Abstract
Ninety percent of plasma fatty acids (FAs) are contained within lipoprotein-triglyceride, and lipoprotein lipase (LPL) is robustly expressed in the heart. Hence, LPL-mediated lipolysis of lipoproteins is suggested to be a key source of FAs for cardiac use. Lipoprotein clearance by LPL occurs at the apical surface of the endothelial cell lining of the coronary lumen. In the heart, the majority of LPL is produced in cardiomyocytes and subsequently is translocated to the apical luminal surface. Here, vascular LPL hydrolyzes lipoprotein-triglyceride to provide the heart with FAs for ATP generation. This article presents an overview of cardiac LPL, explains how the enzyme works, describes key molecules that regulate its activity and outlines how changes in LPL are brought about by physiological and pathological states such as fasting and diabetes, respectively.
Highlights
With uninterrupted contraction being a unique feature of the heart, the cardiomyocyte has a high demand for energy
As LPLmediated lipolysis of lipoproteins is suggested to be a key source of fatty acids (FAs) for cardiac use [2], its regulation and its modification following diabetes require thorough investigation to help us understand the pathophysiology of diabetic heart disease as it relates to the metabolism of FAs, in order to advance its clinical management
We discovered that incubating endothelial cell (EC) in high glucose conditions triggered lysosomal AHpa to be released into the medium [36]
Summary
With uninterrupted contraction being a unique feature of the heart, the cardiomyocyte has a high demand for energy. GPIHBP1 platform enablesitlipoprotein-TG hydrolysis apical side of endothelial cell (4) At this location, a GPIHBP1 platform and enables lipoprotein-TG hydrolysis to generate FAs (5) that are delivered to the cardiomyocyte (6). This is an effective arrangement, as this pool of provides charged LPL is attached (by ionic interaction) to negatively charged heparan sulfatethe heart with aofrapidly reservoir. To reach the vascular lumen, LPL requires cosylphosphatidylinositol-anchored high-density lipoprotein-binding protein 1 detachment from HSPG and navigation across the interstitial space, made possible by (GPIHBP1) [12]. On the apical side of the Ecs, the ability of GPIHBP1 to avidly bind both lipoprotein-TG and LPL allows it to serve as a platform for the lipolytic processing of TG, which releases FAs for use by cardiomyocytes [15,16,17]. An additional difference between the two lipoproteins and LPL action is that lipolysis of VLDL-TG produces FAs that are transported into cells via CD36, an FAs transporter, whereas hydrolysis of chylomicrons generates a greater local concentration of FAs that enter cells by passive flip-flop and/or non-CD36-mediated transport mechanisms [19]
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