Sorbitol (Polyol) Pathway
The Sorbitol Pathway, also called the Polyol Pathway, is a two-step process that converts glucose to fructose. The pathway contributes to diabetic complications affecting the eyes, kidneys, and nerves.
First, glucose is converted into sorbitol, in a reaction catalyzed by aldose reductase. This reaction also uses NADPH, producing NADP+ in the process.
Second, sorbitol is converted into fructose by sorbitol dehydrogenase. This reaction produces NADH from NAD+ in the process.
Deficiencies in sorbitol dehydrogenase activity cause sorbitol accumulation in high glucose states, such as in diabetes mellitus. The major tissues with poor sorbitol dehydrogenase activity are the lens, retina, kidney, and schwann cells of the peripheral nervous system. Sorbitol accumulation contributes to cataracts, retinopathy, renal failure, and peripheral neuropathy, respectively.
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