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Chylomicron structure ApoA, ApoB, ApoC, ApoE (apolipoproteins); T (triacylglycerol); C (cholesterol); green (phospholipids). Chylomicrons transport lipids absorbed from the intestine to adipose, cardiac, and skeletal muscle tissue, where their triglyceride components are hydrolyzed by the activity of the lipoprotein lipase, allowing the released free fatty acids to be absorbed by the tissues.
Very-low-density lipoprotein (VLDL), density relative to extracellular water, is a type of lipoprotein made by the liver. [1] VLDL is one of the five major groups of lipoproteins (chylomicrons, VLDL, intermediate-density lipoprotein, low-density lipoprotein, high-density lipoprotein) that enable fats and cholesterol to move within the water-based solution of the bloodstream.
This core also carries varying numbers of triglycerides and other fats and is surrounded by a shell of phospholipids and unesterified cholesterol, as well as the single copy of Apo B-100. LDL particles are approximately 22 nm (0.00000087 in.) to 27.5 nm in diameter and have a mass of about 3 million daltons. [ 7 ]
Chylomicrons carry triglycerides (fat) from the intestines to the liver, to skeletal muscle, and to adipose tissue. Very-low-density lipoproteins (VLDL) carry (newly synthesised) triglycerides from the liver to adipose tissue. Intermediate-density lipoproteins (IDL) are intermediate between VLDL and LDL.
Measuring the concentration of sd-LDL is expensive. However, since it is produced from VLDL, it can be inferred indirectly by estimating VLDL levels in the blood. That estimate is typically obtained by measuring triglyceride levels after at least eight hours of fasting, when chylomicrons have been totally removed from the blood by the liver.
VLDL is a large, triglyceride-rich lipoprotein secreted by the liver that transports triglyceride to adipose tissue and muscle. The triglycerides in VLDL are removed in capillaries by the enzyme lipoprotein lipase , and the VLDL returns to the circulation as a smaller particle with a new name, intermediate-density lipoprotein (IDL).
It collects triglycerides from very-low-density lipoproteins (VLDL) or Chylomicrons and exchanges them for cholesteryl esters from high-density lipoproteins (HDL), and vice versa. Most of the time, however, CETP does a heteroexchange, trading a triglyceride for a cholesteryl ester or a cholesteryl ester for a triglyceride.
[51] [52] [53] It is also a ligand for α2M, GP330, and VLDL receptors. [23] LPL has been shown to be a ligand for LRP2, albeit at a lower affinity than for other receptors; however, most of the LPL-dependent VLDL degradation can be attributed to the LRP2 pathway. [23] In each case, LPL serves as a bridge between receptor and lipoprotein.