Kinetics of 14C distribution after tracer dose of 14C-lutein in an adult woman

The development and evolution of biological AMS at Livermore: a perspective

Biological accelerator mass spectrometry (AMS) provides ultrasensitive carbon-14 isotopic analysis enabling a deeper understanding of human health concerns by enabling quantification of pharmacokinetics and other molecular endpoints directly in humans. It enables environmentally and human relevant studies of metabolic pathways through the use of very low concentrations of labeled metabolic substrates in cells and organisms. Here, we discuss why AMS is an important tool for the biosciences, the development and evolution of biological AMS at Livermore and discuss technical refinements that will improve the efficiency of operation for the measurement of ultra-trace levels of 14C, which, long term, will enable greater ease of use and sample throughput.

Safety and efficacy of lutein and lutein/zeaxanthin extracts from Tagetes erecta for poultry for fattening and laying (except turkeys)

The Panel on Additives and Products or Substances used in Animal Feed (FEEDAP) evaluated (i) lutein from a saponified extract from Tagetes erecta obtained via extraction and saponification (lutein not less than 85% of total carotenoids (TC)) and (ii) lutein/zeaxanthin extract from Tagetes erecta obtained via extraction, saponification and isomerisation (lutein not less than 45% and zeaxanthin not less than 35% of TC). The maximum proposed use level of 80 mg TC from saponified Tagetes extract/kg complete feed for chickens for fattening and laying hens is safe for these animal categories. This conclusion can be extrapolated to minor poultry species for fattening and laying. The conclusions on saponified Tagetes extract for poultry for fattening and laying are extended to the saponified/isomerised Tagetes extract. The maximum use level of the saponified/isomerised Tagetes extract in breeding minor poultry should not exceed 50 mg TC/kg feed, considering the toxicological potential of zeaxanthin on reproduction. The saponified Tagetes extract is not genotoxic. This conclusion is extended to the saponified/isomerised Tagetes extract. Consumer exposure related to the consumption of animal products is very low compared to the exposure from other sources. The active substance is a viscous paste and may be irritant to skin and eyes; no exposure by inhalation is expected. In the absence of data, the Panel cannot conclude on the safety for the user of commercial preparations. The use of Tagetes extracts in poultry feed raised no concern for the environment. Tagetes extracts at levels up to the proposed maximum use level of 80 mg TC/kg complete feed have the potential to colour the egg yolk of laying hens and the skin of chickens for fattening. This conclusion is extended to minor poultry species for laying and for fattening. The use of the additive in feed and water for drinking is considered bioequivalent.

13C-lutein is differentially distributed in tissues of an adult female rhesus macaque following a single oral administration: a pilot study

Despite the growing awareness regarding lutein's putative roles in eyes and brain, its pharmacokinetics and tissue distribution in primates have been poorly understood. We hypothesized that ¹³C-lutein will be differentially distributed into tissues of an adult rhesus macaque (Macaca mulatta) 3 days following a single oral dose. After a year of prefeeding a diet supplemented with unlabeled lutein (1 μmol/kg/d), a 19-year-old female was dosed with 1.92 mg of highly enriched ¹³C-lutein. Tissues of a nondosed, lutein-fed monkey were used as a reference for natural abundance of ¹³C-lutein. On the third day postdose, plasma and multiple tissues were collected. Lutein was quantified by high-performance liquid chromatography-photodiode array detector, and ¹³C-lutein tissue enrichment was determined by liquid chromatography quadrupole time-of-flight mass spectrometry. In the tissues of a reference monkey, ¹²C-lutein with natural abundance of ¹³C-lutein was detectable. In the dosed monkey, highly enriched ¹³C-lutein was observed in all analyzed tissues except for the macular and peripheral retina, with the highest concentrations in the liver followed by the adrenal gland and plasma. ¹³C-lutein accumulated differentially across 6 brain regions. In adipose depots, ¹³C-lutein was observed, with the highest concentrations in the axillary brown adipose tissues. In summary, we evaluated ¹³C-lutein tissue distribution in a nonhuman primate following a single dose of isotopically labeled lutein. These results show that tissue distribution 3 days following a dose of lutein varied substantially dependent on tissue type.

Intrinsic and Extrinsic Factors Impacting Absorption, Metabolism, and Health Effects of Dietary Carotenoids

Carotenoids are orange, yellow, and red lipophilic pigments present in many fruit and vegetables, as well as other food groups. Some carotenoids contribute to vitamin A requirements. The consumption and blood concentrations of specific carotenoids have been associated with reduced risks of a number of chronic conditions. However, the interpretation of large, population-based observational and prospective clinical trials is often complicated by the many extrinsic and intrinsic factors that affect the physiologic response to carotenoids. Extrinsic factors affecting carotenoid bioavailability include food-based factors, such as co-consumed lipid, food processing, and molecular structure, as well as environmental factors, such as interactions with prescription drugs, smoking, or alcohol consumption. Intrinsic, physiologic factors associated with blood and tissue carotenoid concentrations include age, body composition, hormonal fluctuations, and variation in genes associated with carotenoid absorption and metabolism. To most effectively investigate carotenoid bioactivity and to utilize blood or tissue carotenoid concentrations as biomarkers of intake, investigators should either experimentally or statistically control for confounding variables affecting the bioavailability, tissue distribution, and metabolism of carotene and xanthophyll species. Although much remains to be investigated, recent advances have highlighted that lipid co-consumption, baseline vitamin A status, smoking, body mass and body fat distribution, and genetics are relevant covariates for interpreting blood serum or plasma carotenoid responses. These and other intrinsic and extrinsic factors are discussed, highlighting remaining gaps in knowledge and opportunities for future research. To provide context, we review the state of knowledge with regard to the prominent health effects of carotenoids.

Carrot solution culture bioproduction of uniformly labeled 13C-lutein and in vivo dosing in non-human primates

Lutein is a xanthophyll abundant in nature and most commonly present in the human diet through consumption of leafy green vegetables. With zeaxanthin and meso-zeaxanthin, lutein is a component of the macular pigment of the retina, where it protects against photooxidation and age-related macular degeneration. Recent studies have suggested that lutein may positively impact cognition throughout the lifespan, but outside of the retina, the deposition, metabolism, and function(s) of lutein are poorly understood. Using a novel botanical cell culture system ( Daucus carota), the present study aimed to produce a stable isotope lutein tracer for use in future investigations of dietary lutein distribution and metabolism. Carrot cultivars were initiated into liquid solution culture, lutein production conditions optimized, and uniformly labeled ¹³C-glucose was provided as the sole media carbon source for four serial growth cycles. Lutein yield was 2.58 ± 0.24 µg/g, and mass spectrometry confirmed high enrichment of ¹³C: 64.9% of lutein was uniformly labeled and 100% of lutein was labeled on at least 37 of 40 possible carbons. Purification of carrot extracts yielded a lutein dose of 1.92 mg with 96.0 ± 0.60% purity. ¹³C-lutein signals were detectable in hepatic extracts of an adult rhesus macaque monkey ( Macaca mulatta) dosed with ¹³C-lutein, but not in hepatic samples collected from control animals. This novel botanical biofactory approach can be used to produce sufficient quantities of highly enriched and pure ¹³C-lutein doses for use in tracer studies investigating lutein distribution, metabolism, and function.

Bioavailability of iron, zinc, and provitamin A carotenoids in biofortified staple crops

International research efforts, including those funded by HarvestPlus, a Challenge Program of the Consultative Group on International Agricultural Research (CGIAR), are focusing on conventional plant breeding to biofortify staple crops such as maize, rice, cassava, beans, wheat, sweet potatoes, and pearl millet to increase the concentrations of micronutrients that are commonly deficient in specific population groups of developing countries. The bioavailability of micronutrients in unfortified staple crops in developing regions is typically low, which raises questions about the efficacy of these crops to improve population micronutrient status. This review of recent studies of biofortified crops aims to assess the micronutrient bioavailability of biofortified staple crops in order to derive lessons that may help direct plant breeding and to infer the potential efficacy of food-based nutrition interventions. Although reducing the amounts of antinutrients and the conduction of food processing generally increases the bioavailability of micronutrients, antinutrients still possess important benefits, and food processing results in micronutrient loss. In general, biofortified foods with relatively higher micronutrient density have higher total absorption rates than nonbiofortified varieties. Thus, evidence supports the focus on efforts to breed plants with increased micronutrient concentrations in order to decrease the influence of inhibitors and to offset losses from processing.

Plasma lutein and zeaxanthin and the risk of age-related nuclear cataract among the elderly Finnish population

Oxidative stress plays an important role in cataractogenesis. Previous studies have shown that long-term dietary intake of antioxidants (lutein and zeaxanthin) may decrease the risk of age-related cataracts. The aim of the present study was to examine whether plasma concentrations of lutein and zeaxanthin are related to age-related nuclear cataract in the elderly population. Subjects were participants in the Kuopio Ischaemic Heart Disease Risk Factor Study and they were classified into tertiles according to plasma concentrations of lutein and zeaxanthin. The association of plasma lutein and zeaxanthin concentrations with age-related nuclear cataract in 1689 elderly subjects (aged 61-80 years) was investigated in the present cross-sectional study by using the Cox proportional hazards model. A total of 113 cases of incident age-related cataracts were confirmed, of which 108 cases were nuclear cataracts. After adjustment for age, examination year, sex, BMI, smoking, alcohol consumption, serum LDL-cholesterol, serum HDL-cholesterol, years of education, use of oral corticosteroids, history of diabetes and history of hypertension with current use of antihypertensive medication, subjects in the highest tertiles of plasma concentrations of lutein and zeaxanthin had 42 and 41 % lower risks of nuclear cataract, respectively, compared with those in the lowest tertiles (relative risk (RR) = 0·58, 95 % CI 0·35, 0·98; P = 0·041 for lutein and RR = 0·59, 95 % CI 0·35, 0·99; P = 0·046 for zeaxanthin). In conclusion, we suggest that high plasma concentrations of lutein and zeaxanthin were associated with a decreased risk of age-related nuclear cataract in the elderly population.

Carbon isotopes profiles of human whole blood, plasma, red blood cells, urine and feces for biological/biomedical 14C-accelerator mass spectrometry applications

Radiocarbon ((14)C) is an ideal tracer for in vivo human ADME (absorption, distribution, metabolism, elimination) and PBPK (physiological-based pharmacokinetic) studies. Living plants peferentially incorporate atmospheric (14)CO(2) versus (13)CO(2) versus (12)CO(2), which result in unique signature. Furthermore, plants and the food chains they support also have unique carbon isotope signatures. Humans, at the top of the food chain, consequently acquire isotopic concentrations in the tissues and body fluids depending on their dietary habits. In preparation of ADME and PBPK studies, 12 healthy subjects were recruited. The human baseline (specific to each individual and their diet) total carbon (TC) and carbon isotope (13)C (δ(13)C) and (14)C (F(m)) were quantified in whole blood (WB), plasma, washed red blood cell (RBC), urine, and feces. TC (mg of C/100 μL) in WB, plasma, RBC, urine, and feces were 11.0, 4.37, 7.57, 0.53, and 1.90, respectively. TC in WB, RBC, and feces was higher in men over women, P < 0.05. Mean δ(13)C were ranked low to high as follows: feces < WB = plasma = RBC = urine, P < 0.0001. δ(13)C was not affected by gender. Our analytic method shifted δ(13)C by only ±1.0 ‰ ensuring our F(m) measurements were accurate and precise. Mean F(m) were ranked low to high as follows: plasma = urine < WB = RBC = feces, P < 0.05. F(m) in feces was higher for men over women, P < 0.05. Only in WB, (14)C levels (F(m)) and TC were correlated with one another (r = 0.746, P < 0.01). Considering the lag time to incorporate atmospheric (14)C into plant foods (vegetarian) and or then into animal foods (nonvegetarian), the measured F(m) of WB in our population (recruited April 2009) was 1.0468 ± 0.0022 (mean ± SD), and the F(m) of WB matched the (extrapolated) atmospheric F(m) of 1.0477 in 2008. This study is important in presenting a procedure to determine a baseline for a study group for human ADME and PBPK studies using (14)C as a tracer.

Pharmacokinetics and tissue distribution of 14C-labeled grape polyphenols in the periphery and the central nervous system following oral administration

Grape polyphenols confer potential health benefits, including prevention of neurodegenerative diseases. To determine the absorption and tissue distribution of the complex grape polyphenol mixture, (14)C-labeled polyphenols were biosynthesized by grape cell suspension cultures, during co-incubation with radioisotopically labeled sucrose, and fractionated into polyphenolic subfractions. The pharmacokinetics and distribution of grape polyphenols into blood, brain, and peripheral interstitial fluid were determined by tracking the (14)C label. The blood peak (14)C concentration of the fractions ranged from 15 minutes to 4 hours. Absorption and tissue distribution varied greatly between fractions. Concentrations in interstitial fluid were lower than in blood. The amount of residual label in the brain at 24 hours ranged from 0.1% to 1.7% of the dose, depending on the fraction. (14)C label found in the brain tissue and brain microdialysate indicated that grape polyphenols or their metabolites are able to cross the blood-brain barrier. Using (14)C-labeled plant polyphenols it is possible to track the compounds or their metabolic products into any tissue and determine distribution patterns in spite of low concentrations. A central question regarding the potential role of dietary polyphenolics in neurodegenerative research is whether they are bioavailable in the brain. Our observations indicate that some grape-derived polyphenolics do reach the brain, which suggests their potential value for applications in neurodegenerative disorders.

Calculating radiation exposures during use of (14)C-labeled nutrients, food components, and biopharmaceuticals to quantify metabolic behavior in humans

(14)C has long been used as a tracer for quantifying the in vivo human metabolism of food components, biopharmaceuticals, and nutrients. Minute amounts (< or =1 x 10 (-18) mol) of (14)C can be measured with high-throughput (14)C-accelerator mass spectrometry (HT (14)C-AMS) in isolated chemical extracts of biological, biomedical, and environmental samples. Availability of in vivo human data sets using a (14)C tracer would enable current concepts of the metabolic behavior of food components, biopharmaceuticals, or nutrients to be organized into models suitable for quantitative hypothesis testing and determination of metabolic parameters. In vivo models are important for specification of intake levels for food components, biopharmaceuticals, and nutrients. Accurate estimation of the radiation exposure from ingested (14)C is an essential component of the experimental design. Therefore, this paper illustrates the calculation involved in determining the radiation exposure from a minute dose of orally administered (14)C-beta-carotene, (14)C-alpha-tocopherol, (14)C-lutein, and (14)C-folic acid from four prior experiments. The administered doses ranged from 36 to 100 nCi, and radiation exposure ranged from 0.12 to 5.2 microSv to whole body and from 0.2 to 3.4 microSv to liver with consideration of tissue weighting factor and fractional nutrient. In comparison, radiation exposure experienced during a 4 h airline flight across the United States at 37000 ft was 20 microSv.

Accelerator mass spectrometry-enabled studies: current status and future prospects

Accelerator mass spectrometry is a detection platform with exceptional sensitivity compared with other bioanalytical platforms. Accelerator mass spectrometry (AMS) is widely used in archeology for radiocarbon dating applications. Early exploration of the biological and pharmaceutical applications of AMS began in the early 1990s. AMS has since demonstrated unique problem-solving ability in nutrition science, toxicology and pharmacology. AMS has also enabled the development of new applications, such as Phase 0 microdosing. Recent development of AMS-enabled applications has transformed this novelty research instrument to a valuable tool within the pharmaceutical industry. Although there is now greater awareness of AMS technology, recognition and appreciation of the range of AMS-enabled applications is still lacking, including study-design strategies. This review aims to provide further insight into the wide range of AMS-enabled applications. Examples of studies conducted over the past two decades will be presented, as well as prospects for the future of AMS.

Carotenoid maintenance handicap and the physiology of carotenoid-based signalisation of health

Despite a reasonable scientific interest in sexual selection, the general principles of health signalisation via ornamental traits remain still unresolved in many aspects. This is also true for the mechanism preserving honesty of carotenoid-based signals. Although it is widely accepted that this type of ornamentation reflects an allocation trade-off between the physiological utilisation of carotenoids (mainly in antioxidative processes) and their deposition in ornaments, some recent evidence suggests more complex interactions. Here, we further develop the models currently proposed to explain the honesty of carotenoid-based signalisation of heath status by adding the handicap principle concept regulated by testosterone. We propose that under certain circumstances carotenoids may be dangerous for the organism because they easily transform into toxic cleavage products. When reserves of other protective antioxidants are insufficient, physiological trade-offs may exist between maintenance of carotenoids for ornament expression and their removal from the body. Furthermore, we suggest that testosterone which enhances ornamentation by increasing carotenoid bioavailability may also promote oxidative stress and hence lower antioxidant reserves. The presence of high levels of carotenoids required for high-quality ornament expression may therefore represent a handicap and only individuals in prime health could afford to produce elaborate colourful ornaments. Although further testing is needed, this 'carotenoid maintenance handicap' hypothesis may offer a new insight into the physiological aspects of the relationship between carotenoid function, immunity and ornamentation.

A minute dose of 14C-{beta}-carotene is absorbed and converted to retinoids in humans

Our objective was to quantify the absorption and conversion to retinoids of a 1.01-nmol, 3.7-kBq oral dose of (14)C-beta-carotene in 8 healthy adults. The approach was to quantify, using AMS, the elimination of (14)C in feces for up to 16 d after dosing and in urine for up to 30 d after dosing. The levels of total (14)C in undiluted serial plasma samples were measured for up to 166 d after dosing. Also, the levels of (14)C in the retinyl ester (RE), retinol (ROH), and beta-carotene fractions that were isolated from undiluted plasma using HPLC were measured. The apparent digestibility of the (14)C was 53 +/- 13% (mean +/- SD), based on the mass balance data, and was generally consistent with the area under the curve for zero to infinite period of (14)C that was eliminated in the feces collections made up to 7.5 d after dosing. Metabolic fecal elimination, calculated as the slope per day (% (14)C-dose/collection from d 7.5 to the final day), was only 0.05 +/- 0.02%. The portion of the (14)C dose eliminated via urine was variable (6.5 +/- 5.2%). Participants [except participant 6 (P6)] had a distinct plasma peak of (14)C at 0.25 d post-dose, preceded by a shoulder at approximately 0.1 d, and followed by a broad (14)C peak that became indistinguishable from baseline at approximately 40 d. Plasma (14)C-RE accounted for most of the absorbed (14)C early after dosing and P1 had the longest delay in the first appearance of (14)C-RE in plasma. The data suggest that plasma RE should be considered in estimating the ROH activity equivalent of ingested beta-carotene.

Excentral cleavage of beta-carotene in vivo in a healthy man

BACKGROUND

Excentral cleavage of beta-carotene to retinoids and apocarotenoids occurs in vitro and in animal models. Whether it occurs in humans is unclear.

OBJECTIVE

We tested the hypothesis of whether humans can cleave beta-carotene excentrally.

DESIGN

A healthy man was given an oral dose of all-trans [10,10',11,11'-(14)C]-beta-carotene (1.01 nmol; 100 nCi). Its fate and that of its metabolites were measured in serial plasma samples. Its fate in feces and urine was also measured over time. Selected plasma samples were spiked with reference standards of retinol, beta-apo-12'-carotenal, beta-apo-8'-carotenal, 13-cis-retinoic acid, all-trans-retinoic acid, beta-carotene-5,6-epoxide, all-trans-beta-carotene, and retinyl palmitate and subjected to reverse-phase HPLC fractionation. The plasma, plasma fractions, urine, and feces were measured for (14)C with the use of accelerator mass spectrometry.

RESULTS

Sixty-five percent of administered (14)C was absorbed, and 15.7% was eliminated in urine during the first 21 d after dosing. (14)C-beta-carotene and (14)C-retinyl palmitate appeared in plasma 0.25 d after the dose. (14)C-beta-carotene and (14)C-retinol both appeared at 0.5 d only. On day 3 after the dose, 2 large (14)C peaks appeared in plasma: one matched the retention time of beta-apo-8'-carotenal, and the other did not match any of the reference standards used. The delayed appearance of (14)C-beta-apo-8'-carotenal in plasma suggests that the excentral cleavage occurred after the (14)C-beta-apo-8'-carotene was absorbed into the body.

CONCLUSION

These data suggest that excentral cleavage of ingested beta-carotene occurs in vivo in humans. Confirmation of that possibility and further study to identify and characterize additional metabolites are needed.