Elevated plasma triglycerides (TG) increase the risk of cardiovascular disease, a leading cause of morbidity and mortality in the United States. As the primary determinant of plasma TG levels, lipoprotein lipase (LPL), anchored by the endothelial cell protein GPIHBP1 to the capillary luminal surface, hydrolyzes circulating TG into free fatty acids that are taken up by peripheral tissues. LPL activity is tightly regulated to enable circulating TG be routed into cardiac and skeletal muscles to generate energy during fasting and into white adipose tissue (WAT) for storage in the fed state. However, the molecular mechanisms for regulating tissue-specific LPL activity during the fed-fast cycle are largely unknown. ANGPTL8 (lipasin) is a recently described TG metabolism regulator, which is specifically expressed in liver and adipose tissues. In the liver, which secretes ANGPTL8 into the circulation, ANGPTL8 expression is reduced by fasting and dramatically increased by feeding. In mice, ANGPTL8 deficiency causes hypotriglyceridemia, whereas its hepatic overexpression causes hypertriglyceridemia. Despite having great therapeutic potential in treating dyslipidemia, ANGPTL8?s functions and mechanism of action remain elusive. Based on our solid preliminary data, we propose to study the functional roles of ANGPTL8 and the mechanism by which it regulates TG metabolism.
In Aim 1, we will determine functional roles of ANGPTL8 in regulating TG trafficking, by performing fluxomics analysis with isotope-labeled TG in ANGPTL8 KO mice, wild-type mice with injection of an ANGPTL8 monoclonal TG- lowering antibody, as well as liver and adipose-specific KO mice.
In Aim 2, we will elucidate mechanisms of ANGPTL8-mediated inhibition of GPIHBP1-bound LPL. By using a novel cell-culture system to examine LPL complexed with GPIHBP1 on the endothelial cell surface, we will examine the interactions among ANGPTL8, ANGPTL3, and LPL-GPIHBP1 complexes. Upon completion, we will have revealed the molecular mechanism by which ANGPTL8 regulates LPL to direct TG trafficking to specific tissues during the fed-fast cycle, a physiological process of fundamental importance.

Public Health Relevance

Health Relevance Elevated plasma triglycerides increase the risk of cardiovascular disease, a leading cause of morbidity and mortality in the United States. This project aims to uncover the functions of ANGPTL8 and the mechanism by which it regulates triglyceride metabolism, and will establish ANGPTL8 as a novel drug target in treating hypertriglyceridemia.

Agency
National Institute of Health (NIH)
Institute
National Heart, Lung, and Blood Institute (NHLBI)
Type
Research Project (R01)
Project #
1R01HL134787-01A1
Application #
9381308
Study Section
Integrative Nutrition and Metabolic Processes Study Section (INMP)
Program Officer
Liu, Lijuan
Project Start
2017-06-01
Project End
2022-03-31
Budget Start
2017-06-01
Budget End
2018-03-31
Support Year
1
Fiscal Year
2017
Total Cost
$397,255
Indirect Cost
$103,680
Name
Wayne State University
Department
Genetics
Type
Schools of Medicine
DUNS #
001962224
City
Detroit
State
MI
Country
United States
Zip Code
48202
Chi, Xun; Britt, Emily C; Shows, Hannah W et al. (2017) ANGPTL8 promotes the ability of ANGPTL3 to bind and inhibit lipoprotein lipase. Mol Metab 6:1137-1149