Abstract
Abstract: :
Purpose: Although prospective studies have indicated that higher dietary levels of lutein/zeaxanthin were associated with reduced risk for cataract extraction, the relationship between diet and lens carotenoid concentration has not been demonstrated. These experiments were conducted to determine whether dietary supplementation with zeaxanthin or ß-carotene could alter carotenoid composition in adult lenses. Methods: Newly hatched Japanese quail were raised for 6 months on custom-synthesized carotenoid-deficient (CD) diet or on CD diets supplemented with 35 mg native zeaxanthin/kg food (ZX35). At six months, the CD birds were divided into 4 dietary groups fed CD diet supplemented with 0, 5 or 35 mg ZX/ kg food (CD, CD/ZX5 and CD/ZX35) or with 50 mg ß-carotene/kg (CD/ßC50). At 1 year of age, lenses were collected and analyzed for carotenoids and tocopherols by HPLC. Results: As in human lenses, tocopherol concentrations in quail lenses were several hundred times higher than the carotenoids, and the dominant carotenoids were lutein and zeaxanthin. Female quail had significantly higher concentrations of zeaxanthin and lutein in their sera and lens than males (both P<0.0001). CD/ßC50 birds had no detectable ß-carotene in their lens, and the concentrations of lutein and zeaxanthin were unaffected. The CD/ZX5 females had significantly elevated serum zeaxanthin, but their lens zeaxanthin was the same as that in CD birds (P>0.98). In both ZX35 and the CD/ZX35 females, mean lens zeaxanthin was ~9 times higher than that in CD birds (P<0.005) whereas lutein concentration was unaffected. Moreover, lens zeaxanthin concentrations in ZX35 and CD/ZX35 were not different (P>0.78). The mean lens zeaxanthin concentration was almost 10-fold higher in birds fed high doses of zeaxanthin (CD/ZX35 and ZX35) than in birds fed low doses of zeaxanthin (CD, CD/ßC50, and CD/ZX5; P<0.0001). Lens tocopherol concentrations were not influenced by dietary carotenoids. Conclusions: Dietary ß-carotene had no effect on lens composition. High doses of dietary zeaxanthin significantly increased lens zeaxanthin in adult female quail but not in males; low doses were ineffective. These data provide the first experimental evidence that lens carotenoids are responsive to dietary manipulation, and suggest that the quail may be a useful model for study of lens carotenoids.
Keywords: carotenoids/carotenoid binding proteins • cataract • nutritional factors