Rationale for clinical trials of selenium as an antioxidant for the treatment of the cardiomyopathy of Friedreich's ataxia.

A pure selenium deficiency is harmful to the heart and causes a fatal dilated congestive cardiomyopathy in animals (white muscle disease) and in man (Keshan disease). Both of these syndromes are selenium-responsive. A deficiency of the micronutrient has also been reported in patients with Friedreich's ataxia and there are histological similarities between Friedreich's cardiomyopathy and Keshan disease. A low selenium status results in reduced selenium-dependent glutathione peroxidase activity. This essential antioxidant enzyme protects membrances from oxidative deterioration, a function it shares in common with vitamin E. As iron-induced mitochondrial lipid peroxidation is central to the pathology of Friedreich's ataxia, the administration of selenium supplements should normalize the antioxidant activity of myocardial glutathione peroxidase and slow the progression of the life-shortening cardiomyopathy associated with this illness.