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THE ROLE of the RETINOL-BINDING PROTEIN RECEPTOR STRA6 in REGULATION of DIURNAL INSULIN RESPONSES by CHRISTY M GLINIAK Submitted

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THE ROLE of the RETINOL-BINDING PROTEIN RECEPTOR STRA6 in REGULATION of DIURNAL INSULIN RESPONSES by CHRISTY M GLINIAK Submitted THE ROLE OF THE RETINOL-BINDING PROTEIN RECEPTOR STRA6 IN REGULATION OF DIURNAL INSULIN RESPONSES by CHRISTY M GLINIAK Submitted in partial fulfillment of the requirements For the degree of Doctor of Philosophy Department of Nutrition CASE WESTERN RESERVE UNIVERSITY August, 2017 CASE WESTERN RESERVE UNIVERSITY SCHOOL OF GRADUATE STUDIES We hereby approve the dissertation of Christy M Gliniak candidate for the degree of PhD*. Committee Chair Danny Manor Committee Member J. Mark Brown Committee Member Colleen Croniger Committee Member Roman Kondratov Committee Member Mark Jackson May 22, 2017 *We also certify that written approval has been obtained for any proprietary material contained therein. 2 To Noa Noy 3 Table of Contents List of Tables .............................................................................................. 8 List of Figures ............................................................................................. 9 Acknowledgements .................................................................................. 10 List of Abbreviations ................................................................................. 12 Abstract ..................................................................................................... 14 CHAPTER 1 .............................................................................................. 16 INTRODUCTION AND STATEMENT OF PURPOSE .............................. 16 1.1 INTRODUCTION ................................................................................. 16 1.2 VITAMIN A ........................................................................................ 17 1.3 ABSORPTION, STORAGE AND TRAFFICKING OF VITAMIN A .................... 20 1.3.1 Absorption ............................................................................... 21 1.3.2 Storage ..................................................................................... 23 1.3.3 Trafficking ................................................................................. 24 1.4 STRA6 ............................................................................................ 26 1.4.1 STRA6 Structure ...................................................................... 26 1.4.2 RBP4 Receptor-2 .................................................................... 29 1.4.3 STRA6 expression ................................................................... 30 1.4.4 STRA6 function as ROH transporter ........................................ 30 1.4.5 STRA6 mutations in humans .................................................... 31 1.4.6 STRA6 is a signaling receptor .................................................. 32 1.4.7 Importance of CRBP and LRAT for vitamin A signaling .......... 34 4 1.5 RBP IS ASSOCIATED WITH IMPAIRED GLUCOSE METABOLISM ................ 36 1.5.1 STRA6 mediates RBP's effect on insulin receptor signaling .... 36 1.5.2 RBP and STRA6 are associated with type II diabetes ............. 37 1.6 CIRCADIAN PATTERNS IN INSULIN SENSITIVITY ...................................... 38 1.6.1 Circadian rhythms .................................................................... 38 1.6.2 Circadian clock gene network .................................................. 39 1.6.3 Circadian disruption is pathogenic ........................................... 42 1.7 ROLE OF ADIPOSE TISSUE IN INSULIN SENSITIVITY ................................ 44 CHAPTER 2 .............................................................................................. 46 THE ROLE OF THE RETINOL-BINDING PROTEIN RECEPTOR STRA6 IN REGULATION OF DIURNAL INSULIN RESPONSES ........................ 46 2.1 INTRODUCTION ................................................................................. 46 2.2 MATERIALS AND METHODS ................................................................ 49 2.3 RESULTS .......................................................................................... 54 2.3.1 Key players in vitamin A metabolism and signaling display circadian rhythmicity in white adipose tissue .................................... 54 2.3.2 Serum RBP4 and TTR levels display circadian rhythmicity .... 57 3.2.3 The circadian transcription factor Rev-erbα binds the promoters of STRA6, CRBP1, and LRAT ........................................................... 59 2.3.4 STRA6 regulates diurnal insulin responses in mice ................ 64 2.3.5 STRA6-null mice have altered diurnal carbohydrate metabolism ....................................................................................... 66 5 2.3.6 STRA6 expression opposes gene expression of targets regulated by insulin signaling ........................................................... 67 2.3.7 The activation of STRA6 by holo-RBP is diurnal ...................... 70 2.3.8 STRA6 expression regulates circadian expression of transcriptional targets of STAT5 ........................................................ 72 2.4 DISCUSSION ...................................................................................... 73 CHAPTER 3 .............................................................................................. 82 GENERAL DISCUSSION ......................................................................... 82 3.1 OVERALL SUMMARY ......................................................................... 82 3.2 FUTURE DIRECTIONS ......................................................................... 82 3.2.1 Which genes does STRA6 regulate in WAT? ........................ 82 3.2.2 How does STRA6 signaling regulate downstream gene expression in WAT? ........................................................................ 83 3.2.3 Does STRA6 signaling inhibit insulin receptor responses via SOCS3 in WAT? ................................................................................ 85 3.2.4 How does STRA6 inhibit signaling downstream of insulin receptor? ........................................................................................... 86 3.2.5 Does RBP secreted by adipocytes stimulate autocrine signaling of STRA6? ......................................................................................... 88 3.2.6 Does STRA6 regulate diurnal insulin action in muscle or liver? ............................................................................. 89 3.2.7 Does STRA6 regulate the serum levels or circadian expression of adiponectin or leptin? .................................................................... 90 6 3.2.8 How is the expression of STRA6 regulated? ............................ 90 3.2.9 How does STRA6 level of expression and circadian gene expression change on a high fat diet? ............................................... 91 3.2.10 Does STRA6 have a role the brain? ....................................... 91 3.2.11 Is there a role for calmodulin in STRA6 activity? .................... 92 3.2.12 Development of an STRA6 inhibitor ....................................... 93 3.3 IMPLICATIONS OF FINDINGS ................................................................. 94 APPENDIX ................................................................................................ 95 CHAPTER 2 .......................................................................................... 95 Supplemental table ............................................................................. 95 CHAPTER 3 .......................................................................................... 96 Supplemental figures .......................................................................... 96 REFERENCES ......................................................................................... 98 7 List of Tables Table 2.1. Putative RORE located on mouse and human STRA6, CRBP1, and LRAT ................................................................................... 60 Table a2.1. Primer sequences used for ChIP ........................................... 95 8 List of Figures Figure 1.1 Vitamin A metabolism ............................................................. 18 Figure 1.2 Vitamin A storage and transport .............................................. 25 Figure 1.3 The structure of STRA6 in complex with calmodulin ............... 28 Figure 1.4. Architecture of zebrafish STRA6 protomer ............................. 33 Figure 1.5. The retinol-binding protein receptor STRA6 signaling pathway .................................................................................................... 35 Figure 1.6 The molecular core clock gene network in mammals ............. 41 Figure 2.1. STRA6, CRBP1 and LRAT display circadian patterns of expression in WAT .................................................................................. 55 Figure 2.2. Serum RBP4 and TTR levels display circadian rhythmicity ... 58 Figure 2.3. STRA6, CRBP1, and LRAT expression is inverse to Rev-erbα in WAT ...................................................................................................... 61 Figure 2.4. Rev-erbα binds to the promoters of STRA6, CRBP1, and LRAT.................................................................................................. 63 Figure 2.5. STRA6 regulates diurnal insulin responses in WAT ............... 65 Figure 2.6. STRA6 regulates genes controlled by insulin action ............. 69 Figure 2.7. Effectors downstream of STRA6 signaling show diurnal variations .................................................................................................. 71 Figure a3.1. STRA6 regulates diurnal insulin
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