Lipoprotein
Because cholesterol belongs to the lipid family (that is, fats), it is not water soluble and thus cannot dissolve in our plasma like glucose or sodium and travel freely through our circulation. So it must be carted around in tiny spherical particles called lipoproteins—the final "L" in LDL and HDL—which act like little cargo submarines. As their name suggests, these lipoproteins are part lipid (inside) and part protein (outside); the protein is essentially the vessel that allows them to travel in our plasma while carrying their water-insoluble cargo of lipids, including cholesterol, triglycerides, and phospholipids, plus vitamins and other proteins that need to be distributed to our distant tissues. - Outlive
HDL is more dense because it has more protein relative to lipids.
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LDL is less dense because it carries more lipids (cholesterol and triglycerides) relative to protein.
Wrapped by one apoB with variance of amount of Cholesterol
LDL is wrapped by 1-apoB particle.
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the amount of cholesterol per LDL particle varies >2-fold between individuals - pmc.nih.gov
Ideally LDL-C is in 10 to 20 mg/dL range (Much lower than current guidelines)
“Many doctors, and in fact many of you reading this, might be shocked to see such a low LDL-C target: 10 to 20 mg/dL? Most guidelines consider lowering LDL-C to 70 mg/dL to be “aggressive,” even for secondary prevention in high-risk patients, such as those who have already had a heart attack. It’s also natural to ask whether such extremely low levels of LDL-C and apoB are safe, given the ubiquity and importance of cholesterol in the human body. But consider the following: infants, who presumably require the most cholesterol, in order to meet the enormous demands of their rapidly growing central nervous system, have similarly low levels of circulating cholesterol, without any developmental impairment. Why? Because the total amount of cholesterol contained in all our lipoproteins—not just LDL, but also HDL and VLDL—represents only about 10 to 15 percent of our body’s total pool of cholesterol. So the concern is unwarranted, as demonstrated by scores of studies showing no ill effects from extremely low LDL concentrations.” - Outlive
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Lipoprotein that primarily transports triglycerides (fats) from your liver to tissues throughout your body.
There are also very-low-density lipoproteins, or VLDLs, which we mentioned in the previous chapter, as well as intermediate-density lipoproteins, or IDLs. These carry even more fat than the LDLs, much of it in the form of triglycerides, and they are also marked with apoB. Also: While HDL particles have multiple apoAs, each LDL (or VLDL, or IDL) has only one apoB particle, making it relatively easy to measure their concentration. - Outlive
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HDL and LDL Lipoproteins: Density and Function
The reason they're called high- and low-density lipoproteins (HDL and LDL, respectively) has to do with the amount of fat relative to protein that each one carries. LDLs carry more lipids, while HDLs carry more protein in relation to fat, and are therefore more dense.
Also, these particles (and other lipoproteins) frequently exchange cargo with one another, which is part of what drives me crazy about labeling them "good" and "bad." When an HDL transfers its "good cholesterol" to an LDL particle, does that cholesterol suddenly become "bad"?
The answer is no—because it's not the cholesterol per se that causes problems but the nature of the particle in which it's transported. Each lipoprotein particle is enwrapped by one or more large molecules, called apolipoproteins, that provide structure, stability, and, most importantly, solubility to the particle.
HDL particles are wrapped in a type of molecule called apolipoprotein A (or apoA), while LDL is encased in apolipoprotein B (or apoB). This distinction may seem trivial, but it goes to the very root cause of atherosclerotic disease: every single lipoprotein that contributes to atherosclerosis—not only LDL but several others—carries this apoB protein signature. - Outlive
Children
- HDL = High-Density Lipoprotein
- IDL = Intermediate-density Lipoprotein
- LDL = Low-Density Lipoprotein
- Lp(a)
- VLDL = Very Low-Density Lipoprotein)
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