In vivo effect of lipoic acid on lipid peroxidation in patients with diabetic neuropathy.

The diabetic state, in both humans and experimental animals, is associated with oxidative stress. Lipid peroxidation of nerve membranes has been suggested as a mechanism by which peripheral nerve ischemia and hypoxia could cause neuropathy. Lipoic acid (LA) is a powerful inhibitor of iron-dependent lipid peroxidation and reactive oxygen species. The treatment of diabetic peripheral and cardiac autonomic neuropathy with LA is based on good clinical and experimental evidence.To investigate the magnitude of the oxidative stress, serum ceruloplasmin (Cp) and lipid peroxide (Lp) levels were measured in 10 patients with diabetic neuropathy, before and 70 days after treatment with single dose of 600 mg LA/day. For other 12 healthy age- and sex-matched control subjects the serum Cp and Lp levels were evaluated.Our results show that hyperglycemia is a factor for an increase in serum ceruloplasmin in patients with diabetic neuropathy compared to healthy subjects (p < 0.0001). High serum ceruloplasmin (Cp) level in patients with diabetes may be related to antioxidant defense. The treatment of diabetic neuropathy with LA does not affect significantly the serum Cp activity. The serum Lp levels after LA administration were significantly lower (p < 0.005) than those before treatment.The antioxidant therapy with LA improves and may prevent diabetic neuropathy. This improvement is associated with a reduction in the indexes of lipid peroxidation. Oxidative stress appears to be primarily due to the processes of nerve ischemia and hyperglycemia autooxidation.