The incidence of cardiovascular events correlates inversely with cholesterol efflux capacity (CEC) more than with HDL-cholesterol level. The measurement of CEC is used to qualify cardiovascular disease risk and is conventionally performed with radioisotope (RI)-labeled cholesterol. Here, we established a CEC measurement technique using stable isotope-labeled cholesterol as an alternative, and we compared the new method with RI and fluorescence (boron dipyrromethene difluoride-cholesterol) methods in cells and in patient serum. We incubated J774 cells labeled with [d₇]cholesterol ([d₇]C) with patient serum depleted of apoB, and [d₇]C extracted from the culture medium was quantified by liquid chromatography/quadrupole time-of-flight mass spectrometry. [d₇]C efflux increased with greater apoB-depleted serum concentration and longer incubation time. The assay coefficient of variation (CV) of five consecutive measurements of three sets of samples ranged from 7.3% to 9.5%, and the interassay CV determined by measuring three samples four times ranged from 4.1% to 8.5%, both indicating good precision. We then measured CEC levels of 41 outpatients with serum HDL-cholesterol levels between 36 and 94 mg/dl (mean: 61.7 ± 18.0 mg/dl); in the presence of cAMP, we observed a significant, positive correlation between CEC levels determined with the stable isotope and RI methods that was stronger than the correlation between measurements obtained by the fluorescence and RI methods (r = 0.73, P < 0.0001 vs. r = 0.55, P < 0.001). Therefore, our stable isotope method can be considered useful as a non-RI method and thus deserves evaluation in future clinical studies.

中文翻译：

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一种测量胆固醇流出能力的新方法是使用稳定的同位素标记的胆固醇，而不是放射性标记的胆固醇。

心血管事件的发生与胆固醇外排量（CEC）的相关性比与HDL-胆固醇水平的相关性更大。CEC的测量用于确定心血管疾病的风险，通常按放射性同位素（RI）标记的胆固醇进行。在这里，我们建立了一种使用稳定同位素标记的胆固醇作为替代品的CEC测量技术，并且将新方法与RI和荧光法（硼化二甲基吡啶二氟硼化胆固醇）在细胞和患者血清中的方法进行了比较。我们将用[ d ₇ ]胆固醇（[ d ₇ ] C）标记的J774细胞与贫血的apoB和[ d ₇通过液相色谱/四极杆飞行时间质谱法对从培养基中提取的] C进行定量。[ d ₇随着ApoB耗尽的血清浓度的增加和孵育时间的延长，] C外排量增加。三组样品连续五次测量的测定变异系数（CV）在7.3％至9.5％之间，四次测量三份样品测定的测定间CV在4.1％至8.5％之间，均显示出良好的精密度。然后，我们测量了41位门诊患者的HDC-胆固醇水平在36-94 mg / dl之间的CEC水平（平均值：61.7±18.0 mg / dl）；在存在cAMP的情况下，我们观察到用稳定同位素和RI方法测定的CEC水平之间存在显着的正相关性，该相关性强于通过荧光和RI方法获得的测量值之间的相关性（r = 0.73，P <0.0001 vs. r = 0.55，P <0.001）。因此，我们的稳定同位素方法可以被认为是非RI方法，因此值得在未来的临床研究中进行评估。