Obesity and diabetes have reached epidemic level in the United States. Diabetes and its associated complications are becoming one of the leading causes of morbidity In this country. Although several hypotheses link obesity and Insulin resistance, the role of circadian rhythm in the pathogenesis of diabetes has not been well addressed. Interestingly, there Is a clear circadlan variation In fasting glucose, Insulin sensitivity and glucose tolerance, which Is severely dampened In the condition of obesity and diabetes. The orphan nuclear receptor Rev-erba emerged as a core circadian gene. By repressing gene expression of another clock gene Bmal1, Rev-erba functions as a negative regulator of circadian rhythm. We showed GSK3p-dependent phosphorylation is required for maintaining the protein stability of Rev-erba and is crucial for synchronizing the circadlan oscillation of Email gene In vitro. To extend our knowledge on GSK3pdependent regulation of Rev-erba, we propose two specific aims in the first phase of this application (K99 phase), including:
aim 1. Elucidate the signal patliways upstream of GSKSp mediating Rev-erba degradation in hepatocytes;
aim 2. Determine in vivo roles of Rev-erba phosphorylation by GSKSp in circadian rhythm and metabolism. A mouse model expressing Rev-erba mutant which mimics GSK3P phosphorylation In liver will be created to address these questions. This will be the first analysis to detemnine the role of Rev-erba as a clock protein In liver circadlan rhythm and glucose metabolism. This study will be carried out in the Penn Diabetes Center at University of Pennsylvania under the supervision of Dr. Mitchell Lazar. The center has expertise in diabetes and obesity research, and will provide outstanding environment to conduct the proposed project. Meanwhile, the project will provide superb training for the principle Investigator, Dr. Lel Yin, to develop academic career In the field of diabetes and obesity. The role of the ubiquitln-proteasome pathway (UPP) has not been well-studied In the process of metabolism and energy homeostasis. We recently discovered that Cullln 4A-based E3 ligase regulates protein stability of Rev-erba as well as gene expression Important for gluconeogenesis, suggesting Cullln 4A is a novel modulator functioning in both circadlan rhythm and metabolism. Therefore, the specific aim 3 proposed during the ROO phase will be focused on unraveling roles of the Cullin 4A E3 ubiquitin ligase in regulating circadian rhythm, insulin signaling and glucose metabolism. We expect this work will provide a panel of evidences for the functional Importance of the ubiqultin-proteaspme system in the regulation of metabolism. In addition, this work may shed the new light on Identifying the new therapeutic targets for treating Insulin resistance and diabetes.

Public Health Relevance

Ubiquitin E3 ligase play crucial roles in human physiology, and are becoming attractive drug targets for treating cancer, neural degenerative diseases as well as metabolic disorders. However the complexity of the protein ubiquitination pathways involved and the embryonic lethality of some of the most relevant mouse models has limited our knowledge in identification of specific targets as well as the related biology. By using Adenoviral-assoclated viral (AAV) approaches to circumvent the lethality of Cullin 4A disruption, and characterizing the effects of Cullin 4A E3 ligase on circadlan rhythm, metabolism, and Insulin signaling, we are likely to gain insights that can be translated into novel treatment strategies for metabolic disorders and other circadian-related diseases.

Agency
National Institute of Health (NIH)
Institute
National Institute of Diabetes and Digestive and Kidney Diseases (NIDDK)
Type
Research Transition Award (R00)
Project #
4R00DK077449-03
Application #
7929173
Study Section
Special Emphasis Panel (NSS)
Program Officer
Margolis, Ronald N
Project Start
2009-09-23
Project End
2012-08-31
Budget Start
2009-09-23
Budget End
2010-08-31
Support Year
3
Fiscal Year
2009
Total Cost
$235,300
Indirect Cost
Name
University of Michigan Ann Arbor
Department
Physiology
Type
Schools of Medicine
DUNS #
073133571
City
Ann Arbor
State
MI
Country
United States
Zip Code
48109
Tong, Xin; Zhang, Deqiang; Charney, Nicholas et al. (2017) DDB1-Mediated CRY1 Degradation Promotes FOXO1-Driven Gluconeogenesis in Liver. Diabetes 66:2571-2582
Russo, Lucia; Ghadieh, Hilda E; Ghanem, Simona S et al. (2016) Role for hepatic CEACAM1 in regulating fatty acid metabolism along the adipocyte-hepatocyte axis. J Lipid Res 57:2163-2175
Tong, Xin; Li, Pei; Zhang, Deqiang et al. (2016) E4BP4 is an insulin-induced stabilizer of nuclear SREBP-1c and promotes SREBP-1c-mediated lipogenesis. J Lipid Res 57:1219-30
Zhang, Deqiang; Tong, Xin; Arthurs, Blake et al. (2014) Liver clock protein BMAL1 promotes de novo lipogenesis through insulin-mTORC2-AKT signaling. J Biol Chem 289:25925-35
Tong, Xin; Zhang, Deqiang; Buelow, Katie et al. (2013) Recruitment of histone methyltransferase G9a mediates transcriptional repression of Fgf21 gene by E4BP4 protein. J Biol Chem 288:5417-25
Yin, Lei; Wu, Nan; Lazar, Mitchell A (2010) Nuclear receptor Rev-erbalpha: a heme receptor that coordinates circadian rhythm and metabolism. Nucl Recept Signal 8:e001
Tong, Xin; Muchnik, Marina; Chen, Zheng et al. (2010) Transcriptional repressor E4-binding protein 4 (E4BP4) regulates metabolic hormone fibroblast growth factor 21 (FGF21) during circadian cycles and feeding. J Biol Chem 285:36401-9
Yin, Lei; Joshi, Shree; Wu, Nan et al. (2010) E3 ligases Arf-bp1 and Pam mediate lithium-stimulated degradation of the circadian heme receptor Rev-erb alpha. Proc Natl Acad Sci U S A 107:11614-9
Wu, Nan; Yin, Lei; Hanniman, Elyisha A et al. (2009) Negative feedback maintenance of heme homeostasis by its receptor, Rev-erbalpha. Genes Dev 23:2201-9