DHEA REPLACEMENT AND RESISTANCE EXERCISE IN THE ELDERLY

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This subproject is one of many research subprojects utilizing the resources provided by a Center grant funded by NIH/NCRR. The subproject and investigator (PI) may have received primary funding from another NIH source, and thus could be represented in other CRISP entries. The institution listed is for the Center, which is not necessarily the institution for the investigator. Aging is associated with a loss of muscle mass. Given the close association between muscle mass and bone mineral density (BMD), interventions to increase fat-free mass (FFM) in the elderly are necessary to prevent frailty and loss of functional independence. Furthermore, loss of muscle mass may predispose the older adult to obesity and Type 2 diabetes. Older adults can achieve significant increases in muscular strength in response to resistance exercise training (REX) but gains in FFM are typically modest (about 2 lbs or 1 kg) and less than those achieved by younger adults. The working model for the proposed study is that low levels of anabolic ("building") hormones in older adults limit the gains in FFM with REX. Dehydroepiandrosterone (DHEA) is a hormone secreted by the adrenal gland in diminishing amounts with advancing age. In previous studies, oral DHEA replacement (50 mg/day) increased blood DHEA-sulfate in older adults to young adult levels, and increased FFM and BMD. Thus the research hypothesis is that DHEA replacement in older adults will provide sufficient anabolic support to add to the increases in FFM and BMD in response to REX. To test this hypothesis, 20 healthy women and men, greater than 60 years old, will be recruited to complete a 6-month intervention of REX and DHEA replacement. The volunteers will have completed a 12-month study of DHEA replacement (GCRC protocol #1195) before starting REX. The volunteers were randomly assigned to take DHEA replacement (50 mg/day) or placebo. These assignments will continue for an additional 6 months, and will remain double-blinded. The study groups will be REX+DHEA and REX+placebo. REX will be 3 days per week, of high intensity (80% of maximum strength), using 7 exercises. Body composition will be determined by dual energy x-ray absorptiometry, computed tomography (CT) scans of the abdomen and mid-thigh areas, and circumference measurements. Muscle quality will be determined by one-repetition maximum strength tests, the Continuous-Scale Physical Functional Performance test, and oral glucose tolerance tests for insulin action. Changes in body composition and muscle quality in relation to serum levels of anabolic hormones and growth factors will be examined.