Circadian CLOCK-mediated regulation of target-tissue sensitivity to glucocorticoids: implications for cardiometabolic diseases

The human glucocorticoid receptor

Glucocorticoids are members of steroid hormones that are biosynthesized in the intermediate cellular zone of the adrenal cortex (zona fasciculata) and released into the peripheral blood as final products of the hypothalamic-pituitary-adrenal (HPA) axis, as well as under the control of the circadian biologic system. These molecules regulate every physiologic function of the organism as they bind to an almost ubiquitous hormone-activated transcription factor, the glucocorticoid receptor (GR), which influences the rate of transcription of a huge number of target genes amounting to up to 20% of the mammalian genome. The evolving progress of cellular, molecular and computational-structural biology and the implication of epigenetics in every-day clinical practice have enabled us a deeper and ever-increasing understanding of how target tissues respond to natural and synthetic glucocorticoids. In this chapter, we summarize the current knowledge on the structure, expression, function and signaling of the human glucocorticoid receptor in normal and pathologic conditions.

Overweight/obesity and physiological variables in workers exposed to rotating shift in a food production factory

Introduction

Shift work has been hypothesized as a potential risk factor for overweight/obesity or other metabolic changes. We examined the relationship between work shift and body mass index, waist-hip ratio, lipid profile, and glucose concentration in workers from a food manufacturing factory in Colombia.

Objectives

To investigate the association between shift work and changes in physiological variables in food manufacturing industry workers in Medellín, Colombia.

Methods

This cross-sectional study was conducted with 763 employees from a food manufacturing factory. Information was collected from the medical records from the occupational health provider institution in charge of workers' periodic follow-up.

Results

The study sample consisted of 637 (83.5%) men and 126 (16.5%) women. Mean age was 43.35 ± 9.8 years, and mean body mass index was 25.49 ± 3.23 kg/m2. After adjusting for potential confounders, logistic multivariate regression revealed a statistically significant association between shift work and higher body mass index and higher total cholesterol levels compared with dayshift (p < 0.05). Finally, the analysis of waist-hip ratio for each shift scheme and sex showed that this ratio was higher for rotating shift workers, with a significant difference for women.

Conclusions

Significant associations were observed between shift work and overweight/obesity and hypercholesterolemia. However, these findings should be confirmed by longitudinal studies.

Basic Concepts and Hormonal Regulators of the Stress System

BACKGROUND

Human organisms have to cope with a large number of external or internal stressful stimuli that threaten - or are perceived as threatening - their internal dynamic balance or homeostasis. To face these disturbing forces, or stressors, organisms have developed a complex neuroendocrine system, the stress system, which consists of the hypothalamic-pituitary-adrenal axis and the locus caeruleus/norepinephrine-autonomic nervous system.

SUMMARY

Upon exposure to stressors beyond a certain threshold, the activation of the stress system leads to a series of physiological and behavioral adaptations that help achieve homeostasis and increase the chances of survival. When, however, the stress response to stressors is inadequate, excessive, or prolonged, the resultant maladaptation may lead to the development of several stress-related pathologic conditions. Adverse environmental events, especially during critical periods of life, such as prenatal life, childhood, and puberty/adolescence, in combination with the underlying genetic background, may leave deep, long-term epigenetic imprints in the human expressed genome.

KEY MESSAGES

In this review, we describe the components of the stress system and its functional interactions with other homeostatic systems of the organism; we present the hormonal regulators of the stress response, and we discuss the development of stress-related pathologies.

The neuroendocrinology of stress: the stress-related continuum of chronic disease development

Stress is defined as a state of threatened homeodynamic balance by a wide range of intrinsic or extrinsic, real or perceived challenges or stimuli, defined as stressors. To preserve this optimal homeodynamic state within a physiologic range, organisms have developed a highly sophisticated system, the stress system, which serves self-regulation and adaptability of the organism by energy redirection according to the current needs. Repeated, ephemeral, and motivating stress states lead to adaptive responses and response habituations, being fairly beneficial; in contrast, inadequate, aversive, excessive, or prolonged stress may surpass the regulatory capacity and adjustive resources of the organism and produce maladaptive responses and a chronically altered homeodynamic state associated with compromised mental and physical health and life expectancy. Neuroendocrine responses to stress depend on developmental timing, duration, time of day and nature of stressors leading to a vulnerable phenotype with disrupted stress reactivity (i.e., hyper- or hypoactivation of the stress system), impaired glucocorticoid signaling, and accumulated cacostatic load with cumulatively elevated long-term risk of mental and physical morbidity. This article offers a brief overview on the organization and physiology of the human stress system and its (re)activity, refreshes the plethora of somatic effects of acute and chronic stress and discusses a conceptual model of acute and chronic stress pathophysiology as a continuum in chronic disease development.

Traumatic stress and the circadian system: neurobiology, timing and treatment of posttraumatic chronodisruption

Background: Humans have an evolutionary need for a well-preserved internal 'clock', adjusted to the 24-hour rotation period of our planet. This intrinsic circadian timing system enables the temporal organization of numerous physiologic processes, from gene expression to behaviour. The human circadian system is tightly and bidirectionally interconnected to the human stress system, as both systems regulate each other's activity along the anticipated diurnal challenges. The understanding of the temporal relationship between stressors and stress responses is critical in the molecular pathophysiology of stress-and trauma-related diseases, such as posttraumatic stress disorder (PTSD). Objectives/Methods: In this narrative review, we present the functional components of the stress and circadian system and their multilevel interactions and discuss how traumatic stress can affect the harmonious interplay between the two systems. Results: Circadian dysregulation after trauma exposure (posttraumatic chronodisruption) may represent a core feature of trauma-related disorders mediating enduring neurobiological correlates of traumatic stress through a loss of the temporal order at different organizational levels. Posttraumatic chronodisruption may, thus, affect fundamental properties of neuroendocrine, immune and autonomic systems, leading to a breakdown of biobehavioral adaptive mechanisms with increased stress sensitivity and vulnerability. Given that many traumatic events occur in the late evening or night hours, we also describe how the time of day of trauma exposure can differentially affect the stress system and, finally, discuss potential chronotherapeutic interventions. Conclusion: Understanding the stress-related mechanisms susceptible to chronodisruption and their role in PTSD could deliver new insights into stress pathophysiology, provide better psychochronobiological treatment alternatives and enhance preventive strategies in stress-exposed populations.

Ramadan Intermittent Fasting Affects Adipokines and Leptin/Adiponectin Ratio in Type 2 Diabetes Mellitus and Their First-Degree Relatives

Background

In view of the association of Ramadan intermittent fasting with profound changes in lifestyle both in nondiabetic and diabetic patients, the aim of this study was to investigate the effect of Ramadan fasting on adiponectin, leptin and leptin to adiponectin ratio (LAR), growth hormone (GH), human-sensitive C-reactive protein (hs-CRP), and diabetic and metabolic syndrome factors in patients with Type 2 Diabetes Mellitus (Type 2 DM), their first-degree relatives (FDRs), and healthy controls.

Methods

This cohort study involved 98 Yemeni male subjects aged 30-70 years old: 30 Type 2 DM, 37 FDRs of Type 2 diabetic patients, and 31 healthy control subjects. Subjects' body mass index (BMI), waist circumference (WC), and blood pressure (BP) were measured, and venous blood samples were collected twice: the first samples were collected a couple of days prior to Ramadan fasting (baseline) and the second samples after 3 weeks of fasting.

Results

Ramadan fasting did not affect BMI, WC, and BP in Type 2 DM and their FDRs with respect to the baseline levels prior to Ramadan, whereas triglyceride and cholesterol were borderline significantly decreased in Type 2 DM with no effect in FDRs. Fasting blood glucose was not affected in Type 2 DM but was significantly increased in FDRs and control groups, whereas glycated haemoglobin (HbA1c) was slightly decreased in Type 2 DM, FDRs, and healthy controls. C-peptide, insulin, and insulin resistance (HOMA-IR) were significantly increased in Type 2 DM and FDRs, with no effect in the control group, whereas β-cell function (HOMA-β) was significantly decreased in FDRs and controls with no change in Type 2 DM. Ramadan fasting significantly decreased GH in both FDRs and control groups, and significantly increased hs-CRP in the control with no effect in Type 2 DM and FDRs. Adiponectin was significantly decreased, and leptin and LAR were significantly increased in Type 2 DM, FDRs, and control groups.

Conclusion

Ramadan intermittent fasting decreased adiponectin and increased leptin, LAR, insulin, and insulin resistance in both Type 2 DM and FDRs as well as decreased GH in both FDRs and healthy controls and increased hs-CRP in healthy controls. Moreover, Ramadan intermittent fasting neither worsens a patient's glycemic parameters nor improves it, with the exception of a slight improvement in HbA1c in Type 2 DM, FDRs, and healthy controls.

EDN1-AS, A Novel Long Non-coding RNA Regulating Endothelin-1 in Human Proximal Tubule Cells

Endothelin-1 (ET-1) is a peptide hormone that functions as a vasoconstrictor in the vasculature, whereas in the collecting duct of the kidney it exerts blood pressure-lowering effects via natriuretic actions. Aberrant ET-1 signaling is associated with several pathological states including hypertension and chronic kidney disease. ET-1 expression is regulated largely through transcriptional control of the gene that encodes ET-1, EDN1. Here we report a long, non-coding RNA (lncRNA) that appears to be antisense to the EDN1 gene, called EDN1-AS. Because EDN1-AS represents a potential novel mechanism to regulate ET-1 expression, we examined the regulation of EDN1-AS expression and action. A putative glucocorticoid receptor response (GR) element upstream of the predicted EDN1-AS transcription start site was identified using the ENCODE database and the UCSC genome browser. Two homozygous deletion clones of the element were generated using CRISPR/Cas9. This deletion resulted in a significant increase in the expression of EDN1-AS, which was associated with increased secretion of ET-1 peptide from HK-2 cells (two-fold increase in KO cells vs. CNTL, n = 7, P < 0.05). Phenotypic characterization of these CRISPR clones revealed a difference in cell growth rates. Using a standard growth assay, we determined that the KO1 clone exhibited a three-fold increase in growth over 8 days compared to control cells (n = 4, P < 0.01) and the KO2 clone exhibited a two-fold increase (n = 4, P < 0.01). These results support a role for EDN1-AS as a novel regulatory mechanism of ET-1 expression and cellular proliferation.

Epigenetic Mechanisms of the Glucocorticoid Receptor

The glucocorticoid receptor (GR) has been shown to be important for mediating cellular responses to stress and circulating glucocorticoids. Ligand-dependent transcriptional changes induced by GR are observed across numerous tissues. However, the mechanisms by which GR achieves cell and tissue-specific effects are less clear. Epigenetic mechanisms have been proposed to explain some of these differences as well as some of the lasting, even transgenerational, effects of stress and glucocorticoid action. GR functions in tandem with epigenetic cellular machinery to coordinate transcription and shape chromatin structure. Here, we describe GR interactions with these effectors and how GR acts to reshape the epigenetic landscape in response to the environment.

Validation of the Patient Empowerment Strategies Questionnaire (PES-Q) in Greek adult patients with chronic insomnia: a pilot study on basic psychometric values

Aim:

The objectives of this study were to validate the Patient Empowerment Strategies Questionnaire (PES-Q) in a Greek sample and to study its psychometric properties in a sample of patients diagnosed with chronic insomnia.

Background:

This is a validation of the PES-Q in Attikon General Hospital, School of Medicine, National and Kapodistrian University of Athens. The questionnaire was administered to 93 subjects aged between 18 and 85 years (mean age ± SD: 54.7 ± 15.2, 28% males).

Methods:

The criterion validity of the questionnaire was tested with the use of four specific criteria: the Athens Insomnia Scale, the Pittsburg questionnaire (Pittsburg Sleep Quality Index), the Depression, Anxiety and Stress Scale, and the Self-Esteem Scale.

Findings:

According to factor analysis results, the structure of the original scale was confirmed by the presence of one main factor in the Greek sample, explaining 40.1% of the variance of PES-Q queries. The questionnaire showed satisfactory reliability (Cronbach’s α = 0.887). The results of the current study suggest that the PES-Q may be used as an accurate psychometric instrument for the purposes of chronic insomnia. Future research should examine the psychometric qualities of the PES-Q Greek version in a larger sample.

Cardiomyocyte transcription is controlled by combined MR and circadian clock signalling

We previously identified a critical pathogenic role for MR activation in cardiomyocytes that included a potential interaction between the MR and the molecular circadian clock. While glucocorticoid regulation of the circadian clock is undisputed, MR interactions with circadian clock signalling are limited. We hypothesised that the MR influences cardiac circadian clock signalling, and vice versa. 10nM aldosterone or corticosterone regulated CRY 1, PER1, PER2 and ReverbA (NR1D1) gene expression patterns in H9c2 cells over 24hr. MR-dependent regulation of circadian gene promoters containing GREs and E-box sequences was established for CLOCK, Bmal, CRY 1 and CRY2, PER1 and PER2 and transcriptional activators CLOCK and Bmal modulated MR-dependent transcription of a subset of these promoters. We also demonstrated differential regulation of MR target gene expression in hearts of mice 4hr after administration of aldosterone at 8AM versus 8PM. Our data support combined MR regulation of a subset of circadian genes and that endogenous circadian transcription factors CLOCK and Bmal modulate this response. This unsuspected relationship links MR in the heart to circadian rhythmicity at the molecular level and has important implications for the biology of MR signalling in response to aldosterone as well as cortisol. These data are consistent with MR signalling in the brain where, like the heart, it preferentially responds to cortisol. Given the undisputed requirement for diurnal cortisol release in the entrainment of peripheral clocks, the present study highlights the MR as an important mechanism for transducing the circadian actions of cortisol in addition to the GR in the heart.

Multilevel Interactions of Stress and Circadian System: Implications for Traumatic Stress

The dramatic fluctuations in energy demands by the rhythmic succession of night and day on our planet has prompted a geophysical evolutionary need for biological temporal organization across phylogeny. The intrinsic circadian timing system (CS) represents a highly conserved and sophisticated internal "clock," adjusted to the 24-h rotation period of the earth, enabling a nyctohemeral coordination of numerous physiologic processes, from gene expression to behavior. The human CS is tightly and bidirectionally interconnected to the stress system (SS). Both systems are fundamental for survival and regulate each other's activity in order to prepare the organism for the anticipated cyclic challenges. Thereby, the understanding of the temporal relationship between stressors and stress responses is critical for the comprehension of the molecular basis of physiology and pathogenesis of disease. A critical loss of the harmonious timed order at different organizational levels may affect the fundamental properties of neuroendocrine, immune, and autonomic systems, leading to a breakdown of biobehavioral adaptative mechanisms with increased stress sensitivity and vulnerability. In this review, following an overview of the functional components of the SS and CS, we present their multilevel interactions and discuss how traumatic stress can alter the interplay between the two systems. Circadian dysregulation after traumatic stress exposure may represent a core feature of trauma-related disorders mediating enduring neurobiological correlates of trauma through maladaptive stress regulation. Understanding the mechanisms susceptible to circadian dysregulation and their role in stress-related disorders could provide new insights into disease mechanisms, advancing psychochronobiological treatment possibilities and preventive strategies in stress-exposed populations.

Links between HPA axis and adipokines: clinical implications in paradigms of stress-related disorders

INTRODUCTION

In the human organism, a constant interplay exists between the stress system [which includes the activity of the hypothalamic-pituitary-adrenal (HPA) axis] and the adipose tissue. This interplay is mediated by hormones of the HPA axis such as corticotropin-releasing hormone (CRH), adrenocorticotropic hormone (ACTH) and glucocorticoids (GCs) and adipokines secreted by the adipose tissue.

AREAS COVERED

In this critical review, the bi-directional interactions between HPA axis and the most studied adipokines such as leptin and adiponectin, as well as the pro-inflammatory adipocytokines tumor necrosis factor (TNF) and interleukin (IL) 6 are presented. Furthermore, these interactions are described in normalcy as well as in specific clinical paradigms of stress-related disorders such as eating disorders, hypothalamic amenorrhea, and stress-related endogenous hypercortisolism states. Wherever new therapeutic strategies emerge, they are presented accordingly.

EXPERT COMMENTARY

Additional research is needed to clarify the mechanisms involved in the interplay between the HPA axis and the adipose tissue. Research should be focused, in particular, on the development of new therapeutic means targeting dysfunctional adipose tissue in stress-related situations.

Time-restricted feeding of a high-fat diet in male C57BL/6 mice reduces adiposity but does not protect against increased systemic inflammation

Time-restricted feeding (TRF) limits the duration of food availability without altering diet composition and can combat obesity in humans and mice. For this study we evaluated the effect of timing of food access during a TRF protocol on weight gain, adiposity, and inflammation. Young male C57BL/6 mice were placed on a high-fat (HF) diet (45% fat) for 8 weeks. Food access was unrestricted (HF) or restricted to 6 h per day, either for the first half (HF-early) or the second half (HF-late) of the active phase to resemble a window of time for food consumption early or late in the day in a human population. Weight, obesity-associated parameters, and inflammation were measured. TRF reduced weight gain over the 8-week period in mice consuming the same high-fat diet. Consistent with decreased weight gain in the TRF groups, body fat percentage, liver triglycerides, and plasma leptin and cholesterol levels were reduced. Adipose tissue inflammation, measured by CD11b+F4/80+ macrophage infiltration, was reduced in both TRF groups, but systemic tumor necrosis factor-α was increased in all groups consuming the high-fat diet. The HF-late group gained more weight than the HF-early group and had increased insulin resistance, while the HF-early group was protected. Therefore, a TRF protocol is beneficial for weight management when a high-fat diet is consumed, with food consumption earlier in the day showing greater health benefits. However, increased inflammatory markers in the TRF groups suggest that diet components can still increase inflammation even in the absence of overt obesity.

Ramadan fasting in Saudi Arabia is associated with altered expression of CLOCK, DUSP and IL-1alpha genes, as well as changes in cardiometabolic risk factors

BACKGROUND

During the fasting month of Ramadan, practicing Saudis develop severe disturbances in sleeping and feeding patterns. Concomitantly, cortisol circadian rhythm is abolished, diurnal cortisol levels are elevated and circulating levels of several adipokines are altered favouring insulin resistance.

AIM

To examine changes in the expression of CLOCK and glucocorticoid-controlled genes, such as DUSP1 and IL-1α in Saudi adults before and during Ramadan, and to investigate possible associations with selected cardiometabolic risk factors.

METHODS

Healthy young volunteers (5 females, 18 males; mean age +SEM = 23.2 +1.2 years) were evaluated before Ramadan and two weeks into it. Blood samples were collected at 9 am (±1 hour) and twelve hours later for determination of serum lipid profile, high sensitivity CRP (hsCRP), and adiponectin. The expression of CLOCK, DUSP1 and IL-1α was evaluated in circulating leukocytes.

RESULTS

Mean levels of GGT and morning adiponectin decreased, while those of LDL-c/ HDL-c and atherogenic index (AI) increased significantly in Ramadan compared to Shabaan. There was no significant difference between morning and evening adiponectin during Ramadan, while the diurnal rhythm of hsCRP was lost. CLOCK gene expression mean was significantly higher in morning than in evening during Shabaan. Mean morning and evening DUSP1 mRNA levels showed significant increase during Ramadan compared to Shabaan, however, its diurnal rhythm was maintained. Morning IL-1α mRNA expression remained significantly higher than in the evening during Ramadan, but was markedly decreased compared to Shabaan.

DISCUSSION

Ramadan fasting in Saudi Arabia is associated with improvements in some cardiometabolic risk factors, such as circulating GGT and hsCRP and leukocyte expression of IL-1α mRNA, suggesting that intermittent fasting might have a beneficial component. These benefits may be offset by the previously reported dysregulation in the circadian rhythm, excess glucocorticoid levels and action, and insulin resistance, explaining increased prevalence of cardiometabolic disorders and type 2 diabetes mellitus.

Mining the topography and dynamics of the 4D Nucleome to identify novel CNS drug pathways

The pharmacoepigenome can be defined as the active, noncoding province of the genome including canonical spatial and temporal regulatory mechanisms of gene regulation that respond to xenobiotic stimuli. Many psychotropic drugs that have been in clinical use for decades have ill-defined mechanisms of action that are beginning to be resolved as we understand the transcriptional hierarchy and dynamics of the nucleus. In this review, we describe spatial, temporal and biomechanical mechanisms mediated by psychotropic medications. Focus is placed on a bioinformatics pipeline that can be used both for detection of pharmacoepigenomic variants that discretize drug response and adverse events to improve pharmacogenomic testing, and for the discovery of novel CNS therapeutics. This approach integrates the functional topology and dynamics of the transcriptional hierarchy of the pharmacoepigenome, gene variant-driven identification of pharmacogenomic regulatory domains, and mesoscale mapping for the discovery of novel CNS pharmacodynamic pathways in human brain. Examples of the application of this pipeline are provided, including the discovery of valproic acid (VPA) mediated transcriptional reprogramming of neuronal cell fate following injury, and mapping of a CNS pathway glutamatergic pathway for the mood stabilizer lithium. These examples in regulatory pharmacoepigenomics illustrate how ongoing research using the 4D nucleome provides a foundation to further insight into previously unrecognized psychotropic drug pharmacodynamic pathways in the human CNS.

The Functional and Clinical Significance of the 24-Hour Rhythm of Circulating Glucocorticoids

Adrenal glucocorticoids are major modulators of multiple functions, including energy metabolism, stress responses, immunity, and cognition. The endogenous secretion of glucocorticoids is normally characterized by a prominent and robust circadian (around 24 hours) oscillation, with a daily peak around the time of the habitual sleep-wake transition and minimal levels in the evening and early part of the night. It has long been recognized that this 24-hour rhythm partly reflects the activity of a master circadian pacemaker located in the suprachiasmatic nucleus of the hypothalamus. In the past decade, secondary circadian clocks based on the same molecular machinery as the central master pacemaker were found in other brain areas as well as in most peripheral tissues, including the adrenal glands. Evidence is rapidly accumulating to indicate that misalignment between central and peripheral clocks has a host of adverse effects. The robust rhythm in circulating glucocorticoid levels has been recognized as a major internal synchronizer of the circadian system. The present review examines the scientific foundation of these novel advances and their implications for health and disease prevention and treatment.

Stress-Related and Circadian Secretion and Target Tissue Actions of Glucocorticoids: Impact on Health

Living organisms are highly complex systems that must maintain a dynamic equilibrium or homeostasis that requires energy to be sustained. Stress is a state in which several extrinsic or intrinsic disturbing stimuli, the stressors, threaten, or are perceived as threatening, homeostasis. To achieve homeostasis against the stressors, organisms have developed a highly sophisticated system, the stress system, which provides neuroendocrine adaptive responses, to restore homeostasis. These responses must be appropriate in terms of size and/or duration; otherwise, they may sustain life but be associated with detrimental effects on numerous physiologic functions of the organism, leading to a state of disease-causing disturbed homeostasis or cacostasis. In addition to facing a broad spectrum of external and/or internal stressors, organisms are subject to recurring environmental changes associated with the rotation of the planet around itself and its revolution around the sun. To adjust their homeostasis and to synchronize their activities to day/night cycles, organisms have developed an evolutionarily conserved biologic system, the "clock" system, which influences several physiologic functions in a circadian fashion. Accumulating evidence suggests that the stress system is intimately related to the circadian clock system, with dysfunction of the former resulting in dysregulation of the latter and vice versa. In this review, we describe the functional components of the two systems, we discuss their multilevel interactions, and we present how excessive or prolonged activity of the stress system affects the circadian rhythm of glucocorticoid secretion and target tissue effects.

Potential pleiotropic beneficial effects of adjuvant melatonergic treatment in posttraumatic stress disorder

Loss of circadian rhythmicity fundamentally affects the neuroendocrine, immune, and autonomic system, similar to chronic stress and may play a central role in the development of stress-related disorders. Recent articles have focused on the role of sleep and circadian disruption in the pathophysiology of posttraumatic stress disorder (PTSD), suggesting that chronodisruption plays a causal role in PTSD development. Direct and indirect human and animal PTSD research suggests circadian system-linked neuroendocrine, immune, metabolic and autonomic dysregulation, linking circadian misalignment to PTSD pathophysiology. Recent experimental findings also support a specific role of the fundamental synchronizing pineal hormone melatonin in mechanisms of sleep, cognition and memory, metabolism, pain, neuroimmunomodulation, stress endocrinology and physiology, circadian gene expression, oxidative stress and epigenetics, all processes affected in PTSD. In the current paper, we review available literature underpinning a potentially beneficiary role of an add-on melatonergic treatment in PTSD pathophysiology and PTSD-related symptoms. The literature is presented as a narrative review, providing an overview on the most important and clinically relevant publications. We conclude that adjuvant melatonergic treatment could provide a potentially promising treatment strategy in the management of PTSD and especially PTSD-related syndromes and comorbidities. Rigorous preclinical and clinical studies are needed to validate this hypothesis.

Stress and glucocorticoid receptor transcriptional programming in time and space: Implications for the brain-gut axis

BACKGROUND

Chronic psychological stress is associated with enhanced abdominal pain and altered intestinal barrier function that may result from a perturbation in the hypothalamic-pituitary-adrenal (HPA) axis. The glucocorticoid receptor (GR) exploits diverse mechanisms to activate or suppress congeneric gene expression, with regulatory variation associated with stress-related disorders in psychiatry and gastroenterology.

PURPOSE

During acute and chronic stress, corticotropin-releasing hormone drives secretion of adrenocorticotropic hormone from the pituitary, ultimately leading to the release of cortisol (human) and corticosterone (rodent) from the adrenal glands. Cortisol binds with the GR in the cytosol, translocates to the nucleus, and activates the NR3C1 (nuclear receptor subfamily 3, group C, member 1 [GR]) gene. This review focuses on the rapidly developing observations that cortisol is responsible for driving circadian and ultradian bursts of transcriptional activity in the CLOCK (clock circadian regulator) and PER (period circadian clock 1) gene families, and this rhythm is disrupted in major depressive disorder, bipolar disorder, and stress-related gastrointestinal and immune disorders. Glucocorticoid receptor regulates different sets of transcripts in a tissue-specific manner, through pulsatile waves of gene expression that includes occupancy of glucocorticoid response elements located within constitutively open spatial domains in chromatin. Emerging evidence supports a potentially pivotal role for epigenetic regulation of how GR interacts with other chromatin regulators to control the expression of its target genes. Dysregulation of the central and peripheral GR regulome has potentially significant consequences for stress-related disorders affecting the brain-gut axis.

Associations of Short Sleep and Shift Work Status with Hypertension among Black and White Americans

Objective. The purpose of this study was to investigate whether short sleepers (<6 hrs) who worked the non-day-shift were at greater likelihood of reporting hypertension and if these associations varied by individuals' ethnicity. Methods. Analysis was based on the 2010 National Health Interview Survey (NHIS). A total of 59,199 American adults provided valid data for the present analyses (mean age = 46.2 ± 17.7 years; 51.5% were female). Respondents provided work schedule and estimated habitual sleep durations as well as self-report of chronic conditions. Results. Of the sample, 30.8% reported a diagnosis of hypertension, 79.1% reported daytime shift work, 11.0% reported rotating shift work, and 4.0% reported night shift work. Logistic regression analysis showed that shift work was significantly associated with hypertension among Blacks [OR = 1.35, CI: 1.06–1.72. P < 0.05], but not among Whites [OR = 1.01, CI: 0.85–1.20, NS]. Black shift workers sleeping less than 6 hours had significantly increased odds of reporting hypertension [OR = 1.81, CI: 1.29–2.54, P < 0.01], while their White counterparts did not [OR = 1.17, CI: 0.90–1.52, NS]. Conclusions. Findings suggest that Black Americans working the non-day-shift especially with short sleep duration have increased odds of reporting hypertension.

Clock genes × stress × reward interactions in alcohol and substance use disorders

Adverse life events and highly stressful environments have deleterious consequences for mental health. Those environmental factors can potentiate alcohol and drug abuse in vulnerable individuals carrying specific genetic risk factors, hence producing the final risk for alcohol- and substance-use disorders development. The nature of these genes remains to be fully determined, but studies indicate their direct or indirect relation to the stress hypothalamo-pituitary-adrenal (HPA) axis and/or reward systems. Over the past decade, clock genes have been revealed to be key-players in influencing acute and chronic alcohol/drug effects. In parallel, the influence of chronic stress and stressful life events in promoting alcohol and substance use and abuse has been demonstrated. Furthermore, the reciprocal interaction of clock genes with various HPA-axis components, as well as the evidence for an implication of clock genes in stress-induced alcohol abuse, have led to the idea that clock genes, and Period genes in particular, may represent key genetic factors to consider when examining gene × environment interaction in the etiology of addiction. The aim of the present review is to summarize findings linking clock genes, stress, and alcohol and substance abuse, and to propose potential underlying neurobiological mechanisms.

Stress and inflammatory biomarkers and symptoms are associated with bioimpedance measures

BACKGROUND

This large cross-sectional, multi-centre study evaluated the association of body composition measurements by a novel dual frequency bioimpedance device (BIA-ACC) with chronic stress/inflammation biomarkers and the presence of medically unexplained symptoms (MUS).

MATERIALS AND METHODS

Participants were adult Caucasians of both sexes and included 10,416 lean subjects with no MUS (Group A), 58,710 lean subjects with MUS (Group B) and 30,445 overweight/obese subjects with no MUS and excessive fat mass (FM) (Group C).

RESULTS

Total body extracellular water (ECW) was higher, while intracellular water (ICW) was lower in Group B than both other groups (P < 0.01). Group A had significantly lower FM and higher skeletal mass (SK) and phase angle (PA) than Group B and lower circulating high sensitivity (hs) CRP levels than both other groups. hsCRP was higher in Group C than Group A though (P < 0.01). Salivary cortisol in Group B was lower in the morning and higher in the evening than both other groups (P < 0.001), indicating circadian rhythm obliteration or reversal in this group. ECW correlated positively with serum hsCRP and 8 p.m. salivary cortisol, but negatively with 8 a.m. salivary cortisol, while PA correlated positively with 8 a.m. and negatively with 8 p.m. salivary cortisol and serum hsCRP. Both 8 a.m. and 8 p.m. salivary cortisol and serum hsCRP were associated with the presence of MUS and BIA-ACC measurements, including ECW, ICW, FM, SK and PA.

CONCLUSIONS

MUS is an index of chronic stress and inflammation and BIA-ACC may provide a useful, bloodless and rapid tool in the clinical setting, distinguishing patients with chronic stress/inflammation from healthy subjects and monitoring their response to treatment.

The Healthy Lifestyle and Personal Control Questionnaire (HLPCQ): a novel tool for assessing self-empowerment through a constellation of daily activities

Background

The main goal of stress management and health promotion programs is to improve health by empowering people to take control over their lives. Daily health-related lifestyle choices are integral targets of these interventions and critical to evaluating their efficacy. To date, concepts such as self-efficacy, self-control and empowerment are assessed by tools that only partially address daily lifestyle choices. The aim of this study is to validate a novel measurement tool, the Healthy Lifestyle and Personal Control Questionnaire (HLPCQ), which aims to assess the concept of empowerment through a constellation of daily activities.

Methods

Therefore, we performed principal component analysis (PCA) of 26 items that were derived from the qualitative data of several stress management programs conducted by our research team.

Results

The PCA resulted in the following five-factor solution: 1) Dietary Healthy Choices, 2) Dietary Harm Avoidance, 3) Daily Routine, 4) Organized Physical Exercise and 5) Social and Mental Balance. All subscales showed satisfactory internal consistency and variance, relative to theoretical score ranges. Subscale scores and the total score were significantly correlated with perceived stress and health locus of control, implying good criterion validity. Associations with sociodemographic data and other variables, such as sleep quality and health assessments, were also found.

Conclusions

The HLPCQ is a good tool for assessing the efficacy of future health-promoting interventions to improve individuals’ lifestyle and wellbeing.

Study of the association between 3111T/C polymorphism of the CLOCK gene and the presence of overweight in schoolchildren

OBJECTIVES

To evaluate the association between 3111T/C polymorphism of the CLOCK gene and the presence of obesity and sleep duration in children aged 6-13 years. In adults, this genetic variant has been associated with duration of sleep, ghrelin levels, weight, and eating habits. Although short sleep duration has been linked to obesity in children, no study has aimed to identify the possible molecular mechanisms of this association to date.

METHODS

Weight, height, and circumferences were transformed into Z-scores for age and gender. Genotyping was performed using TaqMan methodology. A questionnaire regarding hours of sleep was provided to parents. The appropriate statistical tests were performed.

RESULTS

This study evaluated 370 children (45% males, 55% females, mean age 8.5 ± 1.5 years). The prevalence of overweight was 18%. The duration of sleep was, on average, 9.7hours, and was inversely related to age (p<0.001). Genotype distribution was: 4% CC, 31% CT, and 65% TT. There was a trend toward higher prevalence of overweight in children who slept less than nine hours (23%) when compared to those who slept more than ten hours (16%, p=0.06). Genotype was not significantly correlated to any of the assessed outcomes.

CONCLUSIONS

The CLOCK 3111T/C polymorphism was not significantly associated with overweight or sleep duration in children in this city.

Recent advances in the molecular mechanisms determining tissue sensitivity to glucocorticoids: novel mutations, circadian rhythm and ligand-induced repression of the human glucocorticoid receptor

Glucocorticoids are pleiotropic hormones, which are involved in almost every cellular, molecular and physiologic network of the organism, and regulate a broad spectrum of physiologic functions essential for life. The cellular response to glucocorticoids displays profound variability both in magnitude and in specificity of action. Tissue sensitivity to glucocorticoids differs among individuals, within tissues of the same individual and within the same cell. The actions of glucocorticoids are mediated by the glucocorticoid receptor, a ubiquitously expressed intracellular, ligand-dependent transcription factor. Multiple mechanisms, such as pre-receptor ligand metabolism, receptor isoform expression, and receptor-, tissue-, and cell type-specific factors, exist to generate diversity as well as specificity in the response to glucocorticoids. Alterations in the molecular mechanisms of glucocorticoid receptor action impair glucocorticoid signal transduction and alter tissue sensitivity to glucocorticoids. This review summarizes the recent advances in our understanding of the molecular mechanisms determining tissue sensitivity to glucocorticoids with particular emphasis on novel mutations and new information on the circadian rhythm and ligand-induced repression of the glucocorticoid receptor.

Circadian endocrine rhythms: the hypothalamic-pituitary-adrenal axis and its actions

The stress system effectively restores the internal balance--or homeostasis--of living organisms in the face of random external or internal changes, the stressors. This highly complex system helps organisms to provide a series of neuroendocrine responses to stressors--the stress response--through coordinated activation of the hypothalamic-pituitary-adrenal (HPA) axis and the locus coeruleus/norepinephrine autonomic nervous systems. In addition to stressors, life is influenced by daily light/dark changes due to the 24-h rotation of Earth. To adjust to these recurrent day/night cycles, the biological clock system employs the heterodimer of transcription factors circadian locomotor output cycle kaput/brain-muscle-arnt-like protein 1 (CLOCK/BMAL1), along with a set of other transcription factors, to regulate the circadian pattern of gene expression. Interestingly, the stress system, through the HPA axis, communicates with the clock system; therefore, any uncoupling or dysregulation could potentially cause several disorders, such as metabolic, autoimmune, and mood disorders. In this review, we discuss the biological function of the two systems, their interactions, and the clinical implications of their dysregulation or uncoupling.

Insulin effects on glucose tolerance, hypermetabolic response, and circadian-metabolic protein expression in a rat burn and disuse model

Insulin controls hyperglycemia after severe burns, and its use opposes the hypermetabolic response. The underlying molecular mechanisms are poorly understood, and previous research in this area has been limited because of the inadequacy of animal models to mimic the physiological effects seen in humans with burns. Using a recently published rat model that combines both burn and disuse components, we compare the effects of insulin treatment vs. vehicle on glucose tolerance, hypermetabolic response, muscle loss, and circadian-metabolic protein expression after burns. Male Sprague-Dawley rats were assigned to three groups: cage controls (n = 6); vehicle-treated burn and hindlimb unloading (VBH; n = 11), and insulin-treated burn and hindlimb unloading (IBH; n = 9). With the exception of cage controls, rats underwent a 40% total body surface area burn with hindlimb unloading, then IBH rats received 12 days of subcutaneous insulin injections (5 units·kg(-1)·day(-1)), and VBH rats received an equivalent dose of vehicle. Glucose tolerance testing was performed on day 14, after which blood and tissues were collected for analysis. Body mass loss was attenuated by insulin treatment (VBH = 265 ± 17 g vs. IBH = 283 ± 14 g, P = 0.016), and glucose clearance capacity was increased. Soleus and gastrocnemius muscle loss was decreased in the IBH group. Insulin receptor substrate-1, AKT, FOXO-1, caspase-3, and PER1 phosphorylation was altered by injury and disuse, with levels restored by insulin treatment in almost all cases. Insulin treatment after burn and during disuse attenuated the hypermetabolic response, increased glucose clearance, and normalized circadian-metabolic protein expression patterns. Therapies aimed at targeting downstream effectors may provide the beneficial effects of insulin without hypoglycemic risk.

Perceived stress scores among Saudi students entering universities: a prospective study during the first year of university life

In this prospective study we wanted to determine whether perceived stress over time among students in the Preparatory Year of King Saud University (KSU) predisposes them to cardiometabolic abnormalities. A total of 110 apparently healthy Saudi students (35 men and 75 women enrolled during the 2010−2011 academic year) were included. Perceived stress was determined at baseline and 1 year later. Anthropometrics were obtained and morning fasting serum glucose, lipid profile and cortisol were measured at both times. Perceived stress was noted among 48.2% of subjects at baseline and was not significantly different after follow-up, with 45.4% scoring high. In men, the prevalence of perceived stress was 48.6% at baseline (13 out of 35) and 37.1% at follow-up (13 out of 35), while in women it was 48% at baseline and 49.3% at follow-up. Interestingly, significant improvements in the blood pressure and lipid profiles, with the exception of HDL-cholesterol, were observed in both men and women, while fasting glucose also improved in women. Serum cortisol was inversely associated to fasting glucose, and total- and LDL-cholesterol (p-values 0.007, 0.04 and 0.04, respectively). These data are opposite to findings in students entering Western universities, in whom increasing stress and a deteriorating cardiometabolic profile have been repeatedly noted. Perceived stress and morning cortisol levels among students of the Preparatory Year in KSU remained constant for both genders over time, yet an improved cardiometabolic profile was observed, suggesting good adaptation among our pre-college students in their first year of university life.

Light stimulates the mouse adrenal through a retinohypothalamic pathway independent of an effect on the clock in the suprachiasmatic nucleus

The brain's master circadian pacemaker resides within the hypothalamic suprachiasmatic nucleus (SCN). SCN clock neurons are entrained to the day/night cycle via the retinohypothalamic tract and the SCN provides temporal information to the central nervous system and to peripheral organs that function as secondary oscillators. The SCN clock-cell network is thought to be the hypothalamic link between the retina and descending autonomic circuits to peripheral organs such as the adrenal gland, thereby entraining those organs to the day/night cycle. However, there are at least three different routes or mechanisms by which retinal signals transmitted to the hypothalamus may be conveyed to peripheral organs: 1) via retinal input to SCN clock neurons; 2) via retinal input to non-clock neurons in the SCN; or 3) via retinal input to hypothalamic regions neighboring the SCN. It is very well documented that light-induced responses of the SCN clock (i.e., clock gene expression, neural activity, and behavioral phase shifts) occur primarily during the subjective night. Thus to determine the role of the SCN clock in transmitting photic signals to descending autonomic circuits, we compared the phase dependency of light-evoked responses in the SCN and a peripheral oscillator, the adrenal gland. We observed light-evoked clock gene expression in the mouse adrenal throughout the subjective day and subjective night. Light also induced adrenal corticosterone secretion during both the subjective day and subjective night. The irradiance threshold for light-evoked adrenal responses was greater during the subjective day compared to the subjective night. These results suggest that retinohypothalamic signals may be relayed to the adrenal clock during the subjective day by a retinal pathway or cellular mechanism that is independent of an effect of light on the SCN neural clock network and thus may be important for the temporal integration of physiology and metabolism.

Molecular clocks in pharmacology

Circadian rhythms regulate a vast array of biological processes and play a fundamental role in mammalian physiology. As a result, considerable diurnal variation in the pharmacokinetics, efficacy, and side effect profiles of many therapeutics has been described. This variation has subsequently been tied to diurnal rhythms in absorption, distribution, metabolism, and excretion, as well as in pharmacodynamic variables, such as target expression. More recently, the molecular basis of circadian rhythmicity has been elucidated with the identification of clock genes, which oscillate in a circadian manner in most cells and tissues and regulate transcription of large sets of genes. Ongoing research efforts are beginning to reveal the critical role of circadian clock genes in the regulation of pharmacologic parameters, as well as the reciprocal impact of drugs on circadian clock function. This chapter will review the role of circadian clocks in the pharmacokinetics and pharmacodynamics of drug response and provide several examples of the complex regulation of pharmacologic systems by components of the molecular circadian clock.

Relative metabolic stability, but disrupted circadian cortisol secretion during the fasting month of Ramadan

BACKGROUND

Chronic feeding and sleep schedule disturbances are stressors that exert damaging effects on the organism. Practicing Muslims in Saudi Arabia go through strict Ramadan fasting from dawn till sunset for one month yearly. Modern era Ramadan practices in Saudi Arabia are associated with disturbed feeding and sleep patterns, namely abstaining from food and water and increasing daytime sleep, and staying awake and receiving food and water till dawn.

HYPOTHESIS

Strict Ramadan practices in Saudi Arabia may influence metabolism, sleep and circadian cortisol secretion.

PROTOCOL

Young, male Ramadan practitioners were evaluated before and two weeks into the Ramadan. Blood samples were collected at 9.00 am and 9.00 pm for measurements of metabolic parameters and cortisol. Saliva was collected serially during the day for cortisol determinations.

RESULTS

Ramadan practitioners had relative metabolic stability or changes expected by the pattern of feeding. However, the cortisol circadian rhythm was abolished and circulating insulin levels and HOMA index were increased during this period.

DISCUSSION

The flattening of the cortisol rhythm is typical of conditions associated with chronic stress or endogenous hypercortisolism and associated with insulin resistance.

CONCLUSIONS

Modern Ramadan practices in Saudi Arabia are associated with evening hypercortisolism and increased insulin resistance. These changes might contribute to the high prevalence of chronic stress-related conditions, such as central obesity, hypertension, metabolic syndrome and diabetes mellitus type 2, and their cardiovascular sequelae observed in the Kingdom.

Stress response and child health

Stress is defined as a state of real or perceived threat to homeostasis. The principal effectors of the stress system are corticotropin-releasing hormone (CRH), arginine vasopressin, the proopiomelanocortin-derived peptides α-melanocyte-stimulating hormone and β-endorphin, the glucocorticoids, and the catecholamines norepinephrine and epinephrine. Appropriate responsiveness of the stress system to stressors is a crucial prerequisite for a sense of well-being, adequate performance of tasks, and positive social interactions. By contrast, inappropriate responsiveness of the stress system may impair growth and development and may account for various endocrine, metabolic, autoimmune, and psychiatric disorders. The development and severity of these conditions primarily depend on the genetic vulnerability of the individual, the exposure to adverse environmental factors, and the timing of stressful event(s). Prenatal life, infancy, childhood, and adolescence are critical periods characterized by increased vulnerability to stressors. This review summarizes the topics presented at the fifth New Inroads to Child Health (NICHe) Conference "Stress Response and Child Health" held at Heraklion, Crete, Greece, in May 2012.

Circadian rhythms of glucocorticoid hormone actions in target tissues: potential clinical implications

Organisms face unforeseen short- and long-term changes in the environment (stressors). To defend against these changes, organisms have developed a stress system that includes the hypothalamic-pituitary-adrenal (HPA) axis, which employs glucocorticoids and the glucocorticoid receptor (GR) for signal transduction. In addition, organisms live under the strong influence of day-night cycles and, hence, have also developed a highly conserved circadian clock system for adjusting their activities to recurring environmental changes. This regulatory system creates and maintains internal circadian rhythmicity by employing a self-oscillating molecular pacemaker composed of the Clock-Bmal1 heterodimer and other transcription factors. The circadian clock consists of a central master clock in the suprachiasmatic nucleus of the brain hypothalamus and peripheral slave clocks in virtually all organs and tissues. The HPA axis and the circadian clock system communicate with each other at multiple levels. The central clock controls the HPA axis, creating the diurnal oscillation of circulating adrenocorticotropic hormone and cortisol, and the HPA axis adjusts the circadian rhythmicity of the peripheral clocks in response to various stressors through the GR. Further, Clock-Bmal1 regulates the response to glucocorticoids in peripheral tissues through acetylation of the GR, possibly antagonizing the biologic actions of diurnally fluctuating circulating cortisol. Importantly, dysregulation in the clock system and the HPA axis may cause similar pathologic manifestations--including obesity, metabolic syndrome, and cardiovascular disease--by uncoupling circulating cortisol concentrations from tissue sensitivity to glucocorticoids.

Metabolic consequences of stress during childhood and adolescence

Stress, that is, the state of threatened or perceived as threatened homeostasis, is associated with activation of the stress system, mainly comprised by the hypothalamic-pituitary-adrenal axis and the arousal/sympathetic nervous systems. The stress system normally functions in a circadian manner and interacts with other systems to regulate a variety of behavioral, endocrine, metabolic, immune, and cardiovascular functions. However, the experience of acute intense physical or emotional stress, as well as of chronic stress, may lead to the development of or may exacerbate several psychologic and somatic conditions, including anxiety disorders, depression, obesity, and the metabolic syndrome. In chronically stressed individuals, both behavioral and neuroendocrine mechanisms promote obesity and metabolic abnormalities: unhealthy lifestyles in conjunction with dysregulation of the stress system and increased secretion of cortisol, catecholamines, and interleukin-6, with concurrently elevated insulin concentrations, lead to development of central obesity, insulin resistance, and the metabolic syndrome. Fetal life, childhood, and adolescence are particularly vulnerable periods of life to the effects of intense acute or chronic stress. Similarly, these life stages are crucial for the later development of behavioral, metabolic, and immune abnormalities. Developing brain structures and functions related to stress regulation, such as the amygdala, the hippocampus, and the mesocorticolimbic system, are more vulnerable to the effects of stress compared with mature structures in adults. Moreover, chronic alterations in cortisol secretion in children may affect the timing of puberty, final stature, and body composition, as well as cause early-onset obesity, metabolic syndrome, and type 2 diabetes mellitus. The understanding of stress mechanisms leading to metabolic abnormalities in early life may lead to more effective prevention and intervention strategies of obesity-related health problems.

Maps and legends: the quest for dissociated ligands of the glucocorticoid receptor

Glucocorticoids are steroid hormones that have pleiotropic effects on development, metabolism, cognitive function and other aspects of physiology. Since the demonstration more than sixty years ago of their capacity to suppress inflammation, synthetic glucocorticoids have been extremely widely used in the treatment of inflammatory diseases. However, their clinical use is limited by numerous, unpredictable and potentially serious side effects. Glucocorticoids regulate gene expression both positively and negatively. Both of these effects are mediated by the glucocorticoid receptor, a ligand-dependent transcription factor. It has become widely accepted that anti-inflammatory effects of glucocorticoids are mostly due to inhibition of transcription, whereas the activation of transcription by the glucocorticoid receptor accounts for the majority of side effects. This dogma (which we refer to as the "transrepression hypothesis") predicts the possibility of uncoupling therapeutic, anti-inflammatory effects from side effects by identifying novel, selective ligands of the glucocorticoid receptor, which preferentially mediate inhibition rather than activation of transcription. It is argued that such "dissociated" glucocorticoid receptor ligands should retain anti-inflammatory potency but cause fewer side effects. Here we critically re-examine the history and foundations of the transrepression hypothesis. We argue that it is incompatible with the complexity of gene regulation by glucocorticoids and poorly supported by experimental evidence; that it no longer aids clear thinking about the actions of the glucocorticoid receptor; and that it will not prove a fruitful basis for continued refinement and improvement of anti-inflammatory drugs that target the glucocorticoid receptor.

Tripartite control of dynamic ACTH-cortisol dose responsiveness by age, body mass index, and gender in 111 healthy adults

BACKGROUND

Recent analyses in small cohorts suggest that pituitary hormones exert time-varying (viz., initial and delayed) dynamic dose-responsive effects on target glands, wherein down-regulating dynamics are inferable on a time scale of single pulses.

HYPOTHESIS

Age, body mass index (BMI), and sex modulate the rapid potency-down-regulating dynamics of pulsatile pituitary ACTH-adrenal cortisol coupling overnight.

LOCATION

The study was conducted at a clinical translational research unit.

SUBJECTS

Subjects included healthy adults (48 women, 63 men; aged 18-77 yr; BMI 18-42 kg/m(2)).

OUTCOMES

Outcomes included analytical dose-response estimates of endogenous ACTH efficacy, dynamic ACTH potency, and adrenal sensitivity from overnight 10-min ACTH-cortisol profiles.

RESULTS

Stepwise backward-elimination, multivariate-regression analysis revealed that in the combined cohorts (n = 111), age was associated with enhanced initial ACTH potency (R = 0.265, P = 0.005). Moreover, age and BMI jointly attenuated adrenal sensitivity (R = 0.334, P = 0.0017) and augmented down-regulated ACTH potency (R = 0.321 and P = 0.0028). Exploratory gender-segmented analyses showed that these outcomes might be explained by: (1) a negative effect of age in men on adrenal sensitivity (R = 0.270, P = 0.034) and (2) positive effects of age in men (R = 0.332, P = 0.0019) and BMI in women (R = 0.331, P = 0.024) on initial ACTH potency.

CONCLUSIONS

In healthy adults, adrenal sensitivity to endogenous ACTH pulses, ACTH efficacy, and ACTH potency is associated with age, BMI, and gender. These findings may explain conflicting data in earlier literature and introduce the need to control all three of age, BMI, and sex in future studies of the stress-adaptive axis.