Diversity Supplement for Genesee Martinez: Novel Liver Signaling Pathways Controlling Adiposity

Grants and Contracts Details


SUMMARY OF THE PARENT GRANT Almost two-thirds of adults in the United States are obese or overweight. Whether obesity arises from genetic factors or high caloric intake, it can still lead to insulin resistance and type II diabetes. Our recent data show that bilirubin (BR), which is considered an antioxidant, may function as a metabolic ligand that signals the nuclear receptor transcription factor PPARα to reduce lipid accumulation. We also found that BR induces the hepatic fibroblast growth factor 21 (FGF21) hormone via PPARα, which is known to have systemic effects on insulin sensitivity. For unknown reasons, BR plasma levels are lower in obese patients, and several obese patients progress to nonalcoholic fatty liver disease (NAFLD), which is likely due to obesity-induced insulin resistance. However, in patients with pathological liver disease such as Crigler-Najjar syndrome, the BR plasma levels are very high. This paradox may be explained by the hepatic UDP-glucuronosyltransferase 1-1 (UGT1A1) enzyme that conjugates BR. In humans, a polymorphism in the UGT1A1 gene (UGT1A1*28), known as Gilbert’s syndrome (GS), reduces expression resulting in increased plasma BR levels but not in liver disease. We have shown that humanized mice with the Gilbert’s polymorphism (UGT1A1*28) on a high-fat diet have significantly higher plasma BR levels, reduced adiposity, and insulin intolerance and are resistant to fatty liver disease. In our preliminary data, we show that microRNA-365 (miR365) suppresses Ugt1a1 expression and increases plasma BR levels. We also found that Ugt1a1 expression is higher in the livers of obese mice, while miR365 and plasma BR levels are lower, which indicates that miR365 targeting Ugt1a1 may increase plasma BR to regulate adiposity. Our central hypothesis is that BR functions as a metabolic ligand that activates the liver PPARα-FGF21 pathway to reduce adiposity and insulin resistance. Our hypothesis will be tested with three primary scientific aims: 1) Determine the selectivity of BR on PPAR isoforms; 2) Determine the systemic effects of BR mediated by hepatic FGF21, and 3) Determine if miR365 elevation of BR reduces adiposity and insulin resistance via PPARα. Collectively, this project is the first systematic investigation of the BR-PPARα-FGF21 module and its control of insulin resistance associated with obesity. The proposal provides advances to new strategies (miR365) for targeting this module to control adiposity, which offers therapeutic benefits. Parent grant Aim 1: Determine the selectivity of BR on PPAR isoforms Parent grant Aim 2: Determine the systemic effects of BR mediated by hepatic FGF21 Parent grant Aim 3: Determine if miR365 elevation of BR reduces adiposity and insulin resistance via PPARα. Collectively, this project is the first systematic investigation of the BR-PPARα-FGF21 module and its control of insulin resistance associated with obesity. THE SCOPE OF THE RESEARCH PLANNED FOR THE CANDIDATE: Genesee will play an integral role in the ongoing research of the approved parent grant as well as improve upon the understanding of bilirubin signaling. The proposed work in this supplement is not an expansion and does not address a change in scope. Additionally, the research proposed was not deleted by the Initial Review Group. This research will provide an understanding of the molecular mechanism defined in Aim 1 through which bilirubin regulates gene expression via PPAR? and extend into a better understanding of whether bilirubin also binds to the Aryl Hydrocarbon Receptor (AHR) to regulate gene expression. Genesee will test these mechanisms as proposed below. Supplement''s research relationship with the parent grant: The work described below is planned work for Ms. Genesee Martinez as part of her thesis work studying if bilirubin interacts with PPAR? or AHR and the selective actions of the molecule for each receptor. Genesee is already becoming familiar and confident in working with several of the technologies used within the lab, such as nuclear receptor ligand binding domains (LBDs) to the GAL4 DNA binding domain (DBD) UAS luciferase system for interrogating nuclear receptor-ligand binding. She has created knockout cell lines using CRISPR technology and used methods to calculate EC50, IC50, and KD values and pharmacological drug docking. All these technologies are important in pharmacology. What this opportunity will build upon and provide is technical skills and professional development to make Genesee a highly competitive candidate in the workforce. Genesee will master state-of-the-art techniques in the nuclear receptor field and be able to integrate pharmacology and physiology. The experiments Genesee will be performing will help develop a mechanism through which PPAR? and possibly AHR interact with bilirubin and alter yet-to-be-determined physiological events. The specific goals of the training are outlined as follows: 1. Learning new technology. To provide Genesee with in-depth training in obesity research and the pharmacological aspects of the interaction between bilirubin and AHR and bilirubin and PPAR?, using state-of-the-art technologies such as the PamGene PamStation, chromatin immunoprecipitation (ChIP) assays to determine gene promoters that bilirubin controls via PPAR? or AHR, bioinformatics and data analysis, histology, confocal microscopy. Genesee will also be trained in the area of animal procedures, including echo MRI, high-fat and low-fat diets, floxed and knockout technologies, mouse anatomy (fat pads, liver, and others), and metabolic cages. 2. Developing scientific writing skills. To enhance her scientific writing skills through publications, meeting abstracts, and poster and oral presentations. 3. Developing scientific communication skills. To expand her verbal communication skills through the Department of Pharmacology and Nutritional Sciences (DPNS) seminar series in which Genesee will give one yearly hour-long talk to our department, as well as presentations at local, state (Kentucky Physiology Society), national, and international conferences (e.g., Experimental Biology, ENDO (Endocrinology), Event at UK for graduate students, and many other opportunities). Additionally, we will develop her ability to communicate science effectively. 4. To promote her understanding of the responsible conduct of research (RCR). 5. Learning networking skills. To provide Genesee ample networking opportunities with senior scientists and peers, as well as the opportunity to learn peer review whenever possible. These experiences will prepare her for an F31 application. These all will lead Genesee to a Ph.D. that is competitive for an academic postdoc fellowship, which is where she would like to focus her career.
Effective start/end date7/3/203/31/25


  • National Institute Diabetes & Digestive & Kidney


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