New Theory Explains Diabetic Damage To Eyes, Heart,... -
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Published on: 11/10/2004
Last Visited: 12/6/2004
"The metabolic imbalances caused by diabetes are quite complex, and that has made it very difficult to gain acceptance or even consideration of our hypothesis," says senior investigator Joseph Williamson, M.D, a retired pathology faculty member at Washington University School of Medicine in St. Louis."Being able to publish the online appendix finally gave us the room we needed to respond to everyone,s concerns."
Williamson,s theory focuses on the energy-producing compound,s reversible transformation between two forms, nicotinamide adenine dinucleotide ,NAD, and NADH ,NAD plus H, or one atom of hydrogen,.
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Williamson and his coauthors used in vitro studies of rat retinas to show that both of these conditions decrease the ratio of NAD to NADH in different ways.Hyperglycemia does it by increasing the rate of transformation of NAD to NADH.Hypoxia makes it difficult for cells to turn NADH back to NAD.
In both conditions the increased NADH is recycled back to NAD by processes that produce free radicals, chemically reactive compounds that can damage tissue.Williamson and his coauthors propose that long-term use of these processes causes the damage seen in diabetes.
"The consequences of these different disruptions to NADH recycling are additive--they have the potential to produce much more damage than you might expect if you looked at either one independently," Williamson explains.
Scientists have known for some time that diabetes increases transformation of NAD to NADH by boosting cells, consumption of glucose through a process known as the sorbitol pathway.
Like glycolysis, the sorbitol pathway transforms NAD to NADH, but only at a small fraction of the level of glycolysis.
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"We,ve still got quite a bit of convincing to do, but I think people are starting to recognize that this seems to be a major mechanism for producing the free radicals that play such an important role in diabetic complications," Williamson says.