Attenuated vascular endothelial dysfunction in late-onset postmenopausal women is mediated by reduced mitochondrial oxidative stress: contribution of the serum lipidome

Postmenopausal women (PMW) who complete menopause at a late age (55+ years) have lower cardiovascular disease (CVD) risk than PMW who complete menopause at a normal age (45-54 years). However, the mechanisms contributing to lower CVD risk in late-onset PMW are not completely understood. Hypothesis: We hypothesized that compared with normal-onset PMW, late-onset PMW would be protected from age- and menopause-related vascular endothelial dysfunction, which would be mediated by lower mitochondrial reactive oxygen species (mitoROS)-related suppression of endothelial function. We also hypothesized that relative to normal-onset PMW, late-onset PMW would exhibit a more favorable circulating milieu that, in turn, ameliorates endothelial cell mitoROS bioactivity largely as a result of lower levels of select lipid-related metabolites. Methods: Vascular endothelial function (brachial artery flow-mediated dilation, FMD BA ) was assessed in late-onset (age 68±1; n=22) and normal-onset (age 68±1; n=49) PMW and a young premenopausal (PRE; age 23±1; n=21) reference group. MitoROS-related suppression of endothelial function was assessed as the change in FMD BA with an acute dose (160 mg) of the mitochondria-targeted antioxidant MitoQ (DFMD BA,MTQ ) in PMW. The effects of serum from late- and normal-onset PMW and PRE on in vitro mitoROS bioactivity in human aortic endothelial cells (HAECs) in culture were assessed using fluorescent microscopy. Metabolomics analyses (including lipidomics, non-lipid metabolomics and oxylipin analyses) in combination with serum metabolite level normalization and HAEC serum exposure experiments were performed to identify the circulating factors contributing to differences in endothelial cell mitoROS bioactivity. Results: FMD BA in late-onset (6.3±0.6%; p=0.02) and normal-onset (4.1±0.4%; p<0.0001) PMW was expectedly lower than in premenopausal women (8.3±0.7%). However, FMD BA was 54% higher (p=0.002) in late- versus normal-onset PMW such that FMD BA was only 24% lower than PRE in late-onset PMW (p=0.012) compared with 51% lower than PRE in normal-onset PMW (p<0.0001). FMD BA was positively related to age at menopause (r=0.32, p=0.007). Age at menopause both as a categorical and continuous variable remained an independent predictor of FMD BA when controlling for age, physical activity and cardiometabolic factors. DFMD BA,MTQ was 54% lower in late- (1.3±0.4%) versus normal-onset (2.8±0.3%; p=0.002) PMW. MitoROS bioactivity in HAECs exposed to serum from late-onset PMW (0.99±0.05 AU) was lower (p=0.008) than in HAECs exposed to serum from normal-onset PMW (1.12±0.02 AU) and not different from HAECs exposed to serum from PRE (1.00±0.05 AU). Seventeen metabolites differed between late- and normal-onset PMW (log 2 (fold change[FC])±0.05 and false discovery rate(FDR)-adjusted p-value<0.05); 15 were lipid-specific; eight were triglyceride (TG)-derived. TG(16:0) was most strongly correlated with mitoROS bioactivity (r=0.53, p=0.016). Normalization of TG(16:0) concentrations in serum from PRE and late-onset PMW to match serum levels in normal-onset PMW abrogated differences in mitoROS bioactivity in serum-treated HAECs (PRE: 1.00±0.02 AU; normal-onset PMW: 1.01±0.01 AU; late-onset PMW 1.05±0.02 AU; all p>0.05). Conclusions: Late-onset PMW demonstrate an attenuation of endothelial dysfunction mediated by lower mitoROS-related oxidative stress. A more favorable profile of circulating lipid metabolites, specifically TG-derived metabolites, contributes to lower endothelial cell mitoROS in late-onset PMW. These findings provide new insight into the potential physiological and biological mechanisms contributing to lower CVD risk in late-onset PMW. F31AG087709A (SD), K01DK115524 and 23CDA1056582 (MJR), R01AG066730 (DRS), F32HL167552 (KOM), K01HL153326 (DHC), F31HL154782 (KAF) 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.