Macular Pigment Lutein Is Antiinflammatory in Preventing Choroidal Neovascularization

The effects of lutein on cardiometabolic health across the life course: a systematic review and meta-analysis

BACKGROUND

The antioxidant lutein is suggested as being beneficial to cardiometabolic health because of its protective effect against oxidative stress, but evidence has not systematically been evaluated.

OBJECTIVE

We aimed to evaluate systematically the effects of lutein (intake or concentrations) on cardiometabolic outcomes in different life stages.

DESIGN

This is a systematic review with meta-analysis of literature published in MEDLINE, Embase, Cochrane Central, Web of Science, PubMed, and Google Scholar up to August 2014. Included were trials and cohort, case-control, and cross-sectional studies in which the association between lutein concentrations, dietary intake, or supplements and cardiometabolic outcomes was reported. Two independent investigators reviewed the articles.

RESULTS

Seventy-one relevant articles were identified that included a total of 387,569 participants. Only 1 article investigated the effects of lutein during pregnancy, and 3 studied lutein in children. Furthermore, 31 longitudinal, 33 cross-sectional, and 3 intervention studies were conducted in adults. Meta-analysis showed a lower risk of coronary heart disease (pooled RR: 0.88; 95% CI: 0.80, 0.98) and stroke (pooled RR: 0.82; 95% CI: 0.72, 0.93) for the highest compared with the lowest tertile of lutein blood concentration or intake. There was no significant association with type 2 diabetes mellitus (pooled RR: 0.97; 95% CI: 0.77, 1.22), but higher lutein was associated with a lower risk of metabolic syndrome (pooled RR: 0.75; 95% CI: 0.60, 0.92) for the highest compared with the lowest tertile. The literature on risk factors for cardiometabolic diseases showed that lutein might be beneficial for atherosclerosis and inflammatory markers, but there were inconsistent associations with blood pressure, adiposity, insulin resistance, and blood lipids.

CONCLUSIONS

Our findings suggest that higher dietary intake and higher blood concentrations of lutein are generally associated with better cardiometabolic health. However, evidence mainly comes from observational studies in adults, whereas large-scale intervention studies and studies of lutein during pregnancy and childhood are scarce.

Chitosan/poly-γ-glutamic acid nanoparticles improve the solubility of lutein

The aim of this study was to improve the solubility of lutein through the use of chitosan (CS)/poly-γ-glutamic acid (γ-PGA) nanoencapsulation. In terms of redispersibility, water-soluble chitosan (WsCS)/γ-PGA nanoparticles (NPs) were better than insoluble chitosan (InCS)/γ-PGA NPs. The lutein-loaded WsCS/γ-PGA NP has a spherical form with a size around 200nm and a narrow size distribution (PDI<0.1). Solubility measures showed that nanoencapsulation of lutein into WsCS/γ-PGA NPs resulted in a significant 12-fold higher solubility compared to that of non-nanoencapsulated lutein (p<0.05). The redispersibility index of the lutein-loaded NPs was 1.01, indicating that they were completely reconstituted into aqueous solution as same as original aqueous solution. These results suggest that WsCS/γ-PGA nanoencapsulation can be used to enhance the solubility of lutein and other poorly water-soluble compounds.

Management of Ocular Diseases Using Lutein and Zeaxanthin: What Have We Learned from Experimental Animal Studies?

Zeaxanthin and lutein are two carotenoid pigments that concentrated in the retina, especially in the macula. The effects of lutein and zeaxanthin on the prevention and treatment of various eye diseases, including age-related macular degeneration, diabetic retinopathy and cataract, ischemic/hypoxia induced retinopathy, light damage of the retina, retinitis pigmentosa, retinal detachment, and uveitis, have been studied in different experimental animal models. In these animal models, lutein and zeaxanthin have been reported to have beneficial effects in protecting ocular tissues and cells (especially the retinal neurons) against damage caused by different etiological factors. The mechanisms responsible for these effects of lutein and zeaxanthin include prevention of phototoxic damage by absorption of blue light, reduction of oxidative stress through antioxidant activity and free radical scavenging, and their anti-inflammatory and antiangiogenic properties. The results of these experimental animal studies may provide new preventive and therapeutic procedures for clinical management of various vision-threatening diseases.

Joint Associations of Diet, Lifestyle, and Genes with Age-Related Macular Degeneration

PURPOSE

Unhealthy lifestyles have been associated with increased odds for age-related macular degeneration (AMD). Whether this association is modified by genetic risk for AMD is unknown and was investigated.

DESIGN

Interactions between healthy lifestyles AMD risk genotypes were studied in relation to the prevalence of AMD, assessed 6 years later.

PARTICIPANTS

Women 50 to 79 years of age in the Carotenoids in Age-Related Eye Disease Study with exposure and AMD data (n=1663).

METHODS

Healthy lifestyle scores (0-6 points) were assigned based on Healthy Eating Index scores, physical activity (metabolic equivalent of task hours/week), and smoking pack years assessed in 1994 and 1998. Genetic risk was based on Y402H in complement factor H (CFH) and A69S in age-related maculopathy susceptibility locus 2 (ARMS2). Additive and multiplicative interactions in odds ratios were assessed using the synergy index and a multiplicative interaction term, respectively.

MAIN OUTCOME MEASURES

AMD presence and severity were assessed from grading of stereoscopic fundus photographs taken in 2001-2004. AMD was present in 337 women, 91% of whom had early AMD.

RESULTS

The odds of AMD were 3.3 times greater (95% confidence interval [CI], 1.8-6.1) in women with both low healthy lifestyle score (0-2) and high-risk CFH genotype (CC), relative to those who had low genetic risk (TT) and high healthy lifestyle scores (4-6). There were no significant additive (synergy index [SI], 1.08; 95% CI, 0.70-1.67) or multiplicative (Pinteraction=0.94) interactions in the full sample. However, when limiting the sample to women with stable diets before AMD assessment (n=728) the odds for AMD associated with low healthy lifestyle scores and high-risk CFH genotype were strengthened (odds ratio, 4.6; 95% CI, 1.8-11.6) and the synergy index was significant (SI, 1.34; 95% CI, 1.05-1.70). Adjusting for dietary lutein and zeaxanthin attenuated, and therefore partially explained, the joint association. There were no significant additive or multiplicative interactions for ARMS2 and lifestyle score.

CONCLUSIONS

Having unhealthy lifestyles and 2 CFH risk alleles increased AMD risk (primarily in the early stages), in an or additive or greater (synergistic) manner. However, unhealthy lifestyles increased AMD risk regardless of AMD risk genotype.

Mitochondrial DNA has a pro-inflammatory role in AMD

Age-related macular degeneration (AMD) is the leading cause of irreversible blindness in the elderly of industrialized nations, and there is increasing evidence to support a role for chronic inflammation in its pathogenesis. Mitochondrial DNA (mtDNA) has been recently reported to be pro-inflammatory in various diseases such as Alzheimer's and heart failure. Here, we report that intracellular mtDNA induces ARPE-19 cells to secrete inflammatory cytokines IL-6 and IL-8, which have been consistently associated with AMD onset and progression. The induction was dependent on the size of mtDNA, but not on specific sequence. Oxidative stress plays a major role in the development of AMD, and our findings indicate that mtDNA induces IL-6 and IL-8 more potently when oxidized. Cytokine induction was mediated by STING (Stimulator of Interferon Genes) and NF-κB as evidenced by abrogation of the cytokine response with the use of specific inhibitors (siRNA and BAY 11-7082, respectively). Finally, mtDNA primed the NLRP3 inflammasome. This study contributes to our understanding of the potential pro-inflammatory role of mtDNA in the pathogenesis of AMD.

Lutein Leads to a Decrease of Factor D Secretion by Cultured Mature Human Adipocytes

Purpose. Complement plays an important role in the pathogenesis of age related macular degeneration (AMD) and trials are currently being conducted to investigate the effect of complement inhibition on AMD progression. We previously found that the plasma level of factor D (FD), which is the rate limiting enzyme of the complement alternative pathway, was significantly decreased following lutein supplementation. FD is synthesized by adipose tissue, which is also the main storage site of lutein. In view of these findings we tested the hypothesis whether lutein could affect FD synthesis by adipocytes. Methods. A cell line of mature human adipocytes was incubated with 50 μg/mL lutein for 24 and 48 h, whereafter FD mRNA and protein expression were measured. Results. Lutein significantly inhibited adipocyte FD mRNA expression and FD protein release into adipocyte culture supernatants. Conclusions. Our earlier observations showing that a daily lutein supplement in individuals with early signs of AMD lowered the level of circulating FD might be caused by blocking adipocyte FD production.

Association of macular pigment optical density with serum concentration of oxidized low-density lipoprotein in healthy adults

PURPOSE

To analyze the association between macular pigment optical density (MPOD), which reflects lutein (L), zeaxanthin (Z), and meso-zeaxanthin (MZ) in the macula, and background characteristics.

METHODS

Fifty-five healthy adult volunteers were analyzed. Macular pigment optical density was measured using a heterochromatic flicker photometry technique, and serum concentrations of carotenoids and lipoproteins were by high-performance liquid chromatography and enzyme-linked immunosorbent assay, respectively. Dietary intake of nutrient was determined by a validated self-administered questionnaire on ingestion frequency.

RESULTS

Macular pigment optical density was positively correlated with serum concentrations of L and Z and dietary L intake and inversely correlated with serum oxidized low-density lipoprotein (LDL). Although MPOD decreased with age (95% confidence interval, -0.011 to -0.002; correlation coefficient, -0.269; P = 0.007), serum L/Z and dietary L intake did not. In contrast, serum oxidized LDL was positively correlated with age (95% confidence interval, 0.69-2.34; correlation coefficient, 0.333; P = 0.0004). After adjusting for age, sex, and oxidized LDL, serum L was positively correlated with MPOD (95% confidence interval, 0.88-1.69; P = 0.000001). After adjusting for age, sex, and serum L, serum oxidized LDL was inversely correlated with MPOD (95% confidence interval, -0.002 to -0.0004; P = 0.006).

CONCLUSION

Macular pigment optical density was inversely correlated with serum oxidized LDL. Further study to know the impact of oxidized LDL on MPOD may be warranted.

IL10-driven STAT3 signalling in senescent macrophages promotes pathological eye angiogenesis

Macrophage dysfunction plays a pivotal role during neovascular proliferation in diseases of ageing including cancers, atherosclerosis and blinding eye disease. In the eye, choroidal neovascularization (CNV) causes blindness in patients with age-related macular degeneration (AMD). Here we report that increased IL10, not IL4 or IL13, in senescent eyes activates STAT3 signalling that induces the alternative activation of macrophages and vascular proliferation. Targeted inhibition of both IL10 receptor-mediated signalling and STAT3 activation in macrophages reverses the ageing phenotype. In addition, adoptive transfer of STAT3-deficient macrophages into eyes of old mice significantly reduces the amount of CNV. Systemic and CD163⁺ eye macrophages obtained from AMD patients also demonstrate STAT3 activation. Our studies demonstrate that impaired SOCS3 feedback leads to permissive IL10/STAT3 signalling that promotes alternative macrophage activation and pathological neovascularization. These findings have significant implications for our understanding of the pathobiology of age-associated diseases and may guide targeted immunotherapy.

Pathological neovascularization causes blinding eye disease. Here the authors show that IL10 activates STAT3 signalling in the macrophages in the ageing eye, promoting their polarization towards a pro-angiogenic phenotype; interfering with this pathway reverses the pathology in a mouse model.

Lutein and Factor D: two intriguing players in the field of age-related macular degeneration

Age-related macular degeneration (AMD) is a progressive eye disease that impairs central vision among elderly populations in Western, industrialized countries. In this review we will focus on the role of factor D (FD) and lutein in AMD. FD is a rate-limiting enzyme of the alternative complement activation pathway that may play an important role in the development of AMD. Several independent studies have shown a significant increase in the level of a number of complement factors of the alternative pathway, including factor D in the blood of AMD patients as compared to healthy individuals, which suggests a systemic involvement in the pathogenesis of AMD. FD, also called adipsin, is mainly produced by adipose tissue. Besides playing a role in the activation of the alternative pathway, FD is also known to regulate the immune system. Of interest is our preliminary finding that lutein supplementation of early AMD cases was shown to lower the level of systemic FD. If confirmed, these findings provide further support for the application of anti-factor D intervention as a new approach to control the development of this disease.

Microalgal carotenoids: beneficial effects and potential in human health

Microalgae are huge natural sources of high-value compounds with health-promoting properties. The carotenoids derived from microalgae have significant antioxidant and anti-inflammatory effects, which allow them to provide health benefits. In this article, the bioactivities of microalgal carotenoids are reviewed. Emphasis is placed on astaxanthin, a ketocarotenoid with extraordinary potential for protecting against a wide range of diseases.

Resveratrol prevents the development of choroidal neovascularization by modulating AMP-activated protein kinase in macrophages and other cell types

The development of choroidal neovascularization (CNV) is a critical step in the pathogenesis of age-related macular degeneration (AMD), a vision-threatening disease. In this study, we used a mouse model of AMD to study the protective effects of resveratrol (RSV) supplementation against CNV as well as the underlying molecular mechanisms. Mice were orally pretreated with RSV daily for 5 days. On the fifth day, the mice underwent laser photocoagulation to induce CNV. One week after laser treatment, CNV volume was significantly lower in the RSV-treated mice compared with vehicle-treated animals. In addition, RSV treatment significantly inhibited macrophage infiltration into the retinal pigment epithelium (RPE)-choroid and suppressed the expression of inflammatory and angiogenic molecules, including vascular endothelial growth factor, monocyte chemotactic protein-1 and intercellular adhesion molecule-1. Importantly, RSV prevented the CNV-induced decrease in activated AMP-activated protein kinase and increase in activated nuclear factor-κB in the RPE-choroid complex. The regulatory effects of RSV on these molecules were confirmed in RPE, microvascular endothelial and macrophage cell lines. Inhibition of macrophage infiltration by RSV was confirmed by in vitro scratch and migration assays. RSV suppressed CNV development, reducing the levels of multiple cytokines secreted from several cell types and inhibiting macrophage migration. The direct effects of RSV on each cell type were confirmed in vitro. Although further studies are needed, RSV could potentially be applied in the clinic to prevent CNV development in AMD.

Roles of NFκB-miR-29s-MMP-2 circuitry in experimental choroidal neovascularization

Background

Previous reports have indicated that matrix metallopeptidase-2 (MMP-2) regulates angiogenic processes, which are involved in choroidal neovascularization (CNV). However, the regulation of MMP-2 in CNV has not been well-characterized. To gain more information about the regulation of MMP-2 in CNV, we analyzed the circuitry associated with MMP-2 regulation in a CNV model and in cell cultures, focusing on NFκB and the microRNA-29 family (miR-29s).

Methods

The CNV model was established by subjecting C57BL/6 mice to fundus photocoagulation with a krypton red laser. In choroidal-retinal pigment epithelial (RPE) tissues of the model, immunohistochemistry was used to evaluate the angiogenesis and MMP-2 expression; reverse-transcription quantitative PCR (RT-qPCR) was used to determine the levels of miR-29s; and western blot was used to analyze the protein levels of nuclear factor kappa-light-chain-enhancer of activated B cells (NFκB) inhibitor, IκBα, and its phosphorylated form, phospho-IκBα. At the cellular level, RT-qPCR was used to examine the levels of miR-29s following NFκB activation by tumor necrosis factor alpha (TNFα); and western blot and luciferase assay were used to determine the regulation of MMP-2 by miR-29s in a human RPE cell line (ARPE-19) and in an umbilical vein endothelial cell line (EA hy926).

Results

MMP-2 staining was increased in the choroidal neovascular membrane of laser-treated retina. Also, the NFκB pathway was induced in choroid-RPE tissue, as evidenced by a lower protein level of IκBα and a higher level of phospho-IκBα in the tissue homogenates than in those from non-treated eyes. During the period when the NFκB pathway was induced, reduced miR-29s were detected in the choroidal-RPE tissue of the laser-treated eyes. In cultured ARPE-19 cells, TNFα decreased miR-29a, b, and c, and the effects were rescued by NFκB decoy. In ARPE-19 and EA hy926, miR-29s mimics reduced the contents of secreted MMP-2 in the culture media. We also documented that miR-29s reduced MMP-2 3’-UTR-mediated luciferase transcription.

Conclusions

The results suggest that in CNV, NFκB activation inhibits miR-29s, which may contribute to angiogenesis by up-regulating the MMP-2 protein level in RPE cells. These observations may help in developing a strategy for resolving CNV by targeting miR-29s levels.

Lipid and protein oxidation in newborn infants after lutein administration

Objectives. To test the hypothesis that neonatal supplementation with lutein in the first hours of life reduces neonatal oxidative stress (OS) in the immediate postpartum period. Methods. A randomized controlled, double-blinded clinical trial was conducted among 150 newborns divided into control group, not supplemented (n = 47), and test group, supplemented with lutein on the first day postpartum (n = 103). Blood Samples were collected at birth from cord and at 48 hrs postpartum while routine neonatal metabolic screenings were taking place. Total hydroperoxide (TH), advanced oxidation protein products (AOPP), and biological antioxidant potential (BAP) were measured by spectrophotometry and data were analyzed by Wilcoxon rank sum test and by multivariate logistic regression analysis. Results. Before lutein supplementation, the mean blood concentrations of AOPP, TH, and BAP were 36.10 umol/L, 156.75 mmol/H₂O₂, and 2361.04 umol/L in the test group. After lutein supplementation, significantly higher BAP increment (0.17 ± 0.22 versus 0.06 versus ± 0.46) and lower TH increment (0.46 ± 0.54 versus 0.34 ± 0.52) were observed in the test group compared to controls. Conclusion. Neonatal supplementation with lutein in the first hours of life increases BAP and reduces TH in supplemented babies compared to those untreated. The generation of free radical-induced damage at birth is reduced by lutein. This trial is registered with ClinicalTrials.gov NCT02068807.

The effect of modified eggs and an egg-yolk based beverage on serum lutein and zeaxanthin concentrations and macular pigment optical density: results from a randomized trial

Increasing evidence suggests a beneficial effect of lutein and zeaxanthin on the progression of age-related macular degeneration. The aim of this study was to investigate the effect of lutein or zeaxanthin enriched eggs or a lutein enriched egg-yolk based buttermilk beverage on serum lutein and zeaxanthin concentrations and macular pigment levels. Naturally enriched eggs were made by increasing the levels of the xanthophylls lutein and zeaxanthin in the feed given to laying hens. One hundred healthy volunteers were recruited and randomized into 5 groups for 90 days. Group one added one normal egg to their daily diet and group two received a lutein enriched egg-yolk based beverage. Group three added one lutein enriched egg and group four one zeaxanthin enriched egg to their diet. Group five was the control group and individuals in this group did not modify their daily diet. Serum lutein and zeaxanthin concentrations and macular pigment densities were obtained at baseline, day 45 and day 90. Macular pigment density was measured by heterochromatic flicker photometry. Serum lutein concentration in the lutein enriched egg and egg yolk-based beverage groups increased significantly (p<0.001, 76% and 77%). A strong increase in the serum zeaxanthin concentration was observed in individuals receiving zeaxanthin enriched eggs (P< 0.001, 430%). No changes were observed in macular pigment density in the various groups tested. The results indicate that daily consumption of lutein or zeaxanthin enriched egg yolks as well as an egg yolk-based beverage show increases in serum lutein and zeaxanthin levels that are comparable with a daily use of 5 mg supplements.

Trial Registration

ClinicalTrials.gov NCT00527553

Genetic evidence for role of carotenoids in age-related macular degeneration in the Carotenoids in Age-Related Eye Disease Study (CAREDS)

PURPOSE

We tested variants in genes related to lutein and zeaxanthin status for association with age-related macular degeneration (AMD) in the Carotenoids in Age-Related Eye Disease Study (CAREDS).

METHODS

Of 2005 CAREDS participants, 1663 were graded for AMD from fundus photography and genotyped for 424 single nucleotide polymorphisms (SNPs) from 24 candidate genes for carotenoid status. Of 337 AMD cases 91% had early or intermediate AMD. The SNPs were tested individually for association with AMD using logistic regression. A carotenoid-related genetic risk model was built using backward selection and compared to existing AMD risk factors using the area under the receiver operating characteristic curve (AUC).

RESULTS

A total of 24 variants from five genes (BCMO1, BCO2, NPCL1L1, ABCG8, and FADS2) not previously related to AMD and four genes related to AMD in previous studies (SCARB1, ABCA1, APOE, and ALDH3A2) were associated independently with AMD, after adjusting for age and ancestry. Variants in all genes (not always the identical SNPs) were associated with lutein and zeaxanthin in serum and/or macula, in this or other samples, except for BCO2 and FADS2. A genetic risk score including nine variants significantly (P = 0.002) discriminated between AMD cases and controls beyond age, smoking, CFH Y402H, and ARMS2 A69S. The odds ratio (95% confidence interval) for AMD among women in the highest versus lowest quintile for the risk score was 3.1 (2.0-4.9).

CONCLUSIONS

Variants in genes related to lutein and zeaxanthin status were associated with AMD in CAREDS, adding to the body of evidence supporting a protective role of lutein and zeaxanthin in risk of AMD.

Role of antioxidant enzymes and small molecular weight antioxidants in the pathogenesis of age-related macular degeneration (AMD)

Cells in aerobic condition are constantly exposed to reactive oxygen species (ROS), which may induce damage to biomolecules, including proteins, nucleic acids and lipids. In normal circumstances, the amount of ROS is counterbalanced by cellular antioxidant defence, with its main components—antioxidant enzymes, DNA repair and small molecular weight antioxidants. An imbalance between the production and neutralization of ROS by antioxidant defence is associated with oxidative stress, which plays an important role in the pathogenesis of many age-related and degenerative diseases, including age-related macular degeneration (AMD), affecting the macula—the central part of the retina. The retina is especially prone to oxidative stress due to high oxygen pressure and exposure to UV and blue light promoting ROS generation. Because oxidative stress has an established role in AMD pathogenesis, proper functioning of antioxidant defence may be crucial for the occurrence and progression of this disease. Antioxidant enzymes play a major role in ROS scavenging and changes of their expression or/and activity are reported to be associated with AMD. Therefore, the enzymes in the retina along with their genes may constitute a perspective target in AMD prevention and therapy.

The effect of lutein supplementation on blood plasma levels of complement factor D, C5a and C3d

Lutein is selectively taken up by the primate retina and plays an important role as a filter for harmful blue light and as an antioxidant. Recent studies have shown that lutein has systemic anti-inflammatory properties. Dietary lutein has been associated with reduced circulating levels of inflammatory biomarkers such as CRP and sICAM. Whether lutein also affects activation of the complement system has not yet been addressed and was the purpose of the study described here. Seventy-two subjects with signs of early macular degeneration were randomly assigned to receive either a 10 mg lutein supplement or a placebo during one year. EDTA blood samples were collected at 0, 4, 8 and 12 months. Complement factor D (CFD), a rate limiting component of the alternative pathway of complement activation and the complement activation products C5a and C3d were determined in the plasma samples by ELISA. A significant 0.11 µg/ml monthly decrease in plasma CFD concentration was observed in the lutein group (p<0.001), resulting in a 51% decrease from 2.3 µg/ml at baseline to 1.0 µg/ml at 12 months. The C5a concentration showed a significant 0.063ng/ml monthly decrease in the lutein group (p<0.001) resulting in a 36% decrease from 2.2ng/ml at baseline to 1.6ng/ml at 12 months. The C3d concentration showed a significant 0.19µg/ml monthly decrease in the lutein group (p=0.004) that gave rise to a 9% decrease from 15.4µg/ml at baseline to 14.4µg/ml at 12 months. In the placebo group we found a significant 0.04 µg/ml monthly decrease in plasma CFD concentration, whereas no changes were observed for C5a and C3d. Lutein supplementation markedly decreases circulating levels of the complement factors CFD, C5a and C3d levels, which might allow a simple method to control this inflammatory pathway of the innate immune system.

The role of lutein in eye-related disease

The lens and retina of the human eye are exposed constantly to light and oxygen. In situ phototransduction and oxidative phosphorylation within photoreceptors produces a high level of phototoxic and oxidative related stress. Within the eye, the carotenoids lutein and zeaxanthin are present in high concentrations in contrast to other human tissues. We discuss the role of lutein and zeaxanthin in ameliorating light and oxygen damage, and preventing age-related cellular and tissue deterioration in the eye. Epidemiologic research shows an inverse association between levels of lutein and zeaxanthin in eye tissues and age related degenerative diseases such as macular degeneration (AMD) and cataracts. We examine the role of these carotenoids as blockers of blue-light damage and quenchers of oxygen free radicals. This article provides a review of possible mechanisms of lutein action at a cellular and molecular level. Our review offers insight into current clinical trials and experimental animal studies involving lutein, and possible role of nutritional intervention in common ocular diseases that cause blindness.

Effect of lutein and antioxidant supplementation on VEGF expression, MMP-2 activity, and ultrastructural alterations in apolipoprotein E-deficient mouse

Oxidative stress is involved in the pathogenesis of several diseases such as atherosclerosis and age-related macular degeneration (AMD). ApoE-deficient mice (apoE^−/−) are a well-established model of genetic hypercholesterolemia and develop retinal alterations similar to those found in humans with AMD. Thus supplementation with lutein or multivitamin plus lutein and glutathione complex (MV) could prevent the onset of these alterations. ApoE^−/− mice (n = 40, 3 months old) were treated daily for 3 months with lutein (AE-LUT) or MV (two doses): AE-MV15 (15 mg/kg/day) and AE-MV50 (50 mg/kg/day) and were compared to controls with vehicle (AE-C). Wild-type mice (n = 10) were also used as control (WT-C). ApoE^−/− mice showed higher retinal lipid peroxidation and increased VEGF expression and MMP-2 activity, associated with ultrastructural alterations such as basal laminar deposits, vacuoles, and an increase in Bruch's membrane thickness. While lutein alone partially prevented the alterations observed in apoE^−/− mice, MV treatment substantially reduced VEGF levels and MMP-2 activity and ameliorated the retinal morphological alterations. These results suggest that oxidative stress in addition to an increased expression and activity of proangiogenic factors could participate in the onset or development of retinal alterations of apoE^−/− mice. Moreover, these changes could be prevented by efficient antioxidant treatments.

Radical scavenging activity-based and AP-1-targeted anti-inflammatory effects of lutein in macrophage-like and skin keratinocytic cells

Lutein is a naturally occurring carotenoid with antioxidative, antitumorigenic, antiangiogenic, photoprotective, hepatoprotective, and neuroprotective properties. Although the anti-inflammatory effects of lutein have previously been described, the mechanism of its anti-inflammatory action has not been fully elucidated. Therefore, in the present study, we aimed to investigate the regulatory activity of lutein in the inflammatory responses of skin-derived keratinocytes or macrophages and to elucidate the mechanism of its inhibitory action. Lutein significantly reduced several skin inflammatory responses, including increased expression of interleukin-(IL-) 6 from LPS-treated macrophages, upregulation of cyclooxygenase-(COX-) 2 from interferon-γ/tumor necrosis-factor-(TNF-) α-treated HaCaT cells, and the enhancement of matrix-metallopeptidase-(MMP-) 9 level in UV-irradiated keratinocytes. By evaluating the intracellular signaling pathway and the nuclear transcription factor levels, we determined that lutein inhibited the activation of redox-sensitive AP-1 pathway by suppressing the activation of p38 and c-Jun-N-terminal kinase (JNK). Evaluation of the radical and ROS scavenging activities further revealed that lutein was able to act as a strong anti-oxidant. Taken together, our findings strongly suggest that lutein-mediated AP-1 suppression and anti-inflammatory activity are the result of its strong antioxidative and p38/JNK inhibitory activities. These findings can be applied for the preparation of anti-inflammatory and cosmetic remedies for inflammatory diseases of the skin.

Environmental light and endogenous antioxidants as the main determinants of non-cancer ocular diseases

The human eye is constantly exposed to sunlight and artificial lighting. Exogenous sources of reactive oxygen species (ROS) such as UV light, visible light, ionizing radiation, chemotherapeutics, and environmental toxins contribute to oxidative damage in ocular tissues. Long-term exposure to these insults places the aging eye at considerable risk for pathological consequences of oxidative stress. Furthermore, in eye tissues, mitochondria are an important endogenous source of ROS. Over time, all ocular structures, from the tear film to the retina, undergo oxidative stress, and therefore, the antioxidant defenses of each tissue assume the role of a safeguard against degenerative ocular pathologies. The ocular surface and cornea protect the other ocular tissues and are significantly exposed to oxidative stress of environmental origin. Overwhelming of antioxidant defenses in these tissues clinically manifests as pathologies including pterygium, corneal dystrophies, and endothelial Fuch's dystrophy. The crystalline lens is highly susceptible to oxidative damage in aging because its cells and their intracellular proteins are not turned over or replaced, thus providing the basis for cataractogenesis. The trabecular meshwork, which is the anterior chamber tissue devoted to aqueous humor drainage, has a particular susceptibility to mitochondrial oxidative injury that affects its endothelium and leads to an intraocular pressure increase that marks the beginning of glaucoma. Photo-oxidative stress can cause acute or chronic retinal damage. The pathogenesis of age-related macular degeneration involves oxidative stress and death of the retinal pigment epithelium followed by death of the overlying photoreceptors. Accordingly, converging evidence indicates that mutagenic mechanisms of environmental and endogenous sources play a fundamental pathogenic role in degenerative eye diseases.

Suppression of experimental choroidal neovascularization by curcumin in mice

Purpose

To investigate the effects of curcumin on the development of experimental choroidal neovascularization (CNV) with underlying cellular and molecular mechanisms.

Methods

C57BL/6N mice were pretreated with intraperitoneal injections of curcumin daily for 3 days prior to laser-induced CNV, and the drug treatments were continued until the end of the study. The CNV area was analyzed by fluorescein-labeled dextran angiography of retinal pigment epithelium (RPE)-choroid flat mounts on day 7 and 14, and CNV leakage was evaluated by fluorescein angiography (FA) on day 14 after laser photocoagulation. The infiltration of F4/80 positive macrophages and GR-1 positive granulocytes were evaluated by immunohistochemistry on RPE-choroid flat mounts on day 3. Their expression in RPE-choroid complex was quantified by real-time PCR (F4/80) and Western blotting (GR-1) on day 3. RPE-choroid levels of vascular endothelial growth factor (VEGF), tumor necrosis factor (TNF)-α, monocyte chemotactic protein (MCP)-1, and intercellular adhesion molecule (ICAM)-1 were examined by ELISA on day 3. Double immunostaining of F4/80 and VEGF was performed on cryo-sections of CNV lesions on day 3. The expression of nuclear factor (NF)-κB and hypoxia-inducible factor (HIF)−1α in the RPE-choroid was determined by Western blotting.

Results

Curcumin-treated mice had significantly less CNV area (P<0.05) and CNV leakage (P<0.001) than vehicle-treated mice. Curcumin treatment led to significant inhibition of F4/80 positive macrophages (P<0.05) and GR-1 positive granulocytes infiltration (P<0.05). VEGF mainly expressed in F4/80 positive macrophages in laser injury sites, which was suppressed by curcumin treatment (P<0.01). Curcumin inhibited the RPE-choroid levels of TNF-α (P<0.05), MCP-1 (P<0.05) and ICAM-1 (P<0.05), and suppressed the activation of NF-κB in nuclear extracts (P<0.05) and the activation of HIF−1α (P<0.05).

Conclusion

Curcumin treatment led to the suppression of CNV development together with inflammatory and angiogenic processes including NF-κB and HIF−1α activation, the up-regulation of inflammatory and angiogenic cytokines, and infiltrating macrophages and granulocytes. This provides molecular and cellular evidence of the validity of curcumin supplementation as a therapeutic strategy for the suppression of age-related macular degeneration (AMD)-associated CNV.

A possible role for lutein and zeaxanthin in cognitive function in the elderly

Epidemiologic studies suggest that dietary lutein and zeaxanthin may be of benefit in maintaining cognitive health. Among the carotenoids, lutein and zeaxanthin are the only two that cross the blood-retina barrier to form macular pigment (MP) in the eye. They also preferentially accumulate in the human brain. Lutein and zeaxanthin in macula from nonhuman primates were found to be significantly correlated with their concentrations in matched brain tissue. Therefore, MP can be used as a biomarker of lutein and zeaxanthin in primate brain tissue. This is of interest given that a significant correlation was found between MP density and global cognitive function in healthy older adults. An examination of a relation between cognition and lutein and zeaxanthin concentrations in the brain tissue of decedents from a population-based study in centenarians found that zeaxanthin concentrations in brain tissue were significantly related to antemortem measures of global cognitive function, memory retention, verbal fluency, and dementia severity after adjustment for age, sex, education, hypertension, and diabetes. In univariate analyses, lutein was related to recall and verbal fluency, but the strength of the associations was attenuated with adjustment for covariates. However, lutein concentrations in the brain were significantly lower in individuals with mild cognitive impairment than in those with normal cognitive function. Last, in a 4-mo, double-blinded, placebo-controlled trial in older women that involved lutein supplementation (12 mg/d), alone or in combination with DHA (800 mg/d), verbal fluency scores improved significantly in the DHA, lutein, and combined-treatment groups. Memory scores and rate of learning improved significantly in the combined-treatment group, who also showed a trend toward more efficient learning. When all of these observations are taken into consideration, the idea that lutein and zeaxanthin can influence cognitive function in older adults warrants further study.

Effect of carotenoid supplementation on plasma carotenoids, inflammation and visual development in preterm infants

OBJECTIVE

Dietary carotenoids (lutein, lycopene and β-carotene) may be important in preventing or ameliorating prematurity complications. Little is known about carotenoid status or effects of supplementation.

STUDY DESIGN

This randomized controlled multicenter trial compared plasma carotenoid levels among preterm infants (n=203, <33 weeks gestational age) fed diets with and without added lutein, lycopene and β-carotene with human milk (HM)-fed term infants. We assessed safety and health.

RESULT

Plasma carotenoid levels were higher in the supplemented group at all time points (P<0.0001) and were similar to those of term HM-fed infants. Supplemented infants had lower plasma C-reactive protein (P<0.001). Plasma lutein levels correlated with the full field electroretinogram-saturated response amplitude in rod photoreceptors (r=0.361, P=0.05). The supplemented group also showed greater rod photoreceptor sensitivity (least squares means 6.1 vs 4.1; P<0.05).

CONCLUSION

Carotenoid supplementation for preterm infants raises plasma concentrations to those observed in HM-fed term infants. Carotenoid supplementation may decrease inflammation. Our results point to protective effects of lutein on preterm retina health and maturation.

Neuroprotective effects of lutein in the retina

Although a large variety of pharmaceutical therapies for treating disease have been developed in recent years, there has been little progress in disease prevention. In particular, the protection of neural tissue is essential, because it is hardly regenerated. The use of nutraceuticals for maintaining the health has been supported by several clinical studies, including cross-sectional and interventional studies for age-related macular disease. However, mechanistic evidence for their effects at the molecular level has been very limited. In this review, we focus on lutein, which is a xanthophyll type of carotenoid. Lutein is not synthesized in mammals, and must be obtained from the diet. It is delivered to the retina, and in humans, it is concentrated in the macula. Here, we describe the neuroprotective effects of lutein and their underlying molecular mechanisms in animal models of vision-threatening diseases, such as innate retinal inflammation, diabetic retinopathy, and light-induced retinal degeneration. In lutein-treated mouse ocular disease models, oxidative stress in the retina is reduced, and its downstream pathological signals are inhibited. Furthermore, degradation of the functional proteins, rhodopsin (a visual substance) and synaptophysin (a synaptic vesicle protein also influenced in other neurodegenerative diseases such as Alzheimer’s disease and Parkinson’s disease), the depletion of brain-derived neurotrophic factor (BDNF), and DNA damage are prevented by lutein, which preserves visual function. We discuss the possibility of using lutein, an antioxidant, as a neuroprotective treatment for humans.

Lutein: more than just a filter for blue light

Lutein is concentrated in the primate retina, where together with zeaxanthin it forms the macular pigment. Traditionally lutein is characterized by its blue light filtering and anti-oxidant properties. Eliminating lutein from the diet of experimental animals results in early degenerative signs in the retina while patients with an acquired condition of macular pigment loss (Macular Telangiectasia) show serious visual handicap indicating the importance of macular pigment. Whether lutein intake reduces the risk of age related macular degeneration (AMD) or cataract formation is currently a strong matter of debate and abundant research is carried out to unravel the biological properties of the lutein molecule. SR-B1 has recently been identified as a lutein binding protein in the retina and this same receptor plays a role in the selective uptake in the gut. In the blood lutein is transported via high-density lipoproteins (HDL). Genes controlling SR-B1 and HDL levels predispose to AMD which supports the involvement of cholesterol/lutein transport pathways. Apart from beneficial effects of lutein intake on various visual function tests, recent findings show that lutein can affect immune responses and inflammation. Lutein diminishes the expression of various ocular inflammation models including endotoxin induced uveitis, laser induced choroidal neovascularization, streptozotocin induced diabetes and experimental retinal ischemia and reperfusion. In vitro studies show that lutein suppresses NF kappa-B activation as well as the expression of iNOS and COX-2. Since AMD has features of a chronic low-grade systemic inflammatory response, attention to the exact role of lutein in this disease has shifted from a local effect in the eye towards a possible systemic anti-inflammatory function.

The relation between serum lipids and lutein and zeaxanthin in the serum and retina: results from cross-sectional, case-control and case study designs

Background

The xanthophyll carotenoids lutein (L) and zeaxanthin (Z) are found in and around the macula of the primate retina, where they are termed macular pigment (MP). Dietary L and Z are absorbed with fat in the gut and transported on lipoproteins to the retina. Both MP and serum lipoproteins have been related to risk for neurodegenerative diseases such as age-related macular degeneration (AMD). L and Z are carried on both HDL (related to reduced risk of AMD) and LDL (related to increased risk). The purpose of this set of studies was to analyze the relation between L and Z in the serum and retina with the circulating lipid profile.

Methods

In all experiments, lipoproteins were measured enzymatically from plasma, and MP optical density (MPOD) was measured using customized heterochromatic flicker photometry. Experiment 1: Relations between serum L and Z, MPOD and lipoprotein levels. 108 young, healthy subjects (M = 23.2, SD = 4.12 years) participated. Lipoprotein levels and MPOD were measured. In a subset of 66 participants, serum L and Z levels were also measured using high-performance liquid chromatography. Experiment 2: Relations between lipoprotein levels and MPOD in statin users. 20 subjects (M = 58.05, SD = 11.08 years) taking statin medication and 20 subjects (M = 57.95, SD = 11.03 years) not taking satin were recruited for participation. MPOD and lipoprotein levels were measured. Experiment 3: lowering lipoprotein levels to impact MPOD. One individual (aged 41 years) with high MP density adhered first to an atorvastatin regimen, then, after a wash-out period, to a rosuvastatin regimen.

Results

Experiment 1: HDL were significantly (p < 0.05) related to MPOD (r = 0.33), to serum L (r = 0.36) and to serum Z (r = 0.26). MPOD was also significantly related to total cholesterol (r = 0.19). Experiment 2: MPOD was not lower in statin users when compared to matched non-statin users, but MPOD decreased significantly with increased duration of statin use (r = −0.63). Experiment 3: Administration of a statin regimen reduced MPOD with atorvastatin (p < 0.05) but not with rosuvastatin.

Conclusions

Serum xanthophylls, retinal xanthophylls and lipoprotein concentrations are significantly related, and changing lipoprotein levels may impact levels of retinal xanthophylls.

The effect of lutein- and zeaxanthin-rich foods v. supplements on macular pigment level and serological markers of endothelial activation, inflammation and oxidation: pilot studies in healthy volunteers

The aim of the present study was to compare the effect of lutein- and zeaxanthin-rich foods and supplements on macular pigment level (MPL) and serological markers of endothelial activation, inflammation and oxidation in healthy volunteers. We conducted two 8-week intervention studies. Study 1 (n 52) subjects were randomised to receive either carrot juice (a carotene-rich food) or spinach powder (a lutein- and zeaxanthin-rich food) for 8 weeks. Study 2 subjects (n 75) received supplements containing lutein and zeaxanthin, β-carotene, or placebo for 8 weeks in a randomised, double-blind, placebo-controlled trial. MPL, serum concentrations of lipid-soluble antioxidants, inter-cellular adhesion molecule 1, vascular cell adhesion molecule 1, C-reactive protein and F2-isoprostane levels were assessed at baseline and post-intervention in both studies. In these intervention studies, no effects on MPL or markers of endothelial activation, inflammation or oxidation were observed. However, the change in serum lutein and zeaxanthin was associated or tended to be associated with the change in MPL in those receiving lutein- and zeaxanthin-rich foods (lutein r 0·40, P = 0·05; zeaxanthin r 0·30, P = 0·14) or the lutein and zeaxanthin supplement (lutein r 0·43, P = 0·03; zeaxanthin r 0·22, P = 0·28). In both studies, the change in MPL was associated with baseline MPL (food study r − 0·54, P < 0·001; supplement study r − 0·40, P < 0·001). We conclude that this 8-week supplementation with lutein and zeaxanthin, whether as foods or as supplements, had no significant effect on MPL or serological markers of endothelial activation, inflammation and oxidation in healthy volunteers, but may improve MPL in the highest serum responders and in those with initially low MPL.

Suppression and regression of choroidal neovascularization in mice by a novel CCR2 antagonist, INCB3344

PURPOSE

To investigate the effect of an intravitreally administered CCR2 antagonist, INCB3344, on a mouse model of choroidal neovascularization (CNV).

METHODS

CNV was induced by laser photocoagulation on Day 0 in wild type mice. INCB3344 or vehicle was administered intravitreally immediately after laser application. On Day 14, CNV areas were measured on retinal pigment epithelium (RPE)-choroid flat mounts and histopathologic examination was performed on 7 µm-thick sections. Macrophage infiltration was evaluated by immunohistochemistry on RPE-choroid flat mounts and quantified by flow cytometry on Day 3. Expression of vascular endothelial growth factor (VEGF) protein in RPE-choroid tissue was examined by immunohistochemistry and ELISA, VEGF mRNA in sorted macrophages in RPE-choroid tissue was examine by real-time PCR and expression of phosphorylated extracellular signal-regulated kinase (p-ERK 1/2) in RPE-choroid tissue was measured by Western blot analysis on Day 3. We also evaluated the efficacy of intravitreal INCB3344 to spontaneous CNV detected in Cu, Zn-superoxide dismutase (SOD1) deficient mice. Changes in CNV size were assessed between pre- and 1week post-INCB3344 or vehicle administration in fundus photography and fluorescence angiography (FA).

RESULTS

The mean CNV area in INCB3344-treated mice decreased by 42.4% compared with the vehicle-treated control mice (p<0.001). INCB3344 treatment significantly inhibited macrophage infiltration into the laser-irradiated area (p<0.001), and suppressed the expression of VEGF protein (p = 0.012), VEGF mRNA in infiltrating macrophages (p<0.001) and the phosphorylation of ERK1/2 (p<0.001). The area of spontaneous CNV in Sod1⁻/⁻ mice regressed by 70.35% in INCB3344-treated animals while no change was detected in vehicle-treated control mice (p<0.001).

CONCLUSIONS

INCB3344 both inhibits newly forming CNV and regresses established CNV. Controlling inflammation by suppressing macrophage infiltration and angiogenic ability via the CCR-2/MCP-1 signal may be a useful therapeutic strategy for treating CNV associated with age-related macular degeneration.

Neuroprotective response after photodynamic therapy: role of vascular endothelial growth factor

Background

Anti-vascular endothelial growth factor (VEGF) drugs and/or photodynamic therapy (PDT) constitute current treatments targeting pathological vascular tissues in tumors and age-related macular degeneration. Concern that PDT might induce VEGF and exacerbate the disease has led us to current practice of using anti-VEGF drugs with PDT simultaneously. However, the underlying molecular mechanisms of these therapies are not well understood.

Methods

We assessed VEGF levels after PDT of normal mouse retinal tissue, using a laser duration that did not cause obvious tissue damage. To determine the role of PDT-induced VEGF and its downstream signaling, we intravitreally injected a VEGF inhibitor, VEGFR1 Fc, or a PI3K/Akt inhibitor, LY294002, immediately after PDT. Then, histological and biochemical changes of the retinal tissue were analyzed by immunohistochemistry and immunoblot analyses, respectively.

Results

At both the mRNA and protein levels, VEGF was upregulated immediately and transiently after PDT. VEGF suppression after PDT resulted in apoptotic destruction of the photoreceptor cell layer in only the irradiated area during PDT. Under these conditions, activation of the anti-apoptotic molecule Akt was suppressed in the irradiated area, and levels of the pro-apoptotic protein BAX were increased. Intravitreal injection of a PI3K/Akt inhibitor immediately after PDT increased BAX levels and photoreceptor cell apoptosis.

Conclusion

Cytotoxic stress caused by PDT, at levels that do not cause overt tissue damage, induces VEGF and activates Akt to rescue the neural tissue, suppressing BAX. Thus, the immediate and transient induction of VEGF after PDT is neuroprotective.

Lutein and zeaxanthin intake and the risk of age-related macular degeneration: a systematic review and meta-analysis

Lutein and zeaxanthin are thought to decrease the incidence of age-related macular degeneration (AMD); however, findings have been inconsistent. We conducted a systematic literature review and meta-analysis to evaluate the relationship between dietary intake of lutein and zeaxanthin and AMD risk. Relevant studies were identified by searching five databases up to April 2010. Reference lists of articles were retrieved, and experts were contacted. Literature search, data extraction and study quality assessment were performed independently by two reviewers and results were pooled quantitatively using meta-analysis methods. The potential sources of heterogeneity and publication bias were also estimated. The search yielded six longitudinal cohort studies. The pooled relative risk (RR) for early AMD, comparing the highest with the lowest category of lutein and zeaxanthin intake, was 0·96 (95 % CI 0·78, 1·17). Dietary intake of these carotenoids was significantly related with a reduction in risk of late AMD (RR 0·74; 95 % CI 0·57, 0·97); and a statistically significant inverse association was observed between lutein and zeaxanthin intake and neovascular AMD risk (RR 0·68; 95 % CI 0·51, 0·92). The results were essentially consistent among subgroups stratified by participant characteristics. The findings of the present meta-analysis indicate that dietary lutein and zeaxanthin is not significantly associated with a reduced risk of early AMD, whereas an increase in the intake of these carotenoids may be protective against late AMD. However, additional studies are needed to confirm these relationships.

The association between macular pigment optical density and CFH, ARMS2, C2/BF, and C3 genotype

Age-related macular degeneration (AMD) is the most common cause of blindness in older people in developed countries, and risk for this condition may be classified as genetic or environmental, with an interaction between such factors predisposing to this disease. This study investigated the relationship between AMD risk genes, macular pigment optical density (MPOD), which may protect against AMD, and serum concentrations of the macular carotenoids, lutein (L) and zeaxanthin (Z). This was a cross-sectional study of 302 healthy adult subjects. Dietary intake of L and Z was assessed by food frequency questionnaire, and MPOD was measured by customized heterochromatic flicker photometry. We also calculated MPOD Area as the area of MP under the spatial profile curve, to reflect MP across the macula. Serum L and Z were measured by HPLC. Genotyping of tag SNPs in the genes CFH, ARMS2, C3, C2 and BF was undertaken with multiplex polymerase chain reaction (PCR) and primer extension methodology (ABI Snapshot, ABI Warrington UK) on DNA extracted from peripheral blood. The mean ± SD (range) age of the subjects in this study was 48 ± 11 (21-66) years. There was a statistically significant association between CFH genotype and family history of AMD, with subjects having two non-risk CFH haplotypes (n = 35), or one non-risk and one protective CFH haplotype (n = 33), being significantly more likely to have a negative family history of AMD (Pearson Chi square: p = 0.001). There was no significant association between the AMD risk genes investigated and either MPOD (One way ANOVA: p > 0.05) or serum concentrations of L or Z (One way ANOVA: p > 0.05, for both). Subjects who were homozygous for risk alleles of both CFH and ARMS2 (n = 4) had significantly lower MPOD at 0.5° and 1° retinal eccentricity (Independent samples t test: p < 0.05) and lower MPOD Area which approached statistical significance (Independent samples t test: p = 0.058), compared to other subjects (n = 291). In conclusion, this study did not detect an association between individual AMD risk genotypes and the putatively protective MP, or serum concentrations of its constituent carotenoids. However, the combination of homozygous risk alleles at both CFH and ARMS2 loci was associated with significantly lower MPOD centrally, despite comparable serum concentrations of the macular carotenoids. These findings suggest that the maculae of subjects at very high genetic risk of AMD represent a hostile environment for accumulation and/or stabilization of MP.

Biological role of lutein in the light-induced retinal degeneration

Lutein, a xanthophyll of a carotenoid, is anticipated as a therapeutic product to prevent human eye diseases. However, its biological mechanism is still unclear. Here, we show the molecular mechanism of lutein's effect to reduce photodamage of the retina. We analyzed the light-exposed retinas of Balb/c mice given lutein-supplemented or normal diet. Visual function was measured by electroretinogram, and histological changes were observed. Immunohistochemical and immunoblot analyses were performed to analyze molecular mechanism. The reactive oxygen species induced in the retina was evaluated by fluorescent probes. In the mice after light exposure, reduction of a-wave and b-wave amplitudes in electroretinogram, indicating visual impairment, and thinning of the photoreceptor cell layer owing to apoptosis were both attenuated by lutein diet. Interestingly, γ-H2AX, a marker for double-strand breaks (DSBs) in DNA, was up-regulated in the photoreceptor cells after light exposure, but this increase was attenuated by lutein diet, suggesting that DSBs caused by photodamage contributed to the photoreceptor cell death and that this change was suppressed by lutein. Moreover, the expression of eyes absent (EYA), which promotes DNA repair and cell survival, was significantly up-regulated with lutein diet in the light-exposed retina. Therefore, lutein induced EYA for DNA repair, which could suppress DNA damage and photoreceptor cell apoptosis. Lutein reduced light-induced oxidative stress in the retina, which might contribute to promote DNA repair. The lutein-supplemented diet attenuated light-induced visual impairment by protecting the photoreceptor cells' DNA.

Nutritional influences on visual development and function

Experiments conducted on many different species reveal a fundamental paradox about the vertebrate eye; it is damaged by its own operation. This vulnerability stems from the need to respond to visible light, often actinic, but also from the intrinsic metabolic and structural state of the eye's internal structures. Photoreceptor outer segments, for instance, have high concentrations of diet-derived long-chain polyunsaturated fatty acids and these membrane lipids are highly prone to peroxidation due to the high oxygen tension of the outer retina. Such a high diathesis for damage would be catastrophic if it were not balanced by an equally impressive system for responding to such stressors. The retina (and to a lesser extent the crystalline lens), for instance, is especially rich in dietary antioxidants such as vitamin E, vitamin C and the macular carotenoids (lutein and zeaxanthin) putatively to retard light-induced oxidative damage. The nutrients that support both essential function (e.g., retinal, the vitamin form of vitamin A, in photopigment) and protection operate in a highly integrated manner. For instance, Vitamin E is a lipophillic chain-breaking anti-oxidant (protecting DHA-rich outer segment membranes) that regenerates itself through reaction with vitamin C (a primary anti-oxidant against aqueous radicals) and is spatially distributed in complement with the carotenoids lutein and zeaxanthin. Nor are these interactions relegated to simply providing protection and the basic elements needed for transduction. Macular lutein and zeaxanthin, for example, improve visual performance (e.g., reduce glare disability and discomfort, speed photostress recovery, and enhance chromatic contrast) through purely optical means (by absorbing short-wave light anterior to the foveal cones). The vulnerability of the eye to exogenous insult, and the sensitivity of the eye to dietary components, is not static: infants have more vulnerable retinas due to clearer lenses and higher metabolic activity; the elderly are more vulnerable due to such factors as increased inflammatory stress and a higher content of photosensitizers (such as lipofuscin) creating cascading oxidative effects. Hence, optimal dietary prophylaxis changes as the eye ages. The eye, perhaps more than most other biological structures, has evolved an exquisite and shifting sensitivity to dietary intake throughout the lifespan, not just for its basic operation (e.g., Vitamin A for transduction), but also for its very preservation.

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.

Neurodegenerative influence of oxidative stress in the retina of a murine model of diabetes

AIMS/HYPOTHESIS

Diabetic retinopathy is a progressive neurodegenerative disease, but the underlying mechanism is still obscure. Here, we focused on oxidative stress in the retina, and analysed its influence on retinal neurodegeneration, using an antioxidant, lutein.

METHODS

C57BL/6 mice with streptozotocin-induced diabetes were constantly fed either a lutein-supplemented diet or a control diet from the onset of diabetes, and their metabolic data were recorded. In 1-month-diabetic mice, reactive oxygen species (ROS) in the retina were measured using dihydroethidium and visual function was evaluated by electroretinograms. Levels of activated extracellular signal-regulated kinase (ERK), synaptophysin and brain-derived neurotrophic factor (BDNF) were also measured by immunoblotting in the retina of 1-month-diabetic mice. In the retinal sections of 4-month-diabetic mice, histological changes, cleaved caspase-3 and TUNEL staining were analysed.

RESULTS

Lutein did not affect the metabolic status of the diabetic mice, but it prevented ROS generation in the retina and the visual impairment induced by diabetes. ERK activation, the subsequent synaptophysin reduction, and the BDNF depletion in the diabetic retina were all prevented by lutein. Later, in 4-month-diabetic mice, a decrease in the thickness of the inner plexiform and nuclear layers, and ganglion cell number, together with increase in cleaved caspase-3- and TUNEL-positive cells, were avoided in the retina of lutein-fed mice.

CONCLUSIONS/INTERPRETATION

The results indicated that local oxidative stress that has a neurodegenerative influence in the diabetic retina is prevented by constant intake of a lutein-supplemented diet. The antioxidant, lutein may be a potential therapeutic approach to protect visual function in diabetes.

Beneficial effect of docosahexanoic acid and lutein on retinal structural, metabolic, and functional abnormalities in diabetic rats

PURPOSE

To assess the effect of docosahexanoic acid (DHA) and lutein (both compounds with anti-inflammatory and antioxidant properties) on experimental diabetic retinopathy.

METHODS

Male Wistar rats were studied: non-diabetic controls, untreated diabetic controls, and diabetic rats were treated with DHA and lutein or the combination of DHA + insulin and lutein + insulin for 12 weeks. Oxidative stress and inflammatory markers, apoptosis, and functional tests were studied to confirm biochemical and functional changes in the retina of diabetic rats. Malondialdehyde (MDA), glutathione concentrations (GSH), and glutathione peroxidase activity (GPx) were measured as oxidative stress markers. TUNEL assay and caspase-3 immunohistochemistry and electroretinogram were performed.

RESULTS

Diabetes increases oxidative stress, nitrotyrosine concentrations, and apoptosis in the retina. At 12 weeks after onset of diabetes, total thickness of retinas of diabetic rats was significantly less than that in control rats. Specifically, the thickness of the outer and inner nuclear layers was reduced significantly in diabetic rats and demonstrated a loss of cells in the GCL. These retinal changes were avoided by the administration of insulin and DHA and lutein alone or in combination with insulin. Impairment of the electroretinogram (b-wave amplitude and latency time) was observed in diabetic rats. DHA and lutein prevented all these changes even under hyperglycemic conditions.

CONCLUSIONS

Lutein and DHA are capable of normalizing all the diabetes-induced biochemical, histological, and functional modifications. Specifically, the cell death mechanisms involved deserve further studies to allow the proposal as potential adjuvant therapies to help prevent vision loss in diabetic patients.

Effects of mayonnaise on postprandial serum lutein/zeaxanthin and beta-carotene concentrations in humans

To clarify the effects of different physical forms of oil on postprandial serum lutein/zeaxanthin and beta-carotene concentrations, we performed a vegetable meal loading test. Eighteen healthy subjects participated in the test, which consisted of broccoli as a control (CON) meal, broccoli with oil (OIL), and broccoli with mayonnaise (MS), consumed in random order. After collection of fasting blood samples, subjects consumed one of the three test meals. Fasting and postprandial changes in serum carotenoids were assessed 2, 4, and 6 h after ingestion of each test meal. Serum lutein/zeaxanthin and beta-carotene concentrations were measured. Although no significant change was noted after the CON meal, the serum lutein/zeaxanthin concentration was higher at 4 h after consumption of the OIL meal, and at 2, 4 and 6 h after consumption of the MS meal, as compared with the fasting state. Serum beta-carotene concentrations did not change after ingestion of either the CON or the OIL meal but were elevated 2, 4, and 6 h after MS ingestion as compared with the fasting state. The incremental areas under the curves (IAUCs) of serum lutein/zeaxanthin and beta-carotene concentrations were higher after the MS meal than after the CON meal. IAUCs after the OIL meal exhibited no statistically significant differences from the CON and MS meals. We suggest that mayonnaise contributes to increase serum lutein/zeaxanthin and beta-carotene concentrations when consumed with vegetables rich in these carotenoids.

Overall diet quality and age-related macular degeneration

PURPOSE

To examine overall diet quality in relation to advanced age-related macular degeneration (AMD).

METHODS

This case-control study identified 437 advanced AMD patients and 259 unrelated controls using stereoscopic color fundus photographs. Participants were predominantly non-Hispanic White men and women from North Carolina and Tennessee. A 97-item Block food frequency questionnaire was used to gather diet information, and overall diet quality was measured using the Healthy Eating Index (HEI) and Alternate Healthy Eating Index (AHEI).

RESULTS

Participants in the highest quartile of diet quality had significantly reduced odds of AMD according to the AHEI score (0.54, 95% confidence interval 0.30-0.99) and non-significantly reduced odds of AMD according to the HEI (0.75, 0.41-1.38). Odds of AMD were also 51% lower in the highest quartile of fish intake compared to the lowest quartile (odds ratio = 0.49, 0.26-0.90).

CONCLUSIONS

We found that advanced AMD was significantly related to overall diet quality. The AHEI score may be a useful instrument for assessing AMD risk due to diet, and it could potentially be improved by incorporating more specific information regarding micronutrient intake.

Effect of zeaxanthin and antioxidant supplementation on vascular endothelial growth factor (VEGF) expression in apolipoprotein-E deficient mice

PURPOSE

Apolipoprotein E(-/-) deficient (apoE(-/-)) mice develop hypercholesterolemia, atherosclerosis, and retinal alterations. We studied the oxidative status and vascular endothelial growth factor (VEGF) expression in murine retinal pigment epithelium-choroid (RPE) and Bruch's membrane (BM) ultrastructure and the effect of zeaxanthin.

METHODS

Ten 6-month-old C57BL/6 and 40 apoE(-/-) mice were divided into four groups (n = 10 each) and fed different diets for 12 weeks based on body weight: wild type (WT) and apoE(-/-) (AE-Con) mice standard rodent chow; apoE(-/-) mice (AES) standard rodent chow with ascorbate (800 mg/kg), tocopherol (1053 mg/kg), and zinc (135 mg/kg); and apoE(-/-) mice the last diet plus zeaxanthin with either 0.4 g/kg (AES-Z04) or 4 g/kg feed (AES-Z4).

RESULTS

Plasma total cholesterol (TC) and triglycerides (TG) and urine lipid peroxidation (isoprostanes) were measured. VEGF expression was determined in RPE-choroid homogenates. Zeaxanthin uptake was assessed in liver and retina by high-performance liquid chromatography; the retinal ultrastructure was analyzed by electron microscopy. AE-Con mice had higher plasma TC (p < 0.001) and TG (p < 0.001) values than WT mice. AE-Con mice had higher RPE-choroid-VEGF levels than WT mice (p < 0.05), BM thickness (p < 0.001) and presence of basal laminar deposits (BLamD). AES-Z4 resulted in lower urinary isoprostanes (p = 0.054) and lower VEGF expression in the RPE-choroid (p < 0.01). BM in the AES-Z4 animals had less confluent BLamD than AE-Con, AES, or AES-Z04 animals.

CONCLUSIONS

We have reported that supplementation with zeaxanthin and antioxidants may delay or reverse alterations in the RPE and deposits in BM, and reduced VEGF expression observed in apoE(-/-) mice.

Antioxidant effect of lutein towards phospholipid hydroperoxidation in human erythrocytes

Peroxidised phospholipid-mediated cytotoxity is involved in the pathophysiology of many diseases; for example, phospholipid hydroperoxides (PLOOH) are abnormally increased in erythrocytes of dementia patients. Dietary carotenoids (especially xanthophylls, polar carotenoids such as lutein) have gained attention as potent inhibitors against erythrocyte phospholipid hydroperoxidation, thereby making them plausible candidates for preventing diseases (i.e. dementia). To evaluate these points, we investigated whether orally administered lutein is distributed to human erythrocytes, and inhibits erythrocyte PLOOH formation. Six healthy subjects took one capsule of food-grade lutein (9·67 mg lutein per capsule) once per d for 4 weeks. Before and during the supplementation period, carotenoids and PLOOH in erythrocytes and plasma were determined by our developed HPLC technique. The administered lutein was incorporated into human erythrocytes, and erythrocyte PLOOH level decreased after the ingestion for 2 and 4 weeks. The antioxidative effect of lutein was confirmed on erythrocyte membranes, but not in plasma. These results suggest that lutein has the potential to act as an important antioxidant molecule in erythrocytes, and it thereby may contribute to the prevention of dementia. Therefore future biological and clinical studies will be required to evaluate the efficacy as well as safety of lutein in models of dementia with a realistic prospect of its use in human therapy.

Possible role for dietary lutein and zeaxanthin in visual development

The possibility that the macular carotenoids, lutein (L), and zeaxanthin (Z), could retard age-related changes in the eye and prevent the eye diseases that result from such changes (namely, cataract and macular degeneration) has been carefully studied. A role for the carotenoids very early in life, however, has received far less attention. Nevertheless, an influence on visual development is likely. Retinal L and Z, for instance, would influence the development of the visual system if they 1) altered input during a critical/sensitive period of visual development and/or 2) influenced maturation and/or 3) protected the retina during a period when it was particularly vulnerable. The available evidence indicates that the pigments may play a role in all three of these areas.