[2H/H] Isotope ratio analyses of [2H5]cholesterol using high-temperature conversion elemental analyser isotope-ratio mass spectrometry: determination of cholesterol absorption in normocholesterolemic volunteers.
This paper validates the use of high-temperature conversion elemental analyser isotope-ratio mass spectrometry (TC-EA/IRMS) for measuring the [(2)H/H] enrichment of plasma [(2)H(5)]cholesterol. From a molecular point of view, the free cholesterol is initially separated from plasma by thin-layer chromatography (TLC) and then injected onto the TC-EA reactor which converts cholesterol molecules into CO and H(2) gases. The slope of the curve of the experimental mole percent excess (MPE((exp.))) versus MPE((theor.)) was very close to 1, demonstrating that no significant isotopic fractionation was observed during all processing of the samples (i.e., isolation of plasma free cholesterol by TLC and pyrolysis in the TC-EA reactor). Excellent linearity (r(2) = 0.9994, n = 4) of delta ( per thousand ) of [(2)H/H] isotopic measurements versus mole percent (MP) was assessed over the range 0 to 0.1 MP. The precision of the [(2)H/H] measurement, evaluated with two calibration points processed with TLC, was delta(2)H(V-SMOW) = -192.5 +/- 3.4 per thousand and delta(2)H(V-SMOW) = -136.9 +/- 2.9 per thousand. The standard deviations of the within-assay and between-assay repeatabilities of the analytical process, evaluated using the quality control (QC) of plasma samples, were 4.6 and 6.1 per thousand, respectively. Plant sterols are known to reduce cholesterol absorption and therefore were used as a positive control in a clinical study performed with normocholesterolemic volunteers. This present method produces biological results consistent with those already reported in the literature.
Godin
Jean-Philippe
JP
Nestec Ltd, Nestlé Research Center, PO Box 44, CH-1000 Lausanne 26, Switzerland. jean-philippe.godin@rdls.nestle.com
Richelle
Myriam
M
Metairon
Sylviane
S
Fay
Laurent-Bernard
LB
D000284:Administration, Oral; D002250:Carbon Radioisotopes; D002784:Cholesterol / Q000008:administration & dosage / Q000032:analysis* / Q000493:pharmacokinetics; D002791:Cholesterol, Dietary; D003903:Deuterium / Q000032:analysis*; D008401:Gas Chromatography-Mass Spectrometry / Q000379:methods*; D006801:Humans; D007275:Injections, Intravenous; D007553:Isotope Labeling; D008297:Male; D015203:Reproducibility of Results
D002250:Carbon Radioisotopes; D002791:Cholesterol, Dietary; D002784:Cholesterol; D003903:Deuterium