Correlations of glutathione peroxidase activity with memory impairment in adults with down syndrome

Background: Down syndrome (DS) is a genetic disorder (trisomy 21 in 96% of cases), associated with an excess of a key enzyme involved with free radical metabolism (FRM), superoxide dismutase-1 (SOD-1), that is encoded by a gene on chromosome 21. Consequently, SOD-1 activity is elevated in DS, which also occurs in conditions of oxidative stress, and is associated with a compensatory increase in glutathione peroxidase activity (GSHPx). Methods: This study examined the relationship of memory function with erythrocyte SOD-1, GSHPx and catalase (CAT) activity in 22–51 year old adults with DS. Results: Mean erythrocyte SOD-1 (p< .02) and GSHPx (p< .01), but not CAT (p = .76), activities were significantly greater in the DS group than the controls. In the DS group, erythrocyte GSHPx, but not SOD-1 or CAT activities, was significantly correlated with memory function (r = .625, p< .025, df = 13 for savings score, r = .631, p< .01, df = 14 for intrusion errors) but not with intelligence quotients. Conclusions: These observations suggest a possible relationship between altered FRM with memory deficits among adults with DS within the age-range in that an age-related increase in the prevalence for Alzheimer’s neuropathology is known to be robust before reaching a plateau of 100%.