Central adiposity and hemodynamic functioning at rest and during stress in adolescents

Endothelin receptor blockade blunts the pressor response to acute stress in men and women with obesity

Obesity is associated with dysregulation of the endothelin system. In individuals with obesity, an exaggerated pressor response to acute stress is accompanied by increased circulating endothelin-1 (ET-1). The impact of combined endothelin A/B receptor (ET_A/B) antagonism on the stress-induced pressor response in overweight/obese (OB) individuals is unknown. The objective of this study is to test the hypothesis that treatment with an ET_A/B antagonist (bosentan) would reduce the stress-induced pressor response and arterial stiffness in overweight/obese compared with normal weight (NW) individuals. Forty participants [normal weight (NW): n = 20, body mass index (BMI): 21.7 ± 2.4 kg/m² and overweight/obese (OB): n = 20, BMI: 33.8 ± 8.2 kg/m²] were randomized to placebo or 125 mg of bosentan twice a day (250 mg total) for 3 days. Hemodynamics were assessed before, during, and after a cold pressor test (CPT). Endothelin-1 was assessed at baseline and immediately after CPT. Following a washout period, the same protocol was repeated with the opposite treatment. The change from baseline in mean arterial pressure (MAP) during CPT following bosentan was significantly lower (P = 0.039) in the OB group than in the NW group (OB: 28 ± 12 vs. NW: 34 ± 15 mmHg). These results suggest that ET_A/B antagonism favorably blunts the pressor response to acute stress in overweight/obese individuals.NEW & NOTEWORTHY Findings from our current translational investigation demonstrate that dual endothelin A/B receptor antagonism blunts the pressor response to acute stress in overweight/obese individuals. These results suggest that modulation of the endothelin system may represent a novel therapeutic target to reduce cardiovascular disease (CVD) risk by blunting the stress response in overweight/obese individuals.

Cardiovascular Stress Reactivity and Health: Recent Questions and Future Directions

OBJECTIVE

High cardiovascular reactions to psychological stress are associated with the development of hypertension, systemic atherosclerosis, and cardiovascular disease. However, it has become apparent that low biological stress reactivity also may have serious consequences for health, although less is known about the mechanisms of this. The objectives of this narrative review and opinion article are to summarize and consider where we are now in terms of the usefulness of the reactivity hypothesis and reactivity research, given that both ends of the reactivity spectrum seem to be associated with poor health, and to address some of the key criticisms and future challenges for the research area.

METHODS

This review is authored by the members of a panel discussion held at the American Psychosomatic Society meeting in 2019, which included questions such as the following: How do we measure high and low reactivity? Can high reactivity ever indicate better health? Does low or blunted reactivity simply reflect less effort on task challenges? Where does low reactivity originate from, and what is a low reactor?

RESULTS

Cardiovascular (and cortisol) stress reactivity are used as a model to demonstrate an increased understanding of the different individual pathways from stress responses to health/disease and show the challenges of how to understand and best use the reconstruction of the long-standing reactivity hypothesis given recent data.

CONCLUSIONS

This discussion elucidates the gaps in knowledge and key research issues that still remain to be addressed in this field, and that systematic reviews and meta-analyses continue to be required.

Adiponectin protects obesity-related glomerulopathy by inhibiting ROS/NF-κB/NLRP3 inflammation pathway

BACKGROUND

Adiponectin is an adipocytokine that plays a key regulatory role in glucose and lipid metabolism in obesity. The prevalence of obesity has led to an increase in the incidence of obesity-related glomerulopathy (ORG). This study aimed to identify the protective role of adiponectin in ORG.

METHODS

Small-interfering RNA (siRNA) against the gene encoding adiponectin was transfected into podocytes. The oxidative stress level was determined using a fluorometric assay. Apoptosis was analyzed by flow cytometry. The expressions of podocyte markers and pyrin domain containing protein 3 (NLRP3) inflammasome-related proteins were measured by qRT-PCR, immunohistochemistry, and Western blot.

RESULTS

Podocytes treated with palmitic acid (PA) showed downregulated expressions of podocyte markers, increased apoptosis, upregulated levels of NLRP3 inflammasome-related proteins, increased production of inflammatory cytokines (IL-18 and IL-1β), and induced activation of NF-κB as compared to the vehicle-treated controls. Decreased adiponectin expression was observed in the serum samples from high fat diet (HFD)-fed mice. Decreased podocin expression and upregulated NLRP3 expression were observed in the kidney samples from high fat diet (HFD)-fed mice. Treatment with adiponectin or the NLRP3 inflammasome inhibitor, MCC950, protected cultured podocytes against podocyte apoptosis and inflammation. Treatment with adiponectin protected mouse kidney tissues against decreased podocin expression and upregulated NLRP3 expression. The knockout of adiponectin gene by siRNA increased ROS production, resulting in the activation of NLRP3 inflammasome and the phosphorylation of NF-κB in podocytes. Pyrrolidine dithiocarbamate, an NF-κB inhibitor, prevented adiponectin from ameliorating FFA-induced podocyte injury and NLRP3 activation.

CONCLUSIONS

Our study showed that adiponectin ameliorated PA-induced podocyte injury in vitro and HFD-induced injury in vivo via inhibiting the ROS/NF-κB/NLRP3 pathway. These data suggest the potential use of adiponectin for the prevention and treatment of ORG.

Impact of obesity with or without hypertension on systemic haemodynamic and renal responses to lower body negative pressure

PURPOSE

Sodium and water handling by the kidney and the sympathetic nervous system have been implicated in the development of obesity-related hypertension and kidney disease. They have seldom been studied together during stress conditions. The objective of this study was to compare the systemic, renal and hormonal responses to lower body negative pressure (LBNP) in adult healthy participants (H), obese normotensive (OBN) and obese hypertensive patients (OBH).

MATERIALS AND METHODS

This was a prospective case-control study. Participants from the three groups were exposed to one hour of LBNP. Systemic and renal haemodynamics, sodium and water excretion and hormones were measured before and after LBNP. Intergroup LBNP responses were tested using a Student t-test or a Wilcoxon rank-sum test. An extension of the Wilcoxon rank-sum test was used to test for a trend across the three groups.

RESULTS

The study included 54 participants (H: 25, OBN: 16, OBH: 13). LBNP induced a stepwise increase in systolic blood pressure (+2.7 ± 4.7 mmHg (H) vs. +4.7 ± 8.8 mmHg (OBN) vs. +8.0 ± 8.6 mmHg (OBH, p = .028)) and heart rate (-1.3 ± 4.9 bpm (H) vs. 2.2 ± 6.1 bpm (OBN) vs. 1.9 ± 4.1 bpm (OBH, p = .041). Urinary output (-2.8 ± 2.1 ml/min vs. -1.4 ± 1.7 ml/min, p = .028) and free water clearance (-1.9 ± 1.7 mOsm/kg vs. -0.7 ± 1.3 mOsm/kg, p = .016) responses were more marked in OBN compared to H.

CONCLUSIONS

These results show that the systemic and the renal response to LBNP differ according to weight and to BP categories. Systolic BP and heart show a progressive increased response form healthy volunteers to OBN and then to obese hypertensive participants while urinary output and free water clearance responses are increased in OBN only, suggesting that the occurrence of hypertension in obese individuals modifies the early kidney responses to stress.

CLINICALTRIAL.GOV IDENTIFIER

NCT01734096.

Impact of age and sex on neural cardiovascular responsiveness to cold pressor test in humans

Prior longitudinal work suggests that blood pressure (BP) reactivity to the cold pressor test (CPT) helps predict hypertension; yet the impact of age and sex on hemodynamic and neural responsiveness to CPT remains equivocal. Forty-three young (21 ± 1yr, means ± SE) men (YM, n = 20) and women (YW, n = 23) and 16 older (60 ± 1yr) men (OM, n = 9) and women (OW, n = 7) participated in an experimental visit where continuous BP (finger plethysmography) and muscle sympathetic nerve activity (MSNA; microneurography) were recorded during a 3- to 5-min baseline and 2-min CPT. Baseline mean arterial pressure (MAP) was greater in OM than in YM (92 ± 4 vs. 77 ± 1 mmHg, P < 0.01), but similar in women (P = 0.12). Baseline MSNA incidence was greater in OM [69 ± 6 bursts/100 heartbeats (hb)] than in OW (44 ± 7 bursts/100 hb, P = 0.02) and lower in young adults (YM: 17 ± 3 vs. YW: 16 ± 2 bursts/100 hb, P < 0.01), but similar across the sexes (P = 0.83). However, when exposed to the CPT, MSNA increased more rapidly in OW (Δ43 ± 6 bursts/100 hb; group × time, P = 0.01) compared with OM (Δ15 ± 3 bursts/100 hb) but was not different between YW (Δ30 ± 3 bursts/100 hb) and YM (Δ33 ± 4 bursts/100 hb, P = 1.0). There were no differences in MAP with CPT between groups (group × time, P = 0.33). These findings suggest that OW demonstrate a more rapid initial rise in MSNA responsiveness to a CPT compared with OM. This greater sympathetic reactivity in OW may be a contributing mechanism to the increased hypertension risk in postmenopausal women.

American Indian young adults display diminished cardiovascular and cortisol responses to acute psychological stress

American Indian adults are at an increased risk for cardiovascular disease compared with non-Hispanic white adults. Scant research exists examining the underlying physiological and psychological mechanisms associated with these risks. This study aimed to examine possible psychological and physiological stress-related mechanisms related to cardiovascular disease risk in healthy American Indian and non-Hispanic white adults. Forty American Indian (60% female, Mean age = 19.93, SD = 2.08 years) and 45 non-Hispanic white (70% female, Mean age = 20.18, SD = 2.22 years) participants attended an in-person laboratory session. Salivary cortisol and cardiovascular activity were measured before (baseline), during, and after exposure to a 10-minute mental arithmetic task. Compared to non-Hispanic white participants, American Indian had diminished salivary cortisol (p < .001), blood pressure (p's < .001), and heart rate (p = .041) responses to acute psychological stress. These effects could not be accounted for by differences in task performance or self-reported engagement. Previous research has shown that exaggerated responses to stress are associated with increased risk of cardiovascular disease. However, diminished responses to stress are associated with early childhood stress and future adverse behaviors (e.g., addiction, obesity). Diminished reactivity may influence behaviors that can impact future development of cardiovascular disease in American Indian populations.

Influence of Acute Physical Activity on Stress Reactivity in Obese and Normal Weight Children: A Randomized Controlled Trial

OBJECTIVE

Physical activity (PA) may influence acute stress reactivity in children differently depending on their weight. This randomized controlled trial investigated the impact of acute PA and of BMI status (overweight/obese (OB/OW) and normal weight (NW) on stress reactivity.

METHOD

50 prepubertal children (24 OW/OB and 26 NW) were randomly assigned to the PA or sedentary arm (SED) for 30 min followed by a stress task. Salivary cortisol, blood pressure (BP), and heart rate (HR) were measured.

RESULTS

An interaction effect between the randomization arms and weight status on salivary cortisol was found after the stress task (p = 0.04). Cortisol increased in the SED, but not in the PA arm (p = 0.004 for differences in time course) of NW children. Time course did not differ between both arms in OW/OB children (p = 0.7). OW/OB SED children had a flat cortisol course, and levels were reduced compared to the NW SED or the OW/OB PA children (p ≤ 0.03). Systolic BP increased only in the SED arm (p = 0.01). HR was higher in the PA than in the SED arm during stress (p < 0.001) and showed different time courses (p = 0.006).

CONCLUSION

PA impacted on acute stress reactivity and influenced stress reactivity differently in NW and OW/OB children.

Relationship between obesity, negative affect and basal heart rate in predicting heart rate reactivity to psychological stress among adolescents

Reduced cardiovascular responses to psychological stressors have been found to be associated with both obesity and negative affect in adults, but have been less well studied in children and adolescent populations. These findings have most often been interpreted as reflecting reduced sympathetic nervous system response, perhaps associated with heightened baseline sympathetic activation among the obese and those manifesting negative affect. However, obesity and negative affect may themselves be correlated, raising the question of whether they both independently affect cardiovascular reactivity. The present study thus examined the separate effects of obesity and negative affect on both cardiovascular and skin conductance responses to stress (e.g., during a serial subtraction math task) in adolescents, while controlling for baseline levels of autonomic activity during rest. Both obesity and negative affect had independent and negative associations with cardiovascular reactivity, such that reduced stress responses were apparent for obese adolescents and those with high levels of negative affect. In contrast, neither obesity nor negative affect was related to skin conductance responses to stress, implicating specifically noradrenergic mechanisms rather than sympathetic mechanisms generally as being deficient. Moreover, baseline heart rate was unrelated to obesity in this sample, which suggests that heightened baseline of sympathetic activity is not necessary for the reduced cardiovascular reactivity to stress.

The effect of overweight/obesity on cardiovascular responses to acute psychological stress in men aged 50-70 years

BACKGROUND

To determine the effect of adiposity in males aged 50-70 years on cardiovascular responses to acute psychological stress.

METHODS

Lean (BMI 20-25 kg/m(2)) (n = 21) and overweight/obese (BMI 27-35 kg/m(2)) (n = 21) men aged 50-70 years were subjected to psychological stress. Systolic blood pressure, diastolic blood pressure, heart rate, total peripheral resistance, and cardiac output were measured by a Finometer during resting (60 min), stress (30 min), and recovery (90 min).

RESULTS

The lean group had a significantly higher SBP stress reactivity when compared to the overweight/obese group (51.5 ± 3.7% vs. 41.0 ± 2.9% (mean ± SEM) ; p < 0.05). A significant effect of time was observed for systolic blood pressure, diastolic blood pressure, heart rate, total peripheral resistance, and cardiac output (p < 0.0001 for all). There were significant time × body type interactions for systolic blood pressure, diastolic blood pressure, heart rate, total peripheral resistance, and cardiac output (p < 0.05 for all). Total peripheral resistance during recovery was higher in the lean compared to the overweight/obese group (p < 0.05). In the lean group, systolic and diastolic blood pressure variability remained elevated after stress (p < 0.05) but returned to resting levels in the overweight/obese group (p > 0.05).

CONCLUSION

Moderate adiposity in men was associated with reduced systolic blood pressure % reactivity, total peripheral resistance, and blood pressure variability after psychological stress. Overweight/obese men appear to be at no greater risk of unfavorable cardiovascular responses to stress.

Cardiovascular and cortisol reactions to acute psychological stress and adiposity: cross-sectional and prospective associations in the Dutch Famine Birth Cohort Study

OBJECTIVE

In recent analyses of data from a large community sample, negative cross-sectional and prospective associations between cardiac stress reactivity and obesity were observed. The present study reexamined the association between cardiovascular reactivity and adiposity in the Dutch Famine Birth Cohort, with the additional aim of examining the association between cortisol reactivity and adiposity.

METHODS

Blood pressure, heart rate, and salivary cortisol were measured at rest and in response to standard laboratory stress tasks in 725 adults. Height, weight, waist-and-hip circumference, and skinfold thickness were measured. Between 4 to 7 years later, 460 participants reported current height and weight. Obesity was defined as a body mass index of 30 kg/m(2) or higher.

RESULTS

Those with a greater body mass index (β = -0.39 beats per minute (bpm)), waist-to-hip ratio (β = -0.15 bpm), and triceps and subscapular skinfold thicknesses (β = -1.0 and -1.8 bpm) or who were categorized as obese (-3.9 bpm) displayed smaller cardiac reactions to acute stress (all p < .001). With the exception of waist-to-hip ratio, the same negative associations emerged for cortisol reactivity (all p ≤ .01). In prospective analyses, low cardiac reactivity was associated with an increased likelihood of becoming or remaining obese in the subsequent 4 to 7 years (odds ratio = 1.03, p = .01). All associations withstood adjustment for a range of possible confounders.

CONCLUSIONS

The present analyses provide additional support for the hypothesis that it is low not high cardiac and cortisol stress reactivity that is related to adiposity.

Anger, stress and blood pressure in overweight children

Among adults, trait anger, patterns of anger expression, and stress have been associated with blood pressure (BP). Less apparent is the effect of these variables on BP in overweight and obese children. To characterize the relationships between these psychological variables and BP, the authors conducted a secondary analysis of data from 73 overweight and obese 9- to 11-year-old children. Findings indicate a positive correlation between trait anger and systolic BP (SBP). Regression results indicate that the overall model significantly predicted SBP by explaining 15.4% of the variance and that trait anger was a significant predictor of SBP.

Stress and inflammation: a biobehavioral approach for nursing research

Despite known advantages, the use of biobehavioral approaches in nursing research remains limited. The purposes of this article are to (1) present applications of stress and inflammation in various health conditions as examples of biobehavioral concepts and (2) stimulate similar applications of biobehavioral concepts in future nursing research. Under a biobehavioral conceptual framework, studies on stress and selective inflammatory biomarkers in cardiovascular, cancer, and pulmonary health are reviewed and summarized. Inflammation underlies many diseases, and stress is a significant source of increased inflammation. Biobehavioral concepts of stress and inflammation are highly relevant to nursing research concerned with health-related issues. Diverse biobehavioral concepts are readily applicable and should be utilized in nursing research with children and adults. To stimulate further biobehavioral research, more training and resources for nurse scientists, more unified conceptual definitions and biobehavioral conceptual frameworks, rigorous and expanded methodologies, and more collaboration are essential.

The physical activity, stress and metabolic syndrome triangle: a guide to unfamiliar territory for the obesity researcher

Research aimed at deciphering the aetiology of obesity and the metabolic syndrome remains focused on two behavioural factors, namely diet and physical activity, even though epidemiologic research suggests that these two cornerstones of treatment and prevention account for only a small-to-moderate portion of the variance in these phenotypes. In recent years, this observation has prompted the intensified investigation of the pathogenic potential of factors that extend beyond the traditional concept of energy imbalance and examine the putative causes of this imbalance. Psychosocial stress has emerged as one such factor, raising the need for researchers to be informed about this expansive and complex literature. The purpose of this review is twofold (i) To introduce obesity researchers to fundamental concepts and historically important theoretical developments in the stress field and (ii) To outline the dyadic and triadic interactions between stress, physical activity and the metabolic syndrome. Although the expansion of the research focus to multiple, diverse and interacting putative causal agents will certainly increase the complexity of the research enterprise, this step seems essential for the comprehension and effective response to the continuing rise in the prevalence of obesity and the metabolic syndrome.

Visceral adipose tissue in children and adolescents: a review

Research conducted among adults has mainly shown that visceral adipose tissue (VAT) is strongly linked to insulin resistance, type 2 diabetes, hypertension and dyslipidaemia, leading to increased risk of CVD or the metabolic syndrome. However, little is known about the aetiology, determinants and consequences of VAT in children. The present article reviews the current literature relating to the factors influencing visceral fat accumulation in children and adolescents. The literature used in the present study was collected by searching a PubMed database, in which studies up to 2008 exploring the factors influencing accumulation of visceral fat among children and youth were found on the basis of appropriate keywords. Further studies concerning different factors influencing deposition of VAT among children and youth should first of all concentrate on: carrying out long-term analyses among children of different ethnical groups, which should begin in the period of prepuberty and which should cover the whole period of puberty till adulthood; drawing up norms specifying the amount of VAT among healthy children; identification of anthropometric indicators which will help to determine the VAT:subcutaneous adipose tissue ratio in the most precise way; broader studies of the influence of eating habits on developing VAT deposit among children and youth.

Adiposity, leptin and stress reactivity in humans

Evidence suggests that individuals who are more obese may be more responsive to stress. Stress activates the sympathetic nervous system (SNS) and the adipose-tissue cytokine leptin stimulates SNS activity in animals. We examined the relationship between adiposity, leptin and physiological responses to acute laboratory stress in 67 women. We predicted that individuals with greater adiposity and/or higher plasma leptin would be more stress-responsive. Adiposity was unrelated to cardiovascular or neuroendocrine stress reactivity. However, women with larger waists had greater stress-induced increases in plasma leptin and interleukin-1 receptor antagonist (IL-1Ra). Similarly, women with higher basal leptin displayed greater stress-induced increases in heart rate and plasma interleukin-6, and larger decreases in heart rate variability and cardiac pre-ejection period. Heightened cardiovascular and inflammatory stress responses are predictive of future cardiovascular risk. Our findings suggest that the cytokines leptin and IL-1Ra may play a role in the association between obesity, stress and cardiovascular health.

Childhood growth and cardiovascular reactivity to psychological stressors in late adulthood

OBJECTIVE

Specific childhood growth patterns relate to risk of cardiovascular (CV) disease later in life, but the underlying mechanisms are unclear. We studied whether CV reactivity, a predictor of CV disease risk, is associated with childhood growth trajectories.

METHODS

A total of 144 (77 women and 67 men) participants of the Helsinki Birth Cohort Study born 1934-1944, whose height and weight were recorded repeatedly during the first 11 years, underwent the Trier Social Stress Test at the average age of 63 years. Beat-to-beat blood pressure was monitored via noninvasive finger photoplethysmograph (Finometer), and CV reactivity scores were determined as the mean increment from baseline.

RESULTS

In both women and men, systolic blood pressure (SBP) reactivity increased by 3.8 mmHg (95% CI 0.8-6.9) and diastolic BP (DBP) reactivity by 1.4 mmHg (95% CI 0.0-2.8) for every standard deviation increase in gain in body mass index (kg m(-2)) between 7 and 11 years. By contrast, effects of height gain were dissimilar between sexes. In women, higher DBP reactivity was associated with a slow gain in height between 0 and 2 years, whilst in men higher SBP reactivity was associated with a slow gain in height between 2 and 7 years, which was preceded by a more rapid gain in height between 0 and 2 years. Adjusting for adult body size, body size at birth or childhood socio-economic status did not change the results.

CONCLUSIONS

We found that growth during childhood is associated with CV reactivity to stress later in adulthood. Early life programming of CV reactivity may partly underlie the link between early growth and CV disease.

Body mass index, abdominal adiposity, obesity, and cardiovascular reactions to psychological stress in a large community sample

OBJECTIVE

To examine the association between adiposity and the magnitude of cardiovascular reactions to acute psychological stress cross-sectionally and prospectively in a large community sample.

METHODS

Blood pressure and heart rate (HR) were measured at rest and in response to a brief time-pressured mental arithmetic stress in 1647 adults. At the same session and 5 years later, height, weight, waist and hip circumference were measured and body mass index (BMI) and waist-hip ratio were computed. Obesity was defined as a body mass index of > or = 30 kg/m(2).

RESULTS

Contrary to expectations, the most robust and consistent results to emerge from cross-sectional analyses were negative associations between all three measures of adiposity and HR reactivity; those with greater BMI and waist-hip ratios and those categorized as obese displayed smaller HR reactions to stress. In prospective analyses, high HR reactivity was associated with a reduced likelihood of becoming obese in the subsequent 5 years.

CONCLUSIONS

Our analyses suggest that it is low, not high, HR reactivity that is related to adiposity. Low HR reactivity, probably by reflecting generally blunted sympathetic nervous system reactions to challenge, may be a risk marker for developing obesity.

Stress reactivity and adiposity of youth

OBJECTIVE

The relationship between stress reactivity and total or central adiposity in children has not been widely studied. Data from two studies were combined to determine the relationship between reactivity to interpersonal stress and the adiposity of children.

RESEARCH METHODS AND PROCEDURES

Stress reactivity to an interpersonal stressor (speech) was measured in 36 boys (9.8 +/- 1.3 years of age) and 27 girls (9.3 +/- 1.3 years of age). Total adiposity (percentage body fat) was estimated from skinfolds and central adiposity from the abdominal girth. Multiple regression was used to establish the associations of change in perceived stress and heart rate reactivity with adiposity. Age, sex, ethnicity, and baseline perceived stress and heart rate served as covariates for total adiposity. Fat mass was included as an additional covariate for the prediction of log abdominal girth (central adiposity).

RESULTS

Based on adjusted beta-weights, change in perceived stress (beta = 1.13, p <or= 0.001) and heart rate reactivity (beta = 0.14, p <or= 0.03) independently predicted percentage body fat. Heart rate reactivity (beta = 0.002, p <or= 0.04) independently predicted log abdominal girth.

DISCUSSION

Reactivity to psychological stress may initiate the antecedents of cardiovascular disease before adolescence by increasing total and central adiposity. Future studies should determine whether stress reactivity increases the adiposity of youth by increasing their consumption of energy-dense snack foods and decreasing their willingness to be physically active.

Exaggerated cardiovascular stress responses and impaired beta-adrenergic-mediated pressor recovery in obese Zucker rats

Clinical studies have demonstrated that the pressor response to acute stress is larger in obese versus lean individuals. We therefore tested the hypotheses that the pressor response to behavioral stress is greater in obese (OZRs) versus lean Zucker rats (LZRs) and that reduced beta-adrenergic-mediated vasodilation contributes to the enhanced pressor response. Animals were restrained and subjected to acute pulsatile air jet stress (3 minutes), followed by a poststress period of 20 minutes; beta-adrenergic blockade was achieved with propranolol (5 mg/kg, IV) given 15 minutes before the start of air jet stress. Mean arterial pressure (MAP) was continuously monitored by telemetry. Untreated OZRs responded with a greater integrated pressor response (area under the curve [AUC]) to acute stress (41.2+/-6.1 versus 21.2+/-3.3 mm Hgx3 minutes, OZR versus LZR; P<0.05) and significantly reduced poststress recovery of MAP. Beta-adrenergic blockade had no effect on stress AUC in either LZRs or OZRs but significantly attenuated the poststress recovery of MAP in LZRs only (poststress AUC: -100.1+/-48.1 versus 49.0+/-13.5 mm Hgx20 minutes, untreated versus propranolol; P<0.05). In anesthetized animals, significantly smaller increases in mesenteric vascular conductance contributed to blunted depressor responses to isoproterenol in OZRs versus LZRs, suggesting that beta-adrenergic stimulation causes a greater reduction in total peripheral resistance in lean versus obese animals. We conclude that beta-adrenergic-mediated vasodilation facilitates blood pressure recovery after stress and that this pathway is compromised in an animal model of morbid obesity, resulting in the impaired ability to regulate blood pressure during stress.

Neuroendocrine mechanisms of innate states of attenuated responsiveness of the hypothalamo-pituitary adrenal axis to stress

Neuroendocrine responses to stress vary between sexes and reproductive states and are influenced by the type of stressor. Stress responses are attenuated in some physiological states, such as lactation and conditions of low visceral adipose tissue. Moreover, some individuals within a species characteristically display reduced stress responses. The neuroendocrine mechanisms for stress hyporesponsiveness are likely to include reduced synthesis and secretion of corticotropin releasing hormone (CRH) and arginine vasopressin (AVP) from the hypothalamus as a result of enhanced glucocorticoid negative feedback and/or reduced noradrenergic stimulatory input from the brain stem. A major limitation of research to date is the lack of direct measures of CRH and AVP secretion. Attenuated stress responsiveness is also commonly associated with reduced pituitary responsiveness to CRH and AVP. The possible roles of inhibitory central inputs to CRH and AVP neurons and of oxytocin and prolactin in attenuating the HPA axis responses to stress are unknown.

Anger suppression and adiposity modulate association between ADRB2 haplotype and cardiovascular stress reactivity

OBJECTIVES

The purpose of this study was to examine how variation in the beta-2 adrenergic receptor gene (ADRB2), in combination with the moderating influences of race, body mass index (BMI), and anger expression style (anger-in, anger-out), affects blood pressure (BP) at rest and in response to acute laboratory stress.

METHODS

Four hundred fifty adolescents (mean age = 18.5 +/- 2.7 years; 228 [124 males] whites and 222 [110 males] blacks completed two stressors (video game challenge, forehead cold pressor). Hemodynamic measures were taken before, during, and after each stressor. Stressors were separated by a 20-minute rest period.

RESULTS

Frequency of detrimental haplotype (Gly16/Glu27) carrier status was greater among whites than blacks (p < .05). A significant three-way interaction among haplotype, BMI, and race for resting systolic blood pressure (SBP) found the highest BP level to be among high BMI carriers, but only for whites. A separate three-way interaction was found to be significant for haplotype, anger-in and race such that high anger-in carriers showed the highest level of resting SBP (p < .05) and total peripheral resistance (TPR) (p < .05) and the greatest TPR reactivity to the cold pressor task (p < .01). Post hoc analyses revealed these interactions with anger-in were only present among blacks. No significant interactions with anger-out for either ethnic group were observed.

CONCLUSIONS

This study demonstrates modulating influences of BMI and anger expression styles on ADRB2 gene associations with hemodynamic function at rest and in response to laboratory stress. These findings support the hypothesis that consideration of gene-environment interactions may better characterize the role of ADRB2 variation in the development of stress-induced essential hypertension.

Central adiposity is associated with cardiovascular reactivity to stress in adolescents

The current study examined the association between central adiposity, measured by waist circumference, and cardiovascular reactivity to stress among 106 White and 105 Black adolescents, approximately 50% of whom were girls. Participants engaged in 4 laboratory tasks while cardiovascular reactivity measures were taken. Independent of body mass index, race, and gender, participants with a greater waist circumference exhibited greater systolic blood pressure reactivity and diastolic blood pressure reactivity (boys only). Race did not affect the results. Results from the present study suggest that central adiposity is associated with blood pressure reactivity early in life, especially in adolescent boys.

Cardiovascular stress responsivity, body mass and abdominal adiposity

OBJECTIVE

To assess the relationship between adiposity and cardiovascular stress reactivity and recovery in middle-aged men and women, and investigate the influence of impaired poststress cardiovascular recovery on changes in body mass index (BMI) and waist-hip ratio over 3 y.

PARTICIPANTS

In total, 225 healthy men and women aged 47-59 y were recruited from the British civil service.

METHODS

Laboratory mental stress testing was carried out, with blood pressure (BP), cardiac output and total peripheral resistance being measured at baseline, during moderately challenging tasks, and during recovery 40-45 min poststress. Weight, height, waist and hip circumference were assessed at the time of mental stress testing and 3 y later.

RESULTS

Behavioural tasks elicited increases in BP sustained by a combination of cardiac activation and raised peripheral resistance. BMI and waist/hip ratio were associated cross-sectionally with impaired poststress recovery of systolic pressure, diastolic pressure and cardiac index independently of age, gender, socioeconomic status, smoking, alcohol consumption and baseline cardiovascular activity. Increases in waist-hip ratio over 3 y were predicted both by impaired poststress recovery of systolic pressure and cardiac index in men, independently of baseline adiposity and other covariates. No associations between subjective stress and BMI or waist-hip ratio were observed.

CONCLUSIONS

Disturbances of cardiovascular responsivity to psychological stress, manifest through impaired poststress recovery, were associated cross-sectionally with BMI, and longitudinally with central adiposity in men. Stress-related cardiovascular dysregulation may contribute to obesity risk.

Comparison of anthropometric parameters as predictors of serum lipids in premenopausal women

No single anthropometric parameter has yet been generally accepted as being superior to others in assessing the metabolic risk associated with abdominal obesity. To compare waist circumference (WC) with waist-to-hip ratio (WHR) and waist-to-height ratio (WHtR), regarding their association with serum lipids, we studied 166 women aged 20 to 48 yr; 53 were obese [body mass index (BMI) 30-39.9 Kg/m2], 50 were overweight (BMI 25-29.9 Kg/m2) and 63 normal weight (BMI 18.5-24.9 Kg/m2). Height, body weight, waist and hip circumferences, total serum cholesterol (Ch), low (LDL) and high density lipoprotein (HDL)-Ch and triglyceride (TG) concentrations were measured. The correlation coefficients between the concentration of serum lipid fractions and each anthropometric parameter did not differ significantly for any lipid variable when WC, WHR and WHtR were compared in the 166 women. The same applied for the obese and the overweight group, whereas in normal weight women there was significant association only between WC and LDL-Ch and between WHR and Ch/HDL-Ch ratio. Stepwise regression analysis showed that the proportion of variance in serum lipids did not change significantly when WHR or WHR+WHtR were added to WC into the regression model (18%, 18% and 18% for Ch; 13%, 18% and 18% for HDL-Ch; 18%, 18% and 12% for LDL-Ch; 35%, 35% and 37% for TG, respectively). These results indicate that WC is the main parameter associated with serum lipid levels and that the ratios studied do not provide additional substantial information in women who need weight management.

Impaired pressure natriuresis in obese youths

OBJECTIVE

To compare the response and recovery of blood pressure (BP) and sodium excretion (U(Na)V) in response to a behavioral stressor in overweight/obese and lean adolescents.

RESEARCH METHODS AND PROCEDURES

Twenty-five lean (12% to 20% body fat) and 59 overweight/obese (>25% body fat) normotensive adolescents were provided all meals for 3 days (average sodium intake, 4000 +/- 200 mg/d), before performing the stressor on the third day. There was a 2-hour pre-stress rest, followed by a 1-hour stress (involving a video game task), and a 2-hour recovery. Percentage of body fat was obtained from DXA. U(Na)V was measured hourly, whereas systolic BP and diastolic BP measurements were obtained at 15-minute intervals, and averaged for each 1-hour period.

RESULTS

There was no significant difference between the lean and overweight/obese group for the response of systolic BP and diastolic BP (group by time interaction, p = 0.60 and p = 0.64, respectively). However, the lean group had a significantly greater increase in U(Na)V in response to the stressor compared with the overweight/obese group (p = 0.02). U(Na)V remained elevated compared with baseline in both groups at the 1-hour (p <or= 0.0001) and 2-hour (p <or= 0.0001) post-time points. Furthermore, there was a tendency for a larger number of sodium retainers in the overweight/obese group compared with the lean group (39.0% vs. 20.0%; chi(2) = 2.85, df = 1, p = 0.09).

DISCUSSION

This study provided evidence that sodium regulation was impaired during a behavioral stress in overweight/obese individuals compared with lean individuals.

Cardiovascular reactivity to stress predicts future blood pressure in adolescence

OBJECTIVE

This study evaluated the prospective relationship between cardiovascular reactivity to psychological stress and increases in resting blood pressure across a 3-year period among a multiethnic pediatric sample (N = 149).

METHODS

Systolic and diastolic blood pressure; EKG heart rate, pre-ejection period, and mean successive difference of R to R intervals; and impedance-derived measures of cardiac output, stroke volume, and total peripheral resistance were collected during performance of four tasks that elicited different hemodynamic response patterns. Changes from baseline to each task were standardized and averaged to form eight composite scores. Analyses adjusted for time 1 baseline blood pressure and age, body mass index at baseline and change to follow-up, and duration of follow-up.

RESULTS

Rises in SBP over the follow-up period were independently predicted by SBP (beta = 0.161, p =.009), DBP (beta = 0.132, p =.02), and CO (beta = 0.144, p =.02) composite measures of reactivity. Rises in DBP over the follow-up period were predicted by DBP (beta = 0.292, p =.003, respectively), and MSD (beta = -0.176, p <.03) composite measures of reactivity. TPR reactivity was not related prospectively to blood pressure rises.

CONCLUSIONS

This study adds to the pediatric literature documenting an association between cardiovascular reactivity to stress and subsequent risk for hypertension. It is the first to show that impedance-derived measures of myocardial function during stress are related to future blood pressure levels.

Impaired skeletal muscle and skin microcirculatory function in human obesity

BACKGROUND

Obesity is associated with exaggerated blood pressure and systemic vascular resistance responses to mental stress.

OBJECTIVE

To test the hypothesis that skin and muscle microvascular dilatation in response to mental stress is blunted in obesity.

DESIGN AND METHODS

Blood pressure, heart rate and forearm and skin blood flow responses to mental stress were compared in 23 obese and 23 age- and sex-matched lean normotensive individuals.

RESULTS

Blood pressure was almost identical in both obese (mean 94 +/- 1 mmHg) and lean (93 +/- 2 mmHg) individuals. The increase in blood pressure during mental stress was similar in obese and lean individuals (2.0 +/- 0.9% compared with 3.1 +/- 4.0%; P = 0.8). Forearm vascular resistance decreased during mental stress in both groups, but this decrease was significantly blunted in obese individuals compared with controls (decreases of 14 +/- 4% and 26 +/- 3%; P < 0.01). Skin microcirculatory dilatation was also significantly blunted in obese individuals compared with controls (decreases of 5 +/- 2 and 17 +/- 4%; P = 0.02).

CONCLUSIONS

Normotensive obese individuals exhibit markedly impaired muscle and skin microcirculatory responses to mental stress. The increased propensity of obese individuals to develop hypertension under conditions of chronic psychosocial stress may underlie obesity-related hypertension and cardiovascular disease.

Threshold values of visceral fat measures and their anthropometric alternatives for metabolic derangement in Japanese obese boys

OBJECTIVE

To determine whether the direct measure of visceral adipose tissue (VAT) by computed tomography (CT) is a superior diagnostic criterion to the anthropometric surrogates and more classical criteria of obesity.

DESIGN

Cross-sectional, clinical study. Obese boys were classified according to the occurrence of abnormal values in either serum triglyceride, alanine aminotransferase or insulin level. A threshold value of each criterion for such metabolic derangement was calculated, using the analysis of receiver operating characteristic (ROC) curve.

SUBJECTS

Seventy-five consecutive outpatient Japanese obese boys, ranging in age from 6 to 14 y, were studied.

MEASUREMENTS

Anthropometric indices measured were height, body weight, waist girth, hip girth, triceps and subscapular skinfold thicknesses. Classical criteria for obesity used were percentage overweight (POW), body mass index (BMI) and percentage body fat. Waist girth, sagittal diameter by CT and waist-hip ratio (WHR) were evaluated as anthropometric surrogates for VAT. The areas of total abdominal fat (TAF), VAT and subcutaneous adipose tissue (SAT) were measured by CT at the level of the umbilicus. Clinical blood biochemistry was analyzed in fasting blood samples of obese boys.

RESULTS

Thirty-three boys were classified into a no-complication group, and 42 into a complication group. TAF, VAT and SAT areas were closely associated with age, body size and degree of overweight and adiposity, while VAT/SAT was not. VAT area, sagittal diameter, TAF area and waist girth were closely correlated with alanine aminotransferase, insulin, TG and HDL-C. VAT/SAT, BMI, SAT area, WHR, percentage body fat and POW were less closely associated with these biochemical indices. The descending order of the values of area under the curve for the ROC curves were as follows: VAT>sagittal diameter>TAF>VAT/SAT>waist girth>BMI>WHR>percentage body fat>POW. Both VAT area and VAT/SAT gave >80% of sensitivity and specificity. Among the anthropometric indices studied, the sagittal diameter was the best surrogate of visceral fat measure. The sensitivity and specificity for the rest of the anthropometric indices were in an unsatisfactory range. The threshold values for VAT area, VAT/SAT and sagittal diameter were 58.0 cm(2), 0.276 and 19.2 cm, respectively.

CONCLUSION

The threshold values for VAT area, VAT/SAT and sagittal diameter for detecting biochemical complication in Japanese obese boys were lower than the respective values reported in adults. These values can be used for classifying the obese boys into two types: those with medical problem and those without.

Impact of Transcendental Meditation on cardiovascular function at rest and during acute stress in adolescents with high normal blood pressure

OBJECTIVE

This study examined the impact of the Transcendental Meditation (TM) program on cardiovascular (CV) reactivity in adolescents with high normal BP.

METHOD

Thirty-five adolescents [34 African Americans (AAs), 1 Caucasian American (CA); ages 15-18 years] with resting systolic blood pressure (SBP) between the 85th and 95th percentile for their age and gender on three consecutive occasions, were randomly assigned to either TM (n=17) or health education control (CTL, n=18) groups. The TM group engaged in 15-min meditation twice each day for 2 months including sessions during school lunch break. Primary CV outcome measures were changes in blood pressure (BP), heart rate (HR), and cardiac output (CO) at rest and in response to two laboratory stressors, a simulated car driving stressor and an interpersonal social stressor interview.

RESULTS

The TM group exhibited greater decreases in resting SBP (P<.03) from pre- to postintervention, compared to the CTL group. The TM group exhibited greater decreases from pre- to postintervention in SBP, HR, and CO reactivity (P's<.03) to the simulated car driving stressor, and in SBP reactivity (P<.03) to the social stressor interview.

CONCLUSION

The TM program appears to have a beneficial impact upon CV functioning at rest and during acute laboratory stress in adolescents at-risk for hypertension.

Critical value for the index of body fat distribution based on waist and hip circumferences and stature in obese girls

OBJECTIVE

To determine the critical value for the standard deviation score (SDS) of waist-hip ratio (WHR)/height (Ht), as an age-adjusted measure of body fat distribution, in relation to occurrence of biochemical complications in obese girls.

DESIGN

Cross-sectional, clinical study. The (WHR/Ht)-SDS was calculated as described previously. Obese girls were classified into two groups according to the occurrence of abnormal values in either serum triglyceride, alanine aminotransferase or insulin level. The criteria for obesity were subjected to the receiver operating characteristic (ROC) analysis.

SUBJECTS

One-hundred and twenty-four outpatient Japanese obese girls, ranging in age from 9 to 15 y.

MEASUREMENTS

Height, body weight, waist girth and hip girth as anthropometric measures. Percentage overweight, waist girth, WHR and (WHR/Ht)-SDS as criteria for obesity. Clinical laboratory analysis for fasting blood samples of obese children.

RESULTS

Fifty-nine girls were classified into the no complication group, and 65 girls into the complication group. Those with complications were older, more obese, and their waist girth and WHR were larger, than the girls without complications. The (WHR/Ht)-SDS was >2-fold higher and lipoprotein profile was more atherogenic in the complication group than in the no complication group. Among the four criteria of obesity, (WHR/Ht)-SDS gave the ROC curve skewed furthest into the top left corner of the diagram. Both sensitivity and specificity for (WHR/Ht)-SDS were >80% at the critical value of 2.00. The sensitivity for waist girth was as high as that for specificity for the rest of the criteria were <80%.

CONCLUSION

Only (WHR/Ht)-SDS showed high enough sensitivity and specificity to predict metabolic derangement in the present obese girls. (WHR/Ht)-SDS can serve as the diagnostic criterion that classifies obesity in Japanese adolescent girls into two types.

Persistent high job demands and reactivity to mental stress predict future ambulatory blood pressure

OBJECTIVE

To test the hypothesis that work stress (persistent high job demands over 1 year) in combination with high reactivity to mental stress predict ambulatory blood pressure.

DESIGN

Assessment of cardiovascular responses to standardized behavioural tasks, job demands, and ambulatory blood pressure over a working day and evening after 12 months.

PARTICIPANTS

We studied 81 school teachers (26 men, 55 women), 36 of whom experienced persistent high job demands over 1 year, while 45 reported lower job demands.

METHODS

Participants were divided on the basis of high and low job demands, and high and low systolic pressure reactions to an uncontrollable stress task. Blood pressure and concurrent physical activity were monitored using ambulatory apparatus from 0900 to 2230 h on a working day.

RESULTS

Cardiovascular stress reactivity was associated with waist/hip ratio. Systolic and diastolic pressure during the working day were greater in high job demand participants who were stress reactive than in other groups, after adjustment for age, baseline blood pressure, body mass index and negative affectivity. The difference was not accounted for by variations in physical activity.

CONCLUSIONS

Cardiovascular stress reactivity and sustained psychosocial stress may act in concert to increase cardiovascular risk in susceptible individuals.