title: 13C tracer recovery in human stools after digestion of a fat-rich meal labelled with [1,1,1-13C3]tripalmitin and [1,1,1-13C3]triolein.
abstract: Lipid metabolism studies focus mainly on oxidation and storage but rarely on faecal elimination, which is needed to assess total lipid distribution during the postprandial period. The purpose of the present work was to set up and validate the analysis of lipid tracers in stools, with an aim of later using this methodology in studies of postprandial lipid tracer metabolism. Eight subjects received a mixture of [1,1,1-(13)C3]tripalmitin and [1,1,1-(13)C3]triolein with a fat-rich meal. The nature and amounts of (13)C lipids excreted in stools during 3 days post-dose were determined by gas chromatography/mass spectrometry (GC/MS) and gas chromatography/combustion/isotope ratio mass spectrometry (GC/C/IRMS) analysis of fatty acid methyl esters (FAMEs) from total fatty acid (TFA), free fatty acid (FFA) and triacylglycerol (TAG) fractions. The results were expressed as the Cumulative Tracer Recovery of the administered dose (CTR%). The quantities and labelling of FAMEs were higher in FFA than in TAG, indicating that label loss was not due to a lack of digestive lipase activity. The labelling was higher for C16:0 than for C18:1. The CTRs were 7.03 ± 0.77% and 6.87 ± 0.91%, respectively, in TFA and FFA for [1-(13)C] C16:0, while they were 0.60 ± 0.15% and 0.51 ± 0.11% for [1-(13)C] C18:1 (mean ± sem). By studying the kinetics of lipid excretion from subjects, two groups emerged. The first one showed rapid excretion in stool #1, whereas the second showed slower excretion in stools #2-#3. A significant difference was found in the FFA in stool #1 for C16:0 (p < 0.01) and C18:1 (p < 0.05). Individual excretion kinetics showed marked variability. Nevertheless, the CTR over the 3-day study period was substantial and homogenous for all subjects. These results confirm that the assessment of faecal elimination is of great importance when establishing total lipid distribution during the postprandial period and validate the analysis of cumulative tracer loss during 72 h post-tracer ingestion.
authors.affiliation: Lyon University, CRNH-RA and Center for European Nutrition, Safety and Health, F-69310 Pierre-Bénite, France.
authors.forename: Laure
authors.initials: L
authors.lastname: Gabert
authors.forename: Cécile
authors.initials: C
authors.lastname: Vors
authors.forename: Corinne
authors.initials: C
authors.lastname: Louche-Pélissier
authors.forename: Valérie
authors.initials: V
authors.lastname: Sauvinet
authors.forename: Stéphanie
authors.initials: S
authors.lastname: Lambert-Porcheron
authors.forename: Jocelyne
authors.initials: J
authors.lastname: Drai
authors.forename: Martine
authors.initials: M
authors.lastname: Laville
authors.forename: Michel
authors.initials: M
authors.lastname: Désage
authors.forename: Marie-Caroline
authors.initials: MC
authors.lastname: Michalski
mesh_terms: D000328:Adult; D002247:Carbon Isotopes / Q000032:analysis; D018592:Cross-Over Studies; D004063:Digestion / Q000502:physiology*; D005243:Feces / Q000737:chemistry*; D008401:Gas Chromatography-Mass Spectrometry / Q000379:methods; D006801:Humans; D007553:Isotope Labeling; D008297:Male; D014280:Triglycerides / Q000008:administration & dosage / Q000737:chemistry / Q000493:pharmacokinetics*; D014304:Triolein / Q000008:administration & dosage / Q000737:chemistry / Q000493:pharmacokinetics*; D055815:Young Adult
chemical_list: D002247:Carbon Isotopes; D014280:Triglycerides; D014304:Triolein; C005859:tripalmitin