Increased plasma and erythrocyte selenium concentrations but decreased erythrocyte glutathione peroxidase activity after selenium supplementation in children with Down syndrome.

An investigation was made of the activity of glutathione peroxidase (GSH-Px) in erythrocytes and the levels of selenium in plasma and erythrocytes before, during and after selenium supplementation in children with Down syndrome (DS). This subject is of interest since it has been suggested that selenium supplementation could enhance the GSH-Px activity in erythrocytes, probably leading to improved protection against oxygen radicals, which might cause damage by lipid peroxidation, especially in the brain. Forty-eight children with DS were treated with selenium-rich yeast tablets (10 micrograms/kg body weight/day) for 6 months. The supplementation was well tolerated and no side effects were observed. Selenium supplementation resulted in increased concentrations of selenium both in plasma and erythrocytes, but decreased GSH-Px-activity in erythrocytes. Plasma and erythrocyte selenium levels but almost regained the initial values 12 months after termination of the supplementation. Erythrocyte GSH-Px activity, on the other hand, remained reduced and did not return to the presupplementation levels. Until we gain more knowledge about the biological functions of selenium in man and the role of oxygen metabolism in the development of presenile dementia in DS, universal selenium supplementation in DS patients cannot be recommended.