Associations between serum carotenoid levels and the risk of non-Hodgkin lymphoma: a case-control study.

Limited studies have investigated the effects of serum carotenoids on the risk of non-Hodgkin lymphoma (NHL), and the findings have been inconclusive. This study aims to assess the association between serum total or specific carotenoid levels and NHL risk. This 1:1 matched, hospital-based case-control study enrolled 512 newly diagnosed (within 1 month) NHL patients and 512 healthy controls who were matched by age (±5 years) and sex in Urumqi, China. Serum carotenoid levels were measured by HPLC. Conditional logistic regression showed that higher serum total carotenoid levels and their subtypes (e.g. α-carotene, ß-carotene, ß-cryptoxanthin and lycopene) were dose-dependently associated with decreased NHL risk. The multivariable-adjusted OR and their 95 % CI for NHL risk for quartile 4 (v. quartile 1) were 0·31 (95 % CI 0·22, 0·48; Pfor trend < 0·001) for total carotenoids, 0·52 (95 % CI 0·33, 0·79; Pfor trend: 0·003) for α-carotene, 0·63 (95 % CI 0·42, 0·94; Pfor trend: 0·031) for ß-carotene, 0·73 (95 % CI 0·49, 1·05; Pfor trend: 0·034) for ß-cryptoxanthin and 0·51 (95 % CI 0·34, 0·75; Pfor trend: 0·001) for lycopene. A null association was observed between serum lutein + zeaxanthin and NHL risk (OR 0·89, 95 % CI 0·57, 1·38; Pfor trend: 0·556). Significant interactions were observed after stratifying according to smoking status, and inverse associations were more evident among current smokers than past or never smokers for total carotenoids, α-carotene and lycopene (Pfor heterogeneity: 0·047, 0·042 and 0·046). This study indicates that higher serum carotenoid levels might be inversely associated with NHL risk, especially among current smokers.

Transformation of naturally occurring (3R,3'R,6'R)-lutein and its fatty acid esters to (3 R)-ß-cryptoxanthin and (3R,6'R)-α-cryptoxanthin.

The objective of this study was to develop straightforward processes that could be applied to the large-scale production of ß-cryptoxanthin in an attempt to facilitate investigation of its biological activity. An oleoresin obtained from crude extracts of marigold flowers (Tagetes erecta) with approximately 24% total lutein fatty acid ester content was directly used as starting material for partial synthesis of (3 R)-ß-cryptoxanthin under mild reaction conditions at ambient temperature. Therefore, acid-catalyzed deoxygenation of lutein esters from marigold oleoresin followed by hydrogenation in the presence of catalytic amount of platinum (Pt) supported on alumina (5%) at ambient temperature gave a mixture of (3 R)-ß-cryptoxanthin fatty acid esters (major) and (3 R,6'R)-α-cryptoxanthin fatty acid esters (minor). Saponification and Z-to-E isomerization of the product followed by crystallization gave a mixture of (3 R)-ß-cryptoxanthin as the major product. Similarly, acid-catalyzed hydrogenation of unesterified (3 R,3'R,6'R)-lutein with Pt/alumina in ethyl acetate gave a mixture of (3 R,6'R)-α-cryptoxanthin acetate (minor) in a one-pot reaction. Alkaline hydrolysis and Z-to-E isomerization of the mixture followed by crystallization provided (3 R)-ß-cryptoxanthin.

Substrate Specificity of Purified Recombinant Chicken ß-Carotene 9',10'-Oxygenase (BCO2).

Provitamin A carotenoids are oxidatively cleaved by ß-carotene 15,15'-dioxygenase (BCO1) at the central 15-15' double bond to form retinal (vitamin A aldehyde). Another carotenoid oxygenase, ß-carotene 9',10'-oxygenase (BCO2) catalyzes the oxidative cleavage of carotenoids at the 9'-10' bond to yield an ionone and an apo-10'-carotenoid. Previously published substrate specificity studies of BCO2 were conducted using crude lysates from bacteria or insect cells expressing recombinant BCO2. Our attempts to obtain active recombinant human BCO2 expressed in Escherichia coli were unsuccessful. We have expressed recombinant chicken BCO2 in the strain E. coli BL21-Gold (DE3) and purified the enzyme by cobalt ion affinity chromatography. Like BCO1, purified recombinant chicken BCO2 catalyzes the oxidative cleavage of the provitamin A carotenoids ß-carotene, α-carotene, and ß-cryptoxanthin. Its catalytic activity with ß-carotene as substrate is at least 10-fold lower than that of BCO1. In further contrast to BCO1, purified recombinant chicken BCO2 also catalyzes the oxidative cleavage of 9-cis-ß-carotene and the non-provitamin A carotenoids zeaxanthin and lutein, and is inactive with all-trans-lycopene and ß-apocarotenoids. Apo-10'-carotenoids were detected as enzymatic products by HPLC, and the identities were confirmed by LC-MS. Small amounts of 3-hydroxy-ß-apo-8'-carotenal were also consistently detected in BCO2-ß-cryptoxanthin reaction mixtures. With the exception of this activity with ß-cryptoxanthin, BCO2 cleaves specifically at the 9'-10' bond to produce apo-10'-carotenoids. BCO2 has been shown to function in preventing the excessive accumulation of carotenoids, and its broad substrate specificity is consistent with this.

Carotenoids in Adipose Tissue Biology and Obesity.

Cell, animal and human studies dealing with carotenoids and carotenoid derivatives as nutritional regulators of adipose tissue biology with implications for the etiology and management of obesity and obesity-related metabolic diseases are reviewed. Most studied carotenoids in this context are ß-carotene, cryptoxanthin, astaxanthin and fucoxanthin, together with ß-carotene-derived retinoids and some other apocarotenoids. Studies indicate an impact of these compounds on essential aspects of adipose tissue biology including the control of adipocyte differentiation (adipogenesis), adipocyte metabolism, oxidative stress and the production of adipose tissue-derived regulatory signals and inflammatory mediators. Specific carotenoids and carotenoid derivatives restrain adipogenesis and adipocyte hypertrophy while enhancing fat oxidation and energy dissipation in brown and white adipocytes, and counteract obesity in animal models. Intake, blood levels and adipocyte content of carotenoids are reduced in human obesity. Specifically designed human intervention studies in the field, though still sparse, indicate a beneficial effect of carotenoid supplementation in the accrual of abdominal adiposity. In summary, studies support a role of specific carotenoids and carotenoid derivatives in the prevention of excess adiposity, and suggest that carotenoid requirements may be dependent on body composition.

Associations between reported intakes of carotenoid-rich foods and concentrations of carotenoids in plasma: a validation study of a web-based food recall for children and adolescents.

OBJECTIVE: To validate estimated intakes of carotenoid-rich foods from a web-based food recall (WebFR) using carotenoids in blood as an objective reference method. DESIGN: Cross-sectional validation study using carotenoids in plasma to evaluate estimated intakes of selected carotenoid-rich foods. Participants recorded their food intake in the WebFR and plasma concentrations of ß-carotene, α-carotene, ß-cryptoxanthin, lycopene, lutein and zeaxanthin were measured. SETTING: Schools and homes of families in a suburb of the capital of Norway. SUBJECTS: A total of 261 participants in the age groups 8-9 and 12-14 years. RESULTS: Spearman's rank correlation coefficients ranged from 0·30 to 0·44, and cross-classification showed that 71·6-76·6 % of the participants were correctly classified, when comparing the reported intakes of carotenoid-rich foods and concentrations of the corresponding carotenoids in plasma, not including lutein and zeaxanthin. CONCLUSIONS: Correlations were acceptable and cross-classification analyses demonstrated that the WebFR was able to rank participants according to their reported intake of foods rich in α-carotene, ß-carotene, ß-cryptoxanthin and lycopene. The WebFR is a promising tool for dietary assessment among children and adolescents.

A 3-hydroxy ß-end group in xanthophylls is preferentially oxidized to a 3-oxo ε-end group in mammals.

We previously found that mice fed lutein accumulated its oxidative metabolites (3'-hydroxy-ε,ε-caroten-3-one and ε,ε-carotene-3,3'-dione) as major carotenoids, suggesting that mammals can convert xanthophylls to keto-carotenoids by the oxidation of hydroxyl groups. Here we elucidated the metabolic activities of mouse liver for several xanthophylls. When lutein was incubated with liver postmitochondrial fraction in the presence of NAD(+), (3'R,6'R)-3'-hydroxy-ß,ε-caroten-3-one and (6RS,3'R,6'R)-3'-hydroxy-ε,ε-caroten-3-one were produced as major oxidation products. The former accumulated only at the early stage and was assumed to be an intermediate, followed by isomerization to the latter. The configuration at the C3' and C6' of the ε-end group in lutein was retained in the two oxidation products. These results indicate that the 3-hydroxy ß-end group in lutein was preferentially oxidized to a 3-oxo ε-end group via a 3-oxo ß-end group. Other xanthophylls such as ß-cryptoxanthin and zeaxanthin, which have a 3-hydroxy ß-end group, were also oxidized in the same manner as lutein. These keto-carotenoids, derived from dietary xanthophylls, were confirmed to be present in plasma of normal human subjects, and ß,ε-caroten-3'-one was significantly increased by the ingestion of ß-cryptoxanthin. Thus, humans as well as mice have oxidative activity to convert the 3-hydroxy ß-end group of xanthophylls to a 3-oxo ε-end group.

Antioxidant micronutrients and the risk of renal cell carcinoma in the Women's Health Initiative cohort.

BACKGROUND: Renal cell carcinoma (RCC) is the eighth leading cancer among women in incidence and commonly is diagnosed at a more advanced stage. Oxidative stress has been considered to play an important role in the pathogenesis of RCC. Various dietary micronutrients have antioxidant properties, including carotenoids and vitamins C and E; thus, diets rich in these nutrients have been evaluated in relation to RCC prevention. The objective of this study was to explore the correlation between antioxidant micronutrients and the risk of RCC. METHODS: In total, 96,196 postmenopausal women who enrolled in the Women's Health Initiative (WHI) between 1993 and 1998 and were followed through July 2013 were included in this analysis. Dietary micronutrient intake was estimated from the baseline WHI food frequency questionnaire, and data on supplement use were collected using an interview-based inventory procedure. RCC cases were ascertained from follow-up surveys and were centrally adjudicated. The risks for RCC associated with intake of α-carotene, ß-carotene, ß-cryptoxanthin, lutein plus zeaxanthin, lycopene, vitamin C, and vitamin E were analyzed using Cox proportional hazards regression adjusted for confounders. RESULTS: Two hundred forty women with RCC were identified during follow-up. Lycopene intake was inversely associated with RCC risk (P = .015); compared with the lowest quartile of lycopene intake, the highest quartile of intake was associated with a 39% lower risk of RCC (hazard ratio, 0.61; 95% confidence interval, 0.39-0.97). No other micronutrient was significantly associated with RCC risk. CONCLUSIONS: The current results suggest that further investigation into the correlation between lycopene intake and the risk of RCC is warranted.

Multicarotenoids at Physiological Levels Inhibit Metastasis in Human Hepatocarcinoma SK-Hep-1 Cells.

Several studies have demonstrated that single carotenoid, including lycopene, ß-carotene, and α-carotene, exhibits antimetastatic effects; however, little is known whether multicarotenoids have similar effects. Herein, we investigated the antimetastatic effect of multicarotenoids at physiological serum levels in Taiwanese (MCT at 1.4 µM) and American (MCA at 1.8 µM) populations using human hepatocarcinoma SK-Hep-1 cells in comparison with single carotenoid, such as lycopene (0.3 or 0.6 µM, respectively), α-carotene (0.1 µM), ß-carotene (0.4 µM), lutein (0.4 or 0.5 µM, respectively), and ß-cryptoxanthin (0.2 µM). Results reveal that MCA treatment exhibited an additive inhibition on invasion, migration and adhesion at 24 and 48 h of incubation, whereas MCT treatment possessed additive inhibition at 48 h of incubation. The antimetastatic action of MCT and MCA involved additive reduction on activities of matrix metalloproteinase (MMP)-2, -9, and protein expression of Rho and Rac 1 but additive promotion on protein expression of tissue inhibitor of MMP (TIMP)-1 and -2. All of these effects were stronger in MCA than in MCT at 24 and 48 h of incubation. These results demonstrate that multi-carotenoids effectively inhibit metastasis of human hepatocarcinoma SK-Hep-1 cells. More in vivo studies are needed to confirm these findings.

Comparative validity of vitamin C and carotenoids as indicators of fruit and vegetable intake: a systematic review and meta-analysis of randomised controlled trials.

Circulating vitamin C and carotenoids are used as biomarkers of fruit and vegetable intake in research, but their comparative validity has never been meta-analysed. PubMed, EMBASE, CENTRAL, CINAHL and Web of Science were systematically searched up to December 2013 for randomised trials of different amounts of fruit and vegetable provision on changes in blood concentrations of carotenoids or vitamin C. Reporting followed PRISMA guidelines. Evidence quality was assessed using the GRADE system. Random effects meta-analysis combined estimates and meta-regression tested for sub-group differences. In all, nineteen fruit and vegetable trials (n 1382) measured at least one biomarker, of which nine (n 667) included five common carotenoids and vitamin C. Evidence quality was low and between-trial heterogeneity (I 2) ranged from 74% for vitamin C to 94 % for α-carotene. Groups provided with more fruit and vegetables had increased blood concentrations of vitamin C, α-carotene, ß-carotene, ß-cryptoxanthin and lutein but not lycopene. However, no clear dose-response effect was observed. Vitamin C showed the largest between-group difference in standardised mean change from the pre-intervention to the post-intervention period (smd 0·94; 95% CI 0·66, 1·22), followed by lutein (smd 0·70; 95% CI 0·37, 1·03) and α-carotene (smd 0·63; 95% CI 0·25, 1·01), but all CI were overlapping, suggesting that none of the biomarkers responded more than the others. Therefore, until further evidence identifies a particular biomarker to be superior, group-level compliance to fruit and vegetable interventions can be indicated equally well by vitamin C or a range of carotenoids. High heterogeneity and a lack of dose-response suggest that individual-level biomarker responses to fruit and vegetables are highly variable.

High serum carotenoids associated with lower risk for the metabolic syndrome and its components among Japanese subjects: Mikkabi cohort study.

Recent epidemiological studies show the association of carotenoids with the metabolic syndrome (MetS), but thorough longitudinal cohort studies regarding this association have not been well conducted. The objective of this study was to investigate longitudinally whether serum carotenoids are associated with the risk of developing the MetS and its components in Japanese subjects. We conducted a follow-up study on 1073 men and women aged 30-79 years at the baseline from the Mikkabi prospective cohort study. Those who participated in the baseline and completed follow-up surveys were examined longitudinally. Over the 10-year period, 910 subjects (295 men and 615 women) took part in the follow-up survey at least once. Over a mean follow-up period of 7·8 (sd 2·9) years, thirty-six men and thirty-one women developed new MetS. After adjustments for confounders, the hazard ratio (HR) for the MetS in the highest tertile of serum ß-carotene against the lowest tertile was 0·47 (95 % CI 0·23, 0·95). On the other hand, significantly lower risks for dyslipidaemia were observed in the highest tertiles of serum α- and ß-carotene and ß-cryptoxanthin (HR 0·66; 95 % CI 0·46, 0·96; HR, 0·54; 95 % CI 0·37, 0·79; and HR 0·66; 95 % CI 0·44, 0·99, respectively). Other significant associations between the risks for obesity, high blood pressure and hyperglycaemia with serum carotenoids were not observed. Our results further support the hypothesis that eating a diet rich in carotenoids might help prevent the development of the MetS and its complications in Japanese subjects.

Prediction of fruit and vegetable intake from biomarkers using individual participant data of diet-controlled intervention studies.

Fruit and vegetable consumption produces changes in several biomarkers in blood. The present study aimed to examine the dose-response curve between fruit and vegetable consumption and carotenoid (α-carotene, ß-carotene, ß-cryptoxanthin, lycopene, lutein and zeaxanthin), folate and vitamin C concentrations. Furthermore, a prediction model of fruit and vegetable intake based on these biomarkers and subject characteristics (i.e. age, sex, BMI and smoking status) was established. Data from twelve diet-controlled intervention studies were obtained to develop a prediction model for fruit and vegetable intake (including and excluding fruit and vegetable juices). The study population in the present individual participant data meta-analysis consisted of 526 men and women. Carotenoid, folate and vitamin C concentrations showed a positive relationship with fruit and vegetable intake. Measures of performance for the prediction model were calculated using cross-validation. For the prediction model of fruit, vegetable and juice intake, the root mean squared error (RMSE) was 258.0 g, the correlation between observed and predicted intake was 0.78 and the mean difference between observed and predicted intake was - 1.7 g (limits of agreement: - 466.3, 462.8 g). For the prediction of fruit and vegetable intake (excluding juices), the RMSE was 201.1 g, the correlation was 0.65 and the mean bias was 2.4 g (limits of agreement: -368.2, 373.0 g). The prediction models which include the biomarkers and subject characteristics may be used to estimate average intake at the group level and to investigate the ranking of individuals with regard to their intake of fruit and vegetables when validating questionnaires that measure intake.

Daily intake of ß-cryptoxanthin prevents bone loss by preferential disturbance of osteoclastic activation in ovariectomized mice.

Although ß-cryptoxanthin, a xanthophyll carotenoid, has been shown to exert an anabolic effect on bone calcification, little attention has been paid thus far to the precise mechanism of bone remodeling. Daily oral administration of ß-cryptoxanthin significantly inhibited osteoclastic activation as well as reduction of bone volume in ovariectomized mice. In vitro studies revealed that ß-cryptoxanthin inhibited differentiation and maturation of osteoclasts by repression of the nuclear factor-κB-dependent transcriptional pathway. Our results suggest that supplementation with ß-cryptoxanthin would be beneficial for prophylaxis and for therapy of metabolic bone diseases associated with abnormal osteoclast activation.

Higher intake of carotenoid is associated with a lower risk of colorectal cancer in Chinese adults: a case-control study.

PURPOSE: The associations between specific carotenoid intake and colorectal cancer risk remain inconsistent. The aim of this study was to examine the association between specific dietary carotenoid intake with colorectal cancer risk in Chinese adults. METHOD: From July 2010 to October 2013, 845 eligible colorectal cancer cases and 845 frequency-matched controls (age and sex) completed in-person interviews. A validated food frequency questionnaire was used to estimate dietary intake. Multivariate logistical regression models were used to calculate the odds ratio (OR) and 95% confidence intervals (95% CIs) of colorectal cancer risk after adjusting for various confounders. RESULTS: A strong inverse association was found between ß-cryptoxanthin intake and colorectal cancer risk. Compared with the lowest quartile, the highest quartile intake showed a risk reduction of 77% (OR 0.23, 95% CI 0.17-0.33, P trend < 0.01) after adjustment for various confounding variables. The inverse associations were also observed for α-carotene (OR 0.50, 95% CI 0.37-0.68, P trend < 0.01), ß-carotene (OR 0.67, 95% CI 0.49-0.91, P trend < 0.01), and lycopene (OR 0.51, 95% CI 0.37-0.70, P trend < 0.01). There was no statistically significant association between lutein/zeaxanthin intake and colorectal cancer risk. These findings were consistent across cancer site, sources of controls, and smoking status. The inverse associations between dietary α-carotene, ß-cryptoxanthin, and lycopene intake and colorectal cancer risk were found in both males and females, while inverse associations between ß-carotene intake and colorectal cancer risk were only observed in males. CONCLUSIONS: Consumption of α-carotene, ß-carotene, ß-cryptoxanthin, and lycopene was inversely associated with colorectal cancer risk. No significant association was found between lutein/zeaxanthin intake and colorectal cancer risk.

Dietary intake of carotenoids and risk of type 2 diabetes.

BACKGROUND AND AIMS: Carotenoids may reduce diabetes risk, due to their antioxidant properties. However, the association between dietary carotenoids intake and type 2 diabetes risk is still unclear. Therefore, the objective of this study was to examine whether higher dietary carotenoid intakes associate with reduced type 2 diabetes risk. METHODS AND RESULTS: Data from 37,846 participants of the European Prospective Investigation into Cancer and Nutrition- Netherlands study were analyzed. Dietary intakes of ß-carotene, α-carotene, ß-cryptoxanthin, lycopene, lutein & zeaxanthin and the sum of these carotenoids were assessed using a validated food frequency questionnaire. Incident type 2 diabetes was mainly self-reported, and verified against general practitioner information. Mean ±SD total carotenoid intake was 10 ± 4 mg/day. During a mean ±SD follow-up of 10 ± 2 years, 915 incident cases of type 2 diabetes were ascertained. After adjustment for age, sex, diabetes risk factors, dietary intake, waist circumference and BMI, higher ß-carotene intakes associated inversely with diabetes risk [Hazard Ratio quartile 4 versus quartile 1 (HR(Q4)): 0.78 (95%CI:0.64,0.95), P-linear trend 0.01]. For α-carotene, a borderline significant reduced risk was observed, with a HR(Q4) of 0.85 (95%CI:0.70,1.03), and P-linear trend 0.05. ß-cryptoxanthin, lycopene, lutein & zeaxanthin, and the sum of all carotenoids did not associate with diabetes risk. CONCLUSIONS: This study shows that diets high in ß-carotene and α-carotene are associated with reduced type 2 diabetes in generally healthy men and women.

Effect of kumquat (Fortunella crassifolia) pericarp on natural killer cell activity in vitro and in vivo.

Natural killer (NK) cells play a key role in innate immune defense against infectious disease and cancer. A reduction of NK activity is likely to be associated with increased risk of these types of disease. In this study, we investigate the activation potential of kumquat pericarp acetone fraction (KP-AF) on NK cells. It is shown to significantly increase IFN-γ production and NK cytotoxic activity in human KHYG-1 NK cells. Moreover, oral administration of KP-AF significantly improves both suppressed plasma IFN-γ levels and NK cytotoxic activity per splenocyte in restraint-stressed mice. These results indicate that raw kumquat pericarp activates NK cells in vitro and in vivo. To identify the active constituents, we also examined IFN-γ production on KHYG-1 cells by the predicted active components. Only ß-cryptoxanthin increased IFN-γ production, suggesting that NK cell activation effects of KP-AF may be caused by carotenoids such as ß-cryptoxanthin.

Assessment of dietary vitamin A intake (retinol, α-carotene, ß-carotene, ß-cryptoxanthin) and its sources in the National Survey of Dietary Intake in Spain (2009-2010).

The aim of this study is to assess the intake of the individual components of vitamin A and major dietary sources in the Spaniards using data on food consumption from Spanish National Dietary Intake Survey (2009-2010). A 24-h dietary recall, 3-day diet diary and a software application that includes HPLC analytical data were used. Average dietary vitamin A intake is 716.4 µg retinol equivalents (RE), which is supplied as retinol (57.9%RE) and as provitamin-A carotenoids (42.1%RE). ß-Carotene represents 71.9% of provitamin-A carotenoids, ß-cryptoxanthin 15.3%, α-carotene 12.8%. Red- and orange-colored fruits and vegetables are major contributors of provitamin-A (1587 µg/day). Spanish diet covers the dietary reference on the intake for vitamin A, provided mainly by foods of animal origin. The main contributors to the intake of provitamin-A carotenoids are carrots, tomatoes, spinach and oranges. Data on the intake of individual components of vitamin A contribute to improving our understanding of the relationship between diet and health.

Beta-cryptoxanthin as a source of vitamin A.

Beta-cryptoxanthin is a common carotenoid that is found in fruit, and in human blood and tissues. Foods that are rich in beta-cryptoxanthin include tangerines, persimmons and oranges. Beta-cryptoxanthin has several functions that are important for human health, including roles in antioxidant defense and cell-to-cell communication. Most importantly, beta-cryptoxanthin is a precursor of vitamin A, which is an essential nutrient needed for eyesight, growth, development and immune response. We evaluate the evidence for beta-cryptoxanthin as a vitamin A-forming carotenoid in this paper. Observational, in vitro, animal model and human studies suggest that beta-cryptoxanthin has greater bioavailability from its common food sources than do alpha- and beta-carotene from theirs. Although beta-cryptoxanthin appears to be a poorer substrate for beta-carotene 15,15' oxygenase than is beta-carotene, animal model and human studies suggest that the comparatively high bioavailability of beta-cryptoxanthin from foods makes beta-cryptoxanthin-rich foods equivalent to beta-carotene-rich foods as sources of vitamin A. These results mean that beta-cryptoxanthin-rich foods are probably better sources of vitamin A, and more important for human health in general, than previously assumed.

Two carotenoid oxygenases contribute to mammalian provitamin A metabolism.

Mammalian genomes encode two provitamin A-converting enzymes as follows: the ß-carotene-15,15'-oxygenase (BCO1) and the ß-carotene-9',10'-oxygenase (BCO2). Symmetric cleavage by BCO1 yields retinoids (ß-15'-apocarotenoids, C20), whereas eccentric cleavage by BCO2 produces long-chain (>C20) apocarotenoids. Here, we used genetic and biochemical approaches to clarify the contribution of these enzymes to provitamin A metabolism. We subjected wild type, Bco1(-/-), Bco2(-/-), and Bco1(-/-)Bco2(-/-) double knock-out mice to a controlled diet providing ß-carotene as the sole source for apocarotenoid production. This study revealed that BCO1 is critical for retinoid homeostasis. Genetic disruption of BCO1 resulted in ß-carotene accumulation and vitamin A deficiency accompanied by a BCO2-dependent production of minor amounts of ß-apo-10'-carotenol (APO10ol). We found that APO10ol can be esterified and transported by the same proteins as vitamin A but with a lower affinity and slower reaction kinetics. In wild type mice, APO10ol was converted to retinoids by BCO1. We also show that a stepwise cleavage by BCO2 and BCO1 with APO10ol as an intermediate could provide a mechanism to tailor asymmetric carotenoids such as ß-cryptoxanthin for vitamin A production. In conclusion, our study provides evidence that mammals employ both carotenoid oxygenases to synthesize retinoids from provitamin A carotenoids.

Serum carotenoid levels and risk of lung cancer death in US adults.

Lung cancer is one of the most common cancers worldwide and is the leading cause of cancer-induced death in the USA. Although much attention has been focused on the anti-carcinogenic effect of consuming carotenoid-containing food or supplements, the results have been inconsistent. We investigated whether serum carotenoid levels were associated with the mortality risk of lung cancer in US adults using data from a nationally representative sample. The data were obtained from the Third Nutrition and Health Examination Survey (NHANES III) database and the NHANES III Linked Mortality File. A total of 10,382 participants aged over 20,years with available serum carotenoid levels and no other missing information on questionnaires and biomarkers at baseline (NHANES III) were included in the present study. Of the 10,382 participants, 161 subjects died due to lung cancer. We found that high serum levels of alpha-carotene and beta-cryptoxanthin at baseline were significantly associated with a lower risk of lung cancer death. When we stratified the risk by current smoking status, the risk of death of current smokers was significantly decreased to 46% (95% confidence interval, 31-94%) for alpha-carotene and 61% (95% confidence interval, 19-80%) for beta-cryptoxanthin. By contrast, no association was observed among never/former smokers at baseline. High serum levels of alpha-carotene and beta-cryptoxanthin are associated with a lower risk of lung cancer death in US adults.

Enzymatic formation of ß-citraurin from ß-cryptoxanthin and Zeaxanthin by carotenoid cleavage dioxygenase4 in the flavedo of citrus fruit.

In this study, the pathway of ß-citraurin biosynthesis, carotenoid contents and the expression of genes related to carotenoid metabolism were investigated in two varieties of Satsuma mandarin (Citrus unshiu), Yamashitabeni-wase, which accumulates ß-citraurin predominantly, and Miyagawa-wase, which does not accumulate ß-citraurin. The results suggested that CitCCD4 (for Carotenoid Cleavage Dioxygenase4) was a key gene contributing to the biosynthesis of ß-citraurin. In the flavedo of Yamashitabeni-wase, the expression of CitCCD4 increased rapidly from September, which was consistent with the accumulation of ß-citraurin. In the flavedo of Miyagawa-wase, the expression of CitCCD4 remained at an extremely low level during the ripening process, which was consistent with the absence of ß-citraurin. Functional analysis showed that the CitCCD4 enzyme exhibited substrate specificity. It cleaved ß-cryptoxanthin and zeaxanthin at the 7,8 or 7',8' position. But other carotenoids tested in this study (lycopene, α-carotene, ß-carotene, all-trans-violaxanthin, and 9-cis-violaxanthin) were not cleaved by the CitCCD4 enzyme. The cleavage of ß-cryptoxanthin and zeaxanthin by CitCCD4 led to the formation of ß-citraurin. Additionally, with ethylene and red light-emitting diode light treatments, the gene expression of CitCCD4 was up-regulated in the flavedo of Yamashitabeni-wase. These increases in the expression of CitCCD4 were consistent with the accumulation of ß-citraurin in the two treatments. These results might provide new strategies to improve the carotenoid contents and compositions of citrus fruits.