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Glutathione Peroxidase Enzyme Activity in Aging

Johns Hopkins Medical Institutions, Baltimore, Maryland.

Address correspondence to Sara E. Espinoza, MD, The University of Texas Health Science Center at San Antonio, 7703 Floyd Curl Drive, Mail Code 7875, San Antonio, TX 78229-3900. E-mail: espinozas2{at}uthscsa.edu

Background. It is hypothesized that free radical damage contributes to aging. Age-related decline in activity of the antioxidant enzyme glutathione peroxidase (GPx) may contribute to increased free radicals. We hypothesized that GPx activity decreases with age in a population of older women with disability.

Methods. Whole blood GPx activity was measured in baseline stored samples from participants in the Women's Health and Aging Study I, a cohort of disabled community-dwelling older women. Linear regression was used to determine cross-sectional associations between GPx activity and age, adjusting for hemoglobin, coronary disease, diabetes, selenium, and body mass index.

Results. Six hundred one participants had complete demographic, disease, and laboratory information. An inverse association was observed between GPx and age (regression coefficient = –2.9, p <.001), indicating that for each 1-year increase in age, GPx activity decreased by 2.9 µmol/min/L. This finding remained significant after adjustment for hemoglobin, coronary disease, diabetes, and selenium, but not after adjustment for body mass index and weight loss.

Conclusion. This is the first study to examine the association between age and GPx activity in an older adult cohort with disability and chronic disease. These findings suggest that, after age 65, GPx activity declines with age in older women with disability. This decline does not appear to be related to diseases that have been previously reported to alter GPx activity. Longitudinal examination of GPx activity and other antioxidant enzymes in diverse populations of older adults will provide additional insight into age- and disease-related changes in these systems.

Key Words: Glutathione peroxidase— • Oxidative stress— • Aging— • Older adult