Adiposity is associated with blunted cardiovascular, neuroendocrine and cognitive responses to acute mental stress

Loneliness mediates the association between trait social anxiety and cardiovascular reactivity to acute psychological stress

The primary aims of the current study are (1) to examine the association between trait social anxiety and cardiovascular reactivity to acute psychological stress, and (2) to identify if loneliness significantly mediates the association between trait social anxiety and cardiovascular reactivity. A sample of 658 participants completed a cardiovascular reactivity protocol consisting of a resting baseline and stressor phase (mental arithmetic and Stroop), with systolic blood pressure (SBP), diastolic blood pressure (DBP) and heart rate (HR) monitored throughout. Participants also completed self-reported measures assessing social anxiety and loneliness. Social anxiety was associated with increased self-reported stress. However, no significant associations between social anxiety and measures of cardiovascular reactivity were observed in regression analyses. Loneliness was significantly associated with lower SBP and DBP reactivity. Additionally, loneliness significantly mediated the association between trait social anxiety and both SBP reactivity and DBP reactivity. Here, trait social anxiety predicted greater levels of loneliness, which in turn was associated with diminished cardiovascular reactivity. No significant associations emerged for HR reactivity. These blunted blood pressure responses to acute stress may indicate a potential mechanism leading to adverse prospective health outcomes.

Stress-induced brain responses are associated with BMI in women

Overweight and obesity are associated with altered stress reactivity and increased inflammation. However, it is not known whether stress-induced changes in brain function scale with BMI and if such associations are driven by peripheral cytokines. Here, we investigate multimodal stress responses in a large transdiagnostic sample using predictive modeling based on spatio-temporal profiles of stress-induced changes in activation and functional connectivity. BMI is associated with increased brain responses as well as greater negative affect after stress and individual response profiles are associated with BMI in females (pperm < 0.001), but not males. Although stress-induced changes reflecting BMI are associated with baseline cortisol, there is no robust association with peripheral cytokines. To conclude, alterations in body weight and energy metabolism might scale acute brain responses to stress more strongly in females compared to males, echoing observational studies. Our findings highlight sex-dependent associations of stress with differences in endocrine markers, largely independent of peripheral inflammation.

Whole-Body Magnetic Resonance Imaging Assessment of the Contributions of Adipose and Nonadipose Tissues to Cardiovascular Remodeling in Adolescents

Background Greater body mass index is associated with cardiovascular remodeling in adolescents. However, body mass index cannot differentiate between adipose and nonadipose tissues. We examined how visceral and subcutaneous adipose tissue are linked with markers of early cardiovascular remodeling, independently from nonadipose tissue. Methods and Results Whole-body magnetic resonance imaging was done in 82 adolescents (39 overweight/obese; 36 female; median age, 16.3 [interquartile range, 14.4-18.1] years) to measure body composition and cardiovascular remodeling markers. Left ventricular diastolic function was assessed by echocardiography. Waist, waist:height ratio, and body mass index z scores were calculated. Residualized nonadipose tissue, subcutaneous adipose tissue, and visceral adipose tissue variables, uncorrelated with each other, were constructed using partial regression modeling to allow comparison of their individual contributions in a 3-compartment body composition model. Cardiovascular variables mostly related to nonadipose rather than adipose tissue. Nonadipose tissue was correlated positively with left ventricular mass (r=0.81), end-diastolic volume (r=0.70), stroke volume (r=0.64), left ventricular mass:end-diastolic volume (r=0.37), and systolic blood pressure (r=0.35), and negatively with heart rate (r=-0.33) (all P<0.01). Subcutaneous adipose tissue was associated with worse left ventricular diastolic function (r=-0.42 to -0.48, P=0.0007-0.02) and higher heart rates (r=0.34, P=0.007) but linked with better systemic vascular resistance (r=-0.35, P=0.006). There were no significant relationships with visceral adipose tissue and no associations of any compartment with pulse wave velocity. Conclusions Simple anthropometry does not reflect independent effects of nonadipose tissue and subcutaneous adipose tissue on the adolescent cardiovascular system. This could result in normal cardiovascular adaptations to growth being misinterpreted as pathological sequelae of excess adiposity in studies reliant on such measures.

Pericardial Fat, Socioeconomic Status, and Biological Responses to Acute Mental Stress

OBJECTIVE

Central adiposity is associated with impaired biological responses to mental stress, and socioeconomic status (SES) might moderate this relationship. However, evidence for associations between pericardial fat, a fat depot implicated in the pathogenesis of cardiovascular disease (CVD), with cardiovascular and inflammatory responses to mental stress is lacking, and moderation by SES is unknown.

METHODS

The sample was 473 healthy men and women (mean age = 62.8 years) from the Whitehall II study. Cardiovascular and inflammatory responses to laboratory-induced mental stress, consisting of a 5-minute Stroop task and 5-minute mirror tracing task, were assessed. Pericardial fat volume was measured using electron bean computed tomography and adjusted for body surface area. SES was defined by grade of employment within the British civil service (higher/intermediate/lower).

RESULTS

Pericardial fat was associated with lower heart rate variability, raised heart rate, plasma interleukin-6, fibrinogen, and C-reactive protein at baseline. Furthermore, greater pericardial fat was associated with lower systolic blood pressure reactivity to mental stress, independent of sociodemographics, smoking status, waist-to-hip ratio, and baseline systolic blood pressure. There were no interactions between pericardial fat and SES for any outcome.

CONCLUSIONS

Greater pericardial fat was associated with numerous cardiovascular and inflammatory factors implicated in CVD. It was also related to reduced systolic blood pressure reactivity to acute mental stress, independent of central adiposity and baseline systolic blood pressure. This association did not vary by SES. Reduced systolic blood pressure reactivity to mental stress might contribute to the association between greater pericardial fat and CVD.

Cardiovascular stress reactivity, habituation, and adiposity

The relationship between adiposity and cardiovascular disease morbidity and mortality is complex. One pathway through which adiposity may influence future health outcomes is by altering how biological systems respond to stress. The current study aimed to examine the association between two metrics of adiposity (body mass index and waist-hip ratio) and two indices of cardiovascular stress responses (reactivity and habituation). A sample of 455 participants (Mean age = 19.47, SD = 1.25 years; BMI = 24.32, SD = 5.04 kg/m² ; 62% female; 17.9% Hispanic/Latino; 65.2% White, 18.7% Asian, 7.9% Black, 0.2% American Indian/Alaska Native, and 7% other) completed two acute psychosocial stress tasks. Heart rate (HR), systolic blood pressure (SBP) and diastolic blood pressure (DBP) were recorded throughout each stressor. In unadjusted and adjusted models, there were no statistically significant associations between adiposity and HR, SBP, or DBP stress reactivity or habituation. The current data do not support the hypothesis that adiposity influences health by altering cardiovascular responses to acute psychological stress. Results are at odds with prior population-level studies and the single prior study examining adiposity and habituation. At the same time, results are in line with mounting evidence that adiposity itself does not drive poor cardiovascular outcomes seen in people classified as overweight or obese.

Child Maltreatment and Inflammatory Response to Mental Stress Among Adults Who Have Survived a Myocardial Infarction

OBJECTIVE

Experiences of child maltreatment are associated with cardiovascular risk and disease in adulthood; however, the mechanisms underlying these associations are poorly understood.

METHODS

We examined associations between retrospectively self-reported exposure to child maltreatment (Early Trauma Inventory Self-Report Short Form) and inflammatory responses to mental stress among adults (mean age = 50 years) who recently had a myocardial infarction ( n = 227). Inflammation was assessed as blood interleukin-6 (IL-6), matrix metalloproteinase-9 (MMP-9), and monocyte chemoattractant protein-1 concentrations, measured before and after a standardized public speaking stress task. We used mixed linear regression models adjusting for cardiovascular disease severity, medication usage, and psychosocial, demographic, and life-style factors.

RESULTS

In women, increases in IL-6 levels and MMP-9 levels with stress were smaller in those exposed to sexual abuse, relative to those unexposed (IL-6 geometric mean increases = 1.6 [95% confidence interval {CI} = 1.4-1.9] pg/ml versus 2.1 [95% CI = 1.8-2.4] pg/ml; MMP-9 geometric mean increases = 1.0 [95% CI = 0.9-1.2] ng/ml versus 1.2 [95% CI = 1.1-1.4] ng/ml). No differences were noted for emotional or physical abuse. By contrast in men, individuals exposed to sexual abuse had larger IL-6 responses than those not exposed to abuse.

CONCLUSIONS

These findings suggest sex differences in stress response among survivors of a myocardial infarction exposed to abuse early in life. They also underscore the importance of examining sex as an effect modifier of relationships between exposure to early life adversity and inflammatory responses to mental stressors in midlife.

The principle of 'brain energy on demand' and its predictive power for stress, sleep, stroke, obesity and diabetes

Does the brain actively draw energy from the body when needed? There are different schools of thought regarding energy metabolism. In this study, the various theoretical models are classified into one of two categories: (1) conceptualizations of the brain as being purely passively supplied, which we call 'P-models,' and (2) models understanding the brain as not only passively receiving energy but also actively procuring energy for itself on demand, which we call 'A-models.' One prominent example of such theories making use of an A-model is the selfish-brain theory. The ability to make predictions was compared between the A- and P-models. A-models were able to predict and coherently explain all data examined, which included stress, sleep, caloric restriction, stroke, type-1-diabetes mellitus, obesity, and type-2-diabetes, whereas the predictions of P-models failed in most cases. The strength of the evidence supporting A-models is based on the coherence of accurate predictions across a spectrum of metabolic states. The theory test conducted here speaks to a brain that pulls its energy from the body on-demand.

Heart rate reactivity to acute mental stress is associated with adiposity, carotid distensibility, sleep efficiency, and autonomic modulation in young men

Acute mental stress (AMS) increases heart rate (HR) and blood pressure. Since obesity can impair the cardiovascular reactivity to AMS, a better understanding of the mechanisms involved in this response is needed. We aimed to evaluate the cardiovascular reactivity to AMS in young men with normal or excess body fat. We also assessed the association between cardiovascular reactivity to AMS and cardiovascular risk factors, including autonomic modulation, carotid artery distensibility, physical activity levels, and sleep efficiency. Sixty-six young men (26.1 ± 4.1 years old) underwent anthropometric and body fat assessment (dual-energy X-ray absorptiometry) and had right-carotid artery ultrasonography. Accelerometers assessed physical activity levels and sleep efficiency. AMS was induced through the Stroop color-word test while blood pressure, HR, and cardiac interval were measured. Analyses were performed in Normal and Excess fat groups divided by fat mass index (FMI). Continuous data was used for multiple linear regression analyses. An interaction between FMI and time for HR reactivity was observed. Cardiac interval variability analysis showed that only participants with normal fat displayed parasympathetic withdrawal during AMS (P < 0.05). Multiple linear regression analysis supported the role of adiposity and autonomic modulation in the HR reactivity to AMS and showed involvement of carotid distensibility and sleep efficiency (P < 0.05). Carotid distensibility was the only predictor for blood pressure reactivity (P < 0.05). Physical activity was not associated with AMS's cardiovascular reactivity. We conclude that increased adiposity is associated with reduced HR reactivity to AMS, which is possibly linked to an impaired parasympathetic withdrawal. Carotid distension and sleep efficiency seem to contribute to this response.

Gender differences in the physiological effects of emotional regulation

Previous research has established that emotional regulation impacts our health; emotional expression is associated with a host of psychological and physiological benefits whereas emotional suppression has negative health consequences. Given that emotional-display rules restrict the range of emotion that men feel comfortable expressing, we hypothesized that gender might moderate the health outcomes associated with emotional regulation strategies. In a laboratory experiment, we instructed participants to either suppress or express their feelings in an interview with a researcher about a film they had watched. These participants provided saliva samples at four different points during the procedure for the later determination of cortisol. A Mixed Model ANOVA revealed that participant gender moderated the effect of emotional regulation strategy on cortisol. Contrary to the health consequences typically associated with emotional regulation strategies, men benefited more from emotional suppression than they did from emotional expression. These findings have important implications for future research and clinical work.

The Relationship Between Perceived Control and Hypothalamic-Pituitary-Adrenal Axis Reactivity to the Trier Social Stress Test in Healthy Young Adults

Psychological factors can modulate the hypothalamic-pituitary-adrenal (HPA) axis activity toward stressors. Animal studies demonstrated that uncontrollability was one critical factor associated with HPA axis stress response, but the results in human studies were inconsistent. The current study adopted a standardized laboratory stress induction procedure, the Trier Social Stress Test (the TSST), as the stressor to regulate the objective controllability level, and young adult participants were asked to rate their subjectively perceived control level toward the stressor and measured their cortisol stress responses (N=54; 19 females and 35 males) to address this concern. Results showed that participants' perceived control on the TSST was related to the cortisol stress response. In other words, under the stress of a certain objective controllability level, the lower the subjectively perceived control level, the greater the HPA axis response. This finding suggested that, in addition to objective controllability, subjectively perceived control is a psychological factor that regulates activation of the HPA axis in young adults.

Diabetes-related distress and daily cortisol output in people with Type 2 diabetes

AIMS

Diabetes-related distress is common in Type 2 Diabetes and is linked with poor diabetes control. However, mechanisms underlying this association are unclear. One pathway that could be involved is neuroendocrine dysfunction, as Type 2 Diabetes is associated with altered diurnal cortisol output. This study investigated the link between diabetes-related distress and diurnal cortisol output.

METHODS

134 people with Type 2 Diabetes provided 5 cortisol samples over the course of a day. Multivariate linear regression models were used to assess whether overall and sub-domains of diabetes-related distress measured by the Diabetes Distress Scale, predicted cortisol parameters (waking cortisol, cortisol awakening response, cortisol slope and evening cortisol).

RESULTS

Physician-related distress was associated with greater waking (B = 2.747, p = .015) and evening cortisol (B = 1.375, p = .014), and a blunted cortisol awakening response (B = -3.472, p = .038) adjusting for age, sex, income, body mass index, smoking and time of awakening. No associations were detected for overall distress, emotional, interpersonal or regimen distress.

CONCLUSION

Physician-related distress was associated with alterations in daily cortisol output. Longitudinal research is required to understand how physician-related distress is associated with diurnal cortisol patterning over time.

The relationship between sleep problems and cortisol in people with type 2 diabetes

BACKGROUND

Sleep problems are linked with negative health outcomes, including coronary heart disease. Neuroendocrine dysfunction has been associated with sleep problems and may be a pathway linking sleep and ill health. Dysregulated cortisol output has observed in people with type 2 diabetes (T2D), though little is known about the links between sleep and cortisol in this population at high risk of coronary disease.

METHOD

This study investigated the association between sleep problems and cortisol over the course of an ordinary day and in response to acute laboratory stress in a sample of 129 individuals with T2D. Sleep problems were assessed using the Jenkins sleep problems questionnaire. Mental stress was induced using two five-minute laboratory stress tasks: a mirror-tracing task and the Stroop color-word interference task.

RESULTS

Sleep problems were positively associated with daily cortisol area under the curve (B = 17.051, C.I. = 6.547 to 27.554, p = 0.002) adjusting for age, sex, marital status, education, household income, body mass index and smoking; suggesting that those with greater sleep problems had greater cortisol concentrations over the course of an ordinary day. Participants reporting greater sleep problems also had raised evening cortisol levels (B = 0.96, C.I. = 0.176 to 1.746, p = 0.017) in adjusted models. In the laboratory sleep problems were negatively associated with cortisol immediately post-task (B = -0.030, C.I. = -0.059 to 0.000, p = 0.048) and 45 minutes post-task (B = -0.037, C.I. = -0.072 to -0.002, p = 0.039) in fully adjusted models; indicating that those who experienced greater sleep problems had lower cortisol concentrations after stress.

CONCLUSIONS

Sleep problems were associated with disturbances in cortisol responses to stress, as well as changes diurnal cortisol output in people with T2D. Further research is needed to assess if neuroendocrine disturbance increases the risk of cardiovascular disease in this population.

Activation of the hypothalamic-pituitary adrenal axis in response to a verbal fluency task and associations with task performance

Speech fluency can be impaired in stressful situations. In this study, it was investigated whether a verbal fluency task by itself, i.e. without the presence of any further stressors, induces responses of the hypothalamic-pituitary adrenal (HPA) axis and of the sympathetic nervous system (SNS). The sample consisted of n = 85 participants (68.2% female; 33.3 ± 15.2 years) who performed two consecutive verbal fluency tasks for two minutes each. The categories were either ‘stress’ or ‘disease’ and ‘animals’ or ‘foods’ which were presented in a randomized order. Three saliva samples were collected, prior to the task (t₀), immediately after (t₁), and ten minutes after it (t₂). Salivary α-amylase and cortisol were assessed. Furthermore, blood pressure, heart rate, and ratings of actual stress perception, level of effort, and tiredness were measured. The verbal fluency task induced a HPA axis response with a maximum cortisol level at t₂ which was independent of task performance. Furthermore, perceived stress and effort, as well as tiredness increased after the task. Moreover, tiredness immediately after the task was negatively correlated with task performance. No α-amylase, blood pressure, or heart rate, and therefore SNS, responses were found. Implications for the integrated specificity model are discussed. We conclude that a verbal fluency task acts like an acute stressor that induces a cortisol and a perceived stress response without the need for further (e.g., social-evaluative) stress components. Therefore, it is a less time-consuming alternative to other stress tasks that can be used in field studies with little effort.

Psychological stress reactivity and future health and disease outcomes: A systematic review of prospective evidence

BACKGROUND

Acute psychological stress activates the sympatho-adrenal medullary (SAM) system and hypothalamo-pituitary adrenal (HPA) axis. The relevance of this stress reactivity to long-term health and disease outcomes is of great importance. We examined prospective studies in apparently healthy adults to test the hypothesis that the magnitude of the response to acute psychological stress in healthy adults is related to future health and disease outcomes.

METHODS

We searched Medline Complete, PsycINFO, CINAHL Complete and Embase up to 15 Aug 2019. Included studies were peer-reviewed, English-language, prospective studies in apparently healthy adults. The exposure was acute psychological stress reactivity (SAM system or HPA axis) at baseline. The outcome was any health or disease outcome at follow-up after ≥1 year.

RESULTS

We identified 1719 papers through database searching and 1 additional paper through other sources. Forty-seven papers met our criteria including 32,866 participants (range 30-4100) with 1-23 years of follow-up. Overall, one third (32 %; 83/263) of all reported findings were significant and two thirds (68 %; 180/263) were null. With regard to the significant findings, both exaggerated (i.e. high) and blunted (i.e. low) stress reactivity of both the SAM system and the HPA axis at baseline were related to health and disease outcomes at follow-up. Exaggerated stress reactivity at baseline predicted an increase in risk factors for cardiovascular disease and decreased telomere length at follow-up. In contrast, blunted stress reactivity predicted future increased adiposity and obesity, more depression, anxiety and PTSD symptoms, greater illness frequency, musculoskeletal pain and regulatory T-Cell percentage, poorer cognitive ability, poorer self-reported health and physical disability and lower bone mass.

CONCLUSION

Exaggerated and blunted SAM system and HPA axis stress reactivity predicted distinct physical and mental health and disease outcomes over time. Results from prospective studies consistently indicate stress reactivity as a predictor for future health and disease outcomes. Dysregulation of stress reactivity may represent a mechanism by which psychological stress contributes to the development of future health and disease outcomes.

A Randomized Controlled Trial of a Mindfulness-Based Weight Loss Intervention on Cardiovascular Reactivity to Social-Evaluative Threat Among Adults with Obesity

Objective

Mindfulness-based interventions have been found to reduce psychological and physiological stress reactivity. In obesity, however, stress reactivity is complex, with studies showing both exaggerated and blunted physiological responses to stressors. A nuanced view of stress reactivity is the "challenge and threat" framework, which defines adaptive and maladaptive patterns of psychophysiological stress reactivity. We hypothesized that mindfulness training would facilitate increased challenge-related appraisals, emotions, and cardiovascular reactivity, including sympathetic nervous system activation paired with increased cardiac output (CO) and reduced total peripheral resistance (TPR) compared to a control group, which would exhibit an increased threat pattern of psychophysiological reactivity to repeated stressors.

Methods

Adults (N=194) with obesity were randomized to a 5.5-month mindfulness-based weight loss intervention or an active control condition with identical diet-exercise guidelines. Participants were assessed at baseline and 4.5 months later using the Trier Social Stress Task. Electrocardiogram, impedance cardiography, and blood pressure were acquired at rest and during the speech and verbal arithmetic tasks to assess pre-ejection period (PEP), CO, and TPR reactivity.

Results

Mindfulness participants showed significantly greater maintenance of challenge-related emotions and cardiovascular reactivity patterns (higher CO and lower TPR) from pre to post-intervention compared to control participants, but groups did not differ in PEP. Findings were independent of changes in body mass index.

Conclusions

Mindfulness training may increase the ability to maintain a positive outlook and mount adaptive cardiovascular responses to repeated stressors among persons with obesity though findings need to be replicated in other populations and using other forms of mindfulness interventions.

Evaluation of the socially evaluated cold-pressor group test (SECPT-G) in the general population

Background

In stress research, economic instruments for introducing acute stress responses are needed. In this study, we investigated whether the socially evaluated cold-pressor group test (SECPT-G) induces salivary alpha-amylase (sAA) and/or cortisol responses in the general population and whether this is associated with anthropometric, experimental, and lifestyle factors.

Methods

A sample of 91 participants from the general population was recruited. Salivary cortisol and sAA levels were assessed prior to (t₀), immediately after (t₁), and 10 min after the SECPT-G (t₂).

Results

A robust cortisol increase was found immediately after the SECPT-G, which further increased between t₁ and t₂. This was independent of most of the control variables. However, men showed a trend toward higher cortisol increases than women (p = 0.005). No sAA responses were found at all. However, sAA levels were dependent on measurement time point with highest levels between 9 pm and 9:30 pm. Participants who immersed their hands into the ice water for the maximally allowed time of 3 min showed higher sAA levels at all time points than participants who removed their hands from the water earlier.

Conclusions

We conclude that the SECPT-G is a good means of an acute stress test when cortisol—but not necessarily sAA—responses are intended.

Socioeconomic status and central adiposity as determinants of stress-related biological responses relevant to cardiovascular disease risk

Stress-related processes have been implicated in the associations between lower socioeconomic status (SES), central adiposity, and cardiovascular disease risk. This study analysed the impact of SES and central adiposity on cardiovascular, inflammatory and neuroendocrine stress responses, and associations with cytomegalovirus (CMV) infection in a sample of 537 men and women aged 53-76 years (mean 62.89 years). SES was defined by grade of employment (higher, intermediate, and lower categories), and central adiposity was indexed by waist-hip ratio (WHR). Cardiovascular, inflammatory and cortisol responses were monitored during administration of a standardized mental stress testing protocol and salivary cortisol was measured repeatedly over the day. Lower SES was associated with raised systolic and diastolic blood pressure (BP), plasma interleukin (IL-6), fibrinogen, C-reactive protein, and salivary cortisol, and a large WHR accentuated SES differences in fibrinogen, C-reactive protein, and likelihood of CMV seropositivity, independently of general adiposity indexed by body mass index. During mental stress testing, return to resting levels (recovery) following behavioural challenge in systolic and diastolic BP and heart rate was impaired among lower SES participants, particularly those with large WHR. Lower SES participants had greater cortisol concentrations across the day, but this pattern did not vary with WHR. These findings extend the evidence relating lower SES to stress-related biological risk factors for cardiovascular disease, and indicate that central adiposity may augment these effects.

Loneliness and biological responses to acute stress in people with Type 2 diabetes

Loneliness is linked with all-cause mortality and coronary heart disease. Altered neuroendocrine and inflammatory responses to stress constitute potential pathways linking loneliness and ill-health. Stress responsivity is modified in people with Type 2 diabetes, but it is unclear whether loneliness influences biological stress responses in this population. We assessed interleukin-6 (IL-6), interleukin-1 receptor antagonist (IL-1RA), monocyte chemoattractant protein-1 (MCP-1), and cortisol responses to acute stress in 135 people with Type 2 diabetes. Loneliness was measured used the Revised UCLA Loneliness Scale. Loneliness was inversely associated with cortisol output poststress (B = -4.429, p = 0.019) independent of age, sex, education, marital status, body mass index, and smoking. Lonelier individuals had raised MCP-1 concentrations 75 min poststress independent of covariates (B = 0.713, p = 0.022). No associations between loneliness and IL-6 or IL-1RA concentrations were detected. These results suggest that loneliness is associated with disturbances in stress responsivity in people with diabetes, and the impact of loneliness on health in people with diabetes may be mediated in part through dysregulation of inflammatory and neuroendocrine systems. Future research is required to understand if such changes increase the risk of poorer outcomes in this population.

Adiposity and Cortisol Response to Stress in Indian Adolescents

OBJECTIVE

We examined associations of different adiposity measures with cortisol responses during the Trier Social Stress Test for children (TSST-C).

DESIGN

Descriptive study.

SETTING

Holdsworth Memorial Hospital, Mysore, India.

PARTICIPANTS

Adolescents aged 13.5y from a birth cohort were recruited (N=269, 133 boys).

METHODS

The stressor (TSST-C) was 5-minutes each of public speaking and mental arithmetic tasks in front of two unfamiliar 'judges'. Salivary cortisol concentrations were measured at baseline and at regular intervals after TSST-C. Weight, height, sub scapular and triceps skinfold thickness, and waist and hip circumference were measured, and percentage body fat was estimated (fat%; bioimpedance). Body mass index (BMI) and Waist-to-hip ratio (WHR) were calculated. All variables were converted into within-cohort SD scores before analysis. Stress-induced change in cortisol concentrations from baseline (cortisol response) was examined in relation to adiposity.

RESULTS

Stress increased cortisol concentrations significantly from baseline (mean (SD): 5.5 (6.4) ng/mL; P<0.001). Higher WHR was associated with lower cortisol response at 20 and 30-minutes after stress (~0.13 SD decrease in cortisol response per SD higher WHR, P<0.05). Higher fat% was also associated with lower cortisol response only in girls 20-minutes post-stress (0.23 SD lower response per SD higher fat%, P=0.004). Sum of skinfold thickness and BMI were not associated with cortisol responses.

CONCLUSION

Abdominal adiposity is associated with reduced hypothalamic-pituitary-adrenal axis reactivity to stress in this adolescent population.

Adiposity and Cortisol Response to Stress in Indian Adolescents

Objective

We examined associations of different adiposity measures with cortisol responses during the Trier Social Stress Test for children (TSST-C).

Design

Descriptive study.

Setting

Holdsworth Memorial Hospital, Mysore, India.

Participants

Adolescents aged 13.5y from a birth cohort were recruited (N=269, 133 boys).

Methods

The stressor (TSST-C) was 5-minutes each of public speaking and mental arithmetic tasks in front of two unfamiliar ‘judges’. Salivary cortisol concentrations were measured at baseline and at regular intervals after TSST-C. Weight, height, sub scapular and triceps skinfold thickness, and waist and hip circumference were measured, and percentage body fat was estimated (fat%; bioimpedance). Body mass index (BMI) and Waist-to-hip ratio (WHR) were calculated. All variables were converted into within-cohort SD scores before analysis. Stressinduced change in cortisol concentrations from baseline (cortisol response) was examined in relation to adiposity.

Results

Stress increased cortisol concentrations significantly from baseline (mean (SD): 5.5 (6.4) ng/mL; P<0.001). Higher WHR was associated with lower cortisol response at 20 and 30-minutes after stress (~0.13 SD decrease in cortisol response per SD higher WHR, P<0.05). Higher fat% was also associated with lower cortisol response only in girls 20-minutes post-stress (0.23 SD lower response per SD higher fat%, P=0.004). Sum of skinfold thickness and BMI were not associated with cortisol responses.

Conclusions

Abdominal adiposity is associated with reduced hypothalamic-pituitary-adrenal axis reactivity to stress in this adolescent population.

Plasma copeptin and metabolic dysfunction in individuals with bipolar disorder

AIM

This study aimed to compare plasma copeptin levels, the c-terminal of provasopressin, between individuals with bipolar disorder (BD) and healthy controls and to assess the relation between copeptin and metabolic parameters.

METHODS

We measured plasma levels of copeptin in individuals with BD (n = 55) and healthy controls (n = 21). Information related to psychiatric/medical history, as well as to metabolic comorbidities and laboratorial parameters was also captured. Insulin resistance and β-cell function in basal state were calculated from fasting plasma glucose and C-peptide using the HOMA2 calculator. Impaired glucose metabolism was defined as pre-diabetes or type 2 diabetes mellitus. Copeptin, adiponectin, and leptin plasma levels were determined by enzyme-linked immunosorbent assay.

RESULTS

Plasma copeptin levels were lower in individuals with BD, relative to healthy controls (P < 0.001). There were significant interactions between BD and plasma copeptin on β-cell function (rate ratio [RR] = 1.048; P = 0.030) and on leptin levels (RR = 1.087; P = 0.012), indicating that there was a positive correlation between these markers in the BD group, but a negative one in healthy controls. Finally, in individuals with BD only, the association between β-cell function, body mass index (RR = 1.007; P < 0.001), and insulin resistance (RR = 1.001; P = 0.037) was moderated by copeptin levels.

CONCLUSION

Copeptin levels were lower in individuals with BD than in healthy controls. There were differential associations between copeptin and metabolic parameters within the BD and healthy control subgroups, suggesting an association between abnormal copeptin and metabolic dysregulation only in the BD population.

Stress-Related Changes in Body Form: Results from the Whitehall II Study

OBJECTIVE

Stress is associated with body mass gain in some people but with body mass loss in others. When the stressor persists, some people adapt with their stress responses, whereas others do not. Heart rate variability (HRV) reflects autonomic variability and is related to stress responses to psychosocial challenges. It was hypothesized that the combined effects of stress exposure and autonomic variability predict long-term changes in body form.

METHODS

Data of 1,369 men and 612 women from the Whitehall II cohort were analyzed. BMI, hip-to-height ratio, and waist-to-height ratio were measured at three time points over a 10-year period. HRV and psychological distress (General Health Questionnaire) were assessed.

RESULTS

Men with high psychological distress were at risk of developing an increased waist-to-height ratio (F = 3.4, P = 0.038). Men with high psychological distress and low HRV were prone to develop an increased body mass and hip-to-height ratio (psychological distress: F = 4.3, P = 0.016; HRV: F = 5.0, P = 0.008). Statistical trends showed that women displayed similar patterns of stress-related changes in body form (P = 0.061; P = 0.063).

CONCLUSIONS

Assessing psychological distress and autonomic variability predicts changes in body form. Psychological distress was found to be associated with an increased risk of developing the wide-waisted phenotype, while psychological distress combined with low autonomic variability was associated with an increased risk of developing the corpulent phenotype.

The behavioural, cognitive, and neural corollaries of blunted cardiovascular and cortisol reactions to acute psychological stress

Recent research shows that blunted cardiovascular and cortisol reactions to acute psychological stress are associated with adverse behavioural and health outcomes: depression, obesity, bulimia, and addictions. These outcomes may reflect suboptimal functioning of the brain's fronto-limbic systems that are needed to regulate motivated behaviour in the face of challenge. In support of this, brain imaging data demonstrate fronto-limbic hypoactivation during acute stress exposure. Those demonstrating blunted reactions also show impairments of motivation, including lower cognitive ability, more rapid cognitive decline, and poorer performance on motivation-dependent tests of lung function. Persons exhibiting blunted stress reactivity display well established temperament characteristics, including neuroticism and impulsivity, characteristic of various behavioural disorders. Notably, the outcomes related to blunted stress reactivity are similar to those that define Reward Deficiency Syndrome. Accordingly, some individuals may be characterised by a broad failure in cardiovascular and cortisol responding to both stress and reward, reflecting fronto-limbic dysregulation. Finally, we proffer a model of blunted stress reactivity, its antecedents and sequelae, and identify future research priorities.

Salivary cortisol and α-amylase: subclinical indicators of stress as cardiometabolic risk

Currently, the potential for cardiovascular (CV) stress-induced risk is primarily based on the theoretical (obvious) side effects of stress on the CV system. Salivary cortisol and α-amylase, produced respectively by the hypothalamus-pituitary-adrenal (HPA) axis and the sympathetic-adrenomedullary (SAM) system during stress response, are still not included in the routine evaluation of CV risk and require additional and definitive validation. Therefore, this article overviews studies published between 2010 and 2015, in which salivary cortisol and α-amylase were measured as stress biomarkers to examine their associations with CV/CMR (cardiometabolic risk) clinical and subclinical indicators. A comprehensive search of PubMed, Web of Science and Scopus electronic databases was performed, and 54 key articles related to the use of salivary cortisol and α-amylase as subclinical indicators of stress and CV/CMR factors, including studies that emphasized methodological biases that could influence the accuracy of study outcomes, were ultimately identified. Overall, the biological impact of stress measured by salivary cortisol and α-amylase was associated with CV/CMR factors. Results supported the use of salivary cortisol and α-amylase as potential diagnostic tools for detecting stress-induced cardiac diseases and especially to describe the mechanisms by which stress potentially contributes to the pathogenesis and outcomes of CV diseases.

A hormonal approach to anti-social behaviour

BACKGROUND

Altered levels of cortisol and testosterone have previously been associated with anti-social personality disorder (ASPD) and psychopathy, but there is some conflicting evidence as to how characteristic these findings are.

AIM

To test the hypothesis that diurnal fluctuations in cortisol and/or testosterone will differentiate ASPD and psychopathy among male forensic psychiatric inpatients and distinguish both groups from healthy men not in treatment.

METHODS

One hundred and sixty-six men participated: 81 patients with ASPD, 42 of whom had a Psychopathy Checklist-Revised (PCL-R) score of 26 or more and 39 with a score of 25 or less, 51 forensic hospital employees and 34 general population men. None in the latter two groups had abnormal personality traits. For each person, diurnal cortisol and testosterone saliva samples were collected.

RESULTS

Both patient groups and the forensic hospital employees showed significantly higher diurnal testosterone levels than the general population, community-based men. The community men showed significantly lower values in their diurnal cortisol variation than the ASPD and psychopathy groups but, in this, were similar to the forensic employee group. Neither cortisol nor testosterone levels differentiated the higher from lower Psychopathy Checklist-Revised scorers.

CONCLUSIONS

We replicated findings of diurnal testosterone deficiencies among men with psychopathy and ASPD, but we were unable to differentiate patients groups from each other or from the hospital employees on cortisol measures. This suggests a case for more research with more diverse comparison groups and more differentiation of personality traits before drawing definitive conclusions about distinctive hormonal patterns among men with psychopathy, as external environmental variables may prove more influential than previously suspected. Copyright © 2015 John Wiley & Sons, Ltd.

Physiological adaptations to chronic stress in healthy humans - why might the sexes have evolved different energy utilisation strategies?

KEY POINTS

The human stress response activates the autonomic nervous system and endocrine systems to increase performance during environmental challenges. This response is usually beneficial, improving the chance of overcoming environmental challenges, but costs resources such as energy. Humans and other animals are known to adapt their responses to acute stress when they are stimulated chronically, presumably to optimise resource utilisation. Characterisation of these adaptations has been limited. Using advanced imaging techniques, we show that cardiovascular and endocrine physiology, reflective of energy utilisation during acute stress, and energy storage (fat) differ between the sexes when they are exposed to chronic stress. We examine possible evolutionary explanations for these differences, related to energy use, and point out how these physiological differences could underpin known disparities between the sexes in their risk of important cardiometabolic disorders such as obesity and cardiovascular disease.

ABSTRACT

Obesity and associated diseases, such as cardiovascular disease, are the dominant human health problems in the modern era. Humans develop these conditions partly because they consume excess energy and exercise too little. Stress might be one of the factors contributing to these disease-promoting behaviours. We postulate that sex-specific primordial energy optimisation strategies exist, which developed to help cope with chronic stress but have become maladaptive in modern societies, worsening health. To demonstrate the existence of these energy optimisation strategies, we recruited 88 healthy adults with varying adiposity and chronic stress exposure. Cardiovascular physiology at rest and during acute stress (Montreal Imaging Stress Task), and body fat distribution were measured using advanced magnetic resonance imaging methods, together with endocrine function, cardiovascular energy use and cognitive performance. Potential confounders such as lifestyle, social class and employment were accounted for. We found that women exposed to chronic stress had lower adiposity, greater acute stress cardiovascular responses and better cognitive performance. Conversely, chronic stress-exposed men had greater adiposity and lower cardiovascular responses to acute stress. These results provide initial support for our hypothesis that differing sex-specific energy conservation strategies exist. We propose that these strategies have initially evolved to benefit humans but are now maladaptive and increase the risk of disorders such as obesity, especially in men exposed to chronic stress.

Predictors of abdominal adipose tissue compartments: 18-year follow-up of young men with and without family history of diabetes

BACKGROUND

Abdominal adipose tissue (AAT) consists of visceral adipose tissue (VAT) and subcutaneous adipose tissue (SAT), which can be further divided into superficial and deep SAT. Despite being a key factor in the development of metabolic and cardiovascular diseases, what predicts future amount of AAT is largely unknown.

OBJECTIVE

To determine long-term predictors of amount of AAT.

METHODS

This was a mean 18-year follow-up study of a cohort of 94 healthy young Caucasian men, with and without a family history of diabetes (FHD). Cardiovascular risk markers were examined both at baseline and at follow-up. At follow-up, computed tomography (CT) of AAT was conducted to assess amount of superficial and deep SAT, and VAT.

RESULTS

In multiple regression analyses, baseline body mass index (BMI) remained a positive predictor of future amount of superficial and deep SAT, while high-density lipoprotein (HDL) cholesterol was a negative predictor of all three sub-compartments. Baseline risk markers were generally stronger predictors among men with FHD, than among men without. In addition, FHD had greater impact on amount of deep SAT and VAT, than on amount of superficial SAT.

CONCLUSION

Our data suggest that the traditional cardiovascular risk markers BMI, HDL cholesterol and family history of diabetes are long-term predictors of the different abdominal adipose tissue compartments from young towards middle age in healthy men. In men with family history of diabetes, cardiovascular risk markers at a young age seem to be of greater importance to future amount of abdominal adipose tissue, than among men without.

Evaluation of response to restraint stress by salivary corticosterone levels in adult male mice

Saliva as a sampling method is a low invasive technique for the detection of physiologically active substances, as opposed to sampling the plasma or serum. In this study, we obtained glucocorticoids transferred from the blood to the saliva from mice treated with 2.0 mg/kg via an intraperitoneal injection of cortisol. Next, to evaluate the effect of restraint stress using mouse saliva—collected under anesthesia by mixed anesthetic agents—we measured plasma and salivary corticosterone levels at 60 min after restraint stress. Moreover, to evaluate salivary corticosterone response to stress in the same individual mouse, an adequate recovery period (1, 3 and 7 days) after anesthesia was examined. The results demonstrate that exogenous cortisol was detected in the saliva and the plasma, in mice treated with cortisol. Restraint stress significantly increased corticosterone levels in both the plasma and saliva (P<0.001). Monitoring the results of individual mice showed that restraint stress significantly increased salivary corticosterone levels in all three groups (1-, 3- and 7-day recovery). However, the statistical evidence of corticosterone increase is stronger in the 7-day recovery group (P<0.001) than in the others (P<0.05). These results suggest that the corticosterone levels in saliva reflect its levels in the plasma, and salivary corticosterone is a useful, less-invasive biomarker of physical stress in mice. The present study may contribute to concepts of Reduction and Refinement of the three Rs in small animal experiments.

Characterization and novel analyses of acute stress response patterns in a population-based cohort of young adults: influence of gender, smoking, and BMI

Dysregulation of the biological stress response system has been implicated in the development of psychological, metabolic, and cardiovascular disease. Whilst changes in stress response are often quantified as an increase or decrease in cortisol levels, three different patterns of stress response have been reported in the literature for the Trier Social Stress Test (TSST) (reactive-responders (RR), anticipatory-responders (AR) and non-responders (NR)). However, these have never been systematically analyzed in a large population-based cohort. The aims of this study were to examine factors that contribute to TSST variation (gender, oral contraceptive use, menstrual cycle phase, smoking, and BMI) using traditional methods and novel analyses of stress response patterns. We analyzed the acute stress response of 798, 18-year-old participants from a community-based cohort using the TSST. Plasma adrenocorticotrophic hormone, plasma cortisol, and salivary cortisol levels were quantified. RR, AR, and NR patterns comprised 56.6%, 26.2%, and 17.2% of the cohort, respectively. Smokers were more likely to be NR than (RR or AR; adjusted, p < 0.05). Overweight and obese subjects were less likely to be NR than the other patterns (adjusted, p < 0.05). Males were more likely to be RR than NR (adjusted, p = 0.05). In addition, we present a novel AUC measure (AUCR), for use when the TSST baseline concentration is higher than later time points. These results show that in a young adult cohort, stress-response patterns, in addition to other parameters vary with gender, smoking, and BMI. The distribution of these patterns has the potential to vary with adult health and disease and may represent a biomarker for future investigation.

Isometric stress in cardiovascular magnetic resonance-a simple and easily replicable method of assessing cardiovascular differences not apparent at rest

INTRODUCTION

Isometric exercise may unmask cardiovascular disease not evident at rest, and cardiovascular magnetic resonance (CMR) imaging is proven for comprehensive resting assessment. This study devised a simple isometric exercise CMR methodology and assessed the hemodynamic response evoked by isometric exercise.

METHODS

A biceps isometric exercise technique was devised for CMR, and 75 healthy volunteers were assessed at rest, after 3-minute biceps exercise, and 5-minute of recovery using: 1) blood pressure (BP) and 2) CMR measured aortic flow and left ventricular function. Total peripheral resistance (SVR) and arterial compliance (TAC), cardiac output (CO), left ventricular volumes and function (ejection fraction, stroke volume, power output), blood pressure (BP), heart rate (HR), and rate pressure product were assessed at all time points.

RESULTS

Image quality was preserved during stress. During exercise there were increases in CO (+14.9 %), HR (+17.0 %), SVR (+9.8 %), systolic BP (+22.4 %), diastolic BP (+25.4 %) and mean BP (+23.2 %). In addition, there were decreases in TAC (-22.0 %) and left ventricular ejection fraction (-6.3 %). Age and body mass index modified the evoked response, even when resting measures were similar.

CONCLUSIONS

Isometric exercise technique evokes a significant cardiovascular response in CMR, unmasking physiological differences that are not apparent at rest.

KEY POINTS

• Isometric exercise unmasks cardiovascular differences not evident at rest. • CMR is the reference standard for non-invasive cardiovascular assessment at rest. • A new easily replicable method combines isometric exercise with CMR. • Significant haemodynamic changes occur and differences are unmasked. • The physiological, isometric CMR stressor can be easily replicated.

Hostility and physiological responses to acute stress in people with type 2 diabetes

OBJECTIVE

Hostility is associated with cardiovascular mortality and morbidity, and one of the mechanisms may involve heightened reactivity to mental stress. However, little research has been conducted in populations at high risk for cardiovascular disease. The aim of the present study was to assess the relationship between hostility and acute stress responsivity in individuals with Type 2 diabetes.

METHODS

A total of 140 individuals (median age [standard deviation] 63.71 [7.00] years) with Type 2 diabetes took part in laboratory-based experimental stress testing. Systolic blood pressure, diastolic blood pressure, heart rate, plasma interleukin-6 (IL-6), and salivary cortisol were assessed at baseline, during two stress tasks, and 45 and 75 minutes later. Cynical hostility was assessed using the Cook Medley Cynical Hostility Scale.

RESULTS

Participants with greater hostility scores had heightened increases in IL-6 induced by the acute stress tasks (B = 0.082, p = .002), independent of age, sex, body mass index, smoking, household income, time of testing, medication, and baseline IL-6. Hostility was inversely associated with cortisol output poststress (B = -0.017, p = .002), independent of covariates. No associations between hostility and blood pressure or heart rate responses were observed.

CONCLUSIONS

Hostile individuals with Type 2 diabetes may be susceptible to stress-induced increases in inflammation. Further research is needed to understand if such changes increase the risk of cardiovascular disease in this population.

Salivary alpha amylase diurnal pattern and stress response are associated with body mass index in low-income preschool-aged children

Physiological stress responses are proposed as a pathway through which stress can "get under the skin" and lead to health problems, specifically obesity. We tested associations of salivary alpha amylase (sAA) diurnal patterns and stress responses with body mass index (BMI) in young, low-income children (51% male; 54% non-Hispanic white). Diurnal saliva samples were collected three times per day across three days for 269 children (M age 50.8 months, SD 6.3). Individual sAA intercept and slope values were calculated using random effect models to represent morning sAA levels and rate of sAA change across the day. A subset of children (n=195; M age 56.6 months, SD 6.9) participated in a lab-based behavioral stress protocol. Area under the curve increase (AUCI) across four timepoints was calculated to represent increase in sAA output during stress elicitation. Children were weighed and height measured and BMI z-score was calculated. Linear regression was used to evaluate associations of sAA intercept, sAA slope, and sAA AUCI with BMI z-score, controlling for child age, sex, and race/ethnicity; maternal weight status; and family income-to-needs ratio. Diurnal and stress-response sAA patterns were related to child adiposity: for each 1-standard deviation unit (SDU) decrease in morning sAA level, the child's BMI z-score increased by 0.11 (SE 0.05) SDU's (p<.04); for each 1-SDU increase in sAA slope across the day, the child's BMI z-score increased by 0.12 (SE 0.05) SDU's (p<.03); and for each 1-SDU decrease in sAA AUCI during the stress elicitation, the child's BMI z-score increased by 0.14 (SE 0.06) SDU's (p<.03). Blunted stress responses and atypical diurnal patterns of sAA have been found following exposure to chronic life stressors such as poverty. Findings suggest that associations of stress, sAA, and elevated body mass index may develop very early in the lifespan.

Is there a "metabolic-mood syndrome"? A review of the relationship between obesity and mood disorders

Obesity and mood disorders are highly prevalent and co-morbid. Epidemiological studies have highlighted the public health relevance of this association, insofar as both conditions and its co-occurrence are associated with a staggering illness-associated burden. Accumulating evidence indicates that obesity and mood disorders are intrinsically linked and share a series of clinical, neurobiological, genetic and environmental factors. The relationship of these conditions has been described as convergent and bidirectional; and some authors have attempted to describe a specific subtype of mood disorders characterized by a higher incidence of obesity and metabolic problems. However, the nature of this association remains poorly understood. There are significant inconsistencies in the studies evaluating metabolic and mood disorders; and, as a result, several questions persist about the validity and the generalizability of the findings. An important limitation in this area of research is the noteworthy phenotypic and pathophysiological heterogeneity of metabolic and mood disorders. Although clinically useful, categorical classifications in both conditions have limited heuristic value and its use hinders a more comprehensive understanding of the association between metabolic and mood disorders. A recent trend in psychiatry is to move toward a domain specific approach, wherein psychopathology constructs are agnostic to DSM-defined diagnostic categories and, instead, there is an effort to categorize domains based on pathogenic substrates, as proposed by the National Institute of Mental Health (NIMH) Research Domain Criteria Project (RDoC). Moreover, the substrates subserving psychopathology seems to be unspecific and extend into other medical illnesses that share in common brain consequences, which includes metabolic disorders. Overall, accumulating evidence indicates that there is a consistent association of multiple abnormalities in neuropsychological constructs, as well as correspondent brain abnormalities, with broad-based metabolic dysfunction, suggesting, therefore, that the existence of a "metabolic-mood syndrome" is possible. Nonetheless, empirical evidence is necessary to support and develop this concept. Future research should focus on dimensional constructs and employ integrative, multidisciplinary and multimodal approaches.

Blunted endocrine and cardiovascular reactivity in young healthy women reporting a history of childhood adversity

BACKGROUND

Chronic or prolonged stress exposure in childhood can alter structural and functional brain development, leading to mental and physical illness and alterations of psychobiological stress systems in adulthood. Recently, attenuation in stress reactivity of the hypothalamic-pituitary-adrenal (HPA) axis and cardiovascular system have been related to the number of adverse childhood experiences (ACEs). We set out to investigate the association of ACE duration and age of ACE occurrence on stress reactivity.

METHODS

104 women in the age range 18-25 years (mean=21.7) free of mental and physical illness underwent psychosocial stress testing with the Montreal Imaging Stress Task (MIST). Free saliva cortisol and heart rate were assessed repeatedly before and after the MIST.

RESULTS

Number of ACEs was associated with attenuated cortisol and heart rate responses to stress in a dose-response relationship. Whereas overall duration of ACEs was significantly associated with an attenuated cortisol response, the specific age of first ACE occurrence did not contribute further to the dampened stress response.

CONCLUSIONS

ACEs are associated with blunted endocrine and cardiovascular stress reactivity in young and healthy women. Adverse life events in childhood, particularly if they occur repeatedly and chronically, show a strong association with alterations in stress reactivity in adulthood, potentially predisposing for later mental or physical disorders.

Measures of adiposity predict interleukin-6 responses to repeated psychosocial stress

OBJECTIVE

Overweight and obese individuals, who comprise approximately two-thirds of the U.S. population, are at increased risk for developing a range of diseases. This increased risk may be due in part to maladaptive stress responses within this group, including heightened low-grade inflammation and HPA axis non-habituation. In this study we tested the relationship between adiposity, plasma interleukin-6 (IL-6) and HPA axis responses to repeated stress.

METHODS

Sixty-seven healthy participants were exposed to the Trier Social Stress Test (TSST) on two consecutive days. We collected saliva for cortisol measurements at baseline and at 1, 10, 30, 60 and 120min post-TSST, and blood for plasma IL-6 measurements at baseline and 30 and 120min post-TSST.

RESULTS

Stress exposure induced significant increases of cortisol and IL-6 on both days (cortisol: F=38, p<0.001; IL-6: F=90.8; p<0.001), and repeated exposure was related with cortisol habituation (F=8.2; p<0.001) and IL-6 sensitization (F=5.2; p=0.022). BMI and body fat were related with higher cortisol responses to repeated stress (BMI: beta=0.34; p=0.014; body fat: beta=0.29; p=0.045), and with higher IL-6 responses to repeated stress (BMI: beta=0.27, p=0.044; body fat: beta=0.37; p=0.006).

CONCLUSIONS

Taken together, individuals with higher measures of adiposity showed less efficient HPA axis habituation as well as sensitization of IL-6 responses to repeated acute stress. These findings point to maladaptive stress response patterns in overweight humans, which, through exposure to higher levels of inflammatory mediators, might partially explain diseases related with overweight and/or obesity.

Phenotypic flexibility as key factor in the human nutrition and health relationship

Metabolic adaptation to a disturbance of homeostasis is determined by a series of interconnected physiological processes and molecular mechanisms that can be followed in space (i.e., different organs or organelles) and in time. The amplitudes of these responses of this "systems flexibility network" determine to what extent the individual can adequately react to external challenges of varying nature and thus determine the individual's health status and disease predisposition. Connected pathways and regulatory networks act as "adaptive response systems" with metabolic and inflammatory processes as a core-but embedded into psycho-neuro-endocrine control mechanisms that in their totality define the phenotypic flexibility in an individual. Optimal metabolic health is thus the orchestration of all mechanisms and processes that maintain this flexibility in an organism as a phenotype. Consequently, onset of many chronic metabolic diseases results from impairment or even loss of flexibility in parts of the system. This also means that metabolic diseases need to be diagnosed and treated from a systems perspective referring to a "systems medicine" approach. This requires a far better understanding of the mechanisms involved in maintaining, optimizing and restoring phenotypic flexibility. Although a loss of flexibility in a specific part of the network may promote pathologies, this not necessarily takes place in the same part because the system compensates. Diagnosis at systems level therefore needs the quantification of the response reactions of all relevant parts of the phenotypic flexibility system. This can be achieved by disturbing the homeostatic system by any challenge from extended fasting, to intensive exercise or a caloric overload.

Rise of ketone bodies with psychosocial stress in normal weight men

BACKGROUND

Ketone bodies are known as alternative cerebral energy substrates to glucose. During psychosocial stress, the brain of a normal weight subject demands for extra glucose from the body to satisfy its increased needs. In contrast, the brain of an obese subject organizes its need, supply and demand in a low-reactive manner. The present study aimed at investigating (i) whether psychosocial stress increases ketone body concentrations and (ii) whether ketone reactivity to a psychosocial challenge differs between normal weight and obese people.

METHODS

Ten normal weight and ten obese men participated in two sessions (stress induced by the Trier Social Stress Test and a non-stress control session). Blood samples were frequently taken to assess serum β-hydroxybutyrate concentrations and stress hormone profiles.

RESULTS

Our main finding was that social stress markedly increased concentrations of serum β-hydroxybutyrate by 454% in normal weight men. The increase in ketone bodies during stress in normal weight subjects was associated with an increase in ACTH, norepinephrine and epinephrine concentrations. Interestingly, we could not detect any increase in serum β-hydroxybutyrate concentrations during stress in obese men.

CONCLUSION

Normal weight men showed high ketone reactivity to a psychosocial challenge.

Experimentally induced stress validated by EMG activity

Experience of stress may lead to increased electromyography (EMG) activity in specific muscles compared to a non-stressful situation. The main aim of this study was to develop and validate a stress-EMG paradigm in which a single uncontrollable and unpredictable nociceptive stimulus was presented. EMG activity of the trapezius muscles was the response of interest. In addition to linear time effects, non-linear EMG time courses were also examined. Taking into account the hierarchical structure of the dataset, a multilevel random regression model was applied. The stress paradigm, executed in N = 70 subjects, consisted of a 3-minute baseline measurement, a 3-minute pre-stimulus stress period and a 2-minute post-stimulus phase. Subjects were unaware of the precise moment of stimulus delivery and its intensity level. EMG activity during the entire experiment was conform a priori expectations: the pre-stimulus phase showed a significantly higher mean EMG activity level compared to the other two phases, and an immediate EMG response to the stimulus was demonstrated. In addition, the analyses revealed significant non-linear EMG time courses in all three phases. Linear and quadratic EMG time courses were significantly modified by subjective anticipatory stress level, measured just before the start of the stress task. Linking subjective anticipatory stress to EMG stress reactivity revealed that subjects with a high anticipatory stress level responded with more EMG activity during the pre-stimulus stress phase, whereas subjects with a low stress level showed an inverse effect. Results suggest that the stress paradigm presented here is a valid test to quantify individual differences in stress susceptibility. Further studies with this paradigm are required to demonstrate its potential use in mechanistic clinical studies.

Body mass index-modified relationship of chronic mental stress with resting blood pressure during 5 years in Japanese middle-aged male workers

BACKGROUND

Chronic mental stress has been reported to be directly or inversely proportional to blood pressure (BP). To explain this inconsistent relationship, we assumed effect-modification by body mass index (BMI).

METHODS AND RESULTS

We examined 1,673 Japanese male local government employees who were not taking antihypertensive drugs or had no history of cardiovascular disease. BP and BMI were recorded at yearly health checkups. Exposure to mental stress, smoking, drinking, exercising, and salty taste were checked by questionnaire in 1997 and 2002. The main effect and interaction of stress and BMI on the averages and changes of resting systolic and diastolic BPs over the 5 years were assessed by a general linear model by adjusting for confounders. Obesity (BMI ≥25kg/m(2)) was significantly related with higher average systolic and diastolic BPs (P<0.001, P<0.001, respectively), whereas mental stress was not, showing a significantly different relationship dependent on BMI (P for interaction =0.002, 0.004): a significant and directly proportional association with systolic and diastolic BPs (P=0.001, 0.001) in the obese, but borderline significant and inversely proportional association (P=0.07, 0.08) in the lean. Only BMI was significantly related to the degree of BP change.

CONCLUSIONS

Whereas BMI was proportionally associated with BP, BMI was a modifier which, depending on its level, inverted the direction of the association between chronic mental stress and resting BP.

Correlates of cortisol in human hair: implications for epidemiologic studies on health effects of chronic stress

Assessment of cortisol concentrations in hair is one of the latest innovations for measuring long-term cortisol exposure. We performed a systematic review of correlates of cortisol in human hair to inform the design, analysis, and interpretation of future epidemiologic studies. Relevant publications were identified through electronic searches on PubMed, WorldCat, and Web of Science using keywords, "cortisol," "hair," "confounders," "chronic," "stress," and "correlates." Thirty-nine studies were included in this review. Notwithstanding scarce data and some inconsistencies, investigators have found hair cortisol concentrations to be associated with stress-related psychiatric symptoms and disorders (e.g., post-traumatic stress disorder), medical conditions indicating chronic activation of the hypothalamic-pituitary-adrenal axis (e.g., Cushing's syndrome), and other life situations associated with elevated risk of chronic stress (e.g., shiftwork). Results from some studies suggest that physical activity, adiposity, and substance abuse may be correlates of hair cortisol concentrations. In contrast to measures of short-term cortisol release (saliva, blood, and urine), cigarette smoking and use of oral contraceptives appear not to be associated with hair cortisol concentrations. Studies of pregnant women indicate increased hair cortisol concentrations across successive trimesters. The study of hair cortisol presents a unique opportunity to assess chronic alterations in cortisol concentrations in epidemiologic studies.

Blunted cortisol response to stress is associated with higher body mass index in low-income preschool-aged children

No known studies have tested the hypothesis that a blunted pattern of cortisol reactivity to stress, which is often found following exposure to chronic life stressors, is associated with a higher body mass index (BMI) in very young children. Low-income children (n=218, mean age 56.6 (range: 38.1-78.5; SD 7.0) months, 49.1% male, 56.4% white, 16.1% black, 11.5% Hispanic/Latino) participated in a series of behavioral tasks designed to elicit stress. Cortisol was sampled in saliva 5 times during the protocol, and area under the curve (AUC), representing total cortisol output during stress elicitation, was calculated. Children were weighed and height measured and body mass index (BMI) z-score was calculated. Linear regression was used to evaluate the association between cortisol AUC and BMI z-score, controlling for child age, sex, and race/ethnicity (non-Hispanic white vs. not); primary caregiver weight status (overweight, defined as BMI ≥ 25 vs. not); and family income-to-needs ratio. Mean child BMI z-score was 0.88 (SD=1.03). Mean cortisol AUC was 6.11 μg/dL/min (SD=10.44). In the fully adjusted model, for each 1-standard deviation unit decrease in cortisol AUC, the child's BMI z-score increased by 0.17 (SE 0.07) standard deviation units (p<0.02). A blunted cortisol response to stress, as is often seen following chronic stress exposure, is associated with increased BMI z-score in very young children. Further work is needed to understand how associations between stress, cortisol, and elevated body mass index may develop very early in the lifespan.

Brain-derived neurotrophic factor expression ex vivo in obesity

Obesity is associated with an increased risk in neurodegenerative diseases. To counteract the neuronal damage, the human body increases brain-derived neurotrophic factor (BDNF) expression, leading to neuronal survival and plasticity. Recently, peripheral blood mononuclear cells (PBMCs) have been found to release BDNF as a potential neuroprotective role of inflammation. Therefore, the purpose of this study was to examine whether lipopolysaccharide (LPS)-induced PBMC activation would lead to differences in BDNF and inflammatory responses between obese and non-obese subjects. Thirty-one subjects (14 obese and 17 non-obese), ages 18 to 30years, were recruited. PBMCs were cultured for 24h with 10ng/mL LPS. BDNF, tumor necrosis factor-α (TNF-α), and interleukin-6 (IL-6) were measured in both plasma and cell culture supernatants. Our results did not illustrate any differences in plasma BDNF levels between obese and non-obese groups. However, obese subjects elicited a greater plasma IL-6 production, which was positively associated with plasma BDNF. Furthermore, LPS-induced PBMCs expressed significantly higher BDNF and IL-6 levels in obese subjects compared to the non-obese subjects. Finally, these BDNF levels were positively correlated with IL-6 response ex vivo. These findings suggest that under a high inflammatory state, PBMCs produce greater BDNF and IL-6 expression which may play a collaborative role to protect against neuronal damage associated with obesity.

Obesity and mental illness: implications for cognitive functioning

A priority research and clinical agenda is to identify determinants of cognitive impairment in individuals with neuropsychiatric disorders (NPD). The bidirectional association between NPD and cognitive performance has been reported to be mediated and/or moderated by obesity in a subset of individuals. Obesity can be conceptualized as a neurotoxic phenotype among individuals with NPD as evidenced by alterations in the structure and function of neural circuits and disseminated networks, diminished cognitive performance, and adverse effects on illness trajectory. The neurotoxic effect of obesity provides a rationale for screening, treating, and preventing obesity in neuropsychiatric populations. Research endeavors that aim to refine mediators and moderators of this association as well as novel strategies to reverse the injurious process of obesity on cognition are warranted.

The corpulent phenotype-how the brain maximizes survival in stressful environments

The reactivity of the stress system may change during the life course. In many—but not all—humans the stress reactivity decreases, once the individual is chronically exposed to a stressful and unsafe environment (e.g., poverty, work with high demands, unhappy martial relationship). Such an adaptation is referred to as habituation. Stress habituation allows alleviating the burden of chronic stress, particularly cardiovascular morbidity and mortality. Interestingly, two recent experiments demonstrated low stress reactivity during a mental or psychosocial challenge in subjects with a high body mass. In this focused review we attempt to integrate these experimental findings in a larger context. Are these data compatible with data sets showing a prolonged life expectancy in corpulent people? From the perspective of neuroenergetics, we here raise the question whether “obesity” is unhealthy at all. Is the corpulent phenotype possibly the result of “adaptive phenotypic plasticity” allowing optimized survival in stressful environments?