Low-Density Lipoprotein (LDL)

A Low-Density Lipoprotein (LDL) is a lipoprotein that transports cholesterol and other fat molecules to peripheral tissues throughout the body via the bloodstream.

• AKA: LDL, Bad Cholesterol, Beta-Lipoprotein.
• Context:
  • It can typically deliver Fat Molecules to cells for membrane maintenance and hormone production.
  • It can typically transport approximately 70% of the blood cholesterol in human circulation.
  • It can typically contain a single apolipoprotein B-100 molecule as its primary structural protein component.
  • It can typically undergo endocytosis through LDL receptor-mediated pathways in peripheral tissues.
  • It can typically regulate cellular cholesterol homeostasis through receptor feedback mechanisms.
  • ...
  • It can often become Oxidized LDL within arterial walls, triggering inflammatory responses.
  • It can often be elevated in hereditary hypercholesterolemia, metabolic syndrome, and high-saturated fat diets.
  • It can often accumulate in arterial intima, forming atherosclerotic plaques over extended time periods.
  • It can often initiate foam cell formation when macrophages ingest oxidized LDL particles.
  • It can often interact with arterial proteoglycans, promoting retention and modification.
  • ...
  • It can range from being a Small Dense LDL to being a Large Buoyant LDL, depending on its particle size and lipid-to-protein ratio.
  • It can range from being a Normal LDL to being a Glycated LDL, depending on its exposure to high blood glucose.
  • It can range from being a Native LDL to being an Oxidized LDL, depending on its oxidative modification status.
  • It can range from being a Beneficial LDL to being an Atherogenic LDL, depending on its particle characteristics and concentration.
  • ...
  • It can have Structural Components including phospholipid monolayer, free cholesterol, cholesteryl esters, and triglycerides.
  • It can have Density Property between 1.019–1.063 g/mL, placing it between intermediate-density lipoprotein and high-density lipoprotein.
  • It can have Particle Size typically ranging from 18-25 nm in diameter.
  • It can have Metabolic Origin from the delipidation of very low-density lipoprotein in the circulation.
  • ...
  • It can be Elevated during familial hypercholesterolemia, hypothyroidism, and nephrotic syndrome.
  • It can be Reduced during statin therapy, PCSK9 inhibitor treatment, and plant-based diet.
  • It can be Modified by oxidative stress, glycation, and lipolytic enzymes.
  • ...
• Examples:
  • LDL Subclasses, such as:
    • Density-Based LDL Subclasses, such as:
      • LDL-I for lowest density LDL fraction.
      • LDL-II for intermediate density LDL fraction.
      • LDL-III for higher density LDL fraction.
      • LDL-IV for highest density LDL fraction.
    • Size-Based LDL Subclasses, such as:
      • Large Buoyant LDL for lower atherogenic risk.
      • Small Dense LDL for higher atherogenic potential.
  • Modified LDL Forms, such as:
    • Chemical Modification LDLs, such as:
      • Oxidized LDL for inflammatory signaling in arterial walls.
      • Glycated LDL for advanced glycation endproduct formation in diabetes.
      • Acetylated LDL for experimental scavenger receptor binding.
    • Physical Modification LDLs, such as:
      • Aggregated LDL for enhanced arterial retention.
      • Electronegative LDL for increased cytotoxicity.
  • Clinical LDL Markers, such as:
    • LDL Cholesterol Measurements, such as:
      • Direct LDL-C for accurate LDL cholesterol quantification.
      • Calculated LDL-C for estimated LDL cholesterol assessment.
    • Advanced LDL Assessments, such as:
      • LDL Particle Number for improved cardiovascular risk prediction.
      • LDL Peak Particle Size for atherogenic profile evaluation.
  • ...
• Counter-Examples:
  • High-Density Lipoprotein, which removes excess cholesterol from peripheral tissues and transports it to the liver for excretion, rather than delivering fat molecules to cells.
  • Very Low-Density Lipoprotein, which primarily transports endogenous triglycerides from the liver to peripheral tissues, rather than mainly carrying cholesterol.
  • Intermediate-Density Lipoprotein, which represents a transitional lipoprotein between VLDL and LDL in the delipidation cascade, rather than the final cholesterol-rich product.
  • Chylomicron, which transports dietary lipids from the intestine to peripheral tissues, rather than endogenous lipids from the liver.
• See: Body Fat, Very Low-Density Lipoprotein, Adipose Visceral Fat, Atherosclerosis, Apolipoprotein B, Familial Hypercholesterolemia, Cardiovascular Disease.

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References

2021

• (Wikipedia, 2021) ⇒ https://en.wikipedia.org/wiki/Low-density_lipoprotein Retrieved:2021-8-26.
  • Low-density lipoprotein (LDL) is one of the five major groups of lipoprotein which transport all fat molecules around the body in the extracellular water. These groups, from least dense to most dense, are chylomicrons (aka ULDL by the overall density naming convention), very low-density lipoprotein (VLDL), intermediate-density lipoprotein (IDL), low-density lipoprotein (LDL) and high-density lipoprotein (HDL). LDL delivers fat molecules to cells. LDL is involved in atherosclerosis, a process in which it is oxidized within the walls of arteries.

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