Editing Intermediate-density lipoprotein (section)

{{short description|One of the five major groups of lipoprotein}}
'''Intermediate-density lipoproteins''' ('''IDLs''') belong to the [[lipoprotein]] particle family and are formed from the degradation of [[very low-density lipoprotein]]s as well as [[high-density lipoprotein]]s.<ref>Narang D, Al-Horani RA. Biochemistry, Intermediate Density Lipoprotein. 2025 Feb 17. In: StatPearls [Internet]. Treasure Island (FL): StatPearls Publishing; 2025 Jan–. PMID: 40198056.</ref><ref>{{cite web |url=https://www.wikipathways.org/index.php/Pathway:WP430 |title = Statin inhibition of cholesterol production (Homo sapiens) - WikiPathways}}</ref> IDL is one of the five major groups of lipoproteins ([[chylomicrons]], [[VLDL]], IDL, [[LDL]], [[High-density lipoprotein|HDL]]) that enable fats and cholesterol to move within the water-based solution of the bloodstream. Each native IDL particle consists of protein that encircles various lipids, enabling, as a water-soluble particle, these lipids to travel in the aqueous [[blood]] environment as part of the fat transport system within the body. Their size is, in general, 25 to 35&nbsp;nm in diameter, and they  contain primarily a range of [[Triglyceride|triglycerides]] and [[cholesterol]] [[ester]]s. They are cleared from the [[Blood plasma|plasma]] into the [[liver]] by [[receptor-mediated endocytosis]], or further degraded by [[hepatic lipase]] to form [[low-density lipoprotein|LDL]] particles.{{cn|date=March 2023}}

Although one might intuitively assume that "intermediate-density" refers to a density between that of high-density and low-density lipoproteins, it in fact refers to a density between that of low-density and very-low-density lipoproteins.{{cn|date=March 2023}}
In general, IDL, somewhat similar to [[low-density lipoprotein]] (LDL), transports a variety of triglyceride fats and cholesterol and, like LDL, can also promote the growth of [[atheroma]].{{Citation needed|date=March 2017}}

[[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). The IDL particles have lost most of their triglyceride, but they retain [[cholesteryl esters]]. Some of the IDL particles are rapidly taken up by the liver; others remain in circulation, where they undergo further triglyceride hydrolysis by [[hepatic lipase]] and are converted to LDL. A distinguishing feature of the IDL particle is their content of multiple copies of the receptor ligand [[Apolipoprotein E|ApoE]] in addition to a single copy of [[Apolipoprotein B|ApoB-100]]. The multiple copies of ApoE allow IDL to bind to the LDL receptor with a very high affinity. When IDL is converted to LDL, the ApoE leaves the particle and only the ApoB-100 remains. Thereafter, the affinity for the [[LDL receptor]] is much reduced.<ref>Brown MS and Goldstein JL (1986). A receptor-mediated pathway for cholesterol homeostasis. Science 232:34–47.</ref>