Factors Regulating Features of Metabolic Syndrome
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University of Kentucky UKnowledge Theses and Dissertations--Pharmacy College of Pharmacy 2017 Factors Regulating Features of Metabolic Syndrome Sonja S. Pijut University of Kentucky, [email protected] Digital Object Identifier: https://doi.org/10.13023/ETD.2017.044 Right click to open a feedback form in a new tab to let us know how this document benefits ou.y Recommended Citation Pijut, Sonja S., "Factors Regulating Features of Metabolic Syndrome" (2017). Theses and Dissertations-- Pharmacy. 70. https://uknowledge.uky.edu/pharmacy_etds/70 This Doctoral Dissertation is brought to you for free and open access by the College of Pharmacy at UKnowledge. It has been accepted for inclusion in Theses and Dissertations--Pharmacy by an authorized administrator of UKnowledge. For more information, please contact [email protected]. STUDENT AGREEMENT: I represent that my thesis or dissertation and abstract are my original work. Proper attribution has been given to all outside sources. I understand that I am solely responsible for obtaining any needed copyright permissions. I have obtained needed written permission statement(s) from the owner(s) of each third-party copyrighted matter to be included in my work, allowing electronic distribution (if such use is not permitted by the fair use doctrine) which will be submitted to UKnowledge as Additional File. I hereby grant to The University of Kentucky and its agents the irrevocable, non-exclusive, and royalty-free license to archive and make accessible my work in whole or in part in all forms of media, now or hereafter known. I agree that the document mentioned above may be made available immediately for worldwide access unless an embargo applies. I retain all other ownership rights to the copyright of my work. I also retain the right to use in future works (such as articles or books) all or part of my work. I understand that I am free to register the copyright to my work. REVIEW, APPROVAL AND ACCEPTANCE The document mentioned above has been reviewed and accepted by the student’s advisor, on behalf of the advisory committee, and by the Director of Graduate Studies (DGS), on behalf of the program; we verify that this is the final, approved version of the student’s thesis including all changes required by the advisory committee. The undersigned agree to abide by the statements above. Sonja S. Pijut, Student Dr. Gregory A. Graf, Major Professor Dr. David J. Feola, Director of Graduate Studies FACTORS REGULATING FEATURES OF METABOLIC SYNDROME ____________________ DISSERTATION ____________________ A dissertation submitted in partial fulfillment of the requirements for the degree of Doctor of Philosophy in the Graduate School at the University of Kentucky By Sonja Sheena Pijut Lexington, Kentucky Director: Dr. Gregory A. Graf, Professor of Pharmaceutical Sciences Lexington, Kentucky 2017 Copyright © Sonja Sheena Pijut 2017 ABSTRACT OF DISSERTATION FACTORS REGULATING FEATURES OF METABOLIC SYNDROME The collective presence of central obesity, low HDL-cholesterol, and elevated triglycerides, blood pressure, and fasting blood glucose constitutes Metabolic Syndrome (MetS), a disease state that increases the risk of cardiovascular disease (CVD) and Type 2 Diabetes Mellitus (T2DM). Nonalcoholic fatty liver disease (NAFLD), present in up to 90% of obese adults, is also linked to MetS. As in CVD, disruptions in cholesterol metabolism play a contributing role in the development of T2DM and NAFLD. Genes involved in cholesterol synthesis, secretion, and catabolism are diurnally regulated in the liver and adipose. Disruptions in the sleep-wake cycle are thought to potentiate metabolic disorders associated with CVD, thus revealing a potential role of disrupted circadian rhythms in the development of MetS phenotypes. We initially observed that a group of clock-controlled genes in the Par bZip family were downregulated in adipose tissue of obese mice and humans. Further studies revealed that deletion of the core clock gene, Bmal1, from adipose tissue alone (ABKO mice) or in combination with the liver (LABKO mice) altered feeding behavior and locomotor activity. Obesity was increased in LABKO mice but there were no further detrimental effects in either ABKO or LABKO mice. Interestingly, high-fat diet suppressed Bmal1 transcript levels in adipose tissue suggesting that the muted effects observed with genetic Bmal1 deletion were likely due to the overpowering effects of a high-fat diet. Cholesterol metabolizing and bile acid synthesizing enzymes oscillate diurnally at the transcriptional level. Promoting cholesterol elimination through bile acid synthesis and biliary secretion is essential for reducing hepatic cholesterol, a perpetrating factor in the progression of NAFLD. Previous studies in animal models demonstrated that deletion of the hepatic cholesterol transporters, Abcg5 and Abcg8 (G5G8), decreased biliary cholesterol secretion and increased obesity and hepatic steatosis. Ursodiol (Urso) increased G5G8 protein expression and in combination with ezetimibe, a cholesterol-lowering agent, showed promise as a therapeutic for NAFLD. However, bile acid synthesis was suppressed in the presence of Urso and ezetimibe, suggesting that the overall effect on cholesterol elimination was minimized. The increase in G5G8 and decrease in bile acid synthesis was associated with an increase in Fgf15/19, a suppressor of bile acid synthesis. In order to determine if and how FGF15/19 regulates G5G8, mice were injected with FGF19. G5G8 protein expression and biliary total cholesterol were increased. Additionally, G5G8 localized to the canalicular surface of hepatocytes. Urso caused a similar localization of G5G8 that appeared to be dependent of the FGF15/19-FGFR4 signaling pathway. Interestingly, G5G8 was not required for maintaining cholesterol homeostasis in the presence of FGF15/19. Data from murine models suggest Urso and ezetimibe promote cholesterol elimination, though the effects may be limited by the suppression of bile acid synthesis. Nonetheless, there may be a therapeutic window in which optimal cholesterol elimination can be reached. Additionally, the effects of Urso and ezetimibe are variable between mice and humans. Given the clinical availability of the two drugs, the translatability into humans and the potential to address whether Urso and ezetimibe can minimize NAFLD is great. KEYWORDS: Obesity, Insulin Resistance, NAFLD, Circadian rhythm, G5G8, FGF15/19 Sonja Sheena Pijut February 22, 2017 Date FACTORS REGULATING FEATURES OF METABOLIC SYNDROME By Sonja Sheena Pijut Gregory A. Graf Director of Dissertation David J. Feola Director of Graduate Studies February 22, 2017 Date ACKNOWLEDGEMENTS The following dissertation was written with the invaluable insights and support of my dissertation chair, dissertation committee, friends, and family. First, my dissertation chair, Dr. Gregory A. Graf, has provided me with experiences and opportunities that have been instrumental in expanding my knowledge and skillset as a scientist. His dedication to research and educating students has been a source of inspiration throughout my training. The qualities of enthusiasm and perseverance he has instilled in me will continue to motivate me as I progress through my professional journey. Thank you to my dissertation committee, Dr. David J. Feola, Dr. Charles D. Loftin, and Dr. Ming C. Gong, for your expertise and advice. The support and guidance you have provided have facilitated my growth and progression though this doctoral program. Finally, thank you to my friends and family for their unconditional love and support. To my parents who have sacrificed so much to provide me with the best life possible, to my sister who is my role model in every aspect, to my husband who encourages me to pursue my dreams, and to my daughter who brings so much joy and happiness, I am indebted to you. iii TABLE OF CONTENTS Acknowledgments........................................................................................................................... iii List of Tables ................................................................................................................................. vii List of Figures ............................................................................................................................... viii Chapter 1: Introduction .................................................................................................................... 1 Overview of Metabolic Syndrome ............................................................................................ 1 History ................................................................................................................................ 1 Etiology and Pathophysiology ............................................................................................ 2 Clinical Significance and Treatment ................................................................................... 3 Obesity ...................................................................................................................................... 3 Adipose Tissue and Obesity................................................................................................ 3 Adipose Tissue Depots ....................................................................................................... 5 Insulin Resistance ...................................................................................................................... 5 Mechanisms of Obesity-Induced