Some VLDL remnants are taken up and can be degraded by the liver after their apo E component binds to the LDL receptor (rather than to the chylomicron remnant receptor as occurs with chylomicron remnants). Other VLDL remnants are converted into LDL (see Fig. 6.5) by a process that is not well understood, but which probably involves another lipase, hepatic triglyceride lipase. A single molecule of apo B100 is present in each particle in this metabolic cascade. The apo B in LDL binds to LDL receptors on cells throughout the body, thereby supplying them with cholesterol when required. The major site of LDL metabolism is the liver, where the level of expression of LDL receptors largely determines the rate of catabolism of plasma LDL.
