The therapeutic use of lipoic acid in diabetes: a current perspective.

Lipoic acid and its reduced derivative, dihydrolipoic acid (DHLA) are highly promising antioxidant agents, which are potent attenuators of reactive species-mediated damage in vitro and in animal studies. Lipoic acid is a universal antioxidant, effective in lipophilic and aqueous environments. In contrast to an equivalent endogenous agent, such as oxidised glutathione (GSSG), lipoic acid acts as an antioxidant in its oxidised form. Lipoic acid has been evaluated in diabetic polyneuropathy, a condition which is thought to result in part from oxidant damage caused by long-term hyperglycaemia. Diabetic patients are prone to incur enhanced cellular free radical formation and reduced antioxidant defence. Treatment with lipoic acid has improved nerve conduction velocity during studies in diabetic animals. Trials in diabetic patients have often observed some relief of neuropathic symptoms during treatment with lipoic acid, but consistent objective benefits have been difficult to establish. Lipoic acid is now used in Germany for the treatment of diabetic neuropathy and definitive evidence of efficacy should arise from postmarketing surveillance studies. It is possible that lipoic acid may be more effective as a long-term dietary supplement aimed at the prophylactic protection of diabetics from complications.