Compound-specific carbon isotope ratio determination of enriched cholesterol.
On-line gas chromatography/combustion/isotope ratio mass spectrometry (GC/C/IRMS) was evaluated for use in stable isotope studies of human cholesterol metabolism. Calibration curves were constructed by analyzing underivatized and TMS-cholesterol over a range of 13C abundances from natural abundance to 0.05 mol of [3,4-13C]cholesterol per mole of unlabeled cholesterol (delta 13C -24 to 27/1000). The calibration curves were highly linear (r2 = 0.99) with slopes of 0.98 and 0.88 for underivatized and TMS-cholesterol, respectively. Higher precision of 13C/12C ratio determination was obtained using TMS-cholesterol, with a detection limit (2 SD) of 0.3/1000 or 0.004 mol% of [3,4-13C]cholesterol. By comparison standard GC/MS had a detection limit of 0.06 mol% for [3,4-13C]cholesterol. A 57-day study of cholesterol elimination was conducted in one human subject with oral administration of 50 mg of [3,4-13C]cholesterol. Peak enrichment was 9/1000 above baseline (40 times the detection limit) and could be followed for 40-50 days. The results indicate that GC/C/IRMS provides 15-fold lower detection limits for [3,4-13C]cholesterol than GC/MS and is useful for human studies of cholesterol metabolism.
Guo
Z K
ZK
University of Chicago, Illinois 60637.
Luke
A H
AH
Lee
W P
WP
Schoeller
D
D
D000328:Adult; D002247:Carbon Isotopes; D002784:Cholesterol / Q000032:analysis* / Q000097:blood; D002791:Cholesterol, Dietary / Q000032:analysis / Q000378:metabolism; D008401:Gas Chromatography-Mass Spectrometry; D006801:Humans; D008297:Male
D002247:Carbon Isotopes; D002791:Cholesterol, Dietary; D002784:Cholesterol