triglyceride-rich lipoprotein particle clearance

Definition

Target type: biologicalprocess

The process in which a triglyceride-rich lipoprotein particle is removed from the blood via receptor-mediated endocytosis and its constituent parts degraded. [GOC:BHF]

Triglyceride-rich lipoprotein (TRL) particle clearance is a complex process involving multiple steps and enzymes, primarily occurring in the liver and extrahepatic tissues.

1. **Lipoprotein Lipase (LPL) Mediated Hydrolysis:** TRLs, primarily chylomicrons (CM) from dietary fat and very-low-density lipoproteins (VLDL) from the liver, circulate in the bloodstream. LPL, an enzyme anchored to the endothelial surface of capillaries, particularly in muscle and adipose tissues, hydrolyzes triglycerides (TGs) within TRLs. This releases free fatty acids (FFAs) and glycerol. The FFAs are taken up by the tissues for energy or storage, while glycerol is transported back to the liver.

2. **Remnant Formation:** After LPL-mediated lipolysis, TRLs are transformed into smaller, denser particles known as remnants, enriched in cholesterol esters and apolipoproteins. These remnants are unable to bind to LPL and thus lose their capacity to undergo further lipolysis.

3. **Hepatic Uptake:** The remnants are then transported through the bloodstream, ultimately reaching the liver. Hepatic lipase (HL), another enzyme present on the surface of liver cells, can further hydrolyze remnant TGs. The remnants are then taken up by the liver via receptor-mediated endocytosis, facilitated by the interaction of apolipoprotein E (apoE) on the remnant surface with the LDL receptor (LDLR) on hepatocytes.

4. **Intracellular Processing:** Once inside the liver, the remnants undergo further processing. TGs are hydrolyzed by intracellular lipases, and cholesterol esters are hydrolyzed by cholesterol esterase. The freed cholesterol can be used for various cellular processes or secreted as bile acids.

5. **Excretion:** The byproducts of intracellular processing, including cholesterol, are then excreted as bile acids or incorporated into newly synthesized lipoproteins, maintaining the balance of lipid homeostasis.

In summary, TRL clearance is a tightly regulated process involving multiple enzymes, receptors, and tissues, primarily in the liver and extrahepatic tissues. It is essential for maintaining lipid homeostasis and ensuring efficient energy supply and storage for the body.'
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Proteins (1)

Compounds (1)