Status, stress, and atherosclerosis: the role of environment and individual behavior

Subcutaneous leiomyosarcoma in a cynomolgus macaque (Macaca fascicularis)

Leiomyosarcoma, a malignant tumour originating from smooth muscle cells, has rarely been documented in non-human primates. In this case study, a 7-year-old female cynomolgus macaque (Macaca fascicularis) presented with a rapidly growing mass overlying the left elbow joint. Radiographs indicated the presence of a soft tissue neoplasm without any associated bone involvement. The mass was surgically resected. Histological and immunohistochemical analyses revealed spindle-shaped cells with eosinophilic cytoplasm that resembled smooth muscle cells, exhibiting positive immunoreactions for vimentin, desmin and smooth muscle actin and a negative reaction for pan-cytokeratin. This is the first reported case of subcutaneous leiomyosarcoma in a cynomolgus macaque and provides important insights into the incidence and characteristics of this condition in this species.

Nanomedicine for Diagnosis and Treatment of Atherosclerosis

With the changing disease spectrum, atherosclerosis has become increasingly prevalent worldwide and the associated diseases have emerged as the leading cause of death. Due to their fascinating physical, chemical, and biological characteristics, nanomaterials are regarded as a promising tool to tackle enormous challenges in medicine. The emerging discipline of nanomedicine has filled a huge application gap in the atherosclerotic field, ushering a new generation of diagnosis and treatment strategies. Herein, based on the essential pathogenic contributors of atherogenesis, as well as the distinct composition/structural characteristics, synthesis strategies, and surface design of nanoplatforms, the three major application branches (nanodiagnosis, nanotherapy, and nanotheranostic) of nanomedicine in atherosclerosis are elaborated. Then, state-of-art studies containing a sequence of representative and significant achievements are summarized in detail with an emphasis on the intrinsic interaction/relationship between nanomedicines and atherosclerosis. Particularly, attention is paid to the biosafety of nanomedicines, which aims to pave the way for future clinical translation of this burgeoning field. Finally, this comprehensive review is concluded by proposing unresolved key scientific issues and sharing the vision and expectation for the future, fully elucidating the closed loop from atherogenesis to the application paradigm of nanomedicines for advancing the early achievement of clinical applications.

Delay discounting as a behavioral phenotype associated with social rank in female and male cynomolgus monkeys: Correlation with kappa opioid receptor availability

Cocaine use disorder (CUD) is a significant problem worldwide, with no FDA-approved treatments. Epidemiological data indicate that only about 17 % of people that use cocaine will meet DSM criteria for CUD. Thus, the identification of biomarkers predictive of eventual cocaine use may be of great value. Two potentially useful predictors of CUD are social hierarchies in nonhuman primates and delay discounting. Both social rank and preference for a smaller, immediate reinforcer relative to a larger, delayed reinforcer have been predictive of CUD. Therefore, we wanted to determine if there was also a relationship between these two predictors of CUD. In the present study, monkeys cocaine-naive responded under a concurrent schedule of 1- vs. 3-food pellets and delivery of the 3-pellet option was delayed. The primary dependent variable was the indifference point (IP), which is the delay that results in 50 % choice for both options. In the initial determination of IP, there were no differences based on sex or social rank of the monkeys. When the delays were redetermined after ~25 baseline sessions (range 5-128 sessions), dominant females and subordinate males showed the largest increases in IP scores from the first determination to the second. Because 13 of these monkeys had prior PET scans of the kappa opioid receptor (KOR), we examined the relationship between KOR availability and IP values and found that the change in IP scores from the first to the second determination significantly negatively predicted average KOR availability in most brain regions. Future studies will examine acquisition to cocaine self-administration in these same monkeys, to determine if IP values are predictive of vulnerability to cocaine reinforcement.

PET imaging of kappa opioid receptors and receptor expression quantified in neuron-derived extracellular vesicles in socially housed female and male cynomolgus macaques

Recent positron emission tomography (PET) studies of kappa opioid receptors (KOR) in humans reported significant relationships between KOR availability and social status, as well as cocaine choice. In monkey models, social status influences physiology, receptor pharmacology and behavior; these variables have been associated vulnerability to cocaine abuse. The present study utilized PET imaging to examine KOR availability in socially housed, cocaine-naïve female and male monkeys, and peripheral measures of KORs with neuron-derived extracellular vesicles (NDE). KOR availability was assessed in dominant and subordinate female and male cynomolgus macaques (N = 4/rank/sex), using PET imaging with the KOR selective agonist [11C]EKAP. In addition, NDE from the plasma of socially housed monkeys (N = 13/sex; N = 6-7/rank) were isolated by immunocapture method and analyzed for OPRK1 protein expression by ELISA. We found significant interactions between sex and social rank in KOR availability across 12 of 15 brain regions. This was driven by female data, in which KOR availability was significantly higher in subordinate monkeys compared with dominant monkeys; the opposite relationship was observed among males, but not statistically significant. No sex or rank differences were observed for NDE OPRK1 concentrations. In summary, the relationship between brain KOR availability and social rank was different in female and male monkeys. This was particularly true in female monkeys. We hypothesize that lower [11C]EKAP binding potentials were due to higher concentrations of circulating dynorphin, which is consistent with greater vulnerability in dominant compared with subordinate females. These findings suggest that the KOR is an important target for understanding the neurobiology associated with vulnerability to abused drugs and sex differences, and detectable in peripheral circulation.

Social status and susceptibility to wildfire smoke among outdoor-housed female rhesus monkeys: A natural experiment

Introduction

Wildfire smoke (WFS) exposure is a growing threat to human health, and lower socioeconomic position (SEP) has been shown to increase pollution susceptibility. Studies of SEP-related susceptibility, however, are often compromised due to spatial confounding between lower-SEP and pollution. Here we examine outdoor-housed nonhuman primates, living in natural social hierarchy in a common location, born during years of high vs. low WFS, to examine the separate and combined effects of WFS and social rank, an analog to SEP, on lung and immune function.

Methods

Twenty-one females were born during extreme WFS events in summer 2008; 22 were born in summer 2009, during low WFS. Pulmonary function and circulating cytokines were measured three years later, in adolescence. We estimated fine particulate (PM_2.5) and ozone exposures during each animal's first 90 days and three years of age using regulatory data. Early-life social status was estimated using maternal rank at birth, as rank in females is relatively stable throughout life, and closely approximates mother's rank. We tested associations among WFS exposure, rank, and endpoints using linear regression and ANOVA.

Results

Higher WFS exposure in infancy was, on average, associated with lower functional residual capacity (FRC), residual volume (RV), tissue compliance (Ct), and IL-8 secretion in adolescence. Higher social rank conferred significantly higher expiratory reserve volume (ERV) and functional residual capacity (FRC) solely among those born in the high-WFS year (2008). Differences in effects of rank between years were not significant after adjustment for multiple comparisons.

Conclusions

Exposure to WFS in infancy generally conferred lower adolescent respiratory volumes and inflammatory cytokines. Higher rank conferred higher respiratory volumes only among females born during WFS, suggesting the possibility that the health benefits of rank may be more apparent under environmental challenge.

Hypothalamus-pituitary-adrenal Axis in Glucolipid metabolic disorders

With the change of life style, glucolipid metabolic disorders (GLMD) has become one of the major chronic disorders causing public health and clinical problems worldwide. Previous studies on GLMD pay more attention to peripheral tissues. In fact, the central nervous system (CNS) plays an important role in controlling the overall metabolic balance. With the development of technology and the in-depth understanding of the CNS, the relationship between neuro-endocrine-immunoregulatory (NEI) network and metabolism had been gradually illustrated. As the hub of NEI network, hypothalamus-pituitary-adrenal (HPA) axis is important for maintaining the balance of internal environment in the body. The relationship between HPA axis and GLMD needs to be further studied. This review focuses on the role of HPA axis in GLMD and reviews the research progress on drugs for GLMD, with the hope to provide the direction for exploring new drugs to treat GLMD by taking the HPA axis as the target and improve the level of prevention and control of GLMD.

The Pathway From Social Status to Physical Health: Taking a Closer Look at Stress as a Mediator

Stress is often invoked as a potential contributor to disparities in physical health as a function of social status. Although there is good reason to believe that stress exposure and stress responses may be an important pathway linking lower social status to poor health, direct evidence is lacking. We summarize the evidence for this pathway and limitations of that evidence, focusing particularly on how stress is conceptualized and measured. We argue that in addition to more direct tests of mediation, the measurement of the mediator—stress—could also be improved. We also propose that measuring theory-specific stress exposures may be more fruitful than assessing general stress exposures (e.g., life events, global perceived stress) by increasing theoretical clarity and predictive utility of stress in this context.

Both diet and Helicobacter pylori infection contribute to atherosclerosis in pre- and postmenopausal cynomolgus monkeys

A number of viruses and bacterial species have been implicated as contributors to atherosclerosis, potentially providing novel pathways for prevention. Epidemiological studies examining the association between Helicobacter pylori and cardiovascular disease have yielded variable results and no studies have been conducted in nonhuman primates. In this investigation, we examined the relationship between H. pylori infection and atherosclerosis development in socially housed, pre- and postmenopausal cynomolgus macaques consuming human-like diets. Ninety-four premenopausal cynomolgus monkeys (Macaca fascicularis) were fed for 36 months an atherogenic diet deriving its protein from either casein lactalbumin(CL) or high isoflavone soy (SOY). Animals were then ovariectomized and fed either the same or the alternate diet for an additional 36 months. Iliac artery biopsies were obtained at the time of ovariectomy and iliac and coronary artery sections were examined at the end of the study. Evidence of H. pylori infection was found in 64% of the monkeys and 46% of animals had live H. pylori within coronary atheromas as determined by mRNA-specific in situ hybridization. There was a significant linear relationship between the densities of gastric and atheroma organisms. Helicobactor pylori infection correlated with increased intimal plaque area and thickness at both the premenopausal and postmenopausal time points and regardless of diet (p< 0.01), although animals consuming the SOY diet throughout had the least amount of atherosclerosis. Additionally, plasma lipid profiles, intimal collagen accumulation, ICAM-1, and plaque macrophage densities were adversely affected by H. pylori infection among animals consuming the CL diet, while the SOY diet had the opposite effect. Plaque measurements were more highly associated with the densities of cagA-positive H. pylori within coronary atheromas than with the densities of gastric organisms, whereas plasma lipid changes were associated with H. pylori infection, but not cagA status. This study provides strong evidence that live H. pylori infects atheromas, exacerbates atherosclerotic plaque development, and alters plasma lipid profiles independently of diet or hormonal status. Finally, socially subordinate animals relative to their dominant counterparts had a greater prevalence of H. pylori, suggesting a stress effect. The results indicate that early H. pylori eradication could prevent or delay development of cardiovascular disease.

Estradiol Replacement Timing and Obesogenic Diet Effects on Body Composition and Metabolism in Postmenopausal Macaques

Whether hormone replacement therapy has beneficial metabolic effects in postmenopausal women remains controversial because of between-study differences in menopausal duration, estrogen formulations, and diet. Additionally, animal studies have not reflected the typical human obesogenic, Western-style diet (WSD). In this study, we determined the effects of immediate 17β-estradiol (ImE) or delayed 17β-estradiol treatment on weight and metabolism parameters in old ovo-hysterectomized rhesus macaques consuming a WSD over a 30-month period. The placebo and ImE groups exhibited progressive gains in weight and fat mass, which ImE initially attenuated but did not prevent. Progression of insulin resistance (IR) was lessened by ImE compared with placebo under both fasting and IV glucose-stimulated conditions, plateauing in all groups between 24 and 30 months. Consequently, relative euglycemia was maintained through lower stimulated insulin levels with ImE than with placebo. Bone mineral density decreased in the placebo group but was maintained in the ImE group, whereas bone mineral content was unaffected by placebo and increased with ImE. Daily activity was reduced while macaques consumed a WSD and was not affected by ImE. Over time, total cholesterol, triglyceride, very-low-density cholesterol, high-density lipoprotein cholesterol (HDL-C), non-HDL-C, and IL-8 levels increased or trended upward in all animals, with only the change in HDL-C affected by ImE. Delayed estrogen treatment (months 24 to 30) had no significant impact on body composition or glucometabolic parameters. In summary, detrimental WSD-induced changes in body composition and metabolism were only temporarily ameliorated by ImE, with the important exception of glucose homeostasis, which benefited from E replacement even as body composition worsened.

Interindividual differences in neonatal sociality and emotionality predict juvenile social status in rhesus monkeys

In humans, socioeconomic status (SES) has profound outcomes on socio-emotional development and health. However, while much is known about the consequences of SES, little research has examined the predictors of SES due to the longitudinal nature of such studies. We sought to explore whether interindividual differences in neonatal sociality, temperament, and early social experiences predicted juvenile social status in rhesus monkeys (Macaca mulatta), as a proxy for SES in humans. We performed neonatal imitation tests in infants' first week of life and emotional reactivity assessments at 2 and 4 weeks of age. We examined whether these traits, as well as the rearing environment in the first 8 months of life (with the mother or with same-aged peers only) and maternal social status predicted juvenile (2-3 years old) social status following the formation of peer social groups at 8 months. We found that infants who exhibited higher rates of neonatal imitation and newborn emotional reactivity achieved higher social status as juveniles, as did infants who were reared with their mothers, compared to infants reared with peers. Maternal social status was only associated with juvenile status for infant dyads reared in the same maternal group, indicating that relative social relationships were transferred through social experience. These results suggest that neonatal imitation and emotional reactivity may reflect ingrained predispositions toward sociality that predict later outcomes, and that nonnormative social experiences can alter socio-developmental trajectories. Our results indicate that neonatal characteristics and early social experiences predict later social outcomes in adolescence, including gradients of social stratification.

Social stress shortens lifespan in mice

Stress and low socioeconomic status in humans confer increased vulnerability to morbidity and mortality. However, this association is not mechanistically understood nor has its causation been explored in animal models thus far. Recently, cellular senescence has been suggested as a potential mechanism linking lifelong stress to age‐related diseases and shorter life expectancy in humans. Here, we established a causal role for lifelong social stress on shortening lifespan and increasing the risk of cardiovascular disease in mice. Specifically, we developed a lifelong chronic psychosocial stress model in which male mouse aggressive behavior is used to study the impact of negative social confrontations on healthspan and lifespan. C57BL/6J mice identified through unbiased cluster analysis for receiving high while exhibiting low aggression, or identified as subordinate based on an ethologic criterion, had lower median and maximal lifespan, and developed earlier onset of several organ pathologies in the presence of a cellular senescence signature. Critically, subordinate mice developed spontaneous early‐stage atherosclerotic lesions of the aortic sinuses characterized by significant immune cells infiltration and sporadic rupture and calcification, none of which was found in dominant subjects. In conclusion, we present here the first rodent model to study and mechanistically dissect the impact of chronic stress on lifespan and disease of aging. These data highlight a conserved role for social stress and low social status on shortening lifespan and increasing the risk of cardiovascular disease in mammals and identify a potential mechanistic link for this complex phenomenon.

Effects of Immediate or Delayed Estradiol on Behavior in Old Menopausal Macaques on Obesogenic Diet

Macaques have served as effective models of human disease, including pathological processes associated with obesity and the metabolic syndrome. This study approached several questions: (1) does a western-style diet (WSD) contribute to sedentary behavior or is sedentary behavior a consequence of obesity and (2) does estradiol (E) hormone therapy offset WSD or ameliorate sedentary behavior? We further questioned whether the timing of E administration (immediately following hysterectomy, ImE; or after a 2-year delay, DE) would impact behavior. Focal observations were taken on the animals in social housing over a period of 2.5 years before and after initiation of the WSD and hysterectomy. In addition, anxiety was assessed through the Human Intruder and Novel Object Tests. All animals gained weight, but ImE delayed the time to maximum weight achieved at 18 months. Over the course of the study, ImE-treated monkeys spent more time "alone" and less time in "close social" contact than placebo-controls. The DE-treated monkeys were not different from placebo-controls in these 2 outcomes. The placebo-control group exhibited more "self-groom" behavior, an indicator of anxiety, than did the ImE-treated group, and DE-treated animals approached levels observed in the ImE-treated animals. All animals exhibited an increase in "consume" behavior over time with no statistical difference between the groups. By the end of the protocol, the placebo-control group exhibited less activity compared to ImE + DE-treated animals combined. Animals also showed increased anxiety after starting on the WSD in the Human Intruder Test and the Novel Object Test. In summary, the data indicated that WSD per se promoted increased consummatory behavior, sedentary behavior, and anxiety-type behaviors, whereas ImE promoted activity. Thus, WSD may precipitate the behaviors observed in humans who then become obese, sedentary, anxious, and socially isolated. ImE replacement ameliorates some of these behaviors, but not all.

Role of social interaction, exercise, diet, and age on developing and untreated diabetes in cynomolgus monkeys

Type 2 diabetes mellitus is the most common form of diabetes that occurs in both human and nonhuman primates. Although spontaneously diabetic nonhuman primates are used extensively in diabetic related research and are a proven valuable tool for the study of the natural history of diabetes, little is known about the key factors that can cause this metabolic disorder and the preventative measures that could be employed to minimize the consequences of diabetes. Using a model of developing and untreated diabetes, this study describes the effects of housing arrangement (socially group- versus individually single-housed), exercise, diet, age, and sex on fasting plasma glucose, key lipids associated with diabetes, and bodyweight in two large cohorts of nonhuman primates. Key findings include exercise/housing arrangement's contribution to significant differences in bodyweight, levels of fasting plasma glucose, total cholesterol, and high- and low-density lipoproteins. Age also had profound effects on glucose, triglyceride and high-density lipoproteins, particularly in single-caged animals. Moreover, females had higher fasting glucose, total cholesterol and triglyceride levels than male counterparts within the same housing situations. These factors may be critical to identifying preventive measures that could eventually be used to minimize obesity and diabetes in humans.

Animal models of atherosclerosis

Atherosclerosis is a significant cause of morbidity and mortality globally. Many animal models have been developed to study atherosclerosis, and permit experimental conditions, diet and environmental risk factors to be carefully controlled. Pathophysiological changes can be produced using genetic or pharmacological means to study the harmful consequences of different interventions. Experiments using such models have elucidated its molecular and pathophysiological mechanisms, and provided platforms for pharmacological development. Different models have their own advantages and disadvantages, and can be used to answer different research questions. In the present review article, different species of atherosclerosis models are outlined, with discussions on the practicality of their use for experimentation.

Conditioned social dominance threat: observation of others' social dominance biases threat learning

Social groups are organized along dominance hierarchies, which determine how we respond to threats posed by dominant and subordinate others. The persuasive impact of these dominance threats on mental and physical well-being has been well described but it is unknown how dominance rank of others bias our experience and learning in the first place. We introduce a model of conditioned social dominance threat in humans, where the presence of a dominant other is paired with an aversive event. Participants first learned about the dominance rank of others by observing their dyadic confrontations. During subsequent fear learning, the dominant and subordinate others were equally predictive of an aversive consequence (mild electric shock) to the participant. In three separate experiments, we show that participants' eye-blink startle responses and amygdala reactivity adaptively tracked dominance of others during observation of confrontation. Importantly, during fear learning dominant vs subordinate others elicited stronger and more persistent learned threat responses as measured by physiological arousal and amygdala activity. Our results characterize the neural basis of learning through observing conflicts between others, and how this affects subsequent learning through direct, personal experiences.

Decoupling social status and status certainty effects on health in macaques: a network approach

BACKGROUND

Although a wealth of literature points to the importance of social factors on health, a detailed understanding of the complex interplay between social and biological systems is lacking. Social status is one aspect of social life that is made up of multiple structural (humans: income, education; animals: mating system, dominance rank) and relational components (perceived social status, dominance interactions). In a nonhuman primate model we use novel network techniques to decouple two components of social status, dominance rank (a commonly used measure of social status in animal models) and dominance certainty (the relative certainty vs. ambiguity of an individual's status), allowing for a more complex examination of how social status impacts health.

METHODS

Behavioral observations were conducted on three outdoor captive groups of rhesus macaques (N = 252 subjects). Subjects' general physical health (diarrhea) was assessed twice weekly, and blood was drawn once to assess biomarkers of inflammation (interleukin-6 (IL-6), tumor necrosis factor-alpha (TNF-α), and C-reactive protein (CRP)).

RESULTS

Dominance rank alone did not fully account for the complex way that social status exerted its effect on health. Instead, dominance certainty modified the impact of rank on biomarkers of inflammation. Specifically, high-ranked animals with more ambiguous status relationships had higher levels of inflammation than low-ranked animals, whereas little effect of rank was seen for animals with more certain status relationships. The impact of status on physical health was more straightforward: individuals with more ambiguous status relationships had more frequent diarrhea; there was marginal evidence that high-ranked animals had less frequent diarrhea.

DISCUSSION

Social status has a complex and multi-faceted impact on individual health. Our work suggests an important role of uncertainty in one's social status in status-health research. This work also suggests that in order to fully explore the mechanisms for how social life influences health, more complex metrics of social systems and their dynamics are needed.

A Biobehavioral Framework to Address the Emerging Challenge of Multimorbidity

Multimorbidity, the co-occurrence of multiple physical or psychological illnesses, is prevalent particularly among older adults. The number of Americans with multiple chronic diseases is projected to increase from 57 million in 2000 to 81 million in 2020. However, behavioral medicine and health psychology, while focusing on the co-occurrence of psychological/psychiatric disorders with primary medical morbidities, have historically tended to ignore the co-occurrence of primary medical comorbidities, such as diabetes and cancer, and their biopsychosocial implications. This approach may hinder our ecologically valid understanding of the etiology, prevention, and treatment for individual patients with multimorbidity. In this selective review, we propose a heuristic behavioral framework for the etiology of multimorbidity. More acknowledgment and systematic research on multiple, co-existing disorders in behavioral medicine are consistent with the biopsychosocial model's emphasis on treating the "whole person," which means not considering any single illness, its symptoms, risk factors, or mechanisms, in isolation. As systems analytics, big data, machine learning, and mixed-model trajectory analyses, among others, come online and become more widely available, we may be able to tackle multimorbidity more holistically, efficiently, and satisfactorily.

The Cost of Color: Skin Color, Discrimination, and Health among African-Americans

In this study, the author uses a nationally representative survey to examine the relationship(s) between skin tone, discrimination, and health among African-Americans. He finds that skin tone is a significant predictor of multiple forms of perceived discrimination (including perceived skin color discrimination from whites and blacks) and, in turn, these forms of perceived discrimination are significant predictors of key health outcomes, such as depression and self-rated mental and physical health. Intraracial health differences related to skin tone (and discrimination) often rival or even exceed disparities between blacks and whites as a whole. The author also finds that self-reported skin tone, conceptualized as a form of embodied social status, is a stronger predictor of perceived discrimination than interviewer-rated skin tone. He discusses the implications of these findings for the study of ethnoracial health disparities and highlights the utility of cognitive and multidimensional approaches to ethnoracial and social inequality.

Examination of the potential association of stress with morbidity and mortality outcomes in patient with heart failure

Objectives:

The high mortality and morbidity rates associated with heart failure are still not well explained. A few psychosocial factors have been studied and explain some of this risk, but other factors, like stress, remain largely unexplored in heart failure. This study aimed to (1) examine the association of stress with 6-month cardiac event-free survival, (2) examine the relationship of stress with salivary cortisol, and (3) examine the association of salivary cortisol level with 6-month cardiac event-free survival.

Method:

A total of 81 heart failure patients participated. Stress was measured using the brief Perceived Stress Scale. Cortisol was measured from unstimulated whole expectorated saliva. Cox regression analyses were used to determine whether stress predicted event-free survival, and if salivary cortisol predicted event-free survival. Linear and multiple regressions were used to determine the association of stress with salivary cortisol.

Results:

Stress was not a significant predictor of event-free survival in heart failure (heart rate = 1.06; 95% confidence interval = 0.95–1.81; p = 0.32). Salivary cortisol was a significant predictor of event-free survival in the unadjusted model (heart rate = 2.30; 95% confidence interval = 0.99–5.927; p = 0.05), but not in the adjusted model. Stress (β 1.06; 95% confidence interval = 0.95–1.18; p = 0.32) was not a significant predictor of salivary cortisol level.

Conclusion:

Stress is a complex phenomenon, and our measure of stress may not have captured it well. Alternatively, the physical stressors acting in heart failure produce levels of neurohormonal activation that mask the effects of psychosocial stressors or an indirect association of stress with outcomes that is mediated through another construct. Future studies are needed to investigate stress in patients with heart failure to provide definitive answers.

CRH receptor antagonism reverses the effect of social subordination upon central GABAA receptor binding in estradiol-treated ovariectomized female rhesus monkeys

Persistent exposure to environmental stressors causes dysregulation of the limbic-hypothalamic-pituitary-adrenal (LHPA) axis and alters GABAA receptor (GABAAR) levels throughout the brain. Social subordination in socially housed female rhesus results in distinctive stress-related physiological and behavioral phenotypes that are dependent on the ovarian hormone estradiol (E2). In the present study, we utilized ovariectomized adult female rhesus monkeys undergoing hormone replacement with E2 to test the hypothesis that the chronic psychosocial stress of subordination alters GABAAR binding potential (GABAAR BPND) in limbic regions implicated in emotional processing including the prefrontal cortex, temporal lobe (amygdala and hippocampus), and hypothalamus. Furthermore, we tested the hypothesis that peripheral administration of a corticotropin-releasing hormone (CRH) receptor antagonist (astressin B) would reverse the alterations in GABAAR binding within these regions in subordinate females. After subjects received astressin B or saline for three consecutive days, GABAAR BPND was determined by positron emission tomography (PET) using (18)F-flumazenil as a radioligand. T1-weighted structural magnetic resonance imaging scans were also acquired for PET scan co-registration, in order to perform a region of interest analysis using the pons as a reference region. Compared to socially dominant females, subordinate females exhibited increased GABAAR BPND in the prefrontal cortex but not in the temporal lobe or the hypothalamus. Administration of astressin B eliminated the status difference in GABAAR BPND in the prefrontal cortex, suggesting that the chronic stressor of social subordination modulates GABAergic tone via effects on CRH and the LHPA axis, at least in prefrontal regions.

Considerations of sex and gender differences in preclinical and clinical trials

Women continue to be underrepresented in clinical trials, particularly in Phases I and II of experimental drug studies in spite of legislative guidelines in the USA, Canada, the European Union, Australia, and Japan requiring the inclusion of women in clinical trials. As such, women remain a vulnerable population subject to the adverse effects of pharmacological therapies. Thus, women experience higher rates of adverse drug reactions than do men and for women of reproductive age or who may be pregnant, therapeutic options may be limited. This chapter provides a brief history of inclusion of sex and gender as variables in clinical trials, summarizes governmental legislation for consideration of sex and gender in clinical trials and provides specific examples of drugs which have been withdrawn from the market because of side effects in women. Additional information related to sex and gender in preclinical testing, trial design, challenges to recruitment of women for clinical trials and statistical methods for analysis of data also is considered.

Nonhuman primate models of social behavior and cocaine abuse

RATIONALE

Although cocaine is often abused in social situations, very few animal studies examine the effects of cocaine in the context of social behavior.

OBJECTIVES

This review highlights studies investigating the behavioral effects of cocaine in the context of social housing conditions using nonhuman primates. In addition, this review presents recent findings examining the effects of self-administering cocaine on social behavior and the effects of manipulations hypothesized to be stressful or enriching on the interactions between cocaine reinforcement and social rank. The following dependent variables are examined: (1) cocaine-induced changes in social behavior and (2) cocaine self-administration in cynomolgus monkeys of varying social ranks. The independent variables examined include several environmental and pharmacological manipulations.

CONCLUSIONS

The studies reviewed here indicate that several variables can differentially affect cocaine self-administration when studied in a social context, rather than in individually housed animals. These variables include the social rank and sex of the individual, drug history, the nature of the "fear"-inducing manipulation, and the reliability of cortisol as an appropriate measure of "stress." While the inclusion of socially housed animals necessitates larger sample sizes, animal models incorporating social behavior are more homologous to the human condition and should be implemented when possible.

Systemic and local ACTH produced during inflammatory states promotes osteochondrogenic mesenchymal cell differentiation contributing to the pathologic progression of calcified atherosclerosis

There are many well-known roles for the proopiomelanocortin (POMC) derived peptides and their receptors, the melanocortin receptors (MC-R). The focus here is on the evolving role of the melanocortin system in inflammation. Chronic inflammatory states such as those occurring in diabetes and obesity are associated with both a hyperactive hypothalamic-pituitary-adrenal (HPA) axis as well as increased incidence of atherosclerosis. An inflammation-induced hyperactive HPA axis along with increased leukocyte infiltration can lead to significant exposure to melanocortin peptides, particularly ACTH, in an inflamed vasculature. Mesenchymal progenitor cells are present throughout the vasculature, express receptors for the melanocortin peptides, and respond to ACTH with increased osteochondrogenic differentiation. Coupled to the increased exposure to ACTH during HPA hyperactivity is increased glucocorticoid (GC) exposure. GCs also promote chondrogenic differentiation of mesenchymal progenitors and increase their expression of MC-R as well as their expression of POMC and its cleavage products. It is hypothesized that during inflammatory states systemically produced ACTH and glucocorticoid as well as ACTH produced locally by macrophage and other immune cells, can influence and potentiate mesenchymal progenitor cell differentiation along the osteochondrogenic lineages. In turn the increase in osteochondrogenic matrix contributes to the pathophysiological progression of the calcified atherosclerotic plaque. The roles of the melanocortin system in inflammation and its resolution have just begun to be explored. Investigations into the ACTH-induced matrix changes among mesenchymal cell populations are warranted. ACTH signaling through the MC-R represents a new therapeutic target for the prevention and treatment of calcified atherosclerosis.

Social subordination impairs hypothalamic-pituitary-adrenal function in female rhesus monkeys

Linear dominance hierarchies organize and maintain stability in female rhesus macaque (Macaca mulatta) social groups regardless of group size. As a consequence of their low social status, subordinate females suffer from an array of adverse outcomes including reproductive compromise, impaired immune function, and poor cardiovascular health. However, data that differentiate limbic-hypothalamic-pituitary-adrenal axis (LHPA) parameters between dominant from subordinate female monkeys are inconsistent, bringing into question whether social subordination alters the LHPA axis in female macaques. One difficulty in examining LHPA function in macaques may be the confounding effects of cycling ovarian steroids that are known to modulate LHPA activity. The current study used ovariectomized dominant and subordinate female rhesus monkeys to examine the effect that social subordination has on LHPA function by measuring morning and diurnal serum cortisol levels, dexamethasone (Dex) suppression of cortisol, metabolic clearance of Dex, and ACTH stimulation of adrenal cortisol release and cortisol response following exposure to acute social isolation. Compared to dominant females, subordinate females showed diminished morning peak cortisol secretion, weakened glucocorticoid negative feedback, and decreased adrenal cortisol response to an ACTH challenge as well as a restrained cortisol response following social isolation. However, the metabolism of Dex did not account for differences in Dex suppression between dominant and subordinate females. These results indicate that the ability to mount and limit glucocorticoid release is significantly reduced by psychosocial stress in female rhesus macaques, suggesting a hyporesponsive LHPA phenotype which resembles that observed in several human psychopathologies.

Nonhuman primates and other animal models in diabetes research

Animal models are important for determining the pathogenesis of and potential treatments for obesity and diabetes. Nonhuman primates (NHPs) are particularly useful for studying these disorders. As in humans, type 2 diabetes mellitus is the most common form of diabetes in NHPs and occurs more often in older obese animals, with a metabolic progression from insulin resistance (IR) and impaired glucose tolerance to overt diabetes. Histopathologic changes in pancreatic islets are also similar to those seen in humans with diabetes. Initially, there is islet hyperplasia with abundant insulin production to compensate for IR, followed by insufficient insulin production with replacement of islets with islet-associated amyloid. Diabetic NHPs also have adverse changes in plasma lipid and lipoprotein concentrations, biomarkers of obesity, inflammation, and oxidative stress, and protein glycation that contribute to the numerous complications of the disease. Furthermore, sex hormones, pregnancy, and environmental factors (e.g., diet and stress) affect IR and can also contribute to diabetes progression in NHPs. Additionally, due to their similar clinical and pathologic characteristics, NHPs have been used in many pharmacological studies to assess new therapeutic agents. For these reasons, NHPs are particularly valuable animal models of obesity and diabetes for studying disease pathogenesis, risk factors, comorbidities, and therapeutic interventions.

The monkey puzzle: a systematic review of studies of stress, social hierarchies, and heart disease in monkeys

BACKGROUND

It is often suggested that psychosocial factors, such as stress, or one's social position, may play an important role in producing social gradients in human disease. Evidence in favour of this model of health inequalities has relied, in part, on studies of the health effects of the natural social hierarchies found among non-human primates. This study aimed to assess the strength of this evidence.

METHODOLOGY/PRINCIPAL FINDINGS

A systematic review was carried out to identify all studies of psychosocial factors and coronary artery disease (CAD) in non-human primates. We searched databases (MEDLINE, PsycInfo, EMBASE, and Primatelit from inception to November 2010) to identify experimental and observational studies of the impact of social reorganisation, social instability, and disruption of dominance hierarchies on primate CAD outcomes. We also handsearched bibliographies and examined the citations to those studies in public health articles. Fourteen studies were found which presented evidence on CAD and social status and/or psychosocial stress. These suggested that the association between social status and disease may be sex-specific: in female monkeys dominant status may be protective, with subordinate females having a greater extent of atherosclerosis. In male monkeys the reverse may be the case.

CONCLUSIONS/SIGNIFICANCE

Overall, non-human primate studies present only limited evidence for an association between social status and CAD, Despite this, there is selective citation of individual non-human primate studies in reviews and commentaries relating to human disease aetiology. Such generalisation of data from monkey studies to human societies does not appear warranted.

Strategies and methods to study sex differences in cardiovascular structure and function: a guide for basic scientists

Background

Cardiovascular disease remains the primary cause of death worldwide. In the US, deaths due to cardiovascular disease for women exceed those of men. While cultural and psychosocial factors such as education, economic status, marital status and access to healthcare contribute to sex differences in adverse outcomes, physiological and molecular bases of differences between women and men that contribute to development of cardiovascular disease and response to therapy remain underexplored.

Methods

This article describes concepts, methods and procedures to assist in the design of animal and tissue/cell based studies of sex differences in cardiovascular structure, function and models of disease.

Results

To address knowledge gaps, study designs must incorporate appropriate experimental material including species/strain characteristics, sex and hormonal status. Determining whether a sex difference exists in a trait must take into account the reproductive status and history of the animal including those used for tissue (cell) harvest, such as the presence of gonadal steroids at the time of testing, during development or number of pregnancies. When selecting the type of experimental animal, additional consideration should be given to diet requirements (soy or plant based influencing consumption of phytoestrogen), lifespan, frequency of estrous cycle in females, and ability to investigate developmental or environmental components of disease modulation. Stress imposed by disruption of sleep/wake cycles, patterns of social interaction (or degree of social isolation), or handling may influence adrenal hormones that interact with pathways activated by the sex steroid hormones. Care must be given to selection of hormonal treatment and route of administration.

Conclusions

Accounting for sex in the design and interpretation of studies including pharmacological effects of drugs is essential to increase the foundation of basic knowledge upon which to build translational approaches to prevent, diagnose and treat cardiovascular diseases in humans.

Dihydrotestosterone differentially modulates the cortisol response of the hypothalamic-pituitary-adrenal axis in male and female rhesus macaques, and restores circadian secretion of cortisol in females

Here we used a within-subject design to evaluate hypothalamic-pituitary-adrenal (HPA) activity following replacement of low and high physiological levels of testosterone (T) to adult, gonadally-suppressed, male rhesus macaques, and replacement with sex-specific low and high physiological doses of dihydrotestosterone (DHT) in the same adult males as well as in adult, gonadally-suppressed, female rhesus macaques. As indexes of HPA axis activation following T and DHT replacement, serum levels of cortisol (CORT) were measured before and following dexamethasone (DEX) inhibition, and corticotrophin-releasing factor (CRF) induced activation. Female monkeys were assessed for differences in response associated with dominant (DOM) and subordinate (SUB) social status. Data show that the high physiological dose of DHT significantly decreased basal CORT in both male and female monkeys irrespective of social status, but reduced CRF-stimulated CORT only in males. SUB female monkeys showed a trend towards increased CRF-stimulated CORT release under high-dose DHT replacement compared to DOM females or males given the same treatment, indicating that androgens likely have no influence on reducing HPA activation under chronic psychosocial stress in females. The normal circadian rhythm of CORT release was absent in placebo-replaced SUB and DOM females and was restored with low-dose DHT replacement. These results indicate that DHT significantly reduces CRF-stimulated CORT release only in male monkeys, and plays a role in maintaining circadian changes in CORT release in female monkeys.

Social class rank, threat vigilance, and hostile reactivity

Lower-class individuals, because of their lower rank in society, are theorized to be more vigilant to social threats relative to their high-ranking upper-class counterparts. This class-related vigilance to threat, the authors predicted, would shape the emotional content of social interactions in systematic ways. In Study 1, participants engaged in a teasing interaction with a close friend. Lower-class participants--measured in terms of social class rank in society and within the friendship--more accurately tracked the hostile emotions of their friend. As a result, lower-class individuals experienced more hostile emotion contagion relative to upper-class participants. In Study 2, lower-class participants manipulated to experience lower subjective socioeconomic rank showed more hostile reactivity to ambiguous social scenarios relative to upper-class participants and to lower-class participants experiencing elevated socioeconomic rank. The results suggest that class affects expectations, perception, and experience of hostile emotion, particularly in situations in which lower-class individuals perceive their subordinate rank.

Fetal and maternal factors associated with infant mortality in vervet monkeys

BACKGROUND

Causes of infant death remain unknown in significant proportions of human and non-human primate pregnancies.

METHODS

A closed breeding colony with high rates of infant mortality had pregnancies assessed (n=153) by fetal measurements and maternal characteristics. Infant outcome was classified as neonatal death (stillborn or died <48 hours from birth), postnatal death (died 2-30 days) or surviving (alive after 30 days).

RESULTS

Fetal size did not predict outcome. Poor maternal glycemic control and low social ranking increased odds for adverse outcome (OR=3.72, P=0.01 and 2.27, P=0.04, respectively). Male sex was over-represented in stillbirths (P=0.04), and many were macrosomic, but size did not associate with maternal glycemic control measured as glycated hemoglobin A1c. Postnatally dead infants were smaller (P<0.01), which associated with behavioral factors and glycemic control.

CONCLUSIONS

Fetal growth estimates predicted gestational age but not fetal outcome. Maternal social status and metabolic health, particularly glycemic control, increased risks of adverse pregnancy outcome.

Impairment of ovarian function and associated health-related abnormalities are attributable to low social status in premenopausal monkeys and not mitigated by a high-isoflavone soy diet

BACKGROUND

Psychological stress may impair premenopausal ovarian function and contribute to risk for chronic disease. Soy isoflavones may also influence ovarian function and affect health. Here, we report the effects of a psychological stressor (subordinate social status) and dietary soy on reproductive function and related health indices in female monkeys. We hypothesized that reproductive compromise and adverse health outcomes would be induced in subordinate when compared with dominant monkeys and be mitigated by exposure to soy.

METHODS

Subjects were 95 adult cynomolgus monkeys (Macaca fascicularis) housed in social groups of five or six. Animals consumed a soy-free, animal protein-based diet during an 8-month Baseline phase and then, during a 32-month Treatment phase, consumed either the baseline diet or an identical diet that substituted high-isoflavone soy protein for animal protein.

RESULTS

Across more than 1200 menstrual cycles, subordinate monkeys consistently exhibited ovarian impairment [increased cycle length (P < 0.02) and variability (P < 0.02) and reduced levels of progesterone (P < 0.04) and estradiol (P < 0.04)]. Subordinate status was confirmed behaviorally and was associated with elevated cortisol (P < 0.04) and relative osteopenia (P < 0.05). Consumption of the soy diet had no significant effects.

CONCLUSIONS

(i) Psychological stress adversely affects ovarian function and related health indices in a well-accepted animal model of women's health; (ii) Similar effects may extend to women experiencing reproductive impairment of psychogenic origin; (iii) soy protein and isoflavones neither exacerbate nor mitigate the effects of an adverse psychosocial environment; and (iv) this study was limited by an inability to investigate the genetic and developmental determinants of social status.

Emergent patterns of social affiliation in primates, a model

Many patterns of affiliative behaviour have been described for primates, for instance: reciprocation and exchange of grooming, grooming others of similar rank, reconciliation of fights, and preferential reconciliation with more valuable partners. For these patterns several functions and underlying cognitive processes have been suggested. It is, however, difficult to imagine how animals may combine these diverse considerations in their mind. Although the co-variation hypothesis, by limiting the social possibilities an individual has, constrains the number of cognitive considerations an individual has to take, it does not present an integrated theory of affiliative patterns either. In the present paper, after surveying patterns of affiliation in egalitarian and despotic macaques, we use an individual-based model with a high potential for self-organisation as a starting point for such an integrative approach. In our model, called GrooFiWorld, individuals group and, upon meeting each other, may perform a dominance interaction of which the outcomes of winning and losing are self-reinforcing. Besides, if individuals think they will be defeated, they consider grooming others. Here, the greater their anxiety is, the greater their "motivation" to groom others. Our model generates patterns similar to many affiliative patterns of empirical data. By merely increasing the intensity of aggression, affiliative patterns in the model change from those resembling egalitarian macaques to those resembling despotic ones. Our model produces such patterns without assuming in the mind of the individual the specific cognitive processes that are usually thought to underlie these patterns (such as recordkeeping of the acts given and received, a tendency to exchange, memory of the former fight, selective attraction to the former opponent, and estimation of the value of a relationship). Our model can be used as a null model to increase our understanding of affiliative behaviour among primates, in particular macaques.

Social subordination and polymorphisms in the gene encoding the serotonin transporter enhance estradiol inhibition of luteinizing hormone secretion in female rhesus monkeys

Psychosocial factors, particularly social stress, may compromise reproduction. However, some individuals may be more susceptible to socially induced infertility. The present study used group-housed, adult, ovariectomized rhesus monkeys to test the hypothesis that exposure to psychosocial stress, imposed by social subordination, would enhance estradiol (E2)-negative feedback inhibition of LH. Because polymorphisms in the gene encoding the serotonin transporter (SLC6A4) may contribute to individual differences in response to adverse environments, we determined whether subordinate females with the short-promoter-length allele (s-variant) would show greater suppression of LH. Subordinate females, particularly those with the s-variant SLC6A4 genotype, received significantly higher rates of noncontact aggression from more dominant cage mates and had consistently lower body weights. Serum LH was not influenced by social status in the absence of E2. In contrast, subordinate females were hypersensitive to E2-negative feedback inhibition of LH. Furthermore, serum LH in subordinate females with s-variant SLC6A4 genotype was maximally suppressed by Day 4 of treatment, whereas nadir concentrations were not reached until later in treatment in other females. Finally, pharmacological elevation of serum cortisol potentiated E2-negative feedback inhibition in all females. The current data suggest that infertility induced by psychosocial stressors may be mediated by hypersensitivity to E2-negative feedback and that polymorphisms in the SLC6A4 gene may contribute to differences in reproductive compromise in response to chronic stress.

Metabolic consequences and vulnerability to diet-induced obesity in male mice under chronic social stress

Social and psychological factors interact with genetic predisposition and dietary habit in determining obesity. However, relatively few pre-clinical studies address the role of psychosocial factors in metabolic disorders. Previous studies from our laboratory demonstrated in male mice: 1) opposite status-dependent effect on body weight gain under chronic psychosocial stress; 2) a reduction in body weight in individually housed (Ind) male mice. In the present study these observations were extended to provide a comprehensive characterization of the metabolic consequences of chronic psychosocial stress and individual housing in adult CD-1 male mice. Results confirmed that in mice fed standard diet, dominant (Dom) and Ind had a negative energy balance while subordinate (Sub) had a positive energy balance. Locomotor activity was depressed in Sub and enhanced in Dom. Hyperphagia emerged for Dom and Sub and hypophagia for Ind. Dom also showed a consistent decrease of visceral fat pads weight as well as increased norepinephrine concentration and smaller adipocytes diameter in the perigonadal fat pad. On the contrary, under high fat diet Sub and, surprisingly, Ind showed higher while Dom showed lower vulnerability to obesity associated with hyperphagia. In conclusion, we demonstrated that social status under chronic stress and individual housing deeply affect mice metabolic functions in different, sometime opposite, directions. Food intake, the hedonic response to palatable food as well as the locomotor activity and the sympathetic activation within the adipose fat pads all represent causal factors explaining the different metabolic alterations observed. Overall this study demonstrates that pre-clinical animal models offer a suitable tool for the investigation of the metabolic consequences of chronic stress exposure and associated psychopathologies.

Plasma lipid-dependent and -independent effects of dietary soy protein and social status on atherogenesis in premenopausal monkeys: implications for postmenopausal atherosclerosis burden

OBJECTIVE

: Atherosclerosis developed during premenopausal years predicts postmenopausal atherosclerosis burden. The objective of this study was to determine the effects of dietary soy protein isolate (SPI) and social status on atherogenesis and arterial gene expression in a premenopausal monkey model.

DESIGN

: Socially housed premenopausal cynomolgus macaques (n = 84) were fed an atherogenic diet deriving protein from casein/lactalbumin or SPI (containing 1.88 mg isoflavones/g). After 36 months of diet consumption, iliac artery biopsies were assessed for atherosclerosis and expression of mRNA transcripts related to inflammation, macrophage and T-cell content, and estrogen receptors (ERs).

RESULTS

: SPI reduced plaque size (P < 0.05), total plasma cholesterol, non-high-density lipoprotein cholesterol (HDLc), and the total plasma cholesterol/HDLc ratio (all P < 0.003), while increasing triglycerides (P < 0.006) and HDLc (P < 0.0001). Arterial mRNA for CD68 (P < 0.001), CD3 (P < 0.02), and CD4 (P < 0.001) and inflammatory markers monocyte chemotactic protein-1, intercellular adhesion molecule-1, and interleukin-6 (all P < 0.0001) were also lower in the group receiving SPI. For most outcomes, this effect remained even after adjustments for plaque size and plasma lipid concentrations. Arterial ER-alpha was inversely associated with atherosclerosis (P < 0.02) and increased with SPI (P < 0.001). Subordinate monkeys had lower ER-beta (P < 0.02) and higher interleukin-6 (P < 0.05) transcripts but did not differ from dominant monkeys in extent of atherosclerosis (P > 0.9).

CONCLUSIONS

: Premenopausal consumption of SPI had plasma lipid-independent beneficial effects on the pathobiological processes involved in atherosclerotic plaque development, thus potentially establishing the basis for reduced postmenopausal complications. Dominant social status provided similar, albeit less extensive, benefits in risk markers.

Continuous expression of corticotropin-releasing factor in the central nucleus of the amygdala emulates the dysregulation of the stress and reproductive axes

An increase in corticotropin-releasing factor (CRF) is a putative factor in the pathophysiology of stress-related disorders. As CRF expression in the central nucleus of the amygdala (CeA) is important in adaptation to chronic stress, we hypothesized that unrestrained synthesis of CRF in CeA would mimic the consequences of chronic stress exposure and cause dysregulation of the hypothalamic-pituitary-adrenal (HPA) axis, increase emotionality and disrupt reproduction. To test this hypothesis, we used a lentiviral vector to increase CRF-expression site specifically in CeA of female rats. Increased synthesis of CRF in CeA amplified CRF and arginine vasopressin peptide concentration in the paraventricular nucleus of the hypothalamus, and decreased glucocorticoid negative feedback, both markers associated with the pathophysiology of depression. In addition, continuous expression of CRF in CeA also increased the acoustic startle response and depressive-like behavior in the forced swim test. Protein levels of gonadotropin-releasing hormone in the medial preoptic area were significantly reduced by continuous expression of CRF in CeA and this was associated with a lengthening of estrous cycles. Finally, sexual motivation but not sexual receptivity was significantly attenuated by continuous CRF synthesis in ovariectomized estradiol-progesterone-primed females. These data indicate that unrestrained CRF synthesis in CeA produces a dysregulation of the HPA axis, as well as many of the behavioral, physiological and reproductive consequences associated with stress-related disorders.Molecular Psychiatry (2009) 14, 37-50; doi:10.1038/mp.2008.91; published online 12 August 2008.

Relationship between social rank and cortisol and testosterone concentrations in male cynomolgus monkeys (Macaca fascicularis)

In nonhuman primate social groups, biological differences related to social status have proven useful for investigating the mechanisms of sensitivity to various disease states. Physiological and neurobiological differences between dominant and subordinate monkeys have been interpreted in the context of chronic social stress. The present experiments were designed to investigate the relationships between basal cortisol and testosterone concentrations and the establishment and maintenance of the social hierarchy in male cynomolgus monkeys. Cortisol concentrations were measured at baseline and following suppression with dexamethasone (DEX) and subsequent administration of adrenocorticotrophic hormone (ACTH) while monkeys were individually housed (n = 20) and after 3 months of social housing (n = 4/group), by which time dominance hierarchies had stabilised. Cortisol was also measured during the initial 3 days of social housing. Neither pre-social housing hormone concentrations, nor hypothalamic-pituitary-adrenal (HPA) axis sensitivity predicted eventual social rank. During initial social housing, cortisol concentrations were significantly higher in monkeys that eventually became subordinate; this effect dissipated within 3 days. During the 12 weeks of social housing, aggressive and submissive behaviours were observed consistently, forming the basis for assignment of social ranks. At this time, basal testosterone and cortisol concentrations were significantly higher in dominant monkeys and, after DEX suppression, cortisol release in response to a challenge injection of ACTH was significantly greater in subordinates. These results indicate that basal cortisol and testosterone concentrations and HPA axis function are state variables that differentially reflect position in the dominance hierarchy, rather than trait variables that predict future social status.

Workplace status and risk of hypertension among hourly and salaried aluminum manufacturing employees

An inverse relationship between workplace status and morbidity is well established; higher job status has been associated with reduced risks of heart disease, hypertension, and injury. Most research on job status, however, has focused on salaried populations, and it remains unclear whether job status operates similarly among hourly workers. Our objectives were to examine whether hourly status itself influences risk of hypertension after adjustment for socioeconomic confounders, and to explore the role of fine-scale job grade on hypertension incidence within hourly and salaried groups. We examined data for 14,999 aluminum manufacturing employees in 11 plants across the U.S., using logistic regression with adjustment for age, sex, race/ethnicity and other individual characteristics. Propensity score restriction was used to identify comparable groups of hourly and salaried employees, reducing confounding by sociodemographic characteristics. Job grade (coded 1 through 30, within hourly and salaried groups) was examined as a more refined measure of job status. Hourly status was associated with an increased risk of hypertension, after propensity restriction and adjustment for confounders. The observed effect of hourly status was stronger among women, although the propensity-restricted cohort was disproportionately male (96%). Among salaried workers, higher job grade was not consistently associated with decreased risk; among hourly employees, however, there was a significant trend, with higher job grades more protective against hypertension. Increasing the stringency of hypertension case criteria also increased the risk of severe or persistent hypertension for hourly employees.

Fasting differentially modulates the immunological system: its mechanism and sex difference

The immunological properties and hormonal metabolism in rodents are affected by physical and psychological stress more strongly in males than in females. To elucidate the mechanism and physiological significance of the sex difference in the susceptibility of animal to stresses, changes in the immunological system in plasma and intestine and hormonal status in plasma were compared among 8-week-old male and female ICR mice before and after fasting. During the fasting of animals, the expression of immunoglobulin A in intestinal mucosa, and cortisol, interleukin-10 and interferon-gamma in plasma increased. These changes occurred more apparently in males than in females. Under identical conditions, the plasma levels of testosterone decreased markedly with concomitant occurrence of apoptosis in the testis, while the plasma levels of estradiol decreased calmly, and no appreciable apoptosis occurred in the ovary. These results indicate that testosterone enhances the stress-induced modulation of the immune system by some mechanism that was antagonized by estradiol.

Anxiety characteristics independently and prospectively predict myocardial infarction in men the unique contribution of anxiety among psychologic factors

OBJECTIVES

This study investigated whether anxiety characteristics independently predicted the onset of myocardial infarction (MI) over an average of 12.4 years and whether this relationship was independent of other psychologic variables and risk factors.

BACKGROUND

Although several psychosocial factors have been associated with risk for MI, anxiety has not been examined extensively. Earlier studies also rarely addressed whether the association between a psychologic variable and MI was specific and independent of other psychosocial correlates.

METHODS

Participants were 735 older men (mean age 60 years) without a history of coronary disease or diabetes at baseline from the Normative Aging Study. Anxiety characteristics were assessed with 4 scales (psychasthenia, social introversion, phobia, and manifest anxiety) and an overall anxiety factor derived from these scales.

RESULTS

Anxiety characteristics independently and prospectively predicted MI incidence after controlling for age, education, marital status, fasting glucose, body mass index, high-density lipoprotein cholesterol, and systolic blood pressure in proportional hazards models. The adjusted relative risk (95% confidence interval [CI]) of MI associated with each standard deviation increase in anxiety variable was 1.37 (95% CI 1.12 to 1.68) for psychasthenia, 1.31 (95% CI 1.05 to 1.63) for social introversion, 1.36 (95% CI 1.10 to 1.68) for phobia, 1.42 (95% CI 1.14 to 1.76) for manifest anxiety, and 1.43 (95% CI 1.17 to 1.75) for overall anxiety. These relationships remained significant after further adjusting for health behaviors (drinking, smoking, and caloric intake), medications for hypertension, high cholesterol, and diabetes during follow-up and additional psychologic variables (depression, type A behavior, hostility, anger, and negative emotion).

CONCLUSIONS

Anxiety-prone dispositions appear to be a robust and independent risk factor of MI among older men.

Perigenual anterior cingulate morphology covaries with perceived social standing

Low socioeconomic status (SES) increases the risk for developing psychiatric and chronic medical disorders. A stress-related pathway by which low SES may affect mental and physical health is through the perception of holding a low social standing, termed low subjective social status. This proposal implicates overlapping brain regions mediating stress reactivity and socioemotional behaviors as neuroanatomical substrates that could plausibly link subjective social status to health-related outcomes. In a test of this proposal, we used a computational structural neuroimaging method (voxel-based morphometry) in a healthy community sample to examine the relationships between reports of subjective social status and regional gray matter volume. Results showed that after accounting for potential demographic confounds, subclinical depressive symptoms, dispositional forms of negative emotionality and conventional indicators of SES, self-reports of low subjective social status uniquely covaried with reduced gray matter volume in the perigenual area of the anterior cingulate cortex (pACC)-a brain region involved in experiencing emotions and regulating behavioral and physiological reactivity to psychosocial stress. The pACC may represent a neuroanatomical substrate by which perceived social standing relates to mental and physical health.

A bio-psycho-socio-molecular approach to pain and stress management

Stress and trauma are interconnected with the experience of pain. This connection is due to a physiological coupling of underlying molecular autoregulatory mechanisms, as well as phenomenological similarities. Nonpharmaceutical therapeutic approaches such as the relaxation response, a process that supports physiological stress reduction and decreases the negative mental and physical effects of stress, also facilitate pain relief, again demonstrating physiological commonalities. These behavioral approaches have a critical impact on molecular patterns of autoregulation, leading to the assumption of a bio-psycho-socio-molecular model of autoregulation, including stress and pain. Thus, molecules and behavior may be seen as two sides of the same problem in pain and stress relief.

Comparative evaluation of atenolol and metoprolol on cardiovascular complications associated with streptozotocin-induced diabetic rats

Recently, various clinical studies have indicated that lipophilic β-blockers reduce the coronary mortality in diabetic patients; however, systematic studies have not been reported. The objective of the present investigation was to compare the effects of chronic treatment with metoprolol and atenolol on cardiovascular complications in streptozotocin (STZ)-induced diabetic rats. Injection of STZ produced hyperglycemia, hypoinsulinemia, hyperlipidemia, increased blood pressure, cardiac hypertrophy, reduction in heart rate, and structural alterations in cardiac tissues. Metoprolol and atenolol effectively prevented the development of hypertension in diabetic rats. Metoprolol treatment produced a slight but significant reduction in serum glucose levels with elevation in serum insulin levels, while atenolol produced a slight increase in glucose levels but no effect on insulin levels. Moreover, neither metoprolol nor atenolol treatment reduced the elevated cholesterol levels in diabetic rats. Metoprolol treatment significantly prevented STZ-induced increase in triglyceride levels, but atenolol failed to produce this effect. Metoprolol exhibited a minimal improvement in STZ-induced bradycardia, whereas atenolol produced a further reduction in heart rate. Histological examination showed metoprolol treatment also prevented STZ-induced hypertrophy and some of the alterations in cardiomyocytes. In conclusion, our data suggest that metoprolol has some beneficial effects over atenolol with respect to cardiovascular complications associated with diabetes mellitus.

Acute psychosocial challenge and cardiac autonomic response in women: the role of estrogens, corticosteroids, and behavioral coping styles

Theoretical statements, as well as clinical and experimental data, suggest that the amplitude of cardiovascular reactivity to acute stressors can be a good predictor of preclinical and clinical cardiovascular states. The aim of the present study is to investigate the role of estrogens, the hypothalamic-pituitary-adrenocortical activity, and the behavioral profile in individual cardiac autonomic reactivity to brief laboratory stressors in women. Thirty-six adult, healthy women were exposed to a stress interview and a mental task test, each lasting 5 min. They were assigned to two experimental groups: D4, i.e. 4 days after menses beginning (follicular phase, n=18), and D14, i.e. 14 days after menses beginning (ovulatory phase, n=18). The cardiac measurements in the baseline, stress and recovery periods consisted in heart rate (average R-R interval) and parasympathetic tone (r-MSSD) quantification, while the HPA axis activity and stress reactivity were assessed via plasma cortisol and dehydroepiandrosterone concentrations. The ethological profile during the interview was drawn by means of non-verbal behavior analysis. The cardiac, adrenocortical and behavioral responses to the two stressors were similar in groups D4 and D14, despite significantly higher estradiol levels in the latter. Subjects with higher pre-stress cortisol levels had higher heart rate and lower vagal activity in the baseline, stress and recovery phases. Women showing higher level of submission were characterized by higher heart rate acceleration and vagal withdrawal during both the interview and the recovery phase. In addition, the subjects that exhibited greater displacement during the interview were also characterized by lower heart rate increments and less pronounced vagal suppression during post-stress recovery. In conclusion, the present results do not support a clear buffering role of estrogens in cardiovascular response to acute stressors. However, they confirm that baseline HPA axis activity can be predictive of cardiac autonomic activity and stress responsiveness. They also highlight the modulating role of the individual style of behavioral coping in cardiac sympathovagal stress reactivity. Therefore, the objective assessment of the individual behavioral profile via the analysis of non-verbal communication patterns might represent a powerful tool for identifying subjects with higher risk of cardiac events.

Cultural consonance and psychological distress: examining the associations in multiple cultural domains

Cultural consonance is the degree to which individuals, in their own beliefs and behaviors, approximate widely shared cultural models. In previous research in Brazil and the United States we found that higher cultural consonance in the cultural domains of lifestyle and social support was associated with lower psychological distress. The aim of this paper is to expand on these results in two ways. First, the measurement of cultural consonance has been improved through a closer link of cultural domain analyses and survey research. Second, the number of domains in which cultural consonance has been examined has been expanded to include-along with lifestyle and social support-family life, national identity, and food. We found that cultural consonance in these five domains can be conceptualized as two latent variables of generalized cultural consonance, and that this generalized cultural consonance is associated with lower psychological distress. These results continue to support the usefulness of cultural consonance as a theoretical construct in the explanation of human social suffering.

Living alone, patient sex and mortality after acute myocardial infarction

BACKGROUND

Psychosocial factors, including social support, affect outcomes of cardiovascular disease, but can be difficult to measure. Whether these factors have different effects on mortality post-acute myocardial infarction (AMI) in men and women is not clear.

OBJECTIVE

To examine the association between living alone, a proxy for social support, and mortality postdischarge AMI and to explore whether this association is modified by patient sex.

DESIGN

Historical cohort study.

PARTICIPANTS/SETTING

All patients discharged with a primary diagnosis of AMI in a major urban center during the 1998-1999 fiscal year.

MEASUREMENTS

Patients' sociodemographic and clinical characteristics were obtained by standardized chart review and linked to vital statistics data through December 2001.

RESULTS

Of 880 patients, 164 (18.6%) were living alone at admission and they were significantly more likely to be older and female than those living with others. Living alone was independently associated with mortality [adjusted hazard ratio (HR) 1.6, 95% confidence interval (CI) 1.0-2.5], but interacted with patient sex. Men living alone had the highest mortality risk (adjusted HR 2.0, 95% CI 1.1-3.7), followed by women living alone (adjusted HR 1.2, 95% CI 0.7-2.2), men living with others (reference, HR 1.0), and women living with others (adjusted HR 0.9, 95% CI 0.5-1.5).

CONCLUSIONS

Living alone, an easily measured psychosocial factor, is associated with significantly increased longer-term mortality for men following AMI. Further prospective studies are needed to confirm the usefulness of living alone as a prognostic factor and to identify the potentially modifiable mechanisms underlying this increased risk.

Social stress, immune functions and disease in rodents

The link between social factors, stress and health has been the focus of many interdisciplinary studies mostly because: (i) animals, including humans, often live in societies; (ii) positive and negative social relationships affect disease and well being; (iii) physiological alterations, which parallel social interactions also modulate immune and neuroendocrine functions. This review will focus on studies conducted on laboratory and wild rodents where social factors such as dyadic interactions, individual housing and differential group housing were investigated. The results obtained allow one to conclude that social factors in rodents are causally linked with immune disorders/disease susceptibility. In particular, lower lymphocyte proliferation and antigen-specific-IgG, granulocytosis and lymphopenia, as well as higher tumor induction and progression, are reliably associated with negative social events. Finally, due to the increasing utilization of social stress-based animal models the reliability of the concept of "social stress" and its evolutionary context are re-evaluated.