Nutritional manipulation of primate retinas, V: effects of lutein, zeaxanthin, and n-3 fatty acids on retinal sensitivity to blue-light-induced damage

The macular carotenoids: A biochemical overview

Among the more than 750 carotenoids identified in nature, only lutein, zeaxanthin, meso-zeaxanthin, and their oxidative metabolites are selectively accumulated in the macula lutea region of the human retina. These retinal carotenoids are collectively referred to as the macular pigment (MP) and are obtained only through dietary sources such as green leafy vegetables and yellow and orange fruits and vegetables. Lutein- and zeaxanthin-specific binding proteins (StARD3 and GSTP1, respectively) mediate the highly selective uptake of MP into the retina. Meso-zeaxanthin is rarely present in the diet, and its unique presence in the human eye results from metabolic conversion from dietary lutein by the RPE65 enzyme. The MP carotenoids filter high-intensity, short-wavelength visible light and are powerful antioxidants in a region vulnerable to light-induced oxidative stress. This review focuses on MP chemistry, absorption, metabolism, transport, and distribution with special emphasis on animal models used for MP study. This article is part of a Special Issue entitled Carotenoids recent advances in cell and molecular biology edited by Johannes von Lintig and Loredana Quadro.

Carotenoid metabolism at the intestinal barrier

Carotenoids exert a rich variety of physiological functions in mammals and are beneficial for human health. These lipids are acquired from the diet and metabolized to apocarotenoids, including retinoids (vitamin A and its metabolites). The small intestine is a major site for their absorption and bioconversion. From here, carotenoids and their metabolites are distributed within the body in triacylglycerol-rich lipoproteins to support retinoid signaling in peripheral tissues and photoreceptor function in the eyes. In recent years, much progress has been made in identifying carotenoid metabolizing enzymes, transporters, and binding proteins. A diet-responsive regulatory network controls the activity of these components and adapts carotenoid absorption and bioconversion to the bodily requirements of these lipids. Genetic variability in the genes encoding these components alters carotenoid homeostasis and is associated with pathologies. We here summarize the advanced state of knowledge about intestinal carotenoid metabolism and its impact on carotenoid and retinoid homeostasis of other organ systems, including the eyes, liver, and immune system. The implication of the findings for science-based intake recommendations for these essential dietary lipids is discussed. This article is part of a Special Issue entitled Carotenoids recent advances in cell and molecular biology edited by Johannes von Lintig and Loredana Quadro.

The Effects of Adjuvant Tamoxifen Use on Macula Pigment Epithelium Optical Density, Visual Acuity and Retinal Thickness in Patients with Breast Cancer

Purpose: We aimed to compare best corrected visual acuity, macular pigment optical density and macular thickness in patients with breast cancer, who received oral adjuvant hormone therapy.Materials and Methods: We enrolled consecutive eligible patients with breast cancer who were receiving regular medical tamoxifen treatment. The participants were divided into two groups as cases and controls. Best-corrected visual acuity and retinal thickness were examined. Macular pigment optical density was measured by fundus reflectometry using the one-wavelength reflection method. The output parameters included max optical density, mean optical density, volume and area of the right eye.Results: A total of 104 eyes, cases (n: 50) and controls (n: 54) were included in the study. Mean age in cases was 49.95 ± 9.2 years and 50.21 ± 9.3 years in controls (p = .151). The mean foveal optical density and the maximum optical density differed between cases (0.13 ± 0.03 density units (DU)/0.35 ± 0.07 DU) and controls (0.18 ± 0.04 DU/0.41 ± 0.06 DU) (p = .002/p = .009). Macular pigment optical density volume was 8102.84 ± 2412.67 in cases versus 8280.18 ± 2904.56 in controls (p = .034), and mean MPOD area was 59567.79 ± 11538.06 in cases versus 61748.14 ± 10591.19 in controls (p = .023). The best corrected visual acuity and retinal thickness were similar in both groups (p > .05).Conclusions: Patients in care of oral tamoxifen therapy were found to have significantly reduced macular pigment optical density. In addition, higher drug use duration correlated significantly with reduced macular pigment optical density, suggesting that the poor long-term effects may play a role in macular pigment absorption and incorporation in the retinal tissue.

Zeaxanthin: Metabolism, Properties, and Antioxidant Protection of Eyes, Heart, Liver, and Skin

Zeaxanthin, a non-provitamin A carotenoid that belongs to the xanthophyll family, has been less studied than its isomer lutein. However, zeaxanthin has also been shown to have a number of beneficial effects for human health due to its ability to quench free radicals, exert antioxidant effects, as well as decrease inflammation. It is the purpose of this review to discuss the metabolism of zeaxanthin, including digestion, absorption, transport, and uptake by tissues, as well as the dietary or other factors which affect zeaxanthin bioavailability. In addition, this review also focuses on specific effects of this carotenoid on eye, skin, liver, and cardiovascular health. Data derived from human interventions, animal models of research, and in vitro and cell studies are discussed in this review.

Investigation of the relationship between macular pigment levels and rod-mediated dark adaptation in intermediate age-related macular degeneration

BACKGROUND

It has been shown that rod-mediated dark adaptation is significantly delayed in ageing, a change which is exacerbated in age-related macular degeneration (AMD). Levels of lutein and zeaxanthin, the two main constituents of macular pigment have been found in rod outer segments, indicating that the macular pigment may have an influence on rod-mediated dark adaptation. The aim of this study was to determine if rod-mediated dark adaptation is associated with central macular pigment levels in individuals with intermediate stage AMD.

METHODS

A cross-sectional observational study included individuals with acuity better than 6/15 Snellen and intermediate stage AMD based on graded fundus photographs using an internationally accepted grading scale. Rod-mediated dark adaptation was assessed at five degrees eccentricity in the superior retina (inferior visual field) using the rod intercept time measure from the MacuLogix AdaptDx. Macular pigment optical density was measured at 0.5 degrees eccentricity using a heterochromatic flicker photometry-based method.

RESULTS

Twenty-seven individuals (mean age 76.7 years) with intermediate stage AMD and 23 age-matched normal controls (mean age 74.0 years) were recruited. Rod-mediated dark adaptation was significantly delayed in intermediate stage AMD compared with healthy controls (32.9 minutes versus 10.7 minutes, p < 0.01). There was no statistically significant correlation between the rod intercept time and the level of macular pigment in those with intermediate AMD (r = -0.04, p = 0.85).

CONCLUSION

The results did not support the hypothesis that higher macular pigment is associated with improved rod-mediated performance or that higher levels of macular pigment protect rod-mediated function in intermediate AMD.

The Role of Nutrients in Reducing the Risk for Noncommunicable Diseases during Aging

An increasing aging population worldwide accounts for a growing share of noncommunicable diseases (NCDs) of the overall social and economic burden. Dietary and nutritional approaches are of paramount importance in the management of NCDs. As a result, nutrition programs are increasingly integrated into public health policies. At present, programs aimed at reducing the burden of NCDs have focused mostly on the excess of unhealthy nutrient intakes whereas the importance of optimizing adequate essential and semi-essential nutrient intakes and nutrient-rich diets has received less attention. Surveys indicate that nutrient intakes of the aging population are insufficient to optimally support healthy aging. Vitamin and mineral deficiencies in older adults are related to increased risk of NCDs including fatigue, cardiovascular disease, and cognitive and neuromuscular function impairments. Reviewed literature demonstrates that improving intake for certain nutrients may be important in reducing progress of NCDs such as musculoskeletal disorders, dementia, loss of vision, and cardiometabolic diseases during aging. Current knowledge concerning improving individual nutrient intakes to reduce progression of chronic disease is still emerging with varying effect sizes and levels of evidence. Most pronounced benefits of nutrients were found in participants who had low nutrient intake or status at baseline or who had increased genetic and metabolic needs for that nutrient. Authorities should implement ways to optimize essential nutrient intake as an integral part of their strategies to address NCDs.

Repeatability of the macular pigment spatial profile: A comparison of objective versus subjective classification

PURPOSE

Classification of macular pigment (MP) spatial profile phenotypes varies and is often based on subjective visualisation. We investigated repeatability of MP optical density (MPOD) comparing an objective versus subjective profiling system.

METHODS

The coefficient of repeatability (CoR) was calculated for point MPOD values (0-3.8°) obtained by dual-wavelength fundus autofluorescence (FAF) from two scans obtained in a single visit of 40 healthy individuals (39 ± 9 years). For each individual's dataset, the MP profile was classified as exponential, ring-like or central dip using an objective method (based on deviations away from an exponential fit), as well as by subjective visual profiling. Existing FAF images of 88 monozygotic (MZ) and 69 dizygotic (DZ) twin pairs were reanalysed using the objective profiling method and concordance and heritability of ring-like profiles determined.

RESULTS

The CoR was 0.23 at 0° and 0.06 at 0.8°. Agreement of objective profiling between scans was excellent (κ = 0.85, 95% CI 0.69 to 1.00; p < 0.0005). Subjective profiling showed moderate agreement between scans (κ = 0.48, 95% CI 0.23 to 0.73; p < 0.0005). Agreement between objective and subjective classification was low (κ = 0.23, 95% CI 0.04 to 0.42; p = 0.02). Concordance for the ring-like profile using objective profiling was 0.74 for MZ compared to 0.36 for DZ twins. Heritability was calculated as 81.5% (95% confidence interval 61.1-93.1%).

CONCLUSION

Compared to visual assessment, objective MP profiling is a more reliable method and should be considered in future observational and interventional studies. In addition, MP profile phenotypes showed high heritability.

Dietary guidance for lutein: consideration for intake recommendations is scientifically supported

Lutein, a yellow xanthophyll carotenoid found in egg yolks and many colorful fruits and vegetables, has gained public health interest for its putative role in visual performance and reducing the risk of age-related macular degeneration. The National Academies of Sciences, Engineering and Medicine's recommended Dietary Reference Intakes (DRIs) focus on preventing deficiency and toxicity, but there is a budding interest in establishing DRI-like guidelines for non-essential bioactives, like lutein, that promote optimal health and/or prevent chronic diseases. Lupton et al. developed a set of nine criteria to determine whether a bioactive is ready to be considered for DRI-like recommendations. These criteria include: (1) an accepted definition; (2) a reliable analysis method; (3) a food database with known amounts of the bioactive; (4) cohort studies; (5) clinical trials on metabolic processes; (6) clinical trials for dose-response and efficacy; (7) safety data; (8) systematic reviews and/or meta-analyses; (9) a plausible biological rationale. Based on a review of the literature supporting these criteria, lutein is ready to be considered for intake recommendations. Establishing dietary guidance for lutein would encourage the consumption of lutein-containing foods and raise public awareness about its potential health benefits.

Lutein and Zeaxanthin Isomers Protect against Light-Induced Retinopathy via Decreasing Oxidative and Endoplasmic Reticulum Stress in BALB/cJ Mice

Oxidative stress (OS) and endoplasmic reticulum stress (ERS) are the major factors underlying photoreceptor degeneration. Lutein, RR-zeaxanthin (3R,3’R-zeaxanthin) and RS (meso)-zeaxanthin (3R,3’S-RS- zeaxanthin) (L/Zi) could protect against cell damage by ameliorating OS in retina. In this study, we examined the effect of L/Zi supplementation in a mouse model of photoreceptor degeneration and investigated whether the treatment of L/Zi ameliorated OS and ERS. BALB/cJ mice after light exposure were used as the animal model. The protective effects of L/Zi were observed by electroretinography (ERG) and terminal deoxyuridine triphosphate nick-end labeling (TUNEL) analysis. The underlying mechanisms related to OS and ERS were explored by Western blotting. After L/Zi treatment, the ERG amplitudes were significantly higher, and the number of TUNEL-positive cells was significantly reduced compared to that of the vehicle group. Western blotting results revealed that OS was ameliorated according to the significant downregulation of phosphorylated c-Jun N-terminal kinase (p-JNK), and significant upregulation of nuclear factor erythroid 2-related factor 2 (Nrf2). In addition, ERS was reduced according to the significant downregulation of 78 kDa glucose-regulated protein (GRP78), phosphorylated protein kinase RNA-like endoplasmic reticulum kinase (p-PERK), activating transcription factor 4 (ATF4) and activating transcription factor (ATF6). Our data shows that L/Zi provided functional and morphological preservation of photoreceptors against light damage, which is probably related to its mitigation of oxidative and endoplasmic reticulum stress.

Protective role of carotenoids in the visual cycle

Exposure to light and accumulation of aberrant visual cycle by-products causes stress in the retina. The physical and chemical properties of carotenoids may provide protection against such scenario. These pigments exist in retinas of many vertebrates, including humans. However, the absence of carotenoids in mice, the preferred ophthalmologic animal model, hindered molecular and biochemical examination of the pigments' role in vision. We established a mouse model that accumulates significant amounts of carotenoids in the retina due to inactivating mutations in the Isx and Bco2 genes. We introduced a robust light damage protocol for the mouse retina using green (532 nm) and blue (405 nm) low-energy lasers. We observed that blue but not green laser light treatment triggered the formation of aberrant retinaldehyde isomers in the retina. The production of these visual cycle by-products was accompanied by morphologic damage in inferior parts of the mouse retina. Zeaxanthin supplementation of mice shielded retinoids from these photochemical modifications. These pigments also reduced the extent of the damage to the retina after the blue laser light insult. Thus, our study discovered a novel role of carotenoids in the visual cycle and indicated that vertebrates accumulate carotenoids to shield photoreceptors from short-wavelength light-induced damage.-Widjaja-Adhi, M. A. K., Ramkumar, S., von Lintig, J. Protective role of carotenoids in the visual cycle.

Carotenoids in human nutrition and health

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

Spectral analysis of fundus autofluorescence pattern as a tool to detect early stages of degeneration in the retina and retinal pigment epithelium

PURPOSE

The aim of this work is the determination of quantitative diagnostic criteria based on the spectral characteristics of fundus autofluorescence to detect early stages of degeneration in the retina and retinal pigment epithelium (RPE).

METHODS

RPE cell suspension samples were obtained from the cadaver eyes with and without signs of age-related macular degeneration (AMD). Fluorescence analysis at an excitation wavelength of 488 nm was performed. The fluorescence lifetimes of lipofuscin-granule fluorophores were measured by counting time-correlated photon method.

RESULTS

Comparative analysis of fluorescence spectra of RPE cell suspensions from the cadaver eyes with and without signs of AMD showed a significant difference in fluorescence intensity at 530-580 nm in response to fluorescence excitation at 488 nm. It was notably higher in eyes with visual pathology than in normal eyes regardless of the age of the eye donor. Measurements of fluorescence lifetimes of lipofuscin fluorophores showed that the contribution of photooxidation and photodegradation products of bisretinoids to the total fluorescence at 530-580 nm of RPE cell suspensions was greater in eyes with visual pathology than in normal eyes.

CONCLUSION

Because photooxidation and photodegradation products of bisretinoids are markers of photodestructive processes, which can cause RPE cell death and initiate degenerative processes in the retina, quantitative determination of increases in these bisretinoid products in lipofuscin granules may be used to establish quantitative diagnostic criteria for degenerative processes in the retina and RPE.

A new perspective on lipid research in age-related macular degeneration

There is an urgency to find new treatment strategies that could prevent or delay the onset or progression of AMD. Different classes of lipids and lipoproteins metabolism genes have been associated with AMD in a multiple ways, but despite the ever-increasing knowledge base, we still do not understand fully how circulating lipids or local lipid metabolism contribute to AMD. It is essential to clarify whether dietary lipids, systemic or local lipoprotein metabolismtrafficking of lipids in the retina should be targeted in the disease. In this article, we critically evaluate what has been reported in the literature and identify new directions needed to bring about a significant advance in our understanding of the role for lipids in AMD. This may help to develop potential new treatment strategies through targeting the lipid homeostasis.

Plasma proteins associated with circulating carotenoids in Nepalese school-aged children

Carotenoids are naturally occurring pigments that function as vitamin A precursors, antioxidants, anti-inflammatory agents or biomarkers of recent vegetable and fruit intake, and are thus important for population health and nutritional assessment. An assay approach that measures proteins could be more technologically feasible than chromatography, thus enabling more frequent carotenoid status assessment. We explored associations between proteomic biomarkers and concentrations of 6 common dietary carotenoids (α-carotene, β-carotene, lutein/zeaxanthin, β-cryptoxanthin, and lycopene) in plasma from 500 6-8 year old Nepalese children. Samples were depleted of 6 high-abundance proteins. Plasma proteins were quantified using tandem mass spectrometry and expressed as relative abundance. Linear mixed effects models were used to determine the carotenoid:protein associations, accepting a false discovery rate of q < 0.10. We quantified 982 plasma proteins in >10% of all child samples. Among these, relative abundance of 4 were associated with β-carotene, 11 with lutein/zeaxanthin and 51 with β-cryptoxanthin. Carotenoid-associated proteins are notably involved in lipid and vitamin A transport, antioxidant function and anti-inflammatory processes. No protein biomarkers met criteria for association with α-carotene or lycopene. Plasma proteomics may offer an approach to assess functional biomarkers of carotenoid status, intake and biological function for public health application. Original maternal micronutrient trial from which data were derived as a follow-up activity was registered at ClinicalTrials.gov: NCT00115271.

Retinal Structure in Pre-Clinical Age-Related Macular Degeneration

PURPOSE

To determine, if there are identifiable retinal structural changes associated with genetic risk for age-related macular degeneration (AMD).

MATERIALS AND METHODS

Seventy-three subjects (range 51.5 to 68.9 years) participated in this prospective study. Subjects were recruited based on the presence of a family history of AMD in one or both parents. All participants underwent a complete ophthalmic exam and imagery for staging of disease severity and genetic testing to assess genetic risk for AMD development. Optical coherence tomography (OCT) imaging was performed on all participants. Semi-automated retinal layer segmentation was performed to assess retinal structural changes.

RESULTS

Of 73 subjects, 47 subjects had normal appearing retina with no evidence of drusen or other changes consistent with AMD, 16 subjects were classified as early AMD, and 13 were designated as intermediate AMD. Retinal volume measures of total retina, outer retina, outer nuclear layer and the retinal pigment epithelium, were not related to AMD classification, genetic risk scores, or age. The thickness of the outer retina showed statistically significant thickening in the foveal region in only the intermediate AMD group and a statistically significant thickening of the RPE in early and intermediate AMD groups in the central retina.

CONCLUSION

No consistent changes were observed in retinal structure at multiple locations that are associated with pre-clinical AMD, based on AMD genetic risk or with aging within the age range of our cohort.

In Vivo Multimodal Imaging of Drusenoid Lesions in Rhesus Macaques

Nonhuman primates are the only mammals to possess a true macula similar to humans, and spontaneously develop drusenoid lesions which are hallmarks of age-related macular degeneration (AMD). Prior studies demonstrated similarities between human and nonhuman primate drusen based on clinical appearance and histopathology. Here, we employed fundus photography, spectral domain optical coherence tomography (SD-OCT), fundus autofluorescence (FAF), and infrared reflectance (IR) to characterize drusenoid lesions in aged rhesus macaques. Of 65 animals evaluated, we identified lesions in 20 animals (30.7%). Using the Age-Related Eye Disease Study 2 (AREDS2) grading system and multimodal imaging, we identified two distinct drusen phenotypes - 1) soft drusen that are larger and appear as hyperreflective deposits between the retinal pigment epithelium (RPE) and Bruch's membrane on SD-OCT, and 2) hard, punctate lesions that are smaller and undetectable on SD-OCT. Both exhibit variable FAF intensities and are poorly visualized on IR. Eyes with drusen exhibited a slightly thicker RPE compared with control eyes (+3.4 μm, P=0.012). Genetic polymorphisms associated with drusenoid lesions in rhesus monkeys in ARMS2 and HTRA1 were similar in frequency between the two phenotypes. These results refine our understanding of drusen development, and provide insight into the absence of advanced AMD in nonhuman primates.

Fluorescence lifetime imaging ophthalmoscopy

Imaging techniques based on retinal autofluorescence have found broad applications in ophthalmology because they are extremely sensitive and noninvasive. Conventional fundus autofluorescence imaging measures fluorescence intensity of endogenous retinal fluorophores. It mainly derives its signal from lipofuscin at the level of the retinal pigment epithelium. Fundus autofluorescence, however, can not only be characterized by the spatial distribution of the fluorescence intensity or emission spectrum, but also by a characteristic fluorescence lifetime function. The fluorescence lifetime is the average amount of time a fluorophore remains in the excited state following excitation. Fluorescence lifetime imaging ophthalmoscopy (FLIO) is an emerging imaging modality for in vivo measurement of lifetimes of endogenous retinal fluorophores. Recent reports in this field have contributed to our understanding of the pathophysiology of various macular and retinal diseases. Within this review, the basic concept of fluorescence lifetime imaging is provided. It includes technical background information and correlation with in vitro measurements of individual retinal metabolites. In a second part, clinical applications of fluorescence lifetime imaging and fluorescence lifetime features of selected retinal diseases such as Stargardt disease, age-related macular degeneration, choroideremia, central serous chorioretinopathy, macular holes, diabetic retinopathy, and retinal artery occlusion are discussed. Potential areas of use for fluorescence lifetime imaging ophthalmoscopy will be outlined at the end of this review.

Lutein and Zeaxanthin Isomers in Eye Health and Disease

Current evidence suggests lutein and its isomers play important roles in ocular development in utero and throughout the life span, in vision performance in young and later adulthood, and in lowering risk for the development of common age-related eye diseases in older age. These xanthophyll (oxygen-containing) carotenoids are found in a wide variety of vegetables and fruits, and they are present in especially high concentrations in leafy green vegetables. Additionally, egg yolks and human milk appear to be bioavailable sources. The prevalence of lutein, zeaxanthin, and meso-zeaxanthin in supplements is increasing. Setting optimal and safe ranges of intake requires additional research, particularly in pregnant and lactating women. Accumulating evidence about variable interindividual response to dietary intake of these carotenoids, based on genetic or metabolic influences, suggests that there may be subgroups that benefit from higher levels of intake and/or alternate strategies to improve lutein and zeaxanthin status.

Systemic and ocular fluid compounds as potential biomarkers in age-related macular degeneration

Biomarkers can help unravel mechanisms of disease and identify new targets for therapy. They can also be useful in clinical practice for monitoring disease progression, evaluation of treatment efficacy, and risk assessment in multifactorial diseases, such as age-related macular degeneration (AMD). AMD is a highly prevalent progressive retinal disorder for which multiple genetic and environmental risk factors have been described, but the exact etiology is not yet fully understood. Many compounds have been evaluated for their association with AMD. We performed an extensive literature review of all compounds measured in serum, plasma, vitreous, aqueous humor, and urine of AMD patients. Over 3600 articles were screened, resulting in more than 100 different compounds analyzed in AMD studies, involved in neovascularization, immunity, lipid metabolism, extracellular matrix, oxidative stress, diet, hormones, and comorbidities (such as kidney disease). For each compound, we provide a short description of its function and discuss the results of the studies in relation to its usefulness as AMD biomarker. In addition, biomarkers identified by hypothesis-free techniques, including metabolomics, proteomics, and epigenomics, are covered. In summary, compounds belonging to the oxidative stress pathway, the complement system, and lipid metabolism are the most promising biomarker candidates for AMD. We hope that this comprehensive survey of the literature on systemic and ocular fluid compounds as potential biomarkers in AMD will provide a stepping stone for future research and possible implementation in clinical practice.

The Pharmacological Effects of Lutein and Zeaxanthin on Visual Disorders and Cognition Diseases

Lutein (L) and zeaxanthin (Z) are dietary carotenoids derived from dark green leafy vegetables, orange and yellow fruits that form the macular pigment of the human eyes. It was hypothesized that they protect against visual disorders and cognition diseases, such as age-related macular degeneration (AMD), age-related cataract (ARC), cognition diseases, ischemic/hypoxia induced retinopathy, light damage of the retina, retinitis pigmentosa, retinal detachment, uveitis and diabetic retinopathy. The mechanism by which they are involved in the prevention of eye diseases may be due their physical blue light filtration properties and local antioxidant activity. In addition to their protective roles against light-induced oxidative damage, there are increasing evidences that L and Z may also improve normal ocular function by enhancing contrast sensitivity and by reducing glare disability. Surveys about L and Z supplementation have indicated that moderate intakes of L and Z are associated with decreased AMD risk and less visual impairment. Furthermore, this review discusses the appropriate consumption quantities, the consumption safety of L, side effects and future research directions.

Carrot solution culture bioproduction of uniformly labeled 13C-lutein and in vivo dosing in non-human primates

Lutein is a xanthophyll abundant in nature and most commonly present in the human diet through consumption of leafy green vegetables. With zeaxanthin and meso-zeaxanthin, lutein is a component of the macular pigment of the retina, where it protects against photooxidation and age-related macular degeneration. Recent studies have suggested that lutein may positively impact cognition throughout the lifespan, but outside of the retina, the deposition, metabolism, and function(s) of lutein are poorly understood. Using a novel botanical cell culture system ( Daucus carota), the present study aimed to produce a stable isotope lutein tracer for use in future investigations of dietary lutein distribution and metabolism. Carrot cultivars were initiated into liquid solution culture, lutein production conditions optimized, and uniformly labeled ¹³C-glucose was provided as the sole media carbon source for four serial growth cycles. Lutein yield was 2.58 ± 0.24 µg/g, and mass spectrometry confirmed high enrichment of ¹³C: 64.9% of lutein was uniformly labeled and 100% of lutein was labeled on at least 37 of 40 possible carbons. Purification of carrot extracts yielded a lutein dose of 1.92 mg with 96.0 ± 0.60% purity. ¹³C-lutein signals were detectable in hepatic extracts of an adult rhesus macaque monkey ( Macaca mulatta) dosed with ¹³C-lutein, but not in hepatic samples collected from control animals. This novel botanical biofactory approach can be used to produce sufficient quantities of highly enriched and pure ¹³C-lutein doses for use in tracer studies investigating lutein distribution, metabolism, and function.

Elevated Fundus Autofluorescence in Monkeys Deficient in Lutein, Zeaxanthin, and Omega-3 Fatty Acids

Purpose

We quantified fundus autofluorescence (FAF) in the nonhuman primate retina as a function of age and diets lacking lutein and zeaxanthin (L/Z) and omega-3 fatty acids.

Methods

Quantitative FAF was measured in a cross-sectional study of rhesus macaques fed a standard diet across the lifespan, and in aged rhesus macaques fed lifelong diets lacking L/Z and providing either adequate or deficient levels of omega-3 fatty acids. Macular FAF images were segmented into multiple regions of interest, and mean gray values for each region were calculated using ImageJ. The resulting FAF values were compared across ages within the standard diet animals, and among diet groups and regions.

Results

Fundus autofluorescence increased with age in the standard diet animals, and was highest in the perifovea. Monkeys fed L/Z-free diets with either adequate or deficient omega-3 fatty acids had significantly higher FAF overall than age-matched standard diet monkeys. Examined by region, those with adequate omega-3 fatty acids had higher FAF in the fovea and superior regions, while monkeys fed the diet lacking L/Z and omega-3 fatty acids had higher FAF in all regions.

Conclusions

Diets devoid of L/Z resulted in increased retinal autofluorescence, with the highest values in animals also lacking omega-3 fatty acids. The increase was equivalent to a 12- to 20-year acceleration in lipofuscin accumulation compared to animals fed a standard diet. Together these data add support for the role of these nutrients as important factors in lipofuscin accumulation, retinal aging, and progression of macular disease.

Lutein acts via multiple antioxidant pathways in the photo-stressed retina

Lutein slows the progression of age-related macular degeneration (AMD), a leading cause of blindness in ageing societies. However, the underlying mechanisms remain elusive. Here, we evaluated lutein's effects on light-induced AMD-related pathological events. Balb/c mice exposed to light (2000 lux, 3 h) showed tight junction disruption in the retinal pigment epithelium (RPE) at 12 h, as detected by zona occludens-1 immunostaining. Substantial disruption remained 48 h after light exposure in the vehicle-treated group; however, this was ameliorated in the mice treated with intraperitoneal lutein at 12 h, suggesting that lutein promoted tight junction repair. In the photo-stressed RPE and the neighbouring choroid tissue, lutein suppressed reactive oxygen species and increased superoxide dismutase (SOD) activity at 24 h, and produced sustained increases in sod1 and sod2 mRNA levels at 48 h. SOD activity was induced by lutein in an RPE cell line, ARPE19. We also found that lutein suppressed upregulation of macrophage-related markers, f4/80 and mcp-1, in the RPE-choroid tissue at 18 h. In ARPE19, lutein reduced mcp-1 mRNA levels. These findings indicated that lutein promoted tight junction repair and suppressed inflammation in photo-stressed mice, reducing local oxidative stress by direct scavenging and most likely by induction of endogenous antioxidant enzymes.

Lutein, Zeaxanthin and Meso-zeaxanthin Supplementation Associated with Macular Pigment Optical Density

The purpose of this study was to evaluate the effects of lutein, zeaxanthin and meso-zeaxanthin on macular pigment optical density (MPOD) in randomized controlled trials (RCTs) among patients with age-related macular degeneration (AMD) and healthy subjects. Medline, Embase, Web of Science and Cochrane Library databases was searched through May 2016. Meta-analysis was conducted to obtain adjusted weighted mean differences (WMD) for intervention-versus-placebo group about the change of MPOD between baseline and terminal point. Pearson correlation analysis was used to determine the relationship between the changes in MPOD and blood xanthophyll carotenoids or baseline MPOD levels. Twenty RCTs involving 938 AMD patients and 826 healthy subjects were identified. Xanthophyll carotenoids supplementation was associated with significant increase in MPOD in AMD patients (WMD, 0.07; 95% CI, 0.03 to 0.11) and healthy subjects (WMD, 0.09; 95% CI, 0.05 to 0.14). Stratified analysis showed a greater increase in MPOD among trials supplemented and combined with meso-zeaxanthin. Additionally, the changes in MPOD were related with baseline MPOD levels (r_AMD = −0.43, p = 0.06; r_{healthy subjects} = −0.71, p < 0.001) and blood xanthophyll carotenoids concentration (r_AMD = 0.40, p = 0.07; r_{healthy subjects} = 0.33, p = 0.05). This meta-analysis revealed that lutein, zeaxanthin and meso-zeaxanthin supplementation improved MPOD both in AMD patients and healthy subjects with a dose-response relationship.

Molecular aspects of β, β-carotene-9', 10'-oxygenase 2 in carotenoid metabolism and diseases

Carotenoids, the carotenes and xanthophylls, are essential components in human nutrition. β, β-carotene-9', 10'-oxygenase 2 (BCO2), also named as β, β-carotene-9', 10'-dioxygenase 2 (BCDO2) catalyzes the asymmetrical cleavage of carotenoids, whereas β, β-carotene-15, 15'-monooxygenase (BCMO1) conducts the symmetrical cleavage of pro-vitamin A carotenoids into retinoid. Unlike BCMO1, BCO2 has a broader substrate specificity and has been considered an alternative way to produce vitamin A. In contrast to BCMO1, a cytoplasmic protein, BCO2 is located in the inner mitochondrial membrane. The difference in cellular compartmentalization may reflect the different substrate specificity and physiological functions with respect to BCMO1 and BCO2. The BCO2 gene mutations are proven to be associated with yellow color of skin and fat tissue and milk in livestock. Mutation in intron 2 of BCO2 gene is also supposed to be related to the expression of IL-18, a pro-inflammatory cytokine associated with obesity, cardiovascular diseases, and type 2 diabetes. Further, BCO2 is associated with the development of mitochondrial oxidative stress, macular degeneration, anemia, and hepatic steatosis. This review of the literature will mostly address recent updates regarding the role of BCO2 in carotenoid metabolism, and discuss the potential impacts of BCO2 protein and the mutations in mammalian diseases.

An exploratory study evaluating the effects of macular carotenoid supplementation in various retinal diseases

Purpose

The aim of this study was to assess the impact of daily oral supplementation with Macushield (10 mg/d meso-zeaxanthin, 10 mg/d lutein, and 2 mg/d zeaxanthin) on eye health in patients with retinal diseases by assessing the macular pigment (MP) profile, the visual function, and the quality of life.

Methods

Fifty-one patients with various retinal diseases were supplemented daily and followed up for 6 months. The MP optical density was measured using the customized heterochromatic flicker photometry and dual-wavelength autofluorescence. Visual function was evaluated by assessing the change in best corrected visual acuity, contrast sensitivity, and glare sensitivity in mesopic and photopic conditions. Vision-related and general quality of life changes were determined using the National Eye Insititute- Visual Function Questionnaire-25 (NEI-VFQ-25) and EuroQoL-5 dimension questionnaires.

Results

A statistically significant increase in the MP optical density was observed using the dual-wavelength autofluorescence (P=0.04) but not with the customized heterochromatic flicker photometry. Statistically significant (P<0.05) improvements in glare sensitivity in low and medium spatial frequencies were observed at 3 months and 6 months. Ceiling effects confounded other visual function tests and quality of life changes.

Conclusion

Supplementation with the three carotenoids enhances certain aspects of visual performance in retinal diseases.

Breastmilk from obese mothers has pro-inflammatory properties and decreased neuroprotective factors

OBJECTIVE

To determine the impact of maternal obesity on breastmilk composition.

STUDY DESIGN

Breastmilk and food records from 21 lean and 21 obese women who delivered full-term infants were analyzed at 2 months post-partum. Infant growth and adiposity were measured at birth and 2 months of age.

RESULT

Breastmilk from obese mothers had higher omega-6 to omega-3 fatty acid ratio and lower concentrations of docosahexaenoic acid, eicosapentaenoic acid, docasapentaenoic acid and lutein compared with lean mothers (P<0.05), which were strongly associated with maternal body mass index. Breastmilk saturated fatty acid and monounsaturated fatty acid concentrations were positively associated with maternal dietary inflammation, as measured by dietary inflammatory index. There were no differences in infant growth measurements.

CONCLUSION

Breastmilk from obese mothers has a pro-inflammatory fatty acid profile and decreased concentrations of fatty acids and carotenoids that have been shown to have a critical role in early visual and neurodevelopment. Studies are needed to determine the link between these early-life influences and subsequent cardiometabolic and neurodevelopmental outcomes.

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.

Synergistic Effects of Human Milk Nutrients in the Support of Infant Recognition Memory: An Observational Study

The aim was to explore the relation of human milk lutein; choline; and docosahexaenoic acid (DHA) with recognition memory abilities of six-month-olds. Milk samples obtained three to four months postpartum were analyzed for fatty acids, lutein, and choline. At six months, participants were invited to an electrophysiology session. Recognition memory was tested with a 70-30 oddball paradigm in a high-density 128-lead event-related potential (ERP) paradigm. Complete data were available for 55 participants. Data were averaged at six groupings (Frontal Right; Frontal Central; Frontal Left; Central; Midline; and Parietal) for latency to peak, peak amplitude, and mean amplitude. Difference scores were calculated as familiar minus novel. Final regression models revealed the lutein X free choline interaction was significant for the difference in latency scores at frontal and central areas (p < 0.05 and p < 0.001; respectively). Higher choline levels with higher lutein levels were related to better recognition memory. The DHA X free choline interaction was also significant for the difference in latency scores at frontal, central, and midline areas (p < 0.01; p < 0.001; p < 0.05 respectively). Higher choline with higher DHA was related to better recognition memory. Interactions between human milk nutrients appear important in predicting infant cognition, and there may be a benefit to specific nutrient combinations.

Lutein and Brain Function

Lutein is one of the most prevalent carotenoids in nature and in the human diet. Together with zeaxanthin, it is highly concentrated as macular pigment in the foveal retina of primates, attenuating blue light exposure, providing protection from photo-oxidation and enhancing visual performance. Recently, interest in lutein has expanded beyond the retina to its possible contributions to brain development and function. Only primates accumulate lutein within the brain, but little is known about its distribution or physiological role. Our team has begun to utilize the rhesus macaque (Macaca mulatta) model to study the uptake and bio-localization of lutein in the brain. Our overall goal has been to assess the association of lutein localization with brain function. In this review, we will first cover the evolution of the non-human primate model for lutein and brain studies, discuss prior association studies of lutein with retina and brain function, and review approaches that can be used to localize brain lutein. We also describe our approach to the biosynthesis of ¹³C-lutein, which will allow investigation of lutein flux, localization, metabolism and pharmacokinetics. Lastly, we describe potential future research opportunities.

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.

Exploratory Metabolomic Analyses Reveal Compounds Correlated with Lutein Concentration in Frontal Cortex, Hippocampus, and Occipital Cortex of Human Infant Brain

Lutein is a dietary carotenoid well known for its role as an antioxidant in the macula, and recent reports implicate a role for lutein in cognitive function. Lutein is the dominant carotenoid in both pediatric and geriatric brain tissue. In addition, cognitive function in older adults correlated with macular and postmortem brain lutein concentrations. Furthermore, lutein was found to preferentially accumulate in the infant brain in comparison to other carotenoids that are predominant in diet. While lutein is consistently related to cognitive function, the mechanisms by which lutein may influence cognition are not clear. In an effort to identify potential mechanisms through which lutein might influence neurodevelopment, an exploratory study relating metabolite signatures and lutein was completed. Post-mortem metabolomic analyses were performed on human infant brain tissues in three regions important for learning and memory: the frontal cortex, hippocampus, and occipital cortex. Metabolomic profiles were compared to lutein concentration, and correlations were identified and reported here. A total of 1276 correlations were carried out across all brain regions. Of 427 metabolites analyzed, 257 were metabolites of known identity. Unidentified metabolite correlations (510) were excluded. In addition, moderate correlations with xenobiotic relationships (2) or those driven by single outliers (3) were excluded from further study. Lutein concentrations correlated with lipid pathway metabolites, energy pathway metabolites, brain osmolytes, amino acid neurotransmitters, and the antioxidant homocarnosine. These correlations were often brain region—specific. Revealing relationships between lutein and metabolic pathways may help identify potential candidates on which to complete further analyses and may shed light on important roles of lutein in the human brain during development.

Light, lipids and photoreceptor survival: live or let die?

Due to its constant exposure to light and its high oxygen consumption the retina is highly sensitive to oxidative damage, which is a common factor in inducing the death of photoreceptors after light damage or in inherited retinal degenerations. The high content of docosahexaenoic acid (DHA), the major polyunsaturated fatty acid in the retina, has been suggested to contribute to this sensitivity. DHA is crucial for developing and preserving normal visual function. However, further roles of DHA in the retina are still controversial. Current data support that it can tilt the scale either towards degeneration or survival of retinal cells. DHA peroxidation products can be deleterious to the retina and might lead to retinal degeneration. However, DHA has also been shown to act as, or to be the source of, a survival molecule that protects photoreceptors and retinal pigment epithelium cells from oxidative damage. We have established that DHA protects photoreceptors from oxidative stress-induced apoptosis and promotes their differentiation in vitro. DHA activates the retinoid X receptor (RXR) and the ERK/MAPK pathway, thus regulating the expression of anti and pro-apoptotic proteins. It also orchestrates a diversity of signaling pathways, modulating enzymatic pathways that control the sphingolipid metabolism and activate antioxidant defense mechanisms to promote photoreceptor survival and development. A deeper comprehension of DHA signaling pathways and context-dependent behavior is required to understand its dual functions in retinal physiology.

Longitudinal Survey of Carotenoids in Human Milk from Urban Cohorts in China, Mexico, and the USA

Emerging evidence indicates that carotenoids may have particular roles in infant nutrition and development, yet data on the profile and bioavailability of carotenoids from human milk remain sparse. Milk was longitudinally collected at 2, 4, 13, and 26 weeks postpartum from twenty mothers each in China, Mexico, and the USA in the Global Exploration of Human Milk Study (n = 60 donors, n = 240 samples). Maternal and neonatal plasma was analyzed for carotenoids from the USA cohort at 4 weeks postpartum. Carotenoids were analyzed by HPLC and total lipids by Creamatocrit. Across all countries and lactation stages, the top four carotenoids were lutein (median 114.4 nmol/L), β-carotene (49.4 nmol/L), β-cryptoxanthin (33.8 nmol/L), and lycopene (33.7 nmol/L). Non-provitamin A carotenoids (nmol/L) and total lipids (g/L) decreased (p<0.05) with increasing lactation stage, except the provitamin A carotenoids α- and β-cryptoxanthin and β-carotene did not significantly change (p>0.05) with lactation stage. Total carotenoid content and lutein content were greatest from China, yet lycopene was lowest from China (p<0.0001). Lutein, β-cryptoxanthin, and β-carotene, and lycopene concentrations in milk were significantly correlated to maternal plasma and neonatal plasma concentrations (p<0.05), with the exception that lycopene was not significantly associated between human milk and neonatal plasma (p>0.3). This enhanced understanding of neonatal exposure to carotenoids during development may help guide dietary recommendations and design of human milk mimetics.

Nutritional supplements in age-related macular degeneration

Age-related macular degeneration (AMD) is the most frequent cause of blindness in the Western World. While with new therapies that are directed towards vascular endothelial growth factor (VEGF), a potentially efficient treatment option for the wet form of the disease has been introduced, a therapeutic regimen for dry AMD is still lacking. There is evidence from several studies that oral intake of supplements is beneficial in preventing progression of the disease. Several formulations of micronutrients are currently available. The present review focuses on the role of supplements in the treatment and prevention of AMD and sums up the current knowledge about the most frequently used micronutrients. In addition, regulatory issues are discussed, and future directions for the role of supplementation in AMD are highlighted.

Nutritional Supplements for Age-Related Macular Degeneration

The Age-Related Eye Disease Study (AREDS) and The Age-Related Eye Disease Study 2 (AREDS2), are the only large-scale, long-term, randomized controlled trials to demonstrate a role of nutritional supplements in reducing risk of progression to advanced forms of age-related macular degeneration (AMD). This review summarizes the study design, main results, and implications of these trials in the clinical care of nonexudative AMD patients. In addition, it discusses other recent prospective studies focusing on efficacy of nutritional supplementation for prevention or slowing progression of AMD as well as briefly discusses possible effect of genotypes on response to AREDS supplementation.

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.

Wogonin modulates hydroperoxide-induced apoptosis via PI3K/Akt pathway in retinal pigment epithelium cells

Background

Oxidative stress causes the defects of retinal pigment epithelial (RPE) cells that contribute to age-related macular degeneration (AMD). This study was conducted to determine whether wogonin could prevent H₂O₂-induced oxidative stress in RPE cells.

Methods

A RPE cell line, ARPE-19, was obtained for the cell model. ARPE-19 cells were pre-treated with various concentrations of wogonin for 24 h before being exposed to H₂O₂ for 2 h to induce oxidative stress. Cell metabolic activity was measured using 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) assay. Cellular apoptosis was quantified by the flow cytometry. Protein level was assed by western blot.

Results

The RPE cells exposed to to 200 mM H₂O₂ demonstrated a significant depression in the cell viability; whereas pre-treatment with 50 and 100 mmol/l wogonin could significantly improve the cell viability in a dose-dependent manner. The proportion of PI-positive cells was increased significantly in RPE cells treated with H₂O₂ alone; whereas pretreatment with 100 mM wogonin significantly reduced H₂O₂ -induced RPE cell death rate. In protein level, the wogonin use could reduce the level of p-Akt significantly and this is the possible mechanism of the antioxidant effect of wogonin.

Conclusions

Our study showed that wogonin pre-treatment can protect RPE cells from H₂O₂-induced apoptosis. This suggests potential effect of wogonin in the prevention of retinal diseases associated with H₂O₂-induced oxidative stress such as AMD.

Virtual Slides

The virtual slide(s) for this article can be found here: http://www.diagnosticpathology.diagnomx.eu/vs/13000_2014_154

Lutein and preterm infants with decreased concentrations of brain carotenoids

OBJECTIVES

Lutein and zeaxanthin are dietary carotenoids that may influence visual and cognitive development. The objective of this study was to provide the first data on distribution of carotenoids in the infant brain and compare concentrations in preterm and term infants.

METHODS

Voluntarily donated brain tissues from 30 infants who died during the first 1.5 years of life were obtained from the Eunice Kennedy Shriver National Institute of Child Health and Human Development Brain and Tissue Bank. Tissues (hippocampus and prefrontal, frontal, auditory, and occipital cortices) were extracted using standard lipid extraction procedures and analyzed using reverse-phase high-pressure liquid chromatography.

RESULTS

Lutein, zeaxanthin, cryptoxanthin, and β-carotene were the major carotenoids found in the infant brain tissues. Lutein was the predominant carotenoid accounting for 59% of total carotenoids. Preterm infants (n = 8) had significantly lower concentrations of lutein, zeaxanthin, and cryptoxanthin in their brain compared with term infants (n = 22) despite similarity in postmenstrual age. Among formula-fed infants, preterm infants (n = 3) had lower concentrations of lutein and zeaxanthin compared with term infants (n = 5). Brain lutein concentrations were not different between breast milk-fed (n = 3) and formula-fed (n = 5) term decedents. In contrast, term decedents with measurable brain cryptoxanthin, a carotenoid that is inherently low in formula, had higher brain lutein, suggesting that the type of feeding is an important determinant of brain lutein concentrations.

CONCLUSIONS

These data reveal preferential accumulation and maintenance of lutein in the infant brain despite underrepresentation in the typical infant diet. Further investigation on the impact of lutein on neural development in preterm infants is warranted.

Macular response to supplementation with differing xanthophyll formulations in subjects with and without age-related macular degeneration

PURPOSE

Our aim was to investigate the macular response to three different supplements containing lutein (L), zeaxanthin (Z) and meso-zeaxanthin (MZ) in normal subjects and those with age-related macular degeneration (AMD).

MATERIALS AND METHODS

Macular pigment optical density (MPOD) and serum xanthophyll concentrations were measured in normal (n = 31) and AMD subjects (n = 32), randomly assigned to: group 1 (20 mg L, 2 mg Z, 0.3 mg MZ), group 2 (10 mg L, 2 mg Z, 10 mg MZ) or group 3 (3 mg L, 2 mg Z, 17 mg MZ). MPOD was measured at baseline, 2, 4, 6 and 8 weeks and at 0.25°, 0.5°, 1.0° and 1.75° of eccentricity using customised heterochromatic flicker photometry and serum xanthophylls by HPLC.

RESULTS

MPOD increased significantly at all eccentricities in each group (p < 0.05), except at 1.75° in group 3 (p = 0.242). There was no difference in MPOD measurements between AMD and normal subjects, except for group 2, where AMD subjects exhibited a greater response at 1.75° (p = 0.012). Final serum concentrations of MZ were positively and significantly related to final MPOD values at each eccentricity in all subjects. Targeted analysis of those subjects receiving the MZ-containing supplements exhibited stronger relationships between serum MZ concentrations and MPOD at 0.25° in group 3 than group 2; in group 2 all associations were positive, but only significant at 1.75°.

CONCLUSIONS

Serum concentrations of MZ were strongly correlated with MPOD after 8 weeks of supplementation with the group 3 formulation, but the inclusion of L in the group 2 formulation may result in greater MPOD augmentation across the spatial profile.

Oxidative photodegradation of ocular tissues: beneficial effects of filtering and exogenous antioxidants

The fact that light is necessary for life is generally accepted as an axiom. The extent to which light interacts and influences human biology, however, is often not fully appreciated. Exposure to sunlight, for instance, can both promote and degrade human health. There is now general scientific consensus that, although the eye evolved to respond to light, it is also damaged by excessive exposure. Light-mediated ocular damage is involved in the pathophysiology of many common forms of blindness. The type of ocular tissue damage induced by light exposure depends on the extent of exposure and wavelength. The tissues of the lens, cornea, and retina contain specific chemical moieties that have been proven to exhibit light-mediated oxidative degradation. Proteins and lipids present in the cornea, lens, and retina, meet all of the physical requirements known to initiate the process of oxidative photodegradation upon exposure to solar radiation. As such, different mechanisms have evolved in the lens, cornea, and retina to ameliorate such light-mediated oxidative damage. It appears, however, that such mechanisms are ill-matched to handle modern conditions: namely, poor diet and longer life-spans (and the degenerative diseases that accompany them). Hence, steps must be taken to protect the eye from the damaging effects of light. Preventative measures include minimizing actinic light exposure, providing exogenous filtering (e.g., through the use of protective lenses), and enhancing antioxidant defenses (e.g., through increased dietary intake of antioxidants). These strategies may yield long-term benefits in terms of reducing oxidative photodegradation of the ocular tissues.

Cellular responses following retinal injuries and therapeutic approaches for neurodegenerative diseases

Retinal neurodegenerative diseases like age-related macular degeneration, glaucoma, diabetic retinopathy and retinitis pigmentosa each have a different etiology and pathogenesis. However, at the cellular and molecular level, the response to retinal injury is similar in all of them, and results in morphological and functional impairment of retinal cells. This retinal degeneration may be triggered by gene defects, increased intraocular pressure, high levels of blood glucose, other types of stress or aging, but they all frequently induce a set of cell signals that lead to well-established and similar morphological and functional changes, including controlled cell death and retinal remodeling. Interestingly, an inflammatory response, oxidative stress and activation of apoptotic pathways are common features in all these diseases. Furthermore, it is important to note the relevant role of glial cells, including astrocytes, Müller cells and microglia, because their response to injury is decisive for maintaining the health of the retina or its degeneration. Several therapeutic approaches have been developed to preserve retinal function or restore eyesight in pathological conditions. In this context, neuroprotective compounds, gene therapy, cell transplantation or artificial devices should be applied at the appropriate stage of retinal degeneration to obtain successful results. This review provides an overview of the common and distinctive features of retinal neurodegenerative diseases, including the molecular, anatomical and functional changes caused by the cellular response to damage, in order to establish appropriate treatments for these pathologies.