Comparison of cholesterol metabolism between the peripheral tissues and the brain

Peripheral tissuesBrain
Source and synthesis of cholesterol
 Source of cholesterolMainly from biosynthesis, partially from dietary intakeAlmost exclusively from biosynthesis
 Cholesterol biosynthesisMainly extrahepatic (85%) and partially hepatic (15%)Mainly by glial cells, especially by astrocytes and partially by neurons
Cholesterol transfer
 LipoproteinsChylomicrons, chylomicron remnants, VLDL, IDL, LDL, HDL, Lp (a)HDL-like particles
 Cholesterol transfer by lipoproteinsMainly from peripheral tissues to the liver by HDL; partially from the intestine to peripheral tissues by chylomicrons; from the liver to peripheral tissues by VLDL, IDL, and LDL.From astrocytes and other glia to neurons by HDL-like particles
 ApolipoproteinsApoA-I, ApoA-II, ApoA-IV, Apo-V, ApoB-48, ApoB-100, ApoC-I, ApoC-II, ApoE, Apo(a), ApoJ, ApoD, etc.ApoE, ApoA-I, ApoJ, ApoD.
 Source of apolipoproteinsMainly from the liver and intestine.ApoE is produced in mainly astrocytes, followed by other glia. ApoA-I is not synthesized in the brain, but may be from plasma HDL.
Cholesterol turnover
 TurnoverCellularly, it is stored in the esterified form, or exported to plasma lipoproteins mainly and converted into oxysterols, bile acids, steroids, vitamin D3 minorly.Systemically, the liver is the only organ that has ability to eliminate cholesterol through its secretion into bile or its transformation into bile salts.Cellularly, it is stored in the esterified form, or converted to 24-OH-cholesterol and excreted to plasma via BBB mainly. It is also exported to ApoA-I containing lipoproteins, then excreted to plasma.

BBB, blood brain barrier; HDL, high-density lipoprotein; IDL, intermediate-density lipoprotein; LDL, low-density lipoprotein; VLDL, very low-density lipoprotein.

Exp Neurobiol 2019;28:554~567
© Exp Neurobiol