We have identified a novel cytosolic-plasma membrane circuit of redox control, dependent on plasma membrane oxidoreductase NQO1 and the cytosolic NADPH-regulating enzyme NAD kinase, which regulates NAD(P)H/NADP+ ratio, level of reactive oxygen intermediates (ROI) and glucose-stimulated insulin secretion (GSIS) from pancreatic beta cells. Our Preliminary Data demonstrate the critical role of these pathways for beta cell function, survival, and GSIS. Furthermore, NQO1 participates in the glucose-dependent process of quinone redox cycling, which regulates cytosolic NADH/NAD+ ratio and enhances GSIS. NAD kinase, a novel NADPH- regulating enzyme, is responsible for the de novo production of NADPH and participates in the protection of beta cells from oxidative stress. NQO1 and NAD kinase are critical for normal cell function, and have not been characterized in pancreatic beta cells. We will employ over- expression or knockdown using shRNA and adenoviral vectors strategies as well as NQO1 knockout pancreatic islets to analyze the role of these components in beta cell intermediary metabolism. We will analyze the role of NQO1 and NAD kinase on the response of beta cells or islets to glucose or other stimulatory agents using a custom-made integrated electrochemical- confocal imaging platform to simultaneously study islet metabolism, respiration, and signaling. These studies will provide greater insight into the mechanism of redox signaling in regulating insulin secretion and identify novel targets for the development of therapeutics for type 2 diabetes.

Public Health Relevance

This application investigates how redox systems in pancreatic beta cells regulate insulin secretion. Our Preliminary and Published Studies have identified a novel cytosolic circuit of redox control, which involves plasma membrane oxidoreductase NQO1 and the NADPH- regulating enzyme NAD kinase, and is responsible for regulation of beta cell redox status, beta cell survival and insulin secretion. These studies will not only lead to better understanding of glucose stimulated insulin secretion, but will also allow design of new therapeutic strategies to enhance beta cell secretory response and treatment of type 2 diabetes.

Agency
National Institute of Health (NIH)
Institute
National Institute of Diabetes and Digestive and Kidney Diseases (NIDDK)
Type
Research Project (R01)
Project #
5R01DK097847-04
Application #
9095314
Study Section
Molecular and Cellular Endocrinology Study Section (MCE)
Program Officer
Sato, Sheryl M
Project Start
2015-06-19
Project End
2018-06-30
Budget Start
2015-07-01
Budget End
2016-06-30
Support Year
4
Fiscal Year
2015
Total Cost
$325,163
Indirect Cost
$107,663
Name
University of South Florida
Department
Physiology
Type
Schools of Medicine
DUNS #
069687242
City
Tampa
State
FL
Country
United States
Zip Code
33612
Gray, Joshua P; Burgos, Delaine Zayasbazan; Yuan, Tao et al. (2016) Thymoquinone, a bioactive component of Nigella sativa, normalizes insulin secretion from pancreatic ?-cells under glucose overload via regulation of malonyl-CoA. Am J Physiol Endocrinol Metab 310:E394-404
Gray, Joshua P; Karandrea, Shpetim; Burgos, Delaine Zayasbazan et al. (2016) NAD(P)H-dependent quinone oxidoreductase 1 (NQO1) and cytochrome P450 oxidoreductase (CYP450OR) differentially regulate menadione-mediated alterations in redox status, survival and metabolism in pancreatic ?-cells. Toxicol Lett 262:1-11
Heart, Emma A; Karandrea, Shpetim; Liang, Xiaomei et al. (2016) Mechanisms of Doxorubicin Toxicity in Pancreatic ?-Cells. Toxicol Sci 152:395-405