Circulating Carotenoid Levels Research Articles

Circulating carotenoids and breast cancer among high-risk individuals

Carotenoids represent 1 of few modifiable factors to reduce breast cancer risk. Elucidation of interactions between circulating carotenoids and genetic predispositions or mammographic density (MD) may help inform more effective primary preventive strategies in high-risk populations. We tested whether women at high risk for breast cancer due to genetic predispositions or high MD would experience meaningful and greater risk reduction from higher circulating levels of carotenoids in a nested case-control study in the Nurses' Health Studies (NHS and NHSII). This study included 1919 cases and 1695 controls in a nested case-control study in the NHS and NHSII. We assessed both multiplicative and additive interactions. RR reductions and 95% CIs were calculated using unconditional logistic regressions, adjusting for matching factors and breast cancer risk factors. Absolute risk reductions (ARR) were calculated based on Surveillance, Epidemiology, and End Results incidence rates. We showed that compared with women at low genetic risk or low MD, those with higher genetic risk scores or high MD had greater ARRs for breast cancer as circulating carotenoid levels increase (additive P-interaction=0.05). Among women with a high polygenic risk score, those in the highest quartile of circulating carotenoids had a significant ARR (28.6%; 95% CI, 14.8-42.1%) compared to those in the lowest quartile of carotenoids. For women with a high percentage MD (≥50%), circulating carotenoids were associated with a 37.1% ARR (95% CI, 21.7-52.1%) when comparing the highest to the lowest quartiles of circulating carotenoids. The inverse associations between circulating carotenoids and breast cancer risk appeared to be more pronounced in high-risk women, as defined by germline genetic makeup or MD.

You are MORE than what you eat! The dietary basis to painted turtle spot and stripe color.

Carotenoid pigments are important condition-dependent indicator traits that generate sexually selected color in birds, fish, and reptiles. One reason carotenoids are indicator traits is because the identity and amount of carotenoid pigments ingested in an animal’s food are often different from amounts and identities of carotenoids deposited in the animal’s skin. Painted turtle spots and stripes are pigmented by yellow xanthophylls and orange-red keto-carotenoids. The objective of this study was twofold: to feed male and female painted turtles nutritious diets with-, or without-, moderate amounts of orange beta-carotene, and investigate 1) how beta-carotene access changed turtle color in male and female turtles, and 2) whether the identities and concentrations of carotenoids in the blood of turtles given access to—or deprived of—beta-carotene differed from those ingested and those deposited in the skin. Results showed that orange beta-carotene access reduced overall brightness of yellow chin stripes and post orbital spots, reduced ultra-violet chroma in the yellow post-orbital spots, and increased yellow chroma in the orange-red fore-limb stripes. There was no sex effect to these color changes. Moreover, beta-carotene access significantly increased circulating levels of beta-carotene only, and did not increase circulating levels of lutein, zeaxanthin, beta cryptoxanthin or neoxanthin. There was no sex effect to the circulating carotenoid levels. Nevertheless, because the identity of carotenoids in the skin differs from the carotenoids circulating in the blood, the yellow, orange and red colors of painted turtle stripes and spots are in part the result of physiological conversion of available carotenoids.

Pollutants and diet influence carotenoid levels and integument coloration in nestlings of an endangered raptor

Carotenoid-based traits or ornaments, such as yellow-red integuments (feathers, beaks, legs or eye-rings) displayed by birds, play key roles in social communication by reliably advertising an individual's quality or health. In some species, these traits are displayed not only by adults but also by nestlings, and function in parent-offspring communication or sibling competition by advertising an individual's physical or physiological condition. Pollutants such as organochlorine compounds (OCs) could have disruptive effects on the coloration of these traits, thereby interfering with communication processes. Such effects have been reported in adult birds, but are still largely unknown for nestlings. Here we investigated associations between polychlorinated biphenyl (PCB) and dichlorodiphenyltrichloroethane (DDT) blood-levels, circulating carotenoid levels and the yellow-orange coloration of the cere and tarsi of wild Black Harrier Circus maurus nestlings, a scarce raptor endemic to southern Africa. As carotenoid pigments must be acquired through the diet, we also tested for an effect of dietary composition. The orangeness-purity of cere and tarsi coloration positively correlated with circulating carotenoid levels, and increased with both nestling age and the proportion of birds consumed in the diet. Circulating carotenoid levels and the orangeness-purity of colored integuments were unrelated to blood PCB levels, although the brightness of integuments (i.e. lack of pigmentation) increased with PCB levels. Nestlings with more DDT had lower levels of circulating carotenoids and reduced carotenoid-based coloration (i.e. higher hue and lower saturation, reflecting a yellow rather than orange and less intense color, respectively). Together, our results are consistent with the hypothesis that OC contaminants, in particular DDT, may disrupt carotenoid-based signaling in exposed nestlings.

Eggshell coloration reflects both yolk characteristics and dietary carotenoid history of female mallards

Summary Avian eggshell coloration has frequently been examined in a functional context (e.g. mimicry, camouflage), but in recent years, an interest has emerged in identifying the mechanisms that drive eggshell colour variation. Eggshell coloration is predominately caused by pigment deposition; one such pigment is the antioxidant biliverdin, and deposition of biliverdin into eggshells may be costly to mothers due to depletion of their antioxidant reserves. Previous work has shown that dietary supplementation during laying with another type of antioxidant – carotenoid pigments – induces females to produce more biliverdin‐rich eggshells. However, the impact of pre‐laying nutrition – including the developmental period early in life – on eggshell coloration has not been investigated. Here, we raised female mallards (Anas platyrhynchos) from hatching, supplemented their diets with carotenoids during early‐, mid‐ or late‐developmental periods, and at adulthood measured female circulating carotenoid levels, yolk carotenoid levels, and eggshell coloration. We found that carotenoid supplementation during the late stages of development (transitional period from juvenile to adult plumage) promoted the laying of eggs with more biliverdin‐rich eggshells. Independent of developmental dietary treatment, females with higher circulating carotenoid levels at the time of egg laying produced more biliverdin‐rich eggshells and more carotenoid‐rich yolks. When controlling for female identity, we found that more biliverdin‐rich eggshells were associated with more carotenoid‐rich, but smaller, yolks. We also detected a laying order effect; later‐laid eggs had larger, less carotenoid‐rich yolks and less biliverdin‐rich eggshells. Taken together, these results demonstrate that eggshell coloration reveals carotenoid status of both mothers and yolks and that diet quality more than 1 month prior to laying can affect eggshell coloration in a waterfowl species. As mallards are considered to be capital breeders in terms of lipid stores, our findings provide a new developmental perspective on the carryover of lipid‐soluble and antioxidant nutrient reserves for breeding.

Carotenoids and Skin Coloration in a Social Raptor

Abstract The outcome of social and sexual competition in animals is typically mediated through the expression of body traits. Conspicuous characters such as yellow, orange, and red colorations in skin, scales, and feathers are often posited as quality-dependent signals, because such colors are made of dietary carotenoids and their use for signaling conflicts with health functions. Raptors often lack brightly colored feathers but most diurnal species display intense orange and yellow hues in the cere and legs. Here we test the hypothesis that integument coloration functions as a signal of status in wild raptors, revealing availability of carotenoid pigments. As study model we used the Black Kite (Milvus migrans), a highly social, long-lived, and sexually monogamous Accipitriform. Regular trapping of adults throughout the breeding season revealed that circulating carotenoid levels were highest in breeding males, whereas breeding females and floaters showed moderate and statistically similar carotenoid titer...

Circulating carotenoid levels are negatively associated with previous reproductive success in Florida Scrub-Jays (Aphelocoma coerulescens)

The relationship between individual fitness and antioxidants and oxidative stress has come under increasing scrutiny of late. In particular, associations between oxidative balance indicators and reproductive success in the wild have been inconsistent in the limited prior work on this topic. Studies spanning multiple seasons and antioxidant types are particularly lacking. Here, we examined associations between reproductive success over two breeding seasons and several metrics of circulating antioxidants (antioxidant capacity, uric acid, carotenoids, and vitamin E, measured in the intervening nonbreeding season) in Florida Scrub-Jays (Aphelocoma coerulescens (Bosc, 1795)). We found that carotenoid levels in the nonbreeding season were negatively associated with reproductive success in the preceding breeding season but unassociated with that in the subsequent breeding season. This correlation may be driven by the cost of reproduction (i.e., carotenoid depletion while breeding) or some other unmeasured and intercorrelated variable such as diet. Antioxidant capacity, uric acid, and vitamin E were not associated with reproductive success. These data are consistent with an emerging theme in physiological ecology: that antioxidants and oxidative stress are but one part of a suite of integrative physiological systems that interact and trade-off in complex ways, making full understanding of their ecological roles challenging.

Immune function is related to adult carotenoid and bile pigment levels, but not dietary carotenoid access during development, in female mallard ducks

Immune function can be modulated by multiple physiological factors, including nutrition and reproductive state. Because these factors can vary throughout an individual's lifetime as a result of environmental conditions (affecting nutrition) or life-history stage (e.g. entering the adult reproduction stage), we must carefully examine the degree to which developmental versus adult conditions shape performance of the immune system. We investigated how variation in dietary access to carotenoid pigments - a class of molecules with immunostimulatory properties that females deposit into egg yolks - during three different developmental time points affected adult immunological and reproductive traits in female mallard ducks (Anas platyrhynchos). In males and females of other avian species, carotenoid access during development affects carotenoid assimilation ability, adult sexual ornamentation and immune function, while carotenoid access during adulthood can increase immune response and reproductive investment (e.g. egg-laying capacity, biliverdin deposition in eggshells). We failed to detect effects of developmental carotenoid supplementation on adult immune function [phytohemagglutinin-induced cutaneous immune response, antibody production in response to the novel antigen keyhole limpet hemocyanin (KLH), or oxidative burst, assessed by changes in circulating nitric oxide levels], carotenoid-pigmented beak coloration, ovarian development, circulating carotenoid levels or concentration of bile pigments in the gall bladder. However, we did uncover positive relationships between circulating carotenoid levels during adulthood and KLH-specific antibody production, and a negative relationship between biliverdin concentration in bile and KLH-specific antibody production. These results are consistent with the view that adult physiological parameters better predict current immune function than do developmental conditions, and highlight a possible, previously unstudied relationship between biliverdin and immune system performance.

Prediagnostic circulating carotenoid levels and the risk of non-Hodgkin lymphoma: the Multiethnic Cohort

AbstractThis analysis examined the association of non-Hodgkin lymphoma (NHL) with prediagnostic carotenoid levels, a marker for a diet rich in fruits and vegetables. We conducted a nested case-control study within the Multiethnic Cohort with 271 NHL cases and 538 controls matched on sex, ethnicity, location (Hawaii or Los Angeles), birth year, date and time of blood draw, and hours fasting before blood draw. Serum carotenoid levels were obtained by high-pressure liquid chromatography with photodiode array detection. Conditional logistic regression was used to calculate odds ratios (ORs) according to tertiles of serum carotenoids and trend tests using continuous variables. Higher total serum carotenoids (ORT3 vs T1 = 0.66 [0.46-0.96]; Ptrend = .02), lycopene (OR = 0.54 [0.38-0.78]; Ptrend = .003), and α-cryptoxanthin (OR = 0.53 [0.36-0.78]; Ptrend = .003) were associated with a lower risk of NHL. For retinol (OR = 0.90 [0.61-1.33]; Ptrend = .04), a statistically significant inverse linear trend was detected. Risk estimates remained unchanged with adjustment for NHL risk factors and were similar in analyses stratified by sex and ethnicity; heterogeneity with NHL subtype was detected only for β-carotene. Other carotenoids, including α-carotene, β-carotene, lutein, β-cryptoxanthin, and zeaxanthin, showed no association with risk. These data provide support for a protective role of carotenoid-rich fruits and vegetables in the etiology of NHL.

Differential Effects of Early- and Late-Life Access to Carotenoids on Adult Immune Function and Ornamentation in Mallard Ducks (Anas platyrhynchos)

Environmental conditions early in life can affect an organism’s phenotype at adulthood, which may be tuned to perform optimally in conditions that mimic those experienced during development (Environmental Matching hypothesis), or may be generally superior when conditions during development were of higher quality (Silver Spoon hypothesis). Here, we tested these hypotheses by examining how diet during development interacted with diet during adulthood to affect adult sexually selected ornamentation and immune function in male mallard ducks (Anas platyrhynchos). Mallards have yellow, carotenoid-pigmented beaks that are used in mate choice, and the degree of beak coloration has been linked to adult immune function. Using a 2×2 factorial experimental design, we reared mallards on diets containing either low or high levels of carotenoids (nutrients that cannot be synthesized de novo) throughout the period of growth, and then provided adults with one of these two diets while simultaneously quantifying beak coloration and response to a variety of immune challenges. We found that both developmental and adult carotenoid supplementation increased circulating carotenoid levels during dietary treatment, but that birds that received low-carotenoid diets during development maintained relatively higher circulating carotenoid levels during an adult immune challenge. Individuals that received low levels of carotenoids during development had larger phytohemagglutinin (PHA)-induced cutaneous immune responses at adulthood; however, dietary treatment during development and adulthood did not affect antibody response to a novel antigen, nitric oxide production, natural antibody levels, hemolytic capacity of the plasma, or beak coloration. However, beak coloration prior to immune challenges positively predicted PHA response, and strong PHA responses were correlated with losses in carotenoid-pigmented coloration. In sum, we did not find consistent support for either the Environmental Matching or Silver Spoon hypotheses. We then describe a new hypothesis that should be tested in future studies examining developmental plasticity.

Carotenoid supplementation and GnRH challenges influence female endocrine physiology, immune function, and egg-yolk characteristics in Japanese quail (Coturnix japonica)

Androgens and carotenoids circulating in plasma affect the physiology and behavior of vertebrates. Much is known about control mechanisms and functions of each of these substances, yet their interactive effects are not well understood. Here we examine possible additive, multiplicative, and interactive effects of testosterone and carotenoids on female endocrine physiology, immunocompetence, and investment in eggs by simultaneously manipulating levels of testosterone [via gonadotropin releasing hormone (GnRH) challenges] and carotenoids (via diet supplementation) in captive female Japanese quail (Coturnix japonica). Females were randomly assigned to one of four treatments: carotenoid supplementation, GnRH challenge, GnRH challenge+carotenoid supplementation, or control. Carotenoid supplementation significantly increased circulating plasma carotenoid levels and acquired immune system performance, but not innate immunity. GnRH challenges elevated circulating testosterone and carotenoid levels, and induced immunosuppression in females. However, females in the GnRH challenge+carotenoid supplementation treatment had higher cell-mediated immune responses than control females and similar responses to those of carotenoid-supplemented females. Hence, availability of carotenoids in female quail seemed to counteract immunosuppressive effects of GnRH challenges. Our results provide further evidence for synergistic effects of carotenoids and testosterone on endocrine physiology and immune function in female birds. Elevated plasma testosterone or carotenoids levels resulted in increased deposition of those compounds to eggs, respectively. Furthermore, because we found that concentrations of testosterone and carotenoids in yolks were correlated within each treatment group, differential deposition of hormones and carotenoids in eggs may not only respond to surrounding social and environmental conditions, but also to other components of the egg.

Developmental immune history affects adult immune function but not carotenoid‐based ornamentation in mallard ducks

Summary1. Sexually selected traits often honestly advertise aspects of individual quality, such as immune function. Such traits have traditionally been thought to reveal real‐time information (e.g. current health state), but they may also reflect immunological conditions experienced during ontogeny, which can fundamentally shape survival prospects, adult immune function, and reproductive performance.2. We tested the effects of immune challenges (injections of sheep red blood cells) during neonatal development on adult immune function and ornamental coloration in male mallard ducks (Anas platyrhynchos). Mallards have a carotenoid‐pigmented beak that plays a role in mate choice, and because carotenoids are also associated with immune responsiveness, carotenoid accumulation in body tissues may change as a function of immunological state during development and into adulthood.3. We found that mallards that received immune challenges at the completion of growth (8–10 weeks old) had a reduced proinflammatory response (as measured by the local swelling response to phytohemagglutinin; PHA) as adults, compared to control birds and those receiving immune challenges at other developmental time points. Mallards that received immune challenges during the acquisition of nuptial plumage (13–15 weeks old) had an increased humoral immune response as adults, as assessed by antibody production to keyhole limpet hemocyanin (KLH). Body mass, adult beak colour, and carotenoid circulation were not affected by immune challenges issued at any point during development.4. Circulating carotenoid levels prior to adult immune challenge and change in carotenoid titre over the course of the adult immune assessment period were correlated with degree of response to PHA and KLH at adulthood, as well as with nitric oxide production, which is associated with innate immunity. However, the direction of these correlations varied by type of immune assessment. Surprisingly, unlike in several previous studies, we found no link between beak coloration and adult immune function.5. These findings demonstrate the importance of developmental immune challenges in shaping adult immune response, although the precise mechanisms remain unidentified. Moreover, we found support for the hypothesis that carotenoids are linked to immune function, because of the relationship between multiple immune responses and both initial and change in circulating carotenoid levels.6. However, our study does not support the hypothesis that sexual signal expression reveals developmental immune history. Taken together, our findings suggest that the relationships between carotenoid physiology, carotenoid‐based ornamentation, and immune function are complex.

Free Radical Exposure Creates Paler Carotenoid-Based Ornaments: A Possible Interaction in the Expression of Black and Red Traits

Oxidative stress could be a key selective force shaping the expression of colored traits produced by the primary animal pigments in integuments: carotenoids and melanins. However, the impact of oxidative stress on melanic ornaments has only recently been explored, whereas its role in the expression of carotenoid-based traits is not fully understood. An interesting study case is that of those animal species simultaneously expressing both kinds of ornaments, such as the red-legged partridge (Alectoris rufa). In this bird, individuals exposed to an exogenous source of free radicals (diquat) during their development produced larger eumelanin-based (black) plumage traits than controls. Here, we show that the same red-legged partridges exposed to diquat simultaneously developed paler carotenoid-based ornaments (red beak and eye rings), and carried lower circulating carotenoid levels as well as lower levels of some lipids involved in carotenoid transport in the bloodstream (i.e., cholesterol). Moreover, partridges treated with a hormone that stimulates eumelanin production (i.e., alpha-melanocyte-stimulating hormone) also increased blood carotenoid levels, but this effect was not mirrored in the expression of carotenoid-based traits. The redness of carotenoid-based ornaments and the size of a conspicuous eumelanic trait (the black bib) were negatively correlated in control birds, suggesting a physiological trade-off during development. These findings contradict recent studies questioning the sensitivity of carotenoids to oxidative stress. Nonetheless, the impact of free radicals on plasma carotenoids seems to be partially mediated by changes in cholesterol metabolism, and not by direct carotenoid destruction/consumption. The results highlight the capacity of oxidative stress to create multiple phenotypes during development through differential effects on carotenoids and melanins, raising questions about evolutionary constraints involved in the production of multiple ornaments by the same organism.

The carotenoid conundrum: improved nutrition boosts plasma carotenoid levels but not immune benefits of carotenoid supplementation

Carotenoids are widely heralded as central to honest signaling due to their dual roles as pigments and antioxidants/immunostimulants. The aim of this study is to test if diet quality and carotenoids alone or in an interaction influence condition, carotenoid availability in plasma and immune responsiveness. Therefore, a diet experiment during the moult of great tits, Parus major, was performed. In a two-way design, we manipulated general quality (digestibility, protein and vitamin content) as well as carotenoid (lutein) content of semi-synthetic diets. Higher quality diet improved individual condition since birds had greater body mass, and to a lesser extent, higher hematocrit. In addition to the expected positive effect of carotenoid supplementation and individual lutein consumption on circulating lutein, there was a positive effect of enhanced diet quality on plasma carotenoid levels. Carotenoid supplementation, but not diet quality, improved the local inflammatory response and maintenance of body mass during a humoral immune reaction. The enhancement of circulating carotenoid levels by improved general quality of the diet or individual condition could provide a testable, mechanistic explanation for the variation in effects of carotenoid supplementation studies.

Changes in macular pigment optical density and serum concentrations of lutein and zeaxanthin in response to weight loss

The objective of the present study was to investigate whether weight loss is associated with changes in serum concentrations of lutein (L) and zeaxanthin (Z), and/or macular pigment optical density (MPOD). We recruited 104 overweight subjects into this randomised controlled weight loss study. For the intervention group (I group), weight was assessed weekly and body composition, including BMI (kg/m2) and body fat (kg and percentage), was assessed at baseline, 6 and 12 months. Weight loss was encouraged using dietary and exercise programmes. MPOD was measured by heterochromatic flicker photometry and serum concentrations of L and Z by HPLC (at baseline, 1, 3, 6 and 12 months). The control (C) group was assessed at baseline and 12 months. Repeated-measures ANOVA (RMA) demonstrated significant weight loss in the I group over the study period (P=0·000). There was no significant weight change in the C group (P=0·993). RMA of dietary L and Z, serum L and Z, and MPOD demonstrated no significant time or time×group interaction effect in any of these parameters (P>0·05 for all), with the exception of a significant decrease in the dietary intake of Z seen in both groups, over the study period (P<0·05). There was a positive and significant relationship between body fat loss (kg) and increase in serum concentrations of L in the I group (r 0·521; P=0·006). Our finding that a reduction in body composition (e.g. fat mass) is related to increases in serum concentrations of L is consistent with the hypothesis that body fat acts as a reservoir for this carotenoid, and that weight loss can positively influence circulating carotenoid levels.

Not as similar as thought: sexual dichromatism in Chimango Caracaras is expressed in the exposed skin but not in the plumage

Many of the mechanisms involved in visual signalling in birds are based on pigment-based plumage ornamentation and colouration rather than the expression of other, non-plumage-based displays. We have analysed the colouration of the tarsi and ceres of free-ranging Chimango Caracaras Milvago chimango, a controversial morphological trait for this species, and examined the proximal causes related to the expression of colour in these featherless body parts. The tarsi–ceres of 81 Chimango Caracaras captured in central Argentina between 2005 and 2008 were either yellow–yellow or bluish–pink coloured. Differences in colour were not linked with plasma carotenoid levels and did not vary seasonally. Rather, expression of the two colours was affected by the gender and age of individuals. Yellow-coloured tarsi and ceres were recorded only in adult males, while the remaining age and gender groups showed pinkish- and bluish-coloured bare parts, which is the suspected neutral developmental stage under low hormonal levels. These results support sexual rather than natural selection forces acting on the expression of yellow colouration in the bare parts of adult males. However, an exaggeration of yellowish colour during mating periods in accordance with an increase of circulating carotenoid levels may be expected due to the sexually-related nature of this trait. This documented partitioning of colour variation among sexes and ages that is unrelated to melanin-dependent plumages is unusual and contrary to the most widely observed types of sexual dichromatism in birds.

Racial differences in correlations between reported dietary carotenoid intakes and plasma carotenoid levels

Because of cost and practicality, a dietary assessment tool that can accurately predict circulating plasma carotenoid levels is of great interest to epidemiologists. However, validity across racial groups needs to be assured. We studied dietary and plasma levels of oxycarotenoid levels (lutein &amp; zeaxanthin, α‐, β‐cryptoxanthin) and hydrocarbons (lycopene, α‐, β‐carotene) among 123 healthy, non‐smoking adult African‐American (AA) and 128 Caucasian (CA) participants from Los Angeles. Age and gender adjusted correlations between diet and plasma differed substantially by race as seen in the Table. Despite similar plasma carotenoid levels, the correlations with dietary intakes were 0.09 to 0.40 lower among AAs. The 6‐day mean intakes from 24‐hr recalls for all carotenoids were lower among the AAs, consistent with similar validation studies. These results suggest that either this dietary assessment tool was less valid among African‐Americans or that other factors influencing circulating carotenoid levels differ between these groups. Supported by NIH R01CA105048. Pearson's Correlations: Diet and Plasma Carotenoids Carotenoid AA N = 123 CA N = 128 Difference Oxy Carotenoids Lutein and Zeaxanathin 0.11 0.51 0.40 Total‐Cryptoxanthin 0.29 0.50 0.21 β‐Cryptoxanthin 0.30 0.50 0.20 α‐Cryptoxanthin 0.12 0.31 0.19 Hydrocarbons Lycopene 0.00 0.09 0.09 β‐Carotene 0.22 0.41 0.19 α‐Carotene 0.18 0.38 0.20

Circulating carotenoids, mammographic density, and subsequent risk of breast cancer.

Mammographic density is one of the strongest predictors of breast cancer risk. Recently, it has been suggested that reactive oxygen species may influence breast cancer risk through its influence on mammographic density. In the current study, we addressed this hypothesis and also assessed if the association between carotenoids and breast cancer risk varies by mammographic density. We conducted a nested case-control study consisting of 604 breast cancer cases and 626 controls with prospectively measured circulating carotenoid levels and mammographic density in the Nurses' Health Study. Circulating levels of alpha-carotene, beta-carotene, beta-cryptoxanthin, lycopene, and lutein/zeaxanthin were measured. We used a computer-assisted thresholding method to measure percent mammographic density. We found no evidence that circulating carotenoids are inversely associated with mammographic density. However, mammographic density significantly modified the association between total circulating carotenoids and breast cancer (P heterogeneity = 0.008). Overall, circulating total carotenoids were inversely associated with breast cancer risk (P trend = 0.01). Among women in the highest tertile of mammographic density, total carotenoids were associated with a 50% reduction in breast cancer risk (odds ratio, 0.5; 95% confidence interval, 0.3-0.8). In contrast, there was no inverse association between carotenoids and breast cancer risk among women with low mammographic density. Similarly, among women in the highest tertile of mammographic density, high levels of circulating alpha-carotene, beta-cryptoxanthin, lycopene, and lutein/zeaxanthin were associated with a significant 40% to 50% reduction in breast cancer risk (P trend < 0.05). Our results suggest that plasma levels of carotenoids may play a role in reducing breast cancer risk, particularly among women with high mammographic density.

Testosterone-mediated trade-offs in the old age: a new approach to the immunocompetence handicap and carotenoid-based sexual signalling

The immunocompetence handicap hypothesis proposes that testosterone mediates a trade-off between sexual signalling and immunocompetence in males. Such a trade-off could favour the reliability of sexual signals on the basis that testosterone required for signal expression also promotes immunosuppression. However, the immunosuppressive activity of testosterone has not been convincingly demonstrated. We propose that the optimal solution to the testosterone-mediated trade-off should change with age, explaining ambiguous results in the past. Testosterone and ageing would promote two simultaneous immunosuppressive challenges unaffordable for low-quality males. Oxidative stress, as intimately related to ageing and immunosenescence, could contribute to enhance signal reliability. In this context, traits coloured by carotenoids (yellow-red traits) could play a crucial role due to the immunostimulatory and antioxidant properties of these pigments. Here, old and middle-aged male red-legged partridges were treated with testosterone or manipulated as controls. In the presence of high-testosterone levels, middle-aged males increased both circulating carotenoid levels and colour expression, whereas their cell-mediated immunity was not significantly altered. However, in old males, neither circulating carotenoids nor sexual signalling increased when treated with testosterone, but immunosuppression was detected. The link between testosterone and carotenoids could favour the reliability of sexual signals throughout the life.

Common Variation in the β-Carotene 15,15′-Monooxygenase 1 Gene Affects Circulating Levels of Carotenoids: A Genome-wide Association Study

Low plasma levels of carotenoids and tocopherols are associated with increased risk of chronic disease and disability. Because dietary intake of these lipid-soluble antioxidant vitamins is only poorly correlated with plasma levels, we hypothesized that circulating carotenoids (vitamin A-related compounds) and tocopherols (vitamin E-related compounds) are affected by common genetic variation. By conducting a genome-wide association study in a sample of Italians (n = 1190), we identified novel common variants associated with circulating carotenoid levels and known lipid variants associated with alpha-tocopherol levels. Effects were replicated in the Women's Health and Aging Study (n = 615) and in the alpha-Tocopherol, beta-Carotene Cancer Prevention (ATBC) study (n = 2136). In meta-analyses including all three studies, the G allele at rs6564851, near the beta-carotene 15,15'-monooxygenase 1 (BCMO1) gene, was associated with higher beta-carotene (p = 1.6 x 10(-24)) and alpha-carotene (p = 0.0001) levels and lower lycopene (0.003), zeaxanthin (p = 1.3 x 10(-5)), and lutein (p = 7.3 x 10(-15)) levels, with effect sizes ranging from 0.10-0.28 SDs per allele. Interestingly, this genetic variant had no significant effect on plasma retinol (p > 0.05). The SNP rs12272004, in linkage disequilibrium with the S19W variant in the APOA5 gene, was associated with alpha-tocopherol (meta-analysis p = 7.8 x 10(-10)) levels, and this association was substantially weaker when we adjusted for triglyceride levels (p = 0.002). Our findings might shed light on the controversial relationship between lipid-soluble anti-oxidant nutrients and human health.

The oxidation handicap hypothesis and the carotenoid allocation trade‐off

The oxidation handicap hypothesis proposes that testosterone mediates the trade-off between the expression of secondary sexual traits and the fight against free radicals. Coloured traits controlled by testosterone can be produced by carotenoid pigments (yellow-orange-red traits), but carotenoids also help to quench free radicals. Recently, it has been shown that testosterone increases the amount of circulating carotenoids in birds. Here, a testosterone-mediated trade-off in the carotenoid allocation between colour expression and the fight against oxidative stress is proposed. Male red-legged partridges were treated with testosterone, anti-androgens or manipulated as controls. Testosterone-treated males maintained the highest circulating carotenoid levels, but showed the palest red traits and no evidence of oxidative damage. Increased levels of a key intracellular antioxidant (i.e. glutathione) indicated that an oxidative challenge was in fact induced but controlled. The trade-off was apparently solved by reducing redness, allowing increased carotenoid availability, which could have contributed to buffer oxidative stress.