Scientists do not know what causes diabetic neuropathy, but several factors are likely to contribute to the disorder. High blood glucose, a condition associated with diabetes, causes chemical changes in nerves. These changes impair the nerves' ability to transmit signals. High blood glucose also damages blood vessels that carry oxygen and nutrients to the nerves. In addition, inherited factors probably unrelated to diabetes may make some people more susceptible to nerve disease than others.

How high blood glucose leads to nerve damage is a subject of intense research. The precise mechanism is not known. Researchers have discovered that high glucose levels affect many metabolic pathways in the nerves, leading to an accumulation of a sugar called sorbitol and depletion of a substance called myoinositol. However, studies in humans have not shown convincingly that these changes are the mechanism that causes nerve damage.

More recently, researchers have focused on the effects of excessive glucose metabolism on the amount of nitric oxide in nerves. Nitric oxide dilates blood vessels. In a person with diabetes, low levels of nitric oxide may lead to constriction of blood vessels supplying the nerve, contributing to nerve damage. Another promising area of research centers on the effect of high glucose attaching to proteins, altering the structure and function of the proteins and affecting vascular function.

Scientists are studying how these changes occur, how they are connected, how they cause nerve damage, and how to prevent and treat damage.

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The Diabetic Newsletter courtesy of NIDDK