory vesicles in beta-cells. SIRT-1 is the founding member of the sirtuin pathway which was implicated in neuronal and beta-cell Zn2+ toxicity, and Wlds overexpresses an NAD+synthetic enzyme.
In aim 3, we will characterize ZnT5 -/-, +/+, Wlds, and SIRT-1-/-animals for diabetes incidence, beta-cell death, Zn2+ staining, and insulin release after MLDS streptozotocin-exposure. These experiments will test novel therapeutic compounds (pyruvate, sirtinol) and mechanisms (NAD+loss, sirtuins) involved in Zn2+ mediation of beta-cell death in type-1 diabetes.

Agency
National Institute of Health (NIH)
Institute
National Institute of Diabetes and Digestive and Kidney Diseases (NIDDK)
Type
Research Project (R01)
Project #
3R01DK073446-05S2
Application #
7998878
Study Section
Cellular Aspects of Diabetes and Obesity Study Section (CADO)
Program Officer
Spain, Lisa M
Project Start
2010-01-15
Project End
2010-03-31
Budget Start
2010-01-15
Budget End
2010-03-31
Support Year
5
Fiscal Year
2010
Total Cost
$57,413
Indirect Cost
Name
Louisiana State Univ Hsc New Orleans
Department
Type
DUNS #
782627814
City
New Orleans
State
LA
Country
United States
Zip Code
70112
Li, Li; Bai, Shi; Sheline, Christian T (2017) hZnT8 (Slc30a8) Transgenic Mice That Overexpress the R325W Polymorph Have Reduced Islet Zn2+ and Proinsulin Levels, Increased Glucose Tolerance After a High-Fat Diet, and Altered Levels of Pancreatic Zinc Binding Proteins. Diabetes 66:551-559
Bai, Shi; Sheline, Christian T (2013) NAD(+) maintenance attenuates light induced photoreceptor degeneration. Exp Eye Res 108:76-83
Aiba, Isamu; West, Adrian K; Sheline, Christian T et al. (2013) Intracellular dialysis disrupts Zn2+ dynamics and enables selective detection of Zn2+ influx in brain slice preparations. J Neurochem 125:822-31
Bai, Shi; Sheline, Carolyn R; Zhou, Yongdong et al. (2013) A reduced zinc diet or zinc transporter 3 knockout attenuate light induced zinc accumulation and retinal degeneration. Exp Eye Res 108:59-67
Sheline, Christian T; Zhu, Julia; Zhang, Wendy et al. (2013) Mitochondrial inhibitor models of Huntington's disease and Parkinson's disease induce zinc accumulation and are attenuated by inhibition of zinc neurotoxicity in vitro or in vivo. Neurodegener Dis 11:49-58
Sheline, Christian T (2012) Involvement of SIRT1 in Zn(2+), Streptozotocin, Non-Obese Diabetic, and Cytokine-Mediated Toxicities of ?-cells. J Diabetes Metab 3:
Aiba, Isamu; Carlson, Andrew P; Sheline, Christian T et al. (2012) Synaptic release and extracellular actions of Zn2+ limit propagation of spreading depression and related events in vitro and in vivo. J Neurophysiol 107:1032-41
Carter, Russell E; Aiba, Isamu; Dietz, Robert M et al. (2011) Spreading depression and related events are significant sources of neuronal Zn2+ release and accumulation. J Cereb Blood Flow Metab 31:1073-84
Sheline, Christian T (2011) Thiamine supplementation attenuated hepatocellular carcinoma in the Atp7b mouse model of Wilson's disease. Anticancer Res 31:3395-9
Sheline, Christian T; Cai, Ai-Li; Zhu, Julia et al. (2010) Serum or target deprivation-induced neuronal death causes oxidative neuronal accumulation of Zn2+ and loss of NAD+. Eur J Neurosci 32:894-904

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