Transport and Retinal Capture of Lutein and Zeaxanthin with Reference to Age-related Macular Degeneration

Abstract

Abstract. Age-related macular degeneration (AMD) is the most common cause of irreversible blindness in the elderly population in the western world. The etiology and pathogenesis of this disease remain unclear. However, there is an increasing body of evidence supporting the hypothesis that the macular pigment carotenoids, lutein and zeaxanthin, play an important role in protection against AMD, by filtering out blue light at a pre-receptoral level, or by quenching free radicals. Lutein and zeaxanthin are dietary xanthophyll carotenoids, which are delivered to the retina via plasma lipoproteins. The biological mechanisms governing retinal capture and accumulation of lutein and zeaxanthin, to the exclusion of other carotenoids, are still poorly understood. Although these mechanisms remain unclear, it is possible that selective capture of these carotenoids is related to lipoprotein, or apolipoprotein, function and profile. Xanthophyll-binding proteins appear to play an important role in the retinal capture of the xanthophyll carotenoids. The Pi isoform of GSTP1 has been isolated as a specific binding protein for zeaxanthin. The binding protein responsible for retinal uptake of lutein remains elusive. This article reviews the literature germane to the mechanisms involved in the capture, accumulation and stabilization of lutein and zeaxanthin by the retina, and the processes involved in their transport in serum. (Surv Ophthalmol 53:68--81, 2008 The central retina, known as the macula, is responsible for central and color vision because of its high concentration of cone photoreceptors. The macula is characterized by a yellow color, attributable to the presence of macular pigment. 81 Macular pigment (MP) is composed of lutein and zeaxanthin, two hydroxycarotenoids, which are entirely of dietary origin. 17 The concentration of MP peaks at the center of the macula, known as the fovea, where zeaxanthin is the dominant carotenoid. In contrast, lutein dominates in the parafoveal region. 16,82 Dietary sources 68

Heritability of the spatial distribution and peak density of macular pigment: a classical twin study

“…A recent population-based study that looked specifically at the spatial profile of MP using dual-wavelength analysis of autofluorescence images found that a ring-like structure of MP was present in almost 20% of the participants, tended to be bilateral and was significantly more common in females and never smokers. 40 Although substantial progress has been made in understanding mechanisms involved in the uptake, metabolism, and deposition of L and Z, 39,41 it is clearly a complex process. The ratio of L/Z/meso-zeaxanthin varies with retinal profile with Z predominant at the central peak and L predominant in the peripheral retina.…”

Blood levels of antioxidants during age-related macular degeneration treatment by rheohaemapheresis

“…Gale et al found that the serum concentration of zeaxanthin was significantly lower in individuals with AMD, compared to those without the disease. Serum concentrations of lutein and of lutein and zeaxanthin combined were also lower but not significantly [10][11][12] . Bláha et al observed, after rheohaemapheresis (RH), not only absorption of soft drusen but also a reduction in or complete disappearance of drusenoid retinal pigment epithelium detachments (RPEDs).…”

Review of nutrient actions on age-related macular degeneration

“…Carotenoids are transported by low-density lipoproteins and high-density lipoproteins, suggesting that the lipid profile may influence the transport and delivery of these carotenoids to the retina with a consequential effect on macular pigment [29]. Many authors have considered the MPOD as a marker of eye health, and there is some evidence that carotenoid supplementation might improve this marker [30].…”