C5] cleavage items; and m/z 279100 for metabo13 lites of [ C10]retinyl acetate. A single one-phase solvent extraction, with no saponification or purification steps, left retinyl esters intact for determination of intestinally-derived retinol in chylomicrons versus retinol in the liver bound 13 to retinol binding protein. Coadministration of [ C10] 13 retinyl acetate with [ C10] -carotene not simply acts as a reference dose for inter-individual variations in absorption and chylomicron clearance rates, but in addition permits for simultaneous determination of an individual’s vitamin A status.– Oxley, A., P. Berry, G. A. Taylor, J. Cowell, M. J. Hall, J. Hesketh, G. Lietz, plus a. V. Boddy. An LC/MS/MS approach for stable isotope dilution studies of -carotene bioavailability, bioconversion, and vitamin A status in humans. J. Lipid Res. 2014. 55: 319?28.Supplementary crucial words -carotene 15,15-monooxygenase ?carotenoid metabolism ?retinol metabolism ?retinyl esters ?tandem mass spectrometryVitamin A deficiency is usually a big public wellness concern within the establishing globe due to inadequate intake of both preformed vitamin A and provitamin A carotenoids within the eating plan (1). However, detection of subclinical deficiency is problematic simply because 85 of vitamin A is stored within the liver although the amount of vitamin A circulating in the blood is below strict homeostatic manage and not indicative of hepatic reserves (2). Growing the intake of provitamin A carotenoids, mostly by way of -carotene, is seen as a safe way of restoring the vitamin A reserves of a person since high doses of preformed vitamin A have adverse wellness effects (three). Even though the current vitamin A equivalency ratio for -carotene is estimated at 12:1 (by weight) (four), large inter-individual variations in each absorption and conversion have already been observed (five?). In the intestinal mucosa, a proportion of absorbed -carotene undergoes centric cleavage by the -carotene 15,15-monooxygenase 1 (BCMO1) enzyme to produce two molecules of retinal which are additional decreased to retinol (vitamin A) (9).1035351-06-4 Chemical name For export in to the circulation, retinol is esterified to a lengthy chain fatty acid, usually palmitate, and incorporated, in conjunction with intact -carotene, into chylomicrons (10).95464-05-4 Chemscene Subsequently, retinyl esters are either stored in hepatic stellate cells or hydrolyzed back to retinol by the liver for repartition to other tissue compartments bound to retinol binding protein (RBP).PMID:23789847 At the moment, steady isotope dilution provides the most accurate determination of -carotene bioefficacy and vitamin A status irrespective of higher endogenous circulating levels of those micronutrients (1, 2). However, the minimum dose to become administered has been dictated by the detection limit of your analytical process (two). Furthermore, isolationThis study was funded by BBSRC (grant reference BB/G004056/1) and supported in component by Cancer Research UK. Manuscript received 21 May well 2013 and in revised type 16 October 2013. Published, JLR Papers in Press, October 24, 2013 DOI 10.1194/jlr.DCopyright ?2014 by the American Society for Biochemistry and Molecular Biology, Inc. This short article is available on the web at http://jlr.orgAbbreviations: APCI, atmospheric pressure chemical ionization; BCMO1, -carotene 15,15-monooxygenase 1; BHT, butylated hydroxytoluene; LOD, limit of detection; LOQ, limit of quantitation; RBP, retinol binding protein; RSD, relative typical deviation; SRM, chosen reaction monitoring; TRL, triglyceride-rich lipoprotein. 1 To whom corre.