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

Natural products for the treatment of age-related macular degeneration

BACKGROUND

Age-related macular degeneration (AMD) is a chronic retinal disease that significantly influences the vision of the elderly.

PURPOSE

There is no effective treatment and prevention method. The pathogenic process behind AMD is complex, including oxidative stress, inflammation, and neovascularization. It has been demonstrated that several natural products can be used to manage AMD, but systematic summaries are lacking.

STUDY DESIGN AND METHODS

PubMed, Web of Science, and ClinicalTrials.gov were searched using the keywords "Biological Products" AND "Macular Degeneration" for studies published within the last decade until May 2023 to summarize the latest findings on the prevention and treatment of age-related macular degeneration through the herbal medicines and functional foods.

RESULTS

The eligible studies were screened, and the relevant information about the therapeutic action and mechanism of natural products used to treat AMD was extracted. Our findings demonstrate that natural substances, including retinol, phenols, and other natural products, prevent the development of new blood vessels and protect the retina from oxidative stress in cells and animal models. However, they have barely been examined in clinical studies.

CONCLUSION

Natural products could be highly prospective candidate drugs used to treat AMD, and further preclinical and clinical research is required to validate it to control the disease.

A mechanistic review on growing multiple therapeutic applications of lutein and its global market research

Lutein is a naturally occurring carotenoid synthesized by plants and algae that has a beneficial effect on several biological processes and associated ailments. Its immediate application is in ophthalmology, where it significantly lowers the incidences of age-related macular degeneration (AMD). It also has anti-inflammatory action, treatment of diabetic retinopathy, and cataracts, and enhancement of visual contrast. To critically assess lutein biosynthesis, therapeutic applicability, and market research literature. We have discussed its theoretical frameworks, experimental evidence, limitations, as well as clinical trial results, and future research prospects. The literature for this review article was mined and compiled by collecting and analyzing articles from several databases, including ScienceDirect, Google Scholar, PubMed, Wiley Online Library, Patentscope, and ClinicalTrials.gov published until March 30, 2022. Patent publications were identified using the search terms like IC:(C07C67/56) AND EN_AB:(lutein) OR EN_TI:(lutein) OR EN_AB:(extraction) OR EN_TI:(process). According to the literature, lutein is an essential nutrient given that it cannot be synthesized in the human body and acts as an antioxidant, affecting AMD, diabetic retinopathy, Rheumatic diseases, inflammation, and cancer. Due to inadequate production and laborious extraction, lutein is expensive despite its high demand and applicability. Market research predicts a 6.3% compound annual growth rate for lutein by 2032. Optimizing lutein extraction for high yield and purity is necessary. Lutein has proven applicability in various ailments as well as cosmetics that can be developed as a candidate drug for various diseases discussed in the review.

Understanding the Impact of Polyunsaturated Fatty Acids on Age-Related Macular Degeneration: A Review

Age-related Macular Degeneration (AMD) is a multifactorial ocular pathology that destroys the photoreceptors of the macula. Two forms are distinguished, dry and wet AMD, with different pathophysiological mechanisms. Although treatments were shown to be effective in wet AMD, they remain a heavy burden for patients and caregivers, resulting in a lack of patient compliance. For dry AMD, no real effective treatment is available in Europe. It is, therefore, essential to look for new approaches. Recently, the use of long-chain and very long-chain polyunsaturated fatty acids was identified as an interesting new therapeutic alternative. Indeed, the levels of these fatty acids, core components of photoreceptors, are significantly decreased in AMD patients. To better understand this pathology and to evaluate the efficacy of various molecules, in vitro and in vivo models reproducing the mechanisms of both types of AMD were developed. This article reviews the anatomy and the physiological aging of the retina and summarizes the clinical aspects, pathophysiological mechanisms of AMD and potential treatment strategies. In vitro and in vivo models of AMD are also presented. Finally, this manuscript focuses on the application of omega-3 fatty acids for the prevention and treatment of both types of AMD.

Developing biopolymer-stabilized emulsions for improved stability and bioaccessibility of lutein

Lutein is essential for infant visual and cognitive development but has low stability and solubility. This study aimed to enhance the stability and bioaccessibility of lutein using oil-in-water emulsions stabilized with biopolymers. Commercially available octenylsuccinylated (OS) starches, including capsule TA® (CTA), HI-CAP®100 (HC), and Purity Gum® 2000 (PG), along with gum Arabic (GA) variants Ticaloid acacia Max® (TAM), TICAmulsion® 3020 (TM), and pre-hydrate gum Arabic (PHGA), were chosen as emulsifiers. By screening the effect of biopolymer concentration and oil volume fraction (Φ), emulsions stabilized with CTA, HC, or TM at 20% and 30% (w/v) concentration and 70% Φ exhibited a gel-like structure and were selected for further assessments. After a week at 25 °C, emulsions stabilized by CTA and HC showed no significant change in droplet size, while TM emulsion exhibited a 1.58-fold increase. At 45 °C, all emulsions exhibited increase in droplet size. Lutein retention is higher in CTA emulsions at both storage temperatures than free lutein. In vitro bioaccessibility of all lutein emulsions was higher than that of free lutein. These findings highlight the superior stability and bioaccessibility of the lutein emulsion stabilized by OS starch, positioning it as a promising carrier to broaden lutein applications in infant foods.

Utilization of Biopolymer-Based Lutein Emulsion as an Effective Delivery System to Improve Lutein Bioavailability in Neonatal Rats

Newborns' eyes and brains are prone to oxidative stress. Lutein has antioxidant properties and is the main component of macular pigment essential for protecting the retina, but has low bioavailability, thereby limiting its potential as a nutritional supplement. Oil-in-water emulsions have been used as lutein delivery systems. In particular, octenylsuccinated (OS) starch is a biopolymer-derived emulsifier safe to use in infant foods, while exhibiting superior emulsifying capacity. This study determined the effects of an OS starch-stabilized lutein emulsion on lutein bioavailability in Sprague-Dawley neonatal rats. In an acute study, 10-day-old pups received a single oral dose of free lutein or lutein emulsion, with subsequent blood sampling over 24 h to analyze pharmacokinetics. The lutein emulsion group had a 2.12- and 1.91-fold higher maximum serum lutein concentration and area under the curve, respectively, compared to the free lutein group. In two daily dosing studies, oral lutein was given from postnatal day 5 to 18. Blood and tissue lutein concentrations were measured. The results indicated that the daily intake of lutein emulsion led to a higher lutein concentration in circulation and key tissues compared to free lutein. The OS starch-stabilized emulsion could be an effective and safe lutein delivery system for newborns.

Measuring macular pigment optical density using reflective images of confocal scanning laser system

PURPOSE

To develop a method to measure the macular pigment optical density (MPOD) using scanning laser ophthalmoscopic images in young adults and children.

STUDY DESIGN

Cross-sectional study.

METHODS

Blue light reflectance fundus images of 32 healthy subjects were used. A profile of the linear reflectance changes across the center of the fovea on a grayscale fundus image was generated. The ratio of the macula-to-periphery reflection was designated as the peak value of the MPOD (MPOD[FR]) based on established fundamentals. In the MPOD profile, the basal width of the pixels at MPOD < 0 (wMP) and width at one-half value of the MPOD[FR] (wMP0.5) were determined. The MOPD at eccentricity of 0.5° was measured by heterochromatic flicker photometry (MPOD[HFP]), and the correlation between the MPOD[FR] and MPOD[HFP] was evaluated.

RESULTS

The MPOD[FR] ranged from 0.17 to 0.73 with a mean of 0.40 ± 0.13. The wMP ranged from 88 to 173 pixels with a mean of 121.7 ± 24.2 pixels, and the wMP0.5 ranged from 38 to 83 pixels with a mean of 54.1 ± 10.3 pixels. A significant correlation was found between the MPOD[FR] and MPOD[HFP] (r = 0.41, P = 0.02).

CONCLUSIONS

This simplified method can provide accurate and reliable values of the MPOD comparable to heterochromatic flicker photometry. Obtaining the fundus images in this fast and easy way should be suitable for children thus enabling clinicians to determine the MPODs for children.

Association of macular pigment optical density with retinal layer thicknesses in eyes with and without manifest primary open-angle glaucoma

OBJECTIVE

To investigate associations between baseline macular pigment optical density (MPOD) and retinal layer thicknesses in eyes with and without manifest primary open-angle glaucoma (POAG) in the Carotenoids in Age-Related Eye Disease Study 2 (CAREDS2).

METHODS AND ANALYSIS

MPOD was measured at CAREDS baseline (2001-2004) via heterochromatic flicker photometry (0.5° from foveal centre). Peripapillary retinal nerve fibre layer (RNFL), macular ganglion cell complex (GCC), ganglion cell layer (GCL), inner plexiform layer (IPL), and RNFL thicknesses were measured at CAREDS2 (2016-2019) via spectral-domain optical coherence tomography. Associations between MPOD and retinal thickness were assessed using multivariable linear regression.

RESULTS

Among 742 eyes (379 participants), manifest POAG was identified in 50 eyes (32 participants). In eyes without manifest POAG, MPOD was positively associated with macular GCC, GCL and IPL thicknesses in the central subfield (P-trend ≤0.01), but not the inner or outer subfields. Among eyes with manifest POAG, MPOD was positively associated with macular GCC, GCL, IPL and RNFL in the central subfield (P-trend ≤0.03), but not the inner or outer subfields, and was positively associated with peripapillary RNFL thickness in the superior and temporal quadrants (P-trend≤0.006).

CONCLUSION

We observed a positive association between MPOD and central subfield GCC thickness 15 years later. MPOD was positively associated with peripapillary RNFL superior and temporal quadrant thicknesses among eyes with manifest POAG. Our results linking low MPOD to retinal layers that are structural indicators of early glaucoma provide further evidence that carotenoids may be protective against manifest POAG.

Xanthophyll pigments dietary supplements administration and retinal health in the context of increasing life expectancy trend

Introduction

Medicine faces nowadays the trend of increasing life expectancy of human population, with the resulting increase of degenerative age related diseases prevalence, combined with the risks of less tempered sun radiations environment exposure. Under these circumstances, our work pointed out on evaluating the effect of some xanthophyll pigments dietary supplements, actually widely recommended, for prevention of retinal degenerative damages and for slowing down the progression of such age related changes if they have already occurred. These dietary supplements are already well known for their total antioxidant activity, proven by photochemiluminescence method using Total Antioxidant Capacity in Lipid soluble-substances procedure.

Materials and methods

The study recruited a number of 120 subjects equally divided on genders. The lot included a first group of 60 patients with comparable ages (all of them over 50 years and divided in 2 segments of age: 50-60 and over 60) and suffering from comparable retinal age-related degenerative abnormalities (mild/medium severity age-related macular degeneration according to Wisconsin Age-Related Maculopathy Grading System), and a second group, considered control, including a similar number of healthy, normal retina subjects belonging to same age and gender categories. There were evaluated at baseline the eye medical status and the retinal risk by specific methods: complete eye check-up, Amsler grid, specific standardized questionnaires focused on visual function and its impact on the quality of current life. Both groups, patients and control, received similar dosages of xanthophyll pigments dietary supplements including lutein and zeaxanthin during 18 months after baseline; at the end of this supplementation period a new evaluation was conducted. In the second part of the research all subjects involved received a new dietary supplement in which the same xanthophylls were enriched with C and E vitamins and oligo-elements Zinc and Copper. At the end of three years duration supplementation, the subjects were reevaluated and the paper presents the conclusions on the matter, pointing on the impact of xanthophyll supplements on visual health.

Results

Correlation tests were applied to the complete set of data. Correlation tests have values between -1 and +1. The value -1 represents the negative correlation (reverse proportionality) meanwhile the value +1 represents the positive correlation (direct proportionality). The charts show the curves that are fitting experimental data. The dependence is linear in nature, and the value R2, as it approaches more the value 1, represents a better match with the experimental data (the data are in a percentage of approximately 99% on these straight lines of type y = ax + b). In the charts, there were noted the average values of the scores for healthy control patients with "Control", and the average values of the scores for the patients with existing age related degenerative retinal pathology at baseline with "Patients".

Discussion

The retinal function and the impact of visual condition on health were both evaluated at baseline, 18 months and 36 months after baseline, by visual acuity, ophthalmoscopy fundus examination, Amsler test and by asking the subjects to answer the visual function questionnaires: EQ-5D, NEI-VFQ-25, as measures of health status quality and of the influence on welfare. The study revealed that under supplementation both control healthy subjects and patients with known degenerative retinal pathology included in the 50-60 years of age group evolved almost the same way, leading to the conclusion that administered xanthophyll pigments-based supplements, simple or enriched, managed to slow down the progression of abnormal degenerative vision loss to a rate comparable to physiological aging-related vision loss. It was also observed that intake of xanthophyll pigments dietary supplements preserved the general health condition and maintained relatively constant vision on the entire 36th months follow-up research duration in patients presented with existing age related degenerative retinal pathology at baseline. For healthy subjects, evaluation showed an improvement in results after dietary supplementation, with maintenance of constant vision and a significantly increase of general condition, in a positive sense. For subjects over the age of 60 dietary supplements intake was even more effective compared to younger group in providing better control of degenerative processes.

Randomized, Placebo-Controlled, Single-Blind Study of Lutein Supplementation on Carotenoid Status and Cognition in Persons with Multiple Sclerosis

BACKGROUND

Multiple sclerosis (MS) is traditionally managed using disease-modifying pharmaceutical therapies as a first line approach for treatment, yet there is increasing interest in lifestyle factors, particularly diet, for managing disease outcomes. Lutein has neuroprotective properties in healthy adults, but no previous research has examined the effects of lutein supplementation in persons with MS.

OBJECTIVES

This study aimed to investigate the efficacy of 4-mo lutein supplementation on carotenoid status and cognition in persons with relapse-remitting MS (RRMS).

METHODS

A randomized controlled, single-blind research design was used among adults with RRMS (N = 21). Participants were randomized into placebo (n = 9) or treatment (20-mg/d lutein, n = 12) groups with outcomes measured before and after 4 mo. Macular pigment optical density (MPOD) was assessed using heterochromatic flicker photometry. Skin carotenoids were assessed using reflection spectroscopy. Serum lutein was measured using high-performance liquid chromatography. Cognition was assessed via the Eriksen flanker with event-related potentials, spatial reconstruction, and the symbol digit modalities tests.

RESULTS

There was a significant group by time interaction for MPOD (F = 6.74, P = 0.02), skin carotenoids (F = 17.30, P < 0.01), and serum lutein (F = 24.10, P < 0.01), whereby the treatment group improved in all carotenoid outcomes. There were no significant group by time interactions for cognitive and neuroelectric outcomes. However, increase in MPOD was positively associated with accuracy during the flanker incongruent trials (r = 0.55, P = 0.03) and the spatial memory task (r = 0.58, P = 0.02) among treatment participants.

CONCLUSIONS

Lutein supplementation increases carotenoid status among persons with RRMS. There is no significant effect on cognitive function but change in macular carotenoids is selectively associated with improved attention and memory. This study provides preliminary support for a fully powered study targeting retinal and neural carotenoids for cognitive benefits in persons with MS. This trial was registered at clinicaltrials.gov as NCT04843813.

Label-free fluorescence microscopy: revisiting the opportunities with autofluorescent molecules and harmonic generations as biosensors and biomarkers for quantitative biology

Over the past decade, the utilization of advanced fluorescence microscopy technologies has presented numerous opportunities to study or re-investigate autofluorescent molecules and harmonic generation signals as molecular biomarkers and biosensors for in vivo cell and tissue studies. The label-free approaches benefit from the endogenous fluorescent molecules within the cell and take advantage of their spectroscopy properties to address biological questions. Harmonic generation can be used as a tool to identify the occurrence of fibrillar or lipid deposits in tissues, by using second and third-harmonic generation microscopy. Combining autofluorescence with novel techniques and tools such as fluorescence lifetime imaging microscopy (FLIM) and hyperspectral imaging (HSI) with model-free analysis of phasor plots has revolutionized the understanding of molecular processes such as cellular metabolism. These tools provide quantitative information that is often hidden under classical intensity-based microscopy. In this short review, we aim to illustrate how some of these technologies and techniques may enable investigation without the need to add a foreign fluorescence molecule that can modify or affect the results. We address some of the most important autofluorescence molecules and their spectroscopic properties to illustrate the potential of these combined tools. We discuss using them as biomarkers and biosensors and, under the lens of this new technology, identify some of the challenges and potentials for future advances in the field.

New Insights on Dietary Polyphenols for the Management of Oxidative Stress and Neuroinflammation in Diabetic Retinopathy

Diabetic retinopathy (DR) is a neurodegenerative and vascular pathology that is considered one of the leading causes of blindness worldwide, resulting from complications of advanced diabetes mellitus (DM). Current therapies consist of protocols aiming to alleviate the existing clinical signs associated with microvascular alterations limited to the advanced disease stages. In response to the low resolution and limitations of the DR treatment, there is an urgent need to develop more effective alternative therapies to optimize glycemic, vascular, and neuronal parameters, including the reduction in the cellular damage promoted by inflammation and oxidative stress. Recent evidence has shown that dietary polyphenols reduce oxidative and inflammatory parameters of various diseases by modulating multiple cell signaling pathways and gene expression, contributing to the improvement of several chronic diseases, including metabolic and neurodegenerative diseases. However, despite the growing evidence for the bioactivities of phenolic compounds, there is still a lack of data, especially from human studies, on the therapeutic potential of these substances. This review aims to comprehensively describe and clarify the effects of dietary phenolic compounds on the pathophysiological mechanisms involved in DR, especially those of oxidative and inflammatory nature, through evidence from experimental studies. Finally, the review highlights the potential of dietary phenolic compounds as a prophylactic and therapeutic strategy and the need for further clinical studies approaching the efficacy of these substances in DR management.

Efficacy of lutein supplements on macular pigment optical density in highly myopic individuals: A randomized controlled trial

INTRODUCTION

Lutein supplementation is beneficial in preventing maculae from developing serious ocular diseases. This study aimed to evaluate the efficacy and safety of lutein administration in patients with high myopia (HM).

METHODS

In a single-center randomized double-blinded placebo-controlled trial conducted over 24 months, 22 eyes were enrolled in lutein and control groups. Among them, 15 eyes in the lutein group and 13 eyes in the control group completed the study. All patients with HM (axial length > 26.00) were administered lutein (20 mg) or placebo once daily for 6 months. The macular pigment optical density (MPOD), rate of change in MPOD, visual acuity, contrast sensitivity, and electroretinogram after administration were examined at baseline, 3 months, and 6 months.

RESULTS

The baseline MPOD in the control and lutein groups was 0.71 ± 0.21 and 0.70 ± 0.22, respectively. The MPOD in the control and lutein groups at 3 months was 0.70 ± 0.21 and 0.70 ± 0.25, respectively, and at 6 months was 0.66 ± 0.20 and 0.72 ± 0.27, respectively, which was not significantly different from those at baseline or between the groups. The MPOD significantly increased from baseline in the lutein group with less than 28.25 mm of axial length at 6 months (from 0.71 ± 0.20 to 0.78 ± 0.22, P = .02, t test). visual acuity, contrast sensitivity, and electroretinogram values were similar between the groups.

CONCLUSION

Lutein supplementation showed significant benefits in MPOD augmentation in patients with HM.

Effects of Astaxanthin, Lutein, and Zeaxanthin on Eye-Hand Coordination and Smooth-Pursuit Eye Movement after Visual Display Terminal Operation in Healthy Subjects: A Randomized, Double-Blind Placebo-Controlled Intergroup Trial

(1) Background: The impairment of eye-hand coordination and smooth-pursuit eye movement caused by visual display terminal (VDT) operation is thought to impair daily living activities, for which no effective methods are currently known. On the other hand, various food ingredients, including astaxanthin, lutein, and zeaxanthin, are known to help improve the eye health of VDT operators. This study aimed to test the hypothesis that the combination of astaxanthin, lutein, and zeaxanthin can prevent the impairment of eye-hand coordination and smooth-pursuit eye movement caused by VDT operation. (2) Methods: We conducted a randomized, placebo-controlled, parallel-group clinical trial. Healthy subjects who regularly worked with VDTs were randomly assigned to the active and placebo groups. All of the subjects took soft capsules containing 6 mg of astaxanthin, 10 mg of lutein, and 2 mg of zeaxanthin or placebo soft capsules once daily for eight weeks. We evaluated the eye-hand coordination, smooth-pursuit eye movements, and macular pigment optical density (MPOD) at 0, two, four, and eight weeks after soft-capsule intake. (3) Results: The active group showed significantly improved eye-hand coordination after VDT operation at eight weeks. However, there was no clear improvement in the effect of the supplementation on smooth-pursuit eye movements. The active group also showed a significant increase in MPOD levels. (4) Conclusions: Consumption of a supplement containing astaxanthin, lutein, and zeaxanthin mitigates the decline of eye-hand coordination after VDT operation.

Quantitative approaches in multimodal fundus imaging: State of the art and future perspectives

When it first appeared, multimodal fundus imaging revolutionized the diagnostic workup and provided extremely useful new insights into the pathogenesis of fundus diseases. The recent addition of quantitative approaches has further expanded the amount of information that can be obtained. In spite of the growing interest in advanced quantitative metrics, the scientific community has not reached a stable consensus on repeatable, standardized quantitative techniques to process and analyze the images. Furthermore, imaging artifacts may considerably affect the processing and interpretation of quantitative data, potentially affecting their reliability. The aim of this survey is to provide a comprehensive summary of the main multimodal imaging techniques, covering their limitations as well as their strengths. We also offer a thorough analysis of current quantitative imaging metrics, looking into their technical features, limitations, and interpretation. In addition, we describe the main imaging artifacts and their potential impact on imaging quality and reliability. The prospect of increasing reliance on artificial intelligence-based analyses suggests there is a need to develop more sophisticated quantitative metrics and to improve imaging technologies, incorporating clear, standardized, post-processing procedures. These measures are becoming urgent if these analyses are to cross the threshold from a research context to real-life clinical practice.

Review of Evidence for the Usage of Antioxidants for Eye Aging

Oxidative stress is one of the common factors leading to age-related eye diseases in older adults. Factors such as high oxygen consumption, high concentration of polyunsaturated fatty acids, and cumulative exposure to high-energy visible light in the eyes, lead to excessive generation of reactive oxygen species, hence triggering apoptosis of ocular cells and giving rise to ophthalmic diseases. Dietary supplements such as carotenoids, anthocyanins, and vitamins have antioxidant properties which may be of benefit in retaining better vision or reversing vision impairment; thus, studies have been conducted to understand the role of dietary supplements in the treatment or prevention of ophthalmic diseases. While high concentration of carotenoids such as lutein and zeaxanthin decrease the risk of developing age-related macular disease, anthocyanins and vitamins play a role in the treatment and prevention of other ophthalmic diseases: saffron extract reduced intraocular pressure in glaucoma patients; bilberry extract prevented impairments in lenses and retina, as well as alleviate symptoms of dry eye disease; high concentration of beta-carotene may reduce the risk of developing cataract. Further studies with clinical measurements are required to investigate the effectiveness of antioxidants on visual function and ophthalmic diseases.

Effect of solid-state fermentation and ultrasonication processes on antimicrobial and antioxidant properties of algae extracts

Algal biomass (AB) is prospective source of valuable compounds, however, Baltic Sea macroalgae have some challenges, because of their high microbial and chemical contamination. These problems can be solved, by using appropriate technologies for AG pre-treatment. The aim of this study was to evaluate the influence of two pre-treatments, solid-state fermentation with the Lactiplantibacillus plantarum LUHS135 and ultrasonication, on the antioxidant and antimicrobial characteristics of macro- (Cladophora rupestris, Cladophora glomerata, Furcellaria lumbricalis, Ulva intestinalis) and Spirulina (Arthrospira platensis) extracts. Also, combinations of extracts and LUHS135 were developed and their characteristics were evaluated. The total phenolic compound content was determined from the calibration curve and expressed in mg of gallic acid equivalents; antioxidant activity was measured by a Trolox equivalent antioxidant capacity assay using the DPPH^• (1,1-diphenyl-2-picrylhydrazyl), ABTS^•+ 2,2′-azinobis-(3-ethylbenzothiazoline-6-sulfonic acid), FRAP (Ferric Reducing Ability of Plasma) discoloration methods. Antimicrobial activity was measured by using agar well diffusion assay and in a liquid medium. The highest DPPH^• and ABTS^•+ was shown by C.rupestris and F.lumbricalis extract × LUHS135 combinations, the highest FRAP - by non-pretreated C.rupestris and F.lumbricalis extract × LUHS135 combinations. Ultrasonicated samples inhibited four out of seven tested pathogens. Finally, the tested pre-treatments showed good perspectives and can be recommended for AB valorization.

Dietary vitamins, carotenoids and their sources in relation to age-related macular degeneration risk in China: a population-based case-control study

Mechanistic studies have suggested that antioxidants have beneficial effects on age-related macular degeneration (AMD). This study aimed to investigate the association between the types and sources of dietary vitamin and carotenoid intakes and AMD risk in China. A matched case-control study of 260 AMD cases and 260 matched controls was performed. The participants were interviewed for dietary information and potential confounders, and comprehensive ophthalmic examinations were performed. Conditional logistic models were used to estimate the odds ratio (OR) and 95 % confidence interval (CI) of specific vitamins and carotenoids and their main sources. When comparing the extreme quartiles, the ORs (95 % CI) were 0·30 (0·10, 0·88) for lutein and 0·28 (0·11, 0·74) for β-cryptoxanthin. The associations for other dietary vitamin and carotenoid intakes were generally weaker and non-significant. Higher intakes of spinach and egg, which are important sources of lutein, were associated with a reduced odds of AMD. ORs (95% CIs) comparing extreme categories were 0·42 (0·20, 0·88) for spinach and 0·52 (95% CI: 0·27, 0·98) for egg. Participants who were in the highest category of both egg intake and spinach intake had a much greater reduced odds of having AMD (OR: 0·23; 95% CI: 0·08, 0·71) than those in the lowest category of egg intake and spinach intake. In conclusion, a higher intake of lutein and lutein-rich foods was associated with a significantly decreased odds of AMD. These findings provide further evidence of the benefits of lutein and lutein-rich foods in the prevention of AMD.

Effect of macular pigment carotenoids on cognitive functions: A systematic review

Lutein and zeaxanthin-xanthophyll carotenoids with antioxidant and anti-inflammatory characteristics-are present in the retina and the brain. High concentrations of these carotenoids have been positively related to cognitive performance. Therefore, this systematic review analyses the relationship between macular pigment density and cognitive functions. Most relevant databases were scoured for studies on healthy people relating cognitive functions to macular pigment optical density (MPOD). There were no age, sex, or race limitations. PROSPERO registration: CRD42021254833. Nineteen studies were included, seven randomized controlled trials (RCT) and eleven observational studies. The general aim of the studies was to examine the association between carotenoids (lutein, meso‑zeaxanthin and zeaxanthin) and cognitive function. Most observational studies correlates MPOD levels with cognitive function or brain activity. Besides, RCTs compared the cognitive function and/or brain activity after increasing lutein and zeaxanthin intake though dietary supplementation or avocado consumption. Dietary lutein and zeaxanthin intake increased MPOD in six of the seven clinical trials and significantly improved most of the cognitive functions studied. A wide variety of test and methodologies for measuring cognitive functions were observed. Memory, processing speed, attention and reasoning were the cognitive function significantly related to MPOD levels in adults. Brain activity also was related to MPOD, but the results were inconsistent. Only four of the eleven observational studies were based on young people and all studies showed a significant relationship between MPOD and cognitive functions. This systematic review showed a direct relationship among cognitive functions, macular pigment and the intake of lutein and zeaxanthin.

Novel Approaches for the Recovery of Natural Pigments with Potential Health Effects

The current increased industrial food production has led to a significant rise in the amount of food waste generated. These food wastes, especially fruit and vegetable byproducts, are good sources of natural pigments, such as anthocyanins, betalains, carotenoids, and chlorophylls, with both coloring and health-related properties. Therefore, recovery of natural pigments from food wastes is important for both economic and environmental reasons. Conventional methods that are used to extract natural pigments from food wastes are time-consuming, expensive, and unsustainable. In addition, natural pigments are sensitive to high temperatures and prolonged processing times that are applied during conventional treatments. In this sense, the present review provides an elucidation of the latest research on the extraction of pigments from the agri-food industry and how their consumption may improve human health.

Identification of major carotenoids from green alga Tetraspora sp. CU2551: partial purification and characterization of lutein, canthaxanthin, neochrome, and β-carotene

The green algae Tetraspora sp. CU2551 was previously identified as a strain with high potential for biohydrogen production; however, its algal biomass characteristics changed from green to reddish orange within 43 days of biohydrogen production. The crude pigments were extracted, partially purified, and characterized by chemical determination. The present study focused on elucidating the carotenoid composition of the selected green alga Tetraspora sp. CU2551. The pigment extract was partially purified and fractionated using thin layer chromatography, and yielded two major and two minor carotenoid bands. The fractions were confirmed by high-performance liquid chromatography with a diode array detector (HPLC-DAD) before being identified and confirmed using Liquid Chromatograph-Quadrupole Time of Flight-Mass Spectrometry (LC-QTOF-MS). The spectral data of these fractions revealed four sub-fractions of interest that were lutein, canthaxanthin, neochrome, and β-carotene, which had percentages in the crude extracts of 30.57%, 25.47%, 7.89%, and 0.71%, respectively. Lutein and canthaxanthin were found to be the major carotenoid pigments present. Our findings in this present study are the first reporting of Tetraspora sp. CU2551 as a potential alternate source for carotenoid pigment production.

Superior Bioavailability of a Novel Lutein and Zeaxanthin Formulation in Healthy Human Subjects

Introduction

Lutein (L) and zeaxanthin (Z) are carotenoids that are found in the macula of the human eye and are known to improve visual functions. However, poor bioavailability of supplemental L and Z poses a challenge to achieving significant benefits after consumption. We developed a novel patented formulation of L and Z (Ocusorb^®) and demonstrated the improved bioavailability in a pharmacokinetic clinical study.

Methods

Ninety adult human volunteers were recruited in this randomized, double-blind, parallel, comparative bioavailability study. Volunteers were randomly assigned to receive single dose of 10 mg lutein and 2 mg zeaxanthin from test (LZO) or reference (LZC) formulations after breakfast. Blood samples were collected pre-dose at − 48, − 24, and 0 h and at 2, 4, 6, 8, 10, 12, 16, 20, 24, 48, and 72 h post-dose. Serum concentrations of L and Z were quantified by using a validated HPLC method. The LZO and LZC formulations were compared for L and Z on the basis of C_max, AUC_0–72, and AUC_0–t.

Results

All 90 subjects completed the study. The LZO group demonstrated significantly higher levels of L and Z in serum at several time points as compared to LZC group. The LZO group showed significantly higher bioavailability for lutein (2.5 times higher C_max, 2.9 times higher AUC_0–72, and 3.2 times higher AUC_0–t) and zeaxanthin (1.8 times higher C_max, 2.2 times higher AUC_0–72, and AUC_0–t) as compared to the LZC group. No safety issues were reported.

Conclusion

The study results show superior bioavailability of lutein and zeaxanthin from our novel LZO formulation as compared to LZC. The enhanced bioavailability from the LZO formulation can be advantageous for individuals looking to quickly improve their L and Z status and enhance their vision performance.

Trial Registration

http://ctri.nic.in/. Identifier: CTRI/2019/11/022082.

Protective Effect of Ribes nigrum Extract against Blue Light-Induced Retinal Degeneration In Vitro and In Vivo

Although blackcurrant has several health benefits, such as antioxidant and anti-inflammatory properties, its effects on the retina remain unclear. In this study, we investigated the efficacy of black currant extract (BCE) in an in vitro and in vivo model of dry age-related macular degeneration (AMD) induced by blue light. Dry macular degeneration is characterized by the abnormal accumulation of lipofuscin (e.g., N-retinylidene-N-retinylethanolamine, A2E) in the retina. Blue light (BL) significantly decreased the viability of A2E-laden human retinal pigment epithelial cells (ARPE-19). However, BCE treatment protected ARPE-19 cells from A2E and BL. A2E, which is oxidized by blue light, generates reactive oxygen species in RPE cells. Treatment with BCE significantly decreased (80.8%) reactive oxygen species levels induced by A2E and BL in a concentration-dependent manner. BCE inhibited A2E accumulation in ARPE-19 cells and significantly downregulated the expression of genes increased by A2E and BL in ARPE-19 cells. In vivo, oral administration of BCE (25–100 mg/kg) ameliorated ocular lesions of BL-induced retinal damage in a mouse model and rescued the thickness of the whole retina, photoreceptor segment layer, outer nuclear layer, and inner nuclear layer. The decrease in the number of nuclei in the outer nuclear layer induced by BL was also rescued by BCE. Additionally, BCE administration rescued (40.0%) the BL-induced reduction in the expression level of superoxide dismutase 1. Taken together, our results suggest that BCE may have preventive and therapeutic effects on dry AMD through its antioxidant activity and inhibition of lipofuscin accumulation in the retina.

Enhancing bioaccessibility and bioavailability of carotenoids using emulsion-based delivery systems

The consumption of foods rich in antioxidants, vitamins, minerals including carotenoids etc. can boost the immune system to help fight off various infections including SARS- CoV 2 and other viruses. Carotenoids have been gaining attention particularly in food and pharmaceutical industries owing to their diverse functions including their role as pro-vitamin A activity, potent antioxidant properties, and quenching of reactive oxygen (ROS), such as singlet oxygen and lipid peroxides within the lipid bilayer of the cell membrane. Nevertheless, carotenoids being lipophilic, have poor solubility in aqueous medium and are also chemically instable. They are susceptible to degrade under stimuli environmental conditions during food processing, storage and gastrointestinal passage. They also exhibit poor oral bioavailability, thus, their applications in aqueous-based foods are limited. As a consequent, suitable delivery systems including colloids-based are needed to enhance the solubility, stability and bioavailability of carotenoids. This review presents challenges of incorporation and delivery of carotenoids focusing on stability and factors affecting bioavailability. Furthermore, designed factors impacting bioaccessibility and bioavailability of carotenoids using emulsion-based delivery systems are explicitly explained. Each delivery system exhibits its own advantages and disadvantages; thus, the delivery systems should be designed based on their targets and their further applications.

IMAGING ARTIFACTS IN FLUORESCENCE LIFETIME IMAGING OPHTHALMOSCOPY

PURPOSE

To investigate and quantify the influence of imaging artifacts on retinal fluorescence lifetime (FLIO) values and to provide helpful hints and tricks to avoid imaging artifacts and to improve FLIO image acquisition quality.

METHODS

A systematic analysis of potential parameters influencing FLIO quality and/or fluorescence lifetime values was performed in a prospective systematic experimental imaging study in five eyes of five healthy subjects. For image acquisition, a fluorescence lifetime imaging ophthalmoscope (Heidelberg Engineering) was used. Quantitative analysis of FLIO lifetime changes due to imaging artifacts was performed.

RESULTS

Imaging artifacts with significant influence on fluorescence lifetimes included too short image acquisition time, insufficient illumination, ocular surface problems, and image defocus. Prior use of systemic or topical fluorescein makes analysis of retinal fluorescence lifetimes impossible.

CONCLUSION

Awareness of possible sources of imaging artifacts is important for FLIO image acquisition and analysis. Therefore, standardized imaging and analysis procedure in FLIO is crucial for high-quality image acquisition and the possibility for systematic quantitative fluorescence lifetime analysis.

Dietary Antioxidants in Age-Related Macular Degeneration and Glaucoma

Age-related macular degeneration (AMD) and glaucoma are ophthalmic neurodegenerative diseases responsible for irreversible vision loss in the world population. Only a few therapies can be used to slow down the progression of these diseases and there are no available treatment strategies for reversing the degeneration of the neural retina. In AMD, the pathological process causes the malfunction and damage of the retinal pigmented epithelium and photoreceptors in the macula. In glaucoma, damage of the retinal ganglion cells and their axons is observed and treatment strategies are limited to intraocular pressure lowering. Therefore, other prophylactic and/or therapeutic methods are needed. Oxidative stress is involved in the neurodegenerative process accompanying both AMD and glaucoma; therefore, the use of antioxidant agents would clearly be beneficial, which is supported by the decreased prevalence and progression of AMD in patients adherent to a diet naturally rich in antioxidants. Dietary antioxidants are easily available and their use is based on the natural route of administration. Many preclinical studies both in vitro and using animal models of retinal degeneration showed the efficacy of dietary antioxidants, which was further proved in clinical trials. Resveratrol is beneficial both in AMD and glaucoma animal models, but confirmed only among AMD patients. For AMD, carotenoids and omega-3 fatty acids were also proved to be sufficient in preventing neurodegeneration. For glaucoma, coenzyme Q10 and alpha-lipoic acid showed efficacy for decreasing retinal ganglion cell loss and inhibiting the accompanying destructive processes. Interestingly, the benefits of vitamins, especially vitamin E was not confirmed, neither in preclinical nor in clinical studies.

The ALGOVUE Clinical Trial: Effects of the Daily Consumption of Eggs Enriched with Lutein and Docosahexaenoic Acid on Plasma Composition and Macular Pigment Optical Density

Background. Carotenoids and docosahexaenoic acid (DHA) were identified as essential components for eye health and are both naturally present in eggs. Objective. We aimed to evaluate the effect of the daily consumption of two eggs enriched with lutein/zeaxanthin and DHA on macular pigment optical density (MPOD) and on circulating xanthophyll and fatty acid concentrations in healthy participants. Methods. Ninety-nine healthy volunteers consumed either two standard eggs or two enriched eggs per day for 4 months. MPOD was measured at baseline (V0) and at follow-up (V4) using a modified confocal scanning laser ophthalmoscope (primary outcome). Blood samples were collected to determine total plasma and lipoprotein fatty acids and lutein/zeaxanthin compositions at V0 and V4 (secondary outcomes). Results. A slight but significant increase in MPOD was observed for all study participants consuming two eggs per day for 4 months at all eccentricities (0.5°, 1°, 2°, and 4°). Plasma and lipoprotein lutein, zeaxanthin, and DHA concentrations significantly increased in both groups but were greater in the enriched group (for the enriched group (V0 vs. V4): lutein, 167 vs. 369 ng/mL; zeaxanthin, 17.7 vs. 29.2 ng/mL; DHA, 1.89 vs. 2.56% of total fatty acids). Interestingly, lutein from high-density lipoprotein (HDL) was strongly correlated with MPOD at 0.5 and 1° eccentricities (rho = 0.385, p = 0.008, and rho = 0.461, p = 0.001, respectively). Conclusions. MPOD was slightly increased in both groups. Lutein, zeaxanthin, and DHA plasma concentrations were strongly enhanced in the enriched group compared with the standard group. A significant correlation was found between MPOD level and lutein concentration in HDL.

Early Pediatric Benefit of Lutein for Maturing Eyes and Brain-An Overview

Lutein is a dietary carotenoid preferentially accumulated in the eye and the brain in early life and throughout the life span. Lutein accumulation in areas of high metabolism and oxidative stress such as the eye and the brain suggest a unique role of this ingredient during the development and maturation of these organs of common embryological origin. Lutein is naturally provided to the developing baby via the cord blood, breast milk and then infant diet. The presence of this carotenoid depends on fruit and vegetable intakes and its bioavailability is higher in breastmilk. This paper aims to review the anatomical development of the eye and the brain, explore the presence and selective deposition of lutein in these organs during pregnancy and infancy and, based on its functional characteristics, present the latest available research on the beneficial role of lutein in the pediatric population. The potential effects of lutein in ameliorating conditions associated with increase oxidative stress such as in prematurity will be also addressed. Since consumption of lutein rich foods falls short of government guidelines and in most region of the world infant formulas lack this bioactive, dietary recommendations for pregnant and breastfeeding women and their child can help to bridge the gap.

Overflow phenomenon in serum lutein after supplementation: a systematic review supported with SNPs analyses

Lutein, a type of carotenoids, is found to delay the onset and progression of age-related macular degeneration (AMD). Several lutein supplementation studies showed that after an initial increase, lutein serum levels demonstrated a subsequent decrease despite continuous supplementation. In this systematic literature review, this obscure phenomenon was tried to be explained. The subsequent drop in lutein levels was postulated due to down-regulation of lutein receptors scavenger receptor class B type I (SR-BI) in the gastrointestinal tract, upregulation of lutein degrading enzyme β-carotene dioxygenase (BCDO2), or perhaps a combination of both. Some single nucleotides polymorphisms (SNPs) that could have influence on the occurrence of this phenomenon. To date, an exact scientific explanation for this phenomenon has not been established. Further research is needed to investigate this phenomenon in depth to reach an irrefutable explanation, giving that lutein is proven to be effective in delaying the onset and progression of AMD and its metabolism in the human body becomes of equal importance.

Effects of anthocyanin, astaxanthin, and lutein on eye functions: a randomized, double-blind, placebo-controlled study

We examined the effects of a test food containing anthocyanin, astaxanthin, and lutein on the eye function in healthy Japanese adults with eye fatigue after operating visual display terminals. Forty-four subjects were randomly but equally assigned to the active or placebo group. Two active or placebo capsules were taken once daily for 6 weeks. Accommodative function, tear film break-up time, visual acuity, the value of Schirmer's test, macular pigment optical density level, muscle hardness, and a questionnaire were evaluated before and after a 6-week intervention. Each group included 20 subjects in the efficacy analysis. The active group showed a significant improvement in the percentage of pupillary response of an average of both eyes and dominant eye pre- and post-visual display terminal operation at 6 weeks compared with the placebo group. Moreover, the active group showed a significant improvement in the scores of "A sensation of trouble in focusing the eyes" and "Difficulty in seeing objects in one's hand and nearby, or fine print" compared with the placebo group between before and after ingestion. Therefore, 6-weeks consumption of the test food inhibited a decrease in the accommodative function caused by visual display terminal operation (UMIN000036989).

Protective Effect of Lutein/Zeaxanthin Isomers in Traumatic Brain Injury in Mice

Previous studies revealed that oxidative stress and inflammation are the main contributors to secondary injury after traumatic brain injury (TBI). In an earlier study, we reported that lutein/zeaxanthin isomers (L/Zi) exert antioxidative and anti-inflammatory effects by activating the nuclear factor-kappa B (NF-κB) and nuclear factor-erythroid 2-related factor 2 (Nrf2) pathways. However, its precise role and underlying mechanisms were largely unknown after TBI. This study was conducted to investigate the potential mechanism of L/Zi isomers in a TBI model induced by a cold injury model in mice. To investigate the effects of L/Zi, male C57BL/6j mice-induced brain injury using the cold trauma model was allocated into two groups (n = 7): (i) TBI + vehicle group and (ii) TBI + L/Zi group (20 mg/kg BW). Brain samples were collected 24 h later for analyses. L/Zi given immediately after the injury decreased infarct volume and blood-brain barrier (BBB) permeability; L/Zi treatment also significantly reduced proinflammatory cytokines, including interleukin1 beta (IL-1β), interleukin 6 (IL-6), and NF-κB levels and increased growth-associated protein 43 (GAP-43), neural cell adhesion molecule (NCAM), brain-derived neurotrophic factor (BDNF), and Nrf2 levels compared with vehicle control. These data suggest that L/Zi improves mitochondrial function in TBI models, possibly decreasing inflammation and activating the Nrf2 pathway.

Carotenoids in Milk and the Potential for Dairy Based Functional Foods

Carotenoids are a family of over 1100 known natural pigments synthesized by plants, algae, fungi and bacteria. Dietary intake of carotenoids is necessary for mammals as they cannot be synthesized in the body. In cows, the nature of the diet consumed strongly influences the composition of milk produced and this includes carotenoid concentration and profile. Fresh forage is the richest source of carotenoids for cows. The main carotenoids identified in forages are lutein, β-carotene, zeaxanthin and epilutein. Manipulating cow feed via carotenoid supplementation increases the carotenoid content of bovine milk. In humans, carotenoids have anti-oxidant, anti-inflammatory and provitamin A activity. Lutein is a major carotenoid in human milk and the brain tissue of adults and infants. Lutein and zeaxanthin are linked to improved eye health and cognitive function. Traditionally for humans, fruit and vegetables have been the main source of carotenoid intake. Functional foods present an opportunity to incorporate these naturally occurring compounds into milk products for added health benefits, widening the range of dietary sources of carotenoids. We offer an overview of the literature to date on carotenoid-fortified dairy products and infant formula. This review will describe and summarize the key mechanisms by which the carotenoid profile of bovine milk can be manipulated. We present findings on the origin and role of carotenoids in bovine and human milk, outline factors that impact the carotenoid content of milk, evaluate carotenoid-fortified milk products and discuss the associated challenges, such as bioaccessibility and stability.

Beyond Nutrient Deficiency-Opportunities to Improve Nutritional Status and Promote Health Modernizing DRIs and Supplementation Recommendations

The US Dietary Guidelines for Americans (DGA) provide dietary recommendations to meet nutrient needs, promote health, and prevent disease. Despite 40 years of DGA, the prevalence of under-consumed nutrients continues in the US and globally, although dietary supplement use can help to fill shortfalls. Nutrient recommendations are based on Dietary Reference Intakes (DRIs) to meet the nutrient requirements for nearly all (97 to 98 percent) healthy individuals in a particular life stage and gender group and many need to be updated using current evidence. There is an opportunity to modernize vitamin and mineral intake recommendations based on biomarker or surrogate endpoint levels needed to 'prevent deficiency' with DRIs based on ranges of biomarker or surrogate endpoints levels that support normal cell/organ/tissue function in healthy individuals, and to establish DRIs for bioactive compounds. We recommend vitamin K and Mg DRIs be updated and DRIs be established for lutein and eicosapentaenoic and docosahexaenoic acid (EPA + DHA). With increasing interest in personalized (or precision) nutrition, we propose greater research investment in validating biomarkers and metabolic health measures and the development and use of inexpensive diagnostic devices. Data generated from such approaches will help elucidate optimal nutrient status, provide objective evaluations of an individual's nutritional status, and serve to provide personalized nutrition guidance.

Comparison of Antioxidant Properties of Dehydrolutein with Lutein and Zeaxanthin, and their Effects on Cultured Retinal Pigment Epithelial Cells

Dehydrolutein accumulates in substantial concentrations in the retina. The aim of this study was to compare antioxidant properties of dehydrolutein with other retinal carotenoids, lutein, and zeaxanthin, and their effects on ARPE-19 cells. The time-resolved detection of characteristic singlet oxygen phosphorescence was used to compare the singlet oxygen quenching rate constants of dehydrolutein, lutein, and zeaxanthin. The effects of these carotenoids on photosensitized oxidation were tested in liposomes, where photo-oxidation was induced by light in the presence of photosensitizers, and monitored by oximetry. To compare the uptake of dehydrolutein, lutein, and zeaxanthin, ARPE-19 cells were incubated with carotenoids for up to 19 days, and carotenoid contents were determined by spectrophotometry in cell extracts. To investigate the effects of carotenoids on photocytotoxicity, cells were exposed to light in the presence of rose bengal or all-trans-retinal. The results demonstrate that the rate constants for singlet oxygen quenching are 0.77 × 10¹⁰, 0.55 × 10¹⁰, and 1.23 × 10¹⁰ M^-1s^-1 for dehydrolutein, lutein, and zeaxanthin, respectively. Overall, dehydrolutein is similar to lutein or zeaxanthin in the protection of lipids against photosensitized oxidation. ARPE-19 cells accumulate substantial amounts of both zeaxanthin and lutein, but no detectable amounts of dehydrolutein. Cells pre-incubated with carotenoids are equally susceptible to photosensitized damage as cells without carotenoids. Carotenoids provided to cells together with the extracellular photosensitizers offer partial protection against photodamage. In conclusion, the antioxidant properties of dehydrolutein are similar to lutein and zeaxanthin. The mechanism responsible for its lack of accumulation in ARPE-19 cells deserves further investigation.

The generation of metabolic changes for the production of high-purity zeaxanthin mediated by CRISPR-Cas9 in Chlamydomonas reinhardtii

BACKGROUND

Zeaxanthin, a major xanthophyll pigment, has a significant role as a retinal pigment and antioxidant. Because zeaxanthin helps to prevent age-related macular degeneration, its commercial use in personalized nutritional and pharmaceutical applications has expanded. To meet the quantitative requirements for personalized treatment and pharmaceutical applications, it is necessary to produce highly purified zeaxanthin.

RESULTS

In this study, to meet the quantitative requirements for industrial applications, we generated a double knockout mutant which is gene-edited by the CRISPR-Cas9 ribonucleoprotein-mediated knock-in system. The lycopene epsilon cyclase (LCYE) was edited to the elimination of α-branch of xanthophyll biosynthesis in a knockout mutant of the zeaxanthin epoxidase gene (ZEP). The double knockout mutant (dzl) had a 60% higher zeaxanthin yield (5.24 mg L^- 1) and content (7.28 mg g^- 1) than that of the parental line after 3 days of cultivation. Furthermore, medium optimization improved the 3-day yield of zeaxanthin from the dzl mutant to 6.84 mg L^- 1.

CONCLUSIONS

A Chlamydomonas strain with the elimination of lutein production by gene editing using CRISPR-Cas9 has been successfully developed. This research presents a solution to overcome the difficulties of the downstream-process for the production of high-purity zeaxanthin.

Photobiomodulation of the Visual System and Human Health

Humans express an expansive and detailed response to wavelength differences within the electromagnetic (EM) spectrum. This is most clearly manifest, and most studied, with respect to a relatively small range of electromagnetic radiation that includes the visible wavelengths with abutting ultraviolet and infrared, and mostly with respect to the visual system. Many aspects of our biology, however, respond to wavelength differences over a wide range of the EM spectrum. Further, humans are now exposed to a variety of modern lighting situations that has, effectively, increased our exposure to wavelengths that were once likely minimal (e.g., “blue” light from devices at night). This paper reviews some of those biological effects with a focus on visual function and to a lesser extent, other body systems.

Phillyrin Mitigates Apoptosis and Oxidative Stress in Hydrogen Peroxide-Treated RPE Cells through Activation of the Nrf2 Signaling Pathway

Oxidative stress-induced dysfunction or apoptosis in retinal pigment epithelial (RPE) cells is an important cause of dry age-related macular degeneration (AMD). Although phillyrin has been shown to exert significant antioxidant effects, the underlying mechanism of action remains unclear. The purpose of this study was to investigate the protective effect of phillyrin on hydrogen peroxide- (H2O2-) induced oxidative stress damage in RPE cells and the potential mechanism involved. It was found that phillyrin significantly protected RPE cells from H2O2 cytotoxicity. Furthermore, phillyrin alleviated oxidative stress-induced apoptosis via inhibition of endogenous and exogenous apoptotic pathways. Compared with the H2O2-treated group, the expressions of cleaved caspase-3, cleaved caspase-9, cleaved polymerase (PARP), death receptor Fas, and cleaved caspase-8, as well as Bax/Bcl-2 ratio were decreased in RPE cells after the phillyrin intervention. In addition, phillyrin reversed the oxidative stress-induced reductions in superoxide dismutase (SOD) and glutathione (GSH) levels and annulled the elevations in reactive oxygen species (ROS) and malondialdehyde (MDA), thereby restoring oxidant-antioxidant homeostasis. Phillyrin treatment upregulated the expressions of cyclin E, cyclin-dependent kinase 2 (CDK2), and cyclin A and downregulated the expressions of p21 and p-p53, thereby reversing the G0/G1 cell cycle arrest in H2O2-treated RPE cells. Pretreatment with phillyrin also increased the expressions of nuclear factor-erythroid 2-related factor 2 (Nrf2), total Nrf2, heme oxygenase-1 (HO-1), and NAD(P)H: quinone oxidoreductases-1 (NQO-1) in RPE cells and inhibited the formation of Kelch-like ECH-associated protein 1 (Keap1)/Nrf2 protein complex. Thus, phillyrin effectively protected RPE cells from oxidative stress through activation of the Nrf2 signaling pathway and inhibition of the mitochondria-dependent apoptosis pathway.

Clinical Effects of Dietary Supplementation of Lutein with High Bio-Accessibility on Macular Pigment Optical Density and Contrast Sensitivity: A Randomized Double-Blind Placebo-Controlled Parallel-Group Comparison Trial

Improvements in macular pigment optical density (MPOD) and contrast sensitivity after administration of 12 mg lutein alone and the timing at which efficacy is observed remain unknown. Therefore, lutein (12 mg), a crystalline formulation, was used in this study, considering its bioaccessibility. This study aimed to determine the effects of lutein administration for 16 weeks on MPOD, contrast sensitivity, and glare sensitivity, and changes in serum lutein levels were determined. The study subjects comprised 59 healthy male and female adults aged 20–69 years. The study diet included a placebo (placebo group) or a diet supplemented with 12 mg of lutein (lutein group). Each study diet was continuously administered for 16 weeks. At weeks 8 and 16, MPOD, contrast sensitivity, glare sensitivity, and serum lutein levels were evaluated. Compared with the placebo group, the lutein group showed significantly improved MPOD, contrast sensitivity, and glare sensitivity at week 16 and significantly increased serum lutein levels at weeks 8 and 16. Continuous administration of lutein for 16 weeks, considering its bioaccessibility, increased MPOD; it made the outlines of visible objects clearer and was effective in inhibiting decreases in visual function caused by glare from light.

A Brief Overview of Dietary Zeaxanthin Occurrence and Bioaccessibility

As it exhibits no provitamin A activity, the dietary intake of zeaxanthin is not considered essential. However, its contribution to ocular health has long been acknowledged. Numerous publications emphasize the importance of zeaxanthin alongside lutein in ocular diseases such as cataracts and age-related macular degeneration which constitute an important health concern, especially among the elderly. Considering that the average dietary ratio of lutein to zeaxanthin favors the first, more bioaccessible food sources of zeaxanthin that can hinder the development and progression of the above-mentioned disorders are of great interest. In this paper, a brief overview of the more recent state of knowledge as regards dietary sources together with their respective zeaxanthin bioaccessibility assessed through a standardized in vitro digestion method was provided.

The human mitochondrial enzyme BCO2 exhibits catalytic activity toward carotenoids and apocarotenoids

The enzyme β-carotene oxygenase 2 (BCO2) converts carotenoids into more polar metabolites. Studies in mammals, fish, and birds revealed that BCO2 controls carotenoid homeostasis and is involved in the pathway for vitamin A production. However, it is controversial whether BCO2 function is conserved in humans, because of a 4-amino acid long insertion caused by a splice acceptor site polymorphism. We here show that human BCO2 splice variants, BCO2a and BCO2b, are expressed as pre-proteins with mitochondrial targeting sequence (MTS). The MTS of BCO2a directed a green fluorescent reporter protein to the mitochondria when expressed in ARPE-19 cells. Removal of the MTS increased solubility of BCO2a when expressed in Escherichia coli and rendered the recombinant protein enzymatically active. The expression of the enzymatically active recombinant human BCO2a was further improved by codon optimization and its fusion with maltose-binding protein. Introduction of the 4-amino acid insertion into mouse Bco2 did not impede the chimeric enzyme's catalytic proficiency. We further showed that the chimeric BCO2 displayed broad substrate specificity and converted carotenoids into two ionones and a central C14-apocarotendial by oxidative cleavage reactions at C9,C10 and C9',C10'. Thus, our study demonstrates that human BCO2 is a catalytically competent enzyme. Consequently, information on BCO2 becomes broadly applicable in human biology with important implications for the physiology of the eyes and other tissues.

Why is Zeaxanthin the Most Concentrated Xanthophyll in the Central Fovea?

Diet-based xanthophylls (zeaxanthin and lutein) are conditionally essential polar carotenoids preferentially accreted in high concentrations (1 mM) to the central retina, where they have the capacity to impart unique physiologically significant biophysical biochemical properties implicated in cell function, rescue, and survival. Macular xanthophylls interact with membrane-bound proteins and lipids to absorb/attenuate light energy, modulate oxidative stress and redox balance, and influence signal transduction cascades implicated in the pathophysiology of age-related macular degeneration. There is exclusive transport, sequestration, and appreciable bioamplification of macular xanthophylls from the circulating carotenoid pool to the retina and within the retina to regions required for high-resolution sensory processing. The distribution of diet-based macular xanthophylls and the lutein metabolite meso-zeaxanthin varies considerably by retinal eccentricity. Zeaxanthin concentrations are 2.5-fold higher than lutein in the cone-dense central fovea. This is an ~20-fold increase in the molar ratio relative to eccentric retinal regions with biochemically detectable macular xanthophylls. In this review, we discuss how the differences in the specific properties of lutein and zeaxanthin could help explain the preferential accumulation of zeaxanthin in the most vulnerable region of the macula.

Macular Pigment Optical Density and Photoreceptor Outer Segment Length as Predisease Biomarkers for Age-Related Macular Degeneration

To explore predisease biomarkers, which may help screen for the risk of age-related macular degeneration (AMD) at very early stages, macular pigment optical density (MPOD) and photoreceptor outer segment (PROS) length were analyzed. Thirty late AMD fellow eyes, which are at high risk and represent the predisease condition of AMD, were evaluated and compared with 30 age-matched control eyes without retinal diseases; there was no early AMD involvement in the AMD fellow eyes. MPOD was measured using MPS2^® (M.E. Technica Co. Ltd., Tokyo, Japan), and PROS length was measured based on optical coherence tomography images. MPOD levels and PROS length in the AMD fellow eyes were significantly lower and shorter, respectively, than in control eyes. MPOD and PROS length were positively correlated in control eyes (R = 0.386; p = 0.035) but not in AMD fellow eyes. Twenty (67%) AMD fellow eyes met the criteria of MPOD < 0.65 and/or PROS length < 35 μm, while only five (17%) control eyes did. After adjusting for age and sex, AMD fellow eyes more frequently satisfied the definition (p < 0.001; 95% confidence interval, 3.50–60.4; odds ratio, 14.6). The combination of MPOD and PROS length may be a useful biomarker for screening predisease AMD patients, although further studies are required in this regard.

Nutrition and the aging retina: A comprehensive review of the relationship between nutrients and their role in age-related macular degeneration and retina disease prevention

Age-related macular degeneration (AMD) is the leading cause of severe vision loss in developed countries and is highly common among aging individuals. Considering the rate at which the global population is aging, the increasing prevalence of AMD and age-related eye disease is cause for concern. AMD is associated with the degeneration of the macula, the most central region of the retina, leading to a loss of central vision. A wide array of research has focused on the ability of lipid soluble nutrients to prevent and mitigate the harmful effects of AMD. These nutrients in question tend to be highly saturated within retinal tissues including the carotenoids lutein and zeaxanthin and the polyunsaturated fatty acid docosahexaenoic acid (DHA). Additionally, the unique presence of very long chain polyunsaturated fatty acids (VLCPUFAs, C24-C36) in the retina may be essential to prevent retinal degeneration as demonstrated by abnormal retinal functioning in the absence of these novel fatty acids. Existing literature has suggested that lutein, zeaxanthin and DHA consumption tend to enhance the health of the retina, protecting against the development of AMD. However, little improvement to the previously deteriorated retina is demonstrated and more research is required to understand the role of these nutrients in the retina and for the prevention of AMD. Considering the global impact of AMD and age-related eye disease, utilizing nutrients to prevent the formation of these debilitating diseases is a highly affordable and promising strategy.

Molecular components affecting ocular carotenoid and retinoid homeostasis

The photochemistry of vision employs opsins and geometric isomerization of their covalently bound retinylidine chromophores. In different animal classes, these light receptors associate with distinct G proteins that either hyperpolarize or depolarize photoreceptor membranes. Vertebrates also use the acidic form of chromophore, retinoic acid, as the ligand of nuclear hormone receptors that orchestrate eye development. To establish and sustain these processes, animals must acquire carotenoids from the diet, transport them, and metabolize them to chromophore and retinoic acid. The understanding of carotenoid metabolism, however, lagged behind our knowledge about the biology of their receptor molecules. In the past decades, much progress has been made in identifying the genes encoding proteins that mediate the transport and enzymatic transformations of carotenoids and their retinoid metabolites. Comparative analysis in different animal classes revealed how evolutionary tinkering with a limited number of genes evolved different biochemical strategies to supply photoreceptors with chromophore. Mutations in these genes impair carotenoid metabolism and induce various ocular pathologies. This review summarizes this advancement and introduces the involved proteins, including the homeostatic regulation of their activities.

Correlation between Macular Pigment Optical Density and Neural Thickness and Volume of the Retina

Macular pigment (MP), which is composed of lutein/zeaxanthin/mezo-zeaxanthin, is concentrated in the central part of the retina, the macula. It protects the macula by absorbing short-wavelength light and suppressing oxidative stress. To evaluate whether MP levels are related to retinal neural protection and resulting health, we analyzed the association between the MP optical density (MPOD), and the macular thickness and volumes. Forty-three eyes of 43 healthy adult volunteers (21 men and 22 women; age: 22–48 (average 31.4 ± 1.1) years) were analyzed. Highly myopic eyes (<-6 diopters) were excluded. MPOD was measured using MPS2®, and the neural retinal thickness and volume were measured using optical coherence tomography. The mean MPOD was 0.589 ± 0.024, and it positively correlated with the central retinal thickness (P = 0.017, R = 0.360) and retinal volume of the fovea (1-mm diameter around the fovea; P = 0.029, R = 0.332), parafovea (1–3-mm diameter; P = 0.002, R = 0.458), and macula (6-mm diameter; P = 0.003, R = 0.447). In the macular area (diameter: 6 mm), MPOD was correlated with the retinal neural volume of the ganglion cell layer (P = 0.037, R = 0.320), inner plexiform layer (P = 0.029, R = 0.333), and outer nuclear layer (P = 0.020, R = 0.353). Thus, MPOD may help in estimating neural health. Further studies should determine the impact of MP levels on neuroprotection.

The Colors of Health: Chemistry, Bioactivity, and Market Demand for Colorful Foods and Natural Food Sources of Colorants

There is an increasing consumer demand for natural colors in foods. However, there is a limited number of available natural food sources for use by the food industry because of technical and regulatory limitations. Natural colors are less stable and have less vibrant hues compared to their synthetic color counterparts. Natural pigments also have known health benefits that are seldom leveraged by the food industry. Betalains, carotenoids, phycocyanins, and anthocyanins are major food colorants used in the food industry that have documented biological effects, particularly in the prevention and management of chronic diseases such as diabetes, obesity, and cardiovascular disease. The color industry needs new sources of stable, functional, and safe natural food colorants. New opportunities include sourcing new colors from microbial sources and via the use of genetic biotechnology. In all cases, there is an imperative need for toxicological evaluation to pave the way for their regulatory approval.

Polarization perception in humans: on the origin of and relationship between Maxwell's spot and Haidinger's brushes

Under specific conditions of illumination and polarization, differential absorption of light by macular pigments is perceived as the entoptic phenomena of Maxwell’s spot (MS) or Haidinger’s brushes (HB). To simulate MS and HB, an existing computational model of polarization-dependent properties of the human macula was extended by incorporating neuronal adaptation to stabilized retinal images. The model predicted that polarized light modifies the appearance of MS leading to the perception of a novel phenomenon. The model also predicted a correlation between the observed diameters of MS and HB. Predictions were tested psychophysically in human observers, whose measured differences in the diameters of each entoptic phenomenon generated with depolarized and linearly polarized light were consistent with the model simulations. These findings support a common origin of each phenomenon, and are relevant to the clinical use of polarization stimuli in detecting and monitoring human eye disorders, including macular degeneration. We conclude: (i) MS and HB both result from differential light absorption through a radial diattenuator, compatible with the arrangement of macular pigments in Henle fibres; (ii) the morphology of MS is dependent on the degree of linear polarization; (iii) perceptual differences between MS and HB result from different states of neural adaptation.