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

Testosterone Depriviation Impairs Cardiac Systolic Function in Orchiectomized Wistar Rats

Several studies have linked low levels of testosterone with increased symptoms of cardiac disease and cardiovascular mortality; however, the effects of testosterone deficiency on cardiac systolic function and morphology are still not completely elucidated. The present study aims to evaluate the influence of testosterone deprivation on cardiac systolic function and morphology. Male Wistar rats were divided into two groups: Sham operation group (Sham): animals underwent sham operation and Orchiectomized group (Orchiec): animals underwent bilateral orchiectomy. The experimental protocol lasted 60 days after the surgery. All animals were weighted and blood samples collected to serum testosterone analysis, determined by chemiluminescence, on first (before orchiectomy) and on 60th days. One day before euthanasia (on the 59th day) echocardiographic parameters were assessed to evaluate left ventricle (LV) systolic function and morphology. Statistical significant difference was set at≤0.05. Orchiec rats presented reduced LV fractional shortening (p=0.032), increased myocardial performance index (MPI) (p=0.043), prolonged mitral valve closure time (p=0.013) and decreased heart rate (p=0.049) when compared to Sham. No statistically significant difference was found in the ejection fraction (p=0.666) between groups. Besides that, heart weight was lower in Orchiec group (p=0.035) when compared to Sham group. Testosterone deprivation reduced cardiac systolic function, changing contraction and relaxation parameters. Testosterone deficiency also changed heart rate and heart weight. The present study demonstrated for the first time that castrated levels of testosterone could alter parameters such as mitral valve closing time and MPI.

Gonadal status modulates large elastic artery stiffness in healthy middle-aged and older men

Hypogonadism is a risk factor for cardiovascular disease (CVD) in men related, in part, to increased oxidative stress. Elevated large artery stiffness and central pulsatile hemodynamics (e.g., pulse pressure and wave reflection magnitude) are independent risk factors for CVD. However, whether large artery stiffness and central pulsatile hemodynamics are (1) elevated in hypogonadal men independent of traditional CVD risk factors and (2) related to increased oxidative stress is unknown. Young men (N = 23; 30 ± 4 years) and middle-aged/older (MA/O) men with normal (> 400-1000 ng/dL; n = 57; 59 ± 7 years) or low testosterone (< 300 ng/dL; n = 21; 59 ± 7 years) underwent assessments of large artery stiffness (carotid ß-stiffness via ultrasonography) and central pulsatile hemodynamics (pulse wave analysis; SphygmoCor XCEL) following an infusion of saline or vitamin C to test the tonic suppression of vascular function by oxidative stress. Carotid stiffness differed by age (p < 0.001) and gonadal status within MA/O men (low testosterone vs. normal testosterone: 9.3 ± 0.7 vs. 8.0 ± 0.3U, p = 0.036). Central pulsatile hemodynamics did not differ by age or gonadal status (p > 0.119). Vitamin C did not alter carotid stiffness in any group (p > 0.171). There was a significant group × infusion interaction on aortic reflection magnitude (p = 0.015). Vitamin C treatment reduced aortic reflection magnitude in young and MA/O men with normal testosterone (both p < 0.001) but not MA/O men with low testosterone (p = 0.891). Collectively, hypogonadism may accelerate age-related large artery stiffening in MA/O men with low testosterone, independent of CVD risk factors; however, this is not related to increased reactive oxygen species sensitive to an acute vitamin C infusion.

Sex differences in the age-related decrease of spontaneous baroreflex function in healthy individuals

The baroreflex is a powerful physiological mechanism for rapidly adjusting heart rate in response to changes in blood pressure. Spontaneous baroreflex sensitivity (BRS) has been shown to decrease with age. However, studies of sex differences in these age-related changes are rare. Here we investigated several markers of spontaneous baroreflex function in a large sample of healthy individuals. Cardiovascular signals were recorded in the supine position under carefully controlled resting conditions. After quality control, n = 980 subjects were divided into five age groups [age < 30 yr (n = 612), 30-39 yr (n = 140), 40-49 yr (n = 95), 50-59 yr (n = 61), and >60 yr (n = 72)]. Spontaneous baroreflex function was assessed in the time domain (bradycardic and tachycardic slope) and in the frequency domain in the low- and high-frequency band (LF-α, HF-α) applying the transfer function. General linear models showed a significant effect of factor age (P < 0.001) and an age × sex interaction effect (P < 0.05) on each indicator of the baroreflex function. Simple main effects showed a significantly higher BRS as indicated by tachycardic slope, LF-α and HF-α in middle-aged women compared with men (30-39 yr) and higher LF-α, bradycardic and tachycardic slope in men compared with women of the oldest age group (>60 yr). Changes in BRS over the lifespan suggest that baroreflex function declines more slowly but earlier in life in men than in women. Our findings could be linked to age-related changes in major sex hormone levels, suggesting significant implications for diverse cardiovascular outcomes and the implementation of targeted preventive strategies.NEW & NOTEWORTHY In this study, we demonstrate that the age-related decrease of spontaneous baroreflex sensitivity is different in men and women by analyzing resting state cardiovascular data of a large sample of healthy individuals.

Guidelines on the use of sex and gender in cardiovascular research

In cardiovascular research, sex and gender have not typically been considered in research design and reporting until recently. This has resulted in clinical research findings from which not only all women, but also gender-diverse individuals have been excluded. The resulting dearth of data has led to a lack of sex- and gender-specific clinical guidelines and raises serious questions about evidence-based care. Basic research has also excluded considerations of sex. Including sex and/or gender as research variables not only has the potential to improve the health of society overall now, but it also provides a foundation of knowledge on which to build future advances. The goal of this guidelines article is to provide advice on best practices to include sex and gender considerations in study design, as well as data collection, analysis, and interpretation to optimally establish rigor and reproducibility needed to inform clinical decision-making and improve outcomes. In cardiovascular physiology, incorporating sex and gender is a necessary component when optimally designing and executing research plans. The guidelines serve as the first guidance on how to include sex and gender in cardiovascular research. We provide here a beginning path toward achieving this goal and improve the ability of the research community to interpret results through a sex and gender lens to enable comparison across studies and laboratories, resulting in better health for all.

Naturally menstruating women exhibit lower cardiovagal baroreflex sensitivity than oral contraceptive users during the lower hormone phase

The present study evaluated cardiovagal baroreflex sensitivity (BRS) across the menstrual/pill cycle in naturally menstruating women (NAT women) and women using oral hormonal contraceptives (OCP women). In 21 NAT women (23 ± 4 years old) and 22 OCP women (23 ± 3 years old), cardiovagal BRS and circulating concentrations of estradiol and progesterone were evaluated during the lower hormone (early follicular/placebo pill) and higher hormone (late follicular to early luteal/active pill) phases. During the lower hormone phase, cardiovagal BRS up, down and mean gain were lower in NAT women (15.6 ± 8.3, 15.2 ± 6.1 and 15.1 ± 7.1 ms/mmHg) compared with OCP women (24.7 ± 9.4, 22.9 ± 8.0 and 23.0 ± 8.0 ms/mmHg) (P = 0.003, P = 0.002 and P = 0.003, respectively), and higher oestrogen (R2  = 0.15, P = 0.024), but not progesterone (R2  = 0.06, P = 0.18), concentrations were predictive of lower BRS mean gain. During the higher hormone phase, higher progesterone concentrations were predictive of lower BRS mean gain (R2  = 0.12, P = 0.024). A multivariate regression model revealed group (NAT or OCP) to be a significant predictor of cardiovagal BRS mean gain in the lower hormone phase when hormone concentrations were adjusted for (R2  = 0.36, P = 0.0044). The multivariate regression model was not significant during the higher hormone phase (P > 0.05). In summary, cardiovagal BRS is lower in NAT compared with OCP women during the lower hormone phase of the menstrual/pill cycle and might be associated with higher oestrogen concentrations. In contrast, during the higher hormone phase of the menstrual/OCP cycle, higher progesterone concentrations were predictive of lower cardiovagal BRS. NEW FINDINGS: What is the central question of this study? Does cardiovagal baroreflex sensitivity (BRS) differ between naturally menstruating women (NAT women) and women using oral contraceptives (OCP women)? What is the main finding and its importance? The main findings are as follows: (1) NAT women exhibit lower cardiovagal BRS than OCP women during the lower hormone phase of the menstrual or pill cycle; and (2) circulating oestrogen concentrations are significant predictors of cardiovagal BRS during the lower hormone phase, with higher oestrogen concentrations predicting lower BRS. The present data advance our understanding of the effect of endogenous ovarian hormones and OCP use on cardiovascular control mechanisms.

Acute nasal breathing lowers diastolic blood pressure and increases parasympathetic contributions to heart rate variability in young adults

There is growing interest in how breathing pace, pattern, and training (e.g., device-guided or -resisted breathing) affect cardiovascular health. It is unknown whether the route of breathing (nasal vs. oral) affects prognostic cardiovascular variables. Because nasal breathing can improve other physiological variables (e.g., airway dilation), we hypothesized that nasal compared with oral breathing would acutely lower blood pressure (BP) and improve heart rate variability (HRV) metrics. We tested 20 adults in this study [13 females/7 males; age: 18(1) years, median (IQR); body mass index: 23 ± 2 kg·m-2, means ± SD]. We compared variables between nasal- and oral-only breathing (random order, five min each) using paired, two-tailed t tests or Wilcoxon signed-rank paired tests with significance set to P < 0.05. We report the median (interquartile range) for diastolic BP and means ± SD for all other variables. We found that nasal breathing was associated with a lower mean BP (nasal: 84 ± 7 vs. oral: 86 ± 5 mmHg, P = 0.006, Cohen's d = 0.70) and diastolic BP [nasal: 68(8) vs. oral: 72(5) mmHg, P < 0.001, Rank-biserial correlation = 0.89] but not systolic BP (nasal: 116 ± 11 vs. oral: 117 ± 9 mmHg, P = 0.48, Cohen's d = 0.16) or heart rate (HR; nasal: 74 ± 10 vs. oral: 75 ± 8 beats·min-1, P = 0.90, Cohen's d = 0.03). We also found that nasal breathing was associated with a higher high-frequency (HF) contribution to HRV (nasal: 59 ± 19 vs. oral: 52 ± 21%, P = 0.04, Cohen's d = 0.50) and a lower low frequency-to-HF ratio at rest (nasal: 0.9 ± 0.8 vs. oral: 1.2 ± 0.9, P = 0.04, Cohen's d = 0.49). These data suggest that nasal compared with oral breathing acutely 1) lowers mean and diastolic BP, 2) does not affect systolic BP or heart rate, and 3) increases parasympathetic contributions to HRV.NEW & NOTEWORTHY There is growing interest in how breathing pace, pattern, and training (e.g., device-guided or -resisted breathing) affect prognostic cardiovascular variables. However, the potential effects of the breathing route on prognostic cardiovascular variables are unclear. These data suggest that nasal compared with oral breathing 1) lowers mean and diastolic blood pressure (BP), 2) does not affect systolic BP or heart rate (HR), and 3) increases parasympathetic contributions to heart rate variability (HRV). These data suggest that acute nasal breathing improves several prognostic cardiovascular variables.