LDL or Low-Density Lipoprotein is often thought as measurement and type of cholesterol in the lipid profile. However, LDL itself is neither a laboratory measurement nor represents quality of the cholesterol. So, what is LDL? To understand LDL, we need to learn about cholesterol, why we need it and what is a role of LDL.
Cholesterol is essential lipid and created in all our cells. Cholesterol is found in cell membrane, which gives fluid like texture to our cells. Cholesterol is also a precursor to our hormones such as testosterone, estrogen, progesterone, cortisol and so on. Without cholesterol, we won’t have any of them, including our cells, and with out them we won’t be alive.
Cholesterol is made in all our cells, however, certain cells cannot produce enough cholesterol and must be transported from other cells, such as liver cells, that can produce more cholesterol. To transport cholesterol the body prefers to send it through our bloodstream. Blood as you may know is made of protein and platelets which is consists of water. Since cholesterol is lipid, which is hydrophobic, it cannot be transferred through bloodstream. Therefore, body creates a vehicle for the cholesterol called lipoprotein. Lipoprotein is partially lipid and partially protein. The lipid side of lipoprotein secure around the lipids including cholesterol and protein side, which is hydrophilic, allow the lipids to be transported from one cell to another through the bloodstream.
Definitions
The name HDL, LDL, and VLDL is referring to the density of lipoprotein. The cholesterol that are transported by those lipoproteins are still an essential lipid. Therefore, LDL itself is neither a laboratory measurement nor represents quality of the cholesterol. Actual measurements for LDL are LDL-C which is LDL cholesterol concentration (optimal: <100mg/dL), which means number of cholesterol carried by LDL. There is also LDL-P which is a particle number for LDL (optimal: <1,000).
Transportation to Cells
When additional cholesterol is required, cells create necessary LDL receptors. Once the LDL particle binds to the receptor, LDL drops off the cholesterol to the cell and repeat the cycle.
Size Pattern
LDL particles can be categorized by its size, large LDL (Pattern A) and small LDL (Pattern B). Some evidence shows that small LDL has correlation with coronary heart disease (CHD) due to its size can penetrate endothelium which is a thin layer of membrane that lines inside of the heart and blood vessels. You may hear from your doctor concerning about small LDL number is because of possible correlation to coronary heart disease.
This risk factor can be increased by lack of physical activity, smoking, poor nutrition habits, poor sleep habit, hypertension and metabolic syndrome which have correlation to damage to endothelium. With damaged endothelium, LDL particles can penetrate more easily, which can lead to plaque build up.
Oxidation
LDL particles can be oxidized from free-radicals, in both lipid and protein portion of lipoprotein in vascular wall. Lipids that are transported by LDL can also be oxidized which can be derived from our diet. When food is rich in processed fat (ex: margarines, chips, majority of cooking oil, etc.) is consumed, it can be oxidized by light and heat prior to entering our body. Oxidized LDL is known to associated with atherosclerosis. Therefore, it is suggested to consume whole natural food source instead of highly processed food.
Kota Shimada
Comments