The role of adipokines in the rapid antidepressant effects of ketamine

We previously found that body mass index (BMI) strongly predicted response to ketamine. Adipokines have a key role in metabolism (including BMI). They directly regulate inflammation and neuroplasticity pathways and also influence insulin sensitivity, bone metabolism and sympathetic outflow; all of these have been implicated in mood disorders. Here, we sought to examine the role of three key adipokines-adiponectin, resistin and leptin-as potential predictors of response to ketamine or as possible transducers of its therapeutic effects. Eighty treatment-resistant subjects who met DSM-IV criteria for either major depressive disorder (MDD) or bipolar disorder I/II and who were currently experiencing a major depressive episode received a single ketamine infusion (0.5 mg kg^-1 for 40 min). Plasma adipokine levels were measured at three time points (pre-infusion baseline, 230 min post infusion and day 1 post infusion). Overall improvement and response were assessed using percent change from baseline on the Montgomery-Asberg Depression Rating Scale and the Hamilton Depression Rating Scale. Lower baseline levels of adiponectin significantly predicted ketamine's antidepressant efficacy, suggesting an adverse metabolic state. Because adiponectin significantly improves insulin sensitivity and has potent anti-inflammatory effects, this finding suggests that specific systemic abnormalities might predict positive response to ketamine. A ketamine-induced decrease in resistin was also observed; because resistin is a potent pro-inflammatory compound, this decrease suggests that ketamine's anti-inflammatory effects may be transduced, in part, by its impact on resistin. Overall, the findings suggest that adipokines may either predict response to ketamine or have a role in its possible therapeutic effects.

Chronic administration of anticonvulsants but not antidepressants impairs bone strength: clinical implications

Major depression and bipolar disorder are associated with decreased bone mineral density (BMD). Antidepressants such as imipramine (IMIP) and specific serotonin reuptake inhibitors (SSRIs) have been implicated in reduced BMD and/or fracture in older depressed patients. Moreover, anticonvulsants such as valproate (VAL) and carbamazepine (CBZ) are also known to increase fracture rates. Although BMD is a predictor of susceptibility to fracture, bone strength is a more sensitive predictor. We measured mechanical and geometrical properties of bone in 68 male Sprague Dawley rats on IMIP, fluoxetine (FLX), VAL, CBZ, CBZ vehicle and saline (SAL), given intraperitoneally daily for 8 weeks. Distinct regions were tested to failure by four-point bending, whereas load displacement was used to determine stiffness. The left femurs were scanned in a MicroCT system to calculate mid-diaphyseal moments of inertia. None of these parameters were affected by antidepressants. However, VAL resulted in a significant decrease in stiffness and a reduction in yield, and CBZ induced a decrease in stiffness. Only CBZ induced alterations in mechanical properties that were accompanied by significant geometrical changes. These data reveal that chronic antidepressant treatment does not reduce bone strength, in contrast to chronic anticonvulsant treatment. Thus, decreased BMD and increased fracture rates in older patients on antidepressants are more likely to represent factors intrinsic to depression that weaken bone rather than antidepressants per se. Patients with affective illness on anticonvulsants may be at particularly high risk for fracture, especially as they grow older, as bone strength falls progressively with age.

Pathological parainflammation and endoplasmic reticulum stress in depression: potential translational targets through the CNS insulin, klotho and PPAR-γ systems

Major depression and bipolar disorder are heterogeneous conditions in which there can be dysregulation of (1) the stress system response, (2) its capacity for counterregulation after danger has passed and (3) the phase in which damaging molecules generated by the stress response are effectively neutralized. The response to stress and depressed mood share common circuitries and mediators, and each sets into motion not only similar affective and cognitive changes, but also similar systemic manifestations. We focus here on two highly interrelated processes, parainflammation and endoplasmic reticulum (ER) stress, each of which can potentially interfere with all phases of a normal stress response in affective illness, including adaptive neuroplastic changes and the ability to generate neural stem cells. Parainflammation is an adaptive response of the innate immune system that occurs in the context of stressors to which we were not exposed during our early evolution, including overfeeding, underactivity, aging, artificial lighting and novel foodstuffs and drugs. We postulate that humans were not exposed through evolution to the current level of acute or chronic social stressors, and hence, that major depressive illness is associated with a parainflammatory state. ER stress refers to a complex program set into motion when the ER is challenged by the production or persistence of more proteins than it can effectively fold. If the ER response is overwhelmed, substantial amounts of calcium are released into the cytoplasm, leading to apoptosis. Parainflammation and ER stress generally occur simultaneously. We discuss three highly interrelated mediators that can effectively decrease parainflammation and ER stress, namely the central insulin, klotho and peroxisome proliferator-activated receptor-γ (PPAR-γ) systems and propose that these systems may represent conceptually novel therapeutic targets for the amelioration of the affective, cognitive and systemic manifestations of major depressive disorder.

Low early morning plasma cortisol in posttraumatic stress disorder is associated with co-morbid depression but not with enhanced glucocorticoid feedback inhibition

BACKGROUND

Co-morbid major depressive disorder (MDD) in individuals with posttraumatic stress disorder (PTSD) confers a more severe clinical course and is associated with distinct biologic abnormalities. Although dysregulation in the hypothalamic pituitary adrenal (HPA) axis has been well established in PTSD, the impact of commonly co-occuring MDD has received scant attention.

METHODS

Overnight (7p.m. to 7a.m.) plasma cortisol, adrenocorticotropic hormone (ACTH), dehydroepiandrosterone sulphate (DHEA-S) were measured at 30 min intervals in 9 participants with PTSD with MDD (PTSD+MDD), 9 with PTSD without MDD (PTSD-MDD) and 16 non-traumatized healthy controls. A low-dose dexamethasone suppression test was administered to evaluate feedback sensitivity to glucocorticoids. Linear mixed models with body mass index (BMI) and age as covariates and Bonferroni corrected post hoc tests assessed group differences.

RESULTS

Compared to healthy controls, subjects with PTSD+MDD, but not those subjects with PTSD-MDD, exhibited lower basal plasma cortisol levels between 1:30 a.m. and 3:30 a.m. and at 4:30 a.m. and 6:30 a.m. (effect size d=0.75). Despite similar plasma ACTH levels between the three groups, the ACTH/cortisol ratio was higher in PTSD+MDD patients compared to controls. We obtained similar results when the patient and control groups were re-studied 1 week later, and when men and current smokers were excluded. Basal plasma DHEA-S levels, and cortisol and ACTH response to a low-dose dexamethasone suppression test were similar in all three groups.

CONCLUSIONS

Lower early morning plasma cortisol levels and a high ACTH/cortisol ratio in subjects with PTSD and co-morbid MDD may not be due to enhanced peripheral sensitivity to glucocorticoids. A central abnormality in glucocorticoid regulation could explain HPA axis dysfunction in this subgroup.

Glucocorticoid receptor gene polymorphisms in premenopausal women with major depression

Glucocorticoid receptor gene polymorphisms are associated with glucocorticoid hypersensitivity and visceral obesity. Perturbations in HPA axis sensitivity to glucocorticoids implicated in the pathogenesis of major depression may result from functional alterations in the glucocorticoid receptor gene. We 1) examined the prevalence of genotype distribution of specific polymorphisms of the glucocorticoid receptor gene (Bcl1, N363S, rs33388, rs33389) in a subset of women from the P.O.W.E.R. Study (which enrolled 21- to 45-year-old premenopausal women with major depression and healthy controls) and 2) explored whether such polymorphisms were associated with visceral obesity and insulin resistance. Women with major depression had a higher body mass index, a higher waist:hip ratio, and more body fat than did controls. No differences were observed in plasma and urinary cortisol or in insulin sensitivity. The G/G genotype of the Bcl1 polymorphism was significantly more common (p<0.03) in women with major depression (n=52) than in controls (n=29). In addition, GG homozygotes (depressed n=10; controls n=2) had higher waist:hip ratios than did non-GG carriers (p<0.02). N363S, rs33388, and rs33389 polymorphisms were not different between groups. In conclusion, premenopausal women with both major depression and the GG genotype of the Bcl1 polymorphism had greater abdominal obesity compared with non-GG carriers.

Potential uses of corticotropin-releasing hormone antagonists

Corticotropin-releasing hormone (CRH), its natural homologs urocortins (UCN) 1, 2, and 3, and several types of CRH receptors (R), coordinate the behavioral, endocrine, autonomic, and immune responses to stress. The potential use of CRH antagonists is currently under intense investigation. Selective antagonists have been used experimentally to clarify the role of CRH-related peptides in anxiety and depression, addictive behavior, inflammatory disorders, acute and chronic neurodegeneration, and sleep disorders, as well as preterm labor.

Development of a human mitochondria-focused cDNA microarray (hMitChip) and validation in skeletal muscle cells: implications for pharmaco- and mitogenomics

Mitochondrial research has influenced our understanding of human evolution, physiology and pathophysiology. Mitochondria, intracellular organelles widely known as 'energy factories' of the cell, also play fundamental roles in intermediary metabolism, steroid hormone and heme biosyntheses, calcium signaling, generation of radical oxygen species, and apoptosis. Mitochondria possess a distinct DNA (mitochondrial DNA); yet, the vast majority of mitochondrial proteins are encoded by the nuclear DNA. Mitochondria-related genetic defects have been described in a variety of mostly rare, often fatal, primary mitochondrial disorders; furthermore, they are increasingly reported in association with many common morbid conditions, such as cancer, obesity, diabetes and neurodegenerative disorders, although their role remains unclear. This study describes the creation of a human mitochondria-focused cDNA microarray (hMitChip) and its validation in human skeletal muscle cells treated with glucocorticoids. We suggest that hMitChip is a reliable and novel tool that will prove useful for systematically studying the contribution of mitochondrial genomics to human health and disease.

Marked suppression of gastric ulcerogenesis and intestinal responses to stress by a novel class of drugs

When exposed to prolonged stress, rats develop gastric ulceration, enhanced colon motility with depletion of its mucin content and signs of physiological and behavioral arousal. In this model, we tested whether antidepressants (fluoxetine and bupropion), anxiolytics (diazepam and buspirone) or the novel nonpeptide corticotropin-releasing hormone (CRH) type-1 receptor (CRH-R1) antagonist, antalarmin, modify these responses. Fluoxetine, bupropion, diazepam and antalarmin all suppressed stress-induced gastric ulceration in male Sprague-Dawley rats exposed to four hours of plain immobilization. Antalarmin produced the most pronounced anti-ulcer effect and additionally suppressed the stress-induced colonic hypermotility, mucin depletion, autonomic hyperarousal and struggling behavior. Intraperitoneal CRH administration reproduced the intestinal but not the gastric responses to stress while vagotomy antagonized the stress-induced gastric ulceration but not the intestinal responses. We conclude that brain CRH-R1 and vagal pathways are essential for gastric ulceration to occur in response to stress and that peripheral CRH-R1 mediates colonic hypermotility and mucin depletion in this model. Nonpeptide CRH-R1 antagonists may therefore be prophylactic against stress ulcer in the critically ill and therapeutic for other pathogenetically related gastrointestinal disorders such as peptic ulcer disease and irritable bowel syndrome.

Organization of the stress system and its dysregulation in melancholic and atypical depression: high vs low CRH/NE states

Stress precipitates depression and alters its natural history. Major depression and the stress response share similar phenomena, mediators and circuitries. Thus, many of the features of major depression potentially reflect dysregulations of the stress response. The stress response itself consists of alterations in levels of anxiety, a loss of cognitive and affective flexibility, activation of the hypothalamic-pituitary-adrenal (HPA) axis and autonomic nervous system, and inhibition of vegetative processes that are likely to impede survival during a life-threatening situation (eg sleep, sexual activity, and endocrine programs for growth and reproduction). Because depression is a heterogeneous illness, we studied two diagnostic subtypes, melancholic and atypical depression. In melancholia, the stress response seems hyperactive, and patients are anxious, dread the future, lose responsiveness to the environment, have insomnia, lose their appetite, and a diurnal variation with depression at its worst in the morning. They also have an activated CRH system and may have diminished activities of the growth hormone and reproductive axes. Patients with atypical depression present with a syndrome that seems the antithesis of melancholia. They are lethargic, fatigued, hyperphagic, hypersomnic, reactive to the environment, and show diurnal variation of depression that is at its best in the morning. In contrast to melancholia, we have advanced several lines of evidence of a down-regulated hypothalamic-pituitary adrenal axis and CRH deficiency in atypical depression, and our data show us that these are of central origin. Given the diversity of effects exerted by CRH and cortisol, the differences in melancholic and atypical depression suggest that studies of depression should examine each subtype separately. In the present paper, we shall first review the mediators and circuitries of the stress system to lay the groundwork for placing in context physiologic and structural alterations in depression that may occur as part of stress system dysfunction.

Major depression and the stress system: a life span perspective

From a transactional developmental perspective, the authors review findings from studies of animals and humans regarding a proposed relation between stress system abnormalities and major depression. The stress system has evolved to promote successful adaptation across the life span, but disruptions in its functioning may increase the risk of pathological outcomes. Emphasis is placed on the role of prenatal and early postnatal experience in contributing to individual differences in postnatal stress reactivity, which may interact with cognitive and psychosocial vulnerabilities to increase susceptibility to later onset of depression. Findings regarding cognitive, psychosocial, and medical sequelae of depression are also reviewed, with a focus on the possible mediating role of the stress system. The authors highlight the importance of multidisciplinary, longitudinal studies in attempting to gain a deeper understanding of the complex developmental processes involved in the onset and course of depression.

Differential gene expression profile of glucocorticoids, testosterone, and dehydroepiandrosterone in human cells

Glucocorticoids are the major immunomodulating hormones in the human body. Recently, increasing interest in androgens as immunomodulators has emerged. In particular, Dehydroepiandrosterone (DHEA) has been suggested as beneficial in the treatment of some autoimmune disorders. However, the action and role of testicular and adrenal androgens on human immune cells remains unclear. This is the first study to provide large-scale gene expression data on the action of different steroids (DHEA, glucocorticoids, and testosterone) on human peripheral blood mononuclear cells using the recently developed genomic-scale technology of microarrays. Novel computational tools and techniques such as Principal Component Analysis (PCA) were used for analysis, clustering and visualization. We have demonstrated that each steroid has its distinct gene expression profile, although DHEA and testosterone co-regulated most genes in a similar direction while glucocorticoids frequently regulated the same genes in an opposite direction. Our data suggest an important and a complex regulatory role for androgens on human immune cells that should be considered in androgen replacement or treatment strategies.

Neuroendocrinology of stress

Stimuli that are interpreted by the brain as extreme or threatening, regardless of their modality, elicit an immediate stereotypic response characterized by enhanced cognition, affective immobility, vigilance, autonomic arousal and a global catabolic state. The brain's ability to mobilize this so-called stress response is paralleled by activation of corticotropin-releasing hormone (CRH) in several nuclei, including the hypothalamus, amygdala and locus ceruleus, and stimulation of the locus ceruleus norepinephrine (LC/NE) system in the brain stem. These systems perpetuate one another, interact with several other transmitter systems in the brain and directly activate the hypothalamic-pituitary-adrenal (HPA) axis and the three components of the autonomic nervous system, namely the sympatho-adrenal, the cranio-sacral parasympathetic and the enteric nervous systems. The widespread body system responses to stress are discussed, and the implications of aberrant stress system activity on physical and mental health are outlined. Moreover, the promise of nonpeptide CRH type-1 receptor antagonists to directly target the stress system in the brain is highlighted.

Expression of corticotropin releasing hormone receptors type I and type II mRNA in suicide victims and controls

Corticotropin-releasing hormone (CRH) is a key neuroendocrine factor implementing endocrine, immune and behavioral responses to stress. CRH exerts its action through two major receptors, CRH-R1 and CRH-R2. Recently novel non-peptidic antagonists directed against CRH-R1 or CRH-R2 have been proposed as promising agents in the treatment of depression, anxiety and eating disorder. However, so far the CRH-receptor system has not been widely studied in humans. Therefore, we employed quantitative TaqMan PCR to analyze the expression and distribution of both CRH-R1 and CRH-R2 in human brain tissue and peripheral organs. Furthermore the expression of CRH receptors was analyzed for the first time in pituitaries of suicide victims by in situ hybridization and quantitative PCR. Our data demonstrated a different expression pattern in humans as compared to rodents. Both CRH-R1 and CRH-R2 were expressed in high amounts in the brain with the strongest expression in the pituitary. As described in rodents, however the CRH-R1 in human was the predominant receptor in the brain (82.7 +/- 11.0%), whilst CRH-R2 was the predominant receptor in peripheral organs (77.0 +/- 15.8%). There was a shift in the ratio of CRH-R1/R2 in the pituitaries of suicide victims. In conclusion, both CRH-R1 and CRH-R2 are widely expressed in human tissues with a distribution substantially different from rodents. Strong expression of both CRH-R1 and CRH-R2 in human pituitaries suggests that particularly under stress, activation of the HPA axis can be maintained through both receptors.

Synchronicity of frequently sampled thyrotropin (TSH) and leptin concentrations in healthy adults and leptin-deficient subjects: evidence for possible partial TSH regulation by leptin in humans

Leptin signals the status of energy reserves to the brain. Leptin stimulates biosynthesis of TRH in vitro and influences the activity of the hypothalamic-pituitary-thyroid axis in vivo in rodents. Because blood levels of both leptin and TSH display diurnal variation with a distinct nocturnal rise, we sought to determine whether a relationship exists between fluctuations in circulating leptin and TSH. We measured serum leptin and TSH levels every 7 min for 24 h in five healthy men and found that both leptin and TSH levels are highly organized and pulsatile. A similar pattern of leptin and TSH rhythms was observed, with TSH and leptin levels reaching a nadir in late morning and a peak in the early morning hours. Importantly, cosinor analysis on the absolute leptin and TSH levels revealed a statistically significant fit for a 24-h period and the two hormones showed similar probabilities of rhythm and superimposable peak values. Furthermore, this study shows a strong positive Pearson correlation between the 24-h patterns of variability of leptin and TSH in healthy subjects. Finally, the ultradian fluctuations in leptin levels showed pattern synchrony with those of TSH as determined by cross-correlation analysis, by cross-approximate enthropy and Bayessian analysis applied independently. To further explore whether these associations could reflect an underlying regulation of TSH secretion by leptin, we also studied frequently sampled leptin and TSH levels in four brothers, members of a family with leptin deficiency (one normal homozygote, two heterozygotes, and one leptin-deficient homozygote). Leptin levels of the homozygous leptin-deficient subject are detectable but bioinactive, and the rhythm of his TSH is disorganized. 24-h pattern of leptin and TSH variability in the heterozygous subjects, although significantly correlated, showed a weaker correlation compared with the strong correlation in the normal subjects. These data are consistent with the possibility that leptin may regulate TSH pulsatility and circadian rhythmicity, but interventional studies are needed to definitively prove whether leptin regulates the minute-to-minute oscillations and ultradian rhythm of TSH levels.

Depression: a major, unrecognized risk factor for osteoporosis?

Existing studies of the relationship between depression and osteoporosis have been heterogeneous in their design and use of diagnostic instruments for depression, which might have contributed to the different results on the comorbidity of these two conditions. Nevertheless, these studies reveal a strong association between depression and osteoporosis. Endocrine factors such as depression-induced hypersecretion of corticotropin-releasing hormone and hypercortisolism, hypogonadism, growth hormone deficiency and increased concentration of circulating interleukin 6, might play a crucial role in the bone loss observed in subjects suffering from major depression.

The NMR-MOUSE: quality control of elastomers

New applications of the NMR-MOUSE (mobile universal surface explorer) to non-destructive quality control of elastomers are reported. One example concern the thermal aging of fast clutches which was probed by measurements of 1H transverse relaxation time. Novel methodological developments show that 1H double-quantum filtered NMR signals can be generated in the inhomogeneous fields of the NMR-MOUSE for characterization of residual dipolar couplings. This technique was applied to characterize reference natural rubber samples with different crosslink density and carbon black and silica fillers.

Increased ACTH and cortisol secretion after interleukin-alpha injection in the common marmoset (Callithrix jacchus jacchus)

We have studied the effect of intravenous injection of interleukin-1 (dose range: from 0.25 to 4.5 microg/kg of body weight) on plasma ACTH and cortisol levels in the marmoset, a primate paradygm of peripheral glucocorticoid resistance. Blood sampling were collected and body temperature recorded 0, 15, 30, 60, 120, 180, 240 and 300 min after injection. Interleukin-1 stimulated secretion of ACTH in a dose-dependent fashion. Maximal secretion occurred 120 min after injection, and lasted up to 240 min. Plasma ACTH levels returned to baseline 300 min after interleukin-1 injection. Plasma cortisol levels were related to ACTH levels. Body temperature elevation, which occurred 10-15 min after injection was dose-dependent, and lasted 3 h. Results suggest that the pyrogenic effect of interleukin is associated, in the marmoset, with integrated activation of the hypothalamic-pituitary-adrenal axis. In light of the proneness of marmosets to hyperimmune disorders, our data are consistent with the hypothesized central biological role of IL-1, as well as the pathophysiological relevance of the neuro-endocrine-immune cross-talk during the acute phase response.

The development of a potential single photon emission computed tomography (SPECT) imaging agent for the corticotropin-releasing hormone receptor type

A high-affinity radioligand for CRHR1 has been prepared that can serve as a template for the development of SPECT imaging agents. The 5-chloro-N-cyclopropylmethyl-N-(2,6-dichloro-4-iodophenyl)-2-methyl-N-propylpyrimidine-4,6-diamine (6b, Ki = 14 nM), and the corresponding 4-bromophenyl analogue (6a, Ki = 21 nM), were synthesized in four steps from compound 3.

Abnormalities in response to vasopressin infusion in chronic fatigue syndrome

Several neuroendocrine studies have suggested hypoactivation of the hypothalamic-pituitary-adrenal axis in chronic fatigue syndrome. One possible determinant of this neuroendocrine abnormality, as well as the primary symptom of fatigue, is reduced hypothalamic secretion of corticotropin-releasing hormone (CRH). Because CRH and vasopressin secreted from the hypothalamus act synergistically at the pituitary to activate ACTH secretion, the ACTH response to peripheral infusion of vasopressin can provide an indirect measure of hypothalamic CRH secretion. We measured the ACTH and cortisol response to a one hour infusion of arginine vasopressin in 19 patients with chronic fatigue syndrome and 19 age and sex matched healthy volunteers. Patients with chronic fatigue syndrome had a reduced ACTH response to the vasopressin infusion and a more rapid cortisol response to the infusion. These results provide further evidence of reduced hypothalamic CRH secretion in patients with chronic fatigue syndrome.

Hypothalamic-pituitary-adrenal axis activity during exercise in African American and Caucasian women

African American women have a greater prevalence of obesity than Caucasian women, but the reasons for this difference are not known. We have investigated whether activity of the hypothalamic-pituitary adrenal axis plays a role in this phenomenon. Previous studies have shown that plasma ACTH immunoreactivity (ACTH-IR) of African American women, measured after ovine CRH (oCRH) stimulation, is significantly greater than ACTH-IR of Caucasian women, but is not accompanied by greater plasma cortisol concentrations. Analysis by high pressure liquid chromatography has demonstrated that after oCRH stimulation, the plasma ACTH-IR of African American women contains many nonintact ACTH fragments not found in Caucasians. To determine whether these racial differences in ACTH-IR secretion are an artifact of exogenous oCRH administration or are also found after a physiological stimulus for ACTH secretion, we measured hormones of the hypothalamic-pituitary adrenal axis before and after a standardized, maximal exercise treadmill test in 16 African American and 19 Caucasian healthy women matched for age, socioeconomic status, and body mass index. The intensity of exercise performed was similar in the two groups, as determined by duration of exercise, perceived intensity of exertion, plasma lactate, maximal heart rate, and maximum oxygen uptake. Basal ACTH-IR measured by RIA or immunoradiometric assay and cortisol were similar in African Americans and Caucasians. Plasma ACTH-IR, measured 10 min after completion of exercise, was significantly greater in African Americans than in Caucasians [by RIA: mean +/- SD ACTH-IR, 47.1 +/- 30.9 vs. 25.4 +/- 16.7 pmol/L (P < 0.01); by immunoradiometric assay: ACTH-IR, 45.9 +/- 43.2 vs. 21.1 +/- 14.6 pmol/L (P < 0.05)]. However, plasma cortisol after exercise was not different (450.2 +/- 157.7 vs. 483.6 +/- 180.4 nmol/L; P = 0.57). We conclude that ACTH-IR is significantly greater in African American than in Caucasian women after intense exercise. The ACTH-IR of African Americans and Caucasians does not appear to be equipotent at adrenal melanocortin-2 receptors, because the greater ACTH-IR of African Americans does not lead to greater cortisol secretion. Whether some components of the ACTH-IR detected in African Americans affect signal transduction of the hypothalamic melanocortin-4 receptors implicated in body weight regulation and thus predispose African American women to weight gain without altering plasma cortisol remains to be determined.

Acute systemic inflammation up-regulates secretory sphingomyelinase in vivo: a possible link between inflammatory cytokines and atherogenesis

Inflammation plays a critical role in atherogenesis, yet the mediators linking inflammation to specific atherogenic processes remain to be elucidated. One such mediator may be secretory sphingomyelinase (S-SMase), a product of the acid sphingomyelinase gene. The secretion of S-SMase by cultured endothelial cells is induced by inflammatory cytokines, and in vivo data have implicated S-SMase in subendothelial lipoprotein aggregation, macrophage foam cell formation, and possibly other atherogenic processes. Thus, the goal of this study was to seek evidence for S-SMase regulation in vivo during a physiologically relevant inflammatory response. First, wild-type mice were injected with saline or lipopolysaccharide (LPS) as a model of acute systemic inflammation. Serum S-SMase activity 3 h postinjection was increased 2- to 2.5-fold by LPS (P < 0.01). To determine the role of IL-1 in the LPS response, we used IL-1 converting enzyme knockout mice, which exhibit deficient IL-1 bioactivity. The level of serum S-SMase activity in LPS-injected IL-1 converting enzyme knockout mice was approximately 35% less than that in identically treated wild-type mice (P < 0.01). In LPS-injected IL-1-receptor antagonist knockout mice, which have an enhanced response to IL-1, serum S-SMase activity was increased 1. 8-fold compared with LPS-injected wild-type mice (P < 0.01). Finally, when wild-type mice were injected directly with IL-1beta, tumor necrosis factor alpha, or both, serum S-SMase activity increased 1. 6-, 2.3-, and 2.9-fold, respectively (P < 0.01). These data show regulation of S-SMase activity in vivo and they raise the possibility that local stimulation of S-SMase may contribute to the effects of inflammatory cytokines in atherosclerosis.

Oral administration of a corticotropin-releasing hormone receptor antagonist significantly attenuates behavioral, neuroendocrine, and autonomic responses to stress in primates

We evaluated the effects of the lipophilic nonpeptide corticotropin-releasing hormone (CRH) type 1 receptor antagonist antalarmin on the behavioral, neuroendocrine, and autonomic components of the stress response in adult male rhesus macaques. After oral administration, significant antalarmin concentrations were detected in the systemic circulation and the cerebrospinal fluid by a mass spectrometry-gas chromatography assay developed specifically for this purpose. Pharmacokinetic and dose-response studies suggested that an oral dose of 20 mg/kg was optimal for behavioral and endocrine effects. We then administered this dose in a double-blind, placebo-controlled fashion to monkeys exposed to an intense social stressor: namely, placement of two unfamiliar males in adjacent cages separated only by a transparent Plexiglas screen. Antalarmin significantly inhibited a repertoire of behaviors associated with anxiety and fear such as body tremors, grimacing, teeth gnashing, urination, and defecation. In contrast, antalarmin increased exploratory and sexual behaviors that are normally suppressed during stress. Moreover, antalarmin significantly diminished the increases in cerebrospinal fluid CRH as well as the pituitary-adrenal, sympathetic, and adrenal medullary responses to stress. We conclude that CRH plays a broad role in the physiological responses to psychological stress in primates and that a CRH type 1 receptor antagonist may be of therapeutic value in human psychiatric, reproductive, and cardiovascular disorders associated with CRH system hyperactivity.

Differential regulation of neuropeptide Y mRNA expression in the arcuate nucleus and locus coeruleus by stress and antidepressants

In rats, circulating corticosterone and insulin are involved in regulation of the hypothalamic neuropeptide Y (NPY) system, which in turn, is involved in regulation of the hypothalamic-pituitary-adrenal (HPA) axis. Since the HPA axis and stress responsivity is altered in diseases such as depression, we investigated interactions between the effects of stress and antidepressant drug treatment on arcuate nucleus and locus coeruleus NPY mRNA expressions using in-situ hybridization histochemistry. After acute (2 h) and repeated immobilization (2 h daily, for 14 days), plasma concentrations of corticosterone increased, and those of insulin decreased. The expression of NPY mRNA was significantly increased in the arcuate nucleus, but was unchanged in the locus coeruleus following acute and repeated immobilization. Adrenalectomized rats with systemic corticosterone replacement (ADX+CORT), whose corticosterone concentration was maintained at approximately 50-100 ng/ml during repeated stress, showed a decrease in plasma insulin and an increase in arcuate nucleus NPY mRNA similar to that observed in sham rats, suggesting that changes in NPY mRNA levels are more closely tied to circulating insulin than to circulating corticosterone. In contrast, locus coeruleus NPY mRNA expressions in ADX+CORT rats were significantly higher than those in sham rats after repeated stress. Desmethylimipramine (DMI) treatment for 24 days did not affect basal plasma concentrations of corticosterone or insulin, or arcuate nucleus NPY mRNA expressions, but significantly decreased basal levels of locus coeruleus NPY mRNA compared to saline-treated rats. After repeated immobilization (2 h daily, for 4 days), DMI significantly reduced the stress-induced rise in locus coeruleus NPY mRNA levels, but potentiated the stress-induced rise in arcuate nucleus NPY mRNA expression. These results demonstrate that: (1) the increase in arcuate nucleus NPY mRNA expressions in stressed rats closely follows the decrease in plasma concentrations of insulin; (2) increases in NPY mRNA expressions occur in the absence of changes in plasma corticosterone; and (3) desipramine treatment potentiated the effect of stress on arcuate nucleus NPY mRNA expressions, but blocked the repeated stress-induced increase in locus coeruleus NPY mRNA expressions. Thus, NPY mRNA expression in the arcuate nucleus and the locus coeruleus is sensitive to the effects of stress and to the antidepressant drug desipramine, but the arcuate nucleus NPY system is regulated by different mechanisms than the locus coeruleus NPY system. The results provide further evidence for the importance of circulating insulin in the regulation of the arcuate nucleus NPY system.

Synthesis and biological activity of fluoro-substituted pyrrolo[2,3-d]pyrimidines: the development of potential positron emission tomography imaging agents for the corticotropin-releasing hormone type 1 receptor

A series of fluoro-substituted 4-(dialkylamino)pyrrolo[2,3-d]pyrimidines was synthesized and their binding affinity for corticotropin-releasing hormone type 1 receptor (CRHR1) was investigated. Compounds 11a and 11b possessed very high CRHR1 affinity (Ki=3.5, 0.91 nM, respectively). They are promising candidates for the development of 18F-containing nonpeptide PET radioligands for CRHR1.

Individual reactivity and physiology of the stress response

The biological response to stress involves the activation of two main neuroendocrine components, the hypothalamic-pituitary-adrenal axis and the sympathoadrenal medullary systems. Looking at the responses to stressors in a laboratory setting, e.g., cortisol production after exercising on a treadmill, is a valid and controlled way to study how people react to psychological and physical stressors. A common finding in such studies is that individuals respond bimodally to stress. More recently, researchers have been interested in the possible reasons why healthy individuals exhibit differential reactivity to stressors. The literature on the neuroendocrine responses to stress, with a particular focus on investigations of individual reactivity to psychological and physical stressors, is reviewed.

Pronounced and sustained central hypernoradrenergic function in major depression with melancholic features: relation to hypercortisolism and corticotropin-releasing hormone

Both stress-system activation and melancholic depression are characterized by fear, constricted affect, stereotyped thinking, and similar changes in autonomic and neuroendocrine function. Because norepinephrine (NE) and corticotropin-releasing hormone (CRH) can produce these physiological and behavioral changes, we measured the cerebrospinal fluid (CSF) levels each hour for 30 consecutive hours in controls and in patients with melancholic depression. Plasma adrenocorticotropic hormone (ACTH) and cortisol levels were obtained every 30 min. Depressed patients had significantly higher CSF NE and plasma cortisol levels that were increased around the clock. Diurnal variations in CSF NE and plasma cortisol levels were virtually superimposable and positively correlated with each other in both patients and controls. Despite their hypercortisolism, depressed patients had normal levels of plasma ACTH and CSF CRH. However, plasma ACTH and CSF CRH levels in depressed patients were inappropriately high, considering the degree of their hypercortisolism. In contrast to the significant negative correlation between plasma cortisol and CSF CRH levels seen in controls, patients with depression showed no statistical relationship between these parameters. These data indicate that persistent stress-system dysfunction in melancholic depression is independent of the conscious stress of the disorder. These data also suggest mutually reinforcing bidirectional links between a central hypernoradrenergic state and the hyperfunctioning of specific central CRH pathways that each are driven and sustained by hypercortisolism. We postulate that alpha-noradrenergic blockade, CRH antagonists, and treatment with antiglucocorticoids may act at different loci, alone or in combination, in the treatment of major depression with melancholic features.

Psychological stress increased corticotropin-releasing hormone mRNA and content in the central nucleus of the amygdala but not in the hypothalamic paraventricular nucleus in the rat

The central administration of corticotropin-releasing hormone (CRH) to experimental animals sets into motion a coordinated series of physiological and behavioral events that promote survival during threatening situation. A large body of evidence suggest that CRH in the central nucleus of the amygdala (CEA) induces fear-related behaviors and is essential to fear conditioning; however, evidence of CRH-mediated activation of the amygdala under physiological situation is still limited. We report here a study of the impact of a psychological stressor on hypothalamic and amygdala CRH systems in the rat. Non-footshocked rats placed in a floored compartment surrounded by footshocked rats were defined as the psychological stress group. Rats were exposed to psychological stress for 15 min, and then sacrificed 1.5 and 3 h after cessation of stress. We found that our psychological stressor induced an increase in both CRH mRNA levels, as assessed by in situ hybridization histochemistry, and CRH content, as assessed by micropunch RIA, in the CEA. Exposure to the psychological stressor also caused a significant increase in CRH mRNA levels with a trend for an increase in CRH content in the dorsolateral subdivision of the bed nucleus of the stria terminalis (BNST) which is anatomically associated with the CEA. In contrast, psychological stress induced a small, but significant increase in type-1 CRH receptor (CRHR-1) mRNA in the hypothalamic paraventricular nucleus (PVN), while it failed to elevate either PVN CRH mRNA levels or content, CRH content in the median eminence (ME), or levels of plasma ACTH or corticosterone (CORT). Thus, in the context of a psychological stressor, the activation of the amygdala CRH system can occur without robust activation of the hypothalamic CRH system. In the light of previous data that the psychological stress-induced loss of sleep was reversed by the central administration of a CRH antagonist, these data suggest that CRH in the CEA may contribute to the psychological stress-evoked fear-related behavior such as hyperarousal. These data also indicate that in response to a psychological stressor, the amygdala CRH system is much more sensitive than is the CRH system emanating from the PVN.

Behavioral and psychophysiological correlates of self-presentation in temperamentally shy children

We examined temporal changes in behavior, regional brain electrical activity (EEG), heart rate, cardiac vagal tone, the startle eyeblink response, and salivary cortisol during a task designed to elicit self-presentation anxiety in a group of 7-year-olds, some of whom were classified as temperamentally shy. We found that temperamentally shy children displayed a significantly greater increase in anxious behavior, a greater increase in right, but not left, frontal EEG activity, and a greater increase in heart rate as the task became more demanding compared with their nonshy counterparts. However, the results failed to reveal any significant group differences on the startle eyeblink and salivary cortisol measures. The present findings extend our prior work, in which we found distinct patterns of psychophysiological activity on baseline measures, to differences on psychophysiological measures collected concurrently during a socially evaluative situation in temperamentally shy children.

Circadian interleukin-6 secretion and quantity and depth of sleep

Patients with pathologically increased daytime sleepiness and fatigue have elevated levels of circulating interleukin-6 (IL-6). The latter is an inflammatory cytokine, which causes sickness manifestations, including somnolence and fatigue, and activation of the hypothalamic-pituitary-adrenal axis. In this study, we examined: 1) the relation between serial measurements of plasma IL-6 and quantity and depth of sleep, evaluated by polysomnography; and 2) the effects of sleep deprivation on the nyctohemeral pattern of IL-6 secretion. Eight healthy young male volunteers were sampled for 24 h twice, at the baseline state, after a normal night's sleep and after total overnight sleep deprivation. At the baseline state, IL-6 was secreted in a biphasic circadian pattern with two nadirs at 0800 and 2100 and two zeniths at 1900 and 0500 (P < 0.01). The baseline amount of sleep correlated negatively with the overall daytime secretion of the cytokine (P < 0.05). Also, depth of sleep at baseline correlated negatively with the postdeprivation increase of daytime secretion of IL-6 (P < 0.05). Sleep deprivation changed the temporal pattern of circadian IL-6 secretion but not the overall amount. Indeed, during the post-deprivation period, the mean daytime (0800-2200 h) levels of IL-6 were significantly higher (P < 0.05), whereas the nighttime (2200-0600 h) levels were lower than the predeprivation values. Thus, sleep-deprived subjects had daytime oversecretion and nighttime under-secretion of IL-6; the former might be responsible for their daylong somnolence and fatigue, the latter for the better quality (depth) of their sleep. These data suggest that a good night's sleep is associated with decreased daytime secretion of IL-6 and a good sense of well-being and that good sleep is associated with decreased exposure of tissues to the proinflammatory and potentially detrimental actions of IL-6. Sleep deprivation increases daytime IL-6 and causes somnolence and fatigue during the next day, whereas postdeprivation decreases nighttime IL-6 and is associated with deeper sleep.

Circadian interleukin-6 secretion and quantity and depth of sleep

Patients with pathologically increased daytime sleepiness and fatigue have elevated levels of circulating interleukin-6 (IL-6). The latter is an inflammatory cytokine, which causes sickness manifestations, including somnolence and fatigue, and activation of the hypothalamic-pituitary-adrenal axis. In this study, we examined: 1) the relation between serial measurements of plasma IL-6 and quantity and depth of sleep, evaluated by polysomnography; and 2) the effects of sleep deprivation on the nyctohemeral pattern of IL-6 secretion. Eight healthy young male volunteers were sampled for 24 h twice, at the baseline state, after a normal night's sleep and after total overnight sleep deprivation. At the baseline state, IL-6 was secreted in a biphasic circadian pattern with two nadirs at 0800 and 2100 and two zeniths at 1900 and 0500 (P < 0.01). The baseline amount of sleep correlated negatively with the overall daytime secretion of the cytokine (P < 0.05). Also, depth of sleep at baseline correlated negatively with the postdeprivation increase of daytime secretion of IL-6 (P < 0.05). Sleep deprivation changed the temporal pattern of circadian IL-6 secretion but not the overall amount. Indeed, during the post-deprivation period, the mean daytime (0800-2200 h) levels of IL-6 were significantly higher (P < 0.05), whereas the nighttime (2200-0600 h) levels were lower than the predeprivation values. Thus, sleep-deprived subjects had daytime oversecretion and nighttime under-secretion of IL-6; the former might be responsible for their daylong somnolence and fatigue, the latter for the better quality (depth) of their sleep. These data suggest that a good night's sleep is associated with decreased daytime secretion of IL-6 and a good sense of well-being and that good sleep is associated with decreased exposure of tissues to the proinflammatory and potentially detrimental actions of IL-6. Sleep deprivation increases daytime IL-6 and causes somnolence and fatigue during the next day, whereas postdeprivation decreases nighttime IL-6 and is associated with deeper sleep.

Sleep deprivation effects on the activity of the hypothalamic-pituitary-adrenal and growth axes: potential clinical implications

OBJECTIVES

Although several studies have shown that sleep deprivation is associated with increased slow wave sleep during the recovery night, the effects of sleep deprivation on cortisol and growth hormone (GH) secretion the next day and recovery night have not been assessed systematically. We hypothesized that increased slow wave sleep postsleep deprivation is associated with decreased cortisol levels and that the enhanced GH secretion is driven by the decreased activity of the HPA axis.

DESIGN AND SUBJECTS

After four consecutive nights in the Sleep Laboratory, 10 healthy young men were totally deprived of sleep during the fifth night, and then allowed to sleep again on nights six and seven. Twenty-four hour blood sampling was performed serially every 30 minutes on the fourth day, immediately following the previous night of sleep and on the sixth day, immediately after sleep deprivation.

MEASUREMENT

Eight-hour sleep laboratory recording, including electroencephologram, electro-oculogram and electromyogram. Plasma cortisol and GH levels using specific immunoassay techniques.

RESULTS

Mean plasma and time-integrated (AUC) cortisol levels were lower during the postdeprivation nighttime period than on the fourth night (P < 0.05). Pulsatile analysis showed significant reduction of both the 24 h and daytime peak area (P < 0.05) and of the pulse amplitude (P < 0.01), but not of the pulse frequency. Also, the amount of time-integrated GH was significantly higher for the first 4 h of the postdeprivation night compared to the predeprivation night (P < 0.05). Cross-correlation analyses between the absolute values of the time-series of each hormone value and percentage of each sleep stage per half hour revealed that slow wave sleep was negatively correlated with cortisol and positively correlated with GH with slow wave sleep preceding the secretion of these hormones. In contrast, indices of sleep disturbance, i.e. wake and stage 1 sleep, were positively correlated with cortisol and negatively correlated with GH.

CONCLUSION

We conclude that sleep deprivation results in a significant reduction of cortisol secretion the next day and this reduction appears to be, to a large extent, driven by the increase of slow wave sleep during the recovery night. We propose that reduction of CRH and cortisol secretion may be the mechanism through which sleep deprivation relieves depression temporarily. Furthermore, deep sleep has an inhibitory effect on the HPA axis while it enhances the activity of the GH axis. In contrast, sleep disturbance has a stimulatory effect on the HPA axis and a suppressive effect on the GH axis. These results are consistent with the observed hypocortisolism in idiopathic hypersomnia and HPA axis relative activation in chronic insomnia. Finally, our findings support previous hypotheses about the restitution and immunoenhancement role of slow wave (deep) sleep.

Chronic administration of the non-peptide CRH type 1 receptor antagonist antalarmin does not blunt hypothalamic-pituitary-adrenal axis responses to acute immobilization stress

Antalarmin is a pyrrolopyrimidine compound that antagonizes corticotropin-releasing hormone (CRH) type 1 receptors (CRHR1). In order to assess the effects of antalarmin treatment on hypothalamic-pituitary-adrenal (HPA) function we measured the plasma concentrations of adrenocorticotropic hormone (ACTH) and corticosterone in animals treated with either antalarmin or vehicle for 1 week or for 8 weeks. We found that antalarmin treatment for 1 week did not affect basal concentrations of ACTH or corticosterone. In contrast, treatment for 8 weeks significantly lowered basal ACTH and corticosterone concentrations and also significantly decreased the basal corticosterone to ACTH ratio, indicating decreased basal adrenocortical responsiveness to ACTH. However, immobilization stress resulted in ACTH and corticosterone concentrations that were the same in animals treated with vehicle or antalarmin for either 1 or 8 weeks. We conclude that even though 8-week antagonism of CRHR1 by the non-peptide antalarmin blunts basal concentrations of ACTH and corticosterone, and affects the adrenal responsiveness to ACTH, it does not blunt the HPA response to acute stress, and it does not appear to cause stress-induced adrenal insufficiency.

Differential hypothalamic-pituitary-adrenal axis reactivity to psychological and physical stress

Healthy men exhibit a differential hypothalamic-pituitary-adrenal axis (HPA) response to exercise stress and fall into two groups: high responders (HR) and low responders (LR). The present study examined whether HR to physical stress also exhibit higher HPA reactivity to psychological stress than LR. We examined 14 HR and 13 LR classified based on their ACTH responses to high intensity exercise after pretreatment with dexamethasone. Both groups were of similar age, height, weight, and fitness level. Trait anxiety scores on the Spielberger Trait Anxiety Scale were not different. Subjects underwent a psychological stress test consisting of an interview and mental arithmetic. This test raised heart rate, blood pressure, and plasma ACTH and cortisol levels in both HR and LR. HR tended to have higher heart rates and blood pressures in anticipation of the psychological stress test than LR. ACTH responses of HR were higher, although not significantly, throughout the psychological stress test than LR. HR had a significantly (P < 0.05) greater net integrated cortisol response to the psychological stress than LR. This suggests that the adrenal cortexes of the HR are hypertropic and/or hypersensitive to ACTH. We conclude that men who are highly responsive to exercise stress are also highly responsive to psychological stress.

Normal CSF oxytocin and NPY levels in OCD

BACKGROUND

Attention has recently been focused on central nervous system neuropeptides as potential mediators of the symptom profile of obsessive-compulsive disorder (OCD). Increased CSF levels of the anxiolytic neuropeptide oxytocin have been reported in OCD. CSF levels of NPY, another anxiolytic neuropeptide, have not been studied.

METHODS

We measured CSF oxytocin and NPY in 14 OCD patients and 26 healthy normal volunteers.

RESULTS

There were no significant differences between the OCD patients and control subjects in CSF oxytocin or NPY levels. In both the OCD and control groups, women had significantly higher CSF oxytocin levels than men.

CONCLUSIONS

These results do not support a prior finding of elevated CSF oxytocin in OCD patients and do not provide any evidence for an abnormality of NPY regulation in OCD.

The impact of the nonpeptide corticotropin-releasing hormone antagonist antalarmin on behavioral and endocrine responses to stress

The nonpeptide CRH antagonist antalarmin has been shown to block both behavioral and endocrine responses to CRH. However, it's potential activity in blunting behavioral and endocrine sequelae of stressor exposure has not been assessed. Because antagonism of central CRH by alpha-helical CRH attenuates conditioned fear responses, we sought to test antalarmin in this regard. In addition, it remains unclear as to whether this is a result of receptor blockade during conditioning or during testing. Thus, we explored whether CRH mediates the induction or expression of conditioned fear (freezing in a context previously associated with 2 footshocks; 1.0 mA, 5 sec each). Furthermore, because rats previously exposed to inescapable shock (IS; 100 shocks, 1.6 mA, 5 sec each), demonstrate enhanced fear conditioning, we investigated whether this effect would be blocked by antalarmin. Antalarmin (20 mg/kg x 2 ml i.p.) impaired both the induction and expression of conditioned fear. In addition, antalarmin blocked the enhancement of fear conditioning produced by prior exposure to IS. Despite the marked behavioral effects observed in antalarmin-treated rats, antalarmin had no effect on IS-induced rises in ACTH or corticosterone. However, antalarmin did block the ACTH response produced by exposure to 2 footshocks.

The endocrinology of melancholic and atypical depression: relation to neurocircuitry and somatic consequences

The cardinal clinical manifestations of major depression with melancholic features include sustained anxiety and dread for the future as well as evidence of physiological hyperarousal (e.g., sustained hyperactivity of the two principal effectors of the stress response, the corticotropin-releasing-hormone, or CRH, system, and the locus ceruleus-norepinephrine, or LC-NE, system). Sustained stress system activation in melancholic depression is thought to confer both behavioral arousal as well as the hypercortisolism, sympathetic nervous system activation, and inhibition of programs for growth and reproduction that consistently occur in this disorder. Data also suggest that activation of the CRH and LC systems in melancholia are involved in the long-term medical consequences of depression such as premature coronary artery disease and osteoporosis, the two-three-fold preponderance of females in the incidence of major depression, and the mechanism of action of antidepressant drugs. In addition, recent data reveal important bidirectional interactions between stress-system hormonal factors in depression and neural substrates implicated in many discrete behavioral alterations in depression (e.g., the medial prefrontal cortex, important in shifting affect based on internal and external cues, the mesolimbic dopaminergic reward system, and the amygdala fear system). We have also advanced data indicating that the hypersomnia, hyperphagia, lethargy, fatigue, and relative apathy of the syndrome of atypical depression are associated with concomitant hypofunctioning of the CRH and LC-NE systems. These data indicate the need for an entirely different therapeutic strategy than that used in melancholia for the treatment of atypical depression, and they suggest that this subtype of major depression will be associated with its own unique repertoire of long-term medical consequences.

Sex differences in circulating human leptin pulse amplitude: clinical implications

Leptin, a product of fat cells, provides a signal of nutritional status to the central nervous system. Leptin concentrations have ultradian and diurnal fluctuations. We conducted this study to assess sex differences in the levels of organization of frequently sampled leptin concentrations in healthy, normal weight women and men. Leptin levels were sampled every 7 min for 24 h in 14 healthy, normal weight individuals (6 women and 8 men). The 14 leptin time series containing a total of 2898 leptin measurements were assessed by 1) algorithms that characterize statistically significant pulsatility, 2) Spectral (Fourier) analysis, 3) analysis of time intervals and variability, and 4) approximate entropy. We found that frequently sampled plasma leptin concentrations have a 24-h profile that is numerically more than twice as high in women as in men, and leptin pulse amplitude is likewise more than twice as high in women. However, healthy men and women have nearly identical concentration-independent and frequency-related 24-h and ultradian patterns. Leptin concentrations have nonrandom fluctuations over 24 h, independent of their absolute value and underlying 24-h periodicity, that are similar in men and women. Ultradian periodicities detected by Fourier time series have similar values in men and women. The strongest distinction between the sexes in the level of organization of leptin concentration is not at the level of pulse organization or oscillation frequency, but, rather, in the mass or amount of leptin released (or removed) per unit time, indicating that women might be more resistant to the effects of leptin than men. Because leptin is clinically relevant to the regulation of body weight, future studies should examine whether the relative leptin resistance exhibited by women might contribute to their increased susceptibility to disorders whose pathophysiology involves dysregulation of food intake and body weight.

Altered expression of type 2 CRH receptor mRNA in the VMH by glucocorticoids and starvation

In the rat, high-dose corticosterone (Cort) administration, the hypercortisolism of starvation, and adrenalectomy are all associated with decreased food intake and weight loss. We report here a study of the effects of high-dose Cort administration, starvation, and adrenalectomy on two peripheral hormones known to influence food intake and energy use, insulin and leptin. We also studied the impact of these interventions on the levels of type 2 corticotropin-releasing hormone receptor (CRHR-2) mRNA in the hypothalamic paraventricular nucleus (PVN) and ventromedial hypothalamus (VMH). The VMH is classically referred to as the satiety center because electrical stimulation of the VMH leads to inhibition of food intake, whereas CRHR-2 are thought to transduce the profound anorexogenic effects of CRH or its related peptide urocortin. Starvation and adrenalectomy each lowered plasma insulin and leptin levels and were associated with decrements in CRHR-2 mRNA levels in the VMH. Cort administration increased plasma leptin levels profoundly, as well as plasma insulin levels and the levels of VMH CRHR-2 mRNA. Under all experimental conditions, a positive correlation was seen between plasma leptin levels and VMH CRHR-2 mRNA. These data suggest that decreased food intake and weight loss after high-dose Cort administration at least partially depend on the profound impact of Cort on plasma leptin secretion in the rat; they suggest, moreover, an additional mechanism for the satiety-inducing effects of leptin, namely increasing CRHR-2 in the VMH. The concordance of a fall in plasma insulin and leptin levels with the fall in VMH CRHR-2 mRNA levels further supports the idea that compensatory responses during starvation and adrenalectomy include not only the disinhibiting effects of reduced insulin and leptin levels on appetite through already-described mechanisms but also via an effect of leptin on VMH CRHR-2. Neither Cort administration, starvation, nor adrenalectomy influenced the levels of CRHR-2 mRNA in the PVN, suggesting that these receptors are differentially regulated in different hypothalamic regions.

High intensity exercise promotes escape of adrenocorticotropin and cortisol from suppression by dexamethasone: sexually dimorphic responses

Exercise promotes escape of ACTH and cortisol from suppression by dexamethasone (DEX) in some healthy men and women. To determine whether stimulus strength, diurnal rhythmicity, or gender influences neuroendocrine escape during DEX suppression, we studied men (n = 5) and women (n = 5) during high intensity exercise tests after taking 4 mg DEX: two tests (one at 90% and one at 100% of maximal aerobic capacity) were conducted in the morning and two were performed in the afternoon on nonconsecutive days. Plasma ACTH and cortisol showed significantly greater increases with the 100% compared to the 90% intensity exercise (ACTH: 90%, 2 +/- 0.4; 100%, 3 +/- 0.5 pmol/L; cortisol: 90%, 53 +/- 5.3; 100% 93 +/- 23.6 nmol/L). Plasma cortisol responses were significantly higher in women than in men (P < 0.01). Plasma arginine vasopressin (AVP) exhibited significant intensity-dependent increases, with higher responses in women than men (P < 0.01). In conclusion, despite high dose glucocorticoid pretreatment, intense exercise can override the glucocorticoid negative feedback of hypothalamic-pituitary-adrenal activation in most normal men and women. This ability to override cortisol negative feedback inhibition may relate to the magnitude of the AVP response, the potency/specificity of the stressor to elicit a CRH/AVP response, and/or the sensitivity of the glucocorticoid negative feedback system at the time of the stress.

Interactions between the hypothalamic-pituitary-adrenal axis and the female reproductive system: clinical implications

The hypothalamic-pituitary-adrenal axis exerts profound, multilevel inhibitory effects on the female reproductive system. Corticotropin-releasing hormone (CRH) and CRH-induced proopiomelanocortin peptides inhibit hypothalamic gonadotropin-releasing hormone secretion, whereas glucocorticoids suppress pituitary luteinizing hormone and ovarian estrogen and progesterone secretion and render target tissues resistant to estradiol. The hypothalamic-pituitary-adrenal axis is thus responsible for the "hypothalamic" amenorrhea of stress, which is also seen in melancholic depression, malnutrition, eating disorders, chronic active alcoholism, chronic excessive exercise, and the hypogonadism of the Cushing syndrome. Conversely, estrogen directly stimulates the CRH gene promoter and the central noradrenergic system, which may explain adult women's slight hypercortisolism; preponderance of affective, anxiety, and eating disorders; and mood cycles and vulnerability to autoimmune and inflammatory disease, both of which follow estradiol fluctuations. Several components of the hypothalamic-pituitary-adrenal axis and their receptors are present in reproductive tissues as autacoid regulators. These include ovarian and endometrial CRH, which may participate in the inflammatory processes of the ovary (ovulation and luteolysis) and endometrium (blastocyst implantation and menstruation), and placental CRH, which may participate in the physiology of pregnancy and the timing of labor and delivery. The hypercortisolism of the latter half of pregnancy can be explained by high levels of placental CRH in plasma. This hypercortisolism causes a transient postpartum adrenal suppression that, together with estrogen withdrawal, may partly explain the depression and autoimmune phenomena of the postpartum period.

Plasma levels of corticotropin-releasing hormone in the inferior petrosal sinuses of healthy volunteers, patients with Cushing's syndrome, and patients with pseudo-Cushing states

The objective of this study was to determine whether measurements of human CRH in the inferior petrosal sinuses could distinguish patients with Cushing's syndrome from those with pseudo-Cushing states or normal physiology. Twenty-five patients with Cushing's disease, 17 patients with the syndrome of ectopic ACTH, 7 patients with Cushing's syndrome of adrenal origin, 6 patients with pseudo-Cushing states, and 11 volunteers believed to have normal hypothalamic-pituitary-adrenal axes were studied. Basal plasma human CRH and ACTH were measured at two time points in the petrosal sinuses and in a peripheral vein. Most subjects were studied after the administration of intravenous diazepam or midazolam and fentanyl, but because of the known inhibitory effects of such sedation on CRH secretion, 2 normal volunteers and 3 patients with pseudo-Cushing states were studied without sedation. Human CRH levels were near or below the detection limit of the assay in all subjects. Although the normal volunteers and patients with pseudo-Cushing states who were studied without sedation had significantly greater inferior petrosal sinus ACTH levels than those who received sedation, there were no differences in measured human CRH levels for any of the groups. We conclude that inferior petrosal sinus human CRH levels are not easily measured in the inferior petrosal sinuses and cannot be used to determine whether individual patients may have hypersecretion of CRH causing their ACTH secretion.

Pathophysiologic and somatic investigations of hypothalamic-pituitary-adrenal axis activation in patients with depression

Preclinical studies of inflammatory and autoimmune illnesses have demonstrated the importance of central components of the HPA axis in disease pathophysiology. The implications of these data for human illness are poorly understood. We have studied the pathophysiology of the hypercortisolism seen in two human illnesses involving the central nervous system, multiple sclerosis (MS) and depression, and looked for demonstrable somatic changes that may be associated with such hypercortisolism. Data from a study of medication-free patients with multiple sclerosis not in acute exacerbation suggest that compared with depression, MS is associated with increased prominence of hypothalamic vasopressin secretion (p < 0.05). Data from studies of depressed patients with mild to moderate hypercorticolism (assessed by 24-hour urinary free cortisol excretion) demonstrate marked reductions in bone mineral density compared to healthy, carefully matched controls (p < 0.001), as well as changes in markers of bone metabolic activity similar to those seen in patients with Cushing's disease or exogenous glucocorticoid treatment (p < 0.05). Taken together, these studies suggest HPA axis dysregulations demonstrated in preclinical models of autoimmune and inflammatory illness also occur in human illness and may have important and lasting somatic sequelae.

Induction of corticotropin-releasing hormone gene expression by glucocorticoids: implication for understanding the states of fear and anxiety and allostatic load

Evidence supports the idea of two distinct corticotropin-releasing hormone (CRH) systems in the brain: one which is constrained by glucocorticoids and the other which is not. It is this latter system that includes two primary sites (central nucleus of the amygdala and the lateral bed nucleus of the stria terminalis) in which the regulation of CRH gene expression can be disassociated from that of the paraventricular nucleus of the hypothalamus. It is this other system that we think is linked to fear and anxiety and to clinical syndromes (excessively shy fearful children, melancholic depression, post-traumatic stress disorder and self-administration of psychotropic drugs). The excess glucocorticoids and CRH, and the state of anticipatory anxiety, contribute to allostatic load, a new term that refers to the wear and tear on the body and brain arising from attempts to adapt to adversity.

Synchronicity of frequently sampled, 24-h concentrations of circulating leptin, luteinizing hormone, and estradiol in healthy women

Leptin, an adipocyte hormone, is a trophic factor for the reproductive system; however, it is still unknown whether there is a dynamic relation between fluctuations in circulating leptin and hypothalamic-pituitary-ovarian (HPO) axis hormones. To test the hypothesis that fluctuations in plasma leptin concentrations are related to the levels of luteinizing hormone (LH) and estradiol, we sampled plasma from six healthy women every 7 min for 24 h during days 8-11 of the menstrual cycle. Cross-correlation analysis throughout the 24-h cycle revealed a relation between release patterns of leptin and LH, with a lag of 42-84 min but no significant cross-correlation between LH and estradiol. The ultradian fluctuations in leptin levels showed pattern synchrony with those of both LH and estradiol as determined by cross-approximate entropy (cross-ApEn). At night, as leptin levels rose to their peak, the pulsatility profiles of LH changed significantly and became synchronous with those of leptin. LH pulses were fewer, of longer duration, higher amplitude, and larger area than during the day. Moreover, the synchronicity of LH and leptin occurred late at night, at which time estradiol and leptin also exhibited significantly stronger pattern coupling than during the day. We propose that leptin may regulate the minute-to-minute oscillations in the levels of LH and estradiol, and that the nocturnal rise in leptin may determine the change in nocturnal LH profile in the mid-to-late follicular phase that precedes ovulation. This may explain the disruption of hypothalamic-pituitary-ovarian function that is characteristic of states of low leptin release, such as anorexia nervosa and cachexia.

Hormonal and metabolic responses to exercise across time of day and menstrual cycle phase

Two studies, each utilizing short-term treadmill exercise of a different intensity, assessed the metabolic and hormonal responses of women to exercise in the morning (AM) and late afternoon (PM). In study 1, plasma concentrations of growth hormone, arginine vasopressin, catecholamines, adrenocorticotropic hormone, cortisol, lactate, and glucose were measured before, during, and after high-intensity exercise (90% maximal O2 uptake) in the AM and PM. In study 2, plasma concentrations of adrenocorticotropic hormone, cortisol, lactate, and glucose were measured before, during, and after moderate-intensity exercise (70% maximal O2 uptake) in the AM and PM in the follicular (days 3-9), midcycle (days 10-16), and luteal (days 18-26) phases of the menstrual cycle. The results of studies 1 and 2 revealed no significant diurnal differences in the magnitude of responses for any measured variable. In addition, study 2 revealed a significant time-by-phase interaction for glucose (P = 0. 014). However, net integrated responses were similar across cycle phases. These data suggest that metabolic and hormonal responses to short-term, high-intensity exercise can be assessed with equal reliability in the AM and PM and that there are subtle differences in blood glucose responses to moderate-intensity exercise across menstrual cycle phase.

Rapid eye movement sleep correlates with the overall activities of the hypothalamic-pituitary-adrenal axis and sympathetic system in healthy humans

To assess the association of the overall amount of rapid eye movement (REM) sleep and the activities of the hypothalamic-pituitary-adrenal axis and sympathetic system, we performed polysomnography and measured 24-h urinary free cortisol and catecholamine excretion in 21 healthy adults. After an adaptation night, each subject was recorded in the sleep laboratory for 3 consecutive nights while 24-h urine specimens were collected. Urinary free cortisol, epinephrine, dihydroxyphenylglycol, and dihydroxyphenylacetic acid levels were significantly and positively correlated with the average values of percent REM sleep (P < 0.05). There were no correlations between hormone values and REM latency, other variables of REM distribution, or REM density, an index of phasic activity during REM sleep. The positive correlations between stress system activity and REM sleep are consistent with hormonal and sleep alterations in melancholic depression, a state characterized by increased cortisol and catecholamine secretion.