Elovl4b knockout zebrafish as a model for ocular very-long-chain PUFA deficiency.

Very-long-chain PUFAs (VLC-PUFAs) are a group of lipids with chain lengths >24 carbons, and the ELOVL4 (elongation of very-long-chain FA-4) enzyme is responsible for vertebrate VLC-PUFA biosynthesis. Studies on the role of VLC-PUFAs in vision have been hindered because of the need for adequate animal models to capture the global loss of VLC-PUFAs. Since homozygous Elovl4 ablation is lethal in neonatal mice because of catastrophic drying from the loss of their protective skin barrier, we established a zebrafish (Danio rerio) model of Elovl4 ablation. We generated Elovl4b KO zebrafish by creating a 56-bp deletion mutation in exon 2 of the Elovl4b gene using CRISPR-Cas9. We used GC-MS and LC-MS/MS to analyze the VLC-PUFA and lipid profiles from wild-type and Elovl4b KO fish eyes. We also performed histology and visual-behavioral tests. We found that heterozygous and homozygous Elovl4b KO zebrafish eyes had altered lipid profiles and a significantly lower C30 to C36 VLC-PUFA abundance than wild-type fish. Moreover, Elovl4b+/- and Elovl4b-/- KO larvae had significantly lower motor activity in response to light-dark cycles than their age-matched controls. Elovl4b-/- adult fish showed no obvious differences in gross retinal morphology and lamination compared with wild type, except for the presence of lipid droplets within the retinal pigment epithelial cell layer of Elovl4b-/- fish. Our data indicate that the loss of Elovl4b in zebrafish changes ocular lipid profiles and leads to visual abnormalities and subtle retinal changes. These findings highlight the use of zebrafish as a model for VLC-PUFA depletion and ELOVL4-related dysfunction.

Retinal bioavailability and functional effects of a synthetic very-long-chain polyunsaturated fatty acid in mice.

Rare, nondietary very-long-chain polyunsaturated fatty acids (VLC-PUFAs) are uniquely found in the retina and a few other vertebrate tissues. These special fatty acids play a clinically significant role in retinal degeneration and development, but their physiological and interventional research has been hampered because pure VLC-PUFAs are scarce. We hypothesize that if Stargardt-3 or age-related macular degeneration patients were to consume an adequate amount of VLC-PUFAs that could be directly used in the retina, it may be possible to bypass the steps of lipid elongation mediated by the retina's ELOVL4 enzyme and to delay or prevent degeneration. We report the synthesis of a VLC-PUFA (32:6 n-3) in sufficient quantity to study its bioavailability and functional benefits in the mouse retina. We acutely and chronically gavage fed wild-type mice and Elovl4 rod-cone conditional knockout mice this synthetic VLC-PUFA to understand its bioavailability and its role in visual function. VLC-PUFA-fed wild-type and Elovl4 conditional knockout mice show a significant increase in retinal VLC-PUFA levels in comparison to controls. The VLC-PUFA-fed mice also had improvement in the animals' visual acuity and electroretinography measurements. Further studies with synthetic VLC-PUFAs will continue to expand our understanding of the physiological roles of these unique retinal lipids, particularly with respect to their potential utility for the treatment and prevention of retinal degenerative diseases.

Assessment of Skin Carotenoid Measurement as a Means to Detect Vitamin A Deficiency in Children and Pregnant Women of Nepal.

BACKGROUND: Vitamin A deficiency (VAD) is an ongoing public health concern among children and pregnant women in Nepal despite robust national efforts to screen and treat this vision- and life-threatening condition. OBJECTIVES: This study aimed to evaluate skin carotenoid scores measured using the Veggie Meter as a rapid, noninvasive screening tool for VAD in Nepali children and pregnant women. METHODS: This comparative cross-sectional study enrolled 164 pregnant women and 168 children (aged 8 to 12 y) from public hospitals in three distinct outlying ecological regions of Nepal (Terai, Hill, and Mountain). The primary outcome assessed whether skin carotenoid status could be a biomarker for VAD. We determined skin carotenoid scores using the Veggie Meter and compared them with serum retinol and total carotenoid concentrations assessed by HPLC. Correlation analysis was used to determine bivariate associations between serum retinol and total carotenoid concentrations, and the Veggie Meter assessed skin carotenoid status. Receiver operating characteristics curves were determined, and a P value <0.05 was considered statistically significant. RESULTS: We found that 8.5% of pregnant women and 13.0% of children in this study had severe VAD (serum retinol < 200 ng/mL). There were significant correlations between skin carotenoid scores with serum retinol and total carotenoid concentrations among pregnant women and children (r = 0.253-0.530, P ≤ 0.001). The Veggie Meter detected severe VAD with 57.1% sensitivity and 82.7% specificity in pregnant women and 61.9% sensitivity and 75.9% specificity in children. CONCLUSIONS: Although sensitivity and specificity were moderate for detecting VAD with the Veggie Meter, skin carotenoid assessment using this rapid, noninvasive portable device could still be valuable for high-risk VAD screening in Nepal and similar developing countries with limited access to laboratory measurement of serum vitamin A concentrations.

Systemic Effects of Prenatal Carotenoid Supplementation in the Mother and her Child: The Lutein and Zeaxanthin in Pregnancy (L-ZIP) Randomized Trial -Report Number 1.

BACKGROUND: Adding carotenoids, particularly lutein (L) and zeaxanthin (Z), to prenatal micronutrient formulations has been promoted to enhance infant visual and neural development and to maintain maternal health. Although these claims are biologically plausible, they are not yet supported by a compelling prospective trial. OBJECTIVE: We investigated the effect of prenatal carotenoid supplementation on biomarkers of maternal and infant systemic carotenoid status. METHODS: We randomly assigned 47 first trimester pregnant subjects by 1:1 allocation to receive standard-of-care prenatal vitamins plus a 10 mg L and 2 mg Z softgel (the Carotenoid group) or standard-of-care prenatal vitamins with a placebo softgel (the Control group) for 6-8 mo. Maternal carotenoid concentrations in the serum and skin at the end of each trimester and postpartum were measured with HPLC and resonance Raman spectroscopy, respectively. Infants' systemic carotenoid status was assessed using similar techniques but optimized for infants. Repeated measures and paired t-tests were determined, and a P value < 0.05 was considered statistically significant. RESULTS: After supplementation, there was a statistically significant increase in maternal serum L + Z concentrations, serum total carotenoid concentrations, and skin carotenoid status (P < 0.001 for all) in the Carotenoid group relative to the Control group at all study time points. Similarly, infants whose mothers were in the Carotenoid group had a significant 5-fold increase in cord blood L + Z concentrations, over a 3-fold increase in cord blood total carotenoids, and a 38% increase in skin carotenoids compared with the Control group (P < 0.0001 for all). In addition, there was a strong positive, statistically significant correlation between postpartum maternal and infant systemic carotenoid status (P < 0.0001). CONCLUSION: Prenatal carotenoid supplementation significantly increased maternal and infant systemic (skin and serum) carotenoid status, which may benefit pregnant women and their infants' health. This trial was registered at clinicaltrials.gov as NCT03750968.

Mechanism for the selective uptake of macular carotenoids mediated by the HDL cholesterol receptor SR-BI.

The macular carotenoids lutein and zeaxanthin are taken up from the bloodstream into the human retina through a selective process, for which the HDL cholesterol receptor scavenger receptor BI (SR-BI) in the cells of retinal pigment epithelium (RPE) is thought to be a key mediator. However, the mechanism of SR-BI-mediated selective uptake of macular carotenoids is still not fully understood. Here, we investigate possible mechanisms using biological assays and cultured HEK293 cells, a cell line without endogenous SR-BI expression. Binding affinities between SR-BI and various carotenoids were measured by surface plasmon resonance (SPR) spectroscopy, which shows that SR-BI cannot bind lutein or zeaxanthin specifically. Overexpression of SR-BI in HEK293 cells results in more lutein and zeaxanthin taken up than ß-carotene, and this effect can be eliminated by an SR-BI mutant (C384Y) whose cholesterol uptake tunnel is blocked. Next, we determined the effects of HDL and hepatic lipase (LIPC), SR-BI's partners in HDL cholesterol transport, on SR-BI-mediated carotenoid uptake. HDL addition dramatically reduced lutein, zeaxanthin, and ß-carotene in HEK293 cells expressing SR-BI, but the cellular lutein and zeaxanthin are higher than ß-carotene. LIPC addition increases the uptake of all three carotenoids in HDL-treated cells, and promotes the transport of lutein and zeaxanthin better than ß-carotene. Our results suggest that SR-BI and its HDL cholesterol partner HDL and LIPC may be involved in the selective uptake of macular carotenoids.

FLUORESCENCE LIFETIME IMAGING OPHTHALMOSCOPY IN PATIENTS WITH MACULAR TELANGIECTASIA TYPE 2 WITH AND WITHOUT DIABETES.

PURPOSE: Macular telangiectasia type 2 (MacTel) is a vision-altering retinal disease with a high prevalence of diabetes. Differences between patients with MacTel with and without diabetes were investigated using fluorescence lifetime imaging ophthalmoscopy (FLIO). METHODS: Eighty-six patients with MacTel (59 ± 12 years) were included. 40 patients (46%) did not have diabetes, 16 patients (19%) were prediabetic, and 30 patients (35%) were diabetic. Of these, seven had diabetic retinopathy. 18 diabetic patients without MacTel and 42 age-matched healthy controls were included. FLIO lifetimes (FLTs) were obtained in short (SSC, 498-560 nm) and long (LSC, 560-720 nm) spectral channels from different areas of interest using a Heidelberg Engineering FLIO. RESULTS: Fundus autofluorescece lifetimes did not show significant differences when comparing diabetic with nondiabetic MacTel eyes (MacTel zone, SSC, diabetic: 243 ± 65 ps; nondiabetic: 232 ± 51 ps; P = 1.0; LSC, diabetic: 327 ± 66 ps; nondiabetic: 309 ± 54 ps; P = 0.582). Longitudinal changes were similarly unrelated to diabetes status. A nonsignificant trend of increased FLT progression with higher body mass index was found. Fundus autofluorescece lifetimes in diabetic patients without MacTel were significantly shorter within the MacTel zone and longer in the periphery compared with diabetic patients with MacTel. CONCLUSION: Although MacTel has a high prevalence of diabetes, FLTs from the MacTel zone are unrelated to diabetes. Fluorescence lifetime imaging ophthalmoscopy retains diagnostic abilities in patients with MacTel even in the presence of prediabetes, diabetes, and advanced diabetic retinopathy. The lack of diabetic FLT changes in the periphery of diabetic patients with MacTel is an interesting finding that needs further investigation.

Macular Pigment Carotenoids and Bisretinoid A2E.

Lutein (L), zeaxanthin (Z), and meso-zeaxanthin (MZ) are the three macular pigments (MP) carotenoids that uniquely accumulate in the macula lutea region of the human retina. L and Z are obtained by humans through dietary intake. The third MP, MZ, is rarely present in diet, and its abundance in the human fovea is due to the metabolic conversion of dietary L by the retinal pigment epithelium's RPE65 enzyme. The major functions of MP in ocular health are to filter high-intensity, phototoxic blue light and to act as effective antioxidants for scavenging free radicals. The pyridinium bisretinoid, N-retinylidene-N-retinylethanolamine (A2E), contributes to drusen formation in dry age-related macular degeneration (AMD) and to the autofluorescent flecks in autosomal recessive Stargardt disease (STGD1). Retinal carotenoids attenuate A2E formation and can directly and indirectly alleviate A2E-mediated oxidative damage. In this chapter, we review these more recently recognized interconnections between MP carotenoids and A2E bisretinoids.

Role of VLC-PUFAs in Retinal and Macular Degeneration.

Very-long-chain polyunsaturated fatty acids (VLC-PUFAs) are a special class of fatty acids that are present in the retina and a few other human tissues. They cannot be synthesized de novo and are rarely present in dietary sources. Structurally, these lipids are composed of a proximal end with a typical saturated fatty acid character and a distal end more characteristic of common PUFAs. They have not been studied in detail until recently due to their low abundance in these tissues and technical difficulties in assaying these lipids by conventional chromatography. This unique class of lipids has chain lengths greater than 24 carbons, with the longest typically 38 carbons long. There is increasing interest in understanding their roles in the maintenance of retinal membrane integrity and the prevention of macular degeneration and inherited retinal diseases.

A connectomics approach to understanding a retinal disease.

Macular telangiectasia type 2 (MacTel), a late-onset macular degeneration, has been linked to a loss in the retina of Müller glial cells and the amino acid serine, synthesized by the Müller cells. The disease is confined mainly to a central retinal region called the MacTel zone. We have used electron microscopic connectomics techniques, optimized for disease analysis, to study the retina from a 48-y-old woman suffering from MacTel. The major observations made were specific changes in mitochondrial structure within and outside the MacTel zone that were present in all retinal cell types. We also identified an abrupt boundary of the MacTel zone that coincides with the loss of Müller cells and macular pigment. Since Müller cells synthesize retinal serine, we propose that a deficiency of serine, required for mitochondrial maintenance, causes mitochondrial changes that underlie MacTel development.

Imaging lutein and zeaxanthin in the human retina with confocal resonance Raman microscopy.

Lutein and zeaxanthin are xanthophyll carotenoids that are highly concentrated in the human macula, where they protect the eye from oxidative damage and improve visual performance. Distinguishing lutein from zeaxanthin in images of the human retina in vivo or in donor eye tissues has been challenging because no available technology has been able to reliably differentiate between these two carotenoids, which differ only in the position of one C = C bond. Here, we report the differential distributions of lutein and zeaxanthin in human donor retinas mapped with confocal resonance Raman microscopy. Zeaxanthin is highly concentrated in the fovea, extending from the inner to the outer limiting membranes, with especially high concentrations in the outer plexiform layer, while lutein is much more diffuse at relatively lower concentration. Our results imply that zeaxanthin may play a more important role than lutein in human macular health and disease.

Influence of very-long-chain polyunsaturated fatty acids on membrane structure and dynamics.

The unique attributes of very-long-chain polyunsaturated fatty acids (VLC-PUFAs), their long carbon chains (n > 24) and high degree of unsaturation, impart unique chemical and physical properties to this class of fatty acids. The changes imparted by VLC-PUFA 32:6 n-3 on lipid packing and the compression moduli of model membranes were evaluated from π-A isotherms of VLC-PUFA in 1,2-distearoyl-sn-3-glycero-phosphocholine (DSPC) lipid monolayers. To compare the attractive or repulsive forces between VLC-PUFA and DSPC lipid monolayers, the measured mean molecular areas (MMAs) were compared with the calculated MMAs of an ideal mixture of VLC-PUFA and DSPC. The presence of 0.1, 1, and 10 mol % VLC-PUFA shifted the π-A isotherm to higher MMAs of the lipids comprising the membrane and the observed positive deviations from ideal behavior of the mixed VLC-PUFA:DSPC monolayers correspond to repulsive forces between VLC-PUFAs and DSPC. The MMA of the VLC-PUFA component was estimated using the measured MMAs of DSPC of 47.1 ± 0.7 Å2/molecule, to be 15,000, 1100, and 91 Å2/molecule at 0.1, 1, and 10 mol % VLC-PUFA:DSPC mixtures, respectively. The large MMAs of VLC-PUFA suggest that the docosahexaenoic acid tail reinserts into the membrane and adopts a nonlinear structure in the membrane, which is most pronounced at 0.1 mol % VLC-PUFA. The presence of 0.1 mol % VLC-PUFA:DSPC also significantly increased the compression modulus of the membrane by 28 mN/m compared with a pure DSPC membrane. The influence of VLC-PUFA on lipid "flip-flop" was investigated by sum-frequency vibrational spectroscopy. The incorporation of 0.1 mol % VLC-PUFA increased the DSPC flip-flop rate fourfold. The fact that VLC-PUFA promotes lipid translocation is noteworthy as retinal membranes require a high influx of retinoids which may be facilitated by lipid flip-flop.

Serine and Lipid Metabolism in Macular Disease and Peripheral Neuropathy.

BACKGROUND: Identifying mechanisms of diseases with complex inheritance patterns, such as macular telangiectasia type 2, is challenging. A link between macular telangiectasia type 2 and altered serine metabolism has been established previously. METHODS: Through exome sequence analysis of a patient with macular telangiectasia type 2 and his family members, we identified a variant in SPTLC1 encoding a subunit of serine palmitoyltransferase (SPT). Because mutations affecting SPT are known to cause hereditary sensory and autonomic neuropathy type 1 (HSAN1), we examined 10 additional persons with HSAN1 for ophthalmologic disease. We assayed serum amino acid and sphingoid base levels, including levels of deoxysphingolipids, in patients who had macular telangiectasia type 2 but did not have HSAN1 or pathogenic variants affecting SPT. We characterized mice with low serine levels and tested the effects of deoxysphingolipids on human retinal organoids. RESULTS: Two variants known to cause HSAN1 were identified as causal for macular telangiectasia type 2: of 11 patients with HSAN1, 9 also had macular telangiectasia type 2. Circulating deoxysphingolipid levels were 84.2% higher among 125 patients with macular telangiectasia type 2 who did not have pathogenic variants affecting SPT than among 94 unaffected controls. Deoxysphingolipid levels were negatively correlated with serine levels, which were 20.6% lower than among controls. Reduction of serine levels in mice led to increases in levels of retinal deoxysphingolipids and compromised visual function. Deoxysphingolipids caused photoreceptor-cell death in retinal organoids, but not in the presence of regulators of lipid metabolism. CONCLUSIONS: Elevated levels of atypical deoxysphingolipids, caused by variant SPTLC1 or SPTLC2 or by low serine levels, were risk factors for macular telangiectasia type 2, as well as for peripheral neuropathy. (Funded by the Lowy Medical Research Institute and others.).

HDL is the primary transporter for carotenoids from liver to retinal pigment epithelium in transgenic ApoA-I-/-/Bco2-/- mice.

Supplementation with antioxidant carotenoids is a therapeutic strategy to protect against age-related macular degeneration (AMD); however, the transport mechanism of carotenoids from the liver to the retina is still not fully understood. Here, we investigate if HDL serves as the primary transporter for the macular carotenoids. ApoA-I, the key apolipoprotein of HDL, was genetically deleted from BCO2 knockout (Bco2-/-) mice, a macular pigment mouse model capable of accumulating carotenoids in the retina. We then conducted a feeding experiment with a mixed carotenoid chow (lutein:zeaxanthin:ß-carotene = 1:1:1) for one month. HPLC data demonstrated that the total carotenoids were increased in the livers but decreased in the serum, retinal pigment epithelium (RPE)/choroids, and retinas of ApoA-I-/-/Bco2-/- mice compared to Bco2-/- mice. In detail, ApoA-I deficiency caused a significant increase of ß-carotene but not lutein and zeaxanthin in the liver, decreased all three carotenoids in the serum, blocked the majority of zeaxanthin and ß-carotene transport to the RPE/choroid, and dramatically reduced ß-carotene and zeaxanthin but not lutein in the retina. Furthermore, surface plasmon resonance spectroscopy (SPR) data showed that the binding affinity between ApoA-I and ß-carotene â‰« zeaxanthin > lutein. Our results show that carotenoids are transported from the liver to the eye mainly by HDL, and ApoA-I may be involved in the selective delivery of macular carotenoids to the RPE.

Inside out: Relations between the microbiome, nutrition, and eye health.

Age-related macular degeneration (AMD) is a complex disease with increasing numbers of individuals being afflicted and treatment modalities limited. There are strong interactions between diet, age, the metabolome, and gut microbiota, and all of these have roles in the pathogenesis of AMD. Communication axes exist between the gut microbiota and the eye, therefore, knowing how the microbiota influences the host metabolism during aging could guide a better understanding of AMD pathogenesis. While considerable experimental evidence exists for a diet-gut-eye axis from murine models of human ocular diseases, human diet-microbiome-metabolome studies are needed to elucidate changes in the gut microbiome at the taxonomic and functional levels that are functionally related to ocular pathology. Such studies will reveal new ways to diminish risk for progression of- or incidence of- AMD. Current data suggest that consuming diets rich in dark fish, fruits, vegetables, and low in glycemic index are most retina-healthful during aging.

Severity of age-related macular degeneration at first presentation in Bhutan: a 3-year national study.

BACKGROUND: Medical services are still developing in Bhutan. There is no published national report on age-related macular degeneration (AMD). We therefore aim to determine the demographic characteristics and severity of AMD at first presentation among Bhutanese patients attending their recently inaugurated vitreoretinal (VR) clinics over a 3-year national survey, and to inform national health policy to develop suitable health program to prevent AMD-related blindness and visual impairment. METHODS: A retrospective cross-sectional consecutive case series study was conducted on all new AMD cases in Bhutan. If a patient presented with asymmetrical AMD, the eye with more severe AMD was considered. If both the eyes had the same severity one eye was chosen randomly. Collection of demographic data and clinical details including diagnostic testing (fundus photography, OCT and fluorescent angiography) and clinical staging were performed. RESULTS: Of 521 new AMD patients aged 71.9 ± 11.3 years, 306/521 (58.7%) were males (p = 0.005). At their first presentation, 234/521 patients (44.9%) already had late-stage AMD. Importantly, 69/234 patients (29.5%), that is half of total neovascular AMD (nAMD) patients, had disciform scars (DS) which were beyond treatment, and 7/234 patients (3.0%) had geographic atrophy (GA). Seven patients had retinal pigment epithelium tear at presentation. Fourteen of nineteen polypoidal choroidal vasculopathy (PCV) patients were younger than 50 years. CONCLUSIONS: Half of nAMD cases presented as DS not amenable to the treatment. Many potentially treatable nAMD patients had already lost central vision and were legally blind. Young people with PCV losing vision early in life with longer morbidity-affected life and socio-economic burden was concerning. GA and DS cases need visual rehabilitation to improve their QoL. Incorporating a screening program for AMD with effective health education, and maintaining a national AMD Registry, would potentially lower AMD-related blindness and visual impairment.

The emerging roles of the macular pigment carotenoids throughout the lifespan and in prenatal supplementation.

Since the publication of the Age-Related Eye Disease Study 2 (AREDS2) in 2013, the macular pigment carotenoids lutein (L) and zeaxanthin (Z) have become well known to both the eye care community and the public. It is a fascinating aspect of evolution that primates have repurposed photoprotective pigments and binding proteins from plants and insects to protect and enhance visual acuity. Moreover, utilization of these plant-derived nutrients has been widely embraced for preventing vision loss from age-related macular degeneration. More recently, there has been growing awareness that these nutrients can also play a role in improving visual performance in adults. On the other hand, the potential benefits of L and Z supplementation at very young ages have been underappreciated. In this review, we examine the biochemical mechanisms and supportive data for L and Z supplementation throughout the lifespan, with particular emphasis on prenatal supplementation. We propose that prenatal nutritional recommendations may aim at improving maternal and infant carotenoid status. Prenatal supplementation with L and Z might enhance infant visual development and performance and may even prevent retinopathy of prematurity, possibilities that should be examined in future clinical studies.

Membrane cholesterol regulates TRPV4 function, cytoskeletal expression, and the cellular response to tension.

Despite the association of cholesterol with debilitating pressure-related diseases such as glaucoma, heart disease, and diabetes, its role in mechanotransduction is not well understood. We investigated the relationship between mechanical strain, free membrane cholesterol, actin cytoskeleton, and the stretch-activated transient receptor potential vanilloid isoform 4 (TRPV4) channel in human trabecular meshwork (TM) cells. Physiological levels of cyclic stretch resulted in time-dependent decreases in membrane cholesterol/phosphatidylcholine ratio and upregulation of stress fibers. Depleting free membrane cholesterol with m-ß-cyclodextrin (MßCD) augmented TRPV4 activation by the agonist GSK1016790A, swelling and strain, with the effects reversed by cholesterol supplementation. MßCD increased membrane expression of TRPV4, caveolin-1, and flotillin. TRPV4 did not colocalize or interact with caveolae or lipid rafts, apart from a truncated ∼75 kDa variant partially precipitated by a caveolin-1 antibody. MßCD induced currents in TRPV4-expressing Xenopus laevis oocytes. Thus, membrane cholesterol regulates trabecular transduction of mechanical information, with TRPV4 channels mainly located outside the cholesterol-enriched membrane domains. Moreover, the biomechanical milieu itself shapes the lipid content of TM membranes. Diet, cholesterol metabolism, and mechanical stress might modulate the conventional outflow pathway and intraocular pressure in glaucoma and diabetes in part by modulating TM mechanosensing.

Lutein and zeaxanthin reduce A2E and iso-A2E levels and improve visual performance in Abca4-/-/Bco2-/- double knockout mice.

Accumulation of bisretinoids such as A2E and its isomer iso-A2E is thought to mediate blue light-induced oxidative damage associated with age-related macular degeneration (AMD) and autosomal recessive Stargardt disease (STGD1). We hypothesize that increasing dietary intake of the macular carotenoids lutein and zeaxanthin in individuals at risk of AMD and STGD1 can inhibit the formation of bisretinoids A2E and iso-A2E, which can potentially ameliorate macular degenerative diseases. To study the beneficial effect of macular carotenoids in a retinal degenerative diseases model, we used ATP-binding cassette, sub-family A member 4 (Abca4-/-)/ß,ß-carotene-9',10'-oxygenase 2 (Bco2-/-) double knockout (KO) mice that accumulate elevated levels of A2E and iso-A2E in the retinal pigment epithelium (RPE) and macular carotenoids in the retina. Abca4-/-/Bco2-/- and Abca4-/- mice were fed a lutein-supplemented chow, zeaxanthin-supplemented chow or placebo chow (~2.6 mg of carotenoid/mouse/day) for three months. Visual function and electroretinography (ERG) were measured after one month and three months of carotenoid supplementation. The lutein and zeaxanthin supplemented Abca4-/-/Bco2-/- mice had significantly lower levels of RPE/choroid A2E and iso-A2E compared to control mice fed with placebo chow and improved visual performance. Carotenoid supplementation in Abca4-/- mice minimally raised retinal carotenoid levels and did not show much difference in bisretinoid levels or visual function compared to the control diet group. There was a statistically significant inverse correlation between carotenoid levels in the retina and A2E and iso-A2E levels in the RPE/choroid. Supplementation with retinal carotenoids, especially zeaxanthin, effectively inhibits bisretinoid formation in a mouse model of STGD1 genetically enhanced to accumulate carotenoids in the retina. These results provide further impetus to pursue oral carotenoids as therapeutic interventions for STGD1 and AMD.

Auditory and olfactory findings in patients with USH2A-related retinal degeneration-Findings at baseline from the rate of progression in USH2A-related retinal degeneration natural history study (RUSH2A).

Sensorineural hearing loss (SNHL) is characteristic of Usher syndrome type 2 (USH2), but less is known about SNHL in nonsyndromic autosomal recessive retinitis pigmentosa (ARRP) and olfaction in USH2A-associated retinal degeneration. The Rate of Progression of USH2A-related Retinal Degeneration (RUSH2A) is a natural history study that enrolled 127 participants, 80 with USH2 and 47 with ARRP. Hearing was measured by pure-tone thresholds and word recognition scores, and olfaction by the University of Pennsylvania Smell Identification Test (UPSIT). SNHL was moderate in 72% of USH2 participants and severe or profound in 25%, while 9% of ARRP participants had moderate adult-onset SNHL. Pure-tone thresholds worsened with age in ARRP but not in USH2 participants. The degree of SNHL was not associated with other participant characteristics in either USH2 or ARRP. Median pure-tone thresholds in ARRP participants were significantly higher than the normative population (p < 0.001). Among 14 USH2 participants reporting newborn hearing screening results, 7 reported passing. Among RUSH2A participants, 7% had mild microsmia and 5% had moderate or severe microsmia. Their mean (±SD) UPSIT score was 35 (±3), similar to healthy controls (34 [±3]; p = 0.39). Olfaction differed by country (p = 0.02), but was not significantly associated with clinical diagnosis, age, gender, race/ethnicity, smoking status, visual measures, or hearing. Hearing loss in USH2A-related USH2 did not progress with age. ARRP patients had higher pure-tone thresholds than normal. Newborn hearing screening did not identify all USH2A-related hearing loss. Olfaction was not significantly worse than normal in participants with USH2A-related retinal degeneration.

The synthesis of the very long chain polyunsaturated fatty acid (VLC-PUFA) 32:6 n-3.

This article describes the synthesis of VLC-PUFA 32:6 n-3, D2-labeled 32:6 n-3, and the uptake of 32:6 n-3 into mouse retinal tissue.