Dissertation
MicroRNA-dependent mechanisms of thrombosis in obesity
University of Iowa
Doctor of Philosophy (PhD), University of Iowa
Summer 2016
DOI: 10.25820/etd.007529
Abstract
Thrombotic events such as myocardial infarction, stroke, and venous thromboembolism are the leading cause of mortality and morbidity worldwide. Obesity has become an epidemic in the industrialized countries and is associated with an increased incidence of thrombotic events. Mechanisms of thrombosis in obesity, however, remain to be defined. As a result, there are no therapeutics to prevent and treat thrombosis specifically in obese individuals. microRNA (miR) are small molecules that mature via sequential processing by the endoribonucleases Drosha and Dicer and function by posttranscriptional inhibition of messenger RNA (mRNA). The goal of the current study was to determine if obesity predisposes to a prothrombotic state via alterations in miR profile.
Chapter 1 summarizes our current knowledge of thrombosis in obesity as well as potential mechanisms that may link these two conditions. Biogenesis and functions of miR are also discussed. Chapter 2 describes a murine model of obesity (diet-induced obesity (DIO)) and the prothrombotic phenotype conferred by this model. We found that DIO accelerated arterial thrombosis, increased the incidence of venous thrombosis, and enhanced platelet activation. Chapter 3 examines effects of DIO on the plasma exosomal miR profile. We observed a phenomenon of global downregulation of exosomal miR in obesity, an unexpected finding. We found that levels of >90% of miR in plasma exosomes were reduced in DIO. Further studies revealed that DIO caused markedly decreased expression of Dicer mRNA and protein and total abrogation of Dicer activity in white adipose tissue (WAT) of obese mice, suggesting a potential mechanism of miR repression in obesity. Chapter 4 describes the identification and characterization of the relationship between miR-148a and plasminogen activator inhibitor-1 (PAI-1) as a specific mechanism of thrombosis in obesity. We found that DIO increased PAI-1 mRNA expression in WAT and PAI-1 protein levels in plasma. Bioinformatic analysis revealed that miR-148a is capable of binding to and inhibiting PAI-1 mRNA. We further found that expression of miR-148a was decreased in WAT of mice with DIO. Transfection of murine endothelial cells and primary adipocytes with a miR-148a mimic suppressed the expression of PAI-1 mRNA, suggesting a causative relationship between miR-148a and PAI-1. Taken together, these data suggest that obesity may confer a prothrombotic state in part via downregulation of miR-148a in WAT and upregulation of PAI-1 expression in WAT and PAI-1 levels in plasma. Chapter 5 outlines future directions, including the potential development of next generation therapeutics based on such technologies as siRNA, CRISPR-Cas9, miR, long non-coding RNA, and bioinformatics techniques.
Details
- Title: Subtitle
- MicroRNA-dependent mechanisms of thrombosis in obesity
- Creators
- Ilya O. Blokhin
- Contributors
- Steven R. Lentz (Advisor)E. Dale Abel (Committee Member)Isabella M. Grumbach (Committee Member)Paul B. McCray Jr (Committee Member)Peter M. Snyder (Committee Member)
- Resource Type
- Dissertation
- Degree Awarded
- Doctor of Philosophy (PhD), University of Iowa
- Degree in
- Molecular and Cellular Biology
- Date degree season
- Summer 2016
- Publisher
- University of Iowa
- DOI
- 10.25820/etd.007529
- Number of pages
- xiii, 111 pages
- Copyright
- Copyright 2016 Ilya O. Blokhin
- Language
- English
- Date submitted
- 04/28/2016
- Description illustrations
- Illustrations, tables, graphs, charts
- Description bibliographic
- Includes bibliographical references (pages 105-111).
- Public Abstract (ETD)
Thrombotic events such as myocardial infarction and stroke are a leading cause of mortality worldwide. Obesity has become an epidemic in developed countries and is associated with an increased incidence of myocardial infarction and stroke. However, the mechanisms by which obesity predisposes to thrombotic events are not clear. Lack of mechanistic insight hampers the development of drugs to prevent and treat thrombosis in obese patients.
The goal of this work was to determine whether obesity causes thrombosis by changing the expression of so-called “microRNA” (miR). miR are small molecules that function to inhibit the expression of target genes. We hypothesized that either increased expression of specific miR leads to decreased levels of antithrombotic proteins or decreased expression of specific miR causes increased levels of prothrombotic proteins in obesity. We found that mice with diet-induced obesity (DIO) had aggravated thrombosis in both arteries and veins. We also found that DIO decreased levels of most of miR in plasma particles called exosomes. We determined that one suppressed miR, miR-148a, can inhibit the expression of a prothrombotic protein called plasminogen activator inhibitor-1 (PAI-1), and that mice with DIO had decreased levels of miR-148a and elevated levels of PAI-1. Next, we showed that increasing the concentrations of miR-148a in cells could lower PAI-1 levels. Thus, our work revealed a novel, miR-dependent mechanism of thrombosis in obesity. This work lays the foundation for the development of miR-148a-based therapeutics to potentially prevent and treat thrombosis in obese patients.
- Academic Unit
- Interdisciplinary Graduate Program in Molecular Medicine
- Record Identifier
- 9984647557902771
Metrics
3 Record Views