Baroreflex sensitivity in obesity: relationship with cardiac autonomic nervous system activity

Dynamic vagal-mediated connectivity of cortical and subcortical central autonomic hubs predicts chronotropic response to submaximal exercise in healthy adults

BACKGROUND

Despite accumulation of a substantial body of literature supporting the role of exercise on frontal lobe functioning, relatively less is understood of the interconnectivity of ventromedial prefrontal cortical (vmPFC) regions that underpin cardio-autonomic regulation predict cardiac chronotropic competence (CC) in response to sub-maximal exercise.

METHODS

Eligibility of 161 adults (mean age = 48.6, SD = 18.3, 68% female) was based upon completion of resting state brain scan and sub-maximal bike test. Sliding window analysis of the resting state signal was conducted over 45-s windows, with 50% overlap, to assess how changes in photoplethysmography-derived HRV relate to vmPFC functional connectivity with the whole brain. CC was assessed based upon heart rate (HR) changes during submaximal exercise (HR change /HRmax (206-0.88 × age) - HRrest).

RESULTS

During states of elevated HRV the vmPFC showed greater rsFC with an 83-voxel region of the hypothalamus (p < 0.001, uncorrected). Beta estimates of vmPFC connectivity extracted from a 6-mm sphere around this region emerged as the strongest predictor of CC (b = 0.283, p <.001) than age, BMI, and resting HRV F(8,144) = 6.30, p <.001.

CONCLUSION

Extensive glutamatergic innervation of the hypothalamus by the vmPFC allows for top-down control of the hypothalamus and its various autonomic efferents which facilitate chronotropic response during sub-maximal exercise.

Attenuated cardiac autonomic function in humans with high-affinity hemoglobin and compensatory polycythemia

During hypoxic exposure, humans with high-affinity hemoglobin (and compensatory polycythemia) have blunted increases in heart rate compared with healthy humans with typical oxyhemoglobin dissociation curves. This response may be associated with altered autonomic control of heart rate. Our hypothesis-generating study aimed to investigate cardiac baroreflex sensitivity and heart rate variability among nine humans with high-affinity hemoglobin [6 females, O2 partial pressure at 50% [Formula: see text] (P50) = 16 ± 1 mmHg] compared with 12 humans with typical affinity hemoglobin (6 F, P50 = 26 ± 1 mmHg). Participants breathed normal room air for a 10-min baseline, followed by 20 min of isocapnic hypoxic exposure, designed to lower the arterial partial pressure O2 ([Formula: see text]) to ∼50 mmHg. Beat-by-beat heart rate and arterial blood pressure were recorded. Data were averaged in 5-min periods throughout the hypoxia exposure, beginning with the last 5 min of baseline in normoxia. Spontaneous cardiac baroreflex sensitivity and heart rate variability were determined using the sequence method and the time and frequency domain analyses, respectively. Cardiac baroreflex sensitivity was lower in humans with high-affinity hemoglobin than controls at baseline and during isocapnic hypoxic exposure (normoxia: 7 ± 4 vs. 16 ± 10 ms/mmHg, hypoxia minutes 15-20: 4 ± 3 vs. 14 ± 11 ms/mmHg; group effect: P = 0.02, high-affinity hemoglobin vs. control, respectively). Heart rate variability calculated in both the time (standard deviation of the N-N interval) and frequency (low frequency) domains was lower in humans with high-affinity hemoglobin than in controls (all P < 0.05). Our data suggest that humans with high-affinity hemoglobin may have attenuated cardiac autonomic function.

Effects of a Stress Management Training in Patients With Lymphedema and Obesity During Rehabilitation

Abstract: Background: Evidence for behavioral weight loss interventions demonstrates promising effects, but stress management training for weight loss and stress reduction in patients with lymphedema and obesity during rehabilitation has not been investigated yet. Aim: This study aims to examine innovative psychological treatment options for weight loss and stress management through a multifaceted approach in patients with lymphedema and obesity. Method: Seventy-one patients with lymphedema and obesity participating in an existing rehabilitation took part in this clinical trial. Half of them ( n = 36) were allocated to an additional stress management intervention. At the beginning of rehabilitation and the end (after 3 weeks; n = 66) participants’ weight, physical fitness, heart rate variability (HRV), and perceived stress were assessed. After around 8 months ( n = 28) chronic and perceived stress were evaluated again. Results: Irrespective of group allocation, rehabilitation had a positive, but short-term effect on perceived stress ( d = 0.60). Although patients receiving the additional stress management training did neither show a decrease in perceived stress nor an increase of HRV from pre- to post-assessment, they lost more weight and improved physical fitness at post-assessment as compared to the control group. Limitations: A stress-reducing effect of the training was not found, thus questioning the underlying mechanism of the applied intervention. Conclusions: Findings suggest a clinically relevant impact of psychological interventions in patients with lymphedema and a promising pathway for further research.

The characteristics of elevated blood pressure in abdominal obesity correspond to primary hypertension: a cross-sectional study

BACKGROUND

Obesity-related hypertension and the associated metabolic abnormalities are considered as a distinct hypertensive phenotype. Here we examined how abdominal fat content, as judged by waist:height ratio, influenced blood pressure and hemodynamic profile in normotensive subjects and never-treated hypertensive patients.

METHODS

The 541 participants (20-72 years) underwent physical examination and laboratory analyses and were divided into age and sex-adjusted quartiles of waist:height ratio. Supine hemodynamics were recorded using whole-body impedance cardiography, combined with analyses of radial tonometric pulse wave form and heart rate variability.

RESULTS

Mean waist:height ratios in the quartiles were 0.46, 0.51, 0.55 and 0.62. Radial and aortic blood pressure, systemic vascular resistance, pulse wave velocity, markers of glucose and lipid metabolism, leptin levels and C-reactive protein were higher in quartile 4 when compared with quartiles 1 and 2 (p < 0.05 for all). Cardiac index was lower in quartile 4 versus quartile 1, while no differences were seen in heart rate variability, augmentation index, plasma renin activity, and aldosterone concentration between the quartiles. Linear regression analyses showed independent associations of abdominal obesity with higher aortic systolic and diastolic blood pressure, systemic vascular resistance, and pulse wave velocity (p < 0.05 for waist:height ratio in all regression models).

CONCLUSION

Higher waist:height ratio was associated with elevated blood pressure, systemic vascular resistance, and arterial stiffness, but not with alterations in cardiac sympathovagal modulation or activation of the circulating renin-angiotensin-aldosterone system. Although obesity-related elevation of blood pressure has distinct phenotypic features, these results suggest that its main characteristics correspond those of primary hypertension.

TRIAL REGISTRATION

ClinicalTrails.gov NCT01742702 (date of registration 5th December 2012).

Association of disrupted sleep with 24-hour blood pressure variability in caregivers

BACKGROUND

A growing body of research highlights the negative impact of caregiving on cardiovascular disease (CVD) risk.

OBJECTIVES

This study aimed to examine associations of psychological symptoms and sleep quality with 24-hour blood pressure variability (BPV), which is an independent predictor of CVD, among family caregivers of community-dwelling individuals with chronic illness.

METHODS

For this cross-sectional study, we assessed caregiving burden and depressive symptoms using questionnaires and 7-day sleep quality (i.e., number of awakenings, wake after sleep onset, sleep efficiency) using an actigraph. The participants carried out a 24-hour ambulatory BP monitoring for systolic and diastolic BPV over 24 h and during awake/sleep times. We performed Pearson's correlations and multiple linear regression.

RESULTS

The analytic sample consisted of 30 caregivers (25 female; mean age 62 years). The number of awakenings during sleep was positively correlated with systolic BPV-awake (r = 0.426, p = 0.019) and diastolic BPV-awake (r = 0.422, p = 0.020). Sleep efficiency was negatively correlated with diastolic BPV-awake (r = -0.368, p = 0.045). Caregiving burden and depressive symptoms were not correlated with BPV. After controlling for age and mean arterial pressure, the number of awakenings was significantly associated with increased systolic BPV-24 h (β = 0.194, p = 0.018) and systolic BPV-awake (β = 0.280, p = 0.002), respectively.

CONCLUSIONS

Caregivers' disrupted sleep may play a role in increased CVD risk. While these findings should be confirmed in large clinical studies, improving sleep quality would need to be considered in CVD prevention for caregivers.

Hepatalin: the missing link in prediabetes, obesity, and type 2 diabetes

Hepatalin is a hormone secreted by the liver in response to pulses of insulin after a mixed nutrient meal, but only if the liver receives two permissive synergistic feeding signals from the stomach. Hepatalin stimulates glucose uptake and storage as glycogen in skeletal muscle, heart, and kidney but not liver, intestines, or adipocytes. Insulin acts primarily on liver and fat. Reduced hepatalin action results in postprandial hyperglycemia, compensatory elevation of insulin secretion, and a resultant shift in partitioning of nutrient energy storage from glycogen in muscle, to fat. Chronic hepatalin suppression leads to a predictable chronology of dysfunctions, first diagnosable as Absence of Meal-induced Insulin Sensitization (AMIS) which progresses to prediabetes, adiposity, and type 2 diabetes. The focus on nutrient partitioning and the role of hepatalin allows AMIS to be diagnosed, prevented, and treated, including through the use of lifestyle interventions.

Sodium Intake and Disease: Another Relationship to Consider

Sodium (Na+) is crucial for numerous homeostatic processes in the body and, consequentially, its levels are tightly regulated by multiple organ systems. Sodium is acquired from the diet, commonly in the form of NaCl (table salt), and substances that contain sodium taste salty and are innately palatable at concentrations that are advantageous to physiological homeostasis. The importance of sodium homeostasis is reflected by sodium appetite, an "all-hands-on-deck" response involving the brain, multiple peripheral organ systems, and endocrine factors, to increase sodium intake and replenish sodium levels in times of depletion. Visceral sensory information and endocrine signals are integrated by the brain to regulate sodium intake. Dysregulation of the systems involved can lead to sodium overconsumption, which numerous studies have considered causal for the development of diseases, such as hypertension. The purpose here is to consider the inverse-how disease impacts sodium intake, with a focus on stress-related and cardiometabolic diseases. Our proposition is that such diseases contribute to an increase in sodium intake, potentially eliciting a vicious cycle toward disease exacerbation. First, we describe the mechanism(s) that regulate each of these processes independently. Then, we highlight the points of overlap and integration of these processes. We propose that the analogous neural circuitry involved in regulating sodium intake and blood pressure, at least in part, underlies the reciprocal relationship between neural control of these functions. Finally, we conclude with a discussion on how stress-related and cardiometabolic diseases influence these circuitries to alter the consumption of sodium.

Normative values of resting heart rate variability in young male contact sport athletes: Reference values for the assessment and treatment of concussion

Objective

The objective of this study was to identify the main determinants of heart rate variability (HRV) in male athletes aged 14 to 21 years who practice competitive contact sports and to integrate these determinants with the aim of defining normative values of short-term HRV in the time and frequency domains.

Methods

Participants (n = 369) were aged 14 to 21 years and included 221 football players and 148 ice hockey players. HRV was measured for 5 min at rest, and standard HRV parameters in the time and frequency domains were calculated. Heart rate (HR), age, body mass index (BMI), number of sports weekly practices (WSP) and concussion history (mTBI) were considered determinants potentially able to influence HRV.

Results

Multiple regression analysis revealed that HR was the primary determinant of standard HRV parameters. The models accounted for 13% to 55% of the total variance of HRV and the contribution of HR to this model was the strongest (β ranged from -0.34 to -0.75). HR was the only determinant that significantly contributes to all HRV parameters. To counteract this dependence, we calculated HRV corrected by the mean RR interval (RRm). Such corrections do not remove any physiological differences in HRV; they simply remove the mathematical bias. HRV parameters were therefore normalized, and their normative limits were developed relative to the mean heart rate. After correction, the correlation coefficients between HR and all corrected HRV parameters were not statistically significant and ranged from -0.001 to 0.045 (p > 0.40 for all). The automatically corrected HRV calculator, which recalculates standard HRV parameters and converts them into corrected parameters in addition to determining whether a given value is within normal limits, facilitates clinical interpretation.

Conclusion

This study provides for the first time corrected normative values of short-term and resting state HRV parameters in competitive contact sport athletes aged 14 to 21 years. These values were developed independently of the major determinants of HRV. The baseline values for HRV parameters given here could be used in clinical practice when assessing and monitoring cerebral concussions. They may assist in decision making for a safe return to play.

Early Vascular Aging in Obese Individuals with Low Cardiovascular Health

INTRODUCTION

The American Heart Association updated the original recommendations for cardiovascular health (CVH) promotion, defining the Life's Essential 8 (L8).

AIM

the aim of this cross-sectional study was to compare vascular function, central hemodynamics and autonomic modulation in obese individuals with low and moderate CVH-L8.

METHODS

Both sexes, aged 40-70 years and Body Mass Index ≥ 30 and < 40 kg/m², were submitted to anthropometric and biochemical evaluation, assessment of heart rate variability, endothelial function by flow-mediated dilatation (FMD) and central parameters by oscillometry. The CVH-L8 score was determined using the eight metrics defined in the new classification.

RESULTS

Patients (n = 82) were divided according to CVH-L8 classification: moderate group (score CVH-L8 ≥ 50 ≤ 79 points, n = 47) and low group (score CVH-L8 ≤ 49 points, n = 35). Peripheral (119 ± 10 vs 125 ± 15 mmHg, p = 0.048) and central (111 ± 10 vs 118 ± 15 mmHg; p = 0.016) systolic blood pressures and pulse wave velocity (PWV) adequacy (- 0.08 ± 0.34 vs 0.15 ± 0.42 m/s, p = 0.008) were significantly higher in low CVH-L8 group. Brachial FMD (9.24 ± 5.41 vs 6.79 ± 4.74%, p = 0.043) were lower in this same group. Only in the low CVH-L8 group low frequency/high frequency (LF/HF) ratio was significantly correlated with PWV (r = 0.338, p = 0.047) and atherogenic index of plasma with Framingham risk score (r = 0.446, p = 0.008), even after adjustment for age and sex.

CONCLUSION

In this sample of obese individuals, low CVH-L8 was associated with higher peripheral and central blood pressures, and evidence of early vascular aging with arterial stiffness and endothelial dysfunction.

Autonomic and circulatory alterations persist despite adequate resuscitation in a 5-day sepsis swine experiment

Autonomic and vascular failures are common phenotypes of sepsis, typically characterized by tachycardia despite corrected hypotension/hypovolemia, vasopressor resistance, increased arterial stiffness and decreased peripheral vascular resistance. In a 5-day swine experiment of polymicrobial sepsis we aimed at characterizing arterial properties and autonomic mechanisms responsible for cardiovascular homeostasis regulation, with the final goal to verify whether the resuscitation therapy in agreement with standard guidelines was successful in restoring a physiological condition of hemodynamic profile, cardiovascular interactions and autonomic control. Twenty pigs were randomized to polymicrobial sepsis and protocol-based resuscitation or to prolonged mechanical ventilation and sedation without sepsis. The animals were studied at baseline, after sepsis development, and every 24 h during the 3-days resuscitation period. Beat-to-beat carotid blood pressure (BP), carotid blood flow, and central venous pressure were continuously recorded. The two-element Windkessel model was adopted to study carotid arterial compliance, systemic vascular resistance and characteristic time constant τ. Effective arterial elastance was calculated as a simple estimate of total arterial load. Cardiac baroreflex sensitivity (BRS) and low frequency (LF) spectral power of diastolic BP were computed to assess autonomic activity. Sepsis induced significant vascular and autonomic alterations, manifested as increased arterial stiffness, decreased vascular resistance and τ constant, reduced BRS and LF power, higher arterial afterload and elevated heart rate in septic pigs compared to sham animals. This compromised condition was persistent until the end of the experiment, despite achievement of recommended resuscitation goals by administered vasopressors and fluids. Vascular and autonomic alterations persist 3 days after goal-directed resuscitation in a clinically relevant sepsis model. We hypothesize that the addition of these variables to standard clinical markers may better profile patients' response to treatment and this could drive a more tailored therapy which could have a potential impact on long-term outcomes.

Global Reach 2018: sympathetic neural and hemodynamic responses to submaximal exercise in Andeans with and without chronic mountain sickness

Andeans with chronic mountain sickness (CMS) and polycythemia have similar maximal oxygen uptakes to healthy Andeans. Therefore, this study aimed to explore potential adaptations in convective oxygen transport, with a specific focus on sympathetically mediated vasoconstriction of nonactive skeletal muscle. In Andeans with (CMS+, n = 7) and without (CMS-, n = 9) CMS, we measured components of convective oxygen delivery, hemodynamic (arterial blood pressure via intra-arterial catheter), and autonomic responses [muscle sympathetic nerve activity (MSNA)] at rest and during steady-state submaximal cycling exercise [30% and 60% peak power output (PPO) for 5 min each]. Cycling caused similar increases in heart rate, cardiac output, and oxygen delivery at both workloads between both Andean groups. However, at 60% PPO, CMS+ had a blunted reduction in Δtotal peripheral resistance (CMS-, -10.7 ± 3.8 vs. CMS+, -4.9 ± 4.1 mmHg·L-1·min-1; P = 0.012; d = 1.5) that coincided with a greater Δforearm vasoconstriction (CMS-, -0.2 ± 0.6 vs. CMS+, 1.5 ± 1.3 mmHg·mL-1·min-1; P = 0.008; d = 1.7) and a rise in Δdiastolic blood pressure (CMS-, 14.2 ± 7.2 vs. CMS+, 21.6 ± 4.2 mmHg; P = 0.023; d = 1.2) compared with CMS-. Interestingly, although MSNA burst frequency did not change at 30% or 60% of PPO in either group, at 60% Δburst incidence was attenuated in CMS+ (P = 0.028; d = 1.4). These findings indicate that in Andeans with polycythemia, light intensity exercise elicited similar cardiovascular and autonomic responses compared with CMS-. Furthermore, convective oxygen delivery is maintained during moderate-intensity exercise despite higher peripheral resistance. In addition, the elevated peripheral resistance during exercise was not mediated by greater sympathetic neural outflow, thus other neural and/or nonneural factors are perhaps involved.NEW & NOTEWORTHY During submaximal exercise, convective oxygen transport is maintained in Andeans suffering from polycythemia. Light intensity exercise elicited similar cardiovascular and autonomic responses compared with healthy Andeans. However, during moderate-intensity exercise, we observed a blunted reduction in total peripheral resistance, which cannot be ascribed to an exaggerated increase in muscle sympathetic nerve activity, indicating possible contributions from other neural and/or nonneural mechanisms.

The impact of age, sex, cardio-respiratory fitness, and cardiovascular disease risk on dynamic cerebral autoregulation and baroreflex sensitivity

Background

Humans display an age-related decline in cerebral blood flow and increase in blood pressure (BP), but changes in the underlying control mechanisms across the lifespan are less well understood. We aimed to; (1) examine the impact of age, sex, cardiovascular disease (CVD) risk, and cardio-respiratory fitness on dynamic cerebral autoregulation and cardiac baroreflex sensitivity, and (2) explore the relationships between dynamic cerebral autoregulation (dCA) and cardiac baroreflex sensitivity (cBRS).

Methods

206 participants aged 18–70 years were stratified into age categories. Cerebral blood flow velocity was measured using transcranial Doppler ultrasound. Repeated squat-stand manoeuvres were performed (0.10 Hz), and transfer function analysis was used to assess dCA and cBRS. Multivariable linear regression was used to examine the influence of age, sex, CVD risk, and cardio-respiratory fitness on dCA and cBRS. Linear models determined the relationship between dCA and cBRS.

Results

Age, sex, CVD risk, and cardio-respiratory fitness did not impact dCA normalised gain, phase, or coherence with minimal change in all models (P > 0.05). cBRS gain was attenuated with age when adjusted for sex and CVD risk (young–older; β = − 2.86 P < 0.001) along with cBRS phase (young–older; β = − 0.44, P < 0.001). There was no correlation between dCA normalised gain and phase with either parameter of cBRS.

Conclusion

Ageing was associated with a decreased cBRS, but dCA appears to remain unchanged. Additionally, our data suggest that sex, CVD risk, and cardio-respiratory fitness have little effect.

Very Low-Calorie Ketogenic Diet Modulates the Autonomic Nervous System Activity through Salivary Amylase in Obese Population Subjects

In obesity, to reduce visceral adipose tissue (VAT), caloric restriction is a valid strategy. Salivary amylase is an enzyme that cleaves large starch carbohydrates molecules and its production is modulated by the central nervous system. In addition, heart rate variability (HRV) is simply a measure of the variation in time between each heartbeat. This variation is controlled by the autonomic nervous system. In the light of this evidence, the aim of this study is to characterize the effect of a very low-calorie ketogenic diet (VLCKD) on the autonomic nervous system in obese patients. Twenty subjects affected by obesity were recruited before and after 8 weeks of VLCKD intervention to evaluate salivary amylase by the ELISA test and HRV analysis. These parameters significantly increased after dietary treatment, and positively correlate to each other. VLCKD exerts a positive effect on salivary amylase and HRV, ameliorating body composition and biochemical features. In brief, this dietary intervention improves the autonomic nervous system activity. This is the first study about the effects of VLCKD upon the autonomic nervous system, but further studies are needed to elucidate the mechanism undergone VLCKD effects.

Obesity-associated hyperleptinemia alters the gliovascular interface of the hypothalamus to promote hypertension

Pathologies of the micro- and macrovascular systems are a hallmark of the metabolic syndrome, which can lead to chronically elevated blood pressure. However, the underlying pathomechanisms involved still need to be clarified. Here, we report that an obesity-associated increase in serum leptin triggers the select expansion of the micro-angioarchitecture in pre-autonomic brain centers that regulate hemodynamic homeostasis. By using a series of cell- and region-specific loss- and gain-of-function models, we show that this pathophysiological process depends on hypothalamic astroglial hypoxia-inducible factor 1α-vascular endothelial growth factor (HIF1α-VEGF) signaling downstream of leptin signaling. Importantly, several distinct models of HIF1α-VEGF pathway disruption in astrocytes are protected not only from obesity-induced hypothalamic angiopathy but also from sympathetic hyperactivity or arterial hypertension. These results suggest that hyperleptinemia promotes obesity-induced hypertension via a HIF1α-VEGF signaling cascade in hypothalamic astrocytes while establishing a novel mechanistic link that connects hypothalamic micro-angioarchitecture with control over systemic blood pressure.

Ablation of TRPV1 Abolishes Salicylate-Induced Sympathetic Activity Suppression and Exacerbates Salicylate-Induced Renal Dysfunction in Diet-Induced Obesity

Sodium salicylate (SA), a cyclooxygenase inhibitor, has been shown to increase insulin sensitivity and to suppress inflammation in obese patients and animal models. Transient receptor potential vanilloid 1 (TRPV1) is a nonselective cation channel expressed in afferent nerve fibers. Cyclooxygenase-derived prostaglandins are involved in the activation and sensitization of TRPV1. This study tested whether the metabolic and renal effects of SA were mediated by the TRPV1 channel. Wild-type (WT) and TRPV1-/- mice were fed a Western diet (WD) for 4 months and received SA infusion (120mg/kg/day) or vehicle for the last 4 weeks of WD feeding. SA treatment significantly increased blood pressure in WD-fed TRPV1-/- mice (p < 0.05) but not in WD-fed WT mice. Similarly, SA impaired renal blood flow in TRPV1-/- mice (p < 0.05) but not in WT mice. SA improved insulin and glucose tolerance in both WT and TRPV1-/- mice on WD (all p < 0.05). In addition, SA reduced renal p65 and urinary prostaglandin E2, prostaglandin F1α, and interleukin-6 in both WT and TRPV1-/- mice (all p < 0.05). SA decreased urine noradrenaline levels, increased afferent renal nerve activity, and improved baroreflex sensitivity in WT mice (all p < 0.05) but not in TRPV1-/- mice. Importantly, SA increased serum creatinine and urine kidney injury molecule-1 levels and decreased the glomerular filtration rate in obese WT mice (all p < 0.05), and these detrimental effects were significantly exacerbated in obese TRPV1-/- mice (all p < 0.05). Lastly, SA treatment increased urine albumin levels in TRPV1-/- mice (p < 0.05) but not in WT mice. Taken together, SA-elicited metabolic benefits and anti-inflammatory effects are independent of TRPV1, while SA-induced sympathetic suppression is dependent on TRPV1 channels. SA-induced renal dysfunction is dependent on intact TRPV1 channels. These findings suggest that SA needs to be cautiously used in patients with obesity or diabetes, as SA-induced renal dysfunction may be exacerbated due to impaired TRPV1 in obese and diabetic patients.

Central and Peripheral Postexercise Blood Pressure and Vascular Responses in Young Adults with Obesity

INTRODUCTION

Adults with obesity are at an increased risk of incident hypertension. Regular aerobic exercise is recommended for the prevention and treatment of hypertension, but whether young adults with obesity exhibit impaired postexercise blood pressure (BP) and vascular responses remains unclear.

PURPOSE

We tested the hypothesis that young adults with obesity exhibit attenuated postexercise hypotension (PEH) and postexercise peripheral vasodilation compared with young adults without obesity.

METHODS

Thirty-six normotensive adults without and with obesity (11 men and 7 women per group) underwent measurements of brachial and central BP, and leg blood flow (Doppler ultrasound) at baseline and at 30, 60, and 90 min after acute 1-h moderate-intensity cycling. Leg vascular conductance (LVC) was calculated as flow/mean arterial pressure.

RESULTS

Both groups exhibited similar brachial and central PEH (peak change from baseline, -2 and -4 mm Hg for brachial and central systolic BPs, respectively, for both groups; time effect, P < 0.05). Both groups also exhibited postexercise peripheral vasodilation, assessed via LVC (time effect, P < 0.05), but its overall magnitude was smaller in young adults with obesity (LVC change from baseline, +47% ± 37%, +29% ± 36%, and +20% ± 29%) compared with young adults without obesity (LVC change from baseline, +88% ± 58%, +59% ± 54%, and +42% ± 51%; group effect, P < 0.05).

CONCLUSIONS

Although obesity did not impair PEH after acute moderate-intensity exercise, young adults with obesity exhibited smaller postexercise peripheral vasodilation compared with young adults without obesity. Collectively, these findings have identified evidence for obesity-induced alterations in the peripheral vasculature after exercise.

Altered Cardiac Autonomic Regulation in Overweight and Obese Subjects: The Role of Age-and-Gender-Adjusted Statistical Indicators of Heart Rate Variability and Cardiac Baroreflex

In the context of functional determinants of cardiovascular risk, a simple excess in body weight, as indexed by a rise in body mass index (BMI), plays a significant, well-recognized causal role. Conversely, BMI reductions toward normal result in an improvement of risk. Obesity is associated with impaired cardiac autonomic regulation (CAR), through either vagal or sympathetic mechanisms, which could favor the tendency to foster hypertension. Here we study the changing properties of the relationship between increasing grades of BMI and CAR in a population of 756 healthy subjects (age 35.9 ± 12.41 years, 37.4% males, 21.6% overweight, and 16% obese). Evaluation of CAR is based on autoregressive spectral analysis of short-term RR interval and systolic arterial pressure variability, from which a multitude of indices, treated overall as autonomic nervous system (ANS) proxies, is derived. Inspection of the study hypothesis that elevated BMI conditions associate significantly with alterations of CAR, independently of age and gender, is carried out using a mix of statistical transformations, exploratory factor analysis, non-parametric testing procedures, and graphical tools particularly well suited to address alterations of CAR as a disturbed process. In particular, to remove the effects of the inter-individual variability, deriving from components like age, gender or ethnicity, and to reduce the number of ANS proxies, we set up six age-and-gender-adjusted CAR indicators, corresponding to four ANS latent domains (oscillatory, amplitude, pressure, and pulse), cardiac baroreflex regulation, and autonomic nervous system index (ANSI). An impairment of the CAR indicators is overall evident in the overweight group and more marked in the obesity group. Empirical evidence is strong (9/9 concordant non-parametric test results) for pressure domain, almost strong (8/9) for ANSI, medium-strong for baroreflex (6/9) and pulse (7/9), weak for oscillatory (2/9) and amplitude (1/9) domains. In addition, the distribution of the CAR indicators corresponding to pressure, pulse, baroreflex, and ANSI is skewed toward the unfavorable abscissa extremity, particularly in the obese group. The significant association of increased BMI with progressive impairments of CAR regarding specifically the pressure domain and the overall ANS performance might underscore the strong hypertensive tendency observed in obesity.

Effects of intracerebroventricular leptin and orexin-A on the baroreflex control of renal sympathetic nerve activity in conscious rats fed a normal or high-fat diet

This study examined the effect of leptin and orexin-A on autonomic baroreflex control in conscious Wistar rats exposed to high-fat (45% fat) or normal (3.4%) diet for 4 weeks. Renal sympathetic nerve activity (RSNA), mean arterial pressure (MAP) and heart rate (HR) were monitored during the generation of baroreflex gain curves and acute volume expansion (VEP). Intracerebroventricular (ICV) leptin (1 μg/min) increased RSNA in the normal diet group (0.31 ± 0.04 vs 0.23 ± 0.03 mV/s) and MAP in the high-fat diet group (115 ± 5 vs 105 ± 5 mm Hg, P < .05). Orexin-A (50 ng/min) increased RSNA, HR and MAP in the high-fat diet group (0.26 ± 0.03 vs 0.22 ± 0.02 mV/s, 454 ± 8 vs 417 ± 12 beats/min, 117 ± 1 vs 108 ± 1 mm Hg) and the normal diet group (0.18 ± 0.05 vs 0.17 ± 0.05 mV/s, 465 ± 10 vs 426 ± 6 beats/min, 116 ± 2 vs 104 ± 3 mm Hg). Baroreflex sensitivity for RSNA was increased during ICV leptin by 50% in the normal diet group, compared to 14% in the high-fat diet group (P < .05). Similarly, orexin-A increased baroreflex sensitivity by 56% and 50% in the high-fat and normal diet groups, respectively (all P < .05). During ICV saline, VEP decreased RSNA by 31 ± 5% (P < .05) after 10 minutes and the magnitude of this response was blunted during ICV infusion of leptin (17 ± 2%, P < .05) but not orexin-A in the normal diet group. RSNA response to VEP was not changed during ICV leptin or orexin-A in the high-fat diet group. These findings indicate possible central roles for leptin and orexin-A in modulating the baroreflexes under normal or increased fat intake in conscious rats and potential therapeutic approaches for obesity associated hypertension.

Effect of air pollution on the autonomic modulation of heart rate in overweight adults

Objective:

To analyze the effect of air pollution on heart rate variability in overweight individuals.

Methods:

A total of 46 adult individuals, both sexes, aged between 18 and 49 years and with body mass index >25kg/m² were analyzed. All volunteers were students from public schools of two cities in the state of São Paulo. The clinical, demographic and anthropometric data of each individual, as well as heart rate variability through time domain, geometric and frequency indices were collected. For the air quality analysis, the following variables were investigated: concentration of carbon dioxide, particulate matter, temperature and relative humidity. The analysis was carried out with descriptive and analytical statistics, adopting a level of significance of 5%.

Results:

There was a reduction in overall heart rate variability in overweight individuals by the following indices: mean standard deviation of all normal RR intervals, long-term standard deviation of continuous RR intervals, ratio of short-and long-term standard deviation of continuous RR intervals. In addition, the indices responsible for parasympathetic control showed a downward trend in their values, as well as the low frequency index, which represented sympathetic action, although not significant.

Conclusion:

Overweight individuals exposed to air pollution had lower heart rate variability than the Control Group.

Effect of obesity on cardiovascular responses to submaximal treadmill exercise in adult males

Context:

Obesity is a major risk factor for chronic diseases. Abnormal changes in cardiovascular responses to exercise indicate the alteration in autonomic activity in obese.

Aims:

To assess and compare the cardiovascular parameters before and after exercise among obese and nonobese adult males.

Subjects and Methods:

Thirty each obese and normal-weight males between the age group 18-45 years were selected as cases and controls, respectively. Heart rate (HR), systolic blood pressure (SBP), diastolic blood pressure (DBP), mean arterial pressure (MAP), corrected QT intervals were measured before and after submaximal treadmill exercise (QT and QTc) were done according to Bruce protocol. HR, SBP, DBP, MAP, QT, and QTc were also measured during passive recovery at 1 min and 5 min after exercise.

Statistical Analysis Used:

One-way analysis of variance and t-test were used to assess changes before and after exercise.

Results:

Resting HR was significantly higher in obese when compared to nonobese (P < 0.05). SBP, DBP, MAP, QT, and QTc were significantly higher in obese when compared to nonobese (P < 0.001). Immediately after exercise HR, SBP, DBP, MAP, QT, and QTc were significantly higher in obese when compared to nonobese (P < 0.001) 1 min after exercise.

Conclusions:

Obese individuals had elevated resting cardiovascular parameters and showed increased responses to steady exercise which could be due to alteration in autonomic functions with sympathetic hyperactivity. Delayed rate of decrease in HR and BP after exercise was also observed in obese, which indicates that they are at risk of developing cardiovascular diseases.

Physiological factors characterizing heat-vulnerable older adults: A narrative review

More frequent and intense periods of extreme heat (heatwaves) represent the most direct challenge to human health posed by climate change. Older adults are particularly vulnerable, especially those with common age-associated chronic health conditions (e.g., cardiovascular disease, hypertension, obesity, type 2 diabetes, chronic kidney disease). In parallel, the global population is aging and age-associated disease rates are on the rise. Impairments in the physiological responses tasked with maintaining homeostasis during heat exposure have long been thought to contribute to increased risk of health disorders in older adults during heatwaves. As such, a comprehensive overview of the provisional links between age-related physiological dysfunction and elevated risk of heat-related injury in older adults would be of great value to healthcare officials and policy makers concerned with protecting heat-vulnerable sectors of the population from the adverse health impacts of heatwaves. In this narrative review, we therefore summarize our current understanding of the physiological mechanisms by which aging impairs the regulation of body temperature, hemodynamic stability and hydration status. We then examine how these impairments may contribute to acute pathophysiological events common during heatwaves (e.g., heatstroke, major adverse cardiovascular events, acute kidney injury) and discuss how age-associated chronic health conditions may exacerbate those impairments. Finally, we briefly consider the importance of physiological research in the development of climate-health programs aimed at protecting heat-vulnerable individuals.

The Role of Exercise in Patients with Obesity and Hypertension

PURPOSE OF REVIEW

This review sought to evaluate the role of exercise in patients with obesity and comorbid hypertension, with a focus on contemporary literature (since January 2015).

RECENT FINDINGS

No reviews have included patients classified with both obesity and hypertension and there is a paucity of randomised controlled trials examining the benefits of exercise in this population. Moreover, just one of 19 reviews examining the role of exercise on blood pressure included studies that met pre-defined inclusion criterion for hypertension, although seven conducted subgroup analyses stratified by mean baseline blood pressure. These demonstrated significantly larger reductions in blood pressure in hypertensive than pre-hypertensive and normotensive samples. There is a significant research-practice gap for understanding and influencing the role of exercise for patients with obesity and hypertension. This review provides recommendations for future research and consensus-based recommendations that promote exercise as a principle therapy for patients with obesity and hypertension.

Vascular Decoupling in Septic Shock: The Combined Role of Autonomic Nervous System, Arterial Stiffness, and Peripheral Vascular Tone

BACKGROUND

Acute inflammation and sepsis are known to induce changes in vascular properties, leading to increased arterial stiffness; at the same time, the autonomic nervous system (ANS) also affects vascular properties by modulating the arterial smooth muscle tone, and it is widely reported that sepsis and septic shock severely impair ANS activity. Currently, clinical guidelines are mainly concerned to resuscitate septic shock patients from hypotension, hypovolemia, and hypoperfusion; however, if the current resuscitation maneuvers have a beneficial effect also on vascular properties and autonomic functionality is still unclear. The objective of this work is to assess the effects of standard resuscitation at vascular level and to verify if there is any association between alterations in vascular properties and ANS activity.

METHODS

Six pigs underwent a protocol of polymicrobial septic shock and resuscitation (fluids and noradrenaline). The arterial blood pressure (ABP) waveform was recorded in the central aorta and in the peripheral radial and femoral artery. The characteristic arterial time constant was computed at the three arterial sites based on the two-element Windkessel model, to characterize the overall arterial vascular tree. Moreover, independent estimates of total arterial compliance (AC) and total peripheral resistance (TPR) were performed. Baroreflex sensitivity (BRS), low frequency (LF, 0.04-0.15 Hz) spectral power of diastolic blood pressure, and indices of heart rate variability (HRV) were computed to assess ANS functionality.

RESULTS

Septic shock induced a severe vascular disarray, decoupling the usual pressure wave propagation from central to peripheral sites; this phenomenon appeared as an inversion of the physiological pulse pressure (PP) amplification, with a higher PP in the central aorta than in the peripheral arteries. The time constant was decreased, together with AC and TPR. ANS dysfunction was described by a reduced BRS, decreased LF power, and suppressed HRV. This compromised condition was not resolved by administration of fluids and noradrenaline. Thus, a persistent vascular and autonomic dysfunction were reported also in the resuscitated animals, and they were found to be significantly correlated.

CONCLUSION

Measures of vascular function and ANS activity could add information to standard hemodynamic and clinical markers, and the current resuscitation strategies could benefit from the adjunction of these additional functional indices.

Ablation of TRPV1 Elevates Nocturnal Blood Pressure in Western Diet-fed Mice

Background: This study tested the hypothesis that genetically ablation of transient receptor potential vanilloid type 1 (TRPV1) exacerbates impairment of baroreflex in mice fed a western diet (WD) and leads to distinct diurnal and nocturnal blood pressure patterns.

Methods: TRPV1 gene knockout (TRPV1^-/-) and wild-type (WT) mice were given a WD or normal diet (CON) for 4 months.

Results: Capsaicin, a selective TRPV1 agonist, increased ipsilateral afferent renal nerve activity in WT but not TRPV1^-/- mice. The sensitivity of renal sympathetic nerve activity and heart rate responses to baroreflex were reduced in TRPV1^-/--CON and WT-WD and further decreased in TRPV1^-/--WD compared to the WT-CON group. Urinary norepinephrine and serum insulin and leptin at day and night were increased in WT-WD and TRPV1^-/--WD, with further elevation at night in TRPV1^-/--WD. WD intake increased leptin, IL-6, and TNF-α in adipose tissue, and TNF-α antagonist III, R-7050, decreased leptin in TRPV1^-/--WD. The urinary albumin level was higher in TRPV1^-/--WD than WT-WD. Blood pressure was not dif-ferent during daytime among all groups, but increased at night in the TRPV1^-/--WD group compared with other groups.

Conclusions: TRPV1 ablation leads to elevated nocturnal but not diurnal blood pressure, which is probably attributed to fur-ther enhancement of sympathetic drives at night.

Anti-obesity therapy with peripheral CB1 blockers: from promise to safe(?) practice

Pharmacological blockers of the cannabinoid receptor type-1 (CB1) have been considered for a long time as the holy grail of obesity pharmacotherapy. These agents were hastily released in the clinical setting, due to their clear-cut therapeutic efficacy. However, the first generation of these drugs, which were able to target both the brain and peripheral tissues, had serious neuropsychiatric effects, leading authorities to ban their clinical use. New peripherally restricted CB1 blockers, characterized by low brain penetrance, have been developed over the past 10 years. In preclinical studies, these molecules seem to overcome the neuropsychiatric negative effects previously observed with brain-penetrant CB1 inhibitors, while retaining or even outperforming their efficacy. The mechanisms of action of these peripherally restricted compounds are only beginning to emerge, and a balanced discussion of the risk/benefits ratio associated to their possible clinical use is urgently needed, in order to avoid repeating past mistakes. Here, we will critically discuss the advantages and the possible hidden threats associated with the use of peripheral CB1 blockers for the pharmacotherapy of obesity and its associated metabolic complications. We will address whether this novel pharmacological approach might 'compete' with current pharmacotherapies for obesity and diabetes, while also conceptualizing future CB1-based pharmacological trends that may significantly lower the risk/benefits ratio associated with the use of these drugs.

Epidemiological evidence of increased waist circumference, but not body mass index, associated with impaired baroreflex sensitivity

Although an inverse relationship between body mass index (BMI) and baroreflex sensitivity (BRS) was found, the effect of waist circumference (WC) on BRS is still inconclusive. The contradictory results of previous studies may be related to the heterogeneity and relatively small sample size of the subjects examined. The aim of this population-based study was to investigate whether the influence of increased WC is more detrimental to BRS than BMI. A total of 760 community dwellers were recruited and they were classified into Q1 (n = 189), Q2 (n = 183), Q3 (n = 192) and Q4 (n = 196) groups, based on WC quartiles. Spontaneous BRS was determined by spectral α coefficient method. Valsalva ratio was the longest RR interval after release of Valsalva maneuver divided by the shortest RR interval during maneuver. Cardiac autonomic function was calculated by power spectrum of heart rate in low and high frequency (LF, 0.04-0.15 Hz; HF, 0.15-0.40 Hz), and LF/HF ratio in supine position for five minutes. There were significant differences in spontaneous BRS and Valsalva ratio among different WC groups. In multivariate analysis, obesity was inversely associated with spontaneous BRS and Valsalva ratio. However, these inverse relationships became insignificant after further adjustment for WC quartiles. In contrast, Q4 vs. Q1, Q3 vs. Q1 and Q2 vs. Q1 of WC were inversely related to spontaneous BRS. Q4 vs. Q1 and Q3 vs. Q1 of WC were negatively associated with the Valsalva ratio. In conclusion, increased and even high-normal WC had a stronger adverse effect on BRS than BMI, independent of cardio-metabolic risk factors.

The relationship between exposure to hot/cold weather and the clinical features of headaches in patients with migraine and tension-type headaches

Background and purpose: This study investigates the relationship between exposure to hot/cold weather and the characteristic clinical features of headaches in patients with migraine and tension-type headaches.Methods: This cross-sectional study was conducted with the participation of 190 patients with migraine, and 140 patients with tension-type headaches. The patients were evaluated using a form that collected data on their sociodemographic profile, the clinical features of their headaches, any accompanying symptoms and their relationships with changes in the weather (hot/cold). The headaches of all the participants in the study were thought to be triggered by exposure to hot/cold weather.Results: In the patients with migraine, the exposure to hot/cold weather as a trigger was not found to have a significant relationship with age, body mass index or the characteristic clinical features of headaches (p > 0.05). In patients with tension-type headaches, exposure to hot/cold weather as a trigger was found to have a significant relationship with body mass index (p = 0.019), but not with age or the characteristic clinical features of headaches (p > 0.05).Conclusions: In obese patients with tension-type headache, it was found that hot weather triggered headache more than cold weather. In patients with migraine and tension-type headaches, no relationship was found between exposure to hot/cold weather as a trigger and the clinical features of headaches. The accurate identification of the factors precipitating headaches by both clinicians and patients can help lower the frequency of headaches.

Device-Based Neuromodulation for Resistant Hypertension Therapy

Despite availability of effective drugs for hypertension therapy, significant numbers of hypertensive patients fail to achieve recommended blood pressure levels on ≥3 antihypertensive drugs of different classes. These individuals have a high prevalence of adverse cardiovascular events and are defined as having resistant hypertension (RHT) although nonadherence to prescribed antihypertensive medications is common in patients with apparent RHT. Furthermore, apparent and true RHT often display increased sympathetic activity. Based on these findings, technology was developed to treat RHT by suppressing sympathetic activity with electrical stimulation of the carotid baroreflex and catheter-based renal denervation (RDN). Over the last 15 years, experimental and clinical studies have provided better understanding of the physiological mechanisms that account for blood pressure lowering with baroreflex activation and RDN and, in so doing, have provided insight into which patients in this heterogeneous hypertensive population are most likely to respond favorably to these device-based therapies. Experimental studies have also played a role in modifying device technology after early clinical trials failed to meet key endpoints for safety and efficacy. At the same time, these studies have exposed potential differences between baroreflex activation and RDN and common challenges that will likely impact antihypertensive treatment and clinical outcomes in patients with RHT. In this review, we emphasize physiological studies that provide mechanistic insights into blood pressure lowering with baroreflex activation and RDN in the context of progression of clinical studies, which are now at a critical point in determining their fate in RHT management.

High salt intake during puberty leads to cardiac remodelling and baroreflex impairment in lean and obese male Wistar rats

Modern lifestyle increases the prevalence of obesity and its co-morbidities in the young population. High-salt (HS) diets are associated with hypertension and cardiac remodelling. The present study evaluated the potential effects of cardiometabolic programming induced by HS intake during puberty in lean and obese rats. Additionally, we investigated whether HS could exacerbate the impairment of cardiovascular parameters in adult life due to postnatal early overnutrition (PO). At postnatal day 3 (PN3), twenty-four litters of Wistar rats were divided into two groups: normal litter (NL, nine pups/dam) and small litter (SL, three pups/dam) throughout the lactation period; weaning was at PN21. At PN30, the pups were subdivided into two more groups: NL plus HS (NLHS) and SL plus HS (SLHS). HS intake was from PN30 until PN60. Cardiovascular parameters were evaluated at PN120. SL rats became overweight at adulthood due to persistent hyperphagia; however, HS exposure during puberty reduced the weight gain and food intake of NLHS and SLHS. Both HS and obesity raised the blood pressure, impaired baro- and chemoreflex sensitivity and induced cardiac remodelling but no worsening was observed in the association of these factors, except a little reduction in the angiotensin type-2 receptor in the hearts from SLHS animals. Our results suggest that the response of newborn offspring to PO and juveniles to a HS diet leads to significant changes in cardiovascular parameters in adult rats. This damage may be accompanied by impairment of both angiotensin signalling and antioxidant defence in the heart.

Heart rate variability reduction is related to a high amount of visceral adiposity in healthy young women

Several heart rate variability (HRV) studies show abnormalities in autonomic nervous control in obese and overweight subjects. However, some of the results appear to be controversial. Here we investigate the HRV profile in seventy adult normotensive women and its association with general and visceral adiposity. Specifically, we recorded the electrocardiographic (ECG) activity in subjects during a supine resting state for five minutes in a quiet room late in the morning. Total fat mass (TFM) and visceral adipose tissue (VAT) were instead estimated using dual-energy X-ray absorptiometry (DXA). Finally, we used simple a linear regression analysis of frequency and time-domain parameters to study the relationship between HRV and adiposity. Our data showed an overall reduction of the HRV related to an increase of TFM although this regression appeared significant only for high frequencies (HF). When the linear regression was applied between HRV variables and VAT, the slope of the line increases, thus unveiling a statistically significant relation (i.e. the more VAT, the lower HRV). Finally, a control analysis showed that age does not alter the relation between HRV and VAT when used as a confounding factor in multiple regression. To conclude, these findings point to abnormal activity of the autonomic nervous system (ANS) in subjects with an excess of VAT and represent a starting point to determine a non-invasive index of cardiac wellness for clinical and nutritional application.

Comparison of Baroreflex Sensitivity and Cardiac Autonomic Function Between Adolescent Athlete and Non-athlete Boys - A Cross-Sectional Study

Introduction: It is well known that regular physical activity improves cardiovascular health, and higher baroreflex sensitivity and heart rate variability are associated with cardiovascular health. Adolescence is the age when an individual’s behavior is easily modified; early intervention at this stage in terms of physical conditioning or training prevents future cardiovascular risk. Hence, we conceived the present study to assess and compare the baroreflex sensitivity and autonomic function between adolescent athletes and non-athletes.

Methods: We recruited school going athletes (n = 30) and non-athlete boys (n = 30) in the 10–19 age group after obtaining their assent and consent from their parents. We assessed height, weight, heart rate, blood pressure, baroreflex sensitivity, and cardiac autonomic function. Comparison between groups was made using the unpaired t-test for height, weight, body mass index, heart rate, blood pressure, and baroreflex sensitivity and using Mann-Whitney U test for cardiac autonomic function parameters.

Results: There was a trend for higher baroreflex sensitivity in athletes. Heart rate variability (total power and SDNN) was higher in athletes. The parasympathetic tone was higher in terms of higher RMSSD, and higher HF power. Parasympathetic reactivity was higher in athletes in terms of higher 30:15 ratio and EI ratio.

Conclusion: Athletic level physical conditioning has a positive influence on baroreflex function and autonomic function that may prove beneficial to the adolescents’ cardiovascular health.

Intermittent energy restriction is comparable to continuous energy restriction for cardiometabolic health in adults with central obesity: A randomized controlled trial; the Met-IER study

BACKGROUND & AIMS

Short bouts of severe energy restriction may have additional, beneficial cardiometabolic effects beyond that of weight loss. We aimed to assess the short-term effects of intermittent fasting on insulin sensitivity and related cardiometabolic mechanisms.

METHODS

This parallel arm, randomized controlled trial compared the short-term effects of intermittent and continuous energy restriction (IER and CER) diets on markers of cardiometabolic health in individuals with central obesity, aiming for equivalent weight loss on both diets. Outcomes were assessed in non-smoking men and women (35-75 y), following 4-wk IER (48 h 600 kcal/d followed by 5-day healthy eating advice) or CER diets (-500 kcal/d healthy eating advice). The primary outcome was the revised quantitative insulin sensitivity check index (R-QUICKI), an indirect estimate of insulin sensitivity. Secondary outcomes included ambulatory blood pressure (ABP), indicators of sympathetic activity (heart rate variability (HRV) and normetanephrine), and markers of glucose homeostasis/insulin resistance, adiposity, lipids and inflammation.

RESULTS

Forty-three participants completed the study. Reductions in body weight were equivalent in both groups: mean loss (%) -2.6; 95% CI -3.3, -1.9 and -2.9; -3.6, -2.1 for CER and IER, respectively, P = 0.464). R-QUICKI increased following IER and CER, with no between-diet differences (overall mean increase (%) 6.6; 3.6, 9.6). Fasting plasma glucose concentrations decreased after CER but not after IER (mean difference CER-IER - 4.8% (0.7, 8.9), P < 0.05) and fasting plasma non-esterified fatty acid concentrations were lower after IER compared to CER (mean difference CER-IER 0.15 mmol/L (0.06, 0.24), P < 0.005). There were no differences in lipids, adipokine/inflammatory markers, ABP or HRV between diets.

CONCLUSIONS

Short-term CER or IER diets are comparable in their effects on most markers of cardiometabolic risk, although adaptive changes in glucose and fatty acid metabolism occur. This study is registered at clinicaltrials.gov as NCT02679989.

Noninvasive assessment of autonomic function in human neonates born at the extremes of fetal growth spectrum

Birth weight is associated with adult cardiovascular disease, such that those at both ends of the spectrum are at increased risk. This may be driven in part by modification to autonomic control, a mechanistic contributor to hypertension. However, birth weight is a relatively crude surrogate of fetal growth; and newborn body composition may more accurately identify the "at risk" infant. Accordingly, we sought to determine whether newborns with high or low body fat have altered autonomic control of vasomotor function and cardiac contractility. Body fat was assessed by air-displacement plethysmography <24 h postnatal. Measures of spontaneous baroreflex sensitivity (sBRS), blood pressure variability (BPV), and dP/dt_max variability were compared between newborns categorized according to established body fat percentiles: high body fat (HBF, >90th percentile, n = 7), low body fat (LBF, ≤10th percentile, n = 12), and normal body fat (control, >25th to ≤75th percentile, n = 23). BPV was similar across body fat percentiles; similarly, low frequency dP/dt_max variability was similar across body fat percentiles. sBRS was reduced in HBF compared to controls (11.0 ± 6.0 vs. 20.1 ± 9.4 msec/mmHg, P = 0.03), but LBF did not differ (18.4 ± 6.0 msec/mmHg, P = 0.80). Across the entire body fat spectrum (n = 62), there was a nonlinear association between newborn body fat and sBRS (P = 0.03) that was independent of birth weight (P = 0.04). Autonomic modulation of vasomotor function and cardiac contractility in the newborn did not differ by body fat, but newborns born with high body fat show depressed baroreflex sensitivity.

Clinical Implications of Baroreflex Sensitivity in Type 2 Diabetes

The evaluation of baroreflex sensitivity (BRS), which maintains systemic circulatory homeostasis, is an established tool to assess cardiovascular autonomic neuropathy in type 2 diabetes mellitus (T2DM). As BRS plays an important function in blood pressure regulation, reduced BRS leads to an increase in blood pressure variability, which further leads to reduced BRS. This sequence of events becomes a vicious cycle. The major risk factors for reduced BRS are T2DM and essential hypertension, but many other risk factors have been reported to influence BRS. In recent years, reports have indicated that glycemic variability (GV), such as short- and long-term GV that are considered important risk factors for macrovascular and microvascular complications, is involved in reductions in BRS independently of blood glucose levels. In this review, we discuss reduced BRS in T2DM, its features, and the potential for its reversal.

Isolated Obesity Is Not Enough to Impair Cardiac Autonomic Modulation in Metabolically Healthy Men

PURPOSE

To evaluate whether excess body mass influences the heart rate variability (HRV) indexes at rest, and to correlate adiposity indicators and the aerobic fitness with cardiac autonomic variables in metabolically healthy young adults.

METHOD

In all, 41 untrained males (M_age = 21.80, SD = 2.14 years), 14 normal weight (M_BMI = 22.28, SD = 1.86 kg∙m^-2), 11 overweight (M_BMI = 26.95, SD = 1.43 kg∙m^-2), and 16 obese (M_BMI = 33.58, SD = 3.06 kg∙m^-2) metabolically healthy (normal values of blood pressure, fasting blood glucose, triglycerides, and total cholesterol), underwent evaluations of the HRV at rest and of the peak oxygen consumption (VO₂ peak) during maximal exercise on a cycle ergometer.

RESULTS

Blood pressure, heart rate, HRV indexes, casual blood glucose, oxidative stress, and antioxidant activity did not differ among the groups. The VO₂ peak (mL∙kg^-1∙min^-1) was lower in the obese group compared with the normal weight and overweight groups. The body mass (r = -.40 to -.45) and abdominal circumference (r = -.39 to -.52) were slightly to moderately correlated with SD1, SD2, RMSSD, SDNN, pNN50, LF, and HF indexes and total power. The VO₂ peak (mL∙kg^-1∙min^-1) was slightly to moderately correlated (r = .48 to .51) with SD2, SDNN, and LF indexes in the individuals with excess body mass.

CONCLUSION

Cardiac autonomic modulation at rest was preserved in metabolically healthy obese young men. However, the indicators of adiposity, as well as the aerobic fitness were correlated with cardiac autonomic modulation in the individuals with excess body mass.

Improved glucose homeostasis in male obese Zucker rats coincides with enhanced baroreflexes and activation of the nucleus tractus solitarius

Young adult male obese Zucker rats (OZR) develop insulin resistance and hypertension with impaired baroreflex-mediated bradycardia and activation of nucleus tractus solitarius (NTS). Because type 1 diabetic rats also develop impaired baroreflex-mediated NTS activation, we hypothesized that improving glycemic control in OZR would enhance compromised baroreflexes and NTS activation. Fasting blood glucose measured by telemetry was comparable in OZR and lean Zucker rats (LZR) at 12-17 wk. However, with access to food, OZR were chronically hyperglycemic throughout this age range. By 15-17 wk of age, tail samples yielded higher glucose values than those measured by telemetry in OZR but not LZR, consistent with reports of exaggerated stress responses in OZR. Injection of glucose (1g/kg ip) produced larger rises in glucose and areas under the curve in OZR than LZR. Treatment with metformin (300 mg·kg^-1·day^-1) or pioglitazone (5 mg·kg^-1·day^-1) in drinking water for 2-3 wk normalized fed glucose levels in OZR with no effect in LZR. After metformin treatment, area under the curve for blood glucose after glucose injection was reduced in OZR and comparable to LZR. Hyperinsulinemia was slightly reduced by each treatment in OZR, but insulin was still greatly elevated compared with LZR. Neither treatment reduced hypertension in OZR, but both treatments significantly improved the blunted phenylephrine-induced bradycardia and NTS c-Fos expression in OZR with no effect in LZR. These data suggest that restoring glycemic control in OZR enhances baroreflex control of heart rate by improving the response of the NTS to raising arterial pressure, even in the presence of hyperinsulinemia and hypertension.

Visit-to-visit HbA1c variability is inversely related to baroreflex sensitivity independently of HbA1c value in type 2 diabetes

BACKGROUND

The relationship between long-term glycemic variability (GV) represented by visit-to-visit HbA1c variability and baroreflex sensitivity (BRS) in type 2 diabetes mellitus (T2DM) has not been clarified by previous literature. The present study is the first to examine the relationships between visit-to-visit HbA1c variability and BRS.

METHODS

This retrospective study initially analyzed data on 94 patients with T2DM. Visit-to-visit HbA1c variability was evaluated using the intrapersonal coefficient of variation (CV), standard deviation (SD), and adjusted SD of 8 or more serial measurements of HbA1c during a 2-year period. The BRS was analyzed using the sequence method. Short-term GV was assessed by measuring the glucose CV during 24-h continuous glucose monitoring (CGM). The primary objective was to determine if there was a relationship between visit-to-visit HbA1c variability (HbA1c CV) and BRS. Secondary objectives were to examine the relationship between other variables and BRS and the respective and combined effects of long-term GV (HbA1c CV) and short-term GV (CGM CV) on BRS.

RESULTS

A total of 57 patients (mean age 67.2 ± 7.7 years, mean HbA1c 7.3 ± 1.0%) who met this study's inclusion criteria were finally analyzed. In the univariate analysis, HbA1c CV (r = - 0.354, p = 0.007), HbA1c SD (r = - 0.384, p = 0.003), and adjusted HbA1c SD (r = - 0.391, p = 0.003) were significantly related to low levels of BRS. Multiple regression analysis showed that HbA1c CV, HbA1c SD, and adjusted HbA1c SD were inversely related to BRS. Furthermore, although the increase in either long-term GV (HbA1c CV) or short-term GV (CGM CV) as determined by 24-h CGM was inversely correlated with BRS, additional reductions in BRS were not shown in participants with both HbA1c CV and CGM CV values above the median.

CONCLUSIONS

Visit-to-visit HbA1c variability was inversely related to BRS independently of the mean HbA1c in patients with T2DM. Therefore, visit-to-visit HbA1c variability might be a marker of reduced BRS in T2DM.

Sympathetic neural reactivity to mental stress differs in black and non-Hispanic white adults

Black adults have a higher risk of hypertension compared with non-Hispanic white (NHW) adults, but physiological mechanisms underlying this predisposition remain unclear. This study compared muscle sympathetic nerve activity (MSNA) responses to mental stress in a group of young black and NHW participants. We hypothesized that the sympathoexcitation associated with mental stress would be greater in black adults compared with NHW participants. Thirty-five male adults (19 black, 23 ± 1 yr; 16 NHW, 22 ± 1 yr) were examined during 5-min supine baseline and 5 min of mental stress (via mental arithmetic). Baseline mean arterial pressure (80 ± 2 vs. 82 ± 1 mmHg), heart rate (61 ± 4 vs. 61 ± 2 beats/min), MSNA (13 ± 1 vs. 15 ± 2 bursts/min), and sympathetic baroreflex sensitivity (-1.1 ± 0.4 vs. -1.5 ± 0.3 bursts·100 heart beats^-1·mmHg^-1) were not significantly different between NHW and black adults ( P > 0.05), respectively. MSNA reactivity to mental stress was significantly higher in NHW compared with black adults (time × race, P = 0.006), with a particularly divergent responsiveness during the first minute of mental stress in NHW (Δ4 ± 1 burst/min) and black (Δ-2 ± 2 burst/min; P = 0.022) men. Blood pressure and heart rate reactivity to mental stress were similar between groups. In summary, black participants demonstrated a lower MSNA responsiveness to mental stress compared with NHW adults. These findings suggest that, despite a higher prevalence of hypertension, black subjects do not appear to have higher neural and cardiovascular responsiveness to mental stress compared with NHW. NEW & NOTEWORTHY Black men have a blunted muscle sympathetic nerve activity response to mental stress compared with non-Hispanic white (NHW) men, especially at the onset of mental stress when muscle sympathetic nerve activity decreased in blacks and increased in NHW men. Thus, despite a high prevalence of hypertension in blacks, normotensive NHW men display a greater peripheral sympathetic neural reactivity to mental stress than black men.

Association of physical capacity with heart rate variability based on a short-duration measurement of resting pulse rate in older adults with obesity

BACKGROUND

Obesity can limit physical capacity and lower physical activity levels in elderly people. Low physical activity levels may be mediated by autonomic dysfunction with decreased heart rate variability (HRV). However, the relationship between autonomic dysfunction and low physical capability remains unclear. This cross-sectional study investigated the association of low physical capability with HRV in older adults with obesity.

MATERIALS AND METHODS

We recruited 231 old man and 210 old women with a mean (range) age of 65.5 (51-78) and 62.9 (52-76) years, respectively. Physical capability was measured using mobility tasks, including functional reach, single-leg stance (SLS), gait speed (GS), timed up and go, and timed chair rise (TCR), and the scores on these tasks were merged and transformed into a global physical capability score (GPCS). HRV was measured using a 7-min resting pulse-based technique, and the time- and frequency-domain indices of HRV were obtained including standard deviation of normal-to-normal intervals (SDNN), root mean square of successive differences at rest (rMSSD), and high-frequency (HF) power. All HRV indices were natural log (ln) transformed for analysis. Participants were divided into high, moderate, and low physical-capability groups according to their physical performance. Multivariate analysis of covariance was performed to test differences in HRV indices among physical-capability groups with participants' characteristics serving as covariates. A stepwise regression model was established to identify the determinants of HRV indices. We used hierarchical regression analysis to identify the association of the GPCS with HRV indices.

RESULTS

In both men and women, the low physical-capability group exhibited significantly increased heart rate (P <0.05) and decreased HRV in terms of a decreased ln[SDNN] (P <0.001), ln[rMSSD] (P <0.05) and ln[HF] (P <0.05), compared with the high physical-capability group. GS positively predicted ln[SDNN], whereas SLS, GS, and TCR were determinants of ln[HF], regardless of gender. The GPCS in older men and women independently accounted for 29.9% (P <0.001) and 23.7% (P <0.001), respectively, in variance in ln[SDNN].

CONCLUSIONS

A low physical-capability level is an independent determinant of decreased HRV in older adults with obesity.

Diabetic status and grade of nonalcoholic fatty liver disease are associated with lower baroreceptor sensitivity in patients with nonalcoholic fatty liver disease

OBJECTIVES

Baroreceptor sensitivity (BRS), a functional consequence of vascular stiffness, may be affected by the presence of diabetes mellitus (DM) and nonalcoholic fatty liver disease (NAFLD). The present study was designed to assess the effect of diabetic status and NAFLD grade on the BRS in patients with NAFLD.

METHODS

Seventy-five individuals (25 NAFLD without DM, 25 NAFLD with DM and 25 controls) were recruited for the study who underwent anthropometric and body composition analysis along with estimation of plasma glucose, serum insulin and serum lipids. BRS and blood pressure variability (BPV) analysis was carried out in both time and frequency domains. Carotid-radial and carotid-dorsalis pedis artery pulse wave velocity, and radial artery augmentation index were computed as measures of arterial stiffness.

RESULTS

BRS was found to be lower in the NAFLD with DM group as well those with grade II NAFLD compared with the controls. Correlation analysis showed a negative correlation of BRS with postprandial blood glucose level (r=-0.39) and BMI (r=-0.467). The diabetic status and grade of NAFLD were associated independently with a decrease in BRS as well as the low-frequency component of diastolic BPV. The augmentation index and carotid-distal pulse wave velocity were higher in the NAFLD with DM group compared with controls.

CONCLUSION

Both the diabetic status and grade of NAFLD were shown to have an independent effect on the decrease in the BRS with a consequent effect on BPV, with a greater influence of diabetic status rather than NAFLD grade on arterial stiffness.

Pulse wave velocity and cardiac autonomic function in type 2 diabetes mellitus

BACKGROUND

Increased carotid-femoral pulse wave velocity (PWV) has been associated with incident cardiovascular disease, independently of traditional risk factors. Cardiac autonomic dysfunction is a common complication of diabetes and has been associated with reduced aortic distensibility. However, the association of cardiac autonomic dysfunction with PWV is not known. In this study we examined the association between cardiac autonomic function and PWV in subjects with type 2 diabetes mellitus.

METHODS

A total of 290 patients with type 2 diabetes were examined. PWV was measured at the carotid-femoral segment with applanation tonometry. Central mean arterial blood pressure (MBP) was determined by the same apparatus. Participants were classified as having normal (n = 193) or abnormal (n = 97) PWV values using age-corrected values. Cardiac autonomic nervous system activity was determined by measurement of parameters of heart rate variability (HRV).

RESULTS

Subjects with abnormal PWV were older, had higher arterial blood pressure and higher heart rate than those with normal PWV. Most of the values of HRV were significantly lower in subjects with abnormal than in those with normal PWV. Multivariate analysis, after controlling for various confounding factors, demonstrated that abnormal PWV was associated independently only with peripheral MBP [odds ratio (OR) 1.049, 95% confidence intervals (CI) 1.015-1.085, P = 0.005], central MBP (OR 1.052, 95% CI 1.016-1.088, P = 0.004), log total power (OR 0.490, 95% CI 0.258-0.932, P = 0.030) and log high frequency power (OR 0.546, 95% CI 0.301-0.991, P = 0.047).

CONCLUSIONS

In subjects with type 2 diabetes, arterial blood pressure and impaired cardiac autonomic function is associated independently with abnormal PWV.

Role of Autonomic Nervous System and Orexinergic System on Adipose Tissue

Adipose tissue, defined as white adipose tissue (WAT) and brown adipose tissue (BAT), is a biological caloric reservoir; in response to over-nutrition it expands and, in response to energy deficit, it releases lipids. The WAT primarily stores energy as triglycerides, whereas BAT dissipates chemical energy as heat. In mammals, the BAT is a key site for heat production and an attractive target to promote weight loss. The autonomic nervous system (ANS) exerts a direct control at the cellular and molecular levels in adiposity. The sympathetic nervous system (SNS) provides a complex homeostatic control to specifically coordinate function and crosstalk of both fat pads, as indicated by the increase of the sympathetic outflow to BAT, in response to cold and high-fat diet, but also by the increase or decrease of the sympathetic outflow to selected WAT depots, in response to different lipolytic requirements of these two conditions. More recently, a role has been attributed to the parasympathetic nervous system (PNS) in modulating both adipose tissue insulin-mediated glucose uptake and fatty free acid (FFA) metabolism in an anabolic way and its endocrine function. The regulation of adipose tissue is unlikely to be limited to the autonomic control, since a number of signaling cytokines and neuropeptides play an important role, as well. In this review, we report some experimental evidences about the role played by both the ANS and orexins into different fat pads, related to food intake and energy expenditure, with a special emphasis on body weight status and fat mass (FM) content.

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.

Cardiac Physiology of Pregnancy

Although the physiology of the heart and vascular system has not changed, there are many things we have learned and are still learning today. Research related to heart adaptations during pregnancy has been performed since the 1930s. Since the mid-1950s, researchers began to look at changes in the maternal cardiovascular system during exercise while pregnant. Research related to exercise during pregnancy and offspring heart development began and has continued since the 1970s. We will review the normal female cardiovascular system adaptations to pregnancy in general. Additionally, topics related to maternal cardiac adaptations to pregnancy during acute exercise, as well as the chronic conditioning response from exercise training will be explored. Since physical activity during pregnancy influences fetal development, the fetal cardiac development will be discussed in regards to acute and chronic maternal exercise. Similarly, the influence of various types of maternal exercise on acute and chronic fetal heart responses will be described. Briefly, the topics related to how and if there is maternal-fetal synchrony will be explained. Lastly, the developmental changes of the fetal cardiovascular system that persist after birth will be explored. Overall, the article will discuss maternal cardiac physiology related to changes with normal pregnancy, and exercise during pregnancy, as well as fetal cardiac physiology related to changes with normal development, and exercise during pregnancy as well as developmental changes in offspring after birth.

Differential changes and interactions of autonomic functioning and sleep architecture before and after 50 years of age

We hypothesize that the time when age-related changes in autonomic functioning and in sleep structure occur are different and that autonomic functioning modulates sleep architecture differently before and after 50 years of age. Sixty-eight healthy subjects (aged 20 to 79 years old, 49 of them women) were enrolled. Correlation analysis revealed that wake after sleep onset, the absolute and relative value of stage 1 (S1; S1%), and relative value of stage 2 (S2) were positively correlated with age; however, sleep efficiency, stage 3 (S3), S3%, and rapid-eye-movement latency (REML) were negatively correlated with age. Significant degenerations of sleep during normal aging were occurred after 50 years of age; however, significant declines of autonomic activity were showed before 50 years of age. Before 50 years of age, vagal function during sleep was negatively correlated with arousal index; however, after 50 years of age, it was positively correlated with S1 and S1%. In addition, sympathetic activity during wake stage was positively related to S2% only after 50 years of age. Our results imply that the age-related changes in autonomic functioning decline promptly as individuals leave the younger part of their adult life span and that age-related changes in sleep slowly develop as individuals enter the older part of their adult life span. Furthermore, while various aspects of sleep architecture are modulated by both the sympathetic and vagal nervous systems during adult life span, the sleep quality is mainly correlated with the sympathetic division after 50 years of age.

Diminished autonomic neurocardiac function in patients with generalized anxiety disorder

BACKGROUND

Generalized anxiety disorder (GAD) is a chronic and highly prevalent disorder that is characterized by a number of autonomic nervous system symptoms. The purpose of this study was to investigate the linear and nonlinear complexity measures of heart rate variability (HRV), measuring autonomic regulation, and to evaluate the relationship between HRV parameters and the severity of anxiety, in medication-free patients with GAD.

METHODS

Assessments of linear and nonlinear complexity measures of HRV were performed in 42 medication-free patients with GAD and 50 healthy control subjects. In addition, the severity of anxiety symptoms was assessed using the State-Trait Anxiety Inventory and Beck Anxiety Inventory. The values of the HRV measures of the groups were compared, and the correlations between the HRV measures and the severity of anxiety symptoms were assessed.

RESULTS

The GAD group showed significantly lower standard deviation of RR intervals and the square root of the mean squared differences of successive normal sinus intervals values compared to the control group (P<0.01). The approximate entropy value, which is a nonlinear complexity indicator, was also significantly lower in the patient group than in the control group (P<0.01). In correlation analysis, there were no significant correlations between HRV parameters and the severity of anxiety symptoms.

CONCLUSION

The present study indicates that GAD is significantly associated with reduced HRV, suggesting that autonomic neurocardiac integrity is substantially impaired in patients with GAD. Future prospective studies are required to investigate the effects of pharmacological or non-pharmacological treatment on neuroautonomic modulation in patients with GAD.