Beta-cell compensation is an adaptive mechanism by which -cells increase insulin secretion to overcome insulin resistance or oxidative stress for maintaining euglycemia in obesity. Beta-cell compensation culminates in the expansion of -cell mass and/or upregulation of insulin synthesis/secretion. Failure of - cells to compensate for insulin resistance or oxidative stress contributes to insulin insufficiency and overt diabetes. How -cells compensate for insulin resistance or oxidative stress and what causes -cell failure are poorly understood. FoxO1 is a transcription factor that integrates insulin (or IGF-1) signaling to target genes in cell survival, proliferation, differentiation, metabolism and anti-oxidation. Human with genetic FoxO1 variants are associated with an increased risk of -cell dysfunction and type 2 diabetes. We show that transgenic mice with RIP (rat insulin promoter)-directed FoxO1 production in islets are protected against fat-induced glucose intolerance and streptozotocin-elicited diabetes. This effect is attributable to augmented glucose-stimulated insulin secretion and increased -cell mass in RIP-FoxO1 transgenic mice. FoxO1 activity is upregulated in islets, correlating with the physiological induction of -cell compensation in dietary obese mice. These new data underscore the importance of FoxO1 in -cell function, spurring the hypothesis that FoxO1 contributes to -cell compensation. To address this hypothesis, we propose three specific aims: 1) To determine the effect of FoxO1 gain-of-function on -cell compensation for insulin resistance; 2) To address the mechanisms by which FoxO1 enhances -cell compensation for oxidative stress; and 3) To determine the effect of FoxO1 loss-of-function on -cell compensation in obesity and diabetes. To achieve these goals, we will employ gene transfer, transgenic expression, gene knockout and siRNA-mediated gene-silencing approaches to achieve -cell specific FoxO1 production and alternatively conditional FoxO1 depletion in mature islets in vivo as well as in human islets ex vivo, followed by determining the ability of -cells with FoxO1 gain- vs. loss-of-function to compensate for insulin resistance and oxidative stress. We have provided proof-of-principle and demonstrated the feasibility for the proposal. Accomplishing this project will deepen our understanding of the mechanisms of -cell compensation and - cell failure in diabetes.

Public Health Relevance

Type 2 diabetes results from beta-cell failure, culminating in the inability of beta-cells to compensate for insulin resistance in at-risk subjects with obesity. The fact that diabetes develops in some but not all insulin resistant subjects with obesity forebodes an intricate interplay between genetic and nutritional cues in the pathogenesis of beta-cell failure. Our goal is to characterize the genetic factor(s) that are responsible for coupling beta-cell compensation with nutrient signals to understand the underlying mechanism of beta-cell failure in diabetes.

Agency
National Institute of Health (NIH)
Institute
National Institute of Diabetes and Digestive and Kidney Diseases (NIDDK)
Type
Research Project (R01)
Project #
5R01DK098437-02
Application #
8791685
Study Section
Cellular Aspects of Diabetes and Obesity Study Section (CADO)
Program Officer
Sato, Sheryl M
Project Start
2014-01-15
Project End
2017-11-30
Budget Start
2014-12-01
Budget End
2015-11-30
Support Year
2
Fiscal Year
2015
Total Cost
$305,047
Indirect Cost
$93,189
Name
University of Pittsburgh
Department
Pediatrics
Type
Schools of Medicine
DUNS #
004514360
City
Pittsburgh
State
PA
Country
United States
Zip Code
15213
Xiao, Xiangwei; Fischbach, Shane; Zhang, Tina et al. (2017) SMAD3/Stat3 Signaling Mediates ?-Cell Epithelial-Mesenchymal Transition in Chronic Pancreatitis-Related Diabetes. Diabetes 66:2646-2658
Xiao, Xiangwei; Chen, Congde; Guo, Ping et al. (2017) Forkhead Box Protein 1 (FoxO1) Inhibits Accelerated ? Cell Aging in Pancreas-specific SMAD7 Mutant Mice. J Biol Chem 292:3456-3465
Garbacz, Wojciech G; Jiang, Mengxi; Xu, Meishu et al. (2017) Sex- and Tissue-Specific Role of Estrogen Sulfotransferase in Energy Homeostasis and Insulin Sensitivity. Endocrinology 158:4093-4104
Lee, Sojin; Dong, H Henry (2017) FoxO integration of insulin signaling with glucose and lipid metabolism. J Endocrinol 233:R67-R79
Coudriet, Gina M; Delmastro-Greenwood, Meghan M; Previte, Dana M et al. (2017) Treatment with a Catalytic Superoxide Dismutase (SOD) Mimetic Improves Liver Steatosis, Insulin Sensitivity, and Inflammation in Obesity-Induced Type 2 Diabetes. Antioxidants (Basel) 6:
Cheng, Xiaoyun; Yamauchi, Jun; Lee, Sojin et al. (2017) APOC3 Protein Is Not a Predisposing Factor for Fat-induced Nonalcoholic Fatty Liver Disease in Mice. J Biol Chem 292:3692-3705
Liu, Yun-Zi; Cheng, Xiaoyun; Zhang, Ting et al. (2016) Effect of Hypertriglyceridemia on Beta Cell Mass and Function in ApoC3 Transgenic Mice. J Biol Chem 291:14695-705
Zhang, Ting; Kim, Dae Hyun; Xiao, Xiangwei et al. (2016) FoxO1 Plays an Important Role in Regulating ?-Cell Compensation for Insulin Resistance in Male Mice. Endocrinology 157:1055-70
Gong, Zhenwei; Su, Kai; Cui, Lingguang et al. (2015) Central effects of humanin on hepatic triglyceride secretion. Am J Physiol Endocrinol Metab 309:E283-92
Zhang, Ting; Dong, H Henry (2015) Glucose-regulated insulin production in the liver improves glycemic control in type 1 diabetic mice. Mol Metab 4:70-6

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