Kawasaki Kenji, Ogiwara Naoko, Sugano Mitsutoshi, Okumura Nobuo, Yamauchi Kazuyoshi
Department of Laboratory Medicine, Shinshu University Hospital, Japan.
Clin Chim Acta. 2009 Apr;402(1-2):61-6. doi: 10.1016/j.cca.2008.12.018. Epub 2008 Dec 24.
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.
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.
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.
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.
脑脊液（CSF）中的载脂蛋白（apo）E富含唾液酸（SA），已知某些蛋白质的唾液酸化可调节生物学功能。本研究的目的是量化脑脊液载脂蛋白E中的唾液酸含量，并对含脑脊液载脂蛋白E的脂蛋白进行更详细的表征。
测定脑脊液载脂蛋白E中唾液酸的方法是基于将唾液酸转化为对氨基苯甲酸乙酯衍生化的N-乙酰甘露糖胺，然后进行高效液相色谱分析。
脑脊液唾液酸和血清唾液酸水平分别为25.9±1.5和2209±196微摩尔/升；然而，当唾液酸值用总蛋白浓度校正时，脑脊液唾液酸值约为血清中的3.5倍。含脑脊液载脂蛋白E的脂蛋白组分中的唾液酸水平占脑脊液总唾液酸的5.3±1.3%，且与脑脊液载脂蛋白E浓度相关。然而，唾液酸与载脂蛋白E的比率与脑脊液脂质浓度成反比。当唾液酸与脑脊液载脂蛋白E的比率较大时，脂蛋白颗粒尺寸较大。
脑脊液载脂蛋白E分子的唾液酸部分可能影响含载脂蛋白E的脂蛋白颗粒的形成以及中枢神经系统中脂质传递的调节。
