Enhanced DNA repair in lymphocytes of Down syndrome patients: the influence of zinc nutritional supplementation.

Oral zinc supplementation is able to correct zinc deficiency and some immune defects present in Down's syndrome (DS), while other beneficial effects can be predicted because of the broad spectrum of biochemical pathways and the great variety of enzymes which depend on zinc bio-availability. To test if the maintenance of DNA integrity is also affected by zinc supplementation, DNA damage and repair after gamma-radiation was studied by alkaline elution assay in phytohemagglutinin-stimulated lymphocytes from Down's syndrome children before and after an oral zinc supplementation given for 4 months to correct their immune defects. In comparison with lymphocytes from normal children the DNA damage induction after ionizing radiation in DS lymphocytes both before and after zinc supplementation was normal. On the other hand, the rate of DNA repair in DS was highly and significantly accelerated before zinc treatment. After supplementation with zinc sulfate, the DNA repair rate was consistently slowed down becoming similar to that of control subjects. This is the first demonstration that a nutritional intervention in humans is apparently able to modify the biochemical steps which control the rate of DNA repair.