Study of β‐Carotene Metabolism in Humans Using <sup>13</sup>C‐β‐Carotene and High Precision Isotope Ratio Mass Spectrometry

Swanson, Joy E.; Marmor, Bonnie; Goodman, Keith J.; Spielman, Amy B.; Brenna, J. Thomas; Viereck, Sharon M.; Canfield, Wesley K.

doi:10.1111/j.1749-6632.1993.tb26160.x

Cited by 64 publications

(55 citation statements)

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“…Isotopes have been used previously to study the bioavailability and metabolism of carotenoids (14)(15)(16)(17)(18)(19)(20)(21)(22)(23)(24)(25)(26)(27)(28)(29)(30)(31)(32). Previous reports of clinical studies have involved administration of pure compounds labeled with deuterium (17,21,22,24,26,27,30), pure compounds labeled with 13 C (15,16,19,32), pure compounds labeled with 14 C (28, 29), plant foods intrinsically labeled with deuterium (30), and plant foods intrinsically labeled with 13 C (10).…”

Section: Discussionmentioning

confidence: 99%

“…Previous reports of clinical studies have involved administration of pure compounds labeled with deuterium (17,21,22,24,26,27,30), pure compounds labeled with 13 C (15,16,19,32), pure compounds labeled with 14 C (28, 29), plant foods intrinsically labeled with deuterium (30), and plant foods intrinsically labeled with 13 C (10). Other than the report of our pilot study (10), this study is the only one in which the nutrients were completely labeled with 13 C in a plant matrix and in which two isotopically labeled carotenoids were fed simultaneously.…”

Section: Discussionmentioning

confidence: 99%

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Plasma appearance of labeled β-carotene, lutein, and retinol in humans after consumption of isotopically labeled kale

Novotny

Kurilich

Britz

et al. 2005

Journal of Lipid Research

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The bioavailability of carotenoids from kale was investigated by labeling nutrients in kale with 13 C, feeding the kale to seven adult volunteers, and analyzing serial plasma samples for labeled lutein, ␤ -carotene, and retinol. Ingested doses of labeled carotenoids were 34 mol for ␤ -carotene and 33 mol for lutein. Peak plasma concentrations, areas under the plasma concentration-time curves (AUCs), and percentages of dose recovered at peak plasma concentrations were calculated. Average peak plasma concentrations were 0.38, 0.068, and 0.079 M for Carotenoids are a large class of compounds that may contribute to the health-promoting effects of plant-based foods by acting as antioxidants in the defense against oxidative stress and free radicals (1-3). Some carotenoids, such as ␤ -carotene, are also precursors to vitamin A and therefore make plant-based foods a potentially important source of vitamin A for humans. Diets high in the carotenoids lutein and zeaxanthin seem to prevent the onset of age-related macular degeneration (4).For health professionals to make recommendations for carotenoid intakes to provide these health benefits, it is necessary to have a clear understanding of carotenoid bioavailability from food sources. Because carotenoids are present in fasting plasma, the mixing of endogenous carotenoid with newly ingested carotenoid complicates bioavailability studies. Labeling compounds with isotopes allows the discernment of newly ingested nutrients from endogenous nutrients. It is additionally helpful if the labeled nutrient can be administered within the food matrix, because absorption of pure carotenoids is much higher than that of carotenoids in foods (5-9).In the present study, we used kale containing ␤ -carotene and lutein labeled with 13 C to study their bioavailability. The kale was fed to volunteers, and plasma responses of the labeled compounds were used to investigate the bioavailability of lutein and ␤ -carotene from kale. EXPERIMENTAL PROCEDURES Intrinsic labeling of kaleThe method for labeling kale nutrients with 13 C has been described previously (10). Briefly, kale ( Brassica oleracea variety acephala cultivar Vates) was grown in a controlled-environment chamber with the only source of carbon being 13 CO 2 to achieve complete 13 C labeling of the kale tissue. The labeling chamber consisted of a clear acrylic box (Plexiglas G; Rohm and Haas, Wilmington, DE) with a separate base. The top fit into a waterfilled trough in the base to provide a leak-proof seal to prevent the exchange of 13 CO 2 with atmospheric CO 2 . Plants were grown in Nalgene bins inside the acrylic box and were subirrigated. The partial pressure of CO 2 inside the chamber was continuously monitored via a WMA-3 PP System and a WMA-3 PID controller (PP Systems, Haverhill, MA), which injected 13 CO 2 ( Ͼ 99% 13 C; Isotec, Inc., Miamisburg, OH) if levels decreased to Ͻ 40 Pa. The acrylic box was placed inside a controlled-environment chamber for maintenance of temperature (24 Њ C), humidity (90%), and

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Section: Discussionmentioning

confidence: 99%

Section: Discussionmentioning

confidence: 99%

Plasma appearance of labeled β-carotene, lutein, and retinol in humans after consumption of isotopically labeled kale

Novotny

Kurilich

Britz

et al. 2005

Journal of Lipid Research

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“…13 C]carotene and its metabolites (retinol and retinyl esters) in human plasma (46,47). The patterns of D 6 ␤-carotene and D 3 retinol in plasma of our subjects (Figure 2, top panel) are consistent with those described earlier for […”

Section: Discussionmentioning

confidence: 99%

Variability of the conversion of β-carotene to vitamin A in women measured by using a double-tracer study design

Lin

Dueker

Burri

et al. 2000

The American Journal of Clinical Nutrition

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Background: Blood ␤-carotene and vitamin A responses to oral ␤-carotene are variable in humans. Some individuals are characterized as responders and others as low-or nonresponders. A better understanding of the conditions that produce the variability is important to help design public health programs that ensure vitamin A sufficiency. Objective: Our objective was to assess variability in absorption and conversion of ␤-carotene to vitamin A in vivo in humans by using a novel double-tracer [hexadeuterated (D 6 ) ␤-carotene and D 6 retinyl acetate] approach. Design: Eleven healthy women were housed at the US Department of Agriculture Western Human Nutrition Research Center metabolic unit for 44 d, where they consumed diets adequate in vitamins and minerals except for carotenoids. After an adaptation period, the women were given 30 mol D 6 retinyl acetate orally, followed 1 wk later with 37 mol D 6 ␤-carotene (approximately equimolar doses). Time-dependent plasma concentration curves were determined for D 6 retinol, D 6 ␤-carotene, and trideuterated (D 3 ) retinol (derived from D 6 ␤-carotene). Results: Mean (± SE) absorption of D 6 ␤-carotene was 3.3 ± 1.3% for all subjects. The mean conversion ratio was 0.81 ± 0.34 mol D 3 retinol to 1 mol D 6 ␤-carotene for all subjects. However, only 6 of the 11 subjects had plasma D 6 ␤-carotene and D 3 retinol concentrations that we could measure. The mean absorption of D 6 ␤-carotene in these 6 subjects was 6.1 ± 0.02% and their conversion ratio was 1.47 ± 0.49 mol D 3 retinol to 1 mol D 6 ␤-carotene. The remaining 5 subjects were low responders with ≤ 0.01% absorption and a mean conversion ratio of 0.014 ± 0.004 mol D 3 retinol to 1 mol D 6 ␤-carotene. Conclusion: Variable absorption and conversion of ␤-carotene to vitamin A both contribute to the variable response to consumption of ␤-carotene. Our double-tracer approach is adaptable for identifying efficient converters of carotenoid to retinoid. Am J Clin Nutr 2000;71:1545-54.

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“…GC-C-IRMS was quickly exploited for low enrichment studies of amino acids, free fatty acids and glucose metabolism in human subjects [31,32]. GC-C-IRMS has been applied to retinol studies using biosynthesised 13 C-β-carotene [33], 13 C 2 -and 13 C 4 -retinol [23]. The development of equivalent techniques for deuterium analysis has lagged behind because of the greater technical challenge imposed by interference from the helium carrier and the low natural abundance of deuterium.…”

Section: Isotope Ratio Ms (Irms)mentioning

confidence: 99%

Existing and Emerging Technologies for Measuring Stable Isotope Labelled Retinol in Biological Samples: Isotope Dilution Analysis of Body Retinol Stores

Preston

2014

International Journal for Vitamin and Nutrition Research

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This paper discusses some of the recent improvements in instrumentation used for stable isotope tracer measurements in the context of measuring retinol stores, in vivo. Tracer costs, together with concerns that larger tracer doses may perturb the parameter under study, demand that ever more sensitive mass spectrometric techniques are developed. GCMS is the most widely used technique. It has high sensitivity in terms of sample amount and uses high resolution GC, yet its ability to detect low isotope ratios is limited by background noise. LCMSMS may become more accessible for tracer studies. Its ability to measure low level stable isotope tracers may prove superior to GCMS, but it is isotope ratio MS (IRMS) that has been designed specifi cally for low level stable isotope analysis through accurate analysis of tracer:tracee ratios (the tracee being the unlabelled species). Compound-specifi c isotope analysis, where GC is interfaced to IRMS, is gaining popularity. Here, individual 13 C-labelled compounds are separated by GC, combusted to CO 2 and transferred on-line for ratiometric analysis by IRMS at the ppm level. However, commercially-available 13 C-labelled retinol tracers are 2 -4 times more expensive than deuterated tracers. For 2 H-labelled compounds, GC-pyrolysis-IRMS has now become more generally available as an operating mode on the same IRMS instrument. Here, individual compounds are separated by GC and pyrolysed to H 2 at high temperature for analysis by IRMS. It is predicted that GC-pyrolysis-IRMS will facilitate low level tracer procedures to measure body retinol stores, as has been accomplished in the case of fatty acids and amino acids. Sample size requirements for GC-P-IRMS may exceed those of GCMS, but this paper discusses sample preparation procedures and predicts improvements, particularly in the effi ciency of sample introduction.

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Study of β‐Carotene Metabolism in Humans Using ¹³C‐β‐Carotene and High Precision Isotope Ratio Mass Spectrometry

Cited by 64 publications

References 5 publications

Plasma appearance of labeled β-carotene, lutein, and retinol in humans after consumption of isotopically labeled kale

Plasma appearance of labeled β-carotene, lutein, and retinol in humans after consumption of isotopically labeled kale

Variability of the conversion of β-carotene to vitamin A in women measured by using a double-tracer study design

Existing and Emerging Technologies for Measuring Stable Isotope Labelled Retinol in Biological Samples: Isotope Dilution Analysis of Body Retinol Stores

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Study of β‐Carotene Metabolism in Humans Using 13C‐β‐Carotene and High Precision Isotope Ratio Mass Spectrometry

Cited by 64 publications

References 5 publications

Plasma appearance of labeled β-carotene, lutein, and retinol in humans after consumption of isotopically labeled kale

Plasma appearance of labeled β-carotene, lutein, and retinol in humans after consumption of isotopically labeled kale

Variability of the conversion of β-carotene to vitamin A in women measured by using a double-tracer study design

Existing and Emerging Technologies for Measuring Stable Isotope Labelled Retinol in Biological Samples: Isotope Dilution Analysis of Body Retinol Stores

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Study of β‐Carotene Metabolism in Humans Using ¹³C‐β‐Carotene and High Precision Isotope Ratio Mass Spectrometry