Evidence of a role of endogenous estrogen in the modulation of autonomic nervous system

Overnight Heart Rate Variability During Sleep Disturbance In Peri- And Postmenopausal Women

OBJECTIVES

Disturbed sleep, common during the climacteric, is associated with increased sympathetic activity, a cardiovascular risk factor. We evaluated sleep disturbance effect on autonomic nervous function in climacteric women.

METHODS

Seventeen perimenopausal and 18 postmenopausal women underwent a sleep study protocol: an adaptation night, a reference night, and a sleep disturbance night, with a hand loosely tied to the bed to allow blood sampling. This procedure was repeated after six months of menopausal hormone therapy (MHT) or placebo. Sleep disturbance and MHT effects on overnight heart rate variability (HRV) were analyzed.

RESULTS

At baseline, sleep disturbance increased vagal HRV in postmenopausal women, but no changes were seen in perimenopausal women. At six months, sleep disturbance increased total HRV power in the perimenopausal placebo group, and increased nonlinear vagal HRV in the postmenopausal placebo group, but no other changes were seen. MHT did not have any effects on HRV, neither at perimenopause nor at postmenopause.

CONCLUSIONS

External sleep disturbance had only minor effects on HRV across menopause. MHT had no detectable HRV effects.

Factors influencing blood pressure variability in postmenopausal women: evidence from the China Health and Nutrition Survey

BACKGROUND

The aim is to identify the factors influencing blood pressure variability in postmenopausal women based on the China Health and Nutrition Survey (CHNS).

MATERIAL AND METHODS

The data on postmenopausal women between 1993 and 2015 were extracted from the CHNS. Group-based trajectory modeling was used to analyze the development track of blood pressure changes, based on which the subjects were separately divided into two groups for systolic blood pressure (SBP) and diastolic blood pressure (DBP). Univariate and multivariate analyzes were performed to analyze the factors influencing SBP and DBP.

RESULTS

A total of 346 women were eligible for the study. Group-based trajectory modeling showed two different trajectories of blood pressure, including the low-level, slowly developed type and the high-level, rapidly developed, stable type of SBP, as well as the low-level, slowly developed type and the high-level, slowly developed type of DBP. In multivariate analysis, age (odds ratio [OR]: 1.118, 95% confidence interval [CI]: 1.082-1.156), body mass index (BMI) (OR: 2.239, 95%CI: 1.010-4.964), antihypertensive agents (OR: 7.293, 95%CI: 2.191-24.275), hip circumference (OR: 1.069, 95%CI: 1.014-1.128) and marital status (OR: 3.103, 95%CI: 1.028-9.361) were found to be the significant factors influencing SBP; age (OR: 1.067, 95%CI: 1.039-1.096), alcohol consumption (OR: 2.741, 95%CI: 1.169-6.429), antihypertensive agents (OR: 4.577, 95%CI: 1.553-13.492), hip circumference (OR: 1.093, 95%CI: 1.049-1.138), and marital status (OR: 3.615, 95%CI: 1.228-10.644) were the predominant factors influencing DBP.

CONCLUSIONS

In postmenopausal women, age, BMI, antihypertensive agents, hip circumference, and marital status are associated with SBP changes, while age, alcohol consumption, antihypertensive agents, hip circumference, and marital status with DBP variability.

MESH KEYWORDS

postmenopausal women, blood pressure, development track, influencing factors, CHNS.

Episodic Migraine and POTS

PURPOSE OF REVIEW

Migraine is prevalent in patients with postural orthostatic tachycardia syndrome (POTS). The purpose of this review is to summarize and interpret studies that examine stress response systems in patients with migraine, focusing on their relevance to the pathologies associated with POTS. Important structural and functional components of the stress response network are also reviewed.

RECENT FINDINGS

In patients with migraine, studies examining the autonomic nervous system have demonstrated interictal sympathetic hypofunction and ictal sympathetic hyperfunction, while those focusing on the hypothalamic-pituitary-adrenal axis have demonstrated elevated responsivity. There is evidence that activation of these stress response systems during a migraine episode may exacerbate vascular dysfunction and play a role in the development of central sensitization. Activation of the stress response systems during an episode of migraine has the potential to exacerbate the pathology of POTS. Treatment approaches for the patient with comorbid episodic migraine and POTS should consider the etiology of POTS.

Which Comes First, Nonalcoholic Fatty Liver Disease or Arterial Hypertension?

Non-alcoholic fatty liver disease (NAFLD) and arterial hypertension (AH) are widespread noncommunicable diseases in the global population. Since hypertension and NAFLD are diseases associated with metabolic syndrome, they are often comorbid. In fact, many contemporary published studies confirm the association of these diseases with each other, regardless of whether other metabolic factors, such as obesity, dyslipidemia, and type 2 diabetes mellites, are present. This narrative review considers the features of the association between NAFLD and AH, as well as possible pathophysiological mechanisms.

Electrocardiographic parameters and the risk of new-onset atrial fibrillation in the general population: the Rotterdam Study

AIMS

We aimed to assess the (shape of the) association and sex differences in the link between electrocardiographic parameters and new-onset atrial fibrillation (AF).

METHODS AND RESULTS

A total of 12 212 participants free of AF at baseline from the population-based Rotterdam Study were included. Up to five repeated measurements of electrocardiographic parameters including PR, QRS, QT, QT corrected for heart rate (QTc), JT, RR interval, and heart rate were assessed at baseline and follow-up examinations. Cox proportional hazards- and joint models, adjusted for cardiovascular risk factors, were used to determine the (shape of the) association between baseline and longitudinal electrocardiographic parameters with new-onset AF. Additionally, we evaluated potential sex differences. During a median follow-up of 9.3 years, 1282 incident AF cases occurred among 12 212 participants (mean age 64.9 years, 58.2% women). Penalized cubic splines revealed that associations between baseline electrocardiographic measures and risk of new-onset AF were generally U- and N-shaped. Sex differences in terms of the shape of the various associations were most apparent for baseline PR, QT, QTc, RR interval, and heart rate in relation to new-onset AF. Longitudinal measures of higher PR interval [fully adjusted hazard ratio (HR), 95% confidence interval (CI), 1.43, 1.02-2.04, P = 0.0393] and higher QTc interval (fully adjusted HR, 95% CI, 5.23, 2.18-12.45, P = 0.0002) were significantly associated with new-onset AF, in particular in men.

CONCLUSION

Associations of baseline electrocardiographic measures and risk of new-onset AF were mostly U- and N-shaped. Longitudinal electrocardiographic measures of PR and QTc interval were significantly associated with new-onset AF, in particular among men.

Effects of Exercise Intensity on Cardiometabolic Parameters of Ovariectomized Obese Mice

The aim of this study was to compare the effects of continuous-moderate vs. high-intensity interval aerobic training on cardiovascular and metabolic parameters in ovariectomized high-fat-fed mice. C57BL/6 female ovariectomized were divided into four groups (n=8): low-fat-fed sedentary (SLF); high-fat-fed sedentary (SHF); high-fat-fed moderate-intensity continuous trained (MICT-HF); and high-fat-fed high-intensity interval aerobic trained (HIIT-HF). The high-fat diet lasted 10 weeks. Ovariectomy was performed in the fourth week. The exercise training was carried out in the last four weeks of protocol. Fasting glycemia, oral glucose tolerance, arterial pressure, baroreflex sensitivity, and cardiovascular autonomic modulation were evaluated. Moderate-intensity continuous training prevented the increase in arterial pressure and promoted a reduction in HR at rest, associated with an improvement in the sympathovagal balance in MICT-HF vs. SHF. The high-intensity interval training reduced blood glucose and glucose intolerance in HIIT-HF vs. SHF and MICT-HF. In addition, it improved sympathovagal balance in HIIT-HF vs. SHF. Moderate-intensity continuous training was more effective in promoting cardiovascular benefits, while high-intensity interval training was more effective in promoting metabolic benefits.

Heart rate fragmentation is impaired in type 2 diabetes mellitus patients

AIMS

To evaluate the heart rate fragmentation (HRF) of type 2 diabetes mellitus (T2DM) patients and its relationship with heart rate variability (HRV) indices.

METHODS

One hundred sixty-four men, aged 47-57 years were retrospectively analyzed from a database. Participants were T2DM (n = 82) and apparently healthy (n = 82). R-R interval time series recorded by electrocardiogram were collected at the supine position for 10 to 15 min. From HRF, the percentage of inflection points (PIP), percentage of words with zero, one, two, or three inflections points (W₀, W₁, W₂, W₃), and percentage with only type hard, soft, or mixed inflections points type (W^H, W^S, W^M) were quantified.

RESULTS

T2DM presented higher PIP, W^S, W^M and W₃, while W^H and W₁ was lower compared with healthy (p < 0.05). Moreover, a positive moderate correlation was found between W^H and root mean square of the successive R-R differences (RMSSD) and high frequency (HF) indices. In contrast, a negative moderate correlation was found between W^S and W^M with RMSSD and HF indices.

CONCLUSIONS

T2DM have increased fragmentation patterns, and words grouped by inflection type are more closely related to HRV. The HRF approach might be useful to assess heart rate dynamic abnormalities in males with type 2 diabetes.

Gender Differences and Cardiometabolic Risk: The Importance of the Risk Factors

Metabolic syndrome (Mets) is a clinical condition characterized by a cluster of major risk factors for cardiovascular disease (CVD) and type 2 diabetes: proatherogenic dyslipidemia, elevated blood pressure, dysglycemia, and abdominal obesity. Each risk factor has an independent effect, but, when aggregated, they become synergistic, doubling the risk of developing cardiovascular diseases and causing a 1.5-fold increase in all-cause mortality. We will highlight gender differences in the epidemiology, etiology, pathophysiology, and clinical expression of the aforementioned Mets components. Moreover, we will discuss gender differences in new biochemical markers of metabolic syndrome and cardiovascular risk.

Heart rate variability and atrial fibrillation in the general population: a longitudinal and Mendelian randomization study

BACKGROUND

Sex differences and causality of the association between heart rate variability (HRV) and atrial fibrillation (AF) in the general population remain unclear.

METHODS

12,334 participants free of AF from the population-based Rotterdam Study were included. Measures of HRV including the standard deviation of normal RR intervals (SDNN), SDNN corrected for heart rate (SDNNc), RR interval differences (RMSSD), RMSSD corrected for heart rate (RMSSDc), and heart rate were assessed at baseline and follow-up examinations. Joint models, adjusted for cardiovascular risk factors, were used to determine the association between longitudinal measures of HRV with new-onset AF. Genetic variants for HRV were used as instrumental variables in a Mendelian randomization (MR) analysis using genome-wide association studies (GWAS) summary-level data.

RESULTS

During a median follow-up of 9.4 years, 1302 incident AF cases occurred among 12,334 participants (mean age 64.8 years, 58.3% women). In joint models, higher SDNN (fully-adjusted hazard ratio (HR), 95% confidence interval (CI) 1.24, 1.04-1.47, p = 0.0213), and higher RMSSD (fully-adjusted HR, 95% CI 1.33, 1.13-1.54, p = 0.0010) were significantly associated with new-onset AF. Sex-stratified analyses showed that the associations were mostly prominent among women. In MR analyses, a genetically determined increase in SDNN (odds ratio (OR), 95% CI 1.60, 1.27-2.02, p = 8.36 × 10^-05), and RMSSD (OR, 95% CI 1.56, 1.31-1.86, p = 6.32 × 10^-07) were significantly associated with an increased odds of AF.

CONCLUSION

Longitudinal measures of uncorrected HRV were significantly associated with new-onset AF, especially among women. MR analyses supported the causal relationship between uncorrected measures of HRV with AF. Our findings indicate that measures to modulate HRV might prevent AF in the general population, in particular in women. AF; atrial fibrillation, GWAS; genome-wide association study, IVW; inverse variance weighted, MR; Mendelian randomization, MR-PRESSO; MR-egger and mendelian randomization pleiotropy residual sum and outlier, RMSSD; root mean square of successive RR interval differences, RMSSDc; root mean square of successive RR interval differences corrected for heart rate, SDNN; standard deviation of normal to normal RR intervals, SDNNc; standard deviation of normal to normal RR intervals corrected for heart rate, WME; weighted median estimator. ^aRotterdam Study n=12,334 ^bHRV GWAS n=53,174 ^cAF GWAS n=1,030,836.

Mat Pilates training reduces blood pressure in both well-controlled hypertensive and normotensive postmenopausal women: a controlled clinical trial study

AIM

The aim of this study was to compare the Mat Pilates training-induced responses in resting and ambulatory blood pressure monitoring (ABPM), blood pressure variability (BPV), and heart rate variability (HRV) in well-controlled hypertensive and normotensive postmenopausal women.

METHODS

Forty-seven postmenopausal women were allocated in well-controlled hypertensive (HT) and normotensive (NT) groups. The exercise program was performed three times a week for 12 weeks. Before and after the intervention resting, blood pressure (BP), ABPM, HRV, and BPV were analyzed.

RESULTS

Student's t-test showed no difference in baseline anthropometric and resting BP values between groups. The generalized estimation equation (GEE) showed no interactions (group*time), but time (p < .05) reductions in resting systolic, diastolic and mean BP after training in both groups. Sleep ambulatory systolic, diastolic and mean BP were higher overall in the HT group (p < .05 in group effect). We also found a time effect (p < .05) with significant increases in BPV in the mean diurnal and nocturnal deviations weighted for the duration of the daytime and nighttime interval (SDdn) in systolic, diastolic and mean BP, and in the average real variability (ARV) in diastolic and mean in both groups. In addition, HRV increases (p < .05 in time effect) through the percentage of pairs of adjacent RR intervals with a difference of at least 50 ms (pNN50) after training in both groups.

CONCLUSION

Both normotensive and well-controlled hypertensive postmenopausal women may have similar Mat Pilates exercise training-induced responses in ambulatory BP, BPV and HRV.

Heart rate variability as a function of menopausal status, menstrual cycle phase, and estradiol level

Low estradiol status is associated with increased cardiovascular risk. We sought to determine the association between heart rate variability (HRV), a marker of cardiovascular risk, at baseline and in response to stressor as a function of menopausal status, menstrual cycle phase and estradiol level. Forty-one healthy women (13 postmenopausal, 28 premenopausal) were studied. Eleven premenopausal women were additionally studied in the high and low estradiol phases of the menstrual cycle. HRV was calculated by spectral power analysis (low Frequency (LF), high frequency (HF) and LF:HF) at baseline and in response to graded Angiotensin II (AngII) infusion. The primary outcomes were differences in HRV at baseline and in response to AngII. Compared to premenopausal women in the low estradiol phase, postmenopausal women demonstrated lower baseline LF (p = 0.01) and HF (p < 0.001) measures, which were not significant after adjustment for age and BMI. In response to AngII, a decrease in cardioprotective HRV (ΔHF = -0.43 ± 0.46 ln ms² , p = 0.005 vs. baseline) was observed in postmenopausal women versus premenopausal women. Baseline HRV parameters did not differ by menstrual phase in premenopausal women. During the low estradiol phase, no differences were observed in the HRV response to AngII challenge. In contrast, women in the high estradiol phase were unable to maintain HRV (ΔLF = -0.07 ± 0.46 ln ms² , p = 0.048 response vs. baseline, ΔHF = -0.33 ± 0.74 ln ms2, p = 0.048 response vs. baseline). No association was observed between any measure of HRV and estradiol level. Menopausal status and the high estradiol phase in premenopausal women were associated with reduced HRV, a marker of cardiovascular risk. Understanding the role of estradiol in the modulation of cardiac autonomic tone may help guide risk reduction strategies in women.

Does climacteric status impact regulation of the autonomic nervous system at the age of 46 years?

OBJECTIVE

To investigate whether an earlier-onset climacteric phase is associated with autonomic imbalance at the age of 46 years.

METHODS

This cross-sectional birth cohort study included 2661 women aged 46 years. Participants were divided into climacteric (n = 359) and preclimacteric (n = 2302) groups based on menstrual history and follicle stimulating hormone values. The mean heart rate (HR), low-frequency (LF) power, high-frequency (HF) power and LF/HF ratio were analyzed from heart rate variability recordings. The variables were compared between the groups using multivariable linear regression models, including body mass index, smoking and physical activity. The effects of hormone therapy and hot flashes on autonomic function were evaluated in sub-analyses.

RESULTS

Climacteric women had a lower mean HR in seated (71.9 ± 10.5 vs. 72.6 ± 10.4 bpm, p = 0.015) and standing (81.2 ± 12.8 vs. 83.6 ± 12.1 bpm, p = 0.002) positions compared to preclimacteric women, and the differences remained significant after the adjustments. In the sub-analyses, more frequent hot flashes were associated with a lower LF power and LF/HF ratio in the sitting position.

CONCLUSIONS

The present study suggested an association between greater parasympathetic activation in women with more advanced climacteric status at the age of 46 years.

Habitual aerobic exercise in healthy postmenopausal women does not augment basal cardiac autonomic activity yet modulates autonomic-metabolic interactions

OBJECTIVES

The aim of the present study was to examine the effects of habitual exercise training and metabolic health on basal cardiac autonomic function and cardiac autonomic recovery after exercise in healthy postmenopausal women (PMW).

METHODS

Habitually aerobically trained PMW (PMW-tr; 56 ± 1y; n = 11), and untrained PMW (PMW-un; 57 ± 1y; n = 13) and premenopausal women (PreM; ages 26 ± 1y; n = 14) were studied. Cardiac autonomic function, assessed using heart rate variability (HRV), was measured before and one hour after 45-minutes of moderate-intensity exercise (60% VO2peak). Fast Fourier frequency domain measures of high (HF; 0.15 Hz-0.4 Hz), low (LF; 0.04 Hz-0.15 Hz), very low (VLF; 0.01 Hz-0.04 Hz), and Total (VLF+LF+HF) HRV were assessed. Serum estradiol, insulin, and glucose were determined, and HOMA-IR, an index of insulin resistance, was calculated.

RESULTS

In PMW groups, body composition and serum markers did not differ (P>0.05). Pre-exercise, heart rate was lower (P<0.05) in PMW-tr than PMW-un, yet HRV did not differ (P>0.05). In PMW-tr only, HF was inversely associated (P<0.05) with insulin (r = -0.738) and HOMA-IR (r = -0.758). In PreM, HRV was higher than PMW (P<0.05) and was positively correlated with estradiol (P<0.05). Postexercise, HRV was decreased within all groups (P<0.05) yet remained higher in PreM (P<0.05), and similar (P>0.05) between PMW.

CONCLUSION

Basal and postexercise HRV does not differ between habitually aerobically trained and untrained PMW. However, greater insulin sensitivity was associated with higher cardiac parasympathetic tone in trained PMW only. Exercise training may favorably modulate cardiac autonomic-metabolic interactions in PMW.

Endogenous and Exogenous Estrogen Exposures: How Women's Reproductive Health Can Drive Brain Aging and Inform Alzheimer's Prevention

After advanced age, female sex is the major risk factor for late-onset Alzheimer's disease (AD), the most common cause of dementia affecting over 24 million people worldwide. The prevalence of AD is higher in women than in men, with postmenopausal women accounting for over 60% of all those affected. While most research has focused on gender-combined risk, emerging data indicate sex and gender differences in AD pathophysiology, onset, and progression, which may help account for the higher prevalence in women. Notably, AD-related brain changes develop during a 10-20 year prodromal phase originating in midlife, thus proximate with the hormonal transitions of endocrine aging characteristic of the menopause transition in women. Preclinical evidence for neuroprotective effects of gonadal sex steroid hormones, especially 17β-estradiol, strongly argue for associations between female fertility, reproductive history, and AD risk. The level of gonadal hormones to which the female brain is exposed changes considerably across the lifespan, with relevance to AD risk. However, the neurobiological consequences of hormonal fluctuations, as well as that of hormone therapies, are yet to be fully understood. Epidemiological studies have yielded contrasting results of protective, deleterious and null effects of estrogen exposure on dementia risk. In contrast, brain imaging studies provide encouraging evidence for positive associations between greater cumulative lifetime estrogen exposure and lower AD risk in women, whereas estrogen deprivation is associated with negative consequences on brain structure, function, and biochemistry. Herein, we review the existing literature and evaluate the strength of observed associations between female-specific reproductive health factors and AD risk in women, with a focus on the role of endogenous and exogenous estrogen exposures as a key underlying mechanism. Chief among these variables are reproductive lifespan, menopause status, type of menopause (spontaneous vs. induced), number of pregnancies, and exposure to hormonal therapy, including hormonal contraceptives, hormonal therapy for menopause, and anti-estrogen treatment. As aging is the greatest risk factor for AD followed by female sex, understanding sex-specific biological pathways through which reproductive history modulates brain aging is crucial to inform preventative and therapeutic strategies for AD.

Structural and functional connections between the autonomic nervous system, hypothalamic-pituitary-adrenal axis, and the immune system: a context and time dependent stress response network

The autonomic nervous system (ANS), hypothalamic-pituitary-adrenal (HPA) axis, and immune system are connected anatomically and functionally. These three systems coordinate the central and peripheral response to perceived and systemic stress signals. Both the parasympathetic and sympathetic components of the autonomic nervous system rapidly respond to stress signals, while the hypothalamic-pituitary-adrenal axis and immune system have delayed but prolonged actions. In vitro, animal, and human studies have demonstrated consistent anti-inflammatory effects of parasympathetic activity. In contrast, sympathetic activity exerts context-dependent effects on immune signaling and has been associated with both increased and decreased inflammation. The location of sympathetic action, adrenergic receptor subtype, and timing of activity in relation to disease progression all influence the ultimate impact on immune signaling. This article reviews the brain circuitry, peripheral connections, and chemical messengers that enable communication between the ANS, HPA axis, and immune system. We describe findings of in vitro and animal studies that challenge the immune system with lipopolysaccharide. Next, neuroimmune connections in animal models of chronic inflammatory disease are reviewed. Finally, we discuss how a greater understanding of the ANS-HPA-immune network may lead to the development of novel therapeutic strategies that are focused on modulation of the sympathetic and parasympathetic nervous system.

Cardioprotective effects of severe calorie restriction from birth in adult ovariectomized rats

AIMS

Menopause is a female condition induced by a reduction of ovarian hormone and is related to an increase in cardiovascular diseases in women. We have shown that severe calorie restriction (SCR) from birth reduces the cardiometabolic risk in adult male Wistar rats. In this study, we investigated the effects of SCR from birth to adulthood on cardiovascular function of ovariectomized rats.

MAIN METHODS

From birth to adulthood, rats were daily fed ad libitum (control group - C) or with 50% of the amount consumed by the control group (calorie-restricted group - R). At 90 days, half of the rats in each group underwent bilateral ovariectomy (OVX), totaling 4 groups: C-Sham, C-OVX, R-Sham, R-OVX. Systolic blood pressure (SBP), heart rate (HR) and, double product (DP) index were recorded by tail-cuff plethysmography. Cardiac function was analyzed by the Langendorff technique and cardiomyocyte diameter was accessed by histologic analysis. Additionally, cardiac SERCA2 content and redox status were evaluated.

KEY FINDINGS

C-OVX rats exhibited reduced cardiac function and cardiac non-enzymatic total antioxidant capacity (TAC). R-Sham animals showed reduced SBP, DP, HR, improved cardiac function, reduced cardiac protein carbonyl derivatives and increased TAC, catalase, and superoxide dismutase activities. R-OVX rats maintained reduced SBP, DP, HR, and increased contractility and relaxation indexes. R-Sham and R-OVX rats exhibited preserved heart mass and reduced cardiomyocyte diameter. Cardiac SERCA2 content did not differ between the groups.

SIGNIFICANCE

Taken together, our findings show cardioprotective effects of SCR from birth in adult ovariectomized rats.

Sex-Bias in Irritable Bowel Syndrome: Linking Steroids to the Gut-Brain Axis

Irritable bowel syndrome (IBS) is a functional gastrointestinal disorder that is more common in females. Despite its high global incidence, the disease mechanism is still unclear and therapeutic options remain limited. The sexual dimorphism in IBS incidence suggests that sex steroids play a role in disease onset and symptoms severity. This review considers sex steroids and their involvement in IBS symptoms and the underlying disease mechanisms. Estrogens and androgens play important regulatory roles in IBS symptomology, including visceral sensitivity, gut motility and psychological conditions, possibly through modulating the gut-brain axis. Steroids are regulators of hypothalamic-pituitary-adrenal activity and autonomic nervous system function. They also modulate gut microbiota and enteric nervous systems, impacting serotonin and mast cell signaling. Sex steroids also facilitate bidirectional cross-talk between the microbiota and host following bacterial transformation and recycling of steroids by the intestine. The sex-specific interplay between sex steroids and the host provides neuroendocrinology insight into the pathophysiology, epigenetics and treatment of IBS patients.

Isoflavone does not promote additional effects on heart rate variability of postmenopausal women performing combined exercise training: a clinical, controlled, randomized, double-blind study

The aim of the study was to investigate the effects of ingesting isoflavones associated with combined aerobic and resistance exercise training on heart rate variability (HRV) indices in postmenopausal women. Twenty-eight healthy postmenopausal women performed 10 weeks of combined exercise training associated with isoflavone (n = 16) or placebo (n = 12) supplementation. The RR intervals (RRi) were collected for 20 min using a heart rate monitor. Analysis of HRV was performed in time (mean squared difference of successive RRi (RMSSD), standard deviation of all normal RRi (SDNN), and percentage of adjacent RRi differing by more than 50 ms (pNN50)), frequency (low-frequency percentage (LF%), high-frequency percentage (HF%), and low-/high-frequency ratio (LF/HF)), and nonlinear domains (standard deviation of the instantaneous variability of the beat-to-beat interval (SD1), long-term variability of the continuous RRi (SD2), and their ratio (SD2/SD1)). Student's t test did not show differences between groups in any general baseline characteristic variables. The results of the generalized estimating equation tests did not demonstrate interaction or group effects for any HRV indices. However, the results reported time effects for mean RR (p < 0.001), RMSSD (p = 0.044), and SD1 (p = 0.044), with increases in these indices in response to exercise training. There were no time effects for LF%, HF%, LF/HF, SDNN, pNN50, SD2, or SD2/SD1. In conclusion, isoflavone supplementation did not promote additional effects on HRV indices of postmenopausal women subjected to 10 weeks of combined exercise training. Novelty Combined training improves heart rate variability in postmenopausal women. Isoflavone supplementation did not promote additional effects on heart rate variability in postmenopausal women.

What's in a name: are menopausal "hot flashes" a symptom of menopause or a manifestation of neurovascular dysregulation?

Hot flashes have typically been classified as "symptoms of menopause" that should be tolerated or treated until they resolve. However, mounting evidence points to hot flashes as a manifestation of one or several underlying pathophysiological processes. Associations exist between the presence, timing of onset, severity, and duration of hot flashes, and the risk of several neurological (affecting sleep, mood, and cognition) and cardiovascular conditions. In addition, four consistent patterns of vasomotor disturbances have been identified across different countries, making it unlikely that these patterns are solely explained by socioeconomic or cultural factors. The changing hormonal environment of menopause may unmask differences in the autonomic neurovascular control mechanisms that put an individual woman at risk for chronic conditions of aging. These differences may have a genetic basis or may be acquired across the life span and are consistent with the variability of the clinical manifestations of aging observed in women after bilateral oophorectomy. It is time to investigate the pathophysiological mechanisms underlying the four patterns of vasomotor symptoms more closely, and to shift from describing hot flashes as symptoms to be tolerated to manifestations of an underlying autonomic neurovascular dysregulation that need to be addressed.

Sex-Specific Physiology and Cardiovascular Disease

Sex differences in cardiovascular diseases can be classified as those which are specific to one sex and those that differ in incidence, prevalence, etiology, symptomatology, response to treatment, morbidity, and mortality in one sex compared to the other. All sex differences in cardiovascular conditions have their basis in the combined expression of genetic and hormonal differences between women and men. This chapter addresses how understanding basic mechanisms of hormone responses, imaging diagnostics, and integration of genomics and proteomics has advanced diagnosis and improved outcomes for cardiovascular conditions, apart from those related to pregnancy that are more prevalent in women. These conditions include obstructive coronary artery disease, coronary microvascular dysfunction, spontaneous coronary artery dissection, diseases of the cardiac muscle including heart failure and takotsubo cardiomyopathy, and conditions related to neurovascular dysregulation including hot flashes and night sweats associated with menopause and effects of exogenous hormones on vascular function. Improvement in technologies allowing for noninvasive assessment of neuronally mediated vascular reactivity will further improve our understanding of the basic etiology of the neurovascular disorders. Consideration of sex, hormonal status, and pregnancy history in diagnosis and treatment protocols will improve prevention and outcomes of cardiovascular disease in women as they age.

Gastric responses to acute psychological stress in climacteric women: a pilot study

OBJECTIVE

Women exhibit reduced ovarian sex hormones during the menopausal period that result in well-known physical and psychological symptoms. However, symptoms related to gastric motility (GM) have not been thoroughly investigated. We hypothesized that stress response gastric motility (SRGM) is lower in postmenopausal (PM) and perimenopausal (PERIM) women than in premenopausal (PREM) women. Estrogenic decline leads to neuroendocrine changes in different areas of the brain. These changes can result in hypothalamic vasomotor symptoms, disorders in eating behaviours, and altered blood pressure, in addition to psychological disorders such as stress, anxiety, depression, and irritability related to alterations in the limbic system.

METHODS

In this pilot study, 55 PREM, PERIM, and PM women were clinically evaluated using the Nowack stress profile (SP) and State-Trait Anxiety Inventory (STAI). GM was assessed via electrical bioimpedance using two psychological stress tests (Stroop and Raven tests).

RESULTS

Basal SP and STAI-anxiety test scores were similar among the three groups of women (P > 0.05). PERIM women had lower GM in the basal state (P < 0.05) than did other women. PREM and PM women had significantly decreased GM during the stress tests (P < 0.05). However, PERIM did not exhibit GM changes during stress tests (P > 0.05).

CONCLUSION

Changes in sex hormones during PERIM may affect GM and SRGM.

Improvement of Menopausal Symptoms with Acupuncture Not Reflected in Changes to Heart Rate Variability

Hypothesis

Studies indicate that menopausal symptoms are relieved by acupuncture. Additional studies have suggested that acupuncture may affect heart rate variability (HRV). This paper reports a pilot study that investigated whether menopausal symptoms responded to acupuncture, and if changes in the spectral analysis of HRV, either suppression of low frequency or augmentation of high frequency bands, corresponded with symptom report.

Methods/interventions

12 healthy menopausal subjects were enrolled in this feasibility study. At baseline, subjects were experiencing moderately distressing menopausal symptoms, scoring at least 22 of a possible 44 points on the Menopausal Rating Scale. 10 traditional Chinese medicine-based, protocol acupuncture treatments were administered over a 4 week period, three times a week for 2 weeks, followed by twice a week for 2 weeks.

Outcome measures

Menopausal Rating Scale questionnaire, 11 menopausal symptoms were evaluated on a zero to four severity scale via self-administered daily checklist for 4 weeks. Dynamic measures of HRV (autoregressive model) were captured before, during and after acupuncture at each session. Spectral analysis of the heart rate was used to compute power in the low frequency and high frequency bands, and their ratio.

Results

All subjects complied fully with the protocol without any reported adverse events. While all 11 symptoms showed significant improvement, and one HRV measure changed, on average over the study period, there was essentially no support for a relationship between HRV, menopausal symptom report and acupuncture intervention.

Maternal exercise, season and sex modify the daily fetal heart rate rhythm

AIM

The knowledge on biological rhythms is rapidly expanding. We aimed to define the longitudinal development of the daily (24-hour) fetal heart rate rhythm in an unrestricted, out-of-hospital setting and to examine the effects of maternal physical activity, season and fetal sex.

METHODS

We recruited 48 women with low-risk singleton pregnancies. Using a portable monitor for continuous fetal electrocardiography, fetal heart rate recordings were obtained around gestational weeks 24, 28, 32 and 36. Daily rhythms in fetal heart rate and fetal heart rate variation were detected by cosinor analysis; developmental trends were calculated by population-mean cosinor and multilevel analysis.

RESULTS

For the fetal heart rate and fetal heart rate variation, a significant daily rhythm was present in 122/123 (99.2%) and 116/121 (95.9%) of the individual recordings respectively. The rhythms were best described by combining cosine waves with periods of 24 and 8 hours. With increasing gestational age, the magnitude of the fetal heart rate rhythm increased, and the peak of the fetal heart rate variation rhythm shifted from a mean of 14:25 (24 weeks) to 20:52 (36 weeks). With advancing gestation, the rhythm-adjusted mean value of the fetal heart rate decreased linearly in females (P < .001) and nonlinearly in males (quadratic function, P = .001). At 32 and 36 weeks, interindividual rhythm diversity was found in male fetuses during higher maternal physical activity and during the summer season.

CONCLUSION

The dynamic development of the daily fetal heart rate rhythm during the second half of pregnancy is modified by fetal sex, maternal physical activity and season.

Molecular pathways of oestrogen receptors and β-adrenergic receptors in cardiac cells: Recognition of their similarities, interactions and therapeutic value

Oestrogen receptors (ERs) and β-adrenergic receptors (βARs) play important roles in the cardiovascular system. Moreover, these receptors are expressed in cardiac myocytes and vascular tissues. Numerous experimental observations support the hypothesis that similarities and interactions exist between the signalling pathways of ERs (ERα, ERβ and GPR30) and βARs (β₁ AR, β₂ AR and β₃ AR). The recently discovered oestrogen receptor GPR30 shares structural features with the βARs, and this forms the basis for the interactions and functional overlap. GPR30 possesses protein kinase A (PKA) phosphorylation sites and PDZ binding motifs and interacts with A-kinase anchoring protein 5 (AKAP5), all of which enable its interaction with the βAR pathways. The interactions between ERs and βARs occur downstream of the G-protein-coupled receptor, through the G_αs and G_αi proteins. This review presents an up-to-date description of ERs and βARs and demonstrates functional synergism and interactions among these receptors in cardiac cells. We explore their signalling cascades and the mechanisms that orchestrate their interactions and propose new perspectives on the signalling patterns for the GPR30 based on its structural resemblance to the βARs. In addition, we explore the relevance of these interactions to cell physiology, drugs (especially β-blockers and calcium channel blockers) and cardioprotection. Furthermore, a receptor-independent mechanism for oestrogen and its influence on the expression of βARs and calcium-handling proteins are discussed. Finally, we highlight promising therapeutic avenues that can be derived from the shared pathways, especially the phosphatidylinositol-3-OH kinase (PI3K/Akt) pathway.

Cardiovascular Autonomic Responses in the VCD Rat Model of Menopause: Effects of Short- and Long-Term Ovarian Failure

After menopause, hypertension elevates the risk of cardiac diseases, one of the major causes of women's morbidity. The gradual depletion of ovarian follicles in rats, induced by 4-vinylcyclohexene diepoxide (VCD), is a model for studying the physiology of menopause. 4-Vinylcyclohexene diepoxide treatment leads to early ovarian failure (OF) and a hormonal profile comparable to menopause in humans. We have hypothesized that OF can compromise the balance between sympathetic and parasympathetic tones of the cardiovascular system, shifting toward dominance of the former. We aimed to study the autonomic modulation of heart and blood vessels and the cardiovascular reflexes in rats presenting short-term (80 days) or long-term (180 days) OF induced by VCD. Twenty-eight-day-old Wistar rats were submitted to VCD treatment (160 mg/kg, intraperitoneally) or vehicle (control) for 15 consecutive days and experiments were conducted at 80 or 180 days after the onset of treatment. Long-term OF led to an increase in the sympathetic activity to blood vessels and an impairment in the baroreflex control of the heart, evoked by physiological changes in arterial pressure. Despite that, long-term OF did not cause hypertension during the 180 days of exposure. Short-term OF did not cause any deleterious effect on the cardiovascular parameters analyzed. These data indicate that long-term OF does not disrupt the maintenance of arterial pressure homeostasis in rats but worsens the autonomic cardiovascular control. In turn, this can lead to cardiovascular complications, especially when associated with the aging process seen during human menopause.

First-night effect on cardiac autonomic function in different female reproductive states

Decreases in heart rate variability, a marker of autonomic nervous system function, are associated with increased cardiovascular mortality. Heart rate variability increases in non-rapid eye movement sleep, peaking in slow-wave sleep. Therefore, decreasing the amount of deep sleep, for example, by introducing patients to a sleep laboratory environment, could decrease heart rate variability, increasing cardiovascular risk. We studied four groups of women with no previous sleep laboratory experience: young [n = 11, 23.1 (0.5) years]; perimenopausal [n = 15, 48.0 (0.4) years]; postmenopausal without hormone therapy [n = 22, 63.4 (0.8) years]; and postmenopausal on hormone therapy [n = 16, 63.1 (0.9) years], using a cross-sectional design. Polysomnography including electrocardiogram was performed over two consecutive nights. Heart rate variability was assessed overnight, and the first-night effect on heart rate variability was analysed. Furthermore, correlations between heart rate variability and sleep variables were analysed. Using combined groups, only minor changes were observed in non-linear heart rate variability, indicating increased parasympathetic tone from the first to the second night. No group differences in first-night effect were seen. Heart rate variability and sleep variables were not significantly correlated. Heart rate variability decreased with increasing age, and it was lowest in the postmenopausal women on hormone therapy. We conclude that a first night in a sleep laboratory elicits only minimal changes in overnight vagally mediated non-linear heart rate variability in women irrespective of reproductive state. This finding warrants further analyses in different sleep stages, but suggests that changes in sleep architecture per se do not predict the autonomic strain of a poor night.

Neural control of blood pressure in women: differences according to age

PURPOSE

The blood pressure "error signal" represents the difference between an individual's mean diastolic blood pressure and the diastolic blood pressure at which 50% of cardiac cycles are associated with a muscle sympathetic nerve activity burst (the "T50"). In this study we evaluated whether T50 and the error signal related to the extent of change in blood pressure during autonomic blockade in young and older women, to study potential differences in sympathetic neural mechanisms regulating blood pressure before and after menopause.

METHODS

We measured muscle sympathetic nerve activity and blood pressure in 12 premenopausal (25 ± 1 years) and 12 postmenopausal women (61 ± 2 years) before and during complete autonomic blockade with trimethaphan camsylate.

RESULTS

At baseline, young women had a negative error signal (-8 ± 1 versus 2 ± 1 mmHg, p < 0.001; respectively) and lower muscle sympathetic nerve activity (15 ± 1 versus 33 ± 3 bursts/min, p < 0.001; respectively) than older women. The change in diastolic blood pressure after autonomic blockade was associated with baseline T50 in older women (r = -0.725, p = 0.008) but not in young women (r = -0.337, p = 0.29). Women with the most negative error signal had the lowest muscle sympathetic nerve activity in both groups (young: r = 0.886, p < 0.001; older: r = 0.870, p < 0.001).

CONCLUSIONS

Our results suggest that there are differences in baroreflex control of muscle sympathetic nerve activity between young and older women, using the T50 and error signal analysis. This approach provides further information on autonomic control of blood pressure in women.

After-exercise heart rate variability is attenuated in postmenopausal women and unaffected by estrogen therapy

OBJECTIVE

Delayed heart rate (HR) recovery in the immediate postexercise period has been linked to adverse cardiovascular prognosis. The after effects of an acute bout of exercise on HR modulation in postmenopausal women (PMW) and the influence of estrogen therapy are unknown.

METHODS

In 13 sedentary PMW (54 ± 2 y, mean ± SEM), we assessed HR variability (HRV)--an index of HR modulation--and the influence of estrogen therapy on HRV. HRV in the frequency domain was quantified during supine rest and again 60 minutes after treadmill exercise for 45 minutes, at 60% VO2peak. PMW were studied before and after 4 weeks of oral estradiol. To obtain reference values for the after effects of exercise on HRV in healthy young women, 14 premenopausal women (PreM) completed the identical exercise protocol.

RESULTS

Compared with PreM, PMW demonstrated lower high frequency (vagal modulation) and total HRV (P < 0.05) at rest. In PreM, all HRV values were similar before and after exercise. In contrast, in PMW after exercise, despite having identical HR to PreM, high frequency and total HRV were all lower (all P ≤ 0.01) compared with pre-exercise HRV values. Estrogen therapy had no effect on pre or postexercise values for HRV.

CONCLUSIONS

When compared with PreM, PMW have identical HR, but lower vagal HR modulation at rest and delayed HRV recovery after exercise. Estrogen does not restore baseline HRV or accelerate HRV recovery postexercise, suggesting aging rather than estrogen deficiency per se may lower HRV in PMW.

Hot Flash Frequency and Blood Pressure: Data from the Study of Women's Health Across the Nation

BACKGROUND

Vasomotor symptoms (VMS) are highly prevalent among midlife women and have been associated with subclinical cardiovascular disease (CVD). However, the association between VMS frequency and risk factors such as hypertension (HTN) remains unclear.

MATERIALS AND METHODS

We examined VMS frequency and blood pressure (BP) among 2839 participants of the Study of Women's Health Across the Nation (SWAN), a multiethnic, prospective, study of women enrolled from seven U.S. sites between November 1995 and October 1997. Women were age 42-52, with no history of CVD, and not postmenopausal at baseline. VMS was defined by the number of days a woman reported VMS over the 2-week period before each annual visit. Frequent VMS was defined as ≥6 days of VMS; less frequent VMS was defined 1-5 days of symptoms with asymptomatic women the reference group. BP was measured at each visit in addition to demographic and clinic factors.

RESULTS

At baseline, 298 women reported frequent VMS, 794 less frequent VMS and 1747 no VMS. More frequent baseline VMS was associated with higher BP. Compared to no VMS, baseline VMS was associated with HTN (odds ratio [OR] 1.47, 95% confidence interval [CI]; 1.14-1.88 for infrequent VMS, and OR 1.40, (95% CI; 0.97-2.02 for frequent VMS). Risk for incident pre-HTN or HTN during follow-up was increased among women with frequent VMS (hazard ratio of 1.39, 95% CI; 1.09-1.79) after adjustment for multiple covariates.

CONCLUSION

Women with VMS may be more likely to develop HTN compared to women without VMS. Further research related to VMS including frequency of symptoms is warranted.

Ovarian Hormone Deprivation Reduces Oxytocin Expression in Paraventricular Nucleus Preautonomic Neurons and Correlates with Baroreflex Impairment in Rats

The prevalence of cardiovascular diseases including hypertension increases dramatically in women after menopause, however the mechanisms involved remain incompletely understood. Oxytocinergic (OTergic) neurons are largely present within the paraventricular nucleus of the hypothalamus (PVN). Several studies have shown that OTergic drive from PVN to brainstem increases baroreflex sensitivity and improves autonomic control of the circulation. Since preautonomic PVN neurons express different types of estrogen receptors, we hypothesize that ovarian hormone deprivation causes baroreflex impairment, autonomic imbalance and hypertension by negatively impacting OTergic drive and oxytocin levels in pre-autonomic neurons. Here, we assessed oxytocin gene and protein expression (qPCR and immunohistochemistry) within PVN subnuclei in sham-operated and ovariectomized Wistar rats. Conscious hemodynamic recordings were used to assess resting blood pressure and heart rate and the autonomic modulation of heart and vessels was estimated by power spectral analysis. We observed that the ovarian hormone deprivation in ovariectomized rats decreased baroreflex sensitivity, increased sympathetic and reduced vagal outflows to the heart and augmented the resting blood pressure. Of note, ovariectomized rats had reduced PVN oxytocin mRNA and protein expression in all pre-autonomic PVN subnuclei. Furthermore, reduced PVN oxytocin protein levels were positively correlated with decreased baroreflex sensitivity and negatively correlated with increased LF/HF ratio. These findings suggest that reduced oxytocin expression in OTergic neurons of the PVN contributes to the baroreflex dysfunction and autonomic dysregulation observed with ovarian hormone deprivation.

The Metabolic Syndrome in Women

The clustering of metabolic risk factors, overweight and hypertension is of particular importance in postmenopausal women due to the negative effect of menopause on bodyweight, glucose metabolism and the development of hypertension. Menopause acts directly as a risk factor by reducing the direct beneficial effect of ovarian hormones on cardiovascular functions, and indirectly by negatively influencing traditional risk factors for coronary artery disease. All changes occurring after the menopause must be regarded under a unifying mechanism that induces unfavorable changes in cardiovascular risk factors and vascular functions, which interact with each other, amplifying the effect of ovarian hormone deficiency and aging.

Impact of endo- and exogenous estrogens on heart rate variability in women: a review

Measurement of heart rate variability (HRV) is an established method to assess the activity of the autonomic nervous system. The aim of this review was to examine the link between HRV, reproductive life stages and menopausal hormone therapy. A literature review was performed using the Medline database. Based on title and abstract, 45 studies were extracted out of 261 citations screened. Due to different study designs and evaluation methods, HRV indices were not directly comparable. Qualitative comparisons in between the vast majority of studies, however, demonstrated a decrease of the vagal dominance on the heart from the follicular to the luteal cycle phase, although some studies asserted no change. The intake of oral contraceptives appeared not to alter the vagal modulation of the heart. All investigations agreed on a decline of HRV towards higher sympathetic control after menopause. Different menopausal hormone therapy approaches showed a supporting impact of estrogen on HRV in most studies. A combined therapy of estrogen and progestogens revoked this benefit. Further research is needed to demonstrate how this process might be attenuated by different menopausal hormone therapies.

Estrogen receptor ERα plays a major role in ethanol-evoked myocardial oxidative stress and dysfunction in conscious female rats

Our previous studies showed that ethanol elicited estrogen (E2)-dependent myocardial oxidative stress and dysfunction. In the present study we tested the hypothesis that E2 signaling via the estrogen receptor (ER), ERα, mediates this myocardial detrimental effect of alcohol. To achieve this goal, conscious female rats in proestrus phase (highest endogenous E2 level) received a selective ER antagonist (200 μg/kg; intra-venous [i.v.]) for ERα (MPP), ERβ (PHTPP) or GPER (G15) or saline 30 min before ethanol (1 g/kg; i.v.) or saline infusion. ERα blockade virtually abrogated ethanol-evoked myocardial dysfunction and hypotension, while ERβ blockade had little effect on the hypotensive response, but caused delayed attenuation of the ethanol-evoked reductions in left ventricular developed pressure and the rate of left ventricle pressure rise. GPER blockade caused delayed attenuation of all cardiovascular effects of ethanol. All three antagonists attenuated the ethanol-evoked increases in myocardial catalase and ALDH2 activities, Akt, ERK1/2, p38, eNOS, and nNOS phosphorylation, except for a lack of effect of PHTPP on p38. Finally, all three ER antagonists attenuated ethanol-evoked elevation in myocardial ROS, but this effect was most notable with ERα blockade. In conclusion, ERα plays a greater role in, and might serve as a molecular target for ameliorating, the E2-dependent myocardial oxidative stress and dysfunction caused by ethanol.

Oral oestrogen reverses ovariectomy-induced morning surge hypertension in growth-restricted mice

Perinatal growth restriction (GR) is associated with heightened sympathetic tone and hypertension. We have previously shown that naturally occurring neonatal GR programmes hypertension in male but not female mice. We therefore hypothesized that intact ovarian function or post-ovariectomy (OVX) oestrogen administration protects GR female mice from hypertension. Utilizing a non-interventional model that categorizes mice with weanling weights below the tenth percentile as GR, control and GR adult mice were studied at three distinct time points: baseline, post-OVX and post-OVX with oral oestrogen replacement. OVX elicited hypertension in GR mice that was significantly exacerbated by psychomotor arousal (systolic blood pressure at light to dark transition: control 122 ± 2; GR 119 ± 2; control-OVX 116 ± 3; GR-OVX 126 ± 3 mmHg). Oestrogen partially normalized the rising blood pressure surge seen in GR-OVX mice (23 ± 7% reduction). GR mice had left ventricular hypertrophy, and GR-OVX mice in particular had exaggerated bradycardic responses to sympathetic blockade. For GR mice, a baseline increase in baroreceptor reflex sensitivity and high frequency spectral power support a vagal compensatory mechanism, and that compensation was lost following OVX. For GR mice, the OVX-induced parasympathetic withdrawal was partially restored by oestrogen (40 ± 25% increase in high frequency spectral power, P<0.05). In conclusion, GR alters cardiac morphology and cardiovascular regulation. The haemodynamic consequences of GR are attenuated in ovarian-sufficient or oestrogen-replete females. Further investigations are needed to define the role of hormone replacement therapy targeted towards young women with oestrogen deficiency and additional cardiovascular risk factors, including perinatal GR, cardiac hypertrophy and morning surge hypertension.

Cardiac autonomic changes after 40 hours of total sleep deprivation in women

OBJECTIVES

The effect of total sleep deprivation on heart rate variability (HRV) in groups of postmenopausal women on oral hormone therapy (HT) (on-HT, n = 10, 64.2 (1.4) years), postmenopausal women without HT (off-HT, n = 10, 64.6 (1.4) years) and young women (n = 11, 23.1 (0.5) years) was studied using a prospective case-control setup.

METHODS

Polysomnography was performed over an adaptation night, a baseline night, and a recovery night after 40 h of total sleep deprivation. Time and frequency domain and nonlinear HRV from overnight electrocardiogram recordings were compared between groups during baseline and recovery nights. Further, the changes in HRV from baseline to recovery were analysed and compared between groups. Finally, correlations of HRV to percentages of sleep stages and measures of sleep fragmentation were analysed during baseline and recovery.

RESULTS

Young women had higher HRV than older women; the most marked difference was between young and on-HT postmenopausal women. Sleep deprivation induced a decrease in frequency domain HRV in young and in off-HT women, an increase in α2 in off-HT women, and an increase in mean heart rate in on-HT women. The sleep deprivation effect was mainly uncorrelated to changes in sleep parameters.

CONCLUSIONS

Acute total sleep deprivation has a deleterious effect on the autonomic nervous system in young women, but an even more pronounced effect in postmenopausal women. Hormone therapy use in late postmenopause does not give protection against these changes. These harmful effects may partly explain the increased cardiovascular morbidity and overall mortality associated with sleep loss.

Salivary α-amylase and cortisol after exercise in menopause: influence of long-term HRT

OBJECTIVES

This observational prospective study analyzed the effect of an incremental cardiopulmonary exercise test (CPET) on the secretion of salivary biomarkers of the adrenergic nervous system and hypothalamus-pituitary-adrenal (HPA) axis activity by measuring salivary α-amylase and cortisol diurnal trajectories in the setting of long-term hormone replacement therapy (HRT).

METHODS

Fifteen healthy sedentary postmenopausal women who were current HRT users and 15 women who had never used HRT were consecutively recruited. α-Amylase and cortisol were measured in salivary samples collected on the CPET day and on a rest day. Cardiovascular and respiratory fitness parameters were recorded during the CPET challenge.

RESULTS

The participants had very homogeneous somatic characteristics, and they were all in generally good health. The postmenopausal never-HRT users presented an abnormal diurnal pattern of α-amylase at baseline and a flattened response to CPET. In contrast, women on HRT had a physiological α-amylase diurnal pattern and increased salivary α-amylase production during the CPET-induced challenge. The CPET challenge physiologically activated the HPA axis activity, as shown by the increase in the concentration of salivary cortisol during the effort test. HPA axis activity was not affected by long-term HRT. Postmenopausal women using HRT exhibited a cardiorespiratory functional capacity that was significantly (p < 0.05) higher than that of non-users.

CONCLUSIONS

Our findings show that healthy postmenopausal women present an asymmetry between adrenergic nervous system and HPA axis activities under both basal and stress conditions. HRT was able to modify the abnormal adrenergic nervous system activity, most likely by reducing the sympathetic hyperactivity that characterizes menopause.

Estrogen can modulate menopausal women's heart rate variability

The aim of our study was to compare the responses of heart rate variability (HRV) with two different types of hormonal substitution therapy (HT) in post-menopausal women (cross-sectional study) and to reveal an effect of HT shortly after beginning of its administration (follow-up study). To elucidate the influence of menopause and effects of different protocols of a HT on autonomic control of heart rate, we evaluated the heart rate variability (HRV) in 5 groups: premenopausal women (n=140), postmenopausal women without HT (n=360), women on HT with conjugated estrogen only (n=168), women on continuous combined estrogen-progesterone HT (n=117), and men (n=140). Frequency-domain of short-term stationary R-R intervals was performed to evaluate the total variance, low frequency power (LF; 0.04-0.15 Hz), high frequency power (HF; 0.15-0.40 Hz), portion of low frequency power (LF%) and ratio of LF to HF (LF/HF). Significantly lower portion of the LF was found in premenopausal women [46.9 (+/-2.7) nu] when compared to untreated postmenopausal women [54.3 (+/-2.9) nu] and men [55.2 (+/-3.0) nu]. Treatment by estrogen only was proved to decrease the LF% [40.1 (+/-2.1) nu] while no effect on HRV was observed in women treated with combination of estrogen and progesterone [57.2 (+/-3.1) nu]. Also the HF was lower in postmenopausal women [4.16 (+/-0.16) ms(2)] than in premenopausal women [4.79 (+/-0.22) ms(2)] and women treated with estrogen only [4.98 (+/-0.25) ms(2)] while in women treated with combined hormonal therapy the average value [3.99 (+/-0.21) ms(2)] did not significantly differ from that of untreated postmenopausal women. The follow-up study also proved increase of high frequency power already after two months of estrogen substitution therapy [4.86 (+/-0.14) ms(2) vs. 4.19 (+/-0.15) ms(2)]. These results suggest that higher vagal modulation of heart rate that seems typical for younger women becomes after menopause similar to that of men. We also proved a positive shift of HRV parameters toward more beneficial values as for a cardiovascular risk in postmenopausal women treated with estrogens but not in those treated by combined estrogen - progesterone substitution therapy.

Efficacy of a low dose of estrogen on antioxidant defenses and heart rate variability

This study tested whether a low dose (40% less than the pharmacological dose of 17-β estradiol) would be as effective as the pharmacological dose to improve cardiovascular parameters and decrease cardiac oxidative stress. Female Wistar rats (n = 9/group) were divided in three groups: (1) ovariectomized (Ovx), (2) ovariectomized animals treated for 21 days with low dose (LE; 0.2 mg), and (3) high dose (HE; 0.5 mg) 17-β estradiol subcutaneously. Hemodynamic assessment and spectral analysis for evaluation of autonomic nervous system regulation were performed. Myocardial superoxide dismutase (SOD) and catalase (CAT) activities, redox ratio (GSH/GSSG), total radical-trapping antioxidant potential (TRAP), hydrogen peroxide, and superoxide anion concentrations were measured. HE and LE groups exhibited an improvement in hemodynamic function and heart rate variability. These changes were associated with an increase in the TRAP, GSH/GSSG, SOD, and CAT. A decrease in hydrogen peroxide and superoxide anion was also observed in the treated estrogen groups as compared to the Ovx group. Our results indicate that a low dose of estrogen is just as effective as a high dose into promoting cardiovascular function and reducing oxidative stress, thereby supporting the approach of using low dose of estrogen in clinical settings to minimize the risks associated with estrogen therapy.

Should there be sex-specific criteria for the diagnosis and treatment of heart failure?

All-cause mortality from cardiovascular disease is declining in the USA. However, there remains a significant difference in risk factors for disease and in mortality between men and women. For example, prevalence and outcomes for heart failure with preserved ejection fraction differ between men and women. The reasons for these differences are multifactorial, but reflect, in part, an incomplete understanding of sex differences in the etiology of cardiovascular diseases and a failure to account for sex differences in pre-clinical studies including those designed to develop new diagnostic and treatment modalities. This review focuses on the underlying physiology of these sex differences and provides evidence that inclusion of female animals in pre-clinical studies of heart failure and in development of imaging modalities to assess cardiac function might provide new information from which one could develop sex-specific diagnostic criteria and approaches to treatment.

Autonomic regulation across phases of the menstrual cycle and sleep stages in women with premenstrual syndrome and healthy controls

To investigate the influence of menstrual cycle phase and the presence of severe premenstrual symptoms on cardiac autonomic control during sleep, we performed heart rate variability (HRV) analysis during stable non-rapid eye movement (NREM) and REM sleep in 12 women with severe premenstrual syndrome and 14 controls in the mid-follicular, mid-luteal, and late-luteal phases of the menstrual cycle. Heart rate was higher, along with lower high frequency (HF) power, reflecting reduced vagal activity, and a higher ratio of low frequency (LF) to high frequency power, reflecting a shift to sympathetic dominance, in REM sleep compared with NREM sleep in both groups of women. Both groups of women had higher heart rate during NREM and REM sleep in the luteal phase recordings compared with the mid-follicular phase. HF power in REM sleep was lowest in the mid-luteal phase, when progesterone was highest, in both groups of women. The mid-luteal phase reduction in HF power was also evident in NREM sleep in control women but not in women with PMS, suggesting some impact of premenstrual syndrome on autonomic responses to the hormone environment of the mid-luteal phase. In addition, mid-luteal phase progesterone levels correlated positively with HF power and negatively with LF/HF ratio in control women in NREM sleep and with the LF/HF ratio during REM sleep in both groups of women. Our findings suggest the involvement of female reproductive steroids in cardiac autonomic control during sleep in women with and without premenstrual syndrome.

Gender differences in cardiac autonomic modulation during medical internship

Medical internship is known to be a time of high stress and long working hours, which increases the risk of depression and cardiovascular disease. Gender differences in medical interns' cardiovascular risk have not been reported previously. Thirty-eight medical interns (29 males) were repeatedly tested for depressive symptoms using the Hospital Anxiety and Depression Scale and 5-min spectral analysis of heart rate variability (HRV) at 3-month intervals during their internship. Among the male interns, the variance of the heart rate decreased at 6, 9, 12 months, and a reduced high frequency, which suggests reduced cardiac parasympathetic modulation, was found at 9 and 12 months into their internship. Increased depressive symptoms were also identified at 12 months in the male group. No significant differences in depression or any of the HRV indices were identified among the female interns during their internship.

Sex differences in cardiac autonomic regulation and in repolarisation electrocardiography

The review summarises the present knowledge on the sex differences in cardiac autonomic regulations and in related aspects of electrocardiography with particular attention to myocardial repolarisation. Although some of the sex differences are far from fully established, multitude of observations show consistent differences between women and men. Despite more pronounced parasympathetic cardiac regulation, women have higher resting heart rate and lower baroreflex sensitivity. Of the electrocardiographic phenomena, women have longer QT interval duration, repolarisation sequence more synchronised with the inverse of the depolarisation sequence, and likely increased regional heterogeneity of myocardial repolarisation. Studies investigating the relationship of these sex disparities to hormonal differences led frequently to conflicting results. Although sex hormones seem to play a key role by influencing both autonomic tone and electrophysiological properties at the cellular level, neither the truly relevant hormones nor their detailed actions are known. Physiologic usefulness of the described sex differences is also unknown. The review suggests that new studies are needed to advance the understanding of the physiologic mechanisms responsible for these inequalities between women and men and provides key methodological suggestions that need to be followed in future research.