Brown adipose tissue metabolism in women is dependent on ovarian status.

In rodents, loss of estradiol (E2) reduces brown adipose tissue (BAT) metabolic activity. Whether E2 impacts BAT activity in women is not known. BAT oxidative metabolism was measured in premenopausal (n = 27; 35 ± 9 yr; body mass index = 26.0 ± 5.3 kg/m2) and postmenopausal (n = 25; 51 ± 8 yr; body mass index = 28.0 ± 5.0 kg/m2) women at room temperature and during acute cold exposure using [11C]acetate with positron emission tomography coupled with computed tomograph. BAT glucose uptake was also measured during acute cold exposure using 2-deoxy-2-[18F]fluoro-d-glucose. To isolate the effects of ovarian hormones from biological aging, measurements were repeated in a subset of premenopausal women (n = 8; 40 ± 4 yr; BMI = 28.0 ± 7.2 kg/m2) after 6 mo of gonadotropin-releasing hormone agonist therapy to suppress ovarian hormones. At room temperature, there was no difference in BAT oxidative metabolism between premenopausal (0.56 ± 0.31 min-1) and postmenopausal women (0.63 ± 0.28 min-1). During cold exposure, BAT oxidative metabolism (1.28 ± 0.85 vs. 0.91 ± 0.63 min-1, P = 0.03) and net BAT glucose uptake (84.4 ± 82.5 vs. 29.7 ± 31.4 nmol·g-1·min-1, P < 0.01) were higher in premenopausal than postmenopausal women. In premenopausal women who underwent gonadotropin-releasing hormone agonist, cold-stimulated BAT oxidative metabolism was reduced to a similar level (from 1.36 ± 0.66 min-1 to 0.91 ± 0.41 min-1) to that observed in postmenopausal women (0.91 ± 0.63 min-1). These results provide the first evidence in humans that reproductive hormones are associated with BAT oxidative metabolism and suggest that BAT may be a target to attenuate age-related reduction in energy expenditure and maintain metabolic health in postmenopausal women.NEW & NOTEWORTHY In rodents, loss of estrogen reduces brown adipose tissue (BAT) activity. Whether this is true in humans is not known. We found that BAT oxidative metabolism and glucose uptake were lower in postmenopausal compared to premenopausal women. In premenopausal women who underwent ovarian suppression to reduce circulating estrogen, BAT oxidative metabolism was reduced to postmenopausal levels. Thus the loss of ovarian function in women leads to a reduction in BAT metabolic activity independent of age.

Role of BH4 deficiency as a mediator of oxidative stress-related endothelial dysfunction in menopausal women.

Endothelial function (brachial artery flow-mediated dilation [FMD]) is reduced in estrogen-deficient postmenopausal women, mediated, in part, by reduced nitric oxide (NO) bioavailability, secondary to tetrahydrobiopterin (BH4) deficiency and oxidative stress. FMD is increased, but not fully restored, in postmenopausal women after acute intravenous vitamin C (VITC; superoxide scavenger) or oral BH4 supplementation. In vitro studies demonstrate that coadministration of VITC with BH4 prevents endothelial nitric oxide synthase (eNOS) uncoupling and reductions in NO by peroxynitrite. To investigate mechanisms of endothelial dysfunction in women, we assessed the separate and combined effects of VITC and BH4 to determine whether coadministration of VITC + BH4 improves FMD in healthy postmenopausal women (n = 19, 58 ± 5 yr) to premenopausal (n = 14, 36 ± 9 yr) levels, with exploratory testing in perimenopausal women (n = 8, 51 ± 3 yr). FMD was measured during acute intravenous infusions of saline (control) and VITC (∼2-3 g) ∼3 h after a single dose of oral BH4 (KUVAN, 10 mg/kg body wt) or placebo (randomized crossover, separated by ∼1 mo). Under the placebo condition, FMD was reduced in postmenopausal compared with premenopausal women during the saline infusion (5.6 ± 0.7 vs. 11.6 ± 0.9%, P < 0.001) and increased in postmenopausal women during VITC (+3.5 [1.4, 5.6]%, P = 0.001) and acute BH4 (+1.8 [0.37, 3.2]%, P = 0.01) alone. Coadministration of VITC + BH4 increased FMD in postmenopausal women (+3.0 [1.7, 4.3]%, P < 0.001), but FMD remained reduced compared with premenopausal women (P = 0.02). Exploratory analyses revealed that VITC + BH4 did not restore FMD in perimenopausal women to premenopausal levels (P = 0.045). Coadministration of VITC + BH4 does not restore FMD in menopausal women, suggesting that additional mechanisms may be involved.NEW & NOTEWORTHY Endothelial function is reduced across the menopausal stages related to increased oxidative stress associated with estrogen deficiency. In vitro studies demonstrate that coadministration of VITC with BH4 prevents endothelial nitric oxide synthase (eNOS) uncoupling and reductions in NO by peroxynitrite; however, this remains untested in humans. We demonstrate that the coadministration of BH4 + VITC does not restore endothelial function in perimenopausal and postmenopausal women to the level of premenopausal women, suggesting that other mechanisms contribute.

Age-associated reductions in cardiovagal baroreflex sensitivity are exaggerated in middle-aged and older men with low testosterone.

Aging is associated with reductions in cardiovagal baroreflex sensitivity (cBRS), which increases cardiovascular disease risk. Preclinical data indicate that low testosterone reduces cBRS. We determined whether low testosterone is associated with greater age-associated reductions in cBRS in healthy men. Twenty-six men categorized as young (N = 6; age = 31 ± 4 yr; testosterone = 535 ± 60 ng/dL), middle-aged/older with normal (N = 10; aged 56 ± 3 yr; testosterone = 493 ± 85 ng/dL) or low (N = 10; age = 57 ± 6 yr; testosterone = 262 ± 31 ng/dL) testosterone underwent recordings of beat-by-beat blood pressure and R-R interval during rest and two Valsalva maneuvers, and measures of carotid artery compliance. IL-6, C-reactive protein (CRP), oxidized LDL cholesterol, and total antioxidant status (TAS) were also measured in blood. Middle-aged/older men had lower cBRS compared with young men (17.0 ± 6.5 ms/mmHg; P = 0.028); middle-age/older men with low testosterone had lower cBRS (5.5 ± 3.2 ms/mmHg; P = 0.039) compared with age-matched men with normal testosterone (10.7 ± 4.0 ms/mmHg). No differences existed between groups during Phase II of the Valsalva maneuver; middle-aged/older men with low testosterone had reduced cBRS (4.7 ± 2.6 ms/mmHg) compared with both young (12.8 ± 2.8 ms/mmHg; P < 0.001) and middle-aged/older men with normal testosterone (8.6 ± 4.4 ms/mmHg; P = 0.046). There were no differences in oxidized LDL (P = 0.882) or TAS across groups (P = 0.633). IL-6 was significantly higher in middle-aged/older men with low testosterone compared with the other groups (P < 0.05 for all) and inversely correlated with cBRS (r = -0.594, P = 0.007). Middle-aged/older men had reduced carotid artery compliance compared with young, regardless of testosterone status (P < 0.001). These observations indicate that low testosterone in middle-aged/older men may contribute to reductions in cBRS. These data suggest that increased inflammation may contribute to reductions in cBRS.NEW & NOTEWORTHY Middle-aged/older men with low testosterone have accelerated reductions in cardiovagal BRS compared with middle-aged/older men with normal testosterone. Increased concentrations of the proinflammatory cytokine IL-6 appear to contribute to the reductions in cardiovagal BRS in men with low testosterone.

Adverse cardiovascular events and mortality in men during testosterone treatment: an individual patient and aggregate data meta-analysis.

Background: Testosterone is the standard treatment for male hypogonadism, but there is uncertainty about its cardiovascular safety due to inconsistent findings. We aimed to provide the most extensive individual participant dataset (IPD) of testosterone trials available, to analyse subtypes of all cardiovascular events observed during treatment, and to investigate the effect of incorporating data from trials that did not provide IPD. Methods: We did a systematic review and meta-analysis of randomised controlled trials including IPD. We searched MEDLINE, MEDLINE In-Process & Other Non-Indexed Citations, MEDLINE Epub Ahead of Print, Embase, Science Citation Index, the Cochrane Controlled Trials Register, Cochrane Database of Systematic Reviews, and Database of Abstracts of Review of Effects for literature from 1992 onwards (date of search, Aug 27, 2018). The following inclusion criteria were applied: (1) men aged 18 years and older with a screening testosterone concentration of 12 nmol/L (350 ng/dL) or less; (2) the intervention of interest was treatment with any testosterone formulation, dose frequency, and route of administration, for a minimum duration of 3 months; (3) a comparator of placebo treatment; and (4) studies assessing the pre-specified primary or secondary outcomes of interest. Details of study design, interventions, participants, and outcome measures were extracted from published articles and anonymised IPD was requested from investigators of all identified trials. Primary outcomes were mortality, cardiovascular, and cerebrovascular events at any time during follow-up. The risk of bias was assessed using the Cochrane Risk of Bias tool. We did a one-stage meta-analysis using IPD, and a two-stage meta-analysis integrating IPD with data from studies not providing IPD. The study is registered with PROSPERO, CRD42018111005. Findings: 9871 citations were identified through database searches and after exclusion of duplicates and of irrelevant citations, 225 study reports were retrieved for full-text screening. 116 studies were subsequently excluded for not meeting the inclusion criteria in terms of study design and characteristics of intervention, and 35 primary studies (5601 participants, mean age 65 years, [SD 11]) reported in 109 peer-reviewed publications were deemed suitable for inclusion. Of these, 17 studies (49%) provided IPD (3431 participants, mean duration 9·5 months) from nine different countries while 18 did not provide IPD data. Risk of bias was judged to be low in most IPD studies (71%). Fewer deaths occurred with testosterone treatment (six [0·4%] of 1621) than placebo (12 [0·8%] of 1537) without significant differences between groups (odds ratio [OR] 0·46 [95% CI 0·17-1·24]; p=0·13). Cardiovascular risk was similar during testosterone treatment (120 [7·5%] of 1601 events) and placebo treatment (110 [7·2%] of 1519 events; OR 1·07 [95% CI 0·81-1·42]; p=0·62). Frequently occurring cardiovascular events included arrhythmia (52 of 166 vs 47 of 176), coronary heart disease (33 of 166 vs 33 of 176), heart failure (22 of 166 vs 28 of 176), and myocardial infarction (10 of 166 vs 16 of 176). Overall, patient age (interaction 0·97 [99% CI 0·92-1·03]; p=0·17), baseline testosterone (interaction 0·97 [0·82-1·15]; p=0·69), smoking status (interaction 1·68 [0·41-6·88]; p=0.35), or diabetes status (interaction 2·08 [0·89-4·82; p=0·025) were not associated with cardiovascular risk. Interpretation: We found no evidence that testosterone increased short-term to medium-term cardiovascular risks in men with hypogonadism, but there is a paucity of data evaluating its long-term safety. Long-term data are needed to fully evaluate the safety of testosterone. Funding: National Institute for Health Research Health Technology Assessment Programme.

Decline in endothelial function across the menopause transition in healthy women is related to decreased estradiol and increased oxidative stress.

Endothelial function declines progressively across stages of the menopause transition; however, the mechanisms contributing to this decline are unknown. We hypothesized that differences in endothelial function among pre-, peri, and postmenopausal women are related to differences in estradiol and oxidative stress. Brachial artery flow-mediated dilation (FMD) was measured in 87 healthy women categorized by menopause stage (24 premenopausal, 17 early and 21 late perimenopausal, and 25 postmenopausal) before and after 3 days of ovarian hormone suppression (gonadotropin releasing hormone antagonist [GnRHant]) alone, and an additional 3 days of GnRHant with concurrent transdermal estradiol or placebo add-back treatment. In 82 women, FMD during acute vitamin C (antioxidant) infusion was measured before and after GnRHant + add-back. Before GnRHant, FMD was different among groups (p < 0.005; reduced across stages of menopause). Vitamin C increased FMD in late peri- and post- (p < 0.005) but not pre- or early perimenopausal women (p > 0.54). After GnRHant alone, FMD decreased in pre- and peri- (p < 0.01), but not postmenopausal women, and was restored to premenopausal levels by estradiol add-back in the pre- and perimenopausal groups. Vitamin C improved FMD in pre-, peri-, and postmenopausal women on GnRHant + placebo. There was no effect of vitamin C on FMD in women on GnRHant + estradiol. These observations support the concept that the decline in endothelial function across the menopause transition is related to the loss of ovarian estradiol. The decline in estradiol may alter redox balance, thereby increasing oxidative stress and impairing endothelial function.

Effects of resveratrol or estradiol on postexercise endothelial function in estrogen-deficient postmenopausal women.

Regular exercise enhances endothelial function in older men, but not consistently in estrogen-deficient postmenopausal women. Estradiol treatment improves basal endothelial function and restores improvements in endothelial function (flow-mediated dilation, FMD) to aerobic exercise training in postmenopausal women; however, estradiol treatment is controversial. Resveratrol, an estrogen receptor ligand, enhances exercise training effects on cardiovascular function and nitric oxide (NO) release in animal models, but impairs exercise training effects in men. We conducted a randomized cross-over, double-blinded, placebo-controlled pilot study to determine whether acute (single dose) resveratrol (250-mg tablet) or estradiol (0.05 mg/day transdermal patch) treatment enhances FMD at rest and after a single bout of moderate-intensity aerobic exercise in healthy estrogen-deficient postmenopausal women (n = 15, 58.1 ± 3.2 yr). FMD was measured before and after (30, 60, and 120 min) a 40-min bout of moderate-intensity treadmill exercise (60-75% peak heart rate) under the respective conditions (separated by 1-2 wk). FMD was higher (P < 0.05) before exercise and at all post-exercise time points in the resveratrol and estradiol conditions compared to placebo. FMD was increased from baseline by 120 min postexercise in the estradiol condition (P < 0.001), but not resveratrol or PL conditions. Consistent with our previous findings, estradiol also enhances endothelial function in response to acute endurance exercise. Although resveratrol improved basal FMD, there was no apparent enhancement of FMD to acute exercise and, therefore, may not act as an estradiol mimetic.NEW & NOTEWORTHY The benefits of endurance exercise training on endothelial function are diminished in estrogen-deficient postmenopausal women, but estradiol treatment appears to restore improvements in endothelial function in this group. We show that basal endothelial function is enhanced with both acute estradiol and resveratrol treatments in estrogen-deficient postmenopausal women, but endothelial function is only enhanced following acute endurance exercise with estradiol treatment.

Elevated plasma homocysteine and cysteine are associated with endothelial dysfunction across menopausal stages in healthy women.

Hyperhomocysteinemia is associated with endothelial dysfunction and increased cardiovascular disease (CVD). We determined whether elevated homocysteine (Hcy) and markers of Hcy metabolism were associated with the previously reported endothelial dysfunction across stages of the menopause transition. Brachial artery flow-mediated dilation (FMD) and plasma concentrations of Hcy, cysteine, and methionine were measured in healthy women (n = 128) 22-70 yr of age categorized as premenopausal (n = 35), perimenopausal (early: n = 16; late: n = 21), and postmenopausal (early: n = 21; late: n = 35). Dietary intake of micronutrients involved in Hcy metabolism (e.g., vitamins B6, B12, folate) was assessed in a subpopulation of women. Hcy and cysteine concentrations were progressively higher, and methionine was progressively lower across menopausal stages (all P < 0.005). The higher Hcy and cysteine concentrations correlated with lower circulating estradiol levels (r = -0.49 and -0.50, respectively, both P < 0.001). FMD was inversely correlated with Hcy (r = -0.25, P = 0.004) and cysteine (r = -0.39, P < 0.001) and positively correlated with methionine concentrations (r = 0.25, P = 0.005). Dietary intake of vitamins B6 and B12 (both P < 0.05) were lower in postmenopausal women. Vitamin B12 intake correlated with FMD (r = 0.22, P = 0.006). These data suggest that declines in estradiol across stages of the menopause transition may lead to elevations in Hcy and cysteine that may contribute to endothelial dysfunction in postmenopausal women. Future studies should examine whether targeting Hcy metabolism during the perimenopausal to early postmenopausal period with interventions, including diet, attenuates or reverses the decline in endothelial function in women. NEW & NOTEWORTHY Declines in circulating estradiol across the stages of the menopausal transition may lead to elevations in Hcy and cysteine concentrations that may contribute to endothelial dysfunction. Abnormalities in the Hcy metabolic pathways, possibly related to dietary deficiencies of vitamins B12 and B6 and folate, may contribute to elevations in Hcy and cysteine concentrations. Findings also suggest that higher cysteine levels may be more damaging to the vascular endothelium than Hcy.

Vascular Aging across the Menopause Transition in Healthy Women.

Vascular aging, featuring endothelial dysfunction and large artery stiffening, is a major risk factor for developing cardiovascular disease (CVD). In women, vascular aging appears to be accelerated during the menopause transition, particularly around the late perimenopausal period, presumably related to declines in ovarian function and estrogen levels. The mechanisms underlying endothelial dysfunction and large artery stiffening with the menopause transition are not completely understood. Oxidative stress and the proinflammatory cytokine tumor necrosis factor-α contribute to endothelial dysfunction and large artery stiffening in estrogen-deficient postmenopausal women. Habitual endurance exercise attenuates the age-related increase in large artery stiffness in estrogen-deficient postmenopausal women and can reverse arterial stiffening to premenopausal levels in estrogen-replete postmenopausal women. In contrast, estrogen status appears to play a key permissive role in the adaptive response of the endothelium to habitual endurance exercise in that endothelial improvements are absent in estrogen-deficient women but present in estrogen-replete women. We review here the current state of knowledge on the biological defects underlying vascular aging across the menopause transition, with particular focus on potential mechanisms, the role of habitual exercise in preserving vascular health, and key areas for future research.

Association of serum dehydroepiandrosterone sulfate and cognition in older adults: sex steroid, inflammatory, and metabolic mechanisms.

OBJECTIVE: Dehydroepiandrosterone sulfate (DHEAS) levels and cognitive function decline with age, and a role for DHEAS in supporting cognition has been proposed. Higher DHEAS levels may be associated with better cognitive performance, although potential mechanisms for this relationship are not well established. METHOD: We performed a cross-sectional study of the relationship between serum DHEAS and three aspects of cognition--executive function, working memory, and processing speed--in 49 men and 54 women, aged 60-88 years, with low serum DHEAS levels. We examined three potential mechanisms of DHEAS action--sex hormone sufficiency, inflammatory status, and glucose regulation. RESULTS: After adjustment for multiple covariates, higher serum DHEAS levels were associated with better working memory (standardized beta coefficient 0.50, p < .05), with a trend toward better executive function (standardized beta coefficient 0.37, p < .10) in men only. There was a nonsignificant trend toward a negative association between levels of tumor necrosis factor α (TNFα) and working memory in the combined population (standardized beta coefficient -0.22, p < .10). None of the glucoregulatory measures was associated with cognitive function. CONCLUSIONS: The relationship between DHEAS and cognition is complex and differs by sex and cognitive domain. This study supports the need for further investigations of the sex-specific effects of DHEAS on cognition and its underlying mechanisms of action.

Phosphorylation of the platelet-derived growth factor receptor-beta by G protein-coupled receptor kinase-2 reduces receptor signaling and interaction with the Na(+)/H(+) exchanger regulatory factor.

G protein-coupled receptor kinase-2 (GRK2) can phosphorylate and desensitize the platelet-derived growth factor receptor-beta (PDGFRbeta) in heterologous cellular systems. To determine whether GRK2 regulates the PDGFRbeta in physiologic systems, we examined PDGFRbeta signaling in mouse embryonic fibroblasts from GRK2-null and cognate wild type mice. To discern a mechanism by which GRK2-mediated phosphorylation can desensitize the PDGFRbeta, but not the epidermal growth factor receptor (EGFR), we investigated effects of GRK2-mediated phosphorylation on the association of the PDGFRbeta with the Na(+)/H(+) exchanger regulatory factor (NHERF), a protein shown to potentiate dimerization of the PDGFRbeta, but not the EGFR. Physiologic expression of GRK2 diminished (a) phosphoinositide hydrolysis elicited through the PDGFRbeta but not heterotrimeric G proteins; (b) Akt activation evoked by the PDGFRbeta but not the EGFR; and (c) PDGF-induced tyrosyl phosphorylation of the PDGFRbeta itself. PDGFRbeta desensitization by physiologically expressed GRK2 correlated with a 2.5-fold increase in PDGF-promoted PDGFRbeta seryl phosphorylation. In 293 cells, GRK2 overexpression reduced PDGFRbeta/NHERF association by 60%. This effect was reproduced by S1104D mutation of the PDGFRbeta, which also diminished PDGFRbeta activation and signaling (like the S1104A mutation) to an extent equivalent to that achieved by GRK2-mediated PDGFRbeta phosphorylation. GRK2 overexpression desensitized only the wild type but not the S1104A PDGFRbeta. We conclude that GRK2-mediated PDGFRbeta seryl phosphorylation plays an important role in desensitizing the PDGFRbeta in physiologic systems. Furthermore, this desensitization appears to involve GRK2-mediated phosphorylation of PDGFRbeta Ser(1104), with consequent dissociation of the PDGFRbeta from NHERF.