The carotenoid lutein has been implicated as being protective against the acquired ocular diseases, such as cataracts and age-related macular degeneration. Lutein may act as an antioxidant and as a blue light filter to protect the underlying tissues from photo-oxidative damage. The central part of the retina, the macula, contains macular pigments in which the antixoidant lutein is concentrated.
Many in-vitro and in-vivo studies have demonstrated a beneficial effect of lutein macular degeneration but one large protective only gave very week support a protective role of lutein intake on early age-related macular degeneration [3]. This prospective study followed 71.494 women and 41.564 men for a period of up to 18 years. There was a statistically nonsignificant and nonlinear inverse association between lutein intake and neovascular age-related macular degeneration. For neovascular age-related macular degeneration, a nonlinear inverse association was found among never smokers.
A Japanese study showed that lutein was neuroprotective in rats with uveitis (inflammation of the middle layer of the eye) induced by endotoxins [1]. The study concluded that lutein may have a potential approach for suppressing retinal neural damage during inflammation. The team of scientists lead by Sasaki M induced uveitis in rats by intraperitoneal injection with lipopolysaccharide followed by a subcutaneous injection of lutein. They found that lutein treatment reduced oxidative stress, Stat3 protein activation and expression of rhodopsin, a pigment of the retina that is responsible for both the formation of the photoreceptor cells and the first events in the perception of light. The shortening of the length of the outer segments of the photoreceptor cells was also inhibited by the phytochemical.
Wang M investigated the protective effect of lutein damage on rat retina induced by blue light and came to the conclusion that the phytochemical significantly prevented this damage [2]. Wang M and co-workers exposed rats to blue light exposure for 2 hours after injecting their vitreous body with different doses of lutein. After the treatment they examined changes of retina morphous, thickness of the outer nuclear layer and counted the number of apoptotic photoreceptors. They found that lutein treatment resulted in a thinner outer nuclear layer and more clearly demarcated retina structure and more ordered cells. There was no influence on the number of apopotic photoreceptors. Another study demonstrated the neuroprotective actions of lutein, zeaxanthin and docosahexaenoic acid, a natutral polyunsaturated fatty acid in the retina, on cultured photoreceptors, exposed to oxidants [4]. The researchers treated cultured rat retinal neurons with lutein, zeaxanthin and docosahexaenoic acid before exposing them to the oxidants hydrogen peroxide and paraquat. They found that pretreatment with the phytochemicals and docosahexaenoic acid inhibited oxidative stress. More specifically they inhibited apoptosis of the photoreceptors, preserved mitochondrial potential, prevented cytochrome c release from mitochondria and enhanced cell differentiation.
A study conducted by H Vu and coworkers of University of Melbourne also found an inverse association between a high dietary intake of lutein-zeaxanthin and the prevalence of nuclear cataract [5]. The researchers conducted a follow-up examination of 2322 women, about 5 years after they were recruited. Based on a food-frequency questionnaire and medical examination they found that the odds for nuclear cataract reduced by 40% for every extra intake of 1 mg lutein. However they found no protective effect of lutein on cortical and PSC cataract.
[1] Neuroprotective Effect of an Antioxidant, Lutein, during Retinal Inflammation Invest Ophthalmol Vis Sci. 2008 Nov 7.
[2] Protective effect of lutein against blue light-induced retinal damage in rat. Wei Sheng Yan Jiu. 2008 Jul;37(4):409-12.
[3] Prospective study of lutein/zeaxanthin intake and risk of age-related macular degeneration. Am J Clin Nutr. 2008 Jun;87(6):1837-43.
[4] Lutein and zeaxanthin protect photoreceptors from apoptosis induced by oxidative stress: relation with docosahexaenoic acid. Invest Ophthalmol Vis Sci. 2007 Nov;48(11):5168-77.
[5] Lutein and zeaxanthin and the risk of cataract: the Melbourne visual impairment project. Invest Ophthalmol Vis Sci. 2006 Sep;47(9):3783-6.
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