Physical Activity Is Not Associated with Enhanced Vascular Endothelial Function in Postmenopausal Women: Roles of Mitochondrial Oxidative Stress and the Circulating Milieu

Introduction: Regular physical activity is associated with enhanced vascular endothelial function in older men but has inconsistent effects in estrogen-deficient postmenopausal women (PMW). Lower mitochondrial reactive oxygen species (mitoROS)-related oxidative stress contributes to higher endothelial function in physically active older men, but the effect of regular physical activity on mitoROS-related suppression of endothelial function in PMW has not been established. Moreover, the potential role of the circulating milieu in mediating the effects of physical activity on endothelial function and mitoROS in PMW has not been assessed. Hypothesis: We hypothesized that there would be no differences in vascular endothelial function between sedentary and physically active estrogen-deficient PMW due to comparable mitoROS-related suppression of endothelial function in vivo, which will be coupled with similar modulation of the circulating milieu between groups. Methods and Results: Twenty-nine PMW not taking estrogen-based hormone therapy and >5 years post-menopause were classified as sedentary (N=14) or active (N=15) based on American Heart Association guidelines for physical activity (i.e., ≥150 minutes per week of moderate-intensity aerobic activity, assessed using the Modifiable Activity Questionnaire). There were no differences in age, years since menopause, blood pressure, body composition, blood glucose, or lipid profiles between groups. Endothelial function was assessed as brachial artery flow-mediated dilation (FMD BA ). There were no differences in FMD BA between sedentary (FMD BA = 4.7±3.6%) and active (FMD BA : 5.4±2.3%, P =0.51) PMW. Further, there was no relation between physical activity level and FMD BA­ (r=0.30, P =0.12). MitoROS-associated suppression of endothelial function was determined as the increase in FMD BA from before to 1 hour after an acute oral 160mg supratherapeutic dose of the mitochondrial-targeted antioxidant MitoQ. MitoQ increased FMD BA in both sedentary (to 6.9±3.7%, P =0.009 vs. pre MitoQ) and active (to 8.1±2.3%, P <0.001 vs. pre MitoQ) PMW, but there were no differences in the absolute change in FMD BA with MitoQ between groups (sedentary: 2.2±2.7%; active: 2.7±2.5, P =0.61). There was no relation between physical activity level and the absolute change in FMD BA­ pre-post MitoQ (r=-0.11, P =0.58).The effects of the circulating serum milieu on endothelial cell nitric oxide (NO) production and mitoROS bioactivity in vitro was assessed in human aortic endothelial cells (HAECs) incubated for 2 hours in media with 10% serum from sedentary (n=8) or active (n=8) PMW. Acetylcholine (ACh)-stimulated NO production and basal mitoROS bioactivity normalized to fetal bovine serum were measured via fluorescent microscopy. There were no differences in HAEC ACh-induced NO production (sedentary: 0.97±0.11 AU, active: 0.98±0.15 AU, P =0.86) nor mitoROS bioactivity (sedentary: 0.99±0.11 AU, active: 0.92±0.13 AU, P =0.24) after exposure to serum from sedentary versus active PMW. Conclusions: Regular physical activity in estrogen-deficient PMW is not associated with enhanced vascular endothelial function, at least in part due to the absence of modulatory effects of physical activity on mitoROS-related oxidative stress and the circulating milieu. NIH F31AG087709A (SD), R01AG066730 (DRS), F32HL167552 (KOM) and AHA 23CDA1056582 (MJR). This abstract was presented at the American Physiology Summit 2025 and is only available in HTML format. There is no downloadable file or PDF version. The Physiology editorial board was not involved in the peer review process.