Dorey C Kathleen, Granata Lauren, Nichols Cathleen R, Cheng Kimberly M, Craft Neal E
R&D Consulting, Arlington, MA, USA.
Exp Eye Res. 2005 Oct;81(4):464-77. doi: 10.1016/j.exer.2005.03.007.
Although higher dietary intake of lutein/zeaxanthin has been associated with reduced risk for cataracts, the impact of dietary supplements on lens lutein (L) or zeaxanthin (Z) has not been examined. If higher lens carotenoids do reduce risk for cataract, it would be essential to know whether dietary carotenoids can elevate carotenoids in the adult vertebrate lens. In this study, a covey of Japanese quail were hatched and raised 6 months on carotenoid-deficient diet, then switched to deficient diet supplemented with low or high 3R,3R'-zeaxanthin (5 or 35 mgkg(-1) food) or beta-carotene (50 mgkg(-1) food). Controls included a group of covey-mates that remained on the deficient diet and another raised from birth on the high Z (35 mg Zkg(-1)) diet. At 1 year of age, carotenoids and tocopherols in the lens and in the serum were analysed by HPLC, and compared by analysis of variance. Serum Z was significantly elevated in deficient birds fed the lower or higher Z supplement for 6 months (P<0.0001 for each). Serum Z in birds maintained on the higher Z supplement for 1 year was much higher than that in deficient birds (P<0.0001), but not different from deficient birds given the higher Z supplement. As in humans, the predominant lens carotenoids were lutein (L) and zeaxanthin (Z), and the total carotenoid concentration was of lower magnitude than the concentration of alpha-tocopherol. Responses to Z supplementation were sex-related. Female quail had 5-10 times higher serum concentrations of both Z and L than males (P<0.0001, <0.001), and they also had higher lens Z concentrations than males (P<0.0006); possible effects of estrogen on lens carotenoids are discussed. Lens Z concentration was strongly and positively correlated with serum Z in females (r=0.77; P<0.002). Deficient adult females supplemented with the 35 mgkg(-1) dose of Z for 6 months had a mean lens Z concentration (0.252+/-0.06 microgg(-1) protein) close to that in females fed with the supplement from birth (0.282+/-0.15 microgg(-1) protein). Birds fed with the higher dietary Z supplement for 6 or 12 months had significantly higher lens Z than birds fed lower or no dietary Z (P<0.0001). Lens L was not altered by dietary supplementation with either Z or beta-carotene. beta-Carotene supplements did not result in detectable lens beta-carotene, and had no effect on lens Z. Neither Z nor beta-carotene supplementation had a significant effect on serum or lens tocopherol concentrations. These studies in quail provide the first experimental evidence that lens carotenoids in adult vertebrates can be manipulated by dietary Z supplements.
尽管饮食中较高的叶黄素/玉米黄质摄入量与降低患白内障的风险有关，但膳食补充剂对晶状体叶黄素（L）或玉米黄质（Z）的影响尚未得到研究。如果晶状体中较高的类胡萝卜素确实能降低患白内障的风险，那么了解膳食类胡萝卜素是否能提高成年脊椎动物晶状体中的类胡萝卜素就至关重要。在本研究中，一群日本鹌鹑孵化后在缺乏类胡萝卜素的饮食中饲养6个月，然后改为补充低剂量或高剂量3R,3R'-玉米黄质（5或35毫克/千克食物）或β-胡萝卜素（50毫克/千克食物）的缺乏类胡萝卜素饮食。对照组包括一组继续食用缺乏类胡萝卜素饮食的鹌鹑同伴，以及另一组从出生就以高Z（35毫克Z/千克）饮食饲养的鹌鹑。1岁时，通过高效液相色谱法分析晶状体和血清中的类胡萝卜素和生育酚，并通过方差分析进行比较。喂食低剂量或高剂量Z补充剂6个月的缺乏类胡萝卜素的鹌鹑血清Z显著升高（每次P<0.0001）。以高Z补充剂饲养1年的鹌鹑血清Z远高于缺乏类胡萝卜素的鹌鹑（P<0.0001），但与喂食高Z补充剂的缺乏类胡萝卜素的鹌鹑无差异。与人类一样，晶状体中的主要类胡萝卜素是叶黄素（L）和玉米黄质（Z），总类胡萝卜素浓度低于α-生育酚浓度。对Z补充剂的反应与性别有关。雌性鹌鹑血清中Z和L的浓度比雄性高5至10倍（P<0.0001，<0.001），且其晶状体Z浓度也高于雄性（P<0.0006）；文中讨论了雌激素对晶状体类胡萝卜素可能的影响。雌性鹌鹑晶状体Z浓度与血清Z呈强正相关（r = 0.77；P<0.002）。缺乏类胡萝卜素的成年雌性鹌鹑补充35毫克/千克剂量的Z 6个月后，其晶状体Z平均浓度（0.252±0.06微克/克蛋白质）接近从出生就喂食该补充剂的雌性鹌鹑（0.282±0.15微克/克蛋白质）。喂食高膳食Z补充剂6个月或12个月的鹌鹑晶状体Z显著高于喂食低剂量或不喂食膳食Z的鹌鹑（P<0.0001）。膳食补充Z或β-胡萝卜素均未改变晶状体L。β-胡萝卜素补充剂未在晶状体中检测到β-胡萝卜素，且对晶状体Z无影响。补充Z和β-胡萝卜素对血清或晶状体生育酚浓度均无显著影响。这些在鹌鹑身上的研究提供了首个实验证据，即成年脊椎动物晶状体中的类胡萝卜素可通过膳食Z补充剂进行调控。
