Studies On The Role Of Oxidative Stress In The Development Of Diabetic Cataract And The Effect And Mechanism Of Green Tea On Inhibition In The Formation Of Diabetic Catarac

Objective:To investigate the significantcant roles of oxidative stress in the development of diabetic cataract and the effect of green tea on inhibition in the formation of diabetic cataract and its therapeutical mechanism.Methods:Normal male wistar rats are divided into normol control group(n=10), streptozotocin group(STZ-DM)(n=30),the treated groups with green tea (TEA-DM)(n=30).STZ-DM and TEA-DM groups were treated with STZ injected into the tail vein to establish animal model of diabetic rat cataract.After diabetic rats model were formed, the every rat of TEA-DM group drank green tea 100 ml /day. The progression of lens opacification was recorded using the slit lamp every week . Rats were humanely sacrificed at 4 week after the onset of diabetes, lens were observed with scanning electron microscope. Rats were humanely sacrificed 2,4,8 and 12 weeks after the onset of diabetes. The mRNA expression of uncoupling proteins homologues and MnSOD in lens was detected with RT-PCR. Results:By using the slit lamp we observed the lens of normal group were clear during the experiment. Lens opacification progressed in a biphasic manner in STZ-DM group, an initial slow progression during the first 8 weeks of diabetes followed by a steep increased lens opacification in the next 4 weeks.On 8w 10/13(76.9%)rats exhibited theⅢgrade ,on 12w all the lens were completely opacitas.The Lens opacification of TEA-DM group progressed much slowly than that of STZ-DM group.On 8w lens opacity was mild and 4/14(28.6%)rats exhibited theⅡgrade. On 12w 5/8(62.5%)rats′lens exhibited theⅢgrade;By scanning electron microscope we observed the fibers of normal lens array regularly and homogenously,there are prominences between the fibers.The fibers of STZ-DM group arrayed irregularly which were swollen,dissolved and confluenced. The prominences were deformed and amotic. Degenerated globules appeared. The fibers of TEA-DM group arrayed regularly which were uneven and swollen. The mosaic structure still could be seen. The fibers took a favorable turn compared with STZ-DM group;UCP1,3,4,5 mRNA can not be detected in normal rat lens with RT-PCR. UCP2,MnSOD mRNA expression changed with the courses of disease. UCP2 and MnSOD mRNA increased at 2 weeks after the onset of diabetes. Then the expression decreased gradually and reached the normal level at 12 weeks after the onset of diabetes. UCP2 and MnSOD mRNA expressed at high level straightly after the onset of diabetes in TEA-DM group. Conclusions:The fibers of diabetic cataract rats were destroyed and green tea could relieved the destruction of ultrastructure.UCP2 is expressed in lens of rats. The mRNA expression of UCP2 and MnSOD changed with the courses of diabetes and which is related to the occurrence of diabetic cataract. It is suspected that the mitochondrial reactive oxygen species (ROS) increasing is the key pathway.Green tea accommodated the expression of UCP2 and MnSOD mRNA at high level that restrained the ROS injurying the lens. Oxidative stress may play some significantcant roles in the development of diabetic cataract. Green tea could inhibit and delay the lens opacification progression.