Figure 3. VLDL‐LDL particle metabolism.

This figure illustrates schematically the regulation of VLDL and LDL particle number in plasma. VLDL particles are secreted by the liver into the plasma compartment, from which they are either removed directly by the liver after much of their TG have been removed or converted to LDL particles. At steady state, the rate at which VLDL particles are secreted from the liver is equal to the rate at which they are removed from plasma. Once steady state is achieved, either an increase in the rate of production or a decrease in the rate of removal will produce an increased VLDL particle number. Similarly, the rate at which LDL particles are produced at steady state is equal to the rate at which they are removed from plasma. LDL particles are produced by conversion of VLDL to LDL particles and are removed either by a specific clearance pathway or by multiple nonspecific pathways. Almost all LDL particles are cleared from plasma by the liver. Only a small minority are removed by peripheral cells. IDL indicates intermediate‐density lipoprotein; LDL indicates low‐density lipoprotein; TG, triglycerides; and VLDL, very low‐density lipoprotein.