Serum glycomarkers of endoplasmic reticulum and lysosomal-endosomal system stress in human healthy aging and diseases

To verify the idea that extracellular free oligosaccharides might be able to reflect the functional status of the endoplasmic reticulum (ER) and lysosomal-endosomal system, HPLC-profiles of serum-derived free oligosaccharides (FOS) in human healthy aging, acute myeloproliferative neoplasms, and cardiovascular pathologies were compared with intracellular glycans. After plasma deproteinization and FOS purification the oligosaccharides were labelled with anthranilic acid, separated into the neutral and charged with QAE Sephadex (Q25-120) chromatography and analysed using high-performance liquid chromatography (HPLC). The charged FOS were digested with a sialidase and compared with free oligosaccharides from transferrin for structural decoding. HPLC-profiles of serum-derived FOS revealed mild delay of the dolichol phosphate cycle in ER, moderate intensification of ER-associated degradation (ERAD) and degradation in endosomal-lysosomal system with aging; an inhibition of the dolichol phosphate cycle, intensification of ERAD and increasing of lysosomal exocytosis in acute myeloproliferative neoplasms; intensification of ERAD and glycocojugate degradation with endosomal-lysosomal system in cardiovascular diseases. As serum free oligosaccharides are able to reflect specifically perturbations in ER and endosomal-lysosomal system under wide range of stressors they can serve as extracellular markers of functionality of these organelles.

Sequential microanalyses of free dolichol, dolichyl fatty acid ester and dolichyl phosphate levels in human serum

Sequential microanalyses of free dolichol, dolichyl fatty acid ester and dolichyl phosphate in human serum were made. To determine the level of each dolichol, samples were pretreated using three different methods prior to fluorescent derivatization. To estimate the concentrations of free dolichol, samples were added to alkaline methanol and kept at room temperature for 1 h. In case of dolichyl fatty acid ester, samples were saponified at 100 degrees C for 1 h. To estimate dolichyl phosphate, saponified lipid extracts were treated with acid phosphatase. Each pretreated dolichol was reacted with anthracene-9-carboxylic acid and amounts of 9-anthroyl derivatives were determined fluorometrically by HPLC. This method is simple and three types of dolichols can be estimated using the same HPLC system. This analysis is also sufficiently sensitive for measurement of serum dolichol levels. The contents of free dolichol, dolichyl fatty acid ester and dolichyl phosphate in human serum were found to be 44.9 +/- 10.5 ng/ml (n = 32), 76.4 +/- 24.2 ng/ml (n = 32) and 43.5 +/- 15.1 ng/ml (n = 13), respectively. These levels had apparently no correlation to age or serum total cholesterols. A linear correlation between dolichols and high-density lipoprotein cholesterols reflects the fact that the dolichols are associated with the high-density lipoprotein fraction.

Presence of dolichol and its derivatives in human blood

Optimal conditions for the quantitative estimation of dolichol in human plasma were determined. Because of the large amounts of other lipids present in the blood, the extraction procedure, the procedure for hydrolysis, and the HPLC procedure are of decisive importance. Human plasma contains dolichol, dolichyl esters, and dolichyl phosphate at concentrations of 41, 102, and 55 ng/g, respectively. These polyisoprenoid lipids are associated with the high density lipoprotein fraction. The relative amounts and compositions of dolichyl esters in the plasma are similar to those observed in isolated human liver microsomes and Golgi vesicles. Sixty percent of the fatty acids present are saturated and almost no long-chain polyunsaturated components are present. There is no correlation between blood dolichol content and weight, sex, dietary state, or plasma cholesterol level, but there is an inverse relationship to plasma triglyceride content. A linear increase in the total plasma dolichol content with increasing age was found. In a few pathological conditions where the level of blood cholesterol was increased, the total blood dolichol content was not affected. Apparently, dolichol is a stable lipid component of human high density lipoprotein.