Absorption and retinol equivalence of β-carotene in humans is influenced by dietary vitamin A intake

Lemke, Shawna L.; Dueker, Stephen R.; Follett, Jennifer R.; Lin, Yumei; Carkeet, Colleen; Buchholz, Bruce A.; Vogel, John S.; Clifford, Andrew J.

doi:10.1194/jlr.m300116-jlr200

Cited by 68 publications

(55 citation statements)

References 46 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…We determined that about 43% of the dosed ß-carotene was absorbed in the first 48-hr collection period and that 1 mol ß-carotene converted to 0.6 mol vitamin A. After vitamin A supplementation, higher absorption resulted in larger molar vitamin A values (Lemke, et al, 2003).…”

Section: Resultsmentioning

confidence: 99%

How to Convert Biological Carbon Into Graphite for AMS

et al. 2006

View full text Add to dashboard Cite

Isotope tracer studies, particularly radiocarbon measurements, play a key role in biological, nutritional, and environmental research. Accelerator mass spectrometry (AMS) is now the most sensitive detection method for radiocarbon, but AMS is not widely used in kinetic studies of humans. Part of the reason is the expense, but costs would decrease if AMS were used more widely. One component in the cost is sample preparation for AMS. Biological and environmental samples are commonly reduced to graphite before they are analyzed by AMS. Improvements and mechanization of this multi-step procedure is slowed by a lack of organized educational materials for AMS sample preparation that would allow new investigators to work with the technique without a substantial outlay of time and effort. We present a detailed sample preparation protocol for graphitizing biological samples for AMS and include examples of nutrition studies that have used this procedure.

show abstract

Section: Resultsmentioning

confidence: 99%

How to Convert Biological Carbon Into Graphite for AMS

et al. 2006

View full text Add to dashboard Cite

show abstract

“…A previous study supports the possibility that retinol may increase ␤-carotene absorption. Lemke et al (29) found that ␤-carotene was more efficiently absorbed after a vitamin A supplementation period compared with a period of lower vitamin A intake. These researchers hypothesized that the vitamin A supplementation either improved gut epithelial health or increased biliary ␤-carotene output (which would alter the isotope ratio measured in that study, thus giving the appearance of increased ␤-carotene absorption).…”

Section: Discussionmentioning

confidence: 99%

“…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%

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

View full text Add to dashboard Cite

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

show abstract

“…A substantial amount of the absorbed dietary carotenoids is not cleaved by the BCO enzymes in the intestine (Goodman et al 1966;Blomstrand and Werner 1967;Hickenbottom et al 2002;Lemke et al 2003); hence, humans absorb unchanged ␤-carotene and other carotenoids. The carotenoids get incorporated in chylomicrons to enter the circulation.…”

Section: Discussionmentioning

confidence: 99%

Cell Type-specific Expression of β-Carotene 9', 10'-Monooxygenase in Human Tissues

Lindqvist

Andersson

2005

J Histochem Cytochem.

116

100

View full text Add to dashboard Cite

S U M M A R YThe symmetrically cleaving ␤ -carotene 15,15 Ј -monooxygenase (BCO1) catalyzes the first step in the conversion of provitamin A carotenoids to vitamin A in the mucosa of the small intestine. This enzyme is also expressed in epithelia in a variety of extraintestinal tissues. The newly discovered ␤ -carotene 9 Ј ,10 Ј -monooxygenase (BCO2) catalyzes asymmetric cleavage of carotenoids. To gain some insight into the physiological role of BCO2, we determined the expression pattern of BCO2 mRNA and protein in human tissues. By immunohistochemical analysis it was revealed that BCO2 was detected in cell types that are known to express BCO1, such as epithelial cells in the mucosa of small intestine and stomach, parenchymal cells in liver, Leydig and Sertoli cells in testis, kidney tubules, adrenal gland, exocrine pancreas, and retinal pigment epithelium and ciliary body pigment epithelia in the eye. BCO2 was uniquely detected in cardiac and skeletal muscle cells, prostate and endometrial connective tissue, and endocrine pancreas. The finding that the BCO2 enzyme was expressed in some tissues and cell types that are not sensitive to vitamin A deficiency and where no BCO1 has been detected suggests that BCO2 may also be involved in biological processes other than vitamin A synthesis. T he enzymatic action of ␤ -carotene 15,15 Ј -monooxygenases (BCO1) is crucial for the conversion of provitamin A carotenoids to retinol (vitamin A) in the epithelial cells of the small intestine mucosa. The enzyme cleaves the ␤ -ionone ring containing carotenoids centrally, which results in two aldehyde molecules with polyene chains of identical length. Thus cleavage of the most common carotenoid ␤ -carotene results in two molecules of retinaldehyde (retinal), which will be further converted to retinol by a reductive retinal reductase enzyme present in the same cell as BCO1. Previously, we studied the cell type-specific expression of BCO1 and found that the enzyme is also expressed in epithelia of several extraintestinal tissues, which suggested that these tissues have the capacity to directly convert locally stored carotenoids to vitamin A. Thus this may serve as a backup pathway of vitamin A synthesis during times of insufficient dietary intake of preformed vitamin A and provitamin A carotenoids.Recently, Kiefer et al. (2001) cloned and characterized a second carotenoid-cleaving enzyme termed ␤ -carotene 9 Ј ,10 Ј -monooxygenase (BCO2) because it catalyzes asymmetric cleavage of carotenoids, thus yielding one molecule of ␤ -apo-10 Ј -carotenal and one molecule of ␤ -ionone when ␤ -carotene is used as substrate. Interestingly, the BCO2 enzyme appears to accept a wider variety of substrates as compared with BCO1, including the acyclic carotenoid lycopene, which implies that this enzyme may have physiological roles other than providing precursors for vitamin A synthesis.BCO1 and BCO2 belong to a superfamily of nonheme iron-containing oxygenases, many of whose functions are unknown. The physiological role of BCO1 is now well establ...

show abstract

Absorption and retinol equivalence of β-carotene in humans is influenced by dietary vitamin A intake

Cited by 68 publications

References 46 publications

How to Convert Biological Carbon Into Graphite for AMS

How to Convert Biological Carbon Into Graphite for AMS

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

Cell Type-specific Expression of β-Carotene 9', 10'-Monooxygenase in Human Tissues

Contact Info

Product

Resources

About