title: Quantifying cholesterol synthesis in vivo using (2)H(2)O: enabling back-to-back studies in the same subject.
abstract: The advantages of using (2)H(2)O to quantify cholesterol synthesis include i) homogeneous precursor labeling, ii) incorporation of (2)H via multiple pathways, and iii) the ability to perform long-term studies in free-living subjects. However, there are two concerns. First, the t(1/2) of tracer in body water presents a challenge when there is a need to acutely replicate measurements in the same subject. Second, assumptions are made regarding the number of hydrogens (n) that are incorporated during de novo synthesis. Our primary objective was to determine whether a step-based approach could be used to repeatedly study cholesterol synthesis a subject. We observed comparable changes in the (2)H-labeling of plasma water and total plasma cholesterol in African-Green monkeys that received five oral doses of (2)H(2)O, each dose separated by one week. Similar rates of cholesterol synthesis were estimated when comparing data in the group over the different weeks, but better reproducibility was observed when comparing replicate determinations of cholesterol synthesis in the same nonhuman primate during the respective dosing periods. Our secondary objective was to determine whether n depends on nutritional status in vivo; we observed n of ∼25 and ∼27 in mice fed a high-carbohydrate (HC) versus carbohydrate-free (CF) diet, respectively. We conclude that it is possible to acutely repeat studies of cholesterol synthesis using (2)H(2)O and that n is relatively constant.
authors.affiliation: Atherosclerosis, Merck Research Laboratories, Rahway, NJ, USA. stephen_previs@merck.com
authors.forename: Stephen F
authors.initials: SF
authors.lastname: Previs
authors.forename: Ablatt
authors.initials: A
authors.lastname: Mahsut
authors.forename: Alison
authors.initials: A
authors.lastname: Kulick
authors.forename: Keiana
authors.initials: K
authors.lastname: Dunn
authors.forename: Genevieve
authors.initials: G
authors.lastname: Andrews-Kelly
authors.forename: Christopher
authors.initials: C
authors.lastname: Johnson
authors.forename: Gowri
authors.initials: G
authors.lastname: Bhat
authors.forename: Kithsiri
authors.initials: K
authors.lastname: Herath
authors.forename: Paul L
authors.initials: PL
authors.lastname: Miller
authors.forename: Sheng-Ping
authors.initials: SP
authors.lastname: Wang
authors.forename: Karim
authors.initials: K
authors.lastname: Azer
authors.forename: Jing
authors.initials: J
authors.lastname: Xu
authors.forename: Douglas G
authors.initials: DG
authors.lastname: Johns
authors.forename: Brian K
authors.initials: BK
authors.lastname: Hubbard
authors.forename: Thomas P
authors.initials: TP
authors.lastname: Roddy
mesh_terms: D000818:Animals; D002522:Chlorocebus aethiops; D002784:Cholesterol / Q000096:biosynthesis*; D017666:Deuterium Oxide / Q000737:chemistry* / Q000378:metabolism; D005260:Female; D008401:Gas Chromatography-Mass Spectrometry; D006859:Hydrogen / Q000378:metabolism; D008297:Male; D013058:Mass Spectrometry / Q000379:methods*; D051379:Mice; D009752:Nutritional Status; D035501:Uncertainty
chemical_list: D006859:Hydrogen; D002784:Cholesterol; D017666:Deuterium Oxide