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Glycolysis and Glyceroneogenesis In GLYCOLYSIS AND GLYCERONEOGENESIS IN ADIPOCYTES: EFFECTS OF ROSIGLITAZONE, AN ANTI-DIABETIC DRUG By SOREIYU UMEZU Bachelor of Science in Biochemistry and Molecular Biology Oklahoma State University Stillwater, OK 2005 Submitted to the Faculty of the Graduate College of the Oklahoma State University in partial fulfillment of the requirements for the Degree of DOCTOR OF PHILOSOPHY July, 2010 GLYCOLYSIS AND GLYCERONEOGENESIS IN ADIPOCYTES: EFFECTS OF ROSIGLITAZONE, AN ANTI-DIABETIC DRUG Dissertation Approved: Dr. Jose L Soulages Dissertation Adviser Dr. Chang-An Yu Dr. Andrew Mort Dr. Jack Dillwith Dr. A. Gordon Emslie Dean of the Graduate College ii ACKNOWLEDGMENTS First, I would like to immensely thank my advisor, Dr. Jose Soulages, for his support and guidance throughout my graduate studies. Without Dr. Soulages extensive expertise and knowledge along with his sense of humor I would not have achieved my goal of obtaining my Doctorate in Biochemistry. I would also like to thank Dr. Estela Arrese for her kind and generous advice. Both Dr. Soulages and Dr. Arrese have made a tremendous impact on me personally and professionally. I would like to thank all the members of my committee: Dr. Chang-An Yu, Dr. Andrew Mort, and Dr. Jack Dillwith who have devoted their time reading my dissertation and their patience for my procrastination. Their support and guidance has been invaluable and extremely appreciative. Most importantly, I want to acknowledge my parents: (Dr.) Mrs. Fumie Umezu and (Dr.) Mr. Yasuiki Umezu, for their unwavering support of me throughout my time in the U.S. and for suffering me while I’m doing whatever I want in my life. Lastly, I want to thank to my good friends, Alisha Howard, Philip Verghese, Laticia Rivera, Noah Burns, and Masakazu Hamada. They have provided supports and smile to overcome obstacles in my graduate life. iii TABLE OF CONTENTS Chapter Page I. INTRODUCTION ......................................................................................................1 Diabetes Mellitus .....................................................................................................1 Type II Diabetes .......................................................................................................2 Adipose Tissue and Adipocytes ...............................................................................3 Fatty Acid Toxicity ..................................................................................................4 The Origin of NEFA ................................................................................................5 Metababolic Effects of Rosiglitazone ......................................................................6 Glyceroneogenesis ...................................................................................................7 Glycerol Kinase .......................................................................................................8 Research Objectives and Significance ...................................................................10 II. ESTIMATION OF METABOLISM OF GLUCOSE AND TRIACYLGLYCEROL IN ADIPOCYTES ........12 Introduction ............................................................................................................12 Experimental Procedures .......................................................................................12 Results ....................................................................................................................15 Utilization of glucose carbons for lipid synthesis ......................................15 Actual rates of glucose conversion into the lipids of adipocytes ......................................17 Summary ................................................................................................................19 iv Chapter Page III. CHANGES IN THE METABOLISM OF GLUCOSE AND TG IN ADIPOCTE TREATED WITH ROSIGLITAZONE ......................20 Introduction ............................................................................................................20 Experimental Procedure .........................................................................................21 Results ....................................................................................................................22 Effect of RGZ treatment in fatty acid metabolism................................22 Effect of RGZ treatment in glucose metabolism ..................................26 Effect of RGZ on the activities and expressions of some enzymes involved in TG and glucose metabolism ................21 Summary ................................................................................................................30 IV. CONTRIBUTION OF GLYCOLYISIS AND GLYCERONEOGENESIS TO THE SYNTHESIS OF GLYCERIDE-GLYCEROL: EFFECT OF RGZ ....33 Introduction ............................................................................................................33 Experimental Procedure .........................................................................................34 Results ....................................................................................................................38 Utilization of glucose for the synthesis of glyceride-glycerol and fatty acids: effect of RGZ. ...........38 Utilization of pyruvate for the synthesis of glyceride-glycerol and fatty acids: effect of RGZ ............40 Effect of pyruvate on the metabolism of adipocytes ............................42 Summary ................................................................................................................44 V. DISCUSSION ........................................................................................................45 Summary of the Study ...........................................................................................45 Rosiglitazone and Metabolism of Adipocytes .......................................................46 Lipolysis and FA Oxidation .............................................................................47 Glycolysis and G-G Synthesis .........................................................................49 FA Synthesis and Re-esterification ..................................................................49 Glyceroneogenesis and Glycerol Kinase .........................................................50 REFERENCES ............................................................................................................52 v LIST OF TABLES Table Page Table I: Effects of insulin and isoproterenol on the metabolism of 3T3L-1 adipocytes .......................16 Table II: Glycerol and NEFA release in response to RGZ ..........................................24 Table III: RGZ-induced changes in glycolysis ............................................................26 vi LIST OF FIGURES Figure Page 1. Metabolic routes involved in the synthesis of glyceride-glycerol in adipocytes .................................9 2. Incorporation of glucose carbons into the lipids of adipocytes .............................17 3. Rates of glucose utilization for lipid synthesis. .....................................................18 4. Effects of RGZ concentration and incubation time on NEFA release from adipocytes. ..............................23 5. Average NEFA reduction and increase in lipolysis in RGZ-treated adipocytes ...............................24 6. Effects of RGZ on intracellular FA, tissue TG, and NEFA absorption in adipocytes ...............................25 7. Intracellular glycogen content in 3T3L-1 adipocytesis is altered by RGZ ............27 8. Effect of RGZ on the expression of glycolytic enzymes .......................................28 9. Rosiglitazone up-regulates GK expression but not activity ...................................29 10. Effect of RGZ on the expression of lipases ...........................................................30 11. The overview of the RGZ-activated pathway for the synthesis of G-G from glucose in 3T3L-1 adipocytes. ........32 12. Utilization of glucose for glyceride-glycerol and fatty acids.................................39 13. Rate of glyceroneogenesis .....................................................................................40 14. Contribution of glyceroneongenesis for the synthesis of G-G in adipocytes ........41 15. Relative NEFA production is increased in response to pyruvate...........................43 vii CHAPTER I INTRODUCTION Diabetes Mellitus Diabetes mellitus is the metabolic disorder affecting metabolism of carbohydrates, lipids, proteins in every type of cells in the body. This metabolic disorder is characterized by insensitivity to insulin, insufficient/absent insulin secretion, or both. Currently, around 23.6 million people (7.8% of the population) are affected by this metabolic syndrome in the United States [1]. Moreover, more than 246 millions are estimated to have diabetes worldwide, and this number is expected to increase in the next few decades [2-4]. In the U.S alone, the cost of diabetes, including medical care and social costs, reached around $174 billion in the year of 2007 [5]. This cost is also expected to increase drastically in next few years, therefore diabetes mellitus is now considered as epidemic. There are several forms of diabetes. Among these cases of diabetes, type I and type II are the ones that affect most of the patients (95 to 99%). Type I diabetes (T1D) is caused by pancreas deficiency in insulin production [6, 7] whereas type II diabetes (T2D) is characterized
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