Effects of HRT and exercise training on insulin action, glucose tolerance, and body composition in older women

1 Department of Internal Medicine, Division of Geriatrics and Gerontology, and 3 Department of Obstetrics and Gynecology, Washington University School of Medicine, St. Louis, Missouri 63110; and 2 Department of Medicine, Division of Geriatric Medicine, University of Colorado Health Sciences Center, Denver, Colorado 80262 The independent and combined effects of exercise training and hormone replacement therapy (HRT) on body composition, fat distribution, glucose tolerance, and insulin action were studied in postmenopausal women, aged 68 ± 5 yr, assigned to control ( n = 19), exercise ( n = 18), HRT ( n = 15), and exercise + HRT ( n = 16) groups. The exercise consisted of 2 mo of flexibility exercises followed by 9 mo of endurance exercise. HRT was conjugated estrogens 0.625 mg/day and trimonthly medroxyprogesterone acetate 5 mg/day for 13 days. Total and regional body composition were measured by dual-energy X-ray absorptiometry. Serum glucose and insulin responses were measured during a 2-h oral glucose tolerance test. There were significant main effects of exercise on reductions in total and regional (trunk, arms, legs) fat mass, increase in leg fat-free mass, and improvements in glucose tolerance and insulin action. There were significant main effects of HRT on the reduction of total fat mass (HRT, 3.0 ± 4.0 kg; no HRT, 1.3 ± 2.6 kg), with a strong trend for reductions in trunk and leg fat mass (both P = 0.07). There was also a significant improvement in insulin action in response to HRT. These results suggest that there are independent and additive effects of exercise training and HRT on the reduction in fat mass and improvement in insulin action in postmenopausal women; the effect of HRT on insulin action may be mediated, in part, through changes in central adiposity. hormone replacement therapy; insulin resistance; abdominal obesity; estrogens