Substrate utilization during exercise in postmenopausal women on hormone replacement therapy

Abstract

It has been suggested that due to the slight direct or indirect effect of estrogen on lipolytic activity, the age-related decrease in production associated with the menopause may heighten the risk of cardiovascular and metabolic disease in women. While hormone replacement therapy (HRT) alone may have little or no effect on body mass in postmenopausal women, data suggest it can alter the shift toward abdominal adiposity. Furthermore, estrogen may have a synergistic effect on exercise-induced reduction in fat mass. Accordingly, the purpose of this investigation was to examine the potential influence of HRT on substrate utilization during 30 min of treadmill exercise at approximately 80% maximal oxygen uptake (VO(2max)) in postmenopausal women. Eight women were receiving HRT and nine women were not (NHRT). No significant differences between the HRT and NHRT groups were noted for age, body mass, body fat, VO(2max) or the percentage of VO(2max) maintained during exercise. Expired gas samples were analyzed every 30 s to determine respiratory exchange ratio (R) and % VO(2max). The R, total energy expended and percentage contributions from fats and carbohydrate were averaged over three periods during the exercise (min 1-10, 11-20, and 21-30). There was no effect of HRT on R, total energy expended or substrate contribution. Thus, treatment of postmenopausal women using HRT (primarily conjugated equine estrogens in doses of 0.625-1.25 mg x day(-1)) did not appear to affect the percentages of fat and carbohydrate utilized during 30 min of treadmill exercise at 80% of VO(2max). However, the exercise responses in this group of menopausal women were consistent with a duration-dependent increased reliance on fat as an energy source during exercise of moderate to vigorous intensity as has been demonstrated in younger populations.

Maximal and submaximal aerobic fitness in postmenopausal women: influence of hormone-replacement therapy

“…Nevertheless, different results have been reported for _ V O 2 max in postmenopausal women taking and not taking HRT. No difference in _ V O 2 max related to HRT use has been reported in healthy sedentary women (Johnson et al 2002;McCole et al 2000;Kirwan et al 2004;Moreau et al 2003;Snabes et al 1996) or in endurance-trained women (Green et al 1998;McCole et al 2000;Moreau et al 2002). In contrast, a greater _ V O 2 max in women taking HRT has been observed in sedentary women (Jurca et al 2004;Mercuro et al 2007), in women at risk for coronary artery disease (CAD) (Redberg et al 2000), and in women with CAD (Kirwan et al 2003).…”

“…In our study, the average duration of HRT use was 9.4 ± 5.3 years. There appears to be no difference in _ V O 2 max between non-HRT users and short- (Kirwan et al 2004;Snabes et al 1996) and long-term HRT users (Green et al 1998;Johnson et al 2002;Katyal et al 2003;McCole et al 2000;Moreau et al 2002Moreau et al , 2003. Erickson et al (2007) reported no difference in _ V O 2 peak between short-, mid-, and long-term HRT users.…”

“…In the 3 studies reporting a difference in _ V O 2 max related to HRT use, approximately half the women took unopposed estrogen and half took a combination of estrogen plus progesterone (Jurca et al 2004;Kirwan et al 2003;Redberg et al 2000). In the 7 studies reporting no difference (Green et al 1998;Johnson et al 2002;Kirwan et al 2004;McCole et al 2000;Moreau et al 2002Moreau et al , 2003Snabes et al 1996) , a greater proportion (70%-80%) of HRT users were taking the combination therapy. There is currently debate surrounding the influence of progestins on the effectiveness of estrogen.…”

“…This study was not a randomized trial, and the sample size might not have had adequate power to detect small differences between those taking and not taking HRT. Previous studies of sedentary women have found no difference between HRT and non-HRT groups (Johnson et al 2002;Katyal et al 2003;Kirwan et al 2004;McCole et al 2000;Moreau et al 2003;Snabes et al 1996); however, other differences between the groups made comparisons difficult. Jurca et al (2004) reported a significantly greater _ V O 2 max in a sample of sedentary women taking HRT, but in their study, the mean BMI was 32 kgÁm -2 (obese) and the mean systolic blood pressure was elevated (140 mm Hg).…”

Efeito de uma sobrecarga lipídica sobre o metabolismo energético e hormônios reguladores da fome e saciedade de mulheres pós-menopausadas estratificadas de acordo com o valor do estradiol plasmático

“…Apesar de não haver ainda um papel definido do estrógeno no metabolismo de substratos, há forte evidência de que, tanto em humanos quanto em animais, a oxidação lipídica é maior quando as concentrações de estradiol estão elevadas (JOHNSON et al, 2002).…”