title: Sialic acid moiety of apolipoprotein E and its impact on the formation of lipoprotein particles in human cerebrospinal fluid.
abstract: BACKGROUND
  Apolipoprotein (apo) E in the cerebrospinal fluid (CSF) is abundant with sialic acid (SA), and sialylation of certain proteins is known to modulate biological function. The aim of the present study was to quantify the SA content in CSF apoE and carry out the more detailed characterization of the CSF apoE-containing lipoproteins.
  
  
  METHODS
  The method for the determination of the SA in CSF apoE was based on the conversion of SA into p-aminobenzoic acid ethyl ester-derivatized N-acetylmannosamine, followed by HPLC analysis.
  
  
  RESULTS
  The levels of CSF SA and serum SA were 25.9+/-1.5 and 2209+/-196 micromol/l, respectively; however, when the SA values were corrected by the total protein concentrations, CSF SA values were approximately 3.5-fold of those in the serum. The SA levels in the CSF apoE-containing lipoprotein fractions were 5.3+/-1.3% of total CSF SA, and were correlated with the CSF apoE concentrations. However, the ratios of SA to apoE were inversely proportional to the CSF lipid concentrations. The lipoprotein particle sizes were larger when the ratios of SA to CSF apoE were greater.
  
  
  CONCLUSIONS
  The SA moiety of the CSF apoE molecules may affect the formation of the apoE-containing lipoprotein particles and the regulation of lipid delivery in CNS.
authors.affiliation: Department of Laboratory Medicine, Shinshu University Hospital, Japan.
authors.forename: Kenji
authors.initials: K
authors.lastname: Kawasaki
authors.forename: Naoko
authors.initials: N
authors.lastname: Ogiwara
authors.forename: Mitsutoshi
authors.initials: M
authors.lastname: Sugano
authors.forename: Nobuo
authors.initials: N
authors.lastname: Okumura
authors.forename: Kazuyoshi
authors.initials: K
authors.lastname: Yamauchi
mesh_terms: D000367:Age Factors; D000368:Aged; D001057:Apolipoproteins E / Q000134:cerebrospinal fluid* / Q000737:chemistry / Q000378:metabolism; D002648:Child; D002675:Child, Preschool; D002851:Chromatography, High Pressure Liquid; D005260:Female; D006801:Humans; D008297:Male; D019158:N-Acetylneuraminic Acid / Q000134:cerebrospinal fluid* / Q000737:chemistry; D010316:Particle Size
chemical_list: D001057:Apolipoproteins E; D019158:N-Acetylneuraminic Acid