Elevated Plasma Glucocorticoid Research Articles

Transient Elevation of Plasma Glucocorticoids Supports Psilocybin-Induced Anxiolysis in Mice.

While correlations between drug-induced cortisol elevation, self-reported anxiety, and treatment outcomes have been reported for human studies during psilocybin-assisted psychotherapy, the mechanistic relationship between psychedelic-associated alterations in plasma glucocorticoid responses and the time course of anxious responsiveness remains unclear. Using rodents, both time-bound manipulation of glucocorticoid concentrations and assessment of anxiety-like behaviors can be achieved. Here, 3 mg/kg IP psilocybin was found to have anxiolytic-like effects in C57BL/6 male mice at 4 h after treatment. These effects were not altered by pretreatment with a 5-HT2A antagonist but were blunted by pretreatment with a glucocorticoid receptor antagonist or suppression of psilocybin-induced corticosterone elevations. Anxiolytic-like effects were also observed at 4 h following treatment with the nonpsychedelic 5-HT2A agonist lisuride at a dose causing a similar increase in plasma glucocorticoids as that seen with psilocybin, as well as following stress-induced (via repeated injection) glucocorticoid release alone. Psilocybin's anxiolytic-like effects persisted at 7 days following administration. The long-term anxiolytic effects of psilocybin were lost when psilocybin was administered to animals with ongoing chronic elevations in plasma corticosterone concentrations. Overall, these experiments indicate that acute, resolvable psilocybin-induced glucocorticoid release drives the postacute anxiolytic-like effects of psilocybin in mice and that its long-term anxiolytic-like effects can be abolished in the presence of chronically elevated plasma glucocorticoid elevations.

The GCs-SGK1-ATP Signaling Pathway in Spinal Astrocytes Underlied Presurgical Anxiety-Induced Postsurgical Hyperalgesia

Patients undergoing surgery often feel anxious. Accumulating evidence indicated that presurgical anxiety was related to the more severe postsurgical pain. An animal model was established that exposed Sprague-Dawley rats to a single-prolonged stress (SPS) procedure to induce presurgical anxiety-like behaviors. The experiment revealed that presurgical anxiety not only aggravated but also prolonged postsurgical pain. However, the underlying mechanisms were unknown. The rats in group C + Cort, group I + Cort, group A + Cort, and group AI + Cort were injected with corticosterone. The rats in group C + RU486, group I + RU486, group A + RU486, and group AI + RU486 were injected with mifepristone (RU486). The rats in group C + GSK650394 and group AI + GSK650394 were injected with GSK650394. The rats in group C + FC1 and group AI + FC1 were injected with fluorocitrate (FC) 30 minutes before SPS, 30 minutes before incision, and on postoperative days 1, 2, 3, 4, and 5. The rats in group C + FC2 and group AI + FC2 were injected with FC on postoperative days 7, 8, 9, 10, 11, 12, and 13. The paw withdrawal mechanical threshold was assessed 24 hours before SPS and from postoperative days 1 to 28. The level of corticosterone was determined by enzyme-linked immunosorbent assay. The expression of serum/glucocorticoid regulated kinase 1 (SGK1), interleukin-1β, and tumor necrosis factor-α was visualized by Western blot. The concentrations of adenosine triphosphate (ATP) were measured by ATP assay kit. This study showed SPS elevated plasma glucocorticoids and ATP release from astrocytes, which meant the mechanical pain hypersensitivity in presurgical anxiety-induced postsurgical hyperalgesia was dependent on GCs-SGK1-ATP signaling pathway. SGK1 protein level in astrocytes was increased in response to the glucocorticoid stimuli and enhanced the extracellular release of ATP. Furthermore, spinal astrocytes played a key role in the maintenance. Targeting spinal astrocytes in maintenance phase prevented the pathological progression. These data suggested an important signaling pathway that affected the pain sensitivity after operation caused by presurgical anxiety.

Experimental Manipulation of Corticosterone Does Not Influence the Clearance Rate of Plasma Testosterone in Birds.

In vertebrates, exposure to acute stressors stimulates the secretion of adrenal glucocorticoids such as corticosterone, and in some situations this hormone plays an important role in orchestrating the trade-off that exists between reproduction and self-maintenance. Stressful conditions often lead to a decrease in plasma levels of sex steroids such as testosterone in males, and it has been hypothesized that corticosterone contributes to this decrease. Generally supporting this proposition, glucocorticoids can inhibit the reproductive axis activity at multiple levels, including direct effects on testicular endocrine function. Here we tested for the first time the additional hypothesis that stress-induced glucocorticoids are associated with an increased clearance rate of circulating testosterone. To test this hypothesis, we performed two experiments comparing changes in plasma testosterone as a function of time (6-60 min) after a single injection of this hormone into captive male house finches (Haemorhous mexicanus) that either were intact (controls) or were pharmacologically adrenalectomized by administration of the glucocorticoid synthesis inhibitor mitotane. Control finches rapidly elevated their plasma corticosterone in response to handling, whereas mitotane treatment abolished this response by approximately 95%. Contrary to our prediction, we found no clear evidence that control birds eliminated exogenous testosterone from circulation at a different rate than pharmacologically adrenalectomized finches. These findings do not support the hypothesis that, during acute stress, elevated plasma glucocorticoids stimulate the clearance rate of testosterone. The rapid inhibitory effect of stress on plasma testosterone may rather result from direct actions of glucocorticoids on the gonadal production of the androgen or involve a glucocorticoid-independent mechanism.

Risk-averse personalities have a systemically potentiated neuroendocrine stress axis: A multilevel experiment in Parus major

Hormonal pleiotropy—the simultaneous influence of a single hormone on multiple traits—has been hypothesized as an important mechanism underlying personality, and circulating glucocorticoids are central to this idea. A major gap in our understanding is the neural basis for this link. Here we examine the stability and structure of behavioral, endocrine and neuroendocrine traits in a population of songbirds (Parus major). Upon identifying stable and covarying behavioral and endocrine traits, we test the hypothesis that risk-averse personalities exhibit a neuroendocrine stress axis that is systemically potentiated—characterized by stronger glucocorticoid reactivity and weaker negative feedback. We show high among-individual variation and covariation (i.e. personality) in risk-taking behaviors and demonstrate that four aspects of glucocorticoid physiology (baseline, stress response, negative feedback strength and adrenal sensitivity) are also repeatable and covary. Further, we establish that high expression of mineralocorticoid and low expression of glucocorticoid receptor in the brain are linked with systemically elevated plasma glucocorticoid levels and more risk-averse personalities. Our findings support the hypothesis that steroid hormones can exert pleiotropic effects that organize behavioral phenotypes and provide novel evidence that neuroendocrine factors robustly explain a large fraction of endocrine and personality variation.

Glucocorticoids in Fish Eggs: Variation, Interactions with the Environment, and the Potential to Shape Offspring Fitness.

Wild and captive vertebrates face multiple stressors that all have the potential to induce chronic maternal stress (i.e., sustained, elevated plasma glucocorticoids), resulting in embryo exposure to elevated maternally derived glucocorticoids. In oviparous taxa such as fish, maternally derived glucocorticoids in eggs are known for their capacity to shape offspring phenotype. Using a variety of methodologies, scientists have quantified maternally derived levels of egg cortisol, the primary glucocorticoid in fishes, and examined the cascading effects of egg cortisol on progeny phenotype. Here we summarize and interpret the current state of knowledge on egg cortisol in fishes and the relationships linking maternal stress/state to egg cortisol and offspring phenotype/fitness. Considerable variation in levels of egg cortisol exists across species and among females within a species; this variation is hypothesized to be due to interspecific differences in reproductive life history and intraspecific differences in female condition. Outcomes of experimental studies manipulating egg cortisol vary both inter- and intraspecifically. Moreover, while exogenous elevation of egg cortisol (as a proxy for maternal stress) induces phenotypic changes commonly considered to be maladaptive (e.g., smaller offspring size), emerging work in other taxa suggests that there can be positive effects on fitness when the offspring's environment is taken into account. Investigations into (i) mechanisms by which egg cortisol elicits phenotypic change in offspring (e.g., epigenetics), (ii) maternal and offspring buffering capacity of cortisol, and (iii) factors driving natural variation in egg cortisol and how this variation affects offspring phenotype and fitness are all germane to discussions on egg glucocorticoids as signals of maternal stress.

G6PC2 Modulates Fasting Blood Glucose In Male Mice in Response to Stress.

The glucose-6-phosphatase catalytic 2 (G6PC2) gene is expressed specifically in pancreatic islet beta cells. Genome-wide association studies have shown that single nucleotide polymorphisms in the G6PC2 gene are associated with variations in fasting blood glucose (FBG) but not fasting plasma insulin. Molecular analyses examining the functional effects of these single nucleotide polymorphisms demonstrate that elevated G6PC2 expression is associated with elevated FBG. Studies in mice complement these genome-wide association data and show that deletion of the G6pc2 gene lowers FBG without affecting fasting plasma insulin. This suggests that, together with glucokinase, G6PC2 forms a substrate cycle that determines the glucose sensitivity of insulin secretion. Because genome-wide association studies and mouse studies demonstrate that elevated G6PC2 expression raises FBG and because chronically elevated FBG is detrimental to human health, increasing the risk of type 2 diabetes, it is unclear why G6PC2 evolved. We show here that the synthetic glucocorticoid dexamethasone strongly induces human G6PC2 promoter activity and endogenous G6PC2 expression in isolated human islets. Acute treatment with dexamethasone selectively induces endogenous G6pc2 expression in 129SvEv but not C57BL/6J mouse pancreas and isolated islets. The difference is due to a single nucleotide polymorphism in the C57BL/6J G6pc2 promoter that abolishes glucocorticoid receptor binding. In 6-hour fasted, nonstressed 129SvEv mice, deletion of G6pc2 lowers FBG. In response to the stress of repeated physical restraint, which is associated with elevated plasma glucocorticoid levels, G6pc2 gene expression is induced and the difference in FBG between wild-type and knockout mice is enhanced. These data suggest that G6PC2 may have evolved to modulate FBG in response to stress.

Glucocorticoids Inhibit CRH/AVP-Evoked Bursting Activity of Male Murine Anterior Pituitary Corticotrophs.

Corticotroph cells from the anterior pituitary are an integral component of the hypothalamic-pituitary-adrenal (HPA) axis, which governs the neuroendocrine response to stress. Corticotrophs are electrically excitable and fire spontaneous single-spike action potentials and also display secretagogue-induced bursting behavior. The HPA axis function is dependent on effective negative feedback in which elevated plasma glucocorticoids result in inhibition at the level of both the pituitary and the hypothalamus. In this study, we have used an electrophysiological approach coupled with mathematical modeling to investigate the regulation of spontaneous and CRH/arginine vasopressin-induced activity of corticotrophs by glucocorticoids. We reveal that pretreatment of corticotrophs with 100 nM corticosterone (CORT; 90 and 150 min) reduces spontaneous activity and prevents a transition from spiking to bursting after CRH/arginine vasopressin stimulation. In addition, previous studies have identified a role for large-conductance calcium- and voltage-activated potassium (BK) channels in the generation of secretagogue-induced bursting in corticotrophs. Using the dynamic clamp technique, we demonstrated that CRH-induced bursting can be switched to spiking by subtracting a fast BK current, whereas the addition of a fast BK current can induce bursting in CORT-treated cells. In addition, recordings from BK knockout mice (BK−/−) revealed that CORT can also inhibit excitability through BK-independent mechanisms to control spike frequency. Thus, we have established that glucocorticoids can modulate multiple properties of corticotroph electrical excitability through both BK-dependent and BK-independent mechanisms.

Carboxypeptidase E Protects Hippocampal Neurons During Stress in Male Mice by Up-regulating Pro-survival BCL2 Protein Expression

Prolonged chronic stress causing elevated plasma glucocorticoids leads to neurodegeneration. Adaptation to stress (allostasis) through neuroprotective mechanisms can delay this process. Studies on hippocampal neurons have identified carboxypeptidase E (CPE) as a novel neuroprotective protein that acts extracellularly, independent of its enzymatic activity, although the mechanism of action is unclear. Here, we aim to determine if CPE plays a neuroprotective role in allostasis in mouse hippocampus during chronic restraint stress (CRS), and the molecular mechanisms involved. Quantitative RT-PCR/in situ hybridization and Western blots were used to assay for mRNA and protein. After mild CRS (1 h/d for 7 d), CPE protein and mRNA were significantly elevated in the hippocampal CA3 region, compared to naïve littermates. In addition, luciferase reporter assays identified a functional glucocorticoid regulatory element within the cpe promoter that mediated the up-regulation of CPE expression in primary hippocampal neurons following dexamethasone treatment, suggesting that circulating plasma glucocorticoids could evoke a similar effect on CPE in the hippocampus in vivo. Overexpression of CPE in hippocampal neurons, or CRS in mice, resulted in elevated prosurvival BCL2 protein/mRNA and p-AKT levels in the hippocampus; however, CPE(-/-) mice showed a decrease. Thus, during mild CRS, CPE expression is up-regulated, possibly contributed by glucocorticoids, to mediate neuroprotection of the hippocampus by enhancing BCL2 expression through AKT signaling, and thereby maintaining allostasis.

Genome-Wide Analysis of Glucocorticoid Receptor Binding Regions in Adipocytes Reveal Gene Network Involved in Triglyceride Homeostasis

Glucocorticoids play important roles in the regulation of distinct aspects of adipocyte biology. Excess glucocorticoids in adipocytes are associated with metabolic disorders, including central obesity, insulin resistance and dyslipidemia. To understand the mechanisms underlying the glucocorticoid action in adipocytes, we used chromatin immunoprecipitation sequencing to isolate genome-wide glucocorticoid receptor (GR) binding regions (GBRs) in 3T3-L1 adipocytes. Furthermore, gene expression analyses were used to identify genes that were regulated by glucocorticoids. Overall, 274 glucocorticoid-regulated genes contain or locate nearby GBR. We found that many GBRs were located in or nearby genes involved in triglyceride (TG) synthesis (Scd-1, 2, 3, GPAT3, GPAT4, Agpat2, Lpin1), lipolysis (Lipe, Mgll), lipid transport (Cd36, Lrp-1, Vldlr, Slc27a2) and storage (S3-12). Gene expression analysis showed that except for Scd-3, the other 13 genes were induced in mouse inguinal fat upon 4-day glucocorticoid treatment. Reporter gene assays showed that except Agpat2, the other 12 glucocorticoid-regulated genes contain at least one GBR that can mediate hormone response. In agreement with the fact that glucocorticoids activated genes in both TG biosynthetic and lipolytic pathways, we confirmed that 4-day glucocorticoid treatment increased TG synthesis and lipolysis concomitantly in inguinal fat. Notably, we found that 9 of these 12 genes were induced in transgenic mice that have constant elevated plasma glucocorticoid levels. These results suggested that a similar mechanism was used to regulate TG homeostasis during chronic glucocorticoid treatment. In summary, our studies have identified molecular components in a glucocorticoid-controlled gene network involved in the regulation of TG homeostasis in adipocytes. Understanding the regulation of this gene network should provide important insight for future therapeutic developments for metabolic diseases.

Field study into the efficacy of a medicinal plant based complex for management of Equine Cushings Syndrome in ageing horses

Pituitary Pars Intermedia Dysfunction (PPID), known as Equine Cushings Syndrome, is characterized by elevated plasma glucocorticoid concentration due to adenoma or hyperplasia of the pars intermedia of the pituitary gland. Clinical signs include hirsutism, hyperhidrosis, muscle atrophy, chronic infections, polyuria, polydipsia and laminitis [1]. The dopamine agonist pergolide mesylate is the conventional therapy of choice. Compliance is poor due to expense, poor prognosis and adverse events [2].

Cardiac steroidogenesis and glucocorticoid in the development of cardiac hypertrophy during the progression to heart failure

Elevated plasma glucocorticoid level is an independent predictor of increased mortality risk in chronic heart failure, but local biosynthesis and pathophysiological roles of glucocorticoids in the heart remain unclear. Dahl salt-sensitive rats on high-salt diet and mice with transthoracic aortic banding (TAC) operation (TAC mice), both of which finally represent heart failure, were assessed at compensatory hypertrophic stage. As a model of cardiac-specific activation of steroidogenesis, alpha-myosin heavy chain-steroidogenic acute regulatory protein transgenic mice were used. In hypertrophied hearts of Dahl salt-sensitive rats and TAC mice, the gene expressions of steroidogenic acute regulatory protein and CYP11A, rate limiting factors of steroid biosynthesis, were significantly upregulated and cardiac corticosterone level was increased compared with age-matched control. Although transgenic mice represented no morphological changes at basal condition, TAC induced greater increases in a ratio of left ventricular weight to body weight (4.8 +/- 0.2 vs.4.3 +/- 0.1 mg/g, P < 0.05) and left ventricular corticosterone level (104.5 +/- 13.3 vs. 69.8 +/- 3.8 pg/mg, P < 0.05) in the transgenic mice than in littermates. In neonatal cardiomyocytes, corticosterone increased atrial natriuretic peptide expression, protein synthesis and cell surface area, and provided the additive hypertrophic effects on phenylephrine-induced hypertrophied myocytes. These effects were prevented by glucocorticoid receptor blockade but not by mineralocorticoid receptor blockade. In hypertrophied hearts, cardiac steroidogenesis was activated with an increase in cardiac glucocorticoid level. Glucocorticoid had potential of augmenting cardiac hypertrophy via glucocorticoid receptor even under the activation of alpha-adrenoceptor-mediated hypertrophic signaling. Cardiac steroidogenesis system and local glucocorticoid may play important roles in the development of hypertrophy and the progression to heart failure.

CRH mRNA expression in the hypothalamic paraventricular nucleus is inhibited despite the activation of the hypothalamo-pituitary-adrenal axis during starvation

Corticotropin-releasing hormone (CRH) is one of the anorexigenic neuropeptides, and indeed the expression of hypothalamic CRH is known to be inhibited by starvation. To clarify whether elevated plasma glucocorticoid during starvation is responsible for the CRH suppression, we examined the expression level of hypothalamic CRH mRNA after food deprivation in adrenalectomized, plasma corticosterone (B)-clamped animals. Male Wistar rats were divided into 2 groups: one group had adrenalectomy (ADX) and B pellet implantation (ADX + B, n = 42), and the other group had only sham operation (sham, n = 42). Rats were then treated with either ad libitum food supply or food deprivation for up to 96 h. The expression of CRH mRNA in the paraventricular nucleus (PVN) was estimated by in situ hybridization. After food deprivation, mean plasma B level was markedly elevated in sham group, but almost clamped in the ADX + B group. In this experimental condition, CRH mRNA in the PVN was significantly decreased in the sham group, whereas no change was obtained in the ADX + B group. Our data suggest the decrease in CRH mRNA seems to be related to the elevated glucocorticoid level during starvation. The status of hyperadrenocorticism without activation of CRH led us to speculate that adrenocortical function is predominant in the hypothalamic-pituitary-adrenal (HPA) axis during starvation.

Sub-chronic stimulation of glucocorticoid receptor impairs and mineralocorticoid receptor protects cytosolic Ca2+ responses to glucose in pancreatic β-cells

The development of diabetes associated with stress, obesity, and metabolic syndrome involves elevated plasma glucocorticoid levels. It has been shown that short-term (<1 day) exposure to glucocorticoids reduces insulin secretion from pancreatic islets by affecting several steps of glucose signaling in beta-cells. However, longer term direct effects of glucocorticoids on beta-cells remain to be established. In this study, single beta-cells isolated from rat islets were treated with glucocorticoids, mineralocorticoids, and their receptor agonists/antagonists for 3 days in culture, followed by assessment of the beta-cell responsiveness to glucose by measuring cytosolic Ca2+ concentration ([Ca2+]i) using fura-2. Following treatment with corticosterone at 10-500 ng/ml for 3 days, the first-phase [Ca2+]i response to 8.3 mM glucose in beta-cells was suppressed. Simultaneous administration of RU-486, a glucocorticoid receptor (GR) antagonist, prevented this suppression. RU-486 by itself promoted the beta-cell [Ca2+]i response to glucose. Conversely, dexamethasone (1000 ng/ml), a highly selective GR agonist, impaired beta-cell [Ca2+]i responses to glucose. A mineralocorticoid receptor (MR) antagonist spironolactone, co-administered with corticosterone, further depressed [Ca2+]i responses to glucose, while an MR ligand aldosterone attenuated the corticosterone inhibition of [Ca2+]i responses. Neither spironolactone nor aldosterone by itself affected [Ca2+]i responses. These results indicate that long-term treatment with corticosterone impairs beta-cell [Ca2+)]i responses to glucose. This effect is mediated by GR and attenuated partially by simultaneous MR stimulation by corticosterone. The results show a novel function of MR to protect islet beta-cells against deteriorating glucocorticoid action via GR.

Antidepressant-like effects of mild hypoxia preconditioning in the learned helplessness model in rats

The effects of preconditioning using mild repetitive hypobaric hypoxia (360 Torr for 2 h each of 3 days) have been studied in the learned helplessness model of depression in rats. Male Wistar rats displayed persistent depressive symptoms (depressive-like behaviour in open field, increased anxiety levels in elevated plus maze, ahedonia, elevated plasma glucocorticoids and impaired dexamethasone test) following the exposure to unpredictable and inescapable footshock in the learned helplessness paradigm. Antidepressant treatment (ludiomil, 5 mg/kg i.p.) augmented the development of the depressive state. The hypoxic preconditioning had a clear antidepressive action returning the behavioural and hormonal parameters to the control values and was equally effective in terms of our study as the antidepressant. The findings suggest hypoxic preconditioning as an effective tool for the prophylaxis of post-stress affective pathologies in humans.

Synapse loss from chronically elevated glucocorticoids: Relationship to neuropil volume and cell number in hippocampal area CA3

Individuals with clinical disorders associated with elevated plasma glucocorticoids, such as major depressive disorder and Cushing's syndrome, are reported to have smaller hippocampal volume. To understand how the hippocampus responds at the cellular and subcellular levels to glucocorticoids and how such changes are related to volume measures, we have undertaken a comprehensive study of glucocorticoid effects on hippocampal CA3 volume and identified elements in the neuropil including astrocytic volume and cell and synapse number and size. Male Sprague-Dawley rats were injected with corticosterone (40 mg/kg), the primary glucocorticoid in rodents, or vehicle for 60 days. The CA3 was further subdivided so that the two-thirds of CA3 (nearest the dentate gyrus) previously shown to be vulnerable to corticosterone could be analyzed as two separate subfields. Corticosterone had no effect on neuropil volume or glial volume in the proximal subfield but caused a strong tendency for astrocytic processes to make up a larger proportion of the tissue and for volume of tissue made of constituents other than glial cells (primarily neuronal processes) to be smaller in the middle subfield. Within the neuropil, there were no cellular or subcellular profiles that indicated degeneration, suggesting that corticosterone does not cause prolonged damage. Corticosterone did not reduce cell number or cell or nonperforated synapse size but did cause a pronounced loss of synapses. This loss occurred in both subfields and, therefore, was independent of volume loss. Together, the findings suggest that volume measures can underestimate corticosterone effects on neural structure.

Why Does Acute Hyperglycemia Worsen the Outcome of Transient Focal Cerebral Ischemia?

Hyperglycemia adversely affects the outcome of stroke. Global ischemia data support that the harmful effect of hyperglycemia is mediated by glucose-induced elevated plasma glucocorticoids. Here we sought to evaluate the negative effects of hyperglycemia on transient focal ischemia in the rat, and to test whether these could be prevented by inhibition of either corticosteroid production or neutrophil infiltration. Sprague-Dawley rats (n=217) were used. Ischemia was induced by 1 hour middle cerebral artery occlusion (n=196). Acute hyperglycemia was induced by IP injection of dextrose 30 minutes before ischemia. Neutrophil infiltration was blocked by neutropenia with vinblastine. Corticosterone synthesis was inhibited by chemical adrenalectomy with metyrapone. We measured MRI lesion and tissue infarct volumes, evaluated the neurological function, brain myeloperoxidase and matrix metalloproteinase-9 activities, and protein O-glycosylation. Hyperglycemia significantly enhanced MRI diffusion-weighted imaging alterations, increased cortical, but not subcortical, infarct volume, worsened neurological score, and enhanced brain myeloperoxidase and matrix metalloproteinase-9 activities. Metyrapone did not prevent hyperglycemic brain damage despite successful reduction of plasma corticosterone. Yet, metyrapone tended to reduce cortical infarction and apparent diffusion coefficient lesion volume, indicating some negative contribution of corticosterone. Blocking neutrophil infiltration was also ineffective to prevent the harmful effect of hyperglycemia. A new finding was that O-linked glycosylation of cerebral proteins was increased under hyperglycemia. In transient middle cerebral artery occlusion, the hyperglycemia-exacerbated brain damage cannot be fully explained by the negative effects of plasma corticosteroids or neutrophil infiltration. The contribution of other intrinsic effects of high glucose, such as brain protein O-glycosylation, deserves further investigation.

Social instability in female rats: The relationship between stress-related and anxiety-like consequences

It is generally believed that anxiety and depression develop in response to stressful events that chronically increase glucocorticoid production (which in turn affects various neurotransmitter systems). In contrast to depression, however, the relationship between chronic stress and anxiety is less clear, as anxiety patients often show normal glucocorticoid levels and respond normally to dexamethasone challenge. Here we report on the interaction between symptoms of chronic stress and anxiety in female rats by making use of the social instability model of anxiety. Subjects were exposed to alternating 24 h periods of isolation and moderate crowding for 14 days. Symptoms of chronic stress and anxiety-like behaviour in the social interaction test were evaluated on the 15th day, i.e. 1 day after the last crowding phase. Social instability resulted in decreased weight gain, and chronically elevated plasma glucocorticoid levels only in rats that showed high aggressiveness during the crowding phases. In contrast, anxiety-like behaviour was increased irrespective to crowding-related aggressiveness. Thus, the development of chronic stress symptoms and anxiety-like behaviour dissociated: the former was bound to crowding-induced aggressiveness (i.e. to a higher stress load), whereas the latter occurred also when such aggressiveness was low, and symptoms of chronic stress did not develop. This finding is consistent with human data, and suggests that stressful events lead to anxiety in both cases: when stressors do or do not lead to chronic stress responses. Studying the distinctive features of anxieties associated or not with chronic endocrine stress responses would enhance our understanding of this disorder.

Role of glucocorticoids in mediating effects of fasting and diabetes on hypothalamic gene expression

BackgroundFasting and diabetes are characterized by elevated glucocorticoids and reduced insulin, leptin, elevated hypothalamic AGRP and NPY mRNA, and reduced hypothalamic POMC mRNA. Although leptin replacement can reverse changes in hypothalamic gene expression associated with fasting and diabetes, leptin also normalizes corticosterone; therefore the extent to which the elevated corticosterone contributes to the regulation of hypothalamic gene expression in fasting and diabetes remains unclear. To address if elevated corticosterone is necessary for hypothalamic responses to fasting and diabetes, we assessed the effects of adrenalectomy on hypothalamic gene expression in 48-hour-fasted or diabetic mice. To assess if elevated corticosterone is sufficient for the hypothalamic responses to fasting and diabetes, we assessed the effect of corticosterone pellets implanted for 48 hours on hypothalamic gene expression.ResultsFasting and streptozotocin-induced diabetes elevated plasma glucocorticoid levels and reduced serum insulin and leptin levels. Adrenalectomy prevented the rise in plasma glucocorticoids associated with fasting and diabetes, but not the associated reductions in insulin or leptin. Adrenalectomy blocked the effects of fasting and diabetes on hypothalamic AGRP, NPY, and POMC expression. Conversely, corticosterone implants induced both AGRP and POMC mRNA (with a non-significant trend toward induction of NPY mRNA), accompanied by elevated insulin and leptin (with no change in food intake or body weight).ConclusionThese data suggest that elevated plasma corticosterone mediate some effects of fasting and diabetes on hypothalamic gene expression. Specifically, elevated plasma corticosterone is necessary for the induction of NPY mRNA with fasting and diabetes; since corticosterone implants only produced a non-significant trend in NPY mRNA, it remains uncertain if a rise in corticosterone may be sufficient to induce NPY mRNA. A rise in corticosterone is necessary to reduce hypothalamic POMC mRNA with fasting and diabetes, but not sufficient for the reduction of hypothalamic POMC mRNA. Finally, elevated plasma corticosterone is both necessary and sufficient for the induction of hypothalamic AGRP mRNA with fasting and diabetes.

Glucocorticoids and aging.

Information on the role of glucocorticoids in the aging of vertebrate species is reviewed. There is strong evidence that elevated plasma glucocorticoid levels have a causal role in the rapid deterioration following reproduction in semelparous vertebrate species. If this deterioration is an example of rapid senescence, then it is clear that glucocorticoids can promote aging processes in vertebrate species. However, the evidence that glucocorticoids promote aging in the gradual senescence characteristic of most vertebrate species is not robust. Indeed, there is reason to believe that periods of moderately elevated plasma glucocorticoid levels may retard aging processes in rats, mice, and humans.

Hepatic apolipoprotein production in liver cirrhosis

The liver represents the major site of apolipoprotein metabolism, and therefore determines concentrations of lipoprotein particles. So far there are no data about arterial and hepatic venous apolipoprotein concentrations in patients with documented liver cirrhosis. We have studied 20 patients (Child A=4, Child B=9, Child C=7) of different etiology (cholestatic liver disease= 7, non-cholestatic=13). All studied patients received hepatic venous catherization. Liver blood flow was assessed by ICG steady state infusion method. Arterial and hepatic venous blood samples were obtained and assayed for the concentrations of apolipoprotein (apo) A-I, apoB and apoE using a standardized, nephelome~c assay. The mean concentrations of apoA-I were 96 mg/dl in the artery and 93 mg/dl in the hepatic vein. The liver extraction rate was 16.7 rag/rain (range -51,9-97.0 mg/min). The mean concentrations of apnB were 75 mg/dl in the artery and 76 mg/dl in the hepatic vein. The mean synthesis rate was 8.9 mg/min (range -21.8-43.7). The mean concentrations of apoE Were 9.1 mg/dl in the artery and 10.4 mg/dl in the hepatic vein. ApoA-I and apoB concentrations are significantly higher in Child A patients compared to Child B and C (p=0.009 and p=0.03, respectively). However apoA-I concentration is not correlated with ICG clearance and ICG half-life time. These data confirm the data of the lipoprotein subfractions determined in cirrhotic patients. Interestingly, patients with cholestatic disease have decreased apoB levels as well as decreased production rates (p<0.05) in contrast to apoE, which is significantly increased (p<0.05). In summary, although apoA-I is a good predictor for liver synthesis, it does not correlate with liver function tests in our studied patients and the degree of portal hypertension. ApoE seems to be inverse correlated in cholestatic liver disease compared to apoA-I and apoB. Further studies are required to get more insights into the liver dependent apolipoprotein metabolism. Q ENDOGENOUS GLUCOCORTICOIDS INHIBIT LEUKOCYTE RECRUITMENT TO INFLAMMATORY SITES IN CHOLESTATIC RATS. K. Tiandra, M. Marie, P. Kubcs, M.G. Swain, GIRG, Calgary, Canada. Cholestatic patients have a high incidence of septic complications. Glucocorticoids inhibit leukocyte recruitment to inflammatory sites and we have recently documented elevated plasma glucocorticoid levels (corticosterone; C) in cholestatic rats (Gastroenterology 107:1469,1994). Therefore, we investigated the role of endogenous C in leukocyte recruitment during carrageenan-induced inflammation in cholestatic rats. Rats were bile duct (BDR) or sham (sham) reseeted and injected 5 days later with a 2% carragecnan solution into a preformed air pouch on their hacks. 5 hrs later rats were sacrificed, plasma C levels determined, and the inflammatory response quantitated by measuring exudate cell count (cell#/ml) and MPO activity (U/ml). BDR rats exhibited an impaired inflammatory response reflected by 52 % and 42 % decreases in exudatc cell count and MPO activity respectively compared to sham rats (all p<0.05). Exudate cell differentials by cytospot were similar in BDR and sham rats. Total C levels were similar in BDR and sham rats; however, free C levels (bioactive form) were 5-fold higher in BDR than sham rats (p<0.001). To investigate whether the elevated C levels in BDR rats were suppressing inflammation, we prctreated BDR and sham rats with RU486 (20mg/kg), a C receptor antagonist, before earrageenan injection. Treatment with RU486 significantly increased the inflammatory response in BDR (to sham levels) but not in sham rats; suggesting endogenous C was suppressing the inflammatory response in BDR rats. We have previously shown that BDR plasma is anti-adhesive to lcukocytcs in vitro (Gastroenterology 106; A992,1993). To investigate whether endogenous C in BDR plasma was inhibiting the inflammatory resEonsc by interfering with leukocyte adhesion, we examined PMA-stimulated 51C-labelled rat leukocyte adhesion to a rat biological substratum in vitro. Leukocyte adhesion was inhibited to a similar extent by plasma derived from either BDR or adrenalectomized BDR (devoid of C) rats. Furthermore, the addition of RU486 with BDR plasma did not alter leukocyte adhesion from that observed in the presence of BDR plasma alone. In conclusion, endogenous C contributes to an inhibition of the inflammatory response in BDR rats. This C effect is not due to an inhibition of leukocyte adhesion. Glucocorticoids may inhibit leukocyte recruitment to inflammatory sites in cholestasis by suppressing inflammatory mediator generation or by preventing the upregulation of endothelial adhesion molecules (eg.ICAM-1).