Effects Of Pyruvate On The Experimentally Induced Diabetic Cataract In Rats

Object1. To investigate the inhibition of Pyruvate on cataract in diabetic rats.2. To investigate the effect of Pyruvate on polyol pathway and oxidative damage of lens in diabetic rats.3. To investigate mechanism of lens epithelial cells apoptosis in experimental diabetic rats and the therapeutic mechanism on diabetic cataract treated with Pyruvate.Methods1. 220 Wister rats (weighing about 180 -200g) were divided into 2 groups-. control group (60rats ), experiment group ( 160rats). Rats of experiment group were induced diabetes by a single intravenous administration of streptozotocin (60mg/kg body weight) dissolved freshly in 0.1mmol/L citrate buffer, pH4. 5 made in physiological saline. 3 days after STZ injection , animals having blood sugar exceed 11 mmol/L were randomly divided into two groups as model and treatment group. The model group was maintained on the standard rat chow and ordinary water. The treatment group was received 2% Pyruvate in the diet and drinking.2. The opacification of lens was detected by microscope every 2 week.3. Lens morphogenetic changes were detected using transmission electron microscope.4. The activation of aldose reductase was tested by fluorospectrophotometry.5. On 30d, 60d and 90d of the experiment, glucose, sorbitol, fructose inthe lens were quantified by high - performance liquid chromatography. At each time point, 10 lenses (5 rats) were used from each group. After homogenized in lml of ice cold water and centrifuged at 10000 x g for 4X1. lOjxl lens supernatant was added to high - performance liquid chromatography.6. The level of GSH ( glutathione) , MDA ( malondialdehyde ) in the lens were determined.7. The percentage of lens epithelial cells undergoing apoptosis was measured by Annexin V - PI staining.8. The expression of Caspase —3 was analyzed by Western -blot.9. Statistical analysis SAS10.0 was used, with a P <0.05 considered statistically significant.Results1. Three days after STZ injection, the random blood glucose levels of rats were all exceed llmmol/L. It increased by 4 -6 times in the model group. The blood glucose levels of rats treated with Pyruvate were similar to those of the untreated rats, except in the first 60 days where the blood glucose levels in the Pyruvate - treated group had a tendency to be somewhat lower.The weights of the diabetic rats were significantly lower as compared with those in the control group. The weights of rats treated with Pyruvate had a tendency to be lower in the first 30 days then keep stabilization.2. slit lamp examination indicateDuring the entire experimental period, lenses from control group keep transparent. The rats in model group developed cataract after three weeks, At day 30, 85% of the lenses in model group were in stage I cataract. Feeding of Pytuvate at the 2% level delayed the onset of cataract since only 30% of the lenses in this group demonstrated stage I cataract while 70% of the lenses had not developed any lenticular opacity. Furthermore, maturation of cataract was also slowed by the Pyruvate treatment, as only 20. 8% of the lenses in this group demonstrated stage II cataract and 79. 2% were still in stage I while in model group 75% of the lenses demonstrated stage II cataract and 25% were in stageIll after 90 days.3. Under transmission electron microscope, no changes were presented in control group, but mild changes were showed in treatment group and remarkable changes were found in model group.4. Compared with control group, the activity of aldose reductase in the model group was markedly increased. Compared with model group, the activity of aldose reductase in the treament group was decreased.5. Studys show that there was significant increase of glucose, sorbitol in lenses of model group after STZ injection. Pyruvate treament led to a decreased in the lenses glucose and sorbitol concentration. There was no statistical difference in fructose content in lens between model group and Pyruvate group(P >0. 05).6. The contents of MDA were increased and GSH were decreased in model group compared with control group and the application of Pyruvate decreased the levels of lipid peroxidation ( MDA) and increased the levels of GSH in comparison with model group.7. The apoptosis rate of lens epithelial cells was increase in model group. Pyruvate treatment decreased lens epithelial cells apoptosis.8. Caspase - 3 activity increased in lens epithelial cells in model group and Pyruvate - treat can decrease the activity of Caspase - 3.Conclusions1. Administration of Pyruvate by oral can effectively inhibit diabetic cata-ractogenesis in rats through inhibiting polyol pathway, reducing oxidative damage.2. Polyol pathway and oxidative damage can induce apoptosis of lens epithelial cells. Pyruvate ingested orally can effective inhibit lens epithelial cells apoptosis in rats through inhibiting polyol pathway and oxidative damage.3. Lens epithelial cells apoptosis could be due to he activity of Caspase - 3.