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Introduction

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High-Yield Terms

  • Lipoprotein: complex of variable protein and lipid composition responsible for transport of fats throughout the body

  • Apolipoprotein: lipid-binding proteins of lipoprotein complexes

  • Apolipoprotein A-IV (apoA-IV): synthesized in intestines and hypothalamus, synthesis increased upon fat consumption, inhibits desire for food intake

  • Chylomicron: lipoprotein complex generated from dietary lipids within the enterocytes of the intestines

  • VLDL: lipoprotein complex generated from endogenous (or dietary) lipids within the liver, circulation in the vasculature leads to progressive loss of fatty acids converting these lipoproteins to IDL and finally LDL

  • HDL: high-density lipoprotein involved in the removal of cholesterol from peripheral tissue for return to the liver; the process is referred to as reverse cholesterol transport (RCT)

  • Space of Disse: the space between hepatic sinusoidal endothelium and hepatocytes, LDL and chylomicron remnants can be modified here prior to binding receptors on hepatocytes

  • Acyl-CoA-cholesterol acyltransferase (ACAT): key intracellular enzyme for esterifying cholesterol

  • Lecithin:cholesterol acyltransferase (LCAT) ratio: key HDL-associated enzyme involved in the esterification of cholesterol, removed from peripheral tissue, prior to exchange for triglyceride with VLDL and LDL

  • Cholesterol ester transfer protein (CETP): HDL-associated protein that transfers cholesterol esters from HDLs to VLDL and LDL in exchange of triglycerides from the VLDL/LDL to HDL

  • Paraoxonases (PON): HDL-associated enzymes that impart antioxidant activity of HDL toward LDL

  • Lipoprotein-associated phospholipase A2 (Lp-PLA2): is one of 2 forms of platelet-activating factor acetylhydrolase (PAF-AH), major HDL-associated hydrolase that is responsible for the hydrolysis of oxidized phospholipids

  • Lipoprotein(a) (Lp[a]): clinically significant apolipoprotein disulfide bonded to apoB-100 in LDL, easily oxidized and phagocytosed by macrophages-enhancing pro-inflammatory responses, inhibits the process of fibrin clot dissolution

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Biochemically, a lipoprotein represents a complex assembly of both proteins and lipids. The major lipoproteins are those found in the plasma and are responsible for the mobilization of lipids, primarily fats, throughout the body. The lipid portion of lipoproteins consists of cholesterol, cholesterol esters, triglycerides, and/or phospholipids. Lipoproteins can be derived from dietary lipids via synthesis in enterocytes of the intestine or from endogenous lipids via synthesis in the liver. The generalization of lipoprotein types is defined by the amount of protein and lipid as depicted in Table 28-1.

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Table Graphic Jump Location
TABLE 28-1:Composition of the Lipoproteins in Plasma of Humans

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