Blood dolichols in a patient with abetalipoproteinaemia

Dolichol and dolichyl derivatives have an important function as glycosyl ca rriers in the assembly of the N-asparaginyl-linked origosaccharide core reg ion of glycoproteins. Dolichols are synthesized through the cholesterol bio synthesis pathway in all mammalian organs and are present in all tissues, a nd are also associated with lipoproteins in the blood circulation. However, the origin and metabolic pathway of blood dolichols remain unknown. Abetal ipoproteinaemia is a disorder of the secretion of very low-density lipoprot ein (VLDL) from the liver and of chylomicrons from the intestine into the b lood circulation. Therefore, examination of blood dolichols in this disorde r may provide valuable information on their origin and metabolic pathway. D olichols were exclusively associated with the high-density lipoprotein (HDL ) fraction (80.7 +/- 6.3% of total dolichols) in control human blood. Serum from a patient also contained dolichols in the HDL fraction (82.8% of tota l dolichols). The total amount of dolichols was higher in the patient (207. 0 ng/mL) than in the controls (106.2 +/- 22.7 ng/mL, n = 14). The compositi ons of dolichols were very similar to each other. These results indicated t hat, at least in the patient with abetalipoproteinaemia, the HDL-associated dolichols were possibly derived from the liver not through other lipoprote ins but through dolichol transfer protein, or were possibly taken up and ca rried by HDL from peripheral tissues.