Effect of diabetes and dietary ubiquinone supplementation on the post-translational modification of rat lens beta L crystallin.

The effect of streptozocin diabetes of 14 days duration on the integrity of lenticular crystallins has been determined by the measurement of characteristic markers of protein modification in the lens crystallins of rats. Further, the susceptibility of the crystallins to modification has also been determined by measurement of the same markers after the application of a metal-catalyzed oxidative insult in vitro. The results show that the previously reported increased post-translational modification of lens crystallins in vivo and increased susceptibility to modification in vitro of diabetic crystallins after 21 days of uncontrolled diabetes are also evident after just 14 days of diabetes. Treatment of the diabetic animals with the antioxidant ubiquinone by dietary supplementation was unable to prevent the post-translational modifications sustained by the crystallin when subjected to diabetes in vivo or the increase in susceptibility to an in vitro oxidative stress. While the present results support the proposal that cataract formation is initiated by protein post-translational modification factors such as glycation, ubiquinone supplementation does not appear to be beneficial in the inhibition of post-translational crystallin modification in diabetic cataractogenesis.