Suryanarayana Palla, Krishnaswamy Kamala, Reddy Geereddy Bhanuprakash
National Institute of Nutrition (ICMR), Jamai-Osmania, Hyderabad, India.
Mol Vis. 2003 Jun 9;9:223-30.
Curcumin, the active principle of turmeric, has been shown to have both antioxidant and hypoglycemic activity in vitro and in vivo. The purpose of this study was to investigate the effect of curcumin on the onset and maturation of galactose induced cataract.
Sprague-Dawley rats (21 days old) were divided into 5 groups. The control group (A) received an AIN-93 diet, the galactose group (B) received 30% galactose in the diet, the test groups (C and D) received the B group diet plus 0.002% and 0.01% curcumin respectively, and group (E) received the control diet plus 0.01% curcumin, all for a period of 4 weeks. Cataract progression due to galactose feeding was monitored by slit lamp microscope and classified into 4 stages. At the end of the experiment biochemical parameters such as lipid peroxidation, aldose reductase (AR), sorbitol dehydrogenase (SDH), reduced glutathione, protein content, and protein carbonyls were measured in the lens. Advanced glycated end products (AGE) and protein oxidation were measured by AGE and tryptophon fluorescence respectively. Crystallin profile was analyzed by size exclusion chromatography (HPLC).
Slit lamp microscope observations indicated that curcumin at 0.002% (group C) delayed the onset and maturation of cataract. In contrast even though there was a slight delay in the onset of cataract at the 0.01% level (group D), maturation of cataract was faster when compared to group B. Biochemical analysis showed that curcumin at the 0.002% level appeared to exert antioxidant and antiglycating effects, as it inhibited lipid peroxidation, AGE-fluorescence, and protein aggregation. Though the reasons for faster onset and maturation of cataract in group D rats was not clear, the data suggested that under hyperglycemic conditions higher levels of curcumin (0.01%) in the diet may increase oxidative stress, AGE formation, and protein aggregation. However, feeding of curcumin to normal rats up to a 0.01% level did not result in any changes in lens morphology or biochemical parameters.
These results suggest that curcumin is effective against galactose-induced cataract only at very low amounts (0.002%) in the diet. On the other hand at and above a 0.01% level curcumin seems to not be beneficial under hyperglycemic conditions, at least with the model of galactose-cataract.
姜黄素是姜黄的活性成分，已在体外和体内显示出抗氧化和降血糖活性。本研究的目的是探讨姜黄素对半乳糖诱导的白内障发生和成熟的影响。
将21日龄的Sprague-Dawley大鼠分为5组。对照组（A组）给予AIN-93饮食，半乳糖组（B组）给予含30%半乳糖的饮食，试验组（C组和D组）分别给予B组饮食加0.002%和0.01%姜黄素，E组给予对照饮食加0.01%姜黄素，所有组均持续4周。通过裂隙灯显微镜监测因喂食半乳糖导致的白内障进展，并分为4个阶段。在实验结束时，测量晶状体中的生化参数，如脂质过氧化、醛糖还原酶（AR）、山梨醇脱氢酶（SDH）、还原型谷胱甘肽、蛋白质含量和蛋白质羰基。分别通过晚期糖基化终产物（AGE）和色氨酸荧光测量AGE和蛋白质氧化。通过尺寸排阻色谱法（HPLC）分析晶状体蛋白谱。
裂隙灯显微镜观察表明，0.002%的姜黄素（C组）延迟了白内障的发生和成熟。相比之下，尽管0.01%水平（D组）的白内障发生稍有延迟，但与B组相比，白内障成熟更快。生化分析表明，0.002%水平的姜黄素似乎具有抗氧化和抗糖化作用，因为它抑制脂质过氧化、AGE荧光和蛋白质聚集。虽然D组大鼠白内障发生和成熟更快的原因尚不清楚，但数据表明，在高血糖条件下，饮食中较高水平的姜黄素（0.01%）可能会增加氧化应激、AGE形成和蛋白质聚集。然而，给正常大鼠喂食高达0.01%水平的姜黄素并未导致晶状体形态或生化参数的任何变化。
这些结果表明，姜黄素仅在饮食中含量极低（0.002%）时对半乳糖诱导的白内障有效。另一方面，在高血糖条件下，至少在半乳糖性白内障模型中，0.01%及以上水平的姜黄素似乎并无益处。
