Del Puppo Marina, Crosignani Andrea, Longo Matteo, Zuin Massimo, Podda Mauro, Galli Giovanni, De Fabiani Emma, Ciuffreda Pierangela, Santaniello Enzo, Javitt Norman B, Kienle Marzia Galli
Dipartimento di Medicina Sperimentale, Ambientale e Biotecnologie Mediche (DIMESAB), University of Milano-Bicocca, Via Cadore 48, 20052 Monza, Italy.
Clin Chim Acta. 2005 May;355(1-2):23-31. doi: 10.1016/j.cccn.2004.11.037.
Bile acid synthesis accounts for more than 95% of total cholesterol catabolism per day. We have developed a minimally invasive technique in humans that quantifies the rates of plasma appearance of 7alpha- and 27-hydroxycholesterol, representing the first steps of the "classical" and "alternative" pathways of bile acid synthesis, respectively.
For this purpose, during the intravenous infusion of synthetic deuterated isotopomers of 7alpha-hydroxycholesterol and 27-hydroxycholesterol plasma samples are collected and analysed by a GC-MS based method that allows to quantify the exogenous/natural isotopomer ratio of the two sterols. From this data, the rates of plasma appearance of 7alpha- and 27-hydroxycholesterol are calculated.
In a group of healthy individuals steady state kinetics are obtained during a 2 h period yielding mean values of 2.0+/-0.8 and 3.7+/-0.6 mg/h for 7alpha- and 27-hydroxycholesterol, respectively. The data are consistent with findings using older techniques that require studies over several days.
Considering that at steady state of the exogenous/natural isotopomer ratio the plasma appearance of the two regulatory hydroxysterols are related to the rate of bile acid synthesis via the "classical" and the "alternative" pathways, respectively, the proposed method could be used to evaluate the immediate effects of different diets and drugs and other determinants on cholesterol catabolism.
胆汁酸合成占每日总胆固醇分解代谢的95%以上。我们已开发出一种针对人类的微创技术，可量化7α-羟基胆固醇和27-羟基胆固醇的血浆出现率，分别代表胆汁酸合成“经典”途径和“替代”途径的第一步。
为此，在静脉输注7α-羟基胆固醇和27-羟基胆固醇的合成氘代同位素异构体期间，采集血浆样本，并通过基于气相色谱-质谱联用的方法进行分析，该方法可量化两种固醇的外源性/天然同位素异构体比率。根据这些数据，计算7α-羟基胆固醇和27-羟基胆固醇的血浆出现率。
在一组健康个体中，在2小时内获得了稳态动力学数据，7α-羟基胆固醇和27-羟基胆固醇的平均值分别为2.0±0.8和3.7±0.6mg/h。这些数据与使用需要数天研究的旧技术的结果一致。
考虑到在外源性/天然同位素异构体比率的稳态下，两种调节性羟基固醇的血浆出现率分别通过“经典”途径和“替代”途径与胆汁酸合成速率相关，所提出的方法可用于评估不同饮食、药物和其他决定因素对胆固醇分解代谢的即时影响。
