Carotenoids in human nutrition and health.

Carotenoids are naturally occurring pigments found in most fruits and vegetables, plants, algae, and photosynthetic bacteria. Humans cannot synthesize carotenoids and must ingest them in food or via supplementation. Carotenoids have a range of functions in human health. They primarily exert antioxidant effects, but individual carotenoids may also act through other mechanisms; for example, ß-carotene has a pro-vitamin A function, while lutein/zeaxanthin constitute macular pigment in the eye. The benefit of lutein in reducing progression of age-related macular eye disease and cataracts is strengthening; an intake recommendation would help to generate awareness in the general population to have an adequate intake of lutein rich foods. There is evidence that carotenoids, in addition to beneficial effects on eye health, also produce improvements in cognitive function and cardiovascular health, and may help to prevent some types of cancer. Despite the evidence for the health benefits of carotenoids, large population-based supplementation studies have produced mixed results for some of the carotenoids. To establish and confirm the health benefits of the different carotenoids more research, including clinical studies, is needed.

Vitamin E function and requirements in relation to PUFA.

Vitamin E (α-tocopherol) is recognised as a key essential lipophilic antioxidant in humans protecting lipoproteins, PUFA, cellular and intra-cellular membranes from damage. The aim of this review was to evaluate the relevant published data about vitamin E requirements in relation to dietary PUFA intake. Evidence in animals and humans indicates a minimal basal requirement of 4-5 mg/d of RRR-α-tocopherol when the diet is very low in PUFA. The vitamin E requirement will increase with an increase in PUFA consumption and with the degree of unsaturation of the PUFA in the diet. The vitamin E requirement related to dietary linoleic acid, which is globally the major dietary PUFA in humans, was calculated to be 0·4-0·6 mg of RRR-α-tocopherol/g of linoleic acid. Animal studies show that for fatty acids with a higher degree of unsaturation, the vitamin E requirement increases almost linearly with the degree of unsaturation of the PUFA in the relative ratios of 0·3, 2, 3, 4, 5 and 6 for mono-, di-, tri-, tetra-, penta- and hexaenoic fatty acids, respectively. Assuming a typical intake of dietary PUFA, a vitamin E requirement ranging from 12 to 20 mg of RRR-α-tocopherol/d can be calculated. A number of guidelines recommend to increase PUFA intake as they have well-established health benefits. It will be prudent to assure an adequate vitamin E intake to match the increased PUFA intake, especially as vitamin E intake is already below recommendations in many populations worldwide.

A Systematic Review of Global Alpha-Tocopherol Status as Assessed by Nutritional Intake Levels and Blood Serum Concentrations.

The purpose of this study is to systematically review the published literature reporting vitamin E intake levels and serum concentrations in order to obtain a global overview of α-tocopherol status. Articles published between 2000 and 2012 were considered; 176 articles referring to 132 single studies were included. Applying an RDA (recommended daily allowance) of 15 mg/day and EAR (estimated average requirement) of 12 mg/day to all populations with a minimum age of 14 years, 82 and 61 % of mean and median data points were below the RDA and the EAR, respectively. Regarding serum concentrations, globally 13 % of the included data points were below the functional deficiency threshold concentration of 12 µmol/L, mostly for newborns and children. Several prospective observational studies suggest that a serum α-tocopherol concentration of ≥30 µmol/L has beneficial effects on human health. Of the reported study populations and subpopulations, only 21 % reached this threshold globally. This systematic review suggests that the α-tocopherol status is inadequate in a substantial part of the studied populations.

Fluorescence lifetime imaging ophthalmoscopy and the influence of oral lutein/zeaxanthin supplementation on macular pigment (FLOS) - A pilot study.

BACKGROUND & AIMS: Oral lutein (L) and zeaxanthin (Z) supplementation enhances macular pigment optical density (MPOD) and plays a protective role in the development of age-related macular degeneration (AMD). Fluorescence lifetime imaging ophthalmoscopy (FLIO) is a novel in vivo retinal imaging method that has been shown to correlate to classical MPOD measurements and might contribute to a metabolic mapping of the retina in the future. Our aim was to show that oral supplementation of L and Z affects the FLIO signal in a positive way in patients with AMD. METHODS: This was a prospective, single center, open label cohort study. Patients with early and intermediate AMD received oral L and Z supplementation during three months, and were observed for another three months after therapy termination. All visits included measurements of clinical parameters, serum L and Z concentration, MPOD measurements using heterochromatic flicker photometry, dual wavelength autofluorescence imaging, and FLIO. Correlation analysis between FLIO and MPOD were performed. RESULTS: Twenty-one patients completed the follow up period. Serum L and Z concentrations significantly increased during supplementation (mean difference 244.8 ng/ml; 95% CI: 81.26-419.9, and 77.1 ng/ml; 95% CI: 5.3-52.0, respectively). Mean MPOD units significantly increased (mean difference 0.06; 95% CI: 0.02-0.09; at 0.5°, 202; 95% CI: 58-345; at 2°, 1033; 95% CI: 288-1668; at 9° of eccentricity, respectively) after three months of supplementation with macular xanthophylls, which included L and Z. Median FLIO lifetimes in the foveal center significantly decreased from 277.3 ps (interquartile range 230.2-339.1) to 261.0 ps (interquartile range 231.4-334.4, p = 0.027). All parameters returned to near-normal values after termination of the nutritional supplementation. A significant negative correlation was found between FLIO and MPOD (r2 = 0.57, p < 0.0001). CONCLUSIONS: FLIO is able to detect subtle changes in MPOD after L and Z supplementation in patients with early and intermediate AMD. Our findings confirm the previous described negative correlation between FLIO and MPOD. Macular xanthophylls seem to contribute to short foveal lifetimes. This study is registered at ClinicalTrials.gov (identifier number NCT04761341).

Safety, Tolerability, and Pharmacokinetics of ß-Cryptoxanthin Supplementation in Healthy Women: A Double-Blind, Randomized, Placebo-Controlled Clinical Trial.

BACKGROUND: ß-cryptoxanthin is a dietary carotenoid for which there have been few studies on the safety and pharmacokinetics following daily oral supplementation. METHODS: 90 healthy Asian women between 21 and 35 years were randomized into three groups: 3 and 6 mg/day oral ß-cryptoxanthin, and placebo. At 2, 4, and 8 weeks of supplementation, plasma carotenoid levels were measured. The effects of ß-cryptoxanthin on blood retinoid-dependent gene expression, mood, physical activity and sleep, metabolic parameters, and fecal microbial composition were investigated. RESULTS: ß-cryptoxanthin supplementation for 8 weeks (3 and 6 mg/day) was found to be safe and well tolerated. Plasma ß-cryptoxanthin concentration was significantly higher in the 6 mg/day group (9.0 ± 4.1 µmol/L) compared to 3 mg/day group (6.0 ± 2.6 µmol/L) (p < 0.03), and placebo (0.4 ± 0.1 µmol/L) (p < 0.001) after 8 weeks. Plasma all-trans retinol, α-cryptoxanthin, α-carotene, ß-carotene, lycopene, lutein, and zeaxanthin levels were not significantly changed. No effects were found on blood retinol-dependent gene expression, mood, physical activity and sleep, metabolic parameters, and fecal microbial composition. CONCLUSIONS: Oral ß-cryptoxanthin supplementation over 8 weeks lead to high plasma concentrations of ß-cryptoxanthin, with no impact on other carotenoids, and was well tolerated in healthy women.

ß-Carotene and its cleavage enzyme ß-carotene-15,15'-oxygenase (CMOI) affect retinoid metabolism in developing tissues.

The mammalian embryo relies on maternal circulating retinoids (vitamin A derivatives) for development. ß-Carotene is the major human dietary provitamin A. ß-Carotene-15,15'-oxygenase (CMOI) has been proposed as the main enzyme generating retinoid from ß-carotene in vivo. CMOI is expressed in embryonic tissues, suggesting that ß-carotene provides retinoids locally during development. We performed loss of CMOI function studies in mice lacking retinol-binding protein (RBP), an established model of embryonic vitamin A deficiency (VAD). We show that, unexpectedly, lack of CMOI in the developing tissues further exacerbates the severity of VAD and thus the embryonic malformations of RBP(-/-) mice. Since ß-carotene was not present in any of the mouse diets, we unveiled a novel action of CMOI independent from its ß-carotene cleavage activity. We also show for the first time that CMOI exerts an additional function on retinoid metabolism by influencing retinyl ester formation via modulation of lecithin:retinol acyltransferase (LRAT) activity, at least in developing tissues. Finally, we demonstrate unequivocally that ß-carotene can serve as an alternative vitamin A source for the in situ synthesis of retinoids in developing tissues by the action of CMOI.

A mitochondrial enzyme degrades carotenoids and protects against oxidative stress.

Carotenoids are the precursors for vitamin A and are proposed to prevent oxidative damage to cells. Mammalian genomes encode a family of structurally related nonheme iron oxygenases that modify double bonds of these compounds by oxidative cleavage and cis-to-trans isomerization. The roles of the family members BCMO1 and RPE65 for vitamin A production and vision have been well established. Surprisingly, we found that the third family member, ß,ß-carotene-9',10'-oxygenase (BCDO2), is a mitochondrial carotenoid-oxygenase with broad substrate specificity. In BCDO2-deficient mice, carotenoid homeostasis was abrogated, and carotenoids accumulated in several tissues. In hepatic mitochondria, accumulated carotenoids induced key markers of mitochondrial dysfunction, such as manganese superoxide dismutase (9-fold), and reduced rates of ADP-dependent respiration by 30%. This impairment was associated with an 8- to 9-fold induction of phosphor-MAP kinase and phosphor-AKT, markers of cell signaling pathways related to oxidative stress and disease. Administration of carotenoids to human HepG2 cells depolarized mitochondrial membranes and resulted in the production of reactive oxygen species. Thus, our studies in BCDO2-deficient mice and human cell cultures indicate that carotenoids can impair respiration and induce oxidative stress. Mammalian cells thus express a mitochondrial carotenoid-oxygenase that degrades carotenoids to protect these vital organelles.

ISX is a retinoic acid-sensitive gatekeeper that controls intestinal beta,beta-carotene absorption and vitamin A production.

The uptake of dietary lipids from the small intestine is a complex process that depends on the activities of specific membrane receptors with yet unknown regulatory mechanisms. Using both mouse models and human cell lines, we show here that intestinal lipid absorption by the scavenger receptor class B type 1 (SR-BI) is subject to control by retinoid signaling. Retinoic acid via retinoic acid receptors induced expression of the intestinal transcription factor ISX. ISX then repressed the expression of SR-B1 and the carotenoid-15,15'-oxygenase Bcmo1. BCMO1 acts downstream of SR-BI and converts absorbed beta,beta-carotene to the retinoic acid precursor, retinaldehyde. Using BCMO1-knockout mice, we demonstrated increased intestinal SR-BI expression and systemic beta,beta-carotene accumulation. SR-BI-dependent accumulation of beta,beta-carotene was prevented by dietary retinoids that induced ISX expression. Thus, our study revealed a diet-responsive regulatory network that controls beta,beta-carotene absorption and vitamin A production by negative feedback regulation. The role of SR-BI in the intestinal absorption of other dietary lipids, including cholesterol, fatty acids, and tocopherols, implicates retinoid signaling in the regulation of lipid absorption more generally and has clinical implications for diseases associated with dyslipidemia.

Monoamine reuptake inhibition and mood-enhancing potential of a specified oregano extract.

A healthy, balanced diet is essential for both physical and mental well-being. Such a diet must include an adequate intake of micronutrients, essential fatty acids, amino acids and antioxidants. The monoamine neurotransmitters, serotonin, dopamine and noradrenaline, are derived from dietary amino acids and are involved in the modulation of mood, anxiety, cognition, sleep regulation and appetite. The capacity of nutritional interventions to elevate brain monoamine concentrations and, as a consequence, with the potential for mood enhancement, has not been extensively evaluated. The present study investigated an extract from oregano leaves, with a specified range of active constituents, identified via an unbiased, high-throughput screening programme. The oregano extract was demonstrated to inhibit the reuptake and degradation of the monoamine neurotransmitters in a dose-dependent manner, and microdialysis experiments in rats revealed an elevation of extracellular serotonin levels in the brain. Furthermore, following administration of oregano extract, behavioural responses were observed in mice that parallel the beneficial effects exhibited by monoamine-enhancing compounds when used in human subjects. In conclusion, these data show that an extract prepared from leaves of oregano, a major constituent of the Mediterranean diet, is brain-active, with moderate triple reuptake inhibitory activity, and exhibits positive behavioural effects in animal models. We postulate that such an extract may be effective in enhancing mental well-being in humans.

Knockout of the Bcmo1 gene results in an inflammatory response in female lung, which is suppressed by dietary beta-carotene.

Beta-carotene 15,15'-monooxygenase 1 knockout (Bcmo1 (-/-)) mice accumulate beta-carotene (BC) similarly to humans, whereas wild-type (Bcmo1 (+/+)) mice efficiently cleave BC. Bcmo1 (-/-) mice are therefore suitable to investigate BC-induced alterations in gene expression in lung, assessed by microarray analysis. Bcmo1 (-/-) mice receiving control diet had increased expression of inflammatory genes as compared to BC-supplemented Bcmo1 (-/-) mice and Bcmo1 (+/+) mice that received either control or BC-supplemented diets. Differential gene expression in Bcmo1 (-/-) mice was confirmed by real-time quantitative PCR. Histochemical analysis indeed showed an increase in inflammatory cells in lungs of control Bcmo1 (-/-) mice. Supported by metabolite and gene-expression data, we hypothesize that the increased inflammatory response is due to an altered BC metabolism, resulting in an increased vitamin A requirement in Bcmo1 (-/-) mice. This suggests that effects of BC may depend on inter-individual variations in BC-metabolizing enzymes, such as the frequently occurring human polymorphisms in BCMO1.

Loss of carotene-9',10'-monooxygenase expression increases serum and tissue lycopene concentrations in lycopene-fed mice.

Two enzymes have been identified for the oxidative metabolism of carotenoids in mammals. Carotene-15,15'-monooxygenase (CMO-I) primarily centrally cleaves ß,ß-carotene to form vitamin A. We hypothesize that carotene-9',10'-monooxygenase (CMO-II) plays a key role in metabolism of acyclic nonprovitamin A carotenoids such as lycopene. We investigated carotenoid bioaccumulation in young adult, male, wild-type (WT) mice or mice lacking CMO-II (CMO-II KO). Mice were fed an AIN-93G diet or identical diets supplemented with 10% tomato powder, 130 mg lycopene/kg diet (10% lycopene beadlets), or placebo beadlets for 4 or 30 d. Lycopene preferentially accumulated in CMO-II KO mouse tissues and serum compared with WT mouse tissues. ß-Carotene preferentially accumulated in some CMO-II KO mouse tissues compared with WT mouse tissues. Relative tissue mRNA expression of CMO-I and CMO-II was differentially expressed in mouse tissues, and CMO-II, but not CMO-I, was expressed in mouse prostate. In conclusion, the loss of CMO-II expression leads to increased serum and tissue concentrations of lycopene in tomato-fed mice.

Experiences of peer counselling during inpatient rehabilitation of patients with spinal cord injuries.

Study design: Qualitative study. Objectives: The aim of this study was to evaluate peer counselling during inpatient rehabilitation of patients with spinal cord injuries (SCI). This article describes the experience with peer counselling from the perspective of patients with SCI as well as from the perspective of the peer counsellors. Setting: Inpatient rehabilitation of SCI in the Swiss Paraplegic Centre. Methods: Six interviews with patients and one focus group interview with professional peer counsellors have been evaluated using qualitative content analysis. Results: Patients experienced the peer counselling sessions as solution-oriented, practical, motivating and especially appreciated the authentic, open demeanor of the peer counsellors. Conversations about recreational activities, hobbies and interests supported the development of interpersonal relationships. Peer counsellors experienced the initial visits with patients with high level quadriplegia as a special challenge. The regular presence of all peer counsellors in the hospital facilitated an easier exchange with the patients. Conclusion: Patients feel empowered by peer counselling. Special attention should be placed on the timing of the initial visit. Unplanned meetings between patient and peers seem to be essential and highly valued. Peer counsellors are confronted with stressful situations in their work, therefore the need for support and training of peer counsellors should be further investigated.

"Theory Does Not Get You From Bed to Wheelchair": A Qualitative Study on Patients' Views of an Education Program in Spinal Cord Injury Rehabilitation.

PURPOSE: The aim of this study was to evaluate a new nurse-guided patient education program in spinal cord injury rehabilitation with particular focus on the patients' perspectives and experiences. DESIGN: Longitudinal qualitative study. METHODS: We conducted face-to-face interviews with 10 rehabilitation patients and used the content analysis method to analyze the data. FINDINGS: Patients emphasized the importance of the practical training of the education program. This impacted their well-being as well as their autonomy. They rated discussions with primary nurses and peers about physical or psychological concerns. However, after discharge, the learning process was ongoing, and patients experienced the transition to living at home as a major challenge. CONCLUSIONS AND CLINICAL RELEVANCE: This research provides valuable information from the patients' perspective for enhancing spinal cord injury patient education. Situational learning, based on the practical parts of patient education and working with peers, is highlighted.

In vitro and in vivo characterization of retinoid synthesis from beta-carotene.

Retinoids are indispensable for the health of mammals, which cannot synthesize retinoids de novo. Retinoids are derived from dietary provitamin A carotenoids, like beta-carotene, through the actions of beta-carotene-15,15'-monooxygenase (BCMO1). As the substrates for retinoid-metabolizing enzymes are water insoluble, they must be transported intracellularly bound to cellular retinol-binding proteins. Our studies suggest that cellular retinol-binding protein, type I (RBP1) acts as an intracellular sensor of retinoid status that, when present as apo-RBP1, stimulates BCMO1 activity and the conversion of carotenoids to retinoids. Cellular retinol-binding protein, type II (RBP2), which is 56% identical to RBP1 does not influence BCMO1 activity. Studies of mice lacking BCMO1 demonstrate that BCMO1 is responsible for metabolically limiting the amount of intact beta-carotene that can be absorbed by mice from their diet. Our studies provide new insights into the regulation of BCMO1 activity and the physiological role of BCMO1 in living organisms.

Lycopene biodistribution is altered in 15,15'-carotenoid monooxygenase knockout mice.

15,15'-carotenoid monooxygenase (CMO I) is generally recognized as the central carotenoid cleavage enzyme responsible for converting provitamin A carotenoids to vitamin A, while having little affinity for nonprovitamin A carotenoids, such as lycopene. To investigate the role of CMO I in carotenoid metabolism, approximately 90-d-old C57BL/6 x 129/SvJ [CMO I wild-type (WT)] and B6;129S6-Bcmo1tm1Dnp [CMO I knockout (KO)] mice were fed a high-fat, moderate vitamin A, cholesterol-containing diet supplemented with 150 mg/kg diet of beta-carotene, lycopene, or placebo beadlets for 60 d (n = 12-14). CMO I KO mice fed lycopene (Lyc-KO) exhibited significant decreases in hepatic, spleen, and thymus lycopene concentrations and significant increases in prostate, seminal vesicles, testes, and brain lycopene concentrations compared with WT mice fed lycopene (Lyc-WT). Furthermore, in the serum and all tissues analyzed, excluding the testes, there was a significant increase in the percent lycopene cis isomers in Lyc-KO mice compared with Lyc-WT mice. CMO I KO mice fed beta-carotene (betaC-KO) had significantly lower hepatic vitamin A concentrations (17% of WT mice fed beta-carotene [betaC-WT]). Concordantly, betaC-KO mice had higher serum and tissue beta-carotene concentrations than betaC-WT mice. In addition, phenotypically CMO I KO mice had significantly higher final body weights and CMO I KO female mice had significantly lower uterus weights than CMO I WT mice. In conclusion, CMO I KO mice fed low levels of vitamin A have altered lycopene biodistribution and isomer patterns and do not cleave beta-carotene to vitamin A at appreciable levels.

The Biochemical Basis of Vitamin A3 Production in Arthropod Vision.

Metazoan photochemistry involves cis-trans isomerization of a retinylidene chromophore bound to G protein coupled receptors. Successful production of chromophores is critical for photoreceptor function and survival. For chromophore production, animals have to choose from more than 600 naturally occurring carotenoids and process them by oxidative cleavage and geometric isomerization of double bonds. Vertebrates employ three carotenoid cleavage oxygenases to tailor the carotenoid precursor in the synthesis of 11-cis-retinal (vitamin A1). Lepidoptera (butterfly and moth) possess only one such enzyme, NinaB, which faces the challenge to catalyze these reactions in unison to produce 11-cis-3-hydroxy-retinal (vitamin A3). We here showed that key to this multitasking is a bipartite substrate recognition site that conveys regio- and stereoselectivity for double bond processing. One side performed the specific C11, C12 cis-isomerization and preferentially binds 3-OH-ß-ionone rings sites. The other side maintained a trans configuration in the resulting product and preferentially binds noncanonical ionone ring sites. Concurrent binding of carotenoids containing two cyclohexyl rings to both domains is required for specific oxidative cleavage at position C15, C15' of the substrate. The unique reaction sequence follows a dioxygenase mechanism with a carbocation/radical intermediate. This ingenious quality control system guarantees 11-cis-3-hydroxy-retinal production, the essential retinoid for insect (vitamin A3) vision.

Beta-carotene inhibits UVA-induced matrix metalloprotease 1 and 10 expression in keratinocytes by a singlet oxygen-dependent mechanism.

UVA exposure causes skin photoaging by singlet oxygen (1)O(2)-mediated induction of, e.g., matrix metalloproteases (MMPs). We assessed whether pretreatment with beta-carotene, a (1)O(2) quencher and retinoic acid (RA) precursor, interferes with UVA-induced gene regulation. HaCaT keratinocytes were precultured with beta-carotene at physiological concentrations (0.5, 1.5, and 3.0 microM) prior to exposure to UVA from a Hönle solar simulator (270 kJ/m(2)). HaCaT cells accumulated beta-carotene in a time- and dose-dependent manner. UVA irradiation massively reduced the cellular beta-carotene content. Beta-carotene suppressed UVA-induction of MMP-1, MMP-3, and MMP-10, three major matrix metalloproteases involved in photoaging. We show that regulation by not only MMP-1, but also MMP-10, involves (1)O(2)-dependent mechanisms. Beta-carotene dose-dependently quenched (1)O(2)-mediated induction of MMP-1 and MMP-10. Thus, as in chemical solvent systems, beta-carotene quenches (1)O(2) also in living cells. Vitamin E did not cooperate with beta-carotene to further inhibit MMP induction. HaCaT cells produced weak retinoid activity from beta-carotene, as demonstrated by mild upregulation of RAR beta and activation of an RARE-dependent reporter gene. Beta-carotene did not regulate the genes encoding other RARs, RXRs, or the two beta-carotene cleavage enzymes. These results demonstrate that beta-carotene acts photoprotectively, and that this effect is mediated by (1)O(2) quenching.

Beta-carotene reduces body adiposity of mice via BCMO1.

Evidence from cell culture studies indicates that ß-carotene-(BC)-derived apocarotenoid signaling molecules can modulate the activities of nuclear receptors that regulate many aspects of adipocyte physiology. Two BC metabolizing enzymes, the BC-15,15'-oxygenase (Bcmo1) and the BC-9',10'-oxygenase (Bcdo2) are expressed in adipocytes. Bcmo1 catalyzes the conversion of BC into retinaldehyde and Bcdo2 into ß-10'-apocarotenal and ß-ionone. Here we analyzed the impact of BC on body adiposity of mice. To genetically dissect the roles of Bcmo1 and Bcdo2 in this process, we used wild-type and Bcmo1(-/-) mice for this study. In wild-type mice, BC was converted into retinoids. In contrast, Bcmo1(-/-) mice showed increased expression of Bcdo2 in adipocytes and ß-10'-apocarotenol accumulated as the major BC derivative. In wild-type mice, BC significantly reduced body adiposity (by 28%), leptinemia and adipocyte size. Genome wide microarray analysis of inguinal white adipose tissue revealed a generalized decrease of mRNA expression of peroxisome proliferator-activated receptor γ (PPARγ) target genes. Consistently, the expression of this key transcription factor for lipogenesis was significantly reduced both on the mRNA and protein levels. Despite ß-10'-apocarotenoid production, this effect of BC was absent in Bcmo1(-/-) mice, demonstrating that it was dependent on the Bcmo1-mediated production of retinoids. Our study evidences an important role of BC for the control of body adiposity in mice and identifies Bcmo1 as critical molecular player for the regulation of PPARγ activity in adipocytes.