PROJECT I ? ROLE OF BILIRUBIN IN PROTECTION AGAINST CARDIOMETABOLIC SYNDROME IN OBESITY PROJECT SUMMARY/ABSTRACT Obesity is a significant contributor to cardiometabolic diseases including hypertension, non-alcoholic fatty liver disease (NAFLD) and type II diabetes. All of these conditions contribute to the increased morbidity and mortality rates of obesity. Large population studies have demonstrated a negative correlation between serum bilirubin levels and development of cardiovascular disease and metabolic disorders including NAFLD and type II diabetes. Despite these correlative studies, the mechanism by which bilirubin protects against cardiometabolic disease is not known. We have exciting data demonstrating for the first time that bilirubin signals through nuclear hormone receptors such as peroxisome proliferator-activated receptor (PPAR?) to protect against cardiometabolic disorders. In addition, bilirubin can also inactivate glycogen synthase kinase-3? (GSK3?) to increase PPAR? target genes such as fibroblast growth factor 21 (FGF21); however, the specific roles of GSK3? inactivation/PPAR? activation to the anti-hypertensive, anti-steatotic and anti-diabetic actions of moderate hyperbilirubinemia are not known. Biliverdin reductase (BVR) is the enzyme responsible for reduction of biliverdin to bilirubin. It can generate bilirubin found in the plasma and generated inside the cell. The goal of this proposal is to test the central hypothesis that bilirubin and BVRA protect against obesity- induced hepatic steatosis, insulin resistance and hypertension via activation of the PPAR??signaling axis.
Aim 1 will test the hypothesis that chronic moderate hyperbilirubinemia resulting from bilirubin treatment or antagonism of hepatic UGT1A1 lowers blood pressure and reverses dietary obesity-induced hepatic steatosis and hepatic insulin resistance.
Aim 2 will test the hypothesis that moderate hyperbilirubinemia lowers blood pressure and reverses hepatic steatosis and insulin resistance via activation of PPAR?.
Aim 3 will test the hypothesis that that specific loss of hepatic bilirubin generation enhances hepatic steatosis and insulin resistance through a GSK3??mediated pathway that decreases PPAR? activity. Findings of these studies will have profound implications on development of moderate hyperbilirubinemia as a novel therapy for treatment of obesity-induced cardiometabolic disease. These studies will also determine the novel role of bilirubin as a nuclear hormone receptor signaling molecule and the role of this mechanism in protection against obesity- induced cardiometabolic diseases such as hypertension, NAFLD and type II diabetes.

Public Health Relevance

PROJECT I ? ROLE OF BILIRUBIN IN PROTECTION AGAINST CARDIOMETABOLIC SYNDROME IN OBESITY PROJECT NARRATIVE Obesity is a significant contributor to cardiovascular diseases such as hypertension, non-alcoholic fatty liver disease (NAFLD) and type II diabetes all of which place a heavy burden on our economy. Bilirubin is a naturally produced bile pigment which has been correlated with decreased incidence of cardiovascular disease including hypertension, NAFLD and diabetes; however, the mechanism by which bilirubin may have these beneficial actions is unknown. This proposal will determine effective strategies for increasing bilirubin levels as well as determine the role of PPAR? in the beneficial actions of bilirubin to reverse obesity induced cardiovascular disease.

Agency
National Institute of Health (NIH)
Institute
National Institute of General Medical Sciences (NIGMS)
Type
Exploratory Grants (P20)
Project #
5P20GM104357-07
Application #
9745637
Study Section
Special Emphasis Panel (ZGM1)
Project Start
Project End
Budget Start
2019-05-01
Budget End
2020-04-30
Support Year
7
Fiscal Year
2019
Total Cost
Indirect Cost
Name
University of Mississippi Medical Center
Department
Type
DUNS #
928824473
City
Jackson
State
MS
Country
United States
Zip Code
39216
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