Comparison of cholesterol metabolism between the peripheral tissues and the brain
| Peripheral tissues | Brain | |
|---|---|---|
| Source and synthesis of cholesterol | ||
| Source of cholesterol | Mainly from biosynthesis, partially from dietary intake | Almost exclusively from biosynthesis |
| Cholesterol biosynthesis | Mainly extrahepatic (85%) and partially hepatic (15%) | Mainly by glial cells, especially by astrocytes and partially by neurons |
| Cholesterol transfer | ||
| Lipoproteins | Chylomicrons, chylomicron remnants, VLDL, IDL, LDL, HDL, Lp (a) | HDL-like particles |
| Cholesterol transfer by lipoproteins | Mainly 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 |
| Apolipoproteins | ApoA-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 apolipoproteins | Mainly 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 | ||
| Turnover | Cellularly, it is stored in the esterified form, or exported to plasma lipoproteins mainly and converted into oxysterols, bile acids, steroids, vitamin D3 minorly. | 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.