The macular carotenoids: A biochemical overview

Association between circulating antioxidants and sleep disorders: comprehensive results from NHANES 2017-2018

Background: Oxidative stress plays an important role in the occurrence and pathological process of numerous human diseases. A bidirectional relationship was found between sleep disorders and oxidative stress. However, the association between circulating antioxidant levels and the risk of sleep disorders at the population-scale has yet to be determined. Methods: We used the dataset from the National Health and Nutrition Examination Survey (NHANES) 2017-2018 data release cycle and included 3062 adult participants aged 25-75 years. The circulating antioxidants levels in serum were measured, and the sleep status was assessed by self-reported sleep disorder questionnaire tests. We investigated the association and exposure-response relationship between the 12 main circulating antioxidants and sleep disorders using a generalized additive model (GAM), multiple linear, binary logistic, and restricted cubic spline (RCS) regression models. Multiple sensitivity analyses were conducted to validate the results of our study. Results: Significantly lower serum concentrations of ten antioxidants were observed in the group which had trouble sleeping symptoms compared to the control group. After adjusting for all the covariates, the binary logistic regression models indicated that six of the circulating antioxidants including alpha-carotene, alpha-cryptoxanthin, trans-beta-carotene, beta-cryptoxanthin, lutein and zeaxanthin, and vitamin C, showed a significant association with the risk of overall trouble sleeping symptoms, with odds ratios corresponding to 0.88 (95% CI: 0.80-0.96), 0.74 (95% CI: 0.62-0.87), 0.87 (95% CI: 0.79-0.97), 0.85 (95% CI: 0.75-0.95), 0.72 (95% CI: 0.61-0.84), and 0.83 (95% CI: 0.74-0.93), respectively. The GAM and multiple linear regression revealed similar associations whereas the RCS regression models further confirmed their significant negative exposure-response relationship. Conclusions: The circulating carotenoids and vitamin C levels were negatively correlated with the risk of sleep disorders. Higher circulating antioxidant levels were significantly associated with a lower risk of sleep disorders. The potential health risk of low circulating antioxidants levels was higher in the female population than in the male population.

Macular Pigment Assessment in Indian Population Using Degree of Polarization Threshold: Impact of Diet on Macular Pigment Density

Purpose

To determine macular pigment (MP) density scores in healthy Indians and examine correlations with demographic and lifestyle variables.

Methods

We observed 484 Indians without an ocular pathology. Body mass index (BMI) and self-reported lifestyle factors (sunglasses usage, physical activity, and smoking) were noted. MP density was assessed as the threshold of perception of the shadow of their macular pigments on their retina using a new MP assessment tool (MP-eye). Lutein and zeaxanthin intake was assessed using a prevalidated questionnaire regionally designed for the Indian diet. Clusters of participants were created for statistical analysis based on MP-eye scores secondarily to detect any relevant effects in very low, low, medium, and high ranges of MPs.

Results

Data analyzed included 235 males and 249 females with mean age of 36.1 ± 12.9 years (range, 14-72). The median MP-eye score was 6 (range, 0-10, with 10 being high). Most were non-smokers (413, 85.3%) and did not use sunglasses (438, 90.5%), and 314 (64.9%) had low physical activity. Diabetes was present in 62 participants (12.8%) and hypertension in 53 (10.9%). Advancing age (r = -0.209; P < 0.000) and BMI (r = -0.094; P = 0.038) had weak negative correlation with MP-eye scores. Hypertension was less prevalent (7/88) in the cluster with the highest median MP-eye score (P = 0.033). Dietary intake of MPs and other lifestyle factors did not correlate significantly with MP-eye score overall or when analyzed in clusters.

Conclusions

MP-eye scores of an Indian population were normally distributed. Higher age, high BMI, and presence of hypertension were weakly associated with lower MP-eye scores. The impact of diet on MPs requires further evaluation.

Translational Relevance

This normative regional database enables risk stratification of macular degeneration.

Current Insights on the Photoprotective Mechanism of the Macular Carotenoids, Lutein and Zeaxanthin: Safety, Efficacy and Bio-Delivery

Ocular health has emerged as one of the major issues of global health concern with a decline in quality of life in an aging population, in particular and rise in the number of associated morbidities and mortalities. One of the chief reasons for vision impairment is oxidative damage inflicted to photoreceptors in rods and cone cells by blue light as well as UV radiation. The scenario has been aggravated by unprecedented rise in screen-time during the COVID and post-COVID era. Lutein and Zeaxanthin are oxygenated carotenoids with proven roles in augmentation of ocular health largely by virtue of their antioxidant properties and protective effects against photobleaching of retinal pigments, age-linked macular degeneration, cataract, and retinitis pigmentosa. These molecules are characterized by their characteristic yellow-orange colored pigmentation and are found in significant amounts in vegetables such as corn, spinach, broccoli, carrots as well as fish and eggs. Unique structural signatures including tetraterpenoid skeleton with extensive conjugation and the presence of hydroxyl groups at the end rings have made these molecules evolutionarily adapted to localize in the membrane of the photoreceptor cells and prevent their free radical induced peroxidation. Apart from the benefits imparted to ocular health, lutein and zeaxanthin are also known to improve cognitive function, cardiovascular physiology, and arrest the development of malignancy. Although abundant in many natural sources, bioavailability of these compounds is low owing to their long aliphatic backbones. Under the circumstances, there has been a concerted effort to develop vegetable oil-based carriers such as lipid nano-emulsions for therapeutic administration of carotenoids. This review presents a comprehensive update of the therapeutic potential of the carotenoids along with the challenges in achieving an optimized delivery tool for maximizing their effectiveness inside the body.

Combined 6-benzylaminopurine and H2O2 stimulate the astaxanthin biosynthesis in Xanthophyllomyces dendrorhous

Astaxanthin is one of the most attractive carotenoids due to its high antioxidant activity and beneficial biological properties, while Xanthophyllomyces dendrorhous is one of its main microbial sources. Since astaxanthin is synthesized as a response to oxidative stress, several oxidative agents have been evaluated to increase X. dendrorhous astaxanthin yields. However, the extent of the stimulation is determined by the cellular damage caused by the applied oxidative agent. Phytohormones have also been reported as stimulants of astaxanthin biosynthesis acting directly on its metabolic pathway and indirectly promoting cellular resistance to reactive oxygen species. We reasoned that both oxidative agents and phytohormones lead to increased astaxanthin synthesis, but the latter could mitigate the drawbacks of the former. Thus, here, the stimulation on astaxanthin biosynthesis, as well as the cellular and transcriptional responses of wild type X. dendrorhous to phytohormones (6-benzylaminopurine, 6-BAP; abscisic acid, ABA; and indole-3-acetic acid, IAA), and oxidative agents (glutamate, menadione, H2O2, and/or Fe2+) were evaluated as a single or combined treatments. ABA and 6-BAP were the best individual stimulants leading to 2.24- and 2.60-fold astaxanthin biosynthesis increase, respectively. Nevertheless, the effect of combined 6-BAP and H2O2 led to a 3.69-fold astaxanthin synthesis increase (0.127 ± 0.018 mg astaxanthin/g biomass). Moreover, cell viability (> 82.75%) and mitochondrial activity (> 82.2%) remained almost intact in the combined treatment (6-BAP + H2O2) compared to control (< 52.17% cell viability; < 85.3% mitochondrial activity). On the other hand, mRNA levels of hmgR, idi, crtYB, crtR, and crtS, genes of the astaxanthin biosynthetic pathway, increased transiently along X. dendrorhous fermentation due to stimulations assayed in this study. KEY POINTS: • Combined 6-BAP and H2O2 is the best treatment to increase astaxanthin yields in X. dendrorhous. • 6-BAP preserves cell integrity under oxidative H2O2 stress conditions. • 6-BAP and H2O2 increase transcriptional responses of hmgR, idi, and crt family genes transiently.

Scavenging of Cation Radicals of the Visual Cycle Retinoids by Lutein, Zeaxanthin, Taurine, and Melanin

In the retina, retinoids involved in vision are under constant threat of oxidation, and their oxidation products exhibit deleterious properties. Using pulse radiolysis, this study determined that the bimolecular rate constants of scavenging cation radicals of retinoids by taurine are smaller than 2 × 107 M-1s-1 whereas lutein scavenges cation radicals of all three retinoids with the bimolecular rate constants approach the diffusion-controlled limits, while zeaxanthin is only 1.4-1.6-fold less effective. Despite that lutein exhibits greater scavenging rate constants of retinoid cation radicals than other antioxidants, the greater concentrations of ascorbate in the retina suggest that ascorbate may be the main protectant of all visual cycle retinoids from oxidative degradation, while α-tocopherol may play a substantial role in the protection of retinaldehyde but is relatively inefficient in the protection of retinol or retinyl palmitate. While the protection of retinoids by lutein and zeaxanthin appears inefficient in the retinal periphery, it can be quite substantial in the macula. Although the determined rate constants of scavenging the cation radicals of retinol and retinaldehyde by dopa-melanin are relatively small, the high concentration of melanin in the RPE melanosomes suggests they can be scavenged if they are in proximity to melanin-containing pigment granules.

Treatment of Dry Eye Disease (DED) in Asia: Strategies for Short Tear Film Breakup Time-Type DED

Dry eye disease (DED) is a multifactorial disorder in which tear fluid homeostasis is lost, resulting in increased tear film osmolarity and ocular surface irritation. In Asia, the short tear film breakup time-type DED, which has become a global problem in recent years, is common. While the mainstay of DED treatment in the West is the suppression of inflammation, the first goal of treatment is the stabilization of the tear film in Asia. To date, artificial tears and steroid eye drops have been the main treatment for DED. However, artificial tears require frequent administration of eye drops and thus pose adherence problems, while steroids have problems with side-effects (cataracts, increased intraocular pressure). This review evaluates the new generation therapies in Asia based on what is known about them and demonstrates that they are more effective for DED than traditional therapies such as artificial tears and steroids. Based on considerations, it is proposed that the optimal treatment for the short tear film breakup time-type DED is the initial application of mucin-secretion-enhancing eye drops (long-acting diquafosol) and oral supplements; and if additional treatment is needed, cyclosporine eye drops and the adjunctive therapies presented in this review are added.

An overview of food lipids toward food lipidomics

Increasing evidence regarding lipids' beneficial effects on human health has changed the common perception of consumers and dietary officials about the role(s) of food lipids in a healthy diet. However, lipids are a wide group of molecules with specific nutritional and bioactive properties. To understand their true nutritional and functional value, robust methods are needed for accurate identification and quantification. Specific analytical strategies are crucial to target specific classes, especially the ones present in trace amounts. Finding a unique and comprehensive methodology to cover the full lipidome of each foodstuff is still a challenge. This review presents an overview of the lipids nutritionally relevant in foods and new trends in food lipid analysis for each type/class of lipids. Food lipid classes are described following the LipidMaps classification, fatty acids, endocannabinoids, waxes, C8 compounds, glycerophospholipids, glycerolipids (i.e., glycolipids, betaine lipids, and triglycerides), sphingolipids, sterols, sercosterols (vitamin D), isoprenoids (i.e., carotenoids and retinoids (vitamin A)), quinones (i.e., coenzyme Q, vitamin K, and vitamin E), terpenes, oxidized lipids, and oxylipin are highlighted. The uniqueness of each food group: oil-, protein-, and starch-rich, as well as marine foods, fruits, and vegetables (water-rich) regarding its lipid composition, is included. The effect of cooking, food processing, and storage, in addition to the importance of lipidomics in food quality and authenticity, are also discussed. A critical review of challenges and future trends of the analytical approaches and computational methods in global food lipidomics as the basis to increase consumer awareness of the significant role of lipids in food quality and food security worldwide is presented.

Solid lipid nanoparticles of lutein with improved dissolution behavior and oral absorption

The present study aimed to develop solid lipid nanoparticles of lutein (SLN/LT) with improved dissolution behavior and oral absorption. SLN/LT were prepared by a flash nanoprecipitation method using a multi-inlet vortex mixer, and their physicochemical, photochemical, and pharmacokinetic properties were evaluated. The mean particle size of SLN/LT re-dispersed in water was 237 nm, and small spherical particles with no significant aggregation were observed. LT significantly generated singlet oxygen upon exposure to pseudo-sunlight (250 W/m2, 1 h), suggesting its high photoreactivity. The remaining LT in LT solution, crystalline LT, and SLN/LT after irradiation with pseudo-sunlight (250 W/m2, 2 h) were 56.3, 86.7, and 101%, respectively. SLN/LT showed improved dissolution behavior of LT in simulated intestinal fluid, and the dissolved amounts of LT at 2 h were at least 50 times higher than that of crystalline LT. Orally administered SLN/LT (100 mg-LT/kg) exhibited enhanced oral absorption of LT, as evidenced by a relative bioavailability of 3.7 to crystalline LT in rats. SLN/LT may be a promising dosage form for orally available LT supplements, possibly leading to enhanced nutritional functions of LT.

Quantitative Profiling of Carotenoids, Tocopherols, Phytosterols, and Fatty Acids in the Flower Petals of Ten Marigold (Tagetes spp. L.) Cultivars

Marigold (Tagetes spp.) flower petals are the most vital sources of carotenoids, especially lutein esters, for the production of natural lutein to use for food, feed, and pharmaceutical industries. Several marigold cultivars are cultivated globally; however, their lutein ester composition and contents have not been widely investigated. Considering this, this study aimed to identify and quantify prominent carotenoid esters from the flower petals of ten marigold cultivars by liquid chromatography (LC)-diode-array detection (DAD)-mass spectrometry (MS). In addition, tocopherols, phytosterols, and fatty acids were analyzed by gas chromatography (GC)-flame ionization detection (FID) and GC-MS. Furthermore, the 2,2'-azino-bis(3-ethylbenzothiazoline-6-sulfonic acid (ABTS•+) and 2,2-diphenyl-1-picrylhydrazyl (DPPH•) radical scavenging abilities of lipophilic extracts were determined. The total carotenoid contents varied significantly (p < 0. 05, Tukey HSD) among cultivars, ranging from 25.62 (cv. Alaska)-2723.11 µg/g fresh weight (cv. Superboy Orange). Among the five major lutein-diesters, (all-E)-lutein-3-O-myristate-3'-O-palmitate and lutein dipalmitate were predominant. Among the studied cultivars, α-tocopherol was recorded, ranging from 167.91 (cv. Superboy Yellow) to 338.50 µg/g FW (cv. Taishan Orange). Among phytosterols, β-sitosterol was the most prevalent phytosterol, ranging between 127.08 (cv. Superboy Yellow) and 191.99 µg/g FW (cv. Taishan Yellow). Palmitic acid (C16:0; 33.36-47.43%) was the most dominant among the fatty acids. In this study, the highest contents of lutein were recorded from cv. Superboy Orange; however, due to the substantially higher flower petal yield, the cv. Durango Red can produce the highest lutein yield of 94.45 kg/ha. These observations suggest that cv. Durango Red and cv. Superboy Orange are the ideal candidates for lutein fortification in foods and also for commercial lutein extraction.

Revisiting carotenoids as dietary antioxidants for human health and disease prevention

Humans are unique indiscriminate carotenoid accumulators, so the human body accumulates a wide range of dietary carotenoids of different types and to varying concentrations. Carotenoids were once recognized as physiological antioxidants because of their ability to quench singlet molecular oxygen (1O2). In the 1990s, large-scale intervention studies failed to demonstrate that supplementary β-carotene intake reduces the incidence of lung cancer, although its antioxidant activity was supposed to contribute to the prevention of oxidative stress-induced carcinogenesis. Nevertheless, the antioxidant activity of carotenoids has attracted renewed attention as the pathophysiological role of 1O2 has emerged, and as the ability of dietary carotenoids to induce antioxidant enzymes has been revealed. This review focuses on six major carotenoids from fruit and vegetables and revisits their physiological functions as biological antioxidants from the standpoint of health promotion and disease prevention. β-Carotene 9',10'-oxygenase-derived oxidative metabolites trigger increases in the activities of antioxidant enzymes. Lutein and zeaxanthin selectively accumulate in human macular cells to protect against light-induced macular impairment by acting as antioxidants. Lycopene accumulates exclusively and to high concentrations in the testis, where its antioxidant activity may help to eliminate oxidative damage. Dietary carotenoids appear to exert their antioxidant activity in photo-irradiated skin after their persistent deposition in the skin. An acceptable level of dietary carotenoids for disease prevention should be established because they can have deleterious effects as prooxidants if they accumulate to excess levels. Finally, it is expected that the reason why humans are indiscriminate carotenoid accumulators will be understood soon.

Carotenoids from Starfish Patiria pectinifera: Therapeutic Activity in Models of Inflammatory Diseases

The carotenoids mixture (MC) isolated from the starfish Patiria. pectinifera contains more than 50% astaxanthin, 4-6% each zeaxanthine and lutein, and less pharmacologically active components such as free fatty acids and their glycerides. Astaxanthin, the major component of MC, belongs to the xanthophyll class of carotenoids, and is well known for its antioxidant properties. In this work, in vitro and in vivo studies on the biological activity of MC were carried out. The complex was shown to exhibit anti-inflammatory, anti-allergic and cancer-preventive activity, without any toxicity at a dose of 500 mg/kg. MC effectively improves the clinical picture of the disease progressing, as well as normalizing the cytokine profile and the antioxidant defense system in the in vivo animal models of inflammatory diseases, namely: skin carcinogenesis, allergic contact dermatitis (ACD) and systemic inflammation (SI). In the skin carcinogenesis induced by 7,12-dimethylbenzanthracene, the incidence of papillomas was decreased 1.5 times; 1% MC ointment form in allergic contact dermatitis showed an 80% reduced severity of pathomorphological skin manifestations. Obtained results show that MC from starfish P. pectinifera is an effective remedy for the treatment and prevention of inflammatory processes.

How Do Xanthophylls Protect Lipid Membranes from Oxidative Damage?

Here, we address the problem of the antioxidant activity of carotenoids in biomembranes. The activity of lutein and zeaxanthin in the quenching of singlet oxygen generated by photosensitization was monitored in lipid vesicles using a singlet oxygen-sensitive fluorescent probe and with the application of fluorescence lifetime imaging microscopy. The antioxidant activity of xanthophylls was interpreted on the basis of electron paramagnetic resonance oximetry results showing that xanthophylls constitute a barrier to the penetration of molecular oxygen into lipid membranes: to a greater extent in the 13-cis configuration than in all-trans. These results are discussed in relation to the trans-cis photoisomerization of xanthophylls observed in the human retina. It can be concluded that photoisomerization of xanthophylls is a regulatory mechanism that is important for both the modulation of light filtration through the macula and photoprotection by quenching singlet oxygen and creating a barrier to oxygen permeation to membranes.

An Overview of Lutein in the Lipid Membrane

Lutein, zeaxanthin, and meso-zeaxanthin (a steroisomer of zeaxanthin) are macular pigments. They modify the physical properties of the lipid bilayers in a manner similar to cholesterol. It is not clear if these pigments are directly present in the lipid phase of the membranes, or if they form complexes with specific membrane proteins that retain them in high amounts in the correct place in the retina. The high content of macular pigments in the Henle fiber layer indicates that a portion of the lutein and zeaxanthin should not only be bound to the specific proteins but also directly dissolved in the lipid membranes. This high concentration in the prereceptoral region of the retina is effective for blue-light filtration. Understanding the basic mechanisms of these actions is necessary to better understand the carotenoid-membrane interaction and how carotenoids affect membrane physical properties-such as fluidity, polarity, and order-in relation to membrane structure and membrane dynamics. This review focuses on the properties of lutein.

Mechanistic Understanding of the Antiviral Properties of Pistachios and Zeaxanthin against HSV-1

The search for alternative clinical treatments to fight resistance and find alternative antiviral treatments for the herpes simplex virus (HSV) is of great interest. Plants are rich sources of novel antiviral, pharmacologically active agents that provide several advantages, including reduced side effects, less resistance, low toxicity, and different mechanisms of action. In the present work, the antiviral activity of Californian natural raw (NRRE) and roasted unsalted (RURE) pistachio polyphenols-rich extracts was evaluated against HSV-1 using VERO cells. Two different extraction methods, with or without n-hexane, were used. Results showed that n-hexane-extracted NRRE and RURE exerted an antiviral effect against HSV-1, blocking virus binding on the cell surface, affecting viral DNA synthesis as well as accumulation of ICP0, UL42, and Us11 viral proteins. Additionally, the identification and quantification of phenolic compounds by RP-HPLC-DAD confirmed that extraction with n-hexane exclusively accumulated tocopherols, carotenoids, and xanthophylls. Amongst these, zeaxanthin exhibited strong antiviral activity against HSV-1 (CC50: 16.1 µM, EC50 4.08 µM, SI 3.96), affecting both the viral attachment and penetration and viral DNA synthesis. Zeaxanthin is a dietary carotenoid that accumulates in the retina as a macular pigment. The use of pistachio extracts and derivates should be encouraged for the topical treatment of ocular herpetic infections.

The impact of nutrition on visual cognitive performance in the nutrition, vision, and cognition in sport study

Introduction

The purpose of this study was to examine the influence of nutritional intake on visual perceptual-cognitive performance (VCP) in young healthy adults.

Methods

Ninety-eight healthy men (n = 38) and women (n = 60) aged 18-33 years participated and maintained their usual dietary intake throughout the study. VCP was measured using the NeuroTracker^™ CORE (NT) 3-Dimensional (3-D) software program (15 training sessions) over a 15-day period. Food logs and extensive lifestyle measures including body composition, cardiovascular health, sleep and exercise patterns, and general readiness to perform were collected. Mean intake from 10 food logs collected over the 15 days were analyzed using Nutribase software. Statistical analyses were performed in SPSS using repeated measures ANOVA including significant covariates when appropriate.

Results

Males consumed significantly more calories, macronutrients, cholesterol, choline, and zinc and performed significantly better on VCP than the females. Participants who consumed more than 40% of kcals from carbohydrates (p = 0.038), less than 24% of kcals from protein (p = 0.009), more than 2,000 μg/day lutein/zeaxanthin or more than 1.8 mg/ day vitamin B2 performed significantly better on VCP than those who consumed less than those amounts, respectively.

Discussion

VCP is an important dimension of cognitive function and in the present study is influenced by higher carbohydrate, lutein/ zeaxanthin, and vitamin B2 dietary intake while high protein consumption and the female sex negatively impacted VCP.

Exploring linker's sequence diversity to fuse carotene cyclase and hydroxylase for zeaxanthin biosynthesis

Fusion of catalytic domains can accelerate cascade reactions by bringing enzymes in close proximity. However, the design of a protein fusion and the choice of a linker are often challenging and lack of guidance. To determine the impact of linker parameters on fusion proteins, a library of linkers featuring various lengths, secondary structures, extensions and hydrophobicities was designed. Linkers were used to fuse the lycopene cyclase (crtY) and β-carotene hydroxylase (crtZ) from Pantoea ananatis to create fusion proteins to produce zeaxanthin. The fusion efficiency was assessed by comparing the carotenoids content in a carotenoid-producer Escherichia coli strain. It was shown that in addition to the orientation of the enzymes and the size of the linker, the first amino acid of the linker is also a key factor in determining the efficiency of a protein fusion. The wide range of sequence diversity in our linker library enables the fine tuning of protein fusion and this approach can be easily transferred to other enzyme couples.

Potential roles of dietary zeaxanthin and lutein in macular health and function

Lutein, zeaxanthin, and meso-zeaxanthin are three xanthophyll carotenoid pigments that selectively concentrate in the center of the retina. Humans cannot synthesize lutein and zeaxanthin, so these compounds must be obtained from the diet or supplements, with meso-zeaxanthin being converted from lutein in the macula. Xanthophylls are major components of macular pigments that protect the retina through the provision of oxidant defense and filtering of blue light. The accumulation of these three xanthophylls in the central macula can be quantified with non-invasive methods, such as macular pigment optical density (MPOD). MPOD serves as a useful tool for assessing risk for, and progression of, age-related macular degeneration, the third leading cause of blindness worldwide. Dietary surveys suggest that the dietary intakes of lutein and zeaxanthin are decreasing. In addition to low dietary intake, pregnancy and lactation may compromise the lutein and zeaxanthin status of both the mother and infant. Lutein is found in modest amounts in some orange- and yellow-colored vegetables, yellow corn products, and in egg yolks, but rich sources of zeaxanthin are not commonly consumed. Goji berries contain the highest known levels of zeaxanthin of any food, and regular intake of these bright red berries may help protect against the development of age-related macular degeneration through an increase in MPOD. The purpose of this review is to summarize the protective function of macular xanthophylls in the eye, speculate on the compounds' role in maternal and infant health, suggest the establishment of recommended dietary values for lutein and zeaxanthin, and introduce goji berries as a rich food source of zeaxanthin.

Prenatal Carotenoid Supplementation With Lutein or Zeaxanthin Ameliorates Oxygen-Induced Retinopathy (OIR) in Bco2-/- Macular Pigment Mice

Purpose

Premature infants at risk of retinopathy of prematurity (ROP) miss placental transfer of the carotenoids lutein (L) and zeaxanthin (Z) during the third trimester. We previously demonstrated that prenatal L and Z supplementation raised carotenoid levels in infants at birth in the Lutein and Zeaxanthin in Pregnancy (L-ZIP) study (NCT03750968). Based on their antioxidant effects and bioavailability, we hypothesized that prenatal maternal supplementation with macular carotenoids would reduce the risk of ROP. To test this hypothesis, we utilized "macular pigment mice" genetically engineered to take up L and Z into the retina in a model of oxygen-induced retinopathy (OIR).

Methods

Pregnant Bco2-/- mice were divided into nine experimental subgroups based on the type of supplementation (L, Z, or placebo) and on the maternal supplementation start date corresponding to the three trimesters of human fetal development (E0, E11, and P1). Pups and nursing mothers were exposed to 75% O2 for 5 days (P7-P12) and returned to room air for 5 days (P12-P17). Pups were killed at P12 and P17, and their retinas were analyzed for vaso-obliteration and intravitreal neovascularization.

Results

Pups of pregnant mice supplemented with L or Z had significant reductions in areas of vaso-obliteration and intravitreal neovascularization compared to placebo. Prenatal carotenoid supplementation starting at E0 or E11 was significantly more protective against OIR than postnatal supplementation starting at P1.

Conclusions

Prenatal supplementation with L and Z was beneficial in a mouse OIR model. We recommend testing prenatal L and Z supplementation in future human clinical trials to prevent ROP.

Lutein Encapsulated in PLGA–Phospholipid Nano-Carrier Effectively Mitigates Cytokines by Inhibiting Tumor Necrosis Factor TNF-α and Nuclear Factor NF-κB in Mice Retina

Lutein, a photo- and thermo-labile macular pigment, prevents the retina from suffering ocular inflammation with its antioxidant and anti-inflammatory activity. However, its biological activity is poor due to poor solubility and bioavailability. Therefore, we developed a PLGA NCs (+PL), (poly (lactic-co-glycolic acid) nanocarrier with phospholipid) to improve the biological availability and bioefficacy of lutein in the retina of lipopolysaccharide (LPS)-induced lutein-devoid (LD) mice. The effect of lutein-loaded NCs with/without PL was studied in comparison with micellar lutein. The induction of inflammation by LPS significantly increased the production of nitrites in the LPS-induced group, revealing higher levels of nitric oxide (NO) in the serum (760%) and retina (891%) compared to the control group. Malondialdehyde (MDA) levels in the serum (93%) and retina (205%) of the LPS-induced group were higher compared to the control group. LPS induction resulted in increased protein carbonyls in the serum (481%) and retina (487%) of the LPS group compared to the control group. Further, to conclude, lutein-PLGA NCs (+PL) effectively down-regulated inflammatory complications in the retina.

Green Solvents: Emerging Alternatives for Carotenoid Extraction from Fruit and Vegetable By-Products

Carotenoids have important implications for human health and the food industry due to their antioxidant and functional properties. Their extraction is a crucial step for being able to concentrate them and potentially include them in food products. Traditionally, the extraction of carotenoids is performed using organic solvents that have toxicological effects. Developing greener solvents and techniques for extracting high-value compounds is one of the principles of green chemistry and a challenge for the food industry. This review will analyze the use of green solvents, namely, vegetable oils, supercritical fluids, deep eutectic solvents, ionic liquids, and limonene, combined with nonconventional techniques (ultrasound-assisted extraction and microwave), for carotenoid extraction from fruit and vegetable by-products as upcoming alternatives to organic solvents. Recent developments in the isolation of carotenoids from green solvents and their inclusion in food products will also be discussed. The use of green solvents offers significant advantages in extracting carotenoids, both by decreasing the downstream process of solvent elimination, and the fact that the carotenoids can be included directly in food products without posing a risk to human health.

Twins' Macular Pigment Optical Density Assessment and Relation with SCARB1 Gene Polymorphism

THE AIM OF THE STUDY

to assess the influence of genetic and environmental factors using twin studies and evaluate the associations of SCARB1 gene variants (rs11057841) with AMD and MPOD.

MATERIAL AND METHODS

a total of 108 healthy twins (56 MZ and 52 DZ twins) were tested in this study. The MPOD was measured using the one-wavelength reflectometry method. Fundus reflectance (Visucam 500, reflectance of a single 460 nm wavelength) was used to measure the MPOD levels, MPOD parameters including max and mean optical density (OD), and area and volume. Real-time polymerase chain reaction was used to detect single nucleotide polymorphisms.

RESULTS

we detected a positive correlation of MPOD in the right and left eyes in MZ twin pairs (r = 0.830 and r = 0.860, respectively) (p < 0.0001) and a negative correlation of MPOD in the right and left eyes in DZ twin pairs (r = 0.314 and r = 0.408, respectively) (p < 0.05). The study was able to identify statistically significant differences in mean MPOD values in the right and left eyes between subjects with a wild-type CC genotype and a CT genotype with a risk allele. A decrease in the mean MPOD value was observed in group II with a CT genotype (0.110 d.u.) compared with the CC genotype (0.117 d.u.) in the right eye (p = 0.037) and in the left eye with a CT genotype (0.109 d.u.) compared with a CC genotype in the subjects (0.114 d.u.) (p = 0.038). In the right eye, in group II (0.101-0.128 d.u.), those with a CT genotype (n = 6) with one risk allele had a statistically significantly lower (0.110 d.u.) mean average MPOD value compared with those with a wild-type CC genotype (n = 25) (0.117 d.u.) (p = 0.037).

CONCLUSION

this twin study showed a strong heritability of the retina pigment, which was 86% prevalent in Lithuania. Individuals with a CT genotype of the SCARB1 rs11057841 with a risk allele had statistically significantly lower mean MPOD values in both eyes compared to subjects with a wild-type CC genotype.

Lutein-Fortified Plant-Based Egg Analogs Designed to Improve Eye Health: Formation, Characterization, In Vitro Digestion, and Bioaccessibility

Lutein is a carotenoid found in real eggs that has been reported to have beneficial effects on eye health by reducing the risk of age-related macular degeneration. However, lutein is not often included in plant based (PB) egg analogs. It would, therefore, be advantageous to fortify PB eggs with this health-promoting carotenoid. Moreover, lutein is a natural pigment with a bright red to yellowish color depending on its concentration and environment. It can, therefore, also be used as a plant-based pigment to mimic the desirable appearance of egg yolk. Some of the main challenges to using lutein as a nutraceutical and pigment in PB foods are its poor water-solubility, chemical stability, and bioavailability. In this study, we encapsulated lutein in oil-in-water emulsions, which were then utilized to formulate whole egg analogs. Ribulose-1,5-bisphosphate carboxylase/oxygenase (RuBisCO) protein isolated from a sustainable plant-based source (duckweed) was used to mimic the thermally irreversible heat-set gelling properties of globular egg proteins, with the aim of obtaining a similar cookability and texture as real eggs. The lutein content (80 mg/100 g) of the egg analogs was designed to be at a level where there should be health benefits. The protein (12.5 wt.%) and oil (10 wt.%) contents of the egg analogs were selected to match those of real egg. The effects of oil droplet size and oil type on the bioaccessibility of the encapsulated lutein were examined using the INFOGEST in vitro digestion model. For the emulsions formulated with long chain triglycerides (LCTs, corn oil), lutein bioaccessibility significantly increased when the initial droplet diameter decreased from around 10 to 0.3 μm, which was attributed to more rapid and complete digestion of the lipid phase for smaller droplets. For medium chain triglycerides (MCTs), however, no impact of droplet size on lutein bioaccessibility was observed. A high lutein bioaccessibility (around 80%) could be obtained for both LCTs and MCTs emulsions containing small oil droplets. Thus, both types of oil can be good carriers for lutein. In summary, we have shown that lutein-fortified PB eggs with good digestibility and bioaccessibility can be created, which may play an important role in ensuring the health of those adopting a more plant-based diet.

Carotenoids in Drug Discovery and Medicine: Pathways and Molecular Targets Implicated in Human Diseases

Carotenoids are isoprenoid-derived natural products produced in plants, algae, fungi, and photosynthetic bacteria. Most animals cannot synthesize carotenoids because the biosynthetic machinery to create carotenoids de novo is absent in animals, except arthropods. Carotenoids are biosynthesized from two C20 geranylgeranyl pyrophosphate (GGPP) molecules made from isopentenyl pyrophosphate (IPP) and dimethylallyl pyrophosphate (DMAPP) via the methylerythritol 4-phosphate (MEP) route. Carotenoids can be extracted by a variety of methods, including maceration, Soxhlet extraction, supercritical fluid extraction (SFE), microwave-assisted extraction (MAE), accelerated solvent extraction (ASE), ultrasound-assisted extraction (UAE), pulsed electric field (PEF)-assisted extraction, and enzyme-assisted extraction (EAE). Carotenoids have been reported to exert various biochemical actions, including the inhibition of the Akt/mTOR, Bcl-2, SAPK/JNK, JAK/STAT, MAPK, Nrf2/Keap1, and NF-κB signaling pathways and the ability to increase cholesterol efflux to HDL. Carotenoids are absorbed in the intestine. A handful of carotenoids and carotenoid-based compounds are in clinical trials, while some are currently used as medicines. The application of metabolic engineering techniques for carotenoid production, whole-genome sequencing, and the use of plants as cell factories to produce specialty carotenoids presents a promising future for carotenoid research. In this review, we discussed the biosynthesis and extraction of carotenoids, the roles of carotenoids in human health, the metabolism of carotenoids, and carotenoids as a source of drugs and supplements.

Nanoscale Delivery Systems of Lutein: An Updated Review from a Pharmaceutical Perspective

Carotenoids are natural lipid-soluble pigments that produce yellow to red colors in plants as well as providing bright coloration in vegetables and fruits. Lutein belongs to the xanthophyll subgroup of the carotenoid family, which plays an essential role in photosynthesis and photoprotection in nature. In the human body, lutein, together with its isomer zeaxanthin and its metabolite meso-zeaxanthin, accumulates in the macula of the eye retina, which is responsible for central, high-resolution, and color vision. As a bioactive phytochemical, lutein has essential physiological functions, providing photoprotection against damaging blue light, along with the neutralization of oxidants and the preservation of the structural and functional integrity of cellular membranes. As a potent antioxidant and anti-inflammatory agent, lutein unfortunately has a low bioavailability because of its lipophilicity and a low stability as a result of its conjugated double bonds. In order to enhance lutein stability and bioavailability and achieve its controlled delivery to a target, nanoscale delivery systems, which have great potential for the delivery of bioactive compounds, are starting to be employed. The current review highlights the advantages and innovations associated with incorporating lutein within promising nanoscale delivery systems, such as liposomes, nanoemulsions, polymer nanoparticles, and polymer–lipid hybrid nanoparticles, as well as their unique physiochemical properties.

Chemical characterization of baru oil and its by-product from the northwest region of Minas Gerais, Brazil

This study investigated baru oil and partially defatted baru flour from the northwest region of Minas Gerais, Brazil. The physicochemical characterization of the oil was made by determining the fatty acid profile using gas chromatography, lutein, and α- and β- carotenes by means of high-performance liquid chromatography, and total carotenoids by spectrophotometry. The flour was analyzed for its chemical composition, fiber, and mineral contents. Baru oil presented excellent quality parameters and high contents in unsaturated fatty acids and carotenoids. The flour showed relevant levels of proteins, lipids, and dietary fiber, in addition to having representative mineral contents for food such as manganese, magnesium, and copper. Thus, baru oil and the by-product of its extraction offer a rich chemical composition, and their application may add nutritional value to foods in addition to reducing negative environmental impacts.

Is There an Optimal Combination of AREDS2 Antioxidants Zeaxanthin, Vitamin E and Vitamin C on Light-Induced Toxicity of Vitamin A Aldehyde to the Retina?

Vitamins C and E and zeaxanthin are components of a supplement tested in a large clinical trial-Age-Related Eye Disease Study 2 (AREDS2)-and it has been demonstrated that they can inhibit the progression of age-related macular degeneration. The aim of this study was to determine the optimal combinations of these antioxidants to prevent the phototoxicity mediated by vitamin A aldehyde (ATR), which can accumulate in photoreceptor outer segments (POS) upon exposure to light. We used cultured retinal pigment epithelial cells ARPE-19 and liposomes containing unsaturated lipids and ATR as a model of POS. Cells and/or liposomes were enriched with lipophilic antioxidants, whereas ascorbate was added just before the exposure to light. Supplementing the cells and/or liposomes with single lipophilic antioxidants had only a minor effect on phototoxicity, but the protection substantially increased in the presence of both ways of supplementation. Combinations of zeaxanthin with α-tocopherol in liposomes and cells provided substantial protection, enhancing cell viability from ~26% in the absence of antioxidants to ~63% in the presence of 4 µM zeaxanthin and 80 µM α-tocopherol, and this protective effect was further increased to ~69% in the presence of 0.5 mM ascorbate. The protective effect of ascorbate disappeared at a concentration of 1 mM, whereas 2 mM of ascorbate exacerbated the phototoxicity. Zeaxanthin or α-tocopherol partly ameliorated the cytotoxic effects. Altogether, our results suggest that the optimal combination includes upper levels of zeaxanthin and α-tocopherol achievable by diet and/or supplementations, whereas ascorbate needs to be at a four-fold smaller concentration than that in the vitreous. The physiological relevance of the results is discussed.

Natural Antioxidant Evaluation: A Review of Detection Methods

Antioxidants have drawn the attention of the scientific community due to being related to the prevention of various degenerative diseases. The antioxidant capacity has been extensively studied in vitro, and different methods have been used to assess its activity. However, the main issues related to studying natural antioxidants are evaluating whether these antioxidants demonstrate a key role in the biological system and assessing their bioavailability in the organism. The majority of outcomes in the literature are controversial due to a lack of method standardization and their proper application. Therefore, this study aims to compile the main issues concerning the natural antioxidant field of study, comparing the most common in vitro methods to evaluate the antioxidant activity of natural compounds, demonstrating the antioxidant activity in biological systems and the role of the main antioxidant enzymes of redox cellular signaling and explaining how the bioavailability of bioactive compounds is evaluated in animal models and human clinical trials.

Insights on the Bioaccessibility of Natural Pigments from Diatom Chaetoceros calcitrans

This study aimed to investigate the bioaccessibility of carotenoids and chlorophylls from the biomass of microalgae Chaetoceros calcitrans. The samples were submitted to an in vitro digestion protocol, and the compounds were determined by HPLC-PDA-MS/MS. A total of 13 compounds were identified in all tests. After in vitro digestion, the relative bioaccessibility of carotenoids and chlorophylls ranged from 4 to 58%. The qualitative profile of carotenoids reflected the initial sample, with all-E-zeaxanthin (57.2%) being the most bioaccessible compound, followed by all-E-neochrome (31.26%), the latter being reported for the first time in the micellar fraction. On the other hand, among the chlorophylls only pheophytin a (15.01%) was bioaccessible. Furthermore, a chlorophyll derivative (Hydroxypheophytin a’) was formed after in vitro digestion. Considering all compounds, xanthophylls (12.03%) and chlorophylls (12.22%) were significantly (p < 0.05) more bioaccessible than carotenes (11.22%). Finally, the considerable individual bioaccessibilities found, especially for zeaxanthin, demonstrate the bioactive potential of this bioresource. However, the large reduction in the totality of compounds after in vitro digestion suggests that additional technological strategies should be explored in the future to increase the efficiency of micellarization and enhance its bioactive effects.

Stevia (Stevia rebaudiana) Improves Carotenoid Content in Eggs When Fed to Laying Hens

Stevia rebaudiana Bertoni is a shrub with leaves that have a high concentration of carotenoids such as lutein and zeaxanthin. Egg yolks are a bioavailable source of lutein and zeaxanthin. The consumption of these carotenoids has been linked with improved human health. To investigate the impact of dried stevia leaves at 0%, 1% and 2% on the quality variables, the chemical composition and antioxidant content of eggs, the experiment involved 90 Hy-Line Brown laying hens, housed in 30 enriched layer cages, in groups of three from 22 to 26 weeks of age. The impact on the internal qualities of stored eggs was also examined. Yolks from hens fed stevia had an enriched color compared with the controls. At the end of the experiment, the whole egg, without shell, of birds fed 2% stevia had a higher total carotenoid content (p < 0.001) compared with birds fed 1% and 0% stevia, i.e., 5.16 (µg/g), 4.23 (µg/g) and 2.96 (µg/g), respectively. Storage reduced albumen height and increased albumen pH (p < 0.001). Stevia supplementation did not interact (p > 0.05) with storage time among the egg quality variables. Consuming eggs from hens fed stevia may increase carotenoids in human diet.

Carotenoids: Dietary Sources, Extraction, Encapsulation, Bioavailability, and Health Benefits-A Review of Recent Advancements

Natural carotenoids (CARs), viz. β-carotene, lutein, astaxanthin, bixin, norbixin, capsanthin, lycopene, canthaxanthin, β-Apo-8-carotenal, zeaxanthin, and β-apo-8-carotenal-ester, are being studied as potential candidates in fields such as food, feed, nutraceuticals, and cosmeceuticals. CAR research is advancing in the following three major fields: (1) CAR production from natural sources and optimization of its downstream processing; (2) encapsulation for enhanced physical and chemical properties; and (3) preclinical, clinical, and epidemiological studies of CARs’ health benefits. This review critically discusses the recent developments in studies of the chemistry and antioxidant activity, marketing trends, dietary sources, extraction, bioaccessibility and bioavailability, encapsulation methods, dietary intake, and health benefits of CARs. Preclinical, clinical, and epidemiological studies on cancer, obesity, type 2 diabetes (T2D), cardiovascular diseases (CVD), osteoporosis, neurodegenerative disease, mental health, eye, and skin health are also discussed.

Investigation of Serum and Macular Carotenoids in Central Serous Chorioretinopathy

Purpose

This study aimed to evaluate serum lutein and zeaxanthin levels and macular pigment optical density (MPOD) in central serous chorioretinopathy (CSC).

Methods

Fifty-four patients with acute CSC (28–56 years old; 44 men and 10 women) and 62 matched controls were enrolled. Serum lutein and zeaxanthin were measured using the high-performance liquid chromatography–tandem mass spectrometry (HPLC–MS/MS) method. MPOD was measured at 7° of eccentricity and reported in parameters as “max” and “mean” optical density (OD) (Visucam 200; Carl Zeiss Meditec). MPOD was re-measured in 9 patients whose subretinal fluid was absorbed.

Results

The average max OD and the mean OD in CSC were 0.275 ± 0.047 d.u. and 0.098 ± 0.018 d.u., respectively, which were significantly lower than the control (p &lt; 0.001). The average MPOD value in the unaffected eyes of patients with CSC was 0.298 ± 0.045 for max OD, 0.106 ± 0.017 for mean OD, and both were significantly lower compared with the affected eyes (p &lt; 0.001 for max OD, p = 0.01 for mean OD). In the 9 follow-up patients, the decrease in MPOD was partially recovered. The mean serum level was 409.80 ± 182.52 ng/ml for lutein and 22.97 ± 12.23 ng/ml for zeaxanthin in patients with CSC. In controls, the mean serum level was 393.38 ± 202.44 ng/ml for lutein and 22.16 ± 10.12 ng/ml for zeaxanthin. The difference was not statistically significant (p = 0.649, p = 0.698, respectively).

Conclusion

MPOD decreased within 7° of eccentricity in CSC without serum lutein and zeaxanthin changes. The decrease may be due to the subretinal fluid. Whether local oxidative stress is involved in CSC and the supplementation with lutein and zeaxanthin is helpful for CSC requires further investigation.

The Associations of Plasma Carotenoids and Vitamins With Risk of Age-Related Macular Degeneration: Results From a Matched Case-Control Study in China and Meta-Analysis

Background and Purpose

Data from studies support a beneficial effect of carotenoids and vitamins on an age-related macular degeneration (AMD) risk. However, studies on the relations between blood levels of these nutrients and AMD are limited and provided conflicting results. The objective of this case-control study and meta-analysis was to examine whether the blood concentrations of carotenoids and vitamins were associated with the risk of AMD.

Methods

A total of 164 cases of AMD and an equal number of controls are individually matched according to age and gender among the participants, who provided blood samples in the Xi'an Eye Study. Plasma carotenoids and vitamins were measured using reversed-phase high-performance liquid chromatography. Bonferroni-corrected covariate-adjusted conditional logistic regression were used to estimate AMD risk by category of these nutrients in the multivariable-adjusted model. Nine studies were identified for the meta-analysis and calculated pooled risk estimates by means of a random-effects model.

Results

Plasma concentrations of examined carotenoids and vitamins were significantly lower in patients with AMD than those in controls. Plasma concentrations of examined carotenoids and vitamins were significantly lower in patients with AMD than those in controls. After a multivariate adjustment for body mass index, blood cholesterol, and other lifestyle risk factors, higher lutein/zeaxanthin content in plasma was significantly associated with a decreased risk of AMD, and the odds ratio (OR) comparing the top and bottom tertiles was 0.21 (95% CI: 0.05, 0.84; P_trend = 0.024). Associations for β-carotenes (OR: 0.11; 95% CI: 0.02, 0.50; P_trend < 0.001), and β-cryptoxanthin (OR: 0.08, 95% CI: 0.02, 0.39; P_trend < 0.001) were similar to that for lutein/zeaxanthin. Inverse associations were also observed for a higher level of retinol (OR: 0.14, 95% CI: 0.03, 0.61; P_trend = 0.006) and α-tocopherol (OR: 0.25, 95% CI: 0.06, 0.98; P_trend = 0.006). In the meta-analysis, a protective effect was detected for AMD among the participants with high blood lutein/zeaxanthin level (OR: 0.53, 95% CI: 0.40, 0.72, P < 0.001), compared to those with low level. Similar inverse associations were seen for β-carotene (OR: 0.48, 95% CI: 0.28, 0.84, P = 0.010), β-cryptoxanthin (OR: 0.48, 95% CI: 0.23, 1, P = 0.049), lycopene (OR: 0.70, 95% CI: 0.54, 0.90, P = 0.006) and α-tocopherol (OR: 0.50, 95% CI: 0.31, 0.81, P = 0.005).

Conclusions

Results of the case-control study were consistent with findings from the meta-analysis, indicating that higher concentrations of carotenoids and vitamins were inversely associated with the AMD risk. Our finding supports the current notion that these nutrients are likely to affect the development of AMD and may help to refine the strategies for the prevention of age-related eye diseases.

Toxic effect of BDE-47 on the marine alga Skeletonema costatum: Population dynamics, photosynthesis, antioxidation and morphological changes

The toxic effects of 2,2',4,4'-tetrabromodiphenyl ether (BDE-47) on the marine alga Skeletonema costatum were studied, including the population dynamics, chlorophyll fluorescence characteristics, pigment content, superoxide dismutase (SOD) activity, malondialdehyde (MDA) content and morphology. High doses (200-600 μg L^-1) of BDE-47 significantly suppressed the population growth of S. costatum, with a 96 h EC₅₀ value of 293 μg L^-1. Photosynthetic parameters (F_v/F_m, rETR_max and Φ_PSⅡ) of photosystem II (PSII) were significantly inhibited with increasing BDE-47 concentrations. The chlorophyll c (chl c) concentration was also inhibited by exposure to BDE-47. In contrast, chl a and carotenoid concentrations were elevated after exposure to high concentrations of BDE-47 for 72 and 96 h. The SOD activity was generally higher at concentrations of 100-600 μg L^-1 than those of the control when the exposure time was less than 48 h. With increasing time, the SOD activity generally decreased, and significantly higher SOD activity only occurred in the treatment with high doses of BDE-47. High MDA contents occurred after exposure for 96 h in all BDE-47 treatments. With increasing BDE-47 concentrations, drastic deformation of the silicious valve and detachment of the strutted processes were found. In addition, drastic decreases in the BDE-47 concentration in culture medium indicated the bioaccumulation of BDE-47 by S. costatum. Our results revealed multiple responses of S. costatum to BDE-47 exposure, and indicated the potential risk of BDE-47 in the East China Sea based on these responses.

Bacterial Carotenoids: Extraction, Characterization, and Applications

Natural carotenoids are secondary metabolites that exhibit antioxidant, anti-inflammatory, and anti-cancer properties. These types of compounds are highly demanded by pharmaceutical, cosmetic, nutraceutical, and food industries, leading to the search for new natural sources of carotenoids. In recent years, the production of carotenoids from bacteria has become of great interest for industrial applications. In addition to carotenoids with C40-skeletons, some bacteria have the ability to synthesize characteristic carotenoids with C30-skeletons. In this regard, a great variety of methodologies for the extraction and identification of bacterial carotenoids has been reported and this is the first review that condenses most of this information. To understand the diversity of carotenoids from bacteria, we present their biosynthetic origin in order to focus on the methodologies employed in their extraction and characterization. Special emphasis has been made on high-performance liquid chromatography-mass spectrometry (HPLC-MS) for the analysis and identification of bacterial carotenoids. We end up this review showing their potential commercial use. This review is proposed as a guide for the identification of these metabolites, which are frequently reported in new bacteria strains.

Growth and Carotenoid Contents of Intercropped Vegetables in Building-Integrated Urban Agriculture

Sustainable food security due to climate and social change is more important than ever. This study was conducted to increase plant growth and bioactive contents using intercropping technology in urban agriculture. Tomatoes (Solanum lycopersicum L.) and sunflowers (Helianthus annuus L.) were intercropped in different ratios in outdoor rooftop, and lettuce (Lactuca savita L.) was grown with chicory (Cichorium intybus. L.) in the indoor LED plant growth chambers. Carotenoids in plant foods were analyzed using an ultraperformance liquid chromatography with photodiode array detection. Chlorophyll contents were determined by the soil analysis development chlorophyll meter. Tomatoes planted with sunflowers (3 : 1) had a significantly larger stem diameter ( $p<0.05$ ), a large number of leaves ( $p<0.05$ ), and significantly higher lycopene at d88 ( $p<0.05$ ), d102 ( $p<0.001$ ), and d115 ( $p<0.01$ ), and β-carotene contents at d102 ( $p<0.05$ ) as compared to those of monocultured tomatoes. Lettuce planted in a ratio of 1 : 3 with lettuce and chicory had significantly higher contents of chlorophyll ( $p<0.05$ ), β-carotene ( $p<0.05$ ), and lutein ( $p<0.01$ ), than lettuce planted alone. On the other hand, intercropping of chicory and lettuce did not have a beneficial effect on the growth and carotenoid content of chicory. The current study indicates that plant growth and carotenoid content can be substantially modified by cocultivation, and the effects may vary depending on the type of plant and the crop ratio.

Biochemical and Immunological implications of Lutein and Zeaxanthin

Throughout history, nature has been acknowledged for being a primordial source of various bioactive molecules in which human macular carotenoids are gaining significant attention. Among 750 natural carotenoids, lutein, zeaxanthin and their oxidative metabolites are selectively accumulated in the macular region of living beings. Due to their vast applications in food, feed, pharmaceutical and nutraceuticals industries, the global market of lutein and zeaxanthin is continuously expanding but chemical synthesis, extraction and purification of these compounds from their natural repertoire e.g., plants, is somewhat costly and technically challenging. In this regard microbial as well as microalgal carotenoids are considered as an attractive alternative to aforementioned challenges. Through the techniques of genetic engineering and gene-editing tools like CRISPR/Cas9, the overproduction of lutein and zeaxanthin in microorganisms can be achieved but the commercial scale applications of such procedures needs to be done. Moreover, these carotenoids are highly unstable and susceptible to thermal and oxidative degradation. Therefore, esterification of these xanthophylls and microencapsulation with appropriate wall materials can increase their shelf-life and enhance their application in food industry. With their potent antioxidant activities, these carotenoids are emerging as molecules of vital importance in chronic degenerative, malignancies and antiviral diseases. Therefore, more research needs to be done to further expand the applications of lutein and zeaxanthin.

Retinal pigment epithelium 65 kDa protein (RPE65): An update

Vertebrate vision critically depends on an 11-cis-retinoid renewal system known as the visual cycle. At the heart of this metabolic pathway is an enzyme known as retinal pigment epithelium 65 kDa protein (RPE65), which catalyzes an unusual, possibly biochemically unique, reaction consisting of a coupled all-trans-retinyl ester hydrolysis and alkene geometric isomerization to produce 11-cis-retinol. Early work on this isomerohydrolase demonstrated its membership to the carotenoid cleavage dioxygenase superfamily and its essentiality for 11-cis-retinal production in the vertebrate retina. Three independent studies published in 2005 established RPE65 as the actual isomerohydrolase instead of a retinoid-binding protein as previously believed. Since the last devoted review of RPE65 enzymology appeared in this journal, major advances have been made in a number of areas including our understanding of the mechanistic details of RPE65 isomerohydrolase activity, its phylogenetic origins, the relationship of its membrane binding affinity to its catalytic activity, its role in visual chromophore production for rods and cones, its modulation by macromolecules and small molecules, and the involvement of RPE65 mutations in the development of retinal diseases. In this article, I will review these areas of progress with the goal of integrating results from the varied experimental approaches to provide a comprehensive picture of RPE65 biochemistry. Key outstanding questions that may prove to be fruitful future research pursuits will also be highlighted.

Dietary Supplementation of Antioxidant Compounds Prevents Light-Induced Retinal Damage in a Rat Model

Light-induced retinal damage (LD) is characterized by the accumulation of reactive oxygen species leading to oxidative stress and photoreceptor cell death. The use of natural antioxidants has emerged as promising approach for the prevention of LD. Among them, lutein and cyanidin-3-glucoside (C3G) have been shown to be particularly effective due to their antioxidant and anti-inflammatory activity. However, less is known about the possible efficacy of combining them in a multicomponent mixture. In a rat model of LD, Western blot analysis, immunohistochemistry and electroretinography were used to demonstrate that lutein and C3G in combination or in a multicomponent mixture can prevent oxidative stress, inflammation, gliotic and apoptotic responses thus protecting photoreceptor cells from death with higher efficacy than each component alone. Combined efficacy on dysfunctional electroretinogram was also demonstrated by ameliorated rod and cone photoreceptor responses. These findings suggest the rationale to formulate multicomponent blends which may optimize the partnering compounds bioactivity and bioavailability.

Metabolic engineering for high yield synthesis of astaxanthin in Xanthophyllomyces dendrorhous

Astaxanthin is a carotenoid with a number of assets useful for the food, cosmetic and pharmaceutical industries. Nowadays, it is mainly produced by chemical synthesis. However, the process leads to an enantiomeric mixture where the biologically assimilable forms (3R, 3'R or 3S, 3'S) are a minority. Microbial production of (3R, 3'R) astaxanthin by Xanthophyllomyces dendrorhous is an appealing alternative due to its fast growth rate and easy large-scale production. In order to increase X. dendrorhous astaxanthin yields, random mutant strains able to produce from 6 to 10 mg/g dry mass have been generated; nevertheless, they often are unstable. On the other hand, site-directed mutant strains have also been obtained, but they increase only the yield of non-astaxanthin carotenoids. In this review, we insightfully analyze the metabolic carbon flow converging in astaxanthin biosynthesis and, by integrating the biological features of X. dendrorhous with available metabolic, genomic, transcriptomic, and proteomic data, as well as the knowledge gained with random and site-directed mutants that lead to increased carotenoids yield, we propose new metabolic engineering targets to increase astaxanthin biosynthesis.

A Systematic Review of Carotenoids in the Management of Diabetic Retinopathy

Diabetic retinopathy, which was primarily regarded as a microvascular disease, is the leading cause of irreversible blindness worldwide. With obesity at epidemic proportions, diabetes-related ocular problems are exponentially increasing in the developed world. Oxidative stress due to hyperglycemic states and its associated inflammation is one of the pathological mechanisms which leads to depletion of endogenous antioxidants in retina in a diabetic patient. This contributes to a cascade of events that finally leads to retinal neurodegeneration and irreversible vision loss. The xanthophylls lutein and zeaxanthin are known to promote retinal health, improve visual function in retinal diseases such as age-related macular degeneration that has oxidative damage central in its etiopathogenesis. Thus, it can be hypothesized that dietary supplements with xanthophylls that are potent antioxidants may regenerate the compromised antioxidant capacity as a consequence of the diabetic state, therefore ultimately promoting retinal health and visual improvement. We performed a comprehensive literature review of the National Library of Medicine and Web of Science databases, resulting in 341 publications meeting search criteria, of which, 18 were found eligible for inclusion in this review. Lutein and zeaxanthin demonstrated significant protection against capillary cell degeneration and hyperglycemia-induced changes in retinal vasculature. Observational studies indicate that depletion of xanthophyll carotenoids in the macula may represent a novel feature of DR, specifically in patients with type 2 or poorly managed type 1 diabetes. Meanwhile, early interventional trials with dietary carotenoid supplementation show promise in improving their levels in serum and macular pigments concomitant with benefits in visual performance. These findings provide a strong molecular basis and a line of evidence that suggests carotenoid vitamin therapy may offer enhanced neuroprotective effects with therapeutic potential to function as an adjunct nutraceutical strategy for management of diabetic retinopathy.

Predictors of macular pigment and contrast threshold in Spanish healthy normolipemic subjects (45-65 years) with habitual food intake

Introduction

The dietary carotenoids lutein (L) and zeaxanthin (Z) are transported in the bloodstream by lipoproteins, sequestered by adipose tissue, and eventually captured in the retina where they constitute macular pigment. There are no L&Z dietary intake recommendations nor desired blood/tissue concentrations for the Spanish general population. Our aim was to assess the correlation of L&Z habitual dietary intake (excluding food supplements), resulting serum concentrations and lipid profile with macular pigment optical density (MPOD) as well as the contrast sensitivity (CT), as visual outcome in normolipemic subjects (n = 101) aged 45–65.

Methods

MPOD was measured by heterochromatic flicker photometry, serum L&Z by HPLC, the dietary intake by a 3-day food records and CT using the CGT-1000-Contrast-Glaretester at six stimulus sizes, with and without glare.

Results

Lutein and zeaxanthin concentrations (median) in serum: 0.361 and 0.078 μmol/L, in dietary intake: 1.1 mg L+Z/day. MPOD: 0.34du. L+Z intake correlates with their serum concentrations (rho = 0.333, p = 0.001), which in turn correlates with MPOD (rho = 0.229, p = 0.000) and with fruit and vegetable consumption (rho = 0.202, p = 0.001), but not with lutein+zeaxanthin dietary intake. MPOD correlated with CT, with and without glare (rho ranges: -0.135, 0.160 and -0.121, –0.205, respectively). MPOD predictors: serum L+Z, L+Z/HDL-cholesterol (β-coeficient: -0.91±0.2, _95%CI: -1.3,-0.5) and HDL-cholesterol (R² = 15.9%). CT predictors: MPOD, mainly at medium and smaller visual angles (corresponding to spatial frequencies for which sensitivity declines with age) and gender (β-coefficients ranges: -0.95,-0.39 and -0.13,-0.39, respectively).

Conclusion

A higher MPOD is associated with a lower ratio of L+Z/HDL-cholesterol and with a lower CT (higher contrast sensitivity). The HDL-cholesterol would also act indirectly on the CT improving the visual function.

Light-Modulated Sunscreen Mechanism in the Retina of the Human Eye

The functioning of the human eye in the extreme range of light intensity requires a combination of the high sensitivity of photoreceptors with their photostability. Here, we identify a regulatory mechanism based on dynamic modulation of light absorption by xanthophylls in the retina, realized by reorientation of pigment molecules induced by trans-cis photoisomerization. We explore this photochemically switchable system using chromatographic analysis coupled with microimaging based on fluorescence lifetime and Raman scattering, showing it at work in both isolated human retina and model lipid membranes. The molecular mechanism underlying xanthophyll reorientation is explained in terms of hydrophobic mismatch using molecular dynamics simulations. Overall, we show that xanthophylls in the human retina act as "molecular blinds", opening and closing on a submillisecond timescale to dynamically control the intensity of light reaching the photoreceptors, thus enabling vision at a very low light intensity and protecting the retina from photodegradation when suddenly exposed to strong light.