Disease relevance of Zeaxanthin

• RESULTS: Intakes of beta-carotene from food and supplements, lutein/zeaxanthin, and vitamin A from foods were weakly inversely associated with breast cancer risk in premenopausal women [1].
• This hypothesis was confirmed by the analysis of two recombinant proteins obtained by overexpression of the Lhcb5 apoprotein in Escherichia coli and reconstitution in vitro with either violaxanthin or zeaxanthin [2].
• Erwinia herbicola, a nonphotosynthetic bacterium, is yellow colored due to the accumulation of unusually polar carotenoids, primarily mono- and diglucosides of zeaxanthin [3].
• The proposed reaction center quenching is an important protective mechanism because antenna and zeaxanthin cycle-dependent quenching are not present in cyanobacteria [4].
• BACKGROUND: Zeaxanthin is hypothesized to reduce the risk of age-related macular degeneration; however, kinetic information is limited [5].

High impact information on Zeaxanthin

• Here we show that in Arabidopsis thaliana overexpression of the chyB gene that encodes beta-carotene hydroxylase--an enzyme in the zeaxanthin biosynthetic pathway--causes a specific twofold increase in the size of the xanthophyll cycle pool [6].
• Stress protection is probably due to the function of zeaxanthin in preventing oxidative damage of membranes [6].
• The carotenoid zeaxanthin may serve as the chromophore for a photoreceptor involved in blue-light-activated stomatal opening [7].
• We propose a simple mechanism for the xanthophyll-related, slow component of nonphotochemical quenching in LHC-II, by which excess energy is transferred to a zeaxanthin replacing violaxanthin in its binding site, and dissipated as heat [8].
• The same effect was observed in wild-type CP26 upon treatment that leads to the accumulation of zeaxanthin in the membrane and was interpreted as the consequence of a conformational change [2].

Chemical compound and disease context of Zeaxanthin

• Comparison of maximum catalytic activities as well as selectivity experiments carried out in the presence of both utilizable substrates indicated that the CrtZ enzymes from marine bacteria converted canthaxanthin to astaxanthin preferentially, whereas the Erwinia CrtZ possessed a favorability to the formation of zeaxanthin from beta-carotene [9].
• OBJECTIVE: Our aim was to examine the relations between dietary intakes of beta-carotene, alpha-carotene, beta-cryptoxanthin, lycopene, and lutein + zeaxanthin and breast cancer risk in a large cohort study of Canadian women [10].
• In this review, the role of main dietary carotenoids, ie, lycopene, beta-carotene, alpha-carotene, beta-cryptoxanthin, lutein, and zeaxanthin, in the prevention of heart diseases is discussed [11].
• PURPOSE: To assess the associations of plasma lutein and zeaxanthin and other carotenoids with the risk of age-related maculopathy (ARM) and cataract in the population-based Pathologies Oculaires Liées à l'Age (POLA) Study. METHODS: Retinal photographs were graded according to the international classification [12].
• Our study confirmed the inverse associations between lycopene, other carotenoids such as zeaxanthin, lutein, and beta-cryptoxanthin, and prostate cancer [13].

Biological context of Zeaxanthin

• The high levels of zeaxanthin in npq2 affected the kinetics of induction and relaxation but not the extent of nonphotochemical quenching [14].
• To investigate the roles of xanthophylls in photoprotection, we isolated and characterized extragenic suppressors of the npq1 lor1 double mutant of Chlamydomonas reinhardtii, which lacks zeaxanthin and lutein and undergoes irreversible photooxidative bleaching and cell death at moderate to high light intensities [15].
• These results confirm that LHC proteins exist in multiple conformations, an idea suggested by previous spectroscopic measurements (Moya et al., 2001), and imply that the switch between the different LHC protein conformations is activated by the binding of zeaxanthin to the allosteric site L2 [2].
• Here, we describe three suppressor strains that carry point mutations in the coding sequence of the zeaxanthin epoxidase gene, resulting in the constitutive accumulation of zeaxanthin in a range of concentrations [15].
• We have identified and functionally characterized the Crocus zeaxanthin 7,8(7',8')-cleavage dioxygenase gene (CsZCD), which codes for a chromoplast enzyme that initiates the biogenesis of these derivatives [16].

Anatomical context of Zeaxanthin

• Our results are consistent with an antioxidant role of zeaxanthin in the quenching of singlet oxygen and/or free radicals in the thylakoid membrane in vivo [15].
• Our data suggest that a stepwise sequence exists that involves the oxidative cleavage of zeaxanthin in chromoplasts followed by the sequestration of modified water-soluble derivatives into the central vacuole [16].
• Lutein and zeaxanthin are abundant in egg yolks and accumulate in the macular region of the retina, where they may affect visual function [17].
• Serum zeaxanthin concentrations were greater than at baseline only at 4 wk, whereas buccal cell and adipose tissue concentrations of zeaxanthin did not change [18].
• Multiple linear regression analysis revealed significant associations of vitamin C, vitamin E, beta-cryptoxanthin, lutein/zeaxanthin, beta-carotene, and retinol with FEV(1)% when these variables were investigated individually after adjustment for other covariates (smoking status, pack-years of smoking, weight, eosinophil count, and education) [19].

Associations of Zeaxanthin with other chemical compounds

• The npq1 mutants are unable to convert violaxanthin to zeaxanthin in excessive light, whereas the npq2 mutants accumulate zeaxanthin constitutively [14].
• Excess light triggers protective nonradiative dissipation of excitation energy in photosystem II through the formation of a trans-thylakoid pH gradient that in turn stimulates formation of zeaxanthin and antheraxanthin [20].
• The amino acid sequence derived from the zeaxanthin glucosyltransferase gene shows a small region of high similarity with other glucuronosyl- and glucosyltransferases that use either UDP-activated glucuronic acid or a sugar as one of their substrates [3].
• Identification and characterization of a Pi isoform of glutathione S-transferase (GSTP1) as a zeaxanthin-binding protein in the macula of the human eye [21].
• We analyzed the association of FEV(1) and FVC with serum vitamins C and E, retinol, and carotenoids (beta-cryptoxanthin, lutein/zeaxanthin, beta-carotene, and lycopene) in a cross-sectional study [19].

Gene context of Zeaxanthin

• Plasma retinol, beta-carotene, alpha-tocopherol, and zeaxanthin were inversely correlated with DNA damage, especially in subjects lacking the "protective" GSTM1 gene [22].
• H+ pumping was induced by blue light in isolated guard cell protoplasts from the wild type, from the single mutants of phototropins (phot1-5 and phot2-1), and from the zeaxanthin-less mutant (npq1-2), but not from the phot1 phot2 double mutant [23].
• With cultures of Th1 cells and unprimed spleen cells, astaxanthin and zeaxanthin augmented the number of immunoglobulin M Ab-secreting cells [24].
• Plasma lutein and zeaxanthin and other carotenoids as modifiable risk factors for age-related maculopathy and cataract: the POLA Study [12].
• Leaves and chloroplasts from Arabidopsis plants with increased amounts of PsbS protein showed the same percentage increase in nonphotochemical quenching in comparison to the wild type both in the presence and absence of zeaxanthin [25].

Analytical, diagnostic and therapeutic context of Zeaxanthin

• The product zeaxanthin diglucoside and its intermediate monoglucoside were identified by thin layer chromatography [3].
• HPLC/ultraviolet-visible (UV-VIS) absorption detection was used to measure concentrations of zeaxanthin and alpha-tocopherol [26].
• Lutein and zeaxanthin were analyzed by high-performance liquid chromatography and their concentrations expressed relative to membrane protein [27].
• Thus, higher body fat content and body mass index (BMI) may be expected to influence the quantities of L and Z in the retina (measured as macular pigment optical density, MPOD) [28].
• The robust response to zeaxanthin supplementation identifies the quail as an animal model for exploration of factors regulating delivery of dietary carotenoids to the retina [29].

References